IE42724B1 - Improvements relating to protective covers for cooker top plates - Google Patents

Description

The invention relates to protective covers for the top plates of electric cookers.

During cooking and frying on electric cookers the top plates (hereinafter referred to as stove plates) thereof, which are generally stainless steel or white enamelled, are frequently stained by the food which is being cooked overflowing, drops of fat spitting out, etc.

There is practically no protection against this and after cooking or frying the housewife must clean her stove LO plates with a cloth or sponge and in some cases with a detergent. This is an unpleasant and time-consuming task. Cleaning the stove plate in this manner is particularly irksome when the stains on the stove plate are practically burnt in by the heat produced during cooking and they then .5 adhere particularly securely to the stove plate.

Metallic covering hoods, which are laid individually on the hot plates, are known means of covering the hot plates when the latter are not being used. These covering hoods are removed to enable cooking or frying and they !0 protect neither the stove plate nor the surfaces between the hot plates but only these hot plates themselves.

With many electric cookers a covering plate is hinged to the rear edge of the stove plate and is swung down to cover the entire stove plate including the hot '.5 plates when said stove plate is not in use, and is swung ·> 4 back up again to enable use. The covering plate must be swung up and is thus unsuitable for covering the stove plate during cooking, since the thickness of said covering plate and its lack of abutment or uneven abutment against the hot plates during cooking completely precludes or at least strongly reduces the transmission of heat to the pans.

This prior art shows that means have still not been provided with which the whole stove plate can be covered during cooking and frying to afford protection against staining. It is therefore desirable to provide a protective cover for stove plates of electric cookers, which cover is simple and economical both in construction and in utilisation. In accordance with the invention, a protective cover for a top plate of an electric cooker comprises a sheet of heat-resistant metal foil having bulges which are embossed therein and which correspond in shape, size and opening to the hot plates of said top plate.

A commercially available metal foil which is only fractions of a millimeter thick, is an ideal heat conductor, which does not inhibit the transmission of heat from the hot plates to the pan or frying pan? although it is only thin the metal foil is nevertheless sufficiently strong and impenetrable with respect to water, steam, drops of fat and the like, to prevent the stove plate from being stained with these substances and thus to keep it clean.

The bulges which are embossed in the sheet and which enclose the hot plates, hold said sheet on the stove plate, preventing it from slipping and shifting. It would impede cooking, frying and general tasks at the cooker if the metal foil and a pan, which might for example be disposed thereon, were to slip to and fro during stirring. - 4 The metal foil catches the stains caused by food boiling over, spitting out and being spilled, and prevents them from reaching the stove plate. After a meal has been cooked these stains may be washed off with a damp cloth, or I possibly in a wash basin under running water. A protective cover according to the invention may be used several times. Compared with its price the metal foil sheet thus has a long life-span and the cost per meal amounts to only a few half pennies. On the other hand, its life-span is limited .0 to only a few days. The housewife will, therefore, not clean the sheet with the same thoroughness and resultant difficulty as she would a stove plate. Cleaning is therefore restricted to a simple wipedown and the housewife is in no danger of damaging her fingernails as she might during hard rubbing of the stove plate with a sponge and/or detergent.

A particular advantage in the utilisation of the metal foil to protect the cooker is tbqt the cooking and frying times are shortened and consequently energy is saved.

In the case of an electric cooker, the heat does not only pass from the hot plate through the pan or frying pan into the food being cooked or fried, but also flows into the regions of the stove plate surrounding the hot plates by simple heat transmissions. The stove plate heats up and, as is known, reaches such high temperatures that it too can no longer be touched with the fingers. The high temperature of the hot plate leads to transmission of heat to the surrounding air space. This transmission of heat is effected both by convection and radiation. Such heating of the surrounding air space is unnecessary and represents a heat loss. When the hot plate is covered by the metal foil sheet, which is disposed just above the hot plate. - 5 this transmission of heat to the air space is interrupted or at least greatly reduced. A cushion of practically unmoving air is produced between the hot plate and the metal foil. This cushion stems the transmission of heat. An accumulation of heat is produced which returns to the hot plate. This in turn leads to an increase in the temperature at the hot plate. When the electrical energy supplied remains constant the cooking or frying time is reduced. Alternatively the amount of electrical energy supplied can be reduced.

Tests have shown that the cooking or frying time and thus the amount of energy used are approx. 10% below the values obtained when the metal foil is not used as a protective cover.

The shape and dimensions of the bulges are advantageously adapted to the shape and dimensions of the hot plates such that the bulges lie with a sliding fit on the hot plates. The protective cover is then adequately protected against slipping. At the same time the crease lines defining the bulges in the metal foil sheet are not sharp enough for the sheet to tear at these points and thus become permeable.

The bulges can be formed particularly advantageously and simply, merely by pressing the metal foil against the hot plates by hand. To this end the housewife places a sheet of metal foil of accurately dimensioned length on the stove plate and then presses the foil down in the regions between the hot plates. The circular shape of the bulges, which corresponds to the shape of the hot plates, is made in the foil by the housewife placing both hands on the metal foil in the region of a hot plate and then pressing 2724 the foil down gently along the edges of the hot plate.

Any readily shaped metal and any alloy which can resist the temperatures of up to approx. 600°C constitutes a suitable material for the foil. Foils made of aluminium or an aluminium alloy are particularly advantageous. Foils made of aluminium and aluminium alloys are known and are on the market. Although the commercially available widths are not suitable for the production of the protective cover according to the invention, the manufacturers are attuned to the idea of rolling such foils and correspondingly economical production in large quantities is possible.

The hot plates of electric cookers generally have diameters of varying sizes, some larger, some smaller. Accordingly, the bulges of the protective cover may have various diameters. The length and the width of the protective cover of the invention are not critical, as long as the protective cover covers the stove plate adequately. However, on economical grounds and in order to keep manipulation. easy, the length and width of the protective cover should only correspond to the depth and breadth of the stove plate. The housewife pulls off from a roll the length of foil required for one protective cover. So as to ensure that the length is measured correctly, marks are provided in an advantageous embodiment adjacent at least one of the edges of the foil, which marks are spaced at a distance corresponding to the depth or breadth of the stove. The housewife pulls the foil out until these marks are reached and then tears it off along the tear blade of the package.

Since many stoves are standardised to a size of cm x 55 cm measured along their edges, the protective - 7 cover of the invention advantageously measures 55 cm x 55 cm along its edges.

However, the protective cover may also project widthways beyond the stove plate at both sides.

As has already been stated the protective cover of the invention may be used several times. The flexibility of the metal foil allows said foil to be smoothed out after cleaning. This is effected simply by placing the foil on an even table top and stroking over it by hand. The foil, whether smoothed over or not, can also be folded up along a line of bend running centrally with respect to its longitudinal or cross dimension. The foil can thus be stored in a space-saving manner until it is next used.

An increasing number (already more than 50%) of frying pans and vessels used today are coated with polytetrafluoroethylene. These PFTE layers prevent adhering during cooking and frying and enable frying with small amounts of fat. However, the layers are only resistant to a temperature of approx. 450°C. When this temperature has been reached, they begin to decompose and emit toxic vapours. Frying vessels and pans of this type may therefore only be heated to approx. 400°C, and the pans and vessels may only be sold with temperature-sensitive indicating and warning devices. An additional safeguard is to be provided with the invention in this respect.

It is therefore proposed that at least one and preferably two strips of a temperature-indicating salt, which changes colour at a temperature of approximately 400°C, be advantageously applied to the protective cover, said strips running over the protective cover in the longitudinal direction so as to extend in use above the associated hot !7 24 - 8 plates. Such temperature-indicating copper, cobalt, nickel chromium, molybdenum and uranium salts exist, which at the required temperature display a change in colour. A strip of one of such salts applied to the protective cover will display a marked change in colour at approx. 400°C. The housewife thereby becomes aware that the temperature must not increase any further and the hot plate must be re-set at a lower level. The colour-change temperature of 400°C is at an adequate level of safety below 45O°C, at which temperature toxic vapours are given off. Furthermore, this temperature is at an adequate level below 600°C, at which temperature the foil is softened by heat and loses its shape.

A salt which can be used for the above purpose and which changes colour from violet to white at a temperature of 400°C is ammonium manganese pyrophosphate (NH^MnP^O^).

The various manufacturers do not always produce cookers with the hot plates disposed in the same positions on the stove plate. However, substantially all manufac) turers produce cookers with hot plates which are disposed such that strips running at a distance of 15 cm from the longitudinal edges of the foil will cover the hot plates. This arrangement for the strips is therefore proposed in an advantageous embodiment in order to ensure direct abutment of the strips against the hot plates, thus ensuring immediate heat transmission.

The invention is further described, by way of example, with reference to the accompanying drawings, in which:Fig. 1 is a perspective view of an electric cooker having a piece .of metal foil situated thereabove, prior to embossment.

Fig. 2 is a perspective view of a package with a piece of metal foil pulled out to exactly the correct extent.

Fig. 3 is a simplified side view in the direction of arrow III in Fig. 1 of a stove plate with hot plates and a piece of metal foil prior to embossment, Fig. 4 is a side view of a stove plate with a protective cover laid thereon and a pan placed thereon.

Fig. 5 is a section along the line of section V-V in Fig. 4, IO Fig. 6 is a perspective view of a protective cover with particular regard to a line of bend running across tne middle and Fig. 7 is a perspective view of a protective cover after having been folded up.

Fig. 1 shows an electric cooker 12 having a stove plate 14 and hot plates 16. A sheet of metal foil 18 cut to the correct length is situated above the cooker. The length A of this sheet of foil corresponds to the depth of the cooker 12 and the width b of the foil corresponds to the breadth of the cooker. The foil is pulled out of a package 20. Fig. 2 shows such a package which is mounted on a wall. The foil is severed along a tearing blade 22.

In order to determine the length of the piece of foil which is to be severed, marks 24 are provided on the foil.

These marks are printed or pressed on in any manner desired.

When a sheet of foil of the correct length 1_ has been pulled out and torn off, it is placed on the stove plate. Figs. 1 and 3 show this positioning of the foil. The foil is then laid over the hot plates 16 and is pressed against and around these plates in the direction of the arrows.

The foil thus acquires its final shape, in which it is - 10 shown in Figs. 4 and 6. The protective cover thus formed has smaller bulges 28 corresponding to the smaller hot plates and larger bulges 30 corresponding to the larger hot plates as can be seen. Tn practice the protective cover does not lie on the stove plate and the hot plates in exactly the shape as shown in Fig. 4 and in section in Fig.

. At some points it lies closer to, and at other points at a greater distance from the stove plate and hot plates.

In practice, this is of no consequence. A frying or cook10 ing vessel, such as the pan 32 illustrated, presses the foil against the hot plate 16 simply by means of its own weight. This is decisive and adequate for the transmission of heat. The metal foil fulfils its main function of protecting the stove plate 14 against staining, irrespective of whether it abuts more or less closely or uniformly against the stove plate 14.

When cooking or frying has ended the protective cover is removed. Fig. 6 shows the foil in this form. The foil is wiped down with a damp cloth, possibly under running water, and can then be smoothed out, the bulges being pressed in in the course thereof. This process can be effected several times. Irrespective of whether prior smoothing out has been effected the foil can be folded along a line of bend 34 into the shape shown in Fig. 7.

When folded up in this manner the foil can be stored away in a space-saving manner until it is next used.

Figs, 2 and 6 also show strips 36 of a salt which changes colour at a temperature of approx. 400°C. In the example shown in Fig. 6 the strips 36 run centrally over the bulges 28 and 30 and in a corresponding manner over the hot plates 16. In another arrangement of the hot plates 2 734 -lithe strips would run to the right and left of such central location with respect to the hot plates. In any case the strips 36 cover the hot plates 16 and can be seen in the region which is not covered by a frying or cooking vessel and their change in colour is immediately recognisable, giving the warning signal that the temperature of the hot plate is to be increased no further.

Claims (14)

1. A protective cover for a top plate of an electric cooker, comprising a sheet of heat-resistant metal foil having bulges which are embossed therein and which correspond in shape, size and spacing to the hot plates of said top plate.

2. A protective cover as claimed In claim 1, in which the shape and dimensions of the bulges are adapted to the shape and dimensions of the hot plates such that the bulges lie with a sliding fit in the hot plates.

3. A protective cover as claimed in claim 1 or 2, in which the bulges are formed in the metal foil by pressing the metal foil against the hot plates by hand.

4. A protective cover as claimed in any of claims 1 to 3, in which the foil consists of aluminium or an aluminium alloy.

5. A protective cover as claimed in any of claims 1 to 4, in which the bulges are of various diameters.

6. A protective cover as claimed in any of claims 1 to 5, in which the length and width of the sheet of foil correspond to the depth and breadth of the top plate to which the foil is to be applied.

7. A protective cover as claimed in claim 6, in which the sheet of foil measures substantially 55 cm x 55 cm.

8. A protective cover as claimed in any of claims 1 to 5, in which the sheet of foil is dimensioned so that it projects widthways in use beyond the top plate at both sides thereof.

9. A protective cover as claimed in any of claims 1 to 8, in which marks., which are spaced at a distance •42724 - 13 corresponding to the breadth or depth of the stove, are disposed adjacent at least to one of two longitudinal edges of tbe inetal foil sheet.

10. A protective cover as claimed in any of claims 1 5 to 9, in which the sheet of foil has a line of bend running centrally with respect to its longitudinal or cross dimension so that the sheet of foil can be folded up.

11. A protective cover as claimed in any of claims 1 to 10, in which at least one strip of a temperature10 indicating salt, which changes colour at a temperature of approximately 400°C, is applied to the foil so as to extend in use over associated hot plates.

12. A protective cover as claimed in claim 11, in which the salt comprises NH^MnP^O^. 15

13. A protective cover as claimed in claim 11 or 12, in which two strips are applied, each at a distance of substantially 15 cm from a respective longitudinal edge of the foil sheet.

14. A protective cover for a top plate of an electric 20 cooker, substantially as herein described with reference to and as illustrated in Figs. 4 to 7 of the accompanying drawings.