| 摘要 |
<p>1510418 Valves CATERPILLAR TRACTOR CO 25 Oct 1976 [8 March 1976] 44229/76 Heading F2V A valve comprises a reciprocable spool 11 lands 15, 16 defining an annular groove 23, and a metering slot 66 including a cylindrical pocket 69 recessed into the land 16 with its axis at an acute angle to the axis of the spool, and a longitudinally extending groove 72 including an arcuate portion 74 leading from the peripheral surface of the land 15 and a portion 76 tangential to the arcuate portion, parallel to the spool axis and leading to the pocket 69. The cylindrical pocket 69 is produced by an end mill cutter and the groove 66 by advancing a Woodruff key cutter toward the axis of the spool and traversing it at constant radial depth. There are further grooves 77 with arcuate bottom surfaces connecting the peripheral surface of the land 15 with the annular groove 23. The spool is actuated by a pilot valve (56), Fig. 1 (not shown) supplying fluid to chambers (54), (60) at opposite ends of the spool, and when not actuated the spool is centred by a resilient mechanism (51) in a position (Fig. 4) in which the end faces 67, 68 of the lands 15, 16 are located in chambers 29, 30 formed in the bore in which the spool moves and is separated by an annular seat land 34. When the spool is shifted to the left (Fig. 2), fluid is metered out from the groove 23 to the chamber 30, and when it is shifted to the right (Fig. 3, not shown), fluid is metered into the groove 23 from the chamber 29; it is stated that the shape of the metering slot 66 is such that the reaction on the spool due to momentum of metered fluid is equal in magnitude whichever way the spool is shifted and is in a direction tending to assist the movement of the spool.</p> |
