GB2361412A

GB2361412A - Toaster with electrically insulating contact plate

Info

Publication number: GB2361412A
Application number: GB0102125A
Authority: GB
Inventors: Alfred Fraunhofer; Robert Sturm; Thomas Dorn; Rudolf Kloetscher; Matthias Gradi; Hansjuergen Linde; Michael Lechner; Matthias Schaefer
Original assignee: BSH Bosch und Siemens Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2000-02-08
Filing date: 2001-01-26
Publication date: 2001-10-24
Anticipated expiration: 2021-01-26
Also published as: FR2804590A1; GB0102125D0; GB2361412B; DE10005542A1

Abstract

A toaster comprises a heating element 1 for heating articles by contact heating, the element having a sandwich construction. The lower layer 3 functions as a heating device and the upper layer 6 is electrically insulating layer for directly contacting articles to be heated. The lower layer 3 is screened from direct contact with the articles to be heated by the upper layer 6. The upper layer 6 is preferably a heat-resistant glass such as Ceran (RTM), or an aluminium plate coated with polytetrafluoroethylene. The heating device 1 may comprise a thick-film heater or a halogen heater. A further heating element may be contained at the ceiling of the toaster. A support may be moved vertically in order to accommodate food items of different sizes. Moisture feed means such as a piezo atomiser or a hygroscopic material may be included for feeding moisture to the toaster.

Description

2361412 TOASTER The present invention relates to a toaster and has

particular reference to a heating element of a toaster.

Household bread toasters with a toasting chamber or two toasting chambers in the form of a slot, in which the heating elements are arranged to be spaced from the article or articles to be heated, are known. It is disadvantageous with known household bread toasters that due to the spacing of the heating elements from the articles to be heated the efficiency of the toaster is low and the air between the articles and the elements is strongly heated and consequently rises in the chamber and issues from the slot at very high temperature, so that there is a risk of burning the user.

There is accordingly a need for a household bread toaster with good heating efficiency, but reduced risk of burning.

According to the present invention there is provided a household bread toaster comprising at least one toasting chamber and at least one heating element, wherein the element has a sandwich mode of construction with at least two layers in which the layer forming the heating device has no direct contact with the toasting stock and the uppermost layer is electrically insulating, the heating element directly contacting the article or articles, which is or are to be heated, by this uppermost layer as a contact heating element.

In one advantageous embodiment the contact heating element is constructed as a Ceran heating element with at least one layer forming the heating element and a layer of Ceran. In that case the Ceran layer contacts the toasting stock.

The invention also provides a toaster comprising at least one toasting chamber and at least one heating element, wherein the heating element is constructed as a heating mat. A heating mat offers the advantage of adapting to the form of the article or articles to be heated.

The layer forming the heating device can be a thick-film heater. Thick-film heaters are simple to apply to a support in the paste method. Production thereof is favourable in cost in the case of large batches, as the coating can be carried out over a large area, for 2 example by a screen printing method, and it only remains to temper the coated support in a flat continuous oven.

The invention further provides a toaster comprising at least one toasting chamber and at least one heating element, the heating element comprising at least one halogen heater. The halogen heater can in that case be covered by a special glass, for example, Ceran.

In an advantageous embodiment the heating chamber is variable from a flat space to a space with comparable dimensions in all chamber directions. In that case the heating element can be arranged within a vertically displaceable support for the articles. A further heating element is preferably horizontally arranged at the ceiling of the chamber. This heating element is thus arranged opposite the heating element in the support. In the case of a small spacing between the support and ceiling, the heating conditions are comparable with those of a typical toaster, but with the difference that the elements are arranged horizontally and the articles, for example slices of bread, have to be inserted horizontally.

The vertically displaceable support advantageously forms a variable boundary of the chamber. The height of the thus-formed interior space serving as chamber is preferably variable from almost zero to a height having width and depth dimensions in a horizontal plane which exceed the chamber. This offers the advantage that not only slices of bread, but also bread rolls and other dough products can be toasted, crisped or similarly heated.

Advantageously, the interior space, which is formed to a maximum in this manner, of the toaster is completely closed off laterally only in its upper region by side walls. In its lower region it has a large access opening at its lateral boundary. The toaster can be loaded with articles by way of this access opening. For toasting or baking, the support can be lifted into the upper region fully closed laterally by side walls.

Preferably, the support is connected with at least one pinion engaged in at least one stationary rack. In the case of vertical displacement the pinion meshes with the toothing of the rack. In that case, the contact force between pinion and rack preferably determines the damping of return motion, i.e. the support is damped, in defined manner by a predetermined engagement force between pinion and rack, in its downward movement under gravitational force. Advantageously, it additionally comprises at least one device which strongly increases the force of engagement between pinion and rack in such a 3 manner that the downward movement produced by gravitational force is arrested. A plurality of such devices can advantageously be arranged at fixed positions so that the support can be held in defined vertical displacement positions. In an advantageous embodiment the or each device comprises an electromagnet which presses the pinion against the rack. For that purpose the electromagnet can exert a force on an armature which is connected with the pinion by way of a rocker or by way of a lever. At the conclusion of the heating process, the electromagnet is switched off, the support travels down due to its own weight or with the assistance of spring force and the heated article or articles can be removed through the access opening.

However, the stock can, if desired, be motor-driven.

The support is advantageously guided Wth respect to its vertical displacement by means of at least two rods.

In order to arrest the support in defined vertical displacement positions, cletent means can be provided. For this purpose, a protrusion, such as a nose, at an actuating lever for the support can be provided as detent means, which nose engages in recesses of a housing of the toaster. These defined positions of the support preferably correspond to a loading setting, a setting for baking and a setting for toasting.

Preferably, the support is disposed in one of its defined vertical displacement positions at the lower end of the encircling side walls and forms, in co-operation with the encircling side walls and the ceiling of the interior space, a closed chamber. The chamber, which in this embodiment is thus formed to be closed to a maximum extent, serves in advantageous manner for baking or crisping of bakery products. Preferably a Viewing window is arranged in the wall of the baking chamber so that the process of heating can be observed.

In an advantageous embodiment, dust extractor openings are arranged in the wall of the chamber. The temperature level of the toaster or the degree of browning of the article being heated is preferably set by means of a selector disc.

Control of the toaster can also be managed by way of an 'intelligent' electronic system, particularly in the case of a motorised drive of the support.

4 In addition, a moistening device which delivers moisture into the chamber can be provided. The advantages of a moistening device come into play particularly in crisping, as a flakingoff of the crusts of, for example, bread rolls can be prevented. This condition can be further improved by air circulation operation and/or hot air supply.

The moistening device can comprise a substance which absorbs air moisture at room temperature and which delivers the moisture at operating temperatures of the toaster. This substance preferably has the property of extracting the moisture of the ambient air at room temperatures. Substantially all hygroscopic chemical compounds are suitable for that purpose. Advantageously this substance is removably arranged in the toaster so that when the moistening feature is not in use the substance can be removed and inserted into, for example, a refrigerator or freezer for drying purposes. In that case the two advantages are combined of, on the one hand, quickly regenerating this substance so that it can deliver further moisture into the toaster and, on the other hand, protecting the refrigerator against icing. To ease handling, the moisture-absorbing substance is preferably received in a cartridge with an air-permeable casing.

If the substance absorbing air moisture at room temperature is a hygroscopic chemical compound, it has the advantage that it regenerates without the assistance of a user. Typically, a toaster is used for crisping or toasting articles in the morning and thereafter usually remains out of use for a half day or whole day. In this cold state the hygroscopic substance can take up further moisture until it is saturated or can be manually charged with water by a user.

In another advantageous embodiment the substance absorbing moisture at room temperature has a high inner surface by comparison to its outer dimensions. A thin water film, which is evaporated at operating temperature, precipitates on this surface at room temperature.

The substance absorbing the air moisture at room temperature can be zeolite. Zeolite can absorb large quantities of water by virtue of its cellular crystal structure. Moreover, it offers the advantage of being able to be freely shaped and thus able to be accommodated in the toaster in simple manner. Instead of zeolite, any other desired inert drying agent compatible with foodstuffs can be used, for example silica gel.

In another advantageous embodiment the moistening device consists of at least one instillation vaporiser. An instillation vaporiser offers the advantage that the water quantity to be fed can be accurately controlled. The water reservoir of the instillation vaporiser can be filled at any time and without delay. The toaster can thus be operated as frequently as desired. It is not necessary, to wait for a regeneration phase of a drying agent or to actively regenerate this agent. The instillation vaporiser is preferably coupled with a tank by way of a valve. This makes it possible to remove the tank in order to separately fill or empty it. The instillation vaporiser preferably drips water into a vaporising channel with an embossed groove structure. This groove structure divides up the water drops and thus enlarges the overall vaporisation surface so that the introduced water evaporates very effectively. The evaporation process can advantageously be increased if the evaporation channel encloses a heating unit. In that case the supplied water evaporates immediately and does not remain in the form of drops in the toaster.

In yet another embodiment the moistening device comprises at least one evaporator preferably operating in accordance with the principle of a throughflow heater. The tank can then - as in the case of the instillation vaporiser - be coupled with the evaporator by way of a valve. This in turn makes it possible to remove the tank in order to separately fill or empty it. The evaluator is a very hygienic solution for a moistening device, as it can be completely emptied and no water residues remain. The construction of the evaluator Gan be designed in simple manner, for example, connected to a water tank can be a throughflow pipe, which is surrounded by heating coils, and a steam nozzle with an excess pressure valve can be mounted at the front end of the throughflow pipe. A valve, which enables removal of the water tank, can be arranged between the tank and throughflow pipe. The evaporator can preferably have a calcification indicator.

In an another embodiment the moistening device can comprise at least one injection liquid atomiser. An atomiser offers the advantage of optimum atomisation of the liquid in the toaster. The supplied water evaporates immediately after the atornisation and does not remain in the form of drops in the toaster. In that case the atomiser can be constructed as a hand-operated atomiser, which offers the advantage that the introduction of moisture can be directly influenced by the user. Alternatively, an automatic injection unit can be provided to precisely regulate the moisture feed in conjunction with moisture sensors in the chamber.

6 in these embodiments it has proved advantageous if the atomiser delivers the moisture into the air flow of a fan or ventilator. Alternatively, the atomiser can spray liquid onto a baffle plate, in which case the liquid is finely atomised and vaporised without delay, or onto a heating device, where, due to the directly supplied heat and the large surface area of the atomised liquid, this evaporates without delay. Such a heating device is preferably disposed in the air flow of a ventilator.

Moreover, the moistening device can comprise at least one piezo vaporiser, which achieves a good distribution of the supplied water in simple manner.

The moistening device preferably delivers the moisture into the chamber at operating temperatures of the toaster. A formation of drops in the toaster can thus be avoided.

The heating element can be made up from a receiving shell, a micanite heater and a cover plate. The cover plate preferably consists of a heat-resistant glass or a metallic, such as aluminium, plate coated with polytetrafluoroethylene. In that case, the cover plate is, in advantageous manner, removable. As a further advantage it is made of a dishwasherproof material. In that case the cover plate preferably comprises an anti-stick coating.

In another advantageous arrangement the heating element comprises a support plate in which heat conductors are integrated. The heat conductors are preferably contacted by way of a contact strip laterally mounted at the support plate. The support plate is preferably removable from the toaster.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is an exploded perspective view of a first form of heating element in a toaster embodying the invention; and Fig. 2 is a perspective view of a second form of a heating element in a toaster embodying the invention.

7 Referring now to the drawings, there is shown in Fig. 1, in exploded illustration, a heating element 1 of a household bread toaster, the element having a sandwich mode of construction. A frame 3 of a micanite heater 4 is fastened to a receiving shell 2. Heating wires 5 are tensioned across the frame 3. A cover plate 6 is mounted over the unit of shell 2 and heater 4. This cover plate 6 can consist of heat-resistant glass or an aluminiurn plate coated with polytetrafluoroethylene. The articles to be heated, such as slices of bread, in use directly contact the cover plate 6. The heat is uniformly distributed by area introduction into the articles or into a heating chamber of the toaster. The cover plate 6 is provided with an anti-stick coating so that there is little contaminating residue left thereon after operation of the toaster. The cover plate 6 can be removed from the heating element 1 and cleaned in a dishwasher.

Fig. 2 shows a further form of heating element 7 of a toaster, in which integrated heat conductors 8 are accommodated in a support plate 9. The support plate 9 can consist of, for example, a heat-resistant ceramic, glass or glass-ceramic material, such as Ceran. The integrated heat conductors 8 are constructed as conductor tracks and are electrically connected by way of a contact strip 10 at the side of the support plate 9. The high density of the conductor tracks and the good thermal conductivity of the Ceran plate results in a uniform heat distribution, so that the heat is introduced in areal manner into the articles or the heating chamber of the toaster. The heating element 7 is connected by way of a plug coupling, which is not illustrated, in the toaster. in this manner it is removable and thereby easy to clean. The heating element 7 has a flat surface, so that residues are easy to remove after operation of the toaster, and is constructed so that it can be cleaned in a dishwasher. The size of the heated area can be matched to the size of the articles to be heated by means of an'intelligent' control. In that case, only specific area segments of the heating element 7 are switched on.

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Claims

1 A toaster comprising a heating element for heating articles in a heating chamber of the toaster by contact heating, the element having a sandwich construction with a lower layer functioning as a heating device and an electrically insulating upper layer for directly contacting articles to be heated, the lower layer being screened from direct contact with the articles.

2. A toaster as claimed in claim 1, wherein the heating element is a Ceran heating element, the upper layer being made of Ceran.

3. A toaster as claimed in claim 1, wherein the heating element is a heating mat.

4. A toaster as claimed in claim 1, wherein the heating device comprises a thick-film heater.

5. A toaster as claimed in claim 1, wherein the heating device comprises at least one halogen heater.

6. A toaster as claimed in any one of the preceding claims, comprising an upwardly and downwardly displaceable support for articles to be heated in the chamber, the heating element being arranged in the support and the chamber being variable in size from a substantially flat space to a space with dimensions substantially comparable in three mutually perpendicular directions.

7. A toaster as claimed in any one of the preceding claims, comprising a further heating element substantially horizontally arranged at a ceiling of the chamber.

8. A toaster as claimed in claim 6, comprising a pinion engaging a rack and movable along the rack for displacement of the support.

9. A toaster as claimed in claim 6 or claim 8, comprising a plurality of rods for guiding the support with respect to the upward and downward displacement thereof.

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10. A toaster as claimed in any one of claims 6, 8 and 9, comprising detent means to arrest the support in each of a plurality of predetermined positions.

11. A toaster as claimed in claim 10, wherein the predetermined position consists of a position in which the support can be loaded with an article, a position in which a loaded article can be heated in the chamber in the manner of baking and a position in which a loaded article can be heated in the chamber in the manner of toasting.

12. A toaster as claimed in any one of the preceding claims, wherein the chamber is laterally fully closed in an upper region thereof by wall means of a housing of the toaster and is provided in a lower region thereof with a lateral access opening for articles to be heated.

13. A toaster as claimed in any one of the preceding claims, comprising moisture feed means for feeding moisture into the chamber.

14. A toaster as claimed in claim 13, wherein the moisture feed means comprises a substance absorbing atmospheric moisture at room temperature and releasing absorbed moisture at predetermined operating temperatures of the toaster.

15. A toaster as claimed in claim 14, wherein the substance is contained in a cartridge with an air-permeable casing.

16. A toaster as claimed in claim 14 or claim 15, wherein the substance is a hygroscopic material.

17. A toaster as claimed in claim 14 or claim 15, wherein the substance has a high internal surface area by comparison with the external dimension thereof.

18. A toaster as claimed in claim 14 or claim 15, wherein the substance is zeolite.

19. A toaster as claimed in claim 13, wherein the moisture feed means comprises an instillation vaporiser.

20. A toaster as claimed in claim 19, wherein the vaporiser is arranged to deliver liquid to a heating device of the toaster.

21. A toaster as claimed in claim 13, wherein the moisture feed means comprises an atomiser for injecting liquid.

22. A toaster as claimed in claim 21, wherein the atomiser is arranged to deliver moisture into the air flow of a fan of the toaster.

23. A toaster as claimed in claim 21, wherein the atomiser is arranged to spray liquid onto a heating device of the toaster.

24. A toaster as claimed in claim 13, wherein the moisture feed means comprises a piezo atomiser.

25. A toaster as claimed in claim 1, wherein the lower layer of the heating element comprises a micanite heater carried by a carrier and the upper layer comprises a cover plate.

26. A toaster as claimed in claim 25, wherein the cover plate comprises heat-resistant glass or a metallic plate coated with polytetrafluoroethylene.

27. A toaster as claimed in claim 25 or claim 26, wherein the cover plate is removable.

28. A toaster as claimed in claim 27, wherein the cover plate comprises a material resistant to damage through pressure cleaning by water and detergent.

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29. A toaster as claimed in claim 25, wherein the cover plate is provided with a coating of low-friction material.

30. A toaster as claimed in claim 1, wherein the heating element comprises a support plate for articles to be heated in the chamber and heat conductors integrated into the plate.

31. A toaster as claimed in claim 30, wherein the conductors are connected to a contact strip laterally mounted on the plate.

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32. A toaster as claimed in claim 30 or claim 31, wherein the upper plate is removable.

33. A toaster as claimed in any one of claims 30 to 32 wherein the heat conductors are conductor tracks.

34. A toaster substantially as hereinbefore described with reference to the accompanying drawings.