Fluid leak detector

DETAILED DESCRIPTION We claim: 1.
A fluid leak detector comprising: a body member having a chamber provided with a fluid inlet and a fluid outlet, between which is disposed a valve having a valve closure member, the closure member being connected to a diaphragm, the arrangement being such that when fluid is present in the chamber it applies pressure on the diaphragm; the detector further including means for controlling closure of the valve such that the valve is allowed to be open when the pressure differential across the diaphragm between the fluid pressure at said inlet and the ambient pressure external to the body exceeds a predetermined value and that the valve is caused to close when said pressure differential is below said predetermined value; the detector further including safety lock-off means for locking the valve into position when closed, and means for allowing the lock-off means to be released to allow the valve to open in response to a pressure differential across the diaphragm greater than or equal to said predetermined value and means providing a said indication that a pressure differential below said predetermined value has occurred since preceding release of the lock-off means.
2.
A detector according to claim 1, the safety lock-off means being provided by a control shaft attached to the valve closure member in conjunction with a member, the member cooperating with biasing means which move the member into a position when the valve closure member is in the closed position such that a surface of member abuts an end of the control shaft and prevents the valve from opening.
3.
A fluid supply installation incorporating a fluid leak detector according to claim 1.
4.
A detector according to claim 1 in which the means for controlling closure is arranged such that the predetermined pressure differential is less than or equal to the intended working fluid pressure of a system in which the detector is intended to be disposed.
5.
A detector according to claim 1 including an audio or visual alarm at a location remote from the detector to provide at said remote location an indication of a fluid pressure differential below said predetermined value