Energy-saving cooking appliance door having a low front temperature

Abstract

A cooking appliance door having an inner and an outer wall and a perforated wall therebetween. Air flows through the door and the perforated wall, which can be substantially all or a portion of the perforated wall.

Description

The invention relates to a cooking appliance door as claimed in the preamble of claim 1.

Cooking appliance doors ought to fulfil a number of requirements simultaneously: viewing of the cooked goods, minimal heat loss and minimal front temperatures while the system thickness of the baking oven door construction remains as minimal as possible. In particular in the case of cooking appliances with pyrolytic self-cleaning at inner temperatures of 500° C. there is increased requirement for heat insulating effect of the cooking appliance doors. On account of their multifunctional tasks cooking appliance doors can also be thermal weak spots in cooking appliance construction.

A cooking appliance door is known from U.S. Pat. No. 4,084,571, whereby a heat shield is provided between the multipart and rear part designed as trough-shaped door base and the front part designed as front frame with inset pane in the region of a pane packet mounted on the door base between the pane packet or the door base and the front frame or the front glass pane. The heat shield has countless openings for improving the view in and is highly reflective on the side facing the cooking chamber. On the side facing away from the cooking chamber the heat shield is blackened.

DE 43 04 485 A1 also discloses a baking oven door, whereby the metallic door encloses a pane facing the baking oven muffle. Attached to the door base is a front pane. In the region opposite the metallic door floor the mounted front glass pane is partially provided on its inner side facing the cooking chamber with a reflective layer, for example with surface-polished aluminium foil.

EP 1039 2323 A2 discloses a cooking appliance door, wherein a thermal functional part is arranged at a distance from the front part between the front part, to which a door handle is assigned, and a back part. The functional part can be a multilayer insulation film, in particular aluminium, which has integrated air chambers.

A baking oven according to the document U.S. Pat. No. 4,084,571 has a square metallic oven muffle open to the front. This is substantially insulated thermally on all sides in a manner known per se. Heating elements known per se for heating the cooking chamber are also arranged in the oven muffle. The oven muffle can be sealed at the front by an oven door. In general the baking oven door has a window system.

This comprises a mounted pane packet, comprising 2 to 4 generally partially infrared-reflected panes or an additional perforated heat shield (U.S. Pat. No. 4,084,571).

The object of the present invention is to lower the front temperatures in a cooking appliance door.

According to the invention this is achieved by a perforated wall through which air flows being arranged between the inner wall and the outer wall of the door. In a cooking appliance door with an additional perforated partition between hot and cool side and air guiding through this perforation lower front temperatures are achieved and heat loss flows through the door construction are clearly decreased.

Further advantageous embodiments are to be inferred from the independent claims.

In the sole diagrammatic figure a baking oven with a door designed according to the present invention is shown in section. A baking oven known per se has an oven muffle 1, in which focused heating can be applied by way of heating elements—not shown here—and control and operating and display elements of the cooking chamber. The cooking chamber is sealed by the door, which has a front-side outer wall 3, a cooking chamber-side inner wall 5 as well as an intermediate wall 7 arranged therebetween. The door is held together by different fastening and/or mounting elements at the discretion of the expert, while the outer wall 3 and the inner wall 5 comprise glass or glasslike material.

The perforated intermediate wall 7 is arranged between the outer and inner wall 3, 5 of the door, such that forced air flow through the perforated wall 7 is achieved. The air 7 is suctioned at a lower door edge into the door interior and suctioned at an upper door edge from the door interior. Because of the flowthrough of the perforated wall the thickness of the thermal limiting layer, which has a raised temperature as gas layer near the surface, is substantially reduced and thus the heat transport is diminished by the adjacent gas cavity to the outer pane 3; ideally, the region between the thermal limiting layer and the outer pane 3 has the temperature of the suctioned air. At the same time the perforated wall 7 through which air has flowed is cooled by the forced convection. The cooling leads to lower surface temperatures in the perforated wall, resulting in reduced heat radiation exchange with the opposite outer wall surface 3.

In summary, the perforation through which air flows has the following advantages:

The usual convection roller between two walls is hindered by the inventive measure. The air heated on the perforated intermediate wall 7 is aspirated and does not make thermal contact with the cooler outer wall 3. The perforations, or the air ducts promote good thermal coupling of the wall with the air and thus efficient heat energy removal from the intermediate wall 7 to the suctioned air. Cooling the perforated wall lowers its radiation emission, resulting in lower heat radiation losses.

For further reduction of the heat radiation exchange the intermediate wall 7 can be provided with a low-emitting layer (not shown) if required. Thus the surface temperatures of the outside of the baking oven doors are significantly reduced.

The system shows the best results when suctioning of the cooler air takes place in an outer cavity of the door system—also front side—and the aspiration of the heated air takes place in an inner cavity of the door system. The direction of flow of the air flowing through the door is also against the direction of the heat loss through the door.

The perforated wall 7 can have an opening 9 either only in a transparent region of the door or over the entire surface of the cooking appliance door. The position of the perforated wall inside the wall structure of the cooking appliance door or pane packet of the cooking appliance door is not decisive for the physical effect. At least the cavities in front of and behind the perforated wall 7 are to be provided for the air guiding. The suctioned air is taken from the environment outside the cooking appliance and after being heated is again discharged to the exterior on the perforated wall. According to the figure to this end the baking oven has a cooling fan 11, which blows cool air over a frontal open outlet shaft 13 from the baking oven. Through the injector effect as a result of suitable narrowing of the flow channel formed by the discharge shaft 13 air is drawn from the door in a manner known per se.

Alternatively, it can also be provided that the cool air flowing through the intermediate wall 7 flows back at will into the cooking chamber as a result of subpressure building up in the cooking chamber. For this if can for example be provided that a fumes fan and/or the cooling fan 11 draws fumes out of the cooking chamber via a opening (not shown) of the muffle 1. The prerequisite for this however is a flow-technical connection between the door and the cooking chamber. In the event of introducing the heated air into the cooking chamber energy savings is possible by using the pre-heated air; the heat loss occurring with conventional cooking appliance doors is reduced and part of the energy can be recycled to the cooking appliance.

The perforated wall 7 is understood to be a perforated glass pane, a perforated plastic pane, a perforated film or a perforated sheet etc. The perforation comprises the holes 9 or slots with a typical hole diameter or gap width of 100 μm to 1 cm. The surface portion of the perforation on the wall can vary from ca. 0.1% to 50%.

In summary the forced flowthrough of the perforated wall can be accomplished by a ventilator system placed in the cooking appliance (e.g. range hood), or a ventilator system e.g. integrated in the cooking appliance door. If required, a flowthrough of the perforated film can be created indirectly by available air flow, e.g. through the range hood flowing outwards over the upper edge of the cooking appliance door utilising the Venturi effect. To avoid contamination of the perforated wall the suctioned air can be cleaned in advance by an appropriate filter system.

Claims

1-9. (canceled)

10. A cooking appliance door, comprising:

an inner wall;

an outer wall; and

an intermediate wall arranged between said inner wall and said outer wall, said intermediate wall including at least a perforated wall portion through which air flows.

11. The cooking appliance door according to claim 10, including said air enters the door at a front side of said door.

12. The cooking appliance door according to claim 10, wherein said door includes a transparent surface area and said perforated wall portion is provided only in said transparent surface area.

13. The cooking appliance door according to claim 10, including said perforated wall portion is formed from a glass pane.

14. The cooking appliance door according to claim 10, including said perforated wall portion includes holes or slots with a typical hole diameter or a slot width substantially on the order of 100 μm to 1 cm.

15. The cooking appliance door according to claim 10, including the surface of said perforated wall portion is provided on at least one side with an infrared-reflecting coating.

16. The cooking appliance door according to claim 10, including said air is warmed as it flows through the door and said warmed air guided through said perforated wall portion is deflected outwards to the atmosphere.

17. The cooking appliance door according to claim 10, including said air is forced to flowthrough said perforated wall portion by a ventilator system present in the cooking appliance.

18. The cooking appliance door according to claim 10, including the surface portion of said perforated wall portion is substantially on the order of between about 0.1% and 50%.