Roadside construction projects must oftentimes be carried out without stopping roadway traffic. Accordingly, measures are required to maintain safety in the work environment. Temporary warning signs are becoming increasingly popular since the geographic configuration of a work site frequently changes before the work is finished. Also, with the advent of more powerful, complex equipment, roadway repairs and roadside work projects can be completed within a relatively short time, such that erection of permanent warning signs would not be practical.
One class of temporary warning signs includes sign panels made of flexible material, which are maintained in a taut, planar position by backing members extending across the sign panel. These backing members frequently comprise ribs of fiberglass or aluminum material. It has become popular to arrange the sign panel so that it can be quickly and easily detached from the supporting ribs and rolled up for compact storage. Thus, the need arises for releasably securing the rib members to the flexible sign panel.
Initially, pockets for receiving the ends of supporting ribs were formed by joining relatively small pieces of fabric to the corners of the flexible sign panels, so as to form a rib-receiving pocket between the fabric and the sign panel. Roadway warning signs are employed out of doors and are thereby subjected to wind gusts and traffic induced wind bursts which expose the flexible sign panel to substantial amounts of strain, particularly where rib supports are attached to the sign panel. Accordingly, with static and vibratory wind loadings applied to the sign panel, the ends of the supporting ribs were found to wear through the pocket material, requiring substantial repairs to be made to the sign assembly. In time, steps were taken to provide more secure attachment of supporting ribs to portions, usually outside corners, of the sign panel. For example, fabric pockets have been employed in U.S. Pat. Nos. 3,899,843 and 3,526,200, while resilient straps have been proposed in U.S. Pat. No. 4,592,158. Rigid panel pockets have also been proposed in U.S. Pat. Nos. 4,426,800 and 4,490,934. Despite these advancements, improvements in rib supports are still being sought.