Patent GB-1217201-A (GB)
Title: Hydrostatic transmission system
IPC: F15B11/02
Filed: 1968-01-04
Abstract: 1,217,201. Reciprocating motors. APPLIED POWER INDUSTRIES Inc. Jan.4, 1968 [April 25, 1967], No.692/68. Heading F1A. [Also in Division F2] In a hydrostatic transmission system having a variable output pump supplying a fluid motor, the output of the pump, and thereby the speed of the motor, is controlled in accordance with the back pressure created by adjustable throttling means on the discharge side of the motor. The motor comprises a fixed cam plate and a rotary cylinder block 13, Fig. 1, with parallel cylinders 21 therein. It receives fluid from the pump (not shown) through an inlet 61, and discharged the fluid through an outlet 63 to a reservior (not shown). An adjustable valve assembly positioned between the motor, inlet 61 and outlet 63, comprises a fixed plate 18, Figs. 1 and 2a, and a co-operating rotatable plate 44. Arcuate grooves 25, 26 in the face 32 of the plate 18 communicate with shallow bores 35, 36 in the opposite face 34 thereof. Additionally, the face 34 has shallow bores 41, 43 inter-connected by a transfer passage 45 within the plate 18. The plate 44 has three arcuate passages 54, 55, 56, Fig. 3b, therethrough, and is rotatable by a lever 52 from a neutral position, Fig. 3a (not shown) in either direction to control the speed and direction of rotation of the motor. In the position of the plate 44 shown, the cylinders 21 are communicated with the inlet 61 through bore 62, passage 54, bore 36 and groove 26, and with the outlet 63 through groove 25, bore 35, passage 56, transfer passage 45, passage 55 and bore 64. The output of the pump, and thereby the speed of the motor, is controlled by a unit (102), Fig. 6 (not shown), in accordance with the back pressure created upstream of the throttled region M (Fig. 3b). The back pressure is communicated to the pump control unit through bore 43, passage 91, Fig. 4, restriction 112, non-return valve 99 and a line 94 containing a restriction 124 and non-return valve 122, excess fluid being discharged to the reservoir through a restriction 92. Thus, any variation in the motor speed from the value set by the flow area at region M results in suitable adjustment of the pump delivery. However, the line 94 communicates with a device (130), Fig. 6 (not shown) for briefly delaying adjustment of the pump to avoid unnecessary adjustment due to sposmedic pressure variations. Bores 38, 33 communicate the interior of motor housing 12 with outlet 63 and transfer passage 45 respectively to serve as a drain for leakage and as a bleed passage for cooling flow. The inlet bore 62 and outlet bore 64 communicate with transverse bores 76, 78 and 80, 97, 90 respectively through extension bores 62<SP>1</SP> and 64<SP>1</SP>. When the plate 44 is in its neutral position, a bypass passage 83 between bores 76, 80 and an associated by-pass valve 86, establish a main flow from the inlet 61 directly to the outlet 63. Moreover, a small cooling flow is established through a passage 72, an arcuate passage 58 and a passage 18 to the interior of the housing 12. Pressure relief valves are provided in bores 76, 78, 97.