| 摘要 |
1494400 Valves NORDHYDRAULIC AB 7 Nov 1975 [7 Nov 1974] 46173/75 Heading F2V [Also in Division G3] The pilot valve of a directional control valve (13) includes a spool 47 which is movable by a handle 18 through a spring 55 to connect a pressure supply conduit 45 with a proportional pressure outlet 50 through radial passages 64 and axial passage 63 to give a pressure at outlet 50 proportional to the movement of the spool and thus the handle. During this movement a spring-loaded detent ball 58 moves in a groove 59 of an actuating plunger 52. However, the ball can be caused to ride over the land 60 into groove 57 so as to hold the spool 47 in a position in which an outlet 53 is connected directly with the pressure supply conduit via the groove 62. The outlets 50, 53 are connected respectively to the chamber (40) of a single-acting actuating cylinder and a chamber (37) of a double-acting actuating cylinder the other chamber (36) of which is connected to an outlet 50 of a further spool valve of the pilot valve. The piston of the double-acting cylinder is directly connected to the spool of the directional control valve whereas it is connected by lost-motion with the piston of the single-acting cylinder. Pressure supplied to the chambers of the actuating cylinders cause the directional control valve spool to assume forward, reverse and float positions, the spool normally being held in an open-centre central position by a centring spring device. The pilot valve includes a further two spools which are used to actuate a further directional control valve. All of the pilot valve spools are normally biased to the position shown in which both the outlets 50, 53 are connected to drain conduit 46 via the passages in the spool, the connection being cut off by spool lands 65, 61 on downward movement of the spool. The detent ball may be released by an electromagnetically-operated valve 86, 87, which on movement to the left connects passages 77, 76 to connect supply pressure to the right of piston 82 to move it to the left to release the pressure on the ball 58. |
