Patent ID: 7621689

Claim:
An attachment coupler that is attached to an end of an arm of a working machine, an attachment having two attachment pins in parallel being detachably attached to the attachment coupler, the attachment coupler comprising: a pair of locking plates, each one of the locking plates comprising a first U-shaped portion that engages with and supports one of the two attachment pins sideways; and a second U-shaped portion that has an opening that opens downwardly, the other of the two attachment pins being received by the opening upwardly, a rotary hook rotatably supported between two second U-shaped portions of the locking plates and that opens and closes the opening of the second U-shaped portions; the rotary hook including: an engagement securing member that engages with and secures the rotary hook when the rotary hook closes the opening of the second U-shaped portion and when the rotary hook opens the opening of the second U-shaped portion; and a bolt securing member that secures the rotary hook with a bolt passing through aligned holes of the rotary hook and the locking plates when the rotary hook closes the opening of the second U-shaped portion, the engagement securing member including: a lock level tool that is spring-biased to protrude toward the rotary hook; and locking depressions that are formed in the rotary hook, the lock level tool engaging with one of the locking depressions when the rotary hook closes the opening of the second U-shaped portion, and engaging with another one of the locking depressions when the rotary hook opens the opening of the second U-shaped portion.