Optical: systems and elements – Signal reflector
Patent
1996-02-05
1998-10-13
Phan, James
Optical: systems and elements
Signal reflector
359534, 359536, 359541, 359542, 359900, 264 19, 404 12, 404 16, G02B 5126
Patent
active
058221204
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to retroreflective elements which may be placed in pavement markings to guide and direct motorists traveling on a roadway.
BACKGROUND OF THE INVENTION
The use of pavement markings (e.g., paints, tapes, and individually mounted articles) to guide and direct motorists traveling along a roadway is well known. During the daytime the markings may be sufficiently visible under ambient light to effectively signal and guide a motorist. At night, however, especially when the primary source of illumination is the motorist's vehicle headlights, the markings are generally insufficient to adequately guide a motorist because the light from the headlight hits the pavement and marking at a very low angle of incidence and is largely reflected away from the motorist. For this reason, improved pavement markings with retroreflective properties have been employed.
Retroreflection describes the mechanism where light incident on a surface is reflected so that much of the incident beam is directed back towards its source. The most common retroreflective pavement markings, such as lane lines on roadways, are made by dropping transparent glass or ceramic optical elements onto a freshly painted line such that the optical elements become partially embedded therein. The transparent optical elements each act as a spherical lens and thus, the incident light passes through the optical elements to the base paint or sheet striking pigment particles therein. The pigment particles scatter the light redirecting a portion of the light back into the optical element such that a portion is then redirected back towards the light source.
In addition to providing the desired optical effects, pavement markings must withstand road traffic and weathering, adverse weather conditions, and cost constraints.
Vertical surfaces provide better orientation for retroreflection; therefore, numerous attempts have been made to incorporate vertical surfaces in pavement markings, typically by providing protrusions in the marking surface. In addition, vertical surfaces may prevent the build-up of a layer of water over the retroreflective surface during rainy weather which otherwise interferes with the retroreflection mechanism.
One means of providing vertical surfaces is to place raised pavement markers at intervals along a pavement marking line (e.g., U.S. Pat. Nos. 3,292,507, 4,875,798). These markers are relatively large, generally several centimeters in width and 5 to 20 millimeters in height. Typically, the markers require assembling together different components, some of which were previously individually molded or casted. Therefore, the markers are relatively expensive to manufacture. The size of the markers subjects them to substantial impact forces from passing vehicles. As a result, the markers must be substantially secured to the pavement, increasing the installation costs and removal costs when they wear out. Moreover, because the markers are applied at intervals, the bright spots of light are discontinuous, rather than the desired continuous bright line.
Embossed pavement marking tapes are a second means of providing vertical surfaces (e.g., U.S. Pat. Nos. 4,388,359, 4,069,281, and 5,417,515). Although pavement marking tapes effectively retroreflect light, they are relatively expensive compared to conventional painted markings, and thus their use is often limited to critical areas such as unlighted intersections and railway crossings.
A third means of providing vertical surfaces for retroreflection is a composite retroreflective element or aggregate (e.g., U.S. Pat. Nos. 3,252,376, 3,254,563, 4,983,458, 4,072,403; 4,652,172; 5,268,789). Many variations are known, but the retroreflective elements essentially have a core with optical elements embedded in the core surface. Some known embodiments also contain optical elements dispersed throughout the core. The core may be irregular in shape or may be regularly shaped e.g., spheres, tetrahedrons, discs, square tiles, etc. Retroreflective elements are ad
REFERENCES:
patent: 2043414 (1936-06-01), Korff
patent: 2440584 (1948-04-01), Heltzer et al.
patent: 3043196 (1962-07-01), Palmquist et al.
patent: 3171827 (1965-03-01), DeVries et al.
patent: 3175935 (1965-03-01), Vanstrum
patent: 3252376 (1966-05-01), DeVries
patent: 3254563 (1966-06-01), DeVries et al.
patent: 3274888 (1966-09-01), Vanstrum et al.
patent: 3292507 (1966-12-01), Vanstrum
patent: 3418896 (1968-12-01), Rideout
patent: 3486952 (1969-12-01), Vanstrum et al.
patent: 3556637 (1971-01-01), Palmquist
patent: 3709706 (1973-01-01), Sowman
patent: 3849351 (1974-11-01), Jorgensen
patent: 3891451 (1975-06-01), Okazaki et al.
patent: 3935158 (1976-01-01), Watanabe
patent: 3958891 (1976-05-01), Eigenmann
patent: 4035059 (1977-07-01), DeMaster
patent: 4069281 (1978-01-01), Eigenmann
patent: 4072403 (1978-02-01), Eigenmann
patent: 4166147 (1979-08-01), Lange et al.
patent: 4203878 (1980-05-01), Bauer
patent: 4367919 (1983-01-01), Tung et al.
patent: 4388359 (1983-06-01), Ethen et al.
patent: 4564556 (1986-01-01), Lange
patent: 4652172 (1987-03-01), Eigenmann
patent: 4758469 (1988-07-01), Lange
patent: 4772511 (1988-09-01), Wood et al.
patent: 4875798 (1989-10-01), May
patent: 4937127 (1990-06-01), Haenggi et al.
patent: 4969713 (1990-11-01), Wyckoff
patent: 4983458 (1991-01-01), Dejaiffe
patent: 4988541 (1991-01-01), Hedblom
patent: 4988555 (1991-01-01), Hedblom
patent: 5053253 (1991-10-01), Haenggi et al.
patent: 5094902 (1992-03-01), Haenggi et al.
patent: 5124178 (1992-06-01), Haenggi et al.
patent: 5227221 (1993-07-01), Hedblom
patent: 5268789 (1993-12-01), Bradshaw
patent: 5286682 (1994-02-01), Jacobs et al.
patent: 5417515 (1995-05-01), Hachey et al.
patent: 5502593 (1996-03-01), Hedgewick
ASTM test method E 1710--95, "Standard Test Method for Measurement of Retroreflective Pavement Marking Materials with CEN-Prescribed Geometry Using a Portable Retroreflectometer", Jul. 1995, pp. 1-4.
ASTM test method D 4061--81, "Standard Test Method for Retroreflectance of Horizontal Coatings", Dec. 1981, pp. 877-884.
Mahoney Wayne S.
Palazzotto Michael C.
Fagan Lisa M.
Jordan Robert H.
Phan James
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