GB2296088A - Cooking hob - Google Patents

Abstract

A cooking appliance (1) comprises a cooking plate (7), such as a glass ceramic cooking plate, and a housing (9) for one or more radiant electric heaters (11), the housing being adapted to urge the one or more radiant electric heaters against the underside of the cooking plate by a channel shaped bar member (21). The housing is secured to the underside of the cooking plate, for example by means of an adhesive such as double-sided adhesive tape (13), and is dimensioned so as to extend around the one or more radiant electric heaters and to be spaced from the periphery of the cooking plate. The amount of potential movement between the cooking plate and the housing may be limited. The supply of electrical energy to the heaters may be disconnected by a breakable electrically conducting connection between the cooking plate and the housing. <IMAGE>

Description

COOKING APPLIANCE INCORPORATING A COOKING PLATE The present invention relates to a cooking appliance which incorporates a cooking plate, such as a glass ceramic plate.

Glass ceramic cooking appliances are well known in which one or more radiant electric heaters are arranged beneath a glass ceramic cooking plate and energy emitted by the heaters passes through the glass ceramic material to a cooking utensil positioned on the cooking plate.

In order to mount the cooking appliance in a work surface or the like, a frame is generally provided around the periphery of the cooking plate so as to clamp the cooking plate to the frame. A housing for the one or more radiant heaters extends beneath, and is suspended from, the frame and serves to contain the heaters and to urge them against the underside of the glass ceramic cooking plate.

The cooking appliance is mounted in an aperture in the work surface in a manner such that the frame is supported by the edge of the work surface defining the aperture with the housing suspended from the frame. The cooking plate, being clamped by the frame, is also supported by the frame.

The provision of a frame around the cooking plate gives rise to a number of disadvantages.

One disadvantage is that, due to the clamping of the cooking surface by the frame, a part of the frame extends over the peripheral edge of the cooking plate and also, in order to support the cooking appliance, over the edge of the aperture thus giving rise to a raised lip around the periphery of the appliance. The raised lip detracts from the aesthetic appearance of the appliance and can lead to difficulty in cleaning of the cooking plate and the work surface in regions adjacent to the lip.

Another disadvantage is that the peripheral region of the cooking plate is always supported by the frame. This increases the depth of the appliance in the peripheral region thereof and also requires the frame to be dimensioned to extend around the periphery of the cooking plate when the dimensions of the one or more heaters would allow the frame to be significantly smaller and correspondingly less expensive.

It is therefore an object of the present invention to provide a cooking appliance which eliminates the above disadvantages of known cooking appliances which incorporate peripheral frames and which therefore is able to eliminate a raised lip around the periphery of the cooking plate and which also enables the frame to be eliminated and replaced by a housing which is arranged within the periphery of the cooking plate.

According to the present invention there is provided a cooking appliance comprising a cooking plate and a housing for one or more radiant electric heaters, the housing being adapted to urge the one or more radiant electric heaters against the underside of the cooking plate, wherein the housing is secured to the underside of the cooking plate and is dimensioned so as to extend around the one or more radiant electric heaters and to be spaced from the periphery of the cooking plate.

The cooking plate is preferably made of the material having a low coefficient of thermal expansion, for example in the range + 2 x 107/K. The advantage of such a material is that the junction between the cooking surface and the housing is subjected to little or no stress.

The cooking plate is preferably made of a material having a low coefficient of thermal conduction, especially in the plane of the plate. The thermal conduction is preferably in the range up to 3 W/(m K). The advantage of a material of low thermal conductivity, especially in the lateral direction, is that the temperature of the junction between the cooking surface and the housing remains relatively low irrespective of the temperature of the cooking plate immediately above the one or more radiant heaters.

A particularly suitable material for the cooking plate is a glass ceramic material. Such materials generally possess properties of low thermal expansion and low thermal conduction.

The upper surface of the peripheral edge of the cooking plate may be chamfered such that the periphery of the plate is less thick than the region within the periphery. Such an arrangement is aesthetically pleasing and reduces the likelihood of damage to the cooking plate and to the user.

The housing may be secured to the underside of the cooking plate by means of adhesive. We have found that an acrylic adhesive is particularly suitable. For ease of application, the adhesive may be incorporated into a double-sided adhesive tape, preferably using a liner of tear-resistant film. The tape may have a thickness of about 1 mm to allow for dimensional tolerances in the housing and the cooking plate. For example, glass ceramic cooking plates can be burled on their underside.

The housing may be provided with an opening in that part thereof remote from the cooking plate. Such an opening facilitates access to the interior of the cooking appliance and permits inter alia mounting of the radiant electric heaters after the housing has been secured to the cooking plate and also permits repair and maintenance of components, such as the heaters, within the housing.

The appliance may include means which functions in the event of separation of the housing from the cooking plate to restrain relative movement between the housing and the cooking plate. Such restraining means may comprise means secured to the housing and extending through the cooking surface, such as control means for determining the power level setting of the one or more radiant electric heaters.

Alternatively, the restraining means may be positioned on that side of the housing remote from the cooking surface.

Such restraining means may comprise one or more restraining members engaged with the work surface or with the aperture or recess provided therein, for example one or more restraining bars or a restraining mesh.

The appliance may include means which functions in the event of separation of the housing from the cooking plate to de-energise the one or more radiant heaters. Such deenergising means may comprise one or more electrically conductive members connected to electro-mechanical or electronic switch means and arranged such that, in the event of separation, conduction along the one or more electrically conductive members is terminated thus causing the switch means to de-energise the one or more heaters.

The one or more electrically conductive members may comprise an electrically conductive tape which is broken on separation of the housing from the cooking plate or may comprise separate electrically conductive members provided on the housing and the cooking plate, which members are separated in the event of separation of the housing from the cooking plate.

For a better understanding of the present invention and to show more clearly how it may be carried into effect reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is a cross-sectional view of one embodiment of a cooking appliance according to the present invention; Figure 2 is a cross-sectional view taken along the line II II in Figure 1; and Figure 3 is a side elevational view of another embodiment of a cooking appliance according to the present invention.

The cooking appliance 1 shown in Figures 1 and 2 is mounted in a work surface 3 which is formed with a rebate 5 to allow the upper surface of the cooking plate 7 of the appliance to be substantially coplanar with the top of the work surface. Any peripheral gap around the cooking plate 7 may be filled with any suitable filler such as a silicone or mastic material.

The cooking plate 7 is preferably a glass ceramic plate.

Glass ceramic material is noted for its low coefficient of thermal expansion (in the range of + 2 x 10-7/K and more generally in the range of - 1 x 10'/K to + 1.5 x 107/K in the temperature range up to 973 K) and for its low lateral coefficient of thermal conductivity (in the range from 2.2 to 2.7 W/(m K) in the temperature range up to 873 K).

A housing 9 for radiant electric heaters 11 is secured to the underside of the cooking plate 7 by means of a doublesided adhesive tape 13 such as that available from 3M Industrial Tapes and Adhesives Group under No. 4910F. This adhesive tape incorporates an acrylic adhesive arranged on a liner of tear-resistant film and is secured to the cooking plate and to the housing by pressure. The tape has a thickness of about 1 mm.

The housing is spaced inwardly from the peripheral edge of the cooking plate 7 such that the peripheral region of the cooking plate is free of all encumbrances. This facilitates mounting of the appliance in the work surface with the upper surface of the cooking plate substantially coplanar with the upper surface of the work surface. Any gap between the periphery of the cooking plate and the work surface may be filled with any convenient material such as a silicone filler or mastic. Not only is mounting of the cooking plate more convenient, but because the housing is spaced inwardly of the periphery of the cooking surface, the dimensions of the housing may be smaller than in previous cooking appliances and there is no need for a decorative frame. The cooking appliance is therefore more economical to manufacture.The surprising aspect of the cooking appliance according to the invention is that an adhesive, especially the adhesive tape, is sufficient to secure the housing to the underside of the cooking plate.

The housing comprises an assembly of four channel members 15, for example of metal such as zinc plated mild steel, in a generally rectangular framework, the channel members each comprising an upright base member having at the upper and lower ends thereof a leg member which extends laterally towards the centre of the appliance. The adhesive tape is positioned between the lower surface of the cooking surface and the upper side of the upper leg of each of the channel members 15 and the thickness of the tape, which is of the order of 1 mm, allows for minor dimensional tolerances in the housing and for burling, if provided, on the underside of the glass ceramic plate.

The lower legs of the channel members 15 define a generally rectangular opening which is closed by a sheet 17, for example of zinc plated mild steel. The sheet 17 is secured to the lower legs of the channel members by a plurality of fasteners such as metal screws 19.

The channel members 15 of the housing 9 extend around two radiant electric heaters 11, although a greater or fewer number of heaters may be provided if desired. The heaters 11 are maintained in position and urged against the underside of the glass ceramic cooking plate by a channel shaped bar member 21 which is secured by flanges and metal screws 23 at each end thereof to opposed channel members 15. Removal of the bar member 21 is facilitated by the provision of cut-outs in the lower legs of the channel members 15 which correspond to the position of the bar member 21.

The heaters 11 are secured to the upper surface of bar member 21 by means of screws 25 and are provided with suitable control means 27, such as energy regulators or multi-position switches, for determining the power level setting of each of the heaters. In the illustrated embodiment, operating rods for the control means 27 extend through apertures in the cooking plate 7 and control knobs 29 are positioned on the free ends of the operating rods.

The cooking appliance shown in Figure 3 is similar to the appliance shown in Figures 1 and 2 except that in the embodiment of Figure 3 the cooking plate 7 is not received in a rebate in the work surface, but rests directly on the work surface 3. For aesthetic reasons, and to avoid damage to the edge of the cooking plate and/or to the user, the edge of the cooking plate is chamfered.

As an alternative to the channel shaped bar member 21 being secured by flanges and metal screws 23 which are illustrated as extending laterally into the housing, the bar shaped member may be designed so as to allow the screws to extend upwardly into the housing. This arrangement has the advantage of allowing servicing of the appliance from below without the need to remove the appliance from the work surface.

Although the housing is more than adequately secured to the underside of the cooking plate by the adhesive, this is not necessarily apparent to the user or to testing authorities that are required to approve use of the appliance by members of the public. The apparent danger is that the housing will become separated from the underside of the glass ceramic cooking plate and the radiant electric heaters could present an electrical and/or fire hazard. A number of measures can be adopted to surmount this apparent danger. The amount of potential movement between the cooking plate and the housing may be limited and/or the supply of electrical energy to the heaters may be disconnected in the event of separation of the housing from the cooking plate.

The amount of potential movement between the cooking plate and the housing may be limited by employing the control means 27 and the control knobs 29, by securing the control knobs to the operating rods in a manner such that the control knobs limit the amount of movement between the cooking plate and the housing in the event of the housing becoming separated from the cooking plate. Alternatively, a form of restraining means may be positioned on that side of the housing remote from the cooking plate, such as one or more restraining bars or a restraining mesh engageable with the work surface, for example with the underside of the work surface or with the aperture or recess formed therein.

The supply of electrical energy to the heaters may be disconnected by providing a breakable electrically conducting connection between the cooking plate and the housing. The electrical connection may comprise a breakable electrically conductive tape or an electrically conductive member on each of the cooking plate and the housing, the members being in electrical contact when the housing is secured to the cooking plate, but the electrical connection being broken in the event of separation of the housing from the cooking plate. Breakage of the electrical connection may be used to actuate an electromechanical switch (such as a relay) or an electronic switch to deenergise the power supply to the control means and/or the heaters until such time as the housing is again secured to the cooking plate and the electrical connection restored.

Claims (22)

1. A cooking appliance comprising a cooking plate and a housing for one or more radiant electric heaters, the housing being adapted to urge the one or more radiant electric heaters against the underside of the cooking plate, wherein the housing is secured to the underside of the cooking plate and is dimensioned so as to extend around the one or more radiant electric heaters and to be spaced from the periphery of the cooking plate.

2. A cooking appliance as claimed in claim 1, wherein the cooking plate is made of the material having a low coefficient of thermal expansion.

3. A cooking appliance as claimed in claim 1 or 2, wherein the cooking plate is made of a material having a low coefficient of thermal conduction.

4. A cooking appliance as claimed in claim 1, 2 or 3, wherein the cooking plate is made of a glass ceramic material.

5. A cooking appliance as claimed in any preceding claim, wherein the upper surface of the peripheral edge of the cooking plate is chamfered such that the periphery of the plate is less thick than the region within the periphery.

6. A cooking appliance as claimed in any preceding claim, wherein the housing is secured to the underside of the cooking plate by means of adhesive.

7. A cooking appliance as claimed in claim 6, wherein the adhesive comprises an acrylic adhesive.

8. A cooking appliance as claimed in claim 6 or 7, wherein the adhesive is incorporated into a double-sided adhesive tape.

9. A cooking appliance as claimed in claim 8, wherein the adhesive tape comprises a liner of tear-resistant film.

10. A cooking appliance as claimed in claim 8 or 9, wherein the tape has a thickness of about 1 mm.

11. A cooking appliance as claimed in any preceding claim, wherein the housing is provided with an opening in that part thereof remote from the cooking plate.

12. A cooking appliance as claimed in any preceding claim and including means which functions in the event of separation of the housing from the cooking plate to restrain relative movement between the housing and the cooking plate.

13. A cooking appliance as claimed in claim 12, wherein the restraining means comprises means secured to the housing and extending through the cooking surface.

14. A cooking appliance as claimed in claim 13, wherein the restraining means comprises control means for determining the power level setting of the one or more radiant electric heaters.

15. A cooking appliance as claimed in claim 12, wherein the restraining means is positioned on that side of the housing remote from the cooking surface.

16. A cooking appliance as claimed in claim 15, wherein the restraining means comprises one or more restraining members engaged with the work surface or with the aperture or recess provided therein.

17. A cooking appliance as claimed in claim 16, wherein the restraining means comprises one or more restraining bars or a restraining mesh.

18. A cooking appliance as claimed in any preceding claim and including means which functions in the event of separation of the housing from the cooking plate to deenergise the one or more radiant heaters.

19. A cooking appliance as claimed in claim 18, wherein the de-energising means comprises one or more electrically conductive members connected to electro-mechanical or electronic switch means and arranged such that, in the event of separation, conduction along the one or more electrically conductive members is terminated thus causing the switch means to de-energise the one or more heaters.

20. A cooking appliance as claimed in claim 19, wherein the one or more electrically conductive members comprises an electrically conductive tape which is broken on separation of the housing from the cooking plate

21. A cooking appliance as claimed in claim 19, wherein the one or more electrically conductive members comprises separate electrically conductive members provided on the housing and the cooking plate, which members are separated in the event of separation of the housing from the cooking plate.

22. A cooking appliance substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.