Two speed axle shift actuator

Abstract

A low power electric motor slowly load to spring, which rapidly operates a two speed axle shift. An electric motor drives a nonreversing worm gear which engages a gear rack on a shaft. The shaft supports a caged spring. The motor moves the shaft, compressing the spring against one end of the cage, storing energy required for shifting. A solenoid piston holds the cage in position. When the shift is desired, the soleniod is tripped, the piston is raised and the spring moves the cage. An arm on the cage moves the shift lever. The solenoid piston engages the opposite detent in the cage and holds the cage in the new position. As the cage arrives at the new position, a lug trips a microswitch which completes a circuit to operate the motor in the reverse direction. The motor worm slowly drives the gear which slowly drives the rack to move the shaft in the reverse direction, compressing the spring against the opposite end of the cage. When the shaft moves sufficiently to fully load the spring, a lug on the shaft trips the switch turning the motor off. The next pulsing of the solenoid causes the spring to drive the cage in the opposite direction, back towards its first position, where the solenoid locks the cage. A lug in the cage trips the switch, turning the motor on to run in a forward direction, driving the shaft to its original position and compressing the spring until a lug on the shaft engages a switch, turning the motor off.