KEYLESS CHUCK

Abstract: An axially movable sleeve (36) has interference members or lugs (38) associated with the split nut (34) in a chuck. When the chuck is driven by the spindle (18), the axially movable interference members (38) engage the split nut interference members (40) and are restrained from rotation. The nut (34) is also restrained and the chuck jaws (30) open or close depending upon the direction of rotation of the chuck body (24). The sleeve (36) is positioned to be engaged by the jaws (30) as they approach the full open position. The jaws (30) then move the sleeve (36) axially to disengage the interference members (40, 38) and stop further opening of the jaws (30) before they reach a position to wedge or jam in the open position.

Description: KEYLESS CHUCK BACKGROUND OF THE INVENTION Keyless impacting chucks must provide for relative rotation between the split nut which engages the jaws and the jaws. The split nut is classically retained by a retainer (collar) which has a press fit over the split nut. The impact mechanism associated with these chucks impacts the retainer or some other part functionally upstream of the retainer (collar). This means the collar must transmit impact energy to the split nut while the jaws are rotated and therefore actuated. This subjects the press fit between the collar and the split nut to impact stresses which in turn can lead to failure of the press fit. An object of this invention is to avoid stressing the press fit with impact energy and thereby improve the reliability of keyless impacting chucks. Typically, the impacting faces on the impacting lugs are inclined to the axis of the chuck at a different angle depending upon whether it is opening or closing the jaws. The impact angle is greater in the opening direction than in the closing direction, thus ensuring the force which can be delivered to open the jaws will always be greater than that which will be delivered to close the jaws. In theory this means it will always be possible to open the jaws to remove the tool. The drawback with this arrangement is possibility to drive the jaws open into wedging contact with the chuck body with such force that the force available in the closing direction cannot free the jaws. The object of this invention is to solve this problem. CROSS REFERENCE This invention relates to a keyless impacting chuck and constitutes an improvement over the chuck shown in my U.S. Patent No. 4,682,918. SUMMARY OF THE INVENTION This invention provides impact lugs directly on the split nut so that when these lugs are in engagement with the lugs which are restrained against rotation, the impact is delivered directly to the split nut and the retainer (collar) does not transmit the impact energy. The retainer simply performs its functions of retaining the split nut in assembled position. This invention provides an actuating member operative to axially move interference members or lugs into or out of engagement with interference members of lugs associated with the split nut in a chuck. Assuming the chuck is driven by the spindle, when the axially movable interference members engage the split nut interference members and are restrained from rotation, the nut is also restrained and the chuck jaws open or close depending upon the direction of rotation of the chuck body. The actuating member is positioned to be engaged by the jaws as they approach full open position. The jaws then move the actuating member rearward to disengage the interference members and stop further opening of the jaws before they reach a position to weαge or jam in the open position. More specifically, the actuating member is a sleeve on the chuck body. The sleeve has an inside groove engageable by the jaws. The groove is shaped to present a surface generally normal (perpendicular) to the jaw travel. A further feature is that the axially movable interference members are a part of the sleeve. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side elevation of a power drill fitted with a chuck incorporating this invention. Fig. 2 is a vertical section through the chuck mounted on a novel drive spindle. Fig. 3 is a section taken on line 3-3 in Fig. 2. Fig. 4 is a section taken on line 4-4 in Fig. 2. Fig. 5 is a fragmentary schematic view of the lugs. Fig. 6 is a vertical section through a slightly modified chuck (not modified relevant to the mount) threaded on a standard threaded spindle. Fig. 7 is a vertical section through still another chuck. DETAILED DESCRIPTION OF THE DRAWINGS The hand drill 10 has a conventional pistol grip 12, a trigger 14 actuating the power switch and a forward/reverse control 16. Gear case 20 is mounted on the front portion of the drill housing by screws 86 and encloses the customary reduction gearing. Grooves 84 in case 20 give screwdriver access to screws 86. Drive spindle 18 projects out of the front of the gear case 20 and is journaled in bearing 68 retained by tru-arc retainer 69. The spindle has a smooth cylindrical mount 15 beyond shoulder 17 and a reduced diameter end 19 beyond the mount 15. The spindle is reduced at 21 between mount 15 and shoulder 17 to ensure that face 23 can be squarely engaged by shoulder 25 on chuck body 24 when the smooth bore 27 in the body is mounted on the mount 15. When so mounted the diametrically opposed lugs 29 on spindle 18 engage the slots 31 in the body flange. The threaded bore 35 in the body fits over the reduced end 19 of the spindle 18. The threads 35 serve no purpose at this time; they are used to mount the chuck on a mandrel during production of the chuck to enable final grinding of the jaws concentric with the chuck body so that jaws will be concentric with the spindle 18 when the chuck is mounted on a spindle. The chuck is retained on the spindle 18 by screw 26 threaded into the end of the spindle. No torque is transmitted through the threaded connection of the chuck to the spindle through screw 26. All torque is transmitted through the drive lugs 29. Therefore, the chuck is easily removed by pulling it off and when driven in reverse screws (like 26) can no longer break. This mount is applicable to keyed and to keyless chucks. The body is provided with three inclined bores 28 in each of which there is mounted a jaw 30 which moves in the inclined bore 28 in response to relative rotation between the split nut 32 and the jaws. Split nut 32 is retained in assembled position by split nut retainer 34 which is in the form of a ring-like collar having a force fit on the split nut. The retainer 34 and the split nut normally rotate with the body 24, but if the split nut and retainer are restrained from rotation the rotation of the body relative to the split nut will cause the jaws 30 to open or close by moving up or down the inclined bore as determined by the direction of the rotation of the body. Clutch sleeve 36 is provided with lugs 38 facing lugs 40 on the split nut 32. If the clutch sleeve 36 is moveα to the left in Fig. 2, lugs 38 engage lugs 40. The right end of sleeve 36 has inwardly projecting flange segments 48 and a spline ring 80 has inturned flange segments 58 which fit between segments 48 with spring 56 compressed between the spring seats thus provided. Spline ring 80 can be restrained against rotation by tightening screw 79 into nut 81 until it firmly engages gear case 20. This restrains the sleeve 36 against rotation. Therefore, when the sleeve lugs 38 engage the split nut lugs 40, the split nut 32 will also be restrained against rotation causing relative rotation between the body 24 and the split nut 32. This will cause the jaws 30 to move up or down the inclined bores 28 to open or close the jaws depending upon the direction of rotation of the clutch body 24. In Fig. 5 details of lugs 38 and 40 are shown. The jaws 30 will open or close depending upon whether spindle 18 and chuck body 24 are being driven in the forward (F) or reverse (R) direction. Assume the chuck is being driven in the forward (F) direction. Interengaging faces 42, 44 on lugs 38, 40, respectively, are inclined at 27° with respect to the axis of the chuck, as seen in Fig. 5. This is a rather steep angle and will deliver a very sharp impact to the lugs 40 tending to forceably close the jaws. When the jaws grip a tool and cannot move, the face angles will act to cam the clutch sleeve 36 towards the gear case to disengage the lugs. If the operator continues to push the clutch sleeve 36 towards the split nut, non-rotating lugs 38 will re-engage the split nut lugs 40 and deliver repeated impacts. This will repeat as long as the operator persists. This construction will deliver sufficient closing force to the jaws to meet all normal requirements. Opening the chuck is another matter. In this design the forward/reverse switch 16 is actuated to now drive the chuck in reverse direction (R) . This means that when the axially movable sleeve 36 is actuated to bring the non-rotating lugs 38 into engagement with the split nut lugs 40, the inclined faces 64, 66 are inclined at 23° to the axis of the chuck, as may be seen in Fig. 5. This is 4° less than the angle in the jaw closing configuration. This will develop more tangential force on the split nut 32 in the direction opening the jaws than obtained with the 27° face angle in the closing direction. Therefore, opening is assured and there is no need to provide for operation of the chuck with a key or a chuck wrench. The system will deliver sufficient, repeated impacts to open the chuck. It may not open on the first impact, but with the operator holding the sleeve forward, a rapid, series of impacts will be delivered until the chuck opens. An impact can be considered a force spike of much greater magnitude than the friction between the parts. A problem arises, however, if the operator holds the sleeve 36 to drive the jaws 3ϋ to the full open position. Without the present invention, this can result in the jaws wedging in the open position. Since they have been driven open with an impact greater than can be delivered in the closing direction, they can be irrevocably wedged in the open position. This problem is obviated in the present design by locating the clutch sleeve in position to be engaged by the jaws and providing the undercut 46 inside the clutch sleeve 36 in position to receive the inner end of each jaw 30, as shown in dotted lines in Fig. 2. This, then, permits the jaws to drive against the clutch sleeve 36 to push the sleeve to the right to disengage lugs 38 from lugs 40 before there is opportunity to wedge the jaws open. This automatic disengagement prevents a user from inadvertently locking the jaws in the open position. It will be noted that the inner end of jaw 30 has contact with the sleeve in a plane normal to the jaw movement and wedging is not possible. Reference has been made to the fact that the sleeve 36 is biased rearwardly (to the right). That construction will now be described. The flange segments 48 on the right hand end of the sleeve 36 form a spring seat for the compressed spring 56. The spring also seats on segments 58 which are axially fixed. Therefore the spring biases the sleeve 36 to the right with retainer ring 70 limiting travel to the right. The clutch sleeve 36, spring 56, ring 70 and ring 80 are assembled on the chuck before the chuck is mounted on the spindle. Another important feature is the nature of the clutch sleeve 36. The spline ring 80 prevents rotation of the clutch sleeve and when the user pushes the sleeve forward to engage the lugs the sleeve is subject to reciprocating motion as the lugs engage, impact and push the sleeve back and then the user pushes it forward again. If desired the ring 80 can be allowed to rotate. This will result in the clutch sleeve being free to rotate slightly due to impact. The slight rotational force imparted to the sleeve is resisted by the user who can't detect or feel the difference. There is some loss of impact force or magnitude due to the slight rotation of the sleeve on impact. There are many drills in the field which don't have the grooves leading to the screws. Therefore, a keyless chuck mounted without means to restrain rotation of the clutch sleeve 36 remains a desirable product. The mounting of the chuck on the smooth cylinder and driving the chuck through the lugs prevents wedging the chuck on the spindle. Screw 26 will not wedge or jam; it transmits no torque, it only retains the chuck on the spindle. Chuck removal is easy and yet the design retains the threads 35 necessary to proper finish grinding of the jaws concentric with the chuck spindle. It is important to note that without any modification to the chuck the threads 33 can be used to mount the chuck on threaded spindles of existing tools. This is illustrated in Fig. 6 in which spindle 118 has only the threaded end 115 which threads into the body threads 35 until the shoulder 25 seats against should 127. There are no drive lugs in this configuration ... the drive is transmitted through the threads and this entails the drawbacks mentioned above. The construction has a ready market in all the threaded spindle tools in the field. This chuck also omits the spline ring 80 of Fig. 2 which means sleeve 36 is free to rotate but can be restrained by the user with little force. The chuck still offers the advantage of avoiding delivering impact force through the press fit and providing automatic disengagement. An important feature of this invention is the automatic disengagement of the sleeve before the jaws have an opportunity to get wedged in the full open position. Another important feature of this invention is the nature of the clutch sleeve 36. The spline ring 80 prevents rotation of the clutch sleeve and when the user pushes the sleeve forward to engage the lugs the sleeve is subject to axial reciprocating motion as the lugs engage, impact and push the sleeve back and then the user pushes it forward again. The cost of restraining rotation can be avoided by omitting the spline ring. This will result in the clutch sleeve being free to rotate. The slight rotational force imparted to the sleeve is resisted by the user who can't detect or feel the difference. There is some loss of impact force or magnitude due to the slight rotation of the sleeve on impact. Also, some users are reluctant to grasp a rotating part and for them the non-rotational sleeve is preferred. Another variation, and a great simplification, is shown in Fig. 7 in which spring 156 biases the sleeve 136 to engage the lugs 138, 140 at all times with the jaws still operative to disengage the lugs before they can jam open. Spring 156 is compressed between the corner 137 (inside the sleeve) and the shoulder 170 machined on the body 124. This is the lug drive version but it can be either. The lugs 129 engage the recesses 131. The sleeve 136 normally rotates with the chuck and the user then restrains the sleeve to open or close the chuck. The sequence of the drawing figures parallels this development and Fig. 7 represents the final (current) design. This is more compact and "looks" more conventional. It still mounts on the threaded or unthreaded spindles, automatically disengages, and avoids torque transmission through the press fit. This design also has an advantage in that the radial slots 131 permit screw driver blade access to the spring 156 when the chuck is off the drive spindle. The spring can be removed for service in this manner. The chuck can't be mishandled to damage the spring when the chuck is off the tool. Thus, if the sleeve is pulled back, spring 156 "goes solid" and limits sleeve travel and this in turn prevents overstressing the spring.

Claims: C AIMS 1. In combination with a chuck of the type having a chuck body, supporting three jaws on inclined axes equally spaced around the body, a split nut encircling said jaws and having a threaded connection with the jaws whereby said jaws move on said inclined axes in response to relative rotation between said booy and said split nut, a retainer having a press fit on said split nut to retain said split nut assembled, the improvement comprising, means for holding said split nut against rotation with said chuck body, said means including a member mounted on said body for axial movement toward and away from said split nut between first and second positions, interference member integral with both said member and said split nut and operative when engaged to prevent rotation of said split nut when said member is restrained against rotation, whereby rotation of said body causes said jaws to open or close dependent upon the direction of rotation of said body, the press fit of said retainer on said split nut being unstressed by impacts on said split nut interference members. 2. The combination of Claim 1 in which said member comprises a sleeve mounted on said body for axial movement. 3. The combination according to Claim 2 including means restraining saiα sleeve from rotation with said clutch body. 4. The combination according to Claim 3 including means biasing said sleeve away from said split nut. 5. The combination according to Claim 2 including means biasing said sleeve towards said split nut. 6. A chuck according to Claim 1 in which, said inclined axes are positioned relative to the axis of the chuck body so that the jaws move forwardly and inwardly on the axes toward a -fully closed position and rearwardiy and outwardly on said inclined axes towards a fully open position, said means for holding said split nut against rotation comprising a sleeve mounted on said body for axial movement, the outsiαe of said sleeve being manually engaged to move said sleeve axially, said jaws engaging the inside of said sleeve as the jaws approach said fully open position so that the sleeve is moved to disengage said second interference members from said first interference members. 7. The combination according to Claim 6 including an undercut groove on the interior of said sleeve in alignment with said aws when said interference members are engaged so said jaws will push against said groove as said interference members on said sleeve are disengaged from said interference members on said split nut. 8. The combination according to Claim 7 in which said groove inciuαes a surface generally normal to the patn of said jaws. 9. The combination according to Claim 8 including means restraining said sleeve from rotation with said chuck body. 10. The combination according to Claim 9 including means biasing said sleeve away from said split nut.

Inventors: PALM BERNHARD, PALM, BERNHARD
Applicants: MILWAUKEE ELECTRIC TOOL CORP, MILWAUKEE ELECTRIC TOOL CORPORATION
Application year: 1989
Main classification: B23B31
IPC codes: B23B31