GB959622A - Hydraulic system - Google Patents

Abstract

959,622. Fluid-pressure servomotor control systems. NEW YORK AIR BRAKE CO. June 12, 1962 [July 13, 1961], No. 22588/62. Heading G3P. A remote valve 11, Fig. 1, movable into any one of the "float", "lower", "neutral" or "raise" positions by a manual lever 147, controls the movement of a relay valve 12 into any one of four corresponding positions, which relay valve is connected to an hydraulic motor M. With the lever 147 in the neutral position fluid from a small pump P2 flows from relay valve inlet port 102, Fig. 3, to the associated sump port 103 via passage 111, a spool groove 119 and a restricted channel 125 in spool land 122; the back pressure generated by the channel 125 fluid also causes fluid to flow from groove 119 to one chamber 61, Fig. 4, of the differential area motor piston 56, the cylinder 54 of which is connected to the spool valve 27, Fig. 1, of the relay valve 11. A second flow path from passage 111, Fig. 3, also leads to sump port 103 via spool groove 118 and another restricted channel 124 in land 122 whereby the back pressure produced by the latter is conducted by groove 106 to the other chamber 59, Fig. 4, of the piston 56, the pressures across which are equal and of low value so that the cylinder 54 is held in the central position by spring 86; the lands 121, 123, Fig. 3, or the channels 124, 125 may be arranged to compensate for the differential area of the piston 56, Fig. 4. Port 102, Fig. 3, also communicates with a chamber 132 to urge a 'feel' piston 133, to its leftward extremity; a spring 138 preloaded to balance the force developed by the fluid in chamber 132 at idling pressure holds the remote valve spool 117 in the neutral position. Upon moving the spool 117 to the right into the 'raise' position against spring 138 the length of the restricted channels 125, 124 increase and decrease, respectively, so creating a pressure differential in chambers 59, 61, Fig. 4, whereby the cylinder 54 and relay valve 27 are moved to the extreme leftward position against spring 86 so that an inlet port 14, Fig. 1, open to a large capacity pump, is connected via a motor groove 22 to the motor 14, the fluid exhausting therefrom being conducted to a sump port 15 by a groove 17. When the lever 147 is released the spring 138, Fig. 3, returns the spool 117 to the neutral position whereupon the spool 27, Fig. 1, moves correspondingly. Movement of the spool 117, Fig. 3, to the left into the 'lower' position is opposed by the force of the fluid in chamber 132 so providing 'feel', and still further leftward movement of the spool 127 to the 'float' position is opposed by springs 74, 75 as well as spring 86; in this latter position the spool 117 is located by balls 143 engaging grooves 148. In a modification, the remote valve spool 117 is spring centred in both directions and the hydraulic 'feel' device is only operable beyond the 'lower'position.