Fluid handling – Self-proportioning or correlating systems – Self-controlled branched flow systems
Patent
1990-12-12
1992-07-07
Hepperle, Stephen M.
Fluid handling
Self-proportioning or correlating systems
Self-controlled branched flow systems
137557, F16K 1107
Patent
active
051274264
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a valve and more particularly but not exclusively to a valve for controlling the flow of fluid nair or other gas, or liquid) from at least two alterantive supplies in such manner that reduction or cessation of one supply automatically causes the valve to switch to another of the alternative supplies.
Such a valve is hereinafter and in the claims referred to, where required, as "a valve of the kind described".
DE-A-3529487 discloses a valve of the kind described for use with breathing equipment and comprising a first air inlet connectible to a primary air supply and which communicates with an air outlet via a one-and valve, a second air inlet connected to a secondary (reserve) air supply and which is connectible to the air outlet, bypassing the one-way valve, and, between the air inlets abnd the air outlet, first and second spaced parallel bores, whereof the second bore communicates directly with the fluid outlet and is in communication with the first bore via a connecting passage. The first bore accommodates an axially-movable double piston having opposed ends of differential area.
With the primary air supply in use, the double piston is axialy moved to close the connecting passage and so communiation between the first and second bores and the air outlet, the one-way valve is opened, and air is supplied from the primary air supply to the air outlet.
With the secondary air supply in use (the primary air supply having failed, been arrested, or having fallen below a predetermined limit), the double piston is axially moved to plug into and close the primary air inlet, thus causing closure of the one-way valve, and to open the connecting passage between the first and second bore so that air from the secondary air supply is delivered directly to the air outlet the first bore, the connecting passage and the second bore.
DE-A-3529487 discloses the use of an air pressure controlled, spring-loaded indicating pin in communication with the primary air pressure supply such that, when the latter is in use, the pin is in an upper position but, when the secondary air supply is in use, the indicating pin is in a lower position. Thus an indication is given in a visible or tactile manner as to which air supply is operational.
DE-A-3529487 also disclsoes the use of an acoustic signalling device operated by the secondary (reserve) air supply to indicate that it is the secondary (resserve) air supply which is in use.
The valve disclosed in DE-A-3429487 has the disadvantage that the double piston plugs into the primary air inlet to close same when the secondary (reserve) air supply is in use. A danger therefore exists that if, upon exhaustion of the secondary (reserve) air supply, the double piston fails to move axially to open the primary air inlet, for example it jams due to ingress of dirt or other foreign matter, the life of the user will be at risk.
It is an object of the present invention to provide such a valve which avoids this danger, and which additionally provides such a valve of simpler and more compact construction compared with that in DE-A-3529487 and which is, in consequence, more economic to manufacture.
According to the present invention there if provided a valve of the kind described comprising a cylinder having a piston slidable therein in a region between a first fluid inlet and a second fluid inlet, the piston having working surfaces of differential area such that equal pressure on both sides of the piston biases the piston to one end of the cylinder, a fluid outlet from the valve, a first fluid flow path from the first fluid inlet to the fluid outlet, a second fluid flow path from the second fluid inlet to the fluid outlet and including an axial outlet bore, the second fluid flow path being closable by the piston and being opened upon axial movement of the piston towards the first fluid inlet caused when the supply of fluid from the first fluid inlet fails, is arrested or falls below a predetermined limit, the valve being characterised in that the first fluid flow path is permanen
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