Engine starter gearing

Abstract

An engine starter drive adapted to engage an engine ring gear having a tooth driving clutch member which cooperates with a tooth driven clutch member. The driven clutch member further comprises a helical screw shaft with two circular grooves. A control nut threadably mounted on the screw shaft has a spring loaded detent which engages the circular grooves. The control nut is connected to the pinion gear by means of a retaining cup. Rotating the screw shaft causes the control nut to move along the screw shaft to traverse the pinion into mesh with the engine ring gears and crank the engine. When the engine fires, the acceleration of the pinion causes the control nut to move back on the screw shaft until the detent engages the first circular groove. After the engine starts and the pinion rotates to a predetermined speed, the detent withdraws from the first groove in the screw shaft and the control nut withdraws the pinion gear from engaging the engine ring gear. The detent then engages a second groove in the screw shaft to prevent undesired meshing of the pinion to the ring gear. If, during the engine cranking mode, the excessive torque is transmitted to the pinion gear by the ring gear, the driven clutches move away from the ring gear to compress a spring and resilient member to permit movement of the clutch members along splines coupling the driving clutch member to the power shaft and thereby absorb this torque by the resilient member. Indexing means also is provided to rotate the pinion gear to clear any abutment with the engine ring gear and causes the pinion gear to mesh with it.