JP2006272535A - Motor-driven screw driver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a motor-driven screw driver with a torque limiter improved in the feeling of use and convenience for use. <P>SOLUTION: In this motor-driven screw driver, a one-way clutch 38 is provided between a cylindrical part 7 of a tip housing 6 and an output shaft 8 to permit the rotation of the output shaft 8 during the normal rotation of the output shaft 8 and to regulate the rotation of the output shaft during the relative reverse rotation to the cylindrical part 7 of the output shaft 8 accompanied by the operation of a torque limiter provided between an output board 15 and a connecting board 19. A normal-reverse changeover switch 11 and a clutch retainer 42 of the one-way clutch 38 are connected to each other by a link lever 52, a switching sleeve 51 and a connecting plate 54, and the clutch retainer 42 is turned to a clutch release position, by interlocking with the switching operation to the reverse rotation of a motor 4 by a switching operating part 55. Thus, the rotation of the output shaft 8 regulated by the one-way clutch 38 can be released. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric driver including a torque limiter that is used for screw tightening and nut tightening operations and can block torque transmission to an output shaft with a predetermined torque.

  In the electric driver, an output shaft that rotates by driving a motor is supported in a housing incorporating a motor so as to protrude forward, and a screw or nut is tightened by a tip tool such as a driver bit attached to the output shaft. In addition, a torque limiter is provided between the motor and the output shaft so that torque transmission to the output shaft can be interrupted with a predetermined torque of the output shaft so that tightening of screws and the like can be performed with a fixed torque. It has become. As this torque limiter, one internal gear of a planetary gear speed reduction mechanism provided between the motor and the output shaft is rotatably provided, and a pressing member whose cam surface facing the internal gear engages in the rotation direction. The pressing member is pressed toward the internal gear by a biasing means such as a coil spring, and when a predetermined torque is reached, the internal gear disengages from the pressing member and idles to transmit torque. A blocking mechanism is often used. Further, as disclosed in Patent Document 1, for example, torque limiter clutches having clutch pawls that engage with each other in the rotational direction are provided in the rotation transmission portions on the motor side and the tip tool side, respectively, There is also known a mechanism in which torque transmission is similarly interrupted with a predetermined torque by pressing the clutch toward the other side by a biasing means.

Japanese Utility Model Publication No. 50-33759

  When screw tightening is performed using such an electric driver with a torque limiter, a reaction force in the direction opposite to the rotation direction of the output shaft acts on the housing of the electric driver. The housing is supported against this reaction force so as not to rotate. However, if the torque limiter works in this state, the reaction force against the housing is also lost, so the hand that has been supported up to now rotates with the reaction, giving the operator discomfort, and the tip tool from the screw. It may come off and damage the workpiece.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electric driver that can maintain a reaction force during a torque limiter operation and has excellent usability and usability in a case with a torque limiter.

In order to achieve the above object, the invention according to claim 1 allows the output shaft to rotate between the cylindrical portion and the output shaft when the output shaft is rotated forward, and the output shaft accompanying the operation of the torque limiter. A one-way clutch is provided that restricts the rotation of the output shaft during reverse rotation relative to the cylindrical portion, and a release means that can arbitrarily release the rotation restriction during the reverse rotation of the output shaft is provided in the one-way clutch. It is characterized by.
According to the second aspect of the present invention, in addition to the object of the first aspect, the release means operates in conjunction with the switching operation to reverse rotation of the motor in order to reliably operate the release means at the time of reverse rotation of the motor. It is set as the structure to be made.
In addition to the object of the first or second aspect, the invention according to claim 3 is canceled when the forward / reverse rotation switching operation of the motor is performed by a sliding operation of a forward / reverse selector switch provided in the motor drive circuit. In order to link the means with a simple configuration, the forward / reverse changeover switch and the release means are connected by a connecting member so that the release means can be linked to the slide operation of the forward / reverse changeover switch.

According to a fourth aspect of the present invention, in addition to the object of any one of the first to third aspects, in order to form the one-way clutch and the releasing means simply and rationally, the one-way clutch is connected to the cylindrical portion side and the output shaft. And a cylindrical clutch retainer in which a plurality of axial slits are formed in the circumferential direction at predetermined intervals, and an inner peripheral surface on the cylindrical part side in the radial direction of the output shaft. And a rolling element having a diameter slightly larger than the interval between the output shaft and the outer peripheral surface of the output shaft, and an inner peripheral surface on the cylindrical portion side corresponding to the slit, and when the rolling member enters, the rolling element is the outer peripheral surface of the output shaft. And a non-contact relief recess, and an elastic member that is provided in the clutch retainer and urges each rolling element in a reverse rotation direction of the output shaft in a direction away from the relief recess. Each rolling element is missed when the output shaft is stopped. From the clutch set position to move out of the recess, it is obtained by rotatable to the clutch release position to move into the recess flank of the rolling elements when stopping the output shaft.
The “tubular portion side” here includes not only the tubular portion itself but also a separate sleeve that is integrally attached to the inside of the tubular portion.

According to the first aspect of the present invention, during normal screw tightening or the like by forward rotation of the output shaft, the reaction force is not suddenly lost by the action of the one-way clutch even if the torque limiter is operated. It is possible to effectively prevent the occurrence of discomfort and damage to the workpiece, while removing the screws by rotating the output shaft in the reverse direction without using the one-way clutch. Therefore, it is excellent in usability and usability.
According to the second aspect of the present invention, in addition to the effect of the first aspect, when the motor is reversely rotated, the release means can be reliably operated to reversely rotate the output shaft.
According to the third aspect of the invention, in addition to the effect of the first or second aspect, the interlocking of the release means can be realized with a simple configuration.
According to the fourth aspect of the present invention, in addition to the effect of any one of the first to third aspects, the one-way clutch and the release means can be easily and rationally formed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing an example of an electric screwdriver. The electric screwdriver 1 accommodates a motor 4 capable of rotating in the forward and reverse directions behind a main body housing 2 with a handle 3 extending downward (left side in FIG. 1). Then, a front end housing 6 that supports the output shaft 8 by the front cylindrical portion 7 is assembled in front of the main body housing 2. 9 is a switch provided in the drive circuit of the motor 4, and 10 is a switch lever that turns on the switch 9 by a pushing operation. Above the switch 9, a forward / reverse selector switch 11 that can switch the rotation direction of the motor 4 is provided. ing. By sliding the forward / reverse selector switch 11 in the left-right direction, the rotation of the motor shaft 5 can be selected between forward rotation (right rotation toward the front) and reverse rotation (left rotation). Here, forward rotation is performed at the slide position to the right of the forward / reverse switching lever 11, and reverse rotation is performed at the slide position to the left.

  A planetary gear reduction mechanism 12 is housed in front of the motor 4 and includes a carrier 13 supporting the planetary gears 14 and 14 arranged in the rear in the axial direction, and the rotation of the motor shaft 5 is reduced and output. It is possible. An output board 15 is fitted to the final stage carrier 13 so as to be integrally rotatable, and a rear end of a spindle 16 provided in the front end housing 6 is coaxially supported. This spindle 16 is integrally connected to the output shaft 8 in the rotational direction by fitting a square rod 18 extending at the rear end of the output shaft 8 into a square hole 17 provided in the front end axis. At the rear part of the spindle 16, a connecting board 19 having substantially the same diameter as the output board 15 is formed in connecting grooves 20 and 21 that are recessed in the axial direction on the outer peripheral surface of the spindle 16 and the inner peripheral surface of the connecting board 19. The steel balls 22 are fitted so as to straddle and can be integrally rotated and moved in the axial direction.

  In addition, a screw portion 23 is formed in the front portion of the spindle 16, and a disk-like screw feeding plate 24 is screwed into the screw portion 23 in an orthogonal shape, and substantially the same diameter is provided behind the screw feeding plate 24. The disc-shaped spring receiving plate 25 is loosely fitted so as to be movable in the axial direction, and the spring receiving plate 25 is screwed by the bias of the coil spring 26 provided between the spring receiving plate 25 and the rear connecting plate 19. The connection board 19 is pressed against the feed board 24 and the output board 15 respectively. On the front side of the spring receiving plate 25, an insertion groove 28 into which the tip of the driver can be inserted through a window 27 drilled above the tip housing 6 is formed. The radial teeth 29, 29,... That can mesh with the driver inserted into the insertion groove 28 are formed at equal intervals. Therefore, by inserting a screwdriver into the insertion groove 28 and rotating it, the screw feeder 24 is rotated through the teeth 29 and screwed in the axial direction, and the compression amount of the coil spring 26, that is, the pressing force can be adjusted. it can.

  On the other hand, between the connecting board 19 and the output board 15, a plurality of steel balls 32, 32,... Thus, in combination with the pressing force of the coil spring 26, a torque limiter for integrating the connecting board 19 with the output board 15 in the rotational direction is configured. Therefore, the rotation of the output board 15 is transmitted to the connection board 19 via the steel ball 32, and the spindle 16 which is integrally rotated with the connection board 19 is rotated, and the output shaft 8 is integrally rotated in front of it. At the front end of the output shaft 8, an insertion hole 33 for a tip tool such as a driver bit, and a chuck sleeve 34 that prevents the tip tool inserted into the insertion hole 33 from being removed by the balls 35 and 35 and integrated with the output shaft 8. Is exterior.

  In the cylindrical portion 7 of the tip housing 6, ball bearings 36 and 37 that support the output shaft 8 are arranged in the front-rear direction, and a one-way clutch 38 is provided between the ball bearings 36 and 37. . As shown in FIG. 2, the one-way clutch 38 is coaxially inserted into the cylindrical portion 7, and is provided on the inner periphery of the cylindrical portion 7 with a pair of protrusions 40, 40 provided axially to the outer periphery. The fixed sleeve 39 which is held non-rotatable by fitting with the concave grooves 41 and 41 in the same direction and has a relief concave portion 48 which will be described later formed on the inner peripheral surface, and rotates between the fixed sleeve 39 and the output shaft 8. And a cylindrical clutch retainer 42 which is provided to be restricted in the axial direction between the ball bearings 36 and 37, and in which axial slits 43, 43,... Are formed at equal intervals in the circumferential direction, and the output shaft 8 And cylindrical needles 44, 44,... As rolling elements accommodated in the slits 43 of the clutch retainer 42 between the shaft and the fixed sleeve 39, and axial partitions adjacent to the slits 43 in the clutch retainer 42 46,4 Consisting of a cross-section U-shaped leaf spring 45, 45 ... as an elastic member provided in ....

  The fixed sleeve 39 is restricted from moving in the axial direction by abutting against a ball bearing 36 at the front end and a protrusion 47 protruding in the circumferential direction at the rear outer peripheral surface of the clutch retainer 42 at the rear end, On the surface, axial relief recesses 48, 48... Having a circular cross section in the circumferential direction are provided at equal intervals in the circumferential direction of the fixed sleeve 39 by the same number as the needles 44. The needle 44 has a diameter smaller than the distance between the deepest portion of the escape recess 48 and the outer peripheral surface of the output shaft 8 in the radial direction of the output shaft 8, and the inner peripheral surface of the fixed sleeve 39 excluding the escape recess 48. The diameter is slightly larger than the distance from the outer peripheral surface of the output shaft 8.

  In addition, each leaf spring 45 is held by the partitioning portion 46 by inserting one end of a U-shape into a locking groove 49 formed in the axial direction on the outer peripheral surface side of each partitioning portion 46, and adjacent slits 43. The other end projecting inwardly is brought into contact with the needle 44 from the output shaft 8 side, and each needle 44 is rotated in the reverse rotation direction of the output shaft 8 (the direction opposite to the arrow in FIG. 2A). It is biased toward the adjacent partition 46 and fixed sleeve 39 side. Therefore, when the needles 44 and the relief recesses 48 coincide with each other in the circumferential direction, the needles 44 enter the deepest part of the relief recesses 48 and leave the output shaft 8. In addition, on the slit forming surface on the needle 44 side in each partition portion 46, a protruding portion 50 that protrudes between the needle 44 and the output shaft 8 as it goes to the output shaft 8 side is formed, and the relief recess 48 of the needle 44 is formed. Smooth movement to the side is possible.

  On the other hand, a switching sleeve 51 is rotatably mounted on the cylindrical portion 7. The switching sleeve 51 extends rearward below the tip housing 6 and is connected by a link lever 52 coupled to the forward / reverse selector switch 11 and two screws 53, 53. A connecting plate 54 that is screwed to the clutch sleeve 42 loosely inserts the switching sleeve 51 and the cylindrical portion 7 in the radial direction, and the tip is connected to the clutch retainer 42. That is, the link lever 52, the switching sleeve 51, and the connecting plate 54 are connecting members that constitute the releasing means of the present invention. In addition, the loose insertion hole of the connection plate 54 in the cylindrical portion 7 is a long hole that is long in the circumferential direction.

As shown in FIG. 3, the rear end of the link lever 52 is a rectangular switching operation portion 55 that is long in the left-right direction, and is inserted from the front into the main body housing 2 at a position above the switch 9. Projecting left and right of the housing 2. A rectangular engaging recess 56 that is long in the left-right direction is formed on the lower surface of the switching operation unit 55 and is engaged with the forward / reverse selector switch 11 on the upper surface of the switch 9. Reference numeral 57 denotes a guide protrusion that protrudes above the switch 9 and engages with the engaging recess 56 to position the switching operation portion 55 and guide the slide.
Therefore, the link lever 52 can be switched by sliding the forward / reverse selector switch 11 by pushing the left and right ends of the switching operation unit 55, and the switching sleeve is swung left and right following the pushing operation. 51 and the clutch retainer 42 can be rotated.

  Here, when the link lever 52 is in the pushing position of the switching operation portion 55 represented by a solid line in the front view shown on the right side of FIG. 3, the motor 4 is rotated in the forward direction, and the rotation position of the switching sleeve 51 interlocked with the link lever 52. Then, the clutch retainer 42 is in the clutch set position of FIG. 2A and positions each leaf spring 45 closer to the escape recess 48. Therefore, each needle 44 biased by each leaf spring 45 is pressed between the inner peripheral surface of the fixing sleeve 39 and the outer peripheral surface of the output shaft 8 that are displaced in the circumferential direction outside the escape recess 48. On the other hand, when the link lever 52 is in the pushing position of the switching operation portion 55 represented by a dotted line in the front view of FIG. 3, the motor 4 rotates in the reverse direction, and at the rotating position of the switching sleeve 51 in conjunction with the link lever 52, the clutch retainer 42. 2B is located at the clutch release position in FIG. 2B, and the partition 46 is positioned closer to the escape recess 48 in the forward rotation direction of the output shaft 8. Therefore, each needle 44 biased by each leaf spring 45 is pushed to the deepest part in the escape recess 48 in a manner that rides on the protruding part 50 of the partition part 46, and is separated from the output shaft 8.

  In the electric driver 1 configured as described above, the switch 9 is turned on by selecting the forward rotation of the motor 4 and the clutch set position of the clutch retainer 42 by pushing the switching operation portion 55 and pushing the switch lever 10. Then, the motor 4 is driven to transmit the torque of the motor shaft 5 rotating forward to the spindle 16 via the planetary gear speed reduction mechanism 12, and the output shaft 8 is rotated clockwise. Then, each needle 44 that is in contact with the output shaft 8 at the position of FIG. 2A rotates clockwise in the same figure and rolls toward the escape recess 48 against the bias of the leaf spring 45. The rotation of the shaft 8 is not hindered. Therefore, the screw can be tightened with the driver bit attached to the output shaft 8 by the chuck sleeve 34. At the time of this screw tightening, a reaction force acting in the direction opposite to the tightening direction acts on the main body housing 2 or the tip housing 6, so that an operator holding the handle 3 supports the handle 3 against this reaction force. become.

When the tightening of the screw advances and the load on the output shaft 8 increases, and the pressing force of the coil spring 26 against the connecting board 19 engaged with the output board 15 is exceeded in the torque limiter, the connecting board 19 resists the bias of the coil spring 26. In this case, the spindle 16 and the output shaft 8 stop rotating in order to move forward and disengage from the steel balls 32, 32.
Simultaneously with this stop, the reaction force to the main body housing 2 and the tip housing 6 is lost, and the main body housing 2 and the tip housing 6 move in the positive rotation direction of the output shaft 8 by the force that supports the handle 3 against the reaction force. Try to rotate. That is, the output shaft 8 to be stopped tends to rotate in the reverse direction relatively. However, in the one-way clutch 38, each needle 44 comes out of the escape recess 48 by the urging of the leaf spring 45 and is pushed again between the fixed sleeve 39 and the output shaft 8 as shown in FIG. The rotation of the fixed sleeve 39 with respect to the output shaft 8 is prevented, and the rotation of the tip housing 6 and the main body housing 2 integral with the fixed sleeve 39 is also prevented. Therefore, even if the reaction force to the main housing 2 or the like is lost, it can be supported as it is, and the hand holding the handle 3 does not rotate unexpectedly.

  When the output shaft 8 is reversely rotated for removing screws or the like, first, the reverse rotation position of the forward / reverse changeover switch 11 and the clutch release position of the clutch retainer 42 are selected by pushing the switching operation portion 55. When the switch lever 10 is pushed in, the motor shaft 5 rotates in the reverse direction and the spindle 16 and the output shaft 8 rotate in the reverse direction. In the one-way clutch 38, the clutch retainer 42 rotates as shown in FIG. Since each needle 44 moves to the deepest part in the escape recess 48 and is not in contact with the output shaft 8, the one-way clutch 38 does not work and does not affect the reverse rotation of the output shaft 8.

  Thus, according to the electric driver 1 of the said form, rotation of the output shaft 8 is permitted between the cylindrical part 7 and the output shaft 8 at the time of the normal rotation of the output shaft 8, and the output accompanying the action | operation of a torque limiter is permitted. A one-way clutch 38 that restricts the rotation of the output shaft 8 during reverse rotation relative to the cylindrical portion 7 of the shaft 8 is provided, and the rotation restriction during the reverse rotation of the output shaft 8 can be arbitrarily released to the one-way clutch 38. By providing an appropriate release means (selection of the clutch release position of the clutch retainer 42), even when the torque limiter is activated, the one-way clutch 38 is counteracted by the action of the one-way clutch 38 during normal screw tightening by forward rotation of the output shaft 8. The force is not suddenly lost, and it is possible to effectively prevent the operator from feeling uncomfortable and damage to the workpiece, while the output shaft 8 can be used without using the one-way clutch 38. Rotate the can also perform removal and the like of the screw. Therefore, it is excellent in usability and usability.

Further, since the clutch retainer 42 is rotated in conjunction with the switching operation of the motor 4 to the reverse rotation by the forward / reverse changeover switch 11, the release means is reliably operated during the reverse rotation of the motor 4 to output the output shaft. 8 can be rotated in reverse.
Further, the forward / reverse selector switch 11 and the clutch retainer 42 are connected by a connecting member (link lever 52, switching sleeve 51, connecting plate 54), and the clutch retainer 42 rotates in conjunction with the sliding operation of the forward / reverse selector switch 11. By enabling it, the interlocking between the forward / reverse selector switch 11 and the clutch retainer 42 can be realized with a simple configuration.

  The one-way clutch 38 is provided in the clutch retainer 42, the needle 44 accommodated in each slit 43 of the clutch retainer 42, the relief recess 48 formed in the fixed sleeve 39, and the clutch retainer 42. Is formed from a leaf spring 45 that urges the output shaft 8 in the reverse rotation direction away from the escape recess 48, and the release means serves as a clutch retainer 42. When the output shaft 8 is stopped, each needle 44 is escaped from the escape recess 48. The one-way clutch 38 and its releasing means can be easily and simply configured to be able to rotate from the clutch set position to be moved outward to the clutch release position to which each needle 44 is moved into the escape recess 48 when the output shaft 8 is stopped. It can be rationally formed.

The one-way clutch is not limited to the above-described form, and can be changed as appropriate. For example, in the one-way clutch of the above-described form, the escape recess is formed in the fixed sleeve. Can be provided, and the rolling element can be a ball or a roller instead of the needle. Therefore, the elastic member is not limited to the U shape, and a coil spring or the like can be used according to the form of the rolling element.
Further, the connecting member constituting the releasing means is not limited to the link lever and the switching sleeve of the above form, and the number and shape of members, a specific connecting structure, and the like can be appropriately changed.

On the other hand, in the above-described embodiment, the forward / reverse switching switch and the clutch retainer are connected by a connecting member such as a link lever to obtain the interlock of the clutch retainer. The switching operation of the switching member such as a switch may be detected by a micro switch, a proximity sensor, or the like, and the clutch retainer may be rotated by a separately provided rotation driving mechanism to release the one-way clutch.
On the contrary, not only the configuration in which the release means is interlocked with the forward / reverse switching operation of the motor in this way, but also a configuration in which the release means is operated alone. For example, in the above configuration, the link lever connected to the forward / reverse selector switch is eliminated, and the clutch retainer is rotated to the clutch release position by directly rotating the switching sleeve.
In the above embodiment, the release means is realized by rotating the clutch retainer from the clutch set position to the clutch release position. However, the release means is not limited to this structure. For example, the release means is separate from the cylindrical portion like the fixed sleeve of the above embodiment. In the case of a body having a body sleeve, the clutch may be disengaged by making the sleeve rotatable and moving the escape recess.

In addition, instead of the steel ball between the output board and the connection board of the above-mentioned form, the torque limiter can be a cam protrusion having a slanted surface in the circumferential direction that protrudes from the opposing surfaces of the two, or a planetary gear reduction mechanism. One internal gear can be rotated, and a pressing member pressed against the internal gear can be appropriately changed in design, for example, engaged with a steel ball or a cam projection in the rotation direction.

It is a partial longitudinal cross-sectional view of an electric driver. In the enlarged explanatory view of a one-way clutch part, (A) shows a clutch set state, and (B) shows a clutch release state. It is explanatory drawing of the connection structure of a forward / reverse selector switch and a change sleeve, and the upper side shows a plane, the lower side shows a side, and the right shows a front, respectively.

Explanation of symbols

  1 .... Electric screwdriver, 2 .... Main body housing, 3..Handle, 4 .... Motor, 6 .... Front end housing, 7 .... Cylindrical part, 8 .... Output shaft, 9 .... Switch, 11 .... Positive Reverse switch, 12 .... Planetary gear reduction mechanism, 15 .... Output board, 16 .... Spindle, 19 .... Connection board, 26 ... Coil spring, 38 ... One-way clutch, 39 ... Fixed sleeve, 42 ... Clutch Retainer, 43 .. slit, 44 .. needle, 45 .. leaf spring, 46 .. partitioning part, 48 .. relief recess, 51 .. switching sleeve, 52 .. link lever, 55.

Claims (4)

In the housing, a motor that can rotate forward and backward by switching operation is built in, and an output shaft that rotates forward and backward by driving the motor is pivotally supported by a cylindrical portion provided at the front end of the housing and protrudes forward, An electric driver provided with a torque limiter that interrupts rotation transmission from the motor with a predetermined torque of the output shaft between the motor and the output shaft,
Between the tubular portion and the output shaft, the output shaft is allowed to rotate during the forward rotation of the output shaft, and during the reverse rotation of the output shaft relative to the tubular portion accompanying the operation of the torque limiter. An electric driver comprising: a one-way clutch that restricts rotation of the output shaft; and a release means that can arbitrarily release the rotation restriction during reverse rotation of the output shaft.   The electric driver according to claim 1, wherein the release means is operated in conjunction with a switching operation to reverse rotation of the motor.   When the forward / reverse rotation switching operation of the motor is based on the sliding operation of the forward / reverse switching switch provided in the motor drive circuit, the forward / reverse switching switch and the release means are connected by a connecting member, The electric driver according to claim 1, wherein the release means can be interlocked with a slide operation of the forward / reverse selector switch.   A one-way clutch is interposed between the cylindrical portion side and the output shaft, and a cylindrical clutch retainer in which a plurality of axial slits are formed in the circumferential direction at predetermined intervals, is housed in each of the slits, and the output A rolling element having a diameter slightly larger than the distance between the inner peripheral surface of the cylindrical portion side and the outer peripheral surface of the output shaft in the radial direction of the shaft, and the inner peripheral surface of the cylindrical portion side corresponding to the slit Provided, and when the rolling element enters, the rolling element is provided in the clutch retainer so that the rolling element is not in contact with the outer peripheral surface of the output shaft, and each of the rolling elements is retreated in the reverse rotation direction of the output shaft. An elastic member that urges away from the recess, and the release means moves the clutch retainer from the clutch set position that moves the rolling elements out of the escape recess when the output shaft stops. When the stop Electric screwdriver according to any one of claims 1 to 3 is the rolling element that is rotatable to the clutch release position to move into the relief recess.

Images