EP1201998A1

EP1201998A1 - Cooking oven

Info

Publication number: EP1201998A1
Application number: EP00123206A
Authority: EP
Inventors: Riccardo c/o Whirlpool Europe s.r.l. Allera; Giovanni c/o Whirlpool Europe s.r.l. Franzetti; Marco c/o Whirlpool Europe s.r.l. Maritan; Salvatore c/o Whirlpool Europe s.r.l. Sanna; Massimo c/o Whirlpool Europe s.r.l. Maroni; David c/o Whirlpool Europe s.r.l. Ward
Original assignee: Whirlpool Corp
Current assignee: Whirlpool Corp
Priority date: 2000-10-26
Filing date: 2000-10-26
Publication date: 2002-05-02
Anticipated expiration: 2020-10-26
Also published as: ES2255935T3; EP1201998B1; DE60026421D1; DE60026421T2

Abstract

A cooking oven comprises a cavity (12) having a separating and insulating plate (18) which can be inserted horizontally in the cavity (12) in order to split it in two sub-cavities (12b, 12c). Each sub-cavity has heating elements (14, 22) on its side walls (12a). The oven sub-cavities can be singularly or separately and this increases flexibility in use.

Description

The present invention concerns a cooking oven comprising a cavity. It is well known that energy saving is an imperative for all the devices which consume energy and therefore contribute to environment pollution and/or greenhouse effect. This applies to domestic appliances too, and particularly to domestic appliances using high level of energy like electric cooking ovens. It is an object of the present invention to provide an oven with a cavity that improves oven performance (efficiency and effectiveness), provides greater flexibility in use, improved quality of cooking and better cleanability by means of a flexible heating system.
The above object is reached thanks to the features reported in the appended claims.
According to the invention, the oven comprises heating elements placed vertically on side walls of the cavity, in addition to traditional heating elements placed horizontally on top and bottom walls. The concept is applicable to pyrolitic and non-pyrolitic ovens, and includes also the solution according to which the oven cavity does not have the traditional heating elements placed horizontally on top and/or bottom walls.
The use of the separating and insulating plate and of the heating elements according to the invention allows improved energy efficiency due to flexibility in use and optimisation of heat transfer. Moreover it reduces cooking cycle times (effectiveness) due to smaller cavity and improved energy efficiency. The oven cavities of the oven according to the present invention can be run in static and convective modes singularly or separately. This increases flexibility in use. The reduced dimension of the sub-cavities and/or the use of heating elements placed on side walls of the cavity improve temperature uniformity in cavity.
According to an embodiment of the invention, the inclusion of a rotating table on the separating plate improves browning, crisping, heat distribution and hence improves efficiency (time and energy saving) and effectiveness (cooking results).
The present invention will be disclosed in detail with reference to the accompanying drawings, which illustrate a preferred embodiment of the invention by way of example and in which:

Figure 1 is a perspective view of a built-in oven according to the invention, in which the door oven and insulating panels have been removed for sake of clarity,
Figure 2 is a front view of the oven of figure 1,
Figure 3 is an exploded view of the oven of figure 1 in order to show details of heating elements according to a first embodiment of the invention,
Figure 4 is a perspective view of the oven according to a second embodiment of the invention,
Figure 5 is a detail showing the layout of the heater used in the heating elements of the oven shown in figure 4, and
Figure 6 is a top view of the separating plate with the rotating table thereof.

With reference to the drawings, an oven 10 comprises a cavity 12 having four heating elements 14, two for each side 12a of the oven cavity, which are housed in flat plates 16. Two flat plates 16 are located at each side 12a of the cavity and connected electrically through the back plate of the oven. The flat plates 16 are vertically separated in order to form an horizontal slot or guide G in which is slidably inserted a shelf-shaped separating plate 18 that splits the cavity 12 in two sub-cavities 12b and 12c. The separating plate 18 has thermal insulating properties and is provided with a silicone seal (not shown) in the front portion thereof in order to seal the front wall of the cavity i.e. the oven door.
According to a first embodiment of the invention, each flat plate 16 consists of a tubular resistance element 13 cast in a suitably shaped light alloy e.g. aluminium.
According to a second embodiment of the invention, each flat heating element 14 consists of a tubular resistance element 13 clamped to a suitably shaped thin metallic (e.g. steel) plate 16 (figure 3). Each metallic plate 16 has an horizontal central ridge 16a which is used for slidably supporting food trays or grills.
According to a third embodiment (figure 4), the oven cavity comprises four rectangular openings 20 on its side walls in which radiant heating elements or heaters 22 are placed, two for each side. In front of each element there is a dark Ceran® glass 24 fitted so as to protect the heater ribbon 25 from the splattering of food etc. and also filters both visible and I.R. heat. The heaters 22 are mounted flush to the cavity wall and are therefore installed on the outside of the cavity 12. Heat is therefore transmitted from the heater to/through the glass 24 and then into the cavity 12 via radiation and convection. Some conduction is also afforded from the glass to part of the cavity side wall 12a. The separating plate 18 is supported by L-shaped rails 28 fixed to the side wall 12a of the cavity 12 between each couple of openings 20.
The heater ribbon layout (figure 5) is optimised to improve heat distribution in the cavity and thus cooking performance. The shape of the ribbon 25 is similar to a "dickey bow" in which the heat distributed is favoured towards the edges 25a (more exposed ribbon area) rather than centre 25b (less exposed ribbon area).
In any of the above embodiments the installed power for each side wall heater is preferably between 250 W to 1500 W. This power is added to the power of standard grill and lower heating elements.
The oven according to the present invention can be used in a standard mode, without the separating plate 18. In this mode the oven can be used as a standard oven (static and/or lower element) or together with the four side heating elements 14 or 22. In this latter case performance (e.g. cooking results) is comparable or better than the standard radial heater configuration (circular heater around fan).
In a second configuration of the oven, called 'flexible cavity' configuration, the separating plate 18 is used to split the oven cavity 12 thus providing three further modes of operation:

a first mode in which the upper sub-cavity 12b only is used. In this case the heaters used are the two upper side wall radiant heaters 14 or 22 plus the grill element (not shown). The grill element may also be used separately such as for grilling or browning. In such first "flexible" mode the sub-cavity temperature is set and controlled by the same control used for the standard mode. This mode is particularly suited for meat, poultry, grilling etc.
a second mode in which the lower sub-cavity 12c only is used. In this case the heaters used are the two lower side wall radiant heaters 14 or 22 plus the lower heating element of the oven (not shown). The lower heating element may also be used separately such as for warming or crisping. In such mode the lower sub-cavity temperature is set and controlled by a sensor positioned in the lower sub-cavity 12c. This cavity mode is particularly suited for pasta, cakes, baking, pizza etc.
a third mode in which the sub-cavities 12b and 12c can be set at 2 different temperatures up to a typical maximum temperature difference of 100°C e.g. 250°C for the upper sub-cavity 12b and 150°C for the lower sub-cavity 12c. Of course such temperature difference depends on the thermal insulating properties of the separating plate 18 (the lower the heat transfer coefficient, the higher the temperature difference) and degree of sealing.

In all of the above 3 mentioned modes the separating and insulating plate 18 is provided so as to isolate and insulate the two sub-cavities 12b and 12c. This is done by carefully sizing the separating plate 18 to match the cavity interior profile (incl. oven door) and using a silicone rubber seal (not shown) fitted on the front of the separating plate 18. When in use this latter sits on a suitable ledge defined by the heating elements 14 or by the rails 28.
When the separating plate 18 is installed the temperature control and sensor of the lower sub-cavity 12c is enabled e.g. through a micro-switch (not shown) fitted at the rear of the oven cavity 12.
The separating plate 18 splits the cavity volume in half, i.e. it provides the two sub-activities. Although the separating plate 18 can be removed when installed, its position is preferably fixed.
According to tests carried out by the applicant, in the sub-cavity modes typical warm-up times are at least 30% less than the standard mode (in which the separating plate 18 is removed), thus providing greater flexibility in time management. Typical cooking performance (cooking time) is at least 20% better (less) than the standard oven for the same food or dish. This performance improvement leads to lower energy consumption, lower cooking times, and greater flexibility in use.
According to a further embodiment of the invention, the oven can be provided with a turntable or rotating table 30 rotatably supported by the separating plate 18. This consists of a rotating table driven directly by an electric spit roast motor through a mechanical coupling 32. This accessory is especially useful for further improving cooking performance, better browning and crisping and avoids the need to turn (rotate) the food during cooking.
The accessory comprises a drive motor located outside the cavity (not shown), a flexible drive shaft 34 having a end with a toothed gear 34a and a dish or table 36 equipped with gear teeth on its underside. The drive mechanism can be either direct with a solid shaft or direct with a flexible shaft (as shown in figure 6). The drive is connected to the rotating table 30 which can be made part of the above mentioned separating plate 18.
It is possible to use more than one turntable 30 at a time via a replicated drive mechanism. In the embodiment shown in figures 1 and 2 a second rotating plate 40 is shown on the bottom wall of the oven.
For controlling the operation of the two sub-cavities 12b and 12c, the oven according to the invention is provided with twin standard controls (not shown).
A possible configuration of the control panel of the oven has a right hand control for the standard mode and for the upper sub-cavity mode and a lefthand control for the lower sub-cavity mode.

Claims

Cooking oven comprising a cavity (12), characterised in that it further comprises a separating and insulating plate (18) which can be inserted horizontally in the cavity (12) in order to split it in two sub-cavities (12b, 12c), each sub-cavity having at least a heating element (14, 22) on its side wall (12a).
Cooking oven according to claim 1, characterised in that each side wall (12a) of each sub-cavity (12b, 12c) has at least one heating element (14, 22).
Cooking oven according to claim 1 or 2, characterised in that each heating element (22) comprises a glass plate (24) mounted in a corresponding opening (20) of the oven cavity (12) and a heater (25) placed on the side of the glass plate (24) far from the cavity (12) so that heat is transmitted from the heater to/through the glass and then into the cavity via radiation and convection.
Cooking oven according to claim 3, characterised in that each glass plate (24)is mounted substantially flush to the cavity side wall (12a).
Cooking oven according to claim 3 or 4, characterised in that the heater (25) presents a resistance layout which is flat and has a dickey bow shape so that heat generation is higher toward the oven front door and oven rear wall.
Cooking oven according to claim 1 or 2, characterised in that each heating element (14) comprises a tubular resistance element cast in a light alloy.
Cooking oven according to claim 1 or 2, characterised in that each heating element (14) comprises a tubular resistance element (13) clamped to a metallic plate (16).
Cooking oven according to any of the preceding claims, characterised in that it comprises a control unit able to heat only one of the two sub-cavities (12b, 12c) or both, the sub-cavities (12b, 12c) being able to be set at two different temperatures.
Cooking oven according to any of the preceding claims, characterised in that the separating and insulating plate (18) comprises a support for a rotating table (30) driven by an electric motor.
Cooking oven according to claim 9, characterised in that the rotating table (30) has a drive mechanism comprising a drive shaft (34) having a gear device (34a) able to cooperate with corresponding gear teeth on the underside of the rotating table (30, 36).