LIQUID FLOW SENSING DEVICES

摘要

There is disclosed a valve unit for a liquid flow sensing device of the type having a control means which is movable between first and second positions when the flow rate is respectively low and high but biased to the first position. The valve unit comprises three valve sections one of which is movable in response to movement of the control means a second of which is fixed relative to the control means and a third which is movable independently of the other two sections. The valve includes first and second ports, port connecting means, a flow passage and a diaphragm which forms part of the chamber and can close said flow passage. The third valve section can be moved so that the first port is isolated from the second port but coupled to the chamber when the control means is in the first position and moves to the second position. Means are provided for coupling the third valve section to the first valve section such that when the control means reverts to the first position it moves both the first and third sections relative to the second section such that the first port becomes coupled to the second port by the port connecting means and the first port is isolated from the chamber. There is also disclosed a liquid flow sensing device incorporating the valve unit.