Patent ID: 8567865

Claim:
A connecting apparatus, for rotatably and concentrically connecting two members, and for switching between an unlock state in which the two members are configured to rotate and a lock state in which the two members are not configured to rotate, the connecting apparatus comprising: an inner teeth member, attached to one of the two members, and including inner teeth on an inner peripheral surface; a guide member, attached to the other of the two members, and including a rotation support portion rotatably supporting an outer peripheral surface of the inner teeth member; a first outer teeth member and a second outer teeth member, the outer teeth members movably attached on the guide member and including outer teeth configured to mesh with the inner teeth; and a switching member movably supported by the guide member, the switching member configured to switch to the lock state in which the outer teeth mesh with the inner teeth and the unlock state in which the outer teeth do not mesh with the inner teeth when the switching member moves the first and second outer teeth members, wherein: the guide member is formed with a support surface supporting the switching member in the lock state for preventing the first outer teeth member from moving in a direction in which the first outer teeth member disengages from the inner teeth member, the connecting apparatus further comprises a backlash preventing mechanism configured to prevent a backlash of the inner teeth member with respect to the guide member by the switching member pushing the inner teeth member to the rotation support portion of the guide member via the first outer teeth member in the lock state, and a space is formed between the outer teeth of the second outer teeth member and the inner teeth of the inner teeth member in the lock state, the space extends along an outer length of the second outer teeth member and permits the outer teeth of the second outer teeth member and the inner teeth of the inner teeth member to mesh with each other, and forms clearance there-between in an outermost radial direction, wherein the backlash preventing mechanism includes a protruding portion protruding from the support surface of the guide member, and the protruding portion is formed with an inclined surface that causes the switching member to gradually move toward the first outer teeth member in a radial direction with respect to the guide member when the switching member moves from the unlock state to the lock state.