IMPROVED PRESSURE REDUCTION VALVEThe present invention relates to an improved pressure reducing valve and particularly one incorporating a pressure relief valve and a residual pressure device and preferably incorporated in a closure valve unit for a pressurised gas container such as a cylinder.
Pressure reducing valves are well known, for example, such as disclosed in GB 2231137. Residual pressure maintenance devices are also well known and one such is disclosed in GB 2028974. Such devices are often used with closure valves for pressurised gas cylinders to maintain some pressure within a cylinder when most of the gas has been discharged so as to prevent contamination of the interior of the cylinder from moisture which may lead to corrosion or contamination from other substances. Prior reducing valves and residual pressure devices are not entirely satisfactory having regards to cost of manufacture and operation and difficulties in recharging vessels to which they are attached.
According to the present invention there is provided a pressure reducing valve including a residual pressure maintenance device/non-return valve, comprises a body defining an internal chamber having an inlet connectable to a vessel for containing a source of pressurised fluid to be regulated, and an outlet connectable to a point of use of pressurised fluid from said vessel, a pressure-reducing piston arrangement being displaceable in said chamber with the piston being biassed away from said inlet and with said piston having a smaller diameter end adjacent said inlet and displaceable to close said inlet and a larger diameter end adjacent said outlet and of larger surface area than the smaller end, a flow path extending from the end of the chamber adjacent the inlet to the region of said chamber in communication with the larger end of the piston with said pressure reducing piston and biassing means therefor being operable such that pressurised gas entering the chamber via the inlet is pressure regulated to a predetermined pressure, characterised by the feature that the larger end of the piston has a bore in which a residual pressure maintenance device is located and in the form of a spring biassed piston/valve member with outlet closure member with its operative surface in communication with said flow path; said device being operable to close said outlet when said fluid pressure in said vessel falls below a predetermined minimum.
Normally a pressure relief flow passage will be in communication with the end of the chamber adjacent the inlet and have a valve closure member biassed to be displaceable to release pressure when a predetermined pressure is exceeded. Preferably said closure member is a collar or sleeve in the chamber surrounding the smaller end of the pressure reducing piston and sealingly seating on a surface around the inlet and raisable against the action of a compression spring or other bias means when the excess value is reached.
Preferably said compression spring also constitutes the biassing means for the piston i.e. it is a common, shared biassing means.
A relief path or passage leads from said chamber, including the region in which the compression spring is located, to atmosphere. Alternatively a pressure relief valve, such as a check valve, may be located in the duct or passage leading from outlet duct to atmosphere.
When it is desired to charge a pressure vessel or cylinder fitted with a pressure reducing valve according to the invention, it will be necessary to also pressurise or to close the relief path or passage when supplying the pressurised fluid and a suitable coupling device will be needed which will also have a pin on its end which engages the residual pressure/non-return valve to hold it open to permit filling. Alternatively, where the valve closure member of the pressure relief passage is said collar or sleeve, the pressure reducing piston may be mechanically locked in its position away from the inlet normally leading fluid to be consumed from the vessel so that a charging flow of fluid through the chamber in the reverse direction is possible without the pressure reducing piston preventing such. In such arrangement when locking the piston, the relief duct does not have to communicate with the spring chamber. The residual pressure device/non-return valve carried by the pressure reducing piston will here also be held open by a pin on the charging coupling device.
Preferably a combined pressure reducing valve and residual pressure maintenance device/non-return valve according to the invention is combined with or incorporated in the housing of a closure valve.
The invention will be described further, by way of example, with reference to the accompanying drawing which is a schematic cross section through a combined pressure reducing valve and residual pressure maintenance device according to the invention.
The pressure reducing valve comprises a housing or body 1 having an interior cylindrical chamber 2 having an inlet 3 connectable by a threaded male member of the valve housing engageable, in a threaded socket of a vessel (not shown) for containing a fluid (normally gas) under pressure and an internally threaded outlet bore 4 connectable to a point of consumption or a recharging coupling device (not shown). Normally body 1 will be part of a housing incorporating a closure valve (not shown) between connection means for the vessel and said inlet 3.
A pressure reducing cylindrical piston 4 is displaceable in chamber 2 and has a smaller diameter end 5 with peripheral seal 6 and a valve sealing member 5' located in a recess therein and sealable against a valve seat 3' around the inlet 3. A larger diameter end 7 of piston 4 has a peripheral seal 8 and a shoulder 9 against which compression spring 10 abuts to urge piston 4 away from inlet 3 by a force which is overcome by fluid pressure acting through flow passage or duct 11 extending through piston 4 and so that a pressure regulating effect is achieved.
A bore 12 is formed in the centre of end face 7 of piston 4 and has a residual pressure device/nonreturn valve located therein comprising a bobbin valve or piston 13 with seal 14 and slideable in the bore and biassed by spring 15 in a direction out of bore 12. An extension 16 of piston 13 extends into a narrow portion 17 of outlet 4 which has a seat portion 17' against which a closure part of extension portion 16 abuts.
The differential pressure effect between spring 15 and the effecting surface area of piston 13 and the fluid pressure is arranged such that the outlet 17 is closed when a predetermined minimum fluid pressure is exerted on the piston 13.
A vent passage 18 communicates with the chamber 2 the inlet 3 via a passage communicating with chamber region containing the spring 10 and also the bottom of chamber 2 and is normally closed relative to inlet 3 by a relief valve formed by a sleeve or collar 19 around the reduced section of piston 4 and slidable thereon.
The lower end 19' of collar 19 has a face with sealing means on its lower surface sealingly engageable on valve seat 20 formed around seal 3'. Flow passages 21 extend along the outer surface of collar 19 to connect the lower part of chamber 2 with vent passage 18.
If the flow passages 21 are not provided, an extension 18' to vent passagel8is provided as indicated in broken line in the drawing and communicating with the main interior of chamber 2 and as indicated in the drawing in the region surrounding inlet seat 3'.
Instead of collar 19 as a relief valve, a relief valve, such as a check valve 23, might be located above extension point 16 in the valve outlet and might exhaust to atmosphere. In fact the relief valve can alternatively be located anywhere between either end of the chamber 2.
Recharging is effected via outlet duct 4 by means of a coupling device which has an extension or pin which acts on extension 16 to keep the non-return valvethe device (13,14,15,16) open during filling and gay also pressurise passage 18 or close such.
A mechanical locking device 22 may, as an alternative to blocking or pressurising duct 18, be provided engageable in an angular groove in piston 4 to hold such off seal 3' during charging. When there is no fluid pressure, spring 10 lifts piston 4 off seat 3'.
Duct 18 does not have to communicate with the space of the chamber in which spring 10 is located. The charging coupling device will have an extension or pin to hold open the residual pressure maintenance device/non-return valve during charging.
The valve combination according to the invention is economic to manufacture because of its configuration and use of less parts and is simple and efficient.