Abstract: An electric motor assembly for driving a helical feed screw for use in a vending machine. The helical feed screw is intermittently operated through cycles of similar duration and must be accurately positioned at the end of each cycle. Operation of the motor is initiated by the insertion of coins and is continued for the remainder of a cycle by a holding circuit. An actuating member for the holding circuit switch is positioned adjacent a cam which rotates with the helical feed screw. A pawl is positioned between and engages the switch actuating member and the cam. The cam has a notch indicating the end of the cycle which notch receives the pawl thereby allowing the switch actuating member to open the holding circuit and stop the motor. The pawl also has a dog which engages the edge of the cam notch to prevent reverse rotation of the cam at the end of the cycle. The pawl transmits cam forces to the switch actuating member only along the longitudinal axis thereof.