US3785719A

US3785719A - Roadway lane delineator having an elastomeric reflective portion

Info

Publication number: US3785719A
Application number: US00273733A
Authority: US
Inventors: N Jonnes
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1972-07-21
Filing date: 1972-07-21
Publication date: 1974-01-15
Anticipated expiration: 1991-01-15

Abstract

A roadway lane delineator comprising a base portion, an elastomeric reflector portion carried by the base portion, and a retro-reflective structure supported on an exterior surface of the reflector portion.

Description

United States Patent [191 J onnes ROADWAY LANE-DELINEATOR HAVING AN ELASTOMERIC REFLECTIVE PORTION [75] Inventor: Nelson Jonnes, St. Paul, Minn.

[73] Assignee: Minnesota Mining and Manufacturing Company, St. Paul, Minn.

[22] Filed: July 21, 1972 [21] Appl. No.: 273,733

Related U.S. Application Data [63] Continuation of Ser. No. 74,079, Sept. 21, 1970,

abandoned.

[52] U.S. C1 350/105, 94/1.5, 350/109 [51] Int. Cl. G02b 5/12 [58] Field of Search 350/97-109; 94/1.5

[56] v References Cited UNITED STATES PATENTS 3,340,779 9/1967 Mahoney 94/l.5

1.11 3,785,719 Jan. 15, 1974 9/1970 Tomlinson 350/98 3,551,025 12/1970 Bingham 350/105 3,091,997 6/1963 Byrd 94/1.5 3,588,222 6/1971 Jullus 350/100 2,851,935 9/1958 Weeks 94/1.5 3,292,506 12/1966 Kone 94/1.5 3,257,552 6/1966 Converso 94/1.5

.Primary Examiner-David Schonberg Assistant ExaminerMichael J. Tokar Att0meyAlexander, Sell, Steldt & Delahunt [5 7] ABSTRACT A roadway lane delineator comprising a base portion, an elastomeric reflector portion carried by the base portion, and a retro-reflective structure supported on an exterior surface of the reflector portion.

8 Claims, 8 Drawing Figures ROADWAY LANE DELINEATOR HAVING AN ELASTOMERIC REFLECTIVE PORTION This is a continuation of application Ser. No. 74,079, filed Sept. 21, 1970, now abandoned.

' Most commercial forms of roadway lane delineators comprise a mound-shaped flat-bottomed ceramic disc that carries reflex-reflective means in a recess in the top surface, or is covered over a large part of the top surface with reflective glass microspheres, or carries cube-corner reflector inserts. But such delineators cannot be used in geographic areas in which roadways must be plowed to clear them of snow. The delineators are quickly removed by the plowing operation, and since they are rather expensive to manufacture and install, their replacement following a plowing season would be too costly. Further, the delineators are hard, heavy objects that would cause property damage and be injurious if they'were thrown through the air by a snow plow. Lane delineators have been installed in heavy steel jackets on the roadway in an attempt to make them resist plowing, but the cost of manufacture and installation and the lack of reliable results has made these efforts impractical.

A further disadvantage of present lane delineators lies in their failure to provide lasting wet-reflecting characteristics. For a lane delineator covered over its top surface with glass microspheres, the microspheres must be made of a glass having a high index of refrac-' tion (about 2.6) if they are to retroreflect when the delinea tor is covered by a film of water. But high-index glass is mechanically weak and the microspheres soon wear awayunder the abrasion of road traffic. Lane delineators made with retro-reflectors set in a recess in the delineator avoid this problem, but they have the disadvantage that the recess tends to fill with dust that obstructs the passage of light rays to the reflectors.

The present invention provides a roadway lane delineator that is inexpensive to manufacture, can avoid removal by snow-plowing, does not present a danger if it is plowed from the roadway, and has long-lasting wetreflecting capability. Briefly, a lane delineator of this invention comprises a base'portion that is adapted to attach the-delineator to a roadway and a reflector portion carried by the base portion. The reflector portion, which is made of an elastomer"( Elastomer and elastomeric are used in this specification to describe substances that can be stretched at room temperature to at least twice their original lehgth; and after having been stretched and the stress removed, return with force to approximately their original length in a short time.) and is elastically deformable when engaged by a vehicle passing over the supports retro-reflective structure on its exterior surface inposition to retro-reflect light back to vehicles traveling on the roadway when the delineator is in place on the roadway. Further, the retro-reflective structure is preferably in a position such that at least a portion of it is shielded from contact with vehicles traveling on the roadway. Buth dust generally does not accumulate in this shielded area, since the movement of the reflector portion when engaged by vehicles traveling on the roadway moves the retroreflective structure, and this latter movement tends to remove the dust.

In preferred embodiments, the base portion and reflector portion are formed integrally. Also, the retroreflective structure preferably comprises a monolayer of transparent glass microspheres partially embedded in the reflector portion with their embedded surfaces covered with a reflective material. Thus, the retroreflective structure elastically deforms when the reflector portion deforms, and this deformation provides a preferred removal of any dust or the like covering the microspheres.

DETAILED DESCRIPTION A first illustrative lane delineator of the invention is illustrated in FIGS. 1-3. This lane delineator 10 is molded integrally from an elastomer and comprises a shallow, pyramidal-shaped base portion 11 and a reflector portion 12 mounted at the apex of the base portion. The base portion 11 of the lane delineator has a recess 13 beneath the reflector portion 12; as a result, when pressure is applied to the reflector portion, as when a tire of a vehicle passes over the delineator, the reflector portion depresses into the recess 13, as shown in dotted lines in FIG. 2.

cludes a bead-binding layer 20 which often comprises an at least partially cured elastomer, and also includes sheet-adhering layer 21 by which the sheeting is adhered to the reflector portion. The layer 21 may either comprise a layer of adhesive (pressure-sensitive, heatactivatable etc.) or a layer of a vulcanizable elastomer that is vulcanized to the reflector portion during manufacture of the delineator. An elastomeric retroreflective sheeting useful in the delineator shown in FIGS. 1-3 is more fully described in U.S. Pat. No. 3,449,201, and the teachings of that patent are incorporated herein by reference.

Alternatively to forming a layer-like retro-reflective structure on a delineator of the invention by applying sheeting, retro-reflective elements such as glass beads may be cascaded over the exterior surface of the reflector portion while that portion is tacky or covered with a layer of tacky material. Or the layer-like retroreflective structure may be formed by covering the in-' terior of a mold cavity with a layer of retro-reflective elements prior to filling the cavity with the elastomeric material from which the reflector portion is molded. The monolayer of retro-reflective elements may be covered with a layer of transparent material, but because that layer of transparent material may become abraded or marked and thereby reduce the amount of light transmitted to the retro-reflective elements, It is preferably omitted.

As will be seen in FIGS. 1-3, at least a large part of the retro-reflective surfaces Ma and 14c, which are disposed substantially vertically with respect to a roadway and transverse to the direction of traffic on the roadway when the delineator is in place on the roadway, are protected from direct contact with the wheels of a vehicle passing over the delineator because of their verticality. Further, movement of the reflector portion 12 into the recess 13, as shown in dotted lines in FIG. 2,

cleans the reflective surfaces of the reflector portion and prevents dust from accumulating over them.

FIGS. 4 and 5 show a variation of the delineator shown in FIGS. 1-3. The delineator shown in these figures has a monolayer of retro-reflective elements over its whole surface to provide a greater area of reflection. Further, the exterior surface of the delineator carrying the retro-reflective elements is irregular-that is, is formed with a series of small craters 26, as shown best in FIG. 5. Other depressions could also be used. The depressions may be formed by shaping the reflective sheeting against a die surface and then curing the sheeting, or by vacuum-drawing the sheeting into a mold cavity prior to filling the cavity with the elastomeric material that is to form the main body of the reflector portion, etc. When a tire passes over a delineator having such an irregular or roughened surface, the retro-reflective elements within the depressions are protected against abrasion by the tire and therefore have a longer life.

As shown in FIG. 4, a typical method for attaching delineators of the invention to the roadway is through use of a thick layer 27 of a pasty cement such as a butyl rubber-based mastic. Thinner layers of other kinds of adhesive may also be used, but the good confonnability of the mastic to many different highway surfaces makes it desirable.

A different embodiment of the lane delineator of the invention is shown in FIGS. 6 and 7. The delineator 28 illustrated comprises an integrally molded elastomeric panel that is molded so that in longitudinal crosssection it has a hook-shaped configuration. One part 29 of the delineator 28 comprises a base portion while a second part 30, a flexible flap, comprises a reflector portion. The face of the flap 30 that is directed toward traffic when the delineator is in place on a roadway is recessed at four adjacent square-shaped areas 31-34, and the bottom of the recessed portions is covered with retro-reflective structure 35, which typically comprises a monolayer of retro-reflective elements such as glass beads partially embedded in the delineator. As shown in FIG. 6, when the delineator 28 is in place on a roadway, the flap 30 is disposed at an angle with respect to the roadway, such that the retro-reflective structure 35 retro-reflects light from aproaching vehicles back to the drivers of the vehicles The delineator 28 is especially advantageous for use on roadways that are plowed, since, as illustrated, the

delineator may be installed in a recess 37 in a roadway 38 with the only part of the delineator 28 extending above the roadway being the flap 30. The flap is elastically flexed downwardly when it is struck by a plow blade or engaged by another vehicle traveling on the roadway. The ribs 39 at the sides and between the recesses 31-34 protect the retro-reflective elements against abrasion by the tires of vehicles traveling on the roadway as well as from the plow blade. The spacing of the ribs is chosen so as to provide the desired protection. Alternate recesses may incorporate glass beads of different indexes of refraction so the delineator provides both wet and dry reflection. The delineator 28 can be adhere to the roadway with a mastic 40 such as described in FIG. 4.

FIG. 8 illustrates another delineator of the invention, which is similar to that shown in FIGS. 6 and 7, except that the reflector portion of this delineator 41 comprises a flap 42 that is exactly perpendicularly attached to an intermediate point of a base portion 43. The faces of the flap carry retro-reflective structure 44. The delineator 41 may be installed'in a recess in a roadway, so when the flap 42 is struck by a plow blade it will also be flexed to a position substantially parallel to the roadway. Also the retro-reflective structure on the faces of the flap 42 may be made irregular as shown for the embodiment of FIGS. 4 and 5 or the retro-reflective structure may cover the bottom of recesses in the faces of the flap as shown for the embodiment of FIGS. 6 and 7. In addition, while the delineator 41 has only one reflector portion 42, other delineators may include a plurality of reflector portions carried on one base portion. For example, the base portion may comprise a tape applied to form a traffic stripe on a roadway.

A wide variety of elastomeric materials are useful in the invention, including neoprene, polyurethane, butyl, styrene-butadiene, epoxy-based, and natural elastomers, and mixtures of such elastomers. The formulation chosen should be flex-resistant and should be chosen so that the delineator will perform as desired irrespective of the climate and other environmental conditions to which the delineator will be exposed. To further strengthen the delineator, reinforcing fibers or fabrics may be included in it.

Transparent glass microspheres or beads, generally less than about microns in diameter and covered over their embedded surface with a coating of reflective material such as aluminum, are the preferred retroreflective elements in delineators of the invention. Aggregate of glass beads around a rigid core such as taught in U.S. Pat. No. 3,043,l96 may also be used, as may be so called cube-corner" retro-reflective elements.

What is claimed is:

1. A roadway marker comprising 1. a base portion adapted to attach the marker to aroadway, and

2. an elastomeric reflector portion carried by the base portion and elastically deformable when engaged by a vehicle passing over the marker, the reflector portion including elastically deformable retro-reflective structure that forms an exterior surface of the reflector portion, said retro-reflective structure comprising discrete retro-reflective elements and a body of elastomeric material in which the retro-reflective elements are suported, whereby as the retro-reflective structure is stretched, the distance between the centers of adjacent retroreflective elements increases until the stretching force is removed, whereupon the retro-reflective structure returns to its original shape, at least part of said retro-reflective structure being located on the reflector portion such that when the marker is in place on a roadway, said part of the retroreflective structure (a) is in position to retro-reflect light to vehicles traveling toward the marker, (b) is protected from contact with the wheels of vehicles traveling on the roadway by structure of the marker adjacent said retro-reflective structure, and (c) undergoes elastic movement during deformation of the reflector portion whereby the retro-reflective structure is cleaned of road dust and the like.

2. A marker of claim 1 in which the base portion and reflector portion are formed integrally of elastomer.

3. A marker of claim 1 in which the surface of the retro-reflective structure is irregular so as to protect part of the surface from contact by vehicles traveling on the roadway.

4. A marker of claim 1 in which the retro-reflective structure comprises a monolayer of transparent glass microspheres partially embedded in the reflector portion and covered over their embedded surfaces with a reflective material.

5. A marker of claim I in which the retro-reflective structure comprises an elastomeric support sheet and a monolayer of transparent glass microspheres partially embedded in one side of the support sheet and covered over their embedded surface with reflective material, and the support sheet is adhered to the reflector portion.

6. In combination,

A. a roadway, and

B. a roadway marker of claim 1 attached to a recessed portion of the roadway, such that the deformation of the reflector portion moves substantially all of the reflector portion into the recessed portion.

7. A roadway marker comprising 1. an elastomeric base portion adapted to attach the v nel-like member, at least portions of said retroreflective structure being depressed to a level below the level of adjacent portions of the exterior surface of the panel-like member, and said retro-reflective structure comprising discrete transparent glass microspheres, a sheet of elastomeric material in which the glass microspheres are partially embedded, and a base elastomeric part of the panel-like member to which the sheet of elastomeric material is adhered, whereby as the retro-reflective structure is stretched, the distance between the centers of adjacent glass microspheres increases until the stretching force is removed, whereupon the retro-reflective structure returns with force to its original shape, at least part of said retro-reflective structure being located on the reflector portion such that when the marker is in place on a roadway, said part of the retroreflective structure (a) is in position to retro-reflect light to vehicles traveling toward the marker when the marker is in place on the roadway, (b) is protected from contact with the wheels of vehicles traveling on the roadway by structure of the marker that forms said adjacent portions of the exterior surface of the panellike member, and (c) undergoes elastic movement during movement of the panel-like member whereby the retro-reflective structure is cleaned of road dust and the like.

8. In combination, A. a roadway, and B. a roadway marker of claim 7 attached to a recessed portion of the roadway. =l=

Claims

1. A roadway marker comprising 1. a base portion adapted to attach the marker to a roadway, and 2. an elastomeric reflector portion carried by the base portion and elastically deformable when engaged by a vehicle passing over the marker, the reflector portion including elastically deformable retro-reflective structure that forms an exterior surface of the reflector portion, said retroreflective structure comprising discrete retro-reflective elements and a body of elastomeric material in which the retroreflective elements are supported whereby as the retroreflective structure is stretched, the distance between the centers of adjacent retroreflective elements increases until the stretching force is removed, whereupon the retro-reflective structure returns to its original shape, at least part of said retro-reflective structure being located on the reflector portion such that when the marker is in place on a roadway, said part of the retro-reflective structure (a) is in position to retro-reflect light to vehicles traveling toward the marker, (b) is protected from contact with the wheels of vehicles traveling on the roadway by structure of the marker adjacent said retro-reflective structure, and (c) undergoes elastic movement during deformation of the reflector portion whereby the retroreflective structure is cleaned of road dust and the like.

2. an elastomeric reflector portion carried by the base portion and elastically deformable when engaged by a vehicle passing over the marker, the reflector portion including elastically deformable retro-reflective structure that forms an exterior surface of the reflector portion, said retro-reflective structure comprising discrete retro-reflective elements and a body of elastomeric material in which the retro-reflective elements are supported whereby as the retro-reflective structure is stretched, the distance between the centers of adjacent retroreflective elements increases until the stretching force is removed, whereupon the retro-reflective structure returns to its original shape, at least part of said retro-reflective structure being located on the reflector portion such that when the marker is in place on a roadway, said part of the retro-reflective structure (a) is in position to retro-reflect light to vehicles traveling toward the marker, (b) is protected from contact with the wheels of vehicles traveling on the roadway by structure of the marker adjacent said retro-reflective structure, and (c) undergoes elastic movement during deformation of the reflector portion whereby the retro-reflective structure is cleaned of road dust and the like.

2. an elastomeric reflector portion that is formed integrally with the base portion and is elastically deformable when engaged by a vehicle passing over thE marker, the reflector portion

2. including elastically deformable retro-reflective structure that forms an exterior surface of the panel-like member, at least portions of said retro-reflective structure being depressed to a level below the level of adjacent portions of the exterior surface of the panel-like member, and said retro-reflective structure comprising discrete transparent glass microspheres, a sheet of elastomeric material in which the glass microspheres are partially embedded, and a base elastomeric part of the panel-like member to which the sheet of elastomeric material is adhered, whereby as the retro-reflective structure is stretched, the distance between the centers of adjacent glass microspheres increases until the stretching force is removed, whereupon the retro-reflective structure returns with force to its original shape, at least part of said retro-reflective structure being located on the reflector portion such that when the marker is in place on a roadway, said part of the retro-reflective structure (a) is in position to retro-reflect light to vehicles traveling toward the marker when the marker is in place on the roadway, (b) is protected from contact with the wheels of vehicles traveling on the roadway by structure of the marker that forms said adjacent portions of the exterior surface of the panel-like member, and (c) undergoes elastic movement during movement of the panel-like member whereby the retro-reflective structure is cleaned of road dust and the like.

5. A marker of claim 1 in which the retro-reflective structure comprises an elastomeric support sheet and a monolayer of transparent glass microspheres partially embedded in one side of the support sheet and covered over their embedded surfaces with reflective material, and the support sheet is adhered to the reflector portion.

6. In combination, A. a roadway, and B. a roadway marker of claim 1 attached to a recessed portion of the roadway, such that the deformation of the reflector portion moves substantially all of the reflector portion into the recessed portion.

7. A roadway marker comprising

8. In combination, A. a roadway, and B. a roadway marker of claim 7 attached to a recessed portion of the roadway.