Detention coupling
Patent Information
- Application Number
- ES2024163036T
- Authority / Receiving Office
- ES · ES
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2024-03-12
- Publication Date
- 2026-09-14
- Estimated Expiration
- 2044-03-12
Smart Images
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Abstract
Description
Detention coupling The invention relates to a torque-release locking coupling for a portable electric machine tool, particularly a screwdriver, for the selective transmission of torque from a drive shaft to an output shaft coaxial with the drive shaft, and to a method for operating a portable electric machine tool with such a locking coupling. The invention is described below with the example of a screwdriver. In particular, the invention is intended for use in an industrial screwdriver. However, this should not be interpreted restrictively. The invention can also be used in other portable electric handheld machine tools, such as drills or grinders.The screwdrivers considered in this document, or even battery-powered screwdrivers, are used especially for industrial serial screw connections, for example in automobile production. For threaded connections, especially those in industrial settings, a nominal tightening torque is often specified. During the tightening process, the tightening torque increases. Therefore, the screwdriver must be able to interrupt the torque transmission, and specifically switch off the screwdriver motor, when the nominal tightening torque is reached. For this purpose, such screwdrivers feature a stop coupling in their drive train, which opens when an adjustable torque is reached. Such a locking coupling is known, for example, from EP 3361114 B1. In this case, the locking coupling comprises a first coupling element and a second coupling element, which cooperate to transmit a torque, wherein at least one of the two coupling elements is movable relative to the other coupling element and is pre-tensioned by a tensioning element. The two coupling elements are form-coupled via at least one ball, so that a torque can be transmitted between them. At least one coupling element further comprises a cam element for each ball as a form-coupled element. If the torque reaches a certain value, the ball begins to rise, by means of the tangential force exerted on it, to the cam element with an elevation of less than 90 degrees (with respect to the direction of the tangential force).This is how the coupling is released or "opened" when this turning moment is exceeded. Another locking coupling is known from document DE 10 2020 130 665 A1. The two coupling elements for this coupling are a cam ring and a bridge ring, which are also axially pre-tensioned relative to each other and form-coupled by means of balls. The cam ring has a circumferentially closed cam track with at least one lead cam, with which the ball is in contact when the locking coupling is closed. If an activation torque is exceeded, the ball enters a free-running track formed in the cam ring, so that no torque can be transferred between the two coupling elements. The present invention aims to further improve a stop coupling for a portable electric machine tool and to provide a method for using a portable electric machine tool with said stop coupling. This objective is achieved by means of a stopping coupling according to claim 1, a portable electric machine tool with said stopping coupling according to claim 15, and the corresponding method for its operation. The dependent claims contain advantageous embodiments of the invention. A torque-activated stopping coupling according to the invention for a portable electric machine tool, especially for a screwdriver, features, for the selective transmission of torque from a drive shaft to an output shaft coaxial to the drive shaft: - a cam ring, which can be rotationally fixed to the drive shaft or the output shaft, and - a first axially non-slip guide ring, which can be rotationally fixed to the other drive shaft and output shaft. The locking coupling can be taken from a first switching position, in which the cam ring is linked with torque transmission to the first guide ring in a first direction of rotation, especially in the axial direction from the drive shaft to the output shaft viewed clockwise, to a second switching position, in which the cam ring can rotate freely with respect to the first guide ring. Furthermore, the stopping coupling according to the invention features: - at least one switching element, especially a ball, which is guided by the first guide ring in a circumferential and / or radial direction, and - a second guide ring, wherein the cam ring and the second guide ring are axially pre-tensioned against each other, and house at least one switching element axially against each other. The cam ring is designed so that, when the stop coupling is in the first switching position, at least one switching element is deflected when a first activation torque acting in the first direction of rotation relative to the cam ring is exceeded against the effect of the input voltage in the axial direction, so that the stop coupling is put into the second switching position. This facilitates a robust, simple-designed stop coupling that opens reliably when the first activation turning moment is exceeded, thus achieving the goal of improving the stop coupling. The housing of at least one switching element between the cam ring and the second guide ring, which are axially pre-tensioned to each other, is combined together with the guidance of the at least one switching element in a circumferential and / or radial direction through the first guide ring, so that the movement of at least one switching element is always controlled in all directions and the stopping coupling, therefore, cannot accept indefinite states. Since the initial axial stress acting on at least one switching element occurs only between the cam ring and the second guide ring, and the first guide ring is not involved, the first guide ring can be arranged axially in a non-displaceable manner according to the invention. This makes it easier to achieve a rotationally fixed connection between the first guide ring and the drive shaft. of the outlet, especially through a rigid or even one-piece joint, if the first guide ring had to be axially displaceable. Consequently, it is preferred that the cam ring not be axially displaceable, as this makes it easier to achieve a rotationally fixed connection between the cam ring and the drive or output shaft than if the cam ring were axially displaceable. Therefore, it is preferred that the second guide ring be axially displaceable instead, thus achieving the initial axial tension between the cam ring and the second guide ring, as well as the orientability of at least one switching element with respect to this initial tension. The second guide ring, however, does not participate in the transmission of torque from the drive shaft to the output shaft and therefore does not require a rotationally fixed connection to either of these shafts. The locking coupling according to the invention allows for the following application: When a threaded joint is established, especially if it consists of a screw with an external thread and a counterpiece, preferably a fastening section, particularly an opening with an internal thread, in the right-hand direction of travel of the portable machine tool, the locking coupling must open as soon as the nominal tightening torque of the threaded joint is reached. In this case, the initial activation torque must correspond to this nominal tightening torque. The primary application thus serves to protect the threaded joint from excessively high initial tension and, consequently, from potential damage to the screw or the counterpiece. In a preferred embodiment of the invention, the cam ring has: - at least one concavity, especially a ball housing, in which the at least one switching element is housed in the first switching position, where, through the at least one concavity, a first advance cam is formed, with which the at least one switching element is in contact in the first switching position, - a closed, circumferential free-running track, in which at least one switching element can rotate in the second switching position, and - at least one exit track, which connects the at least one concavity and the free-running track, and in which the at least one switching element can move from the at least one concavity to the free-running track, and vice versa. The free-running track and the at least one output track are preferably formed by respective elongated grooves in a surface of the cam ring, which preferably runs in a plane perpendicular to the axial direction. The free-running track and the at least one output track thus preferably form recesses in the surface of the cam ring, which more preferably have a cross-section in the shape of a segment of a circle. The at least one switching element is axially orientable upon overcoming the first activation torque, and the holding coupling can be placed in the second switching position, such that the at least one switching element moves to the free-running track from the at least one recess through the at least one output track. In this way, the first and second switching positions of the stop coupling can be easily and reliably defined by the position of at least one switching element in the at least one recess or on the free-running track. Through the circumferentially closed free-running track, the at least one switching element can also rotate there for as long as desired, allowing the stop coupling to remain in the second switching position, and therefore in the open state, for as long as desired. In a preferred variant of the last described embodiment of the invention, the axial level of the at least one exit track rises from the concavity in the direction of the free-running track and is always lower or of equal height to the axial level of the free-running track. An axial level is defined as a depth on the surface of the cam ring; that is, a deeper axial level means a deeper groove on the surface of the cam ring. To ensure a safe transition from the idler track to the output track, the idler track and the at least one output track preferably have different axial levels. While the idler track is preferably at a constant level, the at least one output track rises from the first advance cam to at least one recess in the cam ring, preferably at a constant rate, until it reaches the level of the idler track at the branch or junction of the two tracks. At this point, the idler track and the at least one output track preferably have the same radii or shapes and blend into a smooth profile. Due to the different axial levels of the idler track and the at least one output track, and their arrangement, a stepped transition is preferably formed between these two tracks, which is positioned transversely to the direction of travel. This stepped transition preferably forms a guide. This ensures that a change of a switching element from the at least one output track to the idler track and vice versa can only be made at the junction between the idler track and the at least one output track. The aforementioned guide at the transition between at least one output track and the free-running track can be particularly advantageous if the stop coupling has more than one switching element and, for each switching element, an output track. The guide ensures that all switching elements simultaneously change at the respective transition between the free-running track and one of the intermediate output tracks. This prevents a situation where, in the event of a change in the direction of rotation, a first switching element changes to one of the output tracks while a second switching element remains on the free-running track. In another preferred embodiment of the invention, an axial slip of the cam ring and / or the second guide ring can be achieved by means of the axial displacement of at least one switching element due to the first activation torque, and the stopping coupling further features a sensor arranged to detect this slip. The detection of axial slippage of the cam ring and / or the second guide ring can be advantageously used to detect the second switching position and, consequently, the open state of the stop coupling. During the operation of a portable machine tool with a stop coupling according to the invention, a change in the direction of rotation of the drive motor of the portable machine tool can then be activated by means of motor control, such that the at least one switching element returns from the free-running track through the at least one output track to the at least one recess, thereby causing the stop coupling to return and close again in the first switching position. In another preferred embodiment of the invention, the first guide ring is designed as a cage ring with at least one opening, and the at least one switching element is housed in the at least one opening. By forming the first guide ring as a cage ring, the housing space for the at least one switching element in the radial direction is closed off with respect to the environment, so that the at least one switching element cannot come out of the first guide ring, even with the action of centrifugal force in the rotation of the stopping coupling, and possibly in this way it can be "lost" inside the housing of the portable machine tool. In a variant of the last described embodiment of the invention, the at least one opening has an elongated shape, especially a straight elongated shape, the direction of extension of which is angled with respect to a radial direction. Alternatively, the opening may have a shape slightly different from a straight shape, for example, a slightly curved shape. An inclination of the extension direction of the at least one opening in the first guide ring with respect to a radial direction is advantageous for the radial movement of the at least one switching element during the transition of the stop coupling from the first to the second switching position, in which the at least one switching element moves radially inward. By tilting the extension direction with respect to a radial direction of the at least one opening, the at least one switching element can "slide down" with this movement to the inner wall of the at least one opening as to an oblique wall, thus reducing friction and preventing automatic immobilization between the at least one switching element and the first guide ring.In another 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 through the edge of the at least one opening. By positioning the first guide ring axially between the cam ring and the second guide ring, the at least one switching element is guided in all directions, namely axially between the cam ring and the second guide ring, as well as radially and / or circumferentially through the first guide ring. The axial projection of the at least one switching element, extending from the lateral surfaces of the first guide ring or from the edge of the at least one opening in the first guide ring, further ensures that the second guide ring can always maintain axial contact with the at least one switching element without colliding with the edge of the at least one opening. The edge of the at least one opening is preferably in a plane with a lateral surface of the first guide ring.Similarly, it is ensured that the cam ring is always in axial contact with the at least one switching element, without colliding with the edge of the at least one 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 so that the above holds true in every axial position of the at least one switching element in the grooves in the cam ring or in the at least one opening in the first guide ring. In one embodiment of the invention with at least one concavity in the cam ring, the at least one concavity is arranged within the cam ring. This means that the concavity, preferably in the form of a recess or a ball housing, is positioned at a distance from the outer circumference of the cam ring. Preferably, the outer circumference of the cam ring in the area of the concavity is higher than the concavity, such that the concavity closes radially outward. Similar to the formation of the first guide ring as a cage ring, this can have the advantage that at least one switching element also does not come out of the cam ring with the action of the centrifugal force in the rotation of the stopping coupling and possibly in this way cannot be "lost" inside the housing of the portable machine tool. In a variant of the last described variant of the invention, the at least one concavity has an elongated shape, transitions at one end to the at least one output track, and has a deeper axial level than the at least one output track. The transition from the concavity to the output track forms the first advance cam. This embodiment of the at least one concavity provides a simple way to form the first advance cam in the grooves of the cam ring and allows the at least one switching element, after passing the first advance cam, to make a direct transition to the at least one output track. The deeper axial level of the at least one concavity compared to the axial level of the at least one output track simultaneously achieves the desired axial deflection of the at least one switching element as it passes the first advance cam. In a variant of the last described variant of the invention, the transition at the first end of the at least one concavity from the at least one concavity to the at least one exit track, viewed in the extension direction of the at least one concavity and the at least one exit track, occurs in an essentially smooth manner. This can cause a smooth and separate movement from the jerk caused by overcoming the first advance cam without jerking of at least one switching element in its path from at least one concavity to at least one exit track. In a variant of the embodiment of the invention with at least one concavity, a free-running track and at least one exit track in the cam ring, the free-running track has a constant axial level. This can result in a particularly smooth movement of at least one switching element in the second switching state. This leads to a shifting procedure with minimal wear, vibration, and / or noise. Furthermore, the constant axial level of the free-running track prevents any additional axial deviation of at least one switching element and the associated axial slippage 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 improved engagement. In another embodiment of the invention with at least one concavity, a free-running track and at least one exit track in the cam ring, the at least one exit track has at least partially the shape of a logarithmic spiral. This can also cause a smooth, jerk-free, radially inward movement of at least one switching element on at least one output track. In another preferred embodiment of the invention, the locking coupling can be taken from a third switching position, in which the cam ring is torque-driven to the first guide ring in a second direction of rotation, opposite to the first direction of rotation, especially axially from the drive shaft to the output shaft viewed counterclockwise, to a fourth switching position, in which the cam ring can rotate freely with respect to the first guide ring. The cam ring is designed so that, when the stop coupling is in the third switching position, at least one switching element is deflected when a second trigger torque acting in the second rotational direction relative to the cam ring is exceeded, counteracting the effect of the input voltage in the axial direction, so that the stop coupling is placed in the fourth switching position. This provides a simple, robust, and reliably opening stop coupling that opens when the second activation torque is exceeded. This embodiment of the locking coupling according to the invention particularly facilitates the following second application case: When loosening a threaded connection rotating to the left of the portable machine tool, in the case of a hard-seated threaded connection, the torque required to loosen it may be greater than the motor's maximum torque. Operating the portable machine tool with such a high torque could damage the motor. Therefore, the locking coupling must open before the motor's maximum torque is reached. In this case, the second activation torque must therefore be slightly lower than the motor's maximum torque. The second application case thus consists of protecting the portable machine tool's motor from overload and damage. In a preferred embodiment of the last described embodiment of the invention, in which at least one concavity is further provided in the cam ring, the at least one switching element is housed in the at least one concavity in the third switching position. A second advance cam is formed by means of this concavity, with which the at least one switching element is in contact in the third switching position. The cam ring further has a cam track that is largely closed in the circumferential direction and interrupted only by the at least one concavity, in which the at least one switching element can circulate in the fourth switching position, at least in sections. Furthermore, the at least one switching element is axially orientable once the second activation torque is exceeded, and the locking coupling can be placed in the fourth switching position, such that the at least one switching element moves from the at least one recess to the cam track. With this embodiment of the cam ring, essentially the same advantages described above for the first and second switching positions can be achieved, namely, that the third and fourth switching positions of the locking coupling can be defined simply and reliably by the position of the at least one switching element in the at least one recess or on the cam track. However, unlike the second switching position, the fourth switching position is only maintained until the at least one switching element falls from the cam track to the next recess.However, the duration of this movement may be sufficient to detect the fourth switching position and react to it. In a preferred variant of the last described embodiment of the invention, the at least one concavity has an elongated shape, changes at a second end to the cam track, and has a deeper axial level than the cam track, where through this transition the second advance cam is formed. This can lead to corresponding advantages, as in the variant described above, in which the at least one concavity changes at a first end to the at least one exit track and has a deeper axial level than the at least one exit track, where by this transition a first advance cam is formed. Preferably, the second end of the at least one concavity with respect to its elongated shape is opposite to said first end. In another preferred variation of the last described embodiment of the invention, an axial slip of the cam ring and / or the second guide ring can be achieved by means of the axial displacement of at least one switching element due to the second activation torque, and the stopping coupling further features a sensor arranged to detect this slip. Similar to the previous method for the second switching position, this can be used to detect the fourth switching position and, consequently, the open state of the stop coupling. However, after this detection, reversing the engine's direction of rotation is not necessary, since in this case at least one switching element can remain on the cam track and can also return to a concave position if the engine continues to rotate in the same direction. This concave position is then the next concave position in the circumference, and in this way, the stop coupling can also return to the third switching position. Naturally, 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 slippage of the cam ring and / or the second guide ring is detected. In a preferred variant of those variants of the invention in which the first and second lead cam are formed respectively by a transition to a first or a second end of the at least one concavity, the inner wall of the at least one concavity is more inclined at its second end than the inner wall of the at least one concavity at its first end, so that the second activation torque is greater than the first activation torque. The described relationship, whereby the activation torque is greater the steeper the transition at the respective end of the at least one recess, results directly from the combined action described above of the at least one switching element with the respective inner wall of the at least one recess (the "ramp") in the wedge gear sense. It may be advantageous for the second activation torque to be greater than the first activation torque, since the maximum torque of the motor, according to which the second activation torque is dimensioned, is generally greater than the nominal tightening torque of a bolted joint, according to which the first tightening torque must be dimensioned. In another preferred variant of the last described embodiment of the invention, the cam track exhibits, except in the area of at least one concavity, a constant axial level. In this way, the same advantages can be achieved as with the corresponding implementation with a constant axial level of the free-running track, namely, that in this case the transition from the third to the fourth switching position can be reliably detected. In another preferred embodiment of the invention, the stopping coupling features an openable and closeable freewheel, which is designed to rest on a housing of the portable electric machine 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. A freewheel with these functions is advantageous when, in the second switching position, the motor's direction of rotation is reversed from the first to the second direction of rotation. This is done to return at least one switching element from the freewheel track, through at least one output track, to at least one recess. In this case, the output shaft must be prevented from rotating as well, since otherwise the required relative rotation between the drive shaft and the output shaft is not achieved. Therefore, the freewheel can be closed, thus blocking the rotation of the output shaft in the second direction of rotation, preventing it from rotating together in that direction. In a preferred embodiment of the last described embodiment of the invention, the freewheel is a ratchet freewheel, wherein at least one freewheel pawl engages with at least one freewheel tooth. The at least one freewheel pawl is arranged in an axially sliding, non-rotating, axially pre-tensioned freewheel pawl ring against the at least one freewheel tooth, and the at least one freewheel tooth is arranged on a front side of the first guide ring. The ratchet-type freewheel design is a standard implementation and is therefore easy to manufacture. Using the first guide ring to accommodate at least one freewheel tooth can be particularly advantageous, as it eliminates the need for any additional parts to position the freewheel tooth. In a preferred variant of the above-described variant of the invention, the freewheel can be closed and opened by an axial sliding of the freewheel ratchet ring, which can be effected by an axial sliding of the second guide ring. 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 axial slippage of the second guide ring, it is also advantageous to cause the opening and closing of the freewheel by means of this slippage. Because the freewheel ratchet ring is axially sliding, it is also advantageous to cause the opening and closing of the freewheel by means of this axial slippage of the freewheel ratchet ring. In this way, the existing movement possibilities of the parts in question are utilized for the opening and closing of the freewheel. The axial sliding action of the free-running ratchet ring by the axial sliding of the second guide ring can thus be either direct or indirect. In the case of direct action, the free-running ratchet ring can bear directly axially on the second guide ring. In the case of indirect action, at least one more force-transmitting element can be arranged between the second guide ring and the free-running ratchet ring, particularly an element attached to the second guide ring and axially sliding with it but not rotating independently. In a preferred variant of the above-described variant of the invention, the cam ring and the first guide ring are arranged axially between the free-running ratchet ring and the second guide ring, and the second guide ring or a piece attached to the second guide ring and not axially sliding with respect to it axially reaches the cam ring and the first guide ring. If the opening and closing of the freewheel are effected by axial sliding of the second guide ring and a resulting axial sliding 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 still axially positioned in between, this can be easily achieved if the second guide ring, or a part attached to the second guide ring and not axially sliding relative to it, axially reaches the latter two parts. This also includes the case where the axial sliding of the freewheel pawl ring is achieved indirectly by the axial displacement of the second guide ring, and another force-transmitting part attached to the second guide ring, but not axially sliding relative to it, axially reaches the cam ring and the first guide ring.In another preferred variant of the last described embodiment of the invention, the free pinion is open in the first switching position and closed in the second switching position. This corresponds to the requirement that the freewheel must be closed if, 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, to prevent the output shaft from rotating together in the second direction of rotation. Because, in contrast to this, it is not necessary to reverse the direction of rotation of the motor after the transition from the third to the fourth switching position, as described above, in this case it is irrelevant whether the freewheel is closed or open. The invention also relates to a portable electric machine tool, especially a screwdriver, with a locking coupling according to the invention. This allows for the reliable and simple implementation of the two applications described above for clockwise or counterclockwise rotation of the portable machine tool's motor. The invention also relates to a method for operating a portable electric machine tool, especially a screwdriver, with a stop coupling according to the invention, comprising the following steps: - drive shaft in the first direction of rotation, with the stop coupling in the first switching position, - stopping the rotation of the drive shaft when a torque is applied in the first direction of rotation, which exceeds the first activation torque, where the stopping coupling is brought to the second switching position by overcoming the first activation torque, - drive the drive shaft in the second direction of rotation, so that the stop coupling is brought back to the first switching position. This corresponds to the first application case already described in detail above, in which the stopping coupling must open as soon as the nominal tightening torque of the bolted joint is reached, and then it must close again. The invention also relates to a method for operating a portable electric machine tool, especially a screwdriver, with a stop coupling, which can also be taken to the third and fourth switching positions, comprising the following steps: - drive shaft in the second direction of rotation, with the stop coupling in the third switching position, - additional drive of the drive shaft in the second direction of rotation, when a torque is applied in the second direction of rotation, which exceeds the second activation torque, where the stop coupling is brought to the fourth switching position by exceeding the second activation torque, - Additional drive of the drive shaft in the second direction of rotation, so that the stop coupling is brought back to the third switching position. This corresponds to the second application case also described in detail above, in which the stopping coupling must open before the maximum torque of the motor is reached, to protect the motor from overload, and then it must close again. Other advantages, features, and application possibilities of the present invention are derived from the following description in relation to the figures. It is shown: Fig. 1 a side view of a stopping coupling according to the invention; Fig. 2 a cross-sectional view of the detent coupling according to Fig. 1; Fig. 3 an exploded view of the stop coupling according to Fig. 1; Fig. 4 The parts of the detent coupling according to Fig. 1, which form the coupling mechanism; Fig. 5 the front side of the cam ring of the detent coupling according to Fig. 1; Fig. 6 The parts of the stop coupling according to Fig. 1 that form the return mechanism. The invention is described in detail below by means of a single embodiment of a locking coupling 1 according to the invention. Figures 1, 2, and 3 show the entire locking coupling 1 in different views, namely, a side view (Fig. 1), a sectional view (Fig. 2), and an exploded view (Fig. 3). Figures 4, 5, and 6 show individual parts or partial modules of the locking coupling 1, namely, the coupling mechanism that opens and closes the locking coupling 1 (Fig. 4), the front side of the cam ring 7 with the various grooves 30 to 35 for the balls 11 (Fig. 5), and the return mechanism, which closes a freewheel when the locking coupling 1 opens (Fig. 6). The stop coupling 1 is intended for mounting on a portable electric rotary machine tool (not shown in the figures), especially a screwdriver, as used, for example, in industrial production. The stop coupling 1 is arranged in the drive train of the portable machine tool between the drive motor and a tool holder, particularly for a screw-driving tool, such as a screwdriver blade or an internal or external hex key. However, the stop coupling 1 according to the invention can also be used on other portable machine tools. All parts of the locking coupling 1 are arranged essentially coaxially with respect to an axis, which also forms the axis of rotation of the rotating parts. The locking coupling 1 is supported by a fixed housing ring 48 in the housing (not shown) of the portable machine tool and is rigidly connected at this point, either directly or indirectly, to the housing. The stopping coupling 1 has a drive shaft 2, the outer end of which is shaped like an external hexagon 20. The external hexagon 20 is designed for a permanent, form-fixed, and rotationally fixed coupling with the drive motor (not shown) of the portable machine tool. Coaxial to the drive shaft 2, the stopping coupling 1 has an output shaft 3, the outer end of which has an internal hexagon 21. The internal hexagon 21 is intended for the rotationally fixed, form-fixed housing of interchangeable tools, particularly screw-driving inserts of any type (not shown). The tools are preferably inserted into the internal hexagon 21 by hand and are preferably held by friction, a locking mechanism, or magnetically. The drive shaft 2 and the output shaft 3 are rotatably housed against each other by means of a ball bearing 17. The balls of the ball bearing 17 are individually loaded into the stop coupling assembly 1 by means of a radial hole in the outer bushing on the drive shaft 2, and this hole is then sealed with a plug 18. The stopping coupling 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 portable machine tool is in the closed position. As soon as the torque transmitted from the drive shaft 2 to the output shaft 3 exceeds a certain adjustable activation torque, the stopping coupling 1 opens, preventing further torque transmission from the drive shaft 2 to the output shaft 3. In particular, the opening of the stopping coupling 1 when the activation torque is exceeded must support the two application cases described above: When making a threaded connection with clockwise rotation on the portable machine tool, the stop coupling 1 must open as soon as the nominal tightening torque of the threaded connection is reached (first application case). However, when loosening a threaded connection with counterclockwise rotation on the portable machine tool, the stop coupling 1 must open if the required loosening torque is greater than the maximum torque of the motor, to protect the portable machine tool motor from overload (second application case). Because the two application scenarios differ, the required activation torque may also differ. Especially in the first application scenario, since the nominal tightening torque varies from one threaded joint to another, the activation torque must be preselected by the portable machine tool operator. To achieve the desired opening of the locking coupling 1 when the respective activation torque is exceeded during clockwise or counterclockwise rotation, the drive shaft 2 is rotationally fixed and, in the one-piece embodiment, connected to a cam ring 7. On the front side of the cam ring 7, axially directed towards the output shaft 3, several grooves with varying axial levels are formed. These grooves are designed to accommodate several balls 11 (in embodiment three) and allow them to move essentially circumferentially. The exact arrangement and operation of the grooves in the cam ring 7 are described in detail below. For each ball 11, at least one position is provided in the grooves of the cam ring 7 where the axial level of the groove changes discontinuously.In other words, the groove in this position presents an axial step. However, the "vertical" wall of the step does not run exactly in the axial direction, but is angled towards it; that is, the step from the lower axial level (in the sense of a deeper groove on the front side of the cam ring 7) to the higher axial level forms an inclined, but not vertical, ramp. In the closed state of the locking coupling 1, the ball 11 is located in the groove on the side of the step with the lower axial level and is in contact with the step such that, with a predetermined direction of rotation of the drive shaft 2 in a circumferential direction, the step presses against the ball 11. In this way, in this state of the locking coupling 1, a torque can first be transmitted from the cam ring 7 to the ball 11.The stop coupling 1 is then in a first switching position. Axially adjacent to the cam ring 7 there is a first guide ring 8 which is rotationally fixed to the output shaft 3 in the one-piece embodiment. Therefore, both the cam ring 7 and the first guide ring 8 are not axially movable. The first guide ring 8 has an opening 10 for each ball 11, into which the portion of the ball 11 that protrudes axially above the cam ring 7 is guided. Each opening 10 is designed in a straight line, i.e., in the form of an elongated hole, and extends in the first guide ring 8 from a radially outward end to a radially inward end in a direction oblique to the radial direction. The radially outward end of the elongated hole is positioned at a distance from the outer circumference of the first guide ring 8. In this way, the entry of each ball 11 into an elongated hole is forced. The loss of a ball 11 is not possible.The axial expansion of the first guide ring 8 is dimensioned such that each ball 11, in any possible position it may occupy in a groove in the cam ring 7, is in contact with the inner walls of the corresponding opening 10 with its largest diameter, and such that at the same time a portion of the ball 11 protrudes axially from the opening 10 on the side opposite the cam ring 7. The first guide ring 8, with the openings 10 arranged therein, thus acts as 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 thereby to the output shaft 3. On the opposite side of the cam ring 7 from the first guide ring 8, a second guide ring 9 is arranged, the front surface of which, facing the first guide ring 8, is completely flat. The second guide ring 9 is mounted on the output shaft 3 in a rotatable and axially sliding manner, preferably by means of a plain bearing. The second guide ring 9 is axially pre-tensioned against the cam ring 7, as will be explained in more detail below, so that its smooth front surface is pressed against the balls 11. In this way, the balls 11 are forced in all directions, i.e., axially through the grooves in the front side of the cam ring 7 and through the smooth front side of the second guide ring 9, as well as radially and circumferentially through the openings 10 in the first guide ring 8. This forced guidance of the balls 11 prevents them from moving uncontrollably during the rotation of the drive shaft 2 and the output shaft 3 and from being lost inside the housing of the portable machine tool. From the description made so far it is clear that in the closed state of the locking coupling 1 a torque can be transmitted from the drive shaft 2 through the cam ring 7, the balls 11 and the first guide ring 8 to the output shaft 3. The second guide ring 9 does not participate in the transmission of the torque itself, but forms part of the axial guidance of the balls 11. As mentioned previously, each ball 11 in the closed state of the detent coupling 1 sits on the corresponding step in a groove on the front side of the cam ring 7, where the step forms an inclined, but not vertical, ramp. A torque can be transmitted in the predefined direction of rotation of the drive shaft 2 from the ramp to the ball 11. The surface of the ball 11 and the ramp thus form a wedge engagement. Simultaneously, the ball 11 is axially pre-tensioned against the front surface of the cam ring 7 by the second guide ring 9. This initial tension is dimensioned such that when the transmitted torque between the ramp and the ball 11 exceeds a first activation torque, the ball 11 "rises" due to the wedging action on the ramp and enters the axially highest part of the groove in the front surface of the cam ring 7. As explained in more detail below, this notch is arranged so that the ball 11 can move freely in the axially highest part of the notch in a circumferential direction. Thus, in this state of the locking coupling 1, no additional torque can be transmitted between the cam ring 7 and the ball 11, and therefore also not between the drive shaft 2 and the output shaft 3. The locking coupling 1 is then in a second switching position and in the open state. The ramp in the groove on the front surface of the cam ring 7 thus acts as a first advance cam 31, whose passage through the ball 11 in a first direction of rotation causes the locking clutch 1 to transition from the closed to the open state. In a second direction of rotation, opposite to the first direction of rotation, this ramp also acts as a first advance cam 31, whose passage through the ball 11 causes the locking clutch to transition from the open to the closed state. The front side of the cam ring 7, with the grooves therein for the balls 11, is now described in detail. In the exemplary embodiment, three balls 11 are provided, and the front side of the cam ring 7 has grooves for each ball 11, offset by 120 degrees, thus creating triple rotational symmetry. The notches for a ball 11 comprise first an elongated ball housing 30, which has a deeper axial level than all other notches on the front side of the cam ring 7. The ball housing 30 extends approximately in the circumferential direction, but is slightly curved radially inwards at one end. The two ends of the ball housing 30, where the deep axial level of the ball housing 30 changes to the higher axial level of the surroundings of the ball housing 30, thus form a first lead cam 31 for a torque transmission with a right-hand rotation or a second lead cam 32 for a torque transmission with a left-hand rotation from the drive shaft 2 to the output shaft 3. When the drive shaft 2 rotates clockwise and the first activation turning moment is overcome, the ball 11 passes the first advance cam 31, as described above, and enters the next output track 33, which spirals radially inwards. The output track 33 is preferably shaped like a logarithmic spiral to allow for smooth, jerk-free movement of the ball 11. The slight inward radial curve of the ball housing 30 is also selected so that it transitions smoothly to the output track 33, again to allow for smooth, jerk-free movement of the ball 11. Simultaneously with its radial inward movement in the output track 33, the ball 11 also moves radially inward along the longitudinal expansion of the opening 10 in the first guide ring 8. Because the opening 10 is not arranged radially, but is angled with respect to a radial direction, the ball 11 can slide downward at an oblique angle on the inner surface of the opening 10, thus reducing friction and preventing possible automatic immobilization during the movement of the ball 11 in the opening. The output track 33 leads into the inner radial zone of the front side of the cam ring 7 in a closed circular free-running track 34 with a constant axial level, in which the ball 11 can rotate along any length. If the ball 11 is located in the output track 33 or in the free-running track 34 and is therefore not opposed by any mechanical resistance in the circumferential direction, the torque can no longer be transmitted from the drive shaft 2 to the output shaft 3. Therefore, the stopping coupling 1 is then in the open state and thus prevents the nominal tightening torque of a threaded joint from being exceeded. Because the output track 33 and the free-running track 34 have a higher axial level than the ball housing 30, the ball 11 moves axially towards the output shaft 3. In this way, the second guide ring 9, which is pre-tensioned against the balls 11 and the cam ring 7, is displaced in this axial direction. The second guide ring 9 is rotatably mounted relative to a sliding ring 40, whose function will be described in more detail, via a ball bearing 6, such that the sliding ring 40 itself does not rotate. The second guide ring 9 and the sliding ring 40 are joined together via the ball bearing 6 as a single unit and, therefore, cannot move axially relative to each other, but can only move together axially. The sliding ring 40 has an opening 42 on its outer perimeter that can house a position indicator, for example, a permanent magnet (not shown). A corresponding sensor, for example, a magnetic sensor (also not shown), is fitted in the housing of the portable machine tool. This sensor can detect the axial movement of the position indicator and, consequently, of the sliding ring 40. Due to the axial sliding of the sliding ring 40, the sensor recognizes that the stopping coupling 1 has moved to the open state and sends the corresponding signal to the drive motor control of the portable machine tool. This shuts off the motor. After the motor's rotational movement stops, the direction of rotation of the drive shaft 2 is reversed. The ball 11, which travels clockwise in the free-running track 34 (in the orientation of the cam ring 7 shown in Figure 5), now travels counterclockwise after the reversal of the direction of rotation and thus reaches the "branch" or outlet 36 of one of the output tracks 33 again, and at its ends, the corresponding ball housing 30 once more.The guide 37, formed by the arrangement and different levels of the free-running track 34 or the exit track 33, ensures that at the outlet 36, the ball 11 always moves from the free-running track 34 to the exit track 33. This is especially important if the stop coupling 1 comprises more than one ball 11. It prevents one ball 11 from being on the free-running track 34 while another ball 11 is on the exit track 33. This ensures that the stop coupling 1 opens and closes safely for the process. The repeated axial movement of the sliding ring 40, linked to the transfer of the ball 11 to the ball housing 30 in the direction of the drive shaft 2, is detected by the sensor, after which the motor control stops the motor's rotation. The stop coupling 1 then returns to the closed state. With a leftward rotation of the drive shaft 2, the ball 11, instead, is in contact with the end opposite the first advance cam 31 of the ball housing 30 in the second advance cam 32, so that a turning moment of the cam ring 7 can be transmitted to the ball 11 and, as described above, via the first guide ring 8, to the output shaft 3. The stopping coupling 1 is then in a third switching position. If, with leftward rotation of the drive shaft 2, the second activation torque is now exceeded, the ball 11 passes the second advance cam 32 and reaches the next cam track 35. The cam track 35 runs on the outer radial edge of the cam ring 7 in a circular shape and concentric with respect to the free-running track 34 and is interrupted only by the ball housings 30. Thus, the cam track 35, apart from the ball housings 30, has a constant axial level that is higher than that of the ball housings 30. Preferably, the ramp at the end of the ball housing 30 formed by the second advance cam 32 is steeper than the ramp at the end of the ball housing 30 formed by the first advance cam 31. Preferably, the second activation torque is also greater than the first activation torque. On cam track 35, ball 11 can travel at least as far as the next ball housing 30, i.e., through a rotation angle range of 5 to 120 degrees, without encountering any mechanical resistance in the circumferential direction. Thus, during this movement of ball 11, no torque can be transmitted from the drive shaft 2 to the output shaft 3. The locking coupling 1 is then in a fourth switching position. In this fourth switching position, the locking coupling 1 is also open and prevents the maximum torque of the motor from being exceeded, especially when it is insufficient to loosen a threaded connection. In this case as well, the sliding ring 40 moves axially when the stopping coupling 1 opens, which is detected by the sensor. The motor control then allows the motor to continue rotating to the left, for example at a reduced speed, until each ball 11 falls back into its corresponding ball housing 30. Reversing the direction of rotation beforehand is not necessary in this case. The stopping coupling 1 then returns to its closed state. It is even possible to stop allowing the motor to continue running at a reduced speed, since, at the latest, with the next use of the portable machine tool, whether rotating to the right or left, the balls 11 will fall back into the ball housings 30 and the stopping coupling 1 will return to its closed state by then. The first and second activation torques can be preset depending on the desired application, especially depending on the nominal tightening torque of a threaded joint to be made, through the initial axial tension of the second guide ring 9 against the balls 11 and the cam ring 7. This initial tension is generated by an axially pre-tensioned compression spring 12, designed as a coil spring, which runs around the output shaft 3. The compression spring 12 is supported at one end by the second guide ring 9 and at the other end by a thrust ring 13. On its inner face, the thrust ring engages with a shoulder (not shown) in a flattening 5 (Fig. 6) on the output shaft 3 and is therefore axially sliding relative to the output shaft 3 but cannot rotate. On the face opposite the compression spring 12 of the thrust ring 13, an adjusting ring 15 is threaded onto a thread 4 of the output shaft 3. The thread 4 is preferably a left-hand thread.On the front side facing the adjusting ring 15 of the thrust ring 13, several (in the embodiment, six) retaining balls 14 are inserted at equal angular distances. These balls can engage with several (in the embodiment, twelve) holes 16, also arranged at equal angular distances, on the opposite front side of the adjusting ring 15. The adjusting ring 15 can thus be rotated against the elastic force of the compression spring 12 by a predetermined angle (in the embodiment, 30 degrees). This is perceived by the user as individual retention steps, allowing the ring to be screwed onto the output shaft 3 or unscrewed from the output shaft 3. With each retention step, the initial tension of the compression spring 12 increases or decreases, and with it the first and second activation torques.The adjustment ring 15 is surrounded on the portable machine tool by a drive ring (not shown), preferably made of a manageable plastic, which can be easily adjusted by the user by hand. As described above, the motor's direction of rotation is momentarily reversed from clockwise to counterclockwise when the motor's right-hand coupling opens after the first activation torque is exceeded. This allows the balls 11 to retract, by means of a relative rotation of the drive shaft 2 and therefore the cam ring 7 with respect to the balls 11 to the left (i.e., counterclockwise), back into their ball housings 30. In this way, the stopping coupling 1 closes again after opening. Because the balls 11 are forced by the first guide ring 8, and the first guide ring 8 is rotationally fixed to the output shaft 3, it is essential to prevent the output shaft 3 from rotating in conjunction with the left-hand rotation of the drive shaft 2; otherwise, the relative rotation between the drive shaft 2 and the output shaft 3 will not occur. The simultaneous rotation of the output shaft 3 can be prevented, for example, by ensuring that the tool remains engaged with the screw after reversing the motor's direction of rotation. However, in practical use of the portable machine tool, it cannot be guaranteed that the user will keep the tool engaged with the screw immediately after the screw reaches its rated tightening torque and the corresponding opening of the locking coupling 1. As soon as the tool is no longer engaged with the screw, simultaneous rotation of the output shaft 3 cannot be ruled out. In order to reliably prevent the joint rotation of the output shaft 3 in each state of the stopping coupling 1 after reversing the direction of rotation of the motor, i.e., during the leftward rotation of the motor, the stopping coupling 1 has a return mechanism which will be described below (see also Figure 6). The return mechanism is activated when the locking coupling 1 is opened by the axial movement of the sliding ring 40 described above. As can be seen more clearly in Fig. 2, the sliding ring 40 reaches outward radially with several claws 41 (three in the embodiment) oriented in the direction of the drive shaft 2 and distributed around the perimeter of the sliding ring 40, the second guide ring 9, the first guide ring 8, the balls 11, and the cam ring 7. The claws 41 bear against a radially outward area of the front surface of a free-running ratchet ring 43, which has a diameter approximately equal to that of the sliding ring 40 and therefore 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 may also have a cylindrical rotating side surface, which is also supported on the outer radial area of the front surface of the free-running ratchet ring 43. The free-running ratchet ring 43 can slide axially but cannot rotate, as it is guided axially by several axially arranged guide pins 51. For this purpose, the free-running ratchet ring 43 has grooves 52, which, together with the guide pins 51, form an axial sliding guide. The guide pins 51 are, in turn, connected on the outer face of a cylindrical section 49 of a fixed housing ring, rigidly attached to it, such that they are inserted into grooves 53 in the cylindrical section 49 of the fixed housing ring 48. The fixed housing ring 48 is rigidly attached via several recesses 50 around its perimeter with raised sections (not shown) to the portable machine tool housing and is therefore neither axially sliding nor rotatable.In this way, the free-running ratchet ring 43 is axially slidably housed in the cylindrical section 49 of the housing fixed ring 48, but cannot rotate due to the guidance of the guide pins 51. The housing fixed ring 48 also serves to support a ball bearing 22 radially from the outside, in which the drive shaft 2 is housed. The bearing between the housing fixed ring 48 and the drive shaft 2 is further secured by a retaining ring 19. Furthermore, between a flange of the housing fixed ring 48 with a diameter larger than that of the cylindrical section 49 and a flange of the free-running ratchet ring 43 with approximately the same diameter as the flange of the housing fixed ring 48, there is a wave-like compression spring 47, which pre-tensions the free-running ratchet ring 43 axially in the direction of the output shaft 3. Instead of a wave-like compression spring, another compression spring, especially a spiral spring, can also be used for this purpose. The elastic force of the wavy compression spring 47 is always less than the elastic force of the compression spring 12, so that the initial tension of the sliding ring unit 40 and the second guide ring 9 against the balls 11 is not suppressed. The free-running pawl ring 43 has several projections distributed along its perimeter on its front side facing the guide ring 8, which serve as free-running pawls 44 (Fig. 6). The front side 45 of a cylindrical addition to the first guide ring 8, which extends radially outward from the cam ring 7 axially, has a sawtooth course when viewed in the circumferential direction. This forms several free-running teeth 46 into which the free-running pawls 44 can engage. In the open state of the detent coupling 1, when the balls 11 are outside the ball housings 30, the free-running pawl ring 43 is axially pressed against the first guide ring 8 by the elastic force of the wave compression spring 47. Then the free-running pawls 44 can mesh with the free-running teeth 46, and the free-running pinion is in the closed state.The direction of the sawtooth path of the front side 45 of the added cylindrical piece of the first guide ring 8 and therefore the arrangement of the free-running teeth 46 is selected so that the first guide ring 8 and therefore the output shaft 3 can only rotate to the right, but not to the left. When the stop coupling 1 is closed, the claws 41 of the sliding ring 40 axially press the free-running pawl ring 43 against the elastic force of the wavy compression spring 47 axially away from the first guide ring 8, so that the free-running pawls 46 cannot engage the free-running teeth 46 and the freewheel is open and has no effect. When the stop coupling 1 is open, the claws 41 of the sliding ring 40 do not press against the free-running pawl ring 43, since the sliding ring 40 and the second guide ring 9 are moved axially by the balls 11 in the direction of the output shaft 3. This causes the wave compression spring 47 to press the free-running pawl ring 43 axially against the first guide ring 8, allowing the free-running pawls 44 to engage the free-running teeth 46 and the freewheel to close. This results in the desired behavior of the freewheel, which closes only when the stop coupling 1 is open, at which point the direction of rotation of the motor is also reversed, thus preventing the output shaft 3 from rotating in conjunction with the leftward rotation of the motor. If, during a leftward rotation of the engine, the stopping coupling 1 opens due to exceeding the second activation torque, the freewheel closes, and the balls 11 are in the cam track 35. However, this has no further consequences, since, as described above, in this case the balls do not have to return from the freewheel track 34 to the ball housings 30, and therefore a reversal of the engine's direction of rotation is not required, which would have prevented a joint rotation of the output shaft 3. The change of state from open to closed of the freewheel has no effect when the stopping coupling 1 opens during leftward engine rotation. List of numerical references 1. Stop coupling 2 Drive shaft 3 Output shaft 4 Thread 5 Flattening 6 Ball bearing 7 Cam ring 8 First guide ring 9 Second guide ring 10 Opening 11 Ball 12 Compression spring 13 Thrust ring 14 Retaining ball 15 Adjustment ring 16 Hole 17 Ball bearing 18 Plug 19 Security ring 20 Outer Hexagon 21 Inner Hexagon 22 Ball bearing 30 Ball housing, concavity 31 First advance cam 32 Second advance cam 33 Starting runway 34 Free walking track 35 Cam track 36 Branching / Mouth 37 Guide 40 Sliding ring 41 Claw 42 Sensor opening 43 Retaining ratchet ring 44 Retaining ratchet 45 Front side of the first guide ring 46 Freewheel tooth 47 Wave compression spring 48 Fixed housing ring 49 Cylindrical section 50 Notch 51 Guide pin 52 Slot in the retaining ratchet ring 53 Slot in the fixed housing ring
Claims
1. A torque-activated locking coupling (1) for a portable electric machine tool, especially a screw gun, for selectively transmitting torque from a drive shaft (2) to an output shaft (3) coaxial with the drive shaft (2), comprising a cam ring (7) that can be rotationally fixed to either the drive shaft (2) or the output shaft (3), and a first axially non-slidable guide ring (8) that can be rotationally fixed to the other drive shaft (2) and output shaft (3). The locking coupling (2) can be brought from a first switching position, in which the cam ring (7) is torque-transmitting to the first guide ring (8) in a first rotational direction, especially axially from the drive shaft (2) to the output shaft (3) viewed clockwise, to a second switching position.wherein the cam ring (7) can rotate freely with respect to the first guide ring (8), with at least one switching element (11), especially a ball, which is guided by the first guide ring (8) in a circumferential and / or radial direction, and with a second guide ring (9), wherein the cam ring (7) and the second guide ring (9) are axially pre-tensioned against each other and house the at least one switching element (11) axially with respect to each other, wherein the cam ring (7) is designed such that, when the detent coupling (1) is in the first switching position, the at least one switching element (11) is deflected when a first activation torque acting in the first direction of rotation relative to the cam ring (7) is exceeded, counteracting the effect of the initial axial tension,so that the stopping coupling (1) is placed in the second switching position.
2. Stopping coupling (1) according to claim 1, characterized in that the cam ring (7) has: - at least one recess (30), especially a ball housing, in which the at least one switching element (11) is housed in the first switching position, where, through the at least one recess (30), a first advance cam (31) is formed, with which the at least one switching element (11) is in contact in the first switching position, - a circumferentially closed free-running track (34), in which the at least one switching element (11) can rotate in the second switching position, - and at least one exit track (33), which connects the at least one recess (30) and the free-running track (34),and wherein the at least one switching element (11) can be moved from the at least one recess (30) to the free-running track (34), and vice versa. wherein the at least one switching element (11) is axially orientable upon overcoming the first activation rotation moment and the stopping coupling (1) can be placed in the second switching position, such that the at least one switching element (11) moves to the free-running track (34) from the at least one recess (30) through the at least one output track (33).
3. Stopping coupling (1) according to claim 2, characterized in that the axial level of the at least one output track (33) rises from the recess (30) in the direction of the free-running track (34) and is always at a height lower than or equal to the axial level of the free-running track (34).
4. Detention coupling (1) according to any of the preceding claims,characterized in that the first guide ring (8) is designed as a cage ring with at least one opening (10) and the at least one switching element (11) is housed in the at least one opening (10).
5. Detent coupling (1) according to claim 4, characterized in that the at least one opening (10) has an elongated shape, especially a straight elongated shape, the direction of extension of which is angled with respect to a radial direction.
6. Detent coupling (1) according to any one of claims 2 to 5, characterized in that the at least one concavity (30) within the cam ring (7) is spaced from its outer circumference.
7. Detent coupling (1) according to any one of claims 2 to 6, characterized in that the free-running track (34) has a constant axial level.
8. Detent coupling (1) according to any one of claims 2 to 7,characterized in that the at least one output track (33) is at least partially in the form of a logarithmic spiral.
9. Detent coupling (1) according to any of the preceding claims, characterized in that the detent coupling (1) can be brought from a third switching position, in which the cam ring (7) is torque-transmitted to the first guide ring (8) in a second direction of rotation opposite to the first direction of rotation, especially in the axial direction from the drive shaft (2) to the output shaft (3) viewed counterclockwise, to a fourth switching position, in which the cam ring (7) can rotate freely with respect to the first guide ring (8), wherein the cam ring (7) is designed such that, when the detent coupling (1) is in the third switching position,The at least one switching element (11) is deflected when a second activation torque acting in the second direction of rotation relative to the cam ring (7) is exceeded, counteracting the effect of the initial axial tension, so that the detent coupling (1) is placed in the fourth switching position.
10. Detent coupling (1) according to claim 2 and claim 9, characterized in that the at least one switching element (11) is housed in the third switching position in the at least one recess (30), where, through the at least one recess (30), a second advance cam (32) is formed, with which the at least one switching element (11) is in contact in the third switching position, where the cam ring (7) further has a cam track (35) that is largely closed in the circumferential direction and interrupted only by the at least one recess (30).wherein the at least one switching element (11) can circulate in the fourth switching position at least in sections. wherein the at least one switching element (11) is axially orientable upon exceeding the second activation torque and the stopping coupling (1) can be placed in the fourth switching position, such that the at least one switching element (11) moves from the at least one recess (30) to the cam track (35).
11. Stopping coupling (1) according to any of the preceding claims, characterized in that the stopping coupling (1) has an openable and closeable freewheel (43-46) designed to rest on a housing of the portable electric machine tool and, in the closed state, permits 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. Stop coupling (1) according to claim 11, characterized in that the freewheel (43-46) is a ratchet freewheel, wherein 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 sliding, non-rotating freewheel pawl ring (43) against the at least one axially pre-tensioned freewheel tooth (46), and the at least one freewheel tooth (46) is arranged on a front side (45) of the first guide ring (8).
13. Stop coupling (1) according to claim 12, characterized in that the freewheel (43-46) can be closed and opened by axial sliding of the freewheel ratchet ring (43),which is possible by axial sliding of the second guide ring (9).
14. Locking coupling (1) according to any one of claims 12 and 13, characterized in that the cam ring (7) and the first guide ring (8) are axially arranged between the free-running ratchet ring (43) and the second guide ring (9), and in that the second guide ring (9) or a part attached to the second guide ring (9) and not axially sliding with respect to it axially reaches the cam ring (7) and the first guide ring (8).
15. Portable electric machine tool, especially a screwdriver, with a locking coupling (1) according to any one of the preceding claims.