DRIVE ELEMENT

Abstract

The present invention relates to a drive element (8) which has an internal driving profile (9) that defines a profile axis (P.sub.I) and has, on its inner side, a plurality of concave drive faces (6) arranged in a manner distributed regularly around the profile axis (P.sub.I), between which a planar or convexly curved transitional faces (7a) are provided, or which has an external driving profile (9) that defines a profile axis (P.sub.A) and has, on its outer side, a plurality of concave drive faces (10) arranged in a manner distributed regularly around the profile axis (P.sub.A), between which planar of convexly curved transitional faces (7a) are provided.

Claims

1. Drive element (8) which has an inner driving profile (5) which defines a profile axis (P.sub.I) and has on its inner side a plurality of concave drive surfaces (6) which are arranged uniformly distributed around the profile axis (P.sub.I) and between which planar or convexly curved transition surfaces (7) are provided, or which has an outer driving profile (9) which defines a profile axis (P.sub.A) and has on its outside a plurality of concave drive surfaces (10) which are arranged distributed uniformly about the profile axis (P.sub.A) and between which planar or convexly curved transition surfaces (7a) are provided, wherein in cross-section, the transition points (P.sub.I) or transitions between the drive surfaces (5, 10) and the transition surfaces (7, 7a) lie on a common inner circle with the inner diameter D.sub.i, and the drive surfaces (5) lie on outer circles of diameter D.sub.a distributed uniformly around the profile axis (P.sub.I, P.sub.A) and are formed symmetrically with respect to their longitudinal central plane enclosing the profile axis (P.sub.I, P.sub.A), wherein the outer diameter D.sub.a and the center-to-center distance L between the centers of the outer circles and of the inner circle are selected as a function of the inner diameter D.sub.i such that the normal force acting at the transition points between in each case one drive surface (6, 10) and the adjacent transition surface (7, 7a) when a torque M.sub.D about the profile axis (P.sub.I, P.sub.A) is introduced into the drive profile (5, 9), is tangential to the drive surface (6, 10) adjacent to the one drive surface (6, 10) or runs within the latter.

2. Drive element according to claim 1, wherein the running ratio K=D.sub.a/D.sub.i is in the range of 0.3 and 2.0.

3. Drive element according to claim 1, wherein the center-to-center distance L is calculated according to the formula L=F(L, D.sub.i)D.sub.i, where F(L, D.sub.i)=0.494 e.sup.(0.605K).

4. Drive element according to claim 1, wherein it comprises an inner driving profile (5) and the drive surfaces (6) of the inner driving profile (5) are inclined with respect to the profile axis (P.sub.a), approaching the profile axis (P.sub.a) starting from an insertion opening (5a) of the inner driving profile (5) towards a rear end of the inner driving profile (5).

5. Drive element according to claim 4, wherein the drive surfaces (6) of the inner driving profile (5) are inclined relative to the profile axis (P.sub.a) by an angle of inclination α.sub.I which is at least 1°, in particular at least 1.5° and/or wherein the drive surfaces (6) of the inner driving profile (5) are inclined relative to the profile axis (P.sub.I) by an angle of inclination α.sub.I of at most 5°, in particular at most 3.5° and preferably at most 3°, the angle of inclination α.sub.I preferably being 2°±0.2° or 3°±0.2°.

6. Drive element according to claim 4, wherein the transition surfaces (7) are inclined with respect to the profile axis (P.sub.I) and approach the profile axis (P.sub.I) starting from an insertion opening (5a) of the inner driving profile (5) towards the rear end of the inner driving profile (5).

7. Drive element according to claim 6, wherein the transition surfaces (7) are inclined relative to the profile axis (P.sub.I) by an angle of inclination β.sub.I which is at least 1°, in particular at least 1.5° and/or wherein the transition surfaces (7) of the inner driving profile (5) are inclined relative to the profile axis (P.sub.I) by an angle of inclination β.sub.I of at most 5°, in particular at most 3.5° and preferably at most 3°, the angle of inclination β.sub.I preferably being 2°±0.2° or 3°±0.2°.

8. Drive element according to claim 6, wherein the angle of inclination α.sub.I of the drive surfaces (6) relative to the profile axis (P.sub.I) is as large as the angle of inclination β.sub.I of the transition surfaces (7) relative to the profile axis (P.sub.I).

9. Drive element according to claim 1, wherein it has an outer driving profile (9) and the drive surfaces (10) of the outer driving profile (9) are inclined with respect to the profile axis (P.sub.A), approaching the profile axis (P.sub.A) towards an insertion end of the outer driving profile (9).

10. Drive element according to claim 9, wherein the drive surfaces (10) are inclined with respect to the profile axis (P.sub.A) by an angle of inclination α.sub.A, which is at least 0.5°, in particular at least 1° and/or is at most 1.5°, the angle of inclination α.sub.A preferably being 1.15°±0.2°.

11. Drive element according to claim 9, wherein the transition surfaces (7a) are inclined with respect to the profile axis (P.sub.A) at an angle of inclination β.sub.A which is greater than 0° and less than 0.7° and is preferably 0.4°±0.05°.

12. Drive element according to claim 11, wherein the angle of inclination β.sub.A of the transition surfaces (7a) relative to the profile axis (P.sub.A) is smaller than the angle of inclination α.sub.A of the drive surfaces (10) relative to the profile axis (P.sub.A), the ratio of the angle of inclination α.sub.A to the angle of inclination β.sub.A being ≥2, in particular ≥2.5, and preferably being 2.8±0.2.

13. Drive element according to claim 1, wherein the outer diameter (D.sub.A) is constant over the axial length of the driving profile (5, 9).

14. Drive element according to e claim 1, wherein the inner diameter (D.sub.I) over the axial length of the driving profile (5, 9) is constant or increases continuously in adaptation to an inclination of the transition surfaces (7, 7a) with respect to the respective profile axis (P.sub.I, P.sub.A) in the case of an inner driving profile (5) in the direction of its insertion opening (5a) and in the case of an outer driving profile (9) starting from its insertion end.

15. Drive element according to claim 1, wherein the driving profile (5, 9) has five or six drive surfaces (6, 10).

16. Drive element according to claim 1, wherein the drive element (1) is a screw and the driving profile (5) is formed on the screw head (4).

17. Drive element according to claim 1, wherein the drive element (8) is a screw bit.

18. Method for connecting two components, in particular a screw (1) and a rotary tool (8), in a rotationally fixed manner, one of the components being designed as a drive element (8) with an outer driving profile (5, 9) and the other component being designed as a drive element (1) with an inner driving profile (5), in which the driving profiles (5, 9) of the two components (1, 8) are plugged together axially in order to produce a rotationally fixed connection between the two components (1, 8), wherein the components are designed as drive elements (1, 8) according to claim 1 and the driving profiles (5, 9) of the drive elements (1, 8) are selected to be complementary to one another in such a way that the drive surfaces (6, 10) of the components (1, 8) come into contact with one another in a 2-dimensional manner when the driving profiles (5, 9) are axially plugged together, so that a frictional and/or clamping connection, via which the components (1, 8) are axially connected to one another, is produced between the components (1, 8).

19. Method according to claim 18, wherein the driving profiles (5, 9) of the two components (1, 8) have drive surfaces (6, 10) inclined to their respective profile axis (P.sub.I, P.sub.A).

20. Method for the rotationally fixed connection of second components according to claim 19, wherein the angle of inclination α.sub.i, by which the drive surfaces (6) of the inner driving profile (5) are inclined with respect to the profile axis (P.sub.I), is greater than the angle of inclination α.sub.A, by which the drive surfaces (6) of the outer driving profile (10) are inclined with respect to the profile axis (P.sub.A).

21. Method for the rotationally fixed connection of second components according to claim 20, wherein the angle of inclination α.sub.i of the drive surfaces (6) of the inner driving profile (5) is 3°±0.2° and the angle of inclination α.sub.A of the drive surfaces (10) of the outer driving profile (6) with respect to the profile axis (P.sub.B) is 1.15°±0.15°, or that the angle of inclination α.sub.i of the drive surfaces (6) of the inner driving profile (5) relative to the profile axis (P.sub.I) is 2°±0.2° and the angle of inclination α.sub.A of the drive surfaces (10) of the outer driving profile (6) relative to the profile axis (P.sub.A) is 1.15°±0.15°.

22. Method for the rotationally fixed connection of two components according to claim 18, wherein the transition surfaces (7, 7a) of the driving profiles (5, 9) of the two components (1, 8) are inclined with respect to the respective profile axis (P.sub.I, P.sub.A), wherein the angle of inclination β.sub.i of the transition surfaces (7) of the inner driving profile (5) relative to the profile axis (P.sub.I) to the angle of inclination (β.sub.A) by which the transition surfaces (7a) of the outer driving profile (9) are inclined relative to the profile axis (P.sub.I) is ≥5, in particular ≥6 and preferably ≥7.5.

23. Method according to claim 18, wherein drive elements (1, 8) are used in which the outer diameter (D.sub.a) of the inner driving profile (5) is smaller, in particular by 1.5-3% and preferably by 2% smaller, than the outer diameter (D.sub.a) of the outer driving profile (6).

24. Method according to claim 18, wherein the drive surfaces (6, 10) of the two components come into surface contact with one another over at least 25%, in particular at least 40% and preferably at least 60% of their extent in the circumferential direction.

25. Method according to claim 18, wherein the two components come into contact with each contact surface (6, 10) on both sides of the longitudinal center plane thereof.

26. Method according to claim 18, wherein the entrainment profiles (5, 9) are designed in such a way that they do not come into contact in the region of the transition surfaces (7, 7a).

Description

[0033] Further features and advantages of the present invention are illustrated with reference to the accompanying drawing. In the drawing shows:

[0034] FIG. 1 a perspective view of a screw with an internal drive profile,

[0035] FIG. 2 a perspective view of a drive element in the form of a screw bit with an outer drive profile according to the invention, which corresponds to the drive profile of the screw according to FIG. 1,

[0036] FIG. 3 schematically an engagement between a screw bit and a screw in a sectional view showing the angle of inclination α of the drive surfaces,

[0037] FIG. 4 an enlarged view of detail X from FIG. 3,

[0038] FIG. 5 schematically the engagement in another sectional view, which shows the angle of inclination β of the transition surface,

[0039] FIG. 6 an enlarged view of unit X from FIG. 5,

[0040] FIG. 7 shows the geometry and the force paths for an external drive profile of a drive element according to the invention,

[0041] FIG. 8 an example of an outer driving profile according to the invention with dimensions.

[0042] FIG. 1 shows an example of a drive element in the form of a screw 1. The screw 1 comprises a shank 2 which carries an external thread 3 and defines a longitudinal axis of the screw 1. A screw head 4 is provided at the upper end of the shank 2, which has on its inner side an inner driving profile 5 open towards the upper side of the screw head 4 and having inner driving surfaces 6, which defines a profile axis P.sub.I lying coaxially with the longitudinal axis of the screw 1. Thereby, the open upper side forms an insertion opening 5a of the inner driving profile 5 for a screw bit.

[0043] In cross-section or in plan view, the inner driving profile 5 has the basic shape of a regular hexagon, the side faces of which form the drive surfaces 6, which are inclined with respect to the profile axis P.sub.A or the longitudinal axis of the screw 1 at an angle of inclination α.sub.I of 2°, so that they approach the profile axis P.sub.A from the insertion opening 5a of the inner driving profile 5 towards the rear end of the inner driving profile 5. In other words, the driving profile 5 tapers in the screw head 4. For small screws, the angle of inclination α.sub.I can also be 3°.

[0044] The drive surfaces 6 of the inner drive profile 5 have a concave cross-section, i.e. they are curved inwards towards the profile axis P.sub.I. Specifically, the concave drive surfaces 6 each have a circular arc segment shape in cross section, whereby the radius of the drive surfaces 6 is constant over their entire axial length.

[0045] The drive surfaces 6 are connected to each other at the six corners by transition areas or transition surfaces 7, which are convexly curved and have the shape of an arc of a circle, as a result of which they project outward in a beam-like manner. The transition between the transition areas 7 and the drive areas 6 is continuous. The transition surfaces 7 are inclined with respect to the profile axis P.sub.I, whereby they approach the profile axis P.sub.I starting from the insertion opening 5a of the inner driving profile 5 towards the rear end of the inner driving profile 5. In this case, the angle of inclination β.sub.I of the transition surfaces 7 with respect to the profile axis P.sub.I is exactly as large as the angle of inclination α.sub.I of the drive surfaces with respect to the profile axis P.sub.I and is thus 2° in the illustrated embodiment example.

[0046] In FIG. 2, a driving element/turning tool 8 in the form of a screw bit is shown, which is designed to operate the screw 1 shown in FIG. 1. The turning tool 8 has an outer driving profile 9, the lower end of which is provided on a shaft of the screw bit that is not shown and is designed to correspond to the driving profile 5 of the screw 1, whereby it defines a profile axis P.sub.A. Correspondingly, the outer driving profile 9 also has the basic shape of the hexagon in cross-section, wherein the drive surfaces 10 of the driving profile 9 are concave, i.e. curved in the direction of the profile axis P.sub.A and run at an angle to the profile axis P.sub.A. Specifically, the drive surfaces 10 of the screw bit are inclined at an angle α.sub.A of 1.15° with respect to the profile axis P.sub.A, whereby they approach the profile axis P.sub.A towards a free insertion end—the upper end in FIG. 2—of the outer driving profile 9, with which the outer driving profile 9 is inserted into the inner driving profile 5 of a screw 1. The drive surfaces 10 of the screw bit thus run somewhat steeper than the drive surfaces 9 of the screw (see FIGS. 3 and 4). The drive surfaces 10 have a circular arc segment-shaped cross section with a radius that is constant over their axial length and has the same value as the radius of curvature of the drive surfaces 6 of the screw 1.

[0047] The drive surfaces 10 are continuously connected to each other by convex transition areas or transition surfaces 7a, which are also tapered and have a circular arc shape.

[0048] As with the inner driving profile 5, the transition surfaces 7a of the outer driving profile 9 are inclined relative to the profile axis P.sub.A, approaching the profile axis P.sub.A towards the insertion end of the outer driving profile 9. Thereby, the angle of inclination β.sub.A of the transition surfaces 7a to the profile axis P.sub.A is 0.4°. This means that the angle of inclination β.sub.A of the transition surfaces 7a relative to the profile axis P.sub.A is significantly smaller than the angle of inclination α.sub.A of the drive surfaces 10 with respect to the profile axis P.sub.A, where the ratio of the angle of inclination α.sub.A/β.sub.A is almost 3. Furthermore, the angle of inclination β.sub.A, by which the transition surfaces 7a of the outer drive profile 9 are inclined relative to the profile axis P, is significantly smaller than the angle of inclination β.sub.I, by which the transition surfaces of the inner drive profile are inclined relative to the profile axis P.sub.I (see FIGS. 5 and 6). In the present case, the ratio β.sub.I/β.sub.A is 7.5. The arrangement is such that the transition areas of the screw 1 and a corresponding screw bit 8 do not come into contact with each other. Accordingly, the radius of curvature of the transition regions 7a in the bit 8 is larger than the radius of curvature of the transition regions 7 in the screw 1.

[0049] In other words, arrangement is made in such a way that a 2-dimensional contact/engagement between the driving profiles 5, 9 takes place exclusively in the region of the drive surfaces 6, 10, but not in the intermediate transition regions 7, 7a, and the contact zones, viewed in the circumferential direction, extend in each case on both sides of the apex of the concavely curved drive surfaces 6, 10. It is desired that there is a 2-dimensional contact between the drive surfaces 6, 10 of the two components 1, 8 in the mated state, so that the two components 1, 8 are aligned exactly coaxially with one another when their two driving profiles 5, 9 are mated axially until a clamping connection is produced between the two components 1, 8 due to the conicity of the driving profiles 5, 9 of the drive surfaces 6, 10. Furthermore, the two-dimensional contact creates a frictional connection via which high torques can be transmitted.

[0050] FIG. 7 shows the geometry of the outer driving profile 5 of bit 8 at its free, tapered end according to the invention.

[0051] It can be seen that the transition surfaces 7 lie on a common circle—the inner circle—with an inner diameter Da. However, the transition surfaces 7 do not have to have a continuous circular arc shape, but can also be flat, for example. It is essential that the transition points between a drive surface 6 and the adjacent transition surface 7, indicated here once by an arrow P1, lie on the common inner circle.

[0052] It is further shown that the drive surfaces 6 are located on outer circles of diameter Da distributed uniformly around the profile axis P.sub.A and are formed symmetrically with respect to their longitudinal center plane enclosing the profile axis P.sub.A.

[0053] The outside diameter D.sub.a as well as the center-to-center distance L between the center points of the inner circle and the outer circles are selected as a function of the inside diameter D.sub.i in such a way that the normal force acting at the transition points between the drive surfaces 6 and the adjacent transition surfaces 7 when a torque M.sub.D about the profile axis P.sub.A is introduced into the drive profile 5 is applied tangentially to the drive surface 6 adjacent to the drive surface. The normal force F.sub.N1 is indicated as an example for the transition point P1 between the upper contact surface 6 and the transition surface 7 adjacent to the left in FIG. 7.

[0054] To generate the desired torque M.sub.D, a lever force F.sub.H1 must act at the point P1. This can be divided into a normal force F.sub.N1, which is directed perpendicularly to the outer circle on which the drive surface 6 lies and thus runs through its center, and a tangential force F.sub.T1 running perpendicularly thereto. As can be seen clearly in FIG. 3, the arrangement is such that the normal force F.sub.N1 runs tangentially to the drive surface 6 located adjacent the upper drive surface 6 to the left thereof. According to the invention, the normal force F.sub.N1 can also run between the drawn normal force F.sub.N1 and the profile axis P.sub.A, as is indicated by way of example for the dashed arrow F.sub.NB in FIG. 3. It is essential that the normal force F.sub.N1 is introduced into the central area of the drive profile 9 or of the component 8 designed as a screw bit and that the beam-shaped transition areas 7 between the drive surfaces 6 are not, or hardly, subjected to bending or shear.

[0055] For a given inner diameter D.sub.i, the outer diameter D.sub.a and the center-to-center distance L between the center of the inner circle and the centers of the outer circles can be calculated according to the following formula

L=F(L,D.sub.i)D.sub.i.

[0056] The running ratio K=Da/D.sub.i can be selected and should be in the range of 0.3 and 2.0.

[0057] An example of the calculation is shown in FIG. 8. The parameters are selected as follows: [0058] D.sub.i=5.6 mm [0059] K=0.8 (freely selected in the above range) [0060] From this, D.sub.a is calculated with D.sub.a=D.sub.i K=5.6 0.8=4.48 [0061] with F(L, D.sub.i)=0.494 e.sup.(0.605K)=0.494 e.sup.(0.605 0.8)=0.8479 can be calculated L [0062] L=F(L, D.sub.i)D.sub.i=0.8479 5.6=4.748.

[0063] From these parameters, the geometry shown in FIG. 4 can be constructed.

[0064] The geometry of the inner drive profile 5 is selected accordingly with the proviso that the outer diameter D.sub.A of the outer drive profile is about 2% smaller than the diameter D.sub.A of the matching inner profile 5. This takes account of the fact that when the drive surfaces are produced by cutting inserts, they are subject to a certain amount of wear, which is greatest in the central area of the drive surfaces because this is where most of the material has to be removed by the cutting inserts. With increasing wear, less material is removed in the central area of the drive surfaces, so that a minimum curvature forms here to compensate for the undersize.

[0065] It is noted that the angle of inclination α of the driving surfaces and the angle of inclination β of the transition surfaces are each measured in the circumferential direction centered from the corresponding surface. Thus, the angle is measured in a center plane of the corresponding surface intersecting the profile axis of the respective driving profile.

LIST OF REFERENCE SIGNS

[0066] 1 screw [0067] 2 shaft [0068] 3 male thread [0069] 4 screw head [0070] 5 inner driving profile [0071] 5a insertion opening [0072] 6 drive surface [0073] 7 transition areas [0074] 7a transition area [0075] 8 drive element/turning tool/bit [0076] 9 external driving profile [0077] 10 drive surface [0078] D.sub.a outer diameter [0079] L center-to center distance [0080] M.sub.D torque [0081] P.sub.I profile axis [0082] P.sub.A profile axis