| 摘要 |
<p>1291507 Valves; machinery safety devices TECHNOMATIC AG 10 Nov1970 [6 May 1970 30 June 1970] 53422/70 Headings F2J and F2V A valve controlling a brake or clutch of a press has solenoid-operated pilot valves 54, 56 which, when energized, admit fluid from inlet 62 to chambers 77, 79 to shift pistons 76, 78 inwards to the positions shown where they close ports 48, 50 (Fig. 3), thereby disconnecting work port 46 from return port 47. Flow then takes place to work port 46 through the interior of pistons 76, 78 via back-pressure check valves. Spring 30 returns the pistons outwards to connect ports 46, 47 when valves 54, 56 are deenergized. Piston 82 responds via passages 92, 94 to the differential pressure in chambers 77, 79 caused by failure of either of valves 54, 56 and operates switch 110 to disable the press. Passages 96, 98 extending from chambers 85, 87 open into the seats 22, 23 whereby if either of pistons 76, 78 fails to move inwards when the valves 54, 56 are energized, or if either piston fails to return when the valves are de-energized, a pressure differential is again established across piston 82 which operates switch 110 as before. In a first modification (Figs. 7 and 8, not shown), instead of the passages through pistons 76, 78, a separate supply valve is provided having a piston (124) which responds to the pressure applied to one of the pistons 76, 78 by the corresponding pilot valve and unseats a valve member to connect the inlet directly to the work port. In a second modification, Fig. 9, the passages through the pistons are again omitted and replaced by angularly-spaced surface grooves which, when pistons 14, 16 are shifted inwards, connect inlet grooves 161, 163 to annular grooves inwards of seal rings 156, 158, thereby conducting to the work port which is located opposite the return port as in Fig. 1. Enlarged outer lands of pistons 14, 16 allow the inlet pressure to return the pistons when valves 54, 56 are de-energized. In each case, the pistons 76, 78 or 14, 16 are preferably of plastics.</p> |
