Road structure – process – or apparatus – Traffic director
Patent
1993-11-05
1995-10-10
Britts, Ramon S.
Road structure, process, or apparatus
Traffic director
404 14, 404 17, E01C 900
Patent
active
054565464
DESCRIPTION:
BRIEF SUMMARY
The invention relates to reflecting bodies made from transparent material for mounting on traffic-bearing surfaces, in particular roads, or on traffic control surfaces, to a method for producing these reflecting bodies and to the use of the same.
So far, reflecting bodies have been known in the form of colorless, transparent glass beads or reflecting beads, which are mounted on horizontal markings, in particular on marking lines, which delimit the lanes. These reflecting beads enhance the night-time visibility of the horizontal marks in the headlamp light of the car. Such reflecting beads and their application to better visualization of horizontal markings are disclosed, in particular, in EP-B-0,280,102 from the same applicant.
Furthermore, FR-A-1,386,085 discloses the provision of glass beads directly on the surface of the pavements, which are partially embedded in the pavement, so that they project from the roadway by a spherical segment and enhance the night-time visibility of the same by reflection of the headlamp light. In this case, it is also mentioned that colored glass beads can be used in order, for example, to color-mark particular route guides.
The visibility of reflecting beads on horizontal markings or pavements in the headlamp light of a car is based essentially on so-called retroreflection, and not on specular reflection at the outer surface of the reflecting beads. Retroreflection is understood as reflection in which the incident light is reradiated in the direction towards the light source. This effect, which will be illustrated more effectively later with the aid of FIG. 3 and is based on refraction and reflection, is produced by those incident light beams which penetrate into the glass bead, experience refraction in the process and reexit from the glass bead on the incident side after internal reflection accompanied by renewed refraction. Since reflecting surfaces oriented perpendicular to the direction of illumination are present seldom or virtually not all, when the reflecting beads are embedded for the purpose of effective adhesion at least by half in the pavement, the light specularly reflected at the outer surface of a reflecting bead is retroreflected largely upwards and not in the direction of illumination, that is to say not to the driver of the car concerned. Consequently, it is virtually exclusively the retroreflection which is decisive for the desired night-time visibility.
However, when mentioning the colored glass beads, the said FR-A-1,386,085 does not explain how an effective retroreflection is to be achieved therewith. If the glass beads are coated with a colored film which transmits virtually no light, no retroreflection can take place. If the glass beads consist of colored glass, the intensity of the retroreflected light beams is more or less attenuated, in accordance with the reduced optical transparency of the material. Furthermore, the background color, that is to say the generally black or dark gray color of the pavement, covers the natural color of the glass beads. These disadvantages have meant that this method in accordance with FR-A-1,386,085 from the year 1964 has attained no practical importance.
Numerous other attempts and means are known for improving road markings: EP-A-0,177,181 describes ceramic microspheres which contain metal oxides and are embedded in marking strips which are, as prefabricated elements, intended for mounting on roadways. EP-A-0,322,671 proposes a pigmented horizontal marking in which clusters are contained which consist of a core and of microspheres which surround this core and are embedded in a transparent binding agent. DE-A-2,216,157 discloses a cover material for roads in the form of a combined composition made from silicon carbide and glass beads. The use of silicon carbide for producing reflecting road surfaces is described in CH-A-562,372.
In DE-A-2,011,238 of the same inventor, originating from the year 1970, it was proposed to provide reflecting bodies with phosphorescent luminescent particles, in order to provide a self-lumi
REFERENCES:
patent: 3005790 (1961-10-01), Wynn et al.
patent: 3215051 (1965-11-01), Gill
Britts Ramon S.
O'Connor Pamela A.
Plastiroute S.A.
Potters-Ballotini Ltd
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