Impact Clutch

Abstract

In an impact clutch with coaxially rotatably mounted hammer body and anvil member, a clutch dog features radially outwardly directed impact surfaces and is coupled for conjoined rotation but axially movable on the anvil member. A spring bias acting against the clutch dog strives constantly to retract the impact surfaces thereof to uncoupled rotation position into a cavity in the hammer body. During relative rotation between the hammer body and clutch dog, cam means therebetween throw the clutch dog and the said surfaces thereof axially forward to impact position against cooperating radially inwardly directed impact surfaces on the hammer body.

Description

This invention relates to impact clutches provided with a rotary anvil member, a hammer body carried coaxially rotatably with respect to the anvil member and a clutch dog movable relative to the anvil member and to the hammer body for taking respectively an impact position and an uncoupled position under the action of respectively cam means engaging the clutch dog and a power bias for constant actuation of the clutch dog. Such impact clutches normally combine good impact action with the disadvantage of a great number of constituent clutch details whereby the embodiment becomes costly and there is run the risk of operational disturbances in an unnecessary great number of points. In some solutions (U.S. Pats. Nos. 2,850,128 and 3,389,756) it has been possible to bring down the number of details inter alia by mounting the clutch dog for conjoined rotation on the anvil member radially or axially movably relative thereto. In the first mentioned radial movement solution the anvil member is weakened undesirably by a through diametrical guiding aperture while the latter solution has the disadvantage of an undesirable long axially extended design.

Thus, with particular reference to impact clutches of the type having the clutch dog rotationally intercoupled with the anvil member for conjoined rotation, the primary object of the invention is to provide a novel impact clutch design combining a small number of constituent details with a greatly improved axial compactness of the clutch. A further object of the invention is to provide a dependable clutch design with good impact action and long operable life for the details thereof.

For the above and other purposes there is according to the invention provided an impact clutch comprising a rotatable anvil member, a rotatable hammer mass coaxially supported with respect to said anvil member, rotatable driving means for said hammer mass, a clutch dog mounted on said hammer mass for conjoined rotation therewith and axially movably relative thereto, cooperating impact surfaces on said clutch dog and forwardly on said hammer body, a cavity in said hammer body, biasing means between said anvil member and said clutch dog for retracting the impact surfaces of said dog to uncoupled freely rotatable position into said cavity, and cam means between said hammer body and said clutch dog responsive to relative rotation therebetween for throwing said impact surfaces of said clutch dog from said cavity to impact position against said cooperating impact surfaces of said hammer body.

The above and other purposes of the invention will become obvious from the following description and from the accompanying drawings in which three embodiments of the invention are illustrated by way of example. It should be understood that these embodiments are only illustrative of the invention and that various modifications thereof may be made within the scope of the appended claims.

In the drawings:

FIG. 1 is a longitudinal section through an impact clutch according to the invention substantially on the line 1--1 in FIG. 2 and taking impact position.

FIG. 2 is a section on the line 2--2 in FIG. 1

FIG. 3 is a section on the line 3--3 in FIG. 1

FIG. 4 is a perspective view of a clutch dog also included in FIG. 1.

FIGS. 5-7 show diagrammatic functional illustrations of the main parts of the impact clutch. More particularly, FIG. 5 shows a plane development of the hammer body, the clutch dog, and the cam means of the impact clutch before delivering an impact and with the clutch dog is uncoupled position. FIG. 6 shows the details in FIG. 5 at the instant of impact with the clutch dog in the impact position. FIG. 7 shows the details in FIG. 5 immediately after the impact.

FIG. 8 shows a longitudinal section through a second embodiment of the impact clutch.

FIG. 9 is a cross section on the line 9--9 in FIG. 8.

FIG. 10 shows a third embodiment of the impact clutch.

FIG. 11 finally is a cross section on the line 11--11 in FIG. 10.

In the figures the impact clutch is shown encased in a motor-driven impact tool 15, preferably in hand-sustained impact wrench. In a housing 16 the impact tool 15 incorporates a motor, not shown in the figures, for example a pneumatic one, which produces reversible rotation of the driving shaft 17. The impact clutch proper is encased between the housing 16 and a frontpiece 18 which supports rotatably a forwardly projecting anvil member 19. The forward end of the anvil member 19 carries a square end 20 intended for carrying a removable tool such as a socket wrench, not shown.

The forward end of the drive shaft 17 has splines 22 thereon which are in engagement with cooperating internal splines 23 at the rear end of a hammer body 24. With a forward diametrically opposed inwardly directed lug 25 and an inwardly directed radial impact cam 21 the hammer body 24 bears rotatably against the intermediate portion of the anvil member 19. The hammer body 24 is formed as a hollow body with a large diameter circularly cylindrical cavity 26 disposed rearwardly of the impact cam 21 and the lug 25 and has furthermore a cylindrical guiding aperture 27 of smaller diameter arranged therebehind. Rearwardly of the guiding aperture 27 the hammer body 24 has internally thereof an axial forwardly directed ball groove 28 shaped as an arc of a circle and taking up a ball 29 therein. The ball 29 is maintained with limited peripheral freedom of movement in the ball groove 29 behind the flange portion of a flange sleeve 30 which is fixed in the hammer body 24 coaxially in front of the splines 23. The ball groove 28 and ball 29 provide axial cam means within the hammer body 24. In the flange sleeve 30 the rear end of the anvil member 19 is rotatably journaled, said rear end being formed as a short pivot 32.

On the anvil member 19 a clutch dog 33, FIG. 4, is guided for conjoined rotation but axially movably. To this end the clutch dog 33 comprises a partly cylindrical shank portion 34 which is axially slidably guided in a partly cylindrical recess 35 equiform with the shank portion 34 and provided in the intermediate portion of the anvil member 19. The surface of the shank portion 34 turned away from the anvil member 19 has a radius of curvature equal to the radii of the intermediate portion of the anvil member 19 and of the guiding aperture 27 of the hammer body 24. Intermediately the shank portion 34 is shaped as a full cylinder providing an integral radial impact cam 37. Rearwardly the clutch dog 33 turns into an annular guiding portion 39 which surrounds the anvil member 19 slidably at a cylindrical portion 38 thereof in front of and adjacent the pivot 32. The guide portion 39 slides in the guiding aperture 27 of the hammer body 24 and carries an integral rearwardly directed and peripherally double-sided axial cam 40 in alignment with the shank portion 34 of the clutch dog 33. The cam 40 provides axial cam means on the clutch dog 33 and is pushed axially into the path of movement of the ball 29 by biasing or spring means such as helical springs 42. The helical springs 42 are inserted in rearwardly pointing axial blind bores 41 in the anvil member 19 and bear against the guiding portion 39 such as to subject the clutch dog 33 constantly to a rearwardly directed power bias. The fully cylindrical impact cam 37 of the clutch dog 33 forms tangentially facing impact surfaces 43, 44 which depending upon the rotational direction of the hammer body cooperate with the respective impact surfaces 45 and 46 provided at the opposite tangentially facing ends of the impact cam 21 on the hammer body 24, FIG. 2.

Let it be supposed that the square end 20 through the medium of a socket wrench is connected to a nut to be screwed tight on a fastener having right-hand threads. The motor of the tool 15 will followingly be set for rotation in clockwise direction when viewed in the direction of the arrows 2, 2 in FIG. 1 and upon starting of the motor the rotation is transmitted by the drive shaft 17 to the hammer body 24 and the ball groove 28. Because of its inertia the ball 29 firstly rolls to the end portion of the ball groove 28 trailing in the rotational direction and thereupon applies itself between the latter and the cam 40 of the clutch dog 33, FIG. 5, since the cam 40 projects into the path of movement of the ball 29 as a result of the power bias produced by the springs 42. During spinning down of the nut the rotational resistance is small and the rotation of the hammer body 24 is transmitted via the axial cam means constituted by the ball 29 and the cam 40 to the clutch dog 33 which in its turn is bound for conjoined rotation with the anvil member 19 by the recess 35 and thus transmits the rotation torque to the anvil member 19. It should be observed that in the described position of the clutch dog 33 the fully cylindrical impact cam 37 thereof and the impact surfaces 43, 44 thereon are disposed in axially retracted relation to the impact cam 21 and lug 25 in uncoupled freely rotatable position within the large cavity 26 of the hammer body 24, the impact cam 37 thus being axially retracted with respect to the impact position shown in FIG. 1 and being axially separated from the impact surfaces 45, 46 of the impact cam 21.

When the nut has been screwed down the rotational resistance increases very rapidly and the anvil member 19 together with the clutch dog 33 are retarded or stopped. The hammer body 24, however, being continuously driven by the drive shaft 17 goes on in its rotation causing the ball 29 to actuate the cam 40 axially and to throw the clutch dog 33 in forward direction to the position illustrated in FIGS. 6 and 1. At such instant the impact cam 37 of the clutch dog 33 is thrown into the path of movement of the impact cam 21 such as to produce a rotary tangential blow through the medium of impact cam 21 with the impact surface 45 thereon hitting against the impact surface 43 of the impact cam 37 while the hammer body 24 is stopped momentarily in its rotation. Immediately subsequent to such action the helical springs 42 throw the clutch dog 33 back axially so that the impact cam 37 is again retracted into cavity 26 and the axial cam 40 is caused to fall into the path of movement of ball 29, this time behind the ball 29 since the latter at impact and momentary retardation or stopping of the hammer body 24 continues its movement alone towards the end portion of the ball groove 28, FIG. 7, leading in the rotational direction. The hammer body 24 thereupon continues its rotation relative to the clutch dog 33 and anvil member 19 under acceleration nearly for a full turn with the ball 29 eventually retaking its position in the end portion of the ball groove 28 trailing in the rotational direction and again coming into engagement with the axial cam 40 of the clutch dog 33, FIG. 5 and throwing forward the clutch dog 33 to the impact position, FIG. 6. During its acceleration the hammer body 24 can rotate freely relative to the impact cam 37 and to the impact surfaces 43, 43 thereon since the impact cam 37 is disposed in uncoupled retracted position in the cavity 26. The above-described impact cycle is repeated until the desired tightening moment has been applied to the nut.

Obviously rotation in counterclockwise direction results in an impact action between the impact surfaces 44, 46 and at the instant of abutting relation of the ball 29 with respect to the opposite side of the axial cam 40, the ball will be disposed at the end of the ball groove 28 opposite to the one illustrated in FIGS. 3, 5. The disposition and angular extension of the ball groove 28 is chosen in such way that the clutch dog 33 in both rotational directions thereof always will cooperate only with the impact cam 21, the lug 25 solely providing a journal for the anvil member 19.

At the instant of impact the fully cylindrical impact cam 37 of the clutch dog 33 will be subjected to a substantially tangential compressive force allowing a favorable impact force distribution between the hammer body 24 and the anvil member 19 and ensuring together with the per se favorable design solution a long operable life for the constituent details of the impact clutch.

In the embodiment illustrated in FIGS. 8, 9 there is present a sleeve-shaped clutch dog 48 with three integral peripheral radially directed impact cams 49 coacting with three inwardly directed radial impact cams 50 on the hammer body 24. The clutch dog 48 is provided with internal splines 51 in engagement with cooperating splines 52 on the anvil member 19. Between a forward flange 53 on the anvil member 19 and the clutch dog 48 is inserted a biasing means provided by a helical spring 54 surrounding the anvil member 19, which spring serves to retract the impact cams 49 into the cavity 26 and to move the cam 40 of the clutch dog 48 into the path of movement of the ball 29 of the hammer body 24. The cam 40 is aligned with the annular portion of the sleeve forming the clutch dog 48. By means of a pivot 55 the rear end of the anvil member 19 is centered rotatably in the forward end of the drive shaft 17. The ball 29 is kept in the ball groove 28 by the aid of an intermediate washer 56 sitting on the pivot 55 between the drive shaft 17 and the anvil member 19.

In the embodiment illustrated in FIGS. 10 and 11 there is likewise provided a sleeve-shaped clutch dog 48 with radial impact cams 49 and actuated by a helical spring 58 projecting into the interior of the anvil member 19. The clutch dog 48 has rearwardly an internal flange 59 against which the helical spring 58 bears. The internal flange 59 is guided on a spacing sleeve 60 extending around an elongated centering pivot 55 passing through the washer 56 and extending through the interior of the anvil member 19, wherein the helical spring 58 is supported, onto the drive shaft 17.

The embodiments illustrated in FIGS. 8, 9 and in FIGS. 10, 11, respectively, are identical in their function with the embodiment in FIGS. 1-7 and a repeated description of the function is therefore deemed unnecessary.

Claims

We claim:

1. An impact clutch comprising a rotatable anvil member, a rotatable hammer means coaxially supported with respect to said anvil member, rotatable driving means for the hammer means, a clutch dog mounted on the anvil member for conjoint rotation therewith and axially movable relatively thereto, an elongated partly cylindrical shank portion on the clutch dog, a partly cylindrical axial recess in the anvil member, said recess being equiform with said shank portion and slidably receiving the clutch dog therein, cooperating impact surfaces on the clutch dog and forwardly on the said hammer means, said impact surfaces of the clutch dog being provided by a fully cylindrical radial impact cam and integral with the shank portion, the hammer means having a cavity, biasing means between said anvil member and the clutch dog for retracting the impact surfaces of said dog to uncoupled freely rotatable position into said cavity, cam means between the hammer means and the clutch dog responsive to relative rotation therebetween for throwing said impact surfaces of the clutch dog from the cavity to impact-receiving position relative to said cooperating impact surfaces of the hammer means.

2. An impact clutch according to claim 1, wherein the clutch dog comprises an annular guiding portion arranged axially slidably around the anvil member and integral with the shank portion.

3. An impact clutch according to claim 2, wherein the biasing means are spring means interposed between said anvil member and the annular guiding portion.

4. An impact clutch according to claim 1, wherein said cam means are in alignment with the shank portion.

5. An impact clutch comprising a rotatable anvil member, a rotatable hammer means coaxially supported with respect to said anvil member, rotatable driving means for the hammer means, a clutch sleeve axially slidably splined on the anvil member for conjoint rotation therewith, at least one radially inwardly directed cam at the forward end of the hammer body and integral therewith, at least one radial cam peripherally on and integral with the clutch sleeve for cooperation with said inwardly directed cam, the hammer body having a cavity, biasing means between the anvil member and said clutch sleeve for retracting the cam of the sleeve to uncoupled freely rotatable position into said cavity, and cam means between said hammer body and the clutch sleeve responsive to relative rotation therebetween for throwing said cam of the clutch dog from the cavity to impact-receiving position relative to said cooperating cam of the hammer body.

6. An impact clutch according to claim 5, wherein the biasing means is a helical spring concentric with the anvil member.

7. An impact clutch according to claim 5, wherein said cam means are spaced from the axis of the sleeve and in axial alignment with the annular portions thereof.

8. An impact clutch comprising a rotatable anvil member, a rotatable hammer means coaxially supported with respect to said anvil member, rotatable driving means for the hammer means, a one-piece clutch sleeve slidably mounted on the hammer means for conjoint rotation therewith, angularly spaced radially outwardly directed clutch teeth on the clutch sleeve and integral therewith, angularly spaced radially inwardly directed clutch teeth forwardly on the hammer body and integral therewith for impacting cooperation with said radially outwardly directed teeth, the hammer body having a cavity, spring means between the anvil member and the clutch sleeve for retracting the teeth of the sleeve to uncoupled freely rotatable position into the cavity, an axial peripherally double-sided cam integral with the clutch sleeve, a ball cooperating with the sides of the double-sided cam, an axial circularly arc-shaped ball groove in said hammer body for receiving the ball therein with limited peripheral freedom of movement relatively to the hammer body, said cam, ball and groove being responsive to relation rotation between the hammer body and sleeve for throwing the teeth of the clutch sleeve from the cavity to impact-recieving position relative to the teeth of the hammer body.