GB2352495A

GB2352495A - Pressure balanced flow control valve

Info

Publication number: GB2352495A
Application number: GB0017123A
Authority: GB
Inventors: Gerald Scudamore
Original assignee: IMI Webber Ltd
Current assignee: IMI Webber Ltd
Priority date: 1999-07-21
Filing date: 2000-07-11
Publication date: 2001-01-31
Also published as: DE20012614U1; GB9916974D0; GB0017123D0

Abstract

A normally closed, 2/2 solenoid fluid flow control valve comprises a pair of chambers 14 and 18 which are in communication with, respectively, the ports 2 and 3 of the valve. In the valve-closed position, fluid pressure present in the port 2 and/or the port 3 provides a downward force on the solenoid armature 7 which counterbalances the upward force exerted on it by fluid pressure present in the ports 2 and/or 3. A compression spring 15 provides, in the valve-closed position, a net downward force on the armature 7 which ensures that a fluid tight seal is maintained, by means of a seal 8 carried by the armature 7, between the ports 2 and 3 so as to isolate them from one another. A cylindrical extension 17 (of reduced diameter) at the end of the armature extends into a blind bore formed in a stem 9 to define the chamber 18. The valve is pressure balanced and bi-directional.

Description

2352495 Fluid Flow Control Valve This invention relates to fluid flow

control valves and more particularly to a normally closed, 2/2 solenoid-operated fluid flow control valve.

Normally closed 2/2 solenoid-operated fluid flow control valves are in general terms well-known. They have two ports which are normally isolated from one another, ie. in the valve-closed position, but which are brought into communication with one another, ie. the valve open position, when the solenoid is energised. Hence the designation "2/2" which is an abbreviation for two port/two position. The valve includes an armature on one end of which is mounted a seal. The seal is, in the closed position of the valve, biased, by means of a compression spring acting on the armature, into sealing contact with an annular valve seat surrounding an orifice located intermediate the two ports. The armature is associated with a solenoid, ie. an electro-magnetic coil, which, when energised, magnetically attracts the armature, and hence the seal, away from the valve seat against the action of the spring, whereupon the two ports are brought into communication with one another via the orifice. When the coil is de-energised, the spring returns the armature and the seal back to the valve-closed position.

In a conventional 2/2 normally closed solenoid valve, the magnetic force required to actuate the armature varies directly with the required return spring load and the load produced by a fluid pressure differential acting over the orifice area. If the pressure exerts a closing force on the armature, a leak tight seal can be achieved with a relatively light compression spring load (ie. pressure assisted sealing). If the pressure exerts an opening force on the armature, the spring load must 2 be high enough to exceed the pressure load by a sufficiently large margin to maintain adequate seat load (ie. pressure opposed sealing). If the pressure differentials are reversed, valves in the first case (pressure assisted sealing) will leak due to inadequate seat load, and valves in the second case (pressure opposed sealing) will require very high magnetic forces to actuate the armature against the combined high spring load plus pressure load. An object of the present invention is to provide an improved construction of normally closed 2/2 solenoid-operated valve which can cope with relatively high pressure differentials, say up to about 14 bar, in either direction. According to the present invention, there is provided a normally closed 2/2 solenoid-operated fluid flow control valve comprising:

a) a first port and a second port; 15 b) a valve seat surrounding an orifice located interinediate the first port and the second port; c) an armature carrying at one end thereof a seal; d) a compression spring acting on the armature so as normally to urge the seal into fluid-tight engagement with the valve seat 20 thereby to close the orifice and isolate the first and second ports from one another (the valve thus being in its closed position); e) an electromagnetic coil operatively associated with the armature and arranged, when energised, to withdraw the armature, and hence the seal, away from the valve seat thereby to open the 25 orifice and bring the first and second ports into communication with one another via the orifice (the valve thus being in its open position); 3 f) a first passageway interconnecting the first port with a first chamber defined in part by a first surface of the armature, whereby, in the valve-closed position, the force exerted by fluid pressure in the first port tending to urge the seal, and hence the armature away from the valve seat is substantially balanced by the force exerted by the fluid pressure in the first chamber on said first surface of the armature and tending to urge the armature, and hence the seal, towards the valve seat; and g) a second passageway formed in the armature and the seal interconnecting the second port with a second chamber isolated from said first chamber, said second chamber being defined in part by a second surface of the armature whereby, in the valve closed position, the force exerted by fluid pressure in the second port tending to urge the seal, and hence the armature, away from the valve seat is substantially balanced by the force exerted by the fluid pressure in the second chamber on said second surface of the armature and tending to urge the armature, and hence the seal, towards the valve seat.

A normally closed 2/2 solenoid-operated valve of the present invention will now be described, by way of example only, with reference to the accompanying drawing which is a sectional side elevation of the valve to a scale of about 3: 1. Referring to the drawing, the valve comprises a base 1 which defines a first port 2 coaxially surrounding a second port 3. In use, the base I would be secured to a sub-base (not shown) having respective ports connectable to a pair of pipelines through which the flow of fluid, in either direction, is to be controlled. A plate 4 is secured to the upper 4 surface of the base I and this retains in place an upstanding, cylindrical pressed steel sleeve 5 which is surrounded by an encapsulated electromagnetic coil assembly 6. The sleeve 5 houses, as an axially sliding fit, a cylindrical armature 7 which carries at its lower end an elastomenic seal 8. The upper end of the sleeve 5 has a stem 9 of magnetisable steel secured in it, the upper end of which protrudes above the coil assembly 6 and is engaged by a circlip 10 which serves to secure the coil assembly 6 in place on the plate 4.

The coil assembly 6 comprises an annular foriner I I on which is wound a coil 12 of insulated wire. Electrical power is fed to the coil 12 through a lead 13 when it is desired to energise the valve.

The armature 7 comprises a main part 7' of magnetisable steel above which is defined an enclosed annular chamber 14. The armature 7 is, when the coil 12 is de-energised, biased downwardly by a light compression spring 15 so that the seal 8 engages an annular seat 16 surrounding an orifice 3' defined by the upper end of the port 3. The ports 2 and 3 are therefore isolated from one another and the valve is in its closed position. However, fluid present in the port 2 is transmitted through an annular clearance 5' between the internal surface of the sleeve 5 and the external surface of the armature part 7' into the chamber 14 so that the fluid pressure in the chamber 14 will equate to the fluid pressure in the port 2.

As can be seen, the seal 8 extends radially beyond the seat 16 to provide an annular peripheral area 8' which is exposed to fluid pressure in port 2. This tends to bias the seal 8, and the armature 7, away from the seat 16, ie. towards the valve-open position. However, the annular area 7" of the upper end of the armature part T, which defines the lower wall of the chamber 14, is approximately the same as the area 8' and there will, therefore, be a substantially net zero fluid force acting on the armature 7. The compression spring 15 serves to maintain a fluid- tight 5 seal between the seal 8 and the seat 16.

The armature 7 further comprises an upper cylindrical extension 17 of reduced diameter secured to the main port 7' and which extends into a blind bore formed in the stem 9. The upper surface 17' of the extension 17 defines the base of an enclosed chamber 18 within the stem 9. The surface 17' also serves as the lower support for the compression spring 15. The extension 17 is a sliding fit in the bore in the stem 9, but the chamber 18 is isolated from the chamber 14 by means of an O-ring seal 19 located in an annular groove formed in the extension 17. The armature part T, the seal 8 and the extension 17 have a small axial bore 20 extending therethrough which communicates the port 3 with the chamber 18. Accordingly, fluid pressure in the port 3 is communicated to the chamber 18. The area of the upper surface 17' of the extension 17 approximates to the cross-sectional area of the orifice 3' (which, for example, may be 4mm. in diameter) and so there will be a substantially net zero fluid force acting on the armature 7. Accordingly, the compression spring 15 will, in the valve-closed position, maintain a fiuid-tight seal between the seal 8 and the seat 16.

It will be appreciated, therefore, that the valve described above is able to control the flow of fluid in either direction at relatively high pressure differentials without the need for a heavy compression spring 15 and hence a relatively large coil 12 and coil current. It would be 6 useful where it may be necessary from time to time to equalise the pressure of fluid, such as compressed air, between, for example, a pair of normally mutually isolated pressure vessels connected respectively to the ports 2 and 3, regardless of which vessel contains fluid at a higher pressure. Thus, in that example, in order to equalise the pressures, the valve would be energised by supplying electrical power to the coil 12 via the lead 13 whereupon the armature 7, and hence the seal 8, are attracted upwardly until the surface 7" of the armature abuts the stem 9. Communication is, therefore, established between the ports 2 and 3 via the now-open orifice 3' and hence between the two vessels. Once pressure equalisation has occurred, the electrical power would be switched off and the armature 7 and seal 8 will return to their normal., valve-closed position under the influence of the spring 15.

A valve of the invention may be made of materials conventionally used for solenoid valves. In the embodiment described with reference to the drawing, it should be noted that, preferably, the extension 17 is made of a non-magnetic material such as brass or a plastics material in order to preserve the efficiency of the magnetic attraction between the armature part 7' and the stem 9 upon energisation of the coil 12. Also, in order to reduce frictional effects during opening of the valve, the 0ring 19 is preferably a loose fit in the annular groove formed in the extension 17 so that its sealing effect is caused by defonnation of it under the influence of fluid pressure present in the chamber 14 or 18, as the case may be, rather than by pure mechanical deformation.

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Claims

CLAIMS:

1. A normally closed 2/2 solenoid-operated fluid flow control valve comprising:

a) a first port and a second port; b) a valve seat surrounding an orifice located intermediate the first port and the second port; c) an armature carrying at one end thereof a seal; d) a compression spring acting on the armature so as normally to urge the seal into fluid-tight engagement with the valve seat thereby to close the orifice and isolate the first and second ports from one another (the valve thus being in its closed position); e) an electromagnetic coil operatively associated with the armature and arranged, when energised, to withdraw the armature, and hence the seal, away from the valve seat thereby to open the orifice and bring the first and second ports into communication with one another via the orifice (the valve thus being in its open position); f) a first passageway interconnecting the first port with a first chamber defined in part by a first surface of the armature, whereby, in the valve-closed position, the force exerted by fluid pressure in the first port tending to urge the seal, and hence the armature away from the valve seat is substantially balanced by the force exerted by the fluid pressure in the first chamber on said first surface of the armature and tending to urge the armature, and hence the seal, towards the valve seat; and g) a second passageway formed in the armature and the seal interconnecting the second port with a second chamber isolated 8 from said first chamber, said second chamber being defined in part by a second surface of the armature whereby, in the valve closed position, the force exerted by fluid pressure in the second port tending to urge the seal, and hence the armature, away from the valve seat is substantially balanced by the force exerted by the fluid pressure in the second chamber on said second surface of the armature and tending to urge the armature, and hence the seal, towards the valve seat.

2. A fluid flow control valve according to claim 1 wherein the first passageway is annular and is defined by the external surface of the annature and by the internal surface of a sleeve in which the armature is an axially sliding fit, the first passageway opening at one end into the first chamber which is defined in part by a peripheral, annular surface of the armature and the internal surface of said sleeve.

3. A fluid flow control valve according to claim 2 wherein the first chamber is further defined by the external surface of a reduced diameter, cylindrical extension of the armature extending upwardly from said annular surface and by a peripheral annular region of the lower surface of a cylindrical stem fori-ned with a blind bore which sealingly receives, as an axially sliding fit, said cylindrical extension, the second chamber being defined by the blind bore and by the upper surface of the cylindrical extension.

4. A fluid flow control valve according to claim 3 wherein the second passageway extends axially through the armature and the cylindrical extension and opens at one end into the second chamber.

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5. A fluid flow control valve according to claim 3 or claim 4 wherein the compression spring is housed in the blind bore and acts on the upper surface of the cylindrical extension of the armature.

6. A fluid flow control valve according to any one of claims 3 to 5 wherein the extemal surface of the cylindrical extension is formed with an annular recess in which is located, as a loose fit, an O-ring, the 0nng being adapted to deform under the influence of fluid pressure in the first or second chamber and thereby form a fluid-tight seal between the cylindrical extension and the wall of the blind bore formed in the 10 cylindrical stem.

7. A normally closed 2/2 solenoid-operated fluid flow control valve substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawing.