Spur tooth, escape wheel provided with the hook tooth, ankle escapement, movement, mechanical timepiece, and torque transmission method

摘要

The invention relates to an escapement gear, an escapement wheel employing the escapement gear, an anchor-shaped escapement, a movement, a mechanical timepiece and a method of torque transmission, capable of rapidly transmitting torque during alternating of impacting surfaces. In the escapement gear (1) of the escapement wheel (2) of the anchor-shaped escapement of the mechanical timepiece, a locking corner (30) which connects a stop surface (10) and an impacting surface (20) becomes a first convexly curved surface portion (31). A convexly curved second portion (21) is arranged on impacting surface (20) at a place being continuous with the first convexly curved surface portion (31) of the locking corner (30). The second convexly curved surface portion (21) may extend over the entire impacting surface (20). At a place further away from the locking corner (30) on the impacting surface (20), the radius of curvature R2 of the second curvedly convex surface portion (21) becomes larger. A portion which is continuous with the second curvedly convex surface portion (21) of the impacting surface (20) surface may be planar.