GB2298780A

GB2298780A - Tank for cooking appliance

Info

Publication number: GB2298780A
Application number: GB9605632A
Authority: GB
Inventors: Lodewijk Josef Theofiel Boyen
Original assignee: NOVA ELECTRO INT
Current assignee: NOVA ELECTRO INT
Priority date: 1995-03-16
Filing date: 1996-03-18
Publication date: 1996-09-18
Also published as: IT240499Y1; BE1009213A5; GB9605632D0; FR2731607A3; ITMI960179U1

Abstract

Tank (100) for a cooking appliance is linked to a heating element (113) in order to heat the cooking medium and exhibits an internal face (101) defining the bottom (104) of the tank and the cooking volume, the said internal face (101) consisting of two parts (102,103), the first part 102 being made of a first material having higher conduction properties than those of the second part (103), which is situated above the bottom (104) of the tank. The lower first part 102 may be in the form of a plate and made of aluminium while the second part may form the walls of the tank and made from stainless steel.

Description

TANK FOR COOKING APPLIANCE This invention concerns a tank for a cooking appliance.

Hitherto the tanks for fryers have exhibited an inside face made of a single material.

During the cooking of foods in oil or fat a solid and adherent layer or coating is formed on the tank walls just above or at the oil level. Below the oil level only a thin coating is formed and it is not very adherent.

The coating formed above the oil level is formed by condensation of oil vapours and their polymerisation, and it is difficult to remove.

In the attempt to resolve this problem, fryers have been proposed with removable tanks in order to facilitate cleaning them. For preference the removable tank is made of stainless steel, as this material is particularly suitable for cleaning. A drawback of these tanks is that stainless steel is not the best material where heat conduction is concerned.

The object of the present invention is a tank that is fully adapted both to cleaning and to transmission of heat to the cooking oil or liquid.

The tank for the cooking appliance according to the invention is designed to contain a cooking medium such as oil or fat in order to cook or fry foods, the said tank being designed to be attached to a heating element in order to heat the cooking medium and cook or fry the foods. The said tank has an interior face defining the bottom of the tank and the internal or cooking volume of the tank.

In the invention the said internal face consists of two parts, a first part being made of a first material having the properties of heat conduction or transfer, while the second part is made of a second material, which second material has the properties of heat conduction or transfer to a lesser degree than the first material. The second material is preferably a material that is easy to clean.

In an advantageous form of implementation the bottom of the tank is made at least partly of the said first material, while the side walls of the tank are made of the said second material.

The said first material is for example aluminium, while the said second material is for example stainless steel or enamelled steel.

According to a detail of one form of implementation the bottom consists of a first part made of the said first material, the second part of the bottom, said part being situated between the said first part and the side walls of the tank, being made of the said second material.

Preferably the said second part of the bottom has a groove of which the bottom is situated at a level lower than the internal face of the bottom of the tank made with the said first material. Such a groove enables particles and bits to collect, and a zone with little turbulence to be formed.

In a particular form of implementation the first part of the bottom is a plate whose edges are supported on the second part of the bottom.

Preferably the plate, in the vicinity of its edges, is furnished with a means of limiting heat conduction from the centre of the plate to the edges.

For example the tank includes a first receptacle made of the said second material and having its bottom partly covered by a plate, so as to define a housing between the bottom of the receptacle and the plate. The said housing contains the heating element, and possibly a temperature pick-up and/or a thermostat and/or a control and/or safety system, the said housing having an opening for transit of an electrical energy lead to the heating element, and a seal that extends into the said opening in order to ensure the housing watertightness. This lead is for example a terminal or tap to be connected to a tap or connector.

Advantageously the plate, on its face whose edges are designed to be supported on the second part of the bottom, has a first protuberance and a second protuberance distant from each other in such a way as to form a groove between them, the first protuberance being, in relation to the second one, more adjacent to the side walls of the tank. The second protuberance has a height adjusted so that the free end of this protuberance is distant from the second part of the bottom. A seal or adhesive seal or flange extends into the said groove, one face of the said seal or flange touching the second part of the bottom in order to ensure watertightness between plate and second part of the bottom.

Thus transit of air from the housing to the joint or flange is possible. Such transit allows ventilation of the groove and, for example, enables the adhesive to harden.

Advantageously the seal has at least one passage, internal channel or cavity in order to increase the crushing effect of the seal parts adjacent to the said passage, channel or cavity.

A further object of the invention is a cooking appliance, in particular a fryer including a tank according to the invention.

The particular features and details of the invention will emerge from the following detailed description, in which reference is made to the attached drawings.

- Figure 1 is a section view of a form of implementation of a tank according to the invention; - Figure 2 is a partial perspective and section view of the tank according to Figure 1; - Figure 3 is a rear perspective view of the plate covering the bottom of the tank in Figure 1; - Figure 4 is a section view of another form of tank according to the invention, and - Figure 5 is a view of a detail of the tank in Figure 4.

Figure 1 shows a form of implementation of a fryer including a tank 1 according to the invention. This tank 1 consists of two parts, namely a lower part 2 in the form of a plate, and an upper part 3 in the form of a bowl.

The bowl 3, which is for example made of stainless steel, has at its ends an annular head 4 designed to be supported on the fryer walls 5.

The heating element 10 is inserted in the lower part of the bowl, for example on the plate 2 made of aluminium.

As the bowl 3 is made of stainless steel, and stainless steel is the material at the levels situated above the upper oil level 0, the tank 1 can be fully cleaned. For preference the tank can be taken out of the fryer but, even in the case of such a tank fixed to or integral with the rest of the fryer, excellent cleaning of the tank can still be carried out.

It is important to note that stainless steel (such as chromium - nickel steel) has a heat conductivity coefficient (+ 15 W/mK) far below that of aluminium (+ 210 W/rnK), so that heat conduction to the head or top rim is reduced.

In this form of implementation the stainless steel bowl obtained by drawing has a bottom 23 on which a (cast) heating plate 2 can be fixed, with interposition of a joint 24 by means of a central screw 25 (broken lines). The stainless steel bottom 23 has one or more openings such as a watertight opening 28 for transit of a temperature pick-up or thermostat, and a watertight opening 26 for transit of a connection 27 (to lead the electric energy to the heating plate 24).

The bowl 3 is a bowl made of ordinary stainless steel with a fitted and perforated bottom made of polished austenitic chromium-nickel steel. With a normal thickness of 0.7 mm, a bowl of this kind weighs about 0.9 kg.

The aluminium bottom plate includes the heating element 10 and is cast under pressure in a corrosion resistant alloy.

This aluminium plate may be furnished with a PTFE (polytetra-fluoroethylene) coating or other heat resistant coating; however a merely polished form is already particularly suitable for cleaning.

With an average thickness of about 6 mm, this plate weighs less than 450 grams, so that the bowl-aluminium bottom plate assembly is no heavier than the present injected bowls.

The aluminium bottom plate 2 preferably has a steel heating element (resistance) cast onto it. In view of its high admissible power density, a small resistance may be used so that considerable space is left free for the temperature pick-up or thermostat.

The outputs or output contacts are made watertight and are bent downwards to pass through an opening on the stainless steel bottom and be linked to a connector. As shown in the sketch of this form of implementation, the stainless steel bottom of the bowl will protect the contacts so as to avoid all deterioration.

The coefficients of expansion of stainless steel and aluminium do not differ very much, but owing to a possible big temperature difference between the bottom plate and the bowl bottom during the heating phase, an expansion difference of 1.2 mm may be expected.

The assembly with plate removable by means of a screw allows dismantling and reassembly operations without watertightness problem, for example by means of an approriate ring seal placed between the edges of the plate and the bowl support face.

Non-removable fixing of the bowl with the plate is likewise possible by joining the aluminium bottom to the stainless steel bowl by means of a heat-resistant silicone adhesive.

Another important difference between an aluminium bowl and a stainless steel bowl is the temperature expected for the side walls, whereby due to the very low heat conductivity of stainless steel walls, a cold-walled fryer can be obtained.

Figure 2 shows local reduced thickness of the aluminium plate, at the level of the temperature pick-up or thermostat, so that the oil temperature and the bottom temperature are measured.

The heating element 10 is located in a chamber 32, which is contained between the bottom 23 of the bowl 3 and the plate 2. The heating element 10 does not touch the bottom 23 of the bowl 3, so that a layer of air provides insulation between heating element 10 and bottom 23. This insulation is obtained by means of a layer or a film of air, which is for preference less than 5 mm thick (preferably from 1 to 2 mm).

The minimal distance between heating element and bottom 23 is thus preferably less than 5 mm, and in particular less than 2 mm.

Figure 4 shows another form of construction of a tank according to the invention.

This fryer tank 100 has an internal face 101 defining the bottom of the tank and the internal or cooking volume of the tank. This internal face 101 comprises two parts, 102 and 103, a first part made of a first material (aluminium) exhibiting heat conductivity or transfer properties, while the second part 103, which is located at least in part at a higher level of the internal face and the tank bottom, is made of a second material (stainless steel) having lower heat conductivity or transfer properties than the first material.

The tank bottom 104 includes a first part 102 made of the said first material, and a second part 103 A. The second part 103A of the bottom is situated between the said first part 102 and the tank side walls 103B, this second part being made of the said second material.

The said second part 103A of the bottom exhibits a groove 105 of which the bottom is located at a level N lower than the internal face 106 of the bottom of the tank made with the said first material.

The first part (102) of the bottom consists of a plate having edges 107 supported on the second part 103A ofthe bottom.

The plate, in the vicinity of its edges, is furnished with a means of limiting heat conduction from the centre of the plate to the edges.

Such means are, for example, one or more reductions in thickness (108, 109) of the plate 102, for example in the vicinity of the edges 107.

In fact the tank has a first container made of the said second material and the bottom of which 111 is partly covered by the plate 102, thus defining a housing 112 between the bottom 111 of the receptacle 1 and the plate 102. The said housing 112 contains the heating element 113, a temperature pick-up, a thermostat and a control and/or fuse system. The said housing 112 has an opening 114 for passage of a connector 115 to lead electrical energy to the heating element, and a seal 116 extending into the said opening in order to ensure that the housing 112 is watertight.

The plate 102, on its face having edges 107 designed to be supported on the second part of the bottom 103 A, has a first protuberance 117 and a second protuberance 118 distant from each other in such a way as to contain a groove 119 between them, the first protuberance 117 being, in relation to the second, more adjacent to the tank side walls 103B. The second protuberance 118 is at a height such that the free end 120 of this protuberance is distant from the second part 103A of the bottom. A seal or adhesive seal or flange 121 extends into the said groove 119, one face of the said seal or flange touching the second part 103 of the bottom in order to ensure watertightness between the plate 107 and the second part 103A of the bottom.

The seal used is shown in Figure 5. It exhibits 2 flanges 122 having a cavity 123 in order to permit a crushing effect in direction X of the seal parts adjacent to the said channel or cavity.

The seal on the face opposite the one with the flanges likewise bears contact lips 124.

The air or gas contained in the cavities acts as cushion or flexible means and thermal barrier.

Claims

CLAIMS:

1. Tank for a cooking appliance, designed to contain a cooking medium to cook or fry foods, the said tank being designed to be connected to a heating element to heat the cooking medium and cook or fry the foods, the said tank exhibiting an internal face defining the bottom of the tank and the internal or cooking volume of the tank, wherein the said internal face consists of two parts, a first part being made of a first material having heat conduction or transfer properties, while the second part, which is situated at least in part at a higher level than the internal face of the tank bottom and the first part, is made of a second material, which has lower heat conduction or transfer properties than the first material.

2. Tank according to claim 1, wherein the tank bottom is at least partly made of the said first material and the tank side walls are made of the said second material.

3. Tank according to claim 1 or 2, wherein the said first material is aluminium, while the said second material is stainless steel or enamelled steel.

4. Tank according to one of the claims 1 to 3, wherein the bottom has a first part made of the said first material, the second part of the bottom situated between the said first part and the tank side walls being made of the said second material.

5. Tank according to claim 4, wherein the said second part of the bottom exhibits a groove of which the bottom is situated at a level lower than the internal face of the part of the tank bottom made of the said first material.

6. Tank according to claim 4 or 5, wherein the first part of the bottom is a plate whose edges are supported on the second part of the bottom.

7. Tank according to claim 6, wherein the plate in the vicinity of its edges, is furnished with a means of limiting heat conduction from the centre of the plate to the edges.

8. Tank according to either of claims 6 and 7, wherein the tank consists of a first receptacle made of the said second material and of which the bottom is partly covered by the plate so as to define a housing between the receptacle bottom and the plate, and by the fact that the said housing contains the heating element, and possibly a temperature pick-up and/or a thermostat and/or a control and/or safety system, the said housing having an opening for transit of an electrical energy lead to the heating element, and a seal extending into the said opening in order to ensure watertightness of the housing.

9. Tank according to one of claims 6 to 8, wherein the plate, on its face of which the edges are designed to be supported on the second part of the bottom, has a first protuberance and a second protuberance, distant from each other in such a way as to form a groove between them, the first protuberance in relation to the second being adjacent to the tank side walls, by the fact that the second protuberance is at an appropriate height so that the free end of this protuberance is distant from the second part of the bottom, and by the fact that a seal or adhesive seal or flange extends into the said groove, with one face of the said seal or flange touching the second part of the bottom in order to ensure watertightness between the plate and the second part of the bottom.

10. Tank according to claim 9, wherein the seal has at least one passage, internal channel or cavity in order to increase the crushing effect of the seal parts adjacent to the said passage, channel or cavity.

11. Fryer consisting of a tank according to any one of claims 1 to 10.

12. Tank substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.