A LIQUID CONTROL VALVE

摘要

A float or a near neutral buoyancy weight (neither depicted) operated liquid pressure control valve includes a body (1A) which together with an end cap (1B) form a cavity and retain a diaphragm (10) therein. A back-pressure chamber (4) is formed between the end cap (1B) and the diaphragm (10) and the diaphragm (10) includes a seal section (10F) which seats on an inlet port (6) formed by a wall (5) projecting into the cavity. The diaphragm (10) seal (10F) also separates the inlet (2) from an outlet (3) formed in the body (1A). A float support arm (7) reciprocally operates a valve opening and closing control pin (8) mounted in an associated bleed passage (9)formed longitudinally through a control pin (8) mounting (16). Mounting (16) is fixed to end cap (1B) and extends through the diaphragm (10), the bleed passage (9) thus joining the inlet (2) to the chamber (4). In an open mode (arm 7 lowered) the bleed passage (9) also vents the chamber (4). In a closed mode (arm 7 raised) owing to the greater area of the diaphragm (10) presented to the chamber (4) than to the inlet (2) the inlet pressure in the chamber (4) displaces the diaphragm (10) to close the valve. A slide (12) is coupled to diaphragm (10) as to be displaced therewith and prevent excessive inlet pressure distorting the diaphragm (10) once the seal (10F) closes on port (6). To that end the slide (12) is a working fit within the bore (1G) of the body (1A) and abuts against a stop (11) formed by shoulder (14)on bore (1G) as the valve closes.