The invention relates to a drive formation for a rotary drive, in particular for a screw drive formation, and to a drive formation of the respective tool.
Cross-shaped depressions are known as screw drive formations, and therefore the screw provided with such a drive formation is referred to as a crosshead screw. The side walls of the depression, which are provided to transfer the torque applied by the operator, extend at a specific incline with respect to a longitudinal section of the screw. Due to the inclined progression, when torque is introduced some of the force is diverted into a force causing the screwdriver to be pushed out from the crosshead.
It is also known to form depressions in screw heads, wherein the side walls of said depressions extend parallel to the longitudinal axis of the screw. An example of screw drive formations of this type is a hexagonal depression or a depression defined by circular arcs oriented so as to be reversed in an alternating manner.
Since screws having countersunk heads are also very frequently used, a depression with a relatively small cross section has to be used in the case of a screw drive formation with side walls extending parallel to the longitudinal axis of the screw, since the width of the depression conforms to the narrowest diameter of the screw head.
Screw drive depressions formed of a plurality of portions of identical cross sectional form but of different size are already known (GB 2390127 A, GB 2285940 A). Gradations are formed between the individual portions and are designed as planar areas extending transverse to the longitudinal axis of the screw. These areas are not available for torque transfer.
A screw drive formation in the form of depression having a non-circular cross section and a central circular blind hole is likewise known. The transition between the drive depression and the blind hole extends in the form of a flat, smooth cone. These areas are also not available for torque transfer (US 2007/0245863 A1).
The object of the invention is to create a screw drive formation that enables application of increased torques, does not generate forces causing the tool to he pushed out, and enables a long service life of the respective tools.
To achieve this object, the invention proposes a drive formation having the features of claim 1 and a drive formation having the features of claim 2. Developments of the invention are disclosed in the dependent claims.
The drive formation proposed by the invention thus makes it possible to additionally utilize the areas surrounding the wing region to apply torque. In specific cases, it is even possible to utilize just the end depressions in this surface or just the end protrusions, formed for example as ribs.
The end depressions, which for example may be formed as notches or grooves, have a base, which extends approximately transverse to the longitudinal axis of the screw or of the tool.
The end protrusions have an axially directed underside, which extends approximately transverse to The longitudinal axis of the screw or of the tool.
In a development of the invention, the proposed drive formation may have at least two axially adjoining wing regions of different cross-sectional size, wherein, in the case of a drive depression, the second region penetrating further into the screw head is smaller than the first region arranged further outward. The second region can thus be oriented toward the smaller size of a countersunk head in the region further removed from the end face, whilst the first region with the larger cross section can better utilize the larger diameter of the countersunk head in the outer region. In spite of the improved adaptation to countersunk heads, there is no force causing the tool to be pushed out from the recess. The same is true in the case of a screw drive formation In the form of a complementary protrusion.
The drive formation proposed by the Invention can be formed on a workpiece, that is to say an element which is to be rotated with the aid of a tool. The typical example of such a workpiece is a screw or a bolt.
To drive such a workpiece in rotation, a tool is used that may have the same drive formation. If it is desired or possible to forego some of the advantages of the invention, a screw of this type can also be rotated using a conventional tool, which for example has only one region in the form of a star with a circular core and radially outwardly protruding wings, or using a flat-head screw driver.
In accordance with a development of the invention, the area surrounding the wing region may be formed at a gradation between two wing regions.
However, it is also possible for the area surrounding the wing region to be formed on a preferably planar end face.
Since, in the case of a screw drive depression, the region with the smaller cross section has to be accessible through the region with the larger cross section, wings of the region with the smaller cross section may only be arranged at the point at which the wings of the region with the larger cross section are also arranged. However, it is possible for the region with the smaller cross section to have a smaller number of wings than the region arranged thereabove. It is particularly expedient, however, if, in accordance with a development of the invention, the number of wings in both regions is identical. Of course, this applies not only to a drive depression, but also to a drive protrusion.
In accordance with the invention, the second region has a smaller cross section. The dimensions of the cross section do not have to be smaller at all points, however. In accordance with a development of the invention, the width of the wings may be identical in both regions.
In accordance with another development of the invention, the side walls of the wings may extend parallel to one another in the axial direction, possibly with the exception of a draft angle.
The side walls of the wings are the part where the tool lies against the workpiece during rotation to transfer torque. It is therefore expedient for these areas to extend perpendicular to the rotation so that no force component causing the tool to be pushed out from the workpiece is produced.
In accordance with a development of the invention, the end walls of the wings of at least one region, preferably the region with the greater cross section, may extend parallel to the axis in the axial direction.
The side walls of the above-mentioned wings transition into the end wall of the respective wing and, at the other end, into the wall of the core. In accordance with the invention, the transition between the end walls of the wings and the side walls of the wings may be formed by an edge, at least in one of the two regions.
It is also possible, however, for this transition to be rounded.
It is possible that the two types of transition are combined with one another in one region, wherein it is also conceivable for both types of transition to be provided between the end wall and the side walls at a single wing.
An edge or rounded transition can also be formed in the case of the transition between the side walls of a wing and the side wall of the core, which is arranged between two wings in each case. These possibilities may also be combined with one another within one region and even within a single wing.
These above-mentioned transitions can be seen in a cross section of the rotary drive formation perpendicular to the longitudinal axis.
Since the wings of the region with the smaller cross section have a shorter radial length than the wings of the region with the greater cross section arranged directly thereabove, the wings of the region with the greater cross section also have a base. In this case, the transition between the end wall of the wing and the base of the wing can be formed by an edge.
It is also possible, however, for this transition to be rounded.
There is naturally also a transition between the base of the wing of the region with the greater cross section and the end wall of the wing with the smaller cross section. This transition can be formed by an edge or by a rounded edge.
These above-mentioned transitions can be seen from an axial section through the drive formation.
In accordance with a further feature, the invention proposes providing the end wall of the wing with a contour that corresponds to a circular arc about the axis of the drive formation.
The transition between the side walls of the wings and the core can be formed by an edge, possibly by a chamfered edge.
It is also possible, however, and likewise proposed by the invention for this transition between the side walls of the wings and the region of the outer wall of the core, which is arranged between two wings in each case, to be rounded.
It has already been mentioned that the side walls of the wings extend in parallel to one another in an axial direction, In accordance with a development according to the invention of the embodiment of the side walls of the wings, these side walls may be planar.
In accordance with the invention, the progression of the two side walls of a wing, said side walls defining the wing, can be designed such that the side walls or the contour thereof converge toward the tip of the wing, wherein the angle moves within a very small range since a real wing tip is not desirable
In accordance with the invention, however, the contours of the side walls of the wings may extend parallel to one another.
As also proposed by the invention, it is even possible for the side walls of the wings to diverge toward the wing tip.
In an alternative embodiment, the contour of the side walls of the wings may also extend in a curved manner, similarly to the end wall of a wing. For example, in accordance with a development, the outer contour of the drive formation may be formed of concave and convex arcs adjoining one another in an alternating manner.
In accordance with the invention, in order to again provide better adaptation to the form of a countersunk head, the size of the cross section can again be reduced continuously at increasing depth in the region with the smaller cross section, so that the side walls of the drive formation converge toward the base in an axial section, preferably along a line that is concave toward the outer face.
It was previously mentioned that the drive formation has two adjoining axially aligned regions of different cross-sectional size. In accordance with a development of the invention, a third region, of yet smaller dross section, may now be adjoined in an axially aligned manner. Two gradations are thus formed in an axial section, instead of just one gradation as in the embodiment with two regions.
For example, this third region may then have a circular cross section in accordance with a first embodiment, that is to say said third region may have no wings The side walls of this region with a circular cross section may lie over a circular cone with a small angle.
It is also possible, however, for this third region to have the cross-sectional form of a star with a circular core and radially outwardly protruding wings. The features mentioned and described with regard to the wings and transitions in the first regions may also be provided, mutatis mutandis, in the third region.
In accordance with another development of the invention, the side walls of the core may lie between the wings over a circular cone in at least one region. By inserting the tool, there is planar contact between the tool and the side walls of the core, which guides and centers the tool during the rotational movement.
Further features, details and advantages of the invention will emerge from the claims and the abstract, of which the wording is hereby incorporated by reference in the content of the description and the following description of preferred embodiments given with reference to the drawings, in which:
Reference is made first to
The form of the cross section of the second region 4 and of the first region 1 can be seen for example in
In the illustrated embodiment the number of wings 7 in both regions 1, 4 is identical. Since the passage in a drive depression to the wings in the lower region 4 passes through, and must pass through, the wings 7 in the upper region 1, the wings 7 in the lower region have to be arranged directly beneath the wings 7 in the upper region 1. In addition, the lower region 4 naturally cannot have more wings 7 than the upper region 1. It may, however, have fewer wings. In the illustrated embodiments however, the lower region 4 has the same number of wings 7 as the upper region 1.
Between the wings, the contour of the side walls of the core lies over a circular arc.
As can be seen best in
The side walls 9 of the wings 7 extend radially and at least approximately parallel to one another.
It has already been mentioned that the transition between the base of the wings 7 in the upper region 1 and the side walls 9 of the wings 7 in the lower region can extend in a rounded manner (see
The transition between the end wall 8 of a. wing and the side walls 9 of this wing 7 can likewise extend in a rounded manner, as can be seen in
It can also be seen from
The transition between the side walls 9 of the wings 7 and the wall 14 of the core 6 formed between the wings 7 extends along an inclined transitional area 15.
It has been mentioned that the gradation 3 can be rounded or sharp-edged.
This sharp-edged transition can also be seen clearly from the perspective illustration in
Whereas only two adjoining regions of different cross section are provided in the embodiments discussed previously, the following
In the embodiment illustrated in
For clarification,
In the case of the drive formation for rotary drives, said drive formation being illustrated in
In the embodiment according to
With regard to the side walls of the core of the cross section in the individual regions, it remains to be mentioned that these side walls lie over a circular conical surface 14 in all embodiments, which can be seen both in the side views and in the perspective illustrations. This cone shape is likewise used to center and guide the tool so as to thus also ensure that the tool remains axially aligned. This is important in particular at high rotational speeds. In addition, the centering process is used to distribute the torque transfer as uniformly as possible over the corresponding areas. For adequate centering and guidance, it may be sufficient for just the lower region to be cone-shaped.
Whilst in the embodiments discussed previously, the end walls 8, 18 of the wings 7 extend parallel to the longitudinal axis of the recess or of the protrusion, the embodiments according to
In the embodiment illustrated in
Whilst in the embodiments illustrated in
It was also mentioned at the outset that the side walls 9 of the wings 7 extend at least approximately parallel to one another in side view or in cross section. The fact that they likewise extend parallel to one another in an axial section is clear from the end view. The following
A wing 7 is defined by an end wall 8 and two side walls 9. The side walls 9 then transition into the outer wall 14 of the core of the star. In the embodiments of
In the highly schematic embodiment in
In the embodiment of
Reference is now made to the embodiment illustrated in
This lower region 4 is adjoined by a transitional region in the form of a gradation 3, in which the side contour of the wings 7 extends in a sweeping manner. The side contour of the wings 7 then transitions into the upper region, in which the original side contour of the wings 7 transitions into the base of a groove. Starting from the end face 2 of the screw, radially extending grooves 48 are formed in the extension of the wings 7 in the lower region 4, it also being possible to refer to said grooves as wings. It is essential (see the perspective illustration in
The form of the transition between the radially extending grooves enabling end-face engagement and the wings of the engagement portion 4 can be seen from the perspective illustration in
The radially extending grooves 48, which form an end depression in the end face 2 of the illustrated screw, have a base, which extends in a transverse plane transverse to the longitudinal axis of the screw in the radial end region. Also in all other embodiments illustrated in the preceding figures, the gradation transition 3 is designed such that the base of this gradation lies very close to a transverse plane. In particular, the invention proposes the possibility of the base enclosing an angle of at most 45°, with the exception of the transition thereof into the two regions connected by the gradation 3, with a plane extending transverse to the longitudinal axis.
That which is illustrated particularly clearly in the embodiment according to
An example for the form of such a tool is illustrated in
In the embodiments discussed previously, with the exception of the embodiment illustrated in
The simplified axial section through a screw drive formation, for example a tool, shows that the end wall 8 of the wings 7 in both regions 1, 4 may also lie over a cone, similarly to the region of the core 6 between the wings 7. In the illustrated example, the cone angle, over which the end walls 8 of the wings 7 lie, is identical to the cone angle of the outer face of the core 6 between the wings 7.
The angle between the longitudinal axis and the end wall 8 is approximately 6° in the axial section.
In the region 4 with the smaller cross-sectional area, the walls of the core 6 and the end walls 8 of the wings 7 extend in a manner similar to that in the embodiment according to
Combinations of the progressions as illustrated herein are, of course, also possible. For example, the end wall 8 of the wings 7 could lie over a conical surface in the first region 1 and over a cylindrical surface in the second region 4. The same also applies to the outer wall of the core 6 between the wings 7.
Number | Date | Country | Kind |
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10 2010 003 014.7 | Mar 2010 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2011/053791 | 3/14/2011 | WO | 00 | 9/13/2012 |