Patent GB-958665-A (GB)
Title: Reversible hydrostatic torque converter
Inventor: YARMAK JULIUS
IPC: F16H39/06
Filed: 1960-07-14
Abstract: 958,665. Hydraulic transmission of power. COAL INDUSTRY (PATENTS) Ltd. July 14, 1960, No. 24583/60. Heading F2C. [Also in Division F1] A reversible automatically-variable power transmission comprises an adjustable-displacement hydraulic pump P adapted to be driven by a prime mover 13 and delivering fluid to a constant displacement motor M adapted to drive an output shaft 21, and means for maintaining displacement of the pump and speed of the output shaft at a maximum until a predetermined minimum torque is reached and to reduce the pump displacement and the speed of the output shaft thereafter in proportion to the increase in torque so as to reduce the speed of the output shaft to zero when the torque has reached a predetermined maximum. The pump may be of the balanced-vane type, such as described in Specification 947,709 and consists of a stator 29 formed with extensions 30, 31 clampable between the two parts 18, 19 of a casing. The stator supports bearings 35, 36 for a shaft 12 which is driven by gears 14, 15 from an electric motor 13 and is keyed to a rotor 11 having vanes 45. The vanes co-operate with abutments 39, 40 fixed to the stator and having projections 43 overlapping projections 44 on radially-adjustable members 41, 42, movement of the members controlling the displacement of the pump. The stator is formed with bores 46, 48 and 47, 49 which are respectively connected in pairs to pipes 53, 58 leading to similar pairs of bores 79, 81 and 80, 82 in the stator 63 of the motor M which is similar to the pump but of constant displacement and is connected by gears 22, 23 to the output shaft 21. The members 41, 42 of the pump are urged radially-outwards by springs 109 into engagement with levers 107, 108 at one end located by pivots 113 to the stator, and at the other end connected by links 119, 120 to a bar having an arm 126 joined by a rod 127 to the piston 118 of an hydraulic motor 131. The piston 118 carries a valve V connected by a flexible line 137 to a valve R which has a shuttle 146 permitting whichever of pipes 53, 58 is at the higher pressure to be connected to the valve V. A spool 134 of the valve V connects a bore 150 leading to a space 130 in the motor 131 to the line 137 or an exhaust passage 151, the spool being movable against an adjustable spring 153, which may have a linear or parabolic characteristic, on a rod 154 secured to the spool. In operation, depending on the direction of rotation of the motor 13, the pump delivers into pipe 53 or 58 to rotate the motor M and shaft 21. When a predetermined minimum torque is reached, the increase in pressure in pipe 53 or 58, is transmitted by the valve R to the spool 134 which, because of the differential areas of lands 147, 152 moves to the left to admit the fluid pressure through the passage 150 to move the piston 118 to the left and move the members 41, 42 inwardly reducing the displacement of the pump until, at a predetermined maximum torque, the displacement is zero. Upon a decrease in torque occurring, the spring 153 moves the spool 134 to the right connecting the space 130 to the exhaust passage 151 so that the piston 118 moves to the right increasing the pump displacement. The pipes 53, 58 are provided with one-way valves 59, 61 to permit fluid in the casing to enter the pipes and replenish losses caused by leakage, and relief valves 60, 62. The pump and motor are immersed in oil in a central compartment of the casing which is formed with separate compartments 92, 97 for the gears 14, 15 and 22, 23. A cooler may be provided internally or externally of the casing. In other embodiments, the pump displacement is adjusted by a double screw or double wedge mechanism instead of levers, and the input and output shafts may or may not be coaxial.