Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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
-2--
.
.. ,. , . , ,, :. .
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~ :
,. . , . . , :. . - .
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.
3 SUMMARY OF THE INVENTION
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 .
.,
lB .
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.
18 BRIEF DESCRIPTION OF THE 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
~.
1~8~
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.
19 DESCRIPTION OF THE PREFERRED EMBODIMENT
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
26
27
28
--7--
: ' . :,:
1~8~L11
.
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~
. 29
~0 ' , .. ..
, . ~ .
.... - . . .
~83~
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.
,, ................ ~ . . .
.. , ' , , .................. : . . .
.
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
--10--
. .
., , , , ; . . ..
.
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.
.. :, .
83~
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
28
-13-
~[s,
. .
. , : ,
~L~8~
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
-14-
., , . . . :
. , . , ~: , :. . ,
~1~83~
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
-15-
:'
: : ,, : . ' ..... '
- . . ,: ,: . : .
- . . : ,
~3~
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
.,.
-- 16-
", , .
'""'''' ', ', ''.' ' " ',. '''"' ' '''' '''"~"~',''.',''"' ''''' '''''.',~;'.''"' ' '
. . .. . . .. ' . .. .. ~ .. . .
1~ ~3~ ~
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.
-17-
.. : : , . , , :, ~ . .: .
10831~L
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
-18-
,' ' ~.
~ ~ ~ 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
26
27
28
-19- :
B
,
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
.
-20-
,, . .. . :.
l [11333L~
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
!
-21
~L~83~1~
~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.
-22-
. ' ' ' . ~ '".
: . : .
,
