GB755594A - Improvements in or relating to engine starter drives - Google Patents

Abstract

755.594. Turning-gear. SIMMS MOTOR UNITS, Ltd., DODDS, R. G., and ROBINSON, E. L. Oct. 20, 1954, No. 30273/54. Class 7(5) In an engine starter drive wherein engagement between a pinion 8 on a starter motor shaft 1 and a gear 9 of the engine to be started is controlled by means including a nut 3 threaded on a screwshaft 2, the nut 3 is restrained against rotation by a brake 43, until the pinion is at least partially in mesh with the engine gear 9, the pinion 8 being splined to the nut 3 so as to permit relative axial motion therebetween. Upon energizing a solenoid 21 the plunger 22 is moved downwardly and closes contacts 25, 29 thereby supplying current to the starter motor through a resistance which may take the form of a field winding, not shown; a trip 30 is simultaneously pressed against the shoulder 31 of a lever 32 to move the latter longitudinally on a pin 40 and cause a friction pad 48 on the brake 43 to bear against the surface 5 of the nut 3 on the screwshaft 2 which is formed on or attached to the shaft 1. The motor rotates slowly and due to the action of the brake 43 the nut 3 traverses the screwshaft 2 and through a spring 10 axially urges the pinion 8 with its barrel 7 along the shaft 1 toward the gear 9 until a shoulder 47 on the barrel 7 moves the brake 43 longitudinally and rotates the lever 32 to disengage the shoulder 31 from the trip 30 and cause closure of a further pair of contacts 24, 28, and withdrawal of the brake 43 due to a spring 33 lifting the lever 32; the resistance is short circuited upon closure of contacts 24, 28 whereupon full torque is applied to the shaft 1. The nut 3 abuts a stop 49 on the screwshaft when the pinion is in the meshed position and a spring-loaded detent 12 enters a depression 14 in the screwshaft to prevent further relative movement between the nut and screwshaft until the engine is selfoperative whereupon the detent is withdrawn by a combination of centrifugal force and the force due to pinion acceleration; when the parts have returned to the idle position the detent co-operates with another depression 13 to hold the nut in the position shown. In the event of tooth abutment the spring 10 is compressed until the nut reaches the stop 49 whereupon it rotates with the shaft 1 and turns the pinion until indexing occurs, the spring then expanding to force the pinion into complete mesh with the gear 9. Specifications 609,093 and 755,595 are referred to.