Bistable indicator device for signalling a pressure drop of a gas in an enclosure

摘要

The pressure detector (5) has a bellows end section (8) which moves one end of a double action arm (10). One arm (13) is anchored whilst the other end contacts the pressure detector. The arm also swivels a second arm. The second arm slides up and down on a vertical tube. The tube has a sliding collar (3) which is moved by the second arm and can cover a red indicator (4) on the tube. A decrease in pressure results in more gas being inlet, by a nozzle (25) actioned by the swinging arms. The arms have a stable position held by a cam and spring mechanism (15) ensuring the correct gas pressure is achieved.