Patent ID: 8177301

Claim:
An armrest comprising: a stationary shaft adapted to be fixed to an external surface of a seat frame: an armrest body into which the stationary shaft is inserted so as to be rotatably supported by said stationary shaft, the armrest body being rotatable in a rotating direction of the armrest body between an armrest-storage position on the seat frame and an armrest-lowered position to which the armrest body is rotated from the seat frame; a lock spring including (a) a coil part that contacts the stationary shaft under a free condition; (b) a stationary-side hook that is locked to the armrest body and radially extends out from one end of the coil part; and (c) a free-side hook that radially extends out from the other end of the coil part; a pivot that is located adjacent to the free-side hook; a canceling block that is rotatably supported by the pivot; and a cam member that has: (a) an unlocking cam part that, by contacting the free-side hook via the canceling block when the armrest body is rotated in an armrest-storing direction, enlarges a diameter of the lock spring so as to unlock the armrest body, and (b) a relocking cam part that is spaced from the unlocking cam part in the rotating direction of the armrest body and that, by contacting the free-side hook via the canceling block when the armrest body is rotated in an armrest-use direction, reduces the diameter of the lock spring so as to lock the armrest body, wherein an end of the canceling block corresponding to the free-side hook is in contact with the unlocking cam part when the armrest body is rotated in the armrest-storing direction from the armrest-lowered position, the diameter of the lock spring is enlarged so that the armrest body is moved into an unlocked condition when the armrest body is further rotated in the armrest-storing direction, and the end has a flat part on the bottom of the end to maintain the unlocked condition by supporting the free-side hook in the unlocked condition, and when the armrest body is rotated in the armrest-use direction, the end of the canceling block is in contact with the relocking cam part, and when the armrest body is further rotated in the armrest-use direction, the diameter of the lock spring is reduced so that the armrest body moved into a locked or relocked condition, and at least one of an inside diameter of the lock spring and an outside diameter of the stationary shaft is tapered in an axial direction of the shaft so that a spacing between an inner surface of the coil part and an outer surface of the stationary shaft is larger on the free-side hook side than on the stationary-side hook side when the diameter of the lock spring is enlarged to the unlocked condition, and when the lock spring shifts to the relocked condition, the reduction of the diameter beginning on the free-side hook side does not stop, and the diameter of the entire coil part is reduced.