CA1255651A - Steering and control system for percussion boring tools - Google Patents

Abstract

STEERING AND CONTROL SYSTEM FOR PERCUSSION BORING TOOLS

ABSTRACT OF THE DISCLOSURE
A steering and control system is disclosed for per-cussion boring tools for boring in the earth at an angle or in a generally horizontal direction. The steering mechanism comprises a slanted-face nose member attached to the anvil of the tool to produce a turning force on the tool and movable tail fins in the trailing end of the tool to be selectively positioned relative to the body of the tool to negate the turning force. The fins assume a neutral position relative to the housing of the tool when the tool is allowed to turn and to assume a spin inducing position relative to the hous-ing of the tool to cause it to rotate when the tool is to move in a straight direction. The tool optionally has a cyl-indrical body with overgage sleeves located over a portion of the outer body affixed so that they can rotate but cannot slide axially. The overgage areas at the front and back of the tool, or alternately, an undergage section in the center of the tool body permits a 2-point contact (front and rear) of the outer housing with the soil wall as opposed to the line contact which occurs without the undercut. The 2-point contact allows the tool to deviate in an arc without distort-ing the round cross-sectional profile of the pierced hole.
Thus, for a given steering force at the front and/or back of the tool, a higher rate of turning is possible since a small-er volume of soil needs to be displaced. A control system guides the tool in a borehole in response to control sig-nals. The control system includes an axial electromagnetic source for generating an axial alternating magnetic field directed along an axial source axis. A sensing assembly remote from the source means includes first and second pickup coils for sensing the alternating magnetic field. Each of the first and second pickup coils has a respective coil axis and is rigidly mounted in respect to the other with their respective axis at a substantial angle with respect to each other, defining a sensing assembly axis substantially normal to both coil axes. Each coil generates a respective null electrical signal when the lines of magnetic flux at the respective coil are normal to the respective coil axis.
Either the source or the sensing assembly is rigidly mounted on the tool, preferably the source. The outputs of the sens-ing coils are used to determine the direction of lines of magnetic flux at the sensing assembly, and indicate the atti-tude of the source relative to the sensing assembly.

Description

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STEERING AN~ CONTROL SYSTEM FOR PERCUSSION BORING TOOLS
~ACXGROUND OF THE _NVENTION
FIELD OF THE INVENTION
This invention relates generally to percusslon boring tools, and to the ste~ring and control of percus6ion boring tools.
DESCRIPTION OF THE PRIOR ART
Utility Companies often find i-t necassary to install or replace piping beneath diff6rent typ0s of surfaces such as streets, driveways, railroad tracks, etc. To reduce costs and public inconvanience by eliminating unnecessary excava-tion and restoration, utilities sometimes use underground boring tools to install the new or replacement pipes. Exist-ing boring tools ara suitable for boring short distances (up to ~0 ft.), but are not sufficiently advanced to provide dir-ectional control ~or longer distances. This lack of control, coupled with the inability of these tools to detect and stser around obstacles, has limited their use to about 20% of all excavations, with the majori~y of the remaining sxcavations being performed by open-cut trenching methods.
Therefore, the development of an economic, guided, horizontal boring tool would be useful to the utility indust-ry, since it would significantly increase the use of boring tools by removing the limitations of poor accuracy and by reducing the occurrence of damage to in-placa utilities. Use of such a tool instead of open-cut methods, particularly in s~

developed areas, should result in the savings of millions of dollars annually in rspair, landscape restoration and road rssurfacing costs.
Conventional pneumatic and hydraullc percussion moles are de6igned to pierce and compact compressible soils for the installation of underground utilities without the necessity of digging large launching and retrieval pits, open cutting of pavemenk or reclamation of largs areas of land. An inter-nal striker or hammer reciprocates under the action of com-pressed air or hydraulic fluid to deliver high energy blowsto ths innar face of the body. These blows propel the tool through the soil to form an sarthen casing within the soil that remains open to allow laying of cable or conduit. ~rom early 1970 to 1972, ~ell Laboratories, in Chester, New Jer-sey, conducted researoh trying to develop a method of steer-ing and tracking moles. A 4-inch Schramm Pneumagopher was fitted with two steerin~ fins and three mutually orthogonal coils which wers used in conjunction with a surface antenna to track the position of the tool. One of thes0 fins was fixed and inclined from the tool's longitudinal a~is while the other fin was rotatable.
Two boring modes could be obtained with this system by changing the position of the rotatable fin relative to the fixsd fin. These were (1) a roll mode in which tha mole was caused to rotate about its longitudinal center line as it advanced into the soil and (2) a stesring mode in which the mole was directed to bore in a curved path.

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The roll mode was used for both straight boring and as a mean~ for selectively positioning the angular orienta-tion of the i'ins for subsequ~nt changes in the bore path.
Rotation of the mole was induced by bringing the rotatable ~in into an anti-parallel alignment with the fixed fin. This positioning r6sults in the gen0ration of a force couple which initi~t~s and mainta~n3 rotation.
The steering mode was actuat~d by locating the rota-table fin parallel to the fixed fin. As tha mole penetratss the 80il, the outer surfaces of the oncoming flns are brought into contact with the soil and a "slipping wsdga" mschanism craated. This motion caused the mole to veer in the same direction as the fins point whan viewed from the back of the tool.
Published information on the actual field performance of the prototype appears limited to a pr6sentation by J. T.
Sibilia of Bell Laboratories to the Edison Electric Institute in Cleveland, Ohio on October 13, 19~2. Sibilia reported that the system was capable of turning the mole at rates of 1 to 1.5 Per foot of travel. However. the Protot~Pe was never commerciali~ed.
Sevaral percussion mole steering systems are revealad in the prior art. Goyne et al, U.S. Patent 3,525,405 dis-closes a steering system which uses a bevelad planar anvil that can be continuously rotated or rigidly locked into a given steering orientation through a clutch assembly. Chepur-~2~ S~
noi et al, U.S. Patent 3,952,813 discloses an off-axis or eccentric hammer steering syætem in which the striking posi-tion of the hammer is controlled by a transmission and motor asaembly. Gagen et al, U.S. Patent X,794,128 discloses a steering system employing one fixed and one rotatable tail fin.
However, in spite of these and other prior art Rys-tems, the practical realization of a technically and cost-effeotive steering system has been 81usiV0 because the prior ~ystems require complex parts and extensiva modifications to existing boring tools, or their staering response has been far too slow to avoid obstacles or significantly change the direction of tha boring path within the borehole lengths ty-pically used.
Several steering systems have been developed in an attempt to alleviate this problem by providing control of the boring direction. However, experienoe indicates that the tool substantially resists sideward movement which seriously limits the steering response. A method is needed by which20 the tool can travel in a curved path without displacing a significant amount of soil inside the curve. Reducing this resistive side force would provide higher steering rates for the tools. The prior art doas not disclose a steerable per-cussion boring tool having means for reducing friction during boring and turning.

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The tools of the prior art have been un3at~sfactory to the extent that their traverse has not been accurats or controllable. All too ~requently other underground utilltiea have been pierced or the ob~ective target has been missed by a substantial margin. It has also be0n dlfficult to steer around obstacles and get back on course.
The d$rectional drilling of holes has probably reach-ad its greatest sophistication in the oil fields. Typical well surveying equipment utilizes magnetometers, inclinome-ters and inertial guldance system6 which ar0 complex and expensive. The wells drilled are substantially vertical.
In respect to utilities, Bell Telephone Laboratories Incorporated has designad a system for boring horizontal holes wherein the direction of drilling is controlled by deploying a three wire antenna system on the surface of the earth and detecting the position and attitude of the drilling tool in respect thereto by pickup coils on th0 tool. The signals detected ar~ then used to develop control signals for controlling the steering of the tool. Sae, for example, MacPherson United States Patent No. 5,656,161. Such control systems have been relatively expensive, and it is no always easy or convenient to deploy the antenna, for exampls, over a busy highway.
Steering control is also known in controlling ve-hicles, aircraft and missiles. In one form of control a radio beacon is used for guidallce, the aircraft sirnply f~.llowing a beacon to a runway.
SUMMARY OF Ti~E INVEN'I'ION
Accordingly, -this invention in one aspect seeks to provide a cost-effective guided horizontal boring tool which can be used to produce small diameter boreholes into which utilities, e~g., electri,c or telephone lines, TV
cable, gas distribution piping, or the like, can be installed.
Further, the present invention seeks to provide a steering system that offers a repeatable and useful steering response in boreholes which is compatible with existing boring equipment and methods and requires only minimal modification of existing boring tools.
Further, this invention seeks to provide a boring tool which is constructed to permit transmittal of the impact force of the tool to the soil while permitting free rotation of the tool.
Still further, this invention seeks to provide an improved control system for monitoring and controlling the direction of a percussion boring tool.
By way of example, the invention in one aspect pertains to a percussion tool ~or drilling holes in the soil comprising a cylindrical housing with a front end shaped for boring, the housing having front and rear portions of a selected outside continuous constant diameter and an intermediate portion of lesser outside diameter providing two spaced continuous circumferential zones of frictional contact with the soil during boring. A first B

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means on the front end is provided for applying a boring Lorce to the soil and a second means in the housing is provided for applying a percussive force to the boring force applying means. The front and rear portions are operable to reduce friction with the wall of the bore formed by the tool and to permit the tool to turn in its path along a shorter radius.
Another aspect of the invention for example ; comprehends a controllable percussion tool for drilling holes in the soil comprising a cylindrical housing with a tapered front end and a first means on the front end for applying a boring force to the soil. A second means in the housing is provided for applying a percussive force to the boring force applying means, the first and second means lS being cooperable to apply an asymmetric boring force. A
rotatable sleeve member is supported on the rear end of the housing and fin means is supported on the rotatable sleeve member and has a fixed angular position thereon, the sleeve member and fins comprising a fin assembly. Means are cooperable with at least one component of the fin assembly to establish one position permitting the fin assembly to rotate freely on the housing during movement through the earth and another position fixed in relation to the housing to cause the housing to rotate on movement through the ~5 earth. The boring means is operable to bore in a straight direction when the fin assembly is in the fixed position and to bore in a curved direction when the fin assembly is freely rotating.
Further, the invention also comprehends a system ~,, ~ ~

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for boring a bore hole comprising a boring tool having a longitudinal tool axis and including a motive means for advancing the tool through the earth and steering means for directing the motion of the tool relative to the tool axis in response to control signals. Axial electromagnetic source means generates an axial alternating magnetic field directed along an axial source axis and a sensing assembly is remote from the source means and includes first and second pickup coils for sensing the alternating magnetic field. Each coil of the first and second pickup coils is responsive to the change of magnetic flux linked thereby by generating respective electrical signals systematically related thereto, has a respective coil axis, and is rigidly mounted in respect to the other coil with the coil axis of the first coil at a substantial angle with respect to the coil axis of the second coil, the coil axes defining a sensing assembly axis substantially normal to both the coil axesO Each coil is also balanced in respect to the sensing assembly axis to generate a respective null electrical signal when the lines of magnetic flux at the respective coil are normal to the respective coil axis at the sensing assembly axis. One and only one of the source means and the sensing assembly is rigidly mounted on the tool.
Indicating means responsive to electrical signals generated by respective first and second pickup coils is provided for indicating the direction of lines of magnetic flux at the sensing assembly relative to the sensing assembly axis, thereby indicating the attitude of the source means relative to the first and second pickup coils, and control means provide control signals for controlling the steering means.
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Othar aspects of tha invsntion w~ ecome apparent from time to tima throughout tha spacification and clalma as her01naftar ralatad.
A guided horizontal boring tool constructsd ln ac-cordance w~th tha pregant invsntion ~111 bensflt utilitiesand rate payars by slgnificantly reducing installation and maintenance costs of undarground utilitias by reducing the u88 oI sxpsnaive, open-cut trenching mathods.
The above noted aspects and othar aspects of ths in-vention are accomplished by an improved steerin~ system forpercusslon boring tools. The steering mechanism compriaes a slanted-face nose member attached to the anvil of the tool to produce a turning force on the tool and movabla tail fins in-corporated into the trailing end of the tool which are ad-apted to ba selectively positioned relative to tha body ofthe tool to negate ths turning forcs. Turning force may also ba impartsd to the tool by an eccentric hammsr which delivers an off-axis impact to the tool anvil. Ths fins also allow the nosepiece to be orisnted in any givan plane for subsequent turnlng or dlraction change.
Ths percussion boring tool may optionally have a cylindrical body with overgage sleeves located over a portion of the outer body afflxed 90 that they can rotate but cannot ~, - 10 -~.~S565~

slide axially. The overgage arsas at th0 front and back of the tool, or altsrnately, an undergage section in the centar of the tool body permits a 2-point contact (front and rear) of tha outer housing with the soil wall as opposed to the line contact which occura without the undercut. The 2-point contact allows the tool to deviate in an arc without distort-ing the round cross-sectional profile of th~ pi0rced hole.
Thus, for a givsn steering force at the front and/or back of the tool, a higher rat0 of turning is possible since a small-er volum0 of 60il needs to be displaced.
The control system for a percussion boring tool in-cludes a coil disposed on the tool and energi~ed at relative-ly low frequency to provide a varying magnetic field extend-ing axially from the tool and providing lines of magnetic flux substantially symm0trically disposed about the tool axis. ~irst and second pickup coils are disposed at a dis-tance from the tool. These coils have respective axes at a substantial angle with respect to each other and are mounted to sense the changing ~lux linked thereby and produce res-pective first and second elactrical signals.
The coil arrangsment provides respe¢tive null signals when the respective axes o~ the pickup coils lie substantial-ly perpandicular to the tool axis and the coils are balanced about the tool axis. The signals therefore indicate the at-titude of the tool relative to the coils. A third pickup coil may be used to sense the range o$ the tool when the ~55i65~

third coil has an axis extending gen~rally toward the tool, with its output used to normalize the detection signals. The axe6 of the three coils are prefsrabl~ at an~les of 9O from each other.
The signals from the respective pickup coils may be used to determine the attitude of the tool relative to ths pickup coils, and the information used to control the ~teer-ing mechanism of he tool. This may be done automatically.
Because this is a null-based system, the control signal may simply oparate th0 steering mechanism to turn the tool the reduce tha deviation from null. This caus6s the systam to be a homing device, like a beacon, and directs the tool along a path to the coils.
On the other hand, it may be desirable to deviate from a straight path, as to miss obstacles. The system may then direct the tool out of the path, around an obstacle, and back on course.
Thus, an important aspect of the present invention is to provide a null detection system to determine the attitude of a horizontal boring tool ralative to detection coils and for controlling the steering of the tool. Another aspect is to provide a control system for such a tool wherein the tool may be steered to home in on the detection coil~.
BRIEF DESCRIPTION OF THE DRA~INGS
Fig. l is a 6chematic view and partial vertical sec-tion through the earth showing a guided horizontal boring 5g~S~

tool illustrating the present invention used with a magnetic attitude ssnsing system.
Figs. 2 and 3 are schematic views, in elevation, of a fixed/lockable tail fin steering system.
Figs. 4 through 7 are schamatic views, in elevation, of a movable tail fin system.
Fig. 8 is a schematic Vi9W, in elevation, of a mov-abl~ fin systarn in combination with an eccentric hammer.
Figs. 9A, 9B, and 9C are segmsnts in longitudinal cross section of a typical boring tool having a slanted nose member and fixed/lockabla fin arrangement in the unlocked position.
Fig. lO is a vertical cross sectional view of the slanted nose member taken along the line lO - lO of Fig. 9A.
Fig. ll is a longitudinal cross section of the fix-ed/lockable tail fin assembly of Fig. 9C in the locked po&i-tion.
Fig. 12 i8 a view, in side elevation, of the fix-ad/lockable tail fin assembly of Fig. 9C in the locked posi-tion.
Fig. 13 i8 a partial elevation of the drive teeth assembly of the fixed/lockable tail fin assembly.
Figs. 14 and 15 are schematic views in ?ongitudinal cross section showing the operation of a typical percussion boring tool according to this invention.

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Figs. 16 through 19 are partial longitudinal cro~s sections of a variation~ of the fixed/lockable fin a6sembly ln the locked or unlocXed positions.
Figa. 20 and 21 are longitudinal cross sections of an alternate embodiment of the flxed/lockable fin assembly u8ing a drive pin arrangement as shown with Figs. 14 and 15, Fig. 22 is a partial elevation of the dowel pin and drive tseth of the fixed/lockable tail fin assembly.
Fig~. ~3, 24, 27, 28, 53 and 34 are partial longitu-dinal cros~ sections of variations of the fixed/lockable finassembly uslng a dowel pl~ and drive teeth driv0, while Fig~.
25 and 26 illu~trate a splined connection, and Figs 29 - 32 show a spline and drive teeth connaction..
Fig. 35 is a longitudinal cross section of a movable tail fin assembly.
Fig. 36 is a vsrtical cros6 section of the movable tail fin asaembly of Fig. 38 taken along line 36 - 36 of Fig.
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Figs. 5~ and 38 are partial longitudinal cross sect-ions of the movable tail fin assembly of Fig. 35 showing theoperati OD .
Fig. 39 is an end Yiew of tha movable tail fin as-sembly showing the fins in the non-parallel position.
~ igs. 40 and 41 are longitudinal cross sactions of a portion of a boring tool including an eccentric hammer ar-rang~ment.

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Fig. 42 i8 a schematic view and partial vertical ~ec-tion through the earth showing a guided horizontal boring tool illustratlng an alternate embodiment of the percussion boring tool with overgage sections on the tool housing and 5illustrating the tool as used with a magnetic attitude sens-ing system Fig. 43 is a view, in elevation, of a percussion bor-ing tool having overgage collars, shown in section, secured in fixad positions at the front and rear of the tool housing.
10Fig. 44 is a view, in elevation, of a peraussion bor-ing tool having overgage collars, shown in section, one in a fixad position at the front and the other supported on bear-ings for rotation at the rear of the tool housing.
Fig. 45 is a view, in elevation, of a percussion bor-15ing tool having overgage collars, shown in section, secured in fixed positions at the front and rear of the tool housing and further showing a slant nosed boring member at the front and spin controlling fins at the rear.
Fig. 46 is a view, in elevation, of a percussion bor-20ing tool having overgage collars, shown in section, one in a fixed position at the front and the other supported on bear-ings for rotation at tha rear of the tool housing and further showing a slant nosed boring member at the front and spin controlling fins at the rear.
25Figs. 47A, 47~, and 47C are segments in longitudinal cross section of a boring tool as shown in Fig 5 having a ~2~ S ilL

slanted nosa member and fixed/lockable l'in arrangement in the unlooked position.
Eig. 4~ is a vertical sectional view, partly dlagram-matic and partly in perspective, of a horizontal borlng opsr-ation, showing a horizontal boring tool controlled by a con-trol system according to the present invention;
Fig. ~9 is a diagrammatic illustration of the sensing system of he control system of the present invention;
Fig. 50A, 50B, 50C and 50D are diagrammatia illu~-trations of relationships ol' one sensing coil and the magnet-ic flux generated by the flux genarator of the sensing system shown in Fig. 49; and Fig. ~1 is a diagrammatic illustration of the elec-trical circuitry of the ssnsing system shown in Fig. 49.
DESCRIPTION OF_THE PREFERRED EMBODIMENTS
Referring to the drawings by numerals of reference, and particularly to Fig. l, there is ~hown a preferred guid-ed horizontal boring tool 10 used with a magnetic field atti-tude sensing system. The boring tool 10 may be used with various sensing systems, and a magnetic attitude sensing system is depicted generally as one example. The usual pro-cedure for using percussion moles is to first loGate and pre-pare the launching and rstrieval pits. The launching pit P
should be dug slightly deaper than the planned boring depth and large enough to provide sufficient movement for the oper-ator. The mole or boring tool 10 is connected to a pneumatic ~Z556S31 or hydraulic ~ource 11, is than startsd in the soil, stopped and properly align0d, prefsrably with a sighting frame and level. The tool is then restarted and boring continued unt$1 the tool axits into th0 retrieval pit (not shown).
Ths boring tool lO may have a pair of coils 12 at the back end, one of which produces a magnetic field parallel to the axis of the tool, and the other produces a magnetic field transverse to the axis of the tool. These coils are inter-mittently excited by a low frequency ganerator 13. To senRe the attitude of the tool, two coils 14 and 15 ar0 poaitioned in the pit P, the axes of which are perpendicular to the de-Rired path o~ the tool. The line perpendicular to the axes of these coils at the coil intersection determines the bore-sit0 axis.
Outputs of th0se Goils can be processed to deYelop the angle of the tool in both the horizontal and vertical direotions with respect to the bor0site axis. Using the transverse field, the same aat of coils can be utilized to d0termine th0 angular rotation of th0 tool to provid0 suffi-~cient control for certain types of steering systems. For th0se systems, the angular rotation of the tool is displayed along with the plane in which the tool is expected to steer upon actuation o~ the guidance control system.
The mechanical guidance of ths tool ¢an also be con-trolled at a display panel 16. From controls located at dis-play pan01 16, both the operation oi~ the tool lO and the ~2~5~

pneumatic or hydraulic actuation of the fins lr ¢an be ac-complished as descrlbed hereinafter.
As shown in ~ig. 1, the boring tool 10 includes a steering system with a slanted-face nose member 18 attach0d to the anvil 33 of the tool to produce a turning force on the tool and tail fins 17 on a rotary housing 19 on the trailing end of the tool adapted to be ~alectively posltioned relative to the body of the tool to negate the turning force. Turning force may also be imparted to the tool by an internal 0ccent-ri¢ hammer (~ig. 41) described hereinafter which delivars an off-axis impact to the tool anvil.
For turning the tool, the tail fins 17 are movad into a position where they may spin about tha longitudinal axis of the tool lO and the slanted nose member 18 or eccentric ham-mer will deflect the tool in a given direction. When the fins 17 are moved to a poaition causing the tool lO to rotat0 about its longltudinal axis, the rotation will negste the turning effect of the nose member 18 or accentrlc hammer as well as provide a means for or~enting the nose piece into any given plane for subsequent turning or direction change. It should be understood that either an eccentric hammer or anvil will produce the desired turning force, since the only re-quirament is that tha axis of the impact does not pass through the frontal center of pressure.
The steering system of the present invention will allow the operator to avoid damaging other underground serv-~Z55~

ices ~such as power cables) or to a~oid placing underground utilitie~ where they may be damaged.
Figs. 2 through 7 illustrate various combinations and implementations of the combination ~lanted nose member and tail fins stearing system schematically and lllustrates the basic operation of each design. The function of the tail fins i8 to pro~id0 a method of executing controlled changes to ths boring direction.
A fix0d/lockable tail fin stearing system 17 i8 il-10 lustated in Figs 2 and 3. To turn the tool 10, the tool isallowed to rotate about th~ longitudinal axis due to the turning force of the tail finq when in the lock~d po~itio~
until khe proper tool fac0 orlentation is obtained (~ig. 2).
The housing 19 is then unlocked and spins freely, whereby the 15 tool moves in a curved path by the turning force of the slanted faoe nose member 18. Straight boring by the tool 10 is accomplished by locking tall fin housing 19 to the main body 20 of the tool 10 (Fig, 3), to rotate the tool body and thus negate the turning action of the slanted nose member 18.
A boring tool 21 having a movable tail fin system is illustrated in Figs. 4 - 7. To turn or change direction of the tool 21, the tail fins 22 are activated to a parallel position relative to the longitudinal axis of the tool body 20 and the tool 21 i~ allowed to turn relative to the longi-25 tudinal axis due to the turning force of the nose member 18 or the eccentric hammer. Proper tool face orientation is ~2~ 6.~3L

obtained (Figs. ~ and 5) by usa of the tail fins in a ske~ed inclined position. Straight boring of the tool is accom-plished by activating the fins 22 to an inclined position r01ative to ths mols axis (Figs. 6 and 7) to rotate tha tool body and thus negate thH turning aation o~ ths slanted ~ose member 18.
~ ig. 8 illustratea a boring tool 23 with a movable tail fln system in combination with an eccentric hammer 24.
It should bs understood that the eccentric hammer may be u~ed in combination with either the fixed/lockabla fin system or tho ~o~able fin systHm ~nd with or without the slanted nose member, depending upon the ~articular application. Either an eccentric hammer or anvil will produce the desired result, since the only requirement is that the axis of the impact does not pass through the frontal center of pr3ssure. Unless nsgated by one of the previously described fin systems, the eocentric hammer 24 provides the side force rsquired to turn the tool.
The eccentric hammer 24 is keyed to the main body 2B
of the tool 23 by a pin 26 or other suitable means to main-tain the larger mass of the hammer on one sids of the longi-tudinal axis of the tool. Turning of the tool 23 i6 accom-p1ished by unlocking the tail fin housing of the fixed/lock-able embodiment from the main mole body or turning the fins of the movable fin embodiment to a position parallsl to ths body axis. The parallel fins or unlocked housing position ~25~

cli~inates the fins ability to negate the eccentric hammer force. To steer the tool 23, th0 tail fin housing is unlock-sd or the fins are activated to a skewad inclined poRition relative to the tool body axis and the tool iB turned by the eccentric hammer force until the proper tool face ori0ntation i 8 obtained.
Straight boring is accomplished in all of the previ-ously described impl0mentations by continuously rotating the tool. This distributes the turnin~ force over 360 and caus-es tha tool to bore a helioal (nearly straight) hole.
~ igs. 9A, 9~, 9C, and lO illustrate a typical boringtool 27 having a slanted nose member and fixed/lockable iin arrangement as described generally in reference to Figs. l and 2. As shown, the boring tool lO comprises an elongated hollow cylindrical outer housing or body 28. The outer front end of th~ body 28 tapers inwardly forming a conical portion 29. The internal diameter of the body 28 tapers inwardly near the front end forming a conical surface 50 which termin-ates in a reduced diameter 31 extending longitudinally inward from the front end. The rear end of the body 28 has internal threads 32 for raceiving a tail fin assembly (sae ~ig. 9C).
An anvil 33 having a conical back portion 34 and an elongated cylindrical front portion 3~ is positionsd in the front end of body 28. The conical back portion 34 of anvil 33 forms an interference fit on the conical surface 30 of the body 28, and the elongated cylindrical portion 35 extends ~25~S~

outwardly a predetermined distance beyond the front end of the body. A flat transverse surface 56 at the back end of anvil 33 reGeives the impact of a reciprocating hammer 37.
R~ciprocating hammsr 37 is an elongated cylindrical member sl$dably received within the cylindrical recass 38 oi' the body 28. A substantial portion of the outer diameter of the hammer 28 is smaller in diameter than the recess 38 of the body 28, forming an annular cavity 39 therebetween. A
relatively shorter portion 40 at the back end of the hammer 37 is of larger diameter to provide a sliding fit against the interior wall of recess 38 of the body 28.
A cantral cavity 41 extends longitudinally inward a distance from the back end of the hammer 37. A cylindrical bushing 42 is slidably disposed within the hammer cavity 41, the oircumference of which provides a 61iding fit against the inner surface of the central cavity 41. The front surface 45 of the front end of the hammer 37 is shaped to provide an im-pact centrally on the flat surface 36 of the anvil 33. As described hereinafter, the hammer configuratlon may also be adapted to d0liver an eccentric impact force on the anvil.
Air passages 44 in the sidewall of hammer 37 inwardly ad~acent the shorter rear portion 40 communicate the central cavity 41 with the annular cavity 39. An air distribution tubs 45 extends centrally through the bushing 42 and has a back and 46 extending outwardly of the body 28 connected by ~ittings 47 to a flexible hose 48. For reciprocating the ~2~65~

hammer 37, the air distribution tube 45 is in permanent com-munication with a compressed air source 11 (Fig. lj. The arrangsment of the passages ~ and the bushlng 42 i8 sueh that, during reciprocation of the hammer 3q, the air distri-bution tube ~5 alternately communicates via the passage3 44,the annular cavity 39 with either the c0ntral cavity 41 or atmosphere at regular intervals.
A cylindrical stop member 49 is secured within the recess 38 in the body 28 near the back end and has a serie6 of longitudinally-extending, circumferentially-spaced pass-ageways 50 for exhausting the interlor of the body 28 to at-mosphere and a central passage through which tha air distri-bution tubs 45 extends.
A slant-end nose member 18 has a cylindrically re-cessed portion 52 with a central cylindrical bore 53 th0rein which is received on the cylindrical portion 35 of the anvil 33 (Figs. ~A and 10). A slot 54 through the sidewall of the cylindrical portion 18 extends longitudinally sub6tantially the length of the central bore 53 and a transvsrse slot ex-tends radially from the bore 53 to the outer circumference of the cylindrical portion, providing flexibility to the cylin-drical portion for clamping the nose rnember to the anvil. A
flat 56 is provided on one side of cylindrical portion 18 and longitudinally spaced holes 5q are drilled therethrough in alignment with threaded bores 58 on the other side. Screws -6S~

59 ar0 received in the holes 57 and bores 58 and tightened to 6ecure the nose membar 18 to the anvil 33.
The sidewall of the nosa membar 18 extends forward from the cylindrical portion 52 and one sid3 iB milled to form a flat inclined surface 60 which tapers to a polnt at the extended end. The length and degree of inclination may vary depending upon the particular application. The nose member 18 may optionally have a flat rectangular ~in 61 (shown in dotted line) se¢urad to the sidewall of th0 cylin-driaal portion 52 to extend substantially the length thereofand radially outward therefrom in a radially opposed position to the inclin0d surfaca 60.
Slanted nose members 18 of 2-1/2" and 3-1/2" dia-meter with an~les from 10 to 40 (as indicated b~ an~le "A") have been tested and show the nosa member to be highly ef-fective in turning the tool with a minimum turning radius of 28 feet b~ing achieved with a 3-1/2 inch 15 degree nose mem-ber. Testing also demonstrated that the turning effect of the nose member was highly repeatable with deviations among tests of any nose membar seldom varying by more than a few inches in 35 feet of bore. Additionally, the slanted nose members w~re shown to have no adverse effect on penetration rate and in some cases, actually increased it.
It has also been found that the turning radius varies linearly with the angle of inclination. ~or a given nose ~l~5~

angle, the turning radius wSll decrease in direct proportion to an increase in area.
A tail fin asssmbly 19 is secured in the back end of the body 28 (Fig. 9C). A fixed/lockable tail fin assembly 19 is illustrated in the example and othsr variations ~ill be de6crib~d hereinaft~r. The tail fin assembly 10 comprisss a cylindrical connecting sub 63 having external threads 64 at the front end which are received within the intarnal threads 32 at the back end of the body 28. Sub 63 has a short re-duced outside dlameter portion 65 forming shoulder 66 there-between and a second reduced diameter 67 ad~acent the short portion 65 forms a second shoulder 68.
An O-ring seal 69 is located on the reduced diameter 65 intermediate the shoulders 66 and 68. The rear portion 70 of the sub 63 is smaller in diameter than the second reduced diameter 67 forming a third shoulder 71 therabetween and provided with a circumferentlal O-ring seal 72 and an intern-al 0-ring seal 73. Internal threads 74 are provided in the rear portion 70 inwardly of the seal 73. A circumferential bu~hing 75 of suitable bearing material such as bronze is provided on the second reduced diameter 67.
A series of longitudinal circumferentially spaced grooYes or keyways 76 are formed on the circumference of the r~ar portion 70 of the sub 63. A hollow cylindrical piston 77 is slidably received on the circumference of the rear por-~2~;S6~

tion 70. A series of longitudinal circumferentially spacsd grooves or kayways ~8 are formed on the interior surface at the front portion of the piaton 77 in opposed relation to ths 6ub keyways 76. A series of keys or dowel pin6 79 ars rs-ceived within the k~yways 76 and 78 to prevent rotary motionbstween the su.b 63 and ths piston 77.
first internal cavity 80 sxtends inwardly from the ~eyway ~8 terminating in a short reduced diam~ter portion 81 which forms a ahoulder 8~ therebetwssn. A second cavity 83 extends lnwardly from the back end 84 of the piston ~ term-inating at the reducod diametar portlon 81. An internal ann-ular 0-ring seal 85 is provided on the reduced diameter por-tion 81. A~ shown in Figs. 9C and 13, a series of drive teeth 86 are formed on the back end of the piston 77. The t0eth 86 comprise a series of circumferentlally 6paced raised surfac0s ~7 having a straight side 88 and an angularly slop-ing side 89 forming a one-way ratchet configuration. A com-presaion spring 90 is received within the first cavity 80 of the piston 77 and is compr6ssed between the back end ~0 of the sub 63 and the shoulder 82 of th6 piston 77 to urga ths pi~ton outwardly from the sub.
An elongated, hollow cylindrical rotating fin sleeve 91 is slidably and rotatably recsived on the out~r periphery of sub 63. Ths fin slesva 91 has a csntral longitudinal bore 92 and a ghort countsrbore 93 of larger diameter extending inwardly from the front end and defining an annular shouldar ~L~5i5~
94 therebetween. The counterbore 93 fits over the short re-duced diameter 65 o~ the sub 63 with the 0-ring 69 providing a rotary seal therebetween. A flat annular bushing 95 of suitable bearlng matsrial such as bronze is disposed between tha shoulders 6~ and 94 to reduce ~riction therebstween. A
sacond counterbore 06 extends inwardly from the back end of th~ fin sleave 91.
A hollow cylindrical slesve 9~ is secured within t~e kecond countarbore 96 by suitable means such as walding. The sleeeve 97 has a central bora 08 substantially the same dia-meter as the second cavity 83 of the piston ~7 and a counter-bore 99 extending inwardly from the back end defining should-er 100 therebetween. As shown in Figs. 9C and 13, a series of drive teeth 101 are formed on the front end of the sleeve 9r. The teeth 101 comprise a series of circumferentially spaced raised surfaces 102 having a straight side 103 and an angularly sloping side 104 forming a one-way ratchet config-uration. The teeth correspond in opposed relationship to the teeth 86 of the piston 77 for operative engagement therewith.
A seriss of flat radially and angularly oppossd fins 105 are secured to the exterior of the fin sleeve 91 to ex-tend radially outward ther~from. (Figs. 9C, 11 and 121 The fins 105 ars secured at opposing angles relative to the lon-gitudinal axis of the sleevs 91 to impart a rotational force on the sleeve.

- 2~ -~SG~l An elongatsd hollow cap ~laeve 106 having external threads 107 at the front end i6 slidably received within the sliding piston 77 and the sleeve 97 and threadedly secured in the internal threads 74 at the rear portion 70 of the sub 63.
The cap sleeve 106 axtends rsarwardly from the threads 107 and an enlarged diameter portion 108 forms a first shoulder 109 spaced from the threaded portion and a 6econd enlargsd diametsr 110 forms a second shoulder 111 spaced from the first 6houlder.
An 0-ring seal 112 is provided on the enlarged dia-meter 108 near the shouldHr 109 and a second 0-ring seal 113 is providsd on the second enlarged diameter 110 near the second ahoulder 111. The 0-ring 112 forms a reciprocating seal on the interior of the second cavity 83 of the piston 77 and the 0-ring 113 forms a rotary seal on the counterbore 99 of the sleeve 97. The 0-ring 85 in the piston 77 forms a reciprocating seal on the extended sidewall of the cap 106.
An annular chamber 114 is formed between the ext0rior of the sidewall of the cap 106 and the second counterbore 83 20 which is sealed at each end by the 0-rings 85 and 112. A
circumferential bushing 115 i6 provided on the first enlargad diameter 108 and an annular bushing 116 on the second enlarg-sd diameter 110 is captured between the shoulders 100 and 111 to reduce friction between ~he sleeve 97 and the oap 106. The rear portion of the cap 106 has small bores 117 arranged to receive a spannsr wrench for effecting the threaded connect-~25~
ion. A threaded bore 118 at the back end of the cap 106 recslves a hose fitting (not shown) and a small passageway 119 extends inwardly from the threaded bore 118 to communi-cate the annular chamber 114 with a fluid or air aource (not shown). A flexible hose extends outwardly of the cap 106 and i9 connected to the fluid or air source for effecting recip-rocation of the piston 77. A second small paRsage~ay 120 communicates th~ first cavity 80 with atmosphere to relieve pressure which might othsrwi6e become trapped therein. Pa6s-age 120 may also be usad for application of pressure to theforward end of the plston 77 for rsturn movem0nt.
OPERATION
Having thus described the ma~or components of tha boring tool assembly, an explanation of the opsration of a typical boring tool and the tail fin assembly follows.
The operation of the percussion boring tool 27 is il-lustrated schematically in Figs. 14 and 15. Under action of compressed alr or hydraulic fluid in the central cavity 41, the hammer 37 moves toward the front of ths body 28. At the foremost position, the hammer imparts an impact on the flat surface 36 of the anvil 33.
In this position (Fig. 14), compressed air is admit-ted through the passagas 44 from ths cantral cavity 41 into the annular cavity 39. Since the effective area of the ham-mer including the larger diametar rsar portion 40 is grsaterthan the affactive area of the central cavity 41, the hammer ~zss~

starts moving in the opposite direction. During this move-ment, the bushing 42 closes ths passages 44 (~ig. 15), thera-by interrupting the admission of compressed air into annular cavity 41.
The hammer 37 continues its movemant by ths e~pansion of the the air in the annular cavity 39 until the passagss 44 ara displaced beyond the end~ of the bushing 42, and the an-nular cavity axhausts to atmosphere through the holes 50 in the stop member 49. In this position, tha air i8 exhausted from tha annular cavity 39 through the passages 44 now above the trailing edge of the bushing 42 and the holes 50 ln the stop member 49. Then the cycle is repeated.
The operation of the tail fin assembly 62 is best seen with reference to Figs. 9C and 11. The compressed air or fluid in the annular cavity 114 moves the plston 77 again-st the force of the spring 9O and toward the front of the sub 63. In the foramost position, the front end of tha piston ~7 contacts the shoulder 71 and the drivs teeth 86 and 101 be-come dis-engaged. In this position (Fig. 9C), compressed air or fluid is admitted through the passage 119 from the source into the annular chamber 114. The fin sleave 91 is than free to rotate relative to tha tool body.
When the air or fluid pressure within the chamber 114 is relieved, ths force of the spring 9O movas the piston 77 in the opposite dirsction (Fig. 11). During this movement, ~2S~

the drive teath 86 and 101 become engaged once again and the fln sleave 91 b0comes locked against rotational movement rel-ativs to the tool body. Pressure which may otherwise become trapped in the first cavity 80 and hindar reciprocation i8 exhausted through the pressure reliaf passage 120 to atmos-phere. The cycle may be selectively repeated as nece6sary for propar alignment tha slanted nose member 18 and attitude ad~ustment of the tool. It should be understood that the passaga 120 may also be connected to a fluid, i.e. liquid or air, source for moving tha pi6ton to the raarward position.
ANOTHER EM~ODIMENT
Another embodiment of the tail fin assembly clutch mechanism is illustrated in Figs. 16 and 17. Some parts are given the same numerals of reference to avoid repetition.
The tail fin assembly 119 comprises a cylindrical connecting sub 163 having extarnal threads 164 at the front end which are received within th0 internal threads 32 at the back end oi the body 2~. Sub 163 has a short reduced outside diamster portion 165 forming a shoulder 166. The raar portion 170 of the sub 163 is smaller in diameter than the reduced diameter 165 forming ~ third shoulder 171 therebetwesn and provided with a circumferential O-ring sea1 172.
A series of longitudinal circumfarentially-spaced grooves or keyways 176 are formed on the rear portion 170 of the sub 163. A hollow cyllndrical piston 1~7 is ~lidably r3ceived on the circumference of the rear portion 170. A
series of longitudinal circumferentially spaced groovss or Xeyways 178 ara formed on the lnterior surface at the front portion of ths piston 177 in oppossd rslation to the sub keyways 176. A ssries of k3ys or dowel pins 179 are recsSved within the Xeyways 176 and 178 to prevent rotary motion be-tween the sub 163 and the piston 177.
A first internal oavity 180 extends inwardly from th3 keyway 178 terminating in a short reduced diameter portion 10 181 which forms a shoulder 182 therebetween. A second cavity 183 smaller than ths first extends inwardly from the bacX end 184 of the piston 77 terminating at the reduaed diameter por-tion 181. O-rlng seals 173 and 18~ ars provided on the inter-ior of the first aavity 180 and reduced diamster portion 181 respectively. As previously shown and d3scribed with refer-ence to Fig. 13, a series of drive teeth 86 are formed on the back end of the piston 177. Th3 teeth 86 comprise a ssries of circumferentially spaced raised surfaces 87 having a straight side 88 and an angularly sloping side 8a forming a one-way ratchet configuration.
An slongated hollow cylindrical rotating fin sleeve 91 i8 rotatably r3ceived on the outer periphsry of th3 sub 163. Th3 fin sleeve 191 has a central longitudinal bore 192.
The bore 192 is rotatably received on the reduced diamster 25 165 of the sub 163 with the O-ring 169 providing a rotary 6S~L

seal therebetween. A flat annular bushing 195 of suitable materi~l such as bronze is disposed between the shoulder 1~8 and tha front of the fin sl0eve 191 to reduce friction.
A hollow cylindrical sl0eve 197 i8 secured within the rear portion of the fin sleeve bore 192 by suitable means such a~ welding. The slaeeve 197 has a central bore 198 sub-stantially the same diam0ter as the second cavity 183 of the piston 177. As previously shown and described with reference to Fig. 13, a series of drive taeth 101 are ~ormed on the front end of the sleeve 197. The teeth 101 comprise a serie of circumferantially spacad raised surfaces 102 having a straight side 103 and an angularly sloping sid3 104 forming a one-way ratchet configuration. Tha teeth correspond in opp-osed relationship to the teeth 86 of the piston 177 for oper-15 ative engagement therewith. An 0-ring 213 and a bushing 215 are provided in the central bore 198.
A series of ~lat, radially and angularly opposed fins 205 are secured to the e~terior of the fin sleeve 191 to ex-tend radially outward therefrom. The fins 205 are secured at 20 opposing angles relative to the longitudinal axis of the sleeve 191 to impart a rotational force on the sleeve.
An elongated hollow cylindrical cylinder cap 206 having external threads 207 at the front end is slidably re-ceived ~ithin tha sliding piston 177 and the sleeve 197 and 25 threadedly secured in the internal threads 174 at tha rear 6~

portion 1~0 of the Rub 163. The circumference of the cap 206 extends rearwardly from the threads 20~ and an enlarged dia-meter portion 208 forms first shoulder 20~ spaced from the threaded portion and a seaond enl~rged diamcter 210 forms sa-cond ~houldar 211 spaced from the first shoulder. An 0-ring seal 212 is provided on the enlarged diameter 208 near the shoulder 209. The 0-ring 212 forms a reciprocating seal on the interior of the se¢ond cavity 183 of the piston 177 and tha 0-ring 213 forms a rotary seal on the central bore 198 of the sleev~ 197. The 0-ring 185 ln the piston 177 forms a reciprocating seal on the extended sidewall of the cap 206.
An annular rear chamber 214 is formed between the exterior of the sidewall of the cap 206 and the second small-er bore 183 which is sealed at each end by the 0-rings 185 and 212. An annular front chamber 216 is formed between the sidewall of the cap 206, the cavity 180, and the back end of the sub 163, which is sealed by the 0-rings lq2, 1~3, and 18~. The side wall of the sub 163 has small bores 21~ ar-ranged to receive a suitable wrench for effecting the ~hread-ed conneotion. A threaded bore 218 at the back end of thecap 206 receives a hose fitt$ng (not shown) and a small pass-ageway 219 extend6 inwardly from the threaded bore 218 to communicate the rear chamber 214 with a fluid or air sourc~
(not shown). Another similar threaded bore at the back ~nd ~2~

of the ¢ap receives a ho~e fltting (not shown) and a small passageway 220 extends inwardly from the threaded bore to communicate the front chamber 216 with a fluid or air source lnot shown). Flexible hoses extend outwardly of the cap ~06 and are connected to the fluid or air source for 0ffecting reciprocation of the piston 177.
The operation of the tail fin assembly 119 i8 illus-trated schematically in Figs. 16 and 17. Under action of compressed air or fluid in the r0ar chamber 214, the piston 177 movas toward the front of the sub 163. When in its fore-most position, the drive teeth 86 and 101 are disengaged and the fin sleevs 191 is free to rotate about the longitudinal axis of thc tool body. In this position (Fig. 16), compress-ed air or fluid in the front chambcr 216 has been exhausted.
To lock the tail fins against rotational movement, compressed air or fluid is admitted through the passage 220 into the front chamber 216 and exhausted from the rear chamber 214 to move the piston 177 in the oppo~ite direction. In this posi-tion (Fig. 17), tha drive teeth 86 and 101 are once again engaged preventing rotational movement. The cycle may be selectively repeated as necessary for proper alignment the slanted nose member and attitude adjustment of the tool.
A FURTHER EMBODIMENT
Another variation of the flxed/lockable tail ~in as-sembly having drive tecth is illustrated ~n Figs. 18 and 19.

~2~S~

To avoid r~petition, some of tha components, detail6, and reference num~rals pr0viou61y 6hown and de6cribsd with r0~-erence to Flgs. 9C and 11 will not be repeated here. Other component~ previously describsd will carry the same numerals of reference.
The tail fin assembly 210 comprise~ a cylindrical connacting sub 263 having external threads at the front and which are r~ceived within ths internal thraads at the back end of the body. The sub 263 has a short reduced diameter portion forming a first shoulder and a second reducad dia-m0ter ad;acent the short portion forms a s0cond shoulder. An annular O-ring seal is provided on th0 first reduced diameter intermediate the first and second shoulders. The sidewall of the sub 263 extends rearwardly from the 6econd shoulder. The rear portion 270 of the sub 263 is smaller in diam0ter than the second reduced diameter forming a third 6houlder 268 and a fourth reduced diam~ter defines a fourth shoulder 271. A
circumferential O-ring seal 272 i8 provided at back end of the sub 263. External threads 274 are provided in the rsar portion 270 inwardly of the seal 272.
A series of circumferentially spaced spherical aper-tures 276 are formed on the circumference of the sidewall of the sub 263 n0ar ths third shoulder 271 and carry a series of balls 279. A hollow cylindri~cal piston 277 is slidably re-ceived on the circumference of the raar portion 270. A ser-~z~s~

ieB of longitudinal circumferentially 6paced groovss or key-ways 278 are formed on the int0rior ~urface at the front por-tion of the piston 277 in oppossd relation to the balls 279.
The balls 279 within apertur~s 276 and keyways 278 prevsnt rotary motion betwaan ~ub 263 and pi~ton 277.
A first cavity 280 extends inwardly from the front end of th3 piaton 27r and terminates in a short reduced dia-meter portion 281 which forms a 6houlder 282. A sacond cav-ity 283 axtends inwardly from tha back end of th~ piston 2~7 terminating at the reducad diameter portion 281. An 0-ring seal 285 is provided on the reduced diamster portion 281. As shown in Fig. 13, a 6~ri0s of drivs teeth 86 ara formed on the back end of the piston 277. The teeth 86 comprise a ~er-ies of circumferantially spaced raised surfaces 87 having a straight side 88 and an angularly sloping side 89 forming a one-way ratchet configuration. A compression spring 290 surrounds the sidewall o~ the sub 263 and the ends of the spring are biased against the shoulder 268 of the sub 270 and the front end of the piston 277 to urge the piston outwardly from the sub.
As previously describ~d a hollow cylindrical rotating fin 61eeve 291 having a rear counterbore 296 is slldably and rotatably received on tha outer periphery of sub 263. A hol-low cylindrical sleeve 297 i8 secured within the 6scond coun-terbora 296 by suitable means such a6 wslding. The slaevs ~z5S~

297 has a central bor0 substantially the 6ame diameter as the second cavity 283 of the piston 277 As shown in Fig. 13, a saries of drive teeth 101 are formad on the front 3nd o~ the sleeve 297. The teeth 101 comprise a series of circumferen-tially ~paced raised surfaces 102 having a straight side 103 and an angularly sloping sida 104 forM1ng a one-way ratchet configuration. The teeth correspond in opposed relation6hip to the te~th 86 of the pi~ton 277 for operative engagement therewith. A s~ries o~ flat radially and angularly opposed fins as previously described are s0cured to the exterior of the fin sle0ve to extend radially outward therefrom.
An elongated hollow cylindrical cylinder cap 306 having internal threads 307 at the front end is slidably re-ceived within the ~liding piston 277 and the sleeve 297 and threadedly secured on tha external threads 274 at the rear portion 270 of tha sub 263. An 0-ring seal 312 is provided on the outer front portion of cap 306 and a second 0-ring seal 313 is provided on the rear portion. The 0-ring 312 forms a reciprocating seal on the interior of cavity 283 of piston 277 and 0-ring 313 forms a rotary saal on ths count-erbore of fin sleeve 291. Tha 0-ring 285 in piston 27~ forms a reciprocating seal on the ~ldewall of cap 306.
An annular chamber 314 is formed between the exterior of the sidewall of the cap 306 and the countarbore 283 which i~ sealad at each end by the 0-rings 285 and 312. Bushings ~55~

as previou~ly described sre provid0d on the sub 263 and cyl-inder cap 306 to reduce friction therebeween. Tha rear por-tion of the cap has a threaded bore 318 at the bacX end of the cap 306 which receives a hose fitting (not shown) and a small passageway 319 e~tends inwardly from the threadsd bore 318 to communicate the annular chamb0r 314 with a fluid or air source (not shown). A flexible hose ext3nds out~ardly of the cap 306 and is connscted to the fluid or air sourcs for effscting reciprocation of the piston 277.
The operation of the tail fin assembly 219 is best seen with reference to Figs. 18 and 19. Compressed air or fluid in the annular cavity 314 moves the piston 277 to over-come th0 force of the spring 290 and move toward the front of sub 263. In the foremost position, the driv0 teeth 86 and lOl b0come disangaged. In this position (Fig. 18), comprass-ed air or fluid is admitted through the passage 319 from the source into the annular chamber 314. The fin sleeve 291 is then free to rotate relative to the tool body.
When the air or fluid pressure within the chamber 314 is relieved, the force of the spring 290 moves tha piston 277 in the opposite diraction (Fig. 19). During this movement, th0 drive t0eth 86 and 101 become engaged once again and the fin sleeve 291 becomes locked against rotational movement relative to the tool body. The cycle may be selectively repeated as necessary for proper operation of the tool.

~s~s~
STILL ANOTHER EMBODIMENT
~ igs. 20 and 21 are longitudinal cross sections of an altarnata embodimant of the fixed/lockable fin assembly which incorporates a driv0 pin arrangement in place of ons of the drive taeth membsrs previously described. It will be noted that tha drive pin arrangement nacassitates moving the ~in sleeve along the longitudinal axis to effect fin positionlng.
The tail fln asAembly 400 compris0s a cylindrical connecting sub 401 having external threads 402 at the front end which are received within the intarnal threads 32 at tha rear portion of th0 body 28. The sub 401 has a first reduced diameter portion 403 forming a first shoulder 404 and a se-cond reduced diameter 405 adjacent the first forms a second shoulder 406 which receives an annular seal 407. The rear 15 portion 408 of sub 401 is smaller in diameter than tha second reduced diameter 406 and extends longitudinally therefrom.
A thin cylindrical retainer ring 409 i~ secursd on the first reduced diametsr 403 of thc sub 401 by screws 410 and a small annular rib 411 on the interior surface of the 20 ring captures the seal 407 within the second shoulder 406.
The rear and of ring 409 ext~nds a short distance beyond seal 407 to surround the forward and of the rear portion 408 of the sub 401.
An elongated, hollow cylindrical rotating fin sleeve 25 412 is slidably and rotatably received within the extended ~z~s~

portion of ring 409 and surround6 the r0ar portion 408 of sub 401. The fin sleeve 412 ha~ a central longitudinal bore 413 and a counterbora 41~ of larger diameter extending inwardly from the back end and defining an annular shoulder 415 ther0-between. An 0-ring seal 416 on fin sls0ve 412 provides a rotary and reciprocating seal on the inner surface of ring 40~. A plurality of circumferentially spaced dowel pins 417 extend radially inwardly through the side wall of the fin sleeve 412 and terminate a short dlstance from th0 clrcumfer-enc0 o~ ~he r0ar portion 408 of the sub 401. An annular 0-ring seal 418 and a bushing 419 is provided on the interior surface of the fin sleeve 412 intermediate thfl dowel pins 41 and shoulder 415.
A series of radially and angularly opposad fins 420 ar~ secur~d to the exterior of the rotating fin sleeve 412 to ~xtend radlally outward therefrom. The fins are secured at opposing angles relative to the longitudinal axis of the sleeve 412 to impart a rotational force on the 61eev~. An elongated hollow cylindrical cap 421 is slidably received on the sub rear portion 408 within fin sleeve 412 and secured to sub 401 by means of a screw 422 at the rear portion theraof.
The cap 421 has a r0duced diamstcr front portion 423 and an enlarged diameter r0ar portion 424 forming a shoulder 425. A
pair of longitudinally spac~d 0-rings 426 are positioned on the rcar portion 424 and a bushing 427 is provid0d intermedi-~zss~

ate the O-rings 426. The enlarged diameter rear portion 424 o~ the cap 421 is rotatably received within counterbore 414 with the O-rings 426 providing a rotary æeal therebetwaen.
As shown in ~igs. 20, 21, and 22, a series of drive teeth 428 are formed on the front end o~ the cap 421. The drlve teeth 428 comprise a series o~ circumferentially ~paced raised surfaces ~29, each having a gsnerally stralght Ride 430 and an angularly sloping sid~ 431 forming a one-way rat-chet conriguratlon. The spacing o~ th0 driv0 teeth 428 rela-tiv0 to the dowel pins 41~ i8 BUCh that the pins will be r~tained by the teeth in the locked position to prevent rot-ary motion between the fin slesve 412 and cap 421 as describ-ed h~reinafter.
Whsn properly po~ition0d, an annular chamber 432 is formed betwean ths should0r 415 of the ~in sleev~ and the should0r 425 of the cap and sealed at each end by the O-r~ngs 418 and 426. A thr0aded bore g33 at the back end of the cap 421 receives a hose fitting (not shown) and a small passags-way 434 extends inwardly from the threaded bore to communi-cate the annular chamber 432 with a fluid or air source (not shown) for reciprocatiing fin sleev0 412.
The operation of the tail fin assembly with dowel pins is best seen with refarence to Figs. 20, 21, and 22.
Compressed alr or fluid ln the annular chamber 432 moves the fin ~leevs 412 toward the front o~ the sub 401. In the fore--~`ss~s~

most position, the front snd of th0 61eeve 412 contact6 ths seal 40~ and the dowel pins 417 disengage from the drive teeth 428. In this position (Fig. 20), comprassed air or fluid is admitted through the passage 434 from the source into the annular chamber 432. Ths fin sleeve 412 is then fre0 to rotate relative to the tool body.
When th0 air or fluid pressure within the chamber 432 is relieved, the driving force of the tool hammer carries the tool including the cap 421 forward (Fig. 21). During this movement, drlve t0sth 428 and dowel pins 417 become engaged once again and fin sleeve 412 becomes locked against rotat-ional movement relative to tha tool body. The cycle may be ~electively r0peated as necessary for proper alignment of the ~lanted nos0 member and attitude ad~ustment of the tool.
A ~URTHER ~MBODIMENT
~igs. 23 and 24 are partial longitudinal cross sect-ions of variations of the fi~ed/lockable fin a6sembly using a drive pin. The tail fin assembly 500 comprises a cylindrical connecting sub 501 having external threads 502 at the front end which are received within the internal threads 32 at ths rear portion of the body 28. The sub 501 has a first reduced diameter portion 505 forming a shoulder 504. Tha rear por-tion 505 of the sub 501 is smallar in diameter than the first reduced diameter 503 forming a second shoulder 506. The rear portion 505 extends longitudinally from shoulder 506 and has ~xt~rior threads 507 at th~ back end.

5~l A thin cylindrical retainer ring 508 i~ received on the reduced diameter 503 of sub 501 by scraws 509. The rear end of ring 508 axtends a short distance beyond the shoulder 506 to surround the forward end of the rear portion 505 of the sub 501.
An elongated hollow cylindrical rotating fin ~leave i~ slidably and rotatably received within the extanded por-tion of ring 508 and surrounds ths rsar portion 505 of sub 501. The fin sleeve 510 has a central longitudinal bore 511 and a counterbore 512 of larger diametsr 0xtending inwardly from the back end and defining an annular shoulder 513. An 0-ring seal 514 on the fin ~leeve 510 provid0s a rotary and reciprocating seal on th~ inner surface of the ring 508. A
plurality of circumferentially 6paced dowel pins 515 extend radially inwardly through the side wall of the fin sl0eve 510 and terminate a short distance from ths oircumference of the rear portion 505 of the sub 501. An 0-ring seal 516 and a bushing 51~ are positioned on the interior surfacs of fin ~leeve 410 intermediata the dowel pins 515 and shoulder 613.
A plurality of radially and angularly opposed fins 518 are secursd to the exterior of the rotating fin sleeve 510 and extend radially outward therefrom. The fins 518 ara securad at opposing angles relative to the longitudinal axis of the ~leeve 510 to impart a rotational forcs on the sleeve.
A tubular cap 519 having a central bore 520 and a threaded counterbore 521 extending inwardly from the front ~.ZS~;6~

end is slidably recsived on the air distribution tube 46 and the sub rear portion 505 within the fin sleeve 510. The cap 519 is threadedly recsived and secured on th0 threads 50~ at the snd of the sub 501. The cap 519 has a raduced diameter front portion 522 and an enlarged diameter rear portion 523 forming a shoulder 524 therebetwaen. A pair of longitudin-ally spaced O-rings 525 are provided on the rear portion 5~3 and a bushing 526 is provided intermediate the O-rings 525.
The enlarged diameter rear portion 523 o~ cap 519 ls rotatably received within the counterbore 512 with O-rings 525 providing a rotary seal. A8 pr0viously shown and des-cribed with reference to ~ig. 22, a plurality of drive teeth 428 are formsd on the front end of the cap 519. The rear portion 523 of the cap 519 has a raduced diametar portion 52~
which removably receives a conical cover member 528. A plur-&lity of circumferentially spaced longitudinal bore~ 529 extend through the rear portion of the cap 519 for communica-tlng the interior of the body 28 with ~tmosphere. The drive taeth ara oonstructed and operate as pr0viously describad for the other embodiments.
When properly positionad, an annular chamber 530 is formed between the shoulder 513 of the fin sleeve and the shouldar 524 o~ the cap and sealed at each end by th0 O-rings 516 and 624. A threaded bore 433 at the back end o~ the cap 519 r0ceives a hose fitting (not shown) and a small pas~age-~2S~S~

way 434 extends inwardly from the threaded bore to communi-cat0 the annular chamber 530 with a fluid or air aourca (not shown) for effecting reciprocation of the fin sleeve 510.
The operation of the tail fin assambly with dowel pins and drive teeth i~ be~t seen with referance to Figs 23 and 24. Compressed air or fluid in tha annular chamber 530 moves the fin slaeve 510 toward the front of the sub 501. In lts foremost position, the front end of the sleavs 510 con-tacts the shoulder 506 and the dowel pins 515 disengage from the drive teeth 428. In this position (Fig. 23), compressed air or fluid i8 admittsd through the passage 454 from the source into the annular chamber 530. The fin sleeve 510 is then free to rotate rslative to the tool body.
When the air or fluid pressure within the chamber 530 is relieved, the driving force of the tool hammer carries the tool ln¢luding the oap 519 forward (Fig. 24). During this movement, the drive teeth 428 and dowel pins 515 engage once again and the fin sleeve 510 i9 locked against rotational movement relative to the tool body. The cycl0 may be select-ively repeated as necessary for proper aligmnent of theslanted nose member and attitude adjustment of the tool.
A STILL FURTHER EMBODIMENT
Flgs. 25 and 26 are partial longitudlnal cross sec-tional views of a variation of the fixed/lockable fin assem-bly using an interlocking lug arrangement to prevent rota-3LZ~S~

tional movement. The tail fin assembly 600 comprises a c~l-indrical connecting sub 601 having external threads at the front end which are received within the internal threads at the rear portion of the body (not shown). The circumfsrence of the sub 601 ha6 a first rsduced diameter portion 602 form-ing a ~irst shoulder 603. The rear portion 604 of the sub 661 is 6maller in diameter than the first reduc~d diametsr 602 forming a second shoulder 605. An annular raised sur~ace 606 on the rear portion 604 is spaced rearwardly from the shoulder 605 and provided with a series of circumferentially 6paced slots 607 forming a series o~ raised lugs or splines 608. The rear portion 604 extends longitudinally from the lug5 608 and iB provided with exterior threads 609 at the back end. ~n annular 0-ring seal 610 is providad on the rear portion 604 lnwardly of the threads 609.
A thin cylindrical retainer ring 508 is received on tha fir~t redu¢0d diameter 602 o~ the sub 601 by screws 509.
The rear end of the r1ng 508 extends a short distance beyond the shoulder 60~ to surround the ~orward end of the rear por-tion 604 of the sub 601.
An elongated hollow cylindrical rotating fin sleeve 611 iB slida~ly and rotatably receivad within tha extended portion of th0 ring 508 and 6urrounds the rear portion 604 o~
the sub 601. The fin sleeve 611 has a central longitudinal bore 612, a front and rear counterbore 613 and 614 rsspsct-;6~3~

ivaly of larger diameter extending inwardly from each end and dsfining annular 6houlders 615 and 616 therebetween. An an-nular 0-ring seal 617 and annular bushing 618 are disposed on central bors 612 intermediate the shoulders 615 and 616, A
reduced diameter 619 is provided on tha inner diameter of tha front counterbore 613 near the front end and provided with a seri~ of circumferentially spaced slots 620 forming a ~eriaR
of raisad lugs or ~plinas 621. An 0-ring seal 622 on the outer circumference of the fin sleevs 611 provides a rotary and reciproaating seal on the inner surface of the ring 508.
A plurality of radially and angularly opposed fins 518 are secured to the exterior of tha rotating fin sleave 611 to extend radially outward therefrom. The fins 518 are secured at opposing angles relative to the longitudinal axis of the sleeve 611 to impart a rotational force on the sleeve.
An elongated hollow oylindrical cap 623 having a central bare 624 and a larger threaded bore 625 extending inwardly from the front end i6 slidably received on the air distribution tube 46 and threadedly secured on the threads 609 at th0 end of the sub 601. Th0 outer circumference of the cap 623 is received within tha rear counterbore 614 of the fin slaeve 611. A pair of longitudinally spaced annular 0-rings 626 ara provided on the outer circumfarenca of the cap 623 and a bushing 62~ iR provided intarmediats 0-rings 626. Ths outer circumferenc0 of the cap 623 is rotatably ~z~s~

rec0ivad within the countsrbore 614 with th0 0-ringa 626 providing a rotary s0al therebetween. Ths rear portion of the cap 623 has a reduced diamet0r portion 628 which remov-ably receives a conical cover member 629. A plurality of circum~ersntially spaced longitudinal bores 630 extend through the r0ar portion o~ the cap for communicating the interior o~ the tool body with atmosphere.
When properly positioned, an annular chamber 631 is formed betwe~n the shoulder 616 of the fin slssve and the forward 0nd of the cap 623 and sealed at 0ach end by the 0-rings 610, 617, and 626. A threaded bore 433 at the back and of the cap 623 receives a hose fitting (not shown) and a small passag6way 434 0xtends inwardly from the threaded bore to communicate the annular chamber 631 with a fluid or air source (not shown) for effecting r0ciprocation of the fin 9 leeve.
The operation of the tail fin assembly 600 i8 best seen with reference to ~ig~. 25 and 26. Under action of compressed air or fluid in the annular chamber 631 the fin slQeve 611 beglns to move toward the front of the sub 601.
Whan in its foremost position, tha front end of the ~leeve 611 contacts the shoulder 605 and the lugs 608 and 621 become disangaged. In this position (~ig. 25), compressed air or fluid is admitted through the passage 434 from the source into the annular chamber 631. Tha fin slesva 611 i8 thsn free to rotate relativ0 to the tool body.

~s~s~

~ han the air or fluid pressure within the chambar 631 is relieved, the driving foroe of the tool hammer carries ths tool including tha cap 623 forward (~ig. 26). During this movement, the drive lugs or splines 608 and 821 become engag-ed once again and the fin sleeve 611 becomes locked against rotational movamsnt relative to the tool body. The cycle may be selectively repeated as neces6ary for proper alignment of thH slanted nose member and attitude adjustment of the tool.
A STILL FURTHER EMBODIMENT
0 ~igB. 27 and 28 are partial longitudinal cro6s sec-tions of another variàtion of the fixed/lockable fin assembly using a drive pin. The tail fin assembly 650 comprises a cylindrical connecting 6ub 651 ha~ing external threads 652 at the front end which are received wlthin the internal threads 15 32 at the r0ar portion of the body 28. The rear portion 653 of the 6ub 651 i8 smaller in diameter than the front portion forming a shouldar 654. The rear portion 653 extends longitu-dinally from the shoulder 654 and has interior threads 655 at th~ back end.
A thin cylindrical retainer ring 656 is received on the front portion of the sub 651 betw0en a raised shoulder 65r and the back end of the body 28. The raar end of the ring 658 axtends a short distance beyond the raisad shoulder 65~ to 6urround the forward end of tha rear portion 853 o~
the 6ub 651. A plurality of circumferantially spaced dowel ~zs~

pins 4lr 0xtend radially outward through th0 side wall of the rear portion 653 and terminate a short diatance from the interior surface of the ring 656.
An elongated hollow cylindrical rotating fln sleeve 659 is slidably and rotatably received within the axtended portion of the ring 656 and surrounds the rear portion 653 of the ~ub 651 including the dowel pins 417. The fin sleeve 65 has a csntral longitudinal bore 660 and a counterbore 661 of larger diameter extending inwardly from the bacX 0nd and defining an annular shoulder 662 therebetween. An 0-ring seal 663 on the outer circumference of the fin sleeve 65g provide~ a rotary and reciprocating seal on the inner surface of the ring 656. An annular 0-ring seal 664 and a pair of bushings 668 are provided on the interior surface of the fin 15sleeve 659. A plurality of drive teeth 428 (as previously shown and described) are formed on the front end of the fin sleeva 659.
A plurality oI radlally and angularly opposed fins 666 are secured to the exterior of the rotating fin sleeve 20659 to extend radially outward therefrom. The fins 666 are sacured at opposing angles rela~ive to the longitudinal axis of the sleeve 659 to impart a rotational force on ths sleeve.
An elongated hollow cylindrical cap 66~ having a central bore 668 and a counterbore 669 extsnding inwardly from the front end is slidably received on the air distri-~s~

bution tube 48 within the fin sleeve 659. Exterior threads 6~0 are provided on the front portion of the cap 667 which are received on the threads 655 at the back end of the sub 651. The rear portion of the cap 667 i8 larger in diameter than the threaded front portlon forming a shoulder 671 there-between.
A pair of longitudinally spaced annular O-rings 672 are provided on the outer circumference of the r0ar portion and a bushing 673 is pro~ided int~rmediate ths O-rings. T~e anlarged diametsr rear portion of the cap 667 i~ rotatably received within the counterbore 661 with the O-rings 6r2 providing a rotary seal therebetween. The rear portion of th0 cap 667 removably receives a conical cover member 674.
To avoid repetition, the detailed description of the drive teeth and their operation will not be repeated here.
When properly positioned, an annular chamber 675 is formed between the shoulder 662 of the fin sleeve and the ~houlder 671 of the cap and sealed at each end by the O-rings 663 and 6~2. A threaded bore 433 at the back end of the cap 667 receives a hose fitting (not shown) and a small passage-way 434 extends inwardly from the threaded bor0 to communi-cate the annular chamber 6~5 with a fluid or air source (not shown) for effecting r0ciprocation of the fin sleeve 659.
Fig. 28 6hows the locked position, and since the operation of th0 tail fin assembly has b0en previously shown and explain-ed, it will not ba repsated here.

S6S~

A STILL ~URTHER_EMBODIMENT
~ igs. 29 and 30 are partial longitudinal cross sec-tions of another variation of the fixed/lockable fln asssmbly using a series of slots or splin0s and dowel pins to prevent rotational movement. The tail fin assembly 700 compri~as a cylindrical connecting sub 701 having external threads 702 at the front end which are received within the internal thraads 32 at the rear portion of the body 28. The circumference of the sub 701 has a first reduced diameter portion 703 forming a first shoulder 704 ther0between. A second reduced diameter 705 forms a second shoulder 706. A third reduced diameter 707 forms a third reduced diameter 708. An enlarged diameter 709 approximately the same diameter as the second is spaced therefrom and provided with a series of circumferentially spaced slots 710 defining a 6eries of raised lugs or splines 711 on the third reduced diameter 707. A fourth diameter 712 smaller than the third forms a fourth shoulder 714 therebs-tween. The fourth diameter 712 extends longitudinally from the ~houlder 714 and is provided with exterior threads 715 at the back end.
A thin cylindrical retainer ring 716 is received on the first reduced diameter 703 of the sub 701 by screws 717.
The rear end of the ring 716 e~tends a short distance beyond the shoulder 706 to surround the forward end of the reduced 25 diameter 705. A rod wiper 718 is oontained on the interior of the rear end of tha ring 716.

~;~5~X~

An alongatsd hollow cylindrical rotating fin aleeve 719 i8 ~lidably and rotatably recsived within the extsnded portion of the ring 716 and surrounds the rear portion of ths sub 701. The fin sleev0 719 has a cen$ral longitudinal bore 5720, a fron~ and rear counterbor0 721 and 722 respectively of largar diam0t0r extending lnwardly from each end and defining annular shoulders 823 and q24 therebetwaen. An annular bush-ing 725 is dispos0d on the inner diamet0r of the counterbore 7~1 and a rod wiper 728 is provided on th0 inner diameter of tha counterbor0 722. A plurality of circumfsr0ntially spaced dowel pins 727 0xt0nd radially inwardly through th0 sids wall of the fin sleeve 719 and terminate a short distancs from the circumference of the third reduced diameter 707 of th0 sub 701. An annular bushing 728 iB provided on the central bore 15q20 intermediate the shoulders 723 and 724.
A plur~lity of radially and angularly opposed fins 729 are secured to the exterior of ths rotating fin sleevs 719 to extand radially outward therefrom. The fins 729 are ~ecured at opposing angles relative to the longitudinal axis of the sleeve rl9 to impart a rotational force on th0 sleeve.
An elongated hollow cylindrical cap 730 having a central bore 731 provided with interior thr0ads 732 and a counterbore 733 s~tending inwardly from the front end is re-ceivad on the threads 715 of the sub 701 and within th0 25counterbore 722 of the -fin sleeve 719. An annular O-ring 734 ~2~5~5~

on the bore 731 provides a seal on the fourth reduced diame-ter 712 of the 6ub ~01. A cylindrical reciprocating piston 735 is ~lidably reeived on the fourth reduced diameter 712 of the 6ub 701 and within the counterbore 733 of the cap 730.
Annular 0-rings 736 and 737 are provided on the inner and outer diameters respectively of the piston 735.
With the piston 735 propsrly positioned, an annular chamber 736 is formed between the fourth reducsd diametar 712 and the counterbore 733 and sealed at each end by the 0-rings 754, 736 and 737. A threaded bore 433 at the bac~ end of the cap 730 re¢aives a hose fitting (not shown) and a small passageway 434 extands inwardly from the threaded bore to communicate the annular chamber 736 with a fluid or air source (not shown) for effecting reciprocation of the piston 735 and fin sleeve 719.
The operation of the tail fin assembly 700 is best seen with referenoe to ~igs. 29 and 30. ~nder action of compressed air or fluid in tha annular chambar 736 the piston 73~ begins to move toward the front of the sub 701 and con-tacts the shoulder 724 of the fin sleeve 719 carr~ing it forward. When in its foremost position, the front end of the piston 735 contact6 the shoulder 714 and the dowel pins 727 become disengaged from the slots or spline6 810. In thi6 position ~Fig. 29), compressed air or fluid is admitted through the passage 434 from the source into th~ annular ~2~

chamber 736. The fin sleeve ~19 is then free to rotate rela-tive to the tool body.
When the air or fluid pressura within the chamber 736 i6 relieved, the driving force of the tool hammer carries the tool including the sub 701 ~orward relative to the fin sleeve 719 (Fig. 24). During thia mo~ement, the 6houlder 724 move6 tha plston rearwardly and the dowel pins 727 become sngaged oncs again in the 610ts 710 and the fin 61eeve 719 becomss lo¢ked against rotational movement relative to the tool body.

The cycle may be selectively repeated a~ nece6sary for proper alignment of the slanted no~e member and attitude ad~ustment o~ th0 tool.
A STILL FURTHER EMBODIMENT
Figs. 31 and 32 are partial longitudinal cro6s sec-tion6 of another variation o~ the fixed/lockabls fin a6semblyusing a serie6 of slot6 or spline6 and dowel pins to prevent rotational movement. The tail fin as6embly 750 comprises a cylindrical connecting ~ub 751 having external threads 752 at the front end which are received within the internal thread6 32 at the rear portion of the body 28. The circumference of the 6ub 751 ha6 a fir6t reduced dlameter portion 753 formlng a first 6houlder 754 therebetween. A second reduced diameter 755 forms a second shouldar 906. A third reduced diamster 757 forms a third shouldar 758. An enlarged diameter 759 approximatsly the 6ams diameter as the second is ~paced ~2SS~
tharefrom and provided with a serias of circumferentially spaced slots 760 defining a series of raised lugs or splins~
761 on the third reduced diameter 757. The third diametsr 757 extends longitudinally from the lugs or splines 761 and i~ provided with exterior threads 762 at th0 baok and.
A th~n cylindrical retainer ring 763 is received on the first reduced diameter 753 of the sub 751 by screws 754.
The rear and of the ring 763 extends a short distance beyond the shoulder 756 to surround the forward end of the reduced diameter 755. A rod wipsr 765 is contained on the interior of the rear end of ths ring 763.
An elongated hollow cylindrical rotating fin sleeve 766 is slidably and rotatably received within the extended portion oI the ring 763 and surrounds the rear portion of the ~ub 751. The fin sleeve 766 has a central longitudinal bore 767, a front and rear counterbore 768 and 769 respectively of larger diameter extending inwardly from each end and defining annular shoulders 770 and 77l therebetween. An annular bu6h-ing 772. is disposed on the inner diameter of the counterbore 768 and a rod wiper 773 is provided on the inner diameter of the rear counterbore 769. A plurality of circumferentially spaced dowel pins 774 extend radially in~ardly through the side ~all of ths fin sleeve 766 and terminate a short dist-ance from the circumf0renca of the third reduced diameter ~57 of the sub 75l.

~s~

A plurality of radially and angularly oppossd fins 775 are secured to the exterior of the rotating fin slssve 766 to extend radially outward thsrefrom. Tha flns 77~ are ~scured at opposing anglss relative to the longitud$nal axis 5of ths sle3Ya ~66 to impart a rotational force on the sle~vs.
An elongatsd hollow cylindrical cap 776 havlng a cen-tral bors ~77 provlded with intsrior threads 778 and a count-srbore 779 extsnding lnwardly from ths front end is rscaived on th~ thr~ads 762 of th0 sub 751 and w$thin th~ counterbore 1076~ of ths fin slesve 766. An annular 0 ring 780 on ths bors r77 provides a ssal on th~ third rsducsd diamstsr 757 of th~
sub 7Bl. An annular bushing 781 is providsd on ths circum-fer~ncs of the cap 776. A cylindrical raciprocating plston 782 is slidably rsceived on the third reduced diamstsr 757 of 15the sub 751 and within the count0rbore 769 of the cap 778. A
rsducsd diamstsr 783 at the front end of ths piston i8 rs-csived within the central bore 767 of ths fin sleeve 766.
Annular 0-rings 784 and 785 ars provid~d on ths innsr and outsr diameters rs6pectivsly of the piston 781.
20With th~ plston 781 propsrly positionsd, an annular chamber 786 i6 formsd between ths circumfsrsncs of ths sub 751 and ths countsrbore 777 and sealsd at each snd by ths 0-rings 780, 784 and 785. A thrsaded bors 433 at ths back snd o~ ths cap 786 rscsives a hose fitting (not shown) and a 25small passagsway 434 extends inwardly from the thrsad~d bors ~Z~5~

to communicate the annular chamber 785 with a fluid or air source (not shown) for affecting reciprocation of the piston 78~ and fin slseva 766.
Tha operation of the tail fln assembly 750 ls best seen with reference to ~igs. 31 and 32. Undar action of compressed air or fluid in the annular chamber 786 the piston 782 begins to move toward the front of the sub 751 and carrias the fin sleeve 766 with it. When in its foremost position, the front end of the piston 782 contacts the lugs or splines 761 and the dowel plns 774 become disengaged from tha slots 760. In this position (fig. 31), compressed air or fluid i9 admitted through the passag0 434 from the source into the annular chamber 786. The fin slaeve 766 is thsn free to rotate relatlve to the tool body.
When tha air or fluid pressure within the chambar 786 is relieved, the driving force of the tool hammer carries the tool including the sub 751 forward relative to tha fin sleeve 766 (Fig. 32). During this movemant, the shouldsr 771 moves the piston rearwardly and the dowel pins 774 become engaged once again in the slots or splines 760 and ths ~in sleeve 766 b~¢omes locked again~t rotational movement relative to ths tool body. The cycle may be selectively repeatsd as necess-ary for proper alignment of the slanted nose membsr and atti-tuda ad~ustment of the tool.

~L2~ 5~

A STILL FURTHER EMBODIMENT
Figs. 33 and 34 are partial longitudinal cross BeC-tions of another variation of the ~ixed/lockable fin assembly using a serias of dowel pins and drive teeth to prevent rota-tional movement. The tail fin as6embly 800 compriss~ a cyl-indrical connecting sub 801 having sxternal threads 802 at the front end which are receivad withi~ the lnternal threads at ths rear portion of the kool body. Th0 circumfersnce of the ~ub 801 has a first reduced diameter portion 803, and a 10second reduced diameter 804 forms a shouldar 805 therebe-twean. A third reducad diametar 806 forms a third shoulder 807. The third diameter 806 extends longitudinally from the shoulder 807 and is provided with exterior threads 808 at the ba¢k end.
15A thin cylindrical retainer ring 809 ia received on the first reduced diameter 803 of the sub 801 by screws 810.
The raar end of the ring 809 extends a short distance beyond the shoulder 805 to surround the forward end of the reduced diameter 804. A rod wiper 811 is contained on the interior of the rear end of the ring 809.
An elongated hollow cylindrical rotating fin sleeve 812 has a central longitudial bore 813, and a rear counter-bore 814 of larger diameter extending inwardly from khe back end and defining an annular shoulder 815 therebetwaen. An annular bushing 816 is provided on the central bore and an-65~L

other bushing 817 i~ provided on the counterbore 814. The outer circumference of th~ fin sleeve 812 is providad with front reduced diam~ter 818 and a rear reduced diameter 819.
The fin sleeve B12 is slidably and rotatably received on the sub 801 with the cantral bora 813 on the second raduced dia-metsr 804 and tha front reduced diameter 818 wlthin the ex~
tand~d portion of the ring 809. A series of drive t0eth 428 previously shown and describad with reference to Fig. 22 are formed on tha back end of the fin sleeve 812.
A plurality of radially alld angularly opposed fins 820 are secured to the exterior of the rotating fin sleeve 812 to axtsnd radially outward therefrom. The fins 820 are secured at opposing angles ralative to the longitudinal axis of the sleeve 812 to impart a rotational forc0 on the sleeve.
An elongatad hollow cylindrical cap 821 having a cantral bore 822 provided with interior thrsads 823 and a ¢ounterbors 824 extending inwardly from the front end and defining a shoulder 825 therebetween is racsived on the thread~ 808 of the sub 801 and within ths counterbora 814 of the fin sleeve 812. An annular 0-ring 826 on the bora 822 providss a seal on the third r~duced diameter 806 of the sub 801, and another 0-ring 82~ on tha counterbore 814 provides a ssal on ths reduced portion of a piston member describad hareinaftar. A plurality of circumferentially spacad dowel pins 828 extand radially outward through the ~ide wall of the fin slsave 812 (shown out of position).

~z~

A cylindrlcal reclprocating piston 829 is slidably received on the third reduced diameter 806 of ths sub 801.
The rear portion 830 of the piston 829 i8 amaller in diameter than the outer circumference defining a shoulder 831 there-between. The outer circumference of ths piston 8Z9 is re-ceived in the annulus between the third rsduc~d diameter 806 and the fin ~leeve counterbore 814 and the rear portion 830 i8 receivad in the annulus between the third raduced diamatsr 806 and countsrbore 824 of the cap 821. An annular 0-ring 10 832 is provided on the inner diam0ter of the piston 829.
With the piston 829 properly positioned, an annular chamber 833 i~ formed between the back end of the piston and the counterbore 824 of the cap 821 and sealed by the 0-rings 826, 82~, and 832.
A threaded bore 433 at tha back end of the cap 821 receives a hose fitting ~not shown) and a small psssageway 434 extends inwardly from the threaded bore to communicate the annular chamber 833 with a fluid or alr source (not shown) for effecting reciprocation of the piston 829 ~nd fin 20 8leeve 812.
A second thin cylindrlcal retainer ring 834 is se-cured on the rear reduced diameter 819 of the fin sleeve 812 by screws 835 and extends rearwardly to surround the drive teeth 428 and the dowel pins 828 . The rear end of the ring 25 834 extends a distance beyond the dowel pins 828 and is pro-vided with a rod wiper 836.

~ 62 -~s~

The operation of the tail fin assembly 800 is bsst ssen with referen¢e to Figs. 33 and 34. Under action of compressed alr or fluid in the annular chamber 833 the piston 829 begins to move toward the front of th0 sub 801 contacting 5the shoulder 815 and carrying the fin sleeve 812 with it.
When in it~ foremost position, the front end of the pigton 829 contacts the shoulder 815 and the drive teeth ecome dis-engaged $rom th0 dowel pins 828. In this position (Fig. 33), compres6ed air or fluid i8 admitted through the passage 434 10from the source into the annular chamber 833. The fin sleeva 812 i~ th~n free to rotate relative to the tool body.
When the air or fluid pressur~ within the chamber 833 is ralievsd, the driving force of the tool hammer carrie~ the tool including the sub 801 forward relative to the fin slesve 15812 (Fig. 34). During this movement, the shoulder 815 moves the piston rearwardly and the drive teeth 428 become engaged once again with the dowel pins 828 and the fin sleeve 812 becomes locked agalnst rotational movemant relative to the tool body. The cycle may be selectively rspe~ted as necess-ary for proper alignment of the slanted no~e member and atti-tude ad~ustment of the tool.
A STILL FIJRTHER EMBODIMENT
Fig. 35 is a longitudinal cross sectional view of a movable tail fin assembly. Fig. 36 is a vertical cross sec-tional view of the movable tail fin assembly of Fig. 35 taken ~X~53L
along line 36 - 3B o~ Fig . 36 . The mo~abl e tall ~in arrange-mant i8 similar to the fixad/lockable tall fins previously described with the exception that it rotates the boring tool through an inclined, anti-parallel or skewed fin arrangement.
When the two fins ara parall01, the soil forces acting on their faces prevents rotation of tho tool housing and allows the nose member or eccentric hammer to produce a net deflec-tiv0 force which causes the tool to veer in a curved tra~ec-tory.
10The movable tail fin assembly 900 comprises a cylin-drical connecting sub 901 having external threads at the front and which are reoeived within the internal threads at the rear portion of the tool body. The outer rear portion of the sub 001 i8 reduced in diameter defining a shoulder 902 and provided with external threads 90~. A series of ciroumferentialy spaced openings 904 extend radially through the side wall of the sub 901 communicatng the interior of the tool to atmosphere. A pair of opposed J-slots 905 extend longitudinally inward from the back end of the sub 901 and terminate a distance from the openings 904.
An annular 0-ring seal 906 on the c~ntral bore 90 provides a seal on the air distribution tube 46. ~ circular opening 908 axtends transversly through the rear portion of the sub 901 and the J-slots 905. In annular arcuata grooYe 25909 i~ formed in the interior of each circular opening 908 ~s~

spaced outwardly ~rom each ~ide of the slots 905 and concen-tric with the opening 008, and a small opening 910 extends from each groove to the outer aurface o~ the sub 901. Ths opening~ are used to fill the grooves with ball bearinga 911 after which they ara 0nclosed by threaded plugs 912, A piston spool 913 is slidably received on the air distribution tube 46. The piston spool 913 comprisss an elongated cylindrical member having a c0ntral longitudinal bore 014 with an 0-ring seal 915 near the back end to seal on the tube 46. Ths front portion of the spool 913 is in the ~orm of a tubular extension 916 and has a short reduced dia-meter 917 at the ~orward end. The rear portion of the Rpool has an enlarged diameter 918 greater than the extension 916 to define a shoulder 919 therebetween. An 0-ring seal 920 is provided on the enlarged dlameter 918. A pair of radially opposed threaded bores 921 and 922 extend longitudinally through the rear portion o~ the spool 913 to receive hose fittings for connection to an air or fluid source (not shown).
A ¢ylindrical piston 923 having a central bore 924 is slidably mounted on the circumference of the tubular exten-sion 916. A pair of radially opposed bores 925 and 926 in axial alignment with the bores 921 and 922 extend longitudin-ally through the piston 923 and are provided with internal 25 threads 92~ at the rear portion. An 0-ring seal 928 disposed in the central bore 924 provides a reciprocating seal on the ~ZS5G~

tubular extsnsion 916. Another 0-ring saal 929 i8 proYided on th~ ¢ir¢umference of ths pi 6 ton 923.
A cylindrical bulkhead 930 having a central bore 931 is mounted on the forward end of the tubular extension 91B.
A pair of radially opposed bores 932 and 933 in axial align-ment with the bora~ g25 and 926 extend longitudinally through tha bulkh~ad 930 and are provided with intarnal 0-ring seal6 934. An 0-ring seal 935 disposed in the cantral bore 931 provids6 ~ seal on tubular extension 916. Anoth~r 0-ring saal 936 i8 provided on the circumference of the bulkhaad 930. A slot 937 extends vertically through one side wall of the bulXhead at the forward and and receives a raotangular key 938 for keying the bulkhead to the back end of sub 901.
An actuating rod 939 having a flat rectangular front portion 940 and a longitudinally offset round tail portion 041 is carried by the piston 923. The front portion of the actuating rod 939 is slidably recived in the elongated por-tion of the J-slot 90B and the tail portion 941 extends out-wardly th~refrom to be slidably received through the bulkhead bore 932 and provided with external threads at the rear snd which are received on the threads 927 of tha bore 925 in the piston 923. The rectangular front portion 940 is provid0d with a transvarse slot 942 which engages tha protruding lug of ~ cup-shap~d mamber described hereinafter. An 0-ring seal ~48 is di6possd on the circumfarence of the tail portion 941 to provida a ssal on the piston bore 925.

3 25S6~

Similarly, a longer, rev0rse actuating rod 943 havlng a flat reatangular front portion 944 and a longitudinally offset round tail portion 943 is carried by the piston 923.
The front portion of the actuating rod 943 is slidably re~
cived in the elongated portion of the opposing d-slot 905 and the tail portion 945 extends outwardly therefrom to be slid-ably received through the opposed bulkhead bore 033 and pro-vided with axternal threads which are received on tha threads 92~ of the bore 926 in the piston 923. A reduced diameter 946 extends rearwardly from the threads 92~ and i8 slidably received within the bore 922 of the piston spool 913. The rectangular front portion 944 is providad with a transverse slot 04r whioh engages the protruding lug of another cup-shaped member (hereinafter described). An 0-ring seal 948 is disposed on the circumference of the tail portion 945 to pro-vide a seal on the plston bor0 926.
An elongated hollow cylindrical outer sleeve 949 is slidably receiv0d on the outer periphery of the bulkhead 930, the piston 923, and the piston sleeve 913. The outer sleave 949 has interior threads 950 at the front portion, a central longitudinal bore 951 0xtending therefrom and terminating at a reduced bore 952 defining an annular shoulder 953 therebe-tween. The outer sleeve 949 i8 threadedly received on the threaded portion of tha sub 901 with a seal 954 provided between the front end and the sub shoulder 902. A pair of ~S6~1 clrcular openings 955 extend transversly through thfl side wall of the sleeva in axial alignment with the opening 908 to receive the cup-shaped members (described hflreinafter). The reducfld bore 952 is r~ceived on a short reduced diameter 956 of the piston spool 913 and the 0-rings 9Z0, 920, and 936 providing a seal on the central bore 951.
In this manner, the abov0 mantioned components are encloead, and the sida wall of the slflev~ form~ a sealed front chamber 957 betwflen the bulkhead 930 and the piston 923. A second rear chamber 958 is formed between the piston 923 and th~ piston 61eeve 913. A small passageway 059 ex-tends inwardly from the back end of the revarse actuating rod 943 and communicates the bore 922 of the piston sleeve 913 with ths front chamber 96r. The oRposed bore 921 of the piston sleeve 913 i8 in communication with tha rflar chamber 9B8. It should be understood that the opposed bores 921 and 922 at the back end of the plston sle0vs receive hose i~it-tings and flexible hoses sxtend outwardly therefrom and to be connectad to the fiuid or air source for effecting reciproca-tion of the piston.
A pair of Rteering fins 960 and 961 each comprising a flat rectangular fin 962 sscured to a cylindrical cup-shapfld membar 963 and 964 ara rotatably r0ceived within the trans-verse circular openings 908 and 955. Each cup-shapfld member i8 provided with an annular 0-ring seal 965 to provida a ~2SS~5~

rotary saal on th0 interior of the opening 908, and a clr¢um-ferential srcuate groove 966 in alignment with the grooves 909 to rec~ira the ball bearings 9ll. After tha bearings 911 are placed in th0 grooves, the tail fins are locked against outward mo~ement, and ara free to rotat0 about the transverse axis within the openings. Th0 opposed cylindrical enda of the cup-ahaped Members 963 and 964 0xtend inwardly to meet at the center of the sub 90l.
An arcuate eliptical cut-away portion extends trana-versly across the ends of each cup-shaped member leaving a flat raised segment 967 and a dimatrically opposed protruding lug 968 whiCh is disposed angularly r~lative to tha longitud-inal axis of the r0ctangular fin 962. In this manner, when the cylindrical ends are in contact, the lugs 968 ara diamst-rically opposed and the elliptical opening surrounds the airdistribution tube 46, whether the fins are rotated to a pos-ition parallel or angularly disposed relative to the longit-udinal axis of the tool. One lug is received in the ~lot 942 of the actuating rod and the oppo~ing lug is received within the alot 947 of the reverse actuating rod.
Th0 operation of the movable tail fin assembly is best seen with reference to Figs. 35, 37, and 38. Under action of compr0ssed air or fluid in tha front chamber 957, the piston 923 moves toward the back of the sub 90l carrying 25 the actuating rods 939 and 943 with it. This action causes ~5~S3l the cup-shaped members 963 and 964 to rotate in opposlte directions relative to the transverse axis. When in it~
rearmost position, tha air or fluid in the rear chamb0r ~58 ha~ been relieved or exhausted. In this position (Fig. ~5), the fins are positioned angularly relative to the longitudi-nal axis of the tool body. When the two fins ara inclined in opposit0 directions, the ~oil ~orces acting on their faces causes the tool housing to rotate about it~ longitudinal axis and the tool bores in a straight direction.
When the air or fluid pres6ure within the rear cham-ber 958 i8 relieved, the front chamber 95~ is pressurized to move the pistons ln the opposite direction (~igs. 37 and 38).
In this position, the fins are positioned parallel to the longitudinal axis of the tool body. In this position, the flns prevent rotation of tha tool housing and the tool boras in a curved direction as a result of the asymmetric boring foroe of the slanted nose member or the eccentric hammer.
The positioning oi the fins in parallel or anti-par-allel positions may be selectively changed as nece6sary for proper alignment and attitude ad~ustment of the tool.
Figs. 40 and ~1 are longitudinal cross sections of a portion of a boring tool including an eccentric hammer ar-rangement. An off-axis or eccentric hammar may be used in combination with the tail fin arrangements described prsv-iously. When the center o~ ma6g of tha hammer is allowed to S~

strike the lnner anvil at a point radially offset from the longitudinal axis of the tool, a deflectiva sid0 force re-sults. This force causes the boring tool to deviate in the direction opposite to the impact point as depi¢ted in ~ig.
40. Orientation may be controllsd by the external rotation of the tool body with tail ~ins. The only internal modif~-¢ation required is the replacem0nt of the existing hammer.
~ ig. 40 ~hows tha front portion dstails of a boring tool 23 whi¢h was shown previously in s¢hematl¢ form in Fig.
8 with a movable tail fin system in ¢ombination with an ec-¢entri¢ hammer 24. Tha rear portion of the hammer 24 is not shown, with the und3rstanding that the rear portion of the hammer 24 would be the same as the ¢on¢entri¢ hammer 3~ shown in Fig 9B. The rear portion o~ the tool is not shown in Figs. 40 or 41 sin¢e the ec¢entri¢ hammer may bs used in ¢ombination with either the fix3d/lo¢kable fin systems or the movable fin systems and with or without th3 slanted nose member previously shown and des¢ribed.
Referring now to Figs. 40, 41 and 9B, th0 boring tool 23 comprises an elongated hollow cylindrical outer housing or body 25. The outer front end of the body 25 tapers inwardly forming a ¢onical portion 29. The int3rnal diameter of the body 23 tapers inwardly near the front end forming a ¢onical surface 30 which terminates in a redu¢ed diameter 31 extend-ing longitudinally inward from the front end. The rear end s~

of tha body is provided with internal threads for receiving a tail fin a6sembly previously described.
An anvil 33 having a conical back portion 3~c and an elongated cylindrical front portion 35 i8 contained within the i'ront end of the body 23. The conical back portion 3~ of the anvil 33 forms and interference fit on th3 conical sur-face 30 of the body 23, and the elongated cylindrical portion 35 extends outwardly a distance beyond the front end of the body. ~ flat surface 36 at the back end of anvil 33 recaive6 the impact of sccentric reciprocating hammer 24.
A slanted nose member 18 having a cylindrical back portion 52 and a central cylindrical bore 53 extending in-wardly therefrom may be secured on the cylindrical portion 35 of the anvil 53 (Fig. 40). A slot 54 through the sidewall of the cylindrical portion 51 extends longitudinally substanti-ally the length of the central bore 53 and a transverse slot ~5 extends radially from the bore 53 to the outer circumfer-ence of the cylindrical portion, providing flexibility to the cylindrica,l portion for clamping the nose member to the an-vil. Longitudinally spaced holes in alignment with threadedbores 58 on the opposing side of the slot 54 receive scre~s 59 which s0cure the nose member 18 to the anvil 33. The sidewall of the nose member 18 extends forward from the cyl-indrical portion 62 and one side is milled to form a flat inclined surface 60.

~ss~s~

Th3 accentric hammer 24 is an elongated cylindrical memb~r slidably received within the internal diameter 38 of the body 23. A substantial portion of the outer diametsr of ths hammer 24 i6 smaller in diameter than the internal dia-metar 38 of the body, forming an annular cavity 39 thereb~-tween. The front portion of the hammer is constructed Ln a manner to offset the center of gravity of the hammer with re6pect to its longitudinal axis. As shown in Fig. 40, the side wall of the hammer is provided with a longitudinal slot 970 which places the center of mass eccentric to the longi-tudinal axis and the front surface 43 of the front end of the hammer 24 is shap3d to provida an impact centrally on the flat surface 36 of the anvil 33. In ~ig. 41, the ide wall of the hammer 24a is provided with a longitudinal slot 9~0 and the front surface 43a is radially offset from the longi-tudinal axis to place the center of mass eccentric to the longitudinal axis and thereby deliver an eccentric impact force on the anvil.
A series of longitudinal circumferentially spaced slots 9~2 are provided on the outar surface of the front of the hammer to allow passage of air or fluid from the front end to the reduced diameter portion.
In order to assurs proper orientation of the hammer, a key or pin 26 is secured through the side wall of the body 25 to extend radially inward and be received within the slot ~s~

~70 to maintain the larger mass of the hammer cn ona side of the longitudinal axis of the tool.
As shown in Fig. 9C, a relatively shorter portion 40 at the back end of the hammer 37 i8 of largsr diameter to provide a ~liding fit against the interior diameter 38 of the body. A central cavity 41 extends longitudinally inward a distance from the back end of the hammsr 37. A cylindrical bushing 42 is ~lidablg disposed within the hammer cavity 41, the circumferenca of which provides a aliding ~it against the inner surface of the central cavlty 41.
Air passages 44 are provided through the sidewall of the hammer 37 inwardly ad;acent the shorter rear portion 40 to oommunicate the central cavity 41 with the annular cavity 59. An air distribution tube 45 extends centrally through the bushing 42 and its back end 46 axtends outwardly of the body 28 and 18 connsGted by fitting6 47 to a flexibls hose 48. For eifecting raciprocation o~ the hammer 3~, the ~ir di~tribution tube 4~ iB in permanent communication with a compressed air source (not shown). The arrangement oi the 20 pa6sages 44 and the bushing 42 is such that, during recipro-cation of the hammer 57, the alr distribution tube 45 alter-nately communicates via the passages 44, the annular cavity 39 with either the central cavity 41 or atmosphere at regular intarvals.

~2~5~5~

A cylindrical ~top member 49 is secured within the inner diameter of the body 28 near ths back end and i8 pro-vided with a series of longitudinally extsnding, circumfer-entially spacsd passageways 50 ~or communicating the interior of the body 28 with atmospher0. The air distrlbution tube 45 i8 centrally disposed within the stop member 49.
Under action of compressed air in the central cavity 41, the hammer 24 mov0a toward the front of the body 25.
When in its foremost position, the hammer imparts an impact on the flat surface 36 of the anvil 33. In this position, compre~sed air is admitted through the passagss 44 from the central cavity 41 into the annular cavity 39. Since tha ef-fective arsa of the hammer including the larger diameter rear portion 40 is greater than the effective area of the central cavity 41, the hammer starts moving in the opposite direct-ion. During this movement, the bushing 42 closes the passag-es 44, thereby interrupting the admission of compressed air into annular cavity 41. The hammer 3r continues its movsment due to th~ expansion of the the air in the annular cavity 39 until the passages 44 are displacéd beyond the ends of the bushing 42, and the annular cavity is placed to communication to atmosphere through the holes 50 in the stop member 49. In thi6 position, the air is exhausted from the annular cavity 39 through the passages 44 now above the trailing edge of the bushing 42 and the holas 50 in the stop mamber 49. Than tha cycle is repeatad.

~2~SI~S~

The eccentric hammer can be used for 6traight boring b~ avera~in~ the deflective side force over 360 b~ rotatin~
the outer body. The ~ins provide orientation capabilities as prevSously described and are brought into an unlocked rotat-ing or straight parallel alignment position when executingturns. Straight boring of the tool i8 accomplished by activ-ating the fins to a apin inducing position counteracting tha tendency of the eccentric hammer to turn the tool.
I~hen the fins are in a position preventing the tool housing from rotating the tool will turn under the influence of the asymmetric boring forces. Either an eccantric hammer or anvil ~ill producs the desired result, since the only re-quirement is that the axis of impact does not pass through tha frontal center of pressure.
STILL ANOTHER EMBODIMENT
This embodiment conslsts of an overgaga sleeve or sleeves looated over a portion of the tool outer surface which are affixed such that they can rotate but cannot slide axially. This permits transmittal of the tool's axial impact force from the tool to the soil while allowing free rotation of the tool during spinning operations. Th0 overgage areas are at the front and bac~ of the tool, or alternately, an un-dergage s~ction in the center of the tool body. This under-cut in the center of the tool permits a 2-point contact (front and rear) of the tool's outer housing with the soil SS6S~

wall ~s opposed to the line contact which occurs ~ithout tha undarcut. The 2-point contact allows the tool to deviate in an arc without distorting the round cross-sectional profile of the pierced hole. Thus, for a given steering force at the front and/or back of the tool, a higher rate of turning iB
possible since a small0r volume of soil is displaced.
In ~ig. 42, tharfl is shown a preferred guSded hori-zontal boring tool 1010, having overgage body sactions, used with a magnetic field attitude sensing system. The boring tool 1010 may be used with various sensing systems, and a magnetic attituds sensing system is dspicted generally as one exampla. The usual procedur0 for using percussion moles is to first lo¢ate and prepare the launching and retrieval pits.
The launching pit P should be dug slightly deeper than the planned boring depth and larga enough to provide sufficient movement for the operator. The boring tool 1010 i8 connected to a pneumatic or hydraulic source ll, is then started in tha soil, stopped and properly aligned, preferably with a sight-ing frame and level. The tool is then restarted and boring continued until the tool e~its into the retrieval pit (not shown).
The boring tool 1010 may have a pair of eoils 12, shown schematieally at the back end, one of which produees a magnetic field parallel to the axis of the tool, and the other produces a magnetic field transverse to the axis of the -- 7' ?' --~2~i5~

tool. These coils are intermittently excited by a low fra-quency generator 13. To sense the attitude of the tool, two coils 14 and 15 are positioned in tha pit P, the axes of which are psrpendicular to the desired path of the tool. The line perpendicular to the axes of the6e coils at the coil intersectlon determine~ the boresite axis.
Outputs of thesQ coils can bs procassed to develop the angle of the tool in both the horizontal and vertical directions with respact to the boresite axis. U~ing the transverse fisld, the same set of coil6 can ba utilized to determina the angular rotat~on of the tool to provide suffi-cient control for certain types of stesring systems. For these systams, the angular rotation of the tool i8 displayed along with the plane in which the tool is expected to steer upon actuation of the guidance control system.
The mechanical guidance of the tool can also be con-trolled at a display panel 16. From controls located at dis-play panel 16, both the operation of the tool 1010 and the pneumatic or hydraulic actuation of tha fins 1017 can be ac-complished as described hereinafter.
As shown in Fig. 42, the boring tool 1010 includes asteering system comprising a slanted-faca nose member 1018 attached to the anvil 1033 of the tool to produce a turning force on the tool and tail fins 1017 on a rotary housing lOl9a on the trailing end of the tool which are adaptad to be ~S6~

selectively po6itionsd relative to the body of ths tool to negate tha turning force. Turning forca may also be imparted to tha tool by an internal sccentric hammer, as shown in Fig.
41, above, delivering an off-axis impact to the tool anvil.
~or turning the tool, the tail fins 1017 are moved i.nto a positlon where they may spin about the longitudinal axis of the tool 1010 and the slanted nose member 1018 or eccantric hammer will deflect the tool in a given direction.
When the fins 1017 are moved to a position causing the tool 1010 to rotate about its longitudinal axis, the rotation will negate the turning affect of the nose member 1018 or eccen-tric hammer as well as provide a means for orienting the nose piece into any given plane for subsequsnt turning or direct-ion change.
The body of the tool 1010 has front 1021 and rear 1022 overgage body sections which giva improved performance of the tool in angular or arcuate boring. These overgage sections are fixed longitudinally on the tool body and may be fixed against rotation or may be mounted on bearings ~hich permit them to rotate.
The sta0ring system of the presant invention will allow the operator to avoid damaging other underground serv-ices (such as power cables) or to avoid placing underground utilities where they may be damaged. The body construction of the tool including the overgage sections cooperates with the steering mechanism to give overall improved performance.

~s~

Figs. 43 through 46 illustrate various embodimsnts of the boring tool with overgage sections on the tool body. In Fig. 43, there is shown a boring tool 1010 having a body 1020 enclosing the percussion mechanism driving the tool. The front end of body 1020 i6 tapered as at 1029 and has the external portion 1035 of the anvil protruding tharefrom for percussion boring.
Front sleeve 1021 and raar sleave 1022 are mounted on tool body or housing 1020 by a shrink or interfersnce fit.
In thls embodiment, overgage sleeves 1021 and 1022 are both fixed against longitudinal or rotational slippage. The slseves may be pinned in place as indicated at 1024. The rear body portion is connected to a hydraulic or air line for supply of a pressurized operating fluid to the tool.
In ~ig. 44, there is shown another embodiment of the boring tool in which one of the overgage sleeves is free to rotate. In this embodiment, boring tool 1010 has a body 1020 enclosing the percussion mechanism driving the tool. The front end of body 1020 is tapered as at 1029 and has the external portion 1035 of the anvil protruding therefrom for percus6ion boring.
Front sleeve 1021 is mounted on tool body or housing 1020 by a shrink or interference fit. The overgage sleeve 1021 is fixed against longitudinal or rotational slippage.
The sleeve 1021 may be piImed in placo as indicated at 1024.
The rear sleeve 1022 is mounted on body 1020 on bearings 1025 ~Z~i5~5~

for rotary motion thereon. The rear body portion i3 connac-ted to a hydraulic or air llne for supply of a pressurizsd operating fluid to the tool.
In the embodiments of Figs. 43 and 44, the protruding anvil portion 1035 was not provided with any special boring surface. In the embodiments of Figs. 45 and 46, the tool has a slanted nose m0mber which causes to tool to deviate ~rom a straight boring path at an angle or along an arcuate path.
The rear of the tool has controllable fins which allow the tool to move without rotation or to rotate about its longi-tudinal a~is. This arrangement is described further belo~.
In Fig. 45, there is shown a boring tool 1010 having a body 1020 enclosing the percussion mechanism driving the tool. The front end of body 1020 is tapered as at 1029 and has the external portion 1036 of the anvil protruding thare-from for percussion boring. The protruding portion 105B of the anvil has a slanted nose member 1018 secured thareon for angular or arcuate boring.
Front sleeve 1021 and rear sleeve 1022 are mounted on tool body or housing 1020 by a shrink or interference fit.
In this embodiment, the overgage sleeves 1021 and 1022 ars both fixed against longitudinal or rotational ~lippage. The sleeves may be pinned in place as indicated at 1024.
At the rear of body 1020, there is a rotatable hous-ing 1019a on which there are fins 101~. The housing and fin ~2~i5S~

assembly is actuatable betw0en an inactive position in which the tool does not rotate about its axis and an actuated posi-tion whare the fins caus~ the tool to rotate. The rear body portion i8 connected to a hydraulic or air line for supply of a pressurized operating fluid to the tool.
In Fig. 46, there is shown another embodiment of the boring tool in whioh one of the overgage sleeves is free to rotat.e. In this embodiment, boring tool 1010 has a body 1020 enclosing the percussion mechanism driving the tool. The 10front end of body 1020 is taperad as at 1029 and has the external portion 1035 of the anvil protruding therefrom for percu6sion boring. The protruding portion 1055 of the anvil has a slanted nose member 1018 secured thereon for angular or arcuate boring.
15Front sleeve 1021 is mounted on tool body or housing 1020 by a shrink or interference fit. The overgage sleeve 1021 is fixed against longitudinal or rotational slippage.
The sleeve 1021 may be pinned in place as indicated at 1024.
The rear sleeve 1022 is mounted on the body 1020 on b0arings 1025 for rotary motion thereon.
At the rear of body 1020, there is a rotatabls hous-ing 1019a on which there are f iIlS lolr . Tha housing and fin assembly is actuatable batween an inactive position in which the tool does not rotate about its axis and an actuated posi-tion where the fins cause the tool to rotate. The rear bodyportion i6 connected to a hydraulic or air line for supply of a pressurized operating fluid to the tool.

~2~56S~

Fi~s. 47A, 47B, and 47C illustrate a boring tool 1027 having a slanted nose member and fixed/lockable fin arrange-mant as dascribed ganerally in raferenca to Figs. 1 and 2 above. As shown, boring tool 1010 comprigas an elongated hollo~ cylindrical outer housing or body 1028. The out0r front end of body 1028 tapars inwardly forming a conical por-tion 1029. Sleeve member 1021 is s0cured on body member 1028 by a shrink or intarferance fit and is fixed against longitu-dinal or rotary slippage as previously described. The out-side diameter of body 1028 tapers inwardly near the front endforming a conical surface 1030 which terminates in a reducad diam0ter 1031 extending longitudinally inward from the ~ront end. The rear and of the body 1028 has intarnal threads 103 for raceiving a tail fin assembly (sea Fig. 47C).
An anvil 1033 having a conical back portion 1034 and an elongated cylindrical front portion 1035 i8 poPitioned in the front 0nd of body 1028. The conical back portion 1034 of anvil 1033 forms an interference fit on tha conical surface 1030 of the body 1028, and the elongated cylindrical portion 1035 exte.nds outwardly a predetarmined distance beyond tha front end of the body. A flat transv0rse surface 1036 at the back end of the anvil 1033 receives the impact of a recipro-cating hammer 1037~
Reciprocating hammer 1037 is an elongated cylindric-al membar slidably received within the cylindrical recesR
1038 of thc body 1028. A substantial portion of the outer ~ 83 -~l25S65~

diameter of the hammer 1037 iR smaller in diameter than the reca~ 1038 of the body 1028, forming an annular cavity 103~
therebetween. A relativsly shorter portion 1040 at the back end of hammer 1037 is of larger diameter to provide a ~liding fit against the interior wall of rec0ss 1038 of body 1028.
A central cavity 1041 sxtends longitudinally inward a distance from the back end of the hammer 1037. A cylindrical bu6hing 1042 i8 slidably disposed within the hammer cavity 1041, the circumference of which provides a sliding fit against the inner surface of the central cavity 1041. The front surface 1043 of the front end of the hammer 1037 is shaped to provide an impact centrally on the flat surface 1036 of the anvil 1033. As described abov0, the hammer con-figuration may also be adapted to deliver an eccentric impact force on the anvil.
Air passages 1044 in the sid0wall of hammer 1037 in-wardly adJacent the shorter rear portion 1040 communicats the central cavity 1041 with the annular cavity 1039. An air distribution tube 1046 e~tends centrally through the bushing 1042 and has a back end 1046 e~tending outwardly of the body 1028 connected by fittings 1047 to a flexible hose 1048. For reciprocating the hammer 1037, the air distribution tube 1045 i~ in permanent communication with a compr0ssed air source 11 (Fig. 42). The arrangement of the passages 1044 and the bushing 1042 is such that, during reciprocation of the hammer ~;~S5~

103~, the air distribution tube 1045 alternately communicates via the pa~sages 1044, thfl annular cavity 1039 with either the central cavity 1041 or atmosphere at regular intervals.
A cylindrical stop member 1049 is secured within the recess 1038 in the body 1028 near the back end and has a series of longitudinally-extanding, circumferentially-spaced passageways lOB0 for exhausting the interior of the body 1028 to atmosphere and a c0ntral passag0 through which the air distribution tube 1045 extends.
A slantsd nose member 1018 has a cylindrically ra-cessed portion 1052 with a central cylindrical bore 1053 thsrsin which is receivsd on the cylindrical portion 1035 of the anvil 1033 (~ig. 4~A). A slot 1054 through the sidewall of the cylindrical portion 1018 extends longitudinally sub-6tantiall~ the length of the central bore 1053 and a trans-verse slot axtends radially from the bore 1053 to the outer circumference of the cylindrical portion, providing flexibil-ity to the cylindrical portion for clamping the nose member to ths anvil. A flat i8 provided on one side of cylindrical portion 1018 and longitudinally spaced holes are drilled therethrough in alignment with threaded bores on the other sida. Scrsw6 1059 are receiv~d in the hol0s and bores 1058 and tightened to secura nose member 1018 to anvil 1033.
The sidewall of the nose membsr 1018 extends forward from the cylindrical portion 1052 and one side is milled to form a flat inclined surface 1060 which tapers to a point at ~S5~S~

the extended end. The length and degree of inclination ma~
vary depending upon the particular application. The nosa member 1018 may optionally have a flat rectangular fin 1061 (shown in dotted line) secured to the sidewall of ths cylin-drical portion 1052 to extend substantially the length there-of and radially outward thsrefrom in a radially opposed posi-tion to the inclined surface 1060.
Slanted nose members 1018 of 2-1/2" and 3-1/2" d$a-meter with an~les from 10 to 40 (as indicated b~ an~le "A") have baen tested and show the nose member to be highly eff-ective in turning the tool with a minimum turning radius of 28 feet bein~ achiaved with a 3-1/2 inch 15 nose member.
Testing also demonstrated that the turning effect of the nose member wa~ highly repeatable with deviations among tests of any nose member seldom varying by more than a few inches in 35 feet o~ bore. Additionally, the slanted nose members were shown to have no adverse effect on penetration rate and in some cases, actually increased it.
It has also been found that the turning radius varies linearly with the angle of inclination. For a given nosa angle, thc turning radius will decrease in direct proportion to an increase in area.
The rear sleeve 1022 is mounted on the rear portion of housing 1028 on bearings 1025 for rotary motion thereon.
The front sleeve 1021 and rear sleeve 1022 provide a 2-point sliding contact on movement of the tool through the hole l~iS6~i~

which ls being bored. Thi3 providcs for reduced friction and facilitates both the linear movement of the tool through ths soil and on rotation of th0 tool by tha fins. A tail fin as6ambly 1062 (19a in Fig. 42) is secured in the bacX end of the body 1028 (Fig. 47C). A fixed~lockable tail fin assembly 1062 is illustrated in the e~ample and other variation6 will b0 describad hereinafter.
The tail fin assembly 1062 comprise6 a cylindrical connecting sub 1063 having external threads 1064 at ths front end whlch are raceived within the internal threads 1032 at the back end of the body 1028. Sub 1063 has a short reduced outside diameter portion 1065 forming a shoulder 1066 there-between and a second reduced diameter 1067 ad;acent the short portion 1065 forms a second shoulder 1068. An 0-ring seal 1069 i6 located on the reduced diameter 1065 intermediate the shoulder6 1066 and 1068. The rear portion 1070 of the sub 1063 is smaller in diameter than the second reduced diameter 1067 forming a third shoulder 1071 thcrebetween and providad with circumferential 0-ring seal 1072 and internal 0-ring seal 1073. Internal threàds 1074 are provided in the rear portion 1070 inwardly of the saal 1073. A circumferential bushing 1075 of suitable bearing material such as bronzc is provided on the second reduced diameter 1067.
A serias of longitudinal circumferentially spaced grooves or keyways 1076 are formed on the circumferenca of the rear portion 1070 of the sub 1063. A hollow cylindrical ~2S565i piston 107~ is slidably received on the circumferencs of the rear portion 1070 A series of longitudinal circumfersntial-ly spaced grooves or keyways 1078 are formed on the interior surface at the front portion of the piston 1077 in opposed relation to the sub keyways 1076. A series of keys or dowal pins 1079 are raceivad within the keyways 1076 and 1078 to prevent rotary motion between sub 1063 and piston 1077.
A first internal cavity 1080 extends inwardly from the keyway 1078 terminating ~n a short reduced diameter por-tion 1081 which forms a shoulder 1082 therebetween. A sacond cavity 1083 extends inwardly from tha back end 1084 of the piston 1077 tarminating at the reduced diameter pcrtion 1081.
An internal annular 0-ring seal 1086 is provided on the re-duced diameter portion 1081. As shown in Fig. 47C, a series of drive teeth 1086 are formed on the back end of the piston 1077. The teeth 1086 comprise a series of circumferentially spaced raised surfaces 1087 having a straight side and an angularly sloping side forming a ratchet. A spring 1090 is received within the first cavity 1080 of the piston 1077 and is compressed between the back end 1070 of the sub 1063 &nd the shoulder 1082 of the piston 1077 to urge the piston out-wardly from the sub.
An elongated, hollow cylindrical rotating fin sleeve 1091 iæ slidably and rotatably received on tha outer peri-phery of ths sub 1063. The fin sleeve 1091 has a central longitudinal bore 1092 and a short counterbore 1093 of larger ~LZSS6S~

diameter sxtending inwardly from the front end and defining an annular shoulder 1094 therebetween. The countsrbors 1093 fits over the short reduced diameter 1065 of the sub 1063 with the 0-ring 106~ providing a rotary seal therebetween. A
flat annular bushing 1095 of suitable bearing material such as bronze is disposed bitween the shoulders 1068 and 1094 to reduce friction therebetween.
A hollow cylindrical sleeve 1097 is secured within sleeve 1091 by suitable means such as welding. The sleeve 1097 ha a central bore 1098 substantially the same diameter as the second cavity 1083 of the piston 10~ and a counter-bore 1099 sxtending inwardly from the back end deii~ing a shouldflr 1100 therebetween. As shown in Fig. 47C, a series of drive teeth 1101 are formed on the front end of the sleave 1097. The teeth 1101 oomprise a series of circumferentially spaced raised surfaces 1102 having a straight side and an angularly sloping side forming a one-way ratchet configura-tion. The teeth correspond in opposed relationship to the teeth 1086 of the piston 107~ for operative engagement there-With~
A series of flat radially and angularly opposed fins 1105 are sscured to the exterior of the fin sleeve 1091 to extend radially outward therefrom. (Fig. 4~C) The fins 1105 ar~ secured at opposing angles rclative to the longitudinal axis of the sleeve 1091 to impart a rotational force on the sleeve.

~5S~

An elongated hollow cap sleave 110 having sxternal thr0ads 110~ at the front end is slidably recelved within the sliding piston 107r and the sleeve 109~ and threadedly ~ecur-ed in the internal threads 1074 at the rear portion 1070 o~
th0 sub 1063. The cap sleeve 1;06 extends rearwardly from the threads 110~ and an enlarged diameter portion 1108 forms a ~irst shoulder 1109 spaced from the threaded portion and a second enlargsd diameter 110 ~orms a second shoulder 1111 spac~d from the first shoulder. An 0-ring seal 1112 is pro-vided on anlarged diameter 1108 nsar shoulder 1109 and a second 0-ring seal 1113 is provided on the second enlarged diameter 1110 near the second shoulder 1111. The 0-ring 1112 forms a reciprocating seal on the interior of the sacond cavity 1083 of the piston 1077 and the 0-ring 113 forms a rotary seal on the counterbore 1099 of the sl3eve 1097. The 0-ring 1085 in the piston 1077 forms a reciprocating seal on the extended sidewall of the cap 1106.
An annular chamber 1114 is formad between the exter-ior oY the sidewall of the cap 1106 and the second counter-bor0 1083 which is sealed at each end by the 0-rings 1085 and 112. A circumferential bushing 115 is provided on the first enlarged diameter 1108 and an annular bushing 116 on the sec-ond enlarged diameter 110 is captured betwaen the shoulders 1100 and 1111 to reduce friction between the sleeve 1097 and the cap 1106. The rear portion of the cap 1106 ha~ small bores 111~ arranged to recaive a spanner wrench for effacting ~2~56~i~

the threaded conneation. A threaded bore 1118 at the back snd of cap 1106 receives a hose fitting (not shown) and mall passageway 1119 extends inwardly from threaded bore 1118 to communicate annular chamber 1114 with a fluid or air source (not shown). A flexible hose extends outwardly of the cap 1106 and i8 connected to the fluid or air source for effect-ing reciprocation of the piston 1077. A second small passage-way 1120 communicates first cavity 1080 with atmosphere to relieve pressure which might otherwise become trapped thers-in. Pa~sage 120 may also be used for application o~ pressureto the ~orward end of piston 1077 for return movemcnt.
OPERATION
The tool described abova is capable of horizontal guidance, has overgage body sections, and is preferably used with a magnetic field attitude sensing system. The boring tool may be used with various sensing systems, and a magnetic attitude sensing system i8 dep~cted generally as one example.
The overgage sleeves may be fixed or rotatable on bearings as described above. Likewise, the overgage sleeves may be used with any percussion boring tool of this general type and ia not limited to the particular guidance arrangement, i.e., the slanted nose member and controllable tail fins, described above. It is especlally noted that any of the arrangements described in our copending patent application can be used with overgage sleeves to obtain the desired advantages.

~S~5~
The procedure for using this psrcussion tool is to first locate and prepare th0 launching and retrieval pits.
As de6cribed above, the launching pit P is dug slightly deep-er than the planned boring depth and large enough to proride sufficient movement for the operator. The boring tool 1010 is connected to a pneumatic or hydraulic source 11, i8 then startsd in tha 60il, stopped and properly aligned, preferably w~ith a sighting frame and level. The tool is than restarted and boring continued until the tool axits into ths retrieval pit (not shown).
The tool can move in a straight directlon when used with an eccentric boring force, a.g., the slantsd nose member or the eccentric hammer or anvil, provided that the fins are positioned to cause the tool the rotate about its longitudin-al axis. When the fins are aet to allow the tool to movewithout rotation about the longitudinal axis, the eccentric boring forces cause it to move either at an angle or along an arcuate path.
As previously described, the overgage sleeves, which are located over a portion o~ the tool outer ~urface, are affixed such that they can rotate but cannot slida axially.
This permits transmittal of the axial impact force from the tool to the soil while allowing free rotation of the tool during spinning operations. The overgage areas are at tha front and back of the tool, or alternataly, an undergage section in the center of the tool body. This undercut in _ 9~ _ ~2~S6~

the csnter of the tool permits a 2-point contact (front and rear) of the tool's outer housing with the soil wall as op-posed to the line contact which occurs without the undercut.
The 2-point contact allows the tool to dsviata in an arc withouk distorting the round cross-sectional profile of the pierced hole. Thus, for a given stearing force at the front and/or back of the tool, a higher rats of turning is possible since a smaller volume of 80il needs to be displaced.
In the embodiment shown, for turning the tool t the tail fins 1017 are moved into a position where they may spin about the longitudinal axis of the tool 1010 and the slanted nose member 1018 or eccentric hammer will deflect the tool in a given direction. When the fins 1017 are moved to a posi-tion causlng the tool 1010 to rotate about its longitudinal axis, the rotation will negate the turning effect of the nose member 1018 or eccentric hammer as well as provide the means for orientlng the nose piece into any given plane for subse-quont turnlng or dircction change.
The front 1021 and rear 1022 overgag~ body sections give improved performance of the tool both in straight boring and in angular or arcuate boring. These overgage sections are $ixed longitudinally on the tool body and may be fixed against rotation or may be mounted on bearings which permit them to rotate.
Whils the overgags sleeves can be used with any per-cussion boring tool, they have been shown in aombination with ~2S5~

one the embodiments described abov0. The operation of this percussion boring tool 1027 is as follows. Under action of compressed alr or hydraulic fluid in the central cavity 1041, the hammer 1037 moves toward the front of the body 1028. At the foremost position, the hammer imparts an impact on the flat surface 1036 of the anvil 1033.
In thi~ position, compressed air i8 admitted through the passages 1044 from central cavity 1041 into ths annular cavity 1039. Since the effective area of the hamm~r includ-ing the larger diameter rear portion 1040 i6 greatsr than the effective area of the central cavity 1041, the hammsr starts moving in the opposite direction. During this movement, the bushing 1042 closes the passage6 1044, thereby interrupting the admission of compressed air into annular cavity 1041.
The hammer 1037 continues its movement by the expanR-ion of the air in the annular cavity 1039 until the passages 1044 are displaced beyond ths ends of the bushing 1042, and the annular cavity exhaust~ to atmosphere through the holes 10~0 in the stop member 1049. Then the cycle is repeated.
The operation of the tail fin as6embly 1062 is best saen with reference to Fig. 47C. The compressed air or fluid in the annular cavity 1114 movas the piston 1077 against the spring 1090 and toward the front of the sub 1063. In the foremost position, the front end of the piston 1077 contacts the Rhoulder 1071 and the drive teeth 1086 and 10101 become ~;~S5~5~

disengaged. In this position, compressed air or ~luia i8 admitted through the passage 1119 from the source lnto the annular chamber 1114. The fin sleeve 1091 is then free to rotate relative to the tool body. Pressure which may other-wise become trapped in the first cavity 1080 and hinder re-ciprocation is exhausted through the pressura ralief passage 1120 to atmosphero.
When the air or fluid pressure within ths chamber 1114 is relieved, the force of the spring 1090 moves the pis-ton 10~ in the opposite direction. During this movement,the drive teeth 1086 and 1101 become engaged once again and the fin sleeve 1091 becomes locked against rotational movem-ent relative to the tool body. The cycle may be selectively repeated as necessary for proper alignment the slanted nose member 1018 and attitude adjustment of the tool. It should be understood that the passage 1120 may also be connected to a fluid source, i.e. liquid or air, for moving the piston to the rearward position.
The reciprocal action of the hammer on the anvil and nose member as previously described produces an eccentric or asymmetric boring force which causes the tool to move forward through the earth along a path which deviates at an angle or along an arcuate path when the tool i8 not rotating. Whe~
the tool is rotated by operation of the fins, it movss along a substantially straight path (actually a very tight spiral).
Th~ overgage sleeves support the tool housing at two separ-~2~565~

at0d points. This 2-point contact ~front and rear) of the tool housing with the 80il wall allows the tool to dsviats in an arc without distorting the round cross-sectional pro-file of the pi~rced hole. Thus, for a given steering force at the front and/or back of the tool, a higher rat0 of turn-ing is possible since a smaller volume of 60il needs to be displaced and the helix length is reduced.
DESCRIPTION 0~ T~E CONTROL SYSTEM
This embodiment relate~ to the control of the guid-ancs of a percussion boring tool, especially using a magneticsensing system or sensing tool location and attitude.
In the installation of conduits and pipes by various utilities, such as gas, telephone and electric utilities, a problem often faced i6 th~ n0ed to install or replace such conduits or pipes under driveways, roads, streets, ditches and/or other structures. To avoid unnecessary excavation and repair of structur0s, th0 utilities use horizontal boring tools to form the bor0 holes in which to install the conduits or pipes. 3uch tools hav0 been unsatisfactory to the extent that th0ir traverse has not been accurate or controllable.
All to frequently other underground utilities hav~ been pierced or the ob;ective target ha~ been mi6sed by a substan-tial margin. It has aso be0n difficult to st0er around ob-stacles and get back on course.
In ~ig. 48 is illustrated horizontal boring operatior.
in which a borehole 1~10 is being bored through the earth 56~

1212 under a roadway 1214 by a horizontal boring tool 1216.
Th0 particular tool illustrated and for which the pre~erred embodiment of the present invention was specifically de~igned is a pneumatic percussion tool, operated like a Jackhammer by a motive m0chanism 1217 using compre6sed air suppliad by a compressor 1218 by way of an air tank 1219 over a supply hose 1220. Ths tool 1216 is elongated and has a tool axis 1222 extending in the direction of its length. Ths lead end of th~ tool 1216 has a piercing point (or edge) 1224 eccentric of he axis 1222. The operation of the percussion tool drives the point 1224 through the earth, advancing the tool forward, but slightly off axi6.
The tool 1216 includes a plurality of staering vanes 1226 which may be aotuated by pneumatic or hydraulic control anargy provided over pneumatic or hydraulic control lines 1228 from a controller 1230 to control the direction and rate rotation of he tool 1216 about its axis. Control signals may also control the operation of the motive mechanism 1217. The controller 1230 is supplied wi~h air from the compressor 1218 over a bore 1232.
The steering vanes 1226 my be turned to cause the tool to rotate at a relatively constant rate. The tool then spirals a bit but advances in a substantially straight line in the direction of the axis 1222 because the piercing point 1224 circles the axi6 and causes the tool to deviate the same amount in each direction, averaging zero. If the vanes 1226 S6S~

are returned to directions parallel to tha axis 1222, the rotation may be stopped with the tool in a desired position, from which it advanoes asymmetrically in a desired dlrsction.
As will be described below, the pre6ent invention permits an operator to identify the rotatonal orientation of the tool 1216 about its axis 1222, and, hence, to direct the advance o~ the tool. Thc ob;ective i8 to bore a hola 1210 relatively horizontally between an input pit 1234 and a tar-get pit 1236 beneath such obstacles as ths roadway 1214.

10The hole 1210 must avoid piercing other utility lines 1238 or sewers 1240 or other buried obstacles. Thesa may be identi-fiad and located from historical æurveyor's drawings or may be located by 60ms other means as by a metal detector or other proximity device 1242.

15Armed with this information, an operator may 6tart the tool off easily enough from the input pit 1236 in a dir-ection that avoids nearby obstacles and may plot a couræe that would miss all mor0 distant obstacles. Thedifficulty is in assuring that the tool follows the plotted course. That is the function of the present invention. The present in-vention is directed to a control system for sensing the atti-tude of the tool 1216 and for controlling the steering vanes 1226 to direct the tool along the plotted course. The con-trol system includes an electromagnetic source 1244 affixed to the tool 1~16 for generating appropriate alternating mag-netic flux, a senslng aæsembly 1246 disposed in ons of the S~

pits 1234, 1236, preferably the target pit 1236, and circuit-ry in the controller 1230 which is powered from a motor-gen-erator set 1248.
Reference may be made to Fig. 49 for an understand$ng of the prsferred arrangement of the electromagnetic source 1244 and the sensing assembly 1246. The electromagnetic source 1244 comprise6 an axial coil 1250 and a tran3verse ooil 1251 rigidly mounted on the tool 1216. The coil~ 12~0 and 1251 are alternatively energized from the motor-generator power source 1248 through a controlled power supply 6ection 1252 of the controller 1230 over lines 1253. The power source 1248 operates at a relatively low frequency, for ex-ample, 1220 ~z.
The axial coil 1250 generates an axial alternatlng magnetic field which produce~ lines of magnetic flux general-ly symmetricall~ about the axis 1222 of the tool 1216, as illustrated in ~ig. 50. The tool 1216 itself is constructed in such manner as to be ¢ompatible with the generation of such magnetic field and, indeed, to shape it appropriately.
The transverse coil 1251 generates a transaxial alternating magnetic field substantially orthogonal to th0 axis 1222 in fixed relation to the diraction o~ deviation of the point 1224 from the axis 1222 and, hence, indicative of the direct-ion thereof.
The eensing assembly 1246 is formed o~ three orthog-onal pickup coils 1254, 1256 and 1258, as shown in Figs. 49 _ 99 _ s~

and 51, which may be called the X, Y and Z coils, respectiv-ely. These pickup coila are axially sensitive and can be of the box or solenoidal forms shown in Figs. 49 and 51. The center of the coils may be taken as the origin of a thrss-dim0nsional coordinate syst0m of coordinate Rystem of ¢oord-inates x, y, ~, where x is the general direction oi' the bore-hole, y i8 vertical and 7~ i5 horizontal. The coils 1254, 1256 and 1258 have respective axes extending from the origin of the coordinate ystem in the respective x, y and z direct-10 i ons .
In Figs. 50A, 50B, 50C and 50D are illustrated fourpossible unique relationships of a sensing coil, the Y coil 1256 as an example, to the lines of flux 60 of the axial magnetic field generated by the axial coil 1250 in the tool 1216. In Fig. 50A is shown the relationship when the X axis and the tool axis 1222 lie in the same plane with the Y axi6 of he coil 12B6 normal to that plane. That is the relation-ship when the tool 1216 lies on the plane XZ (the plane per-pendicular to the Y axis at the X axis) with the axis 1222 of the tool in that plane. In Fig. 50B is shown the relation-ship when the tool 1216 lies in the plane XZ with the tool axis 1222 not in that plane. That is the relationship when the tool 1216 is tilted up or down (up, clockwise, in the ex-ample illustrated). In Fig. 50C is shown the relationship when the tool 1216 is displaoed up or down from the plane gZ
(up, in the example illustrated) with the tool axis 1222 6S~

parallel to the plane XZ. Other relationships involve com-binations of the relationships shown in Figs. 50B and 50C;
that is, where the tool 1216 lies o$f the XZ plane and has a component of motion transvers01y thereof. Shown in Fig. 50D
is the ralationship where the combination of displacement (Fig. 50C) and tilting (Fig. 50B) places tha coil axis Y
normal to the lines of flux 1260 at the coil. The lines of flux shown in Figs. 50A, 50~, 50C and 50D are for condition6 when tool axis 12a2 lines in the XY plans (containing the X

and Y axes), but the principle is the same when the tool lie6 out of such plana. The lines of flux linking Y coil 1256 would be different, and the relativs signals would be some-what differant. There would, however, still be positions of null similar to those illustrated by Figs. 50A and 50D.
As can be seen by inspection and from ths principle of symmetry, the pickup coil 1256 will generate no signal under the condition shown in Fig. 50A because no flux links the coll. On the othar hand, under the conditions of Figs.
50~ and 50C, signals will be generated, of phase dependent upon which direction the magnetic field is tilted or displac-ed from the condition shown in ~ig. 50A. Further, under the condition shown in Fig. 50D, the effect of displacement in one direction is exactly offset by tilting so as to generata no signal. As may also be seen from Fig. 50D, if the tool 1216 is off course (off the XZ plane) but the relationship shown in Fig. 50D is maintained, the tool will move toward 3~;25~6S~

the sensing assembly 1246 keeping the sensing assembly on æ
given line of flux 1260. That is, the tool 1216 will home in on the sensing assembly 1246 and get back on course vertical-ly. Similar relationships exist in respect to the Z coil 1258 and horizontal deviation. The outputs of the pickup colls 1256, 1258 are applied through a 8 ignal conditioner 1262 to a display 1264 in the controller 1230.
Tha ralationships shown in ~ig. 50 can also be anal-yzed geom3trically as shown in Fig. 50, where A is the angle between the tool axis 1222 and a line 1265 connecting the center of ths tool with the center of the pickup co~l 1256, and ~ is the angle between the line 1265 and the refsrence axis X, perpendicular to khe axis Y of the sensing coil 1256.
The well known equation for radial flux density ~R
and angular flux density BA are:
B~ = 122 Kl cos A (1) BA - Kl sin A (2) where Kl is a con~tant proportional to the amper~-turns for the axial coil 1250 and inversely proportional to the cube of th distance between the tool 1216 and the sensing coil 1256.
The singal V thereupon developed in the pickup coil 1256 is proportional to the sum of flux components parallel to the coil axis Y.
That is, V = K2 (BR sin B + BA cos B) ~3) where K2 is a calibration factor betwaen the developed pick-up voltag0 and time-rate-of-change of the magnetic field.

lZS56S~

~rom the combination of Equations (1), (2) and (3~:
V = K3 (2 cos A sin ~ ~ A cos B) (4) when K3= KlK2. As i~ flvident from ~ig. 50D, when tha flu~ at the coil 1266 is normal to its axis Y, the two componsn~s balance, i. e., ~R sin ~ = -BA C08 B, making V = 0.
The circuitry for operating the present invention is shown in greater detail in ~ig. 51 in block diagram form. ~s there shown, the output of the pickup coil 1256 i6 amplified by an amplifiar 1266 and applied to a synchronoua detector 1268 to which the output of a regulated powar supply 1270 is also applied. The regulated power supply 1270 is driven by the same controlled power supply 1252 that drives the coils 1250, 1251 and producas an a.c. voltage of constant amplitude in fixed phase relationship to the voltage applied to the ax-ial coil 1250.
The synchronous detector 1268 therefore produces a d.c. output of magnitude proportional to the output of the Y
coil 12B6 and of polarity indicative of phase relative to that of the power supply 1270. An amplifier 1272 and a syn-chronous detector 1274 produce a similar d. c. output corres-ponding to the output of the Z coil 1258. Tha outputs of ths raspactive synchronous datectors 1268 and 1274 ara appliad to ths display 1264 which displays in y, z coordi-natas the combination of the two signals. This indicates the dirsction or attitude the tool is off course, permitting the operator to provida control signals over the control lines 1228 to ~zs~s~

return the tool to its proper course or to modify the courss to avoid obstaclss, as the case may be.
The ext0nt to which the tool iB off a course leading to the target is indicated by the magnituds of the signals produced in the coils 1256 and 1258. However, the magnitude of the respective signal6 is also affectsd by the range of the tool. That is, the farther away the tool, the lesser the flux denaity and, henc~, the les6er the signals gensrated in the respe¢tive pickup coils 1256 and 1258 for a given daviat-ion. It i8 h0 function of the X coil 12B4 to ramove this variable. The X coil is se~sitive to axial flux density sub-st,antially ex¢lusively. The y and z directed ~lux oomponents have negligible effect on its output where the tool 1216 li0s within a few d0grees of the x direction; e.g., 123.
The signal from the pickup coil 1254 is amplified by an amplifier 1276 and detected by a synchronous detector 1278 to provida a d. c. output proportional to the flux density strength at the X coil 1254. This signal i9 applied to 3 control circuit 128~ which provides a field aurrent control for the power supply 1252. This provides feedback to change the pow0r applied to tha axial coil 1250 in such dirsction as to maintain constant the output of the ~ coil 1254.
Thi6 makes the flux density at the sensing assembly 1246 relatively constant, thus normali7.ing the outputs o~ the Y and Z coils 1256, 1258 and making these outputs relatively independent of range. However, if wide deviations from dir-~5S~S~

ect paths between tha launch and e~it polnts are sxp3cted, the total magnitude of the magnetic flux density should b9 used for this normalizing function. This magnitude may be developad by appropriately combinlng tha outputs from the three pickup coils.
It is one thing to know where the tool iB and it~
attitude. It is anothsr to return it to its course. That i8 the function of the transversa coil 1251. Tha power from the power supply 1252 is appliad to the tool 1216 through a switch 1282.
~ hen in the 6witch 1282 position 121, the axial coil 1250 is ener~ized, providing the mode of operation explained above. With the switch 1282 in position 122, the transverse coil 1261 is energized instead. The resulting magnetic field is substantially orthogonal to that provided by the a~ial coil 1250. The signals generated by the Y and Z pickup coils 1256, 1258 then depend primarily upon the relative displace-ment of th0 coil 1251 around the axis 1222.
~ecause the coil 1251 is mounted in fixed relation-ship to the piercing point 1224, ths displacement of the point is indicated by the relative magnitude of the respect-ive signals from the respective Y and Z coils as detected by the respactive synchronous detectors 1268 and 12~4 and, hence, is indicated on the display 1264.
This enables the operator to position the tool 1216 about its axis by controllinbg the po~ition of the vanes 26 ~?s~?~s~

and thereby cause the tool 1216 to advance in desirea direct-ion relative to i9 axis 1222. The i'eedback by way of the controller circuit 1280 is not used in this mode, as ths sig-nal from ths X coil 1254 is near zero in this mode.
The present invention is useful in a simple form when it is deslrable simply to keep the tool on a straight course.
This is achieved simply by directing the tool 1216 toward the sensing assembly 1246 while kseping th0 outputs picked up by the Y and Z coils 1256, 1258 nulled. As mentioned above, it i9 possible to deviate to avoid obstacles and then return to the course.
Thls is facilitated by keeping track of where the tool is at all times. This requires measurement of the tool advance. within the borehole. Although this is indicated to a degree by the power required to maintaln constant the output of the X coil 1254, it i5 more accurate to measure x dis-placement along the borehole more directly by measuring the length of lines 1253 fed into the borehole or by a distance indicating potentionmeter 1284 tied to the tool 1216 by a llne 1286. This provides a signal on a llne 1288 indicating displacement and incremental displacement of ths tool 1216 within the borehole. This information, in combination with the signal6 from Y and Z coils 1266, 1258 permits the opera-tor to keep track of the location of the tool at all times.

When distance is kept track of and position is deter-mined, it iB possible by more sophisticated electronics to ~2S~

operate with the sensing ass0mbly in the input pit 1234, particularly if the tool 1216 kept substantially on the x ~xis. For example, if the tool is allowed to progress a substantial distance from the desired axis, the angla B be-comes significant and a more complicated set of relationshipsapply than when the siza of the angle B is near O and its cosine 121. That is, Equation (4~ may not be simply approx-imated.
In this case, it will be necessary to continuously develop the position of the tool in ordsr to provide accurate data on its location. In this case, the initial tool orien-tation is determined by means of the sensor coils. Then the tool i8 allowed to advance an incremental di6tance, which is also measured. The new locatioll is then determined based on the initial angle and the in¢remental amount of progress, and integration process. This process is continuously repeated $or continuous determination of the position of tha tool.
Other modi$ications of tha present invention are also possible. For example, the sensing assembly 1246 may be moved from place to placa or its orientation charged during boring in order to change course. Also the sensor coils can be located on tha tool and the source coils can be located on the tool and the source coils placed in either pit. It is also within the scope of the present invantion to provide sensors on the tool 1216 for sensing obstaclas, hence permit--- 10~ --~;25S6~;1 ting control of tha direction of tool advance to avoid th~obstacles.
Other types of boring or drilling systems can ba used in conjunction with the present invention, such as hydraulic peroussion tools, turbo-drill motors (pneumatic or hydraulic) or rotary-drill typ0 tools. The important aspects of the tool are that it include some motivs means and a stsering mechanism that can be controlled by control signala ~rom afar.

Claims (57)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A controllable percussion tool for drilling holes in the soil comprising a cylindrical housing with a tapered front and, a first means on said front end for applying a boring force to the soil, a second means in said housing for applying a percus-sive force to said boring force applying means, said first and second means being cooperable to apply an asymmetric boring force, a rotatable sleeve member supported on the rear end of said housing, a pair of fins supported on said rotatable sleeve member in circumferentially spaced relation and having fixed angular positions thereon, said sleeve member and fins comprising a fin assem-bly, and means cooperable with at least one component of said fin assembly to establish one position permitting said fin assembly to rotate freely on said housing during movement through the earth and another position fixed in relation to said housing to cause said housing to rotate on movement through the earth, said boring means being operable to bore in a straight direction when said fin assembly is in said fixed position and to bore in a curved direction when said fin as-embly is freely rotating.

2. A controllable percussion tool according to claim 1 in which said first means comprises an anvil having a striking surface inside said housing and a boring surface outside said housing, and said second means comprises a reciprocally movable hammer positioned in said housing to apply a percussive force to said anvil striking surface.

3. A controllable percussion tool according to claim 2 in which said anvil boring surface comprises a cylindrical nose portion having a side face extending longitudinally from the tip at an acute angle thereto.

4. A controllable percussion tool according to claim 3 in which said external anvil boring surface comprises a cylin-drical body and said nose portion is removably secured there-on.

5. A controllable percussion tool according to claim 2 in which said hammer member has an asymmetric end portion for applying said asymmetric earth boring force.

6. A controllable percussion tool according to claim 2 in which said hammer member has a cylindrical body portion and an end portion asymmetric to the anvil end of said anvil mem-bar for applying a hammer blow adjacent to the periphery thereof for applying said asymmetric earth boring force.

7. A controllable percussion tool for drilling holes in the soil comprising a hollow cylindrical housing with a tapered front end, a first means on said front end for applying a boring force to the soil comprising an anvil having a striking sur-face inside said housing and a boring surface outside said housing comprising a cylindrical nose portion having a side face extending longitudinally from the tip at an acute angle thereto, said anvil and nose portion being secured in a fixed non-rotatable position in said housing whereby movement of said tool through the soil is deviated from a straight path by reaction of said angled side face against the soil, a second means comprising a reciprocally movable hammer positioned in said housing to apply a percussive force to said anvil striking surface for transmitting a percussive force to said boring force applying means, a plurality of guide fins positioned on the exterior of said housing at the rear end thereof and having a first position permitting non-rotative movement through the soil and a second position causing said housing to rotate about its longitudinal axis on movement through the soil, and means for moving said fins between said first and second positions, said housing having a curved path through the soil when prevented from rotation and a substantially straight path when caused to rotate.

8. A controllable percussion tool according to claim 7 in which said first means comprises an anvil having a striking surface inside said housing and a boring surface outside said housing, and said second means comprises a reciprocally movable hammer positioned in said housing to apply a percussive force to said anvil striking surfaces.

9. A controllable percussion tool according to claim 8 in which said anvil boring surface comprises a cylindrical nose portion having a side face extending longitudinally from the tip at an acute angle thereto.

10. A controllable percussion tool according to claim 8 in which said external anvil boring surface comprises a cylin-drical body and said nose portion is removably secured there-on.

11. A controllable percussion tool according to claim 8 in which said hammer member has an asymmetric end portion for applying said asymmetric earth boring force.

12. A controllable percussion tool according to claim 8 in which said hammer member has a cylindrical body portion and an end portion asymmetric to the anvil and of said anvil mem-ber for applying a hammer blow adjacent to the periphery thereof for applying said asymmetric earth boring force.

13. A controllable percussion tool according to claim 8 in which said hammer is fluid actuated, and said housing has conduit means for connection to a source of actuating fluid.

14. A controllable percussion tool according to claim 13 in which said source of actuating fluid comprises a source of compressed air for pneumatic operation.

15. A controllable percussion tool according to claim 13 in which said source of actuating fluid comprises a source of hydraulic fluid under pressure.

16. A controllable percussion tool according to claim 7 in which a rotatable sleeve member is supported on the rear end of said housing, said fins being supported on said rotatable sleeve member in circumferentially spaced relation and having fixed angular positions thereon, said sleeve member and fins comprising a fin assem-bly, and means cooperable with at least one component of said fin assembly to establish one position permitting said fin assembly to rotate freely on said housing during movement through the earth and another position fixed in relation to said housing to cause said housing to rotate on movement through the earth, said boring means being operable to bore in a straight direction when said fin assembly is in said fixed position and to bore in a curved direction when said fin as-embly is freely rotating.

17. A controllable percussion tool according to claim 16 in which said rear end of said housing includes a supporting sleeve portion, said rotatable sleeve member being supported on said supporting sleeve portion for rotary movement thereon, clutch means operatively interconnecting said rotat-able sleeve member and said supporting sleeve portion and having a first disengaged position permitting rotation of said rotatable sleeve relative to said supporting sleeve portion and a second engaged position securing said rotatable sleeve and said supporting sleeve portion for rotation to-gether, and means to move said clutch means to said engaged and said disengaged positions.

18. A controllable percussion tool according to claim 16 in which said rear end of said housing includes a supporting sleeve portion, said rotatable sleeve member being supported on said supporting sleeve portion for rotary movement thereon and a longitudinally fixed position, clutch means having a first part operatively secured on said rotatable sleeve member and movable therewith, a second part operatively secured on said supporting sleeve portion, and a third part movable into and out of engagement with said first and second parts, said clutch means third part having a first position disengaged from said first and second parts to permit rotat-ion of said rotatable sleeve relative to said supporting sleeve portion and a second position engaged with said first and second parts to secure said rotatable sleeve and said supporting sleeve portion for rotation together, and means to move said third part longitudinally in rela-tion to said first and second parts to said engaged and said disengaged positions.

19. A controllable percussion tool according to claim 18 in which said third part comprises a sleeve member slidably movable of said supporting sleeve portion and within said rotatable sleeve member and having drive surfaces operatively engagable with said rotatable sleeve member and said support-ing sleeve portion to secure the same for movement together.

20. A controllable percussion tool according to claim 19 in which said slidable sleeve member is movable between a pos-ition engaged with and a position disengaged from said rotat-able sleeve member and said supporting sleeve portion.

21. A controllable percussion tool according to claim 19 in which said slidable sleeve member is secured on said sup-porting sleeve member for rotation therewith, said rotatable sleeve member and said slidable sleeve member have at least one recess on one and one protection on the other cooperable when engaged to secure said rotatable sleeve member and said supporting sleeve member together for rotation together, and said slidable sleeve member is movable between a position engaged with and a position disengaged from said rotatable sleeve member.

22. A controllable percussion tool according to claim 16 in which said rear end of said housing includes a supporting sleeve portion, said rotatable sleeve member being supported on said supporting sleeve portion for rotary movement thereon and having a predetermined amount of longitudinal movement, clutch means having one part operatively secured on said rotatable sleeve member and movable therewith and anoth-er part operatively secured on said supporting sleeve por-tion, said clutch means parts having a first disengaged position permitting rotation of said rotatable sleeve rela-tive to said supporting sleeve portion and a second engaged position securing said rotatable sleeve and said supporting sleeve portion for rotation together, and means to move said rotatable sleeve longitudinally in relation to said supporting sleeve portion to move said clutch means parts to said engaged and said disengaged posi-tions.

23. A controllable percussion tool according to claim 22 in which said clutch means parts comprises drive teeth on said rotatable sleeve and said supporting sleeve portion re-spectively, and means for moving said drive teeth into and out of engagement.

24. A controllable percussion tool according to claim 25 in which said drive teeth are positioned for end to end en-gagement

25. A controllable percussion tool according to claim 23 in which said drive teeth are on the inside of said rotatable sleeve and the outside of said supporting sleeve portion res-pectively, and means for moving at least one of said sleeves to engage and disengage said teeth.

26. A controllable percussion tool according to claim 22 in which said clutch means parts comprises drive teeth on one of said sleeves and a drive member on the other sleeve and relatively movable into and out of engagement therewith, and means for moving said drive teeth and drive member into and out of engagement.

27. A controllable percussion tool according to claim 22 in which said clutch means parts comprises a drive slot on one of said sleeves and a drive member on the other sleeve and relatively movable into and out of engagement therewith, and means for moving said drive slot and drive member in-to and out of engagement.

28. A controllable percussion tool according to claim 26 in which said drive member comprises a drive pin.

29. A controllable percussion tool according to claim 27 in which said drive member ccomprises a drive pin.

30. A controllable percussion tool according to claim 22 in which said clutch means parts comprises a drive slot on one of said sleeves and a drive spline on the other sleeve and relatively movable into and out of engagement therewith, and means for moving said drive slot and drive spline into and out of engagement.

31. A controllable percussion tool according to claim r in which a fixed supporting sleeve member is supported on the rear end of said housing, said fins being pivotally supported on said sleeve member in circumferentially spaced relation thereon, said fins each having a first position parallel to the longitudinal axis of said housing and a second position extending at an acute angle to the longitudinal axis of said housing, means cooperable with said fins to move the same to said first position or said second position, and said boring means being operable to bore in a straight direction when said fins are in said second position and to bore in a curved direction when said fins are in said first position.

32. A controllable percussion tool according to claim 31 in which said rear end of said housing includes a supporting sleeve portion, said fixed sleeve member being supported on said supporting sleeve portion, supporting pins for each of said fins extending into the space between said supporting sleeve portion and said fixed sleeve member and having operating means thereon, an operating member slidable on said supporting sleeve portion and engagable with said in operating means, and means to move said operating member longitudinally in relation to said fin operating means to move the same to position said fins in said parallel or said angled position.

33. A controllable percussion tool according to claim 32 in which said pin operating means comprises a rotary member secured on each of said supporting pins, said operating member comprises a slidably movable sleeve, said pin-operating rotary member and said drive sleeve having a recess in one and a protecting drive member on the other cooperable for rotating each of said fin members upon sliding movement of said slidably movable sleeve.

34. A controllable percussion tool for drilling holes in the soil comprising a hollow cylindrical housing with a tapered front end, a first means on said front end for applying a boring force to the soil comprising an anvil having a striking surface inside said housing and a boring surface outside said housing comprising a cylindrical nose portion having a side face extending longidutinally from the tip at an acute angle thereto, said anvil and nose portion being secured in a fixed non-rotatable position in said housing whereby movement of said tool through the soil is deviated from a straight path by reaction of said angled side face against the soil, a second means comprising a reciprocally movable hammer positioned in said housing to apply a percussive force to said anvil striking surface for transmitting a percussive force to said boring force applying means, means for connecting said hammer to an external energy supplying means, a plurality of guide fins positioned on the exterior of said housing at the rear end thereof and having a first position permitting non-rotative movement through the soil and a second position with the fins fixed relative to said housing at an angle causing said housing to rotate about its longitudinal axis on movement through the soil, and externally operated means for moving said fins between said first and second positions, whereby said tool has a curved path through the soil when said housing is prevented from rotation and a substantially straight path when caused to rotate.

35. A controllable percussion tool according to claim 34 in which said hammer is fluid actuated, and said connecting means comprises conduit means for connection to a source of actuating fluid.

36. A controllable percussion tool according to claim 35 in which said source of actuating fluid comprises a source of compressed air for pneumatic operation.

37. A controllable percussion tool according to claim 35 in which said source of actuating fluid comprises a source of hydraulic fluid under pressure.

38. A controllable percussion tool according to claim 34 in which said anvil member and said hammer member comprise earth boring means, and at least one member of said earth boring means in-cluding means for producing an asymmetric earth boring force.

39. A controllable percussion tool according to claim 38 in which said percussion operated tip comprises a cylindrical nose portion having a side face extending longitudinally from the tip at an acute angle thereto.

40. A controllable percussion tool according to claim 39 in which said percussion operated tip comprises a cylindrical body and said nose portion is removably secured thereon.

41. A controllable percussion tool according to claim 38 in which said hammer member has an asymmetric end portion for applying said asymmetric earth boring force.

42. A controllable percussion tool according to claim 38 in which said hammer member has a cylindrical body portion and an end portion asymmetric to the anvil end of said anvil mem-ber for applying a hammer blow adjacent to the periphary thereof for applying said asymmetric earth boring force.

43. A controllable percussion tool according to claim 38 in which a rotatable sleeve member is supported on the rear end of said housing, said fins being supported on said rotatable sleeve member in circumferentially spaced relation and having fixed angular positions thereon, said sleeve member and fins comprising a fin assem-bly, and means cooperable with at least one component of said fin assembly to establish one position permitting said fin assembly to rotate freely on said housing during movement through the earth and another position fixed in relation to said housing to cause said housing to rotate on movement through the earth, said boring means being openable to bore in a straight direction when said fin assembly is in said fixed position and to bore in a curved direction when said fin as-embly is freely rotating.

44. A controllable percussion tool according to claim 43 in which said rear end of said housing includes a supporting sleeve portion, said rotatable sleeve member being supported on said supporting sleeve portion for rotary movement thereon, clutch means operatively interconnecting said rot-atable sleeve member and said supporting sleeve portion and having a first disengaged position permitting rotation of said rotatable sleeve relative to said supporting sleeve portion and a second engaged position securing said rotatable sleeve and said supporting sleeve portion for rotation to-gether, and means to move said clutch means to said engaged and said disengaged positions.

45. A controllable percussion tool according to claim 43 in which said fear end of said housing includes a supporting sleeve portion, said rotatable sleeve member being supported on said supporting sleeve portion for rotary movement thereon and a longitudinally fixed position, clutch means having a first part operatively secured on said rotatable sleeve member and movable therewith, a second part operatively secured on said supporting sleeve portion, and a third part movable into and out of engagement with said first and second parts, said clutch means third part having a first position disengaged from said first and second parts to permit rotat-ion of said rotatable sleeve relative to said supporting sleeve portion and a second position engaged with said first and second parts to secure said rotatable sleeve and said supporting sleeve portion for rotation together, and means to move said third part longitudinally in rela-tion to said first and second parts to said engaged and said disengaged positions.

46. A controllable percussion tool according to claim 43 in which said rear end of said housing includes a supporting sleeve portion, said rotatable sleeve member being supported on said supporting sleeve portion for rotary movement thereon and having a predetermined amount of longitudinal movement, clutch means having one part operatively secured on said rotatable sleeve member and movable therewith and anoth-er part operatively secured on said supporting sleeve por-tion, said clutch means parts having a first disengaged position permitting rotation of said rotatable sleeve relat-ive to said supporting sleeve portion and a second engaged position securing said rotatable sleeve and said supporting sleeve portion for rotation together, and means to move said rotatable sleeve longitudinally in relation to said supporting sleeve portion to move said clutch means parts to said engaged and said disengaged pos-itions.

47. A controllable percussion tool according to claim 38 in which a fixed supporting sleeve member is supported on the rear end of said housing, said fins being pivotally supported on said sleeve member in circumferentially spaced relation thereon, said fins each having a first position parallel to the longitudinal axis of said housing and a second position extending at an acute angle to the longitudinal axis of said housing, means cooperable with said fins to move the same to said first position or said second position, and said boring means being operable to bore in a straight direction when said fins are in said second position and to bore in a curved direction when said fins are in said first position.

48. A controllable percussion tool according to claim 47 in which said rear end of said housing includes a supporting sleeve portion, said fixed sleeve member being supported on said sup-porting sleeve portion, supporting pins for each of said fins extending into the space between said supporting sleeve portion and said fixed sleeve member and having operating means thereon, an operating member slidable on said supporting sleeve portion and engagable with said fin operating means, and means to move said operating member longitudinally in relation to said fin operating means to move the same to position said fins in said parallel or said angled position.

49. A controllable percussion tool according to claim 48 in which said pin operating means comprises a rotary member secured on each of said supporting pins and having a drive recess therein, and said operating member comprises a slidably movable sleeve having a drive member cooperable with said drive re-cess for rotating each of said fin members upon sliding move-ment of said slidably movable sleeve.

50. A controllable percussion tool for drilling holes in the soil comprising a cylindrical housing with a tapered front end, a first means on said front end for applying a boring force to the soil comprising an anvil having a striking sur-face inside said housing and a boring surface outside said housing comprising a cylindrical nose portion having a side face extending longitudinally from the tip at an acute angle thereto, said anvil and nose portion being secured in a fixed non-rotatable position in said housing whereby movement of said tool through the soil is deviated from a straight path by reaction of said angled side face against the soil, a second means comprising a reciprocally movable hammer positioned in said housing to apply a percussive force to said anvil striking surface for transmitting a percussive force to said boring force applying means, at least one guide fin positioned on the exterior of said housing at the rear end thereof having one position preventing rotary motion of said housing about its longitud-inal axis and another position permitting rotary motion of said housing about its longitudinal axis, said housing having a curved path through the soil when prevented from rotation and a substantially straight path when permitted to rotate.

51. A controllable percussion tool for drilling holes in the soil comprising a hollow cylindrical housing with æ tapered front end, a first means on said front end for applying a boring force to the soil, a second means in said housing for applying a percus-sive force to said boning force applying means, said first and second means being cooperable to apply an asymmetric boring force, a rotatable sleeve member supported on the rear end of said housing, a pair of fins supported on said rotatable sleeve member in circumferentially spaced relation and having fixed angular positions thereon, said sleeve member and fins comprising a fin assem-bly, and means cooperable with at least one component of said fin assembly to establish one position permitting said fin assembly to rotate freely on said housing during movement through the earth and another position fixed in relation to said housing to cause said housing to rotate on movement through the earth, said boring means being operable to bore in a straight direction when said fin assembly is in said fixed position and to bore in a curved direction when said fin as-embly is freely rotating.

52. A system for boring a borehole including a percussion tool as defined in claim 1, said tool having a longitudinal axis and steering means including said fin assembly for directing the motion of the load relative to said tool axis in response to control signals and further including axial electromagnetic source means for generating an axial alternating magnetic field directed along an axial source axis;
a sensing assembly remote from said source means and including first and second pickup coils for sensing said alternating magnetic field;
each coil of said first and second pickup coils being responsive to the change of magnetic flux linked thereby by generating respective electrical signals systematically related thereto;
having a respective coil axis;
being rigidly mounted in respect to the other coil with the coil axis of said first coil at a substantial angle with respect to the coil axis of said second coil, said coil axes defining a sensing assembly axis substantially normal to both said coil axes; and being balanced in respect to said sensing assembly axis to generate a respective null electrical signal when the lines of magnetic flux at the respective coil are normal to the respective coil axis at said sensing assembly axis;
one and only one of said source means and said sensing assembly being rigidly mounted on said tool;
indicating means responsive to electrical signals generated by respective said first and second pickup coils for indicating the direction of lines of magnetic flux at said sensing assembly relative to said sensing assembly axis, thereby indicating the attitude of said source means relative to said first and second pickup coils; and control means for providing control signals for controlling said steering means.

53. A system according to claim 52 wherein said source means is mounted on said tool.

54. A system according to claim 53 wherein said sensing assembly is disposed in a pit in advance of said tool.

55. A system according to claim 54 wherein said sensing assembly includes a third pickup coil having a coil axis substantially coincident with said sensing assembly axis for sensing the component of said axial alternating magnetic field extending in the direction of said sensing assembly axis by generating a respective third electric signal systematically related thereto, said control system further comprising feedback means responsive to said third electrical signal for controlling said axial electromagnetic source means to generate said axial alternating magnetic field at such amplitude as to keep said third electrical signal substantially constant irrespective of the distance between said source means and said sensing assembly.

56. A system according to claim 53 wherein said sensing assembly includes a third pickup coil having a coil axis substantially coincident with said sensing assembly axis for sensing the component of said axial alternating magnetic field extending in the direction of said sensing assembly axis by generating a respective third electric signal systematically related thereto, said control system further comprising feedback means responsive to said third electrical signal for controlling said axial electromagnetic source means to generate said axial alternating magnetic field at such amplitude as to keep said third electrical signal substantially constant irrespective of the distance between said source means and said sensing assembly.

57. A system according to claim 52 wherein said sensing assembly includes a third pickup coil having a coil axis substantially coincident with said sensing assembly axis for sensing the component of said axial alternating magnetic field extending in the direction of said sensing assembly axis by generating a respective third electric signal systematically related thereto, said control system further comprising feedback means responsive to said third electrical signal for controlling said axial electromagnetic source means to generate said axial alternating magnetic field at such amplitude as to keep said third electrical signal substantially constant irrespective of the distance between said source means and said sensing assembly.