Patent ID: 7766429
Filing Date: 2010-08-03
Classification: B60N

Abstract:
1. A rotation lock device disposed between a first member and a second member that are coaxially rotatably positioned and connecting the first and second members, the rotation lock device being capable of having an unlocked condition allowing relative rotation of the first and second members and a locked condition preventing the relative rotation of the first and second members, comprising: a ratchet that is coaxially disposed on and connected to one of the first and second members and having a disk-shape, the disk-shaped ratchet having a cylindrical portion axially protruding from an outer peripheral edge portion thereof and having inner teeth that are formed in an inner circumferential surface of the cylindrical portion; a guide that is coaxially disposed on and connected to the other of the first and second members and having a disk-shape, the guide being combined to the ratchet while disc surfaces thereof face each other, so as to be rotated relative to each other; three pawls that are disposed on the guide disc surface facing the ratchet at intervals in a circumferential direction of the guide, the pawls being retained on the guide, so as to be movable only in a radial direction of the guide, and having outer teeth that are formed in radially outer surfaces thereof; and a cam that is coaxially disposed on said guide so as to be axially rotated, the cam being capable of pushing said three pawls from inside to outside along a radial direction of the guide when it is axially rotated, thereby meshing the outer teeth of the pawls with the inner teeth formed in the inner circumferential surface of the cylindrical portion of said ratchet, wherein three spacing distances are defined due to circumferential positioning of said three pawls, one of the spacing distances being determined so as to be greater than the remaining two spacing distances, and wherein a raised flat portion is formed in a portion of the inner circumferential surface of the cylindrical portion of said ratchet at a single site in a circumferential direction thereof, the raised flat portion lacking said inner teeth and being protruded radially inwardly beyond tips of said inner teeth and in which said inner teeth is removed, wherein the smaller remaining two spacing distances are determined so as to be smaller than a circumferential length of said raised flat portion.