SCREW Russian patent published in 2001 - IPC

FIELD: screws with heads having cross like slot. SUBSTANCE: screw with head includes cross like slot in the form of axial recess and four grooves extending normally in pairs from said recess and four indentations arranged between said grooves. Each indentation in plan view is in the form of parabola. Beams of parabola cross with lateral planes of grooves in such a way that distance between mutually opposite apices of parabola is equal to 0.85-0.9 m, where m - spacing between limit points of mutually opposite grooves. Beams of each parabola cross with lateral planes of grooves in points corresponding to minimum mutual distance of those grooves. In the result head of screw is reliably held by means of screw driver providing stable torque transmitted from tool to part. EFFECT: enhanced design of screw head providing optimal tightening moment. 2 cl, 2 dwg