US2764130A

US2764130A - Fluid actuated impact tool

Info

Publication number: US2764130A
Application number: US300737A
Authority: US
Inventors: Bassinger Ross
Original assignee: Individual
Current assignee: Individual
Priority date: 1952-07-24
Filing date: 1952-07-24
Publication date: 1956-09-25
Anticipated expiration: 1973-09-25

Description

Sept. 25, 1956 Filed July 24, 1952 R. BASSINGER FLUID ACTUATED IMPACT TOOL 4 Sheets-Sheet l Ross Bass vger INVENTOR.

ATOR/VEYJ Sem., 25, 1956 R. BAsslNGER FLUID ACTUATED IMPACT TOOL 4 Sheets-Sheet 2 Filed July 24, 1952 RO JJ 50455 099/ INVENTOR.

Sept. 25, 1956 Filed July 24, 1952 Qawm \\wwwwwww R. BASSINGER FLUID ACTUATED IMPACT TOOL 4 Sheets-Sheety 3 V fax` J -Z @j Ross 5mm/nger INVENTOR.

Sept. 25, 1956 R. BAssxNGER FLUID ACTUATED IMPACT TOOL 4 Sheets-Sheet 4 Filed July 24, 1952 www rl .INVENTOIL Byw/ W M w d M M w w m /f /7 f r rM////V/r/r/r/ii ...Wx j l.

United States Patent i O FLUID ACTUATED IMPACT TOOL Ross Bassinger, New Braunfels, Tex. Application Jury 24, 1952, serial No. 300,731

Claims. (Cl. 121--1 6) This invention relates to a fluid actuated impact tool. In one of its aspects, this invention relates to such a uid actuated impact tool particularly adapted for use in the drilling of wells. In another of its aspects, this invention relates to a novel method of drilling wells.

Many efforts have been made to provide a uid actuated impact tool suitable for use in the drilling of wells, such as oil wells. One of the iirst of such tools which has met with any degree of success is of the type shown in my Patent No. 2,507,585 issued May 16, 1950. While this type of tool served very well to deliver percussive energy to a bit, the sleeve-piston arrangement as shown in the above patents drawings results in the tool being closed to huid flow except during its actual operation. The control sleeve is always seated, over the hammer piston when the tool is run into the hole and prevents lluid from entering or leaving the drill string. AS a result, it is necessary to lill the drill string with mud or water as the same is passed into the bore hole. O n the other hand, this arrangement prevents mud from leaving the drill string as the tool is pulled from the hole so that a wet string must be pulled. Further, in a tool constructed according to the above patent drawings, it is normally impossible to ream a bore hole without causing the hammer to beat on the anvil since any flow of the drilling mud will cause the hammer to reciprocate. While the tool shown in the above patent drawings is very useful, it is an object of this invention to provide an improved tool eliminating the above enumerated disadvantages and providing certain other advantages over the old type tool as will be explained below.

It is an object of this invention to provide a fluid actuated impact tool particularly adapted in one of its uses for the drilling of wells, such tool being comparatively simple to operate and yet being susceptible of :use under variously diiferent circumstances.

Another object of this invention is to provide a fluid actuated impact tool which embodies relatively few parts and is simple in construction, very rugged, and has easily replaceable wear parts so that it can be Veunployed in the field by personnel not having extensive training in its repair or use.

Another object ot this invention is to provide -a fluid actuated impact tool which, when used to drill a well, can be run into the hole without lling the dri-11 string `and can be pulled from the hole without .pulling a wet drill string, the tool remaining open for (lluids to pass therethrough during such operation.

Another object ot this invention is to provide a uid actuated impact tool which can be used in the hole while reaming or circulating mud therethrough without .causing any hammering on the bit by the tool and yet such hammering can be started and stopped at will without pulling the tool from the well.

Another object of this invention is -to provide a ll-uid actuated impact tool in which a valve part employed Fto form a uid responsive piston with a hammer is Varranged so that it is movable out of the path of vtravel of said V2,764,136 Patented Sept. 25, 1956 2, hammer, thereby preventingreciprocation ofthe hammer even while lluid is being., circulated through the tool and yet which can be moved into thel path of travel of the hammer without necessarily increasing the rate of uid circulation and withoutpulling the tool, such latter movement being caused by closing a valve thereby effecting an increase in pressure differential within the tool to move the valve part into the path of=travel of the hammer.

Another object of this invention is to provide in such a `tool an arrangement of said valve part so that it seats upon the hammer while the latter is yet travelling in its return stroke whereby the force of the fluid flowing into the tool acts on the hammer to stop it at the end of its return stroke and then to. move it into. its power stroke.

Another object of this invention is to provide a restrictive tiow passage for the purpose of moving a valve part into cooperating position with another valve part on the hammer to cause reciprocation of the latter but also to reduce the force created by the surge of lluid to a bit carrier and anvil upon unseating of the valve parts, thereby decreasing the tendency for such bit carrier to be pushed out of the tool.

Another object of this invention is to provide a method of drilling a well wherein a bit is first employed in a conventional rotary drilling manner and, when the bit becomes dulled, the drilling is continued through the use of percussive energy exerted on the dulled bit.

Other objects, advantages and features of this invention will be apparent to one skilled in the art upon a consideration of the written specificationIl the appended claims and the attached drawings wherein:

Fig. l is a cross-sectional elevational view, diagrammatic in form, showing an embodiment of the tool, the elements thereof being positioned as when the tool is being lowered into a well;

Pig. 2 is a view similar to Fig. 1 except that the tool is shown in operation immediately after the hammer has caused the control valve to become unseated;

Fig. 3 is a further view showing the hammer at or near the end of its return stroke and illustrating overtravel thereof after seating of the control valve;

Figs. 4, 4A, 4B, 4C a-nd 4D are detailed half-sectional elevation views of an embodiment of the 'tool of this invention illustrating the arrangement of its parts; 4

Fig. 5 is a cross-sectional view taken on the line 5 5 of Fig. 4A; and

Fig. 6 is a cross-sectional view taken on 4the line 6-6 of Fig. 4B.

Like characters of reference are used throughout the several views to designate like or eorresponding'parts.

Referring now to Figs. 4 through 4D, it will be understood that these views are of the same tool, the views being properly arranged one after the other in numerical order with Fig. 4 at Ithe top of the tool and Fig. 4D at the bottom of the tool. A'housing designated generally by the numeral 10 is made up of a plurality of parts including a top sub 11, a control sub 12, a hammer case 1'3, and an anvil sub 14. These subs are connected together by conventional pin and box joints and have, in addition, a sealing means at each joint, such as Orings 15a, to prevent seepage along the joints.

Anvil sub 14 sl-idably or telescopica'lly receives an anvil 15 to which can Abe attached -a bit 16 vwith a conventional `fluid passageway 16a therethrough. The upper part of anvil 15 is fashioned into an anvilhead 15b having a striking face 15C. Anvil sub 14 and anvil 15 are each `provided with interlocking

lingers

17 and 18, respectively, so that upon engagement thereof, the anvil is Vprevented from rotating with respect to the anvil sub and the remainder of che housing but is permitted :to move longitudinally with `respect thereto. A neck portion 1 9 of the Aanvil is provided with an elongate annular

ngroove having shoulders

21 and 22. groove is a split ring 23 held in place by O-ring 24. It will be noted that the distance which anvil 15 must move to completely disengage its lingers or extensions 18.,from the corresponding fingers of anvil sub 14 is greater than the distance between the top of split ring 23 and shoulder 21. With this construction, the tool can be picked up without permitting the anvil and bit dropping therefrom and yet longitudinal movement between the anvil sub and anvil is permitted. This relatively free longitudinal movement between the anvil and the anvil sub permits the hammer to beat on the anvil without Situated within thev any substantial transmission of percussive energy to hous- 'f A. hammer 25 which is reciprocal with respect to housingfr 10 is provided and is of suflicient weight that a reasonably large amount of percussive energy per stroke of the hammer can be delivered to the anvil and lyet is light-enough that the frequency of beating can'be maintained relatively high. Hammer 25 comprises a main body which is preferably provided with a replaceable hammer face 26, the latter being connected to the main body by a long taper joint of sticking taper. The upper end of the hammer is tapered as at 27 with respect to the inner wall of hammer case 13 for a purpose which will be described later. In this particular embodiment of thehammer, a fluid ow passage 28 is provided therethrough communicating with the external portion of the hammer through a plurality of radial slots 29 near the upper end of the hammer and continuing downwardly to communicate with a corresponding passage 15d in anvil 15. In this manner, drilling mud or other operating iluid can flow through the hammer, anvil and then out the bit.

It will thus be seen that the hammer and the housing provide a flow passage through the tool; it being understood that such ow passage can include the annular space between the hammer and housing or even consist of such space if it is desired to eliminate passage 28 and make the hammer solid.

Means are provided for biasing the hammer away from the anvil and in the direction of the hammers return stroke. Such means can comprise a spring 30 having one end seated against an external annular shoulder 31 on the hammer and the other end against a seat member 32 which is in the form of a sleeve having an outwardly extending shoulder abutting against another shoulder 33 on the housing. A plurality of flow passages 34 are provided through the seat member in order that fluid may circulate externally of the hammer and keep the annulus between the hammer and the housing clean. Spring 30 is shown to have a rectangular cross-section although it can be round, ov`al or of any desiredv crosssection. Such spring need not be extremely strong and in most cases need only have a strength to easily lift the hammer to its uppermost position in the tool without having any great net upwardly exerted force over that required to lift the hammer.

A uid motor is provided for actuating the hammer during its power stroke towards the anvil and for arresting movement of the hammer away from the anvil near the end of the hammers return stroke. Such fluid motor can comprise a valve part, designated generally by the numeral 35, which is carried by the hammer and another valve part, designated generally by the numeral 36, the two valve parts adapted to engage or seat and form a piston within the housing against which the uid flowing through the housing can act to urge the hammer toward the direction of the anvil. Valve part 35 comprises a ball 37 riding upon a seat 38 on the end of the hammer. Seat 38, as shown in Fig. 6, is provided with a plurality of spaced passages 39 therethrough to permit iluid flow past the seat and yet provide guides to 'maintain the upper end of the hammer centered in the housing. The inner portion of the seat is formed in general conformity with ball 37. but the radius .of curvature of the seat is slightly larger than that of ball 37 so that the ball is free to rotate with respect lto its seat thereby presenting constantly new wear surfaces to valve part 36.

Valve part 36, as shown in the drawings, comprises a control sleeve 40 which is reciprocally mounted with respect to the housing and has a seat portion 41 adapted to seat with and engage ball 37. It will be noted that control sleeve 40 is barrel shaped in order to decrease its weight and this is highly desirable inasmuch as this sleeve must reciprocate at a high frequency and the light weight permits quick reversals of its movement with a minimum of energy. A seal ring 42 is provided around sleeve 40 to form a 'wiping seal with the inner surface 44 of control sub 12. Above the seal is a square shoulder 43 for scraping inner surface 44 of the control sub to keep it clean. Flow passages 45 extend from immediately adjacent scraping shoulder 43 to the inner portion of sleeve 40 so that any` debris scraped from the control sub will be washed into the sleeve and thence out of the tool. Additional flow passages 46 can also be provided to prevent any dashpot action from occurring between the upper part of the sleeve and the part of the housing adjacent thereto.

. A carrier is provided for control sleeve 40 and such carrier is reciprocally mounted in housing 10 so as to be movable from a rst position where sleeve 40 is without the path of travel of the hammer to a second position-.where the sleeve is positioned for movement in a path overlapping part of the path of travel of the hammer. Thus, with the carrier positioned in its first position, sleeve 40 cannot seat on ball 37 and fluid is free to flow through the tool without causing any reciprocation of the hammer. On the other hand, with the carrier in its second position, sleeve 40 is lowered so that it can seat on ball 37 and coact therewith as will be described below.

l The carrier, in one of its embodiments, comprises-a carrier sleeve 50 having an outturned shoulder 51 at its end most removed from the hammer, the shoulder being adapted to abut a stop to limit travel of the sleeve toward the hammer. The stop can comprise a shoulder 52 on the control sub 12, optionally provided with spacer rings 53 for controlling the spacing of the carrier sleeve with regard to the hammer. A control flow valve seat member 54 is carried by the carrier sleeve 50. It will be noted that the seat member 54 has an outer diameter less than the inner diameter of sleeve 50 so that it can be passed therethrough in assembly. A split locking ring 55 is provided to seat on offset but opposing shoulders on sleeve 50 and member 54 to lock member 54 in place. Member 54 supports control sleeve 40 by means of spring 56 which can be threaded to member 54 and sleeve 40. Spring 56 is of such length and strength that it normally urges sleeve 40 against shoulder 57 on sleeve 50 thereby providing a stop to limit upward travel of sleeve 40 away from the hammer. In this manner, sleeve 40 is mounted reciprocally with respect to the carrier and tool housing and is biased in a direction away from the hammer.

Sleeve 40 is also provided with an outwardly extendingV shoulder 60 for abutment with wear ring 61 situated on a shoulder 62,0f control sub 12. In this manner, stop parts are provided to limit travel of sleeve 40 toward the hammer.

In accordance with one important feature of this invention, the valve part carrier is positionable in two positions. As shown in Fig. 4A, the carrier is in its second position so that sleeve 40 is positioned for movement in a path overlapping the travel of the hammer. Means are provided for moving the carrier to its iirst position and for biasing it away from the hammer. Such means can comprise a spring 63 seated on a shoulder .64 of control sub 12 and having its other end ,ac ting against spacer rings 53. Spring 63 is of suicient strength to move the carrier toward and abut it against shoulder 65 on top sub 11 and to thereby position it in its first position under the conditions outlined below. When the carrier is in its upper position, spring 56 pulls sleeve 40 against shoulder 57 and removes sleeve 40 from any possibility of contact with ball 37. Since the strength of spring 56 is greater than the resistance of sleeve 40 to fluid flow when unseated from ball 37, sleeve 40 is maintained on shoulder 57. Hence, with the carrier in its upper or rst position, it will be obvious that lluid is free to flow through the tool without causing the hammer to reciprocate and beat upon the anvil.

To overcome the force of spring 63 and move the carrier from its first position to its second position, means are provided for creating sufficient pressure differential across the carrier that the resulting effective force urging the carrier toward the hammer will be greater than the force of spring 63 urging the carrier away from the hammer. Such means can comprise a valve seatable on the carrier to partially restrict a flow passage across the carrier, such flow passage forming a part of the ilow passage through the tool. As illustrated in the drawings, control flow ball seat member 54 has a central opening therein with a seat 66 upon which a valve element such as ball 67 is seatable. With ball 67 seated, there still remains additional flow passage across the carrier in the form of openings 68 so that fluid can continue to llow through the tool. The total ilow area across the carrier with ball 67 removed is suiciently large that, for the contemplated rate of uid flow through the tool, the pressure drop `'across the carrier will result in a force thereon less than that of spring 63 so that the carrier will be urged upwardly to seat against shoulder 65. However, when ball 67 has been dropped through the tool to seat upon seat 66, the flow is restricted to an extent that the resulting pressure drop across the carrier is of sucient magnitude to overcome the strength of spring 63 and position the carrier and control sleeve 40 as shown in Fig. 4A.

In order to assure that ball 67 will become properly seated when dropped into the tool, a ball guide ring 70 is provided with a tapered shoulder 71 so that the ball will be directed inwardly toward its seat. Also, it will be noted that a flow passage 72 is provided through seat member 54 so that fluid can wash any debris from around member 54. Also, sleeve 50 is provided with a plurality of longitudinal slots 73 permitting free How laterally across the sleeve not only to wash any debris or deposits from spring 63, shoulder 64 or spacer rings 53, but also to prevent sleeve 50 from having any dashpot action with the annular space in sub 12 containing spring 63.

The lower end of sub 12 forms a shoulder 74 against which the upper end 75 of the hammer can abut to limit upward movement thereof. With the tool positioned as shown in Figs. 4 through 4D with the hammer in con tact with the anvil, the spacing between

shoulders

74 and 75 lis less than the distance the carrier can be moved upwardly before abutting shoulder 65. Or stated in another manner, with the apparatus positioned as in Figs. 4 through 4D, the `distance between

shoulders

74 and 75 minus the distance sleeve 40 must travel to abut shoulder 57 must be less than the distance between the top of ring 70 and shoulder 65.` With this construction, the hammer is not stopped in its upward movement by force transmitted through control sleeve 40, sleeve 50 and shoulder 65 but it must first abut shoulder 74. As a result, sleeves 40 Vand 50 can be made of very light weight which is desirable in view of the high frequency of operation of sleeve 40.

In operation, fthe tool can be lowered into the well during which time it will occupy the position shown in Fig. l. I-t will be noted that ball 67 is not then seated in member 54 and that the carrier is pushed to its uppermost position against shoulder 65 by spring 63 thereby removing sleeve 40 from the path of travel of the hammer. The hammer is in its uppermost position, as urged by spring 30 so that its upper end 75 is seated against shoulder 74. Of course, shoulder 65 is sufficiently removed from hammer 25 that fluid flow between sleeve 40 :and ball 37 will not cause suicient pressure ditferen tial across rthe sleeve to pull it down against the ball. It is apparent `that control sleeve 40 cannot seat against ball 37 even `though fluid is flowed through the tool at its normal ratte. The tool is open -to lluid flow when in this position and can be run into the hole or pulled therefrom without necessitating filling the drill string or pulling a wet drill string. It is also possible to ream the hole or to circulate mud through the tool without causing the hammer `to reciprocate.

When` it is desired to cause Athe hammer to beat against the anvil, ball 67 is dropped through the drill string and oaused .to seat on seat 66. This causes the pressure differential across the valve carrier to increase to an extent such that the elective force urging the carrier downwardly overcomes spring 63, causing the carrier tto assume the position shown in Fig. 2. The downward movement of the carrier also moves valve part 36 (of control sleeve 40) downwlardly to a point where it can cont-act ball 37 on the hammer. As soon as the control sleeve seats ont the ball, lthere is formed a iluid piston within lthe housing lacting to drive the hammer downwardly. The effective cross-sectional area of the piston is that within seal 42 on control sleeve gli). The pressure of fluid below sleeve 40 and externally of ball 37 will be substantially that o-f the bore hole while the pressure in the drill string labove ball 37 and within sleeve 40 will be much higher. This pressure differential causes sleeve 40 to follow the hammer downwardly until the sleeve abuts its shoulder 60 against wear ring 61 on shoulder 62. At this point, sleeve 40 stops and the li'iammer continues travelling downwardly until ift strikes the anvil head i519. However, immediately after the control sleeve has become unseated from ball 37, the pressure differential across the flow sleeve is equlalized and spring 56 is then free to exert its force and moves the sleeve upwardly until it abuts against shoulder 57 of carrier sleeve 50. In Fig. 2, the lapparatus is shown immediately after `the hammer has caused ball 37 to be unseated from the control sleeve and just as the control sleeve staats its upward movement. As stated, hammer 25 continues downwardly until it strikes the anvil whereupon the hammer rebounds land, aided by spring 30, moves upwardly. Since sleeve 40 has preceded the hammer in its upward movement and has seated itself against shoulder 57, the hammer will continue travelling upwardly unitil ball 37 seats against the Icontrol sleeve. At the :time of this seating, the hammer will still have considenable upward momentum but the seating of the control sleeve and ball will again form a piston in the housing permitting the down flowing uid to exert its force against Vthe hammer to arrest its upward movement and thence begin |its power stroke. However, due to .the slight compressibility of the fluid and the breathing of `the drill string, the hammer will overtnavel after the ball has seated on the control string and this overtravel is compensated by lifting of the controlvsleeve and the carrier therefor from spacer rings 53, as shown in Fig. 3. Under some circumstances, the. Vhammer may continue travelling upwardly until it strikes shoulder 74 which will completely arrest its upward movement. ln other circumstances, the force of the downllowing iluid will be sulhcient, relative Ito :the upward momentum of the ham mer after the ball and control sleeve have sea-ted, to arrest the upward movement of 4the hammer before it strikes shoulder 74. ln any event, the carrier, control sleeve 49, and hammer move downwardly until the control sleeve seats on spacer rings 53. Thereafter, the

- 7 control sleeve continues its downward travel with the hammer thereby tensioning spring 56 until the control sleeve seats against Wear ring 61. Then the hammer continues downwardly while the control sleeve moves upwardly and lthe cycle is repeated las explained above.

In some circumstances, it may be desirable to stop beating of the hammer on the anvil after ball 67 has been seated. To do this, it will be necessary to either yunseat ball 67 or yto provide a means for locking the hammer in a downward position so that bia-ll 37 is out of Contact with control sleeve 40. Where `it is not possible to backilow ythrough the tool rand unseat ball 67 or Ito fish` ball 67 out of its seat, a small locking brall 76 can be dropped through the drill string to become lodged as shown in Fig. 4B. This ball is sufficiently small that it will pass through passages 68 (Fig. 5) down through the control sleeve around ball 37 through a passage 39 (Fig. 6) land thence down between tapered part 27 o-f the hammer and hammer case 13. Then, as the hammer moves downwardly, ball 76 will follow the same to become wedged and prevent upward movement of the hammer. Radial slots 29 in the hammer are, of course, made suiciently narrow that ball 76 cannot pass therethrough. With ball 76 positioned as in Fig. 4B, circulation `through the tool can be continued without causing hammering on the anvil.

lt should be noted that even with ball 67 in its seat, cessation of flow through the tool will permit spring 63 to lift the carrier lto its first position 'against shoulder 65 thereby opening the valve formed by sleeve 40 and ball 37 permitting pulling of the drill string in a dry condition. It should also be noted that with ball 67 in place, the surge of fluid resulting when sleeve 40 becomes unseated from ball 37 is decreased due to the restricting effect of ball 67. This decrease and surging effect reduc-es the force of the fluid surge upon the anvil thereby lessening the tendency of the fluid tot blow the anvil out of the tool.

In noting further advantages of the type of construction of this tool as shown in drawings, -it is necessary to merely provide three threaded joints to permit ready assembly of the tool as contrasted to at least twice that number used in tools heretofore known. Further, the hammer is provided with a readily replaceable hammer face Z6. As will be apparent, the end of the hammer striking the anvil will, in time, need to be replaced and the type of tapered joint provided herein facilitates such a replacement. ln like manner, the wear ring 61 for control sleeve 40 can be readily replaced and, as the control sleeve seating surface 41 tends to wear -away by contact with the ball, the wear ring 61 likewise wears away and tends to compensate for wear of seat 41. lnasmuch as ball 37 is free to rotate upon the seat, it will wear evenly and, in so doing, will wear seat 41 of the control sleeve evenly also. As the control sleeve wears away, it Will bc possible to remove or replace with thinner ones, the spacer rings 53 to compensate for this wear. Another function of spacer rings 53 is -to permit adjustment of the frequency of beating of the hammer on the anvil. As the combined thickness of the spacer rings is increased, it will be apparent that the hammer must travel further upwardly to seat its ball 37 against control sleeve 40 before its upward movement is arrested. As a result, the frequency will be decreased. On the other hand, by removing or replacing some of Wear rings 53 with thinner ones, the frequency of beating can be increased.

ln accordance with one aspect of this invention, there is provided a new method for drilling a well. According to this method, an impact tool of the above type is particularly adapted to be employed therein, although other types of tools can be employed with less ease. In the method, a bit is run into the hole attached to the tool and employed in a conventional rotary manner to make hole. ln so doing, ball 6,7 is not dropped into its seat so that fluid is free to circulate through the tool without causing hammering. While conducting this conventional rotary drilling, the tool serves the dual function of ai percussive energy thereto and it has been found that in this manner, the life of the bit can be approximately doubled. This nding is based upon the further dis'- covery that a bit which has become too dull for effective rotary drilling can be readily used for percussive type drilling with little, if any, decrease in the effectiveness of the percussive drilling. -1

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the structure.

It will be understood that certain features land subcombinations are of utility and may be employed Without references to other features and subcombinations. This is contemplated by and is Within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimedy l. A fluid actuated impact tool which comprises, in combination, a housing, an anvil, a hammer reciprocally mounted in the housing to beat against the anvil, means biasing the hammer away from the anvil, and la fluid motor for actuating the hammer comprising a first valve part carried by the hammer, a second valve part, a carrier reciprocally mounted in said housing for movement toward and away from said hammer and reciprocally mounting said valve part for movement with respect to the housing, means for exerting a force to bias said carrier to a first position where the second valve part is positioned without the path of travel of said hammer, and means for moving the carrier to a second position where said second valve part is positioned for movement in a path overlapping a part of that of the hammer including a flow passage across the carrier and a valve velement seatable on said carrier to partially restrict said passage to thereby cause a differential of fluid pressure to develop across the carrier and urge the carrier to its second position with a force greater than the force of said means urging the carrier to its first position.

2. A fluid actuated limpact tool which comprises, in combination, a housing, an anvil, a hammer reciprocally mounted in the housing to beat on the anvil, means biasing the hammer away from the anvil, and a fluid motor driving lthe hammer in its power stroke toward the anvil and arresting movement of the hammer at the end of its return stroke comprising a carrier slidably received in the housing in a position more remote from said anvil than said hammer and biased away from the hammer to a first position, a first valve part carried by the hammer, a second valve part reciprocally carried by the carrier and likewise biased away from the hammer, said carrier in its first position maintaining the second valve part out of contact with the first and providing a ow passage thereacross forming a portion of a flow passage through said housing, and a valve for restricting the flow passage through said carrier to an extent that with the valve seated, a pressure differential is developed across said carrier to provide a force sulicient to move the carrier to a second position where the path of travel of said second valve part overlaps a part of the path of travel of said hammer.

3. The tool of claim 2 wherein said carrier has a sleeve portion with the second valve part suspended therefrom by a spring and a stop is provided to limit the travel of said second valve part while seated with the first valve part to be less than the length of the power stroke of said hammer.

4. The tool of claim 3 wherein said valve for restricting flow through said carrier comprises a seat on said carrier and a separate valve element seatable thereon by dropping into said housing from above said carrier, said seat embracing less than the total ow area of said passage across said carrier so as to restrict the fiow through the same.

5. A fluid actuated impact tool which comprises, in combination, a housing, a hammer mounted for reciprocation with respect to the housing, said housing and hammer providing a flow passage through the tool, and a fluid motor for actuating said hammer comprising a first valve part carried by the hammer, a second valve part engageable with the rst, a carrier reciprocally mounting said second valve part in said housing out of the path of movement of said hammer with the carrier in a first position and movable to position said second valve part for movement in a path overlapping that of said hammer with the carrier in a second position, and a valve for partially closing a How passage across said carrier.

6 A fiuid actuated impact tool which comprises, in combination, a housing, an anvil, a hammer reciprocally mounted in said housing for striking said anvil, said hammer and housing providing a fluid passage through the tool, means biasing the hammer away from the anvil and a fluid motor for arresting movement of the hammer away from the anvil and for actuating it during a power stroke toward the anvil comprising valve parts mutually engageable to limit `fluid flow past said hammer, one of the valve parts being carried by the hammer, a carrier slidably mounted in said housing and reciprocally carrying the other valve part, said carrier being movable from a first position where said other valve part is without the path of travel of said hammer to a second position where said other valve part is positioned for movement in a path overlapping a part of that of said hammer, means urging said carrier from its second to its first position, and means for moving the carrier from its first to its second position including a valve seat embracing at least a part of a flow passage across said carrier, and a valve element seatable on said seat to restrict fiuid flow through the carrier ow passage to an extent suicient to develop on effective force of fluid pressure urging the carrier to its second position which is greater than the effective force of said means urging the carrier to its first position.

7. A fiuid actuated impact tool which comprises, in combination, a housing, an anvil, a hammer reciprocally mounted in said housing, means biasing said hammer away from said anvil toward a stop carried by the housing, and a fluid motor arresting movement of the hammer near the end of its return stroke and driving it in its power stroke comprising a first valve part carried by the hammer, a carrier slidable in the housing toward and away from said first valve part and having a iiuid passage forming a part of a passage through the tool, a sleeve valve part slidable in the housing and engageable with said first Valve part to form a piston therewith responsive to fluid ow through the tool, means biasing said sleeve part toward a stop on the carrier and away from the first valve part, a second stop on the housing limiting movement of said sleeve part to be less than the power stroke of said hammer, means exerting a force to urge said carrier away from said first valve part to a first position where said sleeve part is without the path of travel of said first valve part and a valve element seatable across a portion of the fluid passage across said carrier to restrict flow thereacross sufficient to provide a force urging the carrier toward the first valve part of greater magnitude than that of the effective force of said means urging the carrier away from said first valve part.

8. The tool of claim 7 wherein said anvil is reciprocally carried by the housing, said anvil and housing having interengaging longitudinally extending fingers permitting relative longitudinal movement between the anvil and housing but preventing relative rotative movement therebetween.

9. The tool of claim 8 in combination with mutually engageable stop parts carried by the anvil and housing limiting the relative longitudinal movement between the anvil and housing to be less than the effective length of said interengaging fingers.

10. The tool of claim 7 wherein the hammer has a portion tapered in a direction away from said anvil and wherein the fluid passage upstream of the tapered portion is sufficiently large in cross-section to pass an element adapted to become wedged between the housing and hammer to lock the latter away from the sleeve part.

References Cited in the file of this patent UNITED STATES PATENTS 1,861,042 Zublin May 31, 1932 2,283,510 Potter May 19, 1942 2,286,835 Robinson et al. June 16, 1942 2,425,193 Lehr Aug. 5, 1947 2,559,012 Davis et al. July 3, 1951 2,580,203 Topanelian Dec. 25, 1951 2,584,978 Bassinger Feb. 12, 1952 2,662,505 Cline, Jr. Dec. 15, 1953