US2619324A

US2619324A - Percussion tool for wells

Info

Publication number: US2619324A
Application number: US5855A
Authority: US
Inventors: Bassinger Ross
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-02-02
Filing date: 1948-02-02
Publication date: 1952-11-25
Anticipated expiration: 1969-11-25

Description

Nv 25, 1952 R. BAsslNca'iER PERCUSSION '.foor.N FOR WELLS .s sheets-sheet 1 Filed Feb. 2. 1948 Nov; 25, 1952 R. BAsslNGgR PERCUSSION T001. FOR WELLS 3 Sheets-Sheet 2 1&5

Filed Feb. 2, 1948 ss/ngef @ame/gb Nov., 25, 1952 R, BAsslNGER 2,619,324

PERCUSSION 'OOL FOR WELLS Filed Feb. 2, 1948 3 Sheets-Sheet 5 Patented Nov. 25, 1952 UNITED STATES PATENT OFFICE 3 Claims.

This invention relates to new and useful improvements in percussion tools for wells.

The invention represents in many respects an improvement over my co-pending application, Serial No. 686,497, led July 26, 1946, now Patent No. 2,507,585 issued May 16, 1950.

It has been a wide-spread occurrence in the drilling industry, that in drilling wells in certain localities or elds, very hard and rocky formations are sometimes encountered which are very diflicult to drill, resulting in uncommonly high drilling expenses, and at the same time, very slow progress in drilling operations. The usual rock type bits have not proved effective on these formations, as little as one foot of hole drilled before it is necessary to pull the tubing and replace the bit being a fairly common occurrence. Obviously, such conditions greatly delay the completion of a well with the corresponding increase in expenses, as well as creating highly undesirable collateral conditions which are not favorable to the driller.

Heretofore, various percussion type bits have been developed and tried in drilling operations. At the present time, none of these bits have proved successful or answered the need for a drilling assembly capable of eicient operation under the unfavorable conditions usually encountered, or even under favorable conditions.

In some instances, attempts have been made to use a cable tool type bit, but necessarily, such operations were not satisfactory after a certain depth of hole had been obtained.,

It is therefore, one object of this invention to provide an improved percussion tool adaptable for use with a drill bit, which is eiective and operative under normal conditions within a well bore, to deliver a series of hard blows to a drill bit, or to other suitable tools and connections within a drill string.

It is an important object of the invention to provide an improved percussion tool for use in wells, which is responsive to flow .of the drilling uid through a well conductor to deliver intermittent blows of considerable magnitude and force to a drill bit, or other connection in the drilling string.

A further object of the invention is to provide an improved percussion tool having a hammer which is given momentum by the flow of the drilling iiuid and with which blows of considerable intensity and magnitude may be delivered to a suitable connection in a drilling string.

Still another object of the invention is to provide an improved percussion tool for use in wells wherein the upper end of a hammer is adapted to be acted upon by the flow and pressure of the drilling fluid to impart a downward impetus to the hammer, and wherein means are provided coacting with the `upper end of the hammer to react also to the drilling uid and move downwardly as does the hammer, said latter means being stopped a-nd returned to its upward position before the hammer has completed its downward travel under the momentum imparted thereto, so as to receive the upper end vof the hammer upon the return of the latter to its upward position and to commence a subsequent downward travel of said hammer, whereby intermittent blows of considerable intensity are delivered by the hammer to a drill bit or other suitable means.

Yet another object of the invention is to provide an improved percussion tool of the char acter described wherein the portion of .the hammer acted upon by the pressure of the .drilling Huid may rotate with respect to the hammer while being prevented from undergoing longitudinal movement with respect thereto.

Still another object of the invention is to provide an improved percussion tool of the character described wherein a dash-pot structure is provided for the means coacting with the upper portion of the hammer in reaction to the drilling iiuid, said dash-pot means reducing the mechanical shock `imparted to the coacting means as the latter moves upwardly and downwardly within the 4percussion tool.

Another object of the invention is to provide an improved percussion tool having a hammer adapted to react to the iow and pressure of drilling fluid to deliver a series of impact blows wherein `the hammer suspended within the tool from a tension type spring or other type of resilient or tension exerting element.

Yet another object of the invention is to provide an improved percussion tool of the type described having a control sleeve which coacts with the rhammer to cause the latter to reciprocate, wherein the control sleeve is suspended within the tool by a plurality of tension type springs.

A particular object of the invention is to provide an improved method of drilling wells wherein blows of considerable magnitude are imparted to a rock type bit or a roller bit while said bits are being rotated so that substantially all of the` advantages owing from the use of roller bits are realized in addition to those advantages resultant from percussion drilling.

A construction designed to carry out the invention will be hereinafter described together with other features of the invention.

The invention will be more readily understood from a reading of the following specication and by reference to the accompanying drawings, wherein an example of the invention is shown, and wherein:

Fig. 1 is a longitudinal sectional view of the upper portion of a percussion tool constructed in accordance with this invention,

Fig. 2 is a continuation of Fig. 1 and showing A v A the next lower portion of the tool,

Fig. 3 is a continuation of Fig. 2 and illustrating the next lower portion of the tool,

Fig. 4 is a continuation of Fig. 3 and showing the lower end of the tool,

Figs. 5 through 9 are horizontal, cross-sec tional views taken on the corresponding lines of Figs. 1 through 4,

Fig. 10 is a longitudinal, sectional view of a percussion tool constructed in accordance with a modification of this invention,

Fig. 1l is a continuation of Fig. 10, with its lower end broken away, and illustrating the next lower section of the modied form of the invention, and

Figs. 12 through 16 are horizontal, cross-se.,- tional views taken on the corresponding lines of Figs. 10 and 11. 1

In the drawings, the numeral I designates the uppermost section of the tubular housing within which the percussion tool is contained. The section I0 carries a reduced, upwardly extending, screw-threaded pin II upon its upper end for connecting the device to a suitable drilling string, and the pin is provided with an axial bore I2 to which drilling fluid or mud may pass to the interior of the section I0. The lower end of the section is provided with tapered, internal screw-threads I3 which receive the screw-threaded upper end of the next lower housing section I4. Because of the tapered structure of the threads I3, the inside and outside walls of the sections I0 and I4 are substantially continuous and no loss of internal diameter or excessive increase of outside diameter of the housing results.

A spider I is disposed within the lower portion of the section I D and carries an annular marginal collar IB which rests upon an internal, annular shoulder I1 formed in the upper portion of the section I4. The spider I5 is thus held against downward movement with respect to the housing. The spider is provided with a plurality of radially extending webs I8 which are connected between the collar IG and a central, vertical sleeve I9. The upper end of an eye bolt 2D extends through the sleeve I9 and receives a suitable nut 2I above said sleeve so as to limit downward movement of the bolt with respect to the spider. An elongate coiled spring 22 or other type of resilient or tension-exerting element depends from the eye of the bolt 2D and extends downwardly through the bore of the section I4. The spring 22 is relatively heavy and large in diameter so as to be capable of carrying considerable loads yet to undergo the desired elongation when such are applied. l

The housing I4 extends below the lowermost point of expansion of the spring 22 and is provided with internal, tapered screw-threads 23 which receive the screw-threaded pin 24 of'a connecting nipple 25. The nipple 25 is of relatively heavy walled construction but has an outside diameter substantially equal to the outside diameter of the sections I0 and I4. A reduced screw-threaded pin 26 is provided upon the lower end of the nipple and receives the upper end of a third housing section 21 similar to the section I4. A reduced-diameter, depending skirt 28 is formed upon the lower extremity of the pin 26 and projects downwardly into the interior of the housing section 21. Radial ports 29 are cut inA the upper portion of the skirt 28 so as to permit drilling uid to enter the annular space 30 between said skirt and the inner wall of the section 21.

A second nipple 3I is secured to the lower end of the section 21 by a screw-threaded joint 32, said nipple having a reduced-diameter sleeve 33 of considerable length extending upwardly into the interior of the section 21 to a point spaced a short distance below the lower edge of the skirt 28. The sleeve 33 is provided with a smooth axial bore 34 within which an elongate control sleeve 35 has a snug sliding t. The upper edge or end of the sleeve 33 is rounded as shown at 36, and the upper end of the control sleeve 35 is enlarged to form an integral, external, annular ring or flange A31 about said upper end 0f the control sleeve. The ring 31 carries an annular groove 38 in its underside, the groove being semi-circular in cross-section so as to receive the rounded upper end 36 of the sleeve 33. A collar 38 encircles the upper portion of the sleeve 33,` the latter having a sliding fit within the bore of the collar which abuts the underside of the ring 31. The collar is provided with an upstanding marginal lip 39 which lits snugly within a complementary marginal recess 48 provided on the underside of said ring 31.

A suitable compression spring 4I of the coiled type is conned between the lower edge of the collar 38 and the upper end of the nipple 3|, said spring encircling in a relatively snug fashion the outer periphery of the sleeve 33. Thus, the spring serves to urge the collar 38 and therefore the control sleeve 35 upwardly with respect to the sleeve 33 so as to cause the ring 31 to abut the bottom edge of the skirt 28. The control sleeve is free to undergo reciprocal movements within the bore 34, but the spring 4I constantly urges said sleeve upwardly within said bore.

A lower housing section 42 is screw-threadedly connected to the lower end of the nipple 3| and carries an elongate hammer 43 of considerable mass. A cylindrical recess 44 is formed in the center of the upper end of the hammer and receives the enlarged lower end 45 of an elongate cylindrical control piston 46. Chordal bores 41 are cut in the upper end of the hammer and the enlarged portion 45 of the control pistons, said bores being so disposed as to have their center axes tangential to the cylindrical side wall of said enlarged portion 45. Suitable pins 48 are positioned within the bores 41 and by engaging partially within the upper end of the hammer and partially within the enlarged section 45 lock the two elements together and prevent their longitudinal separation. If desired, that portion of the bores 41 which is formed within the enlarged lower end 45 of the control piston may be in the nature of an annular groove 41', semi-circular in cross-section and extending circumferentially of the portion 45 at this point. Such a structure would permit rotation of the portion 45 within the recess 44 while retaining a secure fastening action. An annular groove49`is cut in the wall of the recess 44 adjacent the lower end thereof and receives a distortable packing ring 50 having a circular cross-section. The ring 50 may be formed of synthetic rubber or any other suitable material and serves to pack off the space between the portion 5 of the control piston and the inner' wall of the recess t4.

The control piston i5 is of such an outside diameter to have a snug sliding it within the bore 52 of the control sleeve 35. If desired, the lower end of the control sleeve and the upper end of the piston may be chamfered so as to permit the ready entry of the piston into the sleeve.

For the purpose of suspending the hammer 43 within the section d2, an elongate, flexible metallic cable 53 is provided with an eye 54 and a thimble t5 at its upper end which receive the lower end of the spring 22. The cable 53 extends axially downwardly through the bores of the section It, the nipple 2d, the section 21, and the control sleeve 35, into an axial bore 56 provided in the control piston d6. The bore 56 extends entirely through the control piston 46 and the enlarged portion fili on the lower end thereof, the lower portion of said bore being enlarged within the portion l5 to form a cable socket 5l. That portion of the cable which extends into the socket 'l may be spread and secured therein by the addition of molten metal in the usual fashion. In this manner, the control piston and the hammer are suspended by means of the cable from the spring 22 s0 that the latter constantly urges the hammer upwardly within the housing section 42.

The hammer d2 is of solid cylindrical construction and has an outside diameter less than the inside diameter of the housing section l2 so that an annular now space 53 is provided for the passage of drilling fluid. Near its upper end, the hammer carries radially extending, longitudinal guide ribs 5S which bear against the inner periphy of the section l2 and center the hammer within said section while guiding said hammer in its longitudinal movement within the section. The .flutes @e between adjacent ribs 59 are deepened so as to extend into the body of the harnmer to provide additional flow space for drilling fluid between said ribs. Similar guide ribs 5i are provided at a point near the lower` end of the hammer and cooperate with the guide ribs 59 to maintain the entire length of the hammer substantially centered within the bore of the section 2 while permitting the hammer t0 undergo longitudinally movement therewithin. Because the flow of drilling iiuid between the ribs 6l is reduced, it is not necessary to deepen the flutes between said ribs by cutting them into the body oi the hammer.

An enlarged striking head 62 is formed upon the lower extremity of the hammer and an axial bore E3 extends upwardly through said head into the body of the hammer, said bore terminating at a point spaced above the lower guide ribs 6|. Above said guide ribs, the hammer is provided with a plurality of radial ports Sli extending outwardly from the bore G3 and communicating between said bore and the annular space exterior of the hammer. Thus, drilling iiuid passing downwardly through the annular space 58 may enter into the ports S4 and pass downwardly through the bore 63 to the lower portion of the tool. At the same time, the guide ribs ap'rmit a certain portion of the drilling fluid to pass downwardly exteriorly of the hammer and keep the annular space between the lower end of the ham-mer and the housing section d2 clear of for- 6 eign matter while also preventing the trapping of iiuid within said space.

Internal screw-threads 55 are formed at the extreme lower end of the lower housing section 42 to receive the screw-threaded 56 of a retaining collar Sl. A tubular sleeve t8 extends upwardly from the pin 65 and has a snug t within the lower portion of the housing section 42. A bit carrier 69 is disposed at the lower end of the section #l2 within the collar Sl and is provided with a reduced, tapered, screw-threaded pin 'i5 at its lower end. A tubular shank ll extendsv upwardly from the bit carrier and is provided with an axial bore l2 vertically alined with the bore 63. The upper end of the shank forms an anvil 'i3 upon which the hammer d2 is adapted to strike. Radial ports ifi are provided in the side walls oi the shank near the upper end thereof to permit the circulation of drilling fluid between said shank and the inner periphery of the section d2. A plurality of radially extending splines l5 are formed upon the exterior of the bit carrier and engage within complementary grooves 'iii extending longitudinally of the interior of the retaining collar 67. The splines permit the bit carrier to undergo longitudinal movement with respect to the retaining collar, but present rotative movement 1between the two elements. The splines T5 are less in length than the grooves 'iti so as to permit said movement. However, the grooves terminate short of the bottom of the retaining collar 6l' so as to provide shoulders Tl which receive the splines 'I5 and limit the downward travel of the said carrier with respect to the collar 6l'.

A bit 18, which may be of any desirable type has its screw-threaded box lil engaged by the pin 10, whereby the bit is rigidly secured to the bit carrier 69. The bit is provided with the usual drilling iiuid passages 8l) which communicate with the bore 12 and permit the now of drilling fluid.

A pressure responsive type packing ring 8l is recessed in the outer wall of the shank 'l and engages the inner periphery of the upstanding sleeve 68. This packing ring serves to prevent the 'Elow of drilling fluid downwardly between the shank and the retaining collar 6l, any drilling fluid which reaches this point of the tool being thereby forced to pass through the radial ports 14.

In the operation of this device, the entire assembly is lowered into the well bore upon the usual drilling string (not shown) until the bottom of the hole is reached. A certain amount of weight upon the bit is desirable to allow the splines 15 to ride downwardly within the grooves 16 and eliminate any direct connection between the tubing string and the bit assembly. The lower end of the retaining collar 6'! rests upon the enlarged upper end of the bit, or is elevated slightly thereabove so as to protect the splines 15 against the impact blow delivered by the hammer Q2. Upon starting the mud pump (not shown), drilling fluid or mud is circulated downwardly through the drilling string under pressure and passes through the bores of the sections lli and I4 into the interior of the control sleeve 35.- The drillingY fluid may also ilow through the ports 29 to insure ample circulation about the spring di and within the annular space between the sleeve 33 and the housing section 2l.

Prior to the starting of the circulation of drilling fluid, the spring 4| will maintain the control sleeve pressed against the lower end of the skirt 7 28. At the same time, the spring 22 will hold the control piston 46 and the hammer 42 in their upper position wherein said piston telescopes the lower end of the control sleeve 35.

The pressure under which the drilling fluid is pumped through the tubing is dependent upon the particular well or field and may vary considerably. Usually, the deeper the well, the higher the pumping pressure used, values as high as 2,000 pounds per square inch or higher, sometimes being used. About 250 to 300 pounds per square inch pressure is required to operate the present percussion tool. This, of course, is pressure at the tool itself. Therefore, the pumping pressure already being used may be sufficient or an increase in pressure of 200 to 300 pounds may be required to operate the tool.

The pressure at the tool, which may be anything from several hundred pounds to a thousand or so pounds per square inch, acts upon upper end of the piston 46 and also upon the control sleeve 35. Since the spring 4| is not as strong or stiff as the spring 22, the control sleeve is forced downwardly compressing the spring 4|. Due to the pressure of the drilling fluid, this downward movement is very rapid and occurs very quickly. The control sleeve travels downwardly until the upper end of the sleeve 33 seats within the groove 38. It is pointed out that the enclosing of the upper end of the sleeve 33 between the sleeve 35 and the collar 38 affords a sizable dash-pot action which eliminates to a considerable extent the shock delivered to the control sleeve when seating upon the upper end of the sleeve 33 under the influence of the relatively high pressure of the drilling fluid. Upon seating of the control sleeve, further downward movement of the latter is prevented.

The downward movement of the control sleeve relieves to some extent the pressure of the drilling fluid acting upon the piston 46, and diverts the flow of the fluid therefrom. However, as soon as the sleeve reaches the bottom of its stroke, the full pressure of the drilling fluid as well as the impact resultant from its momentum is directed upon the piston, thereby forcing the piston and hammer downwardly with great rapidity so as to impart considerable velocity and momentum to the hammer while overcoming the force exerted by the spring 22. The weight of the entire column of drilling fluid within the tubing string is behind this impact, so that there is no hesitation in the fiow of the drilling uid, the force brought to bear on the hammer being sufficient to eliminate any delay in its downward movement.

As the hammer moves downwardly, the piston is withdrawn from the bore 52 of the control sleeve. When this occurs, the drilling uid is permitted to flow through the bore into the lower part of the tool, while the hammer continues its downward travel under momentum until the lower end of the hammer strikes the anvil 13 and delivers a blow thereto, which is transmitted through the bit carrier 69 to the bit 78. As soon as this blow is delivered, and the momentum of the hammer is dissipated, the spring 22 is free to return the hammer to its upper position.

The piston is withdrawn from the bore 52 before the hammer strikes the anvil. Otherwise, a fluid lock would occur, and the operation of the device would be impaired if not terminated altogether. However, the time interval or the distance traveled by the hammer after such withdrawal is very small, so that the hammer delivers this blow at substantially peak momentum and velocity. By varying the spacing of the elements so as to change this time interval, the frequency and magnitude of the blows struck may be controlled.

It is not necessary that the piston have a close t within the control sleeve and a certain degree of by-passing of the drilling fluid between these elements will not substantially impair the operation of the tool. Nor is it necessary that the control sleeve reach the lower end of its stroke before the hammer starts to move downwardly. As the spring 4| is compressed, the back pressure on the piston increases, and the critical value necessary to start downward movement of the hammer may be reached well before the sleeve nears the bottom of its stroke, so that when the sleeve does reach its lowermost position, downward movement of the hammer is already well under way.

It is pointed out that as soon as the piston has withdrawn from the control sleeve the pressure acting upon the sleeve is relieved and the latter is returned to its upper position by the spring 4|. As the hammer is returned to its upper position by the spring 22 following the striking of the blow, the control piston is moved into the control sleeve and the latter immediately is moved downwardly by the pressure of the drilling fluid so that a second cycle is commenced. The design and proportions of the various elements of the tool control, to some extent, the frequency of the impact cycles. Several hundred blows per minute upon the anvil '|3 may be obtained, and due to the considerable mass of the hammer, these blows are of large force and power.

It is also pointed out, that as the hammer moves upwardly, the drilling fluid exerts an increasing pressure upon the control sleeve whereby the sleeve may start its downward stroke or travel before the piston and hammer reach their uppermost position. Thus, at this moment the sleeve and the piston would be moving in opposite directions. |This function is dependent upon the design and proportions of the various elements, but in any event, the sleeve would start its downlzard travel as soon as the piston enters the bore In drilling operations, the drilling string may be rotated at the same time that mud is being pumped downwardly through the string, so that the bit 'I8 is rotated over the surface being drilled, and at the same time, several hundred blows of considerable magnitude are delivered each minute through the lower cutting edges of the bit to the formation. In this manner, very fast and efficient drilling of extremely hard formations is obtained while preserving the other desirable characteristics of rotary drilling.

It is to be noted, that the ow of drilling uid through the port 8D of the bit 18, is never interrupted but a continuous lubricating and flushing action is maintained. This worth-while result is obtained by reason of the structure of the piston and control sleeve. As soon as the piston enters or nears the control sleeve on its upward travel, communication through the bore 52 of the control sleeve is reduced or minimized; but, the sleeve immediately begins to move downwardly, thereby displacing drilling uid therebelow. And, as the sleeve nears or reaches the lower end of its stroke, the hammer is moved downwardly displacing additional uid. This action is very rapid, and by this means uid continues to move downwardly at all times during the cycle. The frequency of the cycles is suiiiciently high to insure very little pulsation of the drilling fluid.

In my earlier invention, as set forth in my co'- pending application, Serial N o. 686,497, filed July 26, 1946, the hammer was adapted to be returned to its upper position by means of a compression type spring which encircled a portion of the hammer. Being of a compression style, this spring is subject to columnar stresses and tends to wear and abrade to some extent due to its position in between the hammer and the inner wall of the housing. In the present invention, this problem is overcome through the utilization of the tension-type spring at resilient type 22. This spring remains at all times under a certain minis mum degree of tension, or, in other words, a certain minimum tensile stress is constantly applied to said spring. This stress reaches a substantial minimum when the hammer is at the uppermost point of its travel, and reaches a substantial maximum immediately before the hammer strikes the anvil i3. Being thus under a constant tensile stress, the spring 22 retains a straight line position between the eye bolt 2@ and the upper end of the cable E3. It is not subjected to columnar stresses and does not tend to bow under the applied load and thus abrade against the inner surface of the housing section Id. At the same time, the employment of the iiexible cable 53 compensates for minor misalinements of the various elements and aids in guiding the piston 5t into the bore 52 of the control sleeve 35.

This same desirable result may be achieved with respect to the control sleeve spring 4| which may be replaced by tension-type springs as illustrated in Figs. through 16 of the drawings in the modification of this invention. The structure employed for this modied form of the invention is substantially identical in most respects to that previously described, and only those portions which are altered have been illustrated.

In this modiiication, the upper section lil is replaced by a nipple 82 having an upstanding screw-threaded pin 83 which engages the lower end of the tubing string (not shown). The next lower section 8d of `the housing is extended upwardly and screw-threadedly connected to the lower end of the nipple 82 at `85. The axial bore 86 of the section Sil is reduced in diameter near the upper end of the section so as to form an internal, annular, boss 3l having a counter-bore 88 in vertical alinernent with the bore 85. A pair of diametrically opposed longitudinal grooves Si! are cut in the wall of the bore 88 and extend downwardly from the upper end of the boss 81 to a point near the central portion thereof. A transverse supporting plate Se engages within `the groove 89 and carries a depending eye rod 9| which may be welded or otherwise suitably secured to said plate. The upper end of the hammer spring or tension-exerting element 22 is received within the eye El `and supported thereby, and the upper end cf the cable 53 is suitably connected to the lower end of said spring. The cable extends downwardly through the balance of this modification of the tool and is secured to the control piston 45 in the manner as previously described.

The lower end of the section S4 is connected by a screw-threaded joint 92 to the upper end of the next lower housing section 93. The section 93 is formed with an internal annular shoulder Si?. near its upper end, said shoulder receiving an annular supporting ring 95 which has 'a snug sliding t within the bore of the upper porltion of said section 93. The ring is provided at its lower end with an inwardly extending annular flange St which carries a plurality of downw-ardly extending supporting bolts or pins 91. A suitable coiled, tension-type, spring 98 is secured to the lower end of each of the pins 91, and the lower ends of the springs :98 are in turn secured to the upper ends of a plurality of supporting pins 99 projecting upwardly from the flanged upper end leo of a control sleeve IUI. The control sleeve has a sliding lt within the bore EQ2 of a nipple |03 secured to the lower end of the housing section 33 and has its lower end projecting below the lower end of said nipple. The upper end of the housing section i2 is secured to the lower end of the nipple |03, and the balance of the tool from this point downward is the same as that previously described.

A suitable resilient packing ring HB4, which may be formed of synthetic rubber or any other suitable material, is partially recessed within the outer periphery of the control sleeve adjacent the lower end thereof, the ring lila being greater in thickness than the depth of the recess |05 in which it is positioned so as to project radially outwardly from -all sides of the control sleeve. The ring is adapted to engage within an annular box m3 cut into the lower end of the nipple |03 so as to surround the control sleeve, such engagement taking place when the sleeve moves upwardly within the bore |82. The side wall of the box we is tapered or inclined so that as the ring |36 moves into the box, it encounters increasingly restricted clearance. For this reason, the ring and the box function as :a dash-pot when the control sleeve moves upwardly, and the ring |65 operates as a gently-acting stop ring to limit the upward travel of the control sleeve. The ring may at times engage the bottom or upper end of the box HBS and in such instances operates as -a positive stop. However, because of the uid always present within the box and the balance of the tool, the stopping action of the ring comes into existence with some degree of slowness as the ring, in moving upwardly with the control sleeve, moves into the progressively restricted box |06.

The control sleeve is limited in its downward travel by the engagement of its iianged upper end les with the upper end of the nipple |03, so that when the tool is set in operation, ra positive limit of downward travel for the control sleeve is provided. A dash-potting action is also achieved in accomplishing this stopping function since the upper end of the nipple |03 is counter-bored to form a shoulder |01 upon which the flange |08 seats. The side wall |93 of the counter-bore is flared outwardly so that, as the iiange |00 moves downwardly, it encounters increasing resistance to the displacement of the fluid present between it and the shoulder |87. In this manner, the control sleeve is prevented from seating with destructive :force and velocity upon the shoulder lill, and is caused to engage said shoulder in a Somewhat more gentle fashion and with the yabsence of any mechanical damage.

rlhe utilization of the tension type springs 98 in place of the compression type spring il results in the same advantages and improvements as the replacement of the coiled type compres sion spring for the hammer d2 with the tension type spring 22. The columnar stresses to which the spring 4l is subjected are eliminated, and the resultant wear upon the spring means for support of the control sleeve is eliminated. In addition, by the utilization of a plurality of springs rather than a single spring, mechanical failure is rendered less serious since the percussion tool may continue to operate even though one of the springs 98 has given way.

It is not deemed necessary to provide a detailed description of the operation of this modification of the invention since the functions of the various elements remains substantially the same as previously described. The major differences between the first and second forms of the invention reside in the replacement of the compression type spring 4| with the tension type springs 98, and the modified structure of the control sleeve and its support for affording dashpot action in both directions of movement of said sleeve.

This invention also contemplates an improved method of drilling wells. and in particular, oil wells wherein deep holes of sizable diameter must be forced through earth form-ations of varying degrees of hardness and diculty of drilling. Heretofore, roller type bits have implemented the most successful method of drilling, such method involving rotation of the bit while applying a constant or very slowly changing load or pressure upon said bit.

As previously pointed out, it is preferable to employ a roller type bit with the percussion tools set forth herein, such preference arising from the new method of drilling which ensues. By mounting a roller bit of the type normally employed for drilling hard formations upon the present percussion tool or any other suitable tool capable of delivering a series of impact blows while rotating the bit, extremely eiiicient drilling is obtained. Therefore, this new method broadly encompasses the combination with a percussion tool of a roller bit with the steps of rotating such a bit while delivering impact blows thereto forming the essential portions of the method. Greatly increased drilling speeds have been realized through the utilization of this method in practical eld tests carried out in wells being drilled. Substantially all of the advantages of a roller type bit are retained, while the additional advantages of the percussion tool are added so that the formation is chipped, crushed and broken while at the same time being cut and ground through the rotating of the roller bit.

The foregoing description of the invention is explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction may be made, within the scope of the appended claims, without departing from the spirit of the invention.

What I claim and desire to secure by Letters Patent is:

1. A well percussion tool which comprises a tubular housing, an inlet for the supply of mud fluid to said housing, a mud outlet from said housing, two elements in said housing mounted for axial reciprocation relative thereto, one of said elements having the form of a sleeve fitting slidably in an opening formed by a radially inwardly extending portion of said housing, said portion having an annular recess therein around said sleeve with the wall of said recess tapering toward the sleeve, an outwardly radial circumferential projection from said sleeve of such size as to substantially fill the narrowest portion of said recess when moved thereinto by said sleeve to thereby coact with the sloping wall of said recess and effect a dash-pot action therewith to limit the movement of said sleeve, the other of said elements having the form of a piston fitting slidably in said sleeve, said two elements forming a valve to control the now of mud through said housing from said mud inlet to its outlet, a hammer attached to said piston for reciprocation therewith, a first elastic means for urging said sleeve upwardly, a second elastic means including a coil spring secured to the housing above said sleeve, a cable connecting said piston to said spring, said spring acting in tension to return said piston to its initial position in engagement with said slidable sleeve after said hammer has been forced downwardly in said housing.

2. The tool of claim l wherein said portion has a second annular recess therein facing oppositely from rst said annular recess, the wall of said second recess also sloping inwardly toward said sleeve, a second outwardly radial circumferential extension from said sleeve of such size as to substantially ll the narrowest portion of said second recess when moved thereinto by said sleeve to thereby coact with the sloping wall of said second recess and eiect a dash-pot action therewith and to limit the extent of movement of said sleeve in a direction opposite to that in which it is limited by rst said projection and recess.

3. The tool of claim 2 wherein said rst elastic means is a coil spring connected to said housing and said sleeve and acting in tension to move said sleeve upwardly.

ROSS BASSINGER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Numlber Name Date 1,522,809 Collins Jan. 13, 1925 1,798,480 McCullough Mar. 31, l931 1,861,042 Zubln May 31, 1932 1,892,517 Pennington Dec. 27, 1932 2,102,754 Shannon Dec. 21, 1937 2,224,439 Lee Dec. 10, 1940 2,245,786 Johnson June 17, 1941 2,344,725 Phipps Mar. 21, 1944 2,350,779 Lapkoff June 6, 1944 2,441,881 Hays May 18, 1948 2,459,689 Dickey et al Jan. 18, 1949 2,507,585 Bassinger May 1G, 1950 FOREIGN PATENTS Number Country Date 121,091 Germany 1901