An oven with bottom heating element support sheet and production method thereof

Description

FIELD OF INVENTION

[0001] The present invention relates to ovens with an electric heating element, especially ovens with a support sheet which carries the bottom heating element and production methods thereof.BACKGROUND OF THE INVENTION

[0002] Muffle which delimits the baking chamber in electric ovens is comprising a lower wall extends upwardly from peripheral edges, lateral walls surrounding the lower wall and an upper wall covering the lateral walls from above and a back wall fixed along its outer edges to the lower wall on one side and top wall and lateral walls on the other side. Lateral walls and front edges of lower wall forms an opening accessed by a hinged door.

[0003] A support sheet is used for fixing the bottom heating element to a muffle. The support sheet carries the bottom heating element with muffle at a predetermined distance. DE10314590A1 describes an oven casing has an electric heating element positioned below its base wall and supported by a carrier element attached to the oven casing via at least one fixing section. The fixing sections can be provided by fixing lugs, each secured to an oven casing sidewall at a given distance from the base wall, so that the carrier remains out of contact with the latter. The support element is in multi-part form. It is designed as two separate guide part for easy installation of the bottom heating element. Further prior art can be found in EP 2 390 585 A1.SUMMARY OF THE INVENTION

[0004] The object of the invention is to secure a distance between muffle and bottom heating element of the electric oven due to the thermal stresses that occur when cooking.

[0005] To achieve the above mentioned objective, the invention relates to an oven which comprises a muffle; a one piece support sheet extending under a flat lower wall of the muffle; a bottom heating element disposed horizontally on the support sheet; a flange provided between the lower wall and a side wall of the muffle and adapted to secure the support sheet at a predetermined distance with respect to the lower wall. Oven further comprises a flat metal lug 1 connecting the corresponding ends by extending convexly towards the flange on one side and the support sheet on the other side of both sidewalls such that carrying the support sheet in suspension on the flange. Thanks to the convex extension of the lug, during the operation of oven at high temperatures, in the case of muffle is cambered by thermal stresses, it ensures the keeping the distance between bottom heating element and lower wall substantially by straining support sheet downwardly by the convex form. Thus, heat dissipation of the oven through lower wall keep its homogeneity. The meaning of convex extension is can be a direct radial lug structure but also comprises a stepped structure that bends down when flexing, such as a ladder-like or angular structure that extends at a wide angle extending inwardly.

[0006] In a preferred embodiment of the invention, the lower wall and the support sheet are aligned parallel to each other in an equal intermediate distance. This case provides to form a chamber where the bottom heating element can be disposed easily by sliding it between the lower wall and the support sheet.

[0007] A preferred embodiment of the invention is that the lug comprises a vertically raised hollow fork part. Hollow fork structure makes it easier for the lug to flex down with thermal stresses and push down the support sheet.

[0008] In a preferred embodiment of the invention, the fork part is arranged as perpendicular inverse V form attached to the support sheet from both double ends and from the opposite single end to the flange. By means of the inverse V form, two mounting extensions from the bottom to the support sheet, and a single extension at the top for connection with the flange is obtained. Therefore, mounting of the lug to the flange is facilitated. Also, the heat transfer from the muffle through support sheet is reduced. Alternatively, the strip lug structure in with M or similar zigzag forms can be utilized.

[0009] In a preferred embodiment of the invention, curved shoulder that has a convex bending part is extending in mirror symmetry to each other along both opposing side edges of the support sheet. The curved shoulder structure of the support sheet together with the convex form of the lug facilitates the downward movement of the support sheet under thermal stresses.

[0010] In a preferred embodiment of the invention, curved shoulder and lug are aligned on the same radial path following each other. Since both the curved shoulder and the lug follow the same radial path on the support sheet that is heated during the cooking process of the oven it extends downward evenly and without any distortion at the lug, it allows the support sheet to be pushed down, which substantially maintains the distance between the two ends.

[0011] In preferred embodiment of the invention, a flexible fin is provided at a rear edge of the support sheet. The fin forms a lock which prevents the bottom heating element from being removed by pulling back the bottom heating element by bending it upwards after being disposed on the support sheet. In a possible embodiment, the fin is formed by transversely cutting of the rear edge.

[0012] In a preferred embodiment of the invention a cut-out is formed in the middle of the support sheet to delimit a frame at its outer periphery. Thanks to the internal cut-out, both the thermal load is reduced and a sheet that can be used in a different process is obtained.

[0013] In a preferred embodiment of the invention a stopper is abutting from a front part of the bottom heating element at front edge of the support sheet. The stopper allows blocking the bottom heating element from the front, which is pushed at the rear edge toward the chamber between the lower wall and the support sheet. In this case, the alignment of bottom heating element is provided, and its installation becomes easier.

[0014] In a preferred embodiment of the invention a guide is provided on the support sheet supporting each side of the bottom heating element. Reciprocal guides ensure that the chamber obtained by the distance between the support sheet and the lower wall form a slot structure. Therefore, the bottom heating element is pushed between the guides and is easily disposed in the chamber. Also, the guides prevent the bottom heating element to protrude from the side.

[0015] In a preferred embodiment of the invention, lug is integrated to the lower support sheet. By this means, the lower support sheet is simply secured from the top of the lug to the flange and no separate fixing operation is required from the bottom. The integrated structure allows the lug to heat up with the lower support sheet and it ensures the simulating the thermal stresses thereby allowing the downward movement of the support sheet is equal in each lug. While the lugs may be equal on opposite lateral edges, they are preferably formed in different numbers.

[0016] A preferred embodiment of the invention comprises the processing steps of cutting a flat support sheet with lug forms extending out along the opposite sides of the sheet; radially twisting of the side edge with lug so as to form a curved shoulder; fixing the lug from the upper edge to the flange with a welding seam. With these processing steps, integrated structure of the lug to support sheet is provided and the convexity, which provides downward progress with thermal stresses on the support sheet, helps it to proceed continuous in the same radial path with both the lug and the curved shoulder.

[0017] A preferred embodiment of the invention comprises the processing step of enamelling of the muffle with the support sheet before the processing step of fixing with welding seam. By this means, the support sheet including the lug does not need to be enamelled separately.BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is perspective view of a muffle comprising a representative embodiment of a support sheet used in an oven of the invention with the bottom heating element installed. Figure 2 is perspective view a representative embodiment of a support sheet used in the oven in disassembled position with the bottom heating element not installed. Figure 3 is a perspective view of the support sheet given in Figure 2, enlarged in towards the lug part. Figure 4 is a perspective view of an embodiment of the support sheet given in Figure 2 where the bottom heating element is installed. Figure 5a is a schematic view of a processing step of cutting a flat metal sheet for an oven support sheet production. Figure 5b is a schematic view of a twisting process that is made with deep drawing on the metal sheet which is cut in Figure 5a. Figure 5c is the front schematic view of the welding process of the bent support sheet to the flange and the enamelling together with the muffle in Figure 5b. DETAILED DESCRIPTION OF THE INVENTION

[0019] In this detailed description, the development of the invention has been described without any restrictions and only with references to the examples to better explain the subject matter invention.

[0020] In Figure 1, a muffle (10) of the subject matter oven and a support sheet (30) connected to the muffle (10) are shown in perspective view in an installed position. The oven muffle (10) is in a box-like structure forming an open lip (11) reachable from the outside in the front and is comprised of flat sidewalls (14) secured to each other circumferentially by a welding seam (not shown), rear wall (19) with an upper wall (18) and a lower wall (12). Lower wall (12) extends partially upward from peripheral sides except the lip (11) and a flange (15) is obtained by bending outwardly with adjacent sidewalls (14). The flange (15) has a ribbon-like structure that surrounds the muffle (10) from its outer periphery close to the lower part except the lip. A support sheet (30) which is produced with deep drawing is attached under the lower wall (12) by suspended to flange (15). The support sheet (30) extends below the lower wall (12) at an intermediate distance (a) and parallel to the lower wall (12). A lug (34) extending upwardly from both lateral edges of the lower wall (12) is attached to the flange (15) from the closer part of the sidewalls (14). The lugs (34) are provided as two on one side and three on the opposite side.

[0021] In Figure 2, a support sheet (30) that is attached under the muffle (10) is shown as single perspective. Support sheet (30) in a flat sheet metal structure comprises an inner recess (36) in the middle as forming a frame (32) in its outer periphery. A front edge (31) of the support sheet (30) is twisting inward in a U-like structure. Thus, a vertical stopper (322) at the front edge (31) frame (32) end and a gripper wall (324) in which the upper edge of the stopper (322) is bent backward are appeared.

[0022] Guides in the form of angular hook obtained by bending the flat metal piece (39) are fixed to lateral portions of the frame (32) forming a carrier part (328) from its lower edge facing the inner recess (36) and each other by their open parts. The lateral edges of the support sheet (30) are bent radially upwards from one end to form a curved shoulder (38) each having a radially inclined bend portion (382). Lugs with a hollow isosceles triangle structure (34) is situated in curved shoulder (38) from a lower extension (344) created by bottom edge. It comprises an inverse V-shaped fork part (342) with space between the upper part of the lugs (34) through downwards. Fork part (342) has two bars in the form of a dished extension (343) which is connected with lower extension (344) at the bottom and which is bending outwardly. Dished extension (343) and curved shoulder (38) are twisted at the same bending axis (R). An installation part (341) in the form of cover glass extending outward in parallel with support sheet (34) top of the fork part (342) is obtained by twisting of the lug (34) from its end. Also, installation part (341) has extensions at cover glass structure which is extending inward of fork part (342).

[0023] A fin (37) is formed by cutting of the rear edge (33) on the rear edge (33) of support sheet (30). The fins (37) can be bent upwards by hand. The rear edge (33) of the support sheet (30) has an open entry part (326) in stepped structure.

[0024] In Figure 3, the lugs (34) situated at support sheet (30) is illustrated in an enlarged view. A buckling has been applied to the fork part (342) of the lugs (34) in order to increase the structural strength. Flange (15) provides a flat connection surface, and the lug (34) is welded to flange (15) from installation part (341). In Figure 4, support sheet (30) is shown as installed to the bottom heating element (20). The bottom heating element (20) is an electric resistance in the form of an annular bent pipe. There is no wire rod on the bottom heating element (20). Instead, the bottom heating element (20) is held on the support sheet (30) in a slot delimited circumferentially by the stopper (322) and the retaining wall (324) and the guides (39). Bottom heating element (20) disposed in a slot is held by fins (37) at the rear edge (33). Fins (37) are in horizontal situation before bottom heating element (20) installation. After the bottom heating element (20) is disposed in the slot, by bending upwards by the installation operator, it is ensured that the bottom heating element (20) is held in place by leaning on its rear part (24). The front part (26) of the bottom heating element (20) extending flat abuts on stopper (322) and is retained from top by gripper wall (324). Reciprocal side parts (28) of bottom heating element (20) extending upright is disposed inside of guide (39) in guide (39) clips structure.

[0025] Figure 5a-cillustrates schematically the production method of a support sheet (30) step by step. In Figure 5a, a flat metal plate is cut along a cutting line (k) and the hollow lug (34) extending outward at the edges of the plate, the first structure and the inner space (36) in the middle part that shapes the frame (32) around it is formed. In Figure 5b, the bending axis (R) is given. In a wide radius on the bending axis (R), the ears (34) and the curved shoulder (38) are bent downwardly in thermal stresses by bending the opposite sides of the plate inwards. As shown in Figure 5c from the front, the support sheet (30) has convex fins (34). Each fin (34) abuts on flange (15) from their installation part (341) at the top. The space between installation part (341) and flange (15) are combined with a welding seam (40). Thus, the support sheet (30) is suspended parallel under the lower wall (12) in a way that it maintains the intermediate distance (a). In case the oven is baking, the bottom heating element (20) is heated by energizing it from an inlet (22). In this case, the lower wall (12), which is directly exposed to the heat of both the support sheet (30) and the upper bottom heating element (20) expands and bends downwards. Since the fin (34) is convex, it moves downward supporting the downward movement of the frame (32). The curved shoulder (38) stretches from the bending part (382), helping to push down the support sheet (20) by thermal stress without any distortion. REFERENCE NUMBERS 10Muffle34Lug11Lip341Installation part12Lower wall342Fork part14Sidewall343Dished extension15Flange344Lower extension18Upper wall35Opposite lug19Rear wall36inner recess20Bottom heating element37Fin22Inlet38Curved shoulder24Rear part382Bending part26Front part39Guide28Side part40Welding Seam30Support sheetanintermediate distance31Front edgekCutting line32FrameRBending axis322StopperACutting process324Gripper wallBBending process326Entrance partCWelding process328Carrier partDEnamelling process33Rear edge

Claims

1. An oven comprising a muffle (10); a one piece support sheet (30) extending under a flat lower wall (12) of the muffle (10); a bottom heating element (20) disposed horizontally on the support sheet (30); a flange (15) provided between lower wall (12) and side walls (14) of the muffle (10) and adapted to secure the support sheet (30) at a predetermined distance (a) with respect to the lower wall (12) characterized in that the oven comprises flat metal lugs connecting the corresponding ends by extending convexly towards the flange (15) on one side and the support sheet (30) on the other side of both sidewalls (14) such that carrying the support sheet (30) in suspension on the flange (15), whereby the lugs (34), extending upwardly from both lateral edges of the lower wall (12), are attached to the flange (15) from the closer part of the side walls (14).

2. An oven according to claim 1, wherein the lower wall (12) and the support sheet (30) are aligned parallel to each in an equal intermediate distance (a).

3. An oven according to preceding claims, wherein the lug (34) comprises a hollow fork part (342) raised vertically.

4. An oven according to claim 3, wherein the fork part (342) is arranged as perpendicular inverse V form attached to the support sheet (30) from double ends and from the opposite single end to the flange (15).

5. An oven according to preceding claims, wherein a curved shoulder (38) is having a convex bending part (382) extending in mirror symmetry to each other along both opposing side edges of the support sheet (30).

6. An oven according to claim 5, wherein the curved shoulder (38) and lug (34) are aligned on the same radial path following each other.

7. An oven according to preceding claims, wherein a flexible fin (37) is provided at a rear edge (33) of the support sheet (30).

8. An oven according to preceding claims, wherein a cut-out (36) is formed in the middle of the support sheet (30) to delimit a frame (32) at its outer periphery.

9. An oven according to preceding claims, wherein a stopper (322) is abutting from a front part (26) of the bottom heating element (20) at a front edge (31) of the support sheet (30).

10. An oven according to preceding claims, wherein a guide (39) is provided on the support sheet (30) supporting each opposite side of the bottom heating element (20).

11. An oven according to any of the preceding claims, wherein the lug (34) is integrated to the lower support sheet (30).

12. A method for production an oven according to claim 11, comprises the processing steps of cutting (A) a flat support sheet (30) with lug (34) forms extending out along the opposite sides of the sheet; radially twisting (B) of the side edge with lug (34) so as to form a curved shoulder (38); fixing (C) the lug (34) from the upper edge to the flange (15) with a welding seam (40).

13. A method for production an oven according to claim 12, comprises the processing step of enamelling (D) of the muffle (10) with the supporting sheet (30) before fixing (C) with welding seam processing step.

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