GB2175943A - Road surface marker - Google Patents

Abstract

A road surface marker comprising a reflector unit (30) mounted in a suitable housing for securing to the road surface, said reflector unit including a reflector element made of synthetic plastics material (41) and surfaced at its substantially flat front face with a light transmitting material (43) which is substantially more abrasion resistant than said synthetic plastics material. The lower edge (48) of the reflector is provided with a radiussed edge to minimise abrasion. The reflector is mounted to an elastomeric body (30) which is formed with tension reduction channels which enable the body to flex repeatedly without tearing. <IMAGE>

Description

SPECIFICATION Road surface marker This invention relates to road surface markers and, more particularly, to reflective markers of the type generally referred to as road studs or cat's eyes.

Cat'sere markers generally consist of a metal casting disposed in a pocket cut into the road surface, in which is positioned a core of a resilient material such as a white or brightly coloured elastomeric or rubber composition, supported entirely or partially within the recta ng u la r or otherwise shaped cavity of the metal casting. The core generally is provided with two glass bead type reflectors which are intended to retro-reflectthe headlights of approaching vehicles.

The core is comprised generally of elastomeric or rubber material, such as natural rubber, and includes a portion which can wipethefrontface ofthe glass lens as the upper marker body is depressed by the contact of a tire thereon. Lens members ofthe cube-corner type, if molded of glass, could be used but molded glass cube-corner reflectors do not have the accuracy or reflectivity of plastics cube-corner type reflectors and consequently for many years glass has not been used to make cube-cornertype roadway or automotive reflectors. Indeed plastics has supplanted glass for cube-corner reflectors for both automotive and highway uses since the mid-i 940's.

However since such plastics is subject to abrasion, its use as a lens element in the conventional rubber cat's eye core, where it is subjected to constant wiping action, results in wear ofthe front face, which degrades the reflectivity ofthe markerto a point where it would no longer be effective. While it has been ascertained that positioning a plastics reflector element at an appropriate angle will effecta balancing combination ofwiping and abrasion, such angular construction cannot conveniently be used in existing cat's eye castings because the wiping action could no longer be accomplished either by a tire or by a single wiping element in the core.Plastics cube-corner type reflectors are advantageous over glass beads because they have a higher specific intensity than glass beads, they can be manufactured more economically and, most importantly, they can be consistently molded to provide relatively uniform specific intensity, whereas glass beadsvarywidely in reflectance.

Viewed from one aspect the present invention provides a reflector unit for a road surface marker, such a reflector unit being adapted to be mounted in a suitable housing securable to the road surface, and including a reflector element made of synthetic plastics material and surfaced at its substantially flat front face with a lighttransmitting material which is substantially more abrasion resistant than said synthetic plastics material, said reflector element having a radiused lowermost edge.

The provision ofthe reflector with a radiused lower edgeminimizestheabrasionthatcanoccurwhen a rectangular, relatively sharp edge is repeatedly rub bed orwiped against a neoprene wiper blade. Use of such a radiused surface avoids the "digging" effect that can occur should the upward and downward movement of the core be slightly off a true vertical axis.

It has also been found advantageoustoform tension reduction channels in the core to enable the core to flex repeatedly withouttearing.

In a preferred form the invention provides a reflector assemblyforuse in a metal housing to provide a road surface marker. The metal housing has a generally rectangular cavity with a horizontal base formed therein,frontand rearwallsadaptedtobepositioned perpendicularto the direction of traffic when the housing is secured to the roadway surface, and opposed side walls provided with pairs of integral attachment fingers extending into the cavity, said front, rear and side walls having upper edges extending above the associated road surface when the metal housing is fixedly installed thereon. The reflector assembly comprises a resilient elastomeric body adapted to be removably positioned in the associated metal housing.The body includes a generally rectangular hollow base portion and an upper lens housing portion; the hollow base has a pair of oppositely disposed side walls, each having apertures therein adapted to receive therein the opposing pairs offingers of the associated housing side walls when the body is positioned in the associated cavity. At least oneofthefront or rearwalls ofthe hollow base is provided with an inwardly extending wiper blade extending substantially from one side wall to the other side wall.The lens housing includes generally parallel front and rear walls to be juxtapositioned with the associated front and rear walls of the associated metal housing and includes opposed inwardly inclined side walls extending upwardly from the base portion side walls and joined to a generally flat upperwall positioned almost parallel to the top edges ofthe associated housing. The lens housing has a lens retainer block formed integrally therewith, and corres ponding end ofthefrontorrearwallsofthelens retainer block is provided with a recess therein adapted to receive an elongated lens member.The lens member has a generally flat front face terminating at its lowermost edge in a radiused shoulder position and is provided on the rearface thereofwith a plurality of cube-cornertype reflecting elements for reflecting lightincidentonthefrontfacegenerally parallel and backto the source thereof. The lens member informed of a synthetic organic resin and is provided with an outer lig httransmitting protective surface generally coextensive to the reflective area of the lens member, the outer surface being formed of a more abrasion resistant material than the lens member.

When the body is disposed in the associated housing, engagementofthe lens housing byavehicle tire will cause the lens housing to be depressed within the hollow area provided bythefollow base and into the cavity defined bythe associated housing, and upon such movement the lens memberandthe associated abrasion resistant surface formed thereon will effecta wiping movement relativeto the associ ated wiping blade formed on the base member, and the lens housing then will return to the operable position thereof.Tension reduction channels may be formed in each retainer blockto enable the block to stretch and distend without peripheral tearing while the core is being depressed or is returning to its unstressed operative, or at-rest position.

An embodiment ofthe invention will now be described by way of example with reference to the accompanying drawings in which Fig. lisa perspective view of a reflector assembly accordingto an embodimentofthe present invention, with an associated metal housing shown partially in phantom; Fig. 2 is a perspective ofthetraditional housing used for a cat's eye marker, with a reflector assembly according to an embodiment ofthe present invention shown in phantom; Fig. 3 is an enlarged partial sectional view ofthe lens assembly of the reflector assembly, taken along lines 3-3 in Fig 6; Fig. 4 is a bottom plan viewofthe reflector assembly showing the placement of the tension reduction channels;; Fig. 5 is a sectional view ofthe reflectorassembly taken in the direction ofthe arrows 5-5 in Fig. 4; Fig 6 is a sectional view ofthe unstressed reflector assembly taken in the direction ofthe arrows 6-6 in Fig. 1, and illustrates the assembly in the normal operative position; Fig. 7 is a viewsimilarto.view Fig. 6, but illustrating the lens housing portion ofthe reflector assembly in the depressed condition underthe action of a vehicle tire; Fig. 8 isa detail ofthe circled portion C of Fig. 7, illustrating the radiused lower edge ofthe reflector lens; Fig. is a view along 9-9 of Fig.4, showing the tension reduction channels;; Fig. 10 shows the tension reduction channels of Fig.

9when the body is in its operative unstressed position; and Fig. 11 shows the tension reduction channels when the body is stressed.

Referring nowto the drawings, and more particularlyto Figs. 1 and 2 thereof, reference numeral 10 designates a road markerwhich has as its major components a metal housing in the form of a casting 20 ofthetype generally used for a conventional road stud or cat's eye marker (which may be ofthe type similarfor example to that shown in U.S. Patent No.

2,703,038) in which is mounted a reflectorassembly comprising a core member 30, preferably formed of Neoprene and which includes a reflective lens mem bey 40 for providing a signal function.

Metal casting 20 has a generally rectangular cavity 21 formed therein with a horizontal base 22. The metal casting 20 has parallel front and rear walls designated generally as 23, intended to be disposed generally perpendicularto the direction oftrafficflowwhen the casting is secured to the roadway surface designated "R" in Fig. 2. The casting 20 also is provided with opposed parallel side walls 24. Each of the side walls 24 is provided with pairs of integral attachment fingers 25 extending into the cavity defined by the bottom, side and front and rearwalls. Forillustration purposes, a pairofattachmentfingers 25 is shown in Fig. 6.The front, rearand side walls terminate in upper edges 26 intended to be disposed abovethe associated roadway surface when the metal casting is fixedly installed - therein, and provide an enclosure to provide some protection againstsnow plow blades and the like.

Referring now to Figs. 4 and 5, the reflector assembly, which is intended to be disposed within the otherwise conventional metal casting 20, comprises a body consisting of a resilient elastomeric core 30 adapted to be removably positioned in the associated casting 20. Thecore30 includes a generally rectangu- larhollowbase portion 31 and an upper lens housing portion 32. The entire core 30 is injection molded in a conventional and well-known fashion. The hollow base 31 has a pair of oppositely disposed side walls 33, each having apertures 34formed therein at the time of molding the core 30, which apertures 34are adapted to receive therethrough the opposing pairs of attachmentfingers 25 of the associated casting sidewalls when the core 30 is positioned in the metal casting.

The lens housing 32 includes generally parallel front and rearwalls35A intended to be parallel to the associated front and rearwalls 23 of casting 20. The lens housing 32 also includes opposed inwardly inclined side walls 36, extending inwardly and up wardlyfrom the base portion side walls 33 and integrally joined to a generally flat upperortopwall 37. The lens housing 32further is provided with a lens retainerblock50 having a generally rectangularnotch defining a lens holding "T" shaped pocket 38 on at leastone (or both as shown) ofthefrontor rearfaces thereof, and also is provided with an internal cavity 39 in the top wall 37, permitting flexing of the lens housing during depression under a vehicletire as illustrated in Fig. 7.

The lens pocket 38 (Fig. 4) is intended to receive a composite lens member 40 (Fig. 3) which provides the retroreflective function ofthe roadway marker. In the presentembodiment,the lens member40 consists of a reflector portion 41 which has a generally flat front face and is provided on the reverse face with a plurality of reflector elements 42 thereon ofthe cube-cornertype.

While no specific arrangement of cube-corner elements has been illustrated in the drawings, it will be understood that for purposes ofthis application a cube-cornertype reflector (also known astrihedral or triple mirror reflector) consists ofthree mutually prependicularfaces intended to retroreflect light in a direction generally parallel to the light incident upon the frontface ofthe lens element. The three faces need not be of equal size orequal shape and may include rectangular parallelpipeds, triangles, squares, etc. It is also known in the artthat cube-cornertype reflectors may be designed sothattheir optical axes are aligned with the nominal incidentrayforoptimum reflectivity under certain lighting conditions.

The lens 41 generally is formed of a I ig ht tra nsmitting synthetic organic resin such as polymethylmethacrylate or polyqarbonate. Polycarbonate is preferred because of its impact strength. Normally polycarbonate would not be used because of its susceptibility to abrasion compared with polumethylmethacrylate and its deterioration under untraviolet light, but a protective outer surface serves the double function of protecting against abrasion and offiltering out the effects of ultraviolet lig ht. The lens member40 is provided with a lighttransmitting protective outer surface 43 generally coextensive to the reflector area of the lens member40, the outer surface 43 being formed of a more abrasion resistant material than the lens member.Once such satisfactory material is glass having thickness of about 6 mils. Such glass may be applied to a fashion such as disclosed in U.S. Patent No.4,232,979.

The lens 41 further is provided with a series of parallel, rearwardly extending dividing and peripheral walls 44, which are in turn hermetically secured to a rigid backing plastic member 45. The rear member 45 preferably is "T" shaped such that it has a rearwardly extending leg 45A to facilitate mounting in the "T" shaped pocket 38 ofthe lens housing portion 32. The reflector lens member 40 may be adhered within the lens pocket 38 by use of an appropriate adhesive whereby the lens member is fixedly secured to the elastomeric core 30. Finally, each ofthe front and rear walls 35 ofthe core 30 is provided with a slitorcut line 46 therein which extends substantially between the sidewalls33andseparatestheupperlens housing portion 32 from the base portion 31.The slit is provided in such a fashion so as to leave an inwardly extending lip which forms a wiper blade 47 thereon (Fig. 6). The slit also permits downward movement of the upper lens housing portion 32 pastthe blade 47 and into the hollow base portion 31.

As illustrates in Figs. 6 and 7, upon placement ofthe core 30 into the associated metal casting 20, the upper edge 26 ofthe casting and the top wall 37 will be disposed approximately3/4"abovethe road surface. As a vehicle tire rolls overthe upper body portion 32 and top wall 37, itwill cause wall 37 to flex and to be depressed into the hollow area provided bythe base member 31 and into the cavity defined by the associated casting. Upon such movement, the lens member 40, and particularly abrasion resistantsurface 43, will be moved pastthewiper blade 47 contained on the lower body portion 31 of core 30.

Such movement will affect a debris cleaning and wiping function ofthe front abrasion resistant surface 43 ofthe lens member, thereby maintaining the lens member clean and keeping it in an efficient condition.

As seen in Fig. 8, lens member 40 is formed with a radiused edge 48 thereon to reducedthe drag and resultant wear on wiper blade 47,to extend the efficient wiping action of wiper blade 47 and to shield the lower, sharp edges of surface 43. Shielding the lower edge alleviates chipping of surface 43 and gouging ofthe inner surface of wall 35. A preferred radius is 0.12 inch.

Providing cavities 39,53 and 54 in top wall 37, permits substantial flexing ofthe upper lens housing portion 31 and provides a substantial support area behind the lens member40to prevent deleterious stress which could cause cracking or breakage thereof. As seen in Fig. 9, tension reduction channels 48 are formed in lens retainer block 50. In the embodiment herein shown, tension reduction channels 48 are generally perpendicularto, and communicate with slot 49 of block 50, and open onto cavity 39. Slot 49 is intended to receive leg 45A of reflector 40.

As lens housing 32 is depressed (as seen in Fig. 7), elastomeric core 30 flexes, and tension reduction channels 48 allows core 30 to distort more freely in a horizontal direction than if core 30 were formed without channels 48. In this manner,the life of core 30 is extended by reducing the fatigue associated with repeated twisting, compression, stretching and flexing of elastomeric castings.

It is to be understood that channels 48 may be placed throughout core 30, where desired, to provide protection against material fatigue. Also, it may be appropriate to form the wiper blade 47so that it is curved inwardly in the center thereof, thereby to assure uniform pressure on the lens member 40.

Traditionallythe cat's eye marker has used two glass beads each having a diameter of about .43".

Underthe present system, a single lens member 40 is used; it has a dimension of approximately3/4" high by 1 -" wide and it will provide specific intensity at 0.2" observation angle and 0" entrance angle ofapproximately five times the specific intensity of the typical cat's eye. One would have to use at least five glass bead elements in a similar sized core to obtain the same reflectivity. Using more than two beads is not practical however,fora number of reasons: it would weaken the core element by having the additional lens elements therein; also, there would be incomplete wiping caused by the serrated type wiping surface which would be required. Finally, there is not enough area on the housing to accommodate morethantwo glass beads in their metal cans.It has also been observedthatthe metal prongswhich hold the metal cans in the cat's eye assembly may become exposed as the assembly is worn, weakening the assembly, and possibly exposing sharp points to tires, a result which is avoided in the present arrangement.

The elastomeric body 30 is prererablyformed of Neoprene having a hardness in the range of 48 to 60 durometer, Shore A. In addition, a preferred blend of neoprene will also include a lubricantorcombination of lubricants to further reduce friction andwear upon lens member 40. A lubricating system that has been successfully employed comprises Silane A-I 89, petrolatum, wax petrolatum, and a blend including 20% SilaneA-189,40% petrolatum, and 40% wax petrola- tum.This system is present in a proportion ofabout 2% by weight of the resulting neoprene elastomer, and will extend the useful life of the core as compared to a coreformed of natural rubber; yet itis softand flexible enough to deform and provide the necessary wiping action. Neoprene also has characteristics of not "breaking down" to leave residue on the reflector.

As seen in Figs. loaned 11,core 30 is distorted when depressed, and tension reduction channels 48 allow core 30to absorb the potentially destructive stress forces by allowing core 30 to stretch at critical stress points to a greater degree than if core 30 were formed without channels 48. This reduces the stress concentration to which the core is subjected. This occurs partially as seen in Fig. when core 30 "lengthens" as core segments 52 are stretched during depression of core 30, wherebythe sections of the core about the opposite ends of said lens member effectively lengthen such that during compression of said upper member body, said sections are both deflected and elongated thereby to reduce the tension therein.In this context, the term "stretch" indicates the distribution offorces along core segments 52, with said core segments having relativelynarrowed cross-section configuration, and the elongation of said core segments to absorb said forces. Also, adding to the capacity of core 30 to absorb such forces is the rounding ofthe internal surfaces of core 30, such as shown at 51 of Fig. 4.

It is to be clearly understood thatthere are no particularfeatures oftheforegoing specification, or of any claims appended hereto, which are at present regarded as being essential to the performance ofthe present invention, and that any one or more of such features or combinations thereof may therefore be included in, added to, omitted from or deleted from any of such claims if and when amended duringthe prosecution of this application or in the filing or prosecution of any divisional application based thereon.

Claims (18)

CLAIMS:

1. A reflector assembly for use in an associated metal housing to provide a road surface marker, the associated metal housing having a generally rectangularcavity with a horizontal base formed therein, front and rearwalls adapted to be positioned perpendicularto the direction oftrafficwhen said metal housing is secured to the road surface, and opposed side walls provided with integral attachment fingers extending into the cavity, said front, rear and side walls having upper edges intended to be above the associated road surface when the metal housing is fixedly installed thereon, said reflector assembly comprising; a resilient elastomeric body adapted to be removably positioned in said metal housing and to extend, in a normal operative position, above said metal housing; said body including a hollow base portion of generally rectangularcross-section, and an upper lens housing portion, said hollow base portion having a frontwall, a rearwall, and a pairofoppositely disposed side walls, each said sidewall having aper tures therein adapted to registerwith and receive said opposing pairs of attachment fingers of said metal housing side walls when said body is positioned in said metal housing cavity; said lens housing portion including generally parallel front and rearwalls parallel to said front and rearwallsofsaid metal housing and including opposed inwardly inclined side walls extending upwardly from said base side walls and joined to a generally flat upperwall, at least one of said front and rearwalls ofsaid base portion being provided with an inwardly extending wiper blade extending substantiallyfrom one side wall to the other side wall; a lens retainer block integral with said lens housing portion, said retainer block having a recess therein adapted to receive an elongated lens member, said lens member having a generallyflatfrontface terminating in a radiused lowermost edge and being provided on the rearfacethereofwith a pluralityof cube-cornertype reflecting elements for reflecting light incident on said front face generally parallel and backto the sourceere, thereof, said lens member being formed of a synthetic organic resin and further being provided with an outer lighttransmitting protective surface generally coextensive to the reflective area of said lens member, said outersurface being formed of a more abrasion resistant material than said lens member, whereby upon placement of said body in the associated metal housing, engagement of said upper lens housing portion by a vehicle tire will cause said upper body portion to be forced through a range of movement into and thereafter out ofsaid hollow area provided by said base member and into the cavity defined by said associated housing, said lens member and the associated abrasive resistant surface thereon effecting awiping and debris cleaning movement againstsaid wiping blade formed on said base member during said movement, said lens housing portion resiliently returning to said normal operative position thereof.

2. A reflector assembly according to claim 1, wherein said elastomericcore is formed of Neoprene and has a hardness in the range of 48 to 60 durometers, Shore A.

3. A reflector assembly according to claim 2 wherein said Neopreneincludes a lubricanttherewithin.

4. A reflector assembly according to any of claims 1,2 or3 wherein said protective front face of said lens memberofcomprised ofglass.

5. A reflector assembly according to any preceding claim, wherein one said wiper blade is positioned in use approximately at the plane ofthe associated road surface and adjacent to thefrontface of each said lens member.

6. A reflector assembly according to any preceding claim, wherein said lens member and said wiper blade are configured and arranged so that upon movement of said lens housing portion to the depressed position and return to the said normal position said front face ofsaid lens member moves past said wiper blade and in direct contact therewith whereby said wiper blade effects a debris cleaning and wiping function on said front face.

7. A reflector assembly according to any preceding claim, wherein said lens member is fixedly secured to said lens housing portion by means of a "T" shaped section adhered to the lens member and having a leg ofthe"T"embedded in groove provided in the said lens housing portion.

8. Areflectorassembly according to anypreced- ing claim, wherein said lens housing portion includes an integral body portion depending from the upper wall thereof and disposed belowthe lower edge of said lens membertherebyto provide substantial protection for said lens member during wiping movementofthe lens member pastthewiper blade and during flexing of the body member under vehicle contacttherewith.

9. A reflector assembly according to any preceding claim, wherein said wiper blade is configured such thatthe central portion thereof between said side walls is curved inwardly toward said lens member therebyto assure uniform pressure on said lens member during wiping movement thereof past said wiper blade.

1-0. A refrectoraccording to any preceding claim, wherein said cube-corner type reflecting rearface of said lens member includes a rearwardly extending peripheral wall and a plurality of rearwardly extending dividing walls separating areas of said cube-corner elements into discrete cellular sections, and a rigid backing member secured to said walls thereby to hermeticallysealthesame.

11. A reflector assembly according to any preceding claim, wherein said elastomeric body includes means for reducing the tension generated within said body when said body isforced through said range of movement.

12. A reflector assembly according to claim 12, wherein said tension reducing means includes at least one channel formed within said lens housing portion.

13. A reflector assembly according to claim 13, wherein at least one said channel extends vertically within said lens housing portion.

14. A reflector assembly according to claim 12 or 13, wherein at least one said channel is positioned proximate one said lens member.

15. A reflectorassembly according to claim 12,13 or14wherein at least one said channel is positioned within said lens retaining block.

16. A reflector assembly according to any preceding claim, wherein the sections ofthe body aboutthe opposite ends of said lens member are lengthened such that during compression of said upper body portion, said sections are both deflected and elon gated thereby to reduce the tension therein.

17. A reflector unit for a road surface marker, such a reflector unit being adapted to be mounted in a suitable housing securableto the road surface, and including a reflector element made of synthetic plastics material and surfaced at its substantially flat frontface with a lighttransmitting material which is substantially more abrasion resistant than said synthetic plastics material, said reflector element having a radiused lowermost edge.

18. Areflectorunitfora roadsurfacemarker substantially as herein before described with refer enceto the accompanying drawings.