Road structure – process – or apparatus – Traffic director – Attenuated lane marker type
Patent
1994-08-25
1995-07-25
Buiz, Michael Powell
Road structure, process, or apparatus
Traffic director
Attenuated lane marker type
E01F 900
Patent
active
054356636
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a marking for the creation of a luminescent surface of a substrate which-surface is intended to be used as a marking for directions, warning and/or side marking of roads, streets, quays or parking areas and which surface is subjected to water and tire wearing from passing vehicles which marking comprises a binder which is fluorescing when being irradiated by UV-A-light.
PRIOR ART
The use of glass pearls in and on road markings as reflecting pearls is since long commonly known and is prescribed also by authorities in several countries.
The object of the glass pearls is to re-reflect incoming light from vehicles to the driver of the vehicle during darkness and thereby increase the visibility of the road markings. The function is commonly known as retro-reflection.
The glass pearls fulfils their task during darkness when they are activated by the headlights or dipped headlights of vehicles. The distance of visibility at dipped headlights is however less than half of the corresponding distance for full headlights.
At rain or when the coating with the glass pearls for other reasons are covered with a water film, the incoming light is mirrored away from the vehicle and the vehicle driver so that the marking at the best only is visible a few meter ahead of the vehicle.
In fog the visible light of the vehicle is reflected by the small water drops of which the fog consists and the visible distance of the vehicle driver is often reduced to less than 20 meters, which is almost the same as the reaction distance at a speed of 70 km/h before the driver can start braking. The same occurs also when snowing. The difference is only that it is snowflakes which reflect the light of the vehicle and prevents that it gets its full distance.
To improve the distance of visibility one has tried to equip the vehicles with lamps that emits ultra violet light within the wave length of 320-400 nm, whereby the fluorescing coatings is influenced by the ultra violet light and emits visible light within the area of wave length of 400 nm.
As the ultra violet light is not mirrored away by a water film or re-reflected back by fog or snowflakes the fluorescing coating is activated by the ultra violet light, also under a water film and through fog and snowing and emits visible light which makes the coating visible for the driver also when it is covered by a water film, fog or snowflakes.
The emitted visible light is sent out from the fluorescing coating in all directions and is called a diffuse light, contrary to the light from the vehicle which is reflected back to the vehicle driver from the reflection pearls or reflected away from the vehicle by a water mirror.
The ultra violet light is invisible for meeting vehicle drivers and has therefore no blinding effect. With suitable UV beam lights it is therefore theoretically possible to bring about the same distance of visibility as using complete head lights without blinding meeting vehicle drivers.
In practice, however, the fluorescence effect has shown to be very short-lived.
In several patents proposals for improved fluorescing coatings have been made, for example U.S. Pat. No. 3,253,146, SE, B, 462 109 and GB, A, 2 043 673. The first mentioned publication proposes use of glass pearls which have been covered with fluorescing pigment particles. SE, B, 462 109 proposes the use of crushed rock material and a mineral which melts and have been doped with an agent that gives the mineral fluorescing properties.
Another variation of a fluorescent coating is described in EP 466 671. The coating disclosed therein contains doped glass pearls which fluoresce when being illuminated with ultra violet light. The pearls can be clear or pigmented. The light emitted from these pearls is however weak and can be seen from at most 50 meter, which is far too less when the coating is used for vehicle traffic.
The attempts to increase the intensity of the fluorescence or the emitted light by increasing the strength of the UV-lamps or the intensity of absorpt
REFERENCES:
patent: 4751140 (1988-06-01), Ishihara
patent: 5380549 (1995-01-01), Harvison
Buiz Michael Powell
Cleanosol International AB
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