DISCONNECTING JOINT

Abstract

The invention relates to a torque-dependently releasable shut-off clutch for an electric hand-held power tool, in particular for a screwdriver, for selectively transmitting torque from a drive shaft to an output shaft coaxial with the drive shaft. The shut-off clutch comprises a cam ring, an axially immovable first guide ring, which guides a switching element, in particular a ball, and a second guide ring. The cam ring and the second guide ring are axially preloaded against one another and axially accommodate the switching element between them. The shut-off clutch can be moved from a first, non-torque-transmitting switching position to a second, torque-transmitting switching position.If a first trigger torque is exceeded in the first switching position, the switching element is deflected relative to the cam ring in the axial direction against the effect of the preload, thereby moving the shut-off clutch to the second switching position. This provides a robust and simply constructed shut-off clutch that opens reliably when the first trigger torque is exceeded.

Description

[0001] The invention relates to a torque-dependently releasable shut-off clutch for an electric hand-held power tool, in particular for a screwdriver, for the selective transmission of a torque from a drive shaft to an output shaft coaxial with the drive shaft, and to a method for operating an electric hand-held power tool with such a shut-off clutch.

[0002] The invention is illustrated below using a screwdriver as an example. In particular, the invention is intended for use in an industrial screwdriver. However, this is not intended to be limiting. The invention can also be used in other electrical handheld power tools, such as drills or grinders.

[0003] The screwdrivers or cordless screwdrivers considered here are used in particular for industrial series screw connections, for example in the production of automobiles.

[0004] For screw connections, especially those in industrial applications, a nominal tightening torque is often specified with which the screw connection should be tightened. During the tightening process, the tightening torque increases. Therefore, the screwdriver is required to interrupt the torque transmission and, in particular, to switch off the screwdriver's motor when the nominal tightening torque is reached.

[0005] For this purpose, such screwdrivers have a shut-off clutch in their drive train, which opens when an adjustable torque is reached.

[0006] Such a shut-off clutch is known, for example, from EP 3 361 114 B1. The shut-off clutch comprises a first clutch element and a second clutch element, which cooperate to transmit a torque, with at least one of the two clutch elements being movable relative to the other clutch element and preloaded by a spring element. The two clutch elements are positively coupled via at least one ball, so that a torque can be transmitted between the two clutch elements. At least one clutch element also has a cam element per ball as a positive locking element. When the torque reaches a certain value, the ball begins to climb the cam element at an incline of less than 90 degrees (relative to the direction of the circumferential force) due to the circumferential force acting on it. In this way, the clutch disengages or "opens" when this torque is exceeded.

[0007] Another shut-off clutch is known from DE 10 2020 130 665 A1. The two clutch elements are a cam ring and a switching ring, which are also axially preloaded against each other and positively coupled by balls. The cam ring has a circumferentially closed cam track with at least one switching cam, against which the ball rests when the shut-off clutch is engaged. If a triggering torque is exceeded, the ball is guided into a freewheel track formed in the cam ring, so that no more torque can be transmitted between the two clutch elements.

[0008] The present invention is based on the object of further improving a shut-off clutch for an electric hand-held power tool and of specifying a method for operating an electric hand-held power tool with such a shut-off clutch.

[0009] This object is achieved by a shut-off clutch according to claim 1, an electric hand-held power tool with such a shut-off clutch according to claim 15, and by corresponding methods for operating the same. Advantageous embodiments of the invention are contained in the subclaims.

[0010] A torque-dependently releasable shut-off clutch according to the invention for an electric hand-held power tool, in particular for a screwdriver, for selectively transmitting a torque from a drive shaft to an output shaft coaxial with the drive shaft comprises: a cam ring which is rotatably connected to the drive shaft or to the output shaft, and an axially non-displaceable first guide ring which is rotatably connected to the other of the drive shaft and the output shaft.

[0011] The shut-off clutch can be brought from a first switching position, in which the cam ring is connected to the first guide ring in a first direction of rotation, in particular clockwise as seen in the axial direction from the input shaft to the output shaft, in a torque-transmitting manner, into a second switching position in which the cam ring is freely rotatable relative to the first guide ring.

[0012] Furthermore, the shut-off clutch according to the invention has: at least one switching element, in particular a ball, which is guided by the first guide ring in the circumferential direction and / or in the radial direction, and a second guide ring, wherein the cam ring and the second guide ring are axially prestressed against one another and receive the at least one switching element axially between them.

[0013] The cam ring is designed such that, when the shut-off clutch is in the first switching position, the at least one switching element is deflected relative to the cam ring in the axial direction against the effect of the preload when a first triggering torque acting in the first direction of rotation is exceeded, whereby the shut-off clutch is brought into the second switching position.

[0014] This provides a robust and simply constructed shut-off clutch that opens reliably when the first trigger torque is exceeded, thus solving the problem of improving the shut-off clutch.

[0015] The accommodation of the at least one switching element between the cam ring and the second guide ring, which are axially preloaded against each other, together with the guidance of the at least one switching element in the circumferential direction and / or in the radial direction by the first guide ring, ensures that the movement of the at least one switching element is always controlled in all directions and the shut-off clutch cannot therefore assume any undefined states.

[0016] Since the axial preload acting on the at least one switching element occurs only between the cam ring and the second guide ring, and the first guide ring is not involved, it is possible to arrange the first guide ring in such a way that it cannot be axially displaced according to the invention. This makes it easier to implement the non-rotatable connection between the first guide ring and the input or output shaft, particularly through a rigid or even one-piece connection, than if the first guide ring had to be axially displaceable.

[0017] Accordingly, it is preferred that the cam ring is also not axially displaceable, since this makes it easier to implement the rotationally fixed connection between the cam ring and the drive or output shaft than if the cam ring had to be axially displaceable. Accordingly, it is preferred that the second guide ring be axially displaceable instead, in order to thereby implement the axial preload between the cam ring and the second guide ring, as well as the deflectability of the at least one switching element against this preload. The second guide ring, on the other hand, is not involved in the torque transmission from the drive shaft to the output shaft and therefore does not require a rotationally fixed connection to either of these shafts.

[0018] In particular, the shut-off clutch according to the invention supports the following first application: When producing a screw connection, in particular consisting of a screw with an external thread and a counterpart, preferably a fastening section, in particular an opening, with an internal thread, in clockwise rotation of the hand-held power tool, the shut-off clutch should open as soon as the nominal tightening torque of the screw connection is reached. In this case, the first release torque should therefore correspond to this nominal tightening torque. The first application is therefore to protect the screw connection from excessive tension and thus possible damage to the screw or the counterpart.

[0019] In a preferred embodiment of the invention, the cam ring comprises: at least one depression, in particular a ball pocket, in which the at least one switching element is received in the first switching position, wherein the at least one depression forms a first switching cam against which the at least one switching element rests in the first switching position, a circumferentially closed freewheel track on which the at least one switching element can rotate in the second switching position, and at least one diverting track which connects the at least one depression and the freewheel track and on which the at least one switching element can move from the at least one depression to the freewheel track and vice versa.

[0020] The freewheel track and the at least one diverting track are preferably formed by respective elongated recesses in a surface of the cam ring, which preferably extends in a plane perpendicular to the axial direction. The freewheel track and the at least one diverting track thus preferably form grooves in the surface of the cam ring, which further preferably have a circular segment-shaped cross-section.

[0021] In this case, the at least one switching element can be deflected in the axial direction when the first triggering torque is exceeded and the shut-off clutch can be brought into the second switching position by the at least one switching element moving from the at least one recess via the at least one diversion path into the freewheel path.

[0022] In this way, the first and second switching positions of the shut-off clutch can be easily and reliably defined by the position of the at least one switching element in the at least one recess or in the freewheel track. Furthermore, the circumferentially closed freewheel track allows the at least one switching element to rotate therein for any length of time, allowing the shut-off clutch to remain in the second switching position and thus in the open state for any length of time.

[0023] In a preferred variant of the last-described embodiment of the invention, the axial level of the at least one discharge track rises from the recess in the direction of the freewheel track and is always lower than or equal to the axial level of the freewheel track.

[0024] An axial level is defined as a depth in the surface of the cam ring, i.e. a deeper axial level means a deeper recess in the surface of the cam ring.

[0025] To ensure the reliable transition of a switching element from the freewheel track to the diverting track, the freewheel track and the at least one diverting track preferably have different levels in the axial direction. While the freewheel track preferably has a constant level, the at least one diverting track preferably rises steadily from the first switching cam at the at least one recess in the cam ring until it reaches the level of the freewheel track at the junction or mouth of both tracks. At this point, the freewheel track and the at least one diverting track preferably have the same radii or shapes and merge into one another with a smooth transition.

[0026] Due to the different axial levels of the freewheel track and the at least one diverting track and their arrangement, a stepped transition preferably occurs between these two tracks, arranged transversely to their running direction. This stepped transition preferably forms a guide. This ensures that a switching element can switch from the at least one diverting track to the freewheel track and vice versa exclusively at the junction between the freewheel track and the at least one diverting track.

[0027] The aforementioned guide at the transition between the at least one diverting path and the freewheeling path can be particularly advantageous when the shut-off clutch has more than one switching element and a diverting path for each switching element. This guide ensures that all switching elements used switch between the freewheeling path and one of the diverting paths at the same time at the respective junction. This prevents a first switching element from switching to one of the diverting paths while a second switching element is still in the freewheeling path during a change in rotation direction.

[0028] In a further preferred embodiment of the invention, an axial displacement of the cam ring and / or the second guide ring can be effected by the axial deflection of the at least one switching element as a result of the first triggering torque, and the shut-off clutch further comprises a sensor which is designed to detect this displacement.

[0029] The detection of the axial displacement of the cam ring and / or the second guide ring can advantageously be used to detect the second switching position and thus the open state of the shut-off clutch. During operation of a handheld power tool with a shut-off clutch according to the invention, the motor control for the drive motor of the handheld power tool can then trigger a change in the direction of rotation of the motor, whereby the at least one switching element returns from the freewheeling path via the at least one diversion path into the at least one recess, whereby the shut-off clutch returns to the first switching position and closes again.

[0030] In a further preferred embodiment of the invention, the first guide ring is designed as a cage ring with at least one through-opening, and the at least one switching element is received in the at least one through-opening.

[0031] Due to the design of the first guide ring as a cage ring, the receiving space for the at least one switching element is closed off from the environment, particularly in the radial direction, so that the at least one switching element cannot leave the first guide ring even under the influence of centrifugal force during rotation of the shut-off clutch and thus possibly become "lost" within the housing of the hand-held power tool.

[0032] In a variant of the last-described embodiment of the invention, the at least one through-opening has an elongated, in particular elongated, straight shape, the direction of extension of which is inclined relative to a radial direction. Alternatively, the through-opening can have a shape that deviates from a straight shape, for example, a slightly curved one.

[0033] An inclination of the extension direction of the at least one through-opening in the first guide ring relative to a radial direction is advantageous for the radial movement of the at least one switching element during the transition of the shut-off clutch from the first to the second switching position, in which the at least one switching element moves radially inward. Due to the inclination of the extension direction of the at least one through-opening relative to a radial direction, the at least one switching element can "slide down" the inner wall of the at least one through-opening during this movement, as if on an inclined wall, thereby reducing friction and preventing self-locking between the at least one switching element and the first guide ring.

[0034] In a further variant of the last-described embodiment of the invention, the first guide ring is arranged axially between the cam ring and the second guide ring, and the at least one switching element protrudes axially on both sides beyond the edge of the at least one through-opening.

[0035] By arranging the first guide ring axially between the cam ring and the second guide ring, a positive guidance of the at least one switching element is achieved in all directions, namely axially between the cam ring and the second guide ring and radially and / or in the circumferential direction through the first guide ring.

[0036] The axial projection of the at least one switching element beyond the side surfaces of the first guide ring or beyond the edge of the at least one through-opening in the first guide ring further ensures that the second guide ring can always be in axial contact with the at least one switching element without colliding with the edge of the at least one through-opening. The edge of the at least one through-opening preferably lies in a plane with a side surface of the first guide ring. Likewise, it is ensured that the cam ring can always be in axial contact with the at least one switching element without colliding with the edge of the at least one through-opening in the first guide ring.The axial projection of the at least one switching element on both sides of the first guide ring is preferably dimensioned such that the above applies to each axial position of the at least one switching element in the recesses in the cam ring or in the at least one through-opening in the first guide ring.

[0037] In a variant of the embodiment of the invention with at least one depression in the cam ring, the at least one depression is arranged within the cam ring. This means that the depression, preferably in the form of a recess or a spherical pocket, is arranged at a distance from the outer circumference of the cam ring. Preferably, the outer circumference of the cam ring is higher than the depression in the region of the depression, so that the depression is closed radially outward.

[0038] This can have the advantage, similar to the design of the first guide ring as a cage ring, that at least one switching element cannot leave the cam ring even under the influence of centrifugal force during rotation of the shut-off clutch and thus possibly become "lost" within the housing of the hand-held power tool.

[0039] In a variant of the last-described variant of the invention, the at least one recess has an elongated shape, transitions into the at least one diverting path at a first end, and has a lower axial level than the at least one diverting path. The transition of the recess into the diverting path forms the first switching cam.

[0040] This configuration of the at least one recess provides a simple way to form the first switching cam in the recesses in the cam ring, thereby enabling the at least one switching element to transition directly into the at least one diverting path after overcoming the first switching cam. The lower axial level of the at least one recess than the axial level of the at least one diverting path simultaneously achieves the desired axial deflection of the at least one switching element upon overcoming the first switching cam.

[0041] In a variant of the last-described variant of the invention, the transition at the first end of the at least one depression from the at least one depression into the at least one discharge path is substantially smooth, as seen in the direction of extension of the at least one depression and the at least one discharge path.

[0042] This can bring about a uniform and - apart from the jerk caused by overcoming the first switching cam - jerk-free movement of the at least one switching element on its way out of the at least one recess into the at least one diversion path.

[0043] In a variant of the embodiment of the invention with at least one recess, one freewheel track and at least one diverting track in the cam ring, the freewheel track has a constant axial level.

[0044] This can result in a particularly smooth movement of the at least one switching element in the second switching state. This leads to a low-wear, low-vibration, and / or low-noise switching process. In addition, the constant axial level of the freewheel track prevents any further axial deflection of the at least one switching element and any associated axial displacement of the cam ring and / or the second guide ring, so that the transition from the first to the second switching position can be reliably detected, thus also achieving the objective of improving the shut-off clutch.

[0045] In a further variant of the embodiment of the invention with at least one recess, one freewheel track and at least one diversion track in the cam ring, the at least one diversion track has at least partially the shape of a logarithmic spiral.

[0046] This can also cause a uniform and jerk-free movement of the at least one switching element on the at least one diversion path radially inwards.

[0047] In a further preferred embodiment of the invention, the shut-off clutch can be brought from a third switching position, in which the cam ring is connected to the first guide ring in a second direction of rotation opposite to the first direction of rotation, in particular counterclockwise as seen in the axial direction from the input shaft to the output shaft, in a torque-transmitting manner, into a fourth switching position in which the cam ring is freely rotatable relative to the first guide ring.

[0048] The cam ring is designed such that, when the shut-off clutch is in the third switching position, the at least one switching element is deflected relative to the cam ring against the effect of the preload in the axial direction when a second triggering torque acting in the second direction of rotation is exceeded, whereby the shut-off clutch is brought into the fourth switching position.

[0049] This provides a robust and simply constructed shut-off clutch that opens reliably when the second tripping torque is exceeded.

[0050] This design of the shut-off clutch according to the invention particularly supports the following second application: When loosening a screw connection with the handheld power tool rotating counterclockwise, it may be necessary for a stuck screw connection to require a torque greater than the maximum motor torque. Operating the handheld power tool with such a high torque could damage the motor. Therefore, the shut-off clutch should open before the maximum motor torque is reached. In this case, the second release torque should therefore be slightly lower than the maximum motor torque. The second application thus consists in protecting the motor of the handheld power tool from overload and damage.

[0051] In a preferred variant of the last-described embodiment of the invention, in which at least one recess is further provided in the cam ring, the at least one switching element is received in the at least one recess in the third switching position, wherein the at least one recess forms a second switching cam against which the at least one switching element rests in the third switching position.

[0052] The cam ring further comprises a cam track which is largely closed in the circumferential direction and interrupted only by the at least one recess, on which the at least one switching element can rotate at least partially in the fourth switching position.

[0053] In addition, the at least one switching element can be deflected in the axial direction when the second triggering torque is exceeded and the shut-off clutch can be brought into the fourth switching position by the at least one switching element moving from the at least one recess into the cam track.

[0054] With this design of the cam ring, essentially the same advantages can be achieved as described above for the first and second switching positions, namely that the third and fourth switching positions of the shut-off clutch can be easily and reliably defined by the position of the at least one switching element in the at least one recess or in the cam track. In contrast to the second switching position, however, the fourth switching position is only maintained until the at least one switching element falls from the cam track into the next recess. The duration of this movement can, however, be sufficient to detect the fourth switching position and react to it.

[0055] In a preferred variant of the last-described embodiment of the invention, the at least one recess has an elongated shape, merges into the cam track at a second end and has a lower axial level than the cam track, the second switching cam being formed by this transition.

[0056] This can result in the corresponding advantages as in the variant described above, in which the at least one recess merges into the at least one diversion path at a first end and has a lower axial level than the at least one diversion path, wherein a first switching cam is formed by this transition.

[0057] Preferably, the second end of the at least one recess is opposite such a first end with respect to its elongated shape.

[0058] In a further preferred variant of the last-described embodiment of the invention, an axial displacement of the cam ring and / or the second guide ring can be effected by the axial deflection of the at least one switching element as a result of the second triggering torque, and the shut-off clutch further comprises a sensor which is designed to detect this displacement.

[0059] This can be used—similar to the second switching position above—to detect the fourth switching position and thus the open state of the shut-off clutch. However, following this detection, reversing the motor's direction of rotation is not necessary, since in this case, at least one switching element can remain in the cam track and return to a recess even if the motor continues to operate in the same direction of rotation. This recess then becomes the next recess in the circumferential direction, allowing the shut-off clutch to return to the third switching position.

[0060] Of course, the sensor for detecting the fourth switching position can be identical to the sensor for detecting the second switching position, since in both cases an axial displacement of the cam ring and / or the second guide ring is detected.

[0061] In a preferred variant of those variants of the invention in which the first and the second switching cam are each formed by a transition at a first or at a second end of the at least one recess, the inner wall of the at least one recess at its second end is steeper than the inner wall of the at least one recess at its first end, so that the second triggering torque is greater than the first triggering torque.

[0062] The described relationship, that the tripping torque is greater the steeper the transition at the respective end of the at least one recess, results directly from the above-described interaction of the at least one switching element with the respective inner wall of the at least one recess (the "ramp") in the sense of a wedge mechanism. The fact that the second tripping torque is greater than the first tripping torque can be advantageous, since the maximum motor torque, according to which the second tripping torque should be determined, is generally greater than the nominal tightening torque of a screw connection, according to which the first tripping torque should be determined.

[0063] In a further preferred variant of the last-described embodiment of the invention, the cam track has a constant axial level, except in the region of the at least one recess.

[0064] This can result in the same advantages as in the corresponding design with a constant axial level of the freewheel track, namely that in this case the transition from the third to the fourth switching position can be reliably detected.

[0065] In a further preferred embodiment of the invention, the shut-off clutch has a freewheel which can be opened and closed, which is designed to be supported on a housing of the electric hand-held power tool, and which, in the closed (activated) state, allows rotation of the output shaft in the first direction of rotation and blocks rotation of the output shaft in the second direction of rotation and, in the open (deactivated) state, does not influence the rotatability of the output shaft.

[0066] A freewheel with these functions is advantageous if, in the second switching position, the direction of rotation of the motor is reversed from the first to the second direction of rotation in order to return the at least one switching element from the freewheel track via the at least one diverting track into the at least one recess. In this case, the output shaft must be prevented from rotating, as otherwise the required relative rotation between the input shaft and output shaft cannot occur. In this case, the freewheel can therefore be closed so that it blocks the rotation of the output shaft in the second direction of rotation, thereby preventing the output shaft from rotating in the second direction of rotation.

[0067] In a preferred variant of the last-described embodiment of the invention, the freewheel is a ratchet freewheel, in which at least one freewheel pawl engages with at least one freewheel tooth. The at least one freewheel pawl is arranged on an axially displaceable, non-rotatable freewheel pawl ring that is axially preloaded against the at least one freewheel tooth, and the at least one freewheel tooth is arranged on an end face of the first guide ring.

[0068] The ratchet freewheel design represents a common design for a freewheel and is therefore easy to implement. In particular, the use of the first guide ring for attaching the at least one freewheel tooth can be advantageous because this eliminates the need for an additional component for arranging the freewheel tooth.

[0069] In a preferred variant of the previously described variant of the invention, the freewheel can be closed and opened by an axial displacement of the freewheel pawl ring, which can be effected by an axial displacement of the second guide ring.

[0070] If the transition from the first to the second switching position and / or the transition from the third to the fourth switching position can cause an axial displacement of the second guide ring, it is also advantageous to use this displacement to engage and disengage the freewheel. Since the freewheel pawl ring is axially displaceable, it is also advantageous to also engage and disengage the freewheel by such an axial displacement of the freewheel pawl ring. In this way, the existing movement possibilities of the components involved are utilized for engaging and disengaging the freewheel.

[0071] The axial displacement of the freewheel pawl ring by the axial displacement of the second guide ring can be effected directly or indirectly. In the case of a direct effect, the freewheel pawl ring can be supported axially directly on the second guide ring. In the case of an indirect effect, at least one further force-transmitting component can be arranged between the second guide ring and the freewheel pawl ring, in particular a component connected to the second guide ring and axially displaceable with it, but not rotatable.

[0072] In a preferred variant of the previously described variant of the invention, the cam ring and the first guide ring are arranged axially between the freewheel pawl ring and the second guide ring, and the second guide ring or a component connected to the second guide ring and axially non-displaceable relative thereto axially overlaps the cam ring and the first guide ring.

[0073] If the freewheel is to be opened and closed by an axial displacement of the second guide ring and a resulting axial displacement of the freewheel pawl ring, the second guide ring must be able to act axially on the freewheel pawl ring. If the cam ring and the first guide ring are arranged axially in between, this can be achieved in a simple manner by the second guide ring or a component connected to the second guide ring and not axially displaceable relative to it axially engaging over the latter two components. This therefore also includes the case in which the axial displacement of the freewheel pawl ring is indirectly caused by the axial displacement of the second guide ring and in which another force-transmitting component connected to the second guide ring but not axially displaceable relative to it axially engages over the cam ring and the first guide ring.

[0074] In a further preferred variant of the last-described embodiment of the invention, the freewheel is open in the first switching position and closed in the second switching position.

[0075] This corresponds to the requirement that the freewheel should be closed when, after the transition from the first to the second switching position, the direction of rotation of the motor is reversed from the first to the second direction of rotation in order to prevent the output shaft from rotating in the second direction of rotation.

[0076] In contrast, since a reversal of the motor rotation direction is not required after the transition from the third to the fourth switching position, as described above, it is not relevant in this case whether the freewheel is closed or open.

[0077] The invention further relates to an electric handheld power tool, in particular a screwdriver, with a shut-off clutch according to the invention. This allows the two applications described above for clockwise or counterclockwise rotation of the handheld power tool's motor to be implemented simply and reliably.

[0078] The invention also relates to a method for operating an electric hand-held power tool, in particular a screwdriver, with a shut-off clutch according to the invention, which comprises the steps: Driving the drive shaft in the first direction of rotation while the shut-off clutch is in the first switching position, stopping the rotation of the drive shaft when a torque acts in the first direction of rotation which exceeds the first tripping torque, whereby the shut-off clutch is brought into the second switching position by exceeding the first tripping torque, driving the drive shaft in the second direction of rotation, whereby the shut-off clutch is brought back into the first switching position.

[0079] This corresponds to the first application case already described in detail above, in which the shut-off clutch should open as soon as the nominal tightening torque of the screw connection to be made is reached and should then close again.

[0080] The invention also relates to a method for operating an electric hand-held power tool, in particular a screwdriver, with a shut-off clutch which can also be brought into the third and fourth switching position, which comprises the steps: Driving the drive shaft in the second direction of rotation while the shut-off clutch is in the third switching position, further driving the drive shaft in the second direction of rotation when a torque acts in the second direction of rotation which exceeds the second tripping torque, whereby the shut-off clutch is brought into the fourth switching position by the second tripping torque being exceeded, further driving the drive shaft in the second direction of rotation, whereby the shut-off clutch is brought back into the third switching position.

[0081] This corresponds to the second application case, also described in detail above, in which the shut-off clutch should open before the maximum engine torque is reached in order to protect the engine from overload, and should close again afterwards.

[0082] Further advantages, features, and possible applications of the present invention will become apparent from the following description in conjunction with the figures. These show: Fig. 1 a side view of a shut-off clutch according to the invention; Fig. 2 a section through the shut-off clutch according to Fig. 1 ; Fig. 3 an exploded view of the shut-off clutch according to Fig. 1 ; Fig. 4 the components of the shut-off clutch according to Fig. 1 which form the clutch mechanism; Fig. 5 the front side of the cam ring of the shut-off clutch according to Fig. 1 ; Fig. 6 the components of the shut-off clutch according to Fig. 1 which form the reset mechanism.

[0083] The invention will be described in detail below using a single exemplary embodiment of a shut-off clutch 1 according to the invention. Fig. 1 , 2 and 3 the entire shut-off clutch 1 in different views, namely as a side view ( Fig. 1 ), cut ( Fig. 2 ) and exploded view ( Fig. 3 ). The Fig. 4 , 5 and 6 show individual components or subassemblies of the shut-off clutch 1, namely the clutch mechanism which causes the opening and closing of the shut-off clutch 1 ( Fig. 4 ), the front side of the cam ring 7 with the various recesses 30 to 35 for the balls 11 ( Fig. 5 ) and the reset mechanism, which closes a freewheel when the shut-off clutch 1 is opened ( Fig. 6 ).

[0084] The shut-off clutch 1 is intended for installation in an electric, rotating handheld power tool (not shown in the figures), in particular in a screwdriver, such as those used in industrial production. The shut-off clutch 1 is arranged in the drive train of the handheld power tool between the drive motor and a tool holder, in particular for a screwing tool such as a screwdriver bit or an internal or external hexagon tool. However, the shut-off clutch 1 according to the invention can also be used in other handheld power tools.

[0085] The components of the shut-off clutch 1 are essentially all arranged coaxially to an axis, which simultaneously forms the rotational axis of the rotatable components. At the same time, the shut-off clutch 1 is supported by a ring 48 fixed to the housing of the handheld power tool (not shown) and is rigidly connected to the housing directly or indirectly at this point.

[0086] The shut-off clutch 1 has a drive shaft 2, the outer end of which is designed, for example, in the form of an external hexagon 20. The external hexagon 20 is provided for a permanent, positive-locking and rotationally fixed coupling with the drive motor (not shown) of the hand-held power tool. Coaxial with the drive shaft 2, the shut-off clutch 1 has an output shaft 3, at the outer end of which a hexagon socket 21 is formed. The hexagon socket 21 is provided for the positive-locking, rotationally fixed reception of interchangeable tools, in particular screwdriver bits of any type (not shown). The tools are preferably inserted into the hexagon socket 21 by hand and are preferably held by friction, by a locking mechanism, or magnetically.

[0087] The input shaft 2 and the output shaft 3 are mounted rotatably against each other by a ball bearing 17. During assembly of the shut-off clutch 1, the balls of the ball bearing 17 are individually filled through a radial bore in the outer bearing shell of the input shaft 2, and this bore is then sealed with a plug 18.

[0088] The shut-off clutch 1 is designed to transmit torque from the drive shaft 2, and thus from the drive motor, to the output shaft 3 and thus to the tool when the handheld power tool is in operation. As soon as the torque transmitted from the drive shaft 2 to the output shaft 3 exceeds a specific, adjustable trigger torque, the shut-off clutch 1 is designed to open, so that no more torque can be transmitted from the drive shaft 2 to the output shaft 3.

[0089] In particular, the opening of shut-off clutch 1 when the release torque is exceeded should support the two applications described above: When establishing a screw connection in clockwise rotation of the handheld power tool, shut-off clutch 1 should open as soon as the nominal tightening torque of the screw connection is reached (first application). However, when loosening a screw connection in anticlockwise rotation of the handheld power tool, shut-off clutch 1 should open if the required loosening torque is greater than the maximum motor torque to protect the handheld power tool motor from overload (second application).

[0090] Since the two applications differ, the required release torque may also be different. Since the nominal tightening torque varies from screw connection to screw connection, especially in the first application, the release torque should be preselectable by the user of the hand-held power tool.

[0091] To achieve the desired opening of the shut-off clutch 1 when the respective triggering torque is exceeded in clockwise or anti-clockwise rotation, the drive shaft 2 is connected in a rotationally fixed manner—and in the exemplary embodiment, integrally—to a cam ring 7. Various recesses with different axial levels are formed in the end face of the cam ring 7 facing axially toward the output shaft 3. These recesses are designed such that several balls 11, three in the exemplary embodiment, are received therein and can move therein essentially in the circumferential direction. The exact arrangement and function of the recesses in the cam ring 7 are described in more detail below.

[0092] For each ball 11, at least one location is provided in the recesses in the cam ring 7 where the axial level of the recess changes abruptly. In other words, the recess has an axial step at this location. However, the "vertical" wall of the step does not run exactly in the axial direction, but is inclined relative to it, such that the step forms a steep, but not vertical, ramp from the lower axial level (in the sense of a deeper recess in the face of the cam ring 7) to the higher axial level.

[0093] In the closed state of the shut-off clutch 1, the ball 11 is located in the recess on the side of the step with the lower axial level and rests against the step in such a way that, for a given direction of rotation of the drive shaft 2, the step presses circumferentially against the ball 11. In this way, in this state of the shut-off clutch 1, a torque can initially be transmitted from the cam ring 7 to the ball 11. The shut-off clutch 1 is then in a first switching position.

[0094] Axially adjacent to the cam ring 7 is a first guide ring 8, which is rotationally fixedly connected—in this embodiment, integrally—to the output shaft 3. Thus, both the cam ring 7 and the first guide ring 8 are axially immovable.

[0095] The first guide ring 8 has a through-hole 10 for each ball 11, in which the part of the ball 11 that projects axially beyond the cam ring 7 is guided. Each through-hole 10 is linear, i.e., in the form of an elongated hole, and extends in the first guide ring 8 from a radially outer end to a radially inner end in a direction that is oblique to the radial direction. The radially outer end of the elongated hole is spaced from the outer circumference of the first guide ring 8. This results in a positive guidance of each ball 11 in an elongated hole. The loss of a ball 11 is impossible.The axial extent of the first guide ring 8 is dimensioned such that each ball 11, in every possible position it can assume in a recess in the cam ring 7, rests with its largest diameter against the inner walls of the associated through-hole 10, and that at the same time a part of the ball 11 protrudes axially from the through-hole 10 on the side opposite the cam ring 7. The first guide ring 8, with the through-holes 10 arranged therein, thus acts like a cage for the balls 11. In this way, a torque can always be transmitted between the balls 11 and the second guide ring 8 and thus the output shaft 3.

[0096] On the side of the first guide ring 8 opposite the cam ring 7, a second guide ring 9 is arranged, the end face of which, facing the first guide ring 8, is completely flat. The second guide ring 9 is mounted on the output shaft 3 for rotation and axial displacement, preferably by means of a plain bearing. As will be explained in more detail below, the second guide ring 9 is axially preloaded against the cam ring 7, so that its flat end face is pressed against the balls 11.

[0097] In this way, the balls 11 are positively guided in all directions, namely in the axial direction through the recesses in the end face of the cam ring 7 and through the flat end face of the second guide ring 9 as well as in the radial and circumferential direction through the through openings 10 in the first guide ring 8. This positive guidance of the balls 11 prevents the balls 11 from moving uncontrollably during the rotation of the drive shaft 2 and the output shaft 3 and from getting lost within the housing of the hand-held power tool.

[0098] Based on the previous description, it is clear that when the shut-off clutch 1 is closed, torque can be transmitted from the input shaft 2 to the output shaft 3 via the cam ring 7, the balls 11, and the first guide ring 8. The second guide ring 9 is not involved in the torque transmission itself, but forms part of the axial guidance of the balls 11.

[0099] As mentioned above, when the shut-off clutch 1 is closed, each ball 11 rests against the corresponding step in a recess in the face of the cam ring 7. The step forms a steep, but not vertical, ramp, allowing torque to be transmitted from the ramp to the ball 11 in the specified direction of rotation of the drive shaft 2. The surface of the ball 11 and the ramp form a wedge mechanism. At the same time, the ball 11 is axially preloaded against the face of the cam ring 7 by the second guide ring 9. This preload is such that, when the torque transmitted between the ramp and the ball 11 exceeds a first trigger torque, the ball 11 "climbs" up the ramp due to the wedge effect and enters the axially higher part of the recess in the face of the cam ring 7.

[0100] As explained in more detail below, this recess is arranged so that the ball 11 can move freely in the circumferential direction in the axially higher part of the recess. In this state of the shut-off clutch 1, no more torque can be transmitted between the cam ring 7 and the ball 11—and thus also between the input shaft 2 and the output shaft 3. The shut-off clutch 1 is then in a second switching position and in the open state.

[0101] The ramp in the recess in the end face of the cam ring 7 thus acts as a first switching cam 31, the overcoming of which by the ball 11 in a first direction of rotation causes the shut-off clutch 1 to transition from the closed state to the open state. In a second direction of rotation opposite to the first direction of rotation, this ramp also acts as a first switching cam 31, the overcoming of which by the ball 11 causes the shut-off clutch 1 to transition from the open state to the closed state.

[0102] The end face of the cam ring 7 with the recesses for the balls 11 located therein will now be described in detail. In the exemplary embodiment, three balls 11 are provided, and the end face of the cam ring 7 has recesses offset by 120 degrees for each ball 11, thus providing a threefold rotational symmetry.

[0103] The recesses for a ball 11 initially comprise an elongated ball pocket 30, which has a deeper axial level than all other recesses in the end face of the cam ring 7. The ball pocket 30 extends approximately in the circumferential direction, but is slightly curved radially inward towards one end.

[0104] The two ends of the ball pocket 30, at which the low axial level of the ball pocket 30 merges into the higher axial level of the surroundings of the ball pocket 30, thus form a first switching cam 31 for torque transmission during a clockwise rotation and a second switching cam 32 for torque transmission during a counterclockwise rotation of the drive shaft 2 to the output shaft 3.

[0105] When the first trigger torque is exceeded during a clockwise rotation of the drive shaft 2, the ball 11 overcomes the first switching cam 31, as described above, and enters the adjoining diversion path 33, which spirals radially inward. The diversion path 33 preferably has the shape of a logarithmic spiral to enable a smooth, jerk-free movement of the ball 11. The slight radially inward curvature of the ball pocket 30 is also selected such that the ball pocket 30 transitions smoothly into the diversion path 33, thus also enabling a smooth, jerk-free movement of the ball 11.

[0106] Simultaneously with its radially inward movement along the discharge path 33, the ball 11 also moves radially inward along the longitudinal extent of the through-hole 10 in the first guide ring 8. Since the through-hole 10 is not arranged radially but inclined relative to a radial direction, the ball 11 can slide down the inner surface of the through-hole 10 at an oblique angle, thereby reducing friction and preventing possible self-locking during the movement of the ball 11 in the through-hole 10.

[0107] The discharge path 33 opens in the radially inner region of the end face of the cam ring 7 into a closed, circular freewheel path 34 with a constant axial level, in which the ball 11 can rotate for any length of time.

[0108] When the ball 11 is located in the diverting track 33 or in the freewheel track 34 and thus no mechanical resistance is encountered in the circumferential direction, no more torque can be transmitted from the input shaft 2 to the output shaft 3. The shut-off clutch 1 is then consequently in the open state, thus preventing the nominal tightening torque of a screw connection from being exceeded.

[0109] Since the diversion track 33 and the freewheel track 34 have a higher axial level than the ball pocket 30, the ball 11 moves in the axial direction towards the output shaft 3. As a result, the second guide ring 9, which is preloaded against the balls 11 and the cam ring 7, is also displaced in this axial direction.

[0110] The second guide ring 9 is rotatably mounted relative to a sliding ring 40, whose function will be described in more detail below, by a ball bearing 6, so that the sliding ring 40 itself does not rotate. The second guide ring 9 and the sliding ring 40 are connected to a single unit by the ball bearing 6 and thus cannot move axially relative to each other, but can only be axially displaced together.

[0111] The sliding ring 40 has an opening 42 on its outer circumference, which can contain a position indicator, for example, a permanent magnet (not shown). A corresponding sensor, for example, a magnetic sensor (also not shown), is mounted in the housing of the handheld power tool, which can detect the axial displacement of the position indicator and thus of the sliding ring 40.

[0112] The sensor detects, based on the axial displacement of the sliding ring 40, that the shut-off clutch 1 has entered the open state and transmits a corresponding signal to the control system of the drive motor of the hand-held power tool. The motor is then switched off. After the rotation of the motor has stopped, the direction of rotation of the drive shaft 2 is reversed. The ball 11, which is located in the freewheel track 34 (in the direction shown in Fig. 5 The ball 11, which rotates clockwise (as shown in the orientation of the cam ring 7), rotates counterclockwise after the direction of rotation is reversed and, at the "branch" or opening 36, returns from one of the diverting tracks 33 to this diverting track 33 and, at the end of the diverting track, returns to the associated ball pocket 30. The guide 37, which is created due to the arrangement and the different levels of the freewheel track 34 and the diverting track 33, ensures that the ball 11 always changes from the freewheel track 34 to the diverting track 33 at the opening 36. This is particularly important if the shut-off clutch 1 comprises more than one ball 11. This prevents one ball 11 from being in the freewheel track 34 and another ball 11 from being in the diverting track 33. This ensures reliable opening and closing of the shut-off clutch 1.The renewed axial movement of the sliding ring 40 toward the drive shaft 2 associated with the transfer of the ball 11 into the ball pocket 30 is again detected by the sensor, whereupon the engine control unit stops the rotation of the engine. This causes the shut-off clutch 1 to be closed again.

[0113] When the drive shaft 2 rotates counterclockwise, the ball 11 rests against the second control cam 32 at the end of the ball pocket 30 opposite the first control cam 31, so that a torque can be transmitted from the cam ring 7 to the ball 11 and, as described above, via the first guide ring 8 to the output shaft 3. The shut-off clutch 1 is then in a third switching position.

[0114] If the second trigger torque is exceeded during the counterclockwise rotation of the drive shaft 2, the ball 11 overcomes the second switching cam 32 and enters the adjoining cam track 35. The cam track 35 runs in a circular manner on the outer radial edge of the cam ring 7, concentric with the freewheel track 34, and is interrupted only by the ball pockets 30. Apart from the ball pockets 30, the cam track 35 has a constant axial level, which is higher than that of the ball pockets 30.

[0115] Preferably, the ramp at the end of the ball pocket 30, which forms the second switching cam 32, is steeper than the ramp at the end of the ball pocket 30, which forms the first switching cam 31. Thus, the second triggering torque is preferably also greater than the first triggering torque.

[0116] In the cam track 35, the ball 11 can rotate at least as far as the next ball pocket 30, i.e., over a rotation angle range of 5 degrees to 120 degrees, without encountering any mechanical resistance in the circumferential direction. Thus, during this movement of the ball 11, no torque can be transmitted from the input shaft 2 to the output shaft 3. The shut-off clutch 1 is then in a fourth switching position. In the fourth switching position, the shut-off clutch 1 is also in the open state and prevents the maximum motor torque from being exceeded, especially if this is insufficient to loosen a screw connection.

[0117] In this case too, the sliding ring 40 is displaced axially when the shut-off clutch 1 is opened, which is again detected by the sensor. The motor control then allows the motor to continue rotating counterclockwise, for example at a low speed, until each ball 11 has fallen back into the respective ball pocket 30. A prior reversal of the motor's direction of rotation is not necessary in this case. The shut-off clutch 1 is thus once again in the closed state. Continuing to run the motor at a low speed is even unnecessary, since the next time the hand tool is used - regardless of whether it is in clockwise or anti-clockwise rotation - the balls 11 will fall back into the ball pockets 30 and the shut-off clutch 1 will then be once again in the closed state.

[0118] The first and second release torques can be preset depending on the desired application, in particular depending on the nominal tightening torque of a screw connection to be produced, via the axial preload of the second guide ring 9 against the balls 11 and the cam ring 7.

[0119] This preload is generated by an axially preloaded compression spring 12, which is designed as a spiral spring and runs around the output shaft 3. The compression spring 12 is supported at one end on the second guide ring 9 and at the other end on a pressure ring 13, which on its inner side has a projection (not shown) in a flattened area 5 ( Fig. 6 ) engages on the output shaft 3 and is thus axially displaceable relative to the output shaft 3, but not rotatable. On the side of the thrust ring 13 facing away from the compression spring 12, an adjusting ring 15 is screwed onto a thread 4 of the output shaft 3. The thread 4 is preferably a left-hand thread. In the end face of the thrust ring 13 facing the adjusting ring 15, a plurality of (six in the exemplary embodiment) locking balls 14 are embedded at regular angular intervals, which can engage in a plurality of (twelve in the exemplary embodiment) bores 16, also arranged at regular angular intervals, on the opposite end face of the adjusting ring 15. The adjusting ring 15 can thus be rotated against the spring force of the compression spring 12 by a specific angle (30 degrees in the exemplary embodiment), which the user perceives as individual locking steps, and can thereby be further screwed onto the output shaft 3 or unscrewed from the output shaft 3.With each detent position, the preload of the compression spring 12 increases or decreases, and thus the first and second release torques. In the handheld power tool, the adjusting ring 15 is surrounded by an actuating ring (not shown), preferably made of a non-slip plastic, which can be easily adjusted by hand by the operator.

[0120] As described above, the direction of rotation of the motor is briefly reversed from clockwise to anticlockwise when the clutch has opened during clockwise rotation of the motor due to the first triggering torque being exceeded, so that the balls 11 move back into their ball pockets 30 due to a relative rotation of the drive shaft 2 and thus of the cam ring 7 to the left, i.e. counterclockwise, relative to the balls 11, and the shut-off clutch 1 thereby closes again after opening. Since the balls 11 are positively guided by the first guide ring 8 and the first guide ring 8 is connected in a rotationally fixed manner to the output shaft 3, it must be prevented that the output shaft 3 rotates with the anticlockwise rotation of the drive shaft 2, since otherwise no such relative rotation occurs between the drive shaft 2 and the output shaft 3.

[0121] The co-rotation of the output shaft 3 can be prevented, for example, by ensuring that the tool remains engaged with the previously tightened screw after the motor's direction of rotation has been reversed. However, in practical use of the hand-held power tool, it cannot be guaranteed that the user will keep the tool engaged with the screw immediately after the nominal tightening torque of the screw has been reached and the shut-off clutch 1 has been opened. As soon as the tool is disengaged from the screw, co-rotation of the output shaft 3 can no longer be ruled out.

[0122] In order to reliably prevent the output shaft 3 from rotating in any state of the shut-off clutch 1 after the reversal of the direction of rotation of the motor, ie when the motor is running counterclockwise, the shut-off clutch 1 has a reset mechanism, which is described below (see also Fig. 6 ).

[0123] The reset mechanism is triggered when the shut-off clutch 1 is opened by the previously described axial movement of the sliding ring 40. As best described in Fig. 2 As can be seen, the sliding ring 40 engages radially on the outside with a plurality of claws 41 (three in the exemplary embodiment) directed in the direction of the drive shaft 2 and distributed over the circumference of the sliding ring 40, over the second guide ring 9, the first guide ring 8, the balls 11 and the cam ring 7. The claws 41 are supported on a radially outer region of the end face of a freewheel pawl ring 43, which has a diameter approximately the same as the sliding ring 40 and thus a slightly larger diameter than the cam ring 7, the first guide ring 8 and the second guide ring 9. Instead of a plurality of claws 41, the sliding ring 40 can also have a circumferential, cylindrical outer surface, which is similarly supported on the radially outer region of the end face of the freewheel pawl ring 43.

[0124] The freewheel pawl ring 43 is axially displaceable but not rotatable, as it is guided axially by several axially arranged guide pins 51. For this purpose, the freewheel pawl ring 43 has grooves 52, which together with the guide pins 51 form an axial sliding guide. The guide pins 51 are in turn rigidly connected to the outer side of a cylindrical section 49 of a ring 48 fixed to the housing by being recessed into grooves 53 in the cylindrical section 49 of the ring 48 fixed to the housing. The ring 48 fixed to the housing is rigidly connected to the housing of the hand-held power tool via several recesses 50 around its circumference with projections (not shown) and is therefore neither axially displaceable nor rotatable. In this way, the freewheel pawl ring 43 is mounted axially displaceably on the cylindrical section 49 of the housing-fixed ring 48, but cannot rotate due to the guidance by the guide pins 51.

[0125] The housing-fixed ring 48 also has the function of supporting a ball bearing 22 from the radial outside, in which the drive shaft 2 is mounted radially inside. The bearing between the housing-fixed ring 48 and the drive shaft 2 is further secured by a retaining ring 19.

[0126] Furthermore, a wave spring 47 is arranged between a flange of the housing-fixed ring 48 with a larger diameter than that of the cylindrical portion 49 and a flange of the freewheel pawl ring 43 with a diameter approximately equal to that of the flange of the housing-fixed ring 48, which preloads the freewheel pawl ring 43 axially in the direction of the output shaft 3. Instead of a wave spring, another compression spring, in particular a spiral spring, can be used for this purpose.

[0127] The spring force of the wave spring 47 is always smaller than the spring force of the compression spring 12, so that the preload of the unit consisting of the sliding ring 40 and the second guide ring 9 against the balls 11 is not canceled.

[0128] The freewheel pawl ring 43 has, on its end face directed towards the first guide ring 8, several projections distributed over its circumference, which serve as freewheel pawls 44 ( Fig. 6 ). The end face 45 of a cylindrical extension of the first guide ring 8, which axially engages radially on the outside of the cam ring 7, has a sawtooth-like shape when viewed in the circumferential direction. This forms a plurality of freewheel teeth 46 into which the freewheel pawls 44 can engage. In the open state of the shut-off clutch 1, when the balls 11 are located outside the ball pockets 30, the freewheel pawl ring 43 is pressed axially against the first guide ring 8 by the spring force of the wave spring 47. The freewheel pawls 44 can then engage with the freewheel teeth 46, and the freewheel is in the closed state. The direction of the sawtooth-like shape of the end face 45 of the cylindrical extension of the first guide ring 8 and thus the arrangement of the freewheel teeth 46 is selected such that the first guide ring 8 and thus the output shaft 3 can only rotate clockwise, but not anticlockwise.

[0129] When the shut-off clutch 1 is closed, the claws 41 of the sliding ring 40 press the freewheel pawl ring 43 axially away from the first guide ring 8 against the spring force of the wave spring 47, so that the freewheel pawls 44 cannot engage with the freewheel teeth 46 and the freewheel is open and has no effect.

[0130] When the shut-off clutch 1 is open, however, the claws 41 of the sliding ring 40 do not press against the freewheel pawl ring 43, since the unit consisting of the sliding ring 40 and the second guide ring 9 is axially displaced in the direction of the output shaft 3 by the balls 11, so that the wave spring 47 presses the freewheel pawl ring 43 axially against the first guide ring 8, allowing the freewheel pawls 44 to engage the freewheel teeth 46 and the freewheel to be closed. This results in the desired behavior of the freewheel, namely that it is only closed when the shut-off clutch 1 is open, which also reverses the direction of rotation of the motor, and thus prevents the output shaft 3 from rotating when the motor is running counterclockwise.

[0131] In the event that the shut-off clutch 1 is opened during anti-clockwise rotation of the motor due to the second triggering torque being exceeded, the freewheel closes, and the balls 11 are located in the cam track 35. However, this has no further effects because, as described above, in this case the balls do not have to return from the freewheel track 34 into the ball pockets 30, and thus no reversal of the motor's rotation direction is necessary, which would prevent the output shaft 3 from rotating. The change of state from the open to the closed state of the freewheel has no effect if the shut-off clutch 1 is opened during anti-clockwise rotation of the motor. Bezugszeichenliste

[0132] 1Shut-off clutch 2Input shaft 3Output shaft 4Thread 5Flat 6Ball bearing 7Cam ring 8First guide ring 9Second guide ring 10Through opening 11Ball 12Compression spring 13Thrust ring 14Locking ball 15Adjusting ring 16Bore 17Ball bearing 18Plug 19Retaining ring 20External hexagon 21Inner hexagon 22Ball bearing 30Ball pocket, recess 31First switching cam 32Second switching cam 33Exit track 34Freewheel track 35Cam track 36Branch / orifice 37Guide 40Sliding ring 41Claw 42Opening for sensor 43Freewheel pawl ring 44Freewheel pawl 45End face of the first guide ring 46Freewheel tooth 47Wave spring 48Housing-fixed ring 49Cylindrical section 50Recess 51Guide pin 52Groove in the freewheel pawl ring 53Groove in the housing-fixed ring

Claims

1. A torque-dependently releasable shut-off clutch (1) for an electric hand-held power tool, in particular for a screwdriver, for the selective transmission of torque from a drive shaft (2) to an output shaft (3) coaxial with the drive shaft (2), comprising a cam ring (7) which is rotatably connected to the drive shaft (2) or to the output shaft (3), comprising an axially non-displaceable first guide ring (8) which is rotatably connected to the other of the drive shaft (2) and the output shaft (3), wherein the shut-off clutch (2) can be brought from a first switching position, in which the cam ring (7) is connected to the first guide ring (8) in a first direction of rotation, in particular clockwise as viewed in the axial direction from the drive shaft (2) to the output shaft (3), in a second switching position, in which the cam ring (7) is freely rotatable relative to the first guide ring (8). is,with at least one switching element (11), in particular a ball, which is guided by the first guide ring (8) in the circumferential direction and / or in the radial direction, and with a second guide ring (9), wherein the cam ring (7) and the second guide ring (9) are axially preloaded against one another and axially accommodate the at least one switching element (11) between them, wherein the cam ring (7) is designed such that, when the shut-off clutch (1) is in the first switching position, the at least one switching element (11) is deflected relative to the cam ring (7) against the effect of the preload in the axial direction when a first triggering torque acting in the first direction of rotation is exceeded, whereby the shut-off clutch (1) is brought into the second switching position.

2. Shut-off clutch (1) according to claim 1, characterized in thatthe cam ring (7) has: - at least one recess (30), in particular a ball pocket, in which the at least one switching element (11) is received in the first switching position, wherein the at least one recess (30) forms a first switching cam (31) against which the at least one switching element (11) rests in the first switching position, - a circumferentially closed freewheel track (34) on which the at least one switching element (11) can rotate in the second switching position, - and at least one diversion track (33) which connects the at least one recess (30) and the freewheel track (34) and on which the at least one switching element (11) can move from the at least one recess (30) to the freewheel track (34) and vice versa, wherein the at least one switching element (11) can be deflected in the axial direction when the first triggering torque is exceeded, and the shut-off clutch (1) can be brought into the second switching position,in that the at least one switching element (11) moves from the at least one recess (30) via the at least one diversion path (33) into the freewheel path (34).

3. Shut-off clutch (1) according to claim 2, characterized in that the axial level of the at least one discharge track (33) rises from the recess (30) in the direction of the freewheel track (34) and is always lower than or equal to the axial level of the freewheel track (34).

4. Shut-off clutch (1) according to one of the preceding claims, characterized in that the first guide ring (8) is designed as a cage ring with at least one through-opening (10) and the at least one switching element (11) is received in the at least one through-opening (10).

5. Shut-off clutch (1) according to claim 4, characterized in thatthe at least one through-opening (10) has an elongated, in particular elongated, straight shape, the direction of extension of which is inclined with respect to a radial direction.

6. Shut-off clutch (1) according to one of claims 2 to 5, characterized in that the at least one recess (30) is arranged within the cam ring (7) at a distance from its outer circumference.

7. Shut-off clutch (1) according to one of claims 2 to 6, characterized in that the freewheel track (34) has a constant axial level.

8. Shut-off clutch (1) according to one of claims 2 to 7, characterized in that the at least one discharge path (33) has at least partially the shape of a logarithmic spiral.

9. Shut-off clutch (1) according to one of the preceding claims, characterized in thatthe shut-off clutch (1) can be brought from a third switching position, in which the cam ring (7) is connected to the first guide ring (8) in a second direction of rotation opposite to the first direction of rotation, in particular counterclockwise as seen in the axial direction from the input shaft (2) to the output shaft (3), in a torque-transmitting manner, into a fourth switching position, in which the cam ring (7) is freely rotatable relative to the first guide ring (8), wherein the cam ring (7) is designed such that, when the shut-off clutch (1) is in the third switching position, the at least one switching element (11) is deflected in the axial direction relative to the cam ring (7) against the effect of the preload when a second triggering torque acting in the second direction of rotation is exceeded, whereby the shut-off clutch (1) is brought into the fourth switching position.

10. Shut-off clutch (1) according to claim 2 and according to claim 9, characterized in thatthe at least one switching element (11) is received in the at least one recess (30) in the third switching position, wherein the at least one recess (30) forms a second switching cam (32) against which the at least one switching element (11) rests in the third switching position, wherein the cam ring (7) further comprises a cam track (35) which is largely closed in the circumferential direction and interrupted only by the at least one recess (30), on which cam track the at least one switching element (11) can rotate at least in sections in the fourth switching position, wherein the at least one switching element (11) can be deflected in the axial direction when the second triggering torque is exceeded and the shut-off clutch (1) can be brought into the fourth switching position by the at least one switching element (11) moving from the at least one recess (30) into the cam track (35).

11. Shut-off clutch (1) according to one of the preceding claims, characterized in that the shut-off clutch (1) has a freewheel (43-46) which can be opened and closed, which is designed to be supported on a housing of the electric hand-held power tool, and which, in the closed state, allows rotation of the output shaft (3) in the first direction of rotation and blocks rotation of the output shaft (3) in the second direction of rotation and, in the open state, does not influence the rotatability of the output shaft (3).

12. Shut-off clutch (1) according to claim 11, characterized in thatthe freewheel (43-46) is a ratchet freewheel in which at least one freewheel pawl (44) engages with at least one freewheel tooth (46), wherein the at least one freewheel pawl (44) is arranged on an axially displaceable, non-rotatable freewheel pawl ring (43) which is axially prestressed against the at least one freewheel tooth (46), and the at least one freewheel tooth (46) is arranged on an end face (45) of the first guide ring (8).

13. Shut-off clutch (1) according to claim 12, characterized in that the freewheel (43-46) can be closed and opened by an axial displacement of the freewheel pawl ring (43), which can be effected by an axial displacement of the second guide ring (9).

14. Shut-off clutch (1) according to one of claims 12 and 13, characterized in thatthe cam ring (7) and the first guide ring (8) are arranged axially between the freewheel pawl ring (43) and the second guide ring (9) and that the second guide ring (9) or a component connected to the second guide ring (9) and axially non-displaceable relative thereto axially engages over the cam ring (7) and the first guide ring (8).

15. Electric hand tool, in particular screwdriver, with a shut-off clutch (1) according to one of the preceding claims.