EP0310741B1 - Microwave-proof oven lamp - Google Patents

Abstract

A perforated screening component (50) that surrounds the lamp (4) serving as light source is installed in galvanic contact with a metallic housing (2) having a cap wall (30) penetrated by a lamp cap (3). The screening component (50) consists of a sleeve-shaped metal cage (51) open on both sides and a metal flange (52) on the cap side. The latter (52) is combined with the cap wall (30) of the housing, which retains the cap (3), to form a double-walled component. The screw axis (13) of the lamp (4) extends essentially parallel to the plane of the coupling flange (7) of the housing. The double-walled nature of the metallic boundary of the housing on the cap side effects a microwave-proof sealing of the oven lamp in conjunction with an extremely shallow depth of installation and a low overall volume. <IMAGE>

Description

The invention relates to a microwave-tight stove light according to the preamble of claim 1.

Recessed lights for microwave ovens have to meet special requirements. Particularly when using an incandescent lamp as a light source, microwave-tight shielding of the lamp from the cooking space must be ensured.

There are stove lights in which the microwave-proof, metallic mesh cover made of a mesh can be placed together with the glass cover directly on the cooking chamber side of the muffle wall and locked in the operating position, while the remaining parts of the lamp are attached from the other side to the edge of the muffle wall opening . A gap-free system and a complete galvanic contact of the metallic shield sleeve to the muffle wall is not guaranteed in this known luminaire version, especially if the microwave oven is also operated as a conventional oven in the high temperature range and / or if the locking elements of the metallic shield sleeve are released for cleaning or maintenance purposes will.

From DE-C-2 937 499 a microwave oven with a built-in lamp is known in which an all-round perfect galvanic connection between the shield shell and the muffle wall and thus perfect microwave tightness is to be achieved in that the screen grid and the glass cover are gap-free and with good galvanic contact in a metallic socket are permanently held. The socket is screwed into a holder provided with a connecting flange and fastened to the muffle wall. This known microwave oven light has a considerable size due to the double socket (inner socket and outer holder) and the screwing direction extending at right angles to the installation opening.

The stove lamp of the type mentioned at the outset known from DE-C-3 606 421 has a similarly large construction volume. The lamp housing is made of a cylindrical inner sleeve with a clear width of less than the microwave length and an outer sleeve mechanically connected to the inner sleeve, which is connected to the stove wall. Both sleeves are arranged coaxially on the central axis running at right angles to the installation opening. To ensure microwave tightness, this lamp housing has a sleeve extension with a narrow diameter, in which at least part of the lamp holder lies. This sleeve extension, which surrounds the entire lamp holder, increases the installation depth of the known lighting device and impairs the standardization of the electrical base connections. Above all, it has been shown that the microwave shielding, particularly of the incandescent lamp, is imperfect.

The invention has for its object to provide a comparatively inexpensive to manufacture and assemble stove light available, which enables a compact design and low installation depth with improved microwave shielding.

To solve this problem, the stove light according to the invention has the characterizing features of claim 1.

A stove light is known from US Pat. No. 4,621,180, the central axis of which runs essentially parallel to the associated wall of the hearth muffle, but this is a construction of a different type. The incandescent lamp has no actual housing, but is located in a room above the hearth muffle, its base is attached to a board that forms a detachable part of the upper wall of this room. The lamp cables are led through the board.

According to the invention, however, it is a construction in which the incandescent lamp is accessible from the cooking space, while the lamp base protrudes from the lamp housing. By aligning the central axis parallel to the lighting opening an extremely compact, space-saving design can be achieved, in which the construction depth in particular is very small. The lamp can be manufactured and assembled inexpensively. Above all, it offers very cheap microwave shielding. This is primarily due to the alignment of the screen cover parallel to the lighting opening. In addition, the shield cover covers the lamp beyond its filament, so that the latter is protected, which contributes to extending the life of the bulb. The through openings of the shield cover are preferably arranged beyond the incandescent filament.

Surprisingly, the double-walled unit of base wall and edge flange of the shielding cover acts over its entire extent similar to the outer housing extension used in known lighting devices and ensures the required microwave tightness despite a base wall opening which is penetrated by the lamp base. The elimination of an outer housing extension not only has a favorable effect on a reduction in the overall volume of the stove light, but also enables the use of conventional lamp base connections. In this respect, all electrical components and connections of large-scale stove lights can be used in the microwave-tight stove light according to the invention.

Even stove lights of conventional design can be made microwave-proof by installing a special metallic shielding component. For this purpose, the shielding component according to the invention is placed with its edge flange against the base wall of a stove lamp housing and fixed to the housing, preferably by welding or spot welding. To avoid arcing during microwave operation of the cooker, the circumferential, sleeve-shaped metal body in the installed position should be a minimum distance of 1.5 mm, preferably 2.0 mm, from all metal rear and side walls of the Have housing. The same applies to all other metallic connecting parts which are adjacent to the metal cage or a housing wall in the interior of the housing.

A particular advantage of the invention lies in the fact that all metal parts which are in galvanic connection for shielding remain in the original installation position when the housing interior is accessed either for maintenance or cleaning purposes. The galvanically conductive parts of the luminaire, which are made of corrosion-resistant metal for safety reasons, can be made small and can be designed to be inexpensive and functional as stationary parts. Due to the preferred position of the screw axis of the lamp parallel to the muffle wall, in which the lighting opening is also formed, the installation depth is comparatively small, so that the new lamp is particularly suitable for incorporation into a side muffle wall of the cooking space. The basic size, design and base design of the new microwave oven light can correspond to that of a normal built-in oven light with conventional thermal heating elements.

In a further development of the invention, the metallic shield cover has reliable shielding with only a slight loss of light if it consists of perforated metal sheet or wire with opening cross sections of at most 5 mm.

The housing can be trough-shaped and, in the area of the lighting opening, be delimited in the form of a frame by an integral connecting flange.

The metallic housing is preferably provided on its inside facing the lamp with reflecting surfaces.

In order to be able to fasten the stove light according to the invention, particularly in the connection area along the edge of the muffle opening, and thus microwave-tight, a preferred embodiment of the stove light is characterized in that the connecting flange can be connected to a frame-shaped metallic fastening flange and that the fastening flange is perpendicular to the flange plane on one side has projecting fixed bolts, which are arranged in a predetermined grid and can be pushed through holes arranged in corresponding grids in the muffle wall and the connecting flange. The distance between the adjacent bolts should be for reasons of microwave tightness Do not exceed 40 mm, preferably 30 mm.

The housing, the metallic shield cover, the connecting flange and the mounting flange are usually made of corrosion-resistant metal, e.g. Stainless steel.

The glass cover should be locked in a manner known from conventional oven lights (DE-A 3 428 329) with suitable spring elements of the housing itself. For this purpose, the invention is further developed in that rib-shaped holding members are formed with undercuts on the side of the glass cover facing the interior of the housing, which cooperate with detent springs attached to the housing in such a way that the detent springs engage positively in the undercuts of the glass cover.

A double glass cover with a cavity enclosed between the two glass panes is particularly suitable for use in stoves with pyrolytic cleaning capability. The cover, which consists of glass panes, a cavity, a frame and, if applicable, a circumferential seal, forms thermal insulation to protect the temperature-sensitive light bulb against the high temperatures during pyrolytic cleaning.

Fig. 1

eine Explosionsansicht auf die wesentlichen Komponenten eines ersten Ausführungsbeispiels einer Herdleuchte nach der Erfindung, gesehen parallel zur Einbauwand und quer zur Schraubachse der als Lichtquelle dienenden Glühlampe;

Fig. 2

eine Draufsicht auf das offene Gehäuse der Leuchte gemäß Figur 1, gesehen entgegen der Beleuchtungsrichtung;

Fig. 3

eine Teilschnittansicht entsprechend den Pfeilen III-III in Figur 2;

Fig. 4

eine Draufsicht entsprechend Figur 2 auf den auch in Fig. 1 gezeigten Befestigungsflansch;

Fig. 5

eine Seitenansicht von links in Figur 4;

Fig. 6

in vergrößertem Maßstab eine Seitenansicht,

Fig. 7

eine Stirnansicht und

Fig. 8

eine Teilschnittansicht einer Ausführungsform eines Abschirmbauteils, das in der erfindungsgemäßen Herdleuchte als Schirmhülle verwendet wird;

Fig. 9

eine Seitenansicht und

Fig. 10

eine Draufsicht - entsprechend Fig. 2 - auf ein bevorzugtes Ausführungsbeispiel der Herdleuchte mit dem Abschirmbauteil gemäß Fig. 6 bis 8 in der Einbaulage im Gehäuse;

Fig. 11

einen Teilschnitt entlang der Schnittlinie XI-XI in Fig. 10; und

Fig. 12 bis 14

drei verschiedene Doppelglas-Abdeckungen zur Verwendung bei der beschriebenen Herdleuchte.

Further advantages and details of the invention emerge from the following description of an exemplary embodiment shown schematically in the drawing. The drawing shows:

Fig. 1

an exploded view of the essential components of a first embodiment of a stove light according to the invention, seen parallel to the mounting wall and transverse to the screw axis as Incandescent light source;

Fig. 2

a plan view of the open housing of the lamp according to Figure 1, seen against the direction of illumination;

Fig. 3

a partial sectional view corresponding to the arrows III-III in Figure 2;

Fig. 4

a plan view corresponding to Figure 2 on the mounting flange also shown in Fig. 1;

Fig. 5

a side view from the left in Figure 4;

Fig. 6

on a larger scale a side view,

Fig. 7

a front view and

Fig. 8

a partial sectional view of an embodiment of a shielding component which is used as a shield cover in the stove light according to the invention;

Fig. 9

a side view and

Fig. 10

a plan view - corresponding to Figure 2 - of a preferred embodiment of the stove lamp with the shielding component according to Figures 6 to 8 in the installed position in the housing.

Fig. 11

a partial section along the section line XI-XI in Fig. 10; and

12 to 14

three different double glass covers for use with the stove light described.

The microwave oven light 1 according to the exploded view in FIG. 1 has a metal housing 2 with a base 3 held in the housing, a base socket, a screwed-in incandescent lamp 4, a hollow cylindrical metal cage 5, which forms the shielding cover, and a connecting flange 7 surrounding a lighting opening 6, which is integrally connected to the rest of the housing 2. Furthermore, a mounting flange 10 and a plate-shaped glass cover 11 are shown in FIG. 1.

The trough-shaped housing 2 is welded to avoid microwave-permeable gaps at the joints or connecting points of adjacent metal sections and therefore forms a microwave-proof hood that largely covers the outside of the lighting opening 6. The area of the socket of the incandescent lamp 4 and the exit of the electrical line connections through the base 3 are critical. This area must be made microwave-tight in the exemplary embodiment described as well as in the prior art. This is the purpose of the hollow cylindrical shield cover 5, which is fixed to the housing. In the exemplary embodiment shown, it has circular, approximately 5 mm wide openings 8 (FIG. 2) through which a substantial part of the light emitted by the light source 4 is passed in the direction of the illumination opening 6. Another part of the light can fall through a through opening 9. The through opening 9 is as wide as the inside diameter of the hollow cylindrical metal cage 5 (FIG. 3). It is arranged on the end face of the shield cover 5 opposite the base 3.

Through the front opening 9, the bulb 4 is behind Removing the glass cover 11 accessible and can be unscrewed from its socket in the base 3 in the direction of a screw axis 13. The metal cage 5 serving as a shield cover is fixedly mounted on the housing 2, preferably welded.

The housing surfaces facing the interior of the housing are designed to be reflective, so that the highest possible luminous efficiency can be used for illuminating the cooking space.

The connection flange 7 is placed directly on the edge of the muffle opening when installing the lights. In the exemplary embodiment shown, the attachment to the muffle edge takes place with the aid of a mounting flange 10. The mounting flange 10 carries screw bolts 14 on one side. The screw bolts are arranged in a grid in which the center distance between adjacent bolts is as uniform as possible approximately between 25 and 29 mm. (Only the distance between the bolts flanking the base 3 in the installed position is sufficiently large so that the latter can be easily countered next to the base 3 by means of nuts not shown in the drawing). The mounting flange 10 has an opening 16 corresponding to the lighting opening 6 in terms of size and shape.

According to the grid of the bolts 14, holes 17 are formed in the connecting flange 7 and in the muffle wall, which are adapted to the diameter of the bolts 14. Between the side of the mounting flange 10 carrying the bolts 14 and the muffle rim surrounding the installation opening, a closed seal with a metallic surface is regularly installed, which ensures the galvanic connection between the mounting flange 10 and the muffle wall or the connecting flange 7.

On the side of the glass cover 11 facing the housing and the fastening flange 10, rib-shaped holding members 21 are formed, into which grooves 22 open to the outside are incorporated. In the installed position of the lamp and with the glass cover 11 in place, suitable catch springs 23 (FIG. 11) engage in the grooves, which firmly press the glass cover 11 with its inner edge 20 from the cooking chamber onto the adjacent surface of the fastening flange 10.

The open openings 8 (in the jacket of the metal cage 5) should not exceed a certain cross section, so that the function of the microwave-tight closure of the lamp 4 and its holder does not impair the shielding cover 5. In particular, slit-like light passage openings should be avoided. In addition, the openings 8 can and should be made as large and dense as possible in the interest of good light output and better heat dissipation. The metal cage can also be designed as a latticework.

FIGS. 6 to 8 show a special shielding component 50 which can also be used as a shield cover 5 for the lamp 1 as shown in FIGS. 1 to 3. The component 50 has a sleeve-shaped metal cage 51 with open openings 8 for the passage of light. The metal cage can be made from a rectangular, perforated sheet metal blank which is curved around a central axis 13 and welded along an overlap edge parallel to the axis. A metal flange 52 is connected to the one end face of the metal cage 51 with galvanic contact. The galvanic contact is produced by welding a sleeve-shaped section 53 to the section near the edge of the corresponding sleeve-shaped metal cage 51. Metal cage 51 and metal flange 52 can, however, also be produced as a one-piece molded metal part, for example using the deep-drawing process. Angled Connection tabs 54 are formed on opposite parallel outer edges of the metal flange 52. The connection tabs 54 are used for the galvanic connection of the shielding component 50 to the housing of the stove lamp, as will be explained further below. The cross-sectional shape of both the metal cage 51 and the outline shape of the flange 52 can be adapted to the space and space available in the interior of the stove light. The through opening 9 of the metal cage 51, which is circular here, can be oval or rectangular. The same applies to the approximately rectangular outline shape of the flange 52 shown in the exemplary embodiment.

FIGS. 9 and 10 show an installation example of the shielding component 50, shown enlarged in FIGS. 6 to 8, in a stovetop lamp 1 a, which is otherwise similar to that of the first exemplary embodiment. As can be seen above all in FIG. 10, the flange 52 of the component 50 lies against a base wall 30 of the housing 2 holding the base 3. The metal flange 52 and base wall 30 are welded to one another at spot welding points. Correspondingly, the connecting tabs 54 are also welded to side walls 31 of the housing 2. In this way, the metal flange 52 is joined to the metallic base wall 30 of the housing 2 to form a double-walled structural unit. This reliably prevents leakage of microwave leakage radiation through the area of the base wall, although the base wall is penetrated by the non-metallic (insulating) base 3. As is known per se, the clear width of the metal cage 51 which is open on both end faces should be smaller than the minimum wavelength of the high-frequency waves used. As can be seen, the double-walled design of the 30/52 unit means that there is no need for a shielding extension, so that the base connections can be freely accessible as with normal stove light connections.

Figure 9 shows the preferred parallel position of the central axis 13 to the connection plane of the lamp 1a in the muffle wall, not shown. At least smaller angles of attack between, for example, 20 and 80 ° are, however, easily possible, depending on requirements.

A minimum distance a of 1.5 mm should remain between the outer circumference of the metal cage 51 and the inside of the bottom wall 32 of the housing 2 in order to avoid arcing in microwave operation. The same also applies to the distance b between the free end of the detent springs 23 and the inner sides of the side walls 31 (FIG. 11).

FIGS. 12 to 14 show different embodiments 11a, 11b and 11c of double glass covers, each of which can be used instead of the one-piece glass cover 11 (FIG. 1) in conjunction with the detent springs 23 (FIG. 11) especially for stoves with pyrolytic cleaning options. These double glass covers enable the use of incandescent lamps in the oven light described at the high temperatures typical of pyrolytic cleaning. There are currently no incandescent lamps that can be used at temperatures above 300 ° C. Due to a cavity 40a, 40b and 40c formed between the two glass panes, the temperature reduction between the interior of the oven and the interior of the lamp required for the use of incandescent lamps in the microwave-tight oven light can be achieved.

In the embodiment according to FIG. 12, two flat glass panes 41a are kept at a distance via a temperature-resistant seal 42a. The sandwich component consisting of the two flat glass panes and the seal is kept at a distance by a metal border 43. The metal surround has molded metal catches 44 which interact with complementary catches on the housing.

In the exemplary embodiment according to FIG. 13, two oppositely curved press glasses 41b lie together and are possibly glued to one another along the peripheral edge. A heat-resistant seal 42b is provided on one side of the double glass pane.

The temperatures between the cooking space and the interior of the luminaire can be reduced even further by providing at least one of the glasses 41a, 41b, 41c with a thin, partially reflective coating, for example by vacuum vapor deposition. The coating is preferably deposited on the glass side facing the cavity 40a, 40b, 40c.

In the exemplary embodiment according to FIG. 14, a pressed glass pane 41c is assigned to a flat glass pane 41a. The two disks are kept at a distance by a temperature-resistant seal 42c.

Various modifications are possible within the framework of the inventive concept. In contrast to the housing shapes described, a partially circular or oval housing cross section can be provided. The shielding component 50 can be box-shaped. The stove light according to the invention can be used in an analog design and with the same advantages in connection with other light sources, for example with halogen lamps, and with corresponding sockets and bases, for example with plug-in, pin or bayonet bases. In addition to welding, spot welding, the galvanic connections can also be made by soldering, riveting or screwing. Instead of metallic components, a suitably conductive metal ceramic can also be used under certain circumstances.

In addition, different combinations of individual features of the subclaims with one another are possible.

Claims (14)

1. A microwave-proof oven lamp for installation in a wall of an oven casing enclosing a cooking chamber with at least one incandescent lamp (4), a lamp socket allocated to said incandescent lamp (4), said lamp socket aligned with said incandescent lamp along a central axis (13), a metallic housing (2) with a base wall (30) penetrated by said lamp base (3), a connecting flange (7) connected to said housing surrounding an illuminating aperture (6) in one plane to fix the lamp to the casing wall, a light-transmitting metallic shielding case (5; 50) galvanically connected to the housing and the connecting flange (7) and a glass cover (11; 11a; 11b; 11c) separating the interior of the housing from the cooking chamber, whereby said shielding case (5; 50) comprises a sleeve-shaped metal cage (51) open at both ends positioned around the central axis (13) and a metal flange (52) located on the base side and positioned essentially radially and whereby said metal flange and said metal wall base (30) of said housing (2) are joined together to form a double-walled constructional unit, characterized in that the central axis (13) of the incandescent lamp (4) runs essentially parallel to the plane of the connecting flange (7), the metal shielding case (5; 50) covers the incandescent lamp at least from the lamp base (3) to a position above the spiral-wound filament not less than the side of the spiral-wound filament nearest to the illuminating aperture (6), the metal flange (52) of the shielding case (5; 50) is adjusted in size and circumferential form to the housing base wall (30) surrounding the lamp base (3) thereby preventing the emergence of leakage illumination through the base wall (3).
2. A microwave-proof oven lamp according to claim 1 characterized in that angled sheet metal lugs (54) protrude at radial sections of the metal flange (52) said sheet metal lugs being connected to adjacent housing walls (31) by means of projections, in particular by welded, riveted or screwed methods.
3. A microwave-proof oven lamp according to claim 1 or claim 2 characterized in that the surrounding sleeve-shaped metal case (51) in the installed position in the housing (2) has a minimum distance (a) of, for example, 1.5 mm from all radially adjacent metallic housing walls (31, 32).
4. A microwave-proof oven lamp according to any of claims 1 through 3 characterized in that the metallic shielding case (5, 50) is made of punched sheet metal or wire mesh with sizes of openings not exceeding 5 mm.
5. A microwave-proof oven lamp according to any of claims 1 through 4 characterized in that the connecting flange (7) may be joined with a frame-shaped metallic mounting flange (10) and that protruding fixed screw bolts (14) are mounted on one side of said mounting flange, vertical to the flange plane and arranged according to a prescribed grid and whereby said screw bolts may be inserted into corresponding grids of drill holes in the casing wall and in the connecting flange (7).
6. A microwave-proof oven lamp according to claim 5 characterized in that the distance between adjacent screw bolts (14) is between 20 and 40 mm, preferably between 24 and 29 mm.
7. A microwave-proof oven lamp according to any of claims 1 through 6 characterized in that the housing (2), the metallic shielding case (5; 50), the connecting flange (7) and the mounting flange (10) are made of corrosion-resistant metal, for example stainless steel.
8. A microwave-proof oven lamp according to any of claims 1 through 7 characterized in that rib-shaped retaining members (21) with undercuts (grooves (22)) are formed on the inner side of the glass cover (11) facing the interior of the housing, said rib-shaped retaining members interacting with detend springs (23) fixed on the housing (2) in such manner as to achieve an interlock connection between the detent springs and the undercuts of the glass cover.
9. A microwave-proof oven lamp according to claim 8 characterized in that the minimum distance (b) between the free end of each detent spring (23) and the adjacent side wall (31) of the housing (2) is, for example, 1.5 mm.
10. A microwave-proof oven lamp according to any of claims 1 through 9 characterized in that the glass cover (11) comprises at least two glasses (41a; 41b; 41c) and a hollow closed space between said glasses (40a; 40b; 40c) for the purpose of the thermal insulation of the lamp interior space from the adjacent cooking chamber.
11. A microwave-proof oven lamp according to claim 10 characterized in that a distance is preserved between both glasses (41a; 41b; 41c) by means of temperature-resistant seals and/or spacers (42a; 42c) and that said glasses are held together by means of a preferably metallic frame (43).
12. A microwave-proof oven lamp according to claim 10 or claim 11 characterized in that at least one (41b, 41c) of the two glasses is arched in order to increase the hollow closed space.
13. A microwave-proof oven lamp according to any of claims 10 through 12 characterized in that at least one of the two glasses (41a; 41b; 41c) disposes of a reflective layer preferably on the side of the glass nearest the hollow closed space, in order to reduce the level of heat radiation ermitted from the cooking chamber in the direction of the lamp interior space.
14. A microwave-proof oven lamp according to any of claims 1 through 13 with a metallic shielding case (50) comprising a sleeve-shaped metal cage (51) open at the face end positioned along a central axis (13) and a metal flange (52) attached at a face end and positioned approximately radially characterized in that said metal flange (52) has a sleeve-shaped appenditure (53) galvanically connected with the surrounding metal cage (51) by means of welding.

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