GB2526853A

GB2526853A - Gas valve

Info

Publication number: GB2526853A
Application number: GB1409989.9A
Authority: GB
Inventors: Kenneth Pickles
Original assignee: NSF CONTROLS Ltd
Current assignee: NSF CONTROLS Ltd
Priority date: 2014-06-05
Filing date: 2014-06-05
Publication date: 2015-12-09
Anticipated expiration: 2034-06-05
Also published as: GB2526853A8; GB2526853B8; GB2526853B; GB201409989D0

Abstract

A valve for regulating the flow of gas through a conduit comprises a body 2 having an inlet 4, outlet 6 and an outlet channel 36. The outlet channel 36 has a concave wall acting as a valve seat 26 with at least one aperture 28 therein. A gate 10 is pivotally mounted in the body 2 and has a corresponding convex sealing surface 12 with at least one aperture 14 therein. The gate may be rotated by a solenoid or an electric motor.

Description

Gas valve The present invention relates to a gas valve, for the regulation and, primarily stopping of or allowing the flow of, gas through a conduit. In particular, the present invention relates to a gas valve for use in low volume, for example domestic, gas outlets from a distribution grid.

Most countries provide an infrastructure of pipes for the distribution of natural gas, which comprises principally methane, for the use in the heating of homes and premises. The distribution networks comprise tiered layers of infrastructure resulting ultimately in outlets designed to provide a relatively low flow rates of gas and at which outlets the amount of gas dispensed from that outlet is measured, typically using a metering apparatus. Associated with a metering apparatus is typically a shut off valve for the purposes of allowing or terminating gas flow from the outlet. Such shut off valves may be present, before, as part of, or after a metering device.

With increasing automation in gas distribution there has arisen a need for shut off valves which can be controlled remotely and opened or closed by means of a local actuator associated with the valve and typically integrated with a metering device, the metering device providing or sharing suitable electronics and power for the purposes of receiving a signal to activate the actuator.

Shut off valves suitable for the above use, in conjunction with, and often being an integral part of, a metering apparatus at an outlet of a gas distribution network are required to fulfil several requirements.

First is reliability of operation, it is naturally essential that any closure of gas supply is complete, as beyond the outlet point a customer can, choose or otherwise, to provide a further conduit to take away the gas. However, acceptable leakage rates are defined in the industry, nevertheless a valve with negligible leakage is preferred.

Equally important is reliability on repeated operation over an extended period of time without any maintenance. Reliability over several years of operation and thousands of operations, in a sealed container without the potential for maintenance action is required. The sealed container is typically a metering apparatus cabinet. This sets these types of valves apart from valves used more generally in industry where ready access for maintenance is possible.

A second requirement is robust operation. This is particularly significant where transitory high pressures in the distribution system must be withstood. Hence, whilst an apparatus can be over engineered to continuously withstand a worse case situation it is nevertheless preferably engineered to withstand transitory changes, or at least to fail safe based upon a more economic design. There is therefore a balance to be struck between robust construction and economy of materials, this is particular so in consumer end uses were millions of gas metering apparatus are in use and gas usage by any individual metering apparatus may not be large. A further aspect of the requirement for robust operation, particularly with some instances of domestic supply is that the valve must be capable of withstanding significant shock.

With some current devices it has been found that restoration of a gas supply which has been shut off using a valve may be achieved by significant external shocks being applied to a gas metering device, such as may be deliberately occasioned so as to steal gas.

Third, the design of a gas valve must be mechanically efficient, particularly in terms of the energy used to actuate the valve. Specifically when considering valves enclosed in a metering apparatus cabinet no possibility exists to introduce a fresh power supply and any battery power supply provided normally has two operate over the full life of the apparatus, which is typically many years. Hence, not only is an actuator therefore typically electrically driven, not least because metering apparatus and communications means to control such a valve will also be electrically driven, but the actuator and the valve must consume relatively little energy in operation. This is particular so since gas valves may not be conveniently associated with an electricity supply they must be capable of operating from stored energy, typically in the form of a battery, and to do so over, preferably, the whole life of the device.

The present invention seeks to provide a gas valve, a gas valve apparatus and a point of sale gas metering and dispensing device comprising such a valve which provides one solution to the compromises in design parameters outlined above.

The present invention in its various aspects is as set out in the appended claims.

The present invention provides a gas valve, the valve comprising: a valve body having an inlet and an outlet, the valve body further comprising; an outlet channel having an inlet, upstream, end and an outlet, downstream, end; the inlet end comprising a concave wall having one or more of N apertures therein and acting as a valve seat, the valve seat being concave in the direction of outlet and being in the shape of a segment of a wall of a cylinder; pivoted within the valve body is a gate in the form of a cam, the cam comprising: a sealing surface of curvature in the form of a further segment of a wall of a cylinder and having corresponding, optionally N-i, apertures therein, such that in a closed position the gate and body do not overlap; said further segment being convex and in its outer radius matching the inner radius of the upstream wall of said segment of a cylinder forming the concave wall of the outlet; wherein the gate, in a first position, places the sealing surface in contact with the valve seat so as to close the valve by obstructing the one or more apertures; this defining a valve closed position, and wherein the gate, is rotatable to other, open, positions, and in said other positions places the sealing surface remote from the valve seat so as to not obstruct the one or more apertures and so, in use, permit gas within the valve body to pass through the one or more apertures in the valve seat and exit the outlet channel of the valve, so as to render the valve open.

The upstream end is for, in use, the entry of gas at a pressure higher than present at the downstream end. Therefore, in use, the gas flows from the upstream end to the downstream end when the valve is open and, when close, gases stopped from flowing from the upstream end to the downstream end.

The term cam as used in the present application relates to the normal definition of that word inasmuch as it provides a projection on a rotating part in machinery, designed to make shding contact with another part whie rotating, but which departs from the conventiona' meaning in that it does not impart reciproca or variabe motion to that other part.

The gate is preferably movable between said closed position and said open positions by pivoting about a pivot axis, the pivot axis being parallel to the notional axis of radius of the further segment of a cylinder. The pivot axis is preferably realised in the form of an axle about which the gate rotates, said axle being secured in outer walls of the valve body perpendicular to the surface of the segment of a cylinder forming the valve outlet. The axle may be continuous or one may be present in the form of lugs on the outer sides of the gate, this being preferable as the volume of the valve is therefore not obstructed by the axle and gas flow is less hindered.

The gate may have N apertures therein and the body and having N-i is a corresponding apertures.

The one or more of N apertures are preferably two or more apertures, the two or more apertures being elongate in the axis (i.e. perpendicular to a radius) of said cylinder segments and preferably being of equal dimension and mutually perpendicular to said elongate dimension and said axis of said cylinders segments.

This provides that the gates need only move half the distance it would otherwise need to move to completely remove obstruction if there were one aperture present.

Whilst, logically, the larger the number of apertures the less distance the gate would need to move, it has been found in practice that an optimal number of apertures is two or three apertures, large numbers giving rise to turbulence in gas flow and consequent pressure drop.

Either one, or both of the sealing surface of curvature of the gate or of the concave wall having apertures therein of the valve body preferably comprises an elastomeric polymer layer configured to contact the other of the gate all valve body so as to seal the one or more apertures in the closed position. Such a polymer layer allows for greater changes in tolerance, such as in temperature change, on the above components whilst providing an effective seal.

The concave wall having apertures therein of the valve body may be coated with the elastomeric polymer layer, preferably in the form of a sheet of material, conformal with an underlying surface of the valve outlet surface. This configuration, having no polymer layer on the gate reduces the moment of inertia of the gate and thus the power requirement for gate opening.

The sealing surface of curvature of the gate is preferably covered with said elastomeric polymer layer. This is preferred as it simplifies valve manufacture as it is not necessary to provide an aperture in the polymer layer and the polymer layer is placed upon rather than inserted into a surface. On balance with the specific configurations of valve of the present invention this placement of the layer is preferred.

The elastomeric polymer layer is preferably in the form of a 1 to 3mm sheet of material, conformal with an underlying surface of the gate body. This thickness has been found to give optimal sealing without the potential for undue deformation over time such that the material exudes into the apertures so as to hinder valve operation.

In this respect a time period of several months is relevant.

The elastomeric polymer is preferably acrylonitrile rubber. Whilst many other compositions have been contemplated this has been found to give the best combination of chemical and mechanical characteristics.

The gate is preferably actuated by means of an electrically driven actuator.

The electrical actuator is preferably an electro-mechanical actuator, most preferably an electromagnetic actuator in the form of a motor or solenoid. A solenoid is preferred. This hierarchy of choice has been found optimal for a valve gate of weight between around 1 g to 100g. Further, this hierarchy of selection is particularly preferred were microprocessor/microcontroller mediated control is possible such as in the form of a microprocessor/microcontroller also used for metering purposes.

This is because electromechanical actuators typically provide noise on an electrical power supply bus, this noise can disrupt microprocessor/microcontroller operation. A solenoid will typically give more noise due to its higher power (energy versus time) requirement than a motor. On this basis it was first considered that a motor would be preferred. However, any noise from a motor disrupting processing gives rise to a discontinuity, such as a stop in valve movement, this can leave a valve partially open or partially closed. However, the noise from a solenoid occurs when the solenoid actuates and from that time onwards the valve will either be open or closed. The time required for a processor to reboot is therefore inconsequential as the desired action would have been carried out and, in the present apparatus the duty cycle of turn-on to turn-off is usually at the very minimum in the time period of minutes, more often months.

When used in a sealed metering cabinet or enclosure the valve of the present invention is a particularly effective arrangement since only the outlet of the valve body, which preferably comprises no further apertures other than at its outlet and inlet ends has to be sealed by means of the gate so was to produce an effective valve. Specifically, there is no requirement that the pivot or the actuating mechanism of the gate be in any way sealed so as to be gas tight (as in air tight). There is further no requirement that the electrically actuating mechanism be spark proof since the whole mechanism will be enclosed within a gas filled environment. Hence, the present invention is preferably used within a sealed cabinet, the sealed cabinet having an inlet port and a sole means of outlet by the concave wall having apertures therein of the valve body, the outlet of the valve body being sealed into the wall of the cabinet around its outer periphery, so as to provide an outlet. Thus, the use of an electrical motor such as a motor with brushes is acceptable and even preferable as such motors will have a longer lifespan in a gas (as in methane) filled environment than they would in an oxidising (as in air) filled environment. A motor more readily enables gradations in open position to be achieved.

The sealed cabinet is preferably a metering cabinet comprising an electrical power source, a microprocessor or microcontroller, gas flow measurement sensors and said valve. This is preferably configured so that the microprocessor controls both the measurement sensors and the valve. This is also preferably configured such that the macro processor microcontroller measures gas flow when the valve is in the closed position so as to provide an alert should gas flow be detected when gas flow should not be detected, i.e. in the valve closed position. This, in particular, provides additional security against gas theft as any manipulation of the valve, such as by external shock (to which the present valve is not considered particularly susceptible) will be detectable without having to use any valve position measuring equipment.

The valve is preferably a shut off valve. A shut off valve being a valve in which the flow of gas is significantly hindered only over a shod range of travel of the gate close to the closed position and other positions over the intended range of travel of the gate provides relatively little hindrance to the flow of gas under the conditions to which the valve is designed. Whilst this definition is relative, the skilled person will nevertheless clearly recognise such a valve in comparison to a valve on which the degree of flow of the intended fluid is controlled proportional to the movement of the gate, such as in a ball valve.

A low-volume valve is a valve, of the general type for which the present invention is a candidate, is intended to control a flow of less than 12 m3 per hour of natural gas. Natural gas being a flammable gas. consisting largely of methane and other hydrocarbons, occurhng naturally underground (often in association with petroleum) and used as fuel.

The valve of the present invention has a curved, concave, valve seat and a matching sealing surface of the valve gate. The valve gate is pivoted such that the sealing surface lifts away from the valve seat in moving from the close position to an open position. The valve gate is pivoted such that the sealing surface in lifting away from the valve seat also translates laterally from the valve seat. By providing that for every unit of distance that the sealing surface moves away from the valve seat it translates laterally the same distance or less the force required to move the gate is not substantially affected by the gas pressure.

The valve gate preferably comprises outside walls in the form of two sectors of a circle, having a pivot spindle located proximate the centre of the notional sectors and the sealing surface.

The present invention will now be described with reference to the following figures (all of which are devices of the present invention), the diagrams being schematic in nature, wherein; Figure 1, shows a side elevation cross section through the valve body and valve gate with the valve gate in the closed position; the direction of gas flow is indicated by means of an arrow.

Figure 2, corresponds to figure 1 and shows a side elevation cross section through the valve body and valve gate, as in figure 1, with the valve gate in a fully open position; Figure 3, shows an end elevation, looking in the gas outlet direction (i.e. looking from downstream to upstream), of the valve body, valve gate and externally mounted solenoid actuator; the valve is in the closed position; Figure 4, corresponds to figure 3 and shows an end elevation, looking towards the gas inlet flow direction (i.e. looking from upstream to downstream) of the inlet of the valve body, of the valve body, valve gate and externally mounted solenoid actuator; the valve is in the closed position; Figure 5, corresponds to the diagrams provided in the previous figures in which an external view of the valve body and associated actuator is shown, with the positioning of the gate and internal surfaces (not being visible) in dashed line; the valve being in a closed position; Figure 6, corresponds to figure 5 with the gate and hence the valve, in a fully open position; Figure 7, shows the fully open and closed positions of the solenoid actuator superimposed to show their relative positioning; Figure 8, shows a perspective view the valve of the present invention suitable for use in an enclosed cabinet in which the valve body outlet is sealed into a cabinet wall (or feature which itself is sealed into the cabinet wall) to provide an outlet and the small requirement for external valve body otherwise required to form an effective valve.

This arrangement is preferred an enclosed cabinet, the cabinet, such as a metering cabinet, having a gas inlet formed by the valve and an outlet or outlets in a wall of the chamber. This facilitates the provision of multiple outlets, controlled separately, each using a separate valve from a single metering cabinet acting as a manifold.

Figure 9, shows a further perspective view corresponding to that of figure 8; Figure 10, shows the interrelationship between geometric parameters of the valve; Figure 11, shows the positioning of an, alternative, activation mechanism in the form of an electric motor, shown in the dashed line, in relation to the valve is presented in figure 1 and figure 2; Figure 12 shows an equivalent future that presented in figure 11, but from an opposite side in which a housing from the motor. The motor, and a gear transmission mechanism are shown; Figure 13 shows a cross section through gear train housing enclosing a gear transmission mechanism of the electric motor actuator shown in figures 11 and 12; and Figure 14 shows a cross-section as another elevation through the valve housing of the electric motor actuated valve as shown in Figures 11 and 12 and in which the gate, and gate gearing, for engagement with the gear transmission mechanism are shown.

The following features and functional elements of the present invention, as shown in the diagrams, are annotated as follows: 1 a gas valve of the present invention; 2 valve body; 4 valve inlet; 6 valve outlet; gate; 12 sealing surface of curvature; 14 corresponding aperture of gate; 16 arm of gate; 18 elastomeric polymer layer; 22 concave wall having apertures therein, outlet wall; 24 outlet wall apertures; 26 valve seat; 28 upstream wall; 36 outlet channel; pivot axis; see 100.

42 gate lug(s), being part of the body 2, about which the gate pivots; 44 bearing housing of arm 16 in which lugs 42 are located and can be rotated; 46 pivot axis of solenoid actuator lever; 48 solenoid actuator lever; solenoid actuator; 52 solenoid body comprising actuator coil for being energised to cause movement of the plunger 54; 54 solenoid plunger activatable into linear translation when actuator coil is energised; 56 pivot lug about which the solenoid actuator lever pivots; 58 plunger pivot bar about which the solenoid actuator lever pivots and about which force from the solenoid is transmitted to the lever for further transmission by the pivot lug 56 to the gate; slot in which gate actuator lug moves; 62 gate actuator lug for transmitting force from solenoid actuator lever to gate; 64 first actuator lever arm; 66 second, longer, actuator lever arm linked to gate; 68 helical spring; region of valve outlet tube about which a seal is made for both supporting the valve in an enclosure and for sealing the enclosure against a gas exit (such as from a cabinet); centre of rotation/centre of radius of the valve gate, also being the pivot axis 40; 112 radius of curvature of the valve gate to the elastomeric polymer layer; centre of radius of the valve seat; 122 radius of curvature of the valve seat; centre of radius of pivot lug; 201 gas valve of the present invention with electric motor actuator; 202 first axle about which force, torque, is transmitted from the motor to the gate; 204 motor spindle; 206 electric rotational motor; 208 second axle of gear train; 210 motor and gear train housing; 212 gear train gears comprising major cog and minor cog assembly; each gear train gear (212, 212', 212", 212") engaging with a subsequent gear train gear (212', 212", 212", 212", respectively) to give an overall reduction in rotation rate and increase in torque going from motor to gate; and 214 motor spindle minor gear for engagement with major cog of first gear train gear.

For clarity of reading the same features are not labelled in all drawings and the normal skill of the reader in understanding that features having the same appearance could have been numbered and should be taken to be so numbered, in the same manner, is intended.

A valve according to a first embodiment of the present invention is presented in figure 1, in which the valve 1 comprises a valve body 2 having an inlet 4 and an outlet 6. The inlet 4 is simply a general area of the valve body on another side of the valve seat 22 to that of the outlet 6. An advantage of the valve is that no sealing is required on the inlet 4 side as the valve is particularly suitable for use in an enclosure, not shown, itself-serving as an inlet and having a sole outlet formed by the outlet 6 of the valve, that outlet being sealed in a region of the outlet channel 36, such as on its outer wall near the termination of the outlet 70. The valve further comprises a gate 10 comprising side arms 16 connecting a bearing housing 44, which rotates about a gate lug 42 (which is part of the housing 2). The side arms 16 support a gate face 20 which acts, when suitably positioned in a valve closed position, see figure 1, to coincide with the outlet wall of the housing 2 such as to seal the valve. In more detail, gate face 20 preferably has a covering of an elastomeric polymer layer 18 which serves, insect close position, but against the valve seat 26 source to close the valve. Valve seat 26 comprises a conclave wall having apertures therein, the apertures 24, 24' serve, when the valve is in the open position, see figure 2, to allow gas to transmit from the valve inlet 4 to the valve outlet 6.

As can be seen in comparing figures 1 a 2 the valve gate 10 rotates about pivot 42 between a closed position and an open position. The presence of the outlet wall apertures in combination with the corresponding aperture of the gate 14 provides that rotation of the gate about an angle of approximately 22° enables the gate to move from a fully open to a fully closed position and vice versa. This is particularly useful when a solenoid actuator 50 is used as the distance of travel of a solenoid plunger 54 in a solenoid body 52 in which significant para generated is relatively shod and this throw can therefore correspond to the distance of travel of the gate 10 particular were mediated via a suitable lever mechanism (actuator lever) 48.

Alternatively, a rotational electric motor 206 is used in which case the limited throw of the valve gate provides that a suitably geared low-power motor can exert considerable torque over such a limited distance. The above factors provide that the valve is suited to use limited power so as to open and close in the presence of relatively high external gas pressure. This is particularly so as, overtime, a valve sealing member, such as an elastomeric polymer layer can deform in contact with a valve seat so as to give a particularly strong seal leading considerable force to dislodge. The frequency of actuation of a valve, particularly when used in a gas metering enclosure can be relatively low, such as on a timescale of months or even years. This contrasts with parallel applications in which, for example with pay-as-you-go' metering valve actuation can be frequent, even daily.

Figure 3 shows a valve as present in figures 1 and 2 from in a view from the valve inlet 4 end. Figure 4 shows the valve presented in figures 1, 2 and 3 in a view from the valve outlet 6 end. In these views the solenoid actuator 50 can be seen attached to the valve body 2 and having a solenoid actuator lever 48 to mediate the linear motion of the solenoid plunger into a rotational moment of the gas valve gate by means of force translated through the plunger pivot bar 58, actuator lever 48, pivot lug 56, gate actuator lug 62 so as to enable the gates 10 to rotate about gate lugs 42 in bearing 44. The use of such a lever is helpful since valves used in the manner of the present invention are required to pass very rigorous testing, such as many thousands of actuations without failure and as such defining the valve, in terms of its gas stopping capabilities with respect to the gate and the valve seat is very preferably only carried out once in any given apparatus. However, the actuator, may be sourced from different places or, the forces with which the valve is required to operate may vary between specifications and as such a different level of leverage, a different power output of solenoid or a different voltage/current available for actuation of the solenoid (for example dependent upon regional requirements) means that the basic valve structure (gate, gate sealing surface and housing) can be readily adapted by altering the leverage imparted by the lever simply by changing the relative lengths of the lever arms 64, 66 without redesigning the safety critical sealing arrangement. Furthermore, provision of a range of valves can be readily achieved by using the same basic valve structure and providing different actuator arrangements.

The mechanism of action of the solenoid actuator according to one embodiment of the present invention is as shown in figures 5, 6 and 7. Figure 5 shows the valve 1 in a closed position, c.f. Figure 1, figure 6 shows a valve in an open position, c.f. Figure 2. A 2. Figure 7 shows the open and closed positions superimposed such that the difference in throw between the actuator and the gate lug (which is further amplified in the portion of the gate adjacent to the valve seat) can be readily seen.

Figures 8 and nine show a perspective view of the valve 1 of the solenoid actuator embodiment of the present invention. In this view the compact nature of the valve, its simplicity and its requiring only two sealing surfaces (outlet channel 36 two vessel wall, e.g. 70) and valve gate 10 to valve seat 26 can also be readily seen. This simplicity enables the key features of the valve to be optimised for any given application for quickly as fewer features need to be adjust ted.

A further feature of note of the valve is that only two services, the bearing services between book 42 an bearing 44 on each side of the valve, located on the valve arms 16 are available for abrasive wear (since the gate 10 effectively lifts of the outlet wall 22), it is therefore possible to keep the valve gas tight over many operations.

Whilst many conventional solenoid actuators may be used it is preferable that the solenoid actuator has a bistable configuration in which the valve is biased to the closed position by means of a resilient element, such as a helical spring 68 to provide a failsafe -closed -valve positioning. So as to provide stability in the open position a permanent magnet is preferably positioned such that the plunger in the open position has a resistance to movement during a first distance of travel towards the close position, after which the magnet serves to either have a negligible biasing effect.

In a further embodiment of the present invention the actuator may be in the form of a motor 206 having a spindle 204 on which an armature (not shown) is mounted such that through a conventional brushed or brushless arrangement the armature rotates within the motor housing to form a conventional rotational electric motor. A brushless motor is preferred so as to limit the amount of gas ionisation available from arcing of electrical supply over a commutator. A relatively low-power motor 206 is preferably used and the high-speed, low torque of such motors is translated into a low speed high torque action by means of a gear train in a gear train housing 210, a train comprising a number of, preferably, identical gear train gears (212 etc.) each gear train comprising a major cog having a first plurality of teeth and a minor cog having a second, fewer plurality of teeth. The meshing of the cogs is preferably identical between cogs so that a plurality of identical gear train gears, such as five gear train gears may be used in conjunction so as to transmit force from the motor 206 to the gate 10 so as to open and close the gate.

Claims

Claims, 1. A gas valve, the valve comprising: a valve body having an inlet and an outlet, the valve body further comprising; an outlet channel having an inlet, upstream, end and an outlet, downstream, end; the inlet end comprising a concave wall having one or more of apertures therein and acting as a valve seat, the valve seat being concave in the direction of outlet and being in the shape of a segment of a wall of a cylinder; pivoted within the valve body is a gate in the form of a cam, the cam comprising: a sealing surface of curvature in the form of a further segment of a wall of a cylinder and having corresponding, apertures therein, such that in a closed position the gate and body do not overlap; said further segment being convex and in its outer radius matching the inner radius of the upstream wall of said segment of a cylinder forming the concave wall of the outlet; wherein the gate, in a first position, places the sealing surface in contact with the valve seat so as to close the valve by obstructing the one or more apertures; this defining a valve closed position, and wherein the gate, is rotatable to other, open, positions, and in said other positions places the sealing surface remote from the valve seat so as to not obstruct the one or more apertures and so, in use, permit gas within the valve body to pass through the one or more apertures in the valve seat and exit the outlet channel of the valve, so as to render the valve open.
2. The gas valve of claim 1, wherein the gate is movable between said closed position and said open positions by pivoting about a pivot axis, the pivot axis being parallel to the notional axis of radius of the further segment of a cylinder.
3. The gas valve of claim 2, wherein the pivot axis is in the form of an axle about which the gate rotates, said axle being secured in outer walls of the valve body perpendicular to the surface of the segment of a cylinder forming the valve outlet.
4. The gas valve of any preceding claim wherein the gate has N apertures and N is 2 or more, preferably 3, the body and having N-i apertures.
5. The gas valve of claim 4, wherein the apertures are elongate in the axis (i.e. perpendicular to a radius) of said cylinder segments and preferably being of equal dimension and mutually perpendicular to said elongate dimension and said axis of said cylinders segments.
6. The gas valve of any preceding claim, wherein either one, or both of the sealing surface of curvature of the gate or of the concave wall having one or more apertures therein of the valve body comprises an elastomeric polymer layer configured to contact the other of the gate all valve body so as to seal the one or more apertures in the closed position.
7. The gas valve of claim 6 wherein only the sealing surface of curvature of the gate or of the concave wall having one or more apertures therein of the valve body comprises said elastomeric polymer layer.
8. The gas valve of claim 6 wherein only the sealing surface of curvature of the concave wall having one or more apertures therein of the valve body comprises an elastomeric polymer layer.
9. The gas valve of any preceding claim further comprising an actuator for moving the gate from the first, close, position to an open position.
10. The gas valve of claim 9 wherein the actuator is a solenoid.
ii. The gas valve of claim 10 wherein the solenoid is a bistable solenoid having first and second stable positions corresponding to said first closed position and to a second, fully open, gate position.
12. The gas valve of claim 9 wherein the actuator is a rotational electric motor.
13. An enclosed cabinet comprising the gas valve of any of claims 9 to 12, a gas flow metering device, the gas flow metering device comprising a microprocessor or microcontroller and a source of electrical power, the microprocessor being configured to control both the actuator and the metering device.
14. A gas valve as described hearing with reference to figure is 1, 2, 3, 4,5, 6, 7, 8 and 10 of the description.Amendment to the claims have been filed as follows Claims, 1. A gas valve, the valve comprising: a valve body having an inlet and an outlet, the valve body further comprising; an outlet channel having an inlet, upstream, end and an outlet, downstream, end; the inlet end comprising a concave wall having one or more of apertures therein and acting as a valve seat, the valve seat being concave in the direction of outlet and being in the shape of a segment of a wall of a cylinder; pivoted within the valve body is a gate in the form of a cam, the cam comprising: a sealing surface of curvature in the form of a further segment of a wall of a cylinder and having corresponding, apertures therein, such that in a closed position the gate and body do not overlap; said further segment being convex and in its outer radius matching the o inner radius of the upstream wall of said segment of a cylinder forming LCD the concave wall of the outlet; O wherein the gate, in a first position, places the sealing surface in contact with the valve seat so as to close the valve by obstructing the one or more apertures; this defining a valve closed position, and wherein the gate, is rotatable to other, open, positions, and in said other positions places the sealing surface remote from the valve seat so as to not obstruct the one or more apertures and so, in use, permit gas within the valve body to pass through the one or more apertures in the valve seat and exit the outlet channel of the valve, so as to render the valve open.2. The gas valve of claim 1, wherein the gate is movable between said closed position and said open positions by pivoting about a pivot axis, the pivot axis being parallel to the notional axis of radius of the further segment of a cylinder.3. The gas valve of claim 2, wherein the pivot axis is in the form of an axle about which the gate rotates, said axle being secured in outer walls of the valve body perpendicular to the surface of the segment of a cylinder forming the valve outlet.4. The gas valve of any preceding claim wherein the gate has N apertures, wherein N is 2 or more, the body having N-i apertures.5. The gas valve of claim 4 wherein N is 3.6. The gas valve of claim 4, wherein the apertures are elongate in the axis (i.e. perpendicular to a radius) of said cylinder segments.7. The gas valve of claim 6, wherein the aperturesare of equal dimension and mutually perpendicular to said elongate dimension and said axis of said cylinders segments.8. The gas valve of any preceding claim, wherein either one, or both of o the sealing surface of curvature of the gate or of the concave wall having one or LCD more apertures therein of the valve body comprises an elastomeric polymer layer 0 configured to contact the other of the gate all valve body so as to seal the one or more apertures in the closed position.9. The gas valve of claim 8 wherein only the sealing surface of curvature of the gate or of the concave wall having one or more apertures therein of the valve body comprises said elastomeric polymer layer.10. The gas valve of claim 8 wherein only the sealing surface of curvature of the concave wall having one or more apertures therein of the valve body comprises an elastomeric polymer layer.ii. The gas valve of any preceding claim further comprising an actuator for moving the gate from the first, close, position to an open position.12. The gas valve of claim ii wherein the actuator is a solenoid.13. The gas valve of claim 12 wherein the solenoid is a bistable solenoid having first and second stable positions corresponding to said first closed position and to a second, fully open, gate position.14. The gas valve of claim 11 wherein the actuator is a rotational electric motor.
15. An enclosed cabinet comprising the gas valve of any of claims 11 to 14, a gas flow metering device, the gas flow metering device comprising a microprocessor or microcontroller and a source of electrical power, the microprocessor being configured to control both the actuator and the metering device.
16. A gas valve as described hearing with reference to figure is 1, 2, 3, 4,6 7 8 and 10 of the description.LO