US2836272A - Impact clutch - Google Patents

Description

F. A. KAMAN IMPACT CLUTCH May 27, 195s 2 Sheets-Sheet 1 I-[Fled Jan. 13. 1955 F. A. KAMAN IMPACT CLUTCH May 27, 1958 2 Sheets-She??I 2 HFled Jan. 13. 1955 NVENTOR. Kamm UnitedA States Patent O IMPACT CLUTCH Frank A. Kamari, Aurora, Ill., assigner to Thor Power Tool Company, Aurora, Ill., a corporation of Delaware Application January 13, 1955, Serial No. 481,540

18 Clmfms. (Cl. 192-305) This invention relates to improvements in power operated tools of the type having an impact clutch mechanism. More particularly, the invention relates to a novel and improved cam means for eieeting clutching and declutching of the hammer and anvil members of such an impact clutch mechanism and to other novel and improved structural features thereof.

In one type of impact tool, such as used for setting or removing nuts and bolts, a pair of relatively rotatable hammer and anvil members are provided which are operatively connectible through impact or clutch elements. Suitable actuating means is also provided for effecting repeated clutching and declutching of the hammer and anvil members whereby successive rotational hammer blows are imparted to the anvil member for tightening or loosening a nut or bolt. For example, in W. G. Mitchell Patent No. 2,585,486 the clutch elements for interconnecting the hammer and anvil members are in the form of axially movable impact rods carried by the hammer and adapted to be disengaged from the anvil member through the action of a rotatably driven cam element and a cooperating axially movable cam element supporting the impact rods. in my copending application Serial No. 249,546, filed Gctober 3, 1951, a modilication of the cam means is shown wherein the respective cam elements are operatively interconnected by a plurality of cam balls.

The present invention involves a unique and highly advantageous cam means for use in an impact clutch mechanism of the above-mentioned general type. I have found that a commercially available anti-friction ball bearing unit having concentric inner and outer races with aplurality of ball elements therebetween can be mounted in a novel and unique manner, as hereinafter described, to function as a cam means with highly eifective results. The necessity for specially constructed and costly cam elements with carefully designed cam surfaces is completely eliminated thereby resulting in an extremely simple and durable mechanism which can be manufactured by simple and relatively inexpensive production techniques and which can be replaced in service, if necessary, at a minimum cost.

Accordingly, a primary object of the present invention is to provide in an impact clutch mechanism a novel and improved actuating means for effecting clutching and declutching of the mechanism.

l A further object of the invention is to provide an impact clutch unit having novel and improved cam means for actuating the mechanism.

Another object of the invention is to provide a novel and improved impact clutch mechanism having a simple and inexpensive cam means for actuating the same which is characterized by a high degree of durability and stability of performance and which lends itself to simple and low cost production methods.

Still another object of the invention is to provide a unique and highly advantageous impact clutch mechanism comprising, as part of the cam actuating means thereof, a commercially available anti-friction ball bearing unit.

An additional object of the invention is to provide, in an impact clutch unit of the type having relatively rotatable hammer and anvil members with clutch elements interconnecting the same, novel and improved means for retaining the clutch elements in assembled relation with the hammer.

A still further object of the invention is to provide, in an impact clutch mechanism having a rotatably mounted hammer, novel means for axially moving the hammer and distributing the forces imposed thereon during such axial movement.

Other objects and advantages of the invention will become apparent from the subsequent detailed description taken in conjunction with the accompanying drawings wherein:

Fig. l is a longitudinal sectional View, With portions thereof in elevation,` of an impact tool comprising one specific embodiment of the invention and showing the impact clutch mechanism in fully clutched position;

Fig. 2 is a fragmentary longitudinal sectional view taken along the line 2 2 of Fig. l with portions of the structure being shown in elevation; Fig. 3 is a transverse sectional View` taken along the line 3;*3 of Fig. l;

Fig. 4 is a view similar to Fig. 1 but showing the irnpact clutch mechanism in its opposite operating position at the instant of declutching;

Fig. 5 is a transverse sectional view taken along the line 5 5 of Fig. l;

Fig. 6 is a transverse sectional view taken along the line 6-6 of Fig. l; v

Fig. 7 is a transverse sectional view taken along the line 7-7 of Fig. l with a portion of the structure broken away to show the bearing arrangement;

Fig. S is a fragmentary side elevational view of a modified form of the device having different clutch or impact means interconnecting the hammer and anvil members;

Fig. 9 is a fragmentary side elevational view of another modification of the device having a differently shaped hammer and a slightly different means for holding the impact elements in assembled relation with the hammer; and Y Fig. l() is a fragmentary sectional View of still another modification of the means for holding the impact elements in assembled relation with the hammer.

Referring first to Figs. l to 7 of the drawings, the impact tool illustrated therein comprises a two-part casing or housing including a forward section 11 containing the impact mechanism and the drive gearing and a rear section or field case 12 containing an electric motor (not shown). The two housing sections are detachably connected by a plurality of screws 13. A hollow handle grip 14 having a depressible operating trigger 15 extends from the casing section 12 for manipulating the tool and starting and stopping the motor. A shiftable plunger 16 is also mounted on the handle 14 for eecting reversal of the tool. The details of the reversing switch mechanism contained within the handle grip 14 form no part ofthe present invention, reference being made to myrcopending application Serial No. 475,502, filed December l5, `1954y for a more complete description of this portion of the device.

As seen in Figs. l and 4, the electric motor of the tool has an armature shaft 17 which is journaled at its forward end n a ball bearing unit 18 supported ina center plate 19 carried by the rear casing section 12. Rotary motion of the electric motor contained in the housing section ,1 2 is transmitted to the impact unit within the forward housing section 11 by means of a planetary gear train.` Thus, the forward extremity of the armature shaft 17 is shaped Patented vMay 27, 1958,

tative movement relative to the anvil.

Y to' provide" integral pinion gear 21 which is meshed with fa paireof: diametricallyopposed planetary gears 22A mounted forrotation on short shafts 23 extending rearwardlyrfroma Vspider member or countershaft 24. TheY spider member 24is mounted Vby means' of a bore portion 26 onfthe rear end ofa drive shaft 27v and isl rigidly connected-for rotation'therewith, asby means of a transverse pin-28. The spider24 is also'provided with a pair ofY rearwardlyY extending curved extensions 29 (Figs.V 3 and 4) nwhich are spaced'apart in diametrically opposedfrelation on'V opposite sides of the amature shaft 17.a-d the pinion 21. These curved extensions'29 are received within a combination thrust and radialrballv bearing unit 31 Y f or journaling the rearward end ofl the-spider, the bearing unit 31j also being supported in the center plate 19. 1 The a planetary gears 22amV also-meshed with an: internal ringY gear 32 which is secured in and projects somewhat beyond the; forward' endV of the rear housing section 12.

The `drive1 shaft 27 comprises the main supporting member-for theimpact unit and extends forwardly with- .Y in the Casing section 11 and is received iat its'forward end'gwithinV an axial boreY 33 offfan impact spindle or a'nvil 34V having a square end section 36 disposed exteriorly offthe housing section 11 for mounting and driving a nut or bolt engaging socket (not shown) in the usual manner. The anvilY 34 is rotatable lwithin a bushing 37 mounted in` the forward end or nose portion 38.015 t'he housing section 11.V A rotatable generally cup-shaped hammerV member 39 is mounted on the drive shaft 27V rically'opposite sides ofthe shaft 27, and a pair Vof, Y Vclutch'elements or'jaws in the formY of impact rods 46 "are disposed witha slightly loose tit in the bores 44 so as to. permit removal and replacement ofthe rods. The

hammerV 39, althoughl cup-shaped with Va central recess- 47, has a solid rugged construction and is shaped to provide a mass having the desired inertia ,and operating characteristics. In this particular instance,`the external contour of the hammer 39 is hexagonal (as seen in Figs. 5 Val1-d'6) Vin .orderjto reduce the total Vmass andinertia of the hammer. UThe' lower or forward ends of the impact rods 46 project beyond theforward Vend of the hammer 39, as seen in Fig. l', when the unit is in impactingposition and the ends of the'rods 46 thus extend into engagement with arcuat'ely formed abutment surfaces 48 (Fig. 5)' which are formed in radially extending flange portions 49 on the V anvil 34. As will be explained in detail hereinafter, the impact rods 46 rotate with the hammerV 39 and are adapted to drive and strike the anvil Y 'i 34 at'the abutments 43 to cause rotation of the anvil. Of course, in the opposite direction of rotation of the tool, the impact rods 46 will engage andcstrike a similar pair of arcuate abutment surfaces 51'V provided at the p opposite sides of the radial anges 49.

The upper or rear ends of the impact rods 46 have enlarged head portions 52'which are received in recesses in an `annularshoulder portion 53 at the rearward end ofthe'hammer 39. A collar 54 is mounted around the rear end of the hammer 39 and seats against the shoulder 53in overlying relation with the head'portions 52 of the impact rods 46. A relatively strong compression spring 56 encircles the coliar 54'1and seats thereon so that the ,spring is Y'retained in operating engagement with the rear `end Vof the hammer and also serves tov retain the impact Vrods 46 in assembled relation with the hammer 39. As seen in Figs. 5, 6, and 7, the 'hexagonal external shape'of the hammer 39 provides only a relatively re?v stricted and discontinuous contact area against which the end of the spring 56 couldseat so' that the annular collar 54 isdesirable with this form of 'hammer in order to provide an` adequate seat and retainer Yfor the forward end of the spring 56. The upper or rear end of the vcompression spring 56 seatsL against Vthe peripheral llange portion 57 of a generally cup-shaped spring plate Sti'having a central aperture 59 through which the shaft 27 extends, and la ball thrust bearingrunit 61 is interposed between the spring plate 58 and the forward axial` end of the spider 24 for receiving the thrust of the spring.

YAs will hereinafter appear inconnection with the dei i scription of the operation ofthe tool, the hammer 39 carrying the impact rods Y46V is shiftable rearwardly alongY axially and rearwardly along the shaft 27 are both provided by means of a unique cam'arrangement including a drivingV cam means connected to the` shaft 27 and a Y complementary driven cam means connected to the hamymer 39.

ing 67 havingV an angular bore 68 for mounting the bush-V ing on. the .drive shaft 27,Tthe bushing 67 beingl keyed to the Shaft 27, as by a pin 69, for rotation therewith. By reason of the .angularly disposed or off-center bore 63, it lwill be seen that the bushing 677 vand the bearing unit 62 are thereby mounted so that the axis of rotationA of the races 63 and 64 intersects and is at an angle to the axis of the shaft 27. Consequently, upon rotation lof the drive shaft 27 it will be understood that a wobble movement about the axis of the shaft 27 is impartedy to the cam bearingunit 62 by reason of the rotary driving connection from the Vshaft 27 to the bushing 67 andto the inner race 63, and at the same time the unit 62 and its supporting bushing 67 are restrained against bodily movement relative to the, shaft 27 by 'reason of thefkey or pin 69. A cooperating driven cam means or lifter member'is provided in the form of an annular member 71 received within the hammer recess l47 at the base thereof and rigidly connected to theVV hammer for rotation therewith by means of a key or pin 72. The Vcam member 71 has an enlarged central aperture 73 through which the drive shaftV 27 extends for axial Inove-V ment of the member 71 relative to the shaft 27, and the forward axial-end of the Vcam member 71 has a hat cam surface 74 disposed diagonally at Yan angle to the axis of the shaft 27 and complementing theV angular-'relation between the cam bearing means 62 and the shaft 27 so Vthat the axial edge portions of. the races 63 'and 64 are adapted to engage and seat'against the inclined cam surface 74 for coaction therewith in the manner to be described below.

When a nut or bolt is to be tightened, the operator first places the socket (not shown) carried on the squarey endV portion 36 of the anvil over the nut or bolt head' the hammer 39and the impact rods 46 through camA Y bushing 67 and driving contact between the axial edges of the races 673 and 64 of the driving cam means 6 2 es and the inclined camsurface 74 of they cam or lifter member 71. In this connection, it Vwill readily'beV understood from Figs. l and 2 that the action of the spring 56 urges the hammer 39 and the cam member '71 keyed thereto into tight frictional engagement with the bearing races 63 and 64. Consequently, driving torque is transmitted directly from the rotatably driven inner race 63 to the cam surface 74 in tight spring-pressed frictional engagement therewith, and such driving torque is Ialso transmitted, -as a result of axial spring pressure, from the inner race 63 through the ball elements 66 and the outer race 64 to the cam surface 74 so that tr e bearing unit 62 and the cam member 71 rotate as a unit with the hammer 39 in response to rotation of the drive shaft 27.

At the outset of the tightening operation, the hammer 39 is maintained in fully projected position with the rod ends in engagement with the abutment surfaces 48 of the anvil 34, as shown in Fig. 1, so as to rotate the anvil 34 and the socket mounted thereon and thereby tighten the nut or bolt. As long as the nut or bolt is relatively free r running, the impact rods 46 remain in constant driving engagement with the anvil 34, and the angularly related cam means 62 and 71 remain in fully engaged complementary positions. However, when the nut or bolt approaches tightened position and resistance to rotation becomes suliicient to overcome the driving torque of the tool motor and the expansive force of the spring 56, then. the unitary rotation of the anvil 34, the hammer 39, and the cam member 71 is arrested. At the same time, thedrive'shaft 27, the cam bushing 67, and the inner bearing race 63 continue to rotate under the driving force of the motor and, as a result, a rocking or wobble motion is imparted to the entire bearing unit 62 whereby the rearwardmost portion of the angularly disposed bearing 62 is rotated in the direction of the forwardmost portion of the inclined cam surface 74. As will be most evident from Fig. 4, the eifect of this combined rotary and wobblng movement of the axially fixed cam means 62 is to cause rearward axial displacement or shifting of the cam member 71 and the hammer 39 keyed thereto as the edge of the outer bearing race 64 rocks along the inclined cam surface 74 to the Fig. 4 position of the mechanism. During this rearward camming action only the inner bearing race 63 undergoes rotative movement relative to the cam 71 and the hammer 39 while the outer bearing race 64 simply undergoes a wobblng or rocking action to a more or less reversely inclined position relative to the temporarily non-rotating cam memberV 71. Since the hammer 39 carries and supports the impact rods 46 in unitary relation in the presently illustrated embodiment of the invention, these hammer rods are thus disengaged from the abutment surfaces 48 of the anvil 34. In Fig. 4 the rods 46 are shown at the instant of disengagement from the anvil 34. During this rearward shifting movement of the hammer 39, the needle bearing 42-43 likewise shiftsaxially along the drive shaft 27 so that continuous bearing support is provided in all positions of the hammer along the shaft 27. Y

In the Fig. 4 position of the impact mechanism, the hammer rods 46 are declutched or out of driving engagement with the anvil 34 and hence the hammer 39 is free tofrotate under the driving torque of the motor. Consequently, the hammer 39 now resumes rotationin a tightening direction and the hammer rods pass over the narrow lands on the anvil anges 49 between the arcuate abutment surfaces 48 and 51, and are projected forcibly under the influence of the spring 56 back into the path of the abutrnents 48 so as to impact against these abutment'surfaces upon continued rotation. From the time that driving engagement is broken oi, as above described, until the hammer rods 46 impact against the abutment surfaces 48, the drive shaft 27 accelerates under the 'driving force of the motor at an increasing rate so that the impact rods 46 strike the abutments on the anvil 34 with considerable force which is of substantial magn tude by reason of the solid massive construction of the hammer 39. Moreover, when, the mechanism is in the Fig. 4 declutched position, the coacting inclined 'camsurfaces of the cam means 62 and 71 are then oppositely inclined so as to have substantially a single point of engagement. Consequently, as the hammer 39 and its impact rods 46 rotate toward impacting engagement with the anvil 34, the spring 56 acting on the retainer collar 54 Aforces the hammer 39 and the cam member 71 axially and forwardly thereby coacting with the edge of the outer race 64 and causing accelerated rotation of the outer bearing race 64 relative to the inner race 63. As a result, the hammer 39 and the cam member 71 are caused to accelerate ahead of the drive shaft 27 so that the impact rods 46 strike the spindle 34 with an increased impacting force and at a rate of rotation over and above that of the drive shaft 27. The relative rotative movement of the outer race 64 with respect to the inner race 63 is made possible by the balls 66 so that there is a highly effective spring-actuated return of the hammer to impacting position with very low friction loss. After impact which causes further limited rotational tightening movement of the anvil 34, the impact rods 46 are again withdrawn as above described and are again rotated relative to the anvil 34 and again are ultimately moved into forceful impacting engagement with the abutment surfaces 43. Thus, the impact rods 46 may strike the anvil 34 two impacting blows for each revolution of the hammer 39 and these blows are repeated until the work has been tightened to the desired extent.

When it is desired to utilize the tool for the purpose of loosening a nut or bolt, the operator may shift the reversing plunger or button 16 to its opposite position and the electric motor of the tool will thus operate in the reverse direction thereby driving the shaft 27 in the reverse direction. Since the work is in a tightened condition, the impact rods 46 will immediately commence imparting repeated impacting blows against the anvil 34 until the resistance to rotation offered by the work is less than the driving torque of the cam 'bushing 67 at which point the impacting blows cease and the impact rods 46 remain in constant engagement with the impact spindle or anvil 34 for freely driving the latter. The tool may then be allowed to rotate the work until it is entirely detached or loosened. Of course, it will be understood that during the impacting period of reverse operation the cam action is the same as described above.

From a practical viewpoint, an important operating characteristic of the device results from the fact that the impact rods 46 are loosely received within the hammer bores 44 to permit the rods to be replaced readily when necessary. As a result of this relatively loose fit, the rods 46 are free to rotate within the hammer bores 44, and I have found that under the iniiuence of repeated impacting blows of the rods 46 against the abutment surfaces of the anvil 34, the rods 46 are in fact rotated by slight increments. Presumably, such relative rotation of the rods 46 in the hammer 39 is due to the slight offcenter or eccentric application of impacting force during forceful enagement of the ends of the rods 46 with the anvil abutment surfaces. At any rate, because of the fact that the rods 46 are rotated slightly during repeated impact blows it will be apparent that different circumferential portions of the lower or blow-delivering ends of the rods 46 are presented for engagement with the anvil abutment surfaces during continued operation of the tool. Consequently, the wear on the impacted areas of the rods 46 is distributed substantially uniformly and the rods have a long operable life.

Another operating characteristic which contributes to the durability of the tool is found in the uniform wearing action between the coacting edges of the bearing races 63 and 64 and the inclined cam surface 74. Just prior to outer race V64 is'zacc'elerating ahead' of the inner Arace 63 as describedabove. However, at'the instant of impact Y' the 'inertia of the rotating-outer race Y64 causes it'to rotate slightly relative t-the hammer 39 vand the cam surface 74. Consequently, by repeated rotational increments the race 64 engages the surface-'V74 at new positions so as to distribute the wear uniformly on the parts, particularly on the race 64. Y

By reasonof the angular mounting of the cam means 62 and 7l it will be seen that the camming forces imparted tothe clutch mechanism particularly d g" declutching operation are non-symmetrical or o5-'center with respect to the axis of the drive shaft 27. Consequently, the radial bearing support provide/dior the shaft 27 by the needle bearingy i2-43 immediately adjacent the quite important in the present invention in order te direc. the forces' resulting from operation of the cam mechanism so as to maintain the hammer and anvil in axiallaligned-,relation on theY shaft 27. Although one Vmay use any suitable type of radial bearing. providing an erongated bearing Contact with the shaft 27 or the equivalent thereof together with axial movability relative to the shaft 27, I have found thatY the needle bearing construction i2-43 is well adapted to meet these requirements because of theincreased bearing Vstnface which is proas hereinbefore mentionedathe entire lbearing assembly 142-43 must be axially slidable along the Vshaft 27 to accam means Y Yis commodatc bodily movement of the hammer 39 during bearing unit 62 as a driving cam means in the manner hereinabove described'ahfords a numberof very important advantages. in the first place, the entire arrangement including the bushing 67, the ball bearing unit V6.2, and the cam member Yor lifter element 7i are relatively inexpensive as compared with the Ymore conventional cram devices used in impact clutch mechanisms. special cam cutting machinery and the necessity of close control during the formation of cam surfaces are completely eliminated with obvious savings in manufacturing cost. Moreover, the assembly of the device is extremely simple so that the entire mechanism is readilyadapted for low cost high speed production techniques.

I have also found that the operating ycharacteristics of the tool containing the above-described cam mechanism are extremely advantageous.Y Due'to the lfact thatV Vthe driving cam means 62 has relatively rotatable portions with anti-friction bearing elements therebetween, the energy loss through friction during operation of the cam means is reduced to aV minimum and also, the accelerated rotary movement of the hammer just prior to each impacting blow is'enhanced substantially thereby permitting a more forceful and effective spring-pressed return of the hammer rods into impacting engagement with the anvil. Because of the very simplicitycf the cam construction and the complete elimination of carefully contoured cam surfaces, the device is extremely durable,V has a long operating life, and isV characterized by an exceptionally stable and uniform operation.

Reference isrnow made to Figs, 8, k9, and 10 'of the drawings wherein several modifications of the structure are shown.V ln Fig. 8, a modied impact means is'illushated. The anvil member, designated at 76, is provided in this caseV with a plurality of axiallyextending teeth or The use of v clutch jaws 77 integral with the anvil and adapted to be engaged during impacting by a plurality {5f-corresponding teeth or jaws 73 extending integrally from the bodyof the hammer 79. Thus, the improved impact clutch mechanism constituting the present invention is equally applicable to a hammer-anvil arrangement wherein lthe impact Figs. l to 7. As in the Yfirst described form vof the invern- Y tion, the cam mechanism causes rearward axialretraction of the hammer 79 so as to effect declutching of the device( InvFig. 9,'a different shaped hammer is shown at 81', the external contour of the hammer in this case being circular rather than hexagonal for a tool whereinit is desirable to have a hammer of increasedj mass andinertia, efgl Because of thecircular Y in a pneumatically driven tool. Y contour of the hammer 81, a continuous annular shoulder u. of substantial size is provided around the Vrear axial end of the ham-mer and is of sufficient widthrto provide,V

an adequate seat for the forward end of the spring, indi-VA cated at 83. The impact rods are designated at 84 and` are removably mounted in the hammer 81 with heads of the rods recessed in the shoulder 82 in the same manner .as described above in connection with Figs. l to 7.(V vHow-` ever, because ofthe adequacy of the shoulder-82 on the hammer S1, the separate spring-retaining collar 54 shown in the first embodiment of the invention can be eliminated and the spring 83 seats directly against theV shoulder 82VV ,of the, rods 86 and a pin 88 issecured in the Ybodyy of vthe'V hammer, designated at'89,and extends into thek groove 87 i for retaining each rod 36 axially in the hammer 89 while at the same time permitting relative rotation'of the'rod in the Vhammer bore; Asy shown, the rear ends of the rods 86'are recessed slightly below an annular shoulder 91 Y against which the spring 92 seats. Y.

Itis to be understood that while the invention has been described abovey .with reference' toran impact wrench, theY 'Y very same tooltby 1l eans of special attachments secured on the square spindle. end 36 may -be adapted for other f usesV such as a screwdriver, tapper', reamer, drill, sandeni polishen'wire brush driver, or they like. .When utilized for these latter purposes, the tool may/be primarily free running without impacting operation. However, such impacting featuresV are always available and are permitted-to become etfective when the tool isY used as a screwdriver or, for example, when thetool is used as a drill and the f drilllbit becomes YfrictionallyY bound before the Vdrill hole` has been completed. The impacting blows of theim'pact niechanismare then applied to the drill bit to overcome such Yfrictional resistance and the danger ofzoverload on the motor is eliminated.

VAlthough the invention has been described with particular reference toy certain Vspecific structural embodimentsthereof, it will be understood that-various moditications andk alternative constructions may be resorted toA effecting disengagement of the impact means comprising an anti-friction bearingy unit having relatively rotatable` portions mounted withrthe axis of rotation thereof inter-V secting -the axis of rotation-of the hammer member'- at anY angle thereto, and a 'cooperating'shiftable cam' member operatively engageable with the impact means-.and hav-1 .Ying an angularY caml surface, coacting with said bearing.Y unit for effecting disengaging movement of the impact means in response to relative rotational movement im-w parted to saidbearing unitwith respect vto said cam jmember.

2. In a rotary impact tool having rotatably mounted .1'

axially aligne'dhammerV and Vanvil members with impact' means carried by the hammer member and ,spring4 mearisvr operatively coacting with the impact means for` normallyV retaining the same in clutching relation between the hammer and anvil members, the improvement comprising means for effecting declutching of the hammer and anvil members including anti-frictiony ball bearing means mounted with its axis of rotation angularly intersecting the axis of rotation of the hammer and anvil members, means for restraining said ball bearing means against bodily axial movement, and a coacting lifter member operatively engageable with the'impact means and shiftable axially with respect to said ball bearing means, said lifter member having a complementary inclined cam surface adapted to coact withV the angularly mounted ball bearing means for shifting said Ylifter member against the action of the spring meansV in response to relative rotational movement imparted to said ball bearing means with respect to said lifter member whereby to effect declutching movement of the impact means.

3. In a rotary impact tool having coacting rotatable hammer and anvil members, impact means carried by the hammer member for striking the anvil member, a spring normally urging said impact means into engagement with the anvil member, and driving means for the hammer member; the improvement comprising cam means for connecting said driving means with the hammer member and for disengaging said impact means from the anvil member, said cam means comprising an anti-friction ball bearing unit disposed with its axis of rotation angularly intersecting the axis of rotation of the hammer and anvil members, means for connecting said ball bearing unit to the driving means, and shiftable means operatively connectible with'said impact means and providing an inclined cam surface cooperable with said ball bearing unit for effecting disengaging movement of the impact means in response to rotational movement imparted from the driving means to said ball bearing unit and relative to said shiftable means.

4. In a rotary impact tool having rotatable hammer and anvil members and impact means carried by the hammer member and normally engaging the anvil member but being disengageable therefrom, cam means for effecting disengagement of the impact means comprising a pair of concentric annular races with a plurality of anti-friction bearing elements therebetween, said races being disposed so that their axis of rotation intersects at an angle with the axis of rotation of the hammer member, and a cooperating axially movable cam member having an inclined cam surface disposed at an angle to the axis of rotation of the hammer member and coacting with said cam means, said cam member being operatively engageable with-the impact means for effecting disengagement of the impact means in response to relative rotational movement imparted to at least one of said races with respect to said cam member.

5. The structure of claim 1 further characterized in that said cam member is directly engageable with the hammer member for axially shifting the latter whereby to effect disengagement of the impact means carried by the hammer member.

'6. In a rotary impact tool having rotatable hammer and anvil members and impact means carried by the hammer member and normally engaging the anvil member but being disengageable therefrom, cam means for effecting disengagement 'of the impact means comprising an anti-friction ball bearing unit having concentric inner and Vouter races with a plurality of balls therebetween, mounting means secured to said inner race for imparting rotary movement thereto and positioning said unit with the axis Yof rotation of the races intersecting the axis of rotation of the hammer member at an angle thereto, and a cooperating lifter member axially movable with respect to said unit and operatively connectible with the impact means, said lifter member having an inclined cam surfacedisposed at an angle to the axis of the hammer member and engageable with the axial edge of said outer race whereby to eifect axial shifting of the lifter member and consequent disengagement oftheimpact means in response to rotation of said inner race relative to said lifter member.

7. In a rotary impact tool having rotatable hammer and anvil members and impact means carried 'oy the hammer member and normally engaging the anvil member 'out being disengageable therefrom, cam means for effecting disengagement of the impact means comprising an anti-friction ball bearing unit having concentric inner and outer races with a plurality of balls therebetween permitting relativerotation between said races, means secured to said inner race for rotating the same, said means also retaining said unit against axial movement and in angular relation to the hammer member with the axis of rotation of said races intersecting the axis of rotation of the hammer member at an angle thereto, and a cooperating lifter member mounted for axial movement relative to said unit and operatively connectible with the impact means for etecting disengaging movement of the latter, said lifter member having an inclined cam surface disposed at an angle to the axis of the hammer member for tlatwise driving engagement with the axial edges of said races in one position of said bearing unit whereby said litter member is rotated upon rotation of said means, and said lifter member being shifted axially in an opposite position of said bearing unit by camming engagement between said outer race and said cam surface in response to rotation of said inner race relative to said lifter member whereby to effect disengagement of the impact means.

8. In Va rotary impact tool having rotatable hammer and anvil members and impact means carried by the hammer member and normally engaging the anvil member but being disengageable therefrom, cam means for effecting disengagement of the impact means comprising an anti-friction ball bearing unit having concentric inner and outer races with ball elements therebetween, means for mounting said unit at an angle to the axis of rotation of the hammer member and for imparting rotary driving motion to said inner race relative to said axis whereby said unit undergoes a wobble movement during rotation of said inner race about said axis, and a lifter member axially movable relative to said unit and operatively connectible with the impact means for disengaging the latter, said lifter member having an inclined cam surface complementing and axially engaging said unit whereby said lifter member is shifted axially by the wobble movement of said unit in response to rotation of said inner race relative to the lifter member and thereby elfecting disengagement of the impact means.

9. in a rotary impact tool having rotatable hammer and anvil members and impact means carried by the hammer member and normally engaging the anvil member but being disengageable therefrom, the combination of a drive shaft for rotatably mounting the hammer and anvil members, a bushing secured to said shaft for rotation therewith, an anti-friction ball bearing unit including concentric inner and outer races with balls therebetween, said inner race being secured on said bushing for rotation therewith and said unit being mounted by said bushing at an angle to the axis of said shaft with the axis of rotation of said races angularly intersecting the axis of the shaft, and a lifter member mounted on said shaft for axial movement therealong and operatively connectible with the impact means for disengaging the latter, said lifter member having an inclined cam surface at an angle to the axis of said shaft and axially engageable with said unit whereby to effect axial movement of the lifter member and consequent disengagement of the impact means in response to rotation of said bushing and said inner race relative to said lifter member.

l0. In a rotary impact tool having rotatable hammer and anvil members and impact means carried by the hammer member and normally engaging the anvil member but being disengageable therefrom, the combination essere bushing having an enlarged'diameterhportion .andV a reduced ,diameter portion providing -a radial shoulder therebetween, anti-friction ball bearing unit including Y concentric inner and outer races witha plurality of balls therebetween, said inner racerbeing'fV rigidly ,fitted on said the 'axis'ofirotation of*y said races intersects the axis of said shaft at an angle thereto, and a lifter member mountdon .said shaft for axial movement therealong and operatively'connectible with the impact means for disengaging the latter,said VVlifter member having an inclinedy cani Ysurface at annngle to` the axis ofk said shaft 'and axially Vengageable with said unit whereby to effect axial movement of the lifterzmemberV and consequent disengagenient of the impactxmeans in response to rotationl of said bushing and said inner race relative to said lifter'member.

Q11. ln a rotary impact tool having rotatable axiall aligned hammer and'anvil members and impact means carried by the hammer member and normally engaging Y the anvil member but being disengageable therefromgtheV combination of a drive shaft for mounting the hammer and anvil members,V an anti-friction ball bearing unit including concentric inner and outer races with balls therebetween, means supporting said unit at an angle on said shaft and providing a. driving connection between said ,shaft and V'said inner race whereby to impart a wobble movement to said unit during rotation of said inner race Y aboutvits, axis, a lifter member axially movable along said shaft relative to said unit and engageablerwith the hammer member for shifting the hammer member and Vthe impact means into disengaged position, said lifter member having an inclined cam surface engageable axially with said unit whereby said lifter member is shifted axially by the wobble movement of said unit in response to Vrotation of said inner race relative to the lifter member,

and radial bearing means coacting with said shaft for slidably mounting the hammer member and for maintaining the hammer and anvil members in axial align` including concentric linner and outer` Araces with ballsV therebetween, means supporting said unit at an angle on said shaft with the axis of rotation of theraces intersecting the axis of said shaft atan angle thereto, means providing a driving connection between said shaft and said inner race, a cooperating cam member axially movable v.along said shaft and engageable with the hammer member for shifting the hammer member and the impact means into disengaged position, Asaid cam member having an inclined caml surface axially engaging said unit where'- by said cam member is shifted by the cam action of said unit in response to rotary driving of said inner race relative to said cam member, and elongated roller bearing means coacting with said shaft for slidably mounting the hammer member and for maintaining the hammer and anvil membersV in axial alignment on said shaft under the off-center forces acting on said shaft Vas a A reduced diameter portionof Vsaid bushing and in axial Ven-WV gagement with said shoulder for rotation of said inner ra'ce'rwith said bushing and said drive shaftrrand whereby c c 12 Y result of the camming action between the angularly dis# posed'bearingunit and said cam surface. l f

' 13. Inlcavrotary impactto'ol having rotatable hammer and anvil members andimpact means carried by` the hammerv member and normally engaging-the anvil mem-Vv Y ber but being disengageable therefrom, camV meansrfor effecting `disengagement ofthe impact means comprising an anti-friction bearing unit having relativelyjrotatable Vportionsmountedwith thejaxis of rotation thereof intersectingthe axis of rotation ofthe hammer. member at an angle thereto, aV cooperating cam unit having an angular cam surface Vc'oacting with said Vbearing unit, one of said units being shiftable axially andy operatively engageable 1 with the impact means, and means providing'V a driving connection with the'other of said units for imparting rotational movement to said other unit'and thereby` effect-A ing disengaging movement of said'one'V unit'and the impact means. c Y Y Y 14. In an impact clutch including ananvilfI neniber,V

Ythe combination Vof a rotatable hammer mounted for tions at their forward endsrprojecting forwardly of the'V forward end'of said hammer when in assembled rela-.

tion therewith and head portions at their rearward ends, said hammer and said impact elements beingY movable as a unit and said hammer'being adapted to be moved axially toward and from'V said anvil member to effect engageV ment and disengagementV of said forward portionsV of the impact elements with said anvil, shoulderV means' at the rearward end of said hammer, said head portions of said impact elements being recessed axially relative to said shoulder means, means loosely Vretaining, said impactY elements against forward axial' movement relative to said hammer while permitting free'rotation of the impact elements relative to the hammer, and spring means abutting said shoulder means for normally urging said harnmer ,into its forward impacting position,-V said spring means extending across said head portions but being spaced therefrom so as to avoid interference with freel rotatabilityV of said impact elements' in thehammermeinber. t

15. The structure of claim 14 further characterized in that said impact elements comprise elongated impact rods disposed in cooperating axial bores in saidjhamnier.

16. The structure of claim 15 further characterized in that said impact rods have enlarged head portions for retaining the rods against Vforward axial movement relative to the hammer.

Y 17` The structure of'claim 14 further characterized in that said spring means comprisesV an annular retaining collar extending aroundsaid hammer at its rearward end and seated against said shoulder means, and a springV element engaging said collar for normally urging said hammer into its forward impacting'position, said collar extending across said head portions of saidV impact elements VVand said head portions being'recessed in the .ham- Vmer in spaced relation from said collar. Y

18. Thef structure of claim V14 further ments with the head portions being recessed in the hammer in spaced relation from said'rear axial endportion and the spring element.. Y

References Cited in the le' of thisfpatent`

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