Fluid handling – Line condition change responsive valves – Safety cut-off requiring reset
Patent
1983-09-15
1985-08-20
Cohan, Alan
Fluid handling
Line condition change responsive valves
Safety cut-off requiring reset
137488, 73 405R, F16K 1724, F17D 504
Patent
active
045358044
DESCRIPTION:
BRIEF SUMMARY
In many situations one has need of being able to shut off a pressure conduit or hose at conduit-breaks. This may be the case for instance with regard to pressure oil conduits. One has therefore developed various types of conduit-break valves. As examples of some such valves mention may be made of the published European patent application 79850114.4 (Publ. No. EP-Al-0 013 264) and Swedish Patent 7702588-0 (Publ. No. SE-B-412 946). Common to these prior art valve mechanisms is that in their valve housings they have a throughflow passage and a main slide gate which is movable between an open position and a closed position preventing flow through the throughflow passage, and which is adapted to be actuated by the pressure medium in said space to be kept in the open position against the action of a loading device which is arranged yieldingly to urge the slide gate towards the closed position and, if the pressure of the pressure medium in said space sinks, to move the slide gate to its closed position. The valve according to said published European patent specification further has a pressure relief device which is connected to said space and adapted to relieve the pressure therein if the pressure rises over a predetermined upper limit value. These prior art conduit-break valves, especially the last-mentioned one, function in a satisfactory manner but suffer from certain drawbacks, i.e. that pressure medium, when the upper limit value pressure is exceeded, may get lost and escape to the surroundings at the release of the pressure relief device.
One object of the present invention is to overcome this and other drawbacks and to provide a conduit-break valve which permits a more exact adjustment of the upper limit value pressure and besides makes it possible to avoid pressure medium spillage to the surroundings.
This and other objects of the invention are realized if a conduit-break valve of the afore-mentioned type is designed to operate at a higher pressure in the pressure conduit or hose than that prevailing in the space between the two conduits or hoses and if the conduit-break valve according to the invention is characterised by the features that the pressure relief device has a pilot controlled check valve with a control piston adapted to be actuated by the pressure in said space and, when the upper limit value is exceeded, to open the check valve member yieldingly loaded in accordance with said limit value, thus relieving the pressure in said space. By this design of the conduit-break valve a leakage of the pressure conduit or hose will thus result in an increase of the pressure in the surrounding protective conduit or hose, said pressure increase displacing the control piston and thereby opening the check valve and quickly relieving the pressure in the space between the two conduits or hoses so that the valve member of the main valve by the action of its yieldable load closes the throughflow passage through the conduit-break valve.
In a particularly advantageous embodiment of the invention the pressure relief device is designed as a fluid lock in the form of a piston and cylinder mechanism the piston of which is connected or made in an integral piece with the valve member or body of the main valve and the cylinder chamber of which is normally kept closed by the check valve member of the pilot controlled check valve. With this design of the pressure relief device it is possible to permit the piston of the piston and cylinder mechanism to be urged against an abutment by the action of the pressure in said space and to be kept engaged with this abutment in normal operation when no leakage has occurred on the inner or outer conduit or hose.
When the pressure relief device is designed as a fluid lock it is particularly advantageous according to the present invention to have the cylinder chamber and the space between the two conduits or hoses interconnected via a one-way restrictor the valve member of which is yieldingly loaded towards closed position and adapted to be opened when the pressure in the space between
REFERENCES:
patent: 4338812 (1982-07-01), Lindgren
Cohan Alan
Regioninvest I Norr AB
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