| 摘要 |
971,886. Door operating appliances. WESTINGHOUSE BRAKE & SIGNAL CO. Ltd. March 30, 1961 [March 30, 1960], No. 11154/60. Heading E2M. [Also in Division Fl] A double-acting piston and cylinder assembly operable by a gaseous medium, particularly for opening and closing doors, has means for cushioning the piston when the latter approaches the end of either or both of its strokes at least one of the cushioning means comprising a cushioning valve closure member 9 adapted to co-operate with a main outlet opening 5 to close the latter over a terminal portion of the piston stroke and loosely slidable relative to and axially of the piston rod 2 exteriorly of the same under the action of a spring 8 attached at one end to the valve closure member and at the other end to the piston and piston rod assembly and constituting the sole motive connection between the valve closure member and the assembly, so that the piston is cushioned by the compression of both the gaseous medium and the spring, the trapped and compressed gaseous medium thereafter leaking through the restricted passage between the cushioning valve closure member and the piston rod. The cushioning valve closure member 9 comprises a flat faced valve element 10 and a packing cup 11 held against the element 10 by a locking nut 12 to which one end of the spring 8 is attached. The other end of the spring is attached to a piston follower 15 between which and the piston 17 is fitted a packing cup 18. An oppositely directed packing cup 19 is fitted on the other side of the piston, together with a collar 21 attached to a spring 88 connected to a second cushioning valve closure member 99. When the inlet 22 is coupled to the pressure medium gas flows past the packing cup 111 and acts upon the packing cup 19 thus moving the piston 17 to the left and withdrawing the valve closure member 99 from the right hand end of the cylinder. The piston moves freely until the valve closure member 9 closes the outlet holes 5, after which it is cushioned by the compression of the gas trapped between the packing cups 11 and 18, and the spring 8. The trapped gas escapes slowly through the annular space between the valve closure member 9 and the piston rod 2, the escape being controlled by an adjustable choke valve (not shown). The reverse movement of the piston takes place in a similar manner to that just described. |
