Gas powered heating devices, for example, gas powered soldering irons, gas powered glue guns which incorporate a catalytic converting device for converting fuel gas to heat for in turn working solder, or melting glue, are well known. For example, such a gas powered soldering tool is disclosed in European Patent Specification No. 0,118, 282. Published PCT Patent Application No. WO 01/07173 discloses a glue gun whereby fuel gas is converted to heat by catalytic reaction for melting glue. Typically, the converting device for converting fuel gas to heat in such devices comprises a body member of heat conducting material within which a combustion chamber is formed. A gas catalytic combustion element is located in the combustion chamber, and fuel gas delivered into the combustion chamber is converted to heat by the gas catalytic combustion element, once the combustion element has been raised to its ignition temperature. The heat from the catalytic conversion is radiated into the body member, which in turn transfers the heat to a soldering tool bit, or to a glue melting chamber. Commonly the gas catalytic combustion element comprises a carrier, which is formed by a fibrous element, and the fibres of the fibrous element are coated with a catalytic composition. Retaining such fibrous elements correctly positioned in the combustion chamber can be difficult, and additionally, the fibres tend to deteriorate, which eventually leads to disintegration of the fibrous element and in turn disintegration of the catalytic combustion element.

Catalytic combustion elements which comprise a metal carrier coated with a catalytic composition are also known. Such catalytic combustion elements may comprise a mesh carrier or a sheet carrier which is perforated. Expanded metal mesh may also

be used as a carrier. However, even distribution of fuel gas over the major surfaces of catalytic combustion elements which comprise such a metal carrier can in many cases be difficult. The problem of achieving even distribution of the fuel gas over the major surfaces of the catalytic combustion element arises in particular where the combustion chamber is formed by a bore, and in particular, a circular bore and the catalyst is of arcuate or tubular construction, and located coaxially in the bore. In such cases, it can be difficult to maintain even distribution of the fuel gas over both major surfaces of the carrier of the catalytic combustion element.

There is therefore a need for a converting device for use in a gas powered heating device for catalytically converting fuel gas to heat, which addresses the problems of known converting devices.

The present invention is directed towards providing such a converting device and a gas powered heating device which incorporates the converting device.

According to the invention there is provided a converting device for converting fuel gas to heat, the converting device comprising a body member having a combustion chamber formed therein and a side wall formed by the body member having an inner surface forming at least a portion of the combustion chamber, a fuel gas inlet to the combustion chamber for delivering fuel gas to the combustion chamber, an exhaust port from the combustion chamber through which exhaust gases are delivered from the combustion chamber, and a gas catalytic combustion element located in the combustion chamber for converting fuel gas to heat, wherein the gas catalytic combustion element comprises a perforated carrier coated with a gas catalytic composition, the gas catalytic combustion element having first and second major surfaces, and being located in the combustion chamber with the first major surface facing the inner surface of the side wall formed by the body member, and a first spacing means being provided for spacing portions of the first major surface of the gas catalytic combustion element from the inner surface of the side wall for facilitating the passage of fuel gas between the first major surface of the catalytic combustion element and the inner surface of the side wall.

Preferably, the first spacing means is formed in the carrier of the gas catalytic combustion element. Advantageously, the first spacing means is formed by an inherent part of the carrier of the gas catalytic combustion element.

In one embodiment of the invention the first spacing means comprises a plurality of spaced apart first protuberances extending from the first major surface of the gas catalytic combustion element for engaging the inner surface of the side wall.

Preferably, the first protuberances are formed in the carrier of the gas catalytic combustion element by punching. Advantageously, the perforations are formed in the respective first protuberances.

Ideally, each first protuberance terminates in a corresponding perforation.

In one embodiment of the invention the carrier of the gas catalytic combustion element is formed of sheet metal.

In one embodiment of the invention a retaining means is provided for retaining the gas catalytic combustion element in position in the combustion chamber with the first major surface of the gas catalytic combustion element facing the side wall and spaced apart therefrom by the first spacing means. Preferably, the retaining means retains the catalytic combustion element in position with the first spacing means engaging the inner surface of the side wall formed by the body member.

In one embodiment of the invention the retaining means is located adjacent the second surface of the catalytic combustion element and is spaced apart therefrom by a second spacing means. Preferably, the second spacing means is formed in the retaining means. Advantageously, the second spacing means is formed by an inherent part of the retaining means.

In one embodiment of the invention the retaining means is of sheet material.

In another embodiment of the invention the second spacing means comprises a plurality of second protuberances extending from the retaining means for engaging the second major surface of the gas catalytic combustion element.

In a further embodiment of the invention the sheet material of the retaining means is perforated.

Preferably, perforations are formed in the respective second protuberances.

Advantageously, each second protuberance terminates in a perforation.

In another embodiment of the invention the retaining means is of mesh material.

In a further embodiment of the invention the retaining means is formed of expanded sheet material.

Preferably, the retaining means is of metal.

In one embodiment of the invention the combustion chamber is formed by an elongated main bore extending into the body member and defining a longitudinally extending main central axis, the side wall formed by the body member extending around the main bore for forming the combustion chamber.

Preferably, the carrier of the gas catalytic combustion element is of arcuate shape.

Advantageously, the carrier of the gas catalytic combustion element defines a longitudinally extending axis of generation, and the carrier is located in the combustion chamber with the axis of generation of the carrier substantially coinciding with the main central axis.

In another embodiment of the invention the carrier of the gas catalytic combustion element is of tubular shape defining a longitudinally extending central axis.

Preferably, the central axis of the carrier of the gas catalytic combustion element

substantially coincides with the main central axis of the main bore defining the combustion chamber. Advantageously, the carrier of the gas catalytic combustion element is split longitudinally along one side thereof. Ideally, the carrier of the gas catalytic combustion element is of circular transverse cross-section.

In one embodiment of the invention the main bore forming the combustion chamber is of circular transverse cross-section.

In another embodiment of the invention a secondary bore extends into the body member from the combustion chamber for locating a distribution means in the combustion chamber for distributing fuel gas to the gas catalytic combustion element.

Preferably, the secondary bore defines a secondary central axis which extends parallel to the main central axis. Advantageously, the secondary central axis extends coaxially with the main central axis.

In one embodiment of the invention the transverse cross-section of a portion of the distribution means which extends into the secondary bore is of transverse cross- sectional area less than the transverse cross-sectional area of the secondary bore for accommodating the passage of gases into and out of the secondary bore for facilitating expansion and contraction of the gases therein.

Preferably, the distribution means is located coaxially in the main bore forming the combustion chamber. Advantageously, the distribution means comprises an elongated flat distribution member for distributing fuel gas to the gas catalytic combustion element on respective opposite sides thereof. Ideally, the distribution means extends substantially the length of the main bore forming the combustion chamber.

In one embodiment of the invention the fuel gas inlet is provided by an inlet port, which is located coaxially with the main central axis. Preferably, the distribution

means extends into the inlet port for facilitating distribution of the fuel gas on respective opposite sides of the distribution means. Advantageously, the distribution means is of heat conducting material for conducting heat from the combustion chamber into the body member.

In one embodiment of the invention the retaining means is formed by a tubular member. Advantageously, the retaining means is coaxially located in the main bore forming the combustion chamber. Preferably, the retaining means is split longitudinally along one side thereof. Advantageously, the retaining means is of circular transverse cross-section. Ideally, the retaining means is of resilient material for resiliently urging the gas catalytic combustion element into position in the combustion chamber.

In one embodiment of the invention the exhaust port is formed in the side wall formed by the body member, and is located in the side wall for exposing a portion of the first major surface of the catalytic combustion element, the area of the exhaust port relative to the thickness of the side wall adjacent the exhaust port being such as to permit the root of a flame resulting from flame combustion of the fuel gas exiting through the exhaust port prior to the temperature of the gas catalytic combustion element being raised to its ignition temperature to sit adjacent the first major surface of the gas catalytic combustion element exposed by the exhaust port for raising the temperature of the gas catalytic combustion element to its ignition temperature for initiating catalytic combustion therein.

Preferably, the area of the exhaust port is a function of the thickness of the side wall adjacent the exhaust port. Advantageously, the exhaust port is of circular area, having a diameter which is at least four times the thickness of the side wall adjacent the exhaust port. Ideally, the diameter of the exhaust port is at least six times the thickness of the side wall adjacent the exhaust port, and preferably, the diameter of the exhaust port is at least eight times the thickness of the side wall adjacent the exhaust port.

In one embodiment of the invention the area of the exhaust port is selected so that the flow rate of fuel gas through the exhaust port is such as to permit the root of the flame resulting from flame ignition, prior to the temperature of the gas catalytic combustion element being raised to its ignition temperature, to sit adjacent the first major surface of the gas catalytic combustion element exposed by the exhaust port.

Preferably, the side wall formed by the body member is cylindrical. Ideally, the body member is of heat conducting material.

In one embodiment of the invention a fuel gas supply pipe extends from the fuel gas inlet for supplying fuel gas to the combustion chamber.

In another embodiment of the invention a restrictor is located in the fuel gas supply pipe for restricting the flow of fuel gas therethrough. Preferably, the restrictor acts as a venturi mixer for mixing air with the fuel gas.

In one embodiment of the invention a tool bit extends from the body member.

In another embodiment of the invention the tool bit is a soldering tool bit.

In a further embodiment of the invention the tool bit is a knife.

The invention also provides a gas powered heating device comprising the converting device according to the invention for converting fuel gas to heat. In one embodiment of the invention a fuel gas supply means is provided for supplying fuel gas to the converting device.

Preferably, the fuel gas supply means comprises a fuel gas reservoir.

Advantageously, the fuel gas supply means comprises a control means for controlling the supply of fuel gas to the converting device. Ideally, the converting device is coupled to the fuel gas supply means by a fuel gas supply pipe.

Ideally, the gas powered heating device is a portable device.

In one embodiment of the invention the gas powered heating device is a gas powered heating tool.

In one embodiment of the invention the gas powered heating tool is a soldering iron.

In another embodiment of the invention the gas powered heating tool is a glue gun.

In a still further embodiment of the invention the gas powered heating tool is a heated knife.

The invention further provides a soldering tip for a gas powered soldering iron, the soldering tip comprising the converting device according to the invention.

The advantages of the invention are many. By virtue of the fact that portions of the catalytic combustion element are spaced apart from the side wall formed by the body member, fuel gas can readily pass between the catalytic combustion element and the side wall of the body member, and thus fuel gas is relatively evenly distributed over the first major surface of the catalytic combustion element. This, thus, significantly facilitates conversion of the fuel gas to heat, and in particular, significantly increases the efficiency of the conversion of the fuel gas to heat. Where the carrier of the catalytic combustion element is coated with the catalyst composition on its respective first and second major surfaces, a substantially even distribution of fuel gas is achieved over the respective first and second major surfaces, and thus, efficient conversion of the fuel gas to heat is achieved with virtually no slip of the fuel gas.

By providing a retaining means for retaining and positioning the catalytic combustion element in the combustion chamber, the catalytic combustion element is positively located in the combustion chamber and this, thus, further facilitates the even distribution of fuel gas over the respective first and second major surfaces of the

catalytic combustion element.

By providing the second spacing means for spacing the retaining means from the catalytic combustion element, even distribution of fuel gas over the second major surface of the catalytic combustion element is further enhanced. By locating the catalytic combustion element adjacent the exhaust port, and by appropriately sizing the exhaust port relative to the thickness of the side wall adjacent the exhaust port, the catalytic combustion element can be relatively rapidly and efficiently raised to its ignition temperature by flame ignition of the fuel gas exiting through the exhaust port.

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 gas powered soldering iron according to the invention, which incorporates a converting device also according to the invention for catalytically converting fuel gas to heat, Fig. 2 is a front elevational view of a soldering tip of the soldering iron of Fig.

1, which incorporates the converting device according to the invention, Fig. 3 is an exploded front elevational view of the soldering tip of Fig. 2, Fig. 4 is an exploded side elevational view of the soldering tip of Fig. 2, Fig. 5 is a transverse cross-sectional underneath plan view of the soldering tip of Fig. 2 on the line V-V of Fig. 2, Fig. 6 is a schematic transverse cross-sectional rear elevational view of a portion of the soldering tip of Fig. 2 on the line VI-VI of Fig. 5, Fig. 7 is a schematic transverse cross-sectional side elevational view of a

portion of the soldering tip of Fig. 2 on the line VII-VII of Fig. 5, Fig. 8 is a perspective view of a portion of the soldering tip of Fig. 2, Fig. 9 is another perspective view of the portion of Fig. 8 of the soldering tip of Fig. 2, Fig. 10 is a perspective view of another portion of the soldering tip of Fig. 2, Fig. 11 is a transverse cross-sectional side elevational view of another portion of the soldering tip of Fig. 2 on the line XI-XI of Fig. 2, Fig. 12 is a transverse cross-sectional underneath plan view, similar to the plan view of Fig. 5, of a soldering tip according to another embodiment of the invention, and Fig. 13 is a perspective view of a portion of the soldering tip of Fig. 12.

Referring to the drawings and initially to Figs. 1 to 11, there is illustrated a gas powered heating device according to the invention, which in this case is a gas powered soldering iron, indicated generally by the reference numeral 1. The gas powered soldering iron 1 is somewhat similar to a gas powered soldering iron disclosed in European Patent Specification No. 0,118, 282, and accordingly, only those parts of the soldering iron 1 which are relevant to the present invention will be described in detail. The soldering iron 1 comprises a handle 2 and a soldering tip 3 also according to the invention coupled to the handle 2 by a gas supply pipe 4. In this embodiment of the invention the soldering tip 3 is carried solely on the fuel gas supply pipe 4. The handle 2 is formed by a cylindrical housing 5 of plastics material and houses a rechargeable fuel gas reservoir (not shown), as well as fuel gas control valves (not shown) and a venturi mixer (not shown) for mixing fuel gas with air for supplying a fuel gas/air mixture to the soldering tip 3 through the fuel gas supply pipe 4. The reservoir, the control valves and venturi mixer, none of which are

shown, are substantially similar to those of the soldering iron described in European Patent Specification No. 0,118, 282, and further description should not be required.

A thumb switch 6 located in the housing 5 is operably coupled to an appropriate one of the valves (not shown) for selectively supplying fuel gas from the reservoir (not shown) to the soldering tip 3. A regulator control knob 7 located at an end of the housing 5 is also operably coupled to an appropriate one of the valves (not shown) for regulating the pressure of the fuel gas supply from the reservoir (not shown).

The thumb switch 6 and the control knob 7 are substantially similar to those of the soldering iron disclosed in European Patent Specification No. 0,118, 282, and their operation is also substantially similar.

The soldering tip 3 is formed by a body member 10 of heat conducting material, in this embodiment of the invention nickel plated brass. The body member 10 forms a converting device also according to the invention and indicated generally by the reference numeral 11 for converting a fuel gas/air mixture supplied through the fuel gas supply pipe 4 to heat by a catalytic reaction as will be described below for heating the body member 10 and in turn a soldering tool bit 13, which is integrally formed with and extends from the body member 10. A main bore 12 of circular transverse cross-section extends into the body member 10 for forming a combustion chamber 14 of the converting device 11, within which the fuel gas/air mixture from the gas supply pipe 4 is converted to heat. A cylindrical side wall 15 formed by the body member 10, and forming a part of the converting device 11, extends around the combustion chamber 14, and defines a main central axis 16 which extends coaxially through the main bore 12. An end plug 18 closes an end 19 of the main bore 12. An inlet port 20 is formed centrally in the end plug 18 coaxially with the main central axis 16 for accommodating the fuel gas/air mixture from the gas supply pipe 4 into the combustion chamber 14. The gas supply pipe 4 is secured to the soldering tip 3 in the inlet port 20, and is secured to the handle 2 by a gland nut 21 for coupling and carrying the soldering tip 3 on the handle 2. An exhaust port 23 in the side wall 15 accommodates exhaust gases from the combustion chamber 14. The soldering tool bit 13 extends from the body member 10 coaxially with the main central axis 16.

A gas catalytic combustion element 30 is located in the combustion chamber 14 for converting the fuel gas/air mixture to heat on the catalytic combustion element 30 being raised to its ignition temperature as will be described in more detail below.

The gas catalytic combustion element 30 comprises a carrier 31 of heat conductive material, in this case a perforated metal sheet of steel and aluminium alloy, which is ceramic coated prior to being coated with a precious metal catalytic composition.

The carrier 31 is of arcuate shape, and in this embodiment of the invention is of semi-cylindrical shape, having a first major surface 33 and a second major surface 34. The carrier 31 defines a longitudinally extending axis of generation, and is located in the combustion chamber 14 with its axis of generation coinciding with the main central axis 16, and with the first major surface 237 which forms the outer surface of the carrier 31 facing an inner surface 37 of the side wall 15. A substantial portion of the first major surface 33 of the carrier 31 is spaced apart from the inner surface 37 of the side wall 15 for facilitating passage of the fuel gas/air mixture between the inner surface 37 of the side wall 15 and the first major surface 33 of the carrier 31 so that the fuel gas/air mixture passes along the first major surface 33 and is relatively evenly distributed over the first major surface 33 for conversion to heat.

A first spacing means comprising a plurality of first protuberances 38 are formed in the carrier 31 and extend from the first major surface 33 for engaging the inner surface 37 of the side wall 15 for spacing the substantial portion of the first major surface 33 from the inner surface 37. The first protuberances 38 are inherently formed in the carrier 31, and each first protuberance 38 terminates in a perforation 39. The periphery of each of the first protuberances 38 which define the perforations 39 is irregular for accommodating the passage of the fuel gas/air mixture through the catalytic combustion element 30 between the first and second major surfaces 33 and 34. In this embodiment of the invention the depth of each first protuberance d is approximately 0.2mm. This, it has been found, is sufficient for facilitating the flow of the fuel gas/air mixture between the side wall 15 and the gas catalytic combustion element 30, and for providing a relatively even distribution of the fuel gas/air mixture over the first major surface 33 of the gas catalytic combustion element 30. The diameter of the first protuberances 38 adjacent the root thereof is approximately

1 mm, and in this embodiment of the invention the first protuberances 38 are provided at a density of 30 perforations per cm2.

A retaining means for positioning and retaining the catalytic combustion element 30 in the combustion chamber 14 comprises a tubular retaining member 40. The retaining member 40 in this embodiment of the invention is formed from a resilient perforated metal sheet 41, with similar perforations to those of the carrier 31. The metal sheet 41 has a first major surface 43 and a second major surface 44, and is bent to form the tubular retaining member 40 of circular transverse cross-section with a longitudinal extending slit 42. The retaining member 40 defines a central longitudinally extending central axis which coincides with the main central axis 16.

A second spacing means comprising a plurality of second protuberances 45 extending from the first major surface 43 engage the second major surface 34 of the catalytic combustion element 30 for spacing the retaining member 40 from the catalytic combustion element 30 for facilitating the passage of the fuel gas/air mixture between the retaining member 40 and the catalytic combustion element 30, and for facilitating a relatively even distribution of the fuel gas/air mixture over the second major surface 34 of the catalytic combustion element 30. The second protuberances 45 are inherently formed in the metal sheet 41 by punching, and are of similar dimensions to the first protuberances 38, are provided at a similar density to that of the first protuberances 38, and each terminates in a perforation 46. The periphery of the perforations 46 defined by the second protuberances 45 is irregular for facilitating the passage of the fuel gas/air mixture through the retaining member 40 from the first major surface 43 to the second major surface 44 for further facilitating a relatively even distribution of the fuel gas/air mixture over the second major surface 34 of the catalytic combustion element 30.

The retaining member 40 being resilient urges the catalytic combustion element 30 towards the side wall 15 with the first protuberances 38 engaging the inner surface 37 of the side wall 15. Additionally, the retaining member 40 locates the catalytic combustion element 30 adjacent the exhaust port 23 so that the catalytic combustion

element 30 extends completely across the exhaust port 23.

A fuel gas distribution means comprising a flat distribution member 48 of heat conductive material, in this case flat stock steel extends centrally through the combustion chamber 14 for distributing the fuel gas/air mixture on its respective opposite sides to the catalytic combustion element 30. A first flat plug member 50 extends from one end of the distribution member 48, and is engaged in a secondary bore 51 of circular transverse cross-section which extends into the body member 10 from the main bore 12, and is coaxial therewith for locating one end of the distribution member 48 in the combustion chamber 14. A second plug member 52 extending from the other end of the distribution member 48 engages the fuel gas supply pipe 4. Since the second plug member 52 is of substantially rectangular transverse cross-section, the fuel gas/air mixture from the fuel gas supply pipe 4 is accommodated between the second plug member 52 and the fuel gas supply pipe 4.

The first plug member 50 being of substantially rectangular transverse cross-section accommodates gases into and out of the secondary bore 51 for facilitating expansion and contraction of the gases in the secondary bore 51.

As well as the distribution member 48 distributing the fuel gas/air mixture in the combustion chamber 14 to the catalytic combustion element 30, the distribution member 48 also conducts heat radiated by the catalytic combustion element 30 into the body member 10.

In this embodiment of the invention the exhaust port 23 is of circular cross-section, and is of diameter relative to the thickness of the side wall 15 and adjacent the exhaust port 23 so that prior to the catalytic combustion element 30 reaching its ignition temperature, the fuel gas/air mixture issuing through the exhaust port 23 through the gas catalytic combustion element 30 is ignitable to burn with a flame, the root of which sits on or adjacent the first major surface 33 of the catalytic combustion element 30 in the exhaust port 23 for raising the portion of the catalytic combustion element 30 exposed by the exhaust port 23 to its ignition temperature. On reaching its ignition temperature, the catalytic combustion element 30 commences to convert

the fuel gas to heat, thus rapidly raising the remainder of the catalytic combustion element 30 to the ignition temperature so that all the fuel gas/air mixture passing through the combustion chamber 14 is converted to heat by catalytic conversion, and thus extinguishing the flame in the exhaust port 23. In this embodiment of the invention the diameter of the exhaust port 23 is approximately seven times the thickness t of the side wall 15. In this embodiment of the invention the side wall 15 is of uniform thickness t of approximately 1 mm, and the diameter (P of the exhaust port is approximately 7mm.

It has been found that if the flow rate of the fuel gas/air mixture exiting through the exhaust port 23 is too great, when burning with a flame, the flame is caused to burn with the root of the flame spaced apart from the first major surface 33 of the catalytic combustion element 30. The greater the flow rate of the fuel gas/air mixture through the exhaust port 23, the greater will be the spacing between the root of the flame and the first major surface 33 of the gas catalytic combustion element 30. The greater the spacing between the root of the flame and the gas catalytic combustion element 30, the less will be the heating effect of the flame on the gas catalytic combustion element 30, and thus the catalytic combustion element 30 will fail to reach its ignition temperature. Thus, in order to avoid this problem, it is important that the area of the exhaust port 23 should be such that the flow rate of fuel gas/air mixture through the exhaust port 23 is such that when ignited to burn in a flame externally of the exhaust port 23, the root of the flame sits on or adjacent the first major surface 33 of the catalytic combustion element 30.

A restricting means, in this embodiment of the invention a restrictor element 55, see Fig. 11, may be located in the fuel supply pipe 4 adjacent an upstream end thereof for controlling the supply of fuel gas/air mixture to the combustion chamber 14.

Depending on the heat capacity and requirement of the soldering tip 3, the restrictor element 55, if required, can be selected to have an appropriate bore size to provide the appropriate degree of restriction to the flow of the fuel gas/air mixture to the combustion chamber 14. Additionally, the restrictor element 55 acts as a venturi mixer for mixing air with the fuel gas, and in particular, for mixing additional air with a

fuel gas/air mixture being supplied to the fuel gas supply pipe 4 from the control valves (not shown) in the handle 2. This permits the soldering tip 3 to be supplied for use with different types of gas powered soldering irons, for example, soldering irons in which the ratio of fuel gas to air in the fuel gas/air mixture to the supply pipe 4 may be of a different ratio to that required by the soldering tip 3. The fuel gas control valves in certain types of soldering irons are arranged to provide a fuel gas/air mixture of fuel gas to air ratio appropriate to one particular type of catalytic combustion element, while the fuel gas control valves of other types of soldering irons may be arranged to provide a fuel gas/air mixture of a different fuel gas to air ratio for a different type of catalytic combustion element. Thus, by appropriately selecting the restrictor element 55 and the bore of the restrictor element 55, an appropriate additional amount of air may be added to the fuel gas/air mixture by the restrictor element 55. Needless to say, the fuel gas supply pipe 4 would be secured to the soldering iron so that fuel gas or a fuel gas/air mixture exiting through a nozzle (not shown) in the handle of the soldering iron would be directed into the bore of the restrictor element 55, and a supply of air would be available between the nozzle and the restrictor element 55, so that as the fuel gas or fuel gas/air mixture from the nozzle in the handle of the soldering iron is being directed into the bore of the restrictor element 55, the appropriate amount of air would be drawn in for mixing with the fuel gas or fuel gas/air mixture, and mixed therewith. Accordingly, the provision of the restrictor element 55 permits ready adaptation of the soldering tip 3 according to the invention to be suitable for soldering irons which deliver fuel gas only or a fuel gas/air mixtures of different fuel gas to air ratios. Where the soldering tip is to be provided for use with a soldering iron which provides the fuel gas/air mixture of the correct ratio suitable for the soldering tip 3, the restrictor element 55 would not be required, and the soldering tip would be supplied without a restrictor element 55 in the fuel gas supply pipe 4.

In use, with the soldering tip 3 and the fuel gas supply pipe 4 secured to the handle 2 with the gland nut 21, the soldering iron 1 is ready for use. The regulator knob 7 is rotated for selecting the pressure of the fuel gas, and the thumb switch 6 is operated for supplying fuel gas/air mixture to the fuel gas supply pipe 4, and in turn to the

combustion chamber 14. The fuel gas/air mixture passes through the combustion chamber 14, and the catalytic combustion element 30 and exits through the exhaust port 23. Since initially the catalytic combustion element 30 is cold. The fuel gas/air mixture is ignited to burn in a flame as it exits through the exhaust port 23. The ignition of the fuel gas/air mixture to burn in a flame in the exhaust port 23 may be carried out by any suitable fuel gas igniting means, for example, a flint spark, the flame of a match, or any other suitable means. As the fuel gas/air mixture burns in the exhaust port 23, the root of the flame sits on or adjacent the catalytic combustion element 30, thus raising the temperature of the portion of the catalytic combustion element 30 exposed by the exhaust port 23. On the portion of the catalytic combustion element 30 exposed by the exhaust port 23 reaching its ignition temperature, the catalytic combustion element 30 commences to convert the fuel gas/air mixture to heat by catalytic conversion. The carrier 31 rapidly conducts heat throughout the catalytic combustion element 30, thus raising the entire catalytic combustion element 30 to its ignition temperature. At this stage the fuel gas/air mixture is being completely converted to heat by the catalytic reaction, and thus only exhaust gases exit through the exhaust port 23, thus extinguishing the flame. The heat from the catalytic conversion of the fuel gas/air mixture is radiated to the side wall 15, the fuel gas distribution member 48, and is in turn conducted into the body member 10 for conduction to the soldering tool bit 13. Additionally, heat from the catalytic conversion of the fuel gas/air mixture is also radiated to the body member 10.

Referring now to Figs. 12 and 13, there is illustrated a portion of a soldering tip according to another embodiment of the invention, which is indicated generally by the reference numeral 60. The soldering tip 60 is substantially similar to the soldering tip 3, and similar components are identified by the same reference numerals. The main difference between the soldering tip 60 and the soldering tip 3 is that instead of the retaining member being formed from perforated metal, the retaining member 40 in this embodiment of the invention is formed from a resilient wire mesh gauze material 62. In this embodiment of the invention the wire mesh gauze material 62 is provided in sheet form, and is formed into a tubular member 63

which is longitudinally split at 64. The inherent resilience of the wire mesh gauze material 62 is sufficient for urging the catalytic combustion element 30 towards the side wall 15 with the first protuberances 38 engaging the inner surface 37 of the side wall 15. In this embodiment of the invention the second spacing means for spacing the retaining member 40 from the catalytic combustion element 30 is also inherently formed by the wire mesh material, and the second spacing means is formed by the warps and wefts as the warps and wefts alternately pass each other at 65.

Additionally, the fact that the wire mesh of the retaining member 40 is inherently perforated, the fuel gas/air mixture is readily distributed through the wire mesh of the retaining member 40 to the catalytic combustion element 30.

Otherwise, the soldering tip 60 is similar to the soldering tip 3 and when secured to the soldering iron 1, its use and operation is likewise similar.

While specific first and second spacing means have been described for respectively spacing the catalytic combustion element from the side wall of the body member 10 and for spacing the retaining members from the catalytic combustion element, any other suitable first and second spacing means may be used.

Additionally, while the catalytic combustion element has been described as comprising a perforated sheet carrier, and the perforations are formed in the first protuberances during punching thereof, the first protuberances may be formed by any other suitable means, and needless to say, the perforations instead of being formed in the first protuberances may be formed in any other suitable areas or portions of the carrier. Further, it will be appreciated that other suitable carriers besides a sheet metal carrier may be provided, for example, the carrier of the catalytic combustion element may be provided as a wire mesh carrier. It is also envisaged that the carrier of the catalytic combustion element may be provided by expanded metal mesh. Should the carrier of the catalytic combustion element be formed of wire mesh material or expanded metal mesh material, the warps and wefts of the mesh material as they alternately cross each other would be sufficient for forming the first spacing means, and in the case of expanded metal mesh material,

the first spacing means would be formed inherently by the metal mesh material itself.

While the exhaust port has been described as being of circular shape, the exhaust port may be of any other suitable shape or size, and the relationship between the area of the exhaust port and the thickness of the side wall in which the exhaust port is formed is only relevant where it is desired to raise the temperature of the catalytic combustion element to its ignition temperature by flame ignition in the exhaust port.

If the soldering iron were provided with an alternative form of ignition for raising the temperature of the gas catalytic combustion element to its ignition temperature, the relationship between the area of the exhaust port and the thickness of the side wall would not be critical.

While the catalytic combustion element has been described as extending only partly around the combustion chamber, it is envisaged in certain cases that the catalytic combustion element may extend completely around the combustion chamber.

However, where it is desired to raise the temperature of the catalytic combustion element to its ignition temperature as a result of flame ignition in the exhaust port, it is necessary that the catalytic combustion element be located to substantially cover the exhaust port, and preferably, to entirely cover the exhaust port.

While it is desirable to coat both the first and second major surfaces of the carrier of the catalytic combustion element with the precious metal catalytic composition, in certain cases, it is envisaged that only one major surface of the carrier may be coated with the catalytic composition. However, where only one surface of the carrier is being coated with the catalytic composition, it is desirable that the second major surface which forms the inner surface of the carrier should be coated.

While the retaining means has been described as being provided by perforated sheet metal and wire mesh, any other suitable retaining means may be provided for retaining the catalytic combustion element in position with the first protuberances engaging the inner surface of the side wall. Indeed, in certain cases, it is envisaged that the retaining means may be provided by a retaining means other than a tubular

member formed of sheet material, in certain cases, it is envisaged that the retaining means may be provided by one or more wire hoops which would appropriately locate the catalytic combustion element in the combustion chamber.

While the provision of a distribution means for distributing the fuel gas/air mixture in the combustion chamber is desirable, it is not essential.

While the converting device of the soldering tip has been described as comprising a retaining means for urging the gas catalytic combustion element towards the side wall with the first protuberances engaging the inner surface of the side wall, in certain cases, it is envisaged that the retaining means may be omitted. For example, if the gas catalytic combustion element extends completely around the combustion chamber, if the carrier of the gas catalytic combustion element were of a resilient material, the need for a retaining means may not arise.

While the gas powered heating device according to the invention has been described as a soldering iron, the gas powered heating device may be any other gas powered heating tool, for example, a glue gun, a heated knife, and indeed, it is envisaged that the converting device according to the invention may be used in other gas powered heating devices, besides gas powered heating tools.

Additionally, it is envisaged that in certain cases where a restrictor element is provided located in the fuel supply pipe adjacent the upstream end thereof, the restrictor element may be provided with an expansion chamber which it is believed would also act to slow down the fuel gas/air mixture for improving the efficiency of catalytic conversion of the fuel gas/air mixture to heat by the catalytic combustion element.