Note: Descriptions are shown in the official language in which they were submitted.
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FIELD OF THE INVENTION
The invention relates to a solid rubber highway
guardrail adapter which has an interior surface shaped to
snap-lock over the exterior of an existing sheet metal
highway guardrail.
BACKGROUND OF THE INVENTION
Conventional guardrail assemblies installed along
highways typically have at least one horizontal guardrail
that is supported at spaced locations by vertical posts
anchored in the ground. Generally the guardrail sections
are heavy gauge sheet metal formed into a W-shaped
corrugated section. Guardrails are constructed of
individual sections joined in end to end relationship and
overlapping at the vertical posts where they are connected
with bolts. The corrugation of the W shape imparts rigidity
and strength to the guardrail while being relatively simple
to fabricate.
Metallic guardrails are specificly designed to
yield when impacted upon by a colliding vehicle. The
deformation of the sheet metal guardrail serves to
decelerate the vehicle and guide the vehicle away from
hazards such as slopes, signs or oncoming traffic.
Increasingly however the cost of maintaining sheet metal
guardrails after impact has created a demand for a flexible
guardrail which can decelerate impacting vehicles while
reducing the cost of maintenance by remaining substantially
intact after impact.
In addition metallic guardrails made of steel are
subject to rapid deterioration due to corrosion from
constant exposure to precipitation, salt and stones. In
order to prevent deterioration of the guardrails, the steel
surfaces are generally galvanized with zinc. However,
flying stones and other debris thrown against the guardrail
by passing vehicles or high winds can cause pitting of the
surface and permit corrosion to rapidly deteriorate the
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exposed the steel surfaces. Therefore highway guardrails
are often unsightly even if not particularly damaged by
impacting vehicles.
Especially in areas such as curves or high traffic
concentrations, maintenance of guardrails becomes an
expensive and time consuming process. On busy highways and
around curves on entrance and exit ramps constant
maintenance may be required in order to keep the metal
guardrails in safe and operable condition.
The prior art therefore includes a number of
covers which are attached to existing guardrails to offer a
resilient surface and to rehabilitate the appearance of the
deteriorated guardrails. Examples of rubber covers which
are bolted to or integrally formed onto sheet metal
guardrails are disclosed in French patent publication no.
2460365 published January 23, 1981 - Societe Civile
D'Equipement Public and Swiss patent No. 618488 dated July
31, 1980
A significant disadvantage of both such prior art
devices is that the rubber cover closely follows the
contours of the underlying sheet metal guardrail. The
relatively thin cover of rubber is insufficient to absorb
the impact of a vehicle colliding with the barrier at normal
highway speeds. After such a collisions both the rubber
cover and sheet metal guardrail must be completely
replaced. The relatively thin cover layer of rubber would
simply peel off due to the force of a vehicle scraping along
the composite guardrail. Therefore, thin layers of rubber
covers are ineffectual in preventing damage to the metal
guardrail, are insufficiently flexible to prevent damage to
the impacting vehicle and appear to merely represent an
attempt to rehabilitate the appearance of the sheet metal
guardrail.
German patent No. DE 4135164A1 dated January 28,
1993 discloses a flexible rubber guardrail cover which is
relatively thin such that it may be coiled in cylindrical
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rolls. The guardrail cover rebounds to a C shape when
uncoiled during installation to wrap around an existing
guardrail. Such a cover is insignificant in protecting the
guardrail structure and would merely peel off when impacted
by a colliding vehicle. The primary purpose of such a thin
cover would appear to be economical and rapid rehabilitation
of the appearance of an unsightly guardrail.
Therefore it is desirable to produce a guardrail
adaptor which may be easily snap-fit over an existing
guardrail while also providing a substantial degree of
protection from impacting vehicles for the guardrail.
It is also desirable to produce a resilient
guardrail adaptor which will not simply peel off the
guardrail when impacted by a colliding vehicle.
The danger of dispersing guardrail materials over
the travelled surface of a busy highway presents significant
disadvantages since such debris may cause additional
accidents and delays on the highway. It is desirable
therefore that, on impact with a colliding vehicle, the
sheet metal guardrail and the rubber adaptor remains
substantially intact.
SUMMARY OF THE INVENTION
The invention overcomes the disadvantages of the
prior art in a novel manner in the provision of a solid
rubber adaptor for converting an existing highway barrier,
said barrier comprising an elongate horizontal guardrail of
uniform transverse crossection connected to supporting posts
spaced along the length of the guardrail, the guardrail
having a roadside contoured surface and upper and lower
edges, said adaptor preferably comprising an elongate
channel of uniform transverse crossection having an outer
curbside contoured surface mating the contoured surface of
the guardrail, the channel including a central web portion
with an upper flange and a lower flange outwardly extending
therefrom, the web portion having a thickness greater than
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the thickness of the flanges, the flanges each having outer
ends with opposing return edge bead means for resiliently
engaging the edges of the guardrail.
Also provided is a method of manufacturing such
a solid rubber adaptor comprising the steps of: mixing and
knead melting a mixture of: 80 to 90 percent by weight
particles of recycled waste rubber; 10 to 20 percent by
weight virgin rubber; and an accelerator composition;
forming the mixture to a selected adaptor configuration
thus defining an adaptor; curing the mixture within a
chamber at a temperature of 350°C to 400°C for a period of
time from 3 to 5 hours; and removing the cured barrier from
the chamber.
In one aspect, the present invention provides a
solid rubber adaptor for converting an existing highway
barrier, said barrier comprising an elongate horizontal
guardrail of uniform transverse crossection connected to
supporting posts spaced along the length of the guardrail,
the guardrail having a roadside contoured surface and upper
and lower edges, said adaptor comprising an elongate
channel of uniform transverse crossection having an outer
curbside contoured surface mating the contoured surface of
the guardrail, the channel including a central web portion
with upper and lower flanges outwardly extending from the
web portion, the flanges including integral clamping means
for resiliently engaging the edges of the guardrail.
In another aspect, the present invention provides
a solid rubber adaptor for converting an existing highway
barrier, said barrier comprising an elongate horizontal
guardrail of uniform transverse crossection connected to
supporting posts spaced along the length of the guardrail,
the guardrail having a roadside contoured surface and upper
and lower edges, said adaptor comprising an elongate
channel of uniform transverse crossection having an outer
curbside contoured surface mating the contoured surface of
the guardrail, the channel including a central web portion
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and integral clamping means for resiliently engaging the
edges of the guardrail, wherein said adaptor comprises 80
to 90% by weight recycled rubber and 10 to 20% by weight
virgin rubber.
The invention therefore overcomes the
disadvantage of the prior art in a design wherein the web
has a thickness greater than the thickness of the flanges.
Preferably the web has a thickness which is greater than
one half the height of the web in order to provide a
substantial mass of rubber. The increased.mass provides an
advantage over the prior art in that the sheet metal
guardrail is protected from impacting vehicles to a
substantially greater degree and the adaptor itself is
stiff enough to prevent the adaptor from simply peeling off
of the metal guardrail during impact.
Since the mixture which forms the solid rubber
adaptor is approximately 85% by weight particles of
recycled waste rubber with 15% by weight virgin rubber the
cost of the increased thickness is relatively small. In
fact the garbage disposal and fire hazard risks involved is
disposing of waste vehicular tires are such that many
government agencies are actively investigating means by
which such tires can be recycled or reused. It is fitting
that highway departments provide a demand for recycled
vehicular tires and accordingly such government agencies
are actively involved in using recycled tires for asphalt
mixtures and have created a demand for recycled rubber
vehicular barriers.
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A distinct advantage of the invention is that the
entire adaptor may itself be recycled if deteriorated or
damaged due to its homogeneous composition. No reinforcing
or inserts are required and therefore recycling is very
simple.
In alternative embodiments the adaptor includes
extended flanges which butt up against support posts for
additional resistance to impact. As a result the forces of
an impacting vehicle may be transferred directly by the
rubber adaptor to the support posts rather than depending
entirely upon the sheet metal guardrail attachment to the
support posts for conveying impact forces.
In a further embodiment the adaptor may include
bolt holes in the upper and lower flanges whereby an
elongate bolt may clamp the channel shaped adaptor over the
sheet metal guardrail. Bolts may be spaced along the span
of the guardrail and may additionally connect to the support
posts. As a result of the added thickness of the adaptor
and clamping bolt action, the rubber adaptor is securely
attached to the metal guardrail such that it will not become
disengaged during impact. A disengaged rubber bumper or
debris fragments could extend across the travelled surface
of the highway impeding traffic and potentially causing
additional accidents.
Further aspects of the invention will become
apparent upon review of the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be readily
understood, a preferred embodiment of the invention will be
described by way of example with reference to the
accompanying drawings in which:
Figure 1 is an exploded perspective view of a
solid rubber adapter and an existing highway guardrail; and
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Figure 2 is a perspective view of the adapter
assembled on the guardrail.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
OF THE INVENTION
Figure 1 illustrates a conventional highway
barrier 2 to the right, and to the left a solid rubber
adaptor 1 which is snap-fit to the horizontal metal
guardrail 3. Figure 2 illustrates the assembled condition
with an optional vertical bolt 16 securing the adaptor 1 to
the highway barrier 2.
The rubber adaptor 1 is preferably extruded of a
homogeneous rubber mixture the major portion of which
comprises recycled waste vehicular tire fragments.
The adaptor 1 provides an impact cushioning
surface which decelerates colliding vehicles, and protects
the sheet metal guardrail 3 from extensive damage. The
adaptor 1 will not simply peel off on impact due to
mechanical connection with bolts 16, the secure engagement
of the adaptor flanges 10, and 11 resiliently clamping
around the guardrail 3, and the relatively thick web 9 as
compared to prior art devices. The substantial size and
stiffness of the adaptor 1 and the optional securing of the
adaptor 1 to the guardrail 3 with bolts 16 ensure that the
adaptor 1 remains in place and does not become detached on
impact causing further hazards to automobile traffic.
The rubber adaptor 1 itself is moulded or extruded
of a homogeneous mixture and if damaged or deteriorated in
any way it can be easily removed and recycled for further
use.
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The adaptor 1 is ideally suited to retrofit
existing guardrails 3 where repeated collisions have created
the need for a redesigned guardrail 3 to minimize
maintenance costs. In many cases as well, the extremely
high volume of traffic in certain highway areas make it
undesirable to shut down highway lanes in order to maintain
the guardrail 3 on a periodic basis. For these reasons the
rubber guardrail adaptors 1 minimize maintenance and down
time in busy highway areas or in areas where repeated
maintenance is required due to collisions such as on curves,
exits, or entrances. ,
The invention provides further advantages over the
prior art in flanges 10 and il which extend to butt up
against the vertical post 4 of an existing barrier 2. In
this manner the adaptor 1 itself is used as a horizontal
structural member to convey forces directly to the vertical
posts 4 rather than depending upon the sheet metal guardrail
3 to convey all forces of impact. Therefore not only the
adaptor 1 protects the sheet metal guardrail 3 from damage
but it also aids in conveying impact forces as a composite
beam with the steel guardrail 3 directly to the vertical
posts 4.
To ensure that the adaptor remains engaged on the
guardrail 3 and to further enhance the composite action of
the adaptor 1 and guardrail 3 combination, vertical bolts 16
may be optionally used to span between the flanges 10 and 11
to clamp the flanges 10 and il to the guardrail 3. In order
to dislodge the adaptor 1 from the guardrail 3 during a
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collision, it is first necessary to overcome the resistant
forces of the bolts 16 in the flanges 10 and il.
A detailed description of the adaptor 1, method of
manufacture and its use is presented below.
With reference to Figure 1, a solid rubber adaptor
1 is provided for converting an existing sheet metal highway
barrier 2 to a resilient impact absorbing composite
rubber/metal core barrier. The existing barrier 2 comprises
an elongate horizontal sheet metal guardrail 3. The metal
guardrail 3, as is conventional, has a uniform transverse
cross section. In general use in North America guardrails
are a W-shaped galvanized heavy gauge section roll-formed
with rounded upper and lower edges 6 and 7.
Such guardrails 3 are connected to supporting
posts 4 which are spaced along the length of the guardrail
3. In median divider applications the post 4 may carry
guardrails 3 and adaptors 1 on two opposing sides. The
guardrail 3 has a contoured surface 5 and upper and lower
edges 6 and 7. The contoured surface 5 of the guardrail
imparts substantial strength the heavy gauge sheet metal
structure and provides a central flat portion with bolt
holes for securing the guardrail 3 to the post 4.
Turning to the adaptor 1, the adaptor 1 comprises
an elongate channel of uniform crossection. Advantageously,
the uniform channel shape may be formed by extrusion or
alternatively in an elongate mold. The adaptor 1 has an
outer curb side contoured surface 8 which mates the roadside
contoured surface of the guardrail 3.
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The adaptor channel 1 includes a central web
portion 9 with an upper flange 10 and a lower flange 11
outwardly extending from the upper and lower portions of the
web 9. The web 9 has a thickness substantially greater than
the thickness of the flanges 10 and il in order to provide
enhanced cushioning effect and to protect the metal
guardrail 3 from damage from impacting vehicles. The
flanges 10 and 11 each have outer ends 12 with opposing
return edge beads 13 for resiliently engaging the edges 6
and 7 of the guardrail 3, as shown in the assembled view of
Figure 2. In order to facilitate the snap locking
engagement of the adaptor 1 on the guardrail 3, the edge
beads 13 include lead-in planar tapered guide surfaces 14.
During installation, the lead-in guide surfaces 14 slide on
the guardrail 3 flexibly forcing the flanges 10 and 11 to
open and then snap-lock around the edges 6 and 7 of the
guardrail 3.
In order to facilitate the flexible snap locking
of the adaptor 1 on the guardrail 3, the thickness of the
flanges 10 and 11 are appreciably less than the thickness of
the web 9. Preferably, the web 9 has a thickness which is
greater than one half the height of the web 9. Prior art
adaptors include very thin rubber layers which simply peel
off the guardrail 3, on impact with colliding vehicles, and
disperse debris which pose further risk to other vehicles
travelling on the highway. By providing a relatively thick
web 9, the adaptor 1 in accordance with the invention is
relatively stiff and remains engaged on the guardrail 3
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during and after impact.
To enhance the load bearing capacity of the
guardrail 3 and prevent disengagement of the adaptor 1 from
the guardrail 3, preferably each flange end 12 includes a
vertical face 15. The vertical faces 15 form post abutment
means for engaging the support posts 4 of the barrier as
shown in Figure 2. By bearing the adaptor 1 directly upon
the support posts 4, the forces of an impacting vehicle
colliding with the adaptor 1 are not entirely carried by the
sheet metal guardrail 3, but rather forces are conveyed by
the web 9 and flanges 10 and 11 of the adaptor 1 directly to
the support posts 4.
To further enhance the load carrying capacity of
the composite adaptor 1 and guardrail 3, vertical bolts 16
as shown in Figure 2, are provided. Each flange 10 and il
includes a plurality of longitudinally spaced bolt holes
17. Bolts 16 are used to span between the flanges 10 and
11, and when tightened with nuts, the bolts 16 clamp the
flanges 10 and 11 to the guardrail 3. Although the bolt 16
shown in Figure 2 secures the flanges 10 and 11 to the
supporting posts 4 it will be understood that to further
secure the adaptor 1 to the guardrail 3, a longitudinal
series of bolt holes 17 between the spaced apart posts 4 may
be used and a series of bolts 16 used to clamp the adaptor 1
securely on the guardrail 3 between the vertical posts 4.
With reference to Figure 2, it is preferrable to
form the inward surface 18 which faces the roadway traffic,
as a concave surface. A concave surface 18 prevents
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automobiles from riding over the guardrail 3 on impact since
the concave surface 18 resists upward movement and envelopes
the side of the impacting vehicle. In order to prevent
extensive damage to a vehicle and the guardrail 3 as well as
to facilitate extrusion or moulding the upper surface of the
upper flange 10 and the lower surface of the lower flange il
are also formed in a concave manner with the inward surface
of the web 9 and upper surface of the upper flange 10
arcuately merging together to form a convex inward upper
ridge 19. As well, the inward surface of the web 9 and
lower surface of the lower flange 11 arcuately merge
together to define a convex inward lower ridge 20. The
upper and lower ridges 19 and 20 provide a significant mass
of rubber on the corners of the adaptor 1 to resist impact
and prevent damage to the guardrail 3.
Since recycled tire rubber is increasingly
available and many government bodies including highway
departments actively encourage the use of recycled tires to
prevent a significant waste problem, preferably the adaptor
1 comprises 85% recycled tire rubber and 15% virgin rubber
although the amounts can be varied between 80 to 90%
recycled rubber and 10 to 20% virgin rubber. A mixture is
made with the rubber and an accelerator composition which is
mixed and knead melted then formed into the selected adaptor
configuration by extrusion or forming in a mould. After
forming in the required configuration, the mixture is cured
within a chamber at a temperature of 350°C to 400°C for a
period of three to five hours, preferably at 375°C for four
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hours. After curing, the adaptor is removed from the
chamber and the process may be continued indefinitely to
provide further adaptors.
It will be understood from the above description
that if an existing installed rubber adaptor is damaged
during collision or deteriorates in any way, the damaged
adaptor may simply be removed and replaced. The damaged
adaptor may be ground up in the manner similar to grinding
of waste tires and may be reused indefinitely.
Therefore the solid rubber adaptor 1 provides not
only a means for recycling waste tires but the adaptor 1
itself may be recycled indefinitely. Therefore, the waste
tires are effectively removed from functions which would
contribute to environmental pollution.
As described above, the adaptor 1 according to the
invention provides significant advances over the prior
art. The abutting faces 15 of the adaptor significantly
increase the load bearing capacity of the guardrail 3 in
composition with the adaptor 1 installed on it. The use of
bolts 16 further clamps the adaptor 1 onto the guardrail 3,
prevents disengagement and adds to the composite beam action
of the assembly. Prior art rubber barriers are relatively
thin and are prone to merely peel off during impact
presenting further risks to adjacent traffic.
It will also be understood that use of bolt 16 is
optional and the adaptor 1, due to its resilient snap
locking action, remains engaged on the sheet metal barrier 3
during impact even without bolts 16. The relatively thick
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configuration of the web 9 adds signficant rigidity to the
adaptor 1 and the action of the edge beads 13 wrapping
around the upper and lower edges 6 and 7 of the sheet metal
guardrail 3 ensure that the adaptor 1 and guardrail 3 remain
engaged during impact with a colliding vehicle. The adaptor
1 may be easily installed without disrupting traffic due its
resilient snap-locking capability. The resilient snap-
locking feature renders the adaptor ideally suited for
rapidly reconditioning rusted or dented guardrails 3, for
rapidly converting guardrails in heavy traffic areas and may
be used as a temporary safety feature when roads are
converted for use during automobile or bicycle races.
Although this disclosure has described and
illustrated certain preferred embodiments of the invention,
it is to be understood that the invention is not restricted
to these particular embodiments. Rather, the invention
includes all embodiments which are functional or mechanical
equivalents of the specific embodiments and features that
have been described and illustrated herein.
