Static structures (e.g. – buildings) – Openwork; e.g. – truss – trellis – grille – screen – frame – or... – Three-dimensional space-defining
Reexamination Certificate
2001-01-24
2004-12-28
Slack, Naoko (Department: 3635)
Static structures (e.g., buildings)
Openwork; e.g., truss, trellis, grille, screen, frame, or...
Three-dimensional space-defining
C052S749100, C052S040000, C052S309110
Reexamination Certificate
active
06834469
ABSTRACT:
TECHNICAL FIELD
The invention relates generally to utility line support members and relates more specifically to a hollow composite support member configured as a tangent crossarm or deadend.
BACKGROUND
Utility lines are typically supported by a crossarm mounted horizontally on a utility or “telephone” pole. Crossarms are of two general types; tangent crossarms and deadend crossarms. Tangent crossarms (frequently referred to simply as crossarms) are used to support the generally vertically downward load resulting from the weight of the utility lines. Typically, a utility line is supported by an insulator which in turn is connected to the crossarm.
Deadend crossarms (often-times referred to simply as deadends) are used to support generally horizontal loads in order to retain tension in the utility line. Typically, the utility line is attached to an insulator that in turn is horizontally connected to the deadend. A single deadend can be used at a terminal end, while a pair of deadends can be utilized adjacent to one another on a single utility pole in order to maintain tension in two different directions. In the latter configuration, jumper lines are frequently used to electrically connect the utility lines attached to the two deadends. Most commonly, deadends are used when it is necessary to make turns in the utility line, although deadends are periodically used within a straight run to maintain utility line tension.
Traditionally, most crossarms and deadends have been made of wood, typically either Douglas Fir or Southern Yellow Pine, although some are manufactured from either steel or aluminum. Unfortunately, wood support beams do suffer from several disadvantages. The most obvious problem is the weatherability (or lack thereof) of wood beams. Although wood beams can be treated to improve their weatherability, they still tend to rot over time, thereby requiring replacement. This is especially true in warmer and more humid climates such as the southern United States, where the typical service life of a wood beam is a fraction of that in colder climates.
Because wood is a natural, variable product, crossarms and deadends made from wood can suffer from variations in important performance parameters such as strength due to defects and variations in the grain structure and density of the wood. Moreover, wood beams tend to lose strength as they begin to rot. This can lead to premature failure of the beam. The frequency with which wood beams must be replaced due to excessive or premature weathering leads to a number of problems, including increased labor costs, disposal costs and the risk of injury to linemen.
Another concern with wood beams involves conductivity. Unfortunately, wood is a relatively poor electrical insulator, especially when damp. This results both in losses due to electricity traveling through the beam and down the utility pole, as well as possibly posing a risk to utility linemen. For example, if a lineman touches a hot electrical line and a wood beam, he or she could be electrocuted because the wood beam (especially if wet) could provide a ground. Metal support beams suffer from similar disadvantages, such as weatherability problems due to corrosion and the fact that metal support beams are highly conductive to electricity.
Fiberglass reinforced composite support beams, which can be pultruded or extruded, solve many of the problems associated with wood and metal beams. Fiberglass beams have a high strength to weight ratio and are very good electrical insulators. If treated with a coating that protects the fiberglass from ultraviolet light, fiberglass beams can last as much as five to ten times as long as a comparable wood beam. Moreover, the strength of a fiberglass beam remains relatively constant over the life of the beam, while the strength of a wood beam steadily declines. Fiberglass beams can be manufactured at a cost that compares favorably to wood or metal beams. Further, fiberglass beams are generally immune to insect damage.
Fiberglass beams are not without problems, however. One problem relates to moisture entering the beam and acting as an electrical conductor. This can cause arcing, which is a concern both because of the potential for electrical power outage as well as linemen safety. Another difficulty associated with fiberglass beams involves the compressive damage or “crushing” that can occur when tightening mounting bolts or insulator bolts. This is especially a problem when the linemen are accustomed to mounting wood beams.
Prior attempts to resolve these problems include hollow pultruded beams that are filled with materials such as a polyurethane foam or blocks of polystyrene foam. Unfortunately, these designs may not completely prevent moisture from entering the interior of the beam, so arcing or power loss remain potential problems. Moreover, the foam provides minimal support to prevent compression damage. Adding the foam can also add significantly to the expense of manufacturing the beam.
U.S. Pat. No. 3,715,460 describes a deadend support beam that is a hollow fiberglass tube with metallic mounting members attached to opposite ends. The tube has very thick walls to provide sufficient strength against compression damage. This adds considerably to the expense and complexity involved in manufacturing the beam. It is unclear whether the metallic mounting members are sufficient in preventing moisture from accessing the interior of the beam, thereby possibly causing arcing.
U.S. Pat. No. 4,262,047 describes a support beam that has an outer covering bonded around a fiberglass honeycomb log having adjacent cells throughout the log. While this design reduces concerns over arcing and may provide sufficient strength to resist compression damage, this performance is achieved through a complex manufacturing process that is both difficult to accomplish and quite expensive.
U.S. Pat. No. 5,605,017 describes a hollow support beam having bushings that provide additional resistance to compressive forces. Cylindrical bushings are placed into holes drilled through the support beam and bear any compressive forces that result from either mounting the beam to a utility pole or from mounting other equipment or mounting apparatuses to the beam itself. Unfortunately, this requires rather large holes to be drilled through the beam, which weakens the beam to other forces.
A need remains for a utility line support beam that provides sufficient resistance to compressive forces while preventing moisture from entering the beam. A need remains for a simple, lost cost and easy to manufacture utility line support beam.
SUMMARY
The invention involves a utility line support beam that resists compressive forces while preventing moisture from entering the interior of the beam. In its simplest terms, the invention involves a reinforcing member placed within the interior of the beam. The reinforcing member is positioned to absorb any compressive forces resulting from either mounting the beam on a utility pole or mounting other structures to the beam, as well as forces in use due to factors such as wind and ice. The beam is sealed to prevent moisture from entering.
Accordingly, the invention is found in a utility line support structure that includes a hollow fiber reinforced beam that has a transverse hole extending therethrough. A hollow reinforcing member that has an inner diameter about the same as a diameter of the transverse hole is placed within the beam to coincide with the transverse hole. The reinforcing member has an outer diameter that is greater than the inner diameter of the reinforcing member and is positioned within the beam such that a bolt can be inserted through both the beam itself and the reinforcing member.
The invention is also found in a method of manufacturing a utility line support structure. The method includes pultruding a hollow fiber reinforced beam having a first end and a second end and forming a transverse through hole within the beam. A reinforcing member having an outer diameter greater than a diameter of the transverse hole is positioned within th
Blumentritt Bruce F
Fingerson Conrad F.
Geotek, Inc.
Merchant & Gould P.C.
Slack Naoko
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