Abstract: A screw tightening structure includes an indented concave recess formed on a screw, and mating convex sections provided on a screw tightening tool for tightening the screw: the recess and the mating convex sections including three or more torque transfer portions, respectively, which protrude outward and are disposed at equiangular intervals for concentrically mating engagements; rotating the screw tightening tool causing the torque transfer portions of the mating convex sections to transfer a tightening torque to the screw via the torque transfer portions of the recess; under which outer circumferential edge portions of the torque transfer portions of the mating convex sections to be brought into abutting contact with sidewall of the torque transfer portions of the recess with the tightening torque being transferred to the screw via force application points Q representing resulting abutment portions.

Abstract: A screw tightening structure includes an indented concave recess formed on a screw, and mating convex sections provided on a screw tightening tool for tightening the screw: the recess and the mating convex sections including three or more torque transfer portions, respectively, which protrude outward and are disposed at equiangular intervals for concentrically mating engagements; rotating the screw tightening tool causing the torque transfer portions of the mating convex sections to transfer a tightening torque to the screw via the torque transfer portions of the recess; under which outer circumferential edge portions of the torque transfer portions of the mating convex sections to be brought into abutting contact with sidewall of the torque transfer portions of the recess with the tightening torque being transferred to the screw via force application points Q representing resulting abutment portions.

Abstract: A screw tightening structure includes an indented concave recess formed on a screw, and mating convex sections provided on a screw tightening tool for tightening the screw: the recess and the mating convex sections including three or more torque transfer portions, respectively, which protrude outward and are disposed at equiangular intervals for concentrically mating engagements; rotating the screw tightening tool causing the torque transfer portions of the mating convex sections to transfer a tightening torque to the screw via the torque transfer portions of the recess; under which outer circumferential edge portions of the torque transfer portions of the mating convex sections to be brought into abutting contact with sidewall of the torque transfer portions of the recess with the tightening torque being transferred to the screw via force application points Q representing resulting abutment portions.

Abstract: A threaded fastener wrenching structure includes a fitting hole which is provided in one of a threaded fastener and a wrenching tool for wrenching the threaded fastener; and a fitting protrusion which is provided in the other of the threaded fastener and the wrenching tool and which is to be brought into fitting engagement with the fitting hole; wherein each of the fitting hole and protrusion is three-pronged shaped and has three torque transmitting portions which are angularly spaced apart from each other by 120 degrees about a centerline of the each of the fitting hole and protrusion and which project outwardly in a radial direction of the each of the fitting hole and protrusion, so that a wrenching torque is transmitted through the torque transmitting portions to the threaded fastener, as a result of rotation of the wrenching tool when the fitting hole and protrusion are held in fitting engagement with each other, the threaded fastener wrenching structure being characterized in that the fitting protrusion

Abstract: A threaded fastener capable of being reduced in size and weight. A pair of side wall surfaces of each of six radially outwardly projecting, torque transmitting portions lie on straight lines passing through the center line in a cross section perpendicular to the center line so as to transmit torque through the side wall surface, whereby the direction of a surface orthogonal force N applied to a force-applied point P by a wrenching tool coincides with the direction of an effective wrenching force F. This arrangement reduces an operation force required for rotating the wrenching tool and accordingly the load acting on each of the torque transmitting portions, in comparison with a conventional hexagonal head. That is, it is possible to reduce the diameter of the head portion of the threaded fastener and the size and weight of the head portion, while avoiding deformation of the side wall surfaces through which the torque is transmitted.

Abstract: An air venting belt for use between an outer surface of a tire and an inner surface of an envelope when a retread tire is vulcanized, comprising a base cloth made of woven cloth which is expansible at least in the longitudinal direction of the belt.

Abstract: A flywheel assembly comprising a torque limiting mechanism (14) having an annular holder (40) and drum (45). The holder (40) and drum (45) have, respectively, a flange (51) and a friction portion (54). The flange (51) and a friction portion (54) have formed therebetween a space in which are disposed first and second friction plates (41,44). A driven plate (43) is disposed between the first and second friction plates (41,44). An annular first friction material (46a) is disposed between the flange (51) and the first friction plate (41). An annular second friction material (46b) is disposed between the driven plate (43) and the second friction plate (44). An annular third friction material (46c) is disposed between the second friction plate (44) and the friction portion (54). An annular fourth friction material (46d) is disposed between the friction portion (54) and an end surface (55) of second flywheel (12). A Belleville spring (42) is disposed between the first friction plate (41) and the driven plate (43).