Patent GB-537214-A (GB)
Title: Improvements in and relating to transmission gears
IPC: F16H61/40
Filed: 1939-09-07
Abstract: 537,214. Combined hydromechanical change speed gear. BOULY, H. G. (Acrotorque Co.). Sept. 7, 1939, No. 25332. [Class 80 (ii)] [Also in Group XXIX] An hydraulic transmission gear comprises a pump and a motor, the flow between which is controlled by valves which are alternately opened and closed by mechanical means and which are balanced hydraulically and so require a small actuating effect. The driving- shaft 15, Fig. 1A carries a sun-wheel 16 engaging planet wheels 17 carried by a sleeve 21 freely mounted on the shaft 15 and serving to actuate the pistons 27 of radial pumps associated with which are high and low pressure fluid manifolds 37, 38 from which fluid motors of similar construction to the pump are actuated. The planet wheels 17 engage an internal gear 18 on a hub 19 connected by splines to a driven shaft 53 from which the final drive is obtained through an epicyclic gear 62-72, Fig. 1B, comprising a set of planet-wheels mounted or. a carrier 72 which can be set so that the final drive is in a direction the same as or opposite to that of the shaft 53, or may be free. The drive from the shaft 15 may take place in part mechanically and in part by the hydraulic transmission device. The pistons 27, 56 of the pumps 26 and motors 55, Fig. 2, are reciprocated by means of eccentrics 30, 54, to which curved ends 29 of the pistons are held by means of clamping rings 31, and the eccentrics 54 are secured adjustably to the shaft 53 by means of a sliding bar 77 which can move axially of the shaft 53 and are formed with inclined grooves 78 which engage projections 82 on segmental members 80 secured to the eccentrics. Axial movement of the bar 77 causes the eccentricity of the eccentrics 54 to vary and so varies the strokes of the motor pistons. Connection between the hydraulic manifolds 37, 38 and the cylinders 26, 55 is controlled by balanced piston valves 45 controlled by springs 50 and operated by spring push rods 52, controlled by cams 32, 33 on the sleeve 21 and cams 57, 58 on the hub 19 The valves seat on the enlarged seating surfaces of liners 39, Fig. 17, and are ground so as to have line contact and thus to ensure a leak-proof seal, and are fitted at their upper ends with packing 43. The axial motion of the bar 77 can be effected automatically in dependence upon the load in order to adapt the capacity of the motor to the load. To this end the bar is operated by lever mechanism and an hydraulically operated piston the movements of which are controlled by a fluid servomotor device shown in Figs. 10, 11. The high-pressure manifold 37 is connected to a cylinder 237 in which is a piston 116 acting upon a lever 115 which is also acted upon by an adjustable spring 117. The position of the lever 115 is thus dependent upon the pressure in the manifold 37. This lever is provided with two other sets of arms which at one-end act upon the stem of a ball valve 120, and a valve 124 which controls a passage 126, and at the other end act upon similar valves in connection with the other end of a controlling cylinder. The piston in this cylinder is thus moved in one direction if the pressure increases and in the reverse direction on decrease of pressure, and the pump capacity is varied correspondingly. To counteract the effect of altering the eccentricity of the eccentric 54, the bar 77 is formed with grooves whih are inclined in the opposite direction to the grooves 78, and which move a balance weight radially of the shaft in a direction opposite to that of the eccentric. As shown an auxiliary pump 128 assists in the liquid circulating but this pump need not be used in connection with the transmission circuit. If desired the fluid transmission circuit can be cut out by a manual manipulation which opens up a valve which normally keeps the high and low pressure conduits separate. This arrangement is provided with relief valves in the two conduits for operation when the power-end overruns the driving-end.