Conical Screw Coupling

A screw coupling comprising two bodies, one of which has an external screw thread and another has an internal screw thread complementary thereto, wherein the screw threads are superimposed onto two base surfaces monotonously narrowing and widening respectively in the direction of a central axis, the longitudinal section of each of these screw threads relative to the central axis being a periodic univalent function which is continuous at least at the inflection points, and

• wherein
• the first derivative of the longitudinal section of each screw thread along the base surface is a continuous function;
• the second derivative of the longitudinal section of each screw thread along the base surface is a continuous function;
• the second derivative of the longitudinal section of each screw thread relative to the central axis is a continuous function at least in the region of the inflection points;
• and
• the screw threads are in mutual contact over a substantial surface area differing from line contact.