AU2002213678B2

AU2002213678B2 - Domestic oven heating element

Info

Publication number: AU2002213678B2
Application number: AU2002213678A
Authority: AU
Inventors: Ron Wilson
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-11-08
Filing date: 2001-11-08
Publication date: 2006-02-09
Anticipated expiration: 2021-11-08

Description

WO 02/39021 PCT/AU01/01445 I DOMESTIC OVEN HEATING ELEMENT Technical Field The present invention concerns an electrical heating element for a domestic fan-fQrced oven.

Background of the Invention Heating elements for fan-forced ovens include a heating portion which is designed to fit closely around a fan in the oven such that heat is provided to an airflow generated by the fan. In one arrangement, the heating portion is a generally-circular coil which is mounted such that an axis of the coil is coincident with an axis of the fan. An electrical connection is made to electrical terminals of the heating element via a connection port in the oven, which is usually located in a rear wall of the oven.

The electrical terminals are connected to the heating portion by an extension of the heating portion commonly referred to as the "neck". The heating portion is typically secured to the rear wall by mounting legs permanently fastened at various positions around the coil.

One end of each mounting leg is permanently fastened to the heating portion, and an opposite end of each mounting leg has a foot designed to be secured with screws or bolts to a factory-installed aperture in the rear wall. The number and location of such apertures varies with the brand and model of oven. Similarly, the distance between the connection port and the centre of the fan varies with the brand and model of oven, making it necessary to manufacture heating elements in a range of different WO 02/39021 PCT/AU01/01445 -2configurations. Such variability in oven design makes it necessary for an oven repairer to carry many different types of heating elements, and usually a separate heating element for each commercially-available oven design.

Summary of the Invention A first aspect of the present invention provides a heating element for a domestic fan-forced oven, the heating element comprising electrical terminals, a heating portion for providing heat to the oven, and a neck portion for connecting the terminals to the heating portion, wherein the neck portion is arranged to have an adjustable neck length such that the element can be installed into any one of a plurality of different fan-forced oven types, each oven type requiring a heating element with a different neck length.

The heating element may be universal such that it can be fitted into a number of domestic fan-forced oven types, and preferably most types of domestic fan-forced ovens.

The neck portion may comprise a first neck portion and a second neck portion arranged to be connected together to form any one of a plurality of different neck lengths. The neck portion may be continuously lengthadjustable within a predetermined range of neck lengths.

The neck portion preferably includes an electrical connection means for electrically connecting the first and second neck portions together. The electrical connection means may comprise a plurality of first electrical connectors associated with the first neck portion, and a plurality of second electrical connectors associated with the second neck portion for connecting to the first electrical connectors, whereby to complete a circuit WO 02/39021 PCT/AU01/01445 -3between the terminals and heating portion. The first and second neck portions may be arranged to slide relative to each other during adjustment of the neck length, and the electrical connection means may be arranged to electrically connect the first and second neck portions at each adjusted neck length. Electrical contact between the terminals and the heating portion can therefore be established by connecting the first connectors of the first neck portion to the respective second connectors of the second neck portion. Each of the first connectors may include an elongate conductor arranged on the first neck portion, and each of the respective second electrical connectors may be arranged to connect with one of the respective first connectors at any one of a plurality of different locations along the first connector.

The electrical connection means may also include electrical attachment means to hold the first and second electrical connectors in electrical contact during use.

Preferably, the attachment means includes a plurality of spring-loaded clips, each clip having two opposed holding members for holding one of the second connectors in electrical contact with one of the first connectors. The first electrical connectors may be configured to comprise the respective spring-loaded clips. The electrical attachment means may include fasteners, such as screws or bolts.

In one embodiment, each first connector comprises the spring-loaded clip and is in the form of a conducting channel member with a generally U-shaped cross-section.

The opposed holding members of the clip comprise resiliently-biased walls arranged to receive and hold one of the second connectors between the walls. The first connectors may be held within respective slots in the WO 02/39021 PCT/AU01/01445 -4first neck portion.

The first neck portion may have a first fixed neck length and the second neck portion may have a second fixed neck length. A range of neck lengths may be obtained by combining different proportions of the first and second neck lengths together. For example, the second electrical connector may be connected at any one of a plurality of different positions along a length of the first connector, enabling different proportions of the first neck length to be added to the second neck length. The first and second neck portions may be connected together in either: a first configuration in which the first and second neck lengths of the respective first and second neck portions are additively combined to form a total neck length which is at least as great as the first neck length and the second neck length; or a second configuration in which the first and second neck lengths of the respective first and second neck portions are subtractively combined to form a neck length which is less than or equal to the first neck length and the second neck length.

In one embodiment, the first neck portion comprises an elongate ceramic block having a front face, a rear face on an opposite side to the front face, and first and second end faces at opposite ends. The front face includes a plurality of parallel slots formed therein.

Each slot houses an elongate first connector which is arranged to receive and hold one of the second connectors.

The electrical terminals protrude from a portion of the rear face of the ceramic block adjacent the first end face. The terminals protrude through an aperture in a mounting plate which is arranged to mount the block onto a wall of the oven such that the terminals pass through a WO 02/39021 PCT/AU01/01445 5 connection port. The ceramic block can be mounted in either a first configuration or a second configuration.

In the first configuration, the block is oriented such that the electrical terminals are distal to the heating portion and the second end face is proximal to the heating portion. This configuration is useful for ovens which require a long neck length, since the length of the ceramic block will be added to the length of the neck portion attached to the heating portion. In a second configuration, the ceramic block is oriented such that the electrical terminals are proximal to the heating portion and the second end face is distal to the heating portion.

This configuration is useful for ovens which require an element with a short neck length.

The present invention addresses a significant problem with known heating elements, namely that heating elements are made with a fixed neck length and are therefore only suitable for one particular oven design.

A second aspect of the invention provides a mounting leg for attaching a heating portion of a heating element to a surface inside a domestic fan-forced oven, the mounting leg being arranged to be attached to a pre-existing attachment point on the surface and to releasably engage and hold the heating portion, the mounting leg being further arranged to be installed into any one of a plurality of different oven types, each oven type having a different configuration of one or more of the attachment points.

The mounting leg may be arranged to be used with many and preferably most types of domestic fan-forced ovens and heating elements therefor. The mounting leg is preferably arranged to be used without requiring the oven to be modified.

WO 02/39021 PCT/AU01/01445 6 Each attachment point typically comprises an aperture in a wall of the oven and the aperture is typically prethreaded. One end of the mounting leg may include a foot portion arranged to be fastened to the attachment point with a fastener, such as a screw, bolt, rivet, etc. The foot portion may include an aperture for receiving the fastener. The other end of the mounting leg may include a coupling portion for releasably coupling the mounting leg to the heating portion. The coupling portion may include at least one C-shaped portion arranged to clutch onto at least one loop of the coil. The coupling portion may be arranged to couple to the coil at any one of a plurality of locations around the inner or outer diameter of the coil such that the foot portion aligns with an attachment point. In order to enhance the universality of the mounting leg, the aperture in the foot portion may be enlarged relative to each attachment point such that a fastener may be received at any one of a range of locations within the aperture. In one embodiment, the aperture is elongated to receive a fastener at any one of a range of positions along the length of the aperture.

The mounting leg may be formed from a wire or wire-like material bent into an appropriate shape in order to maximise heat dissipation from the coil in the vicinity of the attachment means, thereby prolonging the life of the coil by avoiding "hot spots".

A third aspect of the invention provides a heating element for a domestic fan-forced oven, the heating element comprising a heating portion and an adjustable attachment means for attaching the heating portion to any one of a plurality of different ovens at one or more attachment points, each oven having a different configuration of the one or more attachment points.

WO 02/39021 PCT/AU01/01445 7 The adjustable attachment means may comprise a mounting leg in accordance with any one of the embodiments described in the second aspect of the invention. The heating element of the third aspect of the invention may be in accordance with the heating element described in the first aspect of the invention.

Throughout this specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or integer or group of elements or integers but not the exclusion of any other element or integer or group of elements or integers.

Brief Description of the Drawings Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings.

Fig 1 is a front view of a prior art heating element shown installed in a fan-forced oven.

Fig 2 shows a side view of the prior art heating element shown in Fig 1.

Fig 3 is a front view of an embodiment of a heating element in accordance with the present invention.

Fig 4 is a partially cross-sectioned side view of the heating element shown in Fig 3 when adjusted to form a neck length L 1 Fig 5 is a partially cross-sectional side view of the heating element shown in Fig 3 when adjusted to form a neck length L 2 Fig 6A is an end view of a spring-loaded clip.

Fig 6B is a top view of the spring-loaded clip shown in Fig 6A.

WO 02/39021 PCT/AU01/01445 8 Fig 7 is a plan view of a ceramic block which houses three of the spring-loaded clips shown in Figs 6A and 6B.

Fig 8 is a sectional view taken along line 8-8 of Fig 7.

Fig 9 is a top view of electrical terminals and a mounting clip of the heating element.

Fig 10 is a pictorial view of the mounting clip for connecting the electrical terminals to the spring-loaded clips in the ceramic block.

Fig 11 is a pictorial view of a mounting plate for mounting the ceramic block shown in (Figs 7 and 8) onto a wall of an oven.

Fig 12 is a pictorial view of the mounting leg shown in Figs Fig 13 is an end view of an alternative embodiment of a spring-loaded clip.

Detailed Description of the Drawings Figs 1 and 2 show a prior art heating element 10 for a domestic fan-forced oven. The heating element includes a heating portion in the form of a double-loop circular coil 20 mounted to a rear wall 30 of the oven such that an axis of the coil is coincident with an axis of a fan Each of the two ends of the coil 20 are connected to electrical terminals 50 via a neck 60. The neck comprises two arms 70 which each extend from a loop 80 of the coil 20 to electrical terminal 50. A mounting plate 110 is screwed to the rear wall 40 of the oven and holds the terminals 50 securely in the centre of a connection port 120 formed in the rear wall 40. The coil 20 is secured to the rear wall 40 by three mounting legs 130, each of which is permanently clamped around sections of the coil 20. Each mounting leg 130 also includes a foot WO 02/39021 PCT/AU01/01445 9 140 which is fastened with a screw 150 to an aperture 160 in the rear wall Although the coils of heating elements for fan-forced ovens all have much the same diameter, there is a substantial amount of variability in the positioning of the connection port 120 relative to the centre of the fan making it necessary to manufacture a variety of different heating elements, each element having a different neck length. Each prior art element has a fixed neck length as shown in Fig 2.

An embodiment of a heating element in accordance with the present invention will now be described with reference to Figs 3-12. The heating element 200 includes a heating portion in the form of a double-loop coil 210. The coil itself is the same as the prior art coil 20 shown in Figs 1 and 2. The heating element 200 includes electrical terminals 200 (mounted in the connection port 120 in the rear wall 40 of the oven) for connecting to an electrical power supply. The coil 210 is electrically connected to the terminals 220 by a neck portion 230 which has an adjustable neck length. The neck portion comprises a first neck portion 240 and a second neck portion 250 which can be joined together to form any one of a plurality of different neck lengths. The second neck portion 250 includes two arms 260 which are extensions of the ends 270 of the coil 210, and are each is bent at an elbow 280. The second neck portion 250 includes three second electrical connectors in the form of two live connection tabs 290 and one earth connection tab 300. The live connection tabs 290 are located at the ends of the respective arms 260, and serve to electrically connect the coil 210 to the first neck portion 240. Each connection tab 290, 300 is formed by a short length of wire folded back on itself to WO 02/39021 PCT/AU01/01445 10 form a small loop 310 at the end. The connection tabs 290, 300 protrude from an inside surface 320 of a mounting clip 330 (shown in Figs 9 and 10). The earth connection tab 300 is located between the two live connection tabs., 290, and serves to earth the mounting clip 330.

The first neck portion 240 includes a ceramic block 340 in which three parallel slots 350 are formed in a front face 360. In use, the front face 360 opposes the inside surface 310 of the mounting clip 320. Each of the three slots 350 holds a first electrical connector in the form of an elongate spring-loaded clip 370 which is designed to receive one of the three connector tabs 290, 300 in a channel 380 formed between opposed holding members in the form of resiliently-biased walls 390 of the clip 370. Each spring-loaded clip 370 comprises a single sheet of metal folded to form a generally U-shaped profile. In this embodiment, each of the opposed walls 390 comprises an inner wall 400 and an outer wall 410.

The outer wall 410 is formed from an extension of the inner wall 400 which has been folded outwardly from the channel 380 back towards the inner wall 400. The spring loading of the opposed walls 390 urges the clip 370 to clutch onto one of the tabs 290, 300 when inserted into the channel 380 such that there is good electrical contact between the clip 370 and the tab 290, 330. The spring loading is partly achieved by forming the clip 370 from an elastically-resilient material which enables the walls 390 to spring back towards each other after a tab is removed.

The spring loading in this embodiment is assisted by the shape of the outer wall 410. The outer wall 410 has a slight concave curvature towards the inner wall 400, and tends to elastically flatten out when the opposed walls 390 are pushed apart, such as when a connection tab is WO 02/39021 PCT/AU01/01445 11 inserted therebetween. When the outer walls 410 are flattened out, they react by applying a restoration force which tends to force the opposed walls 390 against each other. The spring-loaded clips 370 and mounting clip 320 together comprise an electrical attachment means which holds the first and second electrical connectors in electrical contact with each other.

The ceramic block 340 also includes opposite side faces 420, each side face having first and second grooves 430, 435 running along the length of the block. Each first groove 430 is proximal to the front face 360 and designed to engage oppositely-facing ridges 440 on opposed flanges 450 of the mounting clip 330. Each second groove 435 is distal to the front face 360 of the block and designed to engage a mounting plate 460 described in more detail below. The mounting clip 330 can be rapidly connected to the ceramic block 340 by pushing the inside surface 320 of the mounting clip towards the front face 360 of the block 340. During this procedure, the three connection tabs 290, 300 are forced into the channels 380 of the spring-loaded clips 370. At the same time, the opposed flanges 450 of the mounting clip 330 are initially pushed slightly apart as the. oppositely-facing ridges 440 slide over the side faces 420 of the block 340, and then snap back towards each other when the ridges 440 locate within the grooves 430 until the flanges 450 are substantially parallel. The ridges 440 and grooves 430 hold the mounting clip 330 firmly attached to the ceramic block 340, while permitting the mounting clip 330 to slide along the length of the ceramic block 340 when a sufficient pushing force is applied. In this way, the mounting clip 330 can be moved relative to the ceramic block 340, thereby allowing the effective length of the WO 02/39021 PCT/AU01/01445 12 neck 230 to be repeatedly adjusted.

The heating element 10 also includes a mounting plate 460 designed to mount the ceramic block 340 onto the rear wall 40 of the oven. The mounting plate is mounted onto the rear wall 40 with fasteners, and is attached to the ceramic block 340 at a position adjacent a first end face 480 of the block. The mounting plate 460 enables the ceramic block 340 to be mounted in one of two configurations. In the first configuration (shown in Fig 4) first end face 480 of the ceramic block 340 is distal to the coil 210, while in the second configuration (shown in Fig 5) the first end face 480 is proximal to the coil.

As can be seen in the Figures, the first configuration adds a proportion A of the length of the ceramic block 340 to a length B of the arms 260 such that a total neck length L 1 is formed. In the second configuration, a proportion C of the length of the ceramic block 340 is subtracted from the length B of the arms 260, forming a total neck length L 2 which is less than or equal to L 1 The two configurations allow the neck length to be adjusted over a wide range using a relatively short ceramic block 340 and relatively short arms 260. The longest neck length is formed by using the ceramic block in the first configuration and positioning the mounting clip 330 distal to the first end face 480. Alternatively, the neck portion 230 may be arranged to have a neck length which is effectively zero by using the second configuration and adjusting the length C such that it is equal to B.

The three electrical terminals 220 protruding through the connection port 120 in the rear wall 40 are connected to the spring-loaded clips 370 via pins 490 which pass through the ceramic block 340.

WO 02/39021 PCT/AU01/01445 13 The mounting plate 460 (shown in detail in Fig 11) includes a rectangular central aperture 500 for receiving the electrical terminals 220, and an elongate aperture 502 on either side of the central aperture for receiving one or more fasteners when mounting the mounting plate to the rear wall 40. A fastener a screw) can be received at any one of a range of different locations along the length of each elongated aperture 502 so as to coincide with an attachment point in the wall a threaded screw hole). A first pair of opposed flanges 504 extend from the longest edges 506 of the mounting plate, and a second pair of opposed flanges 510, oriented perpendicular to the first opposed flanges 504, extend from opposite edges of the central aperture 500. An inside surface 512 of the mounting plate is designed to seat against the rear face 470 of the ceramic block such that the electrical terminals 220 protrude through the central aperture 500.

The second opposed flanges 510 of the mounting plate 460 also include opposed ridges 516 for engaging the respective second grooves 435 of the ceramic block 340.

The second opposed ridges 516 enable the mounting plate to clutch onto the ceramic block. The second opposed flanges 510 are sufficiently stiff to hold the opposed ridges 516 lodged within the second grooves 435 during use, while also being sufficiently flexible to prevent fracture as the mounting plate is attached or removed from the ceramic block.

Once the second opposed ridges 516 become lodged in the second grooves 435, the first opposed flanges 504 prevent the mounting plate 460 from sliding along the length of the ceramic block. One of the first opposed flanges 504 is designed to fit within a transverse slot 518 in the rear face 470 of the ceramic block 340, and the WO 02/39021 PCT/AU01/01445 14 other of the opposed flanges 504 is designed to rest adjacent and parallel to the first end face 480 of the ceramic block.

Referring now to Fig 12 in conjunction with Figs the coil 210 of the heating element 200 is mounted to the rear wall 40 of the oven with three mounting legs 530.

Each mounting leg 530 includes a coupling portion in the form of two C-shaped portions 540 which firmly clip onto two respective parallel loops 550 in the coil 210. The Cshaped portions 540 are shaped to clutch onto the loops 550 once they are pushed on. Each mounting leg 530 also includes a foot 560 with an aperture 570 for fastening the foot 570 to an attachment point in the rear wall 40, such as a threaded or blind screw hole 580. The aperture 570 in the foot is elongated such that a fastener can be positioned at a range of positions along the aperture 570, depending on the location of an attachment point in the oven relative to the outer diameter of the coil. Each mounting leg 530 can be positioned anywhere along either the outer or inner diameter of the coil 210 such that the aperture 570 in the foot 560 coincides with an attachment point 580. The appropriate number of mounting legs 530 can be used to coincide with the number of attachment points in the oven wall. Mounting legs of the prior art are fixed in position on the coil and do not have an elongated aperture in the foot. Consequently, even if the neck length of a prior art heating element matches that of an oven, the heating element cannot be installed if the aperture in each foot of the mounting legs do not coincide with the attachment points in the oven wall. The mounting leg 530 shown in Fig 12 is formed from a single piece of wire bent into the appropriate shape, and has the advantage of allowing heat to dissipate from the coil WO 02/39021 PCT/AU01/01445 15 between the parallel wire sections 590.

Figure 13 illustrates the profile of an alternative embodiment of a spring-loaded clip 600 which can be used in place of the spring-loaded clip 370 shown in Figs 6A and 6B. The clip 600 includes a channel 605 formed between a base 610 and opposed holding members in the form of opposed walls 620 extending from the base. Converging portions 630 of each wall are normally either in contact, or in very close proximity to each other, when not in use.

Upper portions 640 of the opposed walls 620 extend upwardly and outwardly from the respective converging portions 630 and serve to guide a connection tab 290, 300 into the channel 605 as it is pushed towards the base 610.

The converging portions 630 serve to maintain electrical contact with an inserted connection tab. The walls 620 and base 610 are formed from an elastically-resilient metal which enables the clip to apply a suitable contact force to a connection tab inserted into the channel 605.

The base 610 includes a central portion 650 curved upwardly towards the channel 620 which adds further spring loading to the walls 620.

The ceramic block 340 may be made from any one of a number of different ceramic materials, or a combination of ceramics, suitable for use in ovens. The mounting clip 330, mounting leg 530, mounting plate 460 and springloaded clips 370, 600 can all be made from metals or metal alloys known by a person skilled in the art to be suitable for use within ovens. The clips 370, 600 should be made from an electrically conductive metal or metal alloy.

Although the heating portion shown in the Figures comprises a double-loop coil, the present invention also includes within its scope a heating portion comprising a WO 02/39021 PCT/AU01/01445 16 coil with more or less loops than this, such as a singleloop coil or a treble-loop coil.

It will be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present 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 to be illustrative and not restrictive.

Claims

2. The heating element according to claim 1 wherein the neck portion is arranged to be adjustable to a second neck length after it has been adjusted to a first neck length.
3. The heating element according to any one of the preceding claims wherein the neck portion is arranged to be continuously length-adjustable within a predetermined range of neck lengths.
4. The heating element according to any one of the preceding claims wherein the neck portion comprises a first neck portion and a second neck portion, the first and second neck portions being arranged to be connected together to form any one of a plurality of different neck lengths. The heating element according to claim 4 wherein the neck portion comprises an electrical connection means for electrically connecting the first and second neck portions together.
6. The heating element according to claim wherein the electrical connection means comprises a plurality of first electrical connectors associated with the first neck portion and a plurality of second electrical connectors associated with the second neck portion for connecting to the first electrical connectors, whereby to complete a circuit between the terminals and WO 02/39021 PCT/AU01/01445 18 heating portion.
7. The heating element according to claim 6 wherein the neck portion is arranged to be adjusted by sliding the first and second neck portions relative to each other, and the electrical connection means is arranged to electrically connect the first and second neck portions at each adjusted length.
8. The heating element according to either claim 6 or claim 7 wherein each of the first electrical connectors comprises an elongate conductor and each of the respective second electrical connectors is arranged to connect with one of the respective first connectors at any one of a plurality of different locations along the first connector.
9. The heating element according to claim 8 wherein each first connector is in the form of a generally strip-like member. The heating element according to any one of claims 6-9 wherein each first electrical connector comprises an elongate conductor with a generally U-shaped cross-section.
11. The heating element according to any one of claims 7-10 wherein the electrical connection means further comprises an attachment means arranged to hold the first and second electrical connectors in electrical contact during use.
12. The heating element according to claim wherein each elongate conductor comprises a spring-loaded clip with opposed resiliently-biased walls arranged to receive and hold one of the second connectors between the walls.
13. The heating element according to claim 12 wherein the first electrical connector comprises the spring-loaded clip.
14. The heating element according to either claim 12 or claim 13 wherein the first electrical connectors are held within respective slots in the first neck portion. 19 The heating element according to either claim 12 or claim 13 wherein the second electrical connectors comprise tabs arranged to be received between the opposed walls of the respective spring-loaded clips such that electrical contact is made with the first electrical connectors. 0 16. The heating element according to any one of O claims 4 to 14 wherein the first neck portion has a first fixed length and the second neck portion has a second fixed length, a range of different neck lengths being obtainable by combining the first and second neck lengths. (N 17. The heating element according to claim 16 wherein the first and second neck portions are arranged to be connected together in either: a first configuration in which the lengths of the first and second neck portions are additively combined to form a neck length which is at least as great as the first neck length and the second neck length; or a second configuration in which the lengths of the first and second neck portions are subtractively combined to form a neck length and the second neck length.
18. A heating element substantially as hereinbefore described with reference to Figs 3 to 13. Dated this 7th day of December 2005 RON WILSON By its Patent Attorneys GRIFFITH HACK