| 摘要 |
The coupling and brake of a press receive pressurized fluid through a safety valve. The safety valve comprises two switching valves, so that if one of the switching valves fails and cannot close the other one can be closed. The safety valve is provided with a pressure-responsive switch which generates a shut-off signal commanding that the press be shut off, in response to a variety of malfunction situations, e.g., when the switching valves are closed but nevertheless a pressure build-up is occurring, or when the switching valves are open but the pressure being furnished to the coupling and brake does not reach or suddenly drops below the threshold levels to which the coupling and brake can respond. A differential pressure-responsive switch can be used to sense fluid flow through the safety valve; if the switching valves are moved to open setting, the differential pressure-responsive switch changes setting in response to the resulting fluid flow to the coupling and brake, but thereafter should revert to the previous setting and if it does not this triggers shut-off of the press.
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