Patent GB-678968-A (GB)
Title: Improvements in and relating to hydraulic power installations
IPC: B61C17/12
Filed: 1950-04-25
Abstract: 678,968. Hydraulic gears ; fluid-pressure servomotors. JONES, G. F. April 16, 1951 [April 25, 1950], No. 10191/50. Classes 69 (ii) and 135. A hydraulic power installation comprises two power units and a hydraulic motor 1, Fig. 1, one power unit comprising a pump 2 of constant speed variableoutput type and a compression-ignition engine 3 for driving same and the other comprising a pump 4 of variable speed type and a compression-ignition engine 5, the total output of the pumps being substantially equal to the capacity of the motor, and hand-regulated control gear arranged to bring the constant speed pump up to maximum output before bringing in the variable speed pump, next to bring the latter up to maximum output, and, when desired, to reduce the outputs in reverse order, the gear also operating a power valve which, when the variable speed pump is brought into use, diverts the liquid pumped thereby from an idling circuit to the motor, and when this pump is taken out of use returns the liquid to the idling circuit. When the hand lever 10, which is mounted on a shaft 9 carrying cams 8 and 8<SP>1</SP>, is turned from the start position, the cam 8 depresses a spring-loaded plunger 15, Fig. 2, and moves a link 29 having a slot 28 housing a pin 27 at the end of a valve 17, so that the valve 17 is moved and liquid entering a port 20 therein flows through a duct 24 to move a ram 19 which is connected to the link 29 at 31, and consequent movement of the pivot 31 causes the valve 17 to be moved back again and a link 32 to swing about a pivot at its lower end. The eccentricity of the pump 2 is controlled by a member 6 connected to a draw bar 34 pivoted to the link 32 at 33 so that the above-mentioned movement of the link increases the output of the pump. A valve 62 is spring-loaded to a normal position in which it allows liquid to flow from a port 68 to port 70 and conduit 72 to raise the vane 54 of valve 52 to which is connected a shaft 56 having fixed thereon the plug 57 of the power valve 43, so that the plug connects the output line 44 from the pump 4 to the connection 45 to the tank 38. The valve 62 passes through a trunnion 64 in the link 32 and carries a nut 62<SP>1</SP> at its outer end. When the pump 2 is at full capacity, further movement of the link 32 causes same to contact the nut 62<SP>1</SP> and move the valve 62, liquid then passing from valve 62 via port 69 and conduit 71 to depress the vane 54 and hence turn the plug 57 so that the liquid delivered by the pump is delivered to the connection 46 and thence to the motor 1. The cam 8<SP>1</SP> actuates a rod 7 governing the speed of the engine 5 and hence the output of the pump 4. Supply from the pumps 2 and 4 to the motor 1 is via a manually controlled reversing valve 41, and conduits 47, 48, from which conduits 86, 87 are connected to a cylinder 85 housing a rack having pistons at each end. The rack meshes with a pinion on a shaft 91 rigid with the plug of a bye-pass or coasting valve. Depending upon whether conduit 47 or 48 is the pressure line, pressure in the conduit 86 or 87 will move the rack against the action of centring springs to close the coasting valve. When neither line 47 or 48 is a pressure line, the springs centre the rack and the coasting valve is turned to its open position and liquid "pumped" by the motor 1 is able to idle through the valve. Liquid for operating the valves 17 and 62 is supplied by a pump 77 driven by an engine 78. Specification 598,671 is referred to in the Provisional Specification.