Tools – Wrench – screwdriver – or driver therefor – Having work engaging and force exerting portion inserted...
Reexamination Certificate
2000-05-19
2001-07-24
Smith, James G. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Having work engaging and force exerting portion inserted...
C081S900000
Reexamination Certificate
active
06263771
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a force-transmission profile, in particular on a polygonal screwing tool, for a polygonal-socket mating profile, in particular for a hexagon-socket profile of a screw, having circumferentially similarly formed flanks which adjoin one another at polygon corners, the cross-sectional contour line of each flank having two spaced-apart, convexly extending lines of curvature, and the spacing region between the lines of curvature extending in a set back manner in relation to the tangent connecting the two vertices of the convex lines of curvature.
A force-transmission profile of the type in question is known from EP 0 512 248, in which the spaced-apart, convexly extending lines of curvature intersect one another to form a polygon corner in each case. This means that the convex lines of curvature, starting from the spacing regions and opening out into the polygon corners, are curved uniformly. Because of this formation, a force-transmission profile configured in this way allows a higher torque to be transmitted than known force-transmission profiles.
SUMMARY OF THE INVENTION
The object underlying the subject matter of the invention is to configure a force-transmission profile of the type mentioned such that it is possible to transmit even higher torques without this resulting in the force-transmission profile slipping.
This object is achieved first and foremost with a force-transmission profile wherein the contour-line section between vertex and polygon corner is of shallower curvature than the convexly extending line of curvature or is rectilinear.
Such a configuration gives a force-transmission profile, in particular on a polygonal screwing tool, which is distinguished by increased torque transmission without slipping. In relation to the known solution mentioned in the introduction, in which the convex lines of curvature of two adjacent flanks intersect with formation of a polygon corner, the vertex of the convexly extending line of curvature is adjoined by a contour-line section which is either of shallower curvature or is rectilinear, this being associated with the advantage that there is an increase in the cross section of the force-transmission profile in the corner region. Nevertheless, the plough effect is not relinquished, this consisting in the fact that, from a certain limit torque, the polygon regions of the force-transmission profile engage against the flanks of the polygonal socket and there, with the action of a plough, dig into the inner edge and push the material of the screw head in front of them into the region of the non-convexly formed spacing region. Specifically, the geometrical relationships here are such that the spacing between the vertex and the polygon corner is less than that between vertex and transverse centre line of the force-transmission profile. The polygon corner may then be sharp-edged or slightly rounded. If the contour-line section extends in rectilinear manner, the relevant radius is approximately 0.2 mm, whereas a radius of approximately 0.1 mm should be selected if the contour-line section is of shallow curvature. These slightly rounded formations serve, in particular, for avoiding burr during production. This measure has also proven advantageous in production terms if the force-transmission profile is cold-drawn in the form of a wire. It is also provided that the outer contour-line sections are located on the tangent. This relates to the rectilinear contour-line sections. It is then provided according to the invention that the radius of curvature of the convexly extending line of curvature corresponds approximately to half the width across flats. In this case, the centre point of the convexly extending line of curvature is offset from the centre point of rotation of the force-transmission profile by approximately a fifth of the width across corners. If a contour-line section of shallow curvature is selected, then it is favourable for the outer contour-line section to have a radius of curvature of the magnitude of the width across flats, and for the centre point to be spaced apart from the transverse centre line by approximately the same distance as the centre point of the convexly extending line of curvature. The relevant spacing region between the convex lines of curvature does not extend in a convex manner. Rather, the spacing region between the convex lines of curvature is a concave curve which runs smoothly into the lines of curvature. This means that there are no edges, corners or protrusions which would impair the plough effect during operation in the limit region. The radius of the concave curve is selected to be larger than the width across flats. The radius favourably corresponds approximately to one and a half times the width across flats.
REFERENCES:
patent: 5284075 (1994-02-01), Strauch et al.
patent: 5873290 (1999-02-01), Chaconas
patent: 6016727 (2000-01-01), Morgan
patent: 0512248 (1992-11-01), None
patent: 0630722 (1994-12-01), None
Faber Martin A.
Smith James G.
Wera-Werk Hermann Werner GmbH & Co.
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