Illumination – Supports – Pole or post type support
Reexamination Certificate
2001-02-12
2002-06-04
Husar, Stephen (Department: 2875)
Illumination
Supports
Pole or post type support
C362S265000, C174S0450TD
Reexamination Certificate
active
06398392
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a means and methods for elevating structures, and in particular, to poles anchored in the ground for vertically elevating any type of member or members to an extended distance.
This invention further relates to installation of lighting fixtures in a position elevated above the ground on poles, and in particular, the comprehensive integrated combination of fixture supports and poles, wiring, and electrical components to operate the lighting fixtures.
2. Problems in the Art
A number of structures or things must be suspended from the ground. Examples are light fixtures, sirens, antennas, wires, and the like. Many times these structures need to be rigidly supported. Of course, a conventional means to accomplish this is to utilize an elongated pole.
Commonly known examples of poles of this type are telephone poles, electrical wire poles, light poles, sign poles, and utility poles. Most of these types of poles are anchored in the ground and extend vertically upward to many times tens of feet in height.
The widespread utilization of these types of poles is indicative of the preference to utilize elongated structures or poles to elevate objects in the air. For whatever reasons, whether it be economical or practical, the demand for the poles is very high for a number of different uses.
Poles of this nature can be made of a number of materials and can be erected and installed in a number of ways. While each of the commonly used poles achieves the end result of elevating objects in the air, the different types commonly used have both their advantages and disadvantages.
Wood poles represent the longest used and still today the many times preferred type of pole. They are relatively inexpensive, have a good height to diameter strength ratio, and can be rather easily adapted for a number of uses.
Problems and disadvantages of wood poles, however, are at least:
a. Difficult to find straight wood poles, especially for taller heights;
b. Natural processes decay or at least weaken wood;
c. Wood is fairly heavy;
d. Pole comes in single long length which can be difficult to transport;
e. Environmental problems associated with using trees could effect availability;
f. Appearance;
g. Uncertainty of strength;
h. Bottom end is buried in the ground and therefore even more susceptible to decay and deterioration; and
i. Difficulties in providing adequate foundation and support for the pole.
Wood, therefore, may represent a cheaper, more available source for at least shorter poles, but is not the preferred type of pole because of, in significant part, some of the above mentioned problems.
An alternative pole that has more recently been utilized is one made substantially of concrete. For even significantly tall poles, concrete has great strength in compression and with a steel cable infra structure offers strength in tension. With advances in the nature of concrete, such poles offer a relatively economical and very strong alternative to wood.
Disadvantages of concrete are at least the following, however:
a. Very heavy, even with a hollow core (may not be able to make very long);
b. Require a big crane or other power means to lift them which is expensive;
c. The weight tends to cause them to shift when positioned in the ground;
d. It is somewhat difficult to form holes or otherwise attach structures to such poles; and
e. Such poles present shipping problems due to weight, length, and width.
Again, while concrete poles do provide some advantages, their disadvantages prevent them from being the preferred used type of pole.
These types of above-mentioned deficiencies have resulted in the pole of preference being comprised of a steel pole which is anchored in the ground usually to poured concrete fill. Such a combination allows the use of high strength yet lightweight hollow tube steel for the above ground portion, while utilizing lower cost and high weight concrete as the anchor in the ground. This also aids in installation as the concrete bases can be poured and then the lightweight steel poles mounted thereon.
These advantages do not come without a price however. The disadvantages of this type of pole are at least the following:
a. Most expensive;
b. Concrete and rebar (if used) must be custom designed;
c. Heavy, thick base plate must be welded to the lightweight steel tube;
d. Galvanizing, which is the preferred protective coating, is sensitive to the temperature differences between the thick base and thin tube;
e. Concrete foundations must be accurately constructed on the site according to the custom design;
f. The poles and the concrete fill, and any other hardware many times are required to come from different sources and therefore may not adequately match; and
g. Corrosion problems.
As can be appreciated, the problems with steel and concrete foundation poles are not insignificant. Because the joint between the steel and concrete will have to take much of the stress provided by the long moment arm of the upwardly extending pole, and because of wind load and other factors, it is critical that for each installation the junction between the pole and the foundation be accurately and correctly prepared. This is an intricate matter requiring not only the correct design specifications and construction of the concrete foundation and the steel pole, but also accurate and faithful adherence to design and installation specifications by field personnel in forming the concrete foundation.
The custom design must include not only the height and weight requirements associated with each particular pole, but also must consider the type and strength of concrete used, the design of the rebar cage in the concrete, and the design and placement of hardware attaching the steel pole to the concrete.
As is well understood by those with ordinary skill in the art, a custom design for the concrete foundations requires significant expenditure of resources. Additionally, the success of the design is then entirely dependent upon its implementation in the field.
Unfortunately, a significant and real problem exists in contractors carrying out the installations not doing so accurately. Without a reliable match between the design parameters of the concrete foundation and the parameters associated with the steel pole with its actual installation, the entire pole structure is susceptible to damage or failure. Accordingly, substantial expense may be incurred over designing and installing the concrete foundations to allow for field installation tolerances. Additionally, concrete requires up to 28 days to develop full strength needed for tensile strength and to anchor the bolts used to secure the pole. The compressive qualities of concrete develop more quickly.
A second major problem with steel pole and concrete foundation combinations is that of corrosion. While presently the corrosion problems are addressed by attempting to galvanize all metal components, at least the following impediments exist to that being successful.
The best environment for corrosion is generally within a few feet above and below the ground line. Frequently, concrete and steel poles such as described above have the concrete bases or foundations poured and submerged from close to ground level downwardly. Therefore, the most corrosion-susceptible area of the metal, at or neat the joint with the concrete, is in that area where corrosion is the most likely. Moisture in the form of standing water and condensation is most concentrated in this area. Additionally, this is also an area where the concentration of oxygen is high, which is one of the components of corrosion and rust.
Secondly, as previously mentioned, the joint between the steel pole and the concrete foundation often represents the highest stress area for the combination. It is known in the art that corrosion increases with stress.
Third, the conventional way of securing the joint is to utilize long bolts through a mounting plate of the steel pole into the concrete. These bolts also take a majority of the stress and are therefore
Drost James L.
Gordin Myron K.
Husar Stephen
McKee Voorhees & Sease, P.L.C.
Musco Corporation
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