US3606932A - Rotary impact motor - Google Patents

Abstract

IN A ROTARY BIDIRECTINALLY OPERABLE IMPACT MOTOR FOR POWER DRIVEN FASTENER SETTING TOOLS A RECESSED IMPACT DOG IS JOURNALLED BY ITS CYLINDRICAL BACK PORTION EXTENDING OVER MORE THAN 180 DEGREES IN A JOURNALLING RECESS OF A HAMMER BODY PIVOTALLY ABOUT AN AXIS SPACED FROM BUT PARALLEL WITH THE AXIS OF ROTATION OF THE HAMMER BODY FOR TAKING IMPACT AND RELEASE POSITIONS WITH RESPECT TO OPPOSED IMPACT SURFACES ON AN ANVIL COAXIAL WITH THE HAMMER BODY AND SURROUNDED BY A ROTATION CAVITY THEREIN. THE JOURNALLING RECESS IS OF LARGER DIAMETER THAN SAID ROTATION CAVITY. END SURFACES ON THE IMPACT DOG COOPERATE WITH THE ANVIL FOR PIVOTING THE IMPACT DOG TO IMPACT POSITION WHILE A DRIVE ELEMENT FOR THE HAMMER BODY ENGAGES THE IMPACT DOG FOR PIVOTING IT TO THE RELEASE POSITION. THE END SURFACES ARE TRANSVERSE TO THE BACK PORTION OF THE IMPACT DOG AS WELL AS THE RECESS THEREOF.

Description

P 21, 1971 K. c. SCHOEPS 3,606,932

, ROTARY IMPACT MOTOR Filed June 16, 1970 ZSheets-Sheet 1 Se t. 21, 1971 K. c. SCHOEPS 3,606,932

ROTARY IMPACT MOTOR Filed Jun 16, 1970 2 Sheets-Sheet United States Patent 3,606,932 ROTARY IMPACT MOTOR Knut Christian Schoeps, Nacka, Sweden, assignor to Atlas Copco Aktiebolag, Nacka, Sweden Filed June 16, 1970, Ser. No. 46,765

Claims priority, application Sweden, June 19, 1969,

Int. Cl. B25d 15/00 US. Cl. 17393.5 7 Claims ABSTRACT OF THE DISCLOSURE In a rotary bidirectionally operable impact motor for power driven fastener setting tools a recessed impact dog is journalled by its cylindrical back portion extending over more than 180 degrees in a journalling recess of a hammer body pivotally about an axis spaced from but parallel with the axis of rotation of the hammer body for taking impact and release positions with respect to opposed impact surfaces on an anvil coaxial with the hammer body and surrounded by a rotation cavity therein. The journalling recess is of larger diameter than said rotation cavity. End surfaces on the impact dog cooperate with the anvil for pivoting the impact dog to impact position while a drive element for the hammer body engages the impact dog for pivoting it to the release position. The end surfaces are transverse to the back portion of the impact dog as well as the recess thereof.

The invention relates to a rotary impact motor of the kind used in connection with fastener setting tools, impact wrenches and the like. In such applications is formerly known a type or rotary impact motor with impact action in both rotational directions thereof against the respective of a pair of opposed impact surfaces on a rotatable anvil, in which impact motor a hammer body is carried rotatably coaxially with respect to the axis of rotation of the anvil. The hammer body surrounds the anvil and the impact surfaces thereof by a rotation cavity. A partly cylindrical journalling recess in the hammer body opens out into the rotation cavity. An impact dog has a recess thereon facing the anvil and a partly cylindrical back portion which is supported in the journalling recess for pivotal movement of the impact dog about an axis spaced from but parallel with the axis of rotation of the anvil for taking respectively impact or release position relative to one of the impact surfaces of the anvil. One of the opposed end portions of the impact dog cooperates with the anvil for pivoting the impact dog to impact position and a rotatable drive means is in operative engagement with the impact for pivoting it to release position. The opposed end portions of these formerly known impact motors have always been designed sharply pointed providing cam edges for cooperation with the anvil and impact delivering surfaces in immediate adjacency to the edges.

In the impact motors of the above type there occurs at certain tolerances a canting of the impact dog in the journalling recess by reason of the impact dog tending to fall out into the rotation cavity of the hammer body. The sharply pointed edge and impacting portions of the impact dog and the impact surfaces of the anvil may in such case, because of the unfavourable force distribution, be rapidly fragmented to pieces. For purposes of counteracting this occurrence there has in connection with the journalling previously been provided a special forward supporting groove in the interior of the hammer for positively journalling the forward end of the impact the production cost.

3,606,932 Patented Sept. 21, 1971 ice It is therefore an object of the invention to provide a rotary impact motor of the above stated type in which the journalling of the impact dog is less sensitive to tolerances and assures a better guidance for the impact dog than before. Simultaneously the journalling of the impact dog is to be simplified and the impact surfaces, the impact dog, and the anvil have to be so adapted to one another in their cooperation that the non-sensitiveness to tolerances is supported by an improved shape of the cooperating parts in respect of attaining better strength.

For the above and other purposes there is according to the invention provided a rotary impact motor with impact action in both rotational directions thereof comprising a housing, a rotatable anvil in said housing, opposed impact surfaces on said anvil, a hammer body rotatably carried in said housing coaxially with respect to the axis of rotation of said anvil, a rotation cavity in said hammer body surrounding said anvil and said impact surfaces thereof, a partly cylindrical journalling recess in said hammer body opening up into said rotation cavity thereof and of larger diameter than said rotation cavity an impact dog having a recess thereon facing said anvil and a partly cylindrical back portion extending over more than degrees and supported in said journalling recess for pivotal movement about an axis spaced from but parallel with said axis of rotation for taking respectively impact or release position relative to one of said impact surfaces, opposed end surfaces on said impact dog transverse to said back portion and intersecting said recess thereof, one of said surfaces cooperating with said anvil for pivoting said impact dog to said impact position, and rotatable drive means in said housing in operative engagement with said impact dog for pivoting said impact dog to said release position.

The above and other purposes of the invention will become obvious from the following description and 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 shows a longitudinal section through an impact tool comprising a rotary impact motor according to the invention. FIG. 2 is a cross section on the line 2--2 in FIG. 1. FIGS. 3 and 4 are cross sections respectively on the lines 3-3 and 44 in FIG. 1 when the rotary impact motor is in impact position. FIGS. 5 and 6 correspond to the FIGS. 3 and 4 but show the rotary impact motor in release position immediately after impact. FIGS. 7-9 show the parts of the impact motor in three different intermediate positions between the release position in FIG. 6 and the impact position in FIG. 4 of the impact dog. FIG. 10 and FIG. 11 show cross sections corresponding to FIG. 4 and FIG. 6 through an impact motor having a modified cross section of the anvil. FIG. 12, finally, shows a cross section through a further modification of the impact motor.

The impact tool in FIG. 1 comprises a back piece 10 provided with a handle 11 and a front piece 12. The front piece 12 encloses the rotary impact motor and is provided with a central forward journalling bore 13 through which an anvil 14 projects rotatably.

In the back piece 10 is affixed a rotary suitably powered conventional drive motor, preferably a reversible pneumatic vane motor comprising a rotor 15 carrying radial vanes, not shown. The rotor 15 is rotated in usual manner by compressed air delivered to the vanes of the motor, the air being suitably supplied through the handle 11. The rotor is controlled by a throttle valve, not shown, and a conventional reversing slide 16.

The forward end of the rotor is journalled in a ball bearing 17 and carries straight axially extending splines 18. The forward end of the anvil. 14 has a polygonal end portion 20 for carrying a suitable tool such as a socket Wrench, not shown. In the journalling bore 13 the anvil 14 is journalled by a cylindrical portion 21 which within the front piece 12 passes over into a radial cam 22. The rear end of the anvil 14 has a cylindrical reduced portion 23, which carries rotatably a centering ring 24 which in its turn is rotatably supported by a rotatable cylindrical drive means or element 25. The drive element 25 has a recess 26 at the periphery thereof and a rearwardly directed hub portion 27 which by inner axial splines and grooves 19 is in engagement with the splines 18 of the rotor 15, FIG. 3, and is carried by the rotor 15.

A hammer body 30 is coaxially rotatably journalled about the anvil 14 and fits by a forward journalling sleeve 3-1 rotatably on the cylindrical portion 21 of the anvil 14 behind the joumalling bore 13. The hammer body 13 is provided with a rotation cavity 32 coaxial with the axis of rotation thereof which cavity surrounds the radial cam. 22 of the anvil 14 and allows free rotation of the latter in the rotation cavity 32. Out into the rotation cavity 32- there opens a journalling recess 33 provided by a cylinder surface which has a larger diameter than the rotation cavity 32 and receives an impact dog 34 arcuately arched in cross section. The impact dog has a partly cylindrical convex back portion 35 extending over more than 180 degrees. The impact dog 34 is at the back portion thereof slidably supported along the entire length thereof by the cylinder surface of the journalling recess 33 for pivoting about an axis coaxial with said cylinder surface and falling within the rotation cavity 32 and further extending in parallel but spaced relation to the axis of rotation of the hammer body 30. The rotation cavity 32 is terminated rearwardly by an enlarged cylindrical portion 36 which rotatably takes support against the periphery of the drive element 25.

The radial cam 22 of the anvil 14 has in the embodiment according to FIGS. 1-7 a single lobe which is bordered symmetrically by two cam flanks 37, 38 facing the two opposite rotational directions of the anvil 14, which flanks provide the impact surfaces of the anvil 14 and pass over into a cylindrical cam ridge 39 coaxial with the axis of rotation of the anvil 14. The impact dog 34 is recessed by a concave recess 40 facing the anvil 14 which recess may have an arbitrary suitable shape but preferably is formed by a cylinder surface concentric with the back portion 35 of the impact dog 34. The opposite outer portions of the cylinder surface of the recess 40' provide the impact surfaces of the impact dog cooperating with the cam flanks 37, 38 of the anvil. The cam flanks 37, 38 thus adapted for cooperation with the cylindrical recess 40 are shaped partly cylindrical having the same radius of curvature as the recess 40- and extend with the provision of necessary operating clearance along cylindrical surface which has the same diameter as the recess 40 of the impact dog 34. The cam flanks 37, 38 pass over with a suitable fillet radius into the cylindrical base portion 53 of the radial cam 22.

The recess 40 of the impact dog 34 is separated from the back portion 35 by straight end surfaces 41, 42 transverse to the back portion and to the recess 40 intersecting the latter under a blunt angle along axial cam edges 43, 44 which in case of need may be slightly rounded. The cam edges 43, 44 and the end surfaces 41, 42 provide cam following means for the impact dog cooperating with the radial cam 22 in a manner described hereinafter.

The forward end of the impact dog 34 is supported head-on against a plane bottom surface 54, FIGS. 1, 2, in the journalling recess 33. The rear end of the impact dog 34 has a central extension 45 which mates with the recess 26 of the drive element 25 and is in camming engagement with the latter.

Let it be supposed that the rotor 15 in operation rotates the rotary impact motor and the anvil 14 thereof clockwise via the drive connection consisting of the splines and grooves 18 and 19 and that the polygonal end portion 20 of the anvil 14 via a socket wrench, not shown, transmits the rotation to a threaded fastener. If the parts of the rotary impact motor are in the position depicted in FIGS. 3 and 4, the recess 40 of the impact dog 34, as long as the screw rotates easily, will remain in impact position in engagement with the flank 37 of the radial cam 22, and the rotation of the drive element 25 is thus transmitted at its recess 26 and the extension 45 of the impact dog 34 to the impact dog 34 and thence via the radial cam 22 to the anvil 14, the socket wrench, and the fastener. Thus the impact dog 34 transmits the rotation to the radial cam 27 via the portion thereof trailing in the rotational direction in which direction the corresponding cylinder surface portion of the recess 40 provides the driving Surface. It is true that the drive element 25 during driving strives to pivot the impact dog 34 over the cam ridge 39 to release position, FIGS. 5, 6, by the driving engagement between the recess 26 and the extension 45, FIG. 3, striving in lever-manner to turn the impact dog 34 around the cam flanks 37, 38, which in the position depicted in FIG. 4 are substantially centered on the geometrical axis of the journalling recess 33. Due to friction between the impact dog 34 and the radial cam 22 these parts, however, remain in engagement with one another substantially in the position shown in FIGS. 3, 4, so that the fastener is rotated continuously until it has been screwed down and the resistance to rotation increases sharply.

At sufliciently large rotational resistance the anvil 14 stops, the rotor 15, however, forcing the drive element to continue its rotation. This causes the impact dog 40 through cam action between the recess 26 and the extension 45 of the impact dog 34 to pivot over the radial cam 22 from the impact position in FIGS. 3, 4 to release position in FIGS. 5, 6. The end surface 41 of the impact dog 34 leading in the rotational direction is turned to abut against the base portion 53 of the radial cam 22 beyond the flank 38 and the leading end surface 41 and its cam edge 43 are successively forced to slide around the base portion 53 while the hammer body 13 is rotated by the drive element 25 about the anvil 1-4 in an accelerated movement. The acceleration course is illustrated in FIGS. 7-9. Near the end of the acceleration cycle the end surface 41 of the impact dog 34 leading in the rotational direction runs up onto the flank 37, FIG. 8, of the radial cam 22 which causes a reverse turning of the impact dog 34 about its pivotal axis, followed by a simultaneously performed forward turning and further acceleration of the hammer body 30 in the rotational direction beyond the acceleration delivered thereto by the drive element 25. When the end surface 41 has passed the flank 37 its cam edge 43 runs up onto the cam ridge 39, FIG. 9, of the radial cam which is concentric with the anvil 14 and with the axis of rotation of the hammer body 30. As a result the impact dog 34 is retained positively in impact position by the cam edge 43 taking support against the cam ridge 39 until delivery of an impact. Immediately thereupon the lmpact dog 34, FIGS. 3, 4, delivers its impact against the cam flank 37 by the portion of the recess 40 thereof trailing in the rotational direction so that the kinetic energy of the hammer body 30 is delivered against the anvil 1.4 in the form of a rotational impact transmitted to the socket wrench and the fastener. In direct sequence to the impact the impart dog 34 normally rebounds slightly to the reverse with respect to the cam. flange 37 while the cam edge 43 continues to keep the impact dog 34 positively in the impact position. At the next weak impact against the cam flank 37 the impact dog 34- is free to pivot as a result of the engagement between the recess 26 of the drive element 25 and the extension 45 of the impact dog 34 over the ridge 39 of the radial cam 22 to the position shown in FIGS. 5, 6. Thereupon the next acceleration and impact cycles are performed in analogy with the above described until the desired tightening torque has been reached in the fastener.

The symmetrical design of the rotary impact motor allows analogous impact action at counter-clockwise rotation as well. At such instant the impacts are delivered against the cam flank 38 by the portion of the recess 40 of the impact dog 34 trailing in the rotational direction, while the end surface 42 of the impact dog 34 leading in the rotational direction causes turning of the impact dog to impact position and its cam edge 44 by positive cooperation with the cam ridge 39 maintains the impact dog in impact position before and until the delivery of an impact.

In the embodiment of FIGS. 10, 11 the radial cam 22 of the anvil 14 is designated with two lobes 46, 47 each carrying one of the cam flanks 37, 38. The other parts of the rotary impact motor are analogous with the parts of the embodiment in FIGS. 19. To the lobes 46, 47 are connected cam ridges 48, 49 concentric with the axis of rotation of the anvil 14 which ridges, however, are shortened and pass over into the back-portion 50 of the radial cam, said back portion being angularly bluntly flattened. The back portion 50 and the shortened cam ridges 48, 49 are shaped such that the back portion 50 of the radial cam can be passed by the impact dog 34 during rotation of the hammer body 30 around the anvil 14. As apparent from FIG. the impact dog 43, by reason of the cam ridge 48 being shortened, will be positively guided at the cam edge 43 during a shortened portion of the movement of the impact dog 37 up to impact position which, however, is sufficient for assuring that a sufficiently large portion of the recess 40 hits the respective cam flanks 37, 38. The modified embodiment has a more advantageous shape when it comes to strength considerations of the radial cam 22 and of anvil 14. During the passage of the impact dog 34 past the back portion 50 and over the next lobe 47 (or 46 during rotation in opposite direction), the impact dog performs a swinging movement without impact action which causes a certain loss of energy.

In the embodiment of FIG. 12 the radial cam 22 has straight plane cam flanks 37, 38. The concave recess 40 of the impact dog 34 consists of a pair of plane impact surfaces 51, 52 which form a nearly straight, slightly acute angle with the end surfaces 41, 42 and over a suitable fillet radius are connected to a central plane 55 perpendicular to the central plane of symmetry of the impact dog. In its operation the impact motor of FIG. 12 is analogous with the other above described embodiments.

A central plane similar to the plane 55, FIG. 12, preferably without fillet radii, may in case of need be arranged on the impact dog 34 depicted in FIGS. l9 allowing to provide an increased thickness at the arcuate portion of the impact dog 34.

I claim:

1. A rotary impact motor with impact action in both rotational directions thereof comprising a housing, a rotatable anvil in said housing, opposed impact surfaces on said anvil, a hammer body rotatably carried in said housing coaxially with respect to the axis of rotation of said anvil, a rotation cavity in said hammer body surrounding said anvil and said impact surfaces thereof, a partly cylindrical journalling recess in said hammer body opening up into said rotation cavity thereof and of larger diameter than said rotation cavity, an impact dog having a recess thereon facing said anvil and a partly cylindrical back portion extending over more than degrees and supported in said journaling recess for pivotal movement about an axis spaced from but parallel with said axis of rotation for taking respectively impact or release position relative to one of said impact surfaces, opposed end surfaces on said impact dog transverse to said back portion and said recess thereof, one of said surfaces cooperating with said anvil for pivoting said impact dog to said impact position, and rotatable drive means in said housing in operative engagement with said impact dog for pivoting said impact dog to said release position.

2. A rotary impact motor according to claim 1 in which said impact surfaces are a pair of radial cam flanks facing opposite directions of rotation, the end surface of said impact dog leading in the rotational direction during ro tation of said hammer body relative to said anvil cooperating with the cam flank meeting the rotation thereof for pivoting a portion of the surface forming the recess of said impact dog to impact position aganst that same cam flank.

3. A rotary impact motor according to claim 2 in which the impacting portions of the surface forming said recess of the impact dog are formed by a cylinder surface concentric with said back portion of said impact dog.

4. A rotary impact motor according to claim 2 in which said radial cam flanks form part of a radial cam having a ridge connected to the respective cam flank and coaxial with the axis of rotation of said anvil, cam edges on the impact dog at the intersection between said recess and said end surfaces thereof, and the cam edge leading in the rotational direction cooperating with said cam ridge for positivel retaining said impact dog in the impact position prior to the deliver of an impact.

5. A rotary impact clutch according to claim 3 in which said cam flanks are partly cylindrical having substantially the same radius of curvature as said cylinder surface forming said recess of said impact dog.

6. A rotary impact motor according to claim 5 in which said cam flanks form part of a single cam lobe extending with the provision of operating clearance along a cylindrical surface of equal diameter with the cylinder surface forming the recess of said impact dog.

7. A rotary impact motor according to claim 4 in which said cam edges are blunt.

References Cited UNITED STATES PATENTS 2,343,596 3/1944 Van Sittert et al. l7393.5 2,768,546 10/1956 Amtsberg 173-93.5 3,129,796 4/1964 Karden 173--93.5 3,533,479 10/1970 Madsen et a]. 17393.5

JAMES A. LEPPINK, Primary Examiner

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