GB2342848A

GB2342848A - Electric liquid heating apparatus with clip retaining means

Info

Publication number: GB2342848A
Application number: GB9903105A
Authority: GB
Inventors: Robert Andrew O'neill; John Anthony Howarth
Original assignee: Otter Controls Ltd
Current assignee: Otter Controls Ltd
Priority date: 1998-10-23
Filing date: 1999-02-11
Publication date: 2000-04-26
Also published as: GB9823342D0; GB9903105D0

Abstract

An electric liquid heating apparatus comprises a vessel body 1 having a planar heating element 4 retained by means of clip means 6 engaged with the vessel body, or engaged with formations provided on the vessel body. The planar heating element may be provided with a U-shaped seal around its peripheral edge, with the clip means holding the seal under compression against abutment means. The clip means may comprise a plurality of stainless steel spring clips, with formations adapted to make positive engagement with complementary formations 3 provided in or on the vessel body. There may also be provided additional reinforcing means (20, fig 4) backing up the retention of the heating element by the clip means, such as clamps (22, fig 4) fixed securely to the vessel body, as opposed to being clipped to the vessel body. In another aspect of the invention there may be provided an electric liquid heating apparatus with a plastics vessel body having an electric heating element retained in position by clip means, where the clip means have barbs 7 which bite into the moulded plastics material of the vessel body. In a further aspect of the invention an electric liquid heating apparatus may comprise a moulded plastics body with a planar heating element and seal received in a recess in the base of the body. The vessel body may be formed with a plurality of mounting positions to which retaining means, such as clips and/or clamps, are secured to hold the heating element with the seal in place under compression.

Description

IMPROVEMENTS RELATING TO ELECTRIC WATER HEATING VESSELS Field of the Invention: This invention concerns improvements relating to electric water heating vessels, and more particularly concerns the securing of planar heating elements into water heating vessels.

Background of the Invention: Heating elements for domestic water heating appliances have conventionally been of the metal sheathed immersion heater type in which a resistance heating wire is contained within a tubular metal sheath packed with insulating material. Such sheathed heating elements have conventionally been attached to a head plate enabling the heating element to be mounted in a vessel, a kettle or hot water jug for example.

Planar heating elements are also known. The so-called underfloor type of heating element which comprises a metal plate having a sheathed heating element proper secured to the underside thereof has been popular in mainland Europe for many years, avoiding as it does the intrusion into the water containing volume of the vessel of an immersion type of heating element. Also known and becoming increasingly popular are so-called thick film heating elements which comprise an electrically insulating substrate, commonly a stainless steel plate having an insulating layer formed thereon, having a resistance heating track or layer formed thereon and generally having a further electrically insulating layer formed on top of the resistance heating track or layer for protective purposes, Many different methods have been proposed for the fixing of planar heating elements into water heating vessels such as domestic kettles and hot water jugs. Examples are described in our British Patent Application No.

9821862.1.

Obiects and Summary of the Invention: The principal object of the present invention is to provide a simple, inexpensive and effective means of securing a planar heating element into a water heating vessel.

According to the present invention in one of its aspects a vessel body is provided internally with abutment means defining a seating within the vessel body for a planar heating element, and the planar heating element is urged towards said abutment means by means of clip means engaged with the vessel body or with features provided therein.

The abutment means can for example comprise an internal flange within the bottom of the vessel body, in which case a sealing ring can be captured between the flange and the upper peripheral surface of the planar heating element for sealing the heating element into the vessel. Alternatively, the abutment means can comprise spaced-apart formations within the vessel body, in which case a seal support ring could first be introduced to define a seating for an O-ring seal between the upper peripheral surface of the heating element and the seal support ring, the clip means serving to urge the heating element towards the seal support ring thereby to deform the O-ring seal into an effective sealing configuration. Alternatively, or additionally, a sealing ring arrangement could be provided beneath the planar heating element and around the periphery thereof, the clip means acting on such sealing ring arrangement to ensure effective sealing of the heating element into the vessel.

The clip means can conveniently be of the kind employed in the fixing of trim components in the motor industry and comprising a generally U-shaped member of spring metal for example having barbs directed inwardly from the opposed limbs of the U-shape towards the bight thereof. Such clips are designed to be fitted onto edges of panel members whereupon the opposed barbs prevent or hinder their removal. The present invention contemplates that a plurality of such clips, or an equivalent continuous structure, can be fitted to the bottom edge of a vessel body or to formations provided in the vessel body and can be arranged to bear upon the planar heating element and secure it in the vessel.

Where, as is commonly the case, the vessel body is formed of moulded plastics material, the need may arise to restrict the transfer of heat via the clip means from the heating element to the moulded plastics vessel body to ensure that the vessel body is not heated excessively which might loosen the clip means and cause the vessel to leak. This can be achieved in large measure by use of a grommet seal or other thermal barrier between the heating element and the clip means, and additionally the clip means could be formed to define a long thermal path between the heating element and the vessel wall and/or could be formed of a low thermal conductivity material such as stainless steel for example.

To protect against the possibility that the clip means may not be sufficient to ensure that the heating element does not drop out of the vessel body if the vessel is dropped on its base when full of water, the present invention provides for additional means, such as clamps retained by screw-threaded fasteners engaged with bosses provided in the vessel body, to reinforce the clip structure.

The above and further features of the present invention are set forth in the appended claims and will be well understood from consideration of the following detailed description given with reference to the accompanying drawings.

Description of the Drawings : Figure 1 shows a cross-sectional view of a portion of the body of a water heating vessel and illustrates an embodiment of the present invention; Figures 2A to 2D show respectively end and side elevation views, a top plan view and a perspective view, all much enlarged the dimensions shown being in millimetres, of the clip shown in Figure 1; Figures 3A to 3D show respectively end and side elevation views and two perspective views of a modified form of clip; Figure 4 shows a perspective view illustrating how reinforcing means may additionally be provided to ensure that a heating element retained by clip means as described with reference to Figures 1, 2A to 2D and 3A to 3D cannot accidentally be dislodged; and Figures SA to 5D show an exemplary reinforcing clamp.

Detailed Description of the Embodiments: Referring to Figure 1, a moulded plastics vessel body 1 has an internal flange 2 and a depending skirt portion 3 formed as integrally moulded parts thereof. An electric heating element 4 of the thick film type for example is secured in the vessel body 1 by provision of a generally U-section, temperature resistant grommet seal 5, which is shaped to fit around the periphery of the heating element 4 as shown, and by provision of a plurality of spring metal clips 6, only one of which is shown, which are pushed onto the bottom edge of the skirt portion 3 of the vessel body, the clips 6 having inwardly directed barbs which bite into the plastics material of the skirt portion 3 to inhibit their removal and bearing as shown upon the seal 5 so as to force it and the captured heating element 4 against the underside of the flange 2.

Figures 2A to 2D show enlarged views of one of the clips 6. As can be seen, the clip comprises a sheet metal stamping provided with barbs 7 which is bent into a U-shape and has the ends 8 of the limbs 9 of the U-shape tumed slightly outwardly. As mentioned hereinbefore, clips of this kind are used in the motor industry.

Figures 3A to 3D show a modification of the clip 6 of Figures 2A to 2D, the modification comprising the provision of a part 10 extending from the end of one of the limbs 9 of the U-shaped clip. This provides an extended thermal path from the heating element abutting end of the part 10 to the barbs 7 so as to protect against excess heating of the barbs which could cause the plastics material of the vessel body 1 to soften locally and thereby loosen the respective clips, loosen the sealing of the heating element and give rise to leakage. The clip of Figures 3A to 3D could be manufactured of stainless steel for example which, having a relatively low thermal conductivity, would enhance the thermal isolation of the heating element from the barbs.

Alternatively or additionally a separate thermal barrier could be interposed between the lower surface of the heating element and the clips 6.

The possibility (however unlikely) exists that a heating element secured into a vessel body by means of spring clips as hereinbefore described could fall out of the vessel body if it was inadvertently dropped on its base while full of water. To protect against this, Figure 4 shows an arrangement wherein a number (at least two and preferably four as shown or more) of screwed bosses 20 are formed integrally around the base of the vessel body 1 and securing screw-threaded fasteners 21 are fitted into the bosses to secure in place reinforcing metal clips or clamps 22 which press upon the heating element seal 5 so as to hold the heating element 4 and the seal 5 in place.

Figures 5A, SB, 5C and 5D are detailed plan and elevation views of the metal clamp 22, Figures 5A and 5B being end and side elevation views and Figures 5C and 5D being top and bottom plan views. The clamps 22 may be formed of stainless steel for example which exhibits relatively poor thermal conductivity and have an extended portion 23 to reduce thermal transfer from the heating element 4 to the screws 21 and the bosses 20.

The use of a generally U-section grommet seal has a number of advantages which offset its relatively high cost. The seal provides a thermal barrier which protects the vessel body from the heat of the element and, by being between the element and the clips 6 and 22, also reduces heat transfer along the clips. The seal also helps to centrally locate the heating element relative to the vessel body. A plain rectangular section seal could alternatively be utilized, but would necessitate different heat shielding arrangements, such as longer and/or narrower clip components.

Having thus described the invention by reference to specific embodiments, it is to be appreciated that the embodiments are exemplary only and that modifications and variations are possible without departure from the spirit and scope of the invention. For example, in the described embodiments the clips are affixed to a depending circumferential skirt of the vessel and a cosmetic cover would be provided over and around this skirt to conceal the clips. In an alternative arrangement, there could be discrete formations provided in the bottom of the vessel for co-operation with the clips instead of the skirt portion 3. The clips, as described, are made of metal, but they could be formed of plastics material or as a metal/plastics combination and they could be formed with formations complementary to formations provided at appropriate locations of the vessel body so that the clips positively engage with the vessel body rather than relying upon metal barbs digging into the plastics material of the vessel body. Whereas the described clips are separate, discrete components they could be formed as a continuous strip which, in turn, could be formed into finished components such as closed rings, rectangles etc.

Small sacrifical ribs could be placed around the element receiving aperture in the vessel body to centrally locate the heating element during assembly and avoid substantial contact between the heating element and the vessel body moulding. In the event of the heating element overheating, these ribs would melt away from the heating element, but the heating element would remain centrally clamped by the clip and/or clamp arrangements and the seal would continue to provide heat shielding.

Finally, the clamp arrangement shown in Figure 4 could be employed on its own, that is to say without the clip arrangement of the preceding figures.

The invention provides the advantage of enabling replacement heating elements to be retrofitted readily to water heating vessels designed for other fixing methods. Additionally, tolerance problems are reduced since the barbs on the clips enable them to lock onto the vessel body in any position and do not require the provision of mating features on the clips and on the body to ensure that this is the case.

Claims

CLAIMS : 1. An electric liquid heating apparatus comprising a vessel body having a planar heating element retained therein by means of clip means engaged with the vessel body or with formations provided thereon.
2. An apparatus as claimed in claim 1 wherein the vessel body is provided internally with abutment means defining a seating for a planar heating element and the clip means serves to urge the planar heating element towards said abutment.
3. An apparatus as claimed in claim 2 wherein a seal is provided around the periphery of the heating element and the clip means maintains the seal under compression so as to maintain an effective seal between the planar heating element and the vessel body.
4. An apparatus as claimed in claim 3 wherein the seal has a generally U-shaped cross-section and the peripheral edge of the heating element is embraced by the U-shaped section of the seal.
5. An apparatus as claimed in any of the preceding claims wherein the clip means has formations adapted to make positive engagement with complementary formations provided in or on the vessel body.
6. An apparatus as claimed in any of the preceding claims wherein the vessel body is formed of synthetic plastics material and the clip means has barbs adapted to bite into the plastics material.
7. An apparatus as claimed in claim 6 wherein the clip means is formed of metal.
8. An apparatus as claimed in any of the preceding claims wherein the clip means comprises a plurality of discrete clips spaced about the periphery of the heating element.
9. An apparatus as claimed in claim 8 wherein the clip means are substantially as herein described with reference to Figures 2A to 2D or Figures 3A to 3D or Figures 5A to 5D of the accompanying drawings.
10. An apparatus as claimed in any of the preceding claims and further including reinforcing means backing up the retention of the heating element by the clip means.
11. An apparatus as claimed in claim 10 wherein the reinforcing means comprises additional clip means fixedly secured to the vessel body (as opposed to being clipped thereto).
12. An apparatus as claimed in claim 11 wherein the additional clip means are secured by screw-threaded fastenings to bosses formed on the vessel body.
13. An electric liquid heating apparatus comprising a moulded plastics vessel body having an electric heating element retained therein by means of clip means having barbs which bite into the moulded plastics material of the vessel body.
14. An electric liquid heating apparatus comprising a moulded plastics body having a planar heating element received in a recess in the base thereof with a seal provided between the heating element and the vessel body, and the vessel body is formed with a plurality of mounting positions spaced about said recess and retaining means are secured to said mountings and serve to hold the heating element in place with the seal under compression.
15. An electric liquid heating apparatus substantially as herein described with reference to any of the accompanying drawings.