Patent ID: 7393026

Claim:
A lock mechanism for a moving member capable of approaching and moving away from a main body, for holding said moving member immovably in a locked state and allowing movement in an unlocked state, said lock mechanism comprising: a circulating cam groove formed on one of said main body and said moving member, and having a coupling part; a trace member having a bracket with one trace part and another trace part and formed to be able to sway without twisting on the other of the main body and the moving member, said one trace part circulating along said circulating cam groove in each approaching and moving away operation of said moving member without applying bending and twisting forces to the other trace part, and locking the moving member in a state having coupled with the coupling part of the circulating cam groove; and a wall surface formed on said one of said main body and said moving member, and disposed in a different position from said circulating cam groove so that when the one trace part circulates along the circulating cam groove, said the other trace part does not contact the wall surface, and when the one trace part is coupled with the coupling part, said the other trace part of said trace member is able to contact the wall surfaces, wherein said circulating cam groove and the wall surface are arranged relative to the trace member such that when the one trace part engages the coupling part of the circulating cam groove, the other trace part is located with a predetermined distance away from a recessed part of the wall surface.