GB608518A - Improvements in variable speed driving mechanisms for compressors - Google Patents

Abstract

608,518. Variable-speed gears. MATHIS SOC. ANON. Feb. 25, 1946, No. 5869. Convention date, Dec. 22, 1941. [Class 80 (ii)] [Also in Groups XXIX and XXXIV] A supercharger impeller 7 of an aircraft engine is driven at a speed which varies automatically in accordance with the supercharger delivery-pressure acting through a conduit 46 on an aneroid 44, Fig. 3, controlling, through a fluid-pressure servomotor, a valve 32, which, by progressively throttling the common annular oil-delivery outlet 29, 30 of three gear-pumps 24, which have a common annular inlet 27 and are uniformly spaced about the impeller-axis, applies a variable brake-torque to an internallytoothed ring-gear 21 (or planet-carrier), forming the reaction-member of an epicyclic train driving the impeller, and also having external teeth 21a providing a common drive for all three gear-pumps 24. A manually- and automatically-controlled friction disc-brake 50 is also provided for the reaction ring-gear 21. The epicyclic gear shown comprises a driving planet-carrier 12, secured to the engine crankshaft 9, and carrying stepped planets, the smaller 14 of which engages the reaction ring- gear 21 whilst the larger 15 engages a driven sun 18 secured to the impeller 7. With the pump throttle-valve 32 open, no drive is transmitted and the pumps 24 circulate the oil idly from and to a reservoir. With the valve 32 fully closed, the ring-gear 21 is stationed and the impeller is driven at maximum speed. Intermediate valve positions produce intermediate speeds by allowing varying degrees of slip. To prevent undesired rotation of the reaction ring 21 duo to leakage in the fully throttled position, and also to provide a manual control for obtaining maximum speed irrespective of altitude, the reaction-ring 21 has also a manually and automatically controlled discbrake comprising an inner disc 50 on the ring, which is clamped between stationary lined discs 51, 52 when a rack 54 (not further shown) is moved axially to turn one disc 52 on a screwthread 53 on the other. Alternative gear trains comprise (Fig. 4, not shown) a simple non- stepped planet train driving through a fixed countershaft speed-multiplying train, and (Fig. 5, not shown) a stepped-planet train having driving and driven suns, the planet-carrier being the reaction member. The servomotor operating the speed-controlling throttle-valve 32, Fig. 3, comprises a piston 34, loading the valve to the closed, maximumspeed position by a spring 35, and to the open position by oil-pressure admitted from inlets 41 by a piston-valve 42, operated by the aneroid 44, on which a diaphragm-sealed screw 47 provides a datum setting. One pressure inlet 41 communicates through the valve 42 with a delivery-conduit 55 leading to the frictionbrake operating rack 54 whereby tho friction brake 50 is also automatically applied in the maximum speed position.