GB734450A - Improvements in or relating to power transmission mechanism - Google Patents

Abstract

734,450. One-way clutches. UNITED AIRCRAFT CORPORATION. April 29, 1953, No. 11861/53. Class 80 (2). [Also in Groups XXIX and XXXIII] A fluid coupling which is filled and emptied by speed-responsive means has a direct drive one-way clutch in parallel therewith the clutch being rendered operative by centrifugal means and having baulking means preventing operation of the centrifugal means so long as the input member is over-running the output member. The transmission is for use between an engine and a helicopter rotor (see Group XXXIII). As shown in Fig. 2, the impeller 72 of a fluid coupling is driven by an engine shaft 52 and has an inlet valve 174 which opens centrifugally at a speed (e.g. 2000 r.p.m.) above that (e:g. 1800 r.p.m.) at which an exhaust valve 188 closes centrifugally. A depending cylindrical member 170 acts as a centrifuge to supply oil from a sump 166 to the inlet valve 174. The turbine 90 of the coupling is attached to the output member 96 of a oneway clutch the input member 98 of which is fixed to the engine shaft 52. Clutch rollers 100, Figs. 2 and 3, disposed in a cage 126, Figs. 3 and 4, are movable into and out of the operative position, Fig. 3, which allows drive in one direction and over-running in the other. The centrifugal means for engaging the one-way clutch is shown exploded in Fig. 4. Flyweights 142 are mounted on arms 140 of cranked levers the other arms 144 of which abut a disc 116, Fig. 2, fixed to an extension of the member 98. This extension is splined at 134 to a carrier 132 to which the cranked levers are pivoted at 138. Arms 136 limit outward movement of the weights 142. Lugs 130 on the carrier 132 engage helical slots 128 in the roller cage 126. The baulking means comprises a disc 150 frictionally engaging a shoulder 162 on the member 96 and having tongues 160 which slide in slots 156, 158 in the carrier 132. A spring 148 opposes downward movement of the carrier 132. The spring rate is such that the weights 142 will move the carrier 132 downwardly to engage the clutch at a certain speed, e.g. 1200 r.p.m., the force due to the weights increasing at a greater rate than that due to the spring. Operation.-The engine is accelerated up to the speed at which the valve 174 opens, the valve 188 closing before this speed is reached. The fluid coupling fills and a torque, the value of which is limited to a fraction (e.g. 10 per cent) of the maximum engine torque, speeds the output shaft up to, e.g., 1500 r.p.m. The oneway clutch is not meanwhile operative since drag on the disc 150 will have moved the tongues 160 to the closed ends of the slots 158 and downward movement of the carrier 132 is prevented. The engine is next decelerated, the drag on the disc 150 reversing and moving the tongues 160 to the open ends of the slots 158 where the slots 156 allow axial movement of the tongues 160 and the member 132. The lugs 130 co-operate with the slots 128 to rotate the cage 126 relatively to the member 98 and thus move the rollers 100 to an operative position. Finally the engine is accelerated and a direct drive is transmitted to the output shaft.