Reflector Device

Abstract

A device for reflecting electromagnetic radiation from an elongated radiation source comprising a profiled holder formed as a body having a cavity that provides a supporting surface for a reflecting metal strip. The supporting surface is shaped to partially surround said radiation source and the surface defines a groove preferably arranged behind the radiation source. The reflecting metal strip is secured to the holder by stop members integral with the body of the holder which elastically inflect the reflecting metal strip against the supporting surface. The width of the reflecting metal strip is chosen so that the reflecting metal strip is kept permanently flexed into the groove under elastic deformation in its mounted position throughout the operating temperature range.

Description

Devices for reflection of electromagnetic radiation transmitted from cylindrical or linear bodies at high temperature and manufactured by extruded metallic profiles, the reflecting surfaces of which have been treated and/or coated with reflecting layer and possibly also with protective layer directly in or on the base material, are previously known.

Reflectors built up in this way, however, suffer from several essential drawbacks, resulting in that they cannot be used without problems together with the modern radiation sources having temperatures up to 3,000.degree. K and more which are now available. Here only a few of these drawbacks will be mentioned:

1. A complicated and expensive procedure for manufacturing the reflecting surface.

2. At a heavy dirtying of the reflecting surface of the reflector it is often necessary to replace the whole reflector, as a repair of the reflector is too expensive and it will often be less expensive to buy a new reflector.

3. In order to prevent dirtying of the reflector surfaces, the reflectors are often provided with a glass window, or at higher thermal loading with a window of quartz. This window is in the first hand mechanically very fragile and in second hand it is extremely sensitive for impurities, which due to the high temperature can easily be burnt into the material, which rapidly loses its transparency resulting in a lowering of the efficiency of the reflector.

The present invention refers to a new construction of such a reflector device for reflection of radiation transmitted from a cylindric or linear radiation source preferably at high temperature, disposed so that the main axis of the reflection surface is substantially parallel with the longitudinal axis of the radiation source whereby not only these previously mentioned drawbacks have been eliminated but furthermore simultaneously other essential technical effects have been achieved. Besides the principle construction of the reflector as described more closely in the following, the invention also refers to a system for cooling of the reflector body, reflector surface and radiation source.

The reflector device according to the invention, which is especially, although not limitative, suitable for infrared radiation devices, is characterized in that the holder is formed as a body with a supporting surface for a radiation reflecting metal strip, this body at parallel edges being provided with stopmembers each for engagement with one of parallel rims of the reflecting strip which is elastically inflected against the supporting surface, this supporting surface being provided with at least one groove for enabling the stripmaterial, held between said stopmembers to be flexed therein under elastic deformation, the longitudinal direction of this groove being parallel with the said main axis.

This device thus consists substantially of a reflector body which is shaped optically-geometrically in a suitable manner and a flexible strip adapted to the same reflector body will in this way serve as a holder both for the electro magnetic radiation source and the strip. The strip, which is resiliently fastened in the reflector body, will by its flexibility and resiliency be pressed against the geometrically shaped surface of the said body. The flexible metallic strip has such a surface or is possibly coated such that a reflection, which is well adapted to the radiation source in question, is produced.

Thus the reflector built up according to the present invention is in principle composed by a shaped body and a strip element, which can both be manufactured in continuous processes, and the elements can be cut to suitable lengths and joined in a simple manner. Devices manufactured in a running process will be cheaper than corresponding devices made and treated in another manner. Furthermore the strips can easily be replaced when required, and, as this will cost only a small portion of the whole reflector, the use will be essentially cheaper than in the known devices. As an example of a combination according to the invention the shaped body can consist of an extruded aluminum profile and the reflection strip can consist of a cold-rolled, thin, flexible metal strip provided with a reflecting layer.

In the reflector device according to the invention, in which the supporting surface of the body has at least one longitudinal groove, the reflective metal strip is fastened in the reflector body such that the heat extension, if any, will press the strip against the reflector body, whereby the increased pressure will improve the heat transmission and the cooling of the reflective metal strip by heat conduction. The groove in the supporting surface should be such shaped that it will not disturb or only disturb in a small degree the geometric formation of the reflector strip against the reflector body and that it can contain the excess of material flexed into the groove under elastic deformation by the heat extension due to the fact that the reflector strip has a higher temperature than the reflector body. Also in the event that a strip is taken which is wider than the arc length of the geometrical surface of the reflector body, excessive material of the reflector strip can be flexed into the groove.

It has been proved in practice that the groove furthermore in a non-predictable manner enables a rational introducing of the reflector strip at the mounting or replacement, which, without the said recess, were impossible to carry through under fulfilment of the technically important requirement that the reflector strip shall be effectively pressed against and fill the geometric shape of the reflector body.

In a further embodiment of the reflector device according to the invention the longitudinal groove is arranged substantially behind the radiation source as seen from the main direction of reflected radiation.

In another embodiment the stopmembers are formed integral with the said reflector body. Thus two parallel fixed ledges are formed as stopmembers for the flexible reflective strip.

In using a reflective strip, to be inflected against the shaped body, the device is thus provided with at least one channel, defined by the walls of the groove and the strip covering this groove. According to a further aspect of the invention this channel can be used as a cooling channel for which it must be adapted for being connected to a source of cooling medium. In such a device a gaseous cooling medium can suitably be distributed via a centrally situated inlet. If desired a number of interconnected parallel channels can be formed in the strip supporting surface of the body; in that case the device is provided with a net of channels. A condition for the placing and shaping of these channels is of course that they will not appreciably influence the shaping of the reflector strip in the reflector body, also with regard taken to the placing of the reflector strip with its resilient contact with the reflector body.

The radiation source may be a tubular incandescent lamp, consisting of a quartz tube, which in its center has a helically wound filament. The electrical lead-out conductors are situated at the ends of the quartz tube and hermetically sealed thereto at a foliated portion of the conductors. As quartz and metal have essentially differing heat expansion coefficients, it is important to keep their temperature in use as low as possible so as to increase the life-length of the lamp. According to an embodiment of the device the aforementioned channel is so shaped that the cooling medium is applied to the both ends of the radiation source. In the simpliest way this may be produced thereby that the reflector strip has its ends close to the ends of the lamps, whereby the cooling medium will flow over the ends of the lamp.

According to a further aspect of the invention the reflector device according to the invention is characterized in that the reflector strip at places where it covers the cooling channel or channels, is provided with a number of openings all over the length of the channel for distributing the cooling medium over the reflective surface of the strip.

Preferably the openings are associated with gill-shaped lugs forced through the strip, which are arranged and directed so as to guide the cooling medium to sweep along the surface of the reflecting strips in paths transversal to the longitudinal axis of the radiation source.

Cooling medium under pressure escaping from these openings will then due to known physical laws not only cool the reflector body and the reflector strip but also the radiation source itself which is directly and or indirectly influenced by the said cooling medium. By this aspect of the invention the now heated cooling air can leave the reflector in its optical opening whereby the escaping gaseous medium besides the cooling effect on the whole system will also act as a barrier for dirt, dust or other particles or substances in the surroundings, which are harmful for the surfaces of the reflector, and furthermore in such drying processes or other processes, where the radiator in question is used for vaporization or release of other substances in the radiated medium, act to effectively remove these and thereby in the case of drying will appreciably accelerate the process.

It is also assumed and proved that the cooling effect will be mainly the same if the reflector body at cooling with a gaseous medium is provided with a window in its optical opening, which is transparent for the radiation in question. The ends of the reflector will of course allow free escape for the cooling medium.

The said reflector bodies are further shaped such that they can be joined together to a system of reflectors, without need for any outer supporting construction elements. The reflector bodies can for this purpose for example be provided with corresponding T-shaped grooves or grooves of other shape, which together with a suitably wedge-shaped profile element adapted to the said grooves will form a rigid and supporting joint.

By the described invention a reflector is achieved, in which the optically reflecting surface due to the construction can easily be replaced when desired. The geometrically shaped surface of the reflector body can furthermore be provided with thin, but nevertheless effective thermal insulating layers, which prevent the heat arising in the reflector strip due to the absorbed radiation energy to be led further to the reflector body and thus in a reflector operating at a low power can serve as a safety measure for the case that the cooling air of some reason should be interrupted. The thermal insulating layer can also consist of a thin insulating foil or the like of thin heat-resistant material as for example ceramic fibre.

For the purpose of better cooling the reflector body can of course also be provided with cooling flanges extending in the length direction of the reflector, which flanges increase the heat transmitting surface.

For achieving even more effective cooling it is also possible that the reflector body is provided with separate further channels, through which liquid cooling medium can flow. These channels can also be made in an extruded aluminum profile, if this form for realizing the invention is selected.

It is also possible to increase the cooling effect by using a viscous heat conducting material, such as silicone-compounds between the supporting surface of the reflector body and the reflector strip.

Some embodiments of the invention will now be described with reference to the accompanying drawings, in which

FIG. 1 shows a sectional view through a reflector as seen perpendicular to its length direction,

FIG. 2 shows a similar view as in FIG. 1 except a reflector strip of differing structure,

FIG. 3 shows an end part of the reflector device taken along the lines III--III in FIG. 2, and

FIG. 4 shows a section taken along the lines IV--IV in FIG. 2.

The reflector device in FIG. 1 shows a reflector body 1 in which an elastically flexible reflective strip 2 is attached.

The reflector strip 2 is held flexed against the supporting surface between the parallel rims of the body 1, which are provided with protruding ribs 3 and 4 which form two stopmembers for the strip 2.

The reflector device is also provided with a protective transparent plate 5.

In this reflector body is also arranged an elongated radiation source of which the filament is indicated by 6 and the quartz glass envelope by 7. This source may be formed as a tubular, double-ended infrared heating lamp.

The reflector body 1 is provided with a cavity of parabolic, elliptic or any other shape. Its main axis is parallel with the axis of the elongated light source 6, 7. In this embodiment an elliptically adapted reflector body, the geometric shape of which is adapted to the shape of the source 6, 7 is elected. Of this elliptic surface the foci are arranged at the centre of the filament 6 and at 8.

The supporting surface of the body 1 is provided with a longitudinal groove 9, extending all over the length of that body 1.

This groove 9 functions as an expansion groove, in which a part 10 of the strip can be flexed under the influence of elastic deformation. This can occur as said in the ingress of the specification if the strip as placed between the stopmembers 3 and 4 is a little oversized, or if the strip is expanding under the influence of differing heat expansion between the materials of the body 1 and the strip 2. In all cases the groove 9 functions as a space enabling a compensation for deformation of the strip 2.

The walls of the groove 9 together with the strip form a channel which can be connected to a source of cooling medium at a central duct 11.

The FIG. 2, 3 and 4 show another embodiment of the reflector device according to the invention, where the same references as in FIG. 1 are used for corresponding elements.

In FIG. 4 the central duct 11 is shown. In the channel 9 two openings 14 are provided, where the air flow due to connection strips 16 of the radiation source 6, 7 or in another way is forced across the lead-in wires 6 of the lamp and to cool these parts of the lamps.

The reflector strip is furthermore provided with a number of slits 12 formed by forcing a number of lugs 13 through the strip 2. Seen in the main axis of the reflector body 1 the lugs 13 are gill-shaped. Due to these slits air flows across the reflector surface 2, which air inter alia will draw air from the surroundings of the quartz tube 7 and thus also cause cooling of this tube in a way as appears especially from FIG. 2 especially. If the window 5 is removed, the cooling air heated by the source 6, 7 can escape through the optical opening and be used for drying purposes.

In the drawing 15 designates external grooves for enabling adjacent reflector devices to be joined to a module system. This can be done by sliding a connection member 17 in the grooves 15 of adjacent bodies 1 (see FIG. 1). For connection two reflector bodies such that their main axis become flush a bar 19 is slid in the grooves 15 of adjacent bodies 1.

Claims

What is claimed is:

1. A reflector device for an elongated radiation source comprising a profiled holder formed as a body having an elongated cavity, said body having a surface defining said cavity that is shaped to partially surround said radiation source, said surface having a reentrant portion defining a longitudinally extending groove adjacent said cavity, the main axis of the cavity and the longitudinal axis of said groove being substantially parallel to each other and with the longitudinal axis of said radiation source, a radiation reflecting metal strip within said cavity, and stop members provided at edges of said body adjacent the cavity for engagement with corresponding edges of said reflecting metal strip, thereby causing said reflecting metal strip to elastically inflect against said cavity surface, said reflecting metal strip having a width which keeps said reflecting metal strip permanently flexed into the groove under elastic deformation while in a mounted position.

2. A reflector device as claimed in claim 1 further comprising a source of a cooling medium, cooling channels within said body for distributing said cooling medium, and means for passing said cooling medium over said reflecting metal strip, said means comprising openings in said reflecting metal strip at locations over the length of the cooling channels where said reflecting metal strip covers the cooling channels, and a plurality of lugs forced through the reflecting metal strip at said locations to form gill-shaped guiding members for the cooling medium emanating through the openings, said lugs being arranged and directed to guide the cooling medium to sweep along the surface of the reflecting metal strip in paths traverse to the longitudinal axis of the radiation source.

3. A reflector device as claimed in claim 1 further comprising a viscous heat conducting material between the cavity surface and the reflecting metal strip to increase the heat transfer from the reflecting metal strip to the body of the holder.

4. A reflector device as claimed in claim 1 wherein said groove and said reflecting metal strip form a channel for connection to a source of cooling medium and said body provides a plurality of parallel channels, a first channel being connected to said source of cooling medium and remaining channels being connected through transversal connections with said first channel forming a net of cooling channels.

5. A reflector device for an elongated radiation source comprising a profiled holder formed as a body having an elongated cavity, said body having a surface defining said cavity that is shaped to partially surround said elongated radiation source, said surface having a reetrant part defining a longitudinally extending groove adjacent said cavity, the main axis of the cavity and the longitudinal axis of said groove being substantially parallel to each other and with the longitudinal axis of said elongated radiation source, said profiled holder having outside longitudinal slits, the cross-section of said slits having a wider inner portion and a narrower outer portion for interconnecting with adjacent reflector devices, a radiation reflecting metal strip within said cavity, stop members integral with said body at parallel edges of said body adjacent the cavity for engagement with the parallel edges of said reflecting metal strip thereby causing said reflecting metal strip to elastically inflect against said cavity surface, said reflecting metal strip having a width to keep said reflecting metal strip permanently flexed into the groove under elastic deformation in its mounted position, a source of cooling medium, said groove and the reflector strip forming a channel for connection to said source, a plurality of parallel channels within said reflector body, one channel being connected to said source and the remaining channels being connected through transversal connections to form a net of cooling channels, said channels being shaped so that said cooling medium is supplied to opposite ends of the elongated radiation source, said reflecting metal strip provided with openings over the length of the channels at places where said strip covers the cooling channels for distributing the cooling medium over the surface of the reflecting metal strip, a plurality of lugs forced through said strip at said places to form gill-shaped guiding members with said strip for the cooling medium emanating through the openings, said lugs being arranged and directed to guide the cooling medium to sweep along the surface of the reflecting strip in paths transversal to the longitudinal axis of said radiation source, and a viscous heat conducting material between the supporting surface and the reflector strip for increasing the heat transfer from the reflector strip to the reflector body.