Shaft and boss joint between screw and screwdriver head

摘要

The joint has a profiled shaft exterior and boss interior to give a lobed or splined engagement. The rotation axes (D1) of externally profiled (11) shaft (10) and internally profiled boss (12) can swivel relatively to a limit angle, the shaft composed of cylindrical body with external six-lobe or spline-keyed profile with straight flanks or flanks obliquely or sagitally toothed. The boss on the other hand has an internal profile in a negative spherical shape or single shell hyperboloid itself key-splined or six-lobed on its surface. Thus in the case of an externally profiled (11) screw head and an internally profiled screwdriver head, the two heads engage so that both screw and driver rotate round their respective axes and swivel relatively to a set angle. The internal profile (13) forms a single shell hyperboloid, or again an hyperbolic paraboloid or focussed torus. The internal surface has alternate raised and depressed parts in concave or convex format which go over into one another.