US3301009A - Rotary shock absorbing sub unit - Google Patents

Description

WLDMMELH Jar ROTARY SHOCK ABSORBING SUB UNIT Filed Feb.

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United States Patent O asoman RGTARY SHCK ABSRBING- SUB UNIT .lohn B. Coulter, Jr., Fort Worth, Tex.,. 'assignor`to Chicago Pneumatic Tool Company, New Yon-k, N.Y., a corporation ot New Jersey Filed Feb. 2, 1965. Ser. No. 429,797

` 4 Claims. .(Cl. 64;;23)

This invention is directed toa shock absorbing sub unit for use in the drill string Aof, a rot-aryI earth-boring drill. The conventional rotary earthsboring drill comprises a string of drill pipe at thebottomof which is carried a rotary bit. Rotation of thestringis transmitted to the bit. As the latter rotates, cutters at lthe bottom thereof bore down into the earth. As ,the depth ofthe hole increases,l

lengths of pipe are added as needto the drill string. During drilling operations, drilling tluid is fed through the drill string and bit tothe bottom o-f the hole to aid inthe progress of the work. As the bit is rotated and the cutters roll over the bottom of the hole, vertical vibrations or bounce develop, and are transmitted-back through the drill bit to the `drill string. Vibrations are also produced by other causes,- suchas impacts to the `drill string occurring when the drill is beinglowered into a hole. The thrust or roughness of the vibrations varies according to the earth formations encountered. They are' particularly strong in rough drilling operations, such as where `fractured har-d formations and alternate strata of hard and soft Iformations are encountered. Broken bit teeth, damaged cutter bearings, twisting and failure of sections of the drill string, jammed or -frozen joints, and damage to surface equipment, as well as other damage often result from vibrations developing during drilling operations. The possibility of 4dam-age from vibrations to the drill bit and drill string becomes greater as the depth of the hole and the consequent weight of the drill string increases. Increased rotary speed coupled with undesirable vibrations and a long drill string often result in undesirable twisting and breakage of the drill string. To avoid the possibility of costly damages in rough drilling operations, the-speed of penetration and the weight load on the bit are limited by the operator. This undesirable precaution slows the dri-lling operation, and often results in a hole of relatively shorter depth than mig-ht otherwise be obtained.

The general object of this invention is to provide in a rotary earth-boring Adrill practical and economical means for effectively absorbing vibrations and shocks produced duringearth-boring operations, so as to prevent them from damaging the drilling apparatus. This will save not only the costly expense of repairs and replacement of drilling equipment that might otherwise occur, but it will also enable relatively longer strings to be used, deeper holes to be drilled, and increased rotary speed to be irnprarted to the drill stri-ng. The present invention, whereby these benecial results are obtained and whereby undesirable vibration problems associated with earth-boring drilling operations are substantially solved, represents a desirable technical advance in this particular art.

A further and more specic object of this invention is to provide in the drill string of a rotary earth-boring drill a sub unit for accomplishing this gener-al object. It functions to not only materially absorb and dampen the shocks and vibrations produced during drilling operations, but also functions to transmit the torque of the drill string to the drill bit. This sub unit is preferably located in the drill string just above the drill bit.

A4 feature of the sub unit is a shock assembly comprising a long stack of resilient shock absorbing elements which effectively prevents vibrations occurring during drilling operations from harmfully atecting the drill string. The shock absorbing elements are so arranged in the sub unit that they are protected from attack by settima Patented Jan. 31, 1967 2i drillingnuidnand `destructive drill dust. Another advantage ofthe desirable arrangement'ot the' shock absorbing elements-is that they are separate from one another and maybe individually replaced when w-orn.

. A feature of the shock absorbing elements lies in their particular configuration and in the arrangement of each element between la pair of metal surfaces, whereby compressive action upon'the elements causes them-to become compressed axially and expanded radiallyv to the full extent of their ow characteristics.l

A still furtherfeature of the sub unit is a squared drive shank `which functions to transmit rotary torque'from a driving ,mandrel coupled to the drill string directly toan inner mandrelcarrying the drill bit without any of such torque vpassing through the shock assembly.

In the `accompanying drawings:

FIG. 1 is an elevational View of a bodyin g theinvention; v

FIG. 2 is an enlarged view of a section taken on line 2--2 of FIG. l;

FIG. 3 is a detail .view,'partly in section, of one of the rotary sub unit em` n shock absorbing rings;

FIG..4 is a detail View, partly in section, of one ot the metal spacer rings;V v

FIG. S is a` fragmentary view similar to FIG. l but showing the sub unit in fully loaded or closed condition;

FIG. 6 is a fragmentary view of the sub unit in a partially loaded condition between that of FIGS. l and 5; and

FIGS. 7,-8 and 9 are respectively enlarged views of corresponding portions of FIGS. l, Sand '6 for purposes of comparison.

Reference is now directed to the several gures of the drawings wherein there is disclosed a shock absorbing sub unit generally designated 10. It is adapted to be axially aligned and coupled at one end with a string 11 of drill pipe in a rotary earth-boring drill. It is adapted to be coupled at its opposite end with a rock bit 12. Rotation of the drill string 11 is transmitted through the shock absorbing sub unit 10 to the bit to cause conventional roller cone cutters (not shown), mounted to the bottom of the bit to bore into the earth. Vertical vibrations or bounce developed by impact of the bit and ro tation of the cone cutters during drilling operations are transmitted upwardly through the bit to the sub unit.

. Incorporated in the sub unit is a shock absorbing means or assembly 13 which materially dampens and absorbs these vibrations so as to prevent them from being transmitted from the sub unit upwardly to the string of drill pipe 11. An axial passage 14 through the sub unit serves to allow ow of the usual drilling uid from the drill string to the drill bit. This fluid flows through conventional passages in thelatterto the bottom of the hole where it aids in the' progress of the drilling operation.

The sub unit includes an outer cylindrical open-ended driving mandrel 15.` The latter is adapted to be connected by means of a coupling 16 to the drill string 11 for rotation as a unit with'the latter. The coupling 16 has at one end a screw pin 17 adapted to be screwed into an internally threaded axial recess or box 18 of the drill string 11; and it has at its opposite end a similar screw means of a polygonal or squared shank portion 25 which is engaged in a complementary socket 26 formed in the bottom end of the outer mandrel. The shank portion 25 has axial sliding movement in the socket 26. An annular shoulder 27 at the lower end of the squared shank is cooperable with an overhead end wall 28 of the socket 26 to limit the extent of relative upward movement of the shank portion.

The extent of downward and outward movement of the shank portion relative to the socket is Curbed by an open-ended cylindrical safety header 29 attached to an elongated reduced cylindrical stem 31 at the upper end of the inner mandrel. The attachment of the safety header 29 and stem 31 is defined by a uid tight threaded connection at 32 in which the lower end of the safety header is screwed over the lupper end of the stem. A radially extending plug 33, here of nylon plastic, in the stem 31 may be employed to strengthen the tightness of the connection 32. A shoulder 34 defined by the bottom end wall of the safety header is cooperable with a stop defined by an annular shoulder 35 of a radial internal flange 36 of the -outer mandrel to limit the extent of downward movement of the inner mandrel relative to the outer mandrel. Below the threaded connection 32, the stem 31 has an axial slidable relation with the annular inner diameter wall of the iiange 36. Because of the threaded connection 3.2, the safety header 29 is slidable axially as a unit with the inner mandrel relative to the outer mandrel. In this movement, the safety header bears against a surrounding inner wall area 38 of the outer mandrel 15. The safety header further serves to prevent the inner mandrel 22 from dropping by force of its own weight free of the outer mandrel and 'becoming lost in the hole durin-g the time the drill string is being raised to the surface or lowered into the drill hole.

The shock absorbing means or assembly 13 is arranged in coaxial relation to and `between the inner and outer m'andrels so as to cushion axial thrusts created by opposed movements of one mandrel relative to the other. The shock absorbing means comprises an elongated stack of `resilient shock absorbing rings 39, each separated from the other by means of a spacer ring 41. Here, the rings 39 are `formed of resilient compressible material, such as rubber. The spacers are of rigid construction, and are here formed of steel. The assembly 13 is `confined in an annular channel or space 42 defined between the inner and outer mandrels by an enlargement of the interior of the outer mandrel. The assembly 13 is disposed in surrounding relation to the stern 31 of the inner mandrel and has relative slidable movement therealong. The uppermost resilient ring 39 of the assembly abuts against an annular shoulder 43 defined yby the underside of the internal liange 36. The lowermost resilient ring 39 of the assembly rests upon an annular shoulder 44 defined by a cylindrical enlargement 4S at the base of the stem 31 of the inner mandrel. This enlargement is located between the stem 31 and the squared shank 25 of the inner mandrel; and it is of reduced diameter relative to the squared shank. The cylindrical enlargement 45 extends at all times in part within the annular channel 42; and has axial slidable movement therein in the manner of a piston or ram relative to the shock assembly 13.

It can be seen Iduring drilling operations, that as the drill bit 12 `bores into and moves over hard irregular rock formations at the Kbott-om of a drill hole, the resulting vibrations created will cause the inner Amandrel 22 at tached to the bit to move -up and down relative to the outer mandrel 15. The constant weight of the drill string 11, acting through the outer mandrel and through the flange 36 upon the shock assembly 13, biases the inner mandrel downward. As the inner mandrel is caused, as a result of vibrations developed by the ybit at the bottom of the hole, to move upwardly, it acts through its cylindrical piston portion 45 to exert an upwardly compressive force upon the shock assembly 13 to slide the elements 4 39 and 41 thereof toward each other. The energy exerted by the upward movement or thrusts of the inner mandrel upon the shock assembly is substantially spent in compressive action upon the latter and is thereby materially absorbed and dampened. As a consequence, the upward thrusts of the inner mandrel are prevented from passing through the outer mandrel 15 upwardly to the drill string.

The steel spacer rings 41 have a close slidable relation to the opposed wall areas of the channel 42 and the stem 31 so that they are caused at all times when pressured upwardly or downwardly to slide at right angles Ato the walls o-f the channel 42 and stem 31, and thus `will not turn askew. These spacer rings are highly polished so as to permit them to move in the channel 42 with a minimum of friction. The peripheral edges 46 of the spacer rin-gs are rounded, as indicated in FIG. 4, to prevent scoring of the walls of the channel.

To obtain desirable flow deformation characteristics in the resilient rings 39 when the latter are under compression, these rings are formed so as to provide some free space between them and the side walls of the channel. Here, the rings 39 are hexagonal in cross section, whereby, as `besty shown in FIG. 7, `free spaces 47 are provided adjacent the corners of the rings. This configuration of the rings 39 is of further advantage in that it provides opposed broad upper and lower fiat surfaces 48 centered upon opposed flat faces 50 of the spacer rings 41, whereby a desirable broad support is provided for each resilient ring 39. This hexagonal configuration of the resilient rings 319 is of still further advantage in that opposed side corners 49 thereof are at all times in contact with the opposed walls of the channel 42 and stem 31 whereby undesirable side to side shifting of the rings 39 is avoided. The separable nature of the rings 39 from one another is of further advantage in that the individual rings may be discarded Iwhen worn, and replaced.

During drilling operations, drilling fluid is fed down the string 11 of drill pipe through the flow passage 14 of the sub unit 10 to the drill bit 12 from where it flows through the usual ports in the bit to the bottom of the hole. So as to prevent this fluid from by-passing the flow passage 14 and leaking around the safety header 29 to the shock assembly 13, a nipple or wash pipe 51 is provided. This pipe has an axial fluid tight threaded connection 52 at its upper end in the pin 19 of the top coupling 16. At its lower end the wash pipe has a slide t in the upper portion of the safety header 29. Leakage between the wash pipe and the safety header is sealed out by means of packing 53, best seen in FIG. 5, seated around the wash pipe in a counterbore of the safety header. A gland nut 56, screwed into the countenbore, holds the packing in fluid-tight relation to the wash pipe. As the inner mandrel 22 is caused to move up and down relative to the louter mandrel 15 from vibrations imparted to it, the safety header 29 is carried with it and slides relative to the wash pipe 51. A further seal defined by an O-ring 55 is provided as a precaution in the periphery of the safety header to seal the safety header Huid-tight relative to the inner wall area 38 of the outer mandrel.

It is to be noted that the shock assembly 13 is not subject to rotary torque transmitted from the outer mandrel to the inner mandrel since this torque is transmitted directly to the inner mandrel through the squared drive connection 25, 26. Accordingly, the shock assembly is not subjected to twisting and shearing forces to which it might otherwise be subjected were the torque of the outer mandrel transmitted 4through the shock assembly to the inner mandrel.

It is understood that, as the load on the shock assembly progressively increases, the resilient elements 39 of the shock assembly will be progressively compressed from a condition as in FIGS. 1 and 7 wherein they are under no load, as at the start of operations, until they have reached a solid 0r fully closed condition as shown in FIGS. 5 and 8 wherein they are under maximum load. Up to the time the shock assembly reaches the fully closed or loaded condition of FIGS. and 8, it will provide shock absorbing characteristics. The load upon the shock assembly is progressively increased as the depth of the hole is extended and as further lengths of drill pipe are required to be added to the drill string. FIGS. 6 and 9 show a condition of the shock assembly under partial load intermediately of the conditions shown in FIGS. 1 and 5.

it has been found that a drill having a shock assembly 13 incorporated therein may be operated with shock absorbing characteristics under loads within a range from 0 to a maximum of approximately 200,000 lbs. It is understood that the number of ring elements 39 and spacers #il in the shock assembly may be selectively varied as desired.

It is understood that the sub unit may be located atany selected point in the dril string; it is, however, preferably located as shown immediately adjacent to the drill bit.

The squared portion 25 of the inner mandrel 22 has (FIG. 2) on each of its iiats 57 a longitudinally extending slot 53 built up with a hard metal alloy 59; and a complementary slot 6I on each of the flats 62 of the socket portion 26 of the outer mandrel 15 is similarly built up with a hard metal alloy 63. These areas of hardened metal are preferably located at those points of the socket 26 and shank 2S receiving the greater components of force in the transmission of torque from the outer mandrel to the inner mandrel.

What is claimed is:

l. A shock absorbing sub unit adapted to be coupled in the drill string of a rotary earth-boring drill for absorbing vibrations created by the bit during drilling operations so as to prevent them from being transmitted to the drill string, comprising an inner driven open ended hollow mandrel connectible at its bottom end to the bit, an outer open-ended hollow mandrel in coaxial surrounding relation to the inner mandrel having a vertical slidable relation to the inner mandrel and connectible at its top end to the drill string, shock absorbing means slidably disposed between the inner and outer mandrels providing alternately -arranged compressible resilient members and pressure transmitting members in sleeved relation to the inner mandrel and supporting the outer mandrel upon the inner mandrel, a shoulder on the inner madrel defining a seat for one end of the shock absorbing means, an opposed shoulder internally of the outer mandrel seated upon the opposite end of the shock absorbing means, the interior of the inner mandrel providing a iiuid passage to the bit, a pipe in the outer mandrel providing a liuid passage from the drill string, a sleeve secured to the inner mandrel at one end having a slidable connection at its other with the pipe providing communication of the liuid passages with one another and allowing slidable axial movement of the inner mandrel relative to the pipe, means sealing the sleeve relative to the outer mandrel and the pipe against leakage of fluid around the pipe and sleeve to the shock absorbing means, and means independent of the shock absorbing means forming a sole driving connection between the outer and inner mandrels for transmitting torque of the outer mandrel to the inner mandrel.

2. A sub unit as defined in claim 1, wherein shoulder stop means is provided internally of the outer mandrel above the shock absorbing means, and the Isleeve provides an end shoulder cooperable with the stop means to limit the extent of downward slidable movement of the inner mandrel relative to the outer mandrel,

3. A shock absorbing sub unit comprising an inner mandrel connectable at its bottom to a drill bit, an outer mandrel sleeving the inner mandrel connectable at its top to a drill string and having a vertical slidable relationship with the inner mandrel, opposed longitudinally extending wall portions of the mandrels defining an elongated cylindrical channel between the inner and outer mandrels in surrounding relation to the inner mandrel, shock absorbing means slidably disposed in the channel providing alternately arranged compressible resilient ring members and pressure transmitting ring members in sleeved relation to the inner mandrel and supporting the outer mandrel upon the inner mandrel, a shoulder on the inner mandrel defining a seat for one end of the shock absorbing means, an opposed shoulder internally of the outer mandrel seated upon the opposite end of the shock absorbing means, and means independent of the shock absorbing means forming a sole driving connection between the inner and outer mandrels for transmitting torque of the outer to the inner mandrel; wherein each resilient ring member is of polygonal coniiguration in cross section having an outermost diameter edge defining a circumferential corner and having an innermost diameter edge defining an annular corner respectively in contact with the opposed longitudinally extending walls of the channel, and there being free flow spaces adjacent said corners relative to said walls.

4. A sub unit of the character described comprising an inner mandrel having a pin box at its bottom end adapted to be coupled with the pin of a drill bit, an outer mandrel sleeving the inner mandrel having a pin adapted to be coupled with the pin box of a drill string, the inner mandrel having a vertical slidable relationship with the outer mandrel, an elongated cylindrical channel defined between the inner and outer madrels in surroundig relation to the inner mandrel having an upper annular end wall defined by an internal shoulder of the outer mandrel and lhaving a lower annular end wall defined by a shoulder of the inner mandrel, a plurality of rigid spacer ring members and compressible resilient ring members slidably sleeving the inner mandrel and so arranged that each resilient ring member is spaced from the other by a spacer ring member and wherein the lowermost and uppermost resilient ring members respectively abut the lower and upper end walls of the channel, a iiuid passage through the outer mandrel, a fiuid passage through the inner mandrel having a variable connection with the liuid passage of the outer mandrel, means sealing the channel liuid tight against leakage from the fluid passages around the variable connection to the spacer and resilient ring members, and a squared drive connection between the outer and inner mandrels independent of the resilient ring and spacer members defining a sole means for transmitting rotary torque of the outer mandrel -to the inner mandrel.

References Cited by the Examiner UNITED STATES PATENTS 2,113,651 4/1938 Heaston 64-23 X 2,756,022 7/1956 Sturgeon 64-23 2,876,992 3/1959 Lindsay 175-321 X 3,013,793 12/1961 Howell et al 175-321 X 3,225,566 12/1965 Leathers 64-23 FRED C. MATTERN, JR., Primary Examiner.

HALL C. COE, Examiner.

Claims (1)

1. A SHOCK ABSORBING SUB UNIT ADAPTED TO BE COUPLED IN THE DRILL STRING OF A ROTARY EARTH-BORING DRILL FOR ABSORBING VIBRATIONS CREATED BY THE BIT DURING DRILLING OPERATIONS SO AS TO PREVENT THEM FROM BEING TRANSMITTED TO THE DRILL STRING, COMPRISING AN INNER DRIVEN OPEN ENDED HOLLOW MANDREL CONNECTIBLE AT ITS BOTTOM END TO THE BIT, AN OUTER OPEN-ENDED HOLLOW MANDREL IN COAXIAL SURROUNDING RELATION TO THE INNER MANDREL HAVING A VERTICAL SLIDABLE RELATION TO THE INNER MANDREL AND CONNECTIBLE AT ITS TOP END TO THE DRILL STRING, SHOCK ABSORBING MEANS SLIDABLY DISPOSED BETWEEN THE INNER AND OUTER MANDRELS PROVIDING ALTERNATELY ARRANGED COMPRESSIBLE RESILIENT MEMBERS AND PRESSURE TRANSMITTING MEMBERS IN SLEEVED RELATION TO THE INNER MANDREL AND SUPPORTING THE OUTER MANDREL UPON THE INNER MANDREL, A SHOULDER ON THE INNER MADREL DEFINING A SEAT FOR ONE END OF THE SHOCK ABSORBING MEANS, AN OPPOSED SHOULDER INTERNALLY OF THE OUTER MANDREL SEATED UPON THE OPPOSITE END OF THE SHOCK ABSORBING MEANS, THE INTERIOR OF THE INNER MANDREL PROVIDING A FLUID PASSAGE TO THE BIT, A PIPE IN THE OUTER MANDREL PROVIDING A FLUID PASSAGE FROM THE DRILL STRING, A SLEEVE SECURED TO THE INNER MANDREL AT ONE END HAVING A SLIDABLE CONNECTION AT ITS OTHER WITH THE PIPE PROVIDING COMMUNICATION OF THE FLUID PASSAGES WITH ONE ANOTHER AND ALLOWING SLIDABLE AXIAL MOVEMENT OF THE INNER MANDREL RELATIVE TO THE PIPE, MEANS SEALING THE SLEEVE RELATIVE TO THE OUTER MANDREL AND THE PIPE AGAINST LEAKAGE OF FLUID AROUND THE PIPE AND SLEEVE TO THE SHOCK ABSORBING MEANS, AND MEANS INDEPENDENT OF THE SHOCK ABSORBING MEANS FORMING A SOLE DRIVING CONNECTION BETWEEN THE OUTER AND INNER MANDRELS FOR TRANSMITTING TORQUE OF THE OUTER MANDREL TO THE INNER MANDREL.

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