Apparatus for direction-indicating surface marking and the like

Abstract

This disclosure is concerned with distinctively and unambiguously marking the directions of travel on motoring highways, airports and other surfaces with the aid of a thin novel saw-tooth-like marker strip that is adhered to the traveling surface and the upwardly and downwardly inclining wedges of which are light-transparent, each embedding there-within an upwardly disposed retroreflective member to indicate the direction of travel.

Description

The present invention relates to apparatus for direction-indicating surface marking and the like, being more particularly concerned, for example, with marking highway surfaces in such a manner that the mark will visually indicate to a motorist in a distinctive color, such as red, that such motorist is proceeding in an improper direction of travel. Clearly similar applications exist in airport runway surfaces and on other surfaces, as well, for the same or similar purposes and functions. Accordingly, the term "surface" will be used hereinafter in a general sense, as will the words "horizontal" and "vertical" be used sometimes in connection with orientation of the parts in an illustrative and relative and thus a generic sense, also, since the invention is applicable in many geometric configurations. The term "color" is also used herein in a broad sense to embrace both spectral wavelengths and different shades or hues that provide different surface appearances.

The serious problem has long existed in all major highways of the world of alerting motorists to instant recognition of an improper direction of travel as they proceed along the highway. All too often, an unsuspecting motorist proceeds in the wrong direction of travel and heads directly into opposing traffic. This is a surprisingly common occurrence on divided highways, particularly when the lanes are separated by some distance between them. In such instances, even under ideal weather and visibility conditions, each lane appears to the motorist to be a separate highway without clues to indicate whether it is a two-directional traffic road or a single direction highway. Nor is there any clue indicating either the proper or improper flow of traffic. Initial road signs and other devices that have been in use have proven far from fool-proof.

Recognition of the wrong way to proceed, whether immediate or not, is often exceedingly difficult and sometimes impossible for the motorist to decide. For example, during heavy rain or dense fog, and especially at night, the ensuing confusion has led to many fatal accidents of head-on collisions.

Many dual-lane divided highway motoring surfaces, moreover, have delineator posts positioned along the side of the roadbed every few hundred feet. These delineators usually contain a highly reflective material at their tips so that, at night, with headlight illumination, they may serve visually to indicate the edge of the road. The highly reflective optical material generally used is known as a "retroreflector" that is, a material which returns nearly all of the incident light back along the same direction from whence it came. These reflectors can be of many geometric forms such as a plurality or series of small members such as cubes, pyramids, Fresnel reflectors, or tiny transparent glass or plastic rods, fibers or spheres secured to a light-colored diffusely reflecting surface. The latter is the basis of a commercially available product marketed, for example, by Minnesota Mining and Manufacturing Company, under the trademark "Scotchlite", and incorporated into many highly reflective street signs, stop signs, and other highway visual warning signs, as disclosed, for example, in U.S. Pat. No. 2,407,680. This optical material has also been incorporated with a paint base which may be applied to many surfaces, such as roadways, either by a spray or brush technique, as described, for example, in U.S. Pat. No. 2,824,502.

All of these optical materials are highly efficient retroreflectors at a normal angle of incidence, and so return a large percentage of the incident light back upon itself. As the angle of incidence becomes more oblique, however, these materials become less efficient in the percentage of light they return as retroreflectors. When applied to the surface of a highway to serve as a visual marker, such as a traffic lane divider, as for example, in U.S. Pat. No. 2,232,023, such optical materials are thus only slightly better than ordinary paint, especially when observed by automobile headlights at night, and have not served adequately to solve the above-mentioned problem. Furthermore, their visual appearance is the same when viewed from all directions and thus they do not provide direction discrimination.

The reflected light may be made to appear in a given color by proper selection of reflecting material or binder in which the optical reflecting elements are imbedded. For example, if the background is white, then the retroreflected light will be white. If the optical elements are disposed on a green background, the reflected light will be green. Likewise a red appearance will result from imbedding the optical elements in a red binder or background.

It should be obvious, however, that if a red background has been selected, the appearance of the reflected light will always be red irrespective of the viewing angle. Thus, a road stripe using a red background material in which the optical elements are contained, will always have a red appearance regardless of the viewing angle. This fact has thus precluded use of such a material per se to serve the purposes of a visual highway wrong-direction traffic color indicator in view of its same color appearance from all angles of view.

While it has been proposed to make highways more illuminable, as by constructing roadway surfaces with blocks that would impart a saw-toothed roadway configuration, as in U.S. Pat. No. 2,330,808, thus to reflect light incident upon the road surface from headlights more generally back toward the vehicle to render the road surface more visible, this does not provide unambiguous discrimination of direction of reflection, it inherently produces road chatter and vibration, and, indeed, it is exhorbitantly expensive and not adaptable to be employed in existing roadways and the like. Similarly, the concept of using lenses to improve visibility, even with retroreflective materials, as in U.S. Pat. Nos. 3,292,507 and 3,499,371, requires multiple parts, is subject to similar road chatter, non-universal adaptability for application, and expense disadvantages, among others. Similar disadvantages reside in the use of various-shaped blocks with retroreflective materials, as in U.S. Pat. Nos. 2,579,467 and 3,418,896. Other proposals for improved visibility and marking have been made as in U.S. Pat. Nos. 1,740,501; 1,850,370; 1,981,206; 2,256,636; 3,103,859; 3,252,376; 3,291,011; 3,355,999; 3,529,517; and 3,575,773; but, again, these all lack the either discrimination or other practical features before-discussed that underlie the problem of the present invention.

It has been discovered that through the use of a novel thin saw-toothed strip combined with critically positioned distinctively colored retroreflective material on one set of parallel surfaces, and sometimes optically diffuse and sometimes retroreflective differently colored reflecting surfaces therebetween, all of the above-described disadvantages of prior markers are admirably overcome; and, indeed, the retroreflector is not subject, in its novel orientation herein, to its customary lack of angular discrimination, before discussed, in prior art uses of the same and requires no lens or other light-return supplementing apparatus as in said U.S. Pat. No. 3,292,507. A synergistic combination effect is thus produced, that constitutes a highly novel solution to the problems underlying the invention.

Such a structure is disclosed in my copending application, Ser. No. 478,453, filed June 12, 1974 and entitled "Method of and Apparatus For Direction-Indicating Surface Marking and The Like," embodying a thin novel saw-tooth-like marker strip that is adhered to the travel surface and has distinctively colored successive-wedge surfaces of retroreflecting materials for indicating opposite directions of travel or other travel indications distinctively and unambiguously.

There may be instances, however, for purposes of manufacture or use, or both, where it is not desired to conform the geometry of the retroreflective material closely to that of the surfaces of the saw-tooth wedges of the marker strip; or where it is desired to employ structures with back-to-back vertical strips of retroreflective elements as described, for example, in the before-mentioned U.S. Pat. Nos. 3,292,507 and 3,499,371. It is more particularly to such situations, and also others, that the improvement of the present invention is, in one of its primary aspects, generally directed.

In such prior patent proposals as referenced immediately above, the retroreflection markers used as highway or similar vehicular traffic markers and the like comprise vertically mounted strips of such retroreflective small glass beads or similar material disposed between high refractive index spherical lens-like rods, with wear cap structures above and below to hold the structure together and to enable protection against wear and securing to the roadway or other surface, respectively. In this type of device, the lens-like rods must be positioned external to the retroreflective strip for meaningful focusing action and, indeed, an interface of air between the lens and retroreflective material has been considered to be preferred.

Underlying the present invention, however, is the finding that, contrary to such prior teachings, focusing action is not needed to provide low light-loss effective operation, and, indeed, that the above-mentioned constructional and other restraints of such prior art constructions are by no means inherently required. It has been found, to the contrary, that multi-angle incident light loss can be effectively minimized with a cylindrically curved or substantially hemispherical transparent surface, without any requirement that such surface actually optically focus upon the retroreflective vertical strip in lens-like fashion or that it be external to such strip or even disposed with an air interface. By embedding the vertical retroreflective strip substantially diametrically within an upper substantially hemispherical or similar cylindrically curved transparent surface, to the contrary, a successful marker can be attained void of the necessity for the costly, critically-dimensioned and multi-element structures of the above-described prior art proposed markers.

The hemispherical or similar curved transparent surface, rather than being adjusted to act as a lens for amplification, reduces light loss at its surface as the incident light impinges thereon over a wide range of angles of incidence, and minimizes refraction once the light has entered the same, which could have the deleterious effect of distorting or optically shortening the effective area of the retroreflective strip, producing considerable reflected light losses.

More than this, unlike devices having wearable cap and other structures which, when worn, can no longer hold the marker elements together, the curved saw-toothlike configuration of the present invention, with its retroreflective strip embedded within the protective hemispherical or other surface, will wear as a solid integral unit and still be effective to a significant degree even when worn very thin.

An object of the present invention, accordingly, is to provide a new and improved apparatus for direction-indicating surface marking, as for such purposes as visually warning motorists when they are proceeding in an improper direction, and for other applications.

A further object is to provide such a novel apparatus employing, in a critical manner, retroreflective materials upwardly directed and embedded within successive transverse light-transparent wedges of a longitudinally extending marker strip such as to cause a distinct color or hue to be observed over a wide range of distances when observed from one direction, and a totally different color or color appearance, including, if desired, none at all, when viewed from an opposite direction.

An additional object of the invention is to provide improved landing strips or airport runway markers which will delineate the edges of such runways to the operators of aircraft using these facilities.

Other and further objects will occur hereinafter and are more particularly delineated in the appended claims. In summary, however, from one of its aspects, the invention contemplates a direction-indicating surface marker apparatus comprising a thin longitudinally extending strip provided with successive longitudinally spaced transverse contiguous light-transparent wedges of somewhat saw-tooth configuration. Each wedge embeds substantially centrally therewithin an upwardly disposed transverse retroreflective member, with the upwardly and downwardly inclining surfaces, of the wedge integrally protecting the member and enabling incident light passing through the transparent wedge surfaces to become retroreflected from said member in distinctive predetermined color indicative of direction or the like.

This optical material is preferably secured to the surface of a paved highway or runway in the form of circles, squares, arrows, letters, solid unbroken lines, or dashed lines in much the same way that paint is applied to road surfaces; or it may be applied to posts or signs, as described.

The invention will now be described with reference to the accompanying drawing,

FIG. 1 of which is a longitudinal sectional view of a preferred embodiment applied to a marker strip or the like on a highway or similar surface; and

FIG. 2 is a fragmentary similar view of a modification.

While in the description of this invention, reference is made to optical elements such as refractive spheres, cylinders, rods, or fibers, it should be understood that these elements may be made as individual elements of glass, plastic, or other transparent optical materials, or they may be comprised of molded or otherwise preformed glass or plastic sheets as described, for example, in some of the above-referenced patents.

Referring to FIGS. 1 and 2 of the drawings, the longitudinally extending marker strip 1 of the invention is shown for illustrative purposes as comprising a somewhat saw-toothed or periodically ridged configuration, preferably preformed into, parallel, successively longitudinally spaced contiguous in-line transverse light-transparent wedges 1'. The thin strip, unlike prior art blocks, lens devices and the like, is adapted for facile and universal attachment to road and other surfaces by thin adhesive coatings 10 of thermal-setting cements, such as rubber hydrochloride, "Glyptal" No. 7424 (General Electric) and "Duraplex" D-65-A (Rohm and Haas), and other similar well-known adhesives.

In this embodiment, the light-transparent wedges 1' are, as before mentioned, of substantially cylindrically curved hemispherical shape, integrally formed with or upon the base 1 of the marker strip, and embedding within each wedge an upwardly disposed transverse member 6-6' of retroreflective material(s), integrally bonded in substantially vertical or right-angular position, relative to the substantially horizontal marker strip base 1, substantially centrally of or diametrically within such hemispherical wedge. The member 6-6' is illustrated in the form of similarly or differently colored glass bead or other preferably retroreflective type materials, such as the before-mentioned "Scotchlite" materials, mounted on opposite sides of a thin vertical backing element 11, as later described.

As previously explained, the transparent upwardly and downwardly inclining quadrants of the hemispherical wedges 1' reduce incident light loss as a result of their curvature, and minimize refraction once the incident light has entered the same (as in the direction I or the opposite direction I'), thereby preventing distortion or optical shortening of the effective dimensions of the retroreflective strip 6-6' which could produce considerable reflected light loss. This, again, as previously explained, is quite distinct from prior art lens-focusing proposals and the limitations thereof.

If there is less concern for such losses, the curvature may be varied, even to substantially planar triangular surfaces as illustrated in FIG. 2, but again with the retroreflective member 6-6' upwardly oriented substantially centrally within the transparent wedge, and not following the geometrical surfaces of the wedge as preferred in my said copending application.

In both the embodiments of FIGS. 1 and 2 and in the structures of my said copending application, moreover, the units wear as integral structures and never come apart or become disassembled, but, to the contrary, remain effective even when worn very thin.

In an experimental version, a successful marker strip 1-1' was produced employing retroreflective members 6 and 6', each comprising red and white retroreflective tapes ("Scotchlight"--3M Company) laminated on opposite sides of a 5 mil thick supporting strip 11 of "Lexan" plastic. The laminated member 6-11-6' was about 2 1/2 millimeters tall and about two inches wide, and each such member was embedded within a transparent substantially hemispherical wedge surface of plastic casting resin (in this instance, of fiberglass of the type "Crystal Cast" marketed by The Fibre Glass Evercoat Company of Cincinnati, Ohio), each hemisphere 1' being about 5 millimeters in diameter and being longitudinally spaced from the adjacent transverse parallel wedges along the integral plastic strip 1, about 12 millimeters. The strip was about 2 millimeters thick and was flat to enable securing to the roadway by suitable well-known adhesive as before discussed. With such structures only a few percent loss compared with the retroreflection characteristics without the hemispherical wedges can be attained.

Clearly, much thinner and, if desired, thicker strips can be fabricated and of other suitable well-known plastic materials including, for example, said "Lexan" type or N-butyl-methacrylate polymer resin with silicone covering. Further modifications will also occur to those skilled in this art; such being considered to fall within the spirit and scope of the invention as defined in the appended claims.

Claims

What is claimed is:

1. A direction-indicating surface marker apparatus having, in combination, a continuous longitudinally extending strip having length and width many times its thickness and provided with integral successive longitudinally spaced transverse contiguous light-transparent upwardly and downwardly inclining wedges of somewhat saw-tooth configuration embedding substantially centrally within each wedge, an upwardly disposed substantially planar transverse retroreflective member; the upwardly and downwardly inclining surfaces of the wedge integrally protecting said member and enabling incident light passing through such surfaces to become retroreflected from said member, presenting a predetermined color indicative of direction, said strip having sufficient structural strength to permit it to be handled and secured to a roadway surface by adhesive.

2. A direction-indicating surface marker apparatus as claimed in claim 1 and in which said wedges are of substantially hemispherical contour and said member is substantially diametrically vertically embedded therewithin.

3. A direction-indicating surface marker apparatus as claimed in claim 1 and in which said wedges are of substantially triangular contour and said member is substantially vertically centrally embedded therewithin.

4. A direction-indicating surface marker apparatus as claimed in claim 1 and in which said retroreflective member is provided with different color-presenting means on opposite faces of said member.

5. A direction-indicating surface marker apparatus as claimed in claim 1 and in which said retroreflective member comprises a laminate of retroreflective layers.

6. A direction-indicating surface marker apparatus as claimed in claim 5 and in which said laminate comprises retroreflective tape disposed on opposite sides of a transverse supporting strip.