GB2067265A - Gas valves - Google Patents

Abstract

A gas valve comprises a body (10) having a chamber (13) with co- axial inlet (11) and outlet (12). A partition (14) extends across the chamber and has a valve opening (15) extending through it. The flow of gas is controlled by a valve member (18) movable between open and closed positions. The axial extent of the opening is not less than half the mean diameter of the opening. The opening is defined by an extension (16), which may, alternatively or in addition, extend into the outlet side of the chamber. A thickening (21) around the mouth of the opening may assist gas flow. The interior of the opening may be shaped like a Venturi tube, this also tending to improve gas flow. <IMAGE>

Description

SPECIFICATION Gas valves This invention relates to gas valves and in particular to gas valves of the kind (hereinafter referred to as the kind specified) comprising a valve body having a chamber with an inlet and an outlet, the inlet and outlet being co-axial, and a partition extending across the interior of the chamber, there being a valve opening extending through the partition and a valve member movable between an open position in which it permits the flow of gas from the inlet to the outlet by way of the opening and a closed position in which it prevents or substantially prevents such flow.

An aim of the present invention is to provide an improved construction of gas valve in which the size of the valve opening can be reduced without, in use, a reduction in the rate of flow of gas through the valve when the valve is open. A reduction in the size of the valve opening does, of course, enable the size of the valve member to be correspondingly reduced. It may also lead to a reduction in the size of any operating device that may be provided to move the valve member between its open and closed positions. While the invention is applicable to gas valves having operating devices of a wide variety of kinds, including valves controlled by pneumatic cylinders or diaphragms, it is of particular value when incorporated in electrically-operated valves and especially in solenoid-operated valves.In such a valve an electrically-powered device such as a solenoid or electric motor operates to move the valve member from its closed to its open position.

In operation the device has to overcome a force exerted by the gas or the valve member and substantially equal to the product of the pressure difference across the valve and the area of the opening. A reduction in the size of the opening therefore leads to a corresponding reduction in the force that must be exerted by the device. There is usually a return spring which returns the valve member to its closed position, and the electricallypowered device on operation must also overcome the force exerted by that spring. A reduction in the size of the valve opening may also enable the spring to be replaced by one exerting less force.

Any reduction in the size of the electricallypowered device can lead to considerabie savings in valve costs. For example, at present, about half the cost of the materials for a solenoid-operated gas valve, for controlling gas at a pressure of a few pounds per square inch, is the cost of the copper for the coil of the solenoid. Likewise about one tenth of the cost of the completed valve is the cost of that copper. With a reduction in the size pf the solenoid device there is not only a significant saving in the cost of copper but also a saving in the cost of the other components as well.

Where a valve is controlled by an electric motor operative to move the valve member from its closed position to its open position in a predetermined minimum time, the cost of the motor again represents a significant proportion of the total cost of the valve, so that a reduction in the size of the valve opening, leading to a reduction in the power of the motor, can likewise lead to noticeable savings in cost.

According to the present invention there is provided a gas valve of the kind specified in which the valve opening is axially extensive, the axial extent of the valve opening being not less than half the mean diameter of the opening.

The axis of the valve opening preferably intersects the common axis of the inlet and outlet at right-angles.

The partition preferably has a tubular extension through which the valve opening extends. The extension or part of it preferably projects into that part of the chamber communicating with the inlet, though part or indeed all of the extension may project into that part of the chamber communicating with the outlet. Where the extension, or part of it, projects into that part of the chamber communicating with the inlet, the thickness of the wall of the extension may be increased near the mouth of the extension so as to form an annular projection around the outside of the extension; the presence of the projection may lead to an increase in the rate of flow of gas through the valve opening when the valve is in use.The valve opening itself may be of cylindrical shape, but if desired it may be shaped like a Venturi tube so that its diameter gradually reduces with increasing distance from each end, to a smoothly rounded area where the diameter is at a minimum. This may also lead to an increase in the rate of flow of gas through the opening when the valve is in use.

An embodiment of the present invention will now be more particularly described with reference to the accompanying drawings, in which: Figure 1 is a section through part of a valve embodying the present invention, and Figure 2 is a section similar to a part of Figure 1 but illustrating a modification.

The valve, part of which is shown in Figure 1, includes a body 10 conveniently comprises a metal casting. The body 10 has a tubular inlet 11 and a tubular outlet 12 co-axial with the inlet.

Both the inlet and the outlet are internally screwthreaded to receive the ends of pipes for conducting gas to and from the body. The inlet and outlet communicate with the interior of a chamber 13 which is of cylindrical shape, its axis crossing at right-angles the common axis of the inlet and outlet. A partition 14 extends across the interior of the chamber between the inlet and outlet.

A valve opening 1 5 of circular cross-section is formed at the centre of the partition, the opening being co-axial with the chamber 13. The diameter of the opening is approximately equal to the internal diameter of the inlet and outlet pipes. The opening 1 5 extends through a tubular extension 1 6 which projects upwards from the partition. In the construction illustrated the extension is integrai with the partition and with the remainder of the body. In alternative construction (not illustrated) the extension is formed separately and is subsequently attached to the partition. The axial length of the opening 1 5 is rather more than half the internal diameter of the opening.

The upper edge of the extension 16 is formed with a relatively sharp edge 1 7 which constitutes a seat for a valve member 1 8. The valve member is in the form of a disc with a resilient face for engagement with the seat 1 7. The valve member 18 is fixed to one end of a stem 1 9 co-axial with the extension 1 6 and is movable axially between a closed position in which it seals against the seat 17, preventing any flow of gas through the opening 15, and an open position (as illustrated) in which it is spaced from the seat by a distance equal to one quarter of the diameter of the opening. The stem 1 9 is connected to, or constitutes, the armature of a solenoid coil (not shown) mounted on the valve body.A helical compression spring (not shown) urges the valve member 1 8 towards its closed position, while in use energisation of the solenoid overcomes the force exerted by the spring, as well as the force exerted by the gas, and moves the valve member to its open position.

A closure plate (not shown) secured to the lower face of the body 10 seals the lower end of the chamber 13, while a housing secured to the upper face of the body surrounds the valve member, stem and solenoid coil, and prevents gas escaping from the upper end of the chamber Part of the housing comprises a fixed annular cap 20 which has a central hole through which the stem 19 extends. When the valve member 18 is in its open position it lies close to the cap 20 as illustrated. The presence of the cap prevents the free flow of gas from the chamber 12 into the interior of that part of the housing surrounding the solenoid coil and leads to an improvement in performance referred to in more detail below.

When the valve is in use the valve member 18 is normally in its closed position, preventing gas flowing from the inlet 11 to the outlet 12. On energisation of the solenoid, however, the valve member moves to its open position, thereby allowing gas to flow from the inlet 11 to the outlet 12 by way of the opening 1 5.

The valve described above with reference to Figure 1 may be contrasted with a known type of valve of generally similar construction but lacking the extension 1 6 and the annular baffle. It has been found, unexpectediy, that a valve of the construction described above with reference to the accompanying drawings, when open, can permit gas to flow through it at the same rate at which gas flows through a valve of the known type but in which the diameter of the opening is larger.

The reason for this is not known, but one theory that we favour is that the improvement is connected with the fact that in valves of the known type gas issuing from the inlet into the upper part of the chamber is caused to slow down, due to the increase in cross-section of the space through which it travels and must then increase in speed again as it passes through the valve opening, whereas in a valve of the kind described above with reference to Figure 1 the change in velocity of the gas in passing from the inlet to the opening is lessened.The presence of the cap 20 adjacent to the valve member 18 also helps to restrict the cross-section of the space through which the gas flows between its leaving the inlet 11 and reaching the valve opening 15 ; It has also been found, however, that the provision of a thickened portion around the outside of the extension 1 6, near the seat 17, as indicated at 21 in Figure 1, is also advantageous as it tends to increase the rate of flow of gas through the valve when the valve is open. The reason for this improvement is again not clear.

Figure 2 shows in section an extension 22, similar to the extension 1 5 but of a modified shape. A restriction 23 of annular shape is provided inside the extension near the seat 24 of the extension. The restriction is so shaped that the interior of the extension is shaped like a Venturi tube. The presence of the restriction 23 can also increase the rate of flow of gas through the valve when the valve is open. The restriction 23 is shown as being provided in addition to a thickened portion 25, similar to the portion 21, but the restriction 23 may be provided in the absence of a thicked portion 25, the outside surface of the extension then being cylindrical. Likewise both the restriction 23 and the thickened portion 25 may be omitted if desired.

In each of the valves described above the extension 16 or 22 as the case may be, extends into that part of the chamber communicating with the inlet. In a modified construction (not shown) the extension projects into that part of the chamber communicating with the outlet; in that case the extension may partially project on both sides of the partition or on one side only.

Whatever arrangement is adopted, however, the axial length of the valve opening is at least half the mean diameter of the opening.

In general we find that it is desirable for gas leaving the valve opening to flow into a part of the chamber that is of greater cross-section than the opening. This is in contrast to the preferred situation on the inlet side of the valve opening. For this reason the extension or most of the extension would usually project on the inlet side of the partition.

It is to be understood that any of the foregoing kinds of valves can be modified by arranging for the valve stem to extend through the valve opening and for the solenoid to be mounted on the underside of the body. A closure plate similar to the cap 20 but without a central hole is provided on the upper face of the body, while a sealed housing, surrounding the solenoid coil, is provided on the underside of the body. Furthermore the whole valve may be inverted or used in some other orientation; it is only to simplify an understanding of the construction of the valve that the valve is described above in one particular orientation.

Although the valve member would normally be such as entirely to prevent the flow of gas through the valve opening when it is in its closed position, it is possible that a bleed hole might be provided through the valve member or through a wall of the extension or otherwise so as to permit a relatively small flow of gas through the valve opening when the valve member is in its closed position.

Valves embodying the present invention are suitable for use in controlling the flow of many different kinds of gas, but it is envisaged that they will have a particular application in the control of combustible gas such as the so-called natural gas now supplied nationally through the gas mains in Great Britain. The valves may be such that the diameters of the valve openings vary between three quarters of an inch and two inches, though valves with openings of sizes outside that range are of course within the scope of the invention.

In one particular experiment two similar gas valves were made, the first using a body similar to that shown in Figure 1 and the second having a body that was similar but from which the extension 1 6 was omitted. In each case the diameter of the valve opening was one inch (25.4 mm). When used with natural gas supplied at 2 p.s.i. it was found that the rate of flow of gas through the second valve was greater than that through the first valve, that rates being in the ratio 29.1 to 22.0.

Claims (10)

1. A gas valve of the kind specified in which the valve opening is axially extensive, the axial extent of the valve opening being not less than half the mean diameter of the opening.

2. A gas valve according to claim 1 in which the axis of the valve opening intersects the common axis of the inlet and outlet at right-angles.

3. A gas valve according to either of claims 1 and 2 in which the partition has a tubular extension through which the valve opening extends.

4. A gas valve according to claim 3 in which at least part of the extension projects into that part of the chamber communicating with the inlet.

5. A gas valve according to either of claims 3 and 4 in which at least part of the extension projects into that part of the chamber communicating with the outlet.

6. A gas valve according claim 4 in which the thickness of the wall of the extension is increased neai the mouth of the extension so as to form an annular projection around the outside of the extension.

7. A gas valve according to any one of the preceding claims in which the valve opening is of cylindrical shape.

8, A gas valve according to any one of claims 1 to 6 in which the valve opening is shaped like a Venturi tube so that its diameter gradually reduces with increasing distance from each end, to a smoothly rounded area where the diameter is at a minimum.

9. A gas valve according to any one of the preceding claims in which the mean diameter of the valve opening is between three quarters of an inch (19.05 mm) and two inches (50.8 mm).

10. A gas valve of the kind specified and substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

1 A gas valve according to claim 10 but incorporating the modification substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.