Patent Application
20110089169
The present invention relates to a wave choke system for an oven door of a microwave oven. Further, the present invention relates to an oven door of a microwave oven. Additionally, the present invention relates to a microwave oven.
A microwave oven generates strong electromagnetic fields in order to heat the food stuff. Said electromagnetic fields are potential threat to the health of the operator, if the electromagnetic fields or parts of them leave the cavity. The door of the microwave oven is critical. In particular, the microwaves may leave the cavity through the gap between the door and the cavity.
The gap between the door and the cavity is sealed with respect to microwaves by integrating wave chokes into the door of the microwave oven. Said wave chokes provide a small band stop by a cascaded λ/4-transformation. However, mechanical tolerances of the oven cavity frame and the frame of the oven door can evoke local areas of an increased leakage.
It is an object of the present invention to provide a wave choke system for a microwave oven door, which is more robust against mechanical tolerances of the oven cavity walls and the oven door frame.
This object is achieved by the wave choke system according to claim 1.
According to the present invention the wave trap is subdivided into a plurality of open cells by separating elements on at least one circumferential side of the oven door, so that the open cells are arranged serially along the longitudinal axis of the wave trap, wherein said separating elements are formed as a sheet made of a conductive material.
The main idea of the invention is the wave trap with the separating elements and the resulting open cells. The open cells are small cavities with one open side. The open cells allow that the deepness of the wave trap may be increased compared to the prior art. The greater deepness effect that the wave choke system is more robust against mechanical tolerances.
According to the preferred embodiment of the present invention the distance between two neighbouring separating elements is greater than the half of the effective wavelength inside the single open cell related to an operating frequency of the microwave oven. This guarantees the effect of the invention.
Preferably, the distances between neighbouring separating elements are equal. The equal distances between neighbouring separating elements allow a simple and an automatic manufacturing of the wave trap.
Alternatively, the distances between neighbouring separating elements may be are different. In general, it is not necessary, that the distances between neighbouring separating elements are uniform.
The separating element may be formed as a sheet made of conductive material, in particular of metal or a sheet made of dielectric material with metal coating. Alternatively, the separating element may be formed as a grid made of metal wires.
According to the preferred embodiment of the present invention the distances between the neighbouring separating elements are between 30 mm and 120 mm.
Preferably, the wave trap encloses completely the oven door along the circumferential direction.
The wave trap is made of metal or a dielectric material coated with metal.
Further, the wave trap has substantially a rectangular cross section, which may be bordered by an outer circumferential side, an inner circumferential side, an outer side and an inner side.
For example, the outer circumferential side, the inner circumferential side and the outer side form a U-shaped profile. Thus, the wave trap may be used as a door frame or a part of the door frame.
An open portion of the open channel may be arranged on the inner side of the wave trap. The inner side comprises a plurality of lamellae. Further, a gap is arranged between the lamellae and an inner edge of the outer side of the wave trap. Preferably, the gap has a width between 10 mm and 14 mm.
The separating elements may be rectangular sheets. Thus, the lamellae may fill a part of the cross section of the wave trap.
The open cells are at least partially filled with at least one dielectric material. Additionally or alternatively, the open cells are at least partially filled with air.
Further, the present invention relates to an oven door for a microwave oven comprising the wave choke system as described above.
At last, the present invention relates to a microwave oven comprising the wave choke system and/or the oven door as described above.
The novel and inventive features believed to be the characteristic of the present invention are set forth in the appended claims.
The invention will be described in further detail with reference to the drawing, in which
The wave trap 10 includes an outer circumferential side 12, an inner circumferential side 14, an outer side 16 and an inner side 18. The outer side 16 is a part of the outer side of the oven door. In the same way the inner side 18 is a part of the inner side of the oven door. The outer circumferential side 12 corresponds with a circumferential side of the oven door or with a part of said circumferential side. The inner circumferential side 14 encloses at least partially an inner portion of the oven door. Said inner portion may be a window, for example.
The inner side 18 comprises a plurality of lamellae 20. Said lamellae 20 extend into the direction of the outer circumferential side 12. The outer circumferential side 12, the inner circumferential side 14 and the inner side 16 form a U-shaped profile. Said U-shaped profile is substantially symmetric. The inner side 16 is smaller than the outer side 18. The inner edge of the inner side 18 joins the inner edge of the inner circumferential side 14, so that there is a gap between the inner edge of the outer circumferential side 12 and the outer edge of the inner circumferential side 14. In other words there is a gap 26 between the inner edge of the outer circumferential side 12 and the lamellae 20. In this example the width cg width of the gap 26 is about between 10 mm and 14 mm. The gap 26 and the slots between the lamellae 20 define the open portion of the wave trap 10.
The wave trap 10 is subdivided into a plurality of open cells 24 by separating elements 22. The separating elements 22 are formed as rectangular sheets made of a conductive material. For example, the separating element 22 may be a metal sheet. Further, the separating element 22 may be a web made of metal wire. In this example the distance wse between two neighbouring separating elements 22 is about between 30 mm and 120 mm. The distance wse between two neighbouring separating elements 22 must be more than a half of the wavelength of the microwave.
The open cells 24 between the separating elements 22 allow that the deepness dwt of the wave trap 10 is independent of the wavelength of the microwave. Thus, the deepness dwt of the inventive wave trap 10 may be greater than the deepness of a wave trap according to the prior art. The greater deepness dwt of the inventive wave trap 10 effects that the wave choke system is more robust against mechanical tolerances of the oven cavity wall. This results in a reduced leakage of the oven cavity.
The space between two neighbouring separating elements 22 forms the open cell 24. Preferably, the distances wse between the neighbouring separating elements 22 are uniform. However, different distances wse between the neighbouring separating elements 22 are also possible.
The inner space of the wave trap 10 may be filled by air or an arbitrary dielectric material.
The wave choke system according to the present invention allows a reduced leakage and can be manufactured in a simple way.
Although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawing, it is to be understood that the present invention is not limited to those precise embodiments and that various other changes and modifications may be affected therein by one skilled in the art without departing from the scope or spirit of the invention. All such changes and modifications are intended to be included within the scope of the invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 07017206.9 | Sep 2007 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP08/06275 | 7/30/2008 | WO | 00 | 10/15/2010 |
