Patent GB-891003-A (GB)
Title: Improved means for controlling the delivery of working fluid in a hydraulic circuit
Inventor: SNOWDEN ERIC MCIVOR
IPC: F04B49/12
Filed: 1959-03-18
Abstract: 891,003. Fluid-pressure servomotor-control systems; hydraulic transmission of power. BRITISH-JEFFREY DIAMOND Ltd. Feb. 26, 1960 [March 18, 1959], No. 9394/59. Classes 69 (2) and 135. The haulage unit of a coal-cutting machine is driven by an hydraulic motor 90, Fig. 7, of fixed eccentricity, that is supplied with fluid by a reversible variable-displacement radial-cylinder pump 73 driven by an electric motor 85 ; the pump displacement is varied by a sliding block 1 housing a fixed piston 12, a fixed piston valve 16, spring-centred fluid-actuated valves 8, 9, and a manually-adjustable speed-control valve 3. Fluid is supplied to one or other inlet ports 26, 27 from pumps 19, 20, respectively, under the control of a solenoid valve 21. The pumps 19, 20 may be replaced by one unit having two main pistons of different diameter. With the valve 21 in the position shown, pump 20 is connected to exhaust and pump 19 to inlet 26; upon displacing the valve 3, say to the right, fluid from the inlet 26 displaces valve 8 leftwardly and then acts on the right of piston 12, concomitantly the valve 8 opens the left side of piston 12 to exhaust via ports 30, 31 so that the block 1 moves to the right until ports 28, 31 are closed by lands 4, 5 on valve 3. The valve 8 remains in its displaced position. If the valve 21 is now actuated to connect pump 20 to inlet 27 and pump 19 to exhaust then fluid flows through a port 32, opened when the block 1 moved rightwardly relative to the valve 16, and urges valve 9 rightwardly to admit fluid to the left of piston 12, and since valve 8 is still displaced to the left this fluid traverses ports 30, 31 until it is stopped by land 5 of valve 3 whereupon block 1 is forced to the left and fluid from the right of pistons 12 is exhausted through a port 33 controlled by valve 16; ports 28, 31 are then opened to exhaust enabling the valve 8 to centralize and close port 30 and the block continues its leftward motion until ports 32, 33 are closed by lands 18, 17 of valve 16 and the block 1 is stopped in its original position. Manual switching and speed control is effected by an arm 34, Fig. 2, which is connected by gears 38, 39, 40, 42, a double-jawed clutch 45 and bevel gears 47, 48, 49 to a shaft 44 by which the control switch for the electric motor 85, Fig. 7, is actuated; bevel gear 47, 48, Fig. 2, can be selectively engaged with bevel gear 49 by axial manipulation of a rod 50 to determine the direction of rotation of the electric motor. The speed control valve 3, Fig. 7, is operated through a linkage 71 moved by a knob 67, Fig. 2, through a nut 68 threaded on a shaft 58 connected to the knob 67, and interlocking gears and clutch are provided so that shaft 58 cannot be rotated until the arm 34 in in the " on " position; if the arm 34 is moved to the " off " position whilst the valve 3 is set to a given speed the valve is automatically returned to neutral. In the fluid circuit 89, Fig. 7, between the pump 73 and haulage motor 90 is a by-pass valve 92 which is normally held closed against a spring 94 by fluid pressure from a pump 99 passing through a manual valve 101. To stop the motor 90 the spindle 102 of valve 101 is moved to left, whereby the spring 94 is enabled to open by by-pass valve 92 and fluid in the casing of valve 101 is directed to pistons 108 which operate to centralize a rack 109 in engagement with a gear 110a, Fig. 2, on the shaft 58 and thereby set the valve 3 in the " neutral " position. The electromagnet 25 of valve 21 may be connected in series with the motor 85 so that upon a given load current being exceeded the valve 21 will return the pump 73 to zero eccentricity and stop the motor 90; since this reduces the load current the valve 21 will then be returned to its normal position and the pump 73 to its previous speed setting.