Patent Number: 048809888
Section: description

Detailed Description The radiation arrangement is used in a test apparatus to test permanence of a test sample T (FIG. 2) with respect to influences of light and weather. A tubular cylindrical filter 1 surrounds a radiation source 2. The radiation source, preferably is an elongated tubular source having a longitudinal axis 3 which is arranged parallel to the axis 4 of the cylindrical filter 1. The radiation source is spaced from the axis 4 of the filter 1. The axis 3 of the radiation source 2 and the axis 4 of the filter 1 together define a plane in which an IR radiation accepting element defining a flat surface 5 is located. The surface element 5 subdivides, in the region 15 between radiation source 2 and the inner surface of the filter 1, the interior space of the tubular filter 1. The region 16 between the light source 2 and the other or diametrically opposite wall portion of the filter 1 can be closed off by another IR absorbing element 9 (FIG. 2) or can be left open (FIG. 1) as desired. Looked at in cross section, as seen in FIG. 2, the surface 5 is placed in the region which has the largest spacing between the radiation source and the inner surface of the filter 1, and defined by the axis 4 of the filter and the axis 3 of the radiation source. The inner surface of the filter is coated with a filter layer 6 of a dialectric material which has the characteristic that the radiation from the radiator 2 is selectively divided. The filter layer 6 is transparent for UV radiation and for visible radiation, as schematically shown by arrows 7. The layer 6 is, however, reflective for IR radiation, as schematically shown by arrows 8, which IR radiation is reflected back into the interior space of the filter 1. The reflected IR radiation impinges on the absorbing surface 5. A suitable element forming the surface 5 is a flat sheet-metal structure which is blackened. Radiation accepted by the element defining the surface 5 can thus be readily carried away as heat. It is possible to construct the element defining the surface 5 as a cooled structure, if desired. In order to further suppress IR radiation randomly reflected in the inside of the tube 1, a further absorbent surface 9, similar to surface 5, can be placed in the region 16 (FIG. 2), and co-planar with the surface 5. Preferably, the radiation source 2 is so located that its axis 3 has a distance 10 from the axis 4 of the filter 1 which is about 1.5 times the diameter 11 of the radiator source 2. Preferably the radiation source is a xenon radiator. Further the center of the axis 3 of the radiation 2 is offset at the most by 0.25 of the inner diameter of the filter 1 from the axis 4 of the filter 1. By locating the radiation source 2 eccentrically with respect to the axis 4 of the cylindrical filter 1, the entire reflected IR radiation, reflected from the inner surface of the filter 1, is directed to the absorbing surface 5 and, possibly, any stray radiation to the surface 9, if used. A source 2 may be used which, rather than being cylindrical, is essentially spherical or bulbous in shape. Such a source is schematically shown by the circle 12 (FIG. 1). Since the radiation source, as such, is well known and a standard article of commerce, it need not be further described and any suitable such source may be used. Is an essentially punctiform or bulbeous radiation source if used, it is preferably located at about half the axial height of the cylinder 1. Various changes and modification may be made within the scope of the invention concept. A suitable material for the dielectric IR reflective UV and visible transmissive coating 6 is a compound comprising SiO.sub.2, ThO.sub.2, Al.sub.2 O.sub.3, Fe.sub.2 O.sub.3 ; the material for the tubular cylindrical support is SiO.sub.2.