Abstract: A pressure sensor probe has a first port connectable to a relatively low pressure source in a compressor crankcase and a second port connectable to a relatively high pressure source at the output of an oil pump. A shuttle is slidably disposed in a bore and has a first end which closes the first port when the difference in pressure between the two ports indicative of normal operation exceeds a selected value determined by the relative areas of the shuttle exposed to the respective pressures and by a coil spring which biases the shuttle away from the first port. A passage is formed between the shuttle and the bore leading from the second port to a force receiving surface on the high pressure side of the shuttle. The length and cross sectional area of the passage is selected to provide a desired dampening or time delay between the high pressure source and the force receiving surface. A control circuit includes a reed switch whose state of actuation is dependent upon the position of the shuttle.

Abstract: A sealed pressure-responsive switch is manually resettable and trip-free. The switch has a separate snap-acting, bistable, dished metal disc or disc element disposed between a sealed snap-acting pressure-responsive diaphragm and a spring-biased switch arm. The disc moves to an inverted dished configuration with snap action to move the switch arm to a trip position against the arm bias when the diaphragm moves in response to application of a selected fluid pressure. The disc remains in its inverted shape to releasably hold the arm in tripped position until the switch is manually reset even when the diaphragm returns to its original position after removal of the selected fluid pressure from the diaphragm.