Safety element, and coupling comprising a plurality of said safety elements

Abstract

The invention relates to a safety element (5a) for a coupling (1) comprising two coupling elements (2, 3), wherein, when engaged, a torque can be transmitted between the two coupling elements (2, 3), and wherein the two coupling elements (2, 3) can be shifted, in a torque-dependent manner, into a disengaged state by means of the safety element (5a). The invention also relates to a coupling comprising at least one safety element (5a) according to the invention.

Description

[0001] Safety element and coupling comprising several of these safety elements

[0002] The invention relates to a safety element according to claim 1, which is provided for a coupling. It has the property of disengaging in a torque-dependent manner in the event of a malfunction due to overload. Furthermore, the invention relates to a coupling comprising several safety elements according to the invention, in particular a shaft coupling which can be switched in a torque-dependent manner using these safety elements.

[0003] The safety element is designed for a coupling that comprises two coupling elements that can be regarded as coupling halves. In the case of a shaft coupling, a torque can be transmitted between the two coupling elements in the engaged state, wherein the two coupling elements can be automatically switched into the disengaged state by means of the safety element in a torque-dependent manner, i.e. when a defined torque is exceeded, with the proviso that the safety element comprises: a plunger that is displaceable in its axial direction by means of a provided bearing in order to provide the engaged state or the disengaged state of the coupling in the assembled state, a locking element that bears against the plunger, for example a ball, wherein the locking element preferably bears against a front end of the plunger, a spring device,by means of which a spring force can be transmitted into the tappet and further into the locking element, for example a disc spring assembly, wherein the tappet is provided with a shoulder element which projects in the radial direction on the tappet, preferably a circumferential annular shoulder element, wherein at least one transmission body is provided which is in contact with the shoulder element on the one hand and furthermore with at least one pressure body and cooperates therewith, wherein the transmission body is for example a rolling body and preferably the pressure body is designed as a circumferential annular pressure body, for which the pressure body has a deflection surface and the shoulder element comprises two functional surfaces, namely an inclined surface which also points in the axial direction and a laterally arranged rest surface,wherein the transmission body, in the engaged state of the coupling, is in contact with the inclined surface of the shoulder element, transmitting the spring force, while in the disengaged state of the coupling (neutral) it bears against the lateral resting surface of the shoulder element, and with the further proviso that, in the assembled state, the plunger and the locking element are assigned to a first of the two coupling elements of the coupling, and that a locking area is assigned to the other, second coupling element, e.g. a conical or dome-shaped opening, which locking area is designed to be complementary to the locking element. The locking area expediently forms a component of the safety element or is assigned to it.

[0004] Safety elements of this type, as well as couplings equipped with them, are required for heavy-duty machinery, for example, for machines in mining, the construction industry, or for materials handling systems, such as cranes, such as container cranes. For example, a container crane in a modern port terminal faces special requirements due to increasing automation.

[0005] Also known are safety elements which, after a fault, are in the disengaged position and the coupling elements are separated, cannot automatically return to an engaged state. With this type of safety element, resetting must be carried out manually, which is labor-intensive and always requires an operator on site. An example of this is US 2010 / 0224713 A1, which proposes a safety element and a coupling equipped with it. Each safety element is arranged on one coupling half and comprises a plunger which, when engaged, can transmit a torque to the other coupling half by spring force in an advanced position. After a fault, the plungers and locking elements of all safety elements are pushed back into a position in which no more spring force can be transmitted to the plunger.The transmission of force from the spring mechanism is interrupted or neutralized. To switch the clutch back to torque-transmitting operation, the transmission of spring force to the tappet must be restored and the neutralization canceled. With the current state of the art, this switching can only be accomplished by manual intervention, which can be achieved, for example, by a targeted hammer blow and requires operating personnel.

[0006] In addition, the applicant has proposed in DE 10 2019 110 297 B3 a safety element which has a self-resetting function so that after disengagement it can be re-engaged without having to make manual intervention on each safety element.

[0007] Known safety elements are subject to wear. This wear is essentially made up of a wear component that occurs when the clutch is disengaged while the torque is exceeded, and a wear component that occurs when the clutch is returned to the engaged state. A certain amount of wear occurs both when the clutch is engaged with a targeted hammer blow, and when the safety element is designed to reengage automatically.

[0008] The invention is based on the object of proposing a safety element which has an improved service life and a coupling equipped therewith.

[0009] According to the invention, the object is achieved in that a means for reducing wear is provided at least in the contact area between the transmission body and the tappet and / or a means for reducing wear is provided at least in the contact area between the transmission body and at least one pressure body.

[0010] Furthermore, it is advisable if the components within the housing are operated in the presence of a suitable lubricant.

[0011] The transmission body is expediently designed as a rolling body or a sliding body, wherein the means for reducing wear is designed as a groove for the transmission body. When assembled, the groove acts as a guide for the transmission body. It is particularly advantageous if the cross-sectional shape of the groove conforms to the cross-sectional shape of the transmission body. The groove thus forms a channel which defines the path for movement of the transmission body. By conforming the cross-section of the groove to the cross-section of the transmission body, the surface pressure between the two components can be reduced and the load-bearing capacity of the safety element can be increased. This increases the service life of the safety element.

[0012] It is very expedient if the transmission body is designed as a rolling body, e.g. a ball. In the installed state, a rolling body has three contact points which it has with adjacent components of the safety element, such as a first contact with the tappet, a second contact with the pressure body and a third contact directly or indirectly with the housing. Advantageously, at least one of the three components - tappet, pressure body, housing - is provided with a groove for the transmission body. Preferably, two components are provided with a groove for the transmission body, namely the tappet and the axially movable pressure body. In addition, the third contact point assigned to the housing can also be provided with a groove for the transmission body.

[0013] Even if the transmission element is designed as a rolling element, it does not necessarily have to perform a purely rolling motion; instead, it may have sliding components with the tappet or the thrust elements. This involves a combination of rolling and sliding.

[0014] The groove extends in a radial direction or the shape of the groove has a radial component. When assembled, the groove acts as a guide for the transmission body. The three components mentioned (ram, pressure body, housing) are preferably rotationally symmetrical, and a plurality of grooves extending with a radial component are preferably provided around the circumference of all three components. The grooves of each component are spaced apart from one another by distances that coincide with the grooves and spacings of the other components. When installed, the grooves of the different components lie exactly opposite one another and form a common groove guide for a corresponding number of transmission bodies, wherein each common groove guide preferably accommodates one transmission body.

[0015] As an alternative means for reducing wear, it is expedient to provide that the locking element is made at least partially of a ceramic material and / or that the locking region element is made at least partially of a ceramic material. This alternative means for reducing wear can also be combined with the previously described means of grooves or groove guides or can be provided with a chromium coating, preferably a hard chromium layer.

[0016] As a further means for reducing wear, it can be provided that at least one pressure body and / or at least one transmission body and / or the tappet is at least partially made of a ceramic material or provided with a chromium coating, preferably a hard chromium layer. This alternative means for reducing wear can also be combined with one of the aforementioned means for reducing wear.

[0017] An additional benefit is seen if the rest area of ​​the

[0018] The shoulder element of the plunger is further developed into an action surface which is inclined relative to the axial direction of the plunger, namely inclined at an angle a relative to the axial direction of the plunger. This measure enables self-resetting of the safety elements after a malfunction if they have been switched to a disengaged state after a torque exceedance.

[0019] A clutch disengagement performed for safety purposes can be used, thanks to the self-resetting effect of the proposed safety element, to return a clutch to an operational engaged state. With this proposal, no operator on site needs to manually manipulate the clutch or intervene in all of the clutch's safety elements.

[0020] The direction of the suggested inclination of the resting surface corresponds to the direction in which the inclined surface of the shoulder element is also inclined. A correct angle for the inclination of the resting surface is required for proper function.

[0021] According to this concept, safety elements are provided that are designed for different torques and / or graded according to different sizes. This results in type series. For each safety element in a series, a suitable angle for the inclination of the rest surface on the shoulder element of the plunger is defined. The angle can be determined empirically, for example, for each size or for each desired torque.

[0022] During clutch operation, both coupling elements rotate at a certain speed. If, at this speed, the torque to be transmitted increases and exceeds the capacity of the cumulative safety elements, they automatically disengage, i.e., their plungers are reset against the force of the spring device. In the reset position, the transmission body, which is preferably a ball, rests neutrally on the rest surface.

[0023] In the safety element of US 2010 / 0224713 A1 and DE 10 2019 110 297 B3, a rest surface is provided on the shoulder element of the plunger, which is arranged parallel to the axial direction of the plunger. At the same time, the force of the spring device also acts in a direction parallel to the axial direction of the plunger. The spring force caused by the spring device always presses against the pressure body and this against the ball as the transmission body. However, a transmission of the force from the ball to the plunger is neutralized when the ball rests on the rest surface because the ball cannot cause any further deflection of the spring force into the plunger due to the lack of an inclination of the rest surface. The known parallel rest surface prevents a deflection of force from the transmission body into the plunger.

[0024] In contrast, the new solution proposed here changes the function of the rest surface in a measured way. Instead of being aligned exactly parallel, the rest surface is arranged at an acute angle slightly inclined to the axial direction of the tappet. In this way, the spring force which reaches the transmission body (ball) can be deflected by the ball in a defined transmission ratio which can be adjusted by means of the moderate inclination of the rest surface. By choosing a suitable inclination of the rest surface, it can be ensured that after disengagement due to exceeding a defined torque, re-engagement is only possible with a reduced restoring force in the axial direction for safety reasons. The speed difference between the two clutch elements must be sufficiently small for the reduced restoring force to be sufficient to permit engagement.

[0025] If a technical problem has led to an increased torque load, so that the clutch's safety elements have disengaged as a precaution, the underlying technical problem should first be rectified before the clutch is slowly restarted. During an initial slow rotation of one clutch element, a slight restoring force in the plunger, generated by the transmission ratio of the inclined rest surface, is sufficient to advance the locking element (e.g., ball) back into the engagement area of ​​the other clutch element.

[0026] Due to the inclination of the rest surface, the transmission ratio is specifically selected so that re-engagement of the locking element is only possible at a significantly reduced speed. To do this, the clutch is first brought to a standstill and the cause of the excess torque is searched for and eliminated before being put into operation again. To put the clutch back into operation, each plunger can be moved back to its advanced position without the need for an operator on site. To do this, the clutch only has to be slowly set in rotation again. It is necessary that the movement is slow enough that the spring force, which is low due to the transmission ratio, is sufficient to move the plunger into its advanced, engaged position. The clutch can then again transmit its full torque, for which it is designed.Advantageously, the angle a of the inclination of the resting surface of the shoulder element is in a range of 3 ° to 12 ° , preferably in a range of 5 ° to 10 ° and particularly preferably in a range of 7 ° to 8 ° .

[0027] Advantageously, a first axially movable pressure body and a second pressure body are provided, wherein the second pressure body is arranged fixedly relative to the housing.

[0028] Suitably, both pressure bodies are directly or indirectly spring-loaded, each of the two pressure bodies having an inclined deflection surface, each of the deflection surfaces being in contact with the transmission body, and at least the deflection surface of one of the two pressure bodies being arranged inclined at an acute angle to a radial plane.

[0029] The bearing of the plunger can advantageously be integrated into a housing, wherein the housing has a connecting means designed for easy mounting of the safety element to a coupling element. If the housing has a cylindrical shape, then the connecting means can be, for example, an external thread on the housing, which can be screwed into a complementary internal thread of the coupling element.

[0030] The housing is expediently provided with an adjustment means or a combined fastening and adjustment means, by means of which its axial position relative to the supporting coupling element can be adjusted in the assembled state. For the proposed safety element, it is considered important to enable the axial position of several components which are arranged in a row in the assembled state to be adjustable. The components in question are the plunger, the locking element and the locking area. They should be arranged with as little play as possible or with a defined small amount of play relative to one another. The plunger and the locking element are located in the housing, which is assigned to one coupling element, while the locking area is assigned to the other coupling element.This results in certain positional tolerances between the above-mentioned components in their axial direction, which can be compensated by means of the adjustability of the housing.

[0031] The aforementioned measure is considered not only dependent on the solution to the underlying problem stated above, but also as an independent inventive solution to the differing technical problem arising from the positional tolerances of the aforementioned components. Therefore, based on the preamble of claim 1, a safety element is hereby proposed which is additionally provided with the aforementioned adjustment means for the housing in order to adjust its axial position relative to the supporting coupling element and indirectly to adjust the axial position of the components: plunger, locking element, and locking area relative to one another.

[0032] The aforementioned independent solution for the adjustability of the components mentioned is supplemented by the latching area being designed as an exchangeable latching area element which has a fixed positioning aid, wherein the positioning aid interacts with a stop means of the relevant coupling element in the assembled state.

[0033] Advantageously, in a coupling with a plurality of safety elements, each of the locking elements (e.g. ball) can be brought into contact with each of the engagement area elements without having to pay attention to an aligned position of the two coupling elements, because for example only one engagement area element would be suitably adjusted for each locking element.

[0034] Advantageously, a guide bush is assigned which, in the assembled state, serves to guide the plunger and / or to guide the locking element, wherein the guide bush is also assigned to the first coupling element concentrically to the plunger.

[0035] The guide bush can be assigned as a separate component or it is assigned as an integral part of the safety element, for example assigned to a housing part of the housing safety element.

[0036] The housing can have a closure element as a housing part, wherein the closure element acts as a counter bearing for the spring device and / or acts as a guide for the plunger and / or the locking element.

[0037] The closure element advantageously comprises a means by which its axial position relative to the housing can be adjusted. The closure element is simply provided with a guide bore for the plunger and has an externally threaded rim. The external thread can serve as a fastening means. Furthermore, the external thread can form the aforementioned means for adjusting the axial position.

[0038] The external thread of the locking element expediently interacts with a matching internal thread provided in the housing, preferably this is a fine thread. Furthermore, a locking element can be provided, e.g. a piece of aluminum that is embedded in a blind hole arranged transversely to the external thread. The piece of aluminum extends into the area of ​​the external thread and is only deformed when the external thread is screwed into the internal thread of the housing, creating a stopping effect, similar to the embedded plastic in a self-locking hexagon nut DIN 985, which deforms when screwed in and acts as a screw lock.

[0039] The spring device can comprise at least one disc spring, preferably a disc spring package consisting of several disc springs is provided.

[0040] For the tappet, it is further proposed that this be composed of at least one tappet shaft and a shoulder element that can be connected to it, in particular a shoulder ring. The shoulder ring can have a conical action surface or the conical action surface can additionally be provided with radial grooves. A suitable connection between the tappet shaft and the shoulder ring creates a defined, fixed relationship between the tappet shaft and the shoulder ring, in particular in the axial direction. The two-piece design has the advantage that the shoulder ring can be replaced separately. It is subject to particular wear during operation and may need to be replaced at a time when the tappet shaft can still be used. In this case, the existing tappet shaft is simply provided with a new shoulder ring.In addition, it is possible to subject the shoulder ring to a specific treatment which improves its wear properties and to leave the tappet shaft untreated or to subject it to another suitable treatment.

[0041] The coupling comprises two coupling elements which can be rotated about an axis and which can be switched into a coupled state and a disengaged state, wherein in the coupled state a torque can be transmitted, wherein on one of the coupling elements at a defined diameter and concentric to the axis of rotation of the coupling element at least one safety element according to one of claims 1 to 18 (preferably axially or radially) is arranged and in the case of a plurality of arranged safety elements a defined distance between the safety elements is preferably provided, and wherein on the second coupling element at an identical diameter and concentric to its axis of rotation a corresponding number of latching area elements are arranged and at congruent distances as the safety elements.

[0042] A circumferential groove is provided on the second coupling element, which interacts with the locking elements of the safety elements when disengaged.

[0043] The invention is illustrated below by way of example in a drawing and described in detail with reference to several figures. They show:

[0044] Fig. 1 shows a coupling provided with six safety elements according to the invention,

[0045] Fig. 2 is a partial sectional view of a safety element according to the prior art mounted on a coupling and shown in the engaged state,

[0046] Fig. 3 is a partial sectional view of the known safety element of Fig. 2 in a fictitious separated state of the coupling,

[0047] Fig. 4 is a partial sectional view of a first embodiment of the safety element according to the invention mounted on a coupling and shown in the coupled state,

[0048] Fig. 5 is a partial sectional view of the embodiment of Fig. 4 in a different sectional plane in the coupled state,

[0049] Fig. 6 is a partial sectional view of the embodiment of Figs. 4 and 5 in a separated state of the coupling,

[0050] Fig. 7 is a partial sectional view of a second embodiment of the safety element according to the invention mounted on a coupling and shown in the coupled state,

[0051] Fig. 8 is a partial sectional view of the embodiment of Fig. 7 in a separated state of the coupling,

[0052] Fig. 9 is a perspective view of an alternative plunger for a third embodiment of the safety element according to the invention,

[0053] Fig. 10 is a perspective view of an alternative movable pressure body for the third embodiment of the safety element,

[0054] Fig. 11 is a perspective view of an alternative stationary pressure body for the third embodiment of the safety element,

[0055] Fig. 12 is a perspective view of another alternative plunger for a further embodiment of the security element according to the invention.

[0056] Fig. 1 shows a clutch 1 according to the invention, which has two clutch elements 2 and 3 (clutch halves) that are movable relative to one another and can be switched depending on the torque. In the present example, the clutch elements 2 and 3 can be rotated about a rotational axis 4 of the clutch 1. Therefore, the clutch 1 is a shaft coupling. It is torsionally rigid and switchable. Switching is possible between an engaged and a disengaged state and occurs depending on the torque.

[0057] The coupling 1 is intended, for example, for drive trains of machines, such as machines in mining, the construction industry or in materials handling systems, such as cranes. In particular, it is intended for use in container cranes. In such machines, sudden overloads can occur that endanger components of the machine, such as motors, gearboxes, etc. In order to protect these, the proposed coupling 1 separates the power transmission between the two coupling elements 2 and 3, so that overloads are kept away from the aforementioned components of the machine and these are protected. The coupling 1 can therefore be referred to as a safety coupling or overload coupling.

[0058] To enable clutch 1 to fulfill its torque-dependent safety function, it is provided with six safety elements 5a according to the invention. Each safety element 5a has a specific torque transmission capacity. In the present example, the total torque transmittable by clutch 1 is based on six safety elements 5a, so that clutch 1 essentially has six times the capacity of a single safety element 5a.

[0059] The safety elements 5a are subject to wear. Certain components of the safety element 5a that are critical to operational safety are usually inspected regularly and replaced if necessary.

[0060] In order to increase the lifetime of the security element according to the invention

[0061] 5a they are provided with means to reduce wear, as follows below.

[0062] The coupling element 2 carries the six safety elements 5a. For this purpose, it is designed like a flange. The positions for the safety elements 5a are distributed on the coupling element 2 on a circle (pitch circle) that is coaxial with the axis of rotation 4 of the coupling 1. Each safety element 5a is rotationally symmetrical and has a central axis 6a. It is positioned on the pitch circle of the coupling element 2 with the central axis 6a. In the present example, the central axes 6a of the safety elements 5a are arranged parallel to the axis of rotation 4 of the coupling 1 or the coupling element 2. Alternatively, safety elements 5a can also be arranged in a radial orientation on a coupling element, for example in order to obtain a coupling that acts in the axial direction.

[0063] Figures 2 and 3 show a safety element 5b which is part of the prior art and is attached to a flange-like coupling element 2. The coupling element 2 has a mounting plane 7 which is orthogonal to the axis of rotation 4 and the safety element 5b also has a defined mounting plane 8. In the mounted state shown, the mounting plane 8 of the safety element 5b is in contact with the mounting plane 7 of the coupling element 2. As a result, in this prior art the relative position of the coupling element 2 and the safety element 5b is fixed in the axial direction. The safety element 5b comprises a plunger 9 in a housing 10, with a housing edge 10a defining the mounting plane 8 of the safety element 5b. The plunger 9 is indirectly spring-loaded and presses against a detent ball 11. The detent ball 11 is as shown in Fig.2 is engaged in a locking area 12 which is arranged on the opposite coupling element 3 and is axially adjustable by means of an adjusting screw 13. The plunger 9 has a shaft on which a shoulder element 14 is provided around its circumference. The shoulder element 14 is in contact with balls as transmission bodies 15. Fig. 3 shows the disengaged state of the safety element 5b, in which a cylindrical rest surface 16 as part of the shoulder element 14 has come into contact with the transmission bodies 15. In this position, the transmission of a spring preload into the plunger 9 is neutralized. In order to switch back from the disengaged state to the engaged state, the plunger 9 must be advanced from the outside and the locking ball 11 must be pressed back into the locking area 12.

[0064] As an exemplary embodiment of the invention (without figure), a safety element is proposed which has the spatial physical design according to Figures 2 and 3, wherein a means for reducing wear is additionally provided. The means for reducing wear comprises a transmission body made from a ceramic material. Another exemplary embodiment provides that at least one component is made at least partially from a ceramic material or is at least partially provided with a wear-reducing coating. The component in question is selected from the group of the following components: plunger, plunger shoulder element, movable pressure body, static pressure body, transmission body. A plunger shoulder element means a separate shoulder element which can be assembled with a separate plunger shaft to form a complete plunger.

[0065] Fig. 4 shows a first illustrated embodiment of the security element 5a according to the invention. For the sake of simplicity, the same reference numerals are used for comparable features as previously in the description.

[0066] Fig. 4 shows in particular that the safety element 5a is mounted on a coupling element 2 in a different way than in the prior art. The proposed safety element 5a comprises a rotationally symmetrical plunger 9 which presses with a front end 17 against a spherical locking element (locking ball 11), the plunger 9 being arranged in a housing 10 which has a bearing for the plunger 9 and enables its displacement in its axial direction. The internal structure in the housing 10 of the safety element 5a corresponds at least largely to the structure of the known safety element according to Figures 2 and 3. In contrast to this prior art, however, the safety element dispenses with providing a housing edge as a mounting plane for fixed positioning on the relevant coupling element 2.

[0067] Instead, the housing 10 is provided with a fastening and adjustment means 18, by means of which its axial position relative to the supporting coupling element 2 can be adjusted. The housing 10 is arranged coaxially to the tappet 9 and around the latter and has two end faces 10b and 10c. The end faces 10b and 10c form a bearing which has bearing openings L1 and L2, respectively, which serve as guide bearings for the axial mobility of the tappet 9. A seal S1 and S2, respectively, is arranged in each of the bearing openings. The fastening and adjustment means 18 is simply an external thread 19, which is provided on the outside of a cylindrical side wall 20 of the housing 10. The external thread 19 is expediently designed as a fine thread. To match this, the coupling element 2 is provided with a complementary internal thread 21 into which the external thread 19 of the housing 10 can be screwed.The screw connection consisting of the external thread 19 and the internal thread 21 has a dual function. On the one hand, it is used for assembly and fastening and, on the other hand, for the aforementioned axial adjustability. The axial position of the housing 10 determines the axial position of the tappet 9, which is arranged in a row with the detent ball 11 and in a row with the associated engagement area 12, which is arranged on the other coupling element 3. The appropriate screw-in depth for the housing 10 is found during assembly. The aim is to ensure a play-free connection between the tappet 9 and the detent ball 11 and, consequently, a play-free connection between the detent ball 11 and the engagement area 12.

[0068] In this case, the plunger 9 is also indirectly subjected to a preload generated by a spring device 22 arranged in the housing 10. The spring device 22 comprises a disc spring assembly 23 arranged coaxially around the plunger 9.

[0069] Alternatively, the screw-in depth of the housing 10 can also be selected such that a slight play is provided between the plunger / locking ball / locking area during assembly, for example in order to only achieve freedom from play once the machine has warmed up and reached a predetermined operating state. A certain heat-induced expansion of the components involved can reduce or eliminate play to a defined extent. During assembly, the housing 10 can, for example, be screwed in with a defined torque in order to then turn the housing 10 back in the opposite direction by a defined angle and in this way create a defined play. The final screw-in depth of the housing 10 in the coupling element 2 is expediently secured. A suitable means 24 is provided for securing this, such as a threaded pin 25 in the example in Fig. 4, which is arranged in a bore 26 in the coupling element 2.When screwed in, the threaded pin 25 presses radially against the external thread 19 of the housing 10, fixing its position relative to the coupling element 2. To protect the external thread 19, an intermediate piece 27 made of aluminum, a soft metal, is provided in front of the tip of the threaded pin 25, which is pressed against the external thread 19 of the housing 10 without damaging it. The intermediate piece 27 is deformed, thereby achieving a stopping effect, similar to the plastic of a self-locking hexagon nut DIN 985, which is deformed during screwing in and counteracts the loosening of the screw connection.

[0070] The locking areas 12 for the locking balls 11 of each safety element 5a are arranged on the other coupling element 3. In the present example, the locking areas 12 are each designed as an exchangeable locking area element 28. The locking area element 28 has an external thread which is screwed into an internal thread of the coupling element 3. Each locking area element 28 has a locking recess 29, here a recess with a conical inner surface 30. Furthermore, each locking area element has a fixed positioning aid which in this example comprises a radially projecting collar 31. In the assembled state, the projecting collar 31 interacts with a radial surface of the coupling element 3, which serves as a stop means. The correct axial position is always defined for the locking area element 28.This eliminates the need to bring the two coupling elements into a specific rotational position relative to each other before engaging, as was the case with the prior art. The proposed engagement area elements 28 are manufactured with such a high quality and dimensional accuracy that the locking ball 11 of each safety element 5a of the coupling can interact with any mounted engagement area element 28. In this way, the proposed safety element 5a generally facilitates engagement.

[0071] Figures 5 and 6, like Fig. 4, show the first embodiment. However, it is depicted in a different sectional plane. Fig. 5 shows the engaged state, while Fig. 6 shows the plunger 9 and the detent ball 11 in a retracted position, which they assume when the coupling is disengaged. The detent ball has retracted from the engagement region. In Fig. 6, the engagement region element 28 is shown in simplified form aligned with the plunger and the detent ball. In practice, however, the engagement region element 28 has already rotated further; during further rotation, the engagement recess 29 has pushed the detent ball 11 back into the position shown in Fig. 6. In this respect, Fig. 6 is a simplified theoretical representation of the disengaged state, which shows the engagement region (simplified) in an incorrect rotational position.

[0072] 5 shows a further threaded pin 32 in a further pin bore 33 in the coupling element 2. The section according to Fig. 5 lies in a different section plane than the section in Fig. 4. The threaded pin 32 has a conical tip. It is used to assemble and secure the position of a guide bushing 34 which has a V-shaped circumferential groove on its outer surface. The tip of the threaded pin 32 is screwed into the V-shaped groove and thus fixes the position of the guide bushing 34, which serves to guide the detent ball 11 and also to guide a front end 9a of the plunger 9. For this purpose, the guide bushing 34 is provided with a first cylindrical inner surface 35, which forms the guide for the detent ball 11. A second cylindrical inner surface 36 forms the guide for the front end 9a of the plunger 9.In this example, the locking ball 11 has a larger diameter than the front end 9a of the plunger 9. The two cylindrical inner surfaces 35 and 36 of the guide bushing 34 are adapted to the two aforementioned diameters. Between the cylindrical inner surfaces 35 and 36, the guide bushing 34 has the conical inner surface 37, which serves as a stop to limit the movement of the locking ball 11.

[0073] The coupling element 2 has a larger diameter than the coupling element 3 and accommodates a shaft seal 38 (shaft seal) comprising a sealing lip 39 that bears against the coupling element 3. The shaft seal 38 is arranged in such a way that the ingress of dirt into the guide bushing 34 and the engagement area 12 is counteracted.

[0074] 5 shows two transmission balls 15, each of which is in contact with a stationary pressure body which is designed in an annular manner as a pressure ring 40. In addition, an axially movable pressure body is provided, designed as a movable pressure ring 41. Finally, the tappet 9 has a shoulder element 14 which is designed in an annular manner as a shoulder ring. The shoulder ring comprises two functional surfaces. A first functional surface 42 is an inclined surface which is designed as a circumferential groove 42a. The groove is designed such that its cross section adapts to the shape or radius of the transmission balls 15. A second functional surface 16a of the shoulder element 14 is formed by a cylindrical rest surface 16, which in the present example, as in the prior art, is arranged parallel to the axial direction of the tappet 9.

[0075] Furthermore, Fig. 5 shows the spring device 22, which comprises six disc springs which are combined to form the disc spring assembly 23. In the coupled state shown, the disc spring assembly 23 is in a slightly preloaded state. On the end face 10c of the housing 10, a housing opening is provided with a closure element 43, which serves as a counterbearing for the disc spring assembly 23 and comprises one of the bearing openings for the tappet, which is provided with the seal S2. The closure element 43 is designed to be able to set a preload of the disc spring assembly 23 or to remove preload. For this purpose, a cylindrical inner wall 44 of the housing 10 is provided with an internal thread 45 and the closure element 43 has a cooperating external thread 46.The closure element 43 can be screwed into the housing 10 and preloaded more or less strongly against the disc spring assembly 23 or left unloaded. To secure the desired setting, the cylindrical surface of the closure element 43 provided with the external thread 46 is provided with a pocket, simply a radial blind bore 47, into which a soft material, e.g. an aluminum spacer 48, is embedded. The soft material has no threads, but comes into contact with the internal thread 45 of the housing 10 during assembly and is deformed in the process. The deformed spacer 48 serves to secure the set position of the closure element 43. The deformed spacer 48 achieves a stopping effect, like the embedded plastic of a self-locking hexagon nut DIN 985.

[0076] The spring force of the disc spring assembly 23 acts on the transmission ball 15 via two deflection components, namely the static pressure ring 40 and the movable pressure ring 41. The latter, in turn, deflect a component of the spring force into the annular shoulder element 14 of the plunger 9. The plunger 9 is thereby subjected to a force component that preloads it toward the engagement area 12.

[0077] In Fig. 6, which shows the safety element in a separated state of the coupling, the plunger 9 has retreated from the engagement region 12, as a result of which the transmission balls 15 have been moved radially outwards beyond the first functional surface 42. In this position, the transmission balls 15 rest on the second functional surface 16a, which is designed as a cylindrical rest surface 16. The spring force emanating from the disc spring assembly 23 is thus neutralized. Although the spring force presses against the movable pressure ring 41 and this against the transmission balls 15, the transmission balls 15 cannot introduce any force or movement into the rest surface 16, as a result of which the plunger 9 comes to a standstill. The functionality of the rest surface 16 corresponds to that cylindrical rest surface which can be identified as such in DE 10 2019 110 297 B3.In the publication, it is proposed to provide a spring-operated external actuating lever for switching the plunger 9 to the engaged state. Reference is hereby made to this type of reset; it can be combined with the present first embodiment according to Figures 4 to 6. Alternatively, the plunger 9 can be manually advanced by an operator to restore the engaged state. Manual actuation can be carried out, for example, by striking the plunger with a hammer.

[0078] As a means of reducing wear, in the first embodiment shown in Figures 4-6, at least one component is made at least partially of a ceramic material or is at least partially provided with a wear-reducing coating. The component is selected from the group of the following components: tappet, tappet shoulder element, movable pressure body, static pressure body, transmission body.

[0079] Fig. 7 and Fig. 8 refer to a second illustrated embodiment of the safety element. It comprises a means for reducing wear, which comprises at least one component that is at least partially made of a ceramic material or at least partially provided with a wear-reducing coating. The component is selected from the group of the following components: plunger, plunger-shoulder element, movable pressure body, static pressure body, transmission body.

[0080] 7 and 8 illustrate another essential aspect of this exemplary embodiment of the invention, namely how the safety element 5a is designed to provide simplified self-resetting. The embodiment of FIGS. 7 and 8 differs from the exemplary embodiment of FIGS. 5 and 6 essentially in that it has a modified plunger 9, the second functional surface of which forms an action surface 49 which is inclined relative to the axial direction of the plunger 9. In the present example, the action surface is inclined at an angle α of 7.5° relative to the axial direction of the plunger 9. In the example, the action surface 49 is arranged circumferentially. This results in the action surface 49 having the shape of a truncated cone. First, however, FIG. 7 shows the engaged state of the safety element 5a.The purpose is to be able to restore the engaged state after a malfunction when the clutch 1 is disengaged without having to carry out any external operation on the safety element 5a, in particular without requiring any action on site, for example by an operator.

[0081] Fig. 8 shows the separated state of the coupling 1. The two coupling elements 2 and 3 are disengaged. As in Fig. 6, Fig. 8 is also a simplified theoretical representation of the disengaged state of the safety element 5a. The latching area 12 has pushed the detent ball 11 and the plunger back against the spring force, so that the detent ball 11 has retreated from the latching area 12. The latching area has rotated further, the detent ball 11 rests against a radial surface of the coupling element 3 and in this position can no longer introduce any torque into the coupling element 3.

[0082] In addition, due to the axial retraction of the plunger 9, the transmission balls in Fig. 8 have been pushed radially outward beyond the first functional surface 42. Now the transmission balls 15 rest against the second functional surface, i.e., the action surface 49, which is inclined at an angle a of 7.5° relative to the central axis of the plunger.

[0083] In contrast to the prior art, in the disengaged state, the inclined action surface 49 immediately redirects movement to the transmission balls 15. The origin of the movement is the spring force due to the preload of the disc spring assembly 23, which presses the movable pressure ring 41 against the transmission balls 15. As a result, the transmission balls 15 are pressed radially inward and, via the inclined action surface 49, direct a force component into the plunger 9, which advances it toward the engagement area 12.

[0084] Due to the flat inclination of the action surface 49, the spring force is translated. The translation is selected such that there is a defined limitation of the force component which advances the plunger 9 in the axial direction. The intention is to thereby allow the engagement of the detent balls 11 in the engagement areas 12 in a material-friendly manner. The force is dimensioned such that engagement is preferably only possible with a small speed difference. With a larger speed difference, a larger advancing force in the plunger 9 would be required in order to engage. The invention aims to prevent the associated greater material wear by reducing the axial force which can be introduced into the plunger 9 for advancing and engaging.On the one hand, the low advancing axial force reduces wear immediately after a malfunction, when coupling elements 2 and 3 are still rotating and frictional contact, which wears the material due to a speed difference, occurs. On the other hand, subsequent commissioning also takes place in a material-protecting manner.

[0085] In the first case, when clutch 1 has disengaged in a torque-dependent manner during full operation, clutch elements 2 and 3 are initially still rotating, whereby a certain speed difference can quickly develop. Then, detent balls 11 and engagement areas 12 overtake each other while moving at different speeds and are and remain in a certain frictional contact. This causes a certain amount of wear. However, because the tappets 9 and the detent balls 11 are only subjected to a defined, small advancing axial force, wear can be kept to a minimum during this operating phase.

[0086] During re-commissioning, it is recommended that, starting from the standstill of both coupling elements 2 and 3, the driving coupling element 2 or 3 should only start up slowly in order to be able to use the defined low advancing force that arrives in the tappet 9 to press the locking balls 11 into engagement with the engagement areas 12 on the coupling element 3. If the driving coupling element accelerates too much, the clutch cannot be re-engaged.

[0087] A third illustrated embodiment is explained below with reference to Fig. 9. This represents a perspective view of an alternative plunger, which can be referred to as a grooved plunger 9a. Based on the first illustrated embodiment of Figs. 4-6, its plunger is further developed into the grooved plunger 9a. The grooved plunger 9a can replace the plunger 9 to obtain the third illustrated embodiment of the security element 5a.

[0088] The design of the grooved tappet 9a dispenses with a "built-in" self-resetting function. The grooved tappet 9a has a cylindrical shaft and an annular shoulder element 14 (shoulder ring 14a). The shoulder ring 14a is provided with a cylindrical rest surface 16. In the disengaged state, the effect of the disc spring assembly 23 is neutralized. The shoulder ring 14a is provided with grooves 50, which in the assembled state serve as a guide for the transmission bodies 15. According to the proposal in Fig. 9, the groove design of the grooved tappet 9a represents an inventive means for reducing wear.

[0089] The proposed grooves 50 begin on the inside of the circumferential, fillet-shaped surface of the shoulder ring 14a and extend radially outward. The grooves 50 continue in the axial direction on the cylindrical rest surface 16 of the shoulder ring 14a.

[0090] The functional surfaces are now formed by the groove surfaces. The grooves 50 have adapted cross-sections, which, like the raceways of a rolling bearing provided with rolling elements, are adapted to the shape of the respective transmission bodies 15. As a result, the groove surfaces increase the contact surface for the transmission bodies 15. In this way, the surface pressure is reduced, and this design serves as a wear-reducing means.

[0091] When the safety elements 5a are disengaged, their transmission balls 15a are located in that outer region of the groove 50 which is aligned parallel to the central axis of the grooved plunger 9a. The effect of the spring force of the disc spring assembly 23 is then neutralized. In order to switch the separated clutch 1 back on, the grooved plunger 9a can be actuated from the outside to advance it so that the transmission bodies 15 can move inward again. For switching, the grooved plunger 9a can be advanced manually by an operator, for example by a hammer blow. Alternatively, the external spring-operated mechanism with actuating lever known from DE 10 2019 110 297 B3 can be provided to automate advancement into the engaged state.

[0092] A further advantage is apparent when the safety element 5a is switched between the engaged and disengaged states, which in the first embodiment can mean that neighboring transmission balls 15a can change their distance from one another. In the disengaged state, the distance between the transmission balls 15a is greatest. Without lateral guidance by grooves 50, transmission balls 15a can, under certain circumstances and disadvantageously, move toward or away from one another in the circumferential direction. This can be avoided by means of guidance by the proposed grooves 50 of the grooved tappet 9a.

[0093] With reference to Fig. 10, a further measure is proposed which concerns a modified axially movable pressure body and contributes to a means of wear reduction. The movable pressure body can replace the movable pressure body 41 of the first embodiment shown or it can be used, for example, in a safety element 5a in combination with the grooved tappet 9a. The axially movable pressure body is annular in design as a pressure ring 41a and has wear-reducing radial grooves 51, the cross section of which is also adapted to the shape of the transmission bodies 15, here transmission balls 15a. In the grooves 51, the surface pressure relative to the transmission body 15 is again reduced and the means of wear reduction is thus provided.In order to be able to combine the pressure ring 41a with the grooved tappet 9a, the pressure ring has radial grooves 51 in a congruent arrangement, so that in pairs one groove 50 of the grooved tappet 9a and one groove 51 of the pressure ring can act as a common guide for the transmission body 15.

[0094] With reference to Fig. 11, a further measure is proposed which concerns a modified static pressure body. The static pressure body can replace the static pressure body 40 of the first exemplary embodiment shown, or it can be used in a safety element 5a in combination with the grooved tappet 9a according to Fig. 9 and / or with the movable pressure ring 41a according to Fig. 10. The static pressure body of Fig. 11 is annular in design as a pressure ring 40a and has radial grooves 52, the cross section of which is also adapted to the shape of the transmission bodies 15, here again the transmission balls 15a. For a combination with the grooved tappet 9a and / or with the pressure ring 41a of Fig. 10, the pressure ring 40a also has the radial grooves 52 in a congruent arrangement.Thus, a groove 50 of the plunger and / or a groove 51 of the movable thrust ring can interact in pairs with a groove 52 of the static thrust ring 40a. This results in common guides for the transmission bodies 15.

[0095] Fig. 12 shows a design of an alternative grooved tappet 9b which can replace the tappet 9 of the first embodiment shown and then results in a further embodiment of the safety element 5a according to the invention. The grooved tappet 9b has a cylindrical shaft and an annular shoulder element (shoulder ring 14b) with two functional surfaces based on the functional surfaces of the second embodiment according to Figures 7 and 8. The tappet has a shoulder element with two functional surfaces. The first functional surface is an inclined surface which is designed as a circumferential groove 42a. The second functional surface is the action surface 49 which has an inclination with respect to the axial direction (central axis) of the tappet 9. Just as in the second embodiment, a safety element 5a, which is provided with the grooved plunger 9b, has a self-resetting function.Due to the self-resetting, the grooved tappet 9b, when it is in the disengaged state, is subjected to an axial force which advances it towards its position for the engaged state, as in Fig. 7. According to Fig. 12, additional radial grooves 53 are provided which extend over both functional surfaces, the second functional surface being arranged in the region of the action surface 49 (conical outer surface). Because only the grooves 53 interact with the transmission bodies 15, in the present example the groove surface of each groove 53 serves as a replacement for the frustoconical action surface 49. Advantageously, the grooves 53 have the same inclination as the conical outer surface which forms the action surface 49 in Fig. 7. In the assembled state, the radial grooves 53 in Fig. 12 as a guide for the respective transmission body 15 , preferably rolling elements.In the present example, the proposed transmission balls 15a are provided as the transmission bodies. The cross-sections of the radial grooves 53 are adapted to the shape of the transmission balls 15a, like the raceways of a rolling bearing.

[0096] An important aspect of this embodiment is again to reduce the surface pressure between the transmission bodies 15 and the grooves 53 of the shoulder ring 14b. This is achieved by adapting the cross-sections of the radial grooves 53, as mentioned, to the cross-sections of the transmission bodies 15, such as the transmission balls 15a proposed here.

[0097] A further advantage is also apparent here when the safety element 5a is switched between the engaged and disengaged states. In the first embodiment, this can be accompanied by neighboring transmission balls 15a changing their distance from one another. Generally, in all embodiments, the distance between the transmission balls 15a is greatest in the disengaged state. Without lateral guidance by grooves 53, the transmission balls 15a can, under certain circumstances and disadvantageously, move toward or away from one another in the circumferential direction.

[0098] This can be avoided by means of a guide through the proposed radial grooves 53 of Fig . 12 .

[0099] List of reference symbols Coupling Coupling element Coupling element Rotation axis a Safety element b Safety element a Central axis Mounting plane Mounting plane Tappet a Grooved tappet b Grooved tappet 0 Housing 0a Housing edge 0b Front face 0c Front face (with housing opening) 1 Detent ball 2 Detent area 3 Adjusting screw 4 Shoulder element a Shoulder ring b Shoulder ring Transmission body a Transmission ball Cylindrical resting surface a Second functional surface Pin end (tappet) Fastening and adjustment means External thread Cylindrical side wall (housing) Internal thread Spring device Disc spring element Center Threaded pin Bore Intermediate piece Detent area element Detent recess Inner surface Protruding collar Threaded pin Pin bore Guide bush Cylindrical inner surface Cylindrical inner surface Conical inner surface Shaft seal Sealing lip Thrust ring (stationary) a Thrust ring (stationary) Thrust ring (movable) a Thrust ring (movable) First functional surface 42a Concave groove

[0100] 43 Closure element

[0101] 44 cyl. inner wall

[0102] 45 internal thread (housing 10)

[0103] 46 external thread (closing element)

[0104] 47 Blind hole

[0105] 48 intermediate piece (aluminum)

[0106] 49 Action area

[0107] 50 groove

[0108] 51 groove

[0109] 52 grooves

[0110] 53 groove

[0111] LI warehouse opening

[0112] L2 bearing opening

[0113] 51 Sealing ring

[0114] 52 Sealing ring

Claims

Patent claims 1. Safety element (5a) for a clutch (1) comprising two clutch elements (2, 3), wherein in a coupled state a torque can be transmitted between the two clutch elements (2, 3), and wherein by means of the safety element (5a) the two clutch elements (2, 3) can be switched into a disengaged state depending on the torque, with the proviso that the safety element (5a) comprises: a plunger (9, 9a, 9b) which is displaceable in its axial direction by means of a provided bearing in order to provide the engaged state or the disengaged state of the clutch in the assembled state, a locking element which bears against the plunger, a spring device by means of which a spring force can be transmitted up to the plunger (9, 9a, 9b) and further into the locking element, wherein the plunger (9, 9a, 9b) is provided with a shoulder terelement (14) which is arranged in radial Direction protrudes on the tappet (9, 9a, 9b), wherein at least one transmission body (15, 15a) is provided, which on the one hand is in contact with the shoulder element (14) and furthermore with at least one pressure body (40, 40a, 41, 41a) and cooperates therewith, for which purpose the pressure body (40, 40a, 41, 41a) has a deflection surface and the shoulder element (14) comprises two functional surfaces (16a, 42), namely an inclined surface (42a) also pointing in the axial direction and a laterally arranged rest surface (16), wherein the transmission body (15, 15a) in the engaged state of the clutch (1) is in contact with the inclined surface of the shoulder element (42a) transmitting the spring force, while in the disengaged state of the clutch (1) it rests against the lateral rest surface (16) of the shoulder element, and with with the further proviso that in the assembled state the tappet (9, 9a,9b) and the locking element (11) are assigned to a first of the two coupling elements (2) of the coupling (1), and that the other second coupling element (3) is assigned a locking area (12) which is designed complementarily to the locking element (11), characterized in that at least in the contact area of ​​the transmission body (15, 15a) and the tappet (9, 9a, 9b) a means for reducing wear is provided and / or at least in the contact area of ​​the transmission body (15, 15a) and at least, a pressure body (40, 40a, 41, 41a) is provided with a means for reducing wear.

2. Safety element (5a) according to claim 1, characterized in that the transmission body (15, 15a) is designed as a rolling body or sliding body, and that the means for reducing wear is designed as a groove (50, 51, 52, 53) for the transmission body (15, 15a).

3. Security element (5a) according to claim 2, characterized in that the groove (50, 51, 52, 53) extends in a radial direction or has a radial component which, in the mounted state, acts as a guide for the transmission body (15, 15a).

4. Security element (5a) according to one of claims 1 to 3, characterized in that as a means for reducing wear it is provided that the locking element (11) and / or the locking area element (28) is at least partially made of a ceramic material.

5. Security element (5a) according to one of claims 1 to 4, characterized in that as a means for reducing wear it is provided that at least one pressure body (40, 40a, 41, 41a) and / or at least one transmission body (15, 15a) is at least partially and / or the tappet (9, 9a, 9b) is at least partially made of a ceramic material.

6. Security element (5a) according to one of claims 1 to 5, characterized in that the rest surface (16) of the shoulder element of the plunger (9, 9b) is further developed into an action surface (49) which has an inclination relative to the axial direction of the plunger (9, 9b), namely is inclined by an angle (a) opposite to the axial direction of the plunger (9, 9b) .

7. Safety element (5a) according to claim 6, characterized in that the angle (a) of the inclination of the action surface (49) of the shoulder element (14) is in a range of 3° to 12°, preferably in a range of 5° to 10° and particularly preferably in a range of 7° to 8°.

8. Safety element (5a) according to one of claims 1 to 7, characterized in that a first axially movable pressure body (41, 41a) and a second pressure body (40, 40a) are provided, and that the second pressure body (40, 40a) is arranged stationary relative to the housing (10).

9. Safety element (5a) according to claim 8, characterized in that both pressure bodies (40, 40a, 41, 41a) are spring-loaded, that at least one of the two pressure bodies (40, 40a, 41, 41a) has an inclined deflection surface, that each of the deflection surfaces is in contact with the transmission body (15, 15a), and that at least the deflection surface of one of the two pressure bodies (40, 40a, 41, 41a) is arranged inclined at an angle to a radial plane.

10. Security element (5a) according to one of claims 1 to 9, characterized in that the bearing (LI, L2) of the plunger (9, 9a, 9b) is integrated into the housing (10), and that the housing (10) has a fastening means (18) which is prepared for the purpose of simple assembly of the safety element (5a) on a coupling element (2) .

11. Safety element (5a) according to one of claims 1 to 10, characterized in that the housing (10) is provided with an adjusting means (18) by means of which, in the assembled state, its axial position relative to the supporting coupling element (2) can be adjusted.

12. Security element (5a) according to one of claims 1 to 11, characterized in that the latching area (12) is designed as an exchangeable latching area element (28) which has a fixed positioning aid (31), wherein the positioning aid cooperates with a stop means of the relevant coupling element (3) in the mounted state.

13. Safety element (5a) according to one of claims 1 to 12, characterized in that a guide bush (34) is assigned which, in the assembled state, serves to guide the plunger (9, 9a, 9b) and / or to guide the locking element (11), wherein the guide bush (34) is concentric to the plunger (9, 9a, 9b) and is also assigned to the first coupling element (2).

14. Safety element (5a) according to claim 13, characterized in that the guide bush (34) is assigned as a separate component or is assigned as an integral part of the safety element (5a), for example is assigned to a housing part of the housing (10).

15. Security element (5a) according to one of claims 10 to 14, characterized in that the housing (10) has a closure element (43) as a housing part has the closure element (43) acting as a counter bearing for the spring device (23) and / or as a guide for the plunger (9, 9a, 9b) and / or the locking element (11).

16. Safety element (5a) according to claim 10 to 15, characterized in that the closure element (43) comprises a means by means of which its axial position relative to the housing (10) can be adjusted.

17. Security element (5a) according to one of claims 1 to 16, characterized in that the spring device comprises at least one disc spring, preferably a disc spring package (23) consisting of several disc springs.

18. Security element (5a) according to one of claims 1 to 17, characterized in that the tappet (9, 9a, 9b) is composed of a tappet shaft and a shoulder element connectable thereto.

19. Coupling (1) comprising two coupling elements (2, 3) which are rotatable about an axis (4) and which can be switched into a coupled state and a disengaged state, wherein in the coupled state a torque can be transmitted, wherein on one of the coupling elements (2, 3) on a defined diameter and concentric to the rotational axis (4) of the coupling element (2) several safety elements (5a) according to one of claims 1 to 18 are arranged and have a defined distance from one another, and wherein on the second coupling element (3) on an identical diameter and concentric to its rotational axis (4) a corresponding number of snap-in area elements (28) is arranged at the same distances as the safety elements (5a).

20. Coupling (1) according to claim 19, characterized in that a circumferential groove is provided on the second coupling element (3), which cooperates with the locking elements (11) of the safety elements (5a) in the uncoupled state.

Images