Patent Number: 039492311
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an exemplary embodiment of an infrared radiating unit according to the present invention. This unit is to be used in an infrared analyzer of which the other components have not, however, been illustrated because they do not themselves form part of the invention. Such units in combination with infrared analyzers are of course well known. The novel unit illustrated in FIG. 1 has a mount 1 another portion of which is formed with a central bore and is split along this bore; a carrier 2 of ceramic material has a larger-diameter portion which is located in this bore, and a nut 3 is threaded onto the exterior of the split upper portion of the mount 1 and pushes this portion, or rather the sections of this portion which result from the split, against the larger-diameter part of the carrier 2, thus clamping the same in such a manner that when the nut 3 is loosened, it can be shifted axially or turned. However, when the nut 3 is tightened, then the carrier 2 will be centrally and immovably clamped and held in place. The carrier 2 has a portion 4 of reduced cross-sectional area which extends out of the mount 1 and extends through an opening in a curved portion 14 of a reflector, from an open side of which curved portion there extends a cylindrical portion 13 of the reflector. The portion 4 is formed or provided with two axially spaced flanges 5 and 6 and carries intermediate these flanges a metal-jacketed resistance wire 7 formed as a coil which in the illustrated embodiment is configurated as a double-layer coil. The use of a double-layer coil produces a more homogeneous distribution of the infrared radiation. Within the metal jacket the resistance wire 7 is imbedded in a fire clay or the like, for example in magnesium oxide. Terminals 8 and 9 extend through bores in the carrier 2 to the reduced diameter portion 4 where they are hard-soldered to the wire 7a of the coil 7 and at the locations 10 and 11 where the wire 7a enters into the metal jacket of the coil 7 the open ends of the metal jacket are closed by pouring a ceramic substance into them which hardens and forms plugs. The mount 1 is formed with a recess 12 in which the reflector 13 is secured, for example by a shrink fit. The reflector 13 has a central bore through which the portion 4 extends, and it is composed of the two parts 14 and 15 already mentioned. The inner reflector surface 14a of the part 14 is configurated as a rotationally symmetrical paraboloid which is axially bisected and pushed apart in transverse direction, so that the focal points 16 for the individual paraboloid sectors are located on a circle surrounding the axis of the arrangement, and which circle coincides with the circumference of the coil 7. This arrangement assures that the infrared radiation emitted from the middle of the coil 7 will, after reflection on the surface 14, be converted in axially parallel ways which increases the effectiveness of the unit since a larger proportion of the radiation than would otherwise be possible will now be passing through the measuring receptacle (not shown) to the radiation detector (not shown) of the infrared analyzer. The reflector 13 is also of a material having relatively poor thermal conductivity, for example a rust-resistant steel having a high nickel content, or the like. The inner surface 14a of the portion 14, and if desired also the inner surface of the portion 15, can be polished and gold plated to obtain a particularly good reflection. The unit of FIG. 1 has only small thermal losses due to its construction. The carrier 2 is of ceramic material having poor thermal conductivity, and in addition its portion 4 has a smaller cross-sectional area than the remainder of the carrier 2, so that the flow of thermal energy through the carrier 2 is further reduced thereby. The reflector 13 is heated by the heat of the coil 7, and due to the use of a material having poor thermal conductivity, for instance a rust-resistant steel having a small coefficient of thermal conductivity, the loss of heat by conduction to the mount 1 is maintained low. This effect is reinforced in that the contact area 12 between the mount 1 and the reflector 13 is relatively small. The clamping of the carrier 2 between the arms formed in the mount 1 by the slot provided in the latter, and the clamping action exerted by the nut 3, mounts the carrier 2 centrically and in a very stable manner, so that it will not change its position relative to the optical axis of the arrangement even if the arrangement is subjected to exceptionately strong vibrations or the like. Moreover, this arrangement makes it possible for the carrier 2 and the coil 7 to be readily removed and replaced or inspected, and to be shifted axially or turned in order to select a position of the coil 7 in which a maximum yield and focussing of the radiation is obtained. The embodiment of FIG. 2 is in almost all respects identical with that of FIG. 1, so that the identical portions have not been illustrated. It differs from FIG. 1 in the manner in which the coil 7 is mounted on the carrier 2. For manufacturing reasons it is advisable not to mount the coil 7 directly upon the carrier 2, or rather the portion 4 thereof, since the carrier 2 would have to undergo mechanical stresses during the application of the coil and might break somewhere in its reduced cross-section portion 4. This problem is overcome in FIG. 2 by providing a metallic sleeve 17, again preferably of rust-resistant steel or the like, which is provided with axially spaced flanges or the like, and on which the coil 7 is mounted intermediate these flanges. The portion 4 then of course does not have similar flanges, and the dimension of the sleeve 17 is such that it can be pushed onto the portion 4 where it is secured in place, for example by means of an adhesive. This eliminates any mechanical stresses upon the carrier 2 and maintains all of the advantages outlined with respect to the description of FIG. 1. The ceramic material for the carrier 2 consists of 99.9% pure Al.sub.2 O.sub.3. Instead of a rust-resistant steel as material for the mount 1 and the reflector 13 other materials having a relatively poor thermal conductivity may be used, for example Al.sub.2 O.sub.3 ceramique or glass. A suitable adhesive for securing the sleeve 17 in place on the portion 4 of the carrier is ceramic adhesive sold under the tradename "Thermoguss 2000". An infrared analyzer in which the invention may be used is of the type as described in Luft U.S. Pat. No. 3,162,761. It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above. While the invention has been illustrated and described as embodied in an infrared radiator of unit for infrared analyzers, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.