EP2966361B1

EP2966361B1 - Oven cavity and oven comprising oven cavity

Info

Publication number: EP2966361B1
Application number: EP15163642.0A
Authority: EP
Inventors: Richard Wiesinger; Marco Böckler
Original assignee: Electrolux Appliances AB
Current assignee: Electrolux Appliances AB
Priority date: 2014-07-10
Filing date: 2015-04-15
Publication date: 2017-12-06
Anticipated expiration: 2035-04-15
Also published as: EP2966361A1

Description

In modern household appliances, such as kitchen appliances, long-term quality perception, technical sophistication and ease of operation are becoming more and more important for the customer. Technological development in the area of kitchen ovens has led to oven cavities that are capable of self-cleaning in a catalytic process that involves temperatures as high as 500°C. Such oven cavities are often manufactured from sheet metal that is covered by enamel which provides an excellent long-term quality perception as well as is capable to withstand the high temperatures for a frying and baking process as well as the self-cleaning process over a longer period of time. In order to facilitate the manufacturing process and to provide oven cavities of different sizes and functionality, such oven cavities are often manufactured of plural pieces of sheet metal that are welded to each other.
It will be understood that during the self-cleaning operation of an oven, the temperature gradient ranges from 500°C to the environmental temperature of usually 20°C in a room environment.
Thus, the temperature gradient is rather high and is not linear across the oven cavity. In particular, in the outer area where the oven cavity is fixed to a housing, predominantly temperature ranges in the area of room temperature are present as well as complicated shapes are provided at the border of the oven cavity in order to be able to fix it in the housing respectively there are support structures required for manufacturing and support of the oven cavity. Sheet metal and the enamel used to cover the sheet metal are thus subject to thermal stress. Thermal stress in an area of high temperature gradients, such as occurring in an outer area of the oven cavity in combination with a design that comprises folds, bands and holes may lead to deformations in the oven structure, particular in the area where the oven is supported.
Thus, in an undesirable manner, the enamel covering edges and corners may chip off or form cracks when periodically undergoing heating and cooling during the daily use of an oven. Although, technically, from a viewpoint of proper functioning of the device, smaller cracks could be tolerated, they cannot be tolerated in terms of the influence of quality perception on a potential customer. In particular, thermal hotspots may occur in an area where sheet metal overlaps and is welded against each other. In this area, the thermal capacity of the oven structure is higher and thus takes longer to heat up and cool down during the temperature cycle involved in the daily use and self-cleaning of the oven.
The technical development in the design of ovens, in particular of such ovens that have a self-cleaning function, strives to avoid heat nests and deformation of an oven cavity as much as possible in order to avoid degradation of the surface quality inside of the oven mainly and to prevent the covering enamel from cracking or chipping off.
The document DE 10314500 A1 describes a cooking device cavity. This cavity has a wall structure where sheet metal planarly overlaps and is fixed against each other by welding. Whereas the inside sheet metal is planar, the outside sheet metal comprises a flange that extends in a right angle away from the oven cavity. This flange may serve as a border reinforcement as well as provide good thermal conductance away from the overlap area in which the two sheet metal planes are welded to each other.
Document GB 2107160 describes a heating compartment for a cooking apparatus comprising curled edges of at least two selected from plate elements forming the heating compartment so as to shape into a form with a circular cross section. The plate elements whose ends are curled to shape the form with the circular cross section are a front plate, a base plate having two side walls, and a top plate containing a back plate. The curls overlap but outside a food preparation space.
Document US4563559 is about an inner box for a cooking appliance that comprises a front panel having an opening, a cylindrical barrel section, and a rear panel. The peripheral edge of the opening in the front panel is joined to the front end edge of the barrel, while the rear end edge of the barrel is joined to the outer peripheral end edge of the rear panel. Each of the joints is formed by a crimping operation and at least one of the crimped joints is provided with interlocking elements which engage each other as a result of the crimping operation. A wall with such elements is shown to have no flange.
Document DE 10314500 discloses an oven chamber joint between overlapping sheet sections, which includes a flange projecting outside the chamber. There on an external second sheet end section a flange is constructed. This flange projects from an exterior of the chamber.
Document US 4 563 559 A discloses an inner box for a cooking appliance. The cooking appliance comprises an inner box with different sections or panels which are coupled by means of crimped joints.
Document EP 2 615 377 A1 discloses an oven cavity. The oven cavity comprises multiple wall pieces which are coupled with each other by means of a form-fit connection. Said coupling is obtained by a tongue-like projection which is inserted in a groove of a head piece.
The invention is based on the problem to provide an improved oven cavity and an oven that has a more stable structure and improved thermal properties.
This problem is solved by an oven cavity according to claim 1 and an oven according to claim 17.
Further developments of the invention are given in the dependent claims.
Advantageously, the oven cavity according to an embodiment of the present invention provides form stability in an outer area in all directions of the oven cavity and thus provides a better compensation against thermal stress occurring in different directions in the walls of the oven cavity. It also promotes cooling by facilitating thermal convection at the bending area. This is especially important as this bending area is located at a location of high thermal capacity of the oven cavity where two sheet metal sections overlap.
Beneficially, in order to maximize the effect of the reinforcement of the structure according to a further development of an embodiment of the oven cavity according to the present invention, the flange protrudes in an obtuse angle from a sidewall of the oven cavity; favorably in an angle selected from angles between 70° - 110°, more preferably an angle selected from angles between 85° - 95° and most preferably essentially in a right angle from the sidewall of the oven cavity in order to withstand bending forces as a consequence of thermal stress maximally.
Advantageously, according to a further development of an embodiment of the oven cavity according to the present invention, the bending area forms an obtuse angle and preferably a right angle with the flange and thus maximizes stabilization of the flange and accordingly the sidewall in the direction vertical to the stabilization direction that is provided by the flange. Also favorably, the bending area provides for a better cooling effect as it promotes generation of an airstream parallel to its surface based on thermal convection. Beneficially the generated airflow is unobstructed by other cavity parts as the bending area protrudes freely away from the flange. The first and the second sheet metal sections are welded to each other. In this manner, a very rigid metal connection will be formed that withstands high temperature as well as seals the inside oven cavity to confine fumes generated by baking or frying inside.
Beneficially, according to a further development of an embodiment of the oven cavity according to the present invention, the width of the flange and the width of the bending area correspond to each other in order to provide a similar stabilization effect.
Advantageously, according to a further development of an embodiment of the oven cavity according to the present invention, the width of the bending area and the width of the flange are the same, because this allows a facilitated manufacturing as no additional tooling is required to form the flange as well as the bending area.
Preferably, according to a further development of an embodiment of the oven cavity according to the present invention, the width of the flange is wider than the width of the bending area, because in this manner more flexibility in the design of the walls of the oven cavity can be provided and the flange can be better used to provide support during manufacturing or operation.
Advantageously, according to a further development of an embodiment of the oven cavity according to the present invention, the bending area extends at least partially along the extension of the flange, as in this manner dedicated reinforcement can be performed in weak areas, while at the same time material can be saved. Thus, the shape of the oven cavity and the amount of sheet metal used in forming the structures can be further improved.
Advantageously, according to a further development of an embodiment of the oven cavity according to the present invention, the bending area extends along the total straight length of the flange. In this manner, a maximum support can be achieved that entails a maximum stability against thermal stress at any selected long- or short side of the oven cavity.
Advantageously, according to a further development of an embodiment of the oven cavity according to the present invention, the bending area extends along the most part of a side of an oven cavity along the flange and thus provides significant support for its structures. On the other hand, at the corners, generally more stability is anyway present and thus in some cases no bending area may be required there for technical reasons.
Beneficially, according to a further development of an embodiment of the oven cavity according to the present invention, the bending area extends at both sides of a hole provided in the flange. In this manner, dedicated reinforcement is provided at a weak spot, and a maximum of material such as sheet metal can be saved.
Advantageously, according to a further development of an embodiment of the oven cavity according to the present invention, the bending area forms part of a rear, a top or a bottom of the oven cavity. This, because mostly the oven cavities are manufactured from different parts of sheet metal and not all of them require to have a flange or a bending area that faces outward respectively upward. On the other hand, beneficially, the bending area and the flange according to the present invention are invisible from the inside of the oven cavity and provide additional support. Further beneficially design flexibility is provided by such a solution as the flange respectively bending area can be provided at the part of the oven cavity which is substantially vertical in an operating position of the oven cavity. In this manner a maximum cooling effect by the bending area promoting thermal convection can be achieved
Beneficially, according to a further development of an embodiment of the oven cavity according to the present invention, the bending area extends along the entire flange along the circumference including the corner area and thus provides maximum support for the oven cavity on its external periphery against thermal stress in different directions.
Beneficially, according to a further development of an embodiment of the oven cavity according to the present invention, the bending area extends along a short sidewall in the area of the flange of the oven cavity, as in many manufacturing processes, the sidewall is used to attach support structures for manufacturing or operation, e.g. holes are provided to indicate a type of the cavity or to fix the cavity on a hook during a process where the enamel coating is provided. Short sidewall in case of a rectangular cross section of the oven cavity may be understood as the shorter side of the rectangle as opposed to the longer side of the rectangle. In most cases the shorter side in an operation mode of the oven cavity extends in a vertical direction. A bending area on the shorter side is thus also particularly suitable to promote thermal convection in a vertical direction as the air streams along it and can take away much heat in this manner.
Advantageously, an oven according to the present invention comprises an oven cavity according to the present invention, because such an oven has a rigid oven cavity that withstands high thermal stress to a maximum and thus guarantees a long life and provides a long-term quality perception to the customer, in particular when self-cleaning processes are frequently carried out at the oven.
Subsequently, the invention will further be explained on the basis of examples shown in drawings wherein:

Fig. 1: shows examples of an oven and oven cavities;
Fig. 2: shows a perspective view of a complete oven cavity,
Fig. 3: shows a detail of the oven cavity of Fig. 2;
Fig. 4: shows an example of a rear of an oven cavity;
Fig. 5: shows another example of a rear of an oven cavity; and
Fig. 6: shows a detailed view of a cut through an oven cavity.

Fig. 1 gives examples of different structures of an oven cavity as well as shows a basic representation of an oven according to a preferred embodiment of the present invention. Generally, three types of structures are shown.
One structure is called C-structure 1100. It consists of a sheet metal plane that is bent twice in the shape of a letter C 1120, as also indicated by the bracket 1150. Further, there are a top 1110 and a bottom 1130 to complete the cavity. Usually at the front side, the oven door will be located closing the cavity fully. In the area where the different components of the oven cavity meet e.g. top 1110, wrapper 1120 and bottom 1130, there is a requirement to fix them against each other.
Commonly, this will be done in the area of zones of the different components of the structure overlapping each other and welding them against each other. Other technologies are conceivable, such as a bracing under tension against each other without requiring welding. Also gluing is conceivable, if gluing technology develops into an area where high temperature resistive glue can be provided.
Further, a U-structure 1300 is shown where a U is provided in the form of wrapper structures 1354, 1357 and 1350. The U 1330 is covered by a top 1310 and completed by a rear 1340. Usually, as can be seen, some parts are not flat sheet metal pieces and can be provided e.g. by deep drawing, and / or embossing or bending.
Another type shown is the O-structure where advantageously only two parts need to be provided, one like an O that may be cut from a pipe structure or e.g. bent from sheet metal and e.g. welded. The O 1420 also indicated by a marking 1450 is covered on the rear side by a rear 1440.
Further, an oven 1700 is shown, comprising a housing 1705 and an oven cavity 1100. As oven cavity, any one of the ones shown, be it C-structure, U-structure or O-structure, can be used according to the technical needs and e.g. design constraints.
As Fig. 2 shows, a perspective view of an oven cavity according to a U-structure is comprised of a top 2310, a wrapper 2330 and a rear 2340. A flange 2600 is depicted that extends around the entire oven cavity perpendicular to the sidewalls. The oven cavity may also respectively be comprised of the structural parts disclosed above for different oven cavities.
The rear 2340 is, for instance, manufactured by deep drawing a sheet metal piece. An area for a detailed view 2730 is marked that contains a hole 2700 in the flange 2600. Further, a direction of a cutting of the oven cavity A-A is shown that indicates the view in Fig. 6 which there is perpendicular to the cut direction. Part of the interior of oven cavity 2000 can be seen having a food preparation space 2050. On the perspective view in Fig. 2, it is also shown that such an oven cavity has a complex structure that is formed by e.g. embossing, deep drawing and/or bending. All these structures predominantly serve to stabilize the sheet metal that is usually used to manufacture the oven cavity. The flange 2600, here provided at the rear 2340 of the oven cavity, serves mainly the purpose to stabilize the oven cavity further and to provide a thermal sink in order to cool the oven cavity in an area where the temperature gradient is very high, and thus the structure is very likely to undergo deformations.
As Fig. 3 shows, a detailed view of Fig. 2 has an opening 2700 at a flange 2600. This opening is beneficially accompanied on both sides by a bending area 2449 in order to further stabilize the structural weak spot. In particular, if the flange 2600 stabilizes the oven cavity in one direction, a bending area 2449 stabilizes the oven cavity respectively the flange 2600 in a different direction. Advantageously, the flange protrudes in a right angle from a sidewall of the oven cavity, whereas the bending area protrudes perpendicular to the flange and thus substantially runs parallel to the sidewall of the oven cavity. In this manner very good stability properties are combined with comparatively easy manufacturing and assembly of the oven cavity.
As Fig. 4 shows, an example of a rear of an oven cavity 4440 has a bending area 4448 that completely surrounds the flange 4470. In particular, it is also provided in a corner area 4445. With this structure, a maximum reinforcement of the rear of the oven cavity can be achieved. Here, a width of the flange 4480 is indicated and a width of the bending area 4490 is indicated. Beneficially, the width of the flange 4480 and the width of the bending area 4490 are the same in order to provide a similar effect in stabilizing the rear of the oven cavity. There may, however, be reasons to make one or the other larger in order to tailor the effect on stability of the oven cavity. In particular, it is also possible to avoid the bending area 4448 in the corner area, as per se the corner area 4445 is generally more stable than the long side and the short side of the oven cavity itself. Short side in case of a rectangular cross section of the oven cavity may be understood as the shorter side of the rectangle as opposed to the longer side of the rectangle.
Depending on the structural priorities for the oven cavity, the bending area may not be necessarily provided along the entire length of the flange 4470. In particular, it may only be provided substantially to an extent of 85% of one of the linear sides of the structural part that contains the flange, here e.g. a rear 4440. This means e.g. along the shorter side 4600 or the longer side 4700. More preferably, it may be provided along 90% of the length of the longer or the shorter side 4700, 4600 or most preferably to an extent of 95% of the longer side 4700 and/ or the shorter side 4600. It may also be desirable to only provide the bending area 4448 only at one or at two of the longer or shorter sides of the structural part 4440, here the rear of the oven cavity in order to provide special reinforcement at certain regions of the oven cavity. Also depicted is a circular area 4500 at the rear 4440 that may serve to fix a fan of a fan oven.
As Fig. 5 shows, a side view 5000 of a rear 5440 comprises a stepped sidewall with an area 5700 that is closer to the interior than an area 5750. The wall part 5750 forms an area of overlap 5800, in which for instance another structural part, such as the sidewall of the oven cavity, can be entered e.g. inserted to form an area of parallel overlap between the rear 5440 and the sidewall which is not shown here. Such an area of double material strength may store plenty of thermal energy and as such may require special cooling by a heat sink or the like particularly during a catalytic cleaning process involving higher temperatures. Also higher temperatures lead to more thermal expansion and mechanical stress caused by it. Further depicted are a flange 5480 and a bending area 5449. The bending area has a width 5490 that may be similar to the width of the flange 5600. It is also shown here that the bending area 5449 is only provided in the area of a short side of the rear of the oven cavity assuming a substantially rectangular projection of the rear 5440 in a similar way as shown in the rear of Fig. 4.
Fig. 6 shows a detailed view of a section of an oven cavity, e.g. as shown in Fig. 2. The section is e.g. taken along a direction A-A shown in Fig. 2. A section 6440 of a rear of the oven cavity is shown, and a section of a sidewall 6330 is also shown. Further, the detail 6000 shows an area of overlap 6800 where part of the sidewall 6330 and of the rear 6440 run in parallel. It is further depicted that a part of the rear 6440 identified by 6810 forms a small step in order to allow the sidewall 6330 and the second section of the sheet metal 6310 in this are and the remainder of the rear 6440 to form a planar surface of the oven at the interior of the oven cavity once the two parts are fixed against each other and defining a maximum extension of the food preparation space.
Further, a welding seam 6385 is identified. There is also a flange 6448 which protrudes preferably in an obtuse angle 6700 from the part 6810 of the rear 6440. Preferably this angle 6700 is selected from angles between 70° - 110°, more preferably an angle selected from angles between 85° - 95°, and most preferably essentially is a right angle. Depending on the angle 6700 an anisotropic thermal extension behavior of a sheet metal can be maximally compensated and counteracted.
From there, a bending area 6449 protrudes also preferably in an obtuse angle 6850 from the flange 6448. Preferably this angle 6850 is also selected from angles between 70° - 110°, more preferably an angle selected from angles between 85° - 95° and most preferably essentially is a right angle. Depending on the angle 6850 the form stability of the oven cavity can be tailored respectively maximized.
Thus, the bending area 6449 preferably runs substantially parallel to the sidewall 6440. Here, sidewall and rear are representatively used for the structural parts of the oven cavity as further explained in the context of Fig. 1. It can be any of the structural parts that are adjacent as required.
By the representation 6000 in Fig. 6 it is facilitated to understand that the flange 6448 and the bending area 6449 provide structural support in different directions, the flange in the direction perpendicular to the sidewall 6330 and the bending area 6449 in a direction parallel to the sidewall 6330. Thus, a combined reinforcing effect can be achieved that improves the structural integrity of the oven cavity, respectively the sidewalls forming the oven cavity once subjected to a strong temperature gradient as it occurs during self-cleaning of an oven in a catalytic process.

List of reference numerals

1100, 1200, 1300: structural alternatives
1120: C-wrapper
1130: bottom
1110: top
1150: C-shape
1310: top
1340: rear
1330: U-wrapper
1354, 1357, 1350: U-shape
1420: O-wrapper
1440: rear
1450: O-shape
1700: oven
1705: housing of oven
1100: oven cavity
2000: perspective view of oven cavity
2050: food preparation space
2310: top
2330: C-wrapper
2340: rear
2500: deep-drawing shape
2600: flange at circumference of rear
2700: opening
2720: detail view
A-A: cutting direction
2449: bending area
4000: example of rear no. 1
4440: deep-drawn rear
4500: circular area
4445: corner area
4600: bending area
4490: width of bending area
4480: width of flange
4600: short side
4700: long side
4470: flange
4448: bending area
5700: inward region of sidewall of rear
5750: outwardly stepped sidewall of rear 5440
5440: rear
5600: flange
5480: width of flange
5449: bending area
5450: width of bending area
6000: detailed view of section
6440: section of rear
6700: angle between flange and sidewall
6850: angle between bending area and flange
6800: area of overlap
6810: outward part of step in sidewall, first section in area of overlap
6330: sidewall
6448: flange
6449: bending area
6310: second section, in area of overlap
6385: welding seam

Claims

Oven cavity (2000) enclosing a food preparation space (2050) comprising at least a first sheet metal section (6810) and an adjacent second sheet metal section (6310) that form an area of overlap (6800) where they are substantially parallel to each other and form a part of a wall (6330) of the oven cavity (2000) adjacent to the food preparation space (2050), wherein the first sheet metal section (6810) forms a flange (6448) protruding away from the wall (6330) of the oven cavity (2000), wherein the flange (6448) has a bending area (6449) protruding freely away from the flange (6448) and wherein the first section of sheet metal (6385) and the second section of sheet metal (6810) are welded to each other.
The oven cavity (2000) according to claim 1, wherein the bending area (6449) protrudes in a direction of the wall (6330) of the oven cavity (2000).
The oven cavity (2000) according to any one of the previous claims, wherein the flange (6448) protrudes in an angle selected from angles of 70° - 110°, particularly in the range of 85° - 95°.
The oven cavity (2000) according to any one of the previous claims, wherein the flange (6448) protrudes in a right angle (6700) from the wall (6330).
The oven cavity (2000) according to any one of the previous claims, wherein the bending area (6449) protrudes in a right angle (6850) from the flange (6448).
The oven cavity (2000) according to any one of the previous claims, wherein a width of the flange (4480) and a width of the bending area (4490) correspond to each other.
The oven cavity (2000) according to claim 6, wherein the width of the flange (4480) and the width of the bending area (4490) is the same.
The oven cavity (2000) according to claim 6 wherein the width of the flange (4580) is wider than the width of the bending area (4490).
The oven cavity (2000) according to any one of the previous claims, wherein the bending area (6449) extends partially along the flange (6448).
The oven cavity (2000) according to any one of the previous claims, wherein the bending area (6449) extends around a corner area (4445) of the flange.
The oven cavity (2000) according to any one of the previous claims, wherein the bending area (6449) extends along a straight side of the oven cavity (2000).
The oven cavity (2000) according to any one of the previous claims, wherein the flange (6448) has an opening (2700) and the bending area (6449) extends in the area of the opening (2700).
The oven cavity (2000) according to any one of the previous claims, wherein the bending area (6449) forms part of a rear (1470), top (1310) or bottom (1130) of the oven cavity (2000).
The oven cavity (2000) according to any one of the previous claims, wherein the bending area (6449) extends along the entire flange (6448).
The oven cavity (2000) according to any one of the previous claims, wherein the bending area (6449) extends along a shorter sidewall (4600) of a rectangular cross section of the oven cavity (2000).
Oven (1700) comprising an oven cavity (2000) according to any one of the claims 1 to 15.