Road structure – process – or apparatus – Traffic director
Reexamination Certificate
2000-12-29
2002-07-23
Will, Thomas B. (Department: 3673)
Road structure, process, or apparatus
Traffic director
C052S098000, C256S013100, C403S002000, C040S606040, C040S607060
Reexamination Certificate
active
06422783
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a slip base support for tubular posts. Specifically, the invention describes a slip base unit having a casting which includes a triangular, multi-directional base plate and an integral coupler which secures a support post using an internal locking pin.
2. Related Art
Roadside signs can pose a serious safety hazard to motorists. Signs located next to roads pose potential collision points of impact for vehicles. Effective breakaway devices for roadside signs and light pole supports are necessary to achieve the highest levels of highway safety. Therefore, the U.S. Department of Transportation's Federal Highway Administration (FHWA) policy requires that all roadside sign and light pole supports used on the National Highway System meet the performance criteria contained in the National Cooperative Highway Research Program (NCHRP) Report 350
,Recommended Procedures for the Safety Performance Evaluation of H (Report
350). Similarly, State transportation agencies have similar performance criteria for roadside sign and light pole supports. Report 350 was prepared based on research sponsored by the American Association of State Highway and Transportation Officials (AASHTO) in cooperation with the FHWA, and outlines the required criteria for breakaway or yielding supports for signs and luminaries. The three primary appraisal factors for evaluating crash test performance are 1) structural adequacy, 2) occupant risk, and 3) after-collision vehicle trajectory.
Structural adequacy relates to the support's ability to break away or yield after impact in a predictable manner. The support structure must be able to break away cleanly without undue deformation or any shattering.
Occupant risk relates to the degree of hazard to which occupants in the impacting vehicle would be subjected. Occupant risk is evaluated by the degree of i) detached elements from the support, ii) vehicle rollover, iii) occupant impact velocities, iv) occupant ridedown accelerations, and v) change in vehicle velocity.
Detached elements, fragments or other debris from the sign support structure should not penetrate or show potential for penetrating the occupant compartment of the vehicle, or present an undue hazard to other traffic, pedestrians, or personnel in a work zone. Deformation of, or intrusions into, the occupant compartment that could cause serious injuries should not be permitted. Thus, fragments and components, including connectors, of the sign support system may become dangerous flying projectiles. Units that have unrestrained components, including fasteners and subcomponents, pose a higher number of potential missiles.
Vehicle rollover should not be caused by impact with the sign structure. Systems that have posts that shatter upon impact, creating tire puncture hazards and flipping poles under the vehicle, may pose a rollover hazard.
Occupant impact velocity is the speed at which an unrestrained passenger strikes some part of the vehicle interior such as the instrument panel, window, or door after the vehicle impacts a fixed or moveable object. The maximum allowable occupant impact velocity is 16.40 f.p.s. (5 m/s), with 9.84 f.p.s. (3 m/s) being the preferable maximum. Like occupant ridedown acceleration and change in vehicle velocity, this factor is primarily influenced by the amount of lateral force required to disengage the sign post from its base mounting structure.
Occupant ridedown acceleration is the highest lateral and longitudinal component of resultant vehicular acceleration averaged over any 10-ms interval for the collision pulse subsequent to occupant impact. Occupant ridedown acceleration is a function of the initial change in velocity (acceleration) of the occupant relative to the vehicle immediately after the vehicle impacts a fixed or moveable object. The maximum allowable ridedown acceleration is 20g's, with 15g's being the preferred maximum allowable ridedown acceleration.
Change in vehicle velocity is based on the change in velocity of an 1800# (816.5 kg) vehicle immediately after striking a breakaway support at speeds of 20 mph to 60 mph (32 kmph to 97 kmph). The maximum allowable change in velocity is 16 fps (4.87 mps), but preferably does not exceed 10 fps (3.05 mps).
After-collision vehicle trajectory is a measure of the potential of the post-impact trajectory of the vehicle to cause a subsequent multi-vehicle accident. After collision it is preferable that the vehicle's trajectory not intrude into adjacent traffic lanes. This factor is influenced primarily by the ease with which the sign post breaks away from its base mounting.
To address these and similar safety parameters for crash sign supports, numerous designs have been introduced. Most prior art describes signs that collapse upon impact, but do not “break away”. For example, Hugron (U.S. Pat. No. 5,160,111 —Nov. 3, 1992) describes a collapsible signal post having an insert tube connecting a base post and a sign post. The replaceable tubular insert has a helical cut, which allows the top post to bend upon impact. Deficiencies in this design include the non-reusable nature of the tubular insert, due to designed deformation upon impact, making the system expensive to repair/replace. Daggs et al. (U. S. Pat. No. 4,565,466 —Jan. 21, 1986) discloses a spring loaded return jointed sign post pedestal. The sign post mates with a fluted bell, which prevents rotation. Deficiencies include the inability to replace the sign post without replacing the attached base post, since the strength of the spring must be such that field reattachment of the sign and base posts is not practical. Miller (U. S. Pat. No. 2,141,067 —Dec. 20, 1938) utilizes a spring loaded lightweight post. However, this design lacks the ability to support a large sign, due to strength limitations of the spring and its connections.
A commonly used breakaway system is described by Nehls (U.S. Pat. No. 4,926,592 —May 22, 1990). The device has four main components: a ground engaging mounting post, a pedestal mounting member, a support post mounting member, and a support post for the sign. The ground engaging mounting post is buried in the ground, typically embedded in concrete. The pedestal mounting member, with a triangular plate at one end and a shaft at the other, slides its shaft within the ground engaging mounting post, where it is bolted. The support post mounting member also has a triangular plate at one end, and a vertical standard, typically elongated C-channels that form an open sided square cross-section. The triangular plate of the support post mounting member bolts to the triangular plate of the pedestal mounting member, such that there is a bottom plate (connected to the ground support) and a top plate (for connection to the sign post). The support post holding the sign is slid within the C-channels of the support post mounting member, and the post and channels are bolted together. It essential that the C-channels be bolted tightly against the sign post, which has multiple pre-drilled holes for bolt alignment. The triangular plates have notches in their apexes, through which cam bolts are fastened, securing the top plate to the bottom plate. The cam bolts each have a pair of cam rollers around the shaft of the bolt. The first roller is rollable across the interior of a notch of the support post triangular plate/flange, and the second cam is rollable across the interior of a notch if the pedestal mounting triangular plate/flange. When a vehicle strikes the sign post, the top plate slides off the bottom plate, and the cam bolts are ejected laterally out of the notches as the cams rotate. A friction reducing gasket, preferably made of TEFLON, is between the two triangular plates to facilitate the sliding movement of the top plate off the bottom plate. Deficiencies in the Nehls design include the bolting system of the sign post to
Keeling Law Firm
Northwest Pipe Company
Pechhold Alexandra K.
Will Thomas B.
LandOfFree
Breakaway post slipbase does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Breakaway post slipbase, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Breakaway post slipbase will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2822335