Abstract: A nonexplosive pressure-responsive switch has a housing containing a chamber which is exposed to a source of pressure and a second chamber containing switch elements. A partition separates the two chambers. The chamber connected to the pressure to be monitored has a longitudinal collapsible bellows mounted inside with a first magnet mounted on its end. In an unpressured condition the magnet will normally touch the partition between the chambers. The second chamber containing the switch elements also contains a second magnet which is mounted in an adjustable cylinder. A third magnet is mounted between the adjustable magnet and the switch contacts. When the first magnet is against the partition, the first magnet pulls the movable magnet in the second chamber against the switch contacts, and when the first magnet moves away from the partition, the adjustable magnet attracts the movable magnet, breaking the switch contacts. A second set of switch contacts can be carried by the adjustable magnet's housing.

Abstract: A leak detection apparatus for a dispensing apparatus having a pump and a pressure-sensing apparatus with an output switch responsive to a predetermined pressure has a pump interrupter circuit with a control input. A pump interrupter control circuit has an input and an output connected to the control input of the pump interrupter circuit. A timing circuit has an output, and an input for initiating a signal at the output for a predetermined period of time. The timing circuit is connected through the pressure-sensing apparatus output to the input of the pump interrupter control circuit such that a leak in the dispensing apparatus will cause closure of the output switch, transferring the signal at the output of the timing circuit during the predetermined period of time to the input of the pump interrupter control circuit causing the pump interrupter circuit to interrupt the operation of the pump.

Abstract: A system for detecting a leak in a line consists of an apparatus for detecting a drop to a predetermined pressure in the line; and, once the predetermined pressure is reached, an output is developed by the pressure-sensing apparatus. A bi-state circuit responsive to the output from the detecting apparatus has a first state when no leak is present and a second state when the predetermined pressure is detected. A switching circuit has its input connected through the bi-state circuit. A timing circuit develops a signal at its output after a predetermined time and applies this signal to a bi-state gate circuit. A nonleak detector is coupled to the output of the bi-stable gate circuit to indicate that no leak is present in the system.