In the control of gas powered appliances, in particular, gas powered hand tools, for example, gas powered soldering irons, glue guns and the like, and gas powered hair dryers, curling tongs and the like it is generally necessary to control the temperature at which these appliances operate. In general, the fuel gas supply to the burner of such devices is fed through an isolating valve which is operated in response to the temperature of the device which is sensed by a temperature sensor. Various types of isolating valves are known, however, most such valves suffer from various disadvantages, for example, many valves comprise a vaiving member which co- operates with a valve seat for selectively preventing gas flow through the valve. The valving member is mechanically operated between an open and a closed position by a mechanical linkage. A particular disadvantage of such valves is that because the valving member is operated by mechanical linkage, sealing of the valve is difficult, and because of the movement of the mechanical linkages wear of seals is unavoidable. Other valves suffer from other disadvantages.

Accordingly, there is a need for a valve which is operable without the need for mechanical linkages connected to a valving member of the valve which controls the flow of fluid through the valve.

The present invention is directed towards providing such a valve.

According to the invention there is provided a valve comprising a housing defining a hollow interior region, a fluid inlet communicating with the hollow interior region, for accommodating fluid into the hollow interior region, and a fluid outlet also communicating with the hollow interior region for accommodating fluid from the hollow interior region, a valving member in the hollow interior region moveable

between a first position co-operating with one of the fluid inlet and the fluid outlet for restricting fluid flow into or out of the hollow interior region and a second position permitting communication between the fluid inlet and the fluid outlet through the hollow interior region for permitting fluid flow from the fluid inlet to the fluid outlet through the hollow interior region, and a main magnet means for retaining the valving member in at least one of the first and second positions, wherein a secondary magnet means is located externally of the hollow interior region for selectively co-operating with the main magnet means for causing movement of the valving member from at least one of the first and second positions to the other of the first and second positions.

Preferably, the main magnet means is a permanent magnet.

Advantageously, the main magnet means is located externally of the hollow interior region.

Ideally, the valving member is of magnetic material.

In one embodiment of the invention, the secondary magnet means selectively co- operates with the main magnet means for alternately urging the valving member into the respective first and second positions from the other of the first and second positions.

Advantageously, the polarity of the secondary magnet means is selectively reversable for alternately urging the valving member into the respective first and second positions from the other of the first and second positions.

In one embodiment of the invention, the main magnet means retains the valving member in one of the first and second positions, and a retaining means is provided for retaining the valving member in the other of the first and second positions.

Preferably, the retaining means is located within the hollow interior region.

Advantageously, the retaining means comprises a resilient means for urging the valving member into the said other of the first and second positions and retaining the valving member therein.

Ideally, the retaining means comprises a spring acting between the housing and the valving member, and preferably, the spring comprises a compression spring. in one embodiment of the invention, a flux path means for conducting magnetic flux from the main magnet means through the valving member is provided so that when the valving member is being retained in the said at least one of the first and second positions by the main magnet means the magnetic force exerted on the valving member by the main magnet means for urging the valving member into the said one of the first and second positions is greater than the magnetic force exerted on the valving member by the main magnet means for urging the valving member into the said other of the first and second positions.

In another embodiment of the invention, the flux path means is adapted so that when the valving member is retained in each one of the first and the second positions the magnetic force exerted by the main magnet means on the valving member for urging the valving member into the one of the first and second positions in which the valving member is retained is greater than the magnetic force exerted on the valving member for urging the valving member into the other of the first and second positions.

Preferably, the secondary magnet means co-operates with the flux path means for selectively altering the magnetic flux in the flux path means for facilitating urging the valving member from either one of the first and second positions to the other of the first and second positions.

In one embodiment of the invention, the flux path means comprises a pair of magnetic flux paths through the valving member, one flux path being provided for accommodating magnetic flux from the main magnet means for retaining the valving member in one of the first and second positions, and the other flux path being

provided for accommodating magnetic flux from the main magnet means for retaining the valving member in the other of the first and second positions.

Advantageously, each flux path is in the form of a flux loop. in one embodiment of the invention, the secondary magnet means co-operates with at least one of the flux paths for altering the magnetic flux in the flux path for urging the valving member from one of the first and second positions to the other of the first and second positions.

Preferably, the secondary magnet means co-operates with the respective flux paths for reducing the force of the magnetic flux in the flux path corresponding to the one of the first and second positions in which the valving member is retained by the main magnet means, and increasing the force of the magnetic flux in the other of the flux paths for urging the valving member from the said one of the first and second positions to the other of the said other of the first and second positions.

In one embodiment of the invention, a pair of secondary magnet means are provided, one secondary magnet means being provided for each flux path, and in another embodiment of the invention, each secondary magnet means comprises an electro-magnet.

In one embodiment of the invention each electro-magnet comprises an electro- magnet coil wound on a former, and preferably, each former extends around the housing.

Preferably, each electro-magnet co-operates with the main magnet means so that a pulse signal applied to the electro-magnet is sufficient for altering the magnetic flux in the corresponding magnetic flux path for moving the valving member between the respective first and second positions.

In one embodiment of the invention, the housing comprises an elongated housing which defines a corresponding elongated bore which forms the hollow interior region,

the valving member being slideable longitudinally within the bore of the housing between the first position and the second position.

Preferably, the housing is formed by an elongated sleeve of circular transverse cross-section, and ideally, the housing is of a non-magnetic material.

In one embodiment of the invention, the valving member comprises an elongated spindle.

In another embodiment of the invention, the housing terminates in respective axially opposite end caps of magnetic material.

Preferably, the valving member shuttles within the hollow interior region between the respective end caps from the first position to the second position.

In another embodiment of the invention, a yoke is provided co-operating with the main magnet means and one of the end caps for forming one of the flux paths with the end cap and the valving member, and preferably, a pair of yokes are provided extending from the main magnet means to the respective end caps for forming the two flux paths through the valving member.

In one embodiment of the invention, the main magnet means is located intermediate and spaced apart from the respective end caps, and preferably, the main magnet means is located substantially half way between the respective end caps.

In one embodiment of the invention, two main magnet means are located on respective diametrically opposite sides of the housing, and each yoke is in the form of a U-shaped member having a pair of side members extending on opposite sides of the housing, the side members extending from a transverse end member in engagement with a corresponding end cap to the corresponding main magnet means for forming with the valving member the respective flux paths.

In another embodiment of the invention, the valving member is in engagement with a corresponding one of the end caps in each of the first and second positions, and is disengaged from the other of the end caps for forming an air gap in the magnetic flux path between the valving member and the disengaged end cap for reducing the magnetic force in the magnetic flux path through the disengaged end cap for urging the valving member towards the disengaged end cap so that the magnetic force in the other flux path for urging the valving member into the engaged end cap is greater than the magnetic force for urging the valving member towards the disengaged end cap for retaining the valving member in engagement with the engaged end cap.

Preferably, the fluid inlet is located in one of the end caps, and the fluid outlet is located in the other end cap.

Advantageously, one of the end caps defines a valve seat adjacent the fluid inlet or fluid outlet, and the valving member co-operates with the valve seat for restricting the flow of fluid therethrough.

In one embodiment of the invention, a sealing means is carried on the valving member for co-operating with the valve seat for restricting the flow of fluid therethrough.

In another embodiment of the invention, the valving member is simultaneously subjected to the magnetic flux of the two flux paths.

Ideally, each main magnet means is magnetised in a transverse direction relative to the direction of movement of the valving member between the first and second positions.

In one embodiment of the invention, the valving member sealably closes the one of the fluid inlet and fluid outlet when in the first position. Alternatively, the valving member permits a restricted flow of fluid through the one of the fluid inlet and the fluid outlet when in the first position.

Preferably, the valving member defines with the housing a fluid passageway communicating the fluid inlet and the fluid outlet.

In one embodiment of the invention, the valving member co-operates with the fluid outlet when in the first position.

In another embodiment of the invention, the valve further comprises a control means for providing a pulse signal to each electro-magnet for altering the magnetic flux in each flux path.

In another embodiment of the invention, the control means is responsive to a temperature sensing means for generating a single pulse signal for urging the valving member from the said one or the said other of the first and second positions in response to the temperature being monitored by the temperature sensing means.

In a further embodiment of the invention, the valve is suitable for isolating a fuel gas supply from a fuel gas source to a fuel gas powered appliance.

In a still further embodiment of the invention, the temperature sensing means senses the temperature of the gas powered appliance.

Additionally, the invention provides a gas powered appliance comprising the valve according to the invention for controlling a supply of fuel gas to the fuel gas powered appliance from a fuel gas source.

In one embodiment of the invention, the valve is responsive to a temperature sensing means of the fuel gas powered appliance for controlling the supply of fuel gas to the fuel gas powered appliance from the fuel gas source.

The advantages of the invention are many. A particularly important advantage of the invention is that is provides a valve which is particularly suitable for use in hazardous environments, and which can be operated with the minimum amount of power. By virtue of the fact that the valving member is operable by magnetic forces there is no

need for connection of mechanical linkages to the valving member for operating the valving member. Accordingly, the valving member can be located directly in the fluid path without the need for any external seals and without any danger of leakage therefrom. By virtue of the fact that the main magnet means when provided by a permanent magnet is arranged for retaining the valving member in at least one of the first and second positions, and in most cases in the respective first and second positions, the power requirement of the valve is minimal. In the embodiment of the invention where the valving member is retained in one of the first and second positions by the permanent magnet, and in the other of the first and second positions by the retaining means, again the power requirement of the valve is minimal. By virtue of the fact that the secondary magnet means co-operate with the permanent magnet means for urging the valving member between the respective first and second positions the power requirement is further minimised. In the embodiments of the invention where the secondary magnet means is provided by one or more electro-magnets all that is required is a relative short electrical pulse signal to each electro-magnet for altering the force of the magnetic field retaining the valving member in one of the first and second positions for urging the valving member to the other of the first and second positions.

Furthermore, by virtue of the fact that there is no need for mechanical linkages to the valving member wear in the valve is minimised, and since there is no need for seals for sealing moving linkages for operating the valving member, wear is further minimised. Furthermore, the absence of the need for a mechanical linkage for operating the valving member allows for virtual frictionless movement of the valving member within the hollow interior region. This, thus, further minimises the power requirements for operating the valve.

Because of its relative low power requirement, the valve according to the invention is particularly suitable for use in gas powered hand tools, for example, soldering tools, glue guns, hairdryers, curling tongs, clothes pressing irons which are portable, and in which an electrical power source is typically provided by a relative low energy capacity battery. Furthermore, because of the fact that the valve is suitable for use in a hazardous environment due to the fact that the valving member is

entirely sealed within the valve, the valve is also particularly suitable for use with gas powered appliances. However, it will be readily apparent to those skilled in the art that these advantages of the valve according to the invention also lend to its use for operation in other hazardous environments, whether for controlling the flow of liquid or gaseous fluids, whether hazardous or otherwise.

The invention will be more clearly understood from the following description of some preferred embodiments thereof which are given by way of example only with reference to the accompanying drawings in which: Fig. 1 is a perspective view of a valve according to the invention, Fig. 2 is an enlarged transverse cross-sectional side elevational view of the valve of Fig. 1, with section lines omitted, Fig. 3 is an enlarged transverse cross-sectional plan view of the valve of Fig.

1, Fig. 4 is a circuit diagram of a control circuit for controlling the valve of Fig. 1, Fig. 5 is a perspective view of a valve according to another embodiment of the invention, Fig. 6 is a perspective view of a valve according to a further embodiment of the invention, Fig. 7 is a transverse cross-sectional side elevational view of the valve of Fig.

6, with section lines omitted, Fig. 8 is a perspective view of another valve according to the invention, Fig. 9 is a side elevational view of a portion of the valve of Fig. 8,

Fig. 10 is a transverse cross-sectional end elevational view of the valve of Fig. 8 on the line X-X of Fig. 9, Fig. 11 is a schematic representation of a gas powered soldering iron incorporating the valve of Fig. 1, and Fig. 12 is a schematic representation of a gas powered glue gun incorporating the valve of Fig. 1.

Referring to the drawings and initially to Figs. 1 to 4 there is illustrated a valve according to the invention which in this embodiment of the invention is an isolating valve indicated generally by the reference numeral 1, and which is suitable for isolating a fuel gas supply to a fuel gas powered appliance from a fuel gas source, as will be described below with reference to Figs. 11 and 12. In this particular embodiment of the invention the isolating valve 1 is operated under the control of a control means, namely a control circuit 2 in response to a temperature sensing means, namely a temperature sensor 3 which monitors the temperature of the fuel gas powered appliance. The control circuit 2 will be described in detail below with reference to Fig. 4.

The valve 1 comprises a housing which in this embodiment of the invention is formed by an elongated sleeve 5 which defines a hollow interior region 6, namely, an elongated bore of circular transverse cross-section, and which also defines a longitudinally extending central axis 7. The sleeve 5 is of a non-magnetic material and is closed by a pair of end caps 8 and 9 at respective axially opposite ends. The end caps 8 and 9 are of magnetic material. A fuel gas inlet 10 is provided in the end cap 8 for accommodating fuel gas into the hollow interior region 6 from the fuel gas source, and a fuel gas outlet 12 is located in the end cap 9 for accommodating fuel gas from the hollow interior region 6 to the fuel gas appliance.

An elongated valving member 15 of magnetic material of circular transverse cross- section is centrally located in the hollow interior region 6, and defines with the sleeve 5 a fuel gas passageway through the hollow interior region 6 from the inlet 10 to the

outlet 12. The valving member 15 is slideable longitudinally along the central axis 7 between a first position illustrated in Fig. 2 which in this case is a closed position, with the valving member 15 closing the outlet 12, and a second position, namely an open position illustrated in Fig. 3 with the valving member 15 spaced apart from the outlet 12 for facilitating passage of fuel gas through the hollow interior region 6 from the inlet 10 to the outlet 12. The outlet 12 defines a valve seat 16, and a sealing member 17 provided by a pad of silicone rubber is located and secured in the end of the valving member 15 for sealably engaging the valve seat 16 when the valving member 15 is in the closed position.

A main magnet means, namely, a pair of main permanent magnets 20 is mounted externally on the sleeve 5 substantially half way between the end caps 8 and 9 for alternately retaining the sleeve 5 in the open and in the closed positions as will be described below. The permanent magnets 20 are located on diametrically opposite sides of the sleeve 5, and are separated by an air gap 21. A yoke 25 of magnetic material comprises a pair of transverse end members 26 jointed by side members 27 which extend on opposite sides of the sleeve 5. The end members 26 are in engagement with the corresponding end caps 8 and 9, and the side members 27 are in engagement with the corresponding permanent magnets 20. Thus, the yoke 25 effectively forms a pair of U-shaped members which connect the permanent magnets 20 to the respective end caps 8 and 9 for forming a flux path means, namely, two flux paths, which are each formed by respective pairs of flux loops 24a and 24b, see Fig. 2. The permanent magnets 20 are magnetised in a transverse direction relative to the direction of movement of the valving member 15 between the respective open and closed positions. In other words, the permanent magnets 20 are magnetised in a radial direction relative to the central axis 7 defined by the sleeve 5.

In this case the north poles of the respective magnets 20 abut the side members 27 of the yoke 25, and the south poles abut the sleeve 5. Thus, the flux loops 24 pass through the valving member 15, the end caps 8 and 9 and the end and side members 26 and 27 of the yokes 25 for accommodating magnetic flux from the permanent magnets 20 through the valving member 15, the end caps 8 and 9 and the end and side members 26 and 27, respectively.

The vaiving member 15 is in the shape of an elongated spindle, the ends of which are shaped at 30 for engaging corresponding recesses 31 in the adjacent end cap 8 or 9, so that when the valving member 15 is in either one of the closed and open positions one of the pairs of flux loops 24a and 24b is closed by the valving member 15 engaging the adjacent end cap 8 or 9, while the other of the pair of flux loops 24a and 24b is open by virtue of the valving member 15 being spaced apart from the adjacent end cap 8 or 9 and an air gap being formed therebetween. In this way, the magnetic force of the permanent magnets 20 acting on the valving member 15 for urging the valving member 15 and retaining the valving member 15 in engagement with the end cap 8 or 9 with which it is engaged is greater than the magnetic force of the permanent magnets 20 acting in the opposite direction, and therefore, once the valving member 15 is in engagement with one of the end caps 8 or 9, the magnetic force of the permanent magnets 20 retains the valving member 15 in engagement with that end cap 8 or 9. A plurality of radially axially extending slots 32, only one of which is illustrated in Figs. 2 and 3 extend in the end cap 8 from the fluid inlet 10 for accommodating fuel gas into the hollow interior region 6 from the fuel gas inlet 10 passed the tapered portion 30 of the valving member 15 when the valving member 15 is in the open position engaged with the recess 31 in the end cap 8.

A pair of secondary magnet means, namely, secondary electro-magnets 35a and 35b are mounted on the sleeve 5 between the main permanent magnets 20 and the respective end caps 8 and 9 within the yoke 25 for co-operating with the permanent magnets 20 for altering the magnetic flux in the respective pairs of flux loops 24a and 24b for urging the valving member 15 from either one of the open and closed positions to the other. Each electro-magnet 35 comprises a former 36 which extends around the sleeve 5, and is c-axial with the axis 7 of the sleeve 5. Electro- magnet coils 37a and 37b are wound on the respective formers 36, and are powered under the control of the control circuit 2. The electro-magnet coils 37 are wound on the respective formers 36 so that when the two electro-magnet coils 37 are simultaneously powered by a DC pulse signal going in one direction one of the electro-magnets 35 generates a magnetic field, the flux of which acts in the opposite direction to that of the permanent magnets 20 acting in the corresponding pair of flux loops 24a or 24b for reducing the magnetic force retaining the valving member 15 in

the one of the open and closed positions, while the other electro-magnet 35 generates a magnetic field, the flux of which acts in co-operation with that of the permanent magnets 20 in the corresponding pair of flux loops 24a or 24b, for increasing the magnetic force acting on the valving member 15 for urging the valving member from the one of the open and closed positions to the other of the open and closed positions. In other words, when the valving member 15 is in the closed position as illustrated in Fig. 2 and it is desired to urge the valving member 15 into the open position, the direction of the DC pulse signal in the electro-magnet coils 37a and 37b is such that the electro-magnet 35a adjacent the end cap 9 reduces the force of the magnetic field in the flux loops 24a acting through the valving member 15 and the end cap 9 for reducing the force which is retaining the valving member 15 in the closed position. The electro-magnet 35b adjacent the end cap 8, on the other hand, acts to increase the force of the magnetic field in the flux loops 24b acting through the valving member 15 and the end cap 8 for increasing the magnetic force for urging the valving member 15 into the open position. In other words, the sum of the magnetic forces, namely, the magnetic force of the permanent magnets 20 and that of the electro-magnet 35b act together to urge the vaiving member 15 into the open position, while the magnetic forces of the permanent magnets 20 and the electro-magnet 35a act to cancel each other out or to reduce the magnetic force retaining the valving member 15 in the closed position. Thus, the resultant force of the magnetic forces acting on the valving member 15 urges the valving member 15 into the open position. Once in the open position, the flux loops 24a through the valving member 15 and the end cap 8 are closed, and thereby the magnetic force of the permanent magnets 20 retains the vaiving member 15 in the open position. To return the valving member from the open to the closed position a DC pulse signal going in the opposite direction is applied to the electro-magnets 35 by the control circuit 2.

Turning now to the control circuit 2, a battery B1 powers the control circuit 2 and a micro-processor IC1 through a power supply circuit IC2. The micro-processor IC1 controls the operation of the control circuit 2 in response to the temperature sensor 3. Transistors TR1 to TR4 under the control of the micro-processor IC1 apply the DC pulse signals simultaneously to the coils 37a and 37b as will be described below.

In order to urge the valving member 15 from the closed to the open position a positive going DC pulse is applied to the coil 37a and 37b. Thus, with the transistors TR1 and TR4 switched off the micro-processor IC1 switches on the transistors TR1 and TR3 for an appropriate pulse time period for applying the positive going pulse to the coils 37a and 37b. To return the valving member 15 from the open to the closed position the direction of the pulse signal applied to the coils 37a and 37b are reversed by switching on the transistors TR2 and TR4 for the appropriate pulse time period. The length of the DC pulses required are of relatively short duration, and typically of the order of 200 micro-seconds. The voltage of the DC pulses is determined by the voltage rating of the respective eiectro-magnet coils 37a and 37b.

In use, the micro-controller IC1 reads the temperature of the appliance from the temperature sensor 3. For so long as the temperature of the appliance remains below a pre-determined temperature, which may be set or preset in the micro- controller IC1 the valving member 15 is retained in the open position by the magnetic force of the permanent magnets 20. On the micro-processor IC1 determining that the temperature sensed by the temperature sensor 3 has exceeded the predetermined temperature the transistors TR1 and TR3 are switched for applying a DC pulse simultaneously to the coils 37 of the electro-magnets 35. Thereby urging the valving member 15 into the closed position, and the valving member 15 is retained in the closed position by the magnetic force of the permanent magnets 20. On the temperature of the appliance dropping below the predetermined temperature the micro-controller IC1 switches the transistors TR2 and TR4 for applying a DC pulse signal simultaneously to the respective coils 37 of the electro-magnets 35 for urging the valving member 15 into the open position.

Referring now to Fig. 5 there is illustrated a valve according to another embodiment of the invention which is indicated generally by the reference numeral 40. The valve 40 is substantially similar to the valve 1, and similar components are identified by the same reference numeral. The main difference between the valve 40 and the valve 1 is that instead of the main magnet means being provided by a pair of main permanent magnets, two axially spaced apart pairs of main permanent magnets 41 are provided, and each pair of main permanent magnets 41 is provided with a

corresponding yoke 42. In this embodiment of the invention the permanent magnets 41 are similarily radially magnetised relative to the sleeve 5 and the valving member 15, and the north poles of the permanent magnets 41 abut the side member 27 of the yokes 42, while the south poles abut the sleeve 5. Otherwise, the valve 40 is similar to the valve 1, and its operation is likewise similar.

Referring now to Figs. 6 and 7 there is illustrated a valve 50 according to another embodiment of the invention. The valve 50 is somewhat similar to the valve 1, and similar components are identified by the same reference numerals. The main difference between the valve 50 and the valve 1 is that the main permanent magnets 20 act only to retain the valving member 15 in the closed position. A retaining means, namely, a compression spring 52 is located within the hollow interior region 6 for urging and retaining the valving member 15 in the open position. The compression spring 52 extends around the valving member 15, and acts between the end cap 9 and a shoulder 53 on the valving member 15.

Operation of the valve 50 is substantially similar to that of the valve 1. When the valving member 15 is in the closed position it is retained in the closed position by the magnetic force of the permanent magnets 20 through the flux loops 24. When it is desired to urge the valving member 15 from the closed to the open position, a positive going DC pulse is applied to the coil 37 of the electro-magnet 35. This generates a magnetic field which acts in the opposite direction to that of the permanent magnets 20 and thereby reduces or neutralises the magnetic force acting through the flux loops 24 so that the compression spring 52 urges the valving member 15 into the open position. Once the valving member 15 is in the open position the flux loops 24 are broken by an air gap between the valving member 15 and the end cap 9, and thus the magnetic force in the flux loops 24 caused by the permanent magnets 20 which acts to urge the valving member into the closed position is reduced. In this way the force in the compression spring 52 is sufficient to retain the valving member 15 in the open position against the magnetic force of the permanent magnets 20. When it is desired to urge the valving member 15 into the closed position a negative going pulse signal is applied to the coil 37 of the electro- magnet 35 for generating a magnetic field which co-operates with that of the

permanent magnets 20. The combined effect of the two magnetic fields is sufficient to overcome the compressive force of the compression spring 52 for in turn urging the valving member 15 into the closed position. Once in the closed position the flux path between the valving member 15 and the end cap 9 is closed, and thus, the force of the permanent magnets 20 urging the va !ving member 15 into the closed position is sufficient to overcome the opposite compressive force of the spring 52, and thus the valving member 15 is retained in the closed position by the permanent magnets 20.

Referring now to Figs. 8 to 10, there is illustrated a valve 55 according to a further embodiment of the invention. The valve 55 is substantially similar to the valve 1, with the exception that in this embodiment of the invention the main magnet means comprises a ring shaped permanent magnet 56 which extends circumferentially around the sleeve 5. The permanent magnet 56 is of a flexible polymer material having a plurality of magnetic particles suspended therein and magnetised to form a permanent magnet. The circular magnet 56 is magnetised in a radial direction from its inner circumferential surface to its outer circumferential surface for forming the flux loops 24a and 24b. In this embodiment of the invention the inner circumferential surface of the permanent magnet 56 forms a south pole in engagement with the sleeve 5, and the outer circumferential surface of the permanent magnet 56 forms a north pole which is in engagement with the side members 27 of the yoke 25. In order to provide effective flux loops 24, the side members 27 are shaped to be in engagement with the outer circumferential surface of the permanent magnet 56 over the width of the side members 27, as can be see in particular in Fig. 10. Otherwise the valve 55 and is operation is similar to the valve 1.

Referring now to Fig. 11 there is illustrated a soldering tool according to the invention indicated generally by the reference numeral 60 which incorporates the valve 1. The soldering tool 60 comprises a housing 61 illustrated in broken lines and a soldering tool tip 62 which is carried on the housing 61. Part of the housing 61 forms a handle for holding the soldering tool 60. The construction and shape of such soldering tools will be well known to those skilled in the art, and a typical soldering tool is illustrated in European Patent Specification No. EP-A-0,118,282 of Oglesby & Butler

Technology Limited. The soldering tool tip 62 is heated by a gas catalytic combustion element (not shown) which is located in a combustion chamber 63 in the tool tip 62. Fuel gas 64 is stored in liquid form in a reservoir 64 in the housing 61 and is fed from the reservoir 64 through a pressure regulator 65 and a thumb operated on/off switch to the valve 1 illustrated in Figs. 1 to 4. However, the valve 1 may be replace by the valve 40, the valve 50 or the valve 55. The fuel gas is then fed to a venturi mixer 68 where it is mixed with air and fed to the gas catalytic combustion element (not shown) in the combustion chamber 63. The control circuit 2 is located in the housing 61 and is responsive to the temperature sensor 3 which is located in the soldering tool tip 62 for operating the valve 1 for in turn controlling the fuel gas supply to the gas catalytic combustion element (not shown) in the combustion chamber 63. Thus, the control circuit 2 operates the valve 1 in the open position until the temperature sensed by the temperature sensor 3 exceeds the desired predetermined operating temperature of the soldering tool tip 62. On the predetermined temperature being exceeded by the soldering tool tip 62 the control circuit 2 operates the valve 1 for isolating the fuel gas supply from the catalytic combustion element until the temperature of the soldering tool tip 62 drops below the predetermined temperature, at which stage the valve 1 is operated in the open position.

It is envisaged that the valve 1 may be bypassed by a restricted flow of fuel gas for maintaining a supply of fuel gas to the gas catalytic combustion element (not shown) in the combustion chamber 63 for preventing extinguishing of the gas catalytic combustion element while the valve 1 is operated in the off position by the control circuit 2.

Referring now to Fig. 12 there is illustrated a hot melt glue gun also according to the invention indicated generally by the reference numeral 70, which incorporates the valve 1. The glue gun 70 comprises a housing 71 illustrated in broken lines, and a heated tip portion 72 extending from the housing 71 having a bore 73 extending therefrom for accommodating a stick of hot melt glue for melting therein. Melted glue is extruded through a nozzle 74 extending from the bore 73. The tip portion 72 is heated by a gas catalytic combustion element (not shown) in a combustion chamber

75 which is supplied by gas from a reservoir 76 located in the housing 71. Fuel gas from the reservoir 76 is fed through a pressure regulator 77, a thumb operated on/off switch 78, the valve 1 and a venturi mixer 79 where the fuel gas is mixed with air prior to delivery to the combustion chamber 75. The valve 1 may be replaced with the valve 40, the valve 50 or the valve 55. The control circuit 2 in the housing 71 is responsive to the temperature sensor 3 which is located in the tip portion 72 for controlling the valve 1. The housing is provided with a handgrip, and the construction of such glue guns and housings will be well known to those skilled in the art.

Operation of the glue gun 70 is substantially similar to that of the soldering tool 60 and will be well known to those skilled in the art.

While in the embodiments of the invention described the valves 1,40,50 and 55 have been described as isolating the inlet from the outlet when the valve is the closed position, and thus, no fluid flow is permitted through the valves when the valving member is in the closed position, it is envisaged in certain cases, that the valving member may co-operate with the fluid inlet or the fluid outlet, as the case may be so as not to entirely close off the inlet or the outlet. For example, it is envisaged that either the valve seat, or the valving member or the seal of the valving member may be so shaped as to permit a restricted flow of fluid therethrough when the valving member is in the closed position. Alternatively, a bypass could be provided within the valve or external thereto which would bypass the valve seat in the inlet or outlet, as the case may be.

It will of course be appreciated that while the secondary magnet means has been described as being provided by an electro-magnet for each flux path, any other suitable secondary magnet means could be provided. In particular, it will be appreciated that instead of each electro-magnet being provided with a single coil, each electro-magnet could be provided with double coils which would be wound in opposite directions and the respective coils of each electro-magnet could then be selectively powered for alternately urging the valving member between the first and second positions.

It will also be appreciated that while the main magnet means has been described with reference to the valves of Figs. 1 to 7 as comprising a pair of permanent magnets or pairs of permanent magnets, one single permanent magnet would be sufficient, and while it is preferable that each permanent magnet be magnetised in a radial direction relative to the central axis of the valve, it is envisaged in certain cases that the permanent magnet or permanent magnets may be magnetised in a direction parallel to the central axis of the valves.

It is also envisaged that the main magnet means may be provided by magnet means other than permanent magnets, for example, by a main electro-magnet or electro- magnets.

It will be appreciated that while the circuit diagram of Fig. 4 illustrates two integrated circuits, namely, IC1 which is the micro-processor, and the power supply circuit IC2 which is the power supply, it will be appreciated that the power supply integrated circuit may be omitted, and in certain cases, may be incorporated in the micro- controller, or may be provided by any other suitable power supply.

It will also be appreciated that any other suitable power source besides a battery may be provided, for example, a thermo-electric generator, or any other suitable source. Indeed, in certain cases it is envisaged that the power source may be provided by a mains electricity supply.

It will also be appreciated that a visual display, for example, a digital visual display may be provided for indicating the actual operating temperature of the appliance. tt will be appreciated that the valve according to the invention may be used for regulating the flow of or isolating any fluid, liquid or gas or any material with flowable fluid-like characteristics, such as particulate or granular material.

It is envisaged that the valve may be manufactured from any other suitable materials besides those described.

Indeed, it is envisaged that while the valves 1,40,50 and 55 have been described for use in a soldering iron and a glue gun, the valves may be used in any other gas powered appliance, and it is envisaged that as well as being provided for controlling the temperature of operation of the devices, the valves 1,40,50 and 55 may be used as on/off valves, in which case, the valves would be operated from an electrically input to the control circuit, typically, from an on/off push button electric switch.

Furthermore, the valves may be operated in response to any other parameter besides temperature, for example, time, pressure, volume, liquid level, flow rate and the like.

The valves according to the invention may be used for many uses besides controlling the supply of fuel gas to a soldering iron or a glue gun, for example, the valves may be provided for controlling the supply of fuel gas to gas cookers, to gas powered central heating boilers, to gas powered water heaters, for example, multipoint water heaters, flash boilers for water heating and balanced flue boilers.