Fences – Highway guard
Reexamination Certificate
2001-08-31
2003-09-16
Browne, Lynne H. (Department: 3679)
Fences
Highway guard
C256S001000, C404S006000, C404S009000, C404S010000
Reexamination Certificate
active
06619630
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to highway guardrail systems having a guardrail mounted on posts, and more particularly, to guardrail end treatments designed to meet applicable federal and state safety standards including but not limited to crash worthiness requirements.
BACKGROUND OF THE INVENTION
Along most highways there are hazards which present substantial danger to drivers and passengers of vehicles if the vehicles leave the highway. To prevent accidents from a vehicle leaving a highway, guardrail systems are often provided along the side of the highway. Experience has shown that guardrails should be installed such that the end of a guardrail facing oncoming traffic does not present another hazard more dangerous than the original hazard requiring installation of the associated guardrail systems. Early guardrail systems often had no protection at the end facing oncoming traffic. Sometimes impacting vehicles became impaled on the end of the guardrail causing extensive damage to the vehicle and severe injury to the driver and/or passengers. In some reported cases, the guardrail penetrated directly into the passenger's compartment of the vehicle fatally injuring the driver and passengers.
Various highway guardrail systems and guardrail end treatments have been developed to minimize the consequences resulting from a head-on impact between a vehicle and the extreme end of the associated guardrail. One example of such end treatments includes tapering the ends of the associated guardrail into the ground to eliminate potential impact with the extreme end of the guardrail. Other types of end treatments include breakaway cable terminals (BCT), vehicle attenuating terminals (VAT), the SENTRE end treatment, and breakaway end terminals (BET).
It is desirable for an end terminal assembly installed at one end of a guardrail facing oncoming traffic to attenuate any head-on impact with the end of the guardrail and to provide an effective anchor to redirect a vehicle back onto the associated roadway after a rail face impact with the guardrail downstream from the end terminal assembly. Examples of such end treatments are shown in U.S. Pat. No. 4,928,928 entitled Guardrail Extruder Terminal, and U.S. Pat. No. 5,078,366 entitled Guardrail Extruder Terminal.
A SENTRE end treatment often includes a series of breakaway steel guardrail support posts and frangible plastic containers filled with sandbags. An impacting vehicle is decelerated as the guardrail support posts release or shear and the plastic containers and sandbags are compacted. A cable is often included to guide an impacting vehicle away from the associated guardrail.
A head-on collision with a guardrail support post located at the end of a guardrail system may result in vaulting the impacting vehicle. Therefore, guardrail end treatments often include one or more breakaway support posts which will yield or shear upon impact by a vehicle. Examples of previously available breakaway posts are shown in U.S. Pat. No. 4,784,515 entitled Collapsible Highway Barrier, and U.S. Pat. No. 4,607,824 entitled Guardrail End Terminal. Posts such as shown in the '515 and the '824 Patents include a slip base with a top plate and a bottom plate which are designed to not yield upon lateral impact. When sufficient axial impact force is applied to the upper portion of the associated post, the top plate and the bottom plate will slide relative to each other. If a vehicle contacts the upper part of the post, the associated impact forces tend to produce a bending moment which may reduce or eliminate any slipping of the top plate relative to the bottom plate. Also, improper installation of the top plate relative to the bottom plate, such as over tightening of the associated mechanical fasteners, may prevent proper functioning of the slip base. A breakaway support post is also shown in U.S. Pat. No. 5,503,495 entitled Thrie-Beam Terminal with Breakaway Post Cable Release.
Wooden breakaway support posts are frequently used to releasably anchor guardrail end treatments and portions of the associated guardrail. Such wooden breakaway support posts, when properly installed, generally perform satisfactorily to minimize damage to an impacting vehicle during either a rail face impact or a head-on impact. However, impact of a vehicle with a wooden breakaway support post may often result in substantial damage to the adjacent soil. Removing portions of a broken wooden post from the soil is often both time consuming and further damages the soil. Therefore, wooden breakaway support posts are often installed in hollow metal tubes, sometimes referred to as foundation sleeves, and/or concrete foundations. For some applications, one or more soil plates may be attached to each metal sleeve to further improve the breakaway characteristics of the associated wooden post. Such metal sleeves and/or concrete foundations are relatively expensive and time consuming to install.
Light poles, sign posts or similar items are often installed next to a roadway with a breakable or releasable connection. For some applications, a cement foundation may be provided adjacent to the roadway with three or more bolts projecting from the foundation around the circumference of the pole. Various types of frangible or breakable connections may be formed between the bolts and portions of the light pole or sign post.
Other possible solutions to the problems discussed are found in U.S. patent application Ser. No. 09/074,496, filed May 7, 1998, entitled Breakaway Metal Post for Highway Guardrail End Treatments, and U.S. Provisional Application No. 60/046,015 filed May 9, 1997, entitled A Breakaway Metal Post for Highway Guardrail End Treatments. These solutions have been adequate for their intended purposes, but are not satisfactory in all respects. For example, previous breakaway support post designs have not included reusable parts. For another example, previous breakaway support post designs have included parts which require extensive machining.
SUMMARY OF THE INVENTION
From the foregoing, it may be appreciated that a need has arisen for an apparatus for a breakaway support post for mounting a guardrail thereon as part of a highway guardrail system which is cheaper and more reusable than previous designs. According to one form of the present invention, this need is met by such a breakaway support post which includes an elongated body having an upper portion including a first upper end and a first lower end, and a lower portion including a second upper end and a second lower end. The second lower end is insertable into the soil adjacent to a roadway. The first lower end has a first substantially vertical surface thereon and the second upper end has a second substantially vertical surface thereon. A first arrangement attaches the guardrail to the elongated body adjacent to the first upper end. A second arrangement rotatably couples the upper and lower potions, and releasably secures the upper portion of the elongated body generally aligned with the lower portion of the elongated body, wherein the breakaway support post will resist a rail face impact with the guardrail and wherein an impact with one end of the attached guardrail will tend to rotate the upper portion of the elongated body relative to the lower portion of the elongated body. The second arrangement includes a first plate having a first opening and a second opening therethrough, and having a third substantially vertical surface thereon. A portion of the third substantially vertical surface is disposed against a portion of the first substantially vertical surface. The first plate is secured to the first lower end by a weld. The second arrangement further includes a second plate having a third opening and a fourth opening therethrough, and having a fourth substantially vertical surface thereon. A portion of the fourth substantially vertical surface is disposed against a portion of the second substantially vertical surface. The second plate is secured to the second upper end by a weld. The second plate
Baker & Botts L.L.P.
Browne Lynne H.
Garcia Ernesto
TRN Business Trust
LandOfFree
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