FLUID FLOW CONTROL APPARATUS

摘要

A pillar tap has a main water chamber 4 and a control chamber 10 housed within the main chamber 4. The control chamber 10 has two different sized openings. The smaller opening which is located opposite the main outlet valve seat 8 of the main chamber supports a membrane 12. The membrane 12 in turn supports a valve member 14 for movement into and out of engagement with the valve seat 8. The larger of the two openings is closed by a resilient diaphragm 32. A pair of control valves 15 and 22 control the admission and release of water to and from the control chamber 10. By controlling the control valves 16 and 22 the pressure differential between the main and control chambers 4 and 10 can be varied and so used to control the degree to which the valve member 14 is opened. Once the flow rate through valve seat 8 has been set, the diaphragm 32 responds to pressure variations in the main chamber 4 to alter the position of the valve member 14 in a sense to maintain a substantially constant flow rate irrespective of the pressure variations.