WO2000052391A1

WO2000052391A1 - Improved gas igniter

Info

Publication number: WO2000052391A1
Application number: PCT/AU2000/000126
Authority: WO
Inventors: Michael Instance; Philip Timbrell
Original assignee: Utilux Pty. Limited
Priority date: 1999-02-26
Filing date: 2000-02-23
Publication date: 2000-09-08

Abstract

The present invention relates to an improved gas igniter for igniting gas flames in appliances, such as domestic and commercial ovens, water heaters and boilers. Conventional gas igniters are usually assembled using adhesives to keep the various components together. The present invention discloses an igniter which can be mechanically assembled without the use of any adhesive. An elongate electrode provides a 'skeleton' to which an insulating body and a mounting member can be fitted. A projection on the electrode maintains the electrode within the mounting member and an extruded insulating element provides the insulation.

Description

Improved Gas Igniter

FIELD OF THE INVENTION

The present invention relates to a gas igniter, particularly, but not exclusively, to a gas igniter for igniting gas flames in appliances such as ovens, water heaters, boilers, cooktops and the like.

BACKGROUND TO THE INVENTION Conventional gas igniters comprise an electrode to which a voltage can be applied, to cause a discharge across a gap between the electrode and another conductive element (usually a part of the appliance) , to ignite flammable fluid, such as natural gas. Such igniters are used in appliances such as domestic and commercial cookers, for lighting gas elements, boilers, water heaters and other appliances that utilise flammable fluid which requires ignition.

One known igniter comprises a flat topped electrode having a cylindrical body portion which is crimped to a conductive wire. The flat topped portion of the electrode provides a discharge surface. The cylindrical portion of the electrode and the conductive wire are seated within an insulated housing. It is important that the electrical discharge takes place between the top portion of the electrode and the conductive part of the appliance. Problems occur when there is a defect in the insulation about the cylindrical part of that electrode and tracking may occur which can result in a defective igniter. In order to prevent or reduce the chances of tracking the conductive wire and the electrode may be covered by an insulating layer apart from the insulating housing, and also in order to insure that the electrode does not move out of the housing the assembly will be glued or cemented together. The gas igniter assembly of insulating housing, insulation on the wire, electrode and conductive wire may be mounted in a resilient mounting member to absorb mechanical impacts.

Particularly for gas igniters which are used in cooktops and are therefore mounted adjacent the cooktop flame, there may be a large temperature gradient between the flame end of the igniter and the non-flame end (in order of 600°C difference) . One of the problems with present igniters is that the glue or cement securing the igniter assembly together can melt at the high temperatures experienced at the flame end of the igniter, resulting in failure.

The insulating housings used are usually ceramic insulators . The entire assembly is quite complex and relatively laborious to assemble.

SUMMARY OF THE INVENTION

The present invention provides a gas igniter assembly, comprising: a core body having an electrode discharge portion at one end of the core body, the electrode discharge portion being arranged to provide a discharge surface, a rigid distal portion remote from the discharge portion, and a rigid central portion connecting the discharge and distal portions; electrical insulation provided about the core body; and a mounting member including a passageway for receiving the rigid distal portion to mount the core body, the mounting member being constructed of a resiliently flexible material which grips the distal portion and thus holds the gas igniter assembly together.

Preferably, the electrical insulation is provided about at least the central portion of the core body. Preferably, the rigid distal portion of the core body is provided with a locating means for locating the rigid distal portion in position within the passageway in the mounting member. In a preferred embodiment, the locating means comprises a projection or barb which seats within the passageway within the mounting member and resists removal of the rigid distal portion of the core body from the passageway in the mounting member. In use in an appliance, the mounting member will be seated within a mounting, which may comprise a passageway in a rigid appliance body. Where the location means is a projection or barb, it may force an expansion of the portion of the mounting means that it sits within, so that the mounting means forms an interference fit within the passageway in the mounting in the appliance. If the rigid distal portion extends entirely through the passageway in the mounting in the appliance, the projection still provides an interference fit, preventing the rigid distal portion and mounting member from being withdrawn from the passageway in the mounting in the appliance. Preferably the insulation is an extruded insulating body which sits closely around the core body and is also able to provide support. Preferably the gas igniter assembly is used as an igniter for a cooktop. The use of extruded insulating bodies in cooktop igniters is unknown. The entire gas igniter can be assembled without requiring glue, as the rigid distal portion serves to locate the core body so that the discharge portion is unlikely to move, and the core body can be a close fit with the insulating body. The structure acts as a form of "skeleton" maintaining the physical integrity of the gas igniter assembly. Where the gas igniter is used as a cooktop igniter, the assembly is held at the relatively cool end of the assembly, away from the flame end of the igniter. Preferably, the core body is entirely conductive and the central portion connecting the discharge and distal ends is also a rigid body. The core body therefore forms a single, rigid electrode, with discharge portion, distal portion and central body.

Alternatively to an extruded insulating body being provided, insulation may be deposited directly on the core body, for example by depositing a layer of ceramic thereon. The distal portion preferably includes a further passageway for receiving a conductor, such as a conductive wire. The distal portion is crimped to the wire received in the passageway.

The mounting member also preferably includes an insulating portion which extends from the mounting member, and, preferably, the insulating portion and mounting member are integral. Preferably, the insulating portion extending from the mounting member insulates the distal portion of the core body also overlaps with insulation of a wire conductor (an uninsulated conductive end of which seats within a passageway within the distal end of the core body) .

An advantage of the igniter assembly of the present invention is that it can be assembled mechanically completely free of glue and other such materials. In a further embodiment of the invention, an insulating "fillet" is preferably provided, which extends upwardly at least partially between the insulation and the outside of the core body, from the mounting member. A layer of insulation therefore preferably surrounds the core body where the core body seats within the mounting member. This preferably reduces the possibility of "tracking" between the core body in the proximity of the mounting member and an earthed body, such as the appliance mounting. It also preferably prevents moisture from leaking into the area where the mounting and core body meet, which moisture would facilitate tracking.

The fillet is preferably flexible, so that on assembly, the fillet may bend and buckle as it is forced between the insulation on the outside of the core body. This makes for a long discharge path for any tracking to occur, further reducing the possibility of tracking. The fillet is preferably tapered so that it is flexible. It may act like a grommet . The fillet of material is preferably integral with the mounting member.

In a preferred embodiment, the distal portion of the core body is formed including a relatively narrow portion. The narrow portion preferably meets a broad portion further towards the distal end of the core body. A step is preferably formed between the narrow portion and the broad portion. The passageway in the mounting member is preferably formed including a relatively narrow portion to correspond with narrow portion of the core body. In operation, the broad portion of the distal end is forced through the (resilient) narrow portion of the passageway in the mounting member until it seats within a broader portion of the passageway in the mounting member, and the narrow portion of the core body seats within the narrow portion of the passageway in the mounting member, to provide a secure fit for the distal end of the core body. The fillet preferably extends upwardly from the narrow passageway portion of the mounting member, and inner walls of the fillet define at least part of the narrow portion of the passageway in the mounting body. Preferably, as the fillet is forced into the gap formed between the narrow portion of the core body and the insulating member, it bends and buckles, so that the void between the insulating member and core body is effectively filled by resilient material (preferably silicone) . Preferably, this arrangement substantially eliminates tracking.

BRIEF DESCRIPTION OF THE DRAWINGS Features and advantages of the present invention will become apparent from the following description of an embodiment thereof, by way of example only, with reference the accompanying drawings, in which;

Figure 1 is an exploded view of a gas igniter assembly in accordance with an embodiment of the present invention; Figure 2 is a view from the side of the electrode of the assembly of Figure 1;

Figure 3 is a side view of a mounting member of the assembly of Figure 1; Figure 4 is view from the top of the mounting member of Figure 3;

Figure 5 is an exploded view of a gas igniter assembly in accordance with a further embodiment of the present invention; Figure 6 is a view from the side of the electrode of the assembly of Figure 5;

Figure 7 is a cross-sectional side view of the mounting member of the embodiment of Figure 5;

Figure 8 is a top view of the mounting member of Figure 7;

Figure 9 is detail on A of Figure 7, and Figure 10 is a detail on B of Figure 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Figures 1 to 4 of the drawings, a gas igniter assembly 1 in accordance with an embodiment of the present invention is illustrated. The gas igniter assembly 1 comprises core body 2, in this embodiment being an elongate electrode 2 which comprises a substantially disc- like discharge portion 3, a substantially cylindrical distal portion 4 and a central conductive portion 5 connecting the discharge and distal portions. This embodiment of the gas igniter is intended for use on a cooktop. It will be appreciated that the gas igniter of the present invention may have applications, anywhere gas igniters are required.

The distal portion of the electrode seats within a passage way 6 in a mounting member 7, which is arranged to seat assembly 1 in position in a cooker appliance. The mounting member 7 seats within the passageway 14 in a mounting 15 of the appliance. The mounting 15 may be formed in a partition in the appliance. The mounting member 7 includes a resilient seat portion 8 which is arranged to enable movement of the electrode within the mounting member 7 to take account of movement due to mechanical shock, and an insulating sleeve portion 9 which extends to insulate the distal portion 4 of the electrode 2. In this embodiment, the seat 8 and the insulating sleeve portion 9 are integrally moulded. The central conductive portion 5 is mounted within an insulating body 10, which in this case is an extruded heat resistant plastics insulating body. The insulating body 10 is extruded to such a length that the entire central conductive portion seats within it, with the discharge portion 3 of the electrode 2 extending outwardly from it. A depression 11 is provided in the mounting member 8, surrounding the passage way 9 at the top to receive the base of the insulating member 10. The distal portion 4 of the electrode has a projecting portion 12 which is arranged to interfere with the inner walls of the passage way 6 of the mounting member 7 in order to retain the electrode 2 within position in the mounting member 7. Because the mounting member 8 is resilient, the projecting portion 12 distends the mounting member 7 outwardly as indicated by reference numerals 16 and 17. The distended portions of the mounting member 7 therefore apply pressure against the walls of the passageway 14 in the mounting 15, causing the assembly to be retained within the passageway 14.

The entire assembly 1 is mechanically assembled, without any glue. The electrode 2 is safely retained in position by the projecting member 12 and the insulating body 10. The core body forms a "skeleton", which supports the assembly. The insulating body 10 provides some further support . The distal portion 4 of the electrode includes a passage way 13 within it for receiving an electrical conductor such as a wire, which it will be crimped to.

In operation, when voltage is applied to the electrode 2, a discharge occurs between the discharge portion 3 and a predetermined portion of the appliance, to create a spark and light a fluid such as gas .

Because the assembly is firmly mechanically held together, there is no need for an adhesive or bonding compound to prevent break down of the device by tracking. In an alternative embodiment (not shown) the insulating member 10 may be an insulating layer which is extruded onto the core body, such as an extruded ceramic. Electrode 2 is preferably of stainless steel. Note that the projecting portion 12 may be at any position within the passageway 6. It need not be as shown, but could be further down, relative to passageway 14. Further, the central conductive portion 5 of the electrode need not be solid, but could be a flexible conductor, such as a wire. The distal portion 4 and the discharge portion 3 are rigid but as long as the wire is of the correct length, this will not affect the assembly. In such an alternative embodiment, the insulating member 10 would be required to provide the major supporting structure . A further embodiment of an igniter in accordance with the present invention is illustrated in Figures 5 through 9. The gas igniter assembly 20 in accordance with this embodiment also comprises a core body 21 which in this case is an elongate electrode 21 comprising a discharge portion 22 in the form of a truncated cone having a flat top. This has the effect of increasing the surface area of the discharge portion 22 relative to conventional flat surface area. This has been found to give superior leakage detection performance in arrangements where leakage detection is used to determine whether the flame is still occurring (low voltage supply between the electrode and another conductor and a low current flows via gases ionised by the flame) . The electrode 21 also comprises a distal portion 23 which in this embodiment is formed of a first, narrow portion 24 and a second, broader portion 25, the broader portion 25 being located at the distal end. The electrode 21 also comprises a central conductive portion 26 connecting the discharge 22 and distal 23 portions. The distal portion 23 seats within a passageway 27 in a mounting member 28 which as with the previous embodiment, is arranged to seat the igniter assembly 20 in a mounting (not shown) of an appliance. As with the previous embodiment, the mounting member 28 includes a resilient seat portion 29 (which is of insulating material) and an insulating sleeve portion 30. The mounting member 28 acts to insulate the distal portion 23 of the electrode 21, as with the previous embodiment.

The central conductive portion 26 is mounted within an insulating body 31, which, as with the previous embodiment, is an extruded heat resistant insulating body. Depression 32 is provided in the mounting member 28, about the passageway 27, to receive the base of the insulating member 31. One of the requirements of any igniter assembly is to avoid "tracking" where discharge may occur which is not from the desired discharge portion of the electrode. Tracking can occur where there is a pathway between a conductive part of the electrode and a further (usually earthed) conductive member (for example, part of the appliance in which the igniter assembly is mounted) . One area where tracking could occur, for example, is between the base of an electrode where it is mounted in the appliance and the appliance. The area where the insulating body 10 seats within the depression 11 in the mounting member 28 is an area which is vulnerable to tracking. To reduce the likelihood of tracking occurring, the embodiment of Figures 5 through 9 includes modifications. About the junction 33 between the central portion 26 and distal portion 23 of the electrode 21, the electrode 21 tapers towards the relatively narrow portion 24 of the distal portion 23. A "fillet" 34 of insulating material is formed, integrally in this embodiment, with the mounting member 28 and extends upwardly in the form of an insulating nozzle about the narrow part 24 of the distal portion 23 and tapered portion 33 of the electrode 21. The fillet sits in between and forms a seal between the electrode and the inside of the insulating body 31 where the insulating body 31 seats in the depression 32 in the mounting body 28. The fillet 34 acts as extra insulation at the core vulnerable to tracking.

Figure 10 shows in more detail the effect of the fillet. The fillet is preferably resilient and tapers towards its top. When, on assembly, it is forced into the gap between the insulating member 31 and the narrow portion 24 of the distal end of the core body 26, it tends to bend and fold as shown in figure 10, the filling of the gap is resilient material (which is preferably silicone) . Although not clear in figure 10, the fillet preferably is resilient enough to entirely fill the gap between the narrow portion 24 and insulating body 31 and expel air from the gap.

The inner walls of the fillet 34 form a narrow passageway 35 which receives the narrow portion 24 of the distal portion 23. On assembly, the broad portion 25 of distal portion 23 is inserted through the relatively narrow passageway 35 (which is resilient and so expands to allow the broad portion 25 to be forced through) until the narrow portion 24 seats within the narrow passageway 35. The narrow portion 24 may be slightly broader in diameter than the internal diameter of the passageway 35, in order to expand the passageway and seats securely within it. Further, step 36 formed between the narrow portion 24 and broad portion 25 assists in maintaining the distal portion 23 seated within the mounting member in position. The diameters of the internal passageway of the mounting member 28 and distal portion 23 may be such that the mounting member expands when the distal portion 23 is seated within the passageway, so that the outside of the mounting member forms an interference fit with the appliance mounting. As well as providing extra insulation and sealing against moisture encroaching between the electrode 21 and insulating body 31, the arrangement also provides a "tortured path" for any discharge occurring between the area of the electrode 21 in the vicinity of the depression 32 and the appliance. Any discharge must travel into the depression 32 around the outside of the insulating body 31 then around the base of the insulating body and up the outside wall of the fillet 34 to the electrode 21. This tortuous path would very difficult for a discharge to follow, and makes discharge unlikely.

Note that the dimensions shown in the drawings are for illustrative purposes only and may be varied. It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A gas igniter assembly comprising: a core body having an electrode discharge portion at one end of the core body, the electrode discharge portion being arranged to provide a discharge surface, a rigid distal portion remote from the discharge portion, and a rigid central portion connecting the discharge and distal portions; electrical insulation provided about the core body; and a mounting member including a passageway for receiving the rigid distal portion to mount the core body, the mounting member being constructed of a resiliently flexible material which grips the distal portion and thus holds the gas igniter assembly together.

2. A gas igniter assembly in accordance with claim 1, wherein the igniter assembly is assembled mechanically in the absence of any glue.

3. A gas igniter assembly in accordance with claim 1 or claim 2, wherein the electrical insulation is provided by an extruded insulating body.

4. A gas igniter assembly in accordance with claim 1 or claim 2, wherein the electrical insulation is provided by an insulating material directly deposited on at least part of the electrode core body.

5. A gas igniter assembly in accordance with any preceding claim, wherein a locating means is included in the distal portion of the core body to seat the electrode within the mounting member.

6. A gas igniter assembly in accordance with claim 5, wherein the locating means is a projection projecting from the distal portion of the core body to provide an interference fit with the passageway in the mounting member.

7. A gas igniter assembly in accordance with claim 6, wherein the resilient mounting member is arranged to be received within a passageway in a portion of an appliance for mounting the igniter, the projection distending the resilient mounting member to facilitate retaining the mounting member within the passageway in the portion of the appliance .

8. A gas igniter assembly in accordance with any preceding claim, wherein the mounting member includes an insulating portion which extends about the distal end of the core body.

9. A gas igniter assembly in accordance with claim 8, wherein the mounting member and insulating portion are integral .