US2906502A

US2906502A - Underwater earth boring mechanism

Info

Publication number: US2906502A
Application number: US418286A
Authority: US
Inventors: Edward W Smith
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-03-24
Filing date: 1954-03-24
Publication date: 1959-09-29
Anticipated expiration: 1976-09-29

Description

Sep`t. 29, 1959 E. w. SMITH UNDERWATER EARTH BORING MECHANISM 3 Sheets-Sheet 1 Filed March 24, 1954 e f x n L//- ,f

Ilm my o1 wf mi E. W. SMITH UNDERWATER EARTH BORING MECHANISM sept. 29, 1959 3 sheets-sheet 2 Filed March 24, 1954 INVENTOR. Edmn /,Smh Y N uw; n

sept; 29, 1959 E. w. SMITH 2,906,502

UNDERWATER EARTH BORING MECHANISM Filed March 24, 1954 3 Sheets-Sheet 3 United States Patent O 2,906,502 UNDERWATER EARTH BRING MECHANISM Edward W. Smith, Melrose Highlands, Mass. Application March 24, 1954, Serial No. 418,286 15 Claims. (Cl. Z55-2.5)

'I'he present invention relates to earth boring equipment and procedures and more particularly to a method and means for performing this operation when the area of earth to be bored is submerged to substantial depths in water.

As is well known, the constant search for oil bearing .structures has resulted in prospecting for oil, not only on land surfaces which showed evidence of containing them, but also in areas such as the Gulf of Mexico where the oil bearing structures may be covered by substantial depths of water. While drilling in these areas can be accomplished by the usual rotary rig and procedures providing the depths of Water are reasonably low, say less than 30 feet, it is a much more diiicult problem in greater depths.

This diculty is essentially due to the fact that the usual earth boring equipment consists of a tool or cutting element, mounted on the end of a piece of drill pipe, the Whole being suspended from a rotary table which likewise serves to revolve the drill pipe and hence the tool. It is obvious that such an arrangement presupposes some sort of a rigid bed on which the rotary table can be mounted and permit of a rigid connection between the turn table `and the tool by means of the drill pipe. Such an arrangement cannot be provided from a boat or other floating structure, because wave motion, yawing of the boat, etc., and similar disturbing motions preclude the possibility of maintaining reasonably accurate alignment between the axis of the turntable and axis of the hole being drilled.

One of the purposes of the present invention is to provide a method and means for earth boring under such conditions which does not require the accurate alignment of various elements with the hole being drilled.

Another object of, the invention is to pro-vide a method and means for supplying a ow of drilling mud to the drilling tool and returning it to the surface to the usual type of slush pit Without danger of admixture of the drilling mud with sea water.

Another object of the invention is to provide in effect a exible drill pipe for carrying the drilling mud to the tool and simultaneously providing support for the tool.

Still another object of the invention is to provide a novel tool driving mechanism operated by drilling mud, in which the power necessary for the actual drilling is generated at the tool rather than being transmitted by a rigid drill pipe from the surface.

Still another object of the invention is to provide a means whereby drilling can be accomplished by high frequency oscillation of the drilling tool rather than by continued rotation of the tool as usually understood.

These and other advantages of the present invention will be more clearly understood in connection with the drawings, in which:

Figure l is a longitudinal cross sectional view of the drilling unit taken on the line 1-1 of Figure 2.

Figure 1A is a perspective exploded view of two elements of the drilling unit.

p 2,906,502 Patented sept. 29, 1959 Figures 1B and 1C are schematic diagrams used in explanation of the structure of the drilling unit.

Figure 2 is a cross sectional view of the drilling unit taken along the line 2-2 of Figure 1.

Figure 3 is a cross section taken along the line 3-3 of Figure 1.

Figure 4 is a cross sectional view of the ilexible pipe supporting the drilling unit.

Figure 5 is a section taken along the line 5 5 of Figure 4.

Figure 6 is an end view of the flexible pipe segment of Figure 4.

Figure 7 is a cross sectional elevation of the elements positioned in the floating support.

Figure 8 is a side elevation of the elements shown in Figure 7.

Figure 9 is a detail of the flexible pipe supporting elements at the ocean bottom, and

Figure l0 shows a diagrammatic View of a means for anchoring the supporting barge.

Referring to Figure l, there is shown a drilling unit to which a cutting tool may be attached at the lower end 1 and which is supported at its upper end 2 by a exible tube element 50, Figure 4. The threaded portion 31 of the upper end 2 threads into the recessed portion 28 of the ilexible tube forming a continuous elongated member. This threaded portion 31 is shaped to thread into and be securely held in the lowermost of the interchangeable portions 28 as indicated more fully hereinafter. In this drilling unit there is a mass or backing element 3 having a fairly large moment of inertia. This backing element is cylindrical in shape and forms the upper end of the drilling unit. A downwardly projecting annular ange 3 of the backing element has threaded to its inner lower side a cylindrical tube 4. Within the lower end of this cylindrical tube 4 but not secured directly to it is a tool driving element S, which compared with the backing element has a smaller moment of inertia. This driving element S is cylindrical in shape with projecting ribs 12 and is secured to the backing element 3 by means of a steel tube 6, which tube extends through and is secured by welding or other suitable means at its lower end to the inner wall of the driving element 5 and at its upper end 7 to the inner wall of the backing element 3. This tube 6 has a substantial torsional resilience which permits torsional oscillation of the tool driving element 5 with respect to the backing element 3 in a manner hereinafter described.

From the lower end of the tool driving element 5, there is provided an extension forming a projecting tube member 8 with a centrally located opening 9 continuous with the center of the tube 6. The lower end of this projecting tube 8 is provided with a head 8a for securing the cutting tool 70 suitably aligned with the opening 9. At the lower end of the tube 4, tnere is secured by suitable means, a cylinder 10A having stepped milled slots 10', substantially dividing the cylinder into `a pair of

semicylindrical sections

32 and 33 formed with angular arcs of something less than The milled slots do not extend the entire length of the cylinder 10A as is illustrated in Figure 1A. The longitudinal edges of these sections are formed with

shoulders

34 and 35. When these

sections

32 and 33 are secured to the tube the slots 10 formed between their end edges may each be considered as comprising a recess section 10 and a recess section 11, as schematically illustrated in Figure 1B with the recess section 10 centrally located longitudinally with respect to the recess section 11. It will be noted therefore that recess sections 10 and 11 are portions of slots 10.

The tool driving element 5 is provided with a pair of projecting ribs 12 which are approximately 1% to 11/2 times the width of the recess sections 10. These ribs 12 project into the recess sections 11 dividing the recess sections 11 into two

separate chambers

12a and 12b (see Figure 1C) as well as separating the recess sections 10 into achambper` apartfromV the, recess sections 11 when the unit is in an inoperative position. The upper inner surface 36V ofjthe ribsv 12 t closely tothe surface 37 of the

shoulders

34 and 35 of the sections-32 and 33.

A channel 13 of somewhat smaller diameter than the central channel' 14 through which drilling mud passes to the cutting tool, opens intothe channel 14`at the upper end of the drilling unit. Thiswchannelpasses through the backing element 3V andterminates at a lixed'valve element or restricted orifice 15 at the upper end of the tube ,4. Below this valve element 15- an yannular opening 16 is formed between the wall of the tube 4 and theVY inner tube 6. At the upper end of driving element 5 is provided passages 17 or extensionsl of recess 11 which connect this cylindrical opening 16 with one end of the recess 11; It will be noted that these passages 17 enter the recess 11 at corresponding diametrically opposite positions of the recesses. At the lower end of this drilling unit, a ring 18 fitting around theA projecting tube 8 covers the lowermost end of the recesses 11, but leaves open the recesses 10. This ring 18 is securedl over the driving element 5 by means of a plurality of screws 19, threaded into the drivingelement 5.

In the operation of this drilling unit as shown in Figure l, mud enters the drilling unit at the upper end from the hose connection which will be hereinafter described and passes down throughthe center of the tube 6 to the cutting tool. A portion of the mud however which, enters the tube 6, is by-passed through the channel 13 into the chamber 16 where pressure isbuilt up, which pressure is dependent upon the relative size of the valve 15 and the size of the openings 71 through the cutting tool 70. This cutting tool 70 may be of conventional shape and structure. The openings 71 communicate with passage 9 for passage of drilling mud through the unit.

As will readily be seen in Figure 2, the driving element 5 is mounted concentrically and is partially rotatable within the lower end of the tube 4 with the projecting ribs 12 fitting into and forming separate chambers of the recesses and 11 with each of the recesses 11 divided into two sections by the ribs 12. When mud is being forced down into the chamber 16 and the pressure builds up in this chamber, thermud will force its way into the recesses 11 through the passages 17. As'these recesses 11 are formed withone edge wall constructed as a part of the cylinder 10A and the other edge wall formed by the rib 12, the pressure which is built up will cause these side walls to move apart in a rotational movement. 'Ihe consequent rotation of the driving element 5, twists the tube 6. On suicient rotation ofthe driving element 5, the chambers formed by the recess sections 11 are opened to the chambers formed by the recess sections 10. This 'releases the pressure built up by the mud which may then pass out through the bottom of the recess section 10. The torsional stiffness of the tube 6 which rigidly interconnects the backing element 3 and the driving element 5, will then rotate the element 5 back to and beyond its position of rest, where pressure can again be built up in the recess sections 11. It will be clear that the rapid action just described above, 4applies in eifect a pulsating torque between the driving element 5 on the one hand, and theV rigid aggregation ofthe backing element 3, tube 4, and

elements

32 and 33 on the other hand, thereby periodically twisting the tube 6.

As mentioned previously, I prefer to make the inertia consisting of element 3, tube 4 and

elements

32 and 33 of` the cylinder 10A, large compared to the inertia of the driving element 5 and the tool mounted on it@ Operated as above indicated, the driving element then describes a torsional oscillation at a frequency which is determined byv'the torsional stiffness of the tube 6 andthe inertia of 4 the driving element 5 in cooperation of the total inertia of the backing element 3, the tube 4 and the cylinder 10A.

It will be clear from the foregoing that the above described unit operates in essence as a torsionally resonant system of two degrees of freedom, i.e. both element 5 and element 3 with its associated structures oscillate torsionally but in opposite directions and at angular amplitudes which are inversely proportional to their inertias. Therefore, if as I prefer to do, the inertia of element 3 and its associatedY structures is made large with respect to the inertia of element 5 and the tool it is moving, then this ratioV willV ensure little or substantially no Atorsional amplitude of element 3.

The advantages of such an arrangement become immediately apparent when it is realized that the rotation force exerted by the tool in cutting the structure to be drilled must be backed up in some way if cutting is to be accomplished. In the normal rotary rig this backing is provided by the surface mounting supporting the rig table and perforce such an arrangement meansthat the connection from there to the tool must be substantially rigid. In the present invention, however, the torsional.. oscillation of the tool and element 5 is backed up by an equal and opposite oscillation of element 3, so that the means used to support the unit need only support its weight and does not have to provide backing for the forces exerted by the tool as would ordinarily be the case since these are effectively dynamically balanced by the simultaneous and opposing oscillation of element 3 and its associated structures. The importance of this fact with its application to the problem of underwater drilling will become even more apparent hereinafter.

While it may be assumed that the constant twisting of tube 6 would eventually result in its being fractured, this will not be the'case if its dimensions are so chosen as` to result in a maximum ber'stress in it of not more than 10,000 lbs. sq./in. and the steel is of good quality.

The angular amplitude of element 5 and its frequency of oscillation are somewhat a matter of design depending upon the work to which it is to be put, the maximum permissible diameter of the unit and the type of cutting tool to be employed. Generally speaking, it is desirable to have the angular amplitude such that the cutting teeth of the tool will traverse a distance greater than the tooth spacing so that ridges in the structure being cut will not build up between the teeth as cutting proceeds.

With such an arrangement as has been described above, frequencies of oscillation of the order of 3600 vibrations per minute can be readily built up which ensures rapid cutting. If greater frequencies are desired, as for instance frequencies up to say 7200 vibrations per minute I prefer to use an electrically operated drive such as is shown in my patent application Serial No. 275,496, now

Patent Number 2,803,433, led March 8, 1952 in connection with the supporting elements hereinafter described.

By proper choice of frequency and amplitude the maximum velocity of the cutting teeth may be made far greater than is'possible where the tool must be rotated from the surface. Consequently greater effectivenessA of diamond bits can be attained because with higher velocities on such bits the pressure may be reduced for equivalent cutting and the life of the diamond bit increased.

This drillunit which may be in the neighborhood of 200" long, is supported by a flexible tube 50 formed of a number of uniformunits attached end to end with the number of units dependent on the depth of the hole being drilled. The unit which forms this iexible tube 50 has a rubber or other water resistant flexible tube length 20 fixed securely at its upper end about the downwardly projecting annular iiange 21 of the upper male member 22 by conventional means for bonding rubber to metal. This male member 22 is provided with a central opening23 entering the center of the tube-20 through which the drilling mud being supplied to the drilling unit may pass. At the upper end ofthisfmaley member is athreaded pipe connection 24. At the lower end of this flexible pipe or tube 20, is rigidly secured a female member 25 with an upper annular flange 26 about which the inner side of the tube 20 is fixed. The female member 25 is provided with a lower annular flange 27 and a recess portion 28 which are shaped to receive the upper end of a male connecting element 22 or the upper end of the drilling unit. The annular flange 27 is shaped to project downwardly along the outside of the male connecting element and to fit over a series of O rings 29 fixed in grooves about the male member 22. These O rings provide a water-tight connection when a male and female connecting element are screwed together. The tube 20 as will be seen in Figure 5 is provided with a series of longitudinally extending flexible steel wires 30, which extend the length of the tube 20 and are connected at their upper ends by welding or other suitable attaching means to the male member 22 and at their lower end to the female member 25. This flexible tube 50 is secured to the drilling unit, (Figure l) by means of an interconnecting female section or member 25 and a male member or section 31 at the upper end of the drilling unit which is similar to the male sections of the connecting elements shown in Figure 4. This drilling unit is supported primarily by the steel wires passing through the rubber walls 20, which may be selected in such number and strength as to be more than adequate to support the weight of the drilling unit. For instance, if the carrying capacity equivalent to a 1%", 6 x 19 steel cable is desired, 50 1/a diameter steel wires incorporated in the walls of the tube would give a cross sectional equivalent to the cable just mentioned. Ordinarily this amount of longitudinal reinforcing would not be necessary because the weight of the tool and driving element plus the hose would be less than a rotary drill pipe of equivalent capacity. It will be noted that this construction gives a flexible tube for connecting the tool to the surface and yet has sufficient strength to support any weight likely to be encountered.

A pair of copper wires or other suitable insulated electrical conductors 40 and 41 pass longitudinally through one rubber tube 20 and are connected at their ends by insulated conducting elements to similar

electrical conductors

42 and 43 in the next adjacent tube 20 respectively. The conductors 42 are connected one each to one half of a split slip ring 44 which is positioned at the top of the male element 22 and is insulated from it by an insulating element 45. The lower end of the wires 40 and 41 are connected through the insulated conductor 43 to brush element 46 positioned at the lower end of the female element 25 and insulated from it by the insulation 47. When a series of these units are connected end to end, electrical contacts will be made between the brushes and the split rings permitting the use of this flexible tube to be used in connection with a driving unit such as described in my copending application Serial No.v 275,496, now Patent No. 2,803,433, patented August 20, 1957, mentioned above. In such an application of this flexible tube, the electrical conductors may be used to supply power to the drilling unit, while the interior of this tube may be used for the transmission of drilling mud to the cutting tool element. When such flexible tube is to be used in connection with a drilling unit, such as herein described, the electrical conductors will not be used.

The upper end of the supporting flexible tube when used in under water earth drilling, passes upwardly through an opening in the well 48 of the barge or supporting vessel (Fig. 7). j

The upper end of this supporting tube 50 is supported and secured to the usual type of rig, not shown. Concen'tric with the tube 50 is an outer flexible casing tube 51 which extends downwardly to a point just above the level of the ocean bottom and has bonded to its lower end a fitting 52 threaded at its inner lower surface.

This fitting 52 screws on to a surface casing 53 corresponding to the usual type of surface casing used in wells on dry land. A fitting 54 is bonded to the upper end of this tube and is provided with threads at its upper end for securing the tube and fitting to the steel tubing S5. This steel tubing 55 extends upwards through a platform S6 supported on stanchions 57 and terminates at its upper end in an outwardly extending flange 61. Slidingly fitting about this steel tube 55, above the plat` form 56 is a curved seating ring 58 with its lower curved surface fitting a complementary corresponding surface of the annular ring 59 which in turn is secured about the opening through which the steel tube 55 passes by a series of bolts 60. A helical spring 62 is positioned about the steel tube 55 between the ange 61 and the curved seating ring 58, exerting an upward pressure on the steel tube 55. The platform 56 forms the bottom of the trough having side walls 63 which open at one side into a sluice-way 64. The sluice-way 64 in turn opens into some suitable tank (not shown), on the barge, which acts as a slush pit similar to the type used in the dry land operation.

It will be noted that in this construction the cooperation of the rings 58 and 59 permit the tube 51 to stay in its proper position irrespective of the rolling of the barge.

It will be clear from the above that the arrangement just described performs two essential functions in that it provides a means whereby drilling mud may be supplied to tube 50 and hence to the tool by conventional means and also provides a means of returning the mud from the tool to the slush pit via the annular space between the walls of the hole and tube 50 and between the tube 50 and the enclosing tube 53 to the slush pit from which it may be reused.

In starting such a drilling operation, the barge 49 carrying the above equipment would be secured at the desired location as shown in Figure 10 by semi-permanent moorings 65 spaced conveniently 120 degrees apart to minimize motion of the barge with respect to the chosen location. The tool and tool driving unit would then be lowered through the well and drilling commenced simply using water in place of drilling mud until a hole of sufficient depth has been drilled to permit of setting the bottom casing 53 (Figure 9), and cementing it in place. If care is taken to select a calm day for these initial operations, no difficulty should be encountered in drilling the hole for the surface casing, installing it and cementing it in place.

Once the above casing has been well cemented in place', the connection of the tube 51 to casing 53 may be made by a diver and the upper end of the tube 51 connected to the tube 55 by screwing the latter to it.

It will be noted that the above arrangement makes a very flexible and convenient method for drilling. For instance, if during the course of drilling the weather should become adverse, tube 55 may simply be unscrewed from the upper end of tube 51, after withdrawing tube 50 and the tool and driving mechanism which it supports, after which tube 51 may be temporarily capped by screwing a cap on its upper end and dropped overboard attached to a mooring float so that it can be readily retrieved later, and the barge may proceed to port to await better weather. In the meantime, hose 5l being of flexible material and submerged in addition, is no menace to navigation. When the weather moderates, operations can readily be resumed by reconnecting hose 51 to tube 55 after removing the barge.

It will be clear that drilling conducted as indicated above is not limited by the depth of water at the desired location as long as it is not too great for a diver to work in it, which may be as much as -200 feet, or very much greater depths than is possible where permanent platforms must be built to accommodate conventional drilling equipment. Not only is the cost of the drilling platform avoided, but operations can be sus- Apende'd andreinitiated ata new location witha minimum of 'time and expense. been Completed, the top of the casing may be connected to a valve, and suitable piping laid on the bottom to transmit the oil to some shore location so that subsequent Weather conditions will have no effect on utilizing the output of the Well and getting it to market.

With a mooring arrangement. such as is shown inFigure l0, even under adverse weather conditions,` it is not likely that the motion of the barge would exceed l feet either side of the chosen position. Thus in a depth of Water as'littleV as 50 feet, this would only mean a possible maximum angle away from the vertical of about Furthermore, when the Well. hasV 11.3 degrees and thiswould only involve an elongation 'of the tube 51 by about one footto take care of it, which may easily be Within the contracting abilityr of spring. 62. insofar as tube 50 is concerned, the natural stretch of it as limited by the Wires embedded within it underV load would undoubtedly be sufficient to take up such a small change especially. Vwhen drilling at more than the shallowest depths. In greater depths than 50 feet of Water, the angle would be proportionally less and the' take up or release required by spring 62 would be no more and perhaps less than would be encountered in fty feet of water.

Having now described my invention, I claim:

l. A means for earth boring, including a iluid drilling unit having a pair of mass elements, a resilient member interconnecting said mass elements, means for establishing said mass elements in resonant oscillation in opposite directions n a dynamic state of equilibrium including an expandible chamber partially formed by said mass elements and adapted on expansion. to move said elements in said directions, said last mentioned means also including a iluid conduit and valve means adapted to permit passage of lluid through said chamber for periodic expansion thereof, and a cutting tool secured to one of said mass elements.

2. A means for underwater earth boring adapted to be operated from a floating supporting structure comprising a fluid drilling unit having a pair of mass elements, a resilient member interconnecting said mass elements, means for establishing said mass elements and resilient member in resonant oscillation wherein the oscillation of one element will dynamically balance the oscillation of the other element, said means including an expandible means engaging each of said mass elements, a flexible tubular means secured at one end to the unit and at the other end to said supporting structure for supplying fluid under pressure to the expandible means causing said expandible means to expand and move said mass elements, pressure release means connected to the expandible means for periodically releasing fluid from the expandible means, and a cutting tool secured to one of said mass elements.

3. A means for earth boring comprising a drilling unit having a pair of coaxial tubular mass elements, means including coacting walls formed by said elements adapted to be moved arcuately with respect to the axis of the tubular mass elements to form between said mass elements an expandible chamber, means for introducing lluid pressure into said chamber for expansion of the same, means forming pressure release outlets in said chamber, means including elastic means interconnecting said mass elements adapted to cooperate with said'mass elements on movement of the said wall elements to establish a torsionally resonant oscillating system, aV cutting tool connected to and operated by one of said mass elements, and means for supplying drilling mud to said drilling unit.

4. A means for earth boring comprising a drilling unit having a pair of coaxial tubular mass elements,

'means including coacting walls formed by said elements adapted'to be moved arcuatelywith respect .to thevaxis of the tubular mass elements to form between said mass elements an expandible chamber, Ymeans for introducing fluid pressure into said chamberfor expansion, of the same, means forming pressure release outlets in said chamber, means including` a torsionally resilient tube having each end rigidly fixed to `a different one of said mass elements interconnecting the same and adapted to cooperate with said mass elements, on movement of said wall elements to establish a torsionally resonant oscillating system, a cutting tool connected andv operated by one of said mass elements, an-d means for supplying drilling mud to s'aid drilling unit.

5. In a means for underwater earth boring, a flexible unit for supporting and supplying power to a drilling unit, comprising a plurality of ilexib-le tubular members having interconnecting male and female elements at their ends, a plurality of longitudinally extending reinforcing metal wires in said tubular members anchored at their ends to sai-d male and female elements, an electrical conductor passing longitudinally through each of said tubular members and terminating in the male and female members at its ends in contacting members adapted to make an electrical contact with said contacting members of. adjacent tubular members.

6. In a means for underwater earth boring, a flexible unit extending from a supporting structure at the Water surface to a drilling unit within the earth, comprising a flexible tubular element for supporting and conveying drilling lluid to the drilling unit from the supporting structure, an outer flexible tubular element coaxial with the portion of the first mentioned element in the water, means including a spring member for resiliently and pivotally securing the upper end of said outer llexible element in said supporting structure and means for se'- curing the outer flexible tubularV element to the earth at its lower end.

7. ln a means for underwater earth boring, means for pivotally and resiliently supporting an upwardly extending flexible tubular element comprising a supporting structure, a rigid tubular end piece fixed to the upper end of said element with the end piece having an inwardly extending flange at its upper end, a bearing means spaced from said flange seating means secured to said supporting structure coaxial with and adapted to pivotally engage said bearing means, and spring means interposit'ioned between said flange and bearing means resiliently supporting said end piece.

8. A structure as set forth in claim 7 wherein said seating means comprises an annular ring having'a curved upper surface secured to the supporting structureV with said bearing ring having a curved lower surface complementary to and freely pivotable on said curvedupper surface.

9. ln a system for drilling, a resonant Vstructure having a torsionally resilient elongated member, a pair of mass elements secure-:l one each to each end of said member, said member and elements having an inherent resonant frequency of oscillation about the longitudinal axis of said elongated member, and means for establishing said structure in said resonant oscillation comprising a iluid pressure expandable chamber partially formed by each mass element and having a fluid inlet and pressure release outlet whereby on intro-duction of fluid pressure into said chamber it will periodically expand and contract at said frequency. y

10. A device as set forth in claim 2 providing resilient means securing said llexible tubular means at its upper end to said supporting structure.

ll. A means for earth boring comprising` a torque tube, a pair of coaxial cylindrical massvmembers coaxial with and firmly secured at spaced sections of said tube, means partially formed by and positioned between said members forming an expandible chamber, With opposite movable portions ofsaid chamber positioned-.normality and formed-by each of said members adaptedwhen moved to provide through said members "torque forces to said tube, means for supplying Huid to said chamber for expansion thereof, means for releasing periodically said iluid from said chamber, and a cutting tool secured to one end of said tube.

12. Means for torsionally operating a drilling bit, comprising a torque tube, means providing a driving connection from the torque tube to the drilling bit, two tubes coaxial with said torque tube one about the other and both about the torque tube, one of said two tubes rmly attached to one end and the other to the other end of said torque tube, and fluid operated expandible means between said tubes and partially formed thereby adapted to be periodically expanded and when expanded provide force components perpendicular to the torque tube at the ends of the radius of the torque tube comprising means forming a longitudinal recess in one of the two tubes and a longitudinal projection from the other of the two tubes partially occupying said recess and cooperating therewith to form an expandible chamber, means forming a uid connection from said torque tube to said chamber whereby a portion of fluid owing through said torque tube may be diverted for introduction into and expansion of said chamber, and means forming a pressure release opening for uid in said chamber comprising an opening positioned to be uncovered when said chamber has expanded to a selected volume.

13. A means for earth boring comprising a drilling unit having a cutting tool, a pair of coaxial cylindrical mass elements with one having a moment of inertia greater than the other, torsionally resilient means interconnecting said elements, means formed in part by each element providing an expandible chamber adapted to be expanded on relative movement of said elements, comprising means forming a longitudinal extending recess in one element with a longitudinally extending ange projecting from the other element and forming a movable wall in the other element, means for introducing fluid under pressure into said chamber for expansion thereof, means for periodically releasing said uid from said chamber and a cutting tool secured to said torsionally resilient means.

14. A means for earth boring including movable masses fixed to and coupled by a resilient member, means for providing periodic torsional forces for oscillating said resilient member and thereby oscillating said masses including expandible means formed between said masses with opposing movable portions of the expandible means formed by and positioned normal to the direction of movement of each of said masses, said movable portions adapted when moved to provide torque forces to said resilient member, means for supplying uid for expansion of said expandible means, means for periodically releasing said fluid, and a cutting tool secured to one of said masses.

15. A means for earth boring comprising a pair of mass elements, a resilient member interconnecting the mass elements, walls forming an expandible chamber with at least a portion of the walls formed by the mass elements, means including a uid conduit and valve connected to the chamber and adapted periodically to direct uid under pressure to the chamber for expanding the chamber to establish said mass elements in resonant oscillation in opposite directions in a dynamic state of equilibrium, and a cutting tool secured to one of the mass elements.

References Cited in the ile of this patent UNITED STATES PATENTS OTHER REFERENCES Vibration Problems in Engineering, pages 9-12 inclusive, second edition, by Timoshenko, published July 1937.