CA1083111A - Road marker - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A pavement marker for providing a marking signal on the roadway surface capable of reflecting light impinging thereon and for reflecting light back toward the source thereof so as to be visible to a driver in an oncoming vehicle, comprises a base hav-ing a generally horizontal bottom surface and at least one wall positioned in use in the direction of an oncoming vehicle. A lens member of light-transmitting synthetic resin is carried by the base and has a front face oriented so as to make an acute angle of between about 15° and about 60° with the base to rise above the roadway surface upon which the pavement marker is to be installed.
The base includes means cooperating with the rear surface of the lens member for providing a plurality of hermetically sealed cells, the lens member including a plurality of retro-directive cube-corner-type reflector elements in the portions thereof occupied by the cells, the reflector elements being oriented to reflect light impinging upon the front face of the lens member in the areas corresponding to the cells back toward the source thereof to render the reflector structure highly visible at night. Abrasion-limiting means in the form of a thin glass sheet overlies the front face of the lens member in the areas occupied by the re-flector elements, the glass sheet reducing the degradation of optical efficiency normally caused by abrasive tire contact on the lens member while allowing adequate cleaning by tire wiping action so that optical efficiency of the pavement marker is en-hanced. In a second embodiment, spaced, abrasion-limiting ridges parallel to the direction of traffic are carried by a portion of the front face of the lens member and raised thereabove for form-ing a plurality of channels, the ridges absorbing substantially the full impact forces and abrasive contacts of tires for minimiz-ing abrasion of the other portions of the lens member while adequate cleaning of the lens member is obtained by the action of tires, including a combination of high velocity air and rainwater being forced through the channels by passing tires.

Description

BACRGROUND OF THE INVENTION
In Canadian Patent No . 763,714 there is disclosed a pavement marker adapted to be placed on high~ays and in which the pavement marker front face is inclined at a prede-5 termined angle to the roadway surface so that a self-cleaning -effect is provided by virtue of that predetërmined angle, whereby that pavement marker achieves initial high optical efficiency and the optical deterioration arising ou of con-tact with the tires of oncoming vehicles is substantially re-duced by allowing the face to be periodically wiped clean by contact wlth such vehicle tires. In addition, there is dis-closed in that patent a cube-corner reflex reflective optical system in which the cube axes o thè cube~corner reflective element are inclined ~o as to be substantially coincidental with t~e nominal incoming refracted ray. Pavement markers made in accordance with the 763,714 patent and similar to the

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83~L11 1 structure disclosed therein have been extremely successful 2 in operation, and several millions of them have been in-

3 stalled, primarily in areas where no snowplowing of the roads is required. l`he height of the earlier pavement marker precluded lts practical use under snowplow conditions.
6 Also, such pavement marker, while highly effective as a 7 nighttime signal, is substantially inefective as a day-8 time marker, because of the nature of its construction, and, 9 in particular, the large metallized area of the reflective portion thereof, which metallizing is required because of 11 the epoxy fill. - 7G~ 7J~
B 12 As disclosed in the '_~7-patent, mechanical 13 a~rasion decreases when the angle of the front face of the 14 lens portion of the pavement marker is increased; however, ..
1~ as that angle increases, the cleaning action obtained by 16 tire ~iping on the front face of the lens decreases. The 763 7/~ .
17 '32~ patent further discloses that there is an optimum bal-18 ance of adequate wiping and limiting of abrasion, and L9 optimum optical effectiveness is achieved,when the angle of the ~ront face of the lens member is disposed at 30 to the ; 21 horizontal, with a satisfactory result being obtained where 22 such angle is between 15 and 45.
23 However, when such ~ pavement markers are used 24 in areas where, in winter months, abrasive materials such as sand and salt are deliberately distributed over the 26 roadway surface, the abrasion problem becomes particularly 27 acute, as the wiping action of..the vehicle tires, combined 28 with those abrasive materials, tends to scratch and grind . 2~ :

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1 ~ ~ 3~ ~ 1 1 the front face of the lens and diminish the optical effectiveness 2 of the reflex reflective quality of the pavement marker.

4 Applicants, while utilizing some of the features disclosed in the aforementioned prior art, provide a novel structure which 6 has abrasion-resistant and cleaning qualities in a durable 7 pavement marker having several advantages over those disclosed.
8 The present invention provides structure for the front 9 face of the lens portion of a pavement marker which structure, by itself, minimizes abrasiong and which also permits an in-11 crease in the front face angle of the lens, thereby further 12 minimizing the effects of abrasion, while at the same time 13 permitting sufficient tire action to effect cleaning of the 14 usual dirt and light-impeding film, which dirt and film normally increases as the front face angle is increased.
16 It is an object of the present invention to provide i.n a 17 pavement marher, maximum abrasion resistance to vehicle tires 18 striking the marker, whereby the optical qualities of the face 9 of the reflective portion of the marker are substantially less degraded, thereby increasing the optical efficiency, durability 21 and effectiveness of the marker over a longer time period.
22 According to the present invention there is provided a 23 pavement marker adapted for engagement with an underlying road-24 way for providing a marking visible from an oncoming vehicle on the roadway surface, said pavement marker comprising a lens 26 member of light-transmitting synthetic resin including a front 27 face having a light receiving and refracting portion arra.nged 2~3 to be inclined at an angle of at least 15 to the associated .
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1 roadway surface and a rear face having reflex reflective means 2 on at least a portion thereof for reflecting light transmitted 3 through said light receiving and refracting portion back toward 4 the source thereof, and a thin sheet of glass having a thickness not greater than 8 mils fixedly disposed on said light receiv-6 ing and refracting portion in an area thereof optically over-7 lying at least part of the reflex reflective means, said thin 8 sheet of glass being operable to reduce the degradation of 9 optical efficiency which would otherwise be caused by abrasive tire contact on said light receiving and refracting portion.
11 The glass is preferably untempered, and is in the form of 12 a thin sheet having a thickness of about .005 inch and is 13 bonded to said lens member, the bond not exceeding .001 inch.
14 The invention, both as to its organi7ation and method of operation, together with further objects and advantages 16 thereof, will best be understood by reference to the following 17 specification taken in connection with the accompanying drawings.

19 FIG. 1 is a partially sectioned perspective view of one embodiment of a pavement marker;
21 FIG. 2 is a plan view of the pavement marker of FIG. l;
22 FIG. 3 is an end elevational view of the pavement marker 23 illustrated in FIGS. 1 and 2;
24 FIG. 4 is an enlarged view of the rear face of a lens member forming part of a pavement marker taken in a direction 26 perpendicular to the rear face thereof;
27 FIG. 4A is a fragmentary view, on an enlarged scale, 28 of a portion of the rear reflective surface of the lens member 29 within the circle 4A of FIG. 4, but taken in a direction _5 ~.

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1 parallel to the cube axis of the reflector elements;
2 FIG. 5 is a plan view of the base of the pavement marker;
3 FIG. 6 is a side elevational view of the base, taken in 4 the direction of the line 6-6 in FIG. 5;
FIG. 7 is a greatly enlarged cross-sectional view of 6 the pavement marker, taken along the line 7-7 in FIG. 2, with 7 a portion thereof removed for clarity;
8 FIG. 8 is a greatly enlarged cross-sectional view of 9 the lens member taken along the line 8-8 in FIG. 4;
FIG. 9 is an enlarged partial section view of the lens 11 member taken along the line 9-9 în FIG. 4;
12 FIG. 10 is an end elevational view of a modified pavement 13 marker;
14 FIG. 11 is a fragmentary front view of a lens member incorporated in a pavement marker of the present invention; and 16 FIG. 12 is an enlarged cross-sectional view of the lens 17 member taken along the line 12-12 of FIG. 11, illustrating 18 the front of the lens member at a 45 angle to the base.

Referring now to the drawings, a pavement marker intended 21 primarily for use under snowplowing conditions, it shown in 22 perspective at 10 in FIG. 1. The pavement marker 10 is more 23 completely described in Canadian Patent Application 277303, the 24 disclosure of which is incorporated herein by reference.
The pavement marker 10 includes a body or base 20, of 26 an opaque, light-diffusing synthetic resin having mounted 27 thereon a lens member of light-transmitting synthetic resin 28 generally designated as 30. The base 20 is substantially solid 29 and is formed as a one-piece member to provide a durable struc-ture capable of withstanding impact forces applied to the pave-, , , , ~ , , ; . :

1 ment marker when it is struck by a tire ot an oncoming vehicle.
2 The pavement marker 10 is employed to provide a marking 3 on a generally horizontal roadway surface, the marking being 4 visible from an oncoming vehicle on the roadway to delineate traffic lanes and for edge delineation, as is well recognized 6 in the art. In addition, the pavement marker 10 may be 7 utilized with metal base members of a type illustrated and 8 claimed in Canadian Patent Application 277306.
9 Referring now more particularly to FIGS. 5, 6 and 7, it will be seen that the base 20 is formed as a substantially 11 solid one-piece member, having a generally horizontal bottom 12 surface 21. In order to prevent sinks or shrink stresses in 13 molding, the base 20 may be provided with a plurality of 14 molding recesses 21A (FIGS. 5 and 7). The base further in-cludes a pair of generally vertically disposed sidewalls 22 16 and 23 (FIG. 2), and a generally horizontal top wall 24 having 17 a rectangular channel 24A extending from one sidewall 22 to 18 the opposite sidewall 23.
19 There is provided a pair of inclined support walls 25, disposed at opposite ends of the base 20, and positioned such 21 that in use, they will be facing the direction of oncoming 22 vehicles. Each oF these support walls 25 has a plurality 23 of recesses 26 formed therein, which recesses have substan-24 tially rectangular openings : ' . :,:

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1 intersecting the plane of the wall. The recesses or 2 pockets 26 and the support wall 25 cooperate with the over-~ lying lens member 30 in a manner hereinafter described.
g . The base 20 further includes side edges 27 and 28 disposed on the opposite ends of each of the respective 6 sidewalls 22 and 23, the side edges 27 and 28 extending 7 outwardly beyond the support walls 25, and dèfining a chan-8 nel between the opposite side edges and the adjacent support g wall 25 disposed therebetween. The base 20 also includes L~ a tab opening 29 formed in the sidewalls 22 and 23 adjacen-t 11 to the respective in~lined support walls 25 for purposes of 12 facilitating the alignment of the lens member 30 during 1~ attachment thereof to the base 20.
14 The lens member 30 which provides the reflective - 15 structure for reflecting light back toward the source thereof, 16 thereby renaering the pavement marker highly visible at nigh.t, 17 is best illustrated in FIGS. 4, 7, 8 and 9. The lens member 18 ~30 is formed of a light-transmitting synthetic resin and L9 includes a substantially planar front face 31 and a rear face 32. As illustrated, the~ lens member 30 is generally 21 rectangular and is intended to be positioned in the channel 22 provided by the side edges 27, 28 and the support wall 25 2~ The rear face 32 of the lens member 30 is pro-24 vided with a peripheral edge portion 33 which extends about the entire periphery of the lens me~ber 30 (FIG. 4) and 26 includes a portion 33A which. is originally in the form of a :~
27 generally triangular sealing bead ~F,IGS. & and 9~ The rear ~8 surface 32 further is provided with a plurality of.dividin~
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portions 34, the dividing por~ions 34 in~ersecting the peri-pheral edge portion 33 at equally spaced distances there-along, thereby dividing the len member into a plurality of generally rectangular areas circumscribed by the peripheral edge portion 33 and the dividing portions 34. As illustrat-ed, the ~ividing pertions 34 originally may include a raised triangular sealing bead 34A, and hereinafter, in the specifi-cation, 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 secuxed thereto, preferably by ultrasonic welding. When properly positioned; each of the rectangular areas circum-scribed by the peripheral edge portion 33 and dividing por-tions 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 ovexlie the dividing portions 25A of the support wall 25.
When the lens member 30 is ultrasonically welde~ to the base 20, the sealing beads 33A and 34A become substan-tially flattened as a result of the energy imparted thereto : during the ultrasonic welding procees, whereby the peripheral edge portion 33 directly abuts the support wall 25, as best illustra~ed in Fig. 9, and provide a substantial welded 'surface area visible through the transparent lens mem~er 30.
Similarly, the dividing ribs 34 will become substantially flattened as they are sealed to the underlying dividing walls 25A of the support wall 25.

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The lens member al~o includes an outwardly ex-tending tab 37 adapted t~ be positioned within the ta~ open-ing 29 on the basa 20, and serves as a locatox to fix the lens member 30 in position prior to welding.
After welding the lens mem~er 3Q to the base 20, each of the dividing wall portions 25A o~ the support wall 25, and the periphçral portion thereof, in cooperation with the dividing ribs 34 and peripheral edge portion 33, provide a plurality of hermetically sealed cell 35 having a reakangular con~iguration when viewed in a direction normal to the front face 31.
Ths pavement marker lO i8 provided with a retro-directive 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 pavement marker. As best seen in Fig. 4, the rear face of the lens member 30, in those reatangular areas circumscribed by the dividing ribs 34 and peripheral edge portion 33, is configur- :
ated t~ provide a plurality of cube-aorner-type retxo-direc-tive reflector element~ 40. In the emhodiments ilIustrated herein, the cube-corner elements 40 are intended to be generally reatangular when viewed in a ~irection along the line of the ~ube axis, as be6t illu~trated in Fig. 4A.
Each of the ou~e-corner elements 40 includes cooperating ~aces 41, ~2 and 43, re~pectively, the face~
intersecting to form first and second and third dihedral angle~ in a ~anner well known to those skilled in the art.
In the preferred embodiment illu~trated, two of the dihedral . .

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angles would be on the order of substantially 90 whereas the third dihedral angle would bq formed a~ an angle signifi-cantl~ di~ferent from th~ first and seaond dihedral angles, so that the light reflected by such cube-corner element is caused ~o be diverged ~o a greater extent in one direction than in the other. One such s~ructure is set forth in greater detail in Canadian Patqnt No. 966,529.
In the illustrated e~bodimen~, the different di-hedral angle is formed between those faces designated as 41 an~ 42 in Fig. 4A, whereby the rçflectivity of the reflector will be substantially increased at a greater observation angle, as more fully demonstrated hereinafter.
As seen in Fig. 7, ~he 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 faGt, the apices of the aube-cornerR 4~ may contact the underlying surface 26A defining the interior boundary of the recess 26 there~y furthqr to strengthen the lens member 30 and provide additional support therefor as the lens member is aontacted by a tire of an oncoming vehicle.
To facilitate installakion of the pavement marker on an underlying roadway surface, or on a metal aasting in the event the marker 10 is used in snowplow country, an adhesive impac~-absorbing matçrial or pad 15 is se¢ured .. , . " , , , to the bo~tom 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 u~e, the paper 16 is peeled from the pad 15 and the pavement 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 pavement marker.
As set forth in the aforementioned Canadian Patent application Serial No. 277,303, it is believed that the impact-absorbing material 15, together with the low profile of ~he marker 10 achisved by the low height thereof relative to the roadway surface, effects both a reduction of and absorption o some of the impact energy normally transmitted through to the underlying pavement surface.
It is also believed that the low profile allows the pa~ement 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 markexs o~
a higher elevation. Moreover, it is ~urther believed that the low profile, in combination with the impact-ab~orbing material lS on the bottom surfaae 21 of the base 20, renders the individual cell structure ~ormed by the combined lens member 30 and base 20 more resistant to impac~ damage.

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1 The aforesaid Canadian Patent Application Serial No.
2 277303 includes several Features which permit the important 3 reduction in height.
4 As mentioned above, and as disclosed in applicants' patent 763714, there is an optimum balance obtained in maintaining 6 optical effectiveness by limiting abrasion and achieving ade-7 quate wiping or cleaning of the front face of the marker upon 8 contact by a moving tire. Such optimum balance is achieved 9 when the angle of the front face of the lens member is disposed at approximately 30 to the horizontal, with a satisfactory 11 result being obtained where such angle is approximately from 12 15 to 45.
13 However, the abrasive action on the front face of the 14 marker due to tire contact becomes a much more critical factor than the aforementioned wiping or cleaning action when the 16 pavement marker is used where abrasive materials are purposely 17 placed on the road. Thus, in an area where salt or sand is 18 put on the road during the wintertime, the wiping action by 19 such abrasive materials in contact between the tire and front face of the lens member causes more serious damage to the 21 front face than is the case where those markers are located 22 in other areas of the country where such abrasive materials 23 are not on the roadway. In order to minimize the 1Oss of 24 reflectivity due to abrasion, and to prolong the reflective qualities or optical efficiency of the pavement marker under 26 such conditions, the front surface 31 of the lens member 30 27 of the pavement marker is preferably inclined ~[s, . .

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at an angle of 45 relative to the horizontal surface 21 of the ba~e 20. It will be appreciated that the effects of abrasion may be further minimized by increasing the angle o~ ~he front face about 45; however, it is believed that at front face angles above 60, the cleaning and wiping action by tire contact will be inadequate to maintain optical effectiveness, It is also known that the front surface reflection 106s due to the inherent nature of the material of the lens ~0 membex itfielf, is less at 45 than at 30~. As an example, the typical fLont surface ref~ec~ion loss of a pavemenk marker in which the front surface of the lens is located at 30 to the horizontal would be approximately 24~, whereas tha front surface loss with the reflector at 45 to the 15 horizontaI would only be 12%. Also, by inclining the front .:
face of ~he marker at 45, 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 i8 reduced. Further, by inclining the ~ront face of the marker at ~5, it is possible to ~urther reduce the overall height of the marker because there will be a les~er inclina-tion ~f the cube axis relative to the horizontal than is pro-vided in the prior Canadian patent 763,714, and it will not be nece~sary to tilt the bottom row of c~be-corner elements as much.
It is de~ired to provide abra~ion-limiting means which permi~ an increase of the front face angle thereby improving operatlon of the pavement marker while at the ., , . . . :
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same time providing a substan~ial. reduction in abrasion on the portions of the lens member having reflective elements thereunder, thereby reducing the degradation of optical efficiency normally caused by abras.ive tire contact, while also allowing adequa~.e cleaning of the front face of the len~ member by tire action on the lens member, thereby en-hancing the optical effi~iency of the pavement marker.
In the marker shown in Figure 1, the abrasion-limiting means takes the form of raised ridges 45 carried ~y the front face of the lens member 30 and raised there-above and extending in use generally parallel to the direc-tion of traffic. The ridges 45 are equally spaced along the ~ront 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 opera- :
tion 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 mad2 of a more abrasion-20 resi~tant material ~han the lens member an~ 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 2$ the full i~pact forces and abrasive contacts causea by tires strikin~ the front of the marker, thereby minimizing abrasion on th~ other portions of the lens member 30 80 as :' : : ,, : . ' ..... ' - . . ,: ,: . : .
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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 ace 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 ab~asion resistance, the ridges 4S provide struotural strength to the lens member 30, further serving to maintain the integrity of the cells 26 and reflector element~ 40 under tire impact.
While the ridges 45 have been disclo~ed as being used with a lens memher whiah includes dividing ribs on lS th~ back face thereof, the ridges being respectively dis-posed direc~ly over an~ in alignmen~ with the dividing ribs, it will be understood that the raised ridges 45 could also be used with other forms of pavement markers such as that disclosed in the af~rementioned Canadian Patent No. 763,714.
~s previously de3cribed, 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 ~he support wall 25 within which is disposed the lens member 30. The side edges 27 and 28 provide further struc-2$ tural ~upport a~d protection for the lens member 30 adjacent tho8e areas in which the ultrasonic welding occurs at the c~rner~ of the marker, thereby eerving to substantially .,.

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protect the integrity o~E khe marker at those points. It will also b~ ~oted ~hat the side edge3 27-28 and the ~ront edges of the protective ridge~i ~5, lie in the same plane, in effect defining a p~o~ec~ive barrier for the front face 31 of the mar~er 10.
Figures 11 ~nd 12 ~ihow a pavemen~ marker of the invention and will be described rnore fully after the com-pletion of the description of the pa~ement marker illustrat-sd in Figs. 1 throuyh 10.
As illustrated, the pavement marker 10 may be pro- .
vided with a metal cover plate 19 to overlie and protect the entire top wall 24 thereoE; the cover plate 19 also extend- :
ing beyond and overlying the upper edge of the lens membar 30, a~ beqt seen in Fig. 3. Tha meka} covcr plate lg i8 intended to be u~ed on those embodiments of the pavement marker 10 which are to be in~talled in a metal ca~ting and subjected to posqible contact by studded snvw tires passing over the top Gf the marksr, the oover plate serving to pro- :
vide additional protection again~t such members. ~he ¢o~er plate 19 may be adhe~ively secured ~o ~he top wall 24, or, alternatively, a second impact-ab30rbing pad ~not shown) may be fixedly ~ieoured therebetween.
The rec~angularly ~haped longitudinally extending chann~l 24A provid~d in the cover pla~e l9.and in the ~op wall 24 i~ adapted to receive a retaining mamber $n a well-known manner, the retai~ing member ~erving ~o further hold ~he pavemi~nt marker in pla~e Gn ~he underlying metal casting, if ~uoh retaining m~mber i~ desir~d.

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The arrangemPnt o~ the lens member 30 with its peripheral transparent edge portion 33 and dividing rib~ 34, and the underlying light-dif~using opaque support wall 25, impart~ substantial daytime visibility to the pavement S 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 retro-directive reflector elements 40 in those areas 1~ circumscxibed by the edge portion 33 a~d the dividing ribs 34.
Further, thq use of the rectangular cells 35 and square reflec~or elements 40 Permits the use of vertical sidewall surface~ i~ each recess 26 o~ the marksr, if de6ired, whereby substantially the ~ull ~idth 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 vertiaally disposed parallel ridges 45 results in no loss of reflective a~ea by the ridges 45 while permitting their orientation in the optimu~ diraction for tire contact.
The opaque, light-diffusing base 20 serves to re-flect daylight impinging thereon to an observer. At a dista~ce, the uni~orm spacing of he dividing ribs 34 and dividing wall portions 25A aauses the pavement marker to appear as a su~stantially unif~rm reflective body, with the cellB 35 tending to disappear to the eye of the observer u~der daylight conditions. Alternatively, under nighttime driving conditions, the uni~orm size and spacing o~ the ,' ' ~.

~ ~ ~ 3~ ~ 1 1 cells 35 causes the pavement marker to appear as a uniform 2 reflective member, the dividing ribs 34, which improve day-3 time visibility, tending to disappear under evening driving 4 conditions.
FIG. 11 depicts a fragmentary front face of a lens 6 member 50, generally similar in plan configuration to the 7 lens member 30, except the lens member 50 does not include 8 the raised ridges 45 as are on the front face of the lens 9 member 30. On the rear face of the lens member 50 there are reflex reflector elements 52 substantially identical to the ll reflector elements 40.
l2 The abrasion-limiting means comprises a thin sheet of 13 untempered and non-annealed glass 55. The glass 55 is bonded l4 to the front face of the lens member 50 in at least those areas overlying the reflex reflector elements 52. To protect l6 the perimeter edges of the glass sheet, the front face of l7 the lens member 50 is provided with a raised lip 51 extending 18 about the entire periphery thereof.
19 The lens member 50 is provided with rear dividing ribs 53 so that a pavement marker 10 employing the lens 50 will 2l have substantially the same daytlme and nighttime reflective 22 characteristics as a pavement marker employing the lens member 23 30. While the glass sheet 55 is shown as covering those ~24 portions over the areas occupied on the rear face by the ribs 53, it -19- :

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, 331~1 should be understood that the lens member 50 could be pro-vided with raised ridges 45, with a glass sheet being dis-posed b tween pair~ of ridges 45, ~hereby utilizing both forms of abrasion-limiting means disclosed.
The glass sheet 55 may be adhesively bonded to the front fac~ of the lens member by first applying an adhesive coating to the gla s or lens member and then plac-ing the glass in position on the lens member with the adhe~ive therebetween. Alternatively, the glass may be bonded to the lens member during molding of the lens member.
It has been ~ound that glass having a thickness o~ about O005 inch, bonded with an adhesive of about .001 inch, produces an optimum impact resistance to fracture;
but it i~ believed that glass in the range of .003 to .008 lS inch thick and an adheæive 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 ~etron #26869.
After appliaation of the adhesive and glass to the lens member, the unit should be cured at 70C. to perfect ~he bond. When the lens member is molded about the glass, the bonding surf~ce of the glass may be coated with a resin having an affinity for gla~s and the lens materialO Such resins could be in the silane family, such as Dow Corning's Compound Z-6020 or Z-6040.
It has be~n ound that pavement markers, such as .

the type disclosed in the Canadian Patent 763,714, when provided .

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with the preferred glass thickness and adhesive disclo6ed herei.n, have a retained reflectivity, or improved optical efficiencyt in the range of 12 to 25 times that of an un-modified marker of the type shown in that Canadian Patent

5 when exposed to the same conditions. That is, pavement 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 abr2sion-limiting means.
The front face of the lens member is disposed at an angle of approximately 45 to the horizontal surface 21, while the suppor~ wall 25 is inclined at an angle of approx-imately 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 æurface 21 and similarly the side edges 27 and 28 forming extensions of the side-walls 22 and 23 also are inclined at angles of approximately 53 relative to the underlying surface 21. It will be apparent from the foregoing that the outer edges of the ridges 45 and the side edges 27 and 28 therefore are sub-stantially coplanar and define a barrier plane which pro-vides a protective area for the front surface of the lens member. The ridges 45 may have a width or thickness of approximately .07 inches, 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 5.
The base 20 may be made of acrylonitrile butadiene !

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~tyrene ~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 methacryl-ate or a rubber-modified methyl methacrylate or a polycarbon-ate such as lexan.
Normally, the lens and base ~ill be chosen to pro-vide the same colors, day and nigh~, with the specific col~ being determined by the specific function of ~he marker, e.g., lane delinea~ion v~. median edge delineation.
The pavement marker illu~tra~ed in Fig. 10 is primarily intended to be used independently of any metal housing or cas~ing, In that marker the top wall 24 rather than being ~enerally horizontal, as in the marker illustrat~
ed in Fig. 1, instead has Eurfaces 47 and 48 which incline upwardly in the sams 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 reflec-tive body area for reflecting daylight back to an observer.
me metal cover plate 19 would of course not be used with 20 this marker which would preferably be used under non-snow-plowable condition~. . .
The above detailed desaription is provided by wayof example only. Various details of designs and con~truc-tion may be mo~ified without departing from the true spirit ~5 and scope of the invention as defined in the appended claims.

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Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A pavement marker adapted for engagement with an under-lying roadway for providing a marking visible from an oncoming vehicle on the roadway surface, said pavement 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 reflec-tive 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 8 mils fixedly disposed on said light receiving and refracting portion in an area thereof optically overlying at least part of the reflex reflec-tive 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 pavement marker as claimed in claim 1, wherein the thickness of said glass sheet is at least 0.003 inches.

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

4. A pavement marker as claimed in claim 1, 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 pavement marker as claimed in claim 4, wherein said adhesive is not greater than 0.002 inches in thickness.

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

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