GB1578834A

GB1578834A - Road marker

Info

Publication number: GB1578834A
Application number: GB16861/77A
Authority: GB
Original assignee: Amerace Corp
Current assignee: Amerace Corp
Priority date: 1976-04-30
Filing date: 1977-04-22
Publication date: 1980-11-12
Also published as: FR2349681B1; ZA772482B; BE854093A; JPS6115203B2; FR2349681A1; DE2719877C2; AU509290B2; DE2719877A1; JPS52144123A; NL7704755A; AU2473377A; SE7704892L; CA1083111A

Description

(54) ROAD MARKER (71) We, AMERACE CORPORATION, a Corporation organized and existing under the laws of the State of Delaware, United States of America, of 245 Park Avenue, New York, State of New York, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by whichiit is to be performed, to be particularly described in and by the following statement:: In prior British Patent 1 079 119 there is disclosed a road marker adapted to be placed on highways and in which the road marker front face is inclined at a predetermined angle to the roadway surface so that a self-cleaning effect is provided by virtue of that predetermined angle, whereby that marker achieves initial optical efficiency and the optical deterioration arising out of contact with tires of oncoming vehicles is substantially reduced by allowing the face to be periodically wiped clean by contact with such vehicle tires. In addition, there is disclosed in that patent a cube-corner reflex reflective optical system in which the cube axes of the cubecorner reflective element are inclined so as to be substantially coincidental with the nominal incoming refracted ray.Road markers disclosed in patent 1 079 119 similar to the structure disclosed therein have been extremely successful in operation, and several millions of them have been installed, primarily in areas where no snowplowing of the roads is required. The height of the earlier road marker precluded its practical use under snow plow conditions. Also, such road marker, while highly effective as a night-time signal, is substantially ineffective as a day-time marker, because of the nature of its construc tion, and, in particular, the large metallized area of the reflective portion thereof, which metallizing is required because of the epoxy fill.

As disclosed in patent 1 079 119, mech anical abrasion decreases when the angle of the front face of the lens portion of the marker is increased; however, as that angle increases, the cleaning action obtained by tire wiping on the front face of the lens decreases. The prior patent further discloses that there is an optimum balance of adequate wiping and limiting of abrasion, and optimum optical effectiveness is achieved, when the angle of the front face of the lens member is disposed at 30"to the horizontal, with a satisfactory result being obtained where such angle is between 15"and 45q However, when such road markers are used in areas where, in winter months, abrasive materials such as sand and salt are deliberately distributed over the roadway surface, the abrasion problem becomes particularly acute, as the wiping action of the vehicle tires, com- bined with those abrasive materials, tends to scratch and grind the front face of the lens and diminish the optical effectiveness of the reflex reflective quality of the marker.

Applicants, while utilizing some of the features disclosed in the aforementioned prior art, provide a novel structure which has abrasion-resistant and cleaning qualities in a durable road marker having several advantages over those disclosed.

According to the present invention there is provided a road marker adapted for engagement with an underlying roadway for providing a marking visible from an oncoming vehicle on the roadway surface, said marker comprising a lens member of light-transmitting synthetic resin including a front face having a light receiving and refracting portion arranged to be inclined at an angle of at least 15 to the associated roadway surface and a rear face having reflex reflective means on at least a portion thereof for reflecting light transmitted through said light receiving and refracting portion back toward the source thereof, and a thin sheet of glass having a thickness not greater than 0.008 inches fixedly disposed on said light receiving and refracting portion in an area thereof optically overlying at least part of the reflex reflective means, aaid thin sheet of glass being operable to reduce the degradation of optical efficiency which would otherwise be caused by abrasive tire contact on said light receiving and refracting portion.

In order that the present invention may be more clearly understood and readily carried into effect, reference will now be made to the accompanying drawings, in which Figures 1 to 10 show road markers for a complete understanding of the invention and Figures 11 and 12 show the present invention.

Figure 1 is a partially section perspective view of a road marker, Figure 2 is a plan view of the marker shown in Figure 1, Figure 3 is an end elevational view of the marker shown in Figures 1 and 2.

Figure 4 is an enlarged view of the rear face of a lens member forming part of the marker shown in Figures 1 to 3, taken in a direction perpendicular to the rear face thereof, Figure 4A is a fragmentary view, on an enlarged scale, of a portion of the reflective surface of the lens member within the circle 4A of Figure 4, but taken in a direction parallel to the cube axis of the reflector elements, Figure 5 is a plan view of the base of the marker, Figure 6 is a side elevational view of the base, taken in the direction of the line 6-6 in Figure 5, Figure 7 is a greatly enlarged cross-sectional view taken along the line 7-7 in Figure 2, with a portion thereof removed for clarity, Figure 8 is a greatly enlarged cross-sectional view of the lens member taken along the line 8-8 in Figure 4, Figure 9 is an enlarged partial view of the lens member taken along the line 9-9 of Figure 4, Figure 10 is an end elevational view of an alternative road marker, Figure 11 is a fragmentary front view of a lens member incorporating abrasion-limiting means of the present invention, and Figure 12 is an enlarged cross-sectional view of the lens member taken along the line 12-12 of Figure 11 illustrating the front of the lens member at a 450angle to the base.

Referring now to the drawings, a road marker intended primarily for use under snowplowing conditions, is shown in perspective at 10 in Figure 1.

The road marker 10 includes a body or base 20, of an opaque, light-diffusing synthetic resin having mounted thereon a lens member of light-transmitting synthetic resin generally designated as 30. The base 20 is substantially solid and is formed as a one-piece member to provide a durable structure capable of withstanding impact forces applied to the marker when it is struck by a tire of an oncoming vehicle.

The marker 10 is employed to provide a marking on a generally horizontal surface, the marking being visible from an oncoming vehicle on the roadway to delineate traffic lanes and for edge delineation, as is well recognized in the art. In addition, the marker 10 may be utilized with metal base members.

Referring now more particularly to Figures 5, 6 and 7, it will be seen that the base 20 is formed as a substantially solid one-piece member, having a generally horizontal bottom surface 21. In order to prevent sinks or shrink stresses in molding, the base 20 may be provided with a plurality of molding recesses 21A (Figures 5 and 7). The base further includes a pair of generally vertically disposed sidewalls 22 and 23 (Figure 2), and a generally horizontal top wall 24 having a rectangular channel 24A extending from one sidewall 22 to the opposite sidewall 23.

There is provided a pair of inclined support walls, 25, disposed at opposite ends of the base 20, and positioned such that in use, they will be facing the direction of oncoming vehicles. Each of these support walls 25 has a plurality of recesses 26 formed therein, which recesses have substantially rectangular openings intersecting the plane of the wall. The recesses or pockets 26 and the support wall 25 cooperate with the overlying lens member 30 in a manner hereinafter described.

The base 20 further includes side edges 27 and 28 disposed on the opposite ends of each of the respective sidewalls 22 and 23, the side edges 27 and 28 extending outwardly beyond the support walls 25, and defining a channel between the opposite side edges and the adjacent support wall 25 disposed therebetween. The base 20 also includes a tab opening 29 formed in the sidewalls 22 and 23 adjacent to the respective inclined support walls 25 for purposes of facilitating the alignment of the lens member 30 during attachment thereof to the base 20.

The lens member 30 which provides the reflective structure for reflecting light back toward the source thereof, thereby rendering the road marker highly visible at night, is best illustrated in Figures 4, 7, 8 and 9. The lens member 30 is formed of a light-transmitting synthetic resin and includes a substantially planar front face 31 and a rear face 32. As illustrated, the lens member 30 is generally rectangular and is intended to be positioned in the channel provided by the side edges 27, 28 and the support wall 25.

The rear face 32 of the lens member 30 is provided with a peripheral edge portion 33 which extends about the entire periphery of the lens member 30 (Figure 4) and includes a portion 33 and the dividing portions 34. As a generally triangular sealing bead (Figures 8 and 9). The rear surface 32 further is provided with a plurality of dividing portions 34, the dividing portions 34 intersecting the peripheral edge portion 33 at equally spaced distances therealong, thereby dividing the lens member into a plurality of generally rectangular areas circumscribed by the peripheral edge portion 33 and the dividing portions 24. As illustrated, the dividing portions 34 originally may include a raised triangular sealing bead 34A, and hereinafter, in the specification, for convenience, the dividing portions 34 may be referred to as "dividing ribs".

The lens member 30 is intended to be positioned over the inclined support wall 25 of the base 20 and rigidly secured thereto, preferably by ultrasonic welding. When properly positioned, each of the rectangular areas circumscribed by the peripheral edge portion 33 and dividing portions 34 will coextensively overlie and be in registry with the rectangular-shaped openings of the recesses or pockets 26 formed in the support wall 25, while the dividing portions 34 will overlie the dividing portions 25A of the support wall 25.

When the lens member 30 is ultrasonically welded to the base 20, the sealing beads 33A and 34A become substantially flattened as a result of the energy imparted thereto during the ultrasonic welding process, whereby the peripheral edge portion 33 directly abuts the support wall 25, as best illustrated in Figure 9, and provides a substantial welded surface area visible through the transparent lens member 30. Similarly, the dividing ribs 34 will become substantially flattened as they are sealed to the underlying dividing wall 25A of the support wall 25.

The lens member also includes an outwardly extending tab 37 adapted to be positioned within the tab opening 29 on the base 20, and serves as a locator to fix the lens member 30 in position prior to welding.

After welding the lens member 30 to the base 20, each of the dividing wall portions 25A of the support wall 25, and the peripheral portion thereof, in cooperation with the dividing ribs 34 and peripheral edge portion 33, provide a plurality of hermetically sealed cells 35 having a rectangular configuration when viewed in a direction normal to the front face 31.

The marker 10 is provided with a retrodirective cube-corner-type reflector system to effect the signal function of reflecting light back to the driver of an oncoming vehicle whose headlights illuminate the marker.

As best seen in Figure 4, the rear face of the lens member 30, in those rectangular areas circumscribed by the dividing ribs 34 and peripheral edge portion 33, is configurated to provide a plurality of cube-corner-type retro-directive reflector elements 40. In the embodiment illustrated herein, the cubecorner elements 40 are intended to be generally rectangular when viewed in a direction along the line of the cube axis, as best illustrated in Figure 4A.

Each of the cube-corner elements 40 includes cooperating faces 41, 42 and 43, respectively, the faces intersecting to form first and second and third dihedral angles in a manner well known to those skilled in the art. In the embodiment illustrated, two of the dihedral angles would be on the order of substantially 90"whereas the third dihedral angle would be formed at an angle significantly different from the first and second dihedral angles, so that the light reflected by such cube-corner element is caused to be diverges to a greater extent in one direction than in the other. One such structure is set forth in greater detail in British Patent No.

1 458 434, In the illustrated embodiment, the different dihedral angle is formed between those faces designated as 41 and 42 in Figure 4A, whereby the reflectivity of the reflector will be substantially increased at a greater observation angle, as more fully demonstrated hereinafter.

As seen in Figure 7, the apices of the cube-corner reflective elements 40 extend beyond the peripheral edge portion 33 and the dividing ribs 34, and into the cell 35, when the lens member 30 is secured to the base 20. Although in the embodiment illustrated the cells 35 are substantially large and open, it should of course be understood that the pockets 26 may be recessed less deeply than indicated, and, in fact, the apics of the cube corners 40 may contact the underlying surface 26A defining the interior boundary of the recess 26 thereby further to strengthen the lens member 30 and provide additional support therefor as the lens member is contacted by a tire of an oncoming vehicle.

To facilitate installation of the marker on an underlying roadway surface, or on a metal casting in the event the marker 10 is used in snowplow country, an adhesive impactabsorbing material or pad 15 is secured to the bottom surface 21 of the base 20. The pad 15 may comprise an elastomeric polymeric adhesive material such as, for example, butyl rubber. A protective sheet of release paper 16 is applied to the bottom of the pad. In use, the paper 16 is peeled from the pad 15 and the marker 10 pressed onto the roadway surface.

In installation it may be desirable to use a suitable primer on the roadway to enhance securement of the marker.

It is believed that the impact-absorbing material 15, together with the low profile of the marker 10 achieved by the low height thereof relative to the roadway surface, ettects both a reduction of and absorption of some of the impact energy mormally transmitted through to the underlying road surface.

It is also believed that the low profile allows the marker 10 to be ingested by a tire body so that the tire body rolls over the marker 10 and is still partially supported by the roadway surface, rather than causing the full load of the tire to impact upon the marker, which is what is thought to happen with existing markers of a higher elevation.

Moreover, it is further believed that the low profile, in combination with the impactabsorbing material 15 on the bottom surface 21 of the base 20, renders the individual cell structure formed by the combined lens member 30 and base 20 more resistant to impact damage.

There is an optimum balance obtained in maintaining optical effectiveness by limiting abrasion and achieving adequate wiping or cleaning of the front face of the marker upon contact by a moving tire. Such optimum balance is achieved when the angle of the front face of the lens member is disposed at approximately 300 to the horizontal, with a satisfactory result being obtained where such angle is approximately from 150to 45".

However, the abrasive action on the front face of the marker due to tire contact becomes a much more critical factor than the aforementioned wiping or cleaning action when the marker is used where abrasive materials are purposely placed on the road. Thus, in an area where salt or sand is put on the road during the wintertime, the wiping action by such abrasive materials on contact betwen the tire and front face of the lens member causes more serious damage to the front face than is the case where those markers are located in other areas of the country where abrasive materials are not on the roadway.

In order to minimize the loss of reflectivity due to abrasion, and to prolong the reflective qualities or optical efficiency of the marker under such conditions, the front surface 31 of the lens member 30 of the marker is preferably inclined at an angle of 45" relative to the horizontal surface 21 of the base 20. It will be appreciated that the effects of abrasion may be further minimized by increasing the angle of the front face about 45 ; however, it is believed that at front face angles above 600, the cleaning and wiping action by tire contact will be inadequate to maintain optical effectiveness.

It is also known that the front surface reflection loss due to the inherent nature of the material of the lens member itself, is less at 450than at 300. As an example, the typical front surface reflection loss of a road marker in which the front surface of the lens is located at 300 to the horizontal would be approximately 24%, whereas the front surface loss with the reflector at 450 to the horizontal would only be 12%. Also, by inclining the front face of the marker at 450, there is a smaller area exposed to contact by automobile tire studs or stones carried in the tire treads, and also the pressure on the front surface is reduced.Further, by inclining the front face of the marker at 45 , it is possible to further reduce the overall height of the marker because there will be a lesser inclination of the cube axis relative to the horizontal than is provided in prior markers and it will not be necessary to tilt the bottom row of cubecorner elements as much.

It is desired to provide abrasion-limiting means which permit an increase of the front face angle thereby improving operation of the marker while at the same time providing a substantial reduction in abrasion on the portions of the lens member having reflective elements thereunder, thereby reducing the degradation of optical efficiency normally caused by abrasive tire contact, while also allowing adequate cleaning of the front face of the lens member by tire action on the lens member, thereby enhancing the optical efficiency of the marker.

In the marker shown in Figure 1, the abrasion-limiting means takes the form of raised ridges 45 carried by the front face of the ]ens member 30 and raised thereabove and extending in use generally parallel to the direction of traffic. The ridges 45 are equally spaced along the front face and are respectively disposed directly over and in alignment with and substantially coextensive with the dividing ribs 34 on the back face 32 of the lens member 30, whereby the ridges 45 do not interfere with the operation of the reflex portions 40 on the lens member.

The ridges 45 may be integrally molded with the lens member 30, or, if desired, they could be made of a more abrasion-resistant material than the lens member and thereafter secured to the lens member 30 by welding or adhesive, thereby to provide further protection for the front surface of the marker, The raised ridges 45 serve to absorb substantially the full impact forces and abrasive contacts caused by tires striking the front of the marker, thereby minimizing abrasion on the other portions of the lens member 30 so as to protect the front face 31 from excessive abrasion, and particularly from a grinding action by sand or salt being disposed on the roadway.The ridges 45 also serve to form a plurality of channels on the front face 31 of the lens member 30 which permit adequate cleaning of the front face 31 of the lens member 30 by tire action on the lens member 30, which action includes a combination of high velocity air and rainwater being forced through the channels by passing tires. In addition to improved abrasion resistance, the ridges 45 provide structural strength to the lens member 30, further serving to maintain the integrity of the cells 26 and reflector elements 40 under tire impact.

While the ridges 45 have been disclosed as being used with a lens member which includes dividing ribs on the back face thereof, the ridges being respectively disposed directly over and in alignment with the dividing ribs, it will be understood that the raised ridges 45 could also be used with other forms of road markers such as that disclosed in the aforementioned Patent No 1 079 119.

As previously described, the side edges 27 and 28 extend outwardly beyond the inclined support walls 25 of the base 20, and provide a channel between the side edges and the support wall 25 within which is disposed the lens member 30. The side edges 27 and 28 provide further structural support and protection for the lens member 30 adjacent those areas in which the ultrasonic welding occurs at the corners of the marker, thereby serving to substantially protect the integrity of the marker at those points. It will also be noted that the side edges 27-28 and the front edges of the protective barrier for the front face 31 of the marker 10.

Figures 11 and 12 show a road marker of the present invention and will be described more fully after the completion of the description of the road marker illustrated in Figures 1 through 10.

As illustrated, the marker 10 may be provided with a metal cover plate 19 to overlie and protect the entire top wall 24 thereof; the cover plate 19 also extending beyond and overlying the upper edge of the lens member 30, as best seen in Figure 3. The metal cover plate 19 is intended to be used on those embodiments of the marker 10 which are to be installed in a metal casting and subjected to possible contact by studded snow tires passing over the top of the marker, the cover plate serving to provide additional protection against such members. The cover plate 19 may be adhesively secured to the top wall 24, or, alternatively, a second impact absorbing pad (not shown) may be fixedly secured therebetween.

The rectangularly shaped longitudinally extending channel 24A provided in the cover plate 19 and in the top wall 24 is adapted to receive a retaining member in a well-known manner, the retaining member serving to further hold the pavement marker in place on the underlying metal casting, if such retaining member is desired.

The arrangement of the lens member 30 with its peripheral transparent edge portion 33 and dividing ribs 34, and the underlying light-diffusing opaque support wall 25, imparts substantial daytime visibility to the marker 10, rendering it of greater utility than prior markers.

In the illustrated embodiment, the area occupied by the peripheral edge portion 33 and the dividing ribs 34, is substantially coextensive in total area to that occupied by the retrodirective reflector elements 40 in those areas circumscribed by the edge portion 33 and the dividing ribs 34.

Further, the use of the rectangular cells 35 and square reflector elements 40 permits the use of vertical sidewall surfaces in each recess 26 of the marker, if desired, whereby substantially the full width of the marker 10 is provided with complete reflective elements; moreover, use of the vertical sidewalls 23 and 24 and the vertical dividing wall portions 25A with the substantially vertically disposed parallel ridges 45 results in no loss of reflective area by the ridges 45 while permitting their orientation in the optimum direction for tire contact.

The opaque, light-diffusing base 20 serves to reflect daylight impinging thereon to an observer. At a distance, the uniform spacing of the dividing ribs 34 and dividing wall portions 25A causes the marker to appear as a substantially uniform reflective body, with the cells 35 tending to disappear to the eye of the observer under daylight conditions. Alternatively, under night-time driving conditions, the uniform size and spacing of the cells 35 causes the marker to appear as a uniform reflective member, the dividing ribs 34, which improve daytime visibiltiy, tending to disappear under evening driving conditions.

The road marker of the invention is shown in Figure 11 which depicts a fragmentary front face of a lens member 50, generally similar in plan configuration to the lens member 30, except the lens member 50 does not include the raised ridges 45 as are on the front face of the lens member 30. On the rear face of the lens member 50 there are reflex reflector elements 52 substantially identical to the reflector elements 40.

The abrasion-limiting means comprises a thin sheet of untempered and non-annealed glass 55. The glass 55 is bonded to the front face of the lens member 50 in at least those areas overlying the reflex reflector elements 52. To protect the perimeter edges of the glass sheet, the front face of the lens member 50 is provided with a raised lip 51 extending about the entire periphery thereof.

The lens member 50 is provided with rear dividing ribs 53 so that a marker 10 employing the lens 50 will have substantially the same daytime and nighttime reflective characteristics as a marker employing the lens member 30. While the glass sheet 55 is shown as covering those portions over the areas occupied on the rear face by the ribs 53, it should be understood that the lens member 50 could be provided with raised ridges 45, with a glass sheet being disposed between pairs of ridges 45, thereby utilizing both forms of abrasionlimiting means disclosed.

The glass sheet 55 may be adhesively bonded to the front face of the lens member by first applying an adhesive coating to the glass or lens member and then placing the glass in position on the lens member with the adhesive therebetween. Alternatively, the glass may be bonded to the lens member during molding of the lens member.

It has been found that glass having a thickness of about .005 inch, bonded with an adhesive of about .001 inch produces an optimum impact resistance to fracture; but it is believed that glass in the range of .003 to .008 inch thick and an adhesive bond of up to .002 inch thick will produce satisfactory results.

A suitable glass is that available from Corning Glass Works, as Cover Glass No. 2.

A suitable adhesive for bonding such glass is Hooker Chemical's Hetron [Trade Mark] 26869. After application of the adhesive and glass to the lens member, the unit should be cured at 70 C to perfect the bond. When the lens member is molded about the glass, the bonding surface of the glass may be coated with a resin having an affinity for glass and the lens material. Such resins could be in the silane family, such as Dow Corning's Compound Z-6020 or Z-6040.

It has been found that markers, such as the type disclosed in the patent 1 079 119 when provided with the preferred glass thickness and adhesive disclosed herein, have a retained reflectivity, or improved optical efficiency, in the range of 12 to 25 times that of an unmodified marker of the type shown in that prior patent, when exposed to the same conditions. That is, markers provided with the abrasion-limiting means disclosed herein would incur optical degradation of only 1/4 to 1/7 that of identical markers without such abrasion-limiting means.

The front face of the lens member is disposed at an angle of approximately 45010 the horizontal surface 21 , while the support wall 25 is inclined at an angle of approximately 41".The ridges 45 on the front face 31 of the lens member 30 are positioned at angles of approximately 53"relative to the horizontal surface 21 and similarly the side edges 27 and 28 forming extensions of the sidewalls 22 and 23 also are inclined at angles of approximately 530 relative to the underlying surface 21. It will be apparent from the foregoing that the outer edges of the ridges 35 and the side edges 27 and 28 therefore are substantially coplanar and define a barrier plane which provides a protective area for the front surface of the lens member.The ridges 45 may have a width or thickness of approximately .07 winches, a height above the front face 31 of approximately .06 inches, and the side surfaces of the ridges are inclined with respect to the vertical at draft angles of approximately 5q The base 20 may be made of acrylonitrile butadeine styrene (commonly known as ABS), glass-filled ABS, methyl methacrylate or rubber-modified methyl methacrylate or lexan; while the lenses 30 or 50 may be of methyl methacrylate or a rubber-modified methyl methacrylate or a polycarbonate such as lexan.

Normally, the lens and base will be chosen to provide the same colors, day and night, with specific color being determined by the specific function of the marker, e.g. lane delineation vs. median edge delineation.

The road marker illustrated in Figure 10 is primarily intended to be used independently of any metal housing or casting. In that marker the top wall 24, rather than being generally horizontal, as in the marker illustrated in Figure 1 , instead has surfaces 47 and 48 which incline upwardly in the same general direction as the support walls 25, the inclined surfaces 47 and 48 forming a crown above the height of the lens member to provide additional reflective body area for reflecting daylight back to an observer. The metal cover plate 19 would of course not be used with this marker which would preferably be used under non-snowplowable conditions.

The above detailed description is provided by way of example only. Various details of design and construction may be modified without departing from the scope of the invention as defined in the appended claims.

WHAT WE CLAIM IS: 1. A road marker adapted for engagement with an underlying roadway for providing a marking visible from an oncoming vehicle on the roadway surface, said marker comprising a lens member of light-transmitting synthetic resin including a front face having a light receiving and refracting portion arranged to be inclined at an angle of at least 15 to be associated roadway surface and a rear face having reflex reflective means on at least a portion thereof for reflecting light transmitted through said light receiving and refracting portion back toward the source thereof, and a thin sheet of glass having a thickness not greater than 0.008 inches fixedly disposed on said light receiving and refracting portion in an area thereof optically overlying at least part of the reflex reflective means, said thin sheet of glass being operable to reduce the degradation of optical efficiency which would otherwise be caused by abrasive tire contact on said light receiving and refracting portion.

2. A marker as claimed in claim 1, wherein the thickness of said glass sheet is at least 0.003 inches.

3. A marker as claimed in claim 1, wherein the thickness of said glass sheet is approximately 0.005 winches.

4. A marker as claimed in any of claims 1 to 3, wherein said glass sheet is fixedly disposed on said light receiving and refracting portion by an adhesive bonded to said lens member and to said glass sheet.

5. A marker as claimed in claim 4, wherein said adhesive is not greater than 0.002 inches in thickness.

6. A marker as claimed in claim 4, wherein said adhesive is not greater than 0.001 inches in thickness.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. adhesive of about .001 inch produces an optimum impact resistance to fracture; but it is believed that glass in the range of .003 to .008 inch thick and an adhesive bond of up to .002 inch thick will produce satisfactory results. A suitable glass is that available from Corning Glass Works, as Cover Glass No. 2. A suitable adhesive for bonding such glass is Hooker Chemical's Hetron [Trade Mark] 26869. After application of the adhesive and glass to the lens member, the unit should be cured at 70 C to perfect the bond. When the lens member is molded about the glass, the bonding surface of the glass may be coated with a resin having an affinity for glass and the lens material. Such resins could be in the silane family, such as Dow Corning's Compound Z-6020 or Z-6040. It has been found that markers, such as the type disclosed in the patent 1 079 119 when provided with the preferred glass thickness and adhesive disclosed herein, have a retained reflectivity, or improved optical efficiency, in the range of 12 to 25 times that of an unmodified marker of the type shown in that prior patent, when exposed to the same conditions. That is, markers provided with the abrasion-limiting means disclosed herein would incur optical degradation of only 1/4 to 1/7 that of identical markers without such abrasion-limiting means. The front face of the lens member is disposed at an angle of approximately 45010 the horizontal surface 21 , while the support wall 25 is inclined at an angle of approximately 41".The ridges 45 on the front face 31 of the lens member 30 are positioned at angles of approximately 53"relative to the horizontal surface 21 and similarly the side edges 27 and 28 forming extensions of the sidewalls 22 and 23 also are inclined at angles of approximately 530 relative to the underlying surface 21. It will be apparent from the foregoing that the outer edges of the ridges 35 and the side edges 27 and 28 therefore are substantially coplanar and define a barrier plane which provides a protective area for the front surface of the lens member.The ridges 45 may have a width or thickness of approximately .07 winches, a height above the front face 31 of approximately .06 inches, and the side surfaces of the ridges are inclined with respect to the vertical at draft angles of approximately 5q The base 20 may be made of acrylonitrile butadeine styrene (commonly known as ABS), glass-filled ABS, methyl methacrylate or rubber-modified methyl methacrylate or lexan; while the lenses 30 or 50 may be of methyl methacrylate or a rubber-modified methyl methacrylate or a polycarbonate such as lexan. Normally, the lens and base will be chosen to provide the same colors, day and night, with specific color being determined by the specific function of the marker, e.g. lane delineation vs. median edge delineation. The road marker illustrated in Figure 10 is primarily intended to be used independently of any metal housing or casting. In that marker the top wall 24, rather than being generally horizontal, as in the marker illustrated in Figure 1 , instead has surfaces 47 and 48 which incline upwardly in the same general direction as the support walls 25, the inclined surfaces 47 and 48 forming a crown above the height of the lens member to provide additional reflective body area for reflecting daylight back to an observer. The metal cover plate 19 would of course not be used with this marker which would preferably be used under non-snowplowable conditions. The above detailed description is provided by way of example only. Various details of design and construction may be modified without departing from the scope of the invention as defined in the appended claims. WHAT WE CLAIM IS:

1. A road marker adapted for engagement with an underlying roadway for providing a marking visible from an oncoming vehicle on the roadway surface, said marker comprising a lens member of light-transmitting synthetic resin including a front face having a light receiving and refracting portion arranged to be inclined at an angle of at least 15 to be associated roadway surface and a rear face having reflex reflective means on at least a portion thereof for reflecting light transmitted through said light receiving and refracting portion back toward the source thereof, and a thin sheet of glass having a thickness not greater than 0.008 inches fixedly disposed on said light receiving and refracting portion in an area thereof optically overlying at least part of the reflex reflective means, said thin sheet of glass being operable to reduce the degradation of optical efficiency which would otherwise be caused by abrasive tire contact on said light receiving and refracting portion.

7. A marker as claimed in claim 1, wherein

said glass sheet has a thickness of approximately 0.005 inches and is fixedly disposed on said light receiving and refracting portion by an adhesive having a thickness of between 0.001 inches and 0.002 inches bonded to said lens member and to said glass sheet.

8. A marker as claimed in claim 1 or claim 7, wherein said glass is untempered.

9. A road marker substantially as hereinbefore described with reference to Figures 11 to 12 of the accompanying drawings.