A typical self-lighting portable gas torch has a trigger actuated piezoelectric igniter system electrically connected to an igniter wire extending into a burner tube of the torch. The igniter system generates a spark between the end of the igniter wire and the metal burner tube to ignite a mixture of air and fuel flowing through the tube. A flame holder in the burner tube creates turbulent flow of the air-fuel mixture so that the full diameter of the flowing gas stream is ignited to produce a uniform flame for heating, brazing, or soldering.

To insure reliable flame ignition, the spark-emitting end of the igniter wire is positioned approximately 1/4"upstream of the flame holder to provide a 1/8"spark perpendicular to the gas flow through the burner tube. In typical igniter systems, the position of the igniter wire is maintained by lightly clamping an electrical forked spade terminal to the igniter wire or by using a thin-formed sheet metal wire holder in the tube. Electrical spade terminals and sheet metal wire holders are typically made of metal for strength and are configured to minimize flow restriction. To prevent short-circuiting the spark, the wire end must extend significantly beyond the conductive metal wire holder necessitating frequent visual inspection and adjustment of the wire position to insure the correct spark gap is maintained. Because the flame holder prevents access to the wire end, a threaded removable brass burner tube is typically used to allow access to the igniter wire.

In order to produce a full flame downstream of the flame holder, the air-fuel mixture flow rate must be properly adjusted and an adequate fuel supply must be present. Frequently, operator error or use of a near empty fuel cylinder results in a condition in which the air-fuel mixture flow rate is insufficient to properly ignite the torch flame. When the igniter system is actuated during low flow operation, the resulting flame will encompass the full flowing diameter of the air-fuel mixture upstream of the flame holder causing rapid heating of the wire holder, wire, flame holder, and burner tube. Existing portable torch designs with conductive metal wire holders and removable brass tips prematurely fail as a result of the rapid overheating that occurs during the low flow burn in the torch.

SUMMARY OF THE INVENTION Among the several objects of this invention may be noted the provision of a portable gas torch with an igniter wire holder which is relatively economical to manufacture; the provision of such a torch which is easy to assemble with the igniter wire of the torch properly positioned in the burner tube; the provision of such a torch which reduces maintenance; the provision of such a torch which is durable; the provision of such a torch which facilitates flame ignition during low flow operation; and the provision of such a torch which allows reliable spark gap control.

In general, a portable gas torch of the present invention comprises a metal burner tube defining a gas flow passage through which gas is adapted to flow along a longitudinal axis of the tube to an outlet. An igniter wire in the gas flow passage has a spark end for generating a spark to ignite gas flowing through the passage. The torch has a wire holder for positioning the igniter wire in the gas flow passage and a flame holder in the gas flow passage downstream from the wire holder. The wire holder comprises a central hub having an axial bore generally parallel to the longitudinal axis of the burner tube and at least one spacer on the hub for contacting an inside wall of the burner tube to position the hub at a predetermined radial location in the gas flow passage. The axial bore is sized to enable the spark end of the wire to be inserted through the bore and then held at a selected location downstream from the hub. The wire holder comprises a dielectric material whereby a spark from the spark end of the igniter wire will jump to the inside wall of the burner tube even if the spark end is positioned closer to wire holder than to the inside wall of the tube.

In another aspect of the invention, a portable gas torch comprises a burner tube defining a gas flow passage through which gas is adapted to flow along a longitudinal axis of the tube, the tube having an open end designing an outlet of the torch. An igniter wire in the gas flow passage has a spark end for generating a spark to ignite gas flowing through the passage. The torch has a dielectric wire holder in the burner tube for receiving the igniter wire and positioning the spark end in the gas flow passage and a flame holder in the gas flow passage downstream from the wire holder. The wire holder comprises a central hub having an axial bore generally parallel to the longitudinal axis of the burner tube and a plurality of spacers extending from the hub for contacting an inside wall of the burner tube to position the hub at a predetermined radial position in the gas flow passage. The axial bore is sized to hold the igniter wire in place by an interference fit such that the spark end of the igniter wire is held a substantially fixed distance downstream from the hub whereby a spark from the spark end of the igniter wire will jump to the inside wall of the burner tube even if the spark end is positioned doser to wire holder than to the inside wall of the tube.

Other objects and features will be in part apparent and in part pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective of one embodiment of a portable gas torch of the present invention.

Fig. 2 is a section of a tip assembly of the cutting torch.

Fig. 2A is an enlarged portion of Fig. 2 showing the connection of the tip assembly to a handle of the torch.

Fig. 3 is an enlarged portion of Fig. 2 showing a wire holder and flame holder of the torch.

Fig. 4 is a perspective of the wire holder of the torch.

Fig. 5 is a cross-section taken along the plane including line 5-5 of Fig.

4 4.

Fig. 6 is a cross-section taken along the plane including line 6-6 of Fig.

4.

Fig. 7 is a perspective of a second embodiment of the wire holder.

Fig. 8 is a cross section taken along the p) ane induding tine 8-8 of Fig.

7.

Fig. 9 is a perspective of a third embodiment of the wire holder.

Correspondence parts are designated by corresponding reference numbers throughout the drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawings, and more particularly to Fig. 1, one embodiment of a portable gas torch of the present invention is designated in its entirety by the reference numeral 1. The torch 1 has a handle 3 for connection to a fuel supply tank (not shown), a conventional trigger actuated piezoelectric igniter, generally designated 5, for creating a spark to ignite a flame in the torch, and a tip assembly, generally designated 7, threadably attached to the handle having a metal burner tube 11 defining an outlet 13 of the torch. The torch 1 is configured so that a mixture of air and fuel flowing through the burner tube 11 is ignited by actuating the piezoelectric igniter 5 so that a flame is emitted from the outlet 13 of the torch. The torch 1 is particularly useful in providing a portable flame that can be used in heating, soldering, or brazing various components.

As shown in Figs. 1-3, the handle 3 houses a lead wire 17 electrically connected at one end to the piezoelectric igniter 5 and at its other end to an igniter wire 19 in the tip assembly 7 so that current generated in the piezoelectric igniter is conducted through the igniter wire. The igniter wire 19 may be, for example, a flexible wire comprising one or more conductive elements in a flexible sheath of dielectric material. As shown in Fig. 2A, the tip assembly 7 includes a tip nut 23 that threadably attaches the burner tube 11 to the handle 3. An insulator 25 is received in the tip nut 23 and has an angled bore 27 that receives a proximal end 29 of the igniter wire 19. A conductive ring 31 is held in place around the insulator 25 to electrically connect the igniter wire 19 with the lead wire 17 connected to the piezoelectric igniter 5.

The igniter wire 19 is substantially insulated except for its proximal end 29 in

contact with the conductive ring 31 and its spark end 33 held in the burner tube 11. Current generated by triggering, the piezoelectric igniter 5 travels through the lead wire 17, the conductive ring 31, and the igniter wire 19 to generate a spark at the spark end 33 of the igniter wire as will be described in more detail below.

Referring to Fig. 2, the burner tube 11 of the illustrated embodiment is a stainless steel tube with a cylindrical wall having an inner surface 41 defining a flow path for mixed air and fuel to pass through the torch 1 to an open end forming the outlet 13 of the torch. It will be understood that the tube 11 can be comprised of other suitable metals (i. e. , other steels) or other electrically conductive materials. The tube 11 has straight inlet section 45 extending from the handle 3 of the torch 1, a bent intermediate section 49, and a straight outlet section 53 having a longitudinal axis 55. In the illustrated embodiment, the outlet section 53 is bent approximately 60 degrees with respect to the inlet section 45, but it will be understood that the tube 11 cou) d have other configurations induding straight. As shown in Fig.

2, the burner tube 11 is constructed from a single piece of metal tubing and has a substantially uniform flow diameter through its inlet section 45, intermediate section 49, and outlet section 53. The inlet section 45 of the tube 11 has a telescoping fit with a mixer 57 mounted on the handle 3 of the torch for the flow of mixed air and fuel into the tube.

As shown in Fig. 2, the igniter wire 19 is disposed in the tip assembly 7 with the spark end 33 of the igniter wire held in a fixed radial and longitudinal position in the burner tube 11 by a wire holder 61 received in the outlet section 53 of the tube. As seen in Fig. 2A, the proximal end 29 of the igniter

wire 19 is received in the angled bore 27 in the insulator 25 and secured to the handle 3 of the torch 1 by the retaining nut 23 which, when tightened on the handle, forces the proximal end of the igniter wire into electrical contact with the conductive ring 31. In the embodiment of Fig. 2, the igniter wire 19 is routed from the angled bore 27 in the insulator 25 through the inlet section 45 of the burner tube 11 where the igniter wire is held against the inner surface 41 of the tube. The igniter wire 19 is spaced away from the inner surface 41 of the intermediate section 49 of the tube 11 and extends into the outlet section 53 of the tube where the igniter wire is held in the wire holder 61 approximately along the central axis 55 of the tube. A spiral flame holder 65 is received in the outlet section 53 of the tube 11 between the spark end 33 of the igniter wire 19 and the outlet 13 of the tube to turbulate the flow of gas downstream from the flame holder. As shown in Fig. 3, the flame holder 65 is fixed in the tube 11 by engagement reduced-diameter annular section 69 of the outlet section 53 of the tube. The flame holder 65 is held in the desired position in the burner tube by an interference fit with the reduced-diameter annular section 69. Typically, the flame holder 65 is made from metal (e. g., steel or brass) to withstand the high operating temperatures of the torch 1.

Referring to Figs. 3-6, one embodiment of the wire holder 61 of the present invention comprises a solid cylindrical central hub 81 having a central bore 83 generally parallel to the longitudinal axis 55 of the outlet section 53 of the burner tube 11. As shown in Figs. 4 and 5, the central hub 81 has a flat upstream end surface 89 with a rounded peripheral edge 91, a substantially planar downstream end surface 99, and diametrically opposed arcuate side surfaces 95 extending axially between the end surfaces 89,99. The axial

bore 83 of the hub 81 is sized to enable the spark end 33 of the igniter wire 19 to be inserted through the bore to a position in which the spark end of the wire is held at a fixed radial and longitudinal location downstream from the hub a distance D (Fig. 3). The axial bore 83 has a converging inlet section 103 and a downstream section 105 of uniform diameter. By having an initial diameter approximately equal to the diameter of the igniter wire 19, the inlet section 103 of the bore 83 is configured to facilitate insertion of the igniter wire through the hub 81. The uniform diameter of the downstream section 105 is sized slightly smaller than the diameter of the igniter wire 19 for gripping the wire and holding it in a selected position by an interference fit. The friction fit between the igniter wire 19 and the hub 81 also holds the hub at a fixed longitudinal location in the burner tube 11. By way of example and not limitation, the inlet section 103 of the bore 83 may have an initial diameter ranging from approximately 0.04 to 0.08 inches; the downstream section 105 may have a diameter ranging from approximately 0.02 to 0. 07 inches; and the insulated igniter wire 19 may have an outer diameter ranging from approximately 0.05 to 0.09 inches. In one particular embodiment, the inlet section 103 has an initial diameter of about 0.06 inches, the downstream section 105 has a diameter of about 0.04 inches; and the insulated igniter wire 19 has an outer diameter of about 0.05 inches.

The wire holder 61 further comprises at least one spacer 109 on the hub 81 for positioning the hub at a predetermined radial position in the gas flow passage of the torch 1. In the particular embodiment of Figs. 2-6, two spacers 109 resembling arms extend radially from opposite sides of the hub 81 and contact the inside wall 41 of the burner tube 11 so that the wire holder

61 is held in a predetermined radial position inside the tube, e. g. , a position where the central axis of the hub is substantially coincident with the longitudinal axis 55 of the outlet section 53 of the burner tube. As shown in Figs. 4 and 6, each spacer 109 comprises an elongate solid body 115 integrally formed with the hub 81 with second spacer located approximately 180 degrees from the first spacer. In the embodiment of Figs. 4-6, the spacer body 115 has a rounded upstream end surface 123, a generally planar downstream end surface 127, and two generally parallel side faces 119 extending axially between the end surfaces 123,127. The downstream end surface 127 is generally coplanar with the downstream end surface 99 of the hub 81 and perpendicular to the longitudinal axis 55 of the outlet section 53 of the burner tube 11. The rounded upstream end surfaces 89 and 123 of the hub 81 and the spacers 109 limit the flow disturbance created by the wire holder 61 in the flow path of the air-fuel mixture flowing through the burner tube 11. In one embodiment, the spacers 109 have free outer ends 131 with rounded comers 135 for contact with the inner surface 41 of the burner tube 11. It will be understood that one spacer or more than two spacers can be provided for contacting the burner tube 11 and fixing the wire holder 61 in a predetermined radial position in the tube. Also, the wire holder 61 may have spacers 109 with configurations other than those shown in the illustrated embodiments without deviating from the scope of this invention.

By way of example but not limitation, the overall length of the wire holder 61 may be sized for a slip fit in the burner tube 11 with a total preferred clearance of about 0.004 inches to about 0.008 inches between each free end 131 of the wire holder and the inside wall 41 of the burner

tube. In one embodiment, a typical overall length between opposed free ends 131 of the wire holder 61 may be approximately 0.430 inches and a typical inside diameter of the burner tube may be approximately 0.442 inches. It will be understood that the wire holder 61 may be held in the hub 81 at a predetermined radial position in the tube 11 by other dimensional fits (i. e. , press fit or interference fit) or by other attachment methods (i. e., adhesives or thermal bonding). The wire holder 61 in the embodiment of Figs. 2-6 is a single molded part made of ceramic material but it will be understood that the wire holder can be made from other dielectric materials (i. e. , thermoplastics, composites, etc. ) having suitable strength characteristics and temperature resistance.

The dielectric wire holder 61 of the present invention allows a spark from the spark end 33 of the igniter wire 19 to jump to the inside wall 41 of the burner tube 11 even if the spark end is positioned closer to the wire holder than to the inside wall of the tube. As seen in Figs. 2 and 3, the insulated igniter wire 19 is received in the axial bore 83 of the wire holder 61 and held in a fixed radial position in the burner tube 11 by the interference fit with the wall defining the downstream section 105 of the axial bore of the wire holder.

As seen in Fig. 3, the exposed spark end 33 of the igniter wire 19 extends past the flat downstream end surface 99 of the wire holder hub 81 a distance D so that current in the igniter wire can generate a spark from the exposed end of the wire to the inner surface 41 of the metal burner tube 11.

In prior designs involving metallic wire holders, it was necessary to extend the igniter wire a relatively large distance beyond the wire holder to prevent short circuiting of the spark to the wire holder. Due to the relatively

long unsupported length of flexible wire, a consistent spark gap between the spark end of the wire and the burner tube was difficult to maintain, and frequent manual adjustment during assembly and operation of the torch was often required. This adjustment was facilitated by making the tip of the burner tube removable. In the design of the present invention, the distance D can be made relatively short, since the wire holder 61 is of a dielectric material and the risk of a short circuit of the spark to the wire holder is eliminated. Because distance D is short, the radial location of the spark end 33 of the wire 19 remains substantially fixed during torch assembly and operation so that a more consistent spark gap is maintained. As a result, the need for frequent positioning adjustments of the spark end 33 of the wire 19 is eliminated and the burner tube 11 can be made of a single piece rather than multiple pieces for reduced cost.

By way of example but not lire n, the distance D may be about 0.01 inches to about 0. 08 inches and more preferably from about 0.03 inches to about 0. 06 inches. In the illustrated embodiment, the spark end 33 of the igniter wire 19 is located approximately on the center longitudinal axis 55 of the outlet section 53 of the burner tube 11, but it will be understood that the spark end can be otherwise located in the burner tube without departing from the scope of this invention. Preferably, the spark end 33 of the igniter wire 19 is spaced from the inner surface 41 of the burner tube 11 by about 1 mm to about 6 mm and more preferably about 3 mm to about 4 mm. Also, the spark end 33 of the igniter wire 19 is preferably spaced a distance of approximately 1/4"upstream of the flame holder 65 to facilitate proper flame ignition of the torch 1.

In normal operation, the torch 1 is first properly adjusted so that the air- fuel mixture flows through the burner tube 11 at a sufficient rate to generate a useable flame extending from the outlet 13 of the torch. After, setting the air- fuel mixture flow rate, the piezoelectric igniter 5 is actuated to produce an electrical current flowing through the igniter wire 19 in the tip assembly 7. The electrical current in the igniter wire 19 results in a spark which jumps in a direction substantially perpendicular to the flow of gas through the tube from the exposed end 33 of the igniter wire held in the wire holder 61 to the inner surface 41 of the burner tube 11. The spark ignites a small flame kernel in the air-fuel mixture flowing past the wire holder 61. The flame kernel passes through the flame holder 65 which fully turbulates the air-fuel mixture causing the full flow diameter of the mixture to ignite downstream of the flame holder.

The resulting flame exits the outlet 13 of the burner tube so that the torch 1 emits a fully ignited flame that is suitable for many uses including heating, brazing, soldering, or similar processes.

In an upset condition in which the flow settings of the torch 1 are incorrectly set or the fuel supply is low, the amount of air-fuel mixture flowing through the burner tube 11 will be insufficient to produce a full flowing flame extending from the outlet 13 of the torch. In this low flow condition, the spark between the igniter wire 19 and the inner surface 41 of the burner tube 11 will prematurely ignite the full flow diameter of the mixture to create a flame upstream of be flame holder 65. The flame created during this low flow condition will not propagate through the outlet 13 of the burner tube 11 in an amount sufficient to be a useable flame. The premature ignition of the flame at the low flow condition results in rapid overheating of the wire holder 61, igniter

wire 19, flame holder 65 and burner tube 11. The wire holder 61 of the present invention is designed to minimize flow restriction in the burner tube 11, thus lowering the flow setting at which premature flame ignition occurs.

Also, the flat downstream surfaces 99 and 127 of the wire holder 61 causes the flame to burn far enough downstream of the wire holder to reduce the heat transferred to the wire holder and the igniter wire 19. The configuration of the present invention with ceramic wire holder 61 and a stainless steel burner tube 11 can withstand extreme abuse and high temperatures during low flow operation to allow the portable torch 1 to function properly after proper flow through the torch has been restored.

A second embodiment of a wire holder of the present invention, generally designated 201, is shown in Figs. 7 and 8. The wire holder 201 of this embodiment is a single molded part made from a high-temperature thermoplastic (. e. g., alumina) and molded to have generally an airfoil shape.

The wire holder 201 has a central hub 205 and two aligned radial spacers 209 formed integrally with the hub. The spacers 209 terminate in outer (free) ends 213 that contact the inner surface 41 of the burner tube 11 to fix the wire holder 201 at a predetermined radial position in the tube. As shown in Fig. 8, the hub 205 has an axial bore 217 with an upstream section 221 of converging diameter, a short intermediate section 225 of uniform diameter, and a downstream section 229 of diverging diameter. The hub 205 of this embodiment 201 allows insertion of the igniter wire 19 from either the upstream end or the downstream end of the axial bore 217. The intermediate section 225 of the bore 217 is sized for interference fit with the igniter wire 19 so that the position of the igniter wire is substantially fixed upon insertion into

and through the wire holder 201. Each of the spacers 209 has an airfoil shape with opposed curved axially-extending faces 233 that converge at narrow upstream edges 237 and downstream edges 241. The airfoil shape of the wire holder 201 minimizes the flow disturbance in the burner tube 11 to reduce the flow rate at which premature flame ignition occurs during low flow operation.

A third embodiment of a wire holder of the present invention, generally designated 301, is shown in Fig. 9. This embodiment 301 is substantially similar to the second embodiment 201 except that the wire holder has three spacers 305 extending radially from the hub 309. The three spacers 305 extend from the hub 309 at locations spaced approximately 120 degrees around the circumference of the hub. As in the previous embodiments, the spacers 305 have free outer ends 313 for contacting the inner surface 41 of the burner tube 11 to position the wire holder 301 in a predetermined radial position in the burner tube by a slip fit between the wire holder and the tube.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained. For example, the portable torch 1 of the present invention with dielectric wire holder 61 has fewer parts and is easier to assemble than prior art torches having more complicated electrically conductive wire holders. The configuration of the present invention 1 substantially fixes the position of the spark end 33 of the igniter wire 19 in the burner tube 11, thus eliminating the need for a removable threaded tip to allow access to the wire. The configuration of the wire holder 61 of the present invention also increases durability of the torch 1 by reducing the likelihood of premature flame ignition during low flow operation.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. For example, the wire holder 61 could be made from ceramic, thermoplastic, or other suitable dielectric materials and composites. The wire holder 61 could have one or more than two spacers 109 regardless of the material of construction.

The axial bore 83 of the wire holder 61 could have a single uniform diameter or multiple stepped surfaces of varying diameters to secure the igniter wire 19 in the holder. The insulated igniter wire 19 may have an outer diameter equal to or smaller than the diameter of the axial bore 83 and may be secured in the wire holder 61 by means other than an interference fit with the bore (e. g., the wire may have a flattened upstream and downstream portion deformed to have a width greater than the diameter of the axial bore to prevent the wire from being withdrawn from the wire holder). The spacers 109 of the wire holder 61 may be arm-iike members having circutar cross- sections or other cross-sectional shapes that allow the wire holder to be fixed in the burner tube 11 while minimizing the flow disruption of gas flowing through the tube. The wire holder 61 may be positioned in the burner tube 11 such that the planar end surface 127 of the spacer 109 is the upstream end surface and the rounded end surface 123 of the spacer is the downstream end surface of the wire holder.

When introducing elements of the present invention or the preferred embodiment (s) thereof, the articles"a","an","the"and"said"are intended to mean that there are one or more of the elements. The terms"comprising", "including"and"having"are intended to be inclusive and mean that there may be additional elements other than the listed elements.