Vacuum hysteresis switch operated by pressure medium - has additional contact signalling fault when pressure is outside hysteresis pressure values

摘要

The pressure operated vacuum hysteresis switch has a snap-action contact mounted on a diaphragm. This contact closes a circuit through fixed contacts projecting into the switching chamber, at a certain pressure of the medium, and breaks the circuit at a different pressure. The diaphragm also operates a bridge contact (17) which makes a connection between at least one of the fixed contacts (27, 28) and a fault signalling contact at a limit pressure outside the pressures determining the switch hysteresis. The contact bridge may connect both fixed contacts and the fault signalling contact together.