Static structures (e.g. – buildings) – Mechanism operated relatively movable shaft assembly – Tilts relative to base
Reexamination Certificate
2000-12-05
2004-08-31
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
Mechanism operated relatively movable shaft assembly
Tilts relative to base
C052S118000, C052S123100, C052S745170, C212S347000
Reexamination Certificate
active
06782667
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to tall support towers for large structures, such as wind turbine generators, microwave antennas or the like, and, more specifically, to tall support towers which are constructed of multiple telescopic sections that telescopically extend vertically to the tower's full height and/or to tall support towers which are assembled at the site of installation in a generally horizontal position, and then tilted upwardly to a vertical position. The present invention incorporates both features into unique support tower structures.
2. Description of the Prior Art
Wind-powered windmills and turbines have been in use for many years for producing power for many purposes. Wind power to drive wind turbine generators to generate electrical energy have been used as an alternative energy source for many years, and the development of such uses of wind power is ongoing as exemplified by the following U.S. patents.
11,181
3,495,370
4,323,331
446,744
3,715,852
4,590,718
2,213,870
4,231,200
4,903,442
2,267,705
Initial development of wind turbine generators to produce electrical energy involved relatively small turbines and generators having a capacity of approximately 50 to 65 kilowatts, which were supported by small towers of approximately 50 to 75 feet in height. Towers of this height were typically fabricated from steel truss members of rectangular plan configuration and of lightweight construction. The lightweight construction enabled the towers to be initially positioned generally horizontally with the lower end pivotally connected to a foundation and the wind turbine and generator mounted at the upper end. The tower was then tilted upwardly to a vertical position by a cable and winch assembly or other power source to pull the tower to a vertical position on the foundation from the generally horizontal position. This tilting of the tower provided a relatively inexpensive installation that could be quickly and efficiently completed in a short time and required the use of only small and highly mobile erection equipment. A problem existed, however, in that as the tower was tilted into vertical position, the feet of the tower conflicted with anchor bolts that protruded from the foundation which would prevent the tower from setting flat on the foundation. This was resolved by bolting multiple steel adapter structures to the anchor bolts with the flat upper surface of each adapter receiving one of the feet of the tower. The tower feet were then bolted to the top of the adapters through matching bolt holes in the feet and top surface of the adapter.
More recent wind power generation included the development of larger and more efficient and cost-effective turbines capable of driving larger generators, having capacities up to approximately 750 kilowatts. The larger turbines and higher capacity generators required that taller support towers be provided in order to maximize the use of winds existing at higher elevations which have higher average speeds and smoother air flow characteristics than winds closer to the ground. In order to erect the larger towers to support the wind turbine generators at the higher elevations needed to maximize power production, heavy lift cranes with a lift capacity of up to 230 tons are used. The taller towers, either steel truss or tubular cross-sectional configuration are erected in sections by the crane and assembled in the vertical position. Each section of the tower is rigidly affixed to the adjacent tower sections by means of bolted connections. In the case of tubular cross-section towers the bolted connections are created through use of matching inwardly oriented flanges at each joint which contained matching boltholes to receive the bolts. The wind turbine generators are then mounted on top of the vertically oriented tower. This procedure is effective for towers up to approximately 180 feet in height with turbine and generator assemblies weighing up to approximately 60,000 pounds.
However, as the tower height increased along with the generating capacity and the weight of the wind turbine generator, the costs of installation increased materially. The transportation costs to move a heavy lift crane to a site of installation and then remove it from the site of installation, as well as the rental cost for a heavy lift crane, can be extremely high. A typical heavy lift crane with a lifting capacity of approximately 230 tons is barely capable of installing a 750 kilowatt wind turbine generator on a tower that is about 200 feet tall. Extra-heavy lift cranes with even higher costs are required for taller towers or heavier generators. Use of the extra-heavy lift cranes increases costs dramatically due to the very high rental and transportation costs of these larger units. Additional costs include the requirement for multiple large trucks and trailers for moving the extra-heavy lift crane to and from the job site, increased risk of serious accidents while traveling during movement of the crane to and from the job site, as well as at the job site, and increased wear and tear on public highways and plant site roads.
The massive size of extra-heavy lift cranes and their limited mobility require that work sites be well prepared to assure stability during the erection process. An extra-heavy lift crane work site requires extensive preparation of road bases with minimal tolerance for allowable slope of the road or for side to side pitch and crane working pads which require the use of heavy temporary matting beneath the cranes. Also, once on a job site, the cranes need to be moved frequently from one wind turbine foundation to another which further adds to high maintenance costs on the cranes and roads and expensive time-consuming moving procedures. This is especially problematic at preferred and available job sites which are usually near the top of hills, ridges or mountains which require erection equipment to be highly mobile in order to minimize erection time and cost. Use of the extra-heavy lift cranes means that many of the best sites cannot be used due to the excessive cost of road and pad construction needed for the larger cranes.
Heavy lift cranes are typically near their maximum safe working ranges when erecting wind turbine generators of 600-750 kilowatt capacity on towers as high as 200 feet. This condition makes it necessary to suspend erection work during winds in excess of 20 to 25 miles-per-hour in order to avoid excessive wind loads on the long crane booms and on the structure being lifted that exceed the safe working loads of the crane. In job sites where such towers are erected, it is not unusual for erection work to be delayed for several days during a windy season and work is frequently delayed due to inclement weather such as rain, ice accumulation or snow. Other constraints associated with heavy and extra-heavy lift crane use include requirements for good visibility so that the operator can see hand signals given by a loadmaster, limited availability of extra-heavy lift cranes during periods of high construction activity, limited availability of extra-heavy lift cranes capable of erecting wind turbine generators having a capacity greater than 750 kilowatts and the time and large number of equipment components necessary to move larger capacity lift cranes to and from the site of tower erection.
The cost and availability of extra-heavy lift cranes has become a serious limiting factor to further economic development of wind energy especially in view of the ongoing development of wind turbine generators having a capacity of up to approximately 2,500 kilowatts. Such generators will require towers as tall as 350 feet in height with turbine generator combinations weighing in excess of 150,000 pounds. Accordingly, the use of increasingly heavier wind turbine generators mounted on ever taller towers has reached a point where the cost of construction has become a significant constraint to further development. Likewise, the limited availability of ex
Friedman Carl D.
Jacobson & Holman PLLC
Thissell Jennifer I.
Z-Tek, LLC
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