| 摘要 |
A double safety valve for stamping presses and the like having a monitor responsive to asynchronous pressures, to disenable a press. The assembly comprises two valve stems each being radially supported by a piston at one end and by an outboard bearing at the other end. Each valve stem carries an inlet poppet valve adjacent one end, a spool valve on an intermediate portion and an exhaust valve adjacent the other end. Cross passages connect the inlet poppet valve of each valve stem in series with the spool valve of the other valve stem. A common outlet chamber receives pressurized fluid from both spool valves, this outlet chamber being connected in parallel to both exhaust valves. The assembly thus has the advantages of a double safety valve in which the inlet valves are in series and the exhaust valves in parallel, but is capable of being monitored by a monitor responsive to asynchronous pressures or movements. Pressures at the monitor fluctuate between zero and full pressure with each normal cycle, causing slight shuttle movement which improves monitor reliability. The construction minimizes side loading on the spool valves, thus preventing appreciable wear which could cause leakage upon faulting of one valve element and which in turn could inadvertently continue press operation.
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