Patent GB-992919-A (GB)
Title: Improvements in or relating to hydraulic variable speed devices
Inventor: LINSLEY DOUGLAS FOWLER
IPC: F16H39/08
Filed: 1962-06-06
Abstract: 992,919. Reciprocating pumps and motors. MORGAN DEVELOPMENT LABORATORIES Inc. June 6, 1962, No. 21913/62. Heading F1A. [Also in Division F2] A variable-ratio hydraulic transmission comprises a variable displacement pump P supplying a constant displacement motor M, both the pump and motor comprising two banks of parallel cylinders A1-A5, B1-B5, the pistons of which, in the case of the pump P are driven by eccentrics 32 on a common driving shaft 30, and in the case of the motor M drive eccentrics 32 on a common driven shaft 31. Each pump cylinder is connectable through a rotary valve 39 common to all the pump cylinders to manifolds P33, P34 communicating with lines 35, 36 leading to motor manifolds M33, M34, the lines 35, 36 serving as pressure and return lines according to the direction in which the motor is to be driven. The valve body 39 is geared to the input shaft 30 so as to rotate at the same speed but in the opposite direction thereto, and the phase of the valve rotor relative to the input shaft can be adjusted to adjust the position in the stroke of the piston at which each cylinder is changed over from connection to the manifold P33 to the manifold P34 in order to vary the pump output. This is achieved by the driving shaft 30 carrying a gear 43 which meshes through idlers 42, 41 a gear 40 freely mounted on an extension 39a of the valve body 39. The gear 40 has a straight spline connection with a collar 156 having an internal helical groove formed therein receiving a pin 159 fast with the extension 39a. The axial position of the collar 156 is adjusted by means of a manually operated lever 68 which rotates a pinion 166 engaging a rack 165 shifting the collar through a thrust bearing 163. Each piston 26 of one bank is reciprocated by a separate eccentric 32 on the driving shaft, but each eccentric 32 also actuates a piston of the other bank. The angle between each succeeding eccentric is given by the formula 2 Î 360¸N, where N is the total number of pump cylinders, and the angle between the two banks of cylinders is given by the formula 900¸N, so that for the pump shown having two banks of five cylinders the eccentrics are successively angularly displaced by 72 degrees, and the two banks of cylinders are set at 90 degrees. The pistons of one bank are thus offset by 18 degrees from rows of the other bank which gives a relatively uniform output from the pump. The motor is constructed similarly except that the valve rotor 39 is not adjustable. Make-up liquid is supplied by an input driven gear pump 72 which ensures that the pressure in the return line is sufficient to keep the pistons in contact with the eccentrics during their return strokes. Relief valves 80, 81 limit the maximum pressures obtainable in the lines 35, 36 to prevent over-loading. The X arrangement of the cylinders of the transmission provides a large surface area for cooling purposes. Each piston 26 bears against its eccentric 32 through a roller 27 which is rotatably mounted on a shaft 27b which is guided in slots formed in an enlarged end 26a of the cylinder to keep the roller aligned with its cam.