Fences – Highway guard
Reexamination Certificate
2001-04-25
2003-04-29
Hartmann, Gary S. (Department: 3671)
Fences
Highway guard
C404S006000, C404S010000
Reexamination Certificate
active
06554256
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to an end terminal assembly for a highway guardrail system having a guardrail mounted on posts and a method for dissipating energy from a vehicle impact with the highway guardrail system as required by applicable federal and state standards including but not limited to crash worthiness requirements.
BACKGROUND OF THE INVENTION
Along most highways and roadways 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 the highway, guardrails are often provided along the side of the highway. Experience has shown that guardrails should be installed such that the end of the guardrail facing the flow of oncoming traffic does not present another hazard more dangerous than the original hazard requiring installation of the guardrail. Early guardrails often had no protection at the end facing the oncoming traffic. Sometimes impacting vehicles became impaled on such guardrail ends 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 compartment of the vehicle fatally injuring the driver and passengers.
Various guardrail designs and end terminal assemblies have been developed to minimize consequences resulting from impact between a vehicle and the end of a guardrail. These designs include tapering the end of the guardrail into the ground to eliminate potential contact with the end of the guardrail. Other types of end terminal assemblies 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 to be usable at either end of a guardrail as a means of both attenuating a head on impact as well as providing an effective anchor for an impact along the side of the guardrail downstream from the end terminal assembly. Examples of such end terminal assemblies 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.
Guardrail beams and associated guardrail systems have recently been developed to more evenly spread stresses sustained during a vehicle impact to create a more uniform, stable and predictable response. Such guardrail beams preferably include edge treatments such as folds or curls extending along the top edge and the bottom edge of each guardrail beam. The strength of such guardrail beams and ability to resist damage from a vehicle impact generally meets or surpasses current highway safety standards. Such guardrail beams are often lighter in weight than conventional W-beam guardrails having similar overall geometric configurations.
Recently, increased interest in the need for more stringent safety requirements has culminated in the issuance of the National Cooperative Highway Research Program Report 350 (NCHRP 350). The performance standards of NCHRP 350 require all new safety hardware to be tested with larger vehicles than required by previous standards. NCHRP 350 evaluates all safety hardware within three areas: structural adequacy, occupant risk, and vehicle trajectory. Each area has corresponding evaluation criteria. The Federal Highway Administration (FHWA) officially adopted these new performance standards and has ruled that all safety hardware installed after August of 1998 will be required to meet the new standards.
SUMMARY OF THE INVENTION
In accordance with teachings of the present invention, disadvantages and problems associated with previous guardrail end terminal assemblies used to minimize damage to a vehicle caused by colliding with the end of a highway guardrail system have been substantially reduced or eliminated. The present invention substantially reduces manufacturing costs and installation costs of a guardrail end terminal assembly while at the same time allowing the end terminal assembly to effectively anchor an associated guardrail during a downstream rail face impact and to function satisfactorily during a head on impact with the end of the guardrail without excessive damage to the impacting vehicle.
An end terminal assembly formed in accordance with the present invention preferably includes a kinetic energy absorbing assembly for use with a guardrail system having guardrail beams with edge folds or edge curls. The kinetic energy absorbing assembly preferably stretches or flattens guardrail beams having edge curls or edge folds to dissipate kinetic energy and bends the flattened guardrail beams away from a vehicle impacting the end of the guardrail system. For one embodiment the kinetic energy absorbing assembly preferably includes an arcuate shaped tensioning guide which applies opposing forces to respective edge curls or edge folds of the guardrail to stretch the guardrail laterally and to bend the stretched or flattened portion of the guardrail in a direction away from the impacting vehicle. The tensioning guide preferably includes a top flange and a bottom flange which engage respective top edge folds and bottom edge folds at the end of the guardrail during installation of the associated end terminal assembly. The top and bottom flanges of the tensioning guide cooperate with the respective edge folds of the guardrail to provide uniform, optimum alignment of the kinetic energy absorbing assembly with the guardrail. Securely engaging the kinetic energy absorbing assembly as an integral part of the end of the guardrail substantially minimizes the tendency of the kinetic energy absorbing assembly to rotate relative to the guardrail when impacted by vehicle offset from the center of the kinetic energy absorbing assembly or at an angle relative to the kinetic energy absorbing assembly.
An end terminal assembly incorporating teachings of the present invention preferably includes a kinetic energy absorbing assembly which dissipates impact energy by laterally stretching a W-shaped guardrail beam into a relatively flat sheet and bending the flattened guardrail in an arc directed away from an impacting vehicle. The kinetic energy absorbing assembly preferably includes a tensioning guide which may be fabricated from a single piece of sheet metal using conventional metal bending and stamping techniques.
Technical advantages of the present invention include engaging top and bottom flanges of a kinetic energy absorbing assembly which may be integrally engaged with respective edge folds at one end of a guardrail to provide a more stable end terminal assembly. During a vehicle impact with the energy absorbing assembly, the flanges continue to engage the respective edge folds of the guardrail and deform the guardrail in a manner that absorbs kinetic energy from the impacting vehicle. Engagement between the flanges and the respective edge folds maintains stable interaction between the guardrail and the end terminal assembly. Engagement of the flanges with the respective edge folds results in the kinetic energy absorbing assembly becoming and integral part of the guardrail and maintains this integral relationship during a vehicle impact. The integral relationship between the kinetic energy absorbing assembly and the guardrail combines the overall mass of the associated end terminal assembly to more effectively dissipate energy from a vehicle impacting the one end of the guardrail. During a vehicle impact, the response of the end terminal assembly is more stable and more predictable. The end terminal assembly effectively uses characteristics of the attached guardrail beams to improve alignment with other components of the associated highway,guardrail system and to reduce the effects of a vehicle which collides at an angle to or offset from the end of the guardrail. The present invention allows reducing the overall weight of an end terminal assembly as compared with some conventional end terminals while maintaining desired structural stability and energy absorbing capability.
REFERENCES:
patent: 18
Baker & Botts L.L.P.
Hartmann Gary S.
ICOM Engineering, Inc.
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