| 摘要 |
<p>1299386 Valves EATON YALE & TOWNE Inc 1 April 1970 [29 Oct 1969] 15500/70 Heading F2V [Also in Division G3] In a four-way, automatic return to neutral directional control valve 10, the output from a pump 18 is supplied to the valve inlet 19 wherefrom it is directed by a spool 35 either to one of two working ports 11 and 12 or to a valve exhaust port 22, the spool being movable from the indicated neutral position to either one of two terminal positions by means of a manually operable lever 27. When in the position shown, the working ports 11 and 12 are isolated both from each other and from the supply and exhaust ports so that fluid supplied to inlet 19 passes through openings 66, 67 in the spool bore 38 and thence to exhaust 22. Upon the spool being moved to its extreme leftward position, (as seen in the drawing), the supply fluid is directed by spool recessed portion 58 into working port 12 whilst return fluid from port 11 enters a portion 70 of the valve bore 38 wherefrom it passes into the outlet chamber 65. Simultaneously, a detent 50 of a releasable locking mechanism 46, enters into a groove 51 of a plate 49 which is carried by the spool and is biased into engagement with the detent by a spring 48. Subsequently, when the piston of the piston and cylinder unit 13 reaches the end of its stroke consequent to the pressurization of working port 12, the pressure within inlet chamber 64 rises and so unseats a check valve 78, 79 as a result of which the pressurized supply fluid flows into the outlet chamber 65 via a chamber 75, detent chamber 80 and spool bore portion 70, such flow in portion 70 acting against spring 48 and hence causing plate 49 to move away from the detent 50. The relative displacement of the component parts of the locking mechanism permits a spool centering spring 40 to return the spool to its central or neutral position, shown. In a modification, Fig. 4, not shown, the spool is formed with an additional land (92) which substantially isolates the locking mechanism from the flow issuing from working port 11. Additionally, the spool may be modified to place the working ports in fluid communication with each other when the spool is in its neutral position.</p> |
