High pressure test pump for testing car tank system

摘要

The two membrane separated chambers are connected to the atmosphere and the test piece, respectively, through non-return valves, and are connected to each other through a bypass duct containing an electromagnetic stop valve. The membrane is moved by means of an electromagnet, against a spring pressure, being activated by a switch operated by the position of the membrane. The membrane electromagnet (M) is switched (S) through a resistance (RS), according to the elevation of the membrane and a voltage supply (UB), which is provided through a transistor (TR2) and control lead (42). A bypass stop valve (AAV) is in parallel with the electromagnet and switch circuit. To test an item for leaks, a transistor (TR1) is switched on for a predetermined time, to energise the membrane electromagnet. Then the collector-emitter resistance is made high and the operating voltage is derived from the potential divider (ST) whose mid-point is connected to an analogue-digital convertor (70) and comparator (80).