EP0121893A2

EP0121893A2 - A door for a combination gas or electric and microwave oven

Info

Publication number: EP0121893A2
Application number: EP84103654A
Authority: EP
Inventors: Ruggero Roccari; Arturo Negretti; Walter Zanzani
Original assignee: Industrie Zanussi SpA
Current assignee: Industrie Zanussi SpA
Priority date: 1983-04-07
Filing date: 1984-04-03
Publication date: 1984-10-17
Also published as: ES278206U; ES278206Y; IT8334016V0; EP0121893A3

Abstract

© Described is a door for a gas or electric and microwave oven, comprising an outer peripheral frame having a first glass window secured thereto, an inner door provided with a second glass window, and a perforate metal screen interposed between the two windows. According to the invention, the inner door is detachably secured to the outer door frame and formed of first and second frame members arranged so as to form first and second microwave traps each having a length equal to about one quarter of the wavelength of the radiation employed and being oriented in mutually perpendicular directions. The invention permits a conventional door for a gas or electric oven to be readily modified for use with a combined gas/electric and microwave oven so as to guard against the escape therefrom of microwave energy.

Description

The present invention relates to a door for an oven, particularly for a combination oven for domestic use, in which heating and cooking of foods may be carried out by means of conventional gas or electric heating devices and by means of microwaves. Ovens of this type are already known and require the employ of particularly designed doors capable of providign a seal against the escape in particular of microwave radiation.
While losses of thermic energy may be readily prevented from occurring by the use of conventional gaskets and double glass windows, protection against the escape of microwave energy requires the use of special metal or metallized sealing gaskets or the formation of a microwave trap having a suitable length (i. e. equal to one quarter of the wave length of the radiation generated in the oven cavity or directed thereinto).
Known constructions are accordingly of very complicated design and require the replacement of the conventional door of an oven by a door having specific characteristics.
It is therefore an object of the invention to enable the door provided in a conventional oven to be employed for the stated purpose by modifying it in a structurally simple and convenient manner when the oven is to be equipped with a microwave cooking system, so as to ensure reliable sealing properties against the escape of radiation.
These and other objects of the invention are achieved in a door for an oven, particularly for a combination gas or electric and microwave oven, comprising an outer peripheral frame havign a first glass window secured thereto, an inner door provided with a second glass window, and a perforate metal screen interposed between the two windows. According to the invention, a door of this type is characterized in that the inner door is releasably secured to the outer frame of the door and formed of first and second profile members arranged so as to form first and second microwave traps each having a length equal to one quarter of the wavelength of the radiation employed, and being oriented in mutually perpendicular directions.
The characteristic of the invention will become more evident from the following description of an exemplary embodiment with reference to the accompanying drawing, the only figure of which shows a partial sectional view of an oven door according to the invention.
In the drawing, the door of a conventional oven comprises a frame 12 with an outer glass window 13 secured thereto and provided with a door handle 10.
Interposed between frame 12 and an inner wall 6 of the oven is a conventional sealing gasket 9 for preventing the escape of heat. Gasket 9 may be formed of a microwave-absorbing material such as metallized rubber.
This conventional door may be modified in a simple manner according to the invention if it is desired to equip the conventional gas or electric oven with a microwave heating system.
To this effect, a perforate metal screen 2 may be secured internally to frame 12, such screen being adapted to prevent the escape of microwave energy while permitting the oven cavity to be viewed from outside the oven. Screen 2 is formed with a rim portion projecting towards the interior of the oven and fixedly retained by two profile members 5 and 7, with a sealing gasket 4 interposed therebetween.
A second glass window 1 serves the purpose of protecting screen 2 and outer glass window 13 from contamination in use of the oven. Frame 12, screen 2 and profile members 5 and 7 may be secured to one another by any suitable means (e.g. screws), permitting the individual components of the door to be quickly and readily dismounted in case of need while ensuring a reliable mechanical connection and good electric contact between the metal structural components.
For facilitating assembly, profile members 5 and 7 are of substantially L-shaped configuration, with their edges being provided with suitable sealing gaskets and arranged in the manner shown in the drawing. In particular, the outwards- directed edge of profile member 7 is provided with a sealing gasket of a dielectric heat-resistant material.
According to the invention, profile members 5 and 7 form a first and a second.microwave trap 3 and 8, respectively, each having a length equal to one quarter (λ/4) of the wavelength of the radiation employed.
Trap 3 is of substantially L-shaped configuration, with its longer leg parallel to the main surface of the door, while trap 8 is oriented in a direction perpendicular to the longer leg of trap 3. This double trap solution is effective to ensure against the escape of radiation through the door, formerly requiring the employ of special metal gaskets in the form of waveguides.
Traps 3 and 8 of course extend fully around the opening of the oven cavity.
By suitably dimensioning the interspace 14 between profile member 5 and wall 6 of the oven cavity, the escape of radiation is reliably prevented even if the components of the door are subjected to considerable thermal stresses during manufacture, as during the enamelling process at 800 °C.
As evident from the above description, the present invention enables the existing door of a gas or electric oven to be modified in a simple manner by the addition of a composite inner door structure if the oven is to be modified by the addition thereto of a microwave heating system.

Claims

1. A door for an oven, particularly for a combination gas or electric and microwave oven, comprising an outer peripheral frame having a first glass window secured thereto, an inner door provided with a second glass window, and a perforate metal screen interposed between the two windows, characterized in that said inner door (5, 7) is releasably secured to said outer frame (12) of the door and formed of a first and a second profile member (5 and 7, respectively) arranged so as to form a first and a second microwave trap (3 and 8, respectively) each having a length equal to one quarter of the wave length of the radiation employed and being oriented in mutually perpendicular directions.

2. A door for an oven according to claim 1, characterized in that said profile members (5, 7) of said inner door are of substantially L-shaped configuration, a seal (11) formed of a dielectric heat-resistant material being provided along the outer peripheral edge of at least one of said profile members.