Note: Descriptions are shown in the official language in which they were submitted.
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HIGHWAY MARKER
This invention relates generally to highway markers typically placed along
the centre line of a highway and including a light-reflective plate to make
the marker
visible at night.
BACKGROUND OF THIS INVENTION
The lanes on roads and highways are normally separated by lOcm wide
painted lines. Typically, the lanes are made visible at night by dropping
glass bead
onto the wet paint, to make the lines reflective. This method, however, has a
number of drawbacks. Firstly, the glass bead used is usually not of a high
quality,
thus giving a low initial reflectivity. Secondly, the beads tend to be subject
to wear
by vehicle tires and abrasion from grit on the road. Thirdly, the beads are
positioned against the road surface, and are thus covered with water during
rain.
The film of water interferes with the reflectivity, and makes the line
difficult to see
at night.
Wet night visibility is greatly enhanced by the addition of reflective raised
pavement markers. These raised markers are constituted essentially by a block
of
durable plastic into which a cube-cornered reflector is imbedded. These
markers
are cemented to the road along the painted line, and pick up and reflect the
light of
the approaching vehicle. Such markers have the following advantages. Firstly,
the
reflector is moulded from durable plastic allowing the quality to be
controlled,
therefore producing a consistently high brightness reflector. Secondly, the
reflector
is mounted in the body of the marker in such a way that the reflector is
protected to
some degree from tire wear and abrasion. Thirdly, the reflector is mounted
above
the surface of the road and is not covered with water during rainy weather. It
therefore performs well in rain.
Such raised pavement markers are very effective and are widely used where
climatic conditions are such that snowplowing is unnecessary. Generally, these
raised markers cannot withstand the impact of a snowplow.
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Many attempts have been made to produce a raised marker that will survive
impact from snowplows. There are two basic ways to accomplish this.
The first method is to make a marker that is strong enough to withstand the
impact of a snowplow. The most successful product uses this method. The unit
is a
cast steel insert that is inlaid into the road and retained using epoxy. When
in
position, the casting exhibits two parallel steel ramps protruding up from the
road
surface. A reflector is cemented between the ramps for protection. When
impacted
by the snowplow, the casting deflects the blade upwardly far enough that the
blade
does not make contact with the reflector. Although these units are widely
used, they
do have a number of problems due to the extreme impact. Firstly, although the
ramp height of the marker may be as little as '/ " in 6" , the plow blade will
jump
more than 6" off the road, leaving a strip of road unplowed. Secondly, the
shock of
impact is considerable, and is very uncomfortable for the plow driver. It also
has a
detrimental effect on the mechanicals of the truck. Thirdly, the impact
between the
carbide blade of the plow and the casting often results in cracked blades.
Fourthly,
the casting of the marker is heavy. If it is not installed perfectly, there is
a risk that
the plow blade will catch on the casting and pull it out of the road. If this
happens
at high speeds, the casting can become a projectile which can endanger
oncoming
vehicles and their occupants.
The second method is to make a marker that deflects out of the way on
impact with the plow blade without damaging the marker, thus overcoming the
problems encountered with the cast unit.
The Prior Art
Several previous patents utilize the deflection principle in order to avoid
damage both to the reflector and the plow blade.
U.S. patent 3,901,614, Overacker, issued August 26, 1975, discloses a
reflector unit having a hard transparent material in the upper part of the
body and a
flexible transparent material forming the base. The base is locked into a hole
or
recess in the roadway utilizing a suitable compound. The construction is such
that
the flexible material of the base allows the hard material of the upper
portion to
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move downwardly somewhat under the force of an impact.
U.S. patent 4,504,169, Jones, issued March 12, 1985, provides a road stud
which is displaced downwardly when run over by a vehicle. When this occurs,
special flaps are also displaced downwardly, which causes the reflection
elements to
be wiped by resilient wiping lips to remove dirt.
U.S. patent 4, 597,691, Clarke, issued July 1, 1986, discloses a resilient
structure in which a light-reflective surface is depressed to a level
coincident with or
below the surrounding pavement. Once the force is removed, the light
reflecting
surface returns to an elevation above the road surface.
U.S. patent 5,069,577, Murphy, issued December 3, 1991, discloses a
unitary flexible pavement marker which is hollow and formed in such away that
the
upward dome is depressed or "folded" downwardly into the cavity provided below
it, upon impact by a tire or a snowplow blade. When the tire or blade have
passed
by, the marker returns to its original position.
The foregoing prior art approaches to the design of a marker capable of
deflecting out of the way on impact retain certain disadvantages which it is
an aspect
of this invention to overcome.
The Overacker U.S. patent 3,901.614 requires the provision of a spherical
component with a hard top section and a resilient bottom section, both having
a
particular index of refraction, and both remaining optically transparent. It
is
obvious that repeated abrasion from impact would eventually ruin the optics of
the
various portions of the component and interfere with its light-reflecting
capability.
The U.S. patent 4,504,169, Jones, is directed to a unit that has been tested
in
Ontario with discouraging results. The part of the unit which sits above the
road
and is subject to contact with a snowplow blade is made of an elastomeric
plastic
which is relatively soft and tends to be cut by the jagged edge of the blade.
The
body of the unit is not sealed, and thus allows water and dirt to enter into
the unit.
The water freezes and this causes the unit to seize so that it will not
depress, thus
resulting in failure. The general shape of the unit, which was designed to
include a
method of cleaning the front of the reflectors when depressed, is such that it
is
subject to be being snagged by the snowplow blade.
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U.S. patent 4, 597,691, Clarke, uses only a single dome. The sealing of the
unit is
accomplished by mechanically compressing gaskets, however these sealing
surfaces are
subject to leaking and failure. According to the patent, the housing is hollow
with an
upper open end and a closed lower end. The design of the unit tends to be
quite complex,
utilizing many parts and mechanical fasteners. This results in increased
costs, and greater
likelihood of failure.
U.S. patent 5,069,577, Murphy, is directed to a configuration which was tested
in
Ontario and failed. It is believed that the main reason for failure is that
the soft plastic
material protruding above the road surface, when struck by the plow blade,
tended to be
pinched rather than deflected downward, and the pinching action compressed the
trapped
air to a pressure which ruptured the back side of the dome.
GENERAL DESCRIPTION OF THIS INVENTION
In view of the drawbacks of the prior art described above, it is an object of
one
aspect of this invention to provide a reflective pavement marker comprising:
a hollow, hermetically sealed base having a flexible top wall defining at
least one
downward recess, the base being adapted to be installed in an opening in a
road surface
such that the top wall lies at or below the road surface,
for each said recess, a reflector unit having a lower portion snugly received
in the
recess and an upper portion projecting upwardly above the top wall of the
base, said
upper portion having the shape of a conical frustum converging upwardly such
that
impact from a horizontally moving object will cause a caroming action that
urges the
reflector unit downwardly; and
at least one light-reflecting component supported and protected within an
indentation in said upper portion;
each downward recess in the top wall being substantially cylindrical in
configuration, the lower portion of each reflector unit being also
substantially cylindrical,
the said lower portion being sized so as to achieve a snug fit within the
corresponding
downward recess;
the outer periphery of the lower portion of each reflector unit exhibiting a
flat
region which achieves an asymmetrical, rotation-resistant grip with the
respective
downward recess.
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In accordance with another aspect of the present invention there is provided a
reflective pavement marker comprising:
a hollow, hermetically sealed base having a flexible top wall defining a
plurality
of downward recesses, the base being adapted to be installed in an opening in
a road
S surface such that the top wall lies at or below the road surface,
for each said recess, a reflector unit having a lower portion snugly received
in the
respective recess and an upper portion projecting upwardly above the top wall
of the base,
said upper portion converging upwardly such that impact from a horizontally
moving object will cause a caroming action that urges the reflector unit
downwardly; and
at least one light-reflecting component supported and protected by each said
upper
portion;
the recesses being disposed such that a plow blade passing over the marker
impacts each reflector unit at a different time, thus averaging out the total
impact.
In accordance with yet another aspect of the present invention there is
provided a
reflective pavement marker comprising:
a hollow, hermetically sealed base having a flexible top wall defining a
plurality
of downward recesses, the base being adapted to be installed in an opening in
a road
surface such that the top wall lies at or below the road surface,
for each said recess, a reflector unit having a lower portion snugly received
in the
recess and an upper portion projecting upwardly above the top wall of the
base, said
upper portion converging upwardly such that impact from a horizontally moving
object
will cause a caroming action that urges the reflector unit downwardly; and
at least one light-reflecting component supported and protected within an
indentation in each said upper portion;
each downward recess in the top wall being substantially cylindrical in
configuration, the lower portion of each reflector unit being also
substantially cylindrical,
each said lower portion being sized so as to achieve a snug fit within the
corresponding
downward recess,
the plurality of recesses being disposed such that a plow blade passing over
the
marker impacts each reflector unit at a different time, thus averaging out the
total impact.
GENERAL DESCRIPTION OF THE DRAWINGS
One embodiment of this invention is illustrated in the accompanying drawings
in
which like numerals denote like parts throughout the several views, and in
which:
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Figure 1 is a perspective view of a reflective pavement marker, located in an
opening in a road surface;
Figure 2 is a top plan view of the base of the reflective pavement marker
shown in Figure 1;
5 Figure 3 is a partly broken-away view, both elevational and sectional, of a
reflector unit suitable for use with the base of Figure 1;
Figure 4 is a vertical, axial sectional view through the base of Figure 2
taken
at the line 4-4 in Figure 2;
Figure 5 is a perspective view of the reflector unit shown in Figure 3; and
Figure 6 is an axial sectional view, taken at the line 6-6 in Figure 3.
DETAILED DESCRIPTION OF THE DRAWINGS
Attention is first directed to Figure 1 which shows, in perspective, the upper
surface layer 10 of a typical roadway, containing an opening 12 which is
circular in
plan view and has a substantially flat bottom. Located in the opening 12 is a
reflective payment marker shown generally at 14, which includes a base 16 that
receives a plurality of reflector units 18 described below in greater detail.
Attention is directed to Figures 1, 2 and 4, from which it will be seen that
the base is a hollow, hermetically sealed unit having a flexible top wall 20
which
defines at least one downward recess 22 (four recesses in the embodiment
illustrated).
For each recess 22 there is provided a reflector unit best seen in Figures 3,
5
and 6. The illustrated reflector unit has a lower cylindrical portion 24 sized
to be
snugly received in the corresponding recess 22. Each reflector unit 18 also
defines
an upper portion 26 which projects upwardly above the top wall 20 of the base
16.
As seen, the upper portion 26 has the shape of a conical frustum which
converges
upwardly and terminates at a flat, circular top surface 28. Due to the shape
of the
upwardly converging conical frustum, any impact from a horizontally moving
object
(such as a snowplow blade) will cause a caroming action that urges the
reflector unit
18 downwardly.
The upper portion 26 defines a recess 30 spanning about 60°,
located
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adjacent the larger periphery (outside circular edge) 32 of the frusto-conical
upper
portion 26.
As illustrated, the recess 30 defines a flat bottom surface 34, two
substantially
vertical side surfaces 36, an upper surface 38, and a reflector surface 40.
As seen in Figure 6, the reflector surface 40 is protected by the downward and
inward slope of the upper surface 38.
The lower portion 24 of the reflector unit 18 defines an inward step 42
adjacent an outward flange 44, which in turn defines the bottom of the upper
portion
26.
As can be seen in Figure 4, each recess 22 in the base 16 defines an upward
step 46 which is sized to snugly receive the flange 44 of the respective
reflector unit
18.
Figure 3 shows, in the lower right hand corner, a variant of the construction
for the reflector unit. More specifically, there is provided around the
periphery of the
lower end of the lower portion 24 a continuous or discontinuous "barb" 48
having a
greatest diameter which is somewhat larger than the internal diameter at the
bottom of
the recess 22, thereby providing a "force-fit" between the reflector unit and
the base
16. Because the base 16 (including the portions defining recess 22) is made of
resilient material, the recess 22 can expand to accommodate the barb 48.
Returning to Figure 4, the base 16 is seen to include, in addition to the top
wall
20 and the recess 22 (only one seen in section of Figure 4), a cylindrical
side wall 50
and circular bottom wall 52. The base 16 is preferably made from tough but
flexible
plastic, such that the top wall 20 can deform to allow the reflector units 18
to be
depressed on impact. The trapped air in the hermetically sealed cylinder
defined by
the base 16 acts as an air spring. As can be seen in Figure 4, the preferred
embodiment includes a V-shaped groove 56 adjacent the perimeter of the base,
thus
providing excess material to allow the upper wall 20 to depress without
excessive
warping of the unit. Typically, the base 16 may be cemented into the road
surface
using an epoxy cement, abituminous adhesive or any other appropriate
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material. When installed in this manner, there is no place where water, ice or
sand
can penetrate the unit and stop its action.
Preferably, the reflector units 18 are moulded integrally from a hard, tough,
abrasion-resistant plastic. The reflective surface 40 in the recess 30 can be
made
from high quality durable sheeting such as Reflexite '~, or from crystal bead
material ("Cats' Eyes"), or can be moulded in plastic and combined with the
reflector unit 18 when the same is moulded.
An advantage in using multiple reflector units 18 in a single base 16 is that
the units can be disposed such that a plow blade passing over the marker will
impact
each reflection unit at a different time, thus averaging out the total impact.
This
allows the profile to be kept as low as possible. As a result, the compression
of the
sealed cylinder defined by the base 16 occurs in stages. By making the
reflector
units 18 separate from the base 16, it is possible to use materials that are
best suited
to each of these components.
The structure defined above makes it possible to replace reflector units in
the
field.
Also, the particular construction of the reflector unit 18 allows the
provision
of reflective plates on opposite sides, allowing the units to be utilized as
one-way or
two-way reflectors.
Because the upper portion 26 of each reflector unit 18 has the shape of an
upwardly convergent conical frustum, the same can be impacted from any
direction.
It should be mentioned that the reflective surface 40 of each unit 18 is not
required to be strictly vertical, as illustrated. Vertical orientation may be
utilized
because the reflective materials readily available work in this position.
However, it
is contemplated that the reflector may be installed in such a way that it
slopes
downwardly toward the bottom, since this is expected to reduce the
accumulation of
dirt.
A further variant is to provide a flat such as that shown at 52 in Figure 6,
at
a given location around the bottom of the lower portion 24 of the reflector
unit 18.
This will provide a means of resisting rotation of the reflector unit 18 with
respect
to the base 16.
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Preferably, the reflector units 18 are made as an integral body from a
material which is selected from the group consisting of: thermosetting
plastic,
thermoplastic plastic, concrete and metal.
The provision of the outward step 46 in the recess 22, cooperating with the
outward step 42 seen in Figure 6, ensures a smooth transmission of downward
force
from the reflector unit 18 to the upper wall 20 of the base 16, thus
minimizing stress
concentration and prolonging the life of the pavement marker.
While one embodiment of this invention has been illustrated in the
accompanying drawings and described hereinabove, it will be evident to those
skilled in the art that changes and modifications may be made therein, without
departing from the essence of the invention as set forth in the appended
claims.
