Static structures (e.g. – buildings) – Machine or implement
Reexamination Certificate
1999-07-22
2001-06-12
Purol, David M. (Department: 3634)
Static structures (e.g., buildings)
Machine or implement
Reexamination Certificate
active
06244014
ABSTRACT:
BACKGROUND
The present invention relates to elongated structural members such as pilings, poles and columns, and methods for making such members.
Concrete, steel, and wood are conventionally used for pilings, telephone poles, and the like. However, each of these materials has disadvantages. Concrete and steel pilings are heavy and awkward to maneuver. Neither concrete nor steel pilings make good fender pilings because neither is “forgiving” when impacted. Under impact steel bends and buckles and concrete shatters. Both concrete and steel pilings are expensive to repair. -Furthermore, steel, either standing alone or as a reinforcement in porous concrete, is subject to corrosion.
Wood pilings are plagued by wear and tear and are attacked by wood-boring marine organisms. Wood pilings are typically treated with creosote, but even this material can be ineffective against modern marine borers. These marine borers can only be stopped by wrapping the wood pilings in plastic coverings. However, these plastic coverings cannot withstand much wear and tear, especially abrasion from normal vessel contact. So in addition to a thin plastic wrap, wooden fender piles often require thick plastic wrappings, which are expensive to put in place. Wood used for telephone poles is subject attack from environmental hazards such as woodpeckers, and in desert locations, there can be severe erosion from sandstorms.
Composite pilings are also known, being disclosed for example in U.S. Pat. No. 5,180,531 to Borzakian, that document being incorporated herein by this reference. The '531 patent discloses a plastic pipe having an inner pipe core or mandrel being 6 inches or less in diameter, and a substantially homogenous coating being at least two inches thick. The thick plastic coating provides the bulk of the mechanical strength, being formulated with a desired combination of flexibility, brittleness, and impact resistance for use as pilings including fender pilings of docks, telephone poles, light standards, etc. The plastic pipe of the prior art is not entirely satisfactory in that uniform thick coatings that are free of voids are somewhat difficult to achieve, and longer lengths of the pilings such as from 20 feet to 60 feet normally require assembly of shorter length segments, with consequent degradation of structural and environmental integrity and increased cost of fabrication. Also, when the plastic pipe is provided with the homogenous plastic coating having with a desired flexibility and impact resistance for fender piling applications, the bending strength is less than desired for withstanding side loads that are produced by contact with approaching vessels.
U.S. Pat. No. 5,766,711 to Barmakian discloses a composite camel structure including a pipe mandrel and a thermally bonded plastic cushion surrounding the mandrel, that patent being incorporated herein by this reference. A mold having the mandrel centered therein is filled with molten plastic, the plastic being cooled and solidified by feeding water into the mandrel for progressively solidifying the cushion member along mandrel for producing a thermal bond without excessive tensile strain in the plastic material, thereby to achieve a substantially unbroken outside surface. Although the use of cooling water inside the mandrel reduces the likelihood of cracks and voids in the cushion material, the pipe mandrel is undesirably expensive, and pilings having pipe encapsulated in plastic have structural disadvantages as discussed above.
In view of these problems with conventional pilings and telephone poles, there is a need for pilings and telephone poles that have a long life, are easily installed, environmentally sound, durable in use, and having high bending strength.
SUMMARY
The present invention meets this need by providing a steel-reinforced plastic piling that has particularly high bending strength. In one aspect of the invention, an elongated composite structural member having a cross-sectional area of at least 50 square inches includes a rigid cage including a parallel spaced plurality of main rod members that are connected by a plurality of loop elements, portions of each main rod member being rigidly connected to at least 30 percent of the loop elements; and a cylindrical plastic body encapsulating the rigid cage.
Preferably the loop elements can contact inwardly facing portions of at least some of the main rod members for preventing locally inward movement of the main rod members within the material of the plastic body when the structural member is heavily loaded in bending. Each of the main rod members is preferably rigidly connected to substantially all of the loop elements. The structural plastic member can include a secondary rod member forming the plurality of loop elements. The secondary rod member can be helically formed.
The main rod members and the loop elements can be formed steel reinforcing bars, the rigid connections being welded connections. The main rod members can be in a circularly spaced array, the plastic body being circularly cylindrical, the main rod members being approximately equally spaced from an outside surface of the plastic body. The main rod members can have a nominal diameter of between approximately 4 percent and approximately 10 percent of an outside diameter of the plastic body, the loop elements having a nominal diameter of between 30 percent and approximately 70 percent of the diameter of the main rod members. The loop elements can define a secondary rod envelope, the loop elements having a pitch spacing being approximately half of an outside diameter of the secondary rod envelope.
Preferably the plastic body sealingly surrounds the cage, having a thickness of not less than approximately 4 percent of the outside diameter of the plastic body over each of the main rod members and the loop elements. The outside diameter of the plastic body can be approximately 13 inches, the diameter of the main rod members being approximately 1 inch, the diameter of the loop elements being approximately 0.4 inch diameter, and the loop elements defining a secondary rod envelope having an outside diameter of approximately 9.5 inches. Adjacent ones of the main rod members can be equally spaced.
The plastic body can solidly fill the rigid cage. The plastic body can consist of a main polymeric component and an additive component, the main polymeric component consisting of low-density polyethylene of which at least 60 percent is linear low density polyethylene, the additive component including an effective amount of an ultraviolet inhibitor.
In another aspect of the invention, an elongated composite structural member having a cross-sectional area of at least 80 square inches includes the parallel spaced plurality of main rod members; and the cylindrical plastic body encapsulating the main rod members, each of the main rod members being spaced at least 0.5 inch within an outside contour of the plastic body, wherein the plastic body consists of a main polymeric component and an additive component, the main polymeric component consisting of low-density polyethylene of which at least 60 percent is linear low density polyethylene, the additive component including an effective amount of an ultraviolet inhibitor. Preferably the main polymeric component is at least 90 percent of the plastic body for enhanced resistance to cracking of the material during cooling following the molding process, the plastic body including not more than 5 percent by weight of high-density polyethylene.
In a further aspect of the invention, a method for forming a structural plastic member includes:
(a) helically forming a rod member to have a plurality of loop elements;
(b) welding a parallel spaced plurality of main rod members to the outside of each of the loop elements to form a welded cage; and
(c) encapsulating the welded cage in a plastic body.
The encapsulating can include:
(a) providing an injection mold having an elongate cylindrical cavity;
(b) loading the mold with the welded cage;
(c) centering the welded cage within the mold;
(d) injecting a
Purol David M.
Sheldon & Mak
LandOfFree
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