GB597056A - Improvements in and relating to hydraulic couplings - Google Patents

Abstract

597,056. Variable-speed gearing. WILSON, A. G., and MILLER, A. A. July 2, 1945, No. 16811. [Class 80(ii)] [Also in Group XXIX] In a hydraulic coupling in which epicyclic gearing is used as a series of gear pumps, the relative speeds of the driving and driven shafts being varied by controlling the outlet of the pumps automatically by control valves displaceable by centrifugal force against the resistance of resilient means, the medium is maintained in a ring at the periphery of a central reservoir leaving an air cavity at the central zone. As shown a driving shaft 2 carries a casing 1 in which is journalled a driven shaft 3 having a flange 11 towards its mid-length. On the flange is secured a toothed ring 10 in driving connection with an internally and externally toothed sun gear ring 8. The external teeth of the sun gear mesh with a plurality of planet gears 12 housed in a corresponding series of recesses 21, 22, in the casing 1, the recesses having portions which fit closely to the planet teeth so that gear type pump units are formed. Radial bosses 23 on the casing 1 house spring-loaded piston valves 28 which, under the action of centrifugal force acting against the springs 29, move outwards when the coupling is rotated and progressively restrict the flow of oil from the pump outlet passages 25 so that the hydraulic locking of the pumps increases with the speed of rotation. At starting and slow speeds oil is centrifuged to the planet gears and is circulated freely as the centrifugal force on valve 28 is insufficient to overcome spring 29 and the outlet passages 25, 35, 32, 31, are fully open. At the same time air is admitted to the inlets 26 from the centre of the casing through non-return valve 27. In this condition the transmitted torque is at a minimum. Increasing speed produces an outward radial movement of the valves which partially throttles the outlet passage 35 and at the same time opens the inlet 34 through passages 32, 31. Outward movement of the valve is also prevented by oil pressure from passages 33a, 33b, acting on the outer end of the valve, this oil leaks away at a rate controlled by the diameter of passage 33 in the valve. As speed further increases, the valve moves to its outermost position and shuts off the pump outlet thus providing a substantially direct drive from shaft 2 to shaft 3. Additionally the valves may be manually operated and an annulus employed in addition to or in place of the sun gear. A modification is described in which fibre or similar planet gears are used and means are provided to allow for lateral thermal expansion of such gears.