TORQUE LIMITING DEVICE AND METHOD FOR CALIBRATION THEREOF

Description

field of technology

[0001] The invention relates to a torque limiting device with two torque transmission bodies which, as a result of a helical flank contact during a relative rotation about an axis in the direction of the same axis, can be displaced relative to one another against the restoring force of a spring element which is supported on a shoulder of an abutment which is adjusted in position during a calibration of a limit torque.

[0002] The invention further relates to a calibration method for calibrating a torque transmission device with two torque transmission bodies which, as a result of a helical flank contact during a relative rotation about an axis in the direction of the same axis, can be displaced relative to one another against the restoring force of a spring element which is supported on a shoulder of an abutment which is adjusted in position during a calibration of a limit torque.

[0003] The invention further relates to a plurality of screwing tools, each of which has a torque limiting device of the same design. State of the art

[0004] A torque limiting device of this type is described in DE 10 2014 212 222 A1. A steel shaft has a screwing tool profile at its free end. The opposite end of the shaft has an external thread onto which a nut is screwed. A first torque transmission body, which is connected to the shaft in a rotationally and axially fixed manner, rests on a projection of the shaft. The torque transmission body has torque transmission teeth with sawtooth-like tooth flanks. A second torque transmission body, which is acted upon by a spring element in the axial direction of the shaft, rests on an inclined tooth flank of a torque transmission tooth. The spring element rests on the nut screwed onto the external thread of the shaft.This torque limiting device can be installed in a screwdriving tool; for example, the torque transmission device can be inserted into a handle recess of a screwdriver handle, as shown in EP 1 631 418 B1. The torque limiting device can be calibrated using the nut. Turning the nut changes the preload of the spring element, which is applied to the second torque transmission body in the axial direction. If a torque is generated between the two torque transmission bodies, this leads to a relative rotation of the second torque transmission body, which is axially movable and rotatably associated with the shaft, with respect to the first torque transmission body. During this relative rotation, the two inclined flanks slide against one another, with the result that the two torque transmission bodies move axially away from one another.During this axial displacement of the second torque transmission body, the spring element is tensioned until the torque transmission tooth of the second torque transmission body overruns the torque transmission tooth of the first torque transmission body. The spring preload then reached corresponds to a trigger torque, at which point no more torque is transmitted from one torque transmission body to the other torque transmission body, because the two torque transmission bodies rotate relative to each other when this limit torque is exceeded.

[0005] In the current state of the art, this release torque is adjusted by turning the nut.

[0006] WO 2014 / 035496 A1 discloses a torque limiting device with an abutment acting on a spring element, which is formed of a single material support element attached to a shaft. The torque limiting value is changed by replacing the abutment and / or the spring element.

[0007] In EP 1 092 510 A2, the preload of the spring element is adjusted by selecting individual components, such as a spring element and washers.

[0008] DE 10 2016 013174 A1 also discloses a fixed torque limiter, wherein the torque limiter is set by specifying the relative alignment of two housing components between which the spring element is arranged.

[0009] Furthermore, there are torque limiting devices in the prior art that do not allow calibration of the trigger torque. In the manufacture of such torque limiting devices, spring elements are used whose spring constants lie within a narrow tolerance range. Initial calibration can be performed using washers. Such a screwing tool is described in EP 1 092 510 B1.

[0010] DE 10 2016 013 174 A1 describes a miniature torque tool with a flat housing from which a shaft protrudes, mounted within the housing. Two torque transmission elements are mounted on the shaft, with one torque transmission element being biased against the other by a compression spring. The force with which the compression spring acts on the torque transmission element is determined during assembly of the two housing parts. The two housing parts are biased against each other with a predetermined force and welded together in this state. Summary of the invention

[0011] The invention is based on the object of specifying a screwing tool calibrated using simple means and proposing measures by which the calibrated release torque cannot be subsequently changed, as well as specifying a method by which such a calibration is possible.

[0012] The problem is solved by the invention specified in the claims, wherein the subclaims represent not only advantageous developments of the independent claims, but also independent solutions to the problem.

[0013] First and foremost, it is proposed that the torque limiting device is not calibrated by measuring a triggering torque or limiting torque that can be transmitted by the torque transmission bodies, but rather that the spring element is preloaded using a predetermined force, whereby the preloading of the spring element establishes an axial position of the abutment in which the abutment is irreversibly fixed. By irreversibly fixing the abutment, a triggering torque once set can no longer be changed. This increases the tamper-proof nature of a torque tool calibrated to a specific torque value. The abutment is preferably fixed in the axial position found by applying a predetermined force while the spring element is still subjected to the predetermined force.This can be achieved, for example, by applying a predetermined weight force to the spring element or an intermediate element resting on the spring element, such as a washer. Standard weights can be used for this purpose. Since the spring elements, which are preferably formed by helical compression springs, have lengths and spring constants subject to tolerances, the preloaded spring elements are given an individual axial length in which the preferably helical compression spring, subjected to the predetermined force and compressed, is fixed in position. The axial position of the abutment can be irreversibly determined in various ways, for example by a positive connection, a non-positive connection, or a material connection to a shaft or to another element of the torque-limiting device that is axially fixed to a torque-transmitting body.For example, it is possible to connect an abutment body to a free end of a shaft via a weld point or a soldered connection. However, the shoulder can also be formed by a weld point itself. It is also possible to connect an abutment body to the shaft via an adhesive connection. Form-fitting connections between an abutment body and the shaft are also possible, for example by creating a bore and inserting a cotter pin through it, whereby the spatial assignment of the abutment body to the shaft of the torque limiting device occurs when the spring element is preloaded. Instead of the cotter pin, a wedge can also be used, which is inserted into a longitudinal slot in the shaft and irreversibly fixed there. A nut known from the prior art can, for example, be irreversibly rotationally fixed via a weld point or the like.In a preferred embodiment of the torque limiting device according to the invention, the abutment is created by plastic deformation. In particular, it is provided that a free end of a shaft is plastically deformed so that a shoulder is formed against which the spring element, preferably the helical compression spring made of steel, is supported, optionally with the interposition of an intermediate member, for example a washer. The other end of the spring element can be supported on a torque transmission body that is axially movable relative to the shaft and rotatable relative to the shaft, which forms inclined flanks that bear against inclined flanks of another torque transmission body that is axially and rotationally fixedly connected to the shaft. A second intermediate member, also in the form of a washer, can be provided, which is assigned to the second torque transmission body.The spring element can thus be supported at each end on a washer. The first torque transmission body, which is connected to the shaft in a rotationally fixed manner, can be placed on an insert piece. The insert piece can be inserted into a cavity of the second torque transmission body. The insert piece is preferably a hexagonal drive plate having an external hexagon and an internal hexagon opening. The cavity of the torque transmission body has an internal hexagon profile in which the external hexagon profile of the hexagonal drive plate fits in a form-fitting manner. The flanks of the internal hexagon profile of the hexagonal drive plate rest against a hexagonal section of the shaft. The hexagonal drive plate increases the torque that can be transmitted from the shaft to the second torque transmission body.To displace the two torque-transmitting bodies relative to each other in the axial direction when a relative torque is applied, a lifting device can be provided. This lifting device can be formed by torque-transmitting teeth that form inclined flanks that abut one another and slide off one another during the relative displacement. Alternative designs of a lifting device are also possible. For example, balls can be provided that lie in ball-receiving openings, with each of the two torque-transmitting bodies having one or more ball-receiving openings.

[0014] The method according to the invention allows a large number of essentially identical torque limiting devices to be calibrated in a simple manner. For this purpose, torque transmission bodies are used which have torque transmission teeth with inclined tooth flanks that lie in a surface-to-surface contact with one another when not subjected to torque. However, it can also be provided that only one torque transmission body has one or more inclined flanks, against which, for example, a rounding or other peripheral edge of the other torque transmission body rests. It is essential that the pitch of the inclined flank of the at least one torque transmission body forming an inclined flank lies within a narrow tolerance range.These manufacturing constraints can be adequately met if the torque transmission bodies are plastic or metal injection-molded parts, sintered parts, milled parts, or investment castings. The slope and the axial distance of the inclined surface from the rotational axis define the triggering torque at a given force.

[0015] The calibration method according to the invention uses spring elements which, due to tolerances, have different lengths and different spring constants. According to the invention, the torque limiting device is calibrated during its assembly, whereby firstly the two torque transmission bodies are mounted on a shaft, if necessary a washer is placed on the uppermost torque transmission body and then the spring element, which can be a steel spring, is placed on the uppermost torque transmission body. Optionally, an intermediate member, for example a washer, can be placed on the upwardly facing end of the spring element. The spring element or the intermediate member is projected over by a section of the shaft on which the lower torque transmission body is supported.In a calibration step, the spring element is now subjected to a predefined force from above, for example the weight of a standard weight. This results in the spring element being compressed to a specific length. The spring element is then fixed in position at this calibrated length. This is achieved by positioning a shoulder of an abutment, whereby it is particularly provided that the shoulder is created by plastic deformation when the upward-facing end of the spring element is fixed in position. For example, two pressing jaws can be provided which act on the free end of the shaft in the radial direction so that its cross-section is reduced and shoulders extending transversely to the force application are formed, against which the spring element or the intermediate link can be supported.In this variant of the invention, the predetermined force is used to set a base length of the spring element, which is further reduced when a torque is applied to the two torque-transmitting bodies, down to a trigger length at which the torque-transmitting tooth of the rotatable torque-transmitting body overruns the torque-transmitting tooth of the torque-transmitting body connected to the shaft in a rotationally fixed manner. However, in a variant of the invention, it can also be provided that the predetermined force is used to set the spring preload, which corresponds to the trigger torque. In this second variant of the method, a larger predetermined force is used than in the first variant.While in the first process variant the abutment is created or fixed exactly at the position at which the spring element or the intermediate link is to be supported, in the second process variant the abutment can be created at an axial distance from the upper end of the spring element or the intermediate link, wherein the distance between the upper end of the spring element or the upper end of the intermediate link from the abutment or the shoulder forming the abutment corresponds to the axial displacement path of the movable torque transmission body, for example the height of a torque transmission tooth.Alternatively, when fixing the position of the abutment, the two torque transmission bodies can also be moved into a rotational position in which the torque transmission teeth rest against each other, thus maintaining a spacing position between the torque transmission bodies that is reached when the triggering torque is exceeded. In this position of the torque transmission bodies, the spring element resting on the upper torque transmission body can then be adjusted in length by applying a predetermined force, and the abutment is created or fixed in position in this length setting.

[0016] The invention thus relates to a torque limiting device in which a spring element is clamped between two bearing elements, one of which forms a bearing and the other an abutment. Both the bearing and the abutment are preferably irreversibly fastened to a shaft. According to a further development of the invention, it is proposed that the abutment be formed by an intermediate member or support element. The support element can have a plate-shaped section on which one of the torque transmission bodies or the compression spring is directly supported. The support element is preferably fixed to the shaft accompanied by plastic deformation. This is achieved in the manner described above by subjecting the support element to a predetermined force in the axial direction of the shaft during calibration.The interlocking teeth of the torque transmission bodies can be positioned head to head, thereby setting the force that must be overcome when triggering the limit torque. In a preferred embodiment, the support element, which can be made of a softer material than the preferably hardened shaft, which can also form the screwing tool, has a neck that protrudes from the plate-shaped section. The inner diameter of the neck extending in the axial direction is preferably only slightly larger than the outer diameter of the shaft, so that the support element can be slipped onto the shaft. In a preferred embodiment, the end of the shaft has a recess, which in particular has a conical surface. The recess can also have a step. The conical surface preferably borders on an annular step.During the irreversible fixation of the support element to the shaft, material from the neck is pressed into this recess. This is done using a pressing tool. The pressing takes place while the support element is subjected to a predetermined force in the axial direction. The material of the support element flows into the recess in the shaft to create a positive connection. The recess can extend around the entire shaft. In a further development of the invention, it can be provided that a plain bearing washer is arranged between one end of the spring element and the support element. The plain bearing washer can be formed by a washer. This decouples the contact surface of the spring element from the support element in terms of rotation. Several such plain bearing washers, for example washers, can be installed.They can then be arranged in a stacked manner, allowing the shaft, together with the support element attached to the shaft, to rotate relative to the spring element. The plain bearing disc can be made of a material typical for plain bearings, such as steel, plastic, ceramic, graphite, or sintered materials. Non-ferrous alloys are also possible. Such a plain bearing disc can also be used in designs in which the shaft is plastically deformed to perform a supporting function. Short description of the drawings

[0017] Embodiments of the invention are explained below with reference to the accompanying drawings. They show: Fig. 1a torque transmission device inserted into a screwing tool handle, Fig. 2the top view of the torque transmission device according to Figure 1, Fig. 3 shows the section along the line III-III enlarged, with two torque transmission bodies 1, 2 assuming their basic position and being acted upon by a pre-tensioned spring element 8, Fig. 4 shows a representation according to Figure 3 , however, the two torque transmission bodies 1, 2 have been rotationally displaced against each other until the spring element 8 receives a minimum length L2, Fig. 5 a representation similar to the Figure 3 , but in an assembly position in which the uncompressed spring element 8 has a neutral length L0, Fig. 6 a representation according to Figure 5 after applying a predetermined force F1 to the spring element 8, at which the spring element 8 is compressed to the calibration length L1, Fig. 7 a subsequent illustration in which the upper end of the spring element 8 is fixed in position relative to the shaft 3, Fig. 8 an exploded view, Fig. 9 a section along the line IX-IX in Figure 4, Fig. 10 a further embodiment of the invention in a representation according to Figure 3 , Fig. 11that in the Figure 10 illustrated embodiment after fixing the support element 21 on the shaft 3, Fig. 12 a representation according Figure 11 , but with a spring element 8 which has a different spring characteristic, wherein the support element is fastened in a different axial position to the shaft 3, Fig. 13 a representation of a further embodiment according to Figure 10 . Description of the embodiments

[0018] The torque limiting device has a shaft 3 made of steel, which has a projection or step 16 on which a first torque transmission body 1 is supported. The torque transmission body 1, manufactured, for example, as a plastic injection-molded part, metal injection-molded part, milled part, or investment casting part, is connected to the shaft 3 in a rotationally fixed manner and does not change its axial position relative to the shaft 3. The first torque transmission body 1 has a torque transmission tooth with an inclined flank 4 and a steep flank 6 opposite it. In the exemplary embodiment, a washer 17 is supported on the step 16, on which washer 17, in turn, the torque transmission body 1 is supported. The torque transmission body 1 has a cavity open to the washer 17 with a hexagonal inner profile, into which a hexagonal drive disk 20 made of steel is inserted.This has a polygonal inner profile which is filled by a polygonal outer profile section 3' of the shaft 3.

[0019] A second torque transmission body 2, which can also be designed as a plastic injection-molded part or metal injection-molded part, a milled part, an investment casting part, or a sintered part, can be displaced relative to the first torque transmission body 1 in the axial direction and in the circumferential direction, relative to the axis A. The second torque transmission body 2 can be connected in a rotationally fixed manner to a handle, which, for example, has a cavity in which the torque transmission device is inserted. For this purpose, the second torque transmission body 2 can have circumferential grooves or circumferential ribs 13 extending in the axial direction, which engage with a counter-profile of the cavity of the handle. The second torque transmission body 2 also has torque transmission teeth. The gaps between the two torque transmission teeth form a second inclined flank 5 and a second steep flank 7. The second inclined flank 5 lies in surface contact with the first inclined flank 4.The second steep flank 7 is located in a flat area on the first steep flank 6.

[0020] The second torque transmission body 2 has a support surface 18, against which a lower end of a spring element 8, designed as a steel helical compression spring, rests. In the exemplary embodiment, the support surface 18 is formed by a metal disc 19, which lies in a cavity of the torque transmission body 2.

[0021] The shaft 3 extends through the spring element 8 and projects beyond the upwardly pointing second end of the spring element 8 and a washer resting on the upper end of the spring element 8, forming an intermediate member 11, through whose hole 12 the shaft 3 extends. In this, in the Figure 5In the state shown, the spring element 8, which is not subjected to force, has its neutral length L0. The shaft section 3' of the shaft 3 extending through the spring element 8 preferably has a round profile.

[0022] In a further assembly step, which is carried out in the Figure 6 As shown, the upper end of the spring element 8, or the intermediate member 11 resting thereon and formed by a washer, is subjected to a predetermined force F1 in the axial direction. This leads to a shortening of the length of the spring element 8 to a calibration length L1.

[0023] Instead of a single intermediate link 11, several intermediate links 11 can also be arranged one above the other. The intermediate links 11 then form sliding bearing plates that can slide against each other during a rotational movement of the shaft relative to the spring element 8.

[0024] In the following, in the Figure 7In the method step shown, the spring element 8 is fixed in this length L1. This is done by applying radial forces F2 to the end of the shaft 3 which projects beyond the upper end of the spring element 8 or the washer, which end forms an abutment 9. Due to this force application, which can be carried out using two pressure jaws, the free end of the shaft 3 is deformed into the abutment 9. This creates shoulders on which the washer can be supported. This creates two opposing broad side surfaces 14 whose distance from one another is smaller than the diameter of the shaft, so that a material flow occurs towards the narrow sides 15, which form the shoulders on which the intermediate link 11 is supported.

[0025] It is then the one in the Figures 1 and 3The illustrated operating condition is reached. If, in this state, the first torque transmission body 1 is held stationary and a clockwise torque is applied to the second torque transmission body 2, the two inclined flanks 4, 5 slide against each other. If a torque is applied in the opposite direction, the two steep flanks 6, 7 rest against each other.

[0026] When applying the torque in a clockwise direction, the two inclined flanks 4, 5 can be turned to the position shown in the Figure 4 The two torque transmission bodies 1, 2 slide against each other in the position shown. In this position, the two torque transmission bodies 1, 2 are spaced apart by approximately the height of the torque transmission tooth. The spring element 8 has been compressed from length L1 to the shortened length L2. This position corresponds to a triggering torque, which corresponds to the limit torque that can be transmitted with the torque limiting device.

[0027] In a variant of the calibration of the torque limiting device, in the Figure 6 In the step shown, a larger force F1 is used, which compresses the spring element 8 to the length L2. The stop step of the abutment 9 is then generated at a defined axial distance from the upper edge of the washer 11 or the spring element 8, wherein this axial distance corresponds to the maximum axial displacement path of the second torque transmission body 2 relative to the first torque transmission body 1, i.e. approximately the height of the torque transmission tooth.

[0028] In a further variant of the calibration, the loading of the spring element 8 with a calibration force F1 generated, for example, by a standard weight, as shown in Figure 6 can also be carried out in the Figure 4 shown state when the calibration teeth of the two torque transmission bodies 1, 2 rest against each other.

[0029] In the Figures 10 to 12 In the further embodiment shown, the shaft 3 is made of a hardened material and forms the screwing tool. However, it can also be provided that a chuck is arranged at the free end of the shaft 3 for receiving a screwing tool.

[0030] It is essential that the spring element 8 is supported on a plate-shaped section of a support element 21. The essentially rotationally symmetrical support element 21 has a disc-shaped section that forms the support shoulder 10. A neck 22 protrudes from this section in the axial direction, the inner diameter of which is slightly larger than the outer diameter of the shaft 3. This neck 22 is placed on the end of the shaft 3 and is subjected to an axial force in the manner described above to calibrate the torque limiting device. The teeth of the two torque transmission bodies 1, 2 can mesh with each other, as is the case with the Figure 10 It is also possible that the heads of the teeth of the torque transmission bodies 1, 2 rest on each other, as shown in the Figures 11 and 12 show.

[0031] The irreversible fixation of the support element 21 is achieved by a deformation force applied transversely to the direction of extension of the shaft. The deformation force is generated by deformation jaws (not shown). Several jaws arranged in a star shape can be provided, which move toward each other in a radial direction to secure the neck 22 to the end of the shaft.

[0032] The end of the shaft has a recess 23 with a conical surface 24 adjacent to a step 25. The material, preferably softer than the material of the shaft 3 of the neck 22, is pressed into this recess 23.

[0033] In the Figure 13In the illustrated embodiment, an intermediate member 11 in the form of a plain bearing disk is arranged between the end of the spring element 8 and the support element 21. The plain bearing disk 11 is designed as a washer and can be made of steel, plastic, ceramic, graphite, a sintered material, or a non-ferrous alloy. Several such intermediate members 11 can also be arranged one above the other. The purpose of this intermediate member 11 is to minimize friction. The shaft 3 can rotate relative to the spring element 8 when the limit torque is exceeded. The broad side surface of the intermediate member 11 facing the support element 21 forms a sliding friction surface that rotates relative to a broad side counter surface of the support element 21 upon rotation. The surface friction of the superimposed broad side surfaces is reduced by a friction-reducing surface property.The invention thus also relates to a device in which a sliding disc 11 is arranged between the spring element 8 and the support element 21, which slides against a counter-sliding surface of the support element 21 with a sliding surface.

[0034] The above statements serve to explain the inventions covered by the application as a whole, which each independently develop the state of the art by at least the following combinations of features, whereby two, several or all of these combinations of features can also be combined, namely:

[0035] A torque limiting device, which is characterized in that the abutment 9 is formed of the same material as the shaft 3 or by a support element 11, 21 irreversibly fastened to the shaft 3.

[0036] A torque limiting device, which is characterized in that the support element 21 is fastened to the shaft 3 by forming a positive connection accompanied by a plastic deformation.

[0037] A torque limiting device, which is characterized in that the support element 21 forms a broad side of a plate-shaped section facing the spring element 8 and a neck 22 pointing away from the broad side, which is connected to the shaft 3 with the formation of a plastic deformation.

[0038] A torque limiting device, which is characterized in that the shaft 3 has a recess 23 into which material of the support element 21 or a neck 22 of the support element 21 is pressed.

[0039] A torque limiting device characterized in that the recess 23 has a conical surface 24 and / or a step 25.

[0040] A torque limiting device, which is characterized in that the spring element 8 is supported on the abutment 9 directly or with the interposition of an intermediate member 11, wherein it is provided in particular that the intermediate member 11 is a washer and / or that the spring element 8 is supported on one of the torque transmission bodies 1, 2 with the interposition of a second intermediate member 19, in particular a washer 19.

[0041] A torque limiting device, which is characterized in that the torque transmission bodies 1 are spaced apart from one another by means of a lifting device during relative rotation, wherein the lifting device is formed in particular by a first oblique flank 4 of a first torque transmission body 1, which is fixedly connected to the shaft 3, and a second oblique flank 5 of a second torque transmission body 2, which is rotatable relative to the shaft 3, wherein it is provided in particular that the second torque transmission body 2 is assigned to a handle in a rotationally fixed but axially displaceable manner, wherein it is provided in particular that the torque limiting device is arranged in a cavity of the handle, in which the second torque transmission body 2 can be displaced in the axial direction and / or that the second torque transmission body 2 is axially displaceable as a result of ribbing in a cavity of the handle.

[0042] A torque limiting device which is characterized by a plain bearing disk 11 which bears against a counter surface of the support element 11 in a sliding frictional contact, on which the spring element 8 is supported.

[0043] A method which is characterized in that two torque transmission bodies 1, 2 which can be displaced relative to one another against the restoring force of a prestressed spring element 8 during a relative rotation about the axis A in the direction of the same axis A, wherein the spring element 8, which has a neutral length L0 in the unloaded state, is brought from the neutral length L0 to a calibrated length L1, L2 by axial application of a predetermined external force F1, in which an abutment 9 is irreversibly fixed, characterized in that the length L1, L2 is fixed by a plastic deformation.

[0044] A method which is characterized in that both a bearing 17 and the abutment 9, between which the spring element 8 is clamped, are irreversibly fastened to a shaft 3.

[0045] A method which is characterized in that the abutment 9 is formed of the same material as the shaft 3 or of a support element 11, 21 which is irreversibly fastened to the shaft 3.

[0046] A method which is characterized in that when the abutment 9 is fixed, the torque transmission teeth of the torque transmission bodies 1, 2 are supported on one another.

[0047] A production batch characterized in that the torque limiting device is designed according to one of claims 1 to 7 and the predetermined force F1 is the same for all torque limiting devices.

[0048] A production batch characterized in that the torque limiting device is formed according to a method according to any one of claims 8 to 11, wherein the predetermined force F1 is the same for all torque limiting devices.

[0049] All disclosed features are essential to the invention (individually, but also in combination with one another). List of reference symbols

[0050] 1 Torque transmission body 22 Neck 2 Torque transmission body 23 recess 3 shaft 24 Conical surface 3' Hexagonal section 25 Level 3" circular section 26 groove 4 inclined flank 5 inclined flank 6 Steep flank 7 Steep flank A axis of rotation 8 spring element F1 Power 9 abutment F2 Power 10 Support shoulder L0 Neutral length 11 intermediate link (washer) L1 length 12 Hole 13 rib 14 broadside α angle 15 narrow side 16 Level 17 washer 18 Support surface 19 Intermediate link (washer / plain bearing washer) 20 Hexagonal drive plate 21 Support element

Claims

1. A torque-limiting device having two torque transfer bodies (1, 2), whereof at least one is displaceable during a relative rotation about an axis (A) in the direction of said axis (A) with respect to the other torque transfer body (2, 1) against the restoring force of a spring element (8) clamped with pretensioning between a bearing (17) and an abutment (9) along a shaft (3) extending in the axis (A), wherein the pretensioning of the spring element (8) is set irreversibly by the axial position of the abutment (9) during the production of the torque-limiting device, characterised in that the abutment (9) can be connected to the shaft (3) during assembly in such a way that the axial position of the abutment (9) can be predetermined by applying a predetermined external force (F1) to the spring element (8) before the abutment (9) is fastened to the shaft (3).

2. The torque-limiting device according to claim 1, characterised in that the support element (21) is fastened to the shaft (3) thereby forming a form-fit connection in conjunction with a plastic deformation.

3. The torque-limiting device according to one of the preceding claims, characterised in that the support element (21) forms a wide side of a saucer-shaped section that points towards the spring element (8) and a neck (22), which points away from the wide side and which is connected to the shaft (3) thereby forming a plastic deformation.

4. The torque-limiting device according to claim 2, characterised in that the shaft (3) comprises a recess (23), into which material of the support element (21) or of a neck (22) of the support element (21) is pressed.

5. The torque-limiting device according to claim 4, characterised in that the recess (23) has a conical surface (24) and / or a step (25).

6. The torque-limiting device according to one of the preceding claims, characterised in that the spring element (8) is supported on the abutment (9) directly or with the interposition of an intermediate element (11), it being provided in particular that the intermediate element (11) is a washer and / or that the spring element (8) is supported on one of the torque transfer bodies (1, 2) with the interposition of a second intermediate member (19), in particular a washer (19).

7. The torque-limiting device according to one of the preceding claims, characterised in that the torque transfer bodies (1) move away from one another during the relative rotation by means of a lifting device, wherein the lifting device is formed in particular by a first oblique flank (4) of a first torque transfer body (1), which is fixedly connected to the shaft (3), and a second oblique flank (5) of a second torque transfer body (2), which is rotatable with respect to the shaft (3), or that a second torque transfer body (2) is assigned rotationally fixed but axially displaceable to a handle, or that the torque-limiting device is arranged in a cavity of the handle, in which a second torque transfer body (2) can move in the axial direction or that a second torque transfer body (2) is axially displaceable as a consequence of ribbing in a cavity of the handle.

8. The torque-limiting device according to one of the preceding claims, characterised by a sliding bearing disc (11) lying in sliding friction surface contact against a counter-surface of the support element (11), on which sliding bearing disc the spring element (8) is supported.

9. A method for calibrating a torque-limiting device, according to one of the preceding claims, with two torque transfer bodies (1, 2), which are displaceable during a relative rotation about the axis (A) in the direction of said axis (A) relative to one another against the restoring force of a pretensioned spring element (8), wherein the spring element (8) having a neutral length (L0) in the state when the force is not applied is brought from the neutral length (L0) to a calibrated length (L1, L2) by axial application with a predefined external force (F1), in which calibrated length an abutment (9) is irreversibly fixed, characterised in that the length (L1, L2) is fixed by a plastic deformation.

10. The method according to claim 9, characterised in that both a bearing (17) and the abutment (9), between which the spring element (8) is clamped, are irreversibly fastened to a shaft (3).

11. The method according to one of the claims 9 or 10, characterised in that the abutment (9) is formed uniformly in terms of material by the shaft (3) or by a support element (11, 21) fastened irreversibly to the shaft (3).

12. The method according to one of the claims 9 to 11, characterised in that the torque transfer teeth of the torque transfer bodies (1, 2) rest against one another when the abutment (9) is fixed.

13. A production batch of torque transfer tools which comprises a plurality of screwdrivers with in each case a torque-limiting device, characterised in that the torque-limiting device is constituted according to any one of claims 1 to 8 and the predefined force (F1) is the same in the case of all the torque-limiting devices.

14. A production batch of torque transfer tools which comprises a plurality of screwdrivers with in each case a torque-limiting device, characterised in that the torque-limiting device is produced according to a method according to one of claims 9 to 12, wherein the predefined force (F1) is the same in the case of all the torque-limiting devices.

15. The torque-limiting device according to one of the claims 9 to 12, characterised in that the support element (11, 21) fixes in position the length of the spring element (8) calibrated by application of a predefined force to the spring element (8).