GB853667A - Improvements in or relating to variable speed hydraulic drives - Google Patents

Abstract

853,667. Rotary engines. BREWER, C. E. Dec. 9, 1957 [Dec. 8, 1956], No. 37576/56. Class 110 (2). [Also in Group XXIX] An hydraulic variable-speed gear comprises a sliding vane pump and motor combination with an auxiliary pump for selecting forward, neutral and reverse drive, and the variation in speed ratio is obtained automatically. A pump P and a motor M have vaned rotors 1 fast with an input shaft 3 and an output shaft 3<SP>1</SP>. The pump and motor are similar in construction and each have vanes 11 abutting a cylindrical member 5 and an abutment member 14 which is rotatably mounted on a non-rotatable valve 16 fast with a slide member 25 by means of which the eccentricity of the members 5, 14 with respect to the rotor 1 can be varied. The motor slide member is biased to a position of maximum eccentricity by a spring 35; the pump slide and abutment members are brought to a concentric position by springs 36 acting on the member 5. The spaces between the rotor and the member 5 of the pump communicate with the corresponding spaces of the motor through arcuate ports and ducts 12, 13, the spaces between the rotor and the member 14 of the pump communicate with the corresponding motor spaces through ducts 21 and the valve 16. The auxiliary pump comprises a vaned rotor 1a fast with the pump rotor 1, the vanes engaging members 5a, 14a. The eccentricity of the members is variable by means engaging the member 5a and in one position of eccentricity the auxiliary pump delivers through a pipe 27 to depress a piston 28 acting on the pump slide 25 which is depressed to move the pump members 5, 14 to an eccentric position. The pump therefore delivers to the motor and the output shaft is driven. The piston 28 uncovers a port leading to a duct 33 whence the liquid discharged by the auxiliary pump passes through a non- return valve 34 and pipe 27a to the auxiliary pump inlet. When the members 5a, 14a are moved to the opposite side of their concentric position, a piston 28a is raised and the pump output is reversed to drive the motor in the opposite direction. For both directions of drive, when the pump slide 25 nears its position of maximum eccentricity it engages a lever 32 and thus moves the motor slide 25 to decrease the capacity of the motor so that the gear ratio is further increased. When the auxiliary pump members are in a concentric position the pump output is zero and the transmission is in neutral. To prevent any discharge from the auxiliary pump when in neutral, due to centrifugal force, the pipes 27, 27a are closed by ball valves 29, 29a. As a modification the spaces between the rotors and the members 14 may be shorted by providing clearances or passages at the inner ends of the vanes. The pump may supply two motors to form a differential gear.