AIRFIELD MARKER LIGHT OPERATING AT A RELATIVELY LOW TEMPERATURE

Abstract: An airfield marker light operating at a relatively low temperature. The marker light comprises a metal casing (1) to be flush-mounted in the ground, the casing having a vertical tube (1) with a lower bottom plate (1a) and including in its lower part a lamp (4) for emitting an upwardly directed light bundle, and optical means (5, 6, 7, 8) through which the upwardly directed light bundle passes and which include an upper, at least partially transparent cover plate (8) for emitting at least one light beam. According to the invention, the lamp (4) is mounted in effective heat conductive contact (3, 2) with the metal casing (1) adjacent to the bottom plate (1a), and the optical means include at least one transparent plate (5), which constitutes or is provided with a layer of a light filter and which along the whole circumference thereof is in effective heat conductive contact with the metal tube casing (1).

Description: AIRFIELD MARKER LIGHT OPERATING AT A RELATIVELY LOW TEMPERATURE The invention relates to an airfield marker light, e.g. for runways or taxi strips, comprising a metal casing to be lush-mounted in the ground, said casing having a vertical tube with a lower bottom plate and including in its lower part at least one lamp for emitting an upwardly directed light bundle, and optical means, through which the upwardly directed light bundle passes and which include an upper, at least partially transparent cover plate for emitting at least one light beam, wherein at least one light filter is disposed in the optical path. Such a marker light, although without a light filter, is previously known from US-A-3 , 007, 034 (Reed), and similar devices are also described in DK-C-113 912 (Siemens AG) , EP-B1-22106 (Meta-Fer AG) and US-A-3 , 096 , 024 (Young) . A general problem, however, is the heat development partly from the lamp due to the relatively high power, which is necessary in order to obtain a high light intensity, partly from said light filter, which absorbs a large part of the light energy and converts this energy into heat. These problems with excess heat have so far resulted in a choice between a lower power with a low light intensity and long life of the lamp, on the one hand, and a high power and high light intensity resulting in a relatively short life of the lamp, on the other hand. The object of the invention is to achieve a device, which enables a high light intensity, even upon filtering n said light filter, and still keeps the various parts of the marker light at a relatively low temperature level. Thus, it is desirable to keep the lamp as well as the upper cover plate at a relatively low temperature, and the temperature of the surface of the cover plate must not exceed 160°C because of the requirement that a rubber tire should be able to cover the marker light without being damaged. Due to the relatively low temperature, the life of the lamp will be increased, and the cover plate may be made of epoxy plastic material, which has other favourable properties at lower temperatures, such as a high refractive index, high strength, abrasive resistance and enables repair of surface damages by applying a new surface layer. This object is achieved for a marker light according to the invention, which is characteraized in that - the lamp is mounted in effective heat conductive contact with the metal casing adjacent to the bottom plate; and - the optical means include at least one transparent plate, which constitutes or is provided with a layer of said light filter and which along the whole circu fe- rence thereof is in effective heat conductive contact with the metal tube casing. Hereby, a portion of the heat generated by the lamp will be transferred downwards via the bottom plate, and heat is also conducted sideways via the light filtering plate and the metal tube casing. The light filtering plate can be constituted by a separate light filter plate (claim 2) and/or by the upper cover plate with a light filter layer applied to the underside thereof (claim 3) . Preferably, the optical means include one or more transparent plates located between the lamp and the cover plate, these plates being fitted tightly to the tube casing along the whole circum erence thereof, so as to prevent convection of warm air upwardly towards the cover plate (claim 4) . With such an arrangement, a great amount of heat is transferred to the surroundings, and the upper cover plate is protected against hot air flowing upwardly, so that the marker light can be operated with a high power giving the desired high light intensity, the various parts of the device still being kept at a relative low temperature level ensuring long life. Further advantageous features are stated in claims 5 through 10 and will be apparent from the below detailed description of a preferred embodiment of the marker light according to the invention, reference being made to the appended drawings . Fig. 1 shows a marker light according to the invention in perspective view, wherein half of the device has been cut away through a central, vertical section for increased clarity; Fig. 2 shows the marker light from above; Fig. 3 shows the optical components schematically w th their principal light rays; and Figs 4a and 4b show central sections through the lower part of the marker light with a lamp in two different mounting positions. The marker light shown in Figs 1 and 2 comprises essential¬ ly a cylindrical casing 1 of metal, e.g. an aluminum alloy, having a lower bottom plate la, an upper, substantially rectangular seat lb, a reflector lamp 4 mounted at the bottom plate la on a bracket 2 with a mounting plate 3, a colour filter plate 5, a transparent insulating plate 6, a light refractive plate 7 and an upper transparent cover plate 8 being tightly fitted in the seat lb. As indicated in Fig. 1, the casing 1 is lowered into a well housing 9 with a lid 10, so that the upper surface of the cover plate 8 lies substantially in the ground plane. The lid is pre¬ ferably made of metal for an effective transfer of heat from the upper portion of the tubular casing 1. The upper, substantially rectangular cover plate 8 is preferably made of a transparent epoxy plastic material, i.e. an abrasive resistant material, which, if necessary, can be provided with a fresh surface layer for filling out possible scratches or other damages on the upper surface. To avoid such damages, however, hard, ceramic particles are partially embedded into the surface layers; partly along two longitudinal edge portions 11, 12, partly along a central, transversal strip portion 13. Hereby, the upper surface of the cover plate is divided into two rectangular portions 8a, 8b, each serving to emit a light beam pro¬ pagating closely along the ground plane (compare Fig. 3) . In order to obtain the best possible light intensity near the ground plane, each surface portion 8a, 8b is somewhat inclined, so that it is inclined downwards from the central, transversal portion 13 about 3° relative to the horizontal plane. As appears from Figs 1, 4a and 4b, the bracket 2 holding the reflector lamp 4 consists of a bent metal band, e.g. made of an aluminum alloy which is oriented substantially in parallel to the transversal central portion 13 of the cover plate 8. One end portion 2a of the bracTcet is secured to the bottom plate la, which may likewise be made of an aluminum alloy, in good heat conductive contact with the latter. The other, longer end portion 2b s planar and horizontal, and the rectangular mounting plate 3 is secured to this end portion by means of a screw fastener 14. The reflector lamp 4 with its socket 4a can be mounted on the plate 3 either n a central, straight upwardly directed position according to Fig. 4a or in a somewhat oblique (in a plane through the central, transversal portion 13 of the cover plate 8) position in a corresponding recess 3a m the plate, as appears from Fig. 4b. The electrical feeding wires 15a, 15b of the lamp 4 are drawn through a central hole 16 in the bottom plate la, as appears from Fig. 1. The colour filter plate 5, which is located somewhat above the reflector lamp 4, is made of a toughened glass plate with colouring pigment, said glass plate 5 being horizontal and fitted tightly to the tubular casing 1 around the circum erence thereof, the cireumferenclal portion being secured between two cylindrical tube portions 17, 18 like- wise made of an aluminum alloy, said tube portions being tightly fitted internally within the tubular casing 1. The insulating glass plate 6 is likewise horizontal and rests on the upper end of the upper tube portion 18, the circu ferencial edge thereof being tightly fitted to the surrounding tubular casing 1. The light refractive plate 7 is likewise horizontally disposed and is tightly fitted to the surrounding tubular casing 1 at a small distance below the upper cover plate 8. A portion of the heat generated by the reflector lamp 4 is passed away via the socket 4a, the plate 3, the bracket 2 and the bottom plate la, and a portion of the heat gene- rated during the passage of the light through the plates 5, 6 and 7 is passed away by the heat conductive contact with the tubular casing 1. The insulating glass plate 6 also serves to prevent a heat transfer upwardly by convection. Thus, the upper cover plate 8 can be kept at a advan- tageously low temperature, whereby it becomes more durable and the life of the marker light is substantially increased as compared to prior art devices . As appears from Fig. 3, the reflector lamp 4 emits a well defined, collected light bundle, which passes through the colour filter plate 5 and the insulating plate 6 substan¬ tially without geometrical change, whereupon the light bundle is divided in the light refractive -plate 7, so that the bundle portions L^ and L2 are refracted obliquely upwardly to the left and the bundle portions L3 and L are refracted obliquely upwardly to the right. These bundle portions strike the saw tooth surfaces 8c and 8d of the cover plate 8 at a right angle, thus without refraction, and each bundle portion is thereafter refracted m the upper surface portions 8b and 8a, respectively, of the cover plate, so that narrow light beams L^2 and 34 propagating near the ground plane M are emitted in opposite directions . When the lamp 4 is obliquely positioned according to Fig. 4b, similar optical paths are obtained, although the respective light beam L^2 and L34 is turned sideways, which is utilized at curved portions of e.g. a taxi strip. Thus, the structure is such as to ensure that a large portion of the light from the lamp 4 is maintained as useful, emitted light from the cover plate 8. However, a certain amount of light is absorbed m the filter plate 5, which amount is converted into heat. This heat, however, is effectively passed away via the tubular casing 1. Likewise, the major portion of the heat, which is inevitably gene¬ rated by the lamp 4, is passed away downwards via the socket 4a, the plate 3, the bracket 2 and the bottom plate 1. Minor amounts of heat are also generated m the plates 6 and 7 but are passed away sideways via the tubular casing 1. Likewise, the cover plate 8 will conduct heat via the seat lb of the tubular casing 1 and the lid 10 of the well housing. The lamp 4 and the upper cover plate 8 can thus be kept at a relatively low temperature, even when a relative- ly high light intensity is emitted in the light beams L j _2 and L34. The marker light according to the invention can be modified n many ways by those skilled in the art within the scope of claim 1. The light filter, which can be constituted by a colour, UV or IR filter, may alternatively consist of a layer applied to anyone of the transparent plates, e.g. at the underside of the cover plate. Moreover, the insulating plate 6 can be omitted m certain cases, especially if the light intensity is not required to be high. The light refractive plate 7, if present, will give a corresponding effect, since it prevents the upwardly flowing hot air from reaching the cover plate 8. Of course, the inventive idea can also be utilized at marker lights emitting only one light beam. Furthermore, the metal casing 1 may have any other cross sectional shape than cylindrical, e.g. poly¬ gonal, rectangular or square, wherein the plates 5, 6 and 7 are given a corresponding shape. Finally, it is possible to provide heat transfer means, such as cooling flanges or a heat collecting medium externally of the metal tubular casmg 1.

Claims: C L I M S 1. An airfield marker light operating at a relatively low temperature, comprising a metal casing (1) to be flush- mounted in the ground, said casing having a vertical tube (1) with a lower bottom plate (la) and including in its lower part at least one lamp (4) for emitting an upwardly directed light bundle, and optical means C5,6,7,8), through which the upwardly directed light bundle passes and which include an upper, at least partially transparent cover plate (8) for emitting at least one light beam (L_2 ι L3 >, wherein at least one light filter (5) is disposed in the optical path, c h a r a c t e r i z e d i n that said lamp (4) is mounted in effective heat conductive contact (4a, 3, 2) with the metal casing adjacent to said bottom plate (la), and - said optical means include at least one transparent plate (5), which constitutes or is provided with a layer of said light filter and which along the whole circumference thereof is in effective heat conductive contact with the metal tube casing (1) . 2. Marker light as defined m claim 1, c h a r a c t e ¬ r i z e d i n that said plate is constituted by a separate light filter plate (5) . 3. Marker light as defined in claim i or 2, c h a r a c ¬ t e r i z e d i n that said cover plate, at the lower side thereof, is provided with a light filter layer. 4. Marker light as defined in anyone of claims 1-3, c h a r a c t e r i z e d i n that said optical means include one or more transparent plates (5,6,7) located between the lamp and the upper cover plate (8), said plates being tightly fitted to the tubular casing 1 along the whole circumference thereof. 5. Marker light as defined in claim 4, c h a r a c t e ¬ r i z e d i that one of said tightly fitted plates is constituted by a light refractive plate (7) adapted to divide said upwardly directed light bundle into two bundle portions in opposite directions. 6. Marker light as defined in claim 4 or 5, c h a r a c ¬ t e r i z e d i n that one of said tightly fitted plates is constituted by an insulating plate 6 serving to prevent heat transfer upwardly by convection. 7. Marker light as defined in anyone of claims 4 - 6 in combination with claim 2, c h a r a c t e r i z e d i n that one of sa d tightly fitted plates is constituted by said light filter plate (5) . 8. Marker light as defined in anyone of the preceding claims, c h a r a c t e r i z e d i n that said upper cover plate (8) , along the whole circumference thereof, is tightly fitted to and is in heat conductive contact with the upper portion (lb) of the tubular casing. 9. Marker light as defined in claim 2, 5 or 6, c h a ¬ r a c t e r i z e d i n that the light filter plate (5), the insulating plate (6) and/or the light refractive plate (7) is held by metal tube portions (17,18) inserted internally within the metal tubular casing (1) . 10. Marker light as defined in anyone of the preceding claims, c h a r a c t e r i z e d i n that the metal tubular casing (1), the bottom plate (la) and said metal tube portions (17,18), if present, are made of an aluminum alloy.

Inventors: DAHLBERG ANDERS, DAHLBERG, ANDERS
Applicants: FRANSCH AB
Application year: 1987
Main classification: F21V29
IPC codes: B64F1, F21S2, F21S8, F21V29