Torque-Limiting Device And Method For The Calibration Thereof

Abstract

A torque-limiting device having two torque transfer bodies, which, as a consequence of oblique flank contact during relative rotation about an axis, can be moved relative to each other in the direction of the axis against the restoring force of a spring element, which is supported on a shoulder of an abutment, the position of which shoulder is set during calibration of a limiting torque. The torque-limiting device is calibrated by applying a predefined force to the spring element. The resulting spring length defines the axial position of the shoulder of the abutment, which axial position is irreversibly fixed.

Claims

1-15. (canceled)

16. A torque-limiting device having two torque transfer bodies, whereof at least one is displaceable during a relative rotation about an axis in the direction of said axis with respect to the other torque transfer body against the restoring force of a spring element clamped with pretensioning between a bearing and an abutment along a shaft extending in the axis, wherein the pretensioning of the spring element is set irreversibly by the axial position of the abutment during the production of the torque-limiting device, wherein the abutment is formed uniformly in terms of material by the shaft or by a support element fastened irreversibly to the shaft.

17. The torque-limiting device according to claim 16, wherein the support element is fastened to the shaft thereby forming a form-fit connection in conjunction with a plastic deformation.

18. The torque-limiting device according to claim 16, wherein the support element forms a wide side of a saucer-shaped section that points towards the spring element and a neck, which points away from the wide side and which is connected to the shaft thereby forming a plastic deformation.

19. The torque-limiting device according to claim 17, wherein the shaft comprises a recess, into which material of the support element or of a neck of the support element is pressed.

20. The torque-limiting device according to claim 19, wherein the recess has a conical surface and/or a step.

21. The torque-limiting device according to claim 16, wherein the spring element is supported on the abutment directly or by interposing an intermediate element, and/or that the spring element is supported on a washer and/or that the spring element is supported on a torque transfer body by interposing a second intermediate element, in particular a washer.

22. The torque-limiting device according to claim 16, comprising: torque transfer bodies which move away from one another during relative rotation by means of a lifting device, wherein the lifting device is formed by a first oblique flank of a first torque transfer body which is fixedly connected to a shaft, and a second oblique flank of a second torque transfer body which is rotatable with respect to the shaft, or that a second torque transfer body 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 can move in the axial direction or that a second torque transfer body is axially displaceable as a consequence of ribbing in a cavity of the handle.

23. The torque-limiting device according to claim 16, wherein a sliding bearing disc lying in sliding friction surface contact against a counter-surface of the support element, on which sliding bearing disc the spring element is supported.

24. The torque-limiting device according to claim 16, wherein the bearing is fastened irreversibly to the shaft.

25. The torque-limiting device according to claim 16, wherein the support element fixes in position the length of the spring element calibrated by application of a predefined force to the spring element.

26. A method for calibrating a torque-limiting device, with two torque transfer bodies, whereof at least one is displaceable during a relative rotation about an axis in the direction of said axis with respect to the other torque transfer body against the restoring force of a spring element clamped with pretensioning between a bearing and an abutment along a shaft extending in the axis, wherein the pretensioning of the spring element is set irreversibly by the axial position of the abutment during the production of the torque-limiting device, wherein the abutment is formed uniformly in terms of material by the shaft or by a support element fastened irreversibly to the shaft, the method including the spring element having a neutral length in the state when the force is not applied is brought from the neutral length to a calibrated length by axial application with a predefined external force, in which calibrated length an abutment is irreversibly fixed, and wherein the length is fixed by a plastic deformation.

27. The method according to claim 26, wherein both a bearing and the abutment, between which the spring element is clamped, are irreversibly fastened to a shaft.

28. The method according to claim 26, wherein the abutment is formed uniformly in terms of material by the shaft or by a support element fastened irreversibly to the shaft.

29. The method according to claim 26, wherein the torque transfer teeth of the torque transfer bodies rest against one another when the abutment is fixed.

30. A production batch of torque transfer tools which comprises a plurality of screwdrivers with in each case a torque-limiting device, wherein the torque-limiting device is constituted having two torque transfer bodies, whereof at least one is displaceable during a relative rotation about an axis in the direction of said axis with respect to the other torque transfer body against the restoring force of a spring element clamped with pretensioning between a bearing and an abutment along a shaft extending in the axis, wherein the pretensioning of the spring element is set irreversibly by the axial position of the abutment during the production of the torque-limiting device, wherein the abutment is formed uniformly in terms of material by the shaft or by a support element fastened irreversibly to the shaft and the predefined force is the same in the case of all the torque-limiting devices.

31. A production batch of torque transfer tools which comprises a plurality of screwdrivers with in each case a torque-limiting device having two torque transfer bodies produced according to a method wherein at least one of the two torque transfer bodies is displaceable during a relative rotation about an axis in the direction of said axis with respect to the other torque transfer body against the restoring force of a spring element clamped with pretensioning between a bearing and an abutment along a shaft extending in the axis, wherein the pretensioning of the spring element is set irreversibly by the axial position of the abutment during the production of the torque-limiting device, wherein the abutment is formed uniformly in terms of material by the shaft or by a support element fastened irreversibly to the shaft, wherein the spring element having a neutral length in the state when the force is not applied is brought from the neutral length to a calibrated length by axial application with a predefined external force, in which calibrated length an abutment is irreversibly fixed, wherein the length is fixed by a plastic deformation, and wherein the predefined force is the same in the case of all the torque-limiting devices.

Description

BRIEF DESCRIPTION OF THE INVENTION

[0012] Examples of embodiment of the invention are explained below with the aid of the appended drawings. The figures show the following:

[0013] FIG. 1 a torque transfer device used in a screwdriver handle,

[0014] FIG. 2 the plan view onto the torque transfer device according to FIG. 1,

[0015] FIG. 3 the cross-section through line III-III enlarged, wherein two torque transfer bodies 1, 2 occupy their basic position and are acted upon by a pretensioned spring element 8,

[0016] FIG. 4 a representation according to FIG. 3, wherein however the two torque transfer bodies 1, 2 have been moved rotationally with respect to one another until the spring element 8 acquires a minimum length L2,

[0017] FIG. 5 a representation similar to FIG. 3, but in an assembly position, in which uncompressed spring element 8 has a neutral length L0,

[0018] FIG. 6 a representation according to FIG. 5 after a predefined force F1 has been applied to spring element 8, wherein spring element 8 is compressed to calibration length L1,

[0019] FIG. 7 a sequence representation, in which the upper end of spring element 8 is fixed in position relative to the shaft 3,

[0020] FIG. 8 an exploded representation,

[0021] FIG. 9 a cross-section through line IX-IX in FIG. 4,

[0022] FIG. 10 a further example of embodiment of the invention in a representation according to FIG. 3,

[0023] FIG. 11 the example of embodiment represented in FIG. 10 after fixing of support element 21 to shaft 3,

[0024] FIG. 12 a representation according to FIG. 11, but with a spring element 8 which has a different spring characteristic, wherein the support element is fastened to shaft 3 in another axial position,

[0025] FIG. 13 a representation of a further example of embodiment according to FIG. 10.

DETAILED DESCRIPTION OF THE INVENTION

[0026] The torque transfer device comprises a shaft 3 produced from steel, which comprises a projection or a step 16, on which a first torque transfer body 1 is supported. Torque transfer body 1 produced for example as a plastic injection moulded part, a metal injection moulded part, a milled part, a precision cast part is connected rotationally fixed to shaft 3 and does not change its axial position with respect to shaft 3. First torque transfer body 1 comprises a torque transfer tooth with an oblique flank 4 and a steep flank 6 lying opposite the latter. In the example of embodiment, a washer 17 is supported on step 16, on which torque transfer body 1 is in turn supported. Torque transfer body 1 has a cavity, which is open towards washer 17, with a hexagonal inner profile, into which a hexagonal driver plate 20 produced from steel is inserted. The latter has a multi-edge inner profile, which is filled by a multi-edge outer profile section 3′ of shaft 3.

[0027] A second torque transfer body 2, which can also be constituted as a plastic injection moulded part, a metal injection moulded part, a milled part, a precision cast part or sintered part, can be moved with respect to first torque transfer body 1 in the axial direction and in the circumferential direction, relative to axis A. Second torque transfer body 2 can be connected rotationally fixed to a handle, which for example comprises a cavity, in which the torque transfer device is plugged. For this purpose, second torque transfer body 2 can comprise peripheral grooves or peripheral ribs 13 extending in the axial direction, which engage in a counter-profile of the cavity of the handle. Second torque transfer body 2 also comprises torque transfer teeth. The gaps between the two torque transfer teeth form a second oblique flank 5 and a second steep flank 7. Second oblique flank 5 lies in surface contact with first oblique flank 4. Second steep flank 7 lies in surface contact against first steep flank 6.

[0028] Second torque transfer body 2 comprises a support surface 18, on which a lower end of a spring element 8 constituted as a steel helical compression spring is supported. In the example of embodiment, support surface 18 is constituted by a metal disc 19, which lies in a cavity of torque transfer body 2.

[0029] Shaft 3 extends through spring element 8 and projects beyond the second upward-pointing end of spring element 8 and a washer forming an intermediate element 11 lying on the upper end of spring element 8, through a hole of which washer shaft 3 extends. In this state represented in FIG. 5, spring element 8, to which no force is applied, has its neutral length L0. Shaft section 3′ of shaft 3 extending through spring element 8 preferably has a round profile.

[0030] In a further assembly step, which is represented in FIG. 6, a predefined force F1 is applied in the axial direction to the upper end of spring element 8 or intermediate element 11 formed by a washer lying on said upper end. This leads to a shortening of the length of spring element 8 to a calibration length L1.

[0031] Instead of an intermediate element 11, a plurality of intermediate elements 11 can also be arranged one above the other. Intermediate elements 11 then form sliding bearing plates, which can slide against one another during a rotational movement of the shaft with respect to spring element 8.

[0032] In the following process step represented in FIG. 7, spring element 8 is fixed at this length L1. This takes place by the application of radial forces F2 on the end of shaft 3 projecting beyond the upper end of spring element 8 or the washer, which end of the shaft constitutes an abutment 9. On account of this application of force, which can take place using two pressure cheeks, the free end of shaft 3 is deformed to form abutment 9. Shoulders are thereby formed, on which the washer can be supported. Two mutually opposite wide-side surfaces 14 arise, the distance between which is smaller than the diameter of the shaft, so that a material flow towards narrow sides 15 takes place, which form the shoulders on which intermediate element 11 is supported.

[0033] The state ready for use represented in FIGS. 1 and 3 is then reached. If, in this state, first torque transfer body 1 is held fixed in position and a torque is applied in the clockwise direction to second torque transfer body 2, the two oblique flanks 4, 5 slide over one another. If a torque is applied in the opposite direction, the two steep flanks 6, 7 rest against one another.

[0034] When the torque is applied in the clockwise direction, the two oblique flanks 4, 5 slide over one another until they are in the position represented in FIG. 4. In this position, the two torque transfer bodies 1, 2 have become spaced apart from one another roughly by the height of the torque transfer tooth. Spring element 8 has been compressed from the length L1 to shortened length L2. This position corresponds to a release torque, which corresponds to the limiting torque that can be transferred by the torque-limiting device.

[0035] In a variant of the calibration of the torque-limiting device, a greater force F1 can be used in the step represented in FIG. 6, which compresses spring element 8 to length L2. The striking step of abutment 9 is then produced at a defined axial distance from the upper edge of washer 11 or spring element 8, wherein this axial distance corresponds to the maximum axial displacement path of second torque transfer body 2 with respect to first torque transfer body 1, i.e. roughly the height of the torque transfer tooth.

[0036] In a further variant of the calibration, the application of a calibration force F1 generated for example by a standard weight to spring element 8, as represented in FIG. 6, can also take place in the state represented in FIG. 4, when the calibration teeth of the two torque transfer bodies 1, 2 rest against one another.

[0037] In the further example of embodiment represented in FIGS. 10 to 12, shaft 3 is produced from a hardened material and forms the screwdriver. Provision can however also be made such that a chuck is arranged at the free end of shaft 3 for receiving a screwdriver.

[0038] It is essential that spring element 8 is supported on a saucer-shaped section of a support element 21. Essentially rotation-symmetrical support element 21 comprises a disc-shaped section, which forms support shoulders 10. Projecting from this section in the axial direction is a neck 22, the inner diameter of which is slightly larger than the outer diameter of shaft 3. This neck 22 is pushed onto the end of shaft 3 and is acted upon by an axial force in the manner described above for the calibration of the torque-limiting device. The teeth of the two torque transfer bodies 1, 2 can engage into one another, as is shown in FIG. 10. It is however also possible for the heads of the teeth of torque transfer bodies 1, 2 to rest on one another, as is shown in FIGS. 11 and 12.

[0039] The irreversible fixing of support element 21 takes place by means of a deformation force applied perpendicular to the direction of extension of the shaft. The deformation force is generated by deformation cheeks (not represented). A plurality of cheeks arranged star-shaped can be provided, which move towards one another in the radial direction in order to fasten neck 22 to the end of the shaft.

[0040] The end of the shaft comprises a recess 23, which has a conical surface 24 which is adjacent to a step 25. The preferably softer material than the material of shaft 3 of neck 22 is pressed into this recess 23.

[0041] In the example of the embodiment represented in FIG. 13, an intermediate element 11 in the form of a sliding bearing disc is arranged between the end of spring element 8 and support element 21. Sliding bearing disc 11 is constituted as a washer and can be produced from steel, plastic, ceramics, graphite, a sintered material or a nonferrous alloy. A plurality of such intermediate elements 11 can also be arranged above one another. The purpose of this intermediate element 11 is to reduce friction. When the limiting torque is exceeded, shaft 3 can rotate with respect to spring element 8. The wide-side surface of intermediate element 11 pointing towards support element 21 forms a sliding friction surface, which rotates when there is a rotation with respect to the wide-side surface of support element 21. The surface friction of wide-side surfaces lying one upon the other is reduced by a friction-reducing surface property. The invention thus also relates to a device, wherein a sliding disc 11 is arranged between spring element 8 and support element 21, which sliding disc abuts with a sliding surface against a counter-sliding surface of support element 21.

[0042] The above embodiments serve to explain the inventions covered as a whole by the application, which each also independently develop the prior art at least by the following combinations of features, wherein two, a plurality or all of these combinations of features can also be combined, namely:

[0043] A torque-limiting device, which is characterised in that abutment 9 is formed uniformly in terms of material by shaft 3 or by a support element 11, 21 fastened irreversibly to shaft 3.

[0044] A torque-limiting device, which is characterised in that support element 21 is fastened to shaft 3 thereby forming a form-fit connection in conjunction with a plastic deformation.

[0045] A torque-limiting device, which is characterised in that support element 21 forms a wide side of a saucer-shaped section that points towards spring element 8 and a neck 22, which points away from the wide side and which is connected to shaft 3 thereby forming a plastic deformation.

[0046] A torque-limiting device, which is characterised in that shaft 3 comprises a recess 23, into which material of support element 21 or a neck 22 of support element 21 is pressed.

[0047] A torque-limiting device, which is characterised in that recess 23 has a conical surface 24 and/or a step 25.

[0048] A torque-limiting device, which is characterised in that spring element 8 is supported on abutment 9 directly or with interposing an intermediate element 11, wherein provision is in particular made such that intermediate element 11 is a washer and/or that spring element 8 is supported on one of torque transfer bodies 1, 2 by interposing a second intermediate element 19, in particular a washer 19.

[0049] A torque-limiting device, which is characterised in that 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 shaft 3, and a second oblique flank 5 of a second torque transfer body 2, which is rotatable with respect to shaft 3, wherein in particular provision is made such that second torque transfer body 2 is assigned rotationally fixed but axially displaceable to a handle, wherein in particular provision is made such that the torque-limiting device is arranged in a cavity of the handle, in which second torque transfer body 2 can move in the axial direction and/or second torque transfer body 2 is axially displaceable as a consequence of ribbing in a cavity of the handle.

[0050] A torque-limiting device, which is characterised by a sliding bearing disc 11 lying in sliding friction surface contact against a counter-surface of support element 11, on which sliding bearing disc spring element 8 is supported.

[0051] A method, which is characterised in that two torque transfer bodies 1, 2 are displaceable during a relative rotation about axis A in the direction of said axis A relative to one another against a restoring force of a pretensioned spring element 8, wherein spring element 8 having a neutral length L0 in the state when the force is not applied is brought from 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 length L1, L2 is fixed by a plastic deformation.

[0052] A method, which is characterised in that both a bearing 17 and abutment 9, between which spring element 8 is clamped, are fastened irreversibly to shaft 3.

[0053] A method, which is characterised in that abutment 9 is formed uniformly in terms of material by shaft 3 or by a support element 11, 21 fastened irreversibly to shaft 3.

[0054] A method, which is characterised in that the torque transfer teeth of torque transfer bodies 1, 2 rest against one another when abutment 9 is fixed.

[0055] A production batch, which is characterised in that the torque-limiting device is constituted according to any one of claims 1 to 7 and predefined force F1 is the same in the case of all the torque-limiting devices.

[0056] A production batch, which is characterised in that the torque-limiting device is formed according to a method according to any one of claims 8 to 11, wherein predefined force F1 is the same in the case of all the torque-limiting devices.

[0057] All the disclosed features are essential to the invention (in themselves, but also in combination with one another). In the disclosure of the application, the disclosure content of the associated/appended priority documents (copy of the prior application) are thus also included in their full content, also for the purpose of incorporating features of these documents in claims of the present application. The sub-claims characterize with their features, including without the features of a claim referred to, independent inventive developments of the prior art, in particular in order to make divisional applications on the basis of these claims. The invention specified in each claim can also include one or more of the features indicated in the above description, in particular provided with reference numbers and/or stated in the list of reference numbers. The invention also relates to design forms, wherein individual features stated in the above description are not implemented, in particular insofar as they can evidently be dispensed with for the given intended use or can be replaced by other means which technically have the same effect.