GB497202A - Improvements relating to change-speed gearing for use in the drive to the propellor of an aircraft engine - Google Patents

Abstract

497,202. Change speed gearing. ARMSTRONG SIDDELEY MOTORS, Ltd., and LOMBARDINI, P. C. May 25, 1938, No. 15556. [Class 80 (ii)] In a change-speed gearing between an aircraft engine and a propeller, the gearing includes annuli &c. 14, 17 which can be selectively held to give different speed ratios, the changes being effected substantially instantaneously by control means which consists of a high-pressure hydraulic accumulator 51, Fig. 2, with which are associated plungers 30, 31 operatively connected to mechanism for tightening brake bands &c. 21, 22 on the said annuli respectively and means including valves 70, 71, Fig. 4, for selectively applying the accumulator pressure to the plungers. The invention is shown applied to a two-speed gearing in which sun gears 12, 13 on the engine shaft 11 engage the annuli 14, 17 through sets of planets 15, 18 the carriers 16, 19 of which are fast with the annuli 17 and the propeller shaft 20 respectively. Fluid is supplied from a pump (not shown), driven by the engine shaft through gearing 54, to a passage 61 between the accumulator and the valves 70, 71 through an inlet 52, the pressure in the accumulator being controlled by a spring-loaded plunger 56 and being applied to one or other of the plungers 30, 31 in dependence upon the position of the said valves, the latter being formed with rack teeth for engagement by a common pinion 72. In Fig. 4, the valves are shown with the passage 61 in communication with the cylinder 33 of the plunger 31 and the other cylinder 32 open at 73 to exhaust. The pinion is loaded by a spring 74 so as to be biassed to one or other of its extreme positions, and it is preferably actuated through a lostmotion connection by a lever which is operative only when the accumulator is loaded to a predetermined pressure. The plunger 31 is coupled to the tightening mechanism of the brake band 22 by a rod 40 through the linkage 34 ... 39 shown in Fig. 2, and the said mechanism is mounted on a common shaft with the mechanism of the brake band 21 which is actuated by the plunger 30 in such a manner that when one band is tightened the other is released and vice versa, the linkage (not shown) associated with the plunger 30 including a spring to ensure that one of the brake bands is effective when the control means is not operative to prevent the gearing taking up a neutral position.