DE8802493U1 - Electric oven with self-cleaning and additional microwave heating - Google Patents

Description

Description

electric stove »it self-cleaning and additional microwave heating

The innovation relates to an electric oven with self-cleaning and additional microwave heating according to the preamble of claim 1.

During a pyrolytic self-cleaning process on the electric oven in question, temperatures of approximately 480° to 500° Celsius are reached in the oven chamber. The resulting thermal expansion of the oven chamber container, the so-called muffle shell, is transferred primarily to its front frame, the so-called muffle frame. This surrounding muffle frame serves to support the oven door and its seal and must therefore be completely flat. The deformation forces resulting from the thermal expansion primarily affect the muffle frame, which warps as a result and no longer ensures that the door rests flat, tightly and completely without air gaps. Such material deformations can be permanent and allow the vapors and heat generated during baking or roasting to escape.

In electric ovens with microwave heating, the inside of the doors has so-called

Microwave choke devices, also known as quarter traps, resonance cavities or microwave shields, which must not exceed a certain air gap width, the so-called coupling gap, to the surrounding wall of the muffle shell. Br is normally equal to or less than 2.5 mm on average. This coupling gap, which is formed by the microwave choke device protruding into the cooking chamber (baking chamber) with the surrounding muffle wall, is set during assembly and the door and seal are checked to ensure that they lie flat on the muffle frame and that there is an electrically conductive connection to it. This is the only way to prevent the so-called microwave leakage energy from escaping into the open environment. If the distortion forces described above occur, these requirements may no longer be met and microwave tightness is no longer guaranteed.

The structure of a muffle is known from DE - PS 30 29 648 "Microwave oven". The muffle shell and muffle frame or flange wall are made in one piece. A hand area with slots is located outside the furnace muffle and is therefore no longer exposed to the extremely high temperature during heat cleaning, which at least greatly reduces the risk of subsequent sifting* of the wetting sections. Furthermore , the throttle arrangement that dips into the furnace cover is manufactured very precisely and with accurate dimensions*

Such a construction is expensive in terms of construction and assembly.

&igr;", &igr;" ."..*'« .".4*·. BBHZ-S8/137

2S. February 1388

A muffle structure is also known in which the muffle shell and muffle frame consist of two separate parts. The muffle shell has a circumferential flanged edge on its front opening. The muffle frame rests against this in the closed state. (DE-OS 24 14 072)

However, both parts can only be assembled as follows:

The muffle frame is pushed over the muffle shell from the rear and brought into contact with the surrounding flanged edge. Once the device is fully assembled, the muffle frame can no longer be replaced. Furthermore, the hands of the muffle shell must be completely flat and smooth and must not have any protruding parts, i.e. connection flanges for heating rods or the like or any other required protruding wall parts can only be attached to the rear wall of the muffle.

The innovation is based on the task of effectively avoiding the disadvantages and deficiencies inherent in the state of the art.

This task, according to the innovation, is solved by the characterizing features of claim 1. Further advantageous embodiments of the innovation can be found in the subclaims.

The advantages that can be achieved with the innovation are in particular that the finished enamelled muffle frame can be detachably connected to the pre-assembled (and also enamelled) cooking chamber container, the muffle shell. The design of the muffle shell with regard to protruding parts and the attachment points for stimulation rods and other elements can be chosen as desired. A

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Installation is easier and the associated cost reduction is guaranteed. Thermal expansion and the resulting mechanical deformation of the muffle shell are not transferred to the muffle frame, or are transferred to a much lesser extent, due to the loose connection. The door remains tight and, above all, microwave-tight. Another advantage is that the muffle frame can be easily replaced by customer service on installed devices in the event of enamel damage or similar.

An example of the innovation is shown in the drawing and is explained in more detail below. Bs show:

Fig. 1 shows the arrangement of the muffle shell and muffle frame according to the state of the art including the closed oven door in a partial view as a longitudinal section,

Fig. 2 shows the new arrangement of the muffle shell and muffle frame including the closed oven door in the same representation as Fig. 1.

According to Fig. 2, a muffle shell 1 has a continuous and vertically raised flanged edge 1 at its opening facing the oven door 2. The flanged edge 3 is slightly bent at its transition point 3* to the muffle shell wall; the height of the bent edge corresponds exactly to the sheet thickness of the muffle frame 4. The two edges of the muffle shell 1, which are bent at right angles to the rear and run all the way around, form a "U" with unequal length legs when viewed from the profile . This horseshoe frame 4 is now pushed into the muffle shell 1 from the front until it stops with the flanged edge 3. The shorter leg of its U-profile engages under the aforementioned bent edge and forms a

EBHZ-85/137

Ba/ka

February 25, 1988

The inner wall of the muffle shell 1 is a straight and flat line. Both parts 3,4 can be dimensionally matched so that they fit together under light pressure. Parts that are already pre-assembled on the muffle shell 1 or that protrude to the outside are not to be removed during assembly.

The oven door 2 has on its inside a microwave choke device 6 which projects into the cooking chamber 5 and consists of an inner door plate 7, a multiply angled sheet 8 and a further sheet 8" which creates the mechanically supporting and electrically conductive connection to the part of the oven door 2 located outside the cooking chamber 5. The inner door plate 7 is angled all the way around in the direction of the muffle opening and, in conjunction with the sheet 8, forms the 1/4 pocket 9. The circumferential distance between the top of the angled part of the inner door plate 7 and the inner wall of the muffle shell 1 represents the so-called coupling gap a. Br may be a maximum of 2.5 mm. The sheet 8 is angled upwards several times at the edge of the 1/4 pocket 9 and forms an air gap b which runs parallel to the inner wall of the muffle shell 1 and which is preferably kept at least 0.4 mm smaller than the coupling gap a. The air gap b is therefore a minus 0.4 mm or a maximum of 2.1 mm. This measure results in a further reduction in the microwave leakage energy along a leakage path 10 shown in dashed lines up to the seal 11 of the oven door 2. Finally, the sheet metal is flanged rounded outside the cooking chamber 5. Furthermore, in order to ensure microwave tightness, the radius 8' (on the edge of the 5 /4-thickness 9) must be laid at least by the dimension e on the sheet 8 of the front casserole and behind the upper part 3' (starting from the oven door 2 ) of the bend of the flanged edge 3. The dimension γ must be at least 0J mn. In other words, a

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February 25, 1988

Under no circumstances may the aforementioned radius run-out overlap or cover the transition point 3 *, the beginning of the flanged bend. With the help of the muffle frame 4, which is detachably inserted into the muffle shell 1, a high level of surface parallelism is achieved between the oven door 2 and the muffle frame 4. Even the thermal expansion that occurs during cleaning does not change this or only changes it slightly. This means that the oven door 2 always lies flat and tightly. The coupling gap a and the air gap b retain their specified dimensions.

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Claims (6)

Patent-Verwaltungs-GmbH Protection Claims 1. Electric oven with self-cleaning and additional microwave heating with an oven or cooking chamber muffle consisting of a muffle shell with a surrounding opening flanged edge and a muffle frame as well as an oven door, characterized in that the flanged edge (3) of the muffle shell (1) is designed to run slightly upwards and in a longitudinal direction at its transition point (3*) to the wall of the muffle shell, the height of the flanged edge being dimensioned in accordance with the sheet thickness of the muffle frame (4). 2. Electric oven according to claim 1, characterized in that the muffle frame (4) is designed in its cross-sectional profile in the form of a circumferential "U" with legs of unequal length. 3. Electric oven according to claims 1 or 2, characterized in that the muffle frame (4) can be pushed into the muffle casing (1) from the front up to the flanged edge (3) until it stops, with its shorter U-leg being arranged so as to engage under the bend of the flanged edge (3). 4. Electric oven according to claim 1, characterized in that &bull;in« the microwave throttling device (6) attached to the oven door (2) is equipped with a multiply angled sheet (8). 5.Electric stove according to claim 4, characterized in that the sheet (8) is provided with a radius (8") and
then a with the wall of the muffle shell (1)
parallel air gap (b) of maximum 2.1 mm
is carried out in a formative manner. 6.Electric stove according to claim 5, characterized in that the end of the radius (8'), ie the beginning of the
Air gap (b) is placed a minimum distance (c) behind the beginning of the transition point (3") of the flanged edge (3), where (c) is equal to or greater than 0.1 mm.