Abstract: A system for changing a tool head (24) carried by a robot (20) includes a locking mechanism (23) having a keyhole-shaped slot (37) therein, and a lock key assembly (25) having a key (65). Depression of a button (52) rotates a cam arm (57) to extend the key (65) outwardly where it can be received in the larger opening (38) of the slot (37). Depression of the button (35) of the locking mechanism (23) moves the slot (37) such that the neck (68) of the key (65) is received in the smaller opening (39) of the slot (37). Release of the buttons (52, 35) then allows a spring (71) to retract the key (65) until its head (69) is received in a recess (40) of the locking mechanism (23) to attach the tool head (24) to the robot (20). The parts are detached by again depressing the button (52) which extends the key (65) to remove its head (69) from the recess (40) and then depressing a button (34) to move the slot (37) so that the key (65) is again in the larger opening (38) from where it may be removed.