20110048181 | SCREW HEAD RECESS STRUCTURE AND ITS DRIVING TOOL - A screw head recess structure and its driving tool that maximizes torque are provided, applicable to any kinds of rotational fasteners, such as screws or bolts. A recess has an irregular shape formed by a plurality of lobular grooves arranged around the center point of a fastener as an axis. A plurality of facets of corresponding grooves along both sides of central lines is formed that receive forces when the fastener rotates clockwise and anticlockwise. As a driving tool having a matching configuration with the recess structure rotates the recess, moment arms of forces and reaction forces exerted upon corresponding facets are on the same central lines, thus maximizing the torque generated by the driving tool. In addition to maximizing the torque, the recess structure is also special in that on which ordinary driving tools cannot operate, thereby protecting the fastener against unwanted disassembly. Moreover, the depth of the recess can be kept shallow since operation of which is effort-saving. This makes the present invention especially suitable for applications that require compact and light fasteners. | 03-03-2011 |