US3735820A - Bore hole air hammer - Google Patents

Abstract

An air hammer embodying an outer housing structure connectible to a rotatable drill pipe string through which compressed air is conducted. An upper cylinder sleeve in the housing structure defines an annular air inlet passage therewith, a hammer piston reciprocating in the housing structure with an upper smaller diameter portion slidable in this sleeve and a larger diameter portion in the housing structure below this sleeve, such that high pressure acts over the full cross-sectional area of the larger diameter piston portion in driving the piston downwardly against a companion anvil affixed to a drill bit rotatable by the drill pipe string and housing structure, compressed air acting over a smaller diameter piston area and returning the piston upwardly in the housing structure, all of the air being caused to exhaust through the anvil and bit to clean the bit and the bottom of the bore hole of cuttings.

Description

v 1' 11ii ted States Curington atent 1191 1 1 BORE HOLE AIR HAMMER [75] Inventor: Alfred R. Curington, Houston, Tex.

[73] Assignee: Baker Oil Tools, Inc., Los Angeles,

Calif.

22 Filed:- May 5,1971 21] Appl.No.: 140,515

'Fo'x ..l75/322 1451 May 29,1973

Primary Examiner-James A. Leppink Attorney-Bernard Kriegel and Kendrick, Subkow & Kriegel 4 s7 ABSTRACT An air hammer embodying an outer housing structure connectible to a rotatable drill pipe string through which compressed air is conducted. An'upper cylinder sleeve in the housing structure defines an annular air inlet passage therewith, a hammer piston reciprocating in the housing structure with an upper smaller diameter portion slidable in this sleeve and a larger diameter portion in the housing structure below this sleeve, such that high pressure acts over the full cross-sectional area of the larger diameter piston portion in drivingthe piston downwardly against a companion anvil affixed to a drill bit rotatable by the drill pipe string and housing structure, compressed air acting over a smaller diameter piston area and returning the piston upwardly in the housing structure, all of the air being caused to exhaust through the anvil and bit to clean the bit and the bottom of the bore hole of cuttings.

18 Claims, 9 Drawing Figures li a PATENTEU MAY 2 9 I973 SHEET 2 [IF 3 IZIG 2a..

' sembly of the bit and 1 soRE nous AIR HAMMER The present invention relates to drill pipe apparatus for drilling a bore hole in a formation, and more particularly to pneumatically operated apparatus that imparts a percussive action to a drillbit while the latter is preferably rotated.

Prior air hammers are of the type having a relatively thick housing to feed compressed air through external side ports into the housing for reciprocating a hammer piston therein, which, because of the restricted internal 1970, a relatively large diameter hammer piston is provided on which compressed air will act, despite the v feeding of the compressed air through side ports into the housing, but only a portion of the air used in reciprocating the piston is exhausted through the drill bit connected to the anvil against which the piston impacts. As a result, assurance is not had that the cuttings are cleaned completely from the bottom of the hole and from the bit.

By virtue of the present invention, a larger outside diameter piston can be used for the same outside diameter of confining housing structure, the compressed air acting over the entire cross-sectional area of the piston on its power stroke, thereby enabling the piston to deliver a maximum impact blow against the anvil secured to the drill bit. The larger piston area allows a heavier piston to be used, which is accelerated over a shorter stroke to achieve a desired impact velocity in less time and with lower air consumption, the kinetic energy for each piston blow being greater. The shorter stroke causes the piston to reciprocate at a substantially greater frequency and results in a much-greater horsepower being delivered. In addition, all of the compressed air for reciprocating the piston is exhausted through the bit secured to the anvil against which the piston impacts, to insure effective removal of the cuttings ;from the bottom of the hole and their conveyance around the apparatus and the drill pipe string connected thereto to the top of the bore hole, the exhaust air also maintaining the bit in a clean and cool condition.

Moreover, the invention has for its objective the provision of an integral anvil and bit combination splined to the housing structure of the air hammer, in which the spline connection is more economical to manufacture and is relatively simple in construction, facilitating asanvil with respect to the housing structure.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This fonn is shown in the drawings accompanying and forming part of the present specification. It will now be described detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense.

Referring to the drawings:

FIGS. la and 1b together constitute a longitudinal section through an apparatus embodying the invention, with parts in their relative positions in which the hammer piston has completed delivering an impact blow against its companion anvil and the drill bit secured thereto, FIG. llb being a lower continuation of FIG. 1a;

FIGS. 2a and 2b are views similar to FIGS. la and lb, with the hammer piston approaching its upper position, FIG. 2b being a lower continuation of FIG. 2a;

FIGS. 3a and 3b are views similar to FIGS. 10 and 1b, illustrating the relationship of the parts with the bit off the bottom of the hole, allowing air to be circulated through the apparatus, FIG. 3b being a lower continuation of FIG. 3a;

FIG. 4 is a cross-section taken along the line 4-4 on FIG. 1a;

FIG. 5 is a cross-section taken along the line 55 on FIG. In;

FIG. 6 is a cross-section taken along the line 66 on FIG. 1b.

As illustrated in the drawings, an air hammer apparatus A is provided which is secured to the lower end of a string of drill pipe B by means of which the apparatus is rotated to correspondingly rotate a drill bit C used for drilling a bore hole D while the apparatus delivers repeated impact blows upon the drill bit, compressed air being forced down the drill pipe for actuating the apparatus and to cleaning the cuttings from the bottom of the hole. The apparatus includes anelongate housing structure 10 consisting of a plurality of parts. A main central section 11 'of the housing structure has its upper end threadedly secured to anupper head 12, which, in turn, is threadedly secured to asub 13 having abox 14 threadedly attached to thepin 15 at the lower end of an adjacent drill pipe section B. The lower end of the intermediate housing section is threadedly attached to a lower.head 16 having aspline connection 17 with an anvil l8 integral with the impact drill bit C of any suitable form, against which impact blows will be directed while the drill pipe string B and apparatus A are being rotated, to insure that the cutting portions of the drill bit will cover the entire cross-sectional area of the hole bottom E.

Theupper housing head 12 has one or a plurality ofinlet passages 19 opening through its upper end, their lower ends communicating with anannular inlet passage 20 between the outer housing section 1 l and acylinder sleeve 21 integral with and depending from the housing head. This cylinder sleeve hasupper inlet ports 22 andlower inlet ports 23 communicating with the annular inlet passage and adapted to be placed in communication with thecylinder space 24 within the cylinder sleeve. Below thelower inlet ports 23, thecylinder sleeve 21 carries asuitable seal ring 25 for sealing against awall 26 of the housing section 11, which is of smaller internal diameter than thewall 27 of the housing section portion surrounding theannular inlet passage 20.

Ahammer piston 28 is reciprocable within thehousing structure 10 and itscylinder sleeve 21, this piston being adapted to deliver an impact blow againsttheupper end 29 of the anvil l8 splined to thelower head 16 and extending upwardly into thelower portion 30 of the housing section 11, this lower portion and itsinner wall 26 having a substantially greater internal diameter S than the internal diameter T of thecylinder sleeve 21.

In fact, the internal diameter S of the cylinder section is greater than that of the cylinder sleeve from the location of the cylindersleeve seal ring 25 to the upper end of thelower head 16. An elongate circumferentialinternal groove 31 in the housing wall will function as anannular exhaust passage 32, as described hereinbelow.

Thepiston 28 has an enlargedoutside diameter portion 33 reciprocable along thegreater diameter wall 26 of the housing structure, thelower part 34 of this piston portion having a reduced external diameter so as to clear alimit ring 35 fitting within an internalcircumferential groove 36 in the housing section, and on which a downwardly facingpiston shoulder 37 is adapted to rest when the drill bit has been removed. When the drill bit C is in engagement with the bottom of the bore hole, it is held thereagainst by thelower end 38 of the lower head bearing against an upwardly facing drill bit or anvilshoulder 39, at which time the periphery of anupper head 40 of the anvil within the housing section 11 engages aseal ring 41 mounted in such housing section.

Thehammer piston 28 has alongitudinal impact passage 42 opening through its upper end and having a lowerlateral branch 43 communicating with the annular space orpassage 44 between an upper, smallerdiameter piston portion 45 and the enlargeddiameter wall 26 of the housing section below thehousing sleeve 21. The lower end of thisannular passage 44 is adapted to communicate with theannular exhaust passage 32 which is in communication with alateral exhaust port 46 extending from acentral exhaust passage 47 in the lower portion of the piston to the periphery of the enlarged piston portion. Thiscentral passage 47 receives the upper portion of asleeve valve member 48 piloted within a centralair exhaust passage 49 extending through the anvil, being secured to the anvil in any suitable manner, as bywelding material 48a. Theexhaust passage 49 extends downwardly through theanvil 18 and drill bit C, discharging from the latter against the bottom E of the hole to clean the latter and the drill bit of cuttings, conveying the cuttings upwardly around the housing and the drill pipe B to the top of the bore hole.

The hammer piston or impacting member also has alongitudinal return passage 50 opening through its lower end, its upper portion communicating with aport 51 opening into anannular inlet groove 52 in thesmaller diameter portion 45 of the piston adapted to communicate with thelower inlet ports 23 when the air hammer is in its lower position engaging the anvil, as disclosed in FIGS. la and lb. At this time, theupper inlet ports 22 are closed by the piston.Suitable piston rings 53, 53a, 53b may be mounted on the piston for preventing leakage therealong. As disclosed, anupper piston ring 53 occupies a position above theupper inlet ports 22 during the drilling operation, intermediate andlower piston rings 53a, 53b straddling thelower inlet ports 51 when thehammer piston 28 engages theanvil 18.

The smallerdiameter piston portion 45 has a further reduceddiameter portion 54 below thelower piston ring 53b, which defines an annularair inlet passage 56 with thecylinder sleeve 21, so that upon elevation of the piston in the housing structure and its cylinder sleeve, theannular inlet passage 56 will be placed in communication with thelower inlet ports 23 to permit compressed air to flow from the latter through the annular passage and into thelower end 43 of theimpact passage 42, such compressed air then passing into thecylinder 24 above thepiston 28 for the purpose of forcing the latter downwardly and strike an impact blow against theanvil 18. During the early portion of upward movement of the piston, theupper end 57 of its enlarged piston portion engages thecylinder wall 26 above theannular exhaust groove 32 to shut off communication between theimpact passage 42 andexhaust port 32. Additional upward movement of the piston will then place theannular inlet passage 56 in communication with thelower inlet ports 23 to feed compressed air into theimpact passage 42, as described above.

As the piston moves downwardly, thelower end 58 of the upper piston portion of smaller diameter will move across thelower inlet ports 23 to close them from communication with theannular inlet passage 20, further downward movement then moving the shut-offcorner 57 into theannular exhaust passage 32, allowing the compressed air above the piston and in theimpact passage 42 to exhaust through theexhaust port 46,central exhaust passage 47,inner valve sleeve 48, andexhaust air passage 49 to the bottom of the hole, the energy imparted to thepiston 28 by the compressed air driving it downwardly to impact it against theanvil 18. Just before impact occurs, theannular inlet groove 52 is placed in communication with thelower inlet ports 23, compressed air flowing therethrough and through thereturn passage 50 to the lower end of the piston, such air acting on the piston to drive it back toward its upper position. A relatively short upward travel again places thepiston portion 59 below thegrove 52 across thelower inlet ports 23 to shut off communication between them and thereturn passage 50, the air below the piston expanding and driving the piston upwardly, once again compressing the air in thecylinder space 24 above the piston, the piston reaching the upper end of its stroke with thelower end 60 of the piston moving off thevalve sleeve 48, permitting the compressed air in-thereturn passage 50 and below the piston to exhaust through thecentral exhaust passage 47,valve sleeve 48 andexhaust air passage 49 into the bottom of the bore hole.

Another manner of exhausting the piston return air into the anvil is to lengthen thesleeve 48 so that it always remains slidably secured within thepiston passage 47. As the return air drives the piston upwardly, itslower shoulder 37 will move above the lower end of theexhaust groove 32, allowing the return air to exhaust from below the piston around the reduceddiameter portion 34 into theexhaust groove 32, from where it flows through thepassages 46, 47, 48 and 49 to the bottom of the bore hole D.

It will be noted that immediately before thepiston 28 impacts against theanvil 18, the shut-off corner 57 moves off thecylinder wall 26 above theexhaust groove 32, permitting the compressed air that has driven the piston downwardly to exhaust through thepassages 46, 47, 48 49 into the bottom of the hole. Such exhaust action takes place after thepiston shoulder 58 has moved below thelower inlet ports 23. Shortly before the piston impacts against the upper end of the anvil, theannular inlet groove 52 is placed in communication with thelower inlet ports 23, allowing the compressed air to flow through thereturn passage 50 in order to drive thepiston 28 back upwardly. The

shut-off corner 57 moves above theexhaust groove 31 shortly before thepiston portion 59 below theannular inlet groove 52 moves across thelower inlet ports 52 to shut off air flow into thereturn passage 50, the air below the piston expanding and driving the hammer piston upwardly, compressing the air in thecylinder space 24 above the piston. Near the upper end of the piston stroke, theshoulder 58 moves above the lower 7 ameter over which the compressed air acts, such as the I restriction in the housing imposed by thecylinder sleeve 21. Thus, the area S over which the compressed air is acting on the power stroke of the hammer piston is the sum of the cross-sectional area T of the smaller diameter piston plus the annular area U which is the annular area between the periphery of the smaller diameter piston portion and the periphery of the enlarged piston portion. The compressed air for returning the hammer piston acts across the annular area R between the periphery of the enlarged piston portion and the inner wall of theexhaust passage 47 in the lower portion of the piston. However, such area R need not be large, since the compressed air flowing through thereturn air passage 50 need only return the piston to the upper end of its stroke, compressing the air in thecylinder space 24 above the piston so that it will not impact against thecylinder head 12. However, the energy required to compress the air is recovered when the air later ex-' pands in driving the piston downwardly on its power stroke.

It is to be noted that all of the compressed air entering the apparatus exhausts through the lower end of the bit, insuring that the bottom of the bore hole will be swept free of cuttings, and insuring the maximum penetration of the cutting elements of the bit into the formation.

With the bit C elevated from the bottom E of the bore hole, air can be circulated through it relatively freely. With the bit off bottom (FIGS. 3a, 3b), it will drop downwardly of the housing structure, moving itsanvil portion 18 downwardly until its downwardly facingshoulder 80 engages the upper end of thelower head 16, at which time thehead 40 moves off itsseal ring 41. Thepiston 28 moves downwardly to the extent limited by engagement of its lower end with the upper end of the anvil, theupper end 82 of the piston then being disposed below the upperinlet circulating ports 22. At this time, the shut-off corner 57 at the upper portion of the enlarged diameter of the piston is disposed well within theexhaust groove 31. Accordingly, compressed air can flow from thedrill pipe B through thesub 13 and theinlet passages 19 into theannular inlet passage 20, proceeding through theinlet circulating ports 22 into thecylinder sleeve 21, and then passingthrough theimpact passage 42, 43 to the exterior of the piston, flowing through thegroove 31 and into theexhaust port 46, continuing to flow into the centralexhaust piston passage 47,inner sleeve 48 and through theexhaust air passage 49 from the lower end of the bit.

In FIGS. 1a and lb, the apparatus is illustrated with the bit C resting againstthe bottom E of the hole and thehammer piston 28 having just delivered its blow to theanvil 18. The air in the cylinder above the piston has exhausted through theimpact passage 42 and thegroove 31 into theexhaust port 46, continuing to exhaust through thepassages 47, 48, 49 from the bit and against the bottom of the bore hole. The compressed air flows through thereturn passage 50 to the bottom of the hammer piston, acting in an upward direction over the annular area R of the piston to drive it upwardly. Initially, the shut-off corner 57 moves above theexhaust groove 31 to close it from theimpact pas sage 42, whereupon thepiston 59 below the annular groove shuts off thelower inlet ports 23, the expanding air below the piston continuing to drive upwardly and compressing the air that remains in thecylinder space 24 above the piston, providing an air cushion to pre vent the piston from impacting against thecylinder head 12. The downwardly facingpiston shoulder 58 has now moved above the lowermost ends of thelower inlet ports 23, permitting compressed air to flow from theinlet ports 23 into theannular inlet passage 56, and through theimpact passage 43, 42 to the upper portion of the piston (FIGS. 2a and 2b), which then causes the compressed air to drive thepiston 28 downwardly and deliver an impact blow against the anvil. Near the limit of its downstroke, the shut-off corner57 moves into the region of theexhaust groove 31, permitting the compressed air to exhaust through the bit, as described above, thereturn passage 50 again being placed in communication with thelower inlet ports 23, the piston impacting against the anvil, and the foregoing cycle of operation repeated.

During the reciprocation of thepiston 28 within thehousing structure 10 to deliver repeated impact blows against theanvil 18, the drill pipe string B and apparatus A are being rotated while suitable downweight is imposed on the drill pipe and housing structure, thelower end 38 of thehead 16 continually bearing against the bit oranvil shoulder 39, holding it against the bottom E of the bore hole. Rotary motionis transmitted from thehousing structure 10 through thespline connection 17 to theanvil 18. As disclosed (FIGS. lb, 2b, 3b, 6), the spline connection includes circumferentially spaced external splines orteeth 100 on the exterior of the mandrel that mesh with companion internal splines 1011 on thelower head member 16. This lower head member has an externally threadedportion 102 for threaded connection to the lower end of the housing section ill. However, it is made in two parts orhalves 16a, 16b. It is to be noted that the outside diameter of theexternal splines 100 is within the periphery of the anvil portion on opposite sides thereof, the upper and lower ends of these splines terminating in upper andlower shoulders 80, a, the upper shoulder 88 diverging in an upward direction and being adapted to engage a companion upward facingshoulder 104 on thelower head 16, as disclosed in FIGS. 3a, 3b, when air is being circulated through the apparatus.

Thehead 16 can be placed in assembled relation with respect to the splines of the anvil by forming the head in a plurality of pieces or sections, such as the twosections 16a, 16b illustrated in the drawings. This enables each section to be moved laterally inwardly to place theinternal splines 101 in mesh with theexternal splines 100. The undulatinggroove configuration 105 of eachhead section 16a, 16b has its opposedwalls 106 diverging in a lateral inward direction, which enables each head section to be appropriately shifted laterally to mesh theinternal splines 101 with theexternal splines 100, as shown in FIG. 6. With the two halves of the head member mounted on and in splined relation to theanvil 18, the anvil and head member can be inserted upwardly into the housing section 11 and theexternal threads 102 of thehead member 16 threaded into the companioninternal thread 102a of the housing member to its fullest extent. This secures thehead members 16,1611 together and makes it function as a single head member.

The splines are readily manufactured, as by use of a milling tool, which will cut the grooves in the anvil to produce theexternal splines 100. Similarly, theinternal splines 101 can be produced through use of a suitable machine tool, such as a milling machine.

The spline connection illustrated and described is much simpler than prior spline arrangements found in air hammers. It is more economical to manufacture. It reduces the cost of an integral anvil and bit considerably.

The apparatus disclosed in the drawings also includes a water check valve device 200 (FIG. la). As shown,

theupper housing head 12 has aguide bore 201 opening through its upper end and receiving avalve stem 202 terminating in anupper valve head 203 adapted to engage acentral valve seat 204 on the upper sub. The valve stem and its head are urged upwardly to place thehead 203 in engagement with itscompanion seat 204 by ahelical compression spring 205 bearing against the lower end of the valve stem and against thebase 206 of the guide bore. Ableeder passage 207 is provided in the upper housing head, its upper end communicating with the guide bore 201 and its lower end with alateral bleeder port 208, to avoid trapping of fluid in the bore and its potential interference with the movement of the valve head.

Compressed air pumped down through the drill pipe string B will shift thevalve head 203 downwardly from engagement with itsseat 204, enabling the compressed air to flow into anupper recess 209 in the upper head through which theinlet passages 19 open. Any tendency for water or other liquid to flow upwardly into the apparatus is precluded by the upward seating of thevalve head 203 against itsseat 204.

It will be apparent that an air hammer has been provided in which a larger piston area is available over which compressed air can act in delivering the impact blow to the companion anvil. The piston can be made heavier, its larger area enabling it to be accelerated to a desired velocity at impact. Moreover, such impact velocity can be achieved with the piston having a shorter stroke, resulting in a much higher frequency of operation of the piston in reciprocating within the housing structure. Thus, the increased weight of the piston and its higher frequency of reciprocation with the same impact velocity results in a greatly increased horsepower delivered by the piston to the anvil and bit. It is found that such increased horsepower is achieved with the consumption of substantially less air. By way of example, it is found that 47 percent more horsepower has been developed with a consumption of 21 percent less air, a percent higher energy blow being delivered with approximately the same impact velocity as a well known prior air hammer. Despite the lower air consumption, the increased horsepower results from the use of a heavier piston having a shorter stroke operating at a much higher frequency, for example, a 34 percent higher frequency.

1 claim:

I. In percussion drilling apparatus: a housing structure connectible to a drill string; an anvil in the lower portion of said housing structure and operatively connectible to a drill bit, said anvil having an exhaust passage; said housing structure including a first cylinder portion and a second cylinder portion therebelow of greater internal diameter than the internal diameter of said first cylinder portion, a hammer piston reciprocable in said cylinder portions for intermittently impacting against said anvil, said piston having an upper portion slidably reciprocable in said first cylinder portion and in sealed relation thereto, and a lower portion of greater diameter than said upper portion slidably reciprocable in said second cylinder portion and in sealed relation thereto; said upper piston portion having an effective cross-sectional area substantially equal to the internal cross-sectional area of said first cylinder portion; first means for directing a fluid medium under pressure into said first cylinder portion above said upper piston portion for action upon the full effective cross-section area of said upper piston portion, and into said second cylinder portion above said lower piston portion, for driving said hammer piston downwardly toward said mandrel; second means for directing the fluid medium under pressure into a lower portion of said housing structure for action upon said hammer piston to elevate said hammer piston in said housing structure; and exhaust passage means for exhausting substantially all of the fluid medium from said cylinder portions above said upper and lower piston portions and from said lower portion of said housing structure into said exhaust passage of said anvil.

2. In apparatus as defined in claim 1; said first directing means including an inlet passage in said housing structure opening into said first cylinder portion through a side wall thereof.

3. In apparatus as defined in claim 1; said exhaust passage means including an exhaust passageway in an inner side wall of said second cylinder portion placed in communication by said hammer piston with the interior of said housing structure above said lower piston portion upon downward movement of said hammer piston in said housing structure.

4. In percussion drilling apparatus: a housing structure connectible to a drill string; an anvil in the lower portion of said housing structure and operatively connectible to a drill bit, said anvil having an exhaust passage; said housing structure including a first cylinder portion and a second cylinder portion therebelow of greater internal diameter than the internal diameter of said first cylinder portion, a hammer piston reciprocable in said cylinder portions for intermittently impacting against said anvil, said piston having an upper portion slidably reciprocable in said first cylinder portion and in sealed relation thereto, and a lower portion of greater diameter than said upper portion slidably reciprocable in said second cylinder portion and in sealed relation thereto; first means for directing a fluid medium under pressure into said first cylinder portion above said upper piston portion and into said second cylinder portion above said lower piston portion for driving said hammer piston downwardly toward said mandrel; second means for directing the fluid medium under pressure into a lower portion of said housing structure for action upon said hammer piston to elevate said hammer piston in said housing structure; and exhaust passage means for exhausting substantially all of the fluid medium from said cylinder portions above said upper and lower piston portions and from said lower portion of said housing structure into said exhaust passage of said anvil; said exhaust passage means including an exhaust passageway in an inner side wall of said second cylinder portion placed in communication by said hammer piston with the interior of said housing structure above said lower piston portion upon downward movement of said hammer piston in said housing structure, said exhaust passage means further including an exhaust passage in said hammer piston communicating with said exhaust passageway and said anvil exhaust passage.

5. In percussion drilling apparatus: a housing structure connectible to a drill string; an anvil in the lower portion of said housing structure and operatively connectible to a drill bit, said anvil having an exhaust passageysaid housing structure including a first cylinder portion and a second cylinder portion therebelow .of greater internal diameter than theinternal diameter of said first cylinder portion, a hammer piston reciprocable in said cylinder portions for intermittently impacting against said anvil, said piston having an upper portion slidably reciprocable in said first cylinder portion and in sealed relation thereto, and a lower portion of greater diameter than said upper portion slidably reciprocable in said second cylinder portion and in sealed relation thereto; first means for directing a fluid medium under pressure into said first cylinder portion above said upper piston portion and into said second cylinder portion above said lower piston portion for driving said hammer piston downwardly toward said mandrel; second means for directing the fluid medium under pressure into a lower portion of said housing structure for action upon said hammer piston to elevate said hammer piston in said housing structure; and exhaust passage means for exhausting substantially all of the fluid medium from said cylinder portions above said upper and lower piston portions and from said lower portion of said housing structure into said exhaust passage of said anvil; said first directing means including an impact passage in said piston opening at its upper portion into said first cylinder portion above said upper piston portion and at its lower portion into said second cylinder portion above said lower piston portion, said first directing means further including an inlet passage in said housing structure opening into said first cylinder portion through a side wall thereof and communicating with the lower portion of said impact passage upon upward movement of said piston in said housing structure.

6. In apparatus as defined in claim said exhaust passage means including an exhaust passageway in an inner side wall of said second cylinder portion placed in communication by said hammer piston with said lower portion of said impact passage upon downward movement of said hammer piston in said housing structure, said exhaust passage means further including an exhaust passage in said hammer piston communicating with said exhaust passageway and said anvil exhaust passage.

F iii 7. In apparatus as defined inclaim 5; said second directing means further including a return passage in said piston opening at its lower portion into said lower portion of said housing structure below said piston and at its upper portion into said first cylinder portion in communication with said inlet passage upon downward movement of said piston in said housing structure.

8. In apparatus as defined inclaim 5; said second directing means further including a return passage in said piston opening at its lower portion into said lower portion of said housing structure below said piston and at its upper portion into said first cylinder portion in communication with said inlet passage upon downward movement of said piston in said housing structure; said exhaust passage means including an exhaust passageway in an inner side wall of said second cylinder portion placed in communication by said hammer piston with said lower portion of said impact passage upon downward movement of said hammer piston in said housing structure, said exhaust passage means further including an exhaust passage in said hammer piston communicating with said exhaust passageway and said anvil'exhaust passage and with said housing structure below said piston.

9. In percussion drilling apparatus: a housing structure connectible to a drill string and having an inner cylinder portion and an outer portion surrounding said inner portion and spaced laterally therefrom to provide an annular air inlet passage therebetween, said outer portion extending below the lower end of said inner portion and having an inside diameter substantially greater than the inside diameter of said inner portion to provide an outer cylinder portion of greater internal diameter than said inner portion; an anvil in the lower portion of said housing structure and having an exhaust passage; a hammer piston reciprocable in said housing structure for intermittently impacting against said anvil, said piston having an upper small diameter portion slidably reciprocable in said inner cylinder portion and a lower large diameter portion slidably reciprocable in said outer cylinder portion below said inner cylinder portion; said inner cylinder portion having one or more side ports communicating said annular passage with the interior of said inner cylinder portion; said outer cylinder portion having an exhaust passageway in its inner side wall below said inner cylinder portion; said piston having an impact passage opening at its upper end into said inner cylinder portion and at its lower end into said outer cylinder portion; said piston having a return passage opening at its lower end into said outer cylinder portion below said piston and at its upper end into said inner cylinder portion below the upper end of said piston; said piston having an exhaust passage communicating said exhaust passageway with said anvil exhaust passage, said piston having means thereon coacting with said housing structure to alternately communicate said impact passage with said one or more side ports and said exhaust passageway upon upward and downward movement, respectively, of said piston in said structure, said piston having means thereon coacting with said housing structure to alternately communicate said return passage with said one or more side ports and said piston exhaust passage upon downward and upward movement, respectively, of said piston in said structure.

10. In apparatus as defined in claim 9; and a sleeve in said anvil exhaust passage adapted to extend into said piston exhaust passage.

11. In apparatus as define in claim 9; and a sleeve in said anvil exhaust passage adapted to extend into said piston exhaust passage in sealing relation to said piston; said piston being movable off said sleeve upon elevation of said piston in said structure to permit air below aid piston to exhaust into said anvil passage.

12. In percussion drilling apparatus: a housing structure; an anvil extending into the lower portion of said housing structure; a hammer piston reciprocable in said structure above said anvil; means for reciprocating said piston in said housing structure for intermittently impacting said piston against said anvil; a connection between said housing structure and anvil including V- shaped external splines on said anvil, a member comprising a plurality of separate parts having V-shaped internal splines adapted to mesh. with said external splines, said parts being movable laterally inwardly of said splines.

15. In apparatus as defined inclaim 12; said encompassing and retaining means including external threads on said parts meshing with companion internal threads in said housing structure, the outer ends of said external splines lying on a circle of lesser diameter than the external diameter of said anvil above said splines.

16. In apparatus as defined inclaim 12; said separate parts consisting of two members each having an arcuate extent of about and movable laterally inwardly of said anvil toward each other to mesh said internal splines fully with said external splines without interference from said external splines.

17. In apparatus as defined inclaim 12; said external splines being circumferentially spaced uniformly from each other, said internal splines being circumferentially spaced uniformly from each other an movable laterally inwardly towards each other to mesh said internal splines fully with said external splines without interference from said external splines.

18. In apparatus as defined inclaim 12; said external splines being circumferentially spaced uniformly from each other, said internal splines being circumferentially spaced uniformly from each other; said separate parts consisting of two members each having an arcuate extent of about 180 and movable laterally inwardly of said anvil toward each other to mesh said internal splines fully with said external splines without interference from said external splines.

Claims (18)

1. In percussion drilling apparatus: a housing structure connectible to a drill string; an anvil in the lower portion of said housing structure and operatively connectible to a drill bit, said anvil having an exhaust passage; said housing structure including a first cylinder portion and a second cylinder portion therebelow of greater internal diameter than the internal diameter of said first cylinder portion, a hammer piston reciprocable in said cylinder portions for intermittently impacting against said anvil, said piston having an upper portion slidably reciprocable in said first cylinder portion and in sealed relation thereto, and a lower portion of greater diameter than said upper portion slidably reciprocable in said second cylinder portion and in sealed relation thereto; said upper piston portion having an effective cross-sectional area substantially equal to the internal cross-sectional area of said first cylinder portion; first means for directing a fluid medium under pressure into said first cylinder portion above said upper piston portion for action upon the full effective cross-sectional area of said upper piston portion, and into said second cylinder portion above said lower piston portion, for driving said hammer piston downwardly toward said mandrel; second means for directing the fluid medium under pressure into a lower portion of said housing structure for action upon said hammer piston to elevate said hammer piston in said housing structure; and exhaust passage means for exhausting substantially all of the fluid medium from said cyliNder portions above said upper and lower piston portions and from said lower portion of said housing structure into said exhaust passage of said anvil.

2. In apparatus as defined in claim 1; said first directing means including an inlet passage in said housing structure opening into said first cylinder portion through a side wall thereof.

3. In apparatus as defined in claim 1; said exhaust passage means including an exhaust passageway in an inner side wall of said second cylinder portion placed in communication by said hammer piston with the interior of said housing structure above said lower piston portion upon downward movement of said hammer piston in said housing structure.

4. In percussion drilling apparatus: a housing structure connectible to a drill string; an anvil in the lower portion of said housing structure and operatively connectible to a drill bit, said anvil having an exhaust passage; said housing structure including a first cylinder portion and a second cylinder portion therebelow of greater internal diameter than the internal diameter of said first cylinder portion, a hammer piston reciprocable in said cylinder portions for intermittently impacting against said anvil, said piston having an upper portion slidably reciprocable in said first cylinder portion and in sealed relation thereto, and a lower portion of greater diameter than said upper portion slidably reciprocable in said second cylinder portion and in sealed relation thereto; first means for directing a fluid medium under pressure into said first cylinder portion above said upper piston portion and into said second cylinder portion above said lower piston portion for driving said hammer piston downwardly toward said mandrel; second means for directing the fluid medium under pressure into a lower portion of said housing structure for action upon said hammer piston to elevate said hammer piston in said housing structure; and exhaust passage means for exhausting substantially all of the fluid medium from said cylinder portions above said upper and lower piston portions and from said lower portion of said housing structure into said exhaust passage of said anvil; said exhaust passage means including an exhaust passageway in an inner side wall of said second cylinder portion placed in communication by said hammer piston with the interior of said housing structure above said lower piston portion upon downward movement of said hammer piston in said housing structure, said exhaust passage means further including an exhaust passage in said hammer piston communicating with said exhaust passageway and said anvil exhaust passage.

5. In percussion drilling apparatus: a housing structure connectible to a drill string; an anvil in the lower portion of said housing structure and operatively connectible to a drill bit, said anvil having an exhaust passage; said housing structure including a first cylinder portion and a second cylinder portion therebelow of greater internal diameter than the internal diameter of said first cylinder portion, a hammer piston reciprocable in said cylinder portions for intermittently impacting against said anvil, said piston having an upper portion slidably reciprocable in said first cylinder portion and in sealed relation thereto, and a lower portion of greater diameter than said upper portion slidably reciprocable in said second cylinder portion and in sealed relation thereto; first means for directing a fluid medium under pressure into said first cylinder portion above said upper piston portion and into said second cylinder portion above said lower piston portion for driving said hammer piston downwardly toward said mandrel; second means for directing the fluid medium under pressure into a lower portion of said housing structure for action upon said hammer piston to elevate said hammer piston in said housing structure; and exhaust passage means for exhausting substantially all of the fluid medium from said cylinder portions above said upper and lower piston portions and from said Lower portion of said housing structure into said exhaust passage of said anvil; said first directing means including an impact passage in said piston opening at its upper portion into said first cylinder portion above said upper piston portion and at its lower portion into said second cylinder portion above said lower piston portion, said first directing means further including an inlet passage in said housing structure opening into said first cylinder portion through a side wall thereof and communicating with the lower portion of said impact passage upon upward movement of said piston in said housing structure.

6. In apparatus as defined in claim 5; said exhaust passage means including an exhaust passageway in an inner side wall of said second cylinder portion placed in communication by said hammer piston with said lower portion of said impact passage upon downward movement of said hammer piston in said housing structure, said exhaust passage means further including an exhaust passage in said hammer piston communicating with said exhaust passageway and said anvil exhaust passage.

7. In apparatus as defined in claim 5; said second directing means further including a return passage in said piston opening at its lower portion into said lower portion of said housing structure below said piston and at its upper portion into said first cylinder portion in communication with said inlet passage upon downward movement of said piston in said housing structure.

8. In apparatus as defined in claim 5; said second directing means further including a return passage in said piston opening at its lower portion into said lower portion of said housing structure below said piston and at its upper portion into said first cylinder portion in communication with said inlet passage upon downward movement of said piston in said housing structure; said exhaust passage means including an exhaust passageway in an inner side wall of said second cylinder portion placed in communication by said hammer piston with said lower portion of said impact passage upon downward movement of said hammer piston in said housing structure, said exhaust passage means further including an exhaust passage in said hammer piston communicating with said exhaust passageway and said anvil exhaust passage and with said housing structure below said piston.

9. In percussion drilling apparatus: a housing structure connectible to a drill string and having an inner cylinder portion and an outer portion surrounding said inner portion and spaced laterally therefrom to provide an annular air inlet passage therebetween, said outer portion extending below the lower end of said inner portion and having an inside diameter substantially greater than the inside diameter of said inner portion to provide an outer cylinder portion of greater internal diameter than said inner portion; an anvil in the lower portion of said housing structure and having an exhaust passage; a hammer piston reciprocable in said housing structure for intermittently impacting against said anvil, said piston having an upper small diameter portion slidably reciprocable in said inner cylinder portion and a lower large diameter portion slidably reciprocable in said outer cylinder portion below said inner cylinder portion; said inner cylinder portion having one or more side ports communicating said annular passage with the interior of said inner cylinder portion; said outer cylinder portion having an exhaust passageway in its inner side wall below said inner cylinder portion; said piston having an impact passage opening at its upper end into said inner cylinder portion and at its lower end into said outer cylinder portion; said piston having a return passage opening at its lower end into said outer cylinder portion below said piston and at its upper end into said inner cylinder portion below the upper end of said piston; said piston having an exhaust passage communicating said exhaust passageway with said anvil exhaust passage, said piston having means thereon cOacting with said housing structure to alternately communicate said impact passage with said one or more side ports and said exhaust passageway upon upward and downward movement, respectively, of said piston in said structure, said piston having means thereon coacting with said housing structure to alternately communicate said return passage with said one or more side ports and said piston exhaust passage upon downward and upward movement, respectively, of said piston in said structure.

10. In apparatus as defined in claim 9; and a sleeve in said anvil exhaust passage adapted to extend into said piston exhaust passage.

11. In apparatus as defined in claim 9; and a sleeve in said anvil exhaust passage adapted to extend into said piston exhaust passage in sealing relation to said piston; said piston being movable off said sleeve upon elevation of said piston in said structure to permit air below said piston to exhaust into said anvil passage.

12. In percussion drilling apparatus: a housing structure; an anvil extending into the lower portion of said housing structure; a hammer piston reciprocable in said structure above said anvil; means for reciprocating said piston in said housing structure for intermittently impacting said piston against said anvil; a connection between said housing structure and anvil including V-shaped external splines on said anvil, a member comprising a plurality of separate parts having V-shaped internal splines adapted to mesh with said external splines, said parts being movable laterally inwardly of said anvil toward each other to mesh said internal splines with said external splines, and means on said housing structure encompassing and retaining said separate parts in their lateral inward position.

13. In apparatus as defined in claim 12; said encompassing and retaining means including external threads on said parts meshing with companion internal threads in said housing structure.

14. In apparatus as defined in claim 12; the outer ends of said external splines lying on a circle of lesser diameter than the external diameter of said anvil above said splines.

15. In apparatus as defined in claim 12; said encompassing and retaining means including external threads on said parts meshing with companion internal threads in said housing structure, the outer ends of said external splines lying on a circle of lesser diameter than the external diameter of said anvil above said splines.

16. In apparatus as defined in claim 12; said separate parts consisting of two members each having an arcuate extent of about 180* and movable laterally inwardly of said anvil toward each other to mesh said internal splines fully with said external splines without interference from said external splines.

17. In apparatus as defined in claim 12; said external splines being circumferentially spaced uniformly from each other, said internal splines being circumferentially spaced uniformly from each other and movable laterally inwardly towards each other to mesh said internal splines fully with said external splines without interference from said external splines.

18. In apparatus as defined in claim 12; said external splines being circumferentially spaced uniformly from each other, said internal splines being circumferentially spaced uniformly from each other; said separate parts consisting of two members each having an arcuate extent of about 180* and movable laterally inwardly of said anvil toward each other to mesh said internal splines fully with said external splines without interference from said external splines.

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