US2693867A

US2693867A - Rotary impact tool

Info

Publication number: US2693867A
Application number: US119141A
Authority: US
Inventors: Spencer B Maurer
Original assignee: Individual
Current assignee: Individual
Priority date: 1949-10-01
Filing date: 1949-10-01
Publication date: 1954-11-09
Anticipated expiration: 1971-11-09

Description

s, B. MAURER m ROTARY IMPACT r1300L Filed oct. 1. 194ev 2 Sheets-Sheet l |NVENTOR Spencer B. Maurer ATTO Nov. 9, 1954 Filed Oct. l, 1949 I l y 65 5/ 7 52 S. B. MAURER ROTARY IMPACT TOOL 2 Sheets-Sheet 2 /07 /09 /o //4 //3 H INVENTOR Spencer B. Maurer Y www @7 ATTORNEYS chamber, and the vanes 24 are slidably mounted in radial slots in the rotor and are urged outwardly against the rotor chamber by air pressure in a manner not shown. The air entering the rotor chamber between each adjacent pair of vanes moves the vanes about the rotor axis in the direction to enlarge the space therebetween and permit expansion of the air as it travels toward the exhaust port 26. The valve 17 that controls the direction of rotation of the rotor is manually rotated about its axis by means of the lever 29 between the position shown in the drawing and a second position 90 from the illustrated position. g

The rotor 28 is preferably provided with integrally formed, oppositely projecting, hollow shafts 31 and 32 that are respectively mounted for rotation in ball bearings 33 and 34 carried by the housing section 10. The rotor assembly and bearings are held in place by an externally threaded ring 36.k

The output shaft 37 is journaled in a bushing 38 carried by the housing end in a suitable work driving tip 39. The bushing 38 is sufficiently long to hold the output shaft 37 firmly in alignment with the axis of. the rotor 28 and to permit the clutch assembly to be supported solely by and between the output shaft and the hollow rotor shaft 32, in a manner hereinafter described. The output shaft is provided with a circumferential shoulder portion 41 for retaining the shaft in the bushing 38. A radial projection 43 from the shoulder portion 41 of the output shaft constitutes an anvil 43 and is shaped on opposite sides to provide identical impact surfaces 44 against which a hammer pin or impact delivering element may strike to drive the output shaft in either direction about its axis.

The clutch assembly is constructed around a relatively massive, hollow hammer member 47. One end of this member surrounds the rotor shaft 32 and is keyed thereto to provide a driving connection therebetween. The oppostie end of the hammer member 47 surrounds the inner end portion 42 of the output shaft with a close running tit to permit relative rotation of the hammer member and output shaft while preventing any rapid escape of air therebetween.

A heavy hammer pin or impact delivering element 48 is mounted for longitudinal sliding movement in an aperture drilled through the member 47 in a direction parallel to its axis and spaced radially outwardly therefrom. The pin 48 is adapted to be projected axially into the path of the anvil 43 for driving it in either direction about its axis as determined by the direction of rotation of the motor, and to be withdrawn to permit acceleration of the hammer member after rotational resistance of the output shaft has stalled the motor or has slowed it down nearly to a stalling condition.

To control the axial movement of the hammer pin 48, a reciprocable member or piston 51 having an enlarged forward end portion 52 is mounted in the hammer member 47 with the forward end portion 52 having a relatively close running t therein and the rearward end portion 53 projecting with a close running t into the hollow rotor shaft 32'. The reciprocable member S1 is provided with an axial bore 55 extending from end to end thereof and is mounted in the hammer member 47 for axial sliding movement with respect thereto. The clearance between the piston 51 and both the hammer member 47 and the hollow rotor shaft 32 is maintained as small as possible to prevent rapid escape of air therebetween. The travel of the piston is limited in one direction by contact of the forward end thereof with the inner end surface 45 of the output shaft (Fig. l). Its travel in the opposite direction is limited by an internal shoulder 56 of the hammer member 47 (Fig. 4).

The piston 51 and the hammer pin 48 are constrained to travel together as one body by a valve rod 57 that extends through aligned apertures` therein. The axis of the valve rod S7 passes through the axis of the hammer member 47 in a direction normal thereto, and the valve rod is mounted for limited sliding movement along its own axis between the two extreme positions illustrated in Figs. l and 4. Within the piston 51, the valve rod 57 is provided with a portion 58 of enlarged diameter that serves as a valve in the central bore 55 of the piston for controlling the passage of iiuid therethrough` as hereinafter described. Within the hammer pin 48, one end of the rod 57 is provided with another portion 59 of enlarged diameter that terminates in a head Porsection 11, and terminates at one tion 60. The head portion 60 of the valve rod 57 contacts the hammer pin 48 for limiting movement of the valve rod in one direction, as is most clearly shown in Fig. 5. The other end of the valve rod 57 has a weight 61 mounted thereon and held against removal by any suitable fastening means, such as a snap ring 62. The hammer member 47 is slotted at 63 and 64 to accommodate the valve rod 57 and permit it to travel longitudinally thereof together with the piston 51 and hammer pin 48. The valve portion 58 of the valve rod 57 has an annular surface 67 that is constantly exposed to the pressure of iluid in the axial bore 55 which tends to urge the valve rod toward the extreme position shown in Fig. 4.

Fluid for operating the clutch mechanism is conducted thereto from a branch conduit 71 that may conveniently be integrally formed in the housing section 10 with one end in open communication with the main air conduit 16 and its opposite end in communication with the small chamber 72 through one or more openings 75. A tube 73 extends at one end into the chamber 72, where it is held by a suitable sealing ring 74 of rubber or the like, and the opposite end of the tube 73 projects with a close running fit into the hollow rotor shaft 31. Thus, tluid at the main line pressure of the motor intake manifold is always freely admitted through the conduit 71, chamber 72, and tube 73, into the hollow rotor shaft, and thence through the axial bore 55 of the piston 51 as far as the valve portion 58 of the valve rod 57. A small cut-away portion 68 of the bore of the piston 51 permits the huid to ow freely into contact with the annular surface 67, when the valve rod 57 is in the position shown in Fig. l. This cut-away portion 68 may be formed by means of a drill run through the opposite side of the piston, the hole through the piston wall being subsequently filled by a plug 69.

When the trigger 14 of the impact wrench is actuated to admit air to the motor and to the clutch mechanism, the clutch mechanism is normally in the position shown in Fig. 4. As the hammer member 47 is rotated by the motor, the weight 61 on the valve rod 57 is subjected to the action of centrifugal force tending to move the rod 57 to the position shown in Fig. l At the same time, air under pressure in the axial bore 5S of piston 51 exerts pressure on the annular surface 67 of the valve portion of the valve rod, thus tending to hold the rod in the position shown in Fig. 4. When the rotary speed of the motor and the hammer member 47 reach the point where the centrifugal force on the weight 61 exceeds the force of fluid pressure on the annular surface 67, the valve rod 57 is caused to move with a snap action toward the position shown in Fig. l. This movement causes the valve portion 58 of the rod 57 to close the axial bore 5S, of the piston 51 and open the vent passage 76, and the fluid pressure exerted on the rearward end of the piston 51 causes it to move toward the output shaft 37. The hammer pin 48 moves with the piston 51 and is projected into the path of rotation of the anvil 43. When the hammer pin 48 strikes one of the impact surfaces of the anvil 43, it drives the anvil and the output shaft 37 until rotational resistance afforded by the object to which the impact wrench is applied reaches a magnitude sufficient to stall or nearly stall the motor.

When the motor approaches a stall in the course of driving the output shaft, there is no longer any appreciable centrifugal force acting upon the weight 61. As a result, the pressure on the annular surface 67 causes the valve rod 57 to move back to the position shown in Fig. 4. This opens the axial bore 55 of the piston and permits uid to flow therethrough and out of the forward end 52 of the piston into the space between this end of the piston and the rearward end surface 4S of the output shaft 37 The total area upon which the uid exerts its pressure at this end 52 of the piston 51 is substantially greater than the limited area upon which the uid exerts its pressure at the opposite end 53 of the piston. As a result, the piston is driven rearwardly (to the right as viewed in Fig. l) by the iluid from the position shown in Fig. 1 to the position shown in Fig. 4. Being constrained to move with the piston 51, the hammer pin 48 is thereby withdrawn from the path of rotation of the anvil 43, and the motor is again free to accelerate the clutch mechanism. When the speed of rotation of the clutch mechanism again reaches the point where centrifugal force on the Weight 61 is sufficient to move the valve rod 57 back accomplishI thaty purpose..

lto the position@ shown-ine Fig' l,` the hammer pin-4G vis projected into the@ path: of. the anvik 45;.- as; beior.e;.` for de.- livering another: drivingiblow... In orden for'ainto: escape from between the output. shaft 37 andi the' end 52"o:f. the piston 51 asthe piston drivesrthehammerfpin into the path'. of'A the.' anvil. 43', a fluid passage. 76' isp'rovidedf in: the enlarged. forward portion 525 of the; piston 51:. When the clutchY is inthe positionV shown-in "Fig: 4,. this. fluid passage76: is closed. by the. valve portionrSS of the: valve rod 57. Whenthe-rod 571 is actuated. luy-centrifugal.I force acting on the weight l-howeveng the valve portion-58a of the-:rod- 57 uncovers t the passagez'76 and permits fluid yto owtherethrough and' escape. -intol a: vented portion: of the housing and outthrough. avent passage: 7-7, thus re lieving'the,` pressure' between theoutputtshaitfr 37I andthe piston` S1..

When the motorv is stalledV or nearly stalled; the fluid pressure in the main airv conduit-ladjacent the: motor intake manifold isf at a maximum. valueI determinedl byf the pressure supplied tothe impact. wrenchl throughy the air hosev 13t This insures that the pressure. employed: to di'sengage the hammer pin. from the-anvil. is. suicient Ato Similarly, when. the: motor is stalled. or`nearly stalled, the-pressure; inthe-axialv bore 55. of thepiston. 51 is adequateftormove. the: valve rod S7 from the position shown in Fig'. ll to the. position shown. in Fig. 4-for admittingl theu uid under its'maximum pressure through. the balancefofthel axialy bore of the piston and` out of theend 52.thereof for driving thepiston and the hammer pin. from the-positions shownI in Fig. l to the positions shown in Fig, 4.

A particular advantage. oftlu's type of clutch lies in the fact that actuation of; ther clutch is responsive not only to the speed of the motor but alsoto the-torque output of the motor for effecting both lengagement-and disengagement. of the. clutch solely by uidpressure rather vthan. by a. torque responsive mechanical linkage; In other words, the: clutch is actuated. directly by'uid pressurein timedv relationship tov motor speed and-torque.. So= l'ong as the pressure in the. air hose 13 is. suhcient. to rotate the motor, positive actuation of the clutch: mechanism is insured, and it is unnecessary toE rely for this action upon any type of mechanical springs, or upomanytypef of torque responsive mechanical linkage. both of which have been a common source-oftrouble.

It will be apparent. from the foregoing descriptionio-f `theoperation ofthe clutch mechanism that the impact wrench is admirably. adapted for deliveringi a series of sharp hammer blows on. the anvil ofthe output: shaft-as rapidly as the motor is. capable of accelerating thezfree ly rotatable clutchmechanism to the Aspeed-required for projecting the hammer pin int i the pathl of the anvil'. One characteristic of. a centrifugal valve control of this type. is that once the valve. rod'starts.. to movein-either direction the balance of forces tendingto causerthatamo tion are increasedproviding.A in effect, asnap actionf. AS

.the rotational speed. offthe. clutch increases ther air bias.-

i'ng force acting onv shoulder p creases, the centrifugal. force actingon the weight 61increases and once motionof the-valvenrod' starts atany given speed the centrifugal force. increases dueto-thel increased distance of the center of. gravityvof the weight 6I from its center'ofrotation.. Before'. the vfalvefrod can shift in theopposite direction thespeed mustbedrastically reduced because the weight 61 has itsfmaximum centrifugal, force at its outward. startngvposition. Asl the speed of the tool decreases, the ail-pressure bias.` acting `on shoulder 67? increasesl until. the inward motion. of the valve rod.' starts. at which time Ythe rodsnaps.- toits. inward position.. This. means that theV tool. will rapidly spin-'nuts down to a seated position before thef impactv mechanism will begin to operate. This greatly reduces overall nutrunning time.

Turning now to the. embodiment of. the inventionillus trated in Figs. 6 to 8, there is shown in these figures. a somewhat simplied' clutch mechanism in which fl-uid pressure is employed solely for disengagi'ng the clutch and a mechanicalspring is employed/for engaging the clutch. Except' for differences inthe designof the clutch itself, this embodiment of the: invention may' employ the same general housing and motorfarrangement as `in the first embodiment of. the. invention, describedfahove. Ac lcordingly, only the modifiedclutch: mechanism andll as soilatecgiout-put shaft are illustrated in: Figs: 6; to-'Sz 67 of the valve rod 57T deembodiment. of. the'-invention the .hammer :i

member; 1Mbctnnpriscsfa;relativelysimple,z member having: an. axiah'bore of uniformi diameter substantially from `enrlt to' endzthereoft. One Zend" of the hammerfmember surrounds the motor shaft 32-and. is keyed thereto' for rotation therewith.. The opposite end of they hammer member'100 surrounds an inward: exten.i sion of the output shaft 101. with afree running t.

In this` case., theoutput shaft includes an integrally formed. anvil 43 identical; with that in the first. embodiment. ofthe invention, andan-integrally 'formed shaft portion L02 that. extends. completely lthrough the; hammer member 1'00fandl: into.V the-hollow motor. shaft 32. witha close. running lit., Approximately midway betweenvv the but; massive,

endsof the hammer member 100, the'portion. 102of the outputshaf't. is grooved circumferentially, as indicated at 103,.'and. is drilledhrouglron a diameter, at. 104,I and longitudinally alonggits: axisa-t 106,' to provide-for flow of huid from. the hollow motor shaft 32 into the groove'103.

An impact delivering element 107 is mounted for limitedaxial movement in the hammer member 10.0; as in thel first embodiment ofthe inventiom. but in thisl case the rearward end of the. impact delivering element. is enilarged to form an annular piston surface 108 against which fluid under pressure mayact. The aperture in the hammer member 1.0.0, in" which thef impact delivering element A101 is` mounted, is. similarly enlarged to accommodate-this portion. of. the. impact delivering. element and: toL formv a pressure' cylinderf109. Fluid under pres.- sure froml the-groove 103 isfreely admitted into ythe cylinder109l and. against the annular .surface 10'8fthrough t an aperture or port 110 therebetween..

A spring; chamber 1:15 is partiallyclosed at its rearward or inner end by Aa. perforated-disk 111` held. in place. by anv expanding lock ring.. 112. Thev adjacent end of the. impact delivering element is. provided wit-h a` cup portion 113 that accommodates a compression. spring 11.4. Thespring v114i bearsy at itsopposite ends. against. theA disk 111 andithe end'of the impact delivering: element 107.

The clutch mechanism. of. Figs. 6 to/'Svv performs the same ultimate function, according. tothe same cycle of operation, as thev clutch in the first embodiment of the invention. When. the-motor isstalled, theY iluid` pressurel within thevtool isat a maximum since. the air con'.- su'mption. by the motor is at aminimum. This pressure is transmitted4 through the. axialbore. 10.6 and diametrical bore 10.4 in the shaft extension` 102, throughport 110 inv the hammer member 100,. and actsagainst the annula'r piston. surface. 1.08. The strength of the spring 114 is, selected sov that thefluid pressure atv its maximum value is. ample. to.Y compress the spring and hold` the clutch in its. disengaged condition. illustrated in Fig. 8'. As the motor accelerates, the fluid pressure at the clutc 'drops and the.v spring overcomesvthe pressure of the fluid on the annular piston surface 1208, thereby projecting the impact delivering element again intothe path of the anvil fondelivering another blow' thereto. When the rotary resistance.- of the. object. being turnedv again stalls, or nearly stalls,` the motor,.fthe cycle is repeated.

It. will.v be noted in: the foregoing descriptions of the operation. of bothembodiments of the inventionv that disengagementof the clutchiis stated tov occur when the motor is stalled or nearly stalled.. Under most conditions of operationt, the resistance ofv the: work to= rotationl by the wrench willi quickly and completely stop; rotationv of the motor' int thedrivingxdirection after engagement of the clutch, and'. disengagement. will 'normally' occur while the. motoris fully stopped or rebounding: in the opposite direction. However, as.- long as the resistance' of the work to'- rotation is small, as during; the free running of arnutnontoI abolt, thefclutch will' remain engagedl after the firstjimpact. isvreceived from. the hammer. If the resistance'of the; work; to-rotation -th'enfbuilds up gradi ualiy, the motor speedrwill be gradually reduced and the fluid pressure im the bore. 55j iny the rst embodiment and in. the bore 106=irr the secondi embodiment will slowly build up tof'a. point suliicient;l to disengage the clutch before ther decelerating motor has completely stopped. This' is; a desirable effect, since it permits` the motor quicklyftofaccelerate againanda` second blow to'be struck with arminimumrof delay;l thus-'maintaining a maximum average speed of rotation of the. workvwhile resistance to.V rotatione 'isf relatively' low: and a considerableV number of rapid revolutions of the workf isfdesired.

While disengagement ofi-the clutchvdoesnot necessarily 7 require complete stalling of the motor,` satisfactory operation under all conditions requires that the clutch actuating mechanism be capable of disengaging the clutch when the motor does stall and friction in the mechanism 1s greatest, as will often occur when resistance of the work to rotation is substantially greater than the maximum torque the motor can develop. It is, therefore, entirely accurate to state that the clutch actuating mechanism is responsive to stalling of the motor for disengaging the clutch. However, as mentioned above, the rebound of the hammer may actually cause some slight turning of the motor in the reverse direction when a driving blow is struck, and disengagement of the clutch may occur during the rebound. In any event, disengagement of the clutch will always occur only after the motor'has been slowed down to the point wherethe momentum of the hammer no longer materially adds to the output torque of the motor. This condition isv referred to in the appended claims by stating that the motor is substantially stalled, and it is intended that the expression be so construed. i

From the foregoing disclosure of two embodiments of the invention, it should be' apparent to those skilledv in the art that many variations thereof can readily be devised. For example, referring to Figs. 6 to 8, the same principles involved therein can obviously be applied to engage the clutch by lluid pressure, as by employing variations in the motor exhaust pressure, and to disengage it by spring pressure. Also, while I have shown and described specific embodiments of the invention in which the fluid pressure is exerted upon a conventional piston, it is obvious that equivalent mechanism may be substituted, such as diaphragms and bellows. In the appended claims, the term reciprocable member is employed as a generic term embracing both a piston and its various equivalent mechanical elements. Accordingly, the scope of the invention is not intended to be limited to the particular mechanical arrangements disclosed except to the extent required by the terms of the appended claims.

Having described my invention, I claim:

l. In a rotary impact tool having a uid pressure driving motor and a source of fluid pressure for operating the same; a rotatable output shaft having impact receiving surface means; a rotatable hammer assembly having impact delivering surface means driven by said motor for intermittent engagement with said impact receiving surface means to deliver a rotary blow to said impact receiving surface means, expansible iiuid pressure chamber means, conduit means connecting said source of uid under pressure to said liuid pressure chamber means for supplying thereto uid under pressureto establish a force to expand said chamber means, means operating automatically to increase fluid pressure in said chamber means in response to substantial stalling of said hammer assembly and expand said chamber means with a force which is greater than and increases with increases of the frictional forces set up by the torque of said fluid pressure motor which frictional forces oppose expansion of said chamber means, and a connection between at least one of said impact surface means and said chamber means to produce relative disengaging motion between said impact receiving and delivering surface means when said chamber means expands.

2. In a rotary impact tool having a fluid pressure driving motor and a source of fluid under pressure for operating the same; a rotatable output shaft having impact receiving surface means substantially parallel to the axis of rotation thereof; a rotatable hammer assembly having impact delivering surface means substantially parallel to the axis of rotation thereof driven by said motor for intermittent engagement with said impact receiving surface means to deliver a rotary blow to said impact receiving surface means, fluid pressure chamber means inv said tool which can be expandedby fluid pressure, conduit means connected to said source and to said fiuid pressure chamber means for supplying thereto uid under pressure to cause said chamber means to expand, centrifugally operable valve means operating automatically to increase fluid pressure in said chamber means and expand said chamber means, and a connection between at least one of said impact surface means and said chamber means to produce relative motion between said impact receiving and delivering surface means when said chamber means expands.

3*. pIn a rotary impact tool vhaving a uid pressure driving motor and a source of uid under pressure for operating the same; a rotatable output shaft having impact receiving surface means; a rotatable hammer assembly having impact delivering surface means driven by said motor for intermittent engagement with said impact receiving surface means to deliver a rotary impact blow, fluid pressure chamber means in said tool which can be expanded by uid pressure, conduit means connected to said source and to said iiuid pressure chamber means, centrifugally operable valve means mounted for rotation with said hammer means for controlling ow of uid through said conduit to control the iiuid pressure in said chamber means and operable to decrease'pressure in said chamber means when said hammer assembly rotates at a given high speed and operable when said hammer assembly is substantially stalled to increase uid pressure in said chamber means to establish a force to cause said chamber means to expand, and a connection between at least one of said impact surface means and said chamber means to produce relative disengaging motion between said impact receiving and delivering surface means when said chamber means expands.

4. In a rotary impact tool having a driving motor; a rotatable output shaft having impact receiving surface means, a rotatable hammer assembly having impact delivering surface means driven by said motor for intermittent engagement with said impact receiving surface means to deliver a rotary impact blow, fluid pressure chamber means in said tool which can be expanded by fluid pressure, centrifugaliy operable valve means mounted for rotation with said hammer means for controlling the tiuid pressure in said chamber means operable to decrease pressure in said chamber means when said hammer assembly rotates at a given high speed, fiuid bias means continually exerting a bias force on said valve means in the direction opposite to the direction of centrifugal force on said valve means to move said valve means when said hammer assembly is substantially stalled to increase fluid pressure in said chamber means to establish a force to cause said chamber means to expand, and a connection between at least one of said impact surface means and said chamber means to produce relative disengaging motion between said impact receiving surface means and said impact delivering surface means.

In a rotary impact tool having a fluid pressure driving motor and a source of fluid under pressure for operatingthe same; a rotatable output shaft having impact receiving surface means, a rotatable hammer assembly having impact delivering surface means driven by said motor for intermittent engagement with said impact receiving surface means to deliver a rotary impact blow, expandable fiuid pressure chamber means connected to said source of fluid, automatic control means operative when said hammer assembly is substantially stalled to increase fluid pressure in said chamber means to cause said chamber means to expand to establish a disengaging force, and a reciprocable member connected to at least one of said impact surface means responsive to the expansion of said chamber means to cause relative disengaging motion between said impact surface means, and means exerting a continuous engaging force on said reciprocable member in a direction opposite to the direction of said disengaging force and of a magnitude less than the peak magnitude of said disengaging force.

6. In a rotary impact tool having a uid pressure driving motor and a source of uid under pressure for operating the same; a rotatable output shaft having impact receiving surface means, a rotatable hammer assembly having impact delivering surface means driven by said motor for intermittent engagement with said impact receiving surface means to deliver a rotary impact blow, expandable fluid pressure chamber means connected to said source of fluid, automatic control means operative When said hammer assembly is substantially stalled to increase uid pressure in said chamber means to cause said chamber means to expand to establish a disengaging force, and a reciprocable member connected to at least one of said impact surface means responsive to the expansion of said chamber means to cause relative disengaging motion between said impact surface means, and means responsive to fluid pressure exerting a continuous engaging force on said reciprocable member in a direction oppositefto -the direction of said dismeegaat 9 engaging 'force and `of a magnitude less 'than the peak magnitude of said .disengaging force.

7. In a rotary impact tool lhaving a -driving=motor: "a rotatable :anvil, fa rotatable impact delivering ,element driven by said motor fior-striking and driving-saidfanviL actuating means including fluid-pressure actuated means and r a centrifugally -operated valve for moving said im* pact delivering Jelement into engagement with said anvil when said valve is rotating at a predetermined speed and uid bias means continually exerting -a bias force on Vsaid -valve in the direction opposite -to the-direction of centrifugal -force on said valve for 'moving saidv impact delivering element out of engagement with .said Janvil when said valve Ais lrotating at apredetermined vlower speed. `v

8. rA rotary Yimpact tool compr frame, a rotatable work member and rotatable driving 4means therefor mounted on said frame for rotation relative `to the frame,-an impact receiving elementthrou'ghwhich torque forces may ibe transmitted to lsaid `work member, an impact -deliveryelement driven by said driving 4means and Imovable into and out of the path of rotational travel of said impact receiving element :for respective -engagement -with and disengagement from said impact receivingv element, 'a'pistonmember yreciprocably mounted in -said rotatable driving -means for lactuating said impact delivery element, said piston member comprising two 'piston heads arranged one at -each end 'of the piston member, one -of said piston -heads having ya greater face l-area than the other, a uid pressure -chamber lat one `side o'f the piston having Vthe greater face area, a flluid pressure supply chamber at one side-of the kpiston having the .lesser face area, a 'uid-pressure-supply conduit in -said piston member through which uid under pressure may dow from said supply chamber to the frst mentioned chamber, an exhaust conduit in said piston :leading from the rst vmentioned fluid pressure chamber through which iiuid maybe vented from the-chamber to ithe atmosphere, valve-means operable -to one position for .permitting the iiow of fluid through said fluid pressure supply -conduit from said uid -pressure supply chamber 1to the first mentioned chamber and for `preventing the flow-of fluid from the irst mentioned vchamber through said exhaust conduit to the atmosphere and said-'valve means -being operable to another position for cutitng off the ow-of uid to the first mentioned chamber and for opening said exhaust conduit to -permit "-liuid -under Ipressure iin-'the ifirst mentioned chamber `to `flow tothe :atmosphere, and a centrifuge rotatable by said rotatable driving means and operable-to control the operation of said valvefmeans.

9.- Av yrotary impact-tool comprising a frame, a rotatable work member--and-rotatable driving means there'for mounted on said frame -for rotation relative to the iframe, an impact receiving element through -which torque forces may -be ltransmitted -to said -Work member, an, impact Vdelivery element-driven-by said driving means and movable into and out of the -path of rotational travel of said impact receiving element -for respective engagement with and disengagement lfrom said yimpact-receiving element, fluid pressure actuated means Vhaving a relatively large area over which iiuid under pressure may act to cause it to move said impact-deliveryelement-out of the-rotary path of travel of said impact receiving element and also a relatively small area over which liuid under pressure may act to cause it to act to move said impact delivery element into the rotary path of travel of the impact receiving element, valve means operative to one position to subject the piston of large area to the pressure of uid to cause said fluid pressure actuated means to act to move said impact delivery element out of the path of travel of the impact receiving element, said valve means being operative to another position for cuting off the ow of uid to the piston of larger area and for venting the uid under pressure acting on the piston of larger area to render the fluid pressure actuated means responsive to move said impact delivery element into the path of travel of the impact receiving element, and centrifugal means operative to control the operation of said valve means.

10. A rotary impact tool comprising a frame, a rotatable Work member and rotatable driving means therefor mounted on said frame for rotation relative to the frame, an impact receiving element through which torque forces may be transmitted to said work member, an impact delivery element driven by said driving means and movable into and out of the path of rotational travel of said impact receiving element kfor Irespective engagement with and vdisengagement from said impact receiving element, iiuid pressure actuated means "having a relatively large area over which fluid under pressure may act to cause 4it tofmove said impact fdelivery element out of the rotary path tof Xtravel of said impact `receiving element and also a relatively small area over which fluid'under pressure may act to cause it to actto move said impact delivery element into the rotary -path -of travel of the impact receivingelementfvalve imeans operative to one position to subject-the piston of large area to the pressure of uid vto cause said liuid pressure actuated means to act to '-move said impact 4delivery element out of the path of travel of the timpact receiving element, said valve means being operative to another position for cutting olf the liow 'of uid tothe piston of larger area and for venting the fluid underpressure acting on the piston oflarger area torender the yduid pressure actuated means responsive to move said-impact ldelivery element into theppath of travel of the -impact receiving element, and means responsive 'to the speed of said rotatable driving means for actuating said valve 'means to one of its control positions and being operative upon reduction lin the speed of rotary motion of the driving means for actauting the valve means Ito its other-controlposition.

l1. A rotar-y impact tool comprising a frame, a rotatable lwork member and rotatable driving means therefor mounted on said frame -for lrotation relative to the frame, an iimpac't receiving element through which torque forces may be transmitted to said Work member, an impact delivery velement driven by said driving means and movable into and-out of 'the-'path of rotational travel of said impact receiving element 'for respective engagement with and disengagement from Isaid impact receiving element, uid pressureactuated means for actuating said impact delivery element, centrifugally controlled valve means operative according to the rotational speedof said driving means for vcontrolling the pressure of duid acting on said-duid ,pressure actuated means and thereby controlling thc-operation of the fluid pressure responsive means, and fluid fbias means ycontinually exerting a bias force on said valveim'eans in the-direction opposite to the direction o'f-centrifugal force Jon said valve means to move said valve :means when said impact delivery element is substantially stalled.

' 12. 1n `a rotary impact tool having a fluid pressure driving motor and a source of fluid under pressure for operating the same; a lrotatable output shaft having impact receivingsur'face means, a rotatable hammer assembly having impact 'delivering surface means driven by saidm'otor lfor intermittent engagement with said pact receiving surface means 'to 'deliver a rotary impact blow, expandable kliuid pressure chamber means connected to said source of fluid, centrifugally operable valve means mounted lfor rotation with said hammer means for `controllinggthe uid pressure in said chamber means and operable to decrease pressure in said chamber means when saidrhammer assembly rotates ata givenhigh speed and operablexwhen said hammer assembly is substantially stalled to increasejfluid pressure in said chamber means to cause 'said chamber means to expand to establish a disengaging force, and ay reciprocable member connected to lat least one of said 'impact surface means responsive to 'the 'expansion 'of said chamber'means to cause relative disengaging motion between said impact surface means, and means exerting a continuous engaging force on said reciprocable member in a direction opposite to the direction of said disengaging force and of a magniude less than the peak magnitude of said disengaging orce.

13. In a rotary impact tool having a fluid pressure driving motor and a source of pressure fluid for operating the same; a rotatable output shaft having impact receiving surface means, a rotatable hammer assembly having impact delivering surface means driven by said motor for intermittent engagement with said impact receiving surface means to deliver a rotary impact blow, a reciprocable member connected to one of said impact surface means to cause relative engaging and disengaging motion between said impact surface means, first liuid pressure chamber means connected to said source of pressure iiuid and exerting a continuous force on said reciprocable member in one direction, second fluid pressure chamber means connected to said source of pressure iluid to urge said reciprocable member in the opposite direction, and means operating automatically in response to changes in the speed of rotation of said hammer assembly to vary the force exerted by said second fluid pressure chamber means from a magnitude exceeding the magnitude of said continuous force to a magnitude less than that of said continuous force,` and thereby reciprocate said reciprocable member.

14. In a rotary impact tool having a uid pressure driving motor and a source of fluid under pressure for operating the same; a rotatable output shaft having impact receiving surface means, a rotatable hammer assembly having impact delivering surface means driven by said motor for intermittent engagement with said impact receiving surface means to deliver a rotary impact blow, a reciprocable member connected to one of said impact surface means to cause relative engaging and disengaging motion between said impact surface means, pressure means exerting a continuous force on said reciprocable member to move said reciprocable member in one direction, uid pressure means connected to said source of fluid under pressure and capable of exerting a force of magnitude greater than the magnitude of said continuous force and in a direction opposite to the direction of said continuous force, and centrifugally operated control means mounted for rotation with said hammer assembly for controlling said fluid pressure means to cause the force exerted by said uid pressure means to periodically overcome said continuous force to periodically move said reciprocable member in the opposite direction.

l5. In a rotary impact tool having a fluid pressure driving motor and a source of pressure fluid for operating the same: a rotatable output shaft having impact receiving surface means, a rotatable hammer assembly having impact delivering surface means driven by said motor for intermittent engagement with said impact receiving surface means to deliver a rotary impact blow, a reciprocable member connected to one of said impact surface means to cause relative engaging and disengaging motion between said impact surface means, spring means continuously urging said reciprocable member in a direction to cause said impact surface means to engage thereby to substantially stall said tool, fluid pressure means connected to said source of fluid pressure always urging said reciprocable member in the opposite direction to cause disengagement of said impact surface means thereby to cause said hammer assembly to rotate at an increased speed, the pressure of said fluid at the location of said reciprocable member varying from a high pressure when said hammer assembly is substantially stalled to a low pressure when said hammer assembly is rotating at said increased speed, the force exerted by said uid on said reciprocable member when said hammer assembly is substantially stalled being suicient to compress said spring and move said reciprocable member to cause disengagement of said impact surfaces, and the force exerted by said Iiuid on said reciprocable member when said hammer assembly is rotating at said increased speed being insufficient to overcome the force exerted on said reciprocable member by said spring means thereby causing said reciprocable member to move and cause engagement of said impact surface means.

16. In a rotary impact tool having a Huid pressure driving motor and a source of fluid under pressure for operating the same; a rotatable output shaft having an impact receiving anvil surface spaced from the axis of rotation thereof, an impact delivering element rotatable about said aXis and movable into and out of the path of said anvil surface, means for moving said element alternately into and out of the path of said anvil surface including fluid pressure means connected to said source of Huid for urging said element in one direction, a valve for controlling said fluid pressure means, centrifugal means rotatable with said motor urging said valve in one direction, bias means urging said valve in the opposite direction, said centrifugal means and said bias means providing a net force on said valve in one direction at a predetermined high speed of said motor which increases with movement of said valve in the direction of the net force to effect movement of said valve to a position causing movement of said element into the path of said anvil surface, and a net force in the opposite direction at a predetermined lower speed to eifect movement of said valve in the opposite direction causing movement of said element out of the path of said anvil surface.

17. In a rotary impact tool having a fluid pressure driving motor and a source of fluid under pressure for operating the same, a rotatable output shaft having an impact receiving anvil surface spaced from the axis of rotation thereof, an impact delivering element rotatable about said axis and movable into and out of the path of said anvil surface, means for moving said element alternately into and out of the path of said surface including fluid pressure means connected to said source of uid for urging said element in one direction, a valve for controlling said uid pressure means, actuating means exerting a force varying with the speed of said motor on said valve urging the same in one direction, bias means urging said valve in the opposite direction, said actuating means and said bias means providing a net force on said valve in one direction at a predetermined high speed of said motor which increases with movement of said valve in the direction of the net force to effect movement of said valve in a direction to cause movement of said element into the path of said anvil surface, and a net force in the opposite direction at a predetermined lower speed to effect movement of said valve in the opposite direction to cause movement of said element out of the path of said anvil surface.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,107,108 Mooy Feb. 1, 1938 2,219,883 Amtsberg Oct` 29, 1940 2,313,603 Sittert Mar. 9, 1943 2,326,347 Forss Aug. 10, 1943 2,373,665 Emery Apr. 17, 1945 2,414,359 Carnagua et al. Jan. 14, 1947 2,476,632 Shatf July 19, 1949 2,642,971 Hagenbook June 23, 1953 FOREIGN PATENTS Number Country Date 938,374 France Sept. 13, 1948