THREAD-FORMING SCREW Russian patent published in 2008 - IPC F16B25/00 F16B33/02 

FIELD: machine building.

SUBSTANCE: invention relates to screw. Screw with the threaded rod has an area of force application to transfer torque and a sharp end. The threaded rod consists of a cylinder rod and a self-tapping thread. Thread is made as a screw-line groove with radial height; groove is limited by two side faces converging to the external thread edge. At least, at one thread section, external thread edge comes in radial direction in a wave-form with the certain amplitude between vertexes with height of thread and valleys with height decreased by amplitude. At least, in the area of one side face, in the area of thread edge valleys, the thread has deepenings which intermit the side face and are externally limited by the thread edge. In the areas of thread edge vertexes not intermitted by the deepenings, thread has a certain angle of thread, formed by the side faces. Thread has another angle of thread at the deepest areas of threaded edge valleys. The first thread angle between the thread side faces is within the rage of 30° to 35°, while the second thread angle (α') is 30° up to 58° (maximal value).

EFFECT: reduction of screwing torque while keeping unscrewing torque high.

19 cl, 9 dwg