EP2746671B1

EP2746671B1 - Cooking oven comprising a heating element fastened with fastening means

Info

Publication number: EP2746671B1
Application number: EP13197654.0A
Authority: EP
Inventors: Fabio Gambardella; Matteo Scoponi
Original assignee: Indesit Co SpA
Current assignee: Whirlpool EMEA SpA
Priority date: 2012-12-20
Filing date: 2013-12-17
Publication date: 2016-08-03
Anticipated expiration: 2033-12-17
Also published as: EP2746671A1; ITTO20121110A1

Description

[FIELD OF THE INVENTION]

The present invention refers to an oven for cooking food.

[BACKGROUND]

As known, oven for cooking food comprises one or more heating resistances housed inside the cooking chamber, also known as muffle. The resistances are normally placed upside and/or in the bottom of the muffle and are subjected to the heat deformations being made of a metallic material.
To avoid that these deformations could compromise the heat resistance operation, are normally engaged some fastening means, like the so-called rod-like member, which is a rod that, fixed transversely on some shapes outlined on the side walls of the muffle (as illustrated in Fig. 1), sustains the heating resistance and relieves the weight on the walls to avoid its deformation.
In the following description and in the next claims will be briefly referred to the term "rod-like" to indicate those fastening means of the heating element, comprising in that term: rods, cross bars and similar.
The above mentioned position of the crossbar is not secure, as in the current configuration, it is simply rested on the shaped protrusions designed on the side walls of the muffle, making uncertain its action.
Document EP0610588 relates to an oven muffle with at least one heating element mounted in the muffle interior so as to be pivotable parallel to a muffle wall situated at a short distance therefrom.
Document DE3245597 discloses a baking and roasting oven with a bent jacket-tube radiant heater serving as upper heater, which is mounted close to the muffle ceiling and is arranged running parallel to this in the direction of the charging opening of the muffle. Document EP1464894 discloses an oven that includes a heating element which is held in a position close to and parallel to the top by a wire clip held against a holding extension of the heater by a spring in a first position, the heater being moved to a lower position by pulling the clip into a forward position.
Document DE3703301 A1 discloses an oven that includes a electric heating element and fastening means for holding the electric heating element in a steady position. The fastening means comprises a rod-like member engaging at one wall of a muffle and a projection placed on the wall of the muffle, said projection is made in the piece forming the upper wall of the muffle.
The present invention aims to solve these and other problems, providing an oven with characteristics and functions which allows stable and secure support to the heating resistance.
The basic idea of the present invention is to fasten the rod-like member with the walls of the muffle, in order to obtain a substantially interlocking; this coupling is made making pass the end of the rod-like member over the walls of the muffle.
The features of the present invention are specific object of the appended claims.
These features and other advantages of the present invention will become more apparent from the description of an embodiment shown in the appended drawings, provided for purely exemplary and not limiting purposes, in which:

fig. 1 illustrates a perspective view of the upper internal part of a muffle of a cooking oven according to the prior art;
fig. 2 illustrates a perspective view of the muffle of Fig. 1;
fig. 3 illustrates a view of the inner face of the upper wall included in an oven muffle according to the invention;
fig.4 shows a view along section A-A of Fig. 3;
fig. 5 illustrates a view of the detail C of Fig. 4;
fig. 6 illustrates a view along section B-B of Fig. 3;
fig. 7 illustrates a view of the detail D of Fig. 6;
fig. 8 illustrates a partial perspective view of the inner face of the upper wall of fig. 3;
fig. 9 illustrates a partial perspective view of the outside face of the upper wall of fig. 8.

With reference to Fig. 1 and 2, an oven muffle M according to prior art, includes a front opening, a pair of side walls 2,3 and a rear wall 4, which are typically obtained with molding and subsequent folding of the metal printed sheet in three parts. Furthermore, the muffle M also includes a bottom 5 and a top wall 6, which are also preferably obtained through molding of one or more metal sheets.
According to a possible implementation, the bottom 5 and the top wall 6 are joined by constraint means (weldings, rivets etc.) to the side walls 2,3,4 to achieve a stable position of said walls 2, 3,4 with respect to the lower wall 5 (also called bottom) and to the top wall 6.
The inside of the walls 2,3,4, of the bottom 5 and of the top wall 6, are normally covered with a refractory material, in order to improve the energy efficiency of the oven.
With reference to Fig. 3-9, the oven, according to the invention comprises a muffle 1 like the one already described. We are going now to underline the differences between the muffle 1 and the muffle M for a better comprehension of the object of the invention.
The muffle 1 comprises an upper wall 7, that forms its ceiling, to which are associated some fastening means which comprise also a rod-like element 8 (also called in the following description crossbar), so that this last one can be kept in a steady position. Furthermore, the muffle 1 also comprises at least one electrical resistance 9, preferably two as in the described example, that when operative heats the interior of the muffle 1 allowing the cooking of foods. Such heating element 9 is positioned on the inner ceiling of the muffle 1 and has preferably thin shape, with heating coil develop.
The heating element 9 is cantilever mounted with respect to an edge of the upper wall 7, to which is blocked through its terminal ends 9a that are shaped like ittle plates and are fixed with screws to the muffle as shown, in a known way, in fig. 9.
In order to avoid deformations of the heating element 9 when this is operative and reaches high temperatures that make less rigid the metallic material of which is made, said heating element 9 is held, in its position, also by means of the action of the rod-like member 8 which limits the deformations due to the action of gravity.
The rod-like member 8 comprises coupling means 10, preferably U-bolts, pegs, clamps, rings or similar, to be attached to the electric heating element 9, which is preferably located below; such heat resistance 9 is, therefore, suspended to the rod-like member 8.
Obviously, a person skilled in the art can configure the rod-like member 8 and the resistance 9, so that the former can be below the second.
For assembly reasons, that will be better described later, the coupling means 10 must enable the heating element 9 to move together with the rod-like member 8, being integral with it, however, always bearing the weight of the heating element 9 and /or the rod-like member 8.
In this main embodiment, the coupling means are jumper cables that hold anchored the coils of the heating element to the rod-like member, thus making possible both the heating element 9 and the rod-like member, the control of deformation.
The coupling means 10 can be, advantageously, made of heat insulating material, in order to limit the heat dispersion from the resistor 9 to the cross-member 8. In fact, the rod-like member 8 might disperse the heat to the outside of the muffle 1 through the coupling system (described below). This allows to improve the energy efficiency of the oven object of the invention.
The cross-member 8 comprises a central section 82 and a pair of edge-ends 81 folded back respect to the central section 82, in order to form an angle bracket of preferably 90° which improves the coupling of the cross-member 8 with the muffle 1.
For this purpose, the coupling system of the rod-like member 8 with the muffle 1 comprises, in this case, a pair of projections 11 in correspondence of the respective opposite sides of the upper wall 7; these projections may be obtained by means of deep drawing of metal sheet with which it is made the muffle 1 or with any other appropriate way (for example applying a shaped metal tinplate). On each projection 11 there is an opening 12, preferably a slot, in which can be engaged one of the folded ends 81 of the rod-like member 8.
The projections 11 are preferably placed along the sides of the upper wall 7, which are put on top of the side walls 2,3 of the muffle 1.
The projections 11 preferably protrude toward the inside of the muffle 1, in order not to advantageously increase the external dimensions of the upper wall 7.
However, the projections 11 may be turned outwards without altering the setting of the present invention.
Moreover, they may preferably have a substantially parallelepiped shape with rounded edges in order to allow an advantageously production of the upper wall 7, by means of cold forming of a metal sheet, with no risk of tearing.
The opening 12 is positioned on a wall of the projection 11 in which is included, preferably on the opposite wall to the one which faces towards the rear wall 4, that is, namely on the wall facing towards the front opening of the muffle 1 . This positioning of the opening 12 makes it possible for a user and /or to a technician at the mounting phase of the oven, object of the invention, to see said opening 12, making thereby advantageously possible to disengage/engage the rod-like member 8 from said opening 12 with less chance of damages with the end 81 of the rod-like member 8, the layer of insulating material covering the inner walls of the muffle 1.
The opening's 12 shape is preferably like a closed curve, and even more preferably, circular elongated or ellipsoidal shaped, so advantageously to interfere with the ends 81 of the rod-like member 8, in order to improve the coupling between the rod-like member 8 and the muffle 1.
Furthermore, the opening 12 can be advantageously realized in the molding step of the sheet during the deep drawing operation thanks to a movable cam.
The rod-like member 8 has preferably elongated shape, and is made starting from a metal rod; such rod-like member 8 also includes some folds 83 in the central section 82.
These folds have different functions:

serve as matching part in depressions of the upper part of the upper wall (not shown in the attached figures);
confer flexibility to the rod-like member 8;
reduce the elongation of the central section 82 when the rod-like member 8 is heated.

A method to install the electric heating element 9 in the muffle1 comprises the following steps:

a. coupling the rod-like member 8 with the heating element 9 (already equipped with fixing plates 9a) by means of coupling means 10;
b. positioning the heating element 9 (integral with the rod-like member 8) in an operative position within the upper wall 7, blocking the position of the heat resistance 9, until the ends 81 of the rod-like member 8 engage themselves in the openings 12;
c. putting the heat resistance on the bottom of the muffle letting out the ends 9a of the heating element 9 on the rear of said upper wall 7;
d. Fastening the heat resistance to the muffle through the rear plates (rectangular).

The removal of the heating element 9 from the muffle 1 requires to make, in reverse order, the opposite steps just above described.
Obviously numerous modifications are possible for the described example. Briefly, in the following description will be pointed out only the changing parts of this one and of the subsequent variations to the main embodiment above described.
A first variation (not illustrated in the attached figures) comprises protrusions, similar to the projections 11 of the main embodiment, positioned in the upper parts of the side walls 2 and 3 instead of in the upper wall 7. In this way you can decide which part of the muffle M according to the prior art must be modified to implement the invention.
A second variation (not illustrated in the attached figures) comprises a bottom in which is positioned a heat resistance similar to the one employed in the above described embodiments; this bottom comprises an interlocking system according to the invention similar the above described for the previous variants.
It's still to be noted that the protrusions 11, facing towards the inside or the outside, on the upper wall 7 or on the side walls 2, 3 of the muffle 1 may be absent.
In fact, for the engagement of the rod-like member 8 with the muffle 1 it is necessary that the ends 81 go beyond said walls, in order to achieve an interlocking system that ensures stable and secure support.
Additional variations to the described example are obviously possible that fall, however, within the scope of the following claims.

Claims

Oven comprising
- a muffle (1) comprising at least one front opening and a plurality of walls (2,3,4,5,7),

- at least one electric heating element (9) placed inside the muffle (1) for its heating,

- fastening means for holding the electric heating element (9) in a steady position, the fastening means comprising a rod-like member (8) engaging at least one wall (2,3,4,5,7) of the muffle (1),

- at least one projection (11) placed on a wall (2,3,4,5,7) of the muffle (1), the projection (11) being made in the piece forming the upper wall (7) of the muffle (1),
characterized in that
the at least one projection (11) comprises an aperture (12) wherein the end (81) of the rod-like member (8) can be engaged/disengaged, such that at least a part of one end (81) of said rod-like member (8) extends outside the muffle (1).
Oven according to claim 1, comprising coupling means (10) for coupling the rod-like member (8) to the electric heating element (9).
Oven according to claim 2, wherein the electric heating element (9) has a filiform shape.
Oven according to claim 3, wherein the coupling means (10) comprise U-bolts.
Oven according to any preceding claims, wherein the projection (11) projects towards the inside of the muffle (1).
Oven according to claim 5, wherein the projection (11) has a substantially parallelepiped shape.
Oven according to claim 6, wherein the aperture (12) is placed on a wall of the projection (11).
Oven according to claim 6, wherein the aperture (12) has a substantially circular elongated or ellipsoidal shape.
Oven according to any claims 6 to 8, wherein the aperture (12) is placed on a wall of the projection (11) substantially parallel to a wall of the muffle (1) opposite to the front opening of said muffle (1).