GB2161584A - Electrically controlled fluid valves - Google Patents

Abstract

An electromagnetic fluid valve has a sheet metal arm 15 carrying the valve closure member 16, the arm being subject to magnetic flux for valve closing and opening, and the arm is made integral with a ring 14 extending laterally from the arm and located in a gap in the body so that the ring can move, in particular twist and distort, in the gap and so that for example a variable magnetic flux can give a modulating effect controlling the position of the valve member within fine limits. <IMAGE>

Description

SPECIFICATION Electrically controlled fluid valves This invention relates to electrically controlled fluid valves and is applicable both to on/off valves and to valves of the kind, hereinafter referred to as modulating valves, such that in use the rate of flow of a fluid through the valve can be varied by varying an electric current supplied to the valve. The term fluid is used herein to include both liquids and gases.

According to the present invention there is provided a fluid valve having a fluid passageway extending through a valve seat, and a valve member movable relative to the seat so as in use to vary the rate of flow of fluid along the passageway, the valve member being connected to an arm or arms, and there being flexible and resilient restraining means extending laterally from the arm or arms and spaced from the valve member, the valve also including an electromagnet, with an associated magnetic circuit, of which the arm or each arm or a part coupled to the arm or to each arm, constitutes a part, the arrangement being such that in use when an electric operating current is passed through the electromagnet the arm or each arm is moved in response to the resultant magnetic flux, thus causing movement of the valve member relative to the valve seat, the movement of the arm or each arm being at least in part opposed by resilient deformation of the restraining means.

It is envisaged that in many valves there would be only one arm to which the valve member is connected. Nevertheless it would be possible to provide one or more additional arms, the arms extending outwards, in different directions, from a location where they are connected to the valve member. Each arm would be provided with flexible and resilient restraining means operating in a similar manner. The arms may be integrally connected in the neighbourhood of their interconnection with the valve member. In one configuration there are two mutually aligned arms which extend away from the location where they are connected to the valve member, while in another configuration there are four arms arranged uniformly, like the arms of a cross, and extending away from that location.

In a valve including two or more arms it is generally possible to increase the mechanical forces resisting movement of the valve member. At the same time, however, it may be possible to increase the effect of the magnetic flux, by increasing that part of the magnetic circuit extending through the arms or through parts coupled to the arms, with the result that the valve may have an action more forceful than that of a valve having only a single arm.

A multiple-arm valve may therefore be of particular use in controlling the flow of gases or liquids under pressure.

The arm or each arm preferably comprises ferromagnetic material and constitutes part of the magnetic circuit associated with the electromagnet.

The arm or each arm is preferably flexible and resilient so that when the arm or each arm moves in response to the presence of a magnetic flux the arm or each arm is resiliently deformed. With such an arrangement the arm or each arm is preferably formed integrally with the restraining means; in particular the arm or arms and the associated restraining means may comprise a unitary sheet metal component.

The restraining means preferably extends laterally from both sides of the arm or of each arm rather than from just one side thereof.

The restraining means may be in the shape of a ring or of one or more parts of a ring, and in that case the valve member is preferably at or near the centre of that ring.

In a preferred form of valve, therefore, there is a unitary component formed from ferromagnetic sheet metal and so shaped as to afford a ring with one or more arms projecting radially inwards from it, the arm or arms being connected to the valve member at the middle of the ring, and the ring constituting at least part of the restraining means.

The valve member is preferably attached to the arm or arms and disposed closely adjacent to the arm or arms, the valve member presenting a working face for co-operation with the valve seat. It is normal for the working face of the valve member to be spaced from the arm or arms by a distance equal to the thickness of the valve member. In such a case it is preferred to shape the arm so that at least part thereof lies out of the plane of the ring, the arrangement being such that when the arm and ring are unstressed the working face of the valve member is in the plane of the ring or closer to the plane of the ring than it would be if the arm lay in the plane of the ring.The arm is preferably cranked or stepped, the edges of the adjacent portions of the arm where the arm is cranked or stepped being of non-rectilinear shape, and preferably of arcuate shape so that those edges do not serve as hinges about which the arm can bend.

An embodiment of the present invention will now be described in more detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal section through a valve embodying the present invention, and Figure 2 is a plan view of a component incorporated in the valve shown in Figure 1.

The valve illustrated is intended for use in controlling the flow of combustible gas and is capable of cutting off the flow of gas completely and of modulating the flow of gas as may be required in use. The valve has a casing 1 comprising a body 2 and a cap 3.

The body 2 is made from steel, which is ferromagnetic, while the cap 3 is made from brass or an aluminium alloy, which is not ferromagnetic. The body 2 comprises an axial tube 4, one end portion of which is externally screw-threaded and constitutes a gas inlet 5.

The bore of the other end portion of the tube 4 is of enlarged diameter, as shown. Adjacent to the gas inlet 5 is an outwardly directed end plate 6 of circular shape, the periphery of which is integrally joined to one end of a tubular outer wall 7. The other end part of the outer wall 7 is externally screw-threaded for engagement with the cap 3. The threaded end of the outer wall 7 extends a short way beyond the adjacent end of the axial tube 4.

The cap 3 comprises a circular plate 8 with an axially directed peripheral flange 9. For a part of its axial length the flange 9 is internally screw-threaded with a thread complementary to that on the outer wall 7 of the body 2. At the inner end of the thread inside the flange 9 there is formed an annular, planar shoulder 10. A tubular gas outlet 11 projects axially from a central part of the circular plate 8 and, like the inlet 5, is externally screw-threaded for ready attachment to gas piping or to other pieces of apparatus.

The bore of the outlet 11 extends through the central part of the plate 8 and through a frusto-conical projection 12 on the inner surface of that plate. The end surface of the projection 1 2 is of annular planar shape and constitutes a valve seat.

When the cap 3 is fully tightened onto the body 2, an annular end face of the flange 9 engages a complementary annular shoulder on the body 2. The arrangement is then such that there is a gap of predetermined axial thickness between an annular end face of the outer wall 7 of the body 2 and the annular shoulder 10 in the cap 3.

A valve component 1 3 is mounted in the casing. The component is illustrated in Figure 2 and is made as a pressing from ferromagnetic sheet steel such as shim steel. Alternatively the component may be laser-cut from the sheet. The component 1 3 is of unitary construction and comprises a peripheral ring 14 which is of circular outline and of uniform radial width. The ring has no break in its periphery, although in a modified construction (not illustrated) there is a narrow gap in the periphery. The component also includes an arm 1 5 which projects radially inwards from the ring 1 4 and carries at its inner end a drum-shaped valve member 1 6 which is concentric or co-axial with the ring 14.The valve member 1 6 may be secured to the arm 1 5 in any suitable manner; it may for example be adhesively secured to the arm. As illustrated the arm 1 5 is cranked or stepped at 1 7 about half way along its length. The edges 1 7 of the adjacent portions of the arm where the arm is cranked or stepped are of arcuate shape, as can readily be seen in Figure 2. The fact that those edges 1 7 are not rectilinear stiffens the arm and prevents those edges constituting hinges.The arm 1 5 is cranked or stepped in such a direction that a working face 18 of the valve member 16, which in use engages the valve seat, is brought closer to the plane of the ring 14 than would have been the case if the arm had been flat and had lain in the plane of the ring.

An outer part of the ring 14 is disposed in the gap between the end face of the outer wall 7 of the body 2 and the shoulder 10 in the cap. The outer diameter of the gap is very slightly greater than that of the ring 14 so that movement of the ring in the gap is not constrained by engagement between the outer periphery of the ring and the cylindrical outer wall of the gap. The axial thickness of the gap is rather greater than the thickness of the ring 14 so that when the ring is resiliently twisted, as described below, it is not restrained, at least in the initial stages of twisting, by engagement with the end face of the outer wall 7 of the body 2 or with the shoulder 10. In a typical construction of gas valve the axial thickness of the gap exceeds the thickness of the ring 14 by between 0.004 inches and 0.007 inches (0.10 mm and 0.18 mm).The inner diameter of the ring 14 is rather less than the inner diameter of the annular end face of the outer wall 7, that inner diameter of the annular end face being indicated at 1 9 in Figure 2.

When the valve is assembled, as illustrated, the arm 1 5 is resiliently deformed, to a small extent, so that it causes the valve member 16 to be positively urged into sealing contact with the valve seat.

A coil 20, constituting an electromagnet, is fitted into the body 2, and largely occupies the interior space between the tube 4 and the outer wall 7 thereof. The coil 20 is mounted on a bobbin (not shown) of non-ferromagnetic material, an end portion of which extends axially a short distance beyond the end of the axial tube 4 towards the arm 15; but it does not extend far enough to interfere with movement of the arm. Electric leads (not shown) for the coil 20 extend through a hole or holes in the body which is or are rendered gas-tight.

In use the gas inlet 5 is connected to a source of gas under pressure. As the valve member 1 6 is in sealing engagement with the valve seat no gas can pass from the interior of the casing 1 to the gas outlet 11. If an electric operating current is passed through the coil 20 a magnetic flux is induced in a magnetic circuit that includes the body 2 and the component 1 3. The arm 1 5 is therefore attracted towards the axial tube 4 and lifts the valve member 1 6 off the valve seat, thereby allowing gas to pass through the gas outlet 11. Owing to its cranked or stepped configuration the arm is relatively stiff, though it does flex resiliently to some extent. In addition, however, the ring 14 flexes resiliently.It is difficult to determine exactly the configuration of the ring as it flexes, but it is clear that at least those portions thereof adjacent to the arm are twisted so that they no longer lie in the main plane of the ring. Those portions of the ring therefore constitute restraining means extending laterally from the arm at a location spaced from the valve member 16.

The reaction to the force exerted by the electromagnetic flux is at least partially borne by the end face of the outer wall 7 of the body 2. As the restraining means starts to twist, the reaction is principally taken by the edge 1 9. This is a preferred arrangement, for if the connection between the arm and the ring were beyond the edge 19, and thus overlying the end face of the outer wall 7, the forces exerted on the arm, in use, would be markedly different.

It is found that with an arrangement such as that illustrated it is possible to arrange for the response of the valve to be substantially linear over a relatively large range. In other words a graph representing the volume of gas that flows per unit time plotted against the operating current is substantially a straight line.

It is preferred to operate the valve in such a manner that the operating value never reaches so high a value that the arm is prevented from further opening movement. Nevertheless, if a current of that value or a higher value is passed through the coil 20 the arm strikes the bobbin referred to above so that the magnetic circuit is not fully closed. This encourages immediate return movement of the arm when the current is subsequently reduced below that value.

The valve illustrated superficially resembles that illustrated in the specification of patent application No. 8317350 of Alexander Controls Limited (publication No. 2 1 24 342) but the present valve in fact differs significantly from that earlier valve in that the ring 1 4 is free to flex and is not clamped tightly in position, as was the case in the earlier valve.

While the valve is described as controlling a flow of gas from the gas inlet 5 to the gas outlet 11, the valve could equally well be used in controlling a flow of gas from the outlet 11 to the inlet 5, the roles of the inlet and outlet thus being reversed. This reversal of flow may be particularly useful in some circumstances for it occasionally happens that the arm 1 5 flutters slightly and thus causes unwanted variation in the gas flow. That problem can often be overcome by reversing the direction in which the gas flows through the valve.

The valve illustrated is described as being capable of use as a modulating valve, but it is to be understood that it can be used merely as an on/off valve if desired. The valve is relatively inexpensive to manufacture so that it may prove to be economic to manufacture a single range of valves for use at will as modulating valves or on/off valves. In some circumstances it may be desirable to use two similar valves, each in accordance with the present invention, in series with each other, one as a modulating valve and the other as an on/off valve. In particular, where gas is passed through a modulating valve in a reverse direction there may be a requirement for a more positive on/off valve to be in series with the modulating valve. This can be constituted by a second valve, similar to the modulating valve, disposed in the normal manner first described. When the on/off valve is widely opened in response to a suitable operating current there is little likelihood of the arm of that valve fluttering. Meanwhile any tendency of the arm of the modulating valve to flutter is reduced or overcome by the reverse flow of gas through that valve.

Claims (8)

1. A fluid valve having a fluid passageway extending through a valve seat and a valve member movable relative to the seat so as in use to vary the rate of flow of fluid along the passageway, the valve member being connected to an arm or arms, and there being flexible and resilient restraining means extending laterally from the arm or arms and spaced from the valve member, the valve also including an electromagnet, with an associated magnetic circuit, of which the arm or each arm or a part coupled to the arm or to each arm, constitutes a part, the arrangement being such that in use when an electric operating current is passed through the electromagnet the arm or each arm is moved in response to the resultant magnetic flux, thus causing movement of the valve member relative to the valve seat, the movement of the arm or each arm being at least in part opposed by resilient deformation of the restraining means.

2. A fluid valve as claimed in Claim 1 wherein the laterally extending restraining means form part of a peripheral ring and said arm or arms extend inwardly of the ring.

3. A fluid valve as claimed in Claim 2 in which said ring is circular and located in a circular body of the valve, in a gap which is actually greater than the thickness of the ring and of greater diameter than the ring so that the ring is free to twist and deform.

4. A fluid valve as claimed in Claim 3 wherein the arm is cranked relative to the plane of the ring.

5. A fluid valve as claimed in Claim 4 wherein the edges of the arm are arcuate where cranked to stiffen the arm.

6. A fluid valve as claimed in any of Claims 2 to 5 wherein the ring has a brake in its periphery.

7. A fluid valve as claimed in Claim 3 wherein the valve body is generally tubular housing the electromagnet and has a screwthreadedly engaged cap providing said passageway therein, a gap being provided between the end of the body and the interior of the cap.

8. A fluid valve substantially as described with reference to the accompanying drawing.