GB1389352A - Pressure monitoring device - Google Patents

Abstract

1389352 Fluid-pressure actuated switches PIANCO CONTROLS SpA 4 Dec 1972 [24 Aug 1972] 55843/72 Heading H1N In a device for monitoring fluid pressure changes, as in a vehicle tyre, a diaphragm 12, Fig. 1 for actuating a movable contact 17<1> encloses a chamber 11 containing fluid at substantially the same pressure as that to be monitored and also having the same temperature coefficient of variation of pressure. The arrangement permits equilibrium conditions to be maintained when normal pressure/temperature variations occur in the tyre. The movable contact arm 17<1> is integrally formed to extend from the end of a spring strip 17 which is preloaded by a second spring strip 21 whereby under normal conditions of loading when the pressure in the tyre equals that in the chamber 11 the contact 17<1> engages a fixed fulcrum 20 and is disengaged from a central contact pin 16 (broken lines in Fig. 1). If the tyre pressure drops, contact 17<1> engages contact 16 to close a circuit of signalling apparatus in the motor vehicle. A perforated cover plate 13 limits the movement of the diaphragm 12 to protect it against excessive deformation. In modifications the movable contact may be urged closed by a permanent magnet whereby snap-action closure is obtained. The movable contact 32<1> Fig. 8 may also be bent over at its end and engages a disc 31 attached to the fixed contact 16 whereby the signalling circuit is closed both on over-pressure and under-pressure.