Supports – With component frangible or deformable on impact or overload
Reexamination Certificate
1999-05-11
2001-10-30
King, Anita (Department: 3632)
Supports
With component frangible or deformable on impact or overload
C248S530000, C403S002000
Reexamination Certificate
active
06308927
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to sign posts and, more particularly, to break away sign posts for signs adjacent to roadways.
A roadway sign typically includes an anchor that is driven into the ground, an extended support connected to the anchor and extending above the ground, and a sign attached to the support. Due to their proximity to the roadway, road signs may be a hazard for errant vehicles.
The Federal Highways Administration “FHWA”) has promulgated yielding criteria for sign posts and structures located adjacent to designated traffic areas both to protect the occupants of vehicles and to reduce property damage from collisions with these structures. For small and intermediate roadside supports, the FHWA standards required a structure weak enough to bend upon impact and allow a vehicle to pass over the support structure with minimum deceleration. Thus, occupant interior impact could be avoided and vehicular damage could be minimized. After a collision, however, the entire roadway sign support needs to be replaced, including the anchor in many cases.
To avoid the cost of replacing the anchors after a collision, sign posts have been designed in which the sign support shears from the anchor upon impact so that the anchor may subsequently be reused with a replacement support after a collision. Couplers machined or cast with predetermined break points, such as shear bolts, have been employed with some success to separate the sign support and the anchor so that the anchor is undamaged when a vehicle collides with a sign post. However, the couplers are vulnerable to shearing from wind loads on a sign.
Accordingly, it would be desirable to provide a breakaway connector strong enough to withstand a given wind load allowing it to break or release upon impact within allowable FHWA criteria for vehicle deceleration.
BRIEF SUMMARY OF THE INVENTION
In an exemplary embodiment of the invention, a sign post assembly comprises an anchor member, a breakaway connector, and a support member. The anchor member includes a ground member that is driven into the ground, and an anchor plate attached to an end of the ground member above the surface of the ground. The anchor plate has a threaded opening therethrough.
The breakaway connector includes a shear member and a bushing. The shear member includes a first threaded end and a second threaded end. A necked down portion of smaller cross sectional area extends between the first and second ends. The necked down portion includes flat sides so that the shear member may be gripped with a wrench when erecting a sign or for removal after impact. The first end is threaded into the opening in the anchor plate and attached thereto. The second end of the shear member includes a shoulder and an engagement surface. The bushing is made of rubber, surrounds the shoulder, and spans the necked down portion of the shear member.
The support member includes a sign support and a support plate. The support plate has an aperture therethrough. The second end of the shear member extends through the aperture and is attached to the support plate. The support plate rests on the shoulder of the shear member and the bushing is compressed between the support plate and the anchor plate.
The shear member fractures at a desired location in the necked down portion within FHWA guidelines and while withstanding required wind loads. The bushing surrounding the shear member spreads the wind bearing load over an appreciably greater area than the necked down portion of the shear member but allows the shear member to break away within FHWA standards.
Thus, the break away sign support allows the sign support to survive a strong wind, and the anchor to survive a strong collision. In addition, considerable time and money are saved since the anchor does not need to be replaced. Rather, another sign may be quickly erected after a collision by simply replacing the shear member and the sign support.
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Armstrong Teasdale LLP
King Anita
Morrison Naschica S
LandOfFree
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