ABRASIVE RESISTANT AIRFIELD MARKER LIGHT

Abstract: An airfield marker light, e.g. for runways or taxi strips, comprising a casing (1) with a lower light source (4) and an upper, transparent cover plate (8) situated substantially in the ground plane. According to the invention, an abrasive resistant material, preferably in the form of particles partially embedded into the surface of the cover plate, protrudes upwardly from the cover plate exclusively in at least one dead zone (11, 12, 13), which does not emit any light. The hard material serves to protect the cover plate (8) against mechanical abrasion, for example in connection with snow-clearance by means of steel scrapers.

Description: ABRASIVE RESISTANT AIRFIELD MARKER LIGHT The invention relates to an airfield marker light, e.g. fo runways or taxi strips, comprising a casing to be flush- mounted in the ground and having an upper, at least partially transparent cover plate with an upper, substan- tially planar surface to be placed essentially flush with the ground plane, wherein the casing includes at least one light source and optical means being so adapted that one o more light beams are emitted from at least one portion of the cover plate, said portion constituting an active zone, whereas at least one other portion of the cover plate constitutes a dead zone, from which no light is emitted. Such marker lights of the flush-mounted type are previously known, e.g. from SE-C-7803611-8 CTatis Plas tatmngar AB) , DK-C-113 912 (Siemens AG) and EP-B1-22106 (Meta-Fer AG) The lush-mounted type has of course the advantage that the marker light does not have any protruding portions, and it can therefore be located at will on or adjacent to a runway or a taxi strip and can be run over by the wheels of air crafts or other vehicles. However, a problem in this connection is the cleaning and the snow-clearance of the runways, which requires the use of steel scrapers on the cleaning vehicles in order to obtain the desired result, especially when ce s present, which is often the case due to the heat emitted by the light device. Such steel scrapers often cause scratches and other damages to the upper, light emitting surface of the cover plate. In order to prevent such damages, it is proposed in the above mentioned SE-C-7803611-8 that hard particles are embedded into the light emitting, active zone of the cover plate, these particles protruding upwardly somewhat above the transparent material. Hereby, the light emitting, active zone of the cover plate is of course protected from damages in connection with snow-clearance by means of steel scrapers, but the hard particles will inevitably bring about a disadvantageous reduction of the light intensity and an uncontrollable diffuse spreading of the emitted light. The object of the present invention is to avoid this problem and to accomplish an abrasive resistant marker light without impairing the light emitting properties thereo . This object is achieved according to the invention in that an abrasive resistant material, which is substantially harder than the transparent material of the cover plate, protrudes upwardly from the cover plate exclusively in at least one dead zone, which crosses and/or confines the major part of the cover plate. Such dead zones, which do not emit any light, can extend as a strip across the cover plate and/or along at least a portion of the periphery of the cover plate. Hereby, the desired mechanical protection is achieved, whereas the emitted light is in no way disturbed by the hard material, which is preferably constituted by particles being partially embedded into the surface of the cover plate. Further advantageous features are stated in the dependent claims 4 through 7 and will appear from the following detailed description of a preferred embodiment, reference being made to the appended drawings. Fig. i shows a marker light according to the invention in perspective view, wherein one half of the device is cut away through a central, vertical section for increased clarity; Fig. 2 shows the marker light from above; and Fig. 3 shows the optical components schematically with their principal light rays. The marker light shown in figures 1 and 2 comprises essentially a cylindrical metal casing 1 with a lower bottom plate la and an upper, substantially rectangular seat lb, a reflector lamp 4 mounted at the bottom on a bracket 2, 3, a colour filter 5, a transparent insulating plate 6, a light refracting plate 7 and an upper, transpa¬ rent cover plate 8 fitted tightly into the seat lb. As indicated in Fig. 1, the casing 1 is mounted in a well housing 9 with a lid 10, so that the upper surface of the cover plate 8 lies substan ially in the ground plane. The upper, substantially rectangular cover plate 8 is preferably made of a transparent epoxy plastic material, i.e. a relatively 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. In order to avoid such damages, according to the invention, hard particles are embedded into the surface layer, 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 emitting a light beam, which propagates 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 inclines downwards from the central, transversal portion 13 about 3° relative to the horizontal plane. The longitudinal edge portions 11, 12 and the central, transversal strip portion 13 of the cover plate 8 constitute "dead zones" in the sense that no light is emitted therefrom. However, these zones are located in such a way in relation to the "active zones" 8a, 8b, that they cross and partially confine the major part of the cover plate 8, so that a steel scraper on a snow-clearance vehicle, irrespective of the orientation of the steel scraper (it is assumed that the steel scraper has a substantially greater extension lengthwise than the dimensions of the cover plate), will not contact the active light emitting surface portions 8a, 8b. The hard particles in the dead zones 11, 12, 13 are partially embedded in such a way, that they partially protrude upwards from and have their upper edges situated slightly above the surface of the cover plate. The hard particles are preferably granular and can be constituted by a mineral, a hard metal, a sintered metal or a ceramic material. Alternatively, a unitary strip of such a hard material can be applied onto the respective "dead zone" . The configuration of the dead zones with embedded particles or some other hard material can be modified by those skilled in the art within the scope of claim 1.

Claims: C L A I M S 1. An airfield marker light comprising a casing (1) to be flush-mounted in the ground and having an upper, at least partially transparent cover plate (8) with an upper, substantially planar surface to be placed essentially flus with the ground plane, wherein the casing includes at leas one light source (4) and optical means (7,8) being so adapted that one or more light beams Lj_2 > L, 34 ) are emitte from at least one portion (8a, 8b) of the cover plate, said portion constituting an active zone, whereas at least one other portion (11,12,13) of the cover plate constitutes a dead zone, from which no light is emitted, c h a r a c t e r i z e d i n that an abrasive resistant material, which is substantially harder than the transparent material of the cover plate, protrudes upwardly from the cover plate exlusively in at least one dead zone (11,12,13), which crosses and/or confines the major part of the cover plate (8) . 2. Marker light as defined in claim 1, c h a r a c t e ¬ r i z e d i n that said abrasive resistant material consists of particles being partially embedded in the surface of the cover plate (8) . 3. Marker light as defined in claim 1 or 2 , c h a r a c ¬ t e r i z e d i n that at least one dead zone (13) with said abrasive resistant material extends as a strip across the cover plate (8) . 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 at least one dead zone (11,12) with said abrasive resistant material extends along at least a portion of the periphery of the cover plate ( 8) . 5. Marker light as defined in claim 3, wherein the cover pla.te includes two active zones (8a, 8b), which emit light in opposite directions, c h a r a c t e r i z e d i n that the two active zones (8a, 8b) are separated by a strip- shaped dead zone (13) with said abrasive resistant material . 6. Marker light as defined in claim 5, c h a r a c t e ¬ r i z e d i that the two active zones (8a, 8b) are somewhat inclined downwards from the intermediate dead zone (13) with said hard material. 7. Marker light as defined in claim 5 or 6, c h a r a c ¬ t e r i z e d i n that the two active zones (8a, 8b) are confined at opposite sides thereof by two longitudinal, common dead zones (11,12) with said abrasive resistant material, so that the dead zones (11,12,13) with said abrasive resistant material together form a configuration corresponding to the letter H.

Inventors: DAHLBERG ANDERS, DAHLBERG, ANDERS
Applicants: FRANSCH AB
Application year: 1987
Main classification: B64F1
IPC codes: B64F1, E01F9, F21S2, F21S8, F21V15