Patent Application
20160047966
The present invention relates to an electrical household appliance having an illuminated interior which can be used for keeping or temporarily storing foodstuffs or other products for daily domestic use. A refrigerator, freezing appliance, wine-cooler, stove or microwave oven is an example of such a household appliance.
In order to be able to see dearly the products stowed in the interior, it is expedient to provide an illuminating device by which said interior can be lit up. Recently, light-emitting diodes have been proposed, inter as light sources for such illuminating devices. In some variants of these, the light generated by the light-emitting diodes is fed, on the narrow side, into, for instance, plates, for example glass plates, which are used for depositing the products to be stowed, and the plates which are lit in this way are used to illuminate the interior of the appliance in the most homogeneous manner possible. Examples of such illuminating devices are described in the following published specifications: WO 2010/023086 A1, WO 2007/049935 A2 and U.S. Pat. No. 7,201,487 B2.
By contrast, the invention proposes an electrical household appliance, namely a refrigerating and/or freezing appliance or stove, comprising at least one luminous plate which illuminates an interior of the appliance and a light source device which feeds light into the luminous plate at least on a first narrow side of the latter. According to the invention, the light source device includes at least one light-emitting diode and lens optics which collect at least a major portion of the light radiated by the light-emitting diode and direct it onto the first narrow side of the luminous plate.
A light source device of this kind is distinguished, in particular, by high efficiency and feeds the major portion of the light emitted by the light-emitting diode into the luminous plate. By the arranging of lens optics in the light path between the light-emitting diode and a narrow side of the luminous plate, the light radiated by said light-emitting diode is first of all collected, and is preferably even collimated, before it enters the luminous plate on the narrow side of the latter. As a result, a far greater portion of the light emitted by the light-emitting diode is fed into the luminous plate than would be the case if the light from the light-emitting diode were fed directly into said luminous plate without using lens optics. The light emitted is therefore used more effectively, lights up the luminous plate more brightly and, finally, permits more homogeneous illumination of the interior.
Under these circumstances, the luminous plate may be manufactured from an at least partially transparent material, and may preferably be designed as a transparent glass plate. In this case, the luminous plate may be arranged in the interior of the appliance and serve, for example, for depositing the products to be stowed. It is also conceivably possible to arrange the luminous plate behind a wall that delimits the interior of the appliance or in an access door to said interior, in which case the wall or access door is at least partially light-permeable, such as is the situation, for instance, in the case of a perforated microwave lattice or a transparent oven door glass. The lens optics may be realised by an individual lens or by a plurality of lenses located one behind another. If the light source device comprises a plurality of light-emitting diodes, lens optics having an individual lens in each case, or a plurality of lenses located one behind another, may likewise be made available in association with each of the light-emitting diodes.
In one preferred configuration, the lens optics under consideration collimate, when viewed in a sectional plane orthogonal to the longitudinal extension of the first narrow side, the light of the at least one light-emitting diode that passes to said lens optics, in which case light-dispersing structures are formed in the luminous plate, at a distance from its outer flat sides, in different planes along the thickness of said luminous plate.
Provision may preferably be made for the lens optics to be seated, at least partially but preferably even completely, in a recessed manner in a reflector cavity, the aperture of which faces towards the first narrow side of the luminous plate and the walls of which form a reflective surface for light from the light-emitting diode. In this case, said light-emitting diode can be accommodated in the region of the bottom of the reflector cavity. If the emission angle of the light-emitting diode is sufficiently large for a portion of the light emitted by the light-emitting diode to be radiated past the lens optics, the light emitted by the light-emitting diode is, in this way, kept within the space of the reflector cavity. Light which, from the light-emitting diode, first of all impinges upon a wall of the cavity, is reflected at that point and thus kept within the space of the reflector cavity before it either finally impinges upon the lens optics or is radiated past said lens optics towards the first narrow side of the luminous plate.
Provision may also be made for the lens optics—or at least part thereof—to be constructed in one piece with a light-guide body which is arranged between a bottom of the reflector cavity and said lens optics. It is preferable if said light-guide body fills up, substantially completely, the region of the reflector cavity between the bottom of said cavity and the lens optics. In this case, the light radiated by the light-emitting diode is first of all fed into the light-guide body. Light radiated towards the was of the cavity is then reflected, substantially by total reflection, on the surfaces of the light-guide body—instead of on the walls of the cavity—and is kept inside said light-guide body, before it finally passes out of the light-guide body towards the first narrow side of the luminous plate, if applicable through the lens optics which are constructed in one piece with said light-guide body. This variant is suitable, design-wise, particularly in the case of luminous plates of comparatively large thickness. In this case, the light-guide body may be designed, for instance, as a transparent, solid moulded part.
According to one preferred configuration, the lens optics may comprise a lens which fills up, substantially completely, the region between opposite sides of the cavity, at a distance from the bottom of said cavity. In an arrangement of this kind, substantially the whole of the light radiated by the light-emitting diode impinges upon the lens in order to be collected by the latter and directed towards the first narrow side of the luminous plate. Virtually no light gets past the lens without being collected, as a result of which a still greater portion of the light radiated by the light-emitting diode is fed into the luminous plate. The efficiency is increased accordingly.
An arrangement in which the reflector cavity is closed by the first narrow side of the luminous plate is particularly expedient. This ensures that the whole of the light guided within the reflector cavity is fed into the luminous plate and no light is radiated past said luminous plate. In this case, the reflector cavity may possess a dear aperture width which is no larger than the thickness of the luminous plate on the narrow side and preferably corresponds, at least approximately, to the said thickness of the plate. The efficiency is further increased in these cases.
As regards the configuration of the reflector cavity, this may be designed, lengthwise, in a trench or trough-like manner within the longitudinal extension of the first narrow side and, in this case, the lens optics may comprise a rod lens which is elongated in the trench longitudinal direction. The use of a rod lens arranged in this way is particularly advantageous because it collects the light emitted by the light-emitting diode merely orthogonally to the trench longitudinal direction but not in said longitudinal direction. There is therefore imparted to the light-projecting surface on the first narrow side of the luminous plate, which surface is generated by a single lights emitting diode, an oval shape of a kind that makes it possible—when using a plurality of light-emitting diodes which are arranged one behind another in the trench longitudinal direction—to make the distances between two adjacent light-emitting diodes relatively great without being obliged, in the process, to accept losses with respect to an approximately uniform distribution of light intensity on the first narrow side of the luminous plate. As a result, the light source device is able to manage, design-wise, with a comparatively small number of light-emitting diodes. In addition, a comparatively low structural shape of said light source device is made possible. If use is made of a light-guide body which is constructed in one piece with the rod lens, said body may be designed, for example, as a solid, elongated moulded part or continuously cast part.
If the light source device has a plurality of light-emitting diodes arranged one behind another in the trench longitudinal direction, it may be advantageous if the bottom of the reflector cavity has an undulatory profile in said trench longitudinal direction. In this case, troughs of the undulations are further away from the first narrow side of the luminous plate than are peaks of the undulations. Under these circumstances, the light-emitting diodes may each be arranged in the region of the troughs of the undulations. An undulatory profile of this kind helps to guide the light radiated by the light emitting diodes onto the lens optics, or the first narrow side of the luminous plate respectively, in the most evenly distributed manner possible, intensity-wise.
Basically, it is conceivably possible to not only provide one of the above-described light source devices on the first narrow side of the luminous plate, but to also provide a further light source device on a second narrow side of the latter, which side lies opposite said first narrow side of the luminous plate, in order to thereby achieve the most uniform light distribution possible within the luminous plate as a whole. In another configuration, on the other hand, it is conceivable for only one of two opposed narrow sides of the luminous plate to serve for feeding light in by means of the light source device, and for the other narrow side to be constructed merely for reflecting light which is guided within said luminous plate. A narrow side which is merely reflective can be realised, for example, by the application of an aluminium film in a laminar manner on said narrow side. Under these circumstances, the light reflected back by said film is collected again by the lens optics arranged in the reflector cavity and fed into the luminous plate again.
Through the fact that the light emitted by the light-emitting diode is collected or collimated first, before it enters the luminous plate, a large portion of the light rays fed into said luminous plate has a direction of propagation which is parallel, or virtually parallel, to the flat sides of the luminous plate. In the case of a direction of propagation of the light rays which is not completely parallel, total reflection may also occur because of a very shallow angle when internal impingement upon the flat sides of the luminous plate takes place. A large portion of the light fed in therefore initially remains within said luminous plate.
In order to control the passage of light out of the luminous plate and into the interior of the household appliance in a targeted manner, provision may be made, according to another form of embodiment of the invention, for forming one or more light-dispensing structures in the luminous plate at a distance from its outer flat sides. Light-dispersing structures form, so to speak, points of disruption in the luminous plate at which the light is dispersed, in particular dispersed in a diffuse manner. In contrast to light-dispersing structures which are formed directly on the outer surface of the luminous plate, the arranging of light-dispersing structures on the inside of said luminous plate avoids the creation of a sensitive luminous plate surface which is susceptible, for example, to scratching, contamination or even the use of chemicals. This is particularly advantageous against the background of the fact that, in addition to its illuminating function, the luminous plate is also used, under certain circumstances, for depositing the products which are to be stowed in the interior of the appliance.
If the luminous plate is formed from a single plate element, for instance from a simple glass plate, one or more light-dispersing structures may be formed within the depth of the material of the plate. Light-dispersing structures of this kind may, for example, be produced by three-dimensional laser engraving.
It is also conceivably possible for the luminous plate to be formed by a pair of plate elements which are arranged one on top of the other, and for one or more light-dispensing structures to be formed on at least one of the two flat sides, which face towards one another, of the plate elements. In this case, light-dispersing structures may be produced on the outside of the individual flat sides of the plate elements, for instance by scribing, milling, printing, embossing or engraving, in particular laser engraving. Through the fact that the flat sides in question, which face towards one another, of the plate elements are located on the inside of the luminous plate thus formed, the outer sides of said luminous plate still remain durable
In order to achieve the most homogeneous possible distribution as regards the light passing out of the luminous plate, light-dispersing structures may be arranged in a manner distributed over at least a large portion of said luminous plate. For this purpose, the luminous plate may have, for instance, light-dispersing structures in the form of a pattern of points and/or one or more light-dispersing structures in the form of a pattern of lines. In order to still further improve the distribution of the light, provision may also be made for the light-dispersing structures to be formed in different planes along the thickness of the luminous plate. It is also conceivable to provide light-dispersing structures in the form of motifs, for instance logos or characters which, for the observer, stand out conspicuously on the luminous plate.
The invention will be further explained below with the aid of the appended drawings, in which:
a represents a luminous plate with light-dispersing structures which is formed from a pair of plate elements arranged one on top of the other;
b represents a luminous plate which is formed from a single plate element and has light-dispersing structures at different depths of the material;
c represents a luminous plate with light-dispersing structures in the form of a pattern of lines, in a top view; and
d represents a luminous plate with light-dispersing structures in the form of a pattern of points, in a top view.
Attention is drawn, first of all, to
In the case of the angle of emission of the light-emitting diode 32, which angle is indicated by the broken lines, a portion of the light radiated by said light-emitting diode 32 impinges directly upon the lens 34, and other portions of the light impinge initially upon the reflective surface 40 on which the incident light is initially reflected before it passes to the lens 34. Because of the shape of the reflector cavity 36, even any light which has been reflected back finally reaches the lens 34. The light is then collimated by said lens 34 and subsequently fed into the luminous plate 24 on the narrow side 38. After that, the light fed in is guided within the interior of the luminous plate 24, under which circumstances light rays having a direction of propagation which is not parallel to the flat sides 42 and 44 of the luminous plate 24 pass out of said luminous plate 24, but light rays having a direction of propagation which is parallel, or virtually parallel, to the flat sides 42 and 44 do not initially leave the luminous plate 24 because of total reflections occurring on said flat sides 42 and 44.
The luminous plate 24 may be formed from a light-conducting, at least partially transparent material, for example may be designed as a simple glass plate. The reflector structure 35 forming the reflector cavity 36 is preferably produced from non-metallic material and may be formed by a light-coloured, for instance white, reflector body, for example by an injection-moulded white plastic body. That narrow side of the luminous plate 24 which lies opposite the narrow side 38 and is adjacent to the side wall 16 may additionally be coated with an aluminium film which reflects back the light which is guided within the luminous plate 24.
Viewed in the longitudinal extension of the narrow side 38, that is to say in the direction of depth of the drawing in
In an arrangement which is illustrated according to
The possible configurations of the luminous plate 24 which are not represented in any further detail in the preceding figures will be described below with the aid of
In order to allow a portion of the light which is fed into the luminous plate 24 and the major portion of which is guided (virtually) parallel to the flat sides 42 and 44 to pass out of said luminous plate 24 in a controlled manner, there may be formed on the inside of said luminous plate 24, at a distance from its outer flat sides 42 and 44, one or more light-dispersing structures which function, so to speak, as points of disruption and the effect of which is that the light impinging upon these points is dispersed, in particular dispersed in a diffuse manner, and thereby caused to pass out of the luminous plate 24. By suitably selected distribution of light-dispersing structures over the luminous plate 24, the light guided within said luminous plate 24 can be dispersed in such a way that the intensity of the light passing out of said luminous plate 24 is as evenly distributed as possible, and the most homogeneous possible illumination of the interior 12 is thereby achieved.
a shows, in cross-section, a luminous plate 24a which is formed by a pair of plate elements 46a and 48a which are arranged one on top of the other. Under these circumstances, said two plate elements 46a and 48a may be coupled to one another, for instance mechanically, for example by riveting or by clamping them together on the narrow sides in an aluminium profile. It is also conceivable, for instance, to bond the plate elements 46a and 48a together or join them to one another by ultrasound welding. In the case of each of the two plate elements 46a and 48a, a light-dispersing structure 54a and 56a is formed on the flat side, 50a and 52a respectively, which faces towards the other plate element in each case. In the exemplary case shown, the light-dispersing structures 54a and 56a are designed as indentations which lie opposite one another and the effect of which is that portions of the light which is guided within the plate elements 46a and 48a are dispersed at these points and are caused to pass out of the luminous plate 24a. Under these circumstances, the indentations may, for instance, be machined into the flat sides, 50a and 52a respectively, by scribing, milling, embossing or engraving, in particular laser engraving.
b shows, in cross-section, a luminous plate 24b which is produced from a single plate element. In this case, said luminous plate 24b has formed a plurality of light-dispensing structures 58b within the depth of its plate material. The point-like light-dispensing structures 58b which are shown here as examples are arranged in different planes along the thickness of the luminous plate 24b, as a result of which uniform dispersion of the light guided within said luminous plate 24b is promoted. In this variant, the light-dispersing structures 58b may be produced, for instance, by three-dimensional laser engraving.
c and 5d illustrate exemplary patterns of light-dispersing structures, in a top view of the luminous plates which are shown therein.
d, on the other hand, shows a luminous plate 24d having light-dispersing structures 62d which are distributed in a point-like manner and which together form a pattern of points. In the example shown, the points are distributed substantially uniformly over the luminous plate 24d. Obviously, patterns of points of any other desired kinds are, of course, also conceivably possible. In one variant, use may even be made of point-like light-dispersing structures which are so small that they are scarcely perceptible to the human eye.
Finally, it is also conceivable to design any desired combination of features of the variants described in connection with
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2013 005 988.7 | Apr 2013 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/054678 | 3/11/2014 | WO | 00 |
