GB2360441A

GB2360441A - Electrically-powered liquid-heating vessel

Info

Publication number: GB2360441A
Application number: GB0104532A
Authority: GB
Inventors: Robert Andrew O'neill; Robert Henry Hadfield; Antonio Martin Gaeta
Original assignee: Otter Controls Ltd
Current assignee: Otter Controls Ltd
Priority date: 2000-02-25
Filing date: 2001-02-23
Publication date: 2001-09-26
Also published as: AU3395901A; GB0104532D0; WO2001062129A1; GB0004563D0

Abstract

An electrically-powered liquid-heating vessel such as a kettle comprises an inner body or liner 1 fitted with an outer body or skin 2. The inner body 1 may be of thermally insulating material, particularly plastics or glass, and may be transparent or translucent. The outer body 2 may be metallic, particularly of stainless steel, and may have one or more openings serving as a sight glass for observing the liquid level. Alternatively, the outer body may be of plastics. The inner body 1 may have formations such as axial grooves in its outer surface and crushing ribs 4 facilitating its insertion into the outer body and enabling it to accommodate tolerance variations in the dimensions of the outer body.

Description

2360441 IMPROVEMENTS RELATING TO ELECTRICALLY HEATED VESSELS

Field of the Invention: 5

This invention concerns improvements relating to electrically heated vessels, particularly though not exclusively vessels such as kettles and hot water jugs and the like.

Background of the Invention:

Stainless steel kettles and hot water jugs have a high surface temperature when they are holding boiling water. Plastics material vessels tend to have lower surface temperatures as a result of their greater thickness and lower thermal conductivity. Plastics material surfaces also have higher permitted temperature limits during normal use, since the low thermal conductivity tends to reduce the amount of heat reaching the user's skin to cause damage. Even so, double walled plastics material vessels have been proposed, see GB-A-2286331 and GB-A-2311716 for example, which would have the effect of providing a cooler outer surface in operation though this is not the primary intention, that being to thermally insulate the vessel interior so that boiled water keeps hot for a longer period. However, plastics material vessels do not have the appeal and durability of a stainless steel kettle.

2 Objects and Summgn of the Invention:

The principal object of the present invention thus is to provide a kettle or water heating jug having the outward appearance of a metal appliance with the lower surface temperature of a plastics material vessel.

Another object of the invention is to enable water heating vessels to be customized, as regards their external appearance, by a manufacturer or a user.

According to the present invention, in a first aspect, a metal bodied water heating appliance has a plastics material inner liner which, at least to a certain extent, thermally insulates the metal body of the appliance from hot water within the appliance.

In accordance with another aspect of the present invention, a plastics material bodied water heating appliance has a metal outer skin.

Hereinafter described in detail is an exemplary embodiment of the abovementioned first aspect of the invention in which a moulded plastics material liner is added to the inside of the stainless steel body of a vessel, the liner being close fitting and being held in place by the fitting of a bottom wall to the steel body. The liner need not have a bottom and only needs to fit against the side walls of the vessel. The thickness of the liner will determine the surface temperature of the outer surface. In manufacture of such an embodiment the main part of the vessel body may be deep drawn from a sheet of stainless steel. The resulting domed shape may then be pierced for a spout 3 and a lid opening, if required, and attachments for a handle, level gauges and controls may be spot welded in place. The spout may be fitted either by brazing or by a mechanical clenched join and the lid opening, if any, may be rolled to smooth the edges. At this stage the proposed plastic liner may be fitted through the still open base of the vessel body and pressed into position with its upper edge received in the rolled over edge of the lid opening. The bottom of the vessel may then be fitted and the join scaled, for example by clenching. The bottom can carry a flat heating element, a thick film heating element for example, affixed to its underside. The bottom edges of the liner fit closely against the bottom of the vessel so as to hold the liner securely in place.

In an embodiment of the other aspect of the present invention mentioned above, an otherwise conventional plastics bodied water heating vessel has an outer skin formed of stainless steel or brushed aluminium for example which is fitted onto the vessel. The outer skin enables the vessel to be customized, for example by use of different colours and/or different metal finishes, by the manufacturer and/or the user.

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

4 Description of the Drawings:

Figure 1 is an exploded view showing the component parts of an exemplary embodiment of the present invention; Figure 2Js a sectional view of the assembled embodiment of Figure 1; and Figure 3 is an isometric view of the assembled embodiment of Figures 1 and 2.

Detailed Description of the Embodiment:

Referring to the accompanying drawings, the aforementioned first aspect of the invention is embodied in the addition of a moulded plastics material liner 1 to the inside of the stainless steel body 2 of a vessel exemplied as a water boiling kettle or hot water jug, the liner being close fitting and being held in place by the fitting of a bottom wall 3 to the steel body. The liner 1 does not have a bottom and only fits against the side walls of the vessel. The thickness of the liner will determine the surface temperature of the outer surface of the vessel and will also directly affect the cost. We propose a liner between 2 and 3min as a good compromise between cost, weight and performance.

The main part of the body 2 is deep drawn from a sheet of stainless steel, this process normally including some annealing between several stages depending on the profile and depth of draw. The resulting dome shape is then pierced for a spout and a lid opening, if required, and attachments for a handle, level gauges and controls are spot welded in place. The spout is fitted, either by brazing or by a mechanical clenched join, and the lid opening, if any, is rolled to smooth the edges. At this stage the plastics material liner 1 is fitted through the still open base of the vessel body and pressed into position.

In order to ease assembly, the liner moulding 1 may have axial grooves (not shown) in its outer surface which will allow the liner to collapse slightly as it is pushed into the vessel body 2 and enable the spout projection 7 of the liner to enter the spout proper 13. Once the spout projection 7 is engaged with the body spout 13, the liner is trapped in position which facilitates subsequent steps in the assembly of the vessel. The bottom 3 of the vessel is then fitted and the join sealed, usually by clenching in the same manner as the lid of a tin of baked beans. The bottom 3 of the vessel has a heating element 20 of a sheathed, mineral insulated, wire wound type affixed to its underside, but this could be a heating element of any type, for example a thick film heating element, and a dry boillboil control (not shown) will be affixed under the heating element. The bottom of the liner 1 fits closely against the bottom 3 of the vessel, so as to hold the liner securely in place. The vessel body is then ready for polishing and finishing.

In use, the relatively high thermal expansion of the plastics material (polypropylene is preferred) causes the liner 1 to expand against the inside of the steel body 2, minimising the volume of any trapped water to ensure that 6 cold water is not mixed with hot as it is poured out and also eliminating any trapped stagnant water which might present a health risk.

To improve manufacture we propose to add small (0.5min) crushing ribs 4 to the exterior of the liner 1, to take up tolerances in the form of the drawn steel body 2 which is known to have quite wide manufacturing tolerances. Also small ribs or castellations 5 are provided around the bottom edge of the liner 1 to take up tolerances between the body 2 and base 3 of the vessel. Where the vessel has a lid opening, then the upper edge of the liner may be arranged to fit into the inverted "U" section 6 of the rolled edge of the lid opening to hide the edge of the liner and to provide a firm location. Again, small crushing ribs could be provided in this region to accommodate tolerances.

To provide added value further enhancements are possible for no extra component cost, although the tooling would necessarily be somewhat more complex and costly. A projection 7 may be provided to fit within the spout to provide added location in this area, or the liner 1 itself could form the whole of the visible spout, with a suitable seal around the spout aperture in the vessel body. A separate moulded spout secured to the liner is also possible, to provide something different from the truncated conical shapes normally found on stainless steel kettles. Mountings 8 may be provided within the spout area of the moulding to support a filter 9 to prevent scale and debris being poured out of the vessel. The provision of these mountings represents a cost saving over a normal steel kettle where they have to be provided separately and 7 secured to welded location features. The liner moulding can also provide level markings 6 for "Maximum" fill, which would also conventionally have to be added separately. It is also possible to include a steam tube 11, moulded integrally with the liner and carried by a web 14, which comprises a generally vertical tube which will pass through a hole in the bottom 3 of the kettle to allow steam to reach a base mounted boil control adapted to switch off or reduce the heat output of the heating element when water is boiled and steam is generated in the kettle. The tube 11 would be sealed to the bottom 3 by a resilient seal 12, such as a "Nulox" bush, grommet or "0" ring. Alternatively, steam duct features could be included for a side mounted boil control accessed through a hole in the side wall of the body. Bosses 15 could be moulded within the liner to provide screw anchorages for handles or other external features. It should be noted that little of the liner would be visible externally, so the normal limitations on section changes which cause sink marking or other disfigurations to a smooth surface finish are much less important. The liner could be moulded from a fully transparent material such a polycarbonate (at higher cost than polypropylene) to further enhance the illusion of a wholly stainless steel vessel. The liner moulding could also include features close to its upper edge to enable mounting of a lid for the vessel, for example hinge points and locking points to prevent the lid from opening miadvertently.

The aforementioned first aspect of the invention having been described in the foregoing by reference to a specific embodiment, it is to be well appreciated that the embodiment is exemplary only and that modifications and 8 variations are possible without departure from the spirit and scope of the invention as set forth in the appended claims. For example, the principle of the invention, namely the provision of a thermally insulating inner liner, is applicable to any kettle or jug formed of any metal, such as plated steel or copper or enamelled or painted metal. The invention also extends to double walled kettles where the inner wall is formed of other materials, such as steel or silicone rubber for example, or is applied as a coating, such as a PTFE based coating for example, where the lining is thick enough to have a significant effect on the outer surface temperature, or a foamed material. A ceramic thermally insulating coating, such as a slip coating which is subsequently fired, could be applied. Furthermore, a space may be provided between the inner and outer wall or the liner may be double walled with a space therebetween, since this will enhance the cooling. In the case where the liner is spaced from the outer wall it would be preferable to seal the lining to the outer wall to stop the accumulation of cold water in the gap. Alternatively the gap could be filled with a suitable insulating material such as a plastics material foam.

The invention, in its other aspect, also extends to the inverse of the described embodiment, namely a plastics material vessel provided with an external stainless steel skin rather than a metal vessel provided with a thermally insulating inner liner as described in the foregoing. All of the features described above, such as spout, filter mounting, steam duct, heating element, controls etc may be provided on the plastics moulding, and the 9 plastics moulding may then be fitted within a polished stainless steel or brushed aluminium casing, which is sealed around the lid opening and spout.

In this case we would propose using a heating element mounting method such as is described in GB-A-2 330 064 where the base cover component may be of steel or plastics material and may be arranged to mate with the stainless steel casing of the vessel to complete the external appearance of the appliance.

Alternatively, the inner plastics material vessel can be a complete vessel rather than just a partial liner, and the outer skin can be metallic or formed of plastics material and becomes a decorative cover. The inner plastics material vessel may be clear or translucent and one or more openings may be provided in the outer skin so that the level of liquid in the vessel may be viewed through the clear or translucent plastics thus constituting an integral sight glass or glasses. The inner vessel could be formed of glass with the same result. This has the benefit of providing a leak-proof sight glass. Other decorative piercings may be provided in the outer skin, for example so as to make visible an internally illuminated vessel (see in this connection our British Patent Application No. 0002488.5). Other features, such as the handle for example, may be part of the outer skin so that vessels of different appearances may be formed by use of a common inner part and an outer part selected from a range of different outer skins.

The advantages of the invention over conventional metal bodied vessels are a reduction in the surface temperature of the vessel body, leading to a reduced risk of accident, an improved appearance and durability over a normal plastics material appliance, and a reduced noise level, especially in higher powered appliances, particularly those with thick film heating elements. The increased cost involved in the provision of the plastics material inner is offset by the ability to integrate those features mentioned above within a single inner moulding, leading to reduced component count and a reduced assembly time. Moreover, advantage is obtained by the facility to use the same inner moulding, formed for example as a complete vessel, with a variety of metallic or plastics material outer skins.

Claims

CLAIMS:

1. An electrically powered liquid heating vessel comprising a vessel body formed of plastics material or glass and an outer skin fitted to said vessel body.

2. A vessel as claimed in claim 1 wherein said outer skin is formed of a metallic material.

3. A vessel as claimed in claim 1 wherein said outer skin is formed of a plastics material.

4. A vessel as claimed in any of the preceding claims wherein said outer skin has one or more openings therein exposing the underlying vessel body. 15

5. A vessel as claimed in claim 4 wherein the vessel body is transparent or translucent.

6. A vessel as claimed in any of the preceding claims wherein the outer 20 skin comprises a preformed unit which is removable from the vessel body.

7. A method of manufacturing an electrically powered liquid heating vessel, said method comprising forming a vessel body of plastics material or 12 glass, forming an outer skin designed to be fitted to said vessel body, and fitting said outer skin to said vessel body.

8. An electrically powered liquid heating vessel having a metal outer surface which is thermally insulated from the vessel interior, the vessel comprising a metal outer body provided internally with thermal insulation and the thermal insulation comprising a prefon-ned liner inserted into the metal outer body of the vessel.

9. A vessel as claimed in claim 8 wherein said liner has formations enabling it to accommodate tolerance variations in the dimensions of said metal outer body.

10. A vessel as claimed in claim 8 or 9 wherein said liner has formations facilitating its insertion into said metal outer body.

11. A vessel as claimed in any of claims 8 to 10 wherein the thermal insulation comprises plastics material.

12. A method of manufacturing an electrically powered liquid heating vessel, said method comprising forming an external metal body part of the vessel and providing thermal insulation within said metal body part to 13 thermally insulate the exterior of the vessel from its hot contents by inserting a preformed liner into the metal body part.