GB2263850A

GB2263850A - Supporting an element in a heating unit for a hob

Info

Publication number: GB2263850A
Application number: GB9301685A
Authority: GB
Inventors: Craig Anthony Hill; Trevor William Cheetham
Original assignee: Redring Electric Ltd
Current assignee: Redring Electric Ltd
Priority date: 1992-01-30
Filing date: 1993-01-28
Publication date: 1993-08-04
Anticipated expiration: 2013-01-28
Also published as: GB2263850B; GB9202036D0; GB9301685D0

Abstract

A heating unit 2 for a ceramic hob comprises a heating element 1 retained in position by means of a wire clip 10 secured by means of upstanding end portions 11 of the clip 10 being anchored in the insulation material 5 of the wall. Alternatively the clip may be anchored in the base insulation 5. A plurality of clips may be provided. The clips may alternatively be outwardly directed to secure the element by engaging a shoulder 18 (Fig 6) of the envelope. A bracket 9 may optionally secure the terminal ends 7 of the element. <IMAGE>

Description

A HEATING UNIT FOR A HOB This invention relates to a heating unit for a hob, and in particular, but not exclusively, to a heating unit for a ceramic hob.

Heating units for ceramic hobs are normally formed from a shallow metal container, or "can", which is lined with an insulating material. On this are positioned wire heating elements, which in use radiate infrared energy through the ceramic plate to the cooking utensil.

It is common in many heating units, as described above, to supplement the wire heating element with a halogen type lamp. This normally comprises a very fine tungsten wire surrounded by an inert halogen gas to prevent oxidation of the tungsten element at high temperatures. This gas is contained within a silica envelope normally in the form of a tube through which the tungsten element runs.

Halogen lamps of the above type often comprise a straight tube having an electrical terminal on each end.

These can be mounted across the heating unit container and held in position by being secured at each end to the container.

In order to provide more aesthetically pleasing designs of lamps, the lamps being visible in use through the ceramic plate, and to achieve more uniform heating, tungsten halogen lamps have now been designed which almost form a complete circle with the end portions terminating in close proximity, (see lamp 1 illustrated in Figure 1 of the attached drawings). It will be appreciated that if the lamp is again mounted at its end portions then there is considerable stress on these portions.

According to the present invention there is provided a heating unit for a hob comprising: a container; a layer of thermally insulating material extending over an inner base portion of the container; a wall of thermal insulating material extending around an inner surface of a wall of the container and in contact with the layer of thermally insulating material; a heating element, including a wire element encased in an envelope, positioned above the layer of insulating material and a clip for retaining the heating element envelope in position, the clip extending from between the wall of insulating material and the layer of insulating material, the clip comprising a length of wire, the mid portion of which is substantially U-shaped and extends over the envelope of the heating element and the free ends of which are upstanding relative to the plane of the U-shape and extend into the thermally insulating material.

By employing the present invention the heating element may be maintained in position by means of the clip which can simply be pushed into the insulating material. The clip is very easy and cheap to produce consisting of an appropriately shaped piece of wire, which term for the purposes of this specification includes "wire" shaped members, whether produced by being drawn, stamped or produced by other suitable means, and also includes narrow thin members not necessarily of circular cross section. The use of such a clip does not require any special moulding, shaping or tooling of the other components of the heating unit in order to provide a means of fixing the heating element in position. Furthermore the position of the clip is not crucial to its performance and can simply be positioned by eye.Additional advantages of such a clip are that it restrains the heating envelope while only obscuring a negligible portion of the element, it allows expansion of the heating element and the envelope in which it is contained as well as preventing verticle and lateral displacement of the element.

Preferably: the container is round; the wall of thermally insulating material extends circumferentially around the wall of the container; the heating element extends around a path close to the periphery of the recess defined by the wall of thermally insulating material and the layer of thermally insulating material; and the two ends of the heating element are in close proximity. The advantage of such containers is that the element is in close proximity to the wall around the container and therefore one or more clips can easily be employed to restrain the element.

In one embodiment the invention provides a heating unit wherein the ends of the heating element extend through corresponding apertures in the thermally insulating wall and the wall of the container, and are supported in relation to the wall of the container by means of a bracket connected thereto. In this embodiment the heating element has a fixed location point defined by the bracket and is maintained in this position by the clip and preferably the clip urges the heating element against the bracket.

In an alternative embodiment a heating unit is provided in accordance with the invention wherein the heating element extends through corresponding apertures in the thermally insulating wall and the wall of the container, and the clip extends across the two portions of the heating element adjacent the ends. The clip when in this position provides additional support by the inner surface of the substantially U-shaped portion of the clip acting on the adjacent portions of the heating element to provide additional lateral positional stability.

In a further embodiment the invention provides a heating unit wherein at least one end of the heating element extends through the wall of the container and has a shoulder outside the container over which the clip extends.

When employing the heating unit in accordance with the invention the upstanding free ends of the clip can extend into the layer of the thermally insulating material or alternatively may extend into the wall of thermally insulating material.

Advantageously the heating unit comprises at least two clips each of which urges the heating element towards another clip. Such clips can then be used to position the heating element correctly.

According to the present invention there is also provided a method of making a heating unit in accordance with the invention described above, comprising placing the heating element in the container, pushing the upstanding end portions of the clips into a bottom surface of the wall of thermally insulating material, and inserting the wall of thermally insulating material in the container. Preferably in doing so the heating element is correctly positioned by means of the clips.

The invention will now be described by way of example only with reference to the accompany Figures of which Figures 1, 3, 4 and 5 illustrate heating units in accordance with the invention; Figure 2 shows a partial cross-section through one of the heating units illustrated in Figures 1,3 or 4; and Figure 6 shows a partial cross-section through the line A-A of the heating unit illustrated in Figure 5.

Referring to Figure 1 there is illustrated a heating element 1 consisting of a wire element la encapsulated in a silica envelope lb containing a halogen gas A heating element 1 is contained within a heating unit 2 for position under the ceramic plate of the hob or cooker.

The unit 2 consists of a shallow metal container or "can" 3 having a layer of insulation material 4 on the bottom surface thereof and another wall of insulating material 5 on the inner wall of the container 3.

In addition to the heating element 1, the heating unit also has a conventional wire element 6, fixed to the layer of insulation 4, to provide additional infrared radiation.

The ends of the heating element 1 terminate in a ceramic insulating collar 7 pushed through an aperture 8 in the insulating wall, and corresponding aperture in the wall of the container 3, so that it protrudes from the can. A bracket 9, (shown for means of explanation both attached and unattached), is secured over the aperture 8 in the wall of the container 3 by means of tags 9a, and the insulating collar 7 is restrained in position by means of this bracket.

Diametrically opposite the bracket 9 is a clip 10 comprising a U shaped piece of wire, the ends 11 of which extend vertically into the wall of thermally insulating material 5, as can be seen more clearly from Figure 2.

Although shown extending into the wall 5 it will be appreciated that the clip could be inverted and pushed into the layer of insulating material 4 as shown at 12.

When the heating unit 2 is constructed, the ends 11 of clip 10 are simply pushed into the wall of insulating material 5 which is of a fibre construction. The wall is then placed in the container such that the clip 10 acts on the heating element 1 in the direction of the arrows 13 and 14, such that the heating element 1 is retained in position against bracket 9 of Figure 1.

In Figure 3 an alternative embodiment of the invention is shown where three clips 10 retain the heating element 1 in position, eliminating the need for the bracket 9 of Figure 1. In such an arrangement the heating element 1 is placed on the insulating layer 4, the clips 10 are pushed into the bottom of the insulating wall 5 and the wall inserted into the container 3. The clips 10 automatically act to restrain the heating element 1 in position.

In Figure 4 another alternative embodiment is illustrated where clip 10a extends over the end portions 15 of the heating element 1, thereby further restraining lateral movement.

In Figures 5 and 6 another alternative embodiment is illustrated in which two straight heating elements 16 extend across the heating unit 2 and through apertures in the insulating wall 5 and container 3. Connections to the heating elements 16 are made through terminals 17 at the ends of the heating elements 16. The heating elements 16 taper through a shoulder portion 18 towards the terminals 17. The shoulder portion 18 of the heating element 16 lies outside the container 3. Figure 6 is a partial cross-section through the region A-A as indicated in Figure 5. The clip 10 extends out of the heating unit 2 from between the insulating layer 4 and insulating wall 5 over the shoulder 18 of the heating element 16. The effect of the clip 10 upon the heating element 16 is to apply force in the direction of the arrows 19 and 20 of figure 6. A similar arrangement exists at the opposite end of the heating element 16 thereby securing the element.

Although several embodiments of the invention have been described above, these are not exhaustive. It will be appreciated that various configurations and numbers of clips can be employed within the scope of the present invention.

Additionally this securing means is appropriate to a wide variety of heating element shapes.

Claims

1. A heating unit for a hob comprising: a container; a layer of thermally insulating material extending over an inner base portion of the container; a wall of thermal insulating material extending around an inner surface of a wall of the container and in contact with the layer of thermally insulating material; a heating element, including a wire element encased in an envelope, positioned above the layer of insulating material; and a clip for retaining the heating element envelope in position, the clip extending from between the wall of insulating material and the layer of insulating material, the clip comprising a length of wire, the mid portion of which is substantially U-shaped and extends over the envelope of the heating element and the free ends of which are upstanding relative to the plane of the U-shape and extend into the thermally insulating material.

2. A heating unit as claimed in claim 1, wherein: the container is round; the wall of thermally insulating material extends circumferentially around the wall of the container; the heating element extends around a path close to the periphery of the recess defined by the wall of thermally insulating material and the layer of thermally insulating material; and the two ends of the heating element are in close proximity.

3. A heating unit as claimed in claim 2 wherein the ends of the heating element extend through corresponding apertures in the thermally insulating wall and the wall of the container and are supported in relation to the wall of the container by means of a bracket connected thereto.

4. A heating unit as claimed in claim 3 wherein the clip urges the heating element against the bracket.

5. A heating unit as claimed in claim 2, wherein the ends of the heating element extends through corresponding apertures in the thermally insulating wall and the wall of the container, and the clip extends across the two portions of the heating element adjacent the ends.

6. A heating unit as claimed in claim 1 wherein at least one end of the heating element extends through the wall of the container and has a shoulder outside the container over which the clip extends.

7. A heating unit as claimed in any preceding claim comprising at least two clips each of which urges the heating element towards one other clip.

8. A heating unit as claimed in any preceding claim wherein the clip restrains the heating element form both lateral and verticle displacement.

9. A heating unit as claimed in any preceding claim wherein the upstanding free ends of the clip extend into the layer of thermally insulating material.

10. A heating unit as claimed in any one of claims 1 to 8 wherein the upstanding free ends of the clip extend into the wall of the thermally insulating material.

11. A heating unit as claimed in any preceding claim wherein the heating element comprises a halogen lamp.

12. A heating unit substantially as hereinbefore described with reference to the accompanying figures.

13. A hob comprising a heating unit as claimed in any preceding claim

14. A method of making a heating unit as claimed in any preceding claim comprising placing the heating element in the container, pushing the upstanding end portions of the clip into a bottom surface of the wall of the thermally insulating material and inserting the wall of thermally insulating material in to the container.

15. A method as claimed in claim 14 wherein in inserting the wall of thermally insulating material the heating element is positioned by means of the clip.