US 3162251 A
Abstract available in
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Description (OCR text may contain errors)
DeC- 22, 1964 R. BAsslNGER 3,162,251
ENCLOSED CASE MUD PERCUSSION Toox.
Dec. 22, 1964 R. BAssxNGER ENCLOSED CASE Mun PERCUSSION Tool.
2 Sheets-Sheet 2 Filed Jan. 19, 1960 u n z n 55/ LJ L? Aww@ NNNW 7,7 -.g- L \v\ y n f f www? il A .w
/POJJ Bair/gef IN VEN TOR.
bis operable at high speeds with United States Patent Ofice 3,162,251 Patented Dec. 22, 1964 3,162,251 ENCLGSED CASE MUD FERCUSSIDN "1300L Ross Bassinger, Rte., 11, Box 588, San Antonio, Tex. Fiied Jan. 19, 196i?, Ser. No. 3,300 16 Claims. (Ci. 173-73) This invention relates to new and useful improvements in percussion tools powered by a non-compressible hydraulic iluid.
Rotary bits, jars and other tools having reciprocating high speed percussion elements operated by an incompressible hydraulic fluid have been widely in quarying stone, drilling oil and gas wells through hard formations and in other applications. The percussion mechanisrn of such tools are of two general types; (l) those in which valves or percussion elements are spring actuated,and (2) those in which one surface of a piston driving a hammer in the tool is exposed to constant fluid pressure for driving it in one direction While another opposed larger surface is exposed to intermittent fluid pressure for driving it in the other direction with the admission of fluid pressure to the larger surface controlled by movement of the piston.
Each of these general types of tools has certain disadvantages. For example, springs become fatigued, break and have to be replaced frequently when subjected to tension or compression at a speed of many hundreds of times per minute. Differential piston type tools, as typified by U. S. Patent 1,096,886, eliminate the necessity for springs to operate valves or hammers but have a tendency to trap incompressible hydraulic uid between the hammer and anvil forming essential parts of such tools, thus cushioning the hammer blow and decreasing its effectiveness.
It is an object of this invention to provide an improved percussion tool operated by an incompressible hydraulic fluid in which cushioning of a hammer blow cannot occur.
Another object is to provide a percussion tool operated by incompressible hydraulic fluid in which spring actuation of hammer and valves is eliminated.
j Another object is to provide a percussion tool in which build up of solids that may be present in the actuating hydraulic fluid on the opposed faces of hammer and anvil is substantially eliminated.
Another object is to provide a tool of this class that may be operated at high speeds with little fatigue of valves and percussion elements.
Another object is to provide a tool of this class in which light weight long wearing hydraulic fluid operated reciprocating valves of improved design give positive control of hydraulic iuid pressure applications.
Another object is to provide a tool of this class which substantially no water hammer.
Still another object is to provide a tool of this class having a reciprocating finger valve disposed to open and close an outlet for hydraulic iiuid from the tool in which the finger valve is hydraulically and positively prevented from entering and closing the outlet passage until after thehammer has struck the anvil.
Other objects, advantages and features of this invention will be apparent to one skilled in the art upon a consideration of the written specication, the attached claims and annexed drawings.
In the drawings, wherein like reference characters are used throughout to designate like parts:
FIGS. 1 and 2 are vertical sections through a preferred v embodiment of this invention. FIG. 1 illustrates an upper part of the tool and FIG. 2 a lower part of the same tool, FIG. 2 being a continuation of and to be considered as joined to the lower end of FIG. 1;
FIGS. 3, 4 and 5 are vertical sections through a modication of this tool and illustrate sequential parts of a hammer stroke and show the valve and conduit relationships at sequential parts of the stroke.
The tool illustrated in FIGS. 1 and 2 comprises a housing designated generally by the reference numeral 1. For convenience in manufacturing, this housing preferably is made of three parts; a short upper sub 2, an adjoining thick-walled section 3, and a lower thin-walled section 4.
The upper part of sub 2 preferably is vformed as a tool joint pin 5 having threads 6 suitable for connection to a drill string. Sub 2 has a conduit 7 for entrance of hydraulic uid under pressure, which preferably leads to a cavity 8 in the sub which in turn communicates through several conduits 9 with a space 11 within the upper part of the thick-walled upper section 3. Sub 2 and section 3 preferably are joined by tapered threads as illustrated at 12.
A cylinder 13 of proper size to iit snugly upon a smaller piston 14 of a reciprocating finger valve designated generally as 15 is disposed in sub 2 and communicates with the exterior of the tool through a purge duct 16.
In cavity 11, in the upper end of thick-walled section 3, an annular spacer ring 17 having openings 18 therethrough is disposed and is held in place by a spring 19. Annular spacing ring 18 and spring 19 eliminate the necessity for close tolerance in the manufacture of the joint between sub 2 and the upper thick-walled section 3. Spacer ring 18 serves as a limit for the reciprocating travel of finger valve 15 in a downward direction by supplying a surface which stops the valve by contact with shoulder 21 on the valve. Variation or adjustment in the effective length of the finger valve may be easily accomplished by changing spacer ring18 for a ring of somewhat different thickness. Spring 19 functions merely to hold spacer ring 18 in lirm contact with a shoulder 22 formed on the upper thick-wal1ed section 3 and is not subjected to flextion by movement of hammer 25. A linger portion 24 of valve 15 is slidably disposed through an opening in spacer ring 17.
A hammer designated generally as 25 is slidably disposed within housing 1 for reciprocating movement. Hammer 25 comprises a smaller piston portion disposed in the bore of thick-walled portion 3 and having au annular face 27 constantly exposed to pressure of actuating hydraulic fluid entering the tool through conduit 7, chamber 8, conduit 9, space 11 and openings 18. Hammer 25 also has a larger piston portion 28, shown in FIG. 2, slidable in the larger bore of thin-walled section 4 of the housing. Hammer 25 also has a portion of lesser diameter 29 below piston 28.
Pistons 26 and 28 serve to keep the hammer axially aligned during reciprocating motion in addition to furnishing surfaces against which hydraulic fluid under pressure may act. Since hammer portion 29 below piston 2S is of smaller diameter than the bore of housing section 4; it leaves an unoccupied space 31 within the housing around this portion of the hammer and forms a continuation-of the space between the hammer and anvil.
A passageway for hydraulic fluid extends through the harnmer and comprises an upper portion 32 and branch iconduits 33 extending from the lower end of upper portion 32 `to the space 31 surrounding part 29 of the hamfiner. The passageway through the hammer with an up- ;per central portion 32 and several, preferably three, foranch conduits l33 connecting with the space` 31 in the housiii-'gsuiioiii-iiiihg the iow'e' perror the haininon of some distance above .the -beati'g' f'ce" ofthe' hiiimh as iiihsir'aoo, eliminatessinfonia t t tigue and failure'of the` ltvr of th met dueto this-canse;- Finger valve rsf nii portion 32 yi' triepas- `sage"ayonsso-dispeseoluint-fifi ifm-of di ringe-ivoirenin ent-ei passagewaysain Arospo-nsoA fo positioning of the hammer iiear thel end' of` its up stroke and substantially close thepassageviiay to` fliidy o'yv. 'y Iiithe-1o" endof' "animer, 25g-ao aviiys4jis-fonned, 'oylin rioatporti'onslsgg Are= is posed-i within this cavity andis retained therein by aii arnul'ar nut 3'7 which may be threaded as Showri; Oi' held in" plac; hy-.si'np rings O1' other conyiiientdev e.
Fihger 'valve'4 36 posedE siidhbly' cylinder 35@ ashoulder portieri 42; movement of the finger in cavity 34;` arid? allower iiiigei ii f ger' aininoiejnihsn-pision sa ons 'slidably disposed iii rtihihg' nut'- 37. Thev lower iir'tger 713 preferably is-hlibw withE its hollbwy interior iriwardly tapering tbvvad 'shoulder 42 in order to 'reduce weight of the yall-ve andf to prevent metallic fatigue.: A purge passage 44extnds lgitidially through thevalve; stem aridVI provides a4 passageway-for iliiid coiii`i`1i'nitatingv with the hollow interior of finger 43 and with `cylinder 35@ he# hind' pis'bg. CylrideSS chmihicats with thehindie iiiteiiorfor-housinjgr In strook by hainiher-zs: spiiiiewayssoi sie foiihodi lateral sufra-oe 'or uiohoihhie'r- .Below piston 4s iii radio-1 alignment with s'fpiinowys 51Al in: uioio'we-rehdorb-ousingy Beaiings '52l oie-uisposedwithih meis-'eline nys ond permit relative longitudine nier/ement between the nii-vii ano-housing whiiopfievontingf reisnieifotoiion Ythoreb'etweeh;
fnl 'ii-opeipis'fon portion sisi' irs-- The low-sr ond of the hon-sing s3: is equipped with-snifi 'able means for attaching-cto. a fooi sfs here shown as threads 54a AI "passV "ay foroperating hydrauli Huid extends .from 'the fof itiieiivii-45t-through@ vil and tool to 'a point-'adjacent rof'avr'orlc'sri ne' :P wayfss i'sfaxally'lighedi withi finger- `4 .of 'valve-3 that nger 43, may move forward to enter and 'substanf tially closepassageway v`56 when pressure in 'pa's's'ageway 56issuflicientlyrducedt Y v 'I/ A means for hydraulically preventingfentranoe of n'ger 43v into'pass'ageway-SE until: after hammer: i251 has jstrucli the anvil in its 'reciproca-thigvtrave'lis provided.lk'1`hisV means comprises grooves 57A 'out into the' foefof the ham#-l hier.v These grooves-preferablyare threeinfiiurhbera dl are` radiallyY disposed to communicate with passageway- 56 kand with 'space S17-in the housing around. the 4hamihei and below piston 2 8'. T-The g'ro'ovesxare located at 'the sui-innig interino@ 'of' the iinininef 1an-d 'anvil anni should have a total crosssectional Aarea amounting boltl) nero-oni Vof'uiot*ofionssngs y sog-*nissen jihin oop-@nains iin-on hie fyn o io used desired; grooves 57 .could be located` in the anvil fac'c, orv be formed ogs-aligned groove-sin -b-o-th hainiiier and anvil; 'i
considering FIGS. 3, 4'and 5 which illustrate a tool substantially identical with that just described in FIGS. l and 2, except that spring 19 in cavity 11 is omitted.
FIG. 3 illustrates the position of the parts of the toOl at the instant after impact of the hammer with -the anvil. Incompressible hydraulic fluid, preferably drilling mud, may be considered as entering through supply conduit 7, cavity 8, conduits 9, cavity 11 and openings 18 into the interior of housing 1. The full operating pressure is thus yapplied against lthe lower surface of upper iinger valve 15, driving the valve upward tothe full limit of its reciprocating travel andjholdingit in raised position'. There is also some flow of operatihg fluid through thelongitudinal purge passage in the stemof valve v15 into cylinder 13 and to .the exterior of the tool through vent 16. Flow of huid through the purge vpassage in the valve stem,VV cylinder 13V and verit I6 substantially eliminates water hammer, maintains 'pressure' in oyl'ii'rder 13' between the pressureai whichoperatingiluid is supplied .and that' at'the' outside 'or the tool; 'purgeisi cylinder"- -13 or any; accumulationof 'f soiii4 partidosand insures suhstaniiouy constant flow fr mj cylinder 1'3 to thejoutsideofthe' tool, thus yprevenu Sandi' rock chips and other abrasivemattei' from being drawn intovcylinder", '13. l 'ressur'e of' acttiii'g-iluidirr the body cavity is V applied ageway' 32' in 'gvthe' hammer' and, branch pas= sageways 3 ofthespu-ce 31 aru'nd the l'owerptlrt of the hammer 'within casing l and" from this" space through pen'iiigs' 378` intoL cavity 34 in the lower`V part' ofk the y "fis In positiojirof parts' show-n; pressure from' the huid ilowing through passageway 5'6 inthe anvil has justy been reducedby contact of 'oppbsingfacesof the hammer and anvil". ofactuatingiliiid through`A grooves Sfhas effectively preventedirapping `i'rieonipi-e'ssihlehydraulic iuidV bct'w'cen thenhainmer and ahnL-faces but uponcorrtact of the faces' the restrictioh 'of bw areatothat of the total cross section `of these grooves'has result-:cd ih' a pres= sure dropin conduit 5'6. Y A
FullE pressure of op'er'ath'g' fluid however is upon'v cavity 34 up---the upper sideV Of' 'the shoulders of the Hilger yalye dispose'd'thcrcih. part of this' prs'sliiiete'ndiiig to drive the Viin'ger valve dow-n intoE closingposiiioii in passageway 56 is balanced by pressurev in the oppositediretti-o" `'u poi'i the lower s'i'deof piston 39", Bot-Whe lower 'iid-f the yal-"vev irige'r 'hasanf' area much l'arg'er than that ofpiston'39-L "The reduction iii pressure up'onthe lower end of the 'valve finger caused by Contact of the hammer ad ivilfaces with 'resultiiigf restriction ih rhou/way* cross section has a's'ed' the lingervalve`- tobe d'riv'eit-- into and substantially close-'passageway 551.` I
'through pass f '3i in the housing andV grooves-57 to the fase 'ofv the ,upper iingervlve; 'the lower end off the lower' ringer vaiveisdrown out-or passageway 'sjhy h afnrh-er travel;
i Asf soonY aslthe lower-endi of-theupper' ng'er valve ating pressure applied to; the annular surface 2'7 ofVv L the smaller upper piston-,ofi the hammerthus arresting its @Warst-matige and; Staffing.- thelenimer 9a its .Power stroke. As thev hammertrayel's, downward: i'n-it s powerl "shore if' is' neoesssiy that the iiiooiii'pisssibiehydiouiio fiuid be moved outward through passageway 56 from the space between the decending hammer face and opposing anvil face.
Since this fluid has some viscosity and inertia there will be back pressure upon the lower end of the lower finger valve which is sufficient to keep the valve in raised position. At the same time, there is a flow of some of this iiuid through the longitudinal purge passage in the valve stem and outward through Vvent 45 into a space in the housing above piston Z8. Since this space is variable in size according to the position of the hammer, flow of liquid upward through the purge channel and vent into this space and outward through openings 60 and 61 in the body substantially eliminate entrance of sand, stone chips and other abrasives through openings 60 and 61 in the housing 1. The partis remain in the relative position shown in FIG. 4 until the instant before the hammer strikes the hammer face.
At this instant hammer travel disengages passageway 32 from the lower end of the upper finger valve 15 and pressure again builds up in passageway 32, branch passageways 33, space 31, passage 38, space 34, grooves 57 and in the narrow space between the anvil and hammer. This hydraulic pressure effectively and positively maintains the lower finger valve in its raised position and prevents its engagement with passageway Se in the anvil until after the hammer has struck the anvil. At the instant the hammer strikes the anvil, ow of fluid into passageway 56 and pressure below the lower end of the lower finger valve is restricted because of the smaller area of grooves 57 as compared to the cross-sectional area of passageway 56. Grooves 57 also function at this time to draw off fiuid between contacting faces of the hammer and anvil without any cushioning effect due to retained fluid between these surfaces.
Reduction of pressure below the finger valve is not accompanied by reduction of pressure in cavity 34 and therefore the unbalanced part of the force applied by the fluid to the shoulder of the lower finger valve drives it downward into passageway 56 at very high speed, cutting ofi? flow of fluid therethrough, and the cycle of operations is repeated.
It will be seen that in addition to effectively preventing any cushioning of hammer blows upon the anvil face, the provision of withdrawing fiuid from between the facets made by continuation of flow through grooves 57 permits the faces to be scoured by fluid extruded from between them. This scouring action of the drilling mud is especially important when it may contain grit or other materials which might build up into hard deposits under the force of hammer impacts. If allowed to accumulate such deposits frequently lcause .spalling or other deterioration of the striking surfaces. Build up of deposits and spalling are effectively prevented in the tool of this type.
The purge passageways in the valve stems of both valves permits flow of fluid through their respective cylinders and so prevent accumulation of deposits in these cylinders and entrance of abrasive particles. This purge passageway also is effective in reducing water hammer.
`The particular design of finger valve used has been found to be very effective in reducing metallic fatigue so that the valves are long wearing under severe operating conditions.
The velocity of valve travel in reciprocation can be predetermined by choosing a size of cross-sectional area for vent passageways 45 which gives the required speed of valve operation while reducing the impact load.
n 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 apparatus.
It will be understood thatcertain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the lscope 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 mattter 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 claimed is:
1. A hydraulic percussion tool comprising in combination a housing; an anvil slidably disposed in an end of the housing; a hammer slidably disposed within the housing for reciprocating movement to beat upon the anvil, said hammer having a first piston surface constantly exposed to hydraulic pressure tending to drive it in one direction and a second larger piston surface intermittently exposed to hydraulic pressure to drive it in the opposite direction; a supply conduit for hydraulic fiuid under pressure disposed to introduce said fluid into a space in the housing behand the first piston; a passageway for hydraulic iiuid through the hammer, communieating with said space behind the first piston and with a second space within the housing beyond the second piston and between the hammer and anvil; a reciprocating hydraulically actuated finger valve, responsive to position of the hammer, disposed to enter and substantially close said passageway near the end of the back stroke of the hammer and disposed for sufficient length of reciprocal travel to remain in said passageway during a substantial part of the power stroke of the hammer; a second passageway for hydraulic fiuid through the anvil, communicating with the space in the housing between the hammer and anvil and with the exterior of the tool; a second rhydraulically actuated reciprocating finger valve carried by the hammer in positionto move into and substantially close the passageway through the anvil after contact of the hammer and anvil; and hydrauliclly actuated means for preventing movement of said second finger valve into the passageway through the anvil until contact of hammer and anvil occurs.
2. The tool of claim 1 wherein the hydraulically actuated means for preventing movement of the second finger valve into the second passageway comprises a third owway, having lesser cross-sectional area than the passageway through the anvil, leading from the space behind the second piston tothe passageway through the anvil, disposed where it is not closed by contact of hammer and anvil but is closed by the finger valve on movement of the valve into the second passageway.
3. The tool of claim 2 wherein the flowway is a plurality of radial grooves located at the interface of hammer and anvil.
4. The tool of claim 3 wherein the liowway is a plurality of radial grooves in the hammer face. y5. The tool of claim 4 wherein the radial grooves have a total cross-sectional area amounting to about percent of cross-sectional area of the passageway through the anvil.
6. The tool of claim 1 wherein each of the reciprocating linger valves is disposed in a valve retaining member and comprises a smaller piston disposed in a cylinder cornmunicating with the exterior of the tool through a vent passageway entering the cylinder at a point further within the cylinder than ythat reached by the piston at its maximum distance of travel and a finger slidable -in said valve retaining member, said finger having a larger piston surface than thesurfaceof the smaller piston opposed to the smaller piston surface; a shoulder'on said linger part disposed in a cavity between said valve retaining member and said cylinder and having an annular efectivearea equal to the difference between the area of the piston surface of the finger and-the area of the smaller piston exposed to pressure of fluid withinv the cavity; a stem connecting said smaller pistonand said finger, said stem having a purge passageway therethrough extending through said finger, through said smaller pist'on, and communicatingawith said cylinder behind 'the smaller piston; andA means for varying pressure on' the larger pistonsurface; on the finger part', Varid on said annulararea o'n saidr shoulder responsive to 'movement ofthe hammer to cause reciprocationlof the finger.
7l The tool of claim 1- whereintlle secondl reciprocating finger is disposed in a| valve retaining member carried by they hammer, and theva'l've comprises asmaller piston disposed for. reciprocation in a cylinder in the'hammercommunicating with the exterior of the tool through a vent passageway/connecting the cylinder at a pointr further within the cylinder .than that reached bythe smaller piston at its of travel, with, a space within the body around the hammer betweenV thetpiston surfaces of the hammer, and through openings in the body communicating said space; afinger slidable inV the valve retaining member andhaving a, larger piston vsurface opposed to the smaller piston; a,4 shoulder on the finger disposed in a cavity in the hammer between the valve retaining member and the cylinder and having an. annular area equal to theditference in area between the area of the Ypiston surface of the finger andl the yarea of the smaller pistony exposedto pressure of fluid within the cavity; a stem connecting: the V'smaller piston and the finger; a purge passageway extending longitudinally through thestem, fingerv and smaller piston communicat-V ingl with the interior ofthe cylinder behind `the piston; and means, comprising openings from the cavity intoja space in Vthe, body Vsurroundingthe strikingendlof the hammer, for varying pressure on the larger piston surf` face and on said annularl'areaof the shoulder, responsive to movement of the hammer,l to cause reciprocation Vof they finger. Y
8. The tool of claimfl wherein each of the reciprocating finger valvesis disposed iny a valve retaining member and comprises a smaller piston disposed in a cylinder communicating with the exterior of the tool through a vent passageway entering the cylinder at apoint further within the cylinder than that reached' by the piston at its maximum distance of travel; va finger slidable, in` said valve retaining member, said finger having a larger pis*- ton surfa'cethan the surface of the` smaller piston, opposed to the smaller piston surface;Z a* shoulder ony said ammassi thecavity; a stem connecting thesmaller piston' in the finger; a purge' passagewayV extending longitudinally through the stem, finger and smaller piston communicating with the interior of the cylinder behind the piston; and means, comprising openings 'from' the cavity into a space in the body surrounding-,the lstriking end ofthe hammer, for varying pressure on the larger piston surface andv on-said annular areal of the" 'shoulderresponsive v to movement of the hammer to cause reciprocation of finger party disposednin a cavity'between said valve retain.- Y f ing member and said; cylinder and having anv annular effective'.v area equal to-l the difference between the area of thepiston surface of the finger andthe' Yarea of the smaller piston` exposed to pressure of fluidvwithin .the cavity; a stem connecting said smaller.,pistony and said finger, said stem having a purge passageway therethrough extending .through the finger, rthrough said smaller piston, and comunicating. with 'said cylinder behind' the piston; and means'for varying pressure yon the largerpiston surface on the finger' part,A and on said annular -a'realon saidv shoulder responsive ',to movement of theV Vhammer to'cause reciprocation of the finger.l l ,Y
9. The tool" of claim 1f wherein'theisecondreciprocatingl finger isdisp'osed in a valve reta ingme'nfrb'er carried by the' hammer, and the Vvalvecomprises 'aj-smaller pis- V'tondisposed for reciprocatiniin a cylinder in the hammer Acornnrunieatingwithfthe exterior of the/tool through the bodyfia'round l'the hainrrier'betweenr the piston sur- L a vent'V passageway ,conne'clitingJ thejcylinder, at a point Y lfurther'vvithin the cylinder than that reached' by Vthe fat-:esI ofthe hammer, andfthrough openingsA in the bod'y d communicating-'with said space';` afnger slidahley in the i 'valve retaining inember Y and'havirlg al l'a'r-ger piston Asur-- face opposed ltothe sr-rlalleriinistoinfav shoulder on the fiilge'r/,- disposed in aca in; the llarunner. between the valve retainingmembe'r an 'the.cylinderand'having. 311,1V
the fingen l v 1'0. In ahydraulicpercussion tool wherein a hammer is slidablyl disposed in' a-liousingl to beat upon any anvil, said hammer having a piston surface tending to move the hammer away from the anvil: upon whichphydraulic pressure is alternately increased' and` diminished to cau's'e reciprocat'ion of the hammer, and means for intermittently admitting hydraulic` fluid to press uponv said piston surface is provided, the improvement which comprises an outlet passageway for hydraulic fiuidth'rough the' anvil; a' hydraulically actuated reciprocating finger Vvalve mountedl inthe hammer and disposed; to move into and close the passageway through the anvil`upon Contact o f the hammer with the anvil; and` hydraulic means forV `preventing movement' of" s aid finger valve into' said' passageway through th'eanvil Yuntil contact of hammerand anvil occurs'. Y
1,11. The' tool' of claim l0 wherein'the hydraulc'means V,for preventing movement of" the finger valve' into the passageway comprises a fluid flowway, having lessercross'- sectional arear than the passageway through the anvil,I com'- cunicatingwith the passageway through theanvil and with a Vspace within the housing between the anvil and said piston so disposed that it is not closed by contact of hammer and anvil but is `closed by the finger valvev on movement ofthe valve into the passageway through. the anvil. Y
` 12. TheV t'o'ol of claim l1 wherein the liowway is a plurality of radial grooves located at the interface of hammer'and" anvil. y A y 13. The toolof claim llpwherein the flow'way is a plurality of radial grooves inthe hammer face'.
k14. The tool. of claim 1l wherein the rad'al'g'rooves have' a total cross-'sectional area amounting to about v90 the, surface of the smaller piston opposed to the smaller piston surface; ashoulder'on said finger part disposed in a cavity within thezhammer between said valve retaining member and said cylinder, Ysaid shoulder having an annular effective piston area equal to the difference between the area of the piston' surface kof the finger and the area ofthe small'erpiston, exposed to pressure of fluid in the cavity; astemconnectingvsaid smaller piston and said fingen'saidstem having ajpurg'e passageway therethrough-extending through said finger, through said smaller `piston Vandtoinmunicating with said cylinder behind they piston; and means for varying pressure on the larger piston surface of they finger part, and on said annular, area on said shoulder, responsive tomovement of the hammen; to causereciprocation of the finger.
annular 'area equal toV "the d1fl`erence`in 'area betweelrifA the 'areauo'f Y A s bt smaller piston 'exposed to pressure or fluid within 16. In a hydraulic percussionrtool wherein a hammer is slidably disposed ina housing .to beat uponvan anvil,
saidfhafmmer having a piston surface tending to move. fthe lhammer away from:V the anvil upon'whichhydraulic pressure -is Yalternately increased and diminished to cause reciprocation'of the hammer, and means vfory intermittent- 1y admitting hydraulic iiuid to press upon said piston surface is provided, the improvement which comprises structure including a portion of said housing extending around and enclosing said hammer and a portion of said anvil and supporting said anvil in sliding relationship Within the lower end of said housing, annular passageway means within said housing around the lower portion of said hammer and the upper portion of said anvil, a cavity formed in the lower portion of said hammer, passage means through said hammer connecting said cavity and said annular passageway, an outlet passageway for hydraulic fluid through the anvil, a hydraulically actuated reciprocating finger valve mounted in said cavity extending through the lower end of the hammer and disposed to l@ move into and close the passageway through the anvil upon contact of the hammer with the anvil, and hydraulic means for preventing movement of said linger valve into said passageway through the anvil until contact of hammer and anvil occurs.
References Cited in the file of this patent UNITED STATES PATENTS 1,096,886 Bayles May 19, 1914 2,620,162 Pennington Dec. 2, 1952 2,756,723 Bassinger July 31, 1956 2,774,334 Cline Dec. 18, 1956 2,786,451 Dulaney Mar. 26, 1957 2,859,733 Bassinger et al Nov. ll, 1958