Illumination – With static structure – Pavement
Patent
1993-02-26
1994-08-02
Lazarus, Ira S.
Illumination
With static structure
Pavement
362153, 362299, 362328, F21V 504
Patent
active
053351517
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a marker light according to the preamble of claim 1.
Such marker lights are previously known from WO88/00157 wherein a marker light for airfields, e.g. for runways, taxistrips or the like is described. The marker light according to the invention is, however, generally useful also in other applications, where it is desired to have two oppositely directed light beams being emitted from a light fitting which is flush-mounted in the ground, e.g. in roadways, particularly as a lane marker, in interchanges, parking areas, storage areas and in other vehicle or pedestrian areas.
A well known problem with marker lights of this kind, particularly in airfields where relatively great light intensity is necessary in the emitted light beams, is associated with the heat development originating from the light source and the interaction of the light with different optical components in the fitting. Thus, there always has to be a compromise between the luminous efficiency, on the one hand, and the strength and the functional reliability of the construction materials under working conditions, the working life thereof, etc., on the other hand.
Against this background, the main object with the present invention is to achieve a marker light making it possible to obtain a high luminous efficiency and a high light intensity in spite of a relatively moderate temperature within the fitting and thus to maintain the strength and other functional properties as well as the necessary working life of the construction materials.
Secondary, although equally important objects are to achieve a compact fitting structure, relatively simple and non-expensive manufacture and assembly and low maintenance costs.
The above main object is achieved for a marker light of the kind defined above in that the prism, being located between the light source and the upper cover plate, has an essentially planar lower surface, being perpendicular to the upwardly directed light bundle from the light source, and an upper surface with at least one saw-tooth formation, the inclined surface portions of which having such angles of inclination that the inciding light will be redirected through total reflection at the respective inclined surface portion and be emitted under the least possible refraction in the respective adjacent, inclined surface portion, while at the same time maintaining said essentially perpendicular angle of incidence onto the lower saw-tooth surface portions of the cover plate and said desired vertical angle for the two light beams being emitted from the upper surface of the cover plate.
In this connection it should be mentioned that a prism with upwardly directed, inclined surface portions and a lower, horisontal surface is previously known per se from U.S. Pat No. 4,161,770. In the marker light according to this publication, however, the light beams are emitted directly from the upper pointed portion of the prism, which portion therefore protrudes above the slotted cover of the housing, said cover being located essentially in the ground-level plane. Thus, in this case, the marker light does not comprise an approximately planar transparent cover plate, but the pointed edge portion (with large angles of inclination) protrudes through the slot of the cover, which will lead to considerable inconveniences e.g. by snow clearance, wherein the prism could be damaged or displaced from its accurately adjusted position.
Through appropiate dimensioning of the angles of inclination of the inclined surface portions, taken into account the refractive index of the materials of the cover plate and the prism as well as the desired vertical angle relative to the ground level plane for the emitted light beams, it is possible to optimize the optical arrangements of the marker light according to the invention in such a way that after having been totally reflected at the respective inclined surface portion within the prism, the bundle portions,-being directed obliquely upwards in opposite directions will be refracted very little when being em
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Lazarus Ira S.
Quach Y.
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