GB2164830A - Aerial protection in a microwave oven - Google Patents

Abstract

A microwave oven comprises a rotatable aerial (2) which, for the radiation of microwaves, projects into a heating chamber of the oven. A bowl-shaped protective cover element (12), consisting of material permeable by microwaves, surrounds the aerial part projecting into the heating chamber and is detachably fastened to the neighbouring heating chamber wall (1). <IMAGE>

Description

SPECIFICATION Aerial protection in a microwave oven The present invention relates to a microwave oven.

In microwave ovens with heating of food by means of microwave energy and alternatively by heat from resistance heating elements, for example a grill heater, the problem exists that the aerial and its immediate surroundings are soiled to a greater or lesser degree, particularly during grilling, and cleaning is very laborious. In the case of a rotating, for example Lshaped, aerial for the microwave radiation, the danger also exists that the sensitive aerial might be bent during cleaning. In a known microwave oven (DE-GM 81 18 149), a substantially planar dirt-collecting plate is mounted secure against rotation on the shaft of the Lshaped aerial between the heating chamber wall and an aerial portion bent away and parallel to the wall.By means of this dirt-collecting plate, a cover plate, for example of ceramic material, which is arranged therebehind and fastened in an opening of the chamber space wall, is largely protected against soiling, but not the aerial itself.

There is therefore scope for improving a microwave oven so that soiling of the aerial and of the immediately adjacent region is avoided completely.

According to the present invention there is provided a microwave oven comprising a heating chamber, a rotatable aerial projecting into the chamber for radiation of microwave energy therein, and a bowl-shaped protective cover member of microwave-permeable material surrounding the part of the aerial within the chamber and detachably fastened to an adjacent wall portion of the chamber.

The bowl-like protective cover member surrounds the entire part of the aerial protruding into the heating chamber and can lie closely against the associated chamber wall portion so that dirt particles, for example fat-containing vapour, cannot get to the aerial. Of particular advantage in this case is the possibility of easy removal of the member from the wall portion for cleaning purposes. This can be facilitated by fastening the cover member to the wall portion by means of a quick-acting lock.

In practice, a bayonet fastening is particularly advantageous, as locking and unlocking can be produced by a single small rotation of the member.

In one preferred embodiment, the cover member is fastened by a mounting member with a preferably central recess, in which a cover plate is retained, the plate serving as a bearing for the aerial and as a closure for a feed-through opening in the wall portion. The mounting member can be mounted to the wall portion by simple means, for example screws or spot-welding, so that expensive adaptation of the heating chamber wall as a bearing for the cover plate is unnecessary.

Embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a sectional elevation of a part of a heating chamber wall in a microwave oven with rotating aerial and protective member fastened thereto, in two embodiments of the invention; Fig. 2 is a sectional view, on the line ll-ll of Fig. 3, of the cover member in a first one of the embodiments; Fig. 3 is a plan view of the cover member of Fig. 2; Fig. 4 is a plan view of part of a mounting member for the cover member of the second one of the embodiments; Fig. 5 is a side elevation of the mounting member part shown in Fig. 4; Fig. 6 is a plan view of the cover member of the second embodiment; and Fig. 7 is a sectional view on the line VII-VII of Fig. 6.

Referring now to the drawings, there is shown in Fig. 1 part of a wall 1 which upwardly bounds a parallelepipedonal heating chamber of a microwave oven, the chamber being closable against microwave leakage by an oven door. An L-shaped aerial 2 extends through the wall 1 and comprises a cylindrical aerial shaft 2a and an aerial portion 2b fastened at right angles thereto. The aerial shaft 2a projects into a wave guide (not shown) which is disposed above the wall 1 and is connected in usual manner with a microwave generator (magnetron). A microwave oven of that kind is shown and described in the German (Fed. Rep.) published application 30 12 699. The shaft 2a is rotatably mounted in a disc-shaped cover plate 3, which has a bearing opening 4 for the shaft. The cover plate 3 consists of a material, for example ceramic, permeable to microwaves.An annular retaining element 5 is fastened at the regions 6, for example by means of screws, to the wall 1.

The retaining element 5, consisting of an antimagnetic material, preferably sheet metal, is provided with a central recess 7 bounded by an annular upset shoulder 8, which serves as a mounting for the cover plate 3, a narrow rim projection of the plate 3 being held between the shoulder 8 and the wall 1.

In Fig. 1, a first embodiment of the retaining element 5 is shown on the right of the aerial axis and a second embodiment on the left of the axis. In the first embodiment, the outer annular region 9 of the retaining element 5 is drawn relatively far downwardly and possesses, for example, four locking elements which are distributed around the circumference of the element 5 and have the form of narrowing socket openings 10, as shown in Fig.

3. The openings 10 serve for the quick-action locking of a bowl-like protective cover element 12, a first embodiment of the element 12 being shown in Fig. 1 on the right of the aerial axis and a second embodiment of the element 12' on the left of the axis. These two embodiments differ merely in the rim construction, as explained in the following.

In the first embodiment of the element 12, corresponding, for example four, integrally formed latches 13 are distributed around the circumference (see Fig. 2) at the upper rim of the element, which consists of ceramic material. These latches have abutment shoulders 14 and supporting shoulders 15. On placing the element 12 onto the retaining element 5, the latches 13 are plugged through enlarged portions 10a of the openings 10 and, on rotation of the element 12, supporting shoulders 15 of the latches 13 engage the corresponding boundary edges of narrowed portions 10b of the openings 10. A form of bayonet fastener is thus concerned, with arresting of the element 12 through frictional locking.

Fig. 3 shows a plan view of the retaining element 5 detached from the wall 1 with the element 12 locked. The outer rim 16 of the retaining element 5 is bent downwardly. In this embodiment, the latches 13 are disposed above the rim of the element 12. The element 12, consisting of a material permeable to microwaves, surrounds the rotatable aerial 2 completely and lies closely against the retaining element 5 or the wall 1 so that soiling of the aerial, for example during grilling operation of the oven by way of a resistance heater, does not take place. The element 12 can be taken out of the quick-action lock through slight rotation and, for example, cleaned.

In the other embodiment according to the part of Fig. 1 to the left of the aerial axis and according to the Figs. 4 to 7, the retaining element 5' is provided at its periphery with, for example, four rim portions 17 bent downwardly in U-shape or an annular rim similarly bent down in U-shape. The first mode of construction is illustrated in Figs. 4 and 5. Each rim portion 17 forms a space 18 for the reception of a respective trapezoidal latch 13' integrally formed on the rim of the element 12'. In this case, a spring element 19 is present in each space 18 and is formed by a respective cut-free and bent part of the limb, which is lower in Fig. 1, of the rim portion or portions 17.In the case of arrangement of, for example, three rim portions 17 as shown in Figs. 4 and 5, the element 12' is placed onto the retaining element 5' with the latches 13' beside the rim portions 17 and the latches 13' are then, through slight rotation of the element 12', displaced into the spaces 18, wherein they run up on the spring elements 19 and are pressed closely against the retaining element. In the embodiment with an annular rim portion 17, indicated by chain-dotted lines in Fig. 4, the limb wall, which is lower in Fig. 1, of the rim portion 17 in this embodiment contains recesses which are arranged beside the spring elements 19 and into which the latches 13' of the element 12' can engage. Here, too, arresting of the element 12' takes place through slight rotation as far as the level of the spring elements 19. Porcelain is preferably used as the constituent material of the element 12'.

In all cases, at least one gripping bead 20, preferably several such beads, are integrally provided at the outer region of the trough bottom of the element 12 or 12', whereby gripping of the element is facilitated.

The protective cover element can be provided with a coating, for example a glazing or a synthetic material covering, so that cleaning is facilitated.

Claims (17)

1. A microwave oven comprising a heating chamber, a rotatable aerial projecting into the chamber for radiation of microwave energy therein, and a bowl-shaped protective cover member of microwave-permeable material surrounding the part of the aerial within the chamber and detachably fastened to an adjacent wall portion of the chamber.

2. An oven as claimed in claim 1, wherein the cover member comprises ceramic material.

3. An oven as claimed in claim 1, wherein the cover member comprises glass.

4. An oven as claimed in claim 3, wherein the glass is borosilicate glass.

5. An oven as claimed in any one of the preceding claims, wherein the cover member is fastened to the wall portion by quick-action fastening means.

6. An oven as claimed in claim 5, the fastening means and the cover member being provided with interengaged threaded portions effecting frictional coupling of the member to the fastening means.

7. An oven as claimed in claim 5, the fastening means comprising an annular mounting member mounted on said wall portion and provided at its periphery with a plurality of locking elements, and the cover member being provided with bayonet coupling means engaging the locking elements thereby to couple the protective member to the annular mounting member.

8. An oven as claimed in claim 7, wherein the locking elements are defined by narrowing socket openings in the mounting member.

9. An oven as claimed in claim 7, wherein the locking elements are defined by recesses bounded by U-shaped rim portions of the mounting member.

10. An oven as claimed in claim 9, wherein the mounting member is provided in the recesses with spring elements arranged to press the coupling means of the cover member against the mounting member.

11. An oven as claimed in any one of the preceding claims, wherein the cover member is fastened to said wall portion by fastening means comprising a mounting member mounted on the wall portion, the mounting member being provided with an opening in which a cover element is retained and the cover element being provided with bearing means for the aerial and arranged to close an opening in the wall portion through which the aerial extends.

12. An oven as claimed in claim 11, wherein the mounting member is made of non-magnetic material.

13. An oven as claimed in claim 12, wherein the non-magnetic material is a sheet metal.

14. An oven as claimed in any one of the preceding claims, wherein the cover member is provided with an integral gripping element.

15. An oven as claimed in any one of the preceding claims, wherein the cover member is provided at a surface portion thereof facing into the chamber with a coating of protective material.

16. A microwave oven substantially as hereinbefore described with reference to Figs. 1 to 3 of the accompanying drawings.

17. A microwave oven substantially as hereinbefore described with reference to Figs. 1 and 4 to 7 of the accompanying drawings.