| 摘要 |
859,658. Valves. NEW YORK AIR BRAKE CO. May 19, 1959 [Sept. 17, 1958], No. 16926/59. Class 135. A valve suitable for controlling a double-acting differential-area piston motor 72 for positioning the bucket of a loader used in earth moving equipment has a slidable valve member 35 urged by a spring 67 to a neutral position in which ports 22, 24 communicating with an inlet 12 connected with an hydraulic pump are placed in communication with an outlet 13 leading to a reservoir to unload the pump and ports 19, 26 communicating with the two ends of the motor 72 are isolated. When the valve member is moved to the right the communication between the inlet 12 and outlet 13 is interrupted, the lower side of the motor 72 is connected to the inlet through ports 48, 49 communicating with an axial bore in the valve member, and the upper side of the motor is connected to exhaust through ports 52 which open to a second axial boring communicating with ports,51, 53 which, in this position of the closure member, communicate respectively with exhaust ports 23, 28. Movement of the closure member to the left of the neutral position causes reverse motion of the motor 72 by connecting the upper side thereof with the inlet through ports 52, 53 and the lower side with exhaust through ports 49, 48, the latter then communicating with an exhaust port 17. The lefthand position of the valve member is determined by engagement of an abutment 68 with a stop 66 but the valve member may be moved beyond this position by the application of sufficient pressure to force a shoulder on a sleeve 65 past an elastic, split-ring 63 so that the central land 41 of the valve member enters the bore between ports 21, 22. In this position both sides of the motor 72 are connected with each other through ports 51, 53 and are also connected with ports 21, 25 which are interconnected by means of a passage 33 incorporating a restriction 56 leading to the port 22. By this means the motor 72 is free to descend under the weight of the bucket owing to the unequal volumes on the two sides of the piston of the motor 72 due to the piston-rod the rate of descent will be limited by the rate at which fluid can pass through the restriction. The inlet 12 to the valve incorporates a relief valve 34. A check valve (not shown) is incorporated within the closure member adjacent the ports 48 to prevent return flow of fluid from the conduit 73 when the closure member has been moved to the right but before the pump has developed sufficient pressure to operate the motor 72. |
