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I. Field of the Invention
The present invention relates generally to elevating support structures or towers. More particularly, the present invention is directed to a partially counter-balanced, multi-stage pivoting support tower assembly for supporting a conventional elevated operating device of interest, such as an electric power generating wind turbine, in which ease of raising the tower and lowering the tower to service the device of interest are advantages.
II. Related Art
Support towers for electric power generating wind turbine devices, radio transmitters, cellular phone relay stations, television antennae equipment and other such elevated devices have been in use for many years. These towers usually are assembled from successive sections raised by derrick cranes or the like and bolted into place by workers who have scaled the assembled portion. The device of interest is normally fixed to a mast attached to the top section of the tower. In order to service or repair a wind turbine or other device carried by the upper-most section of the tower, service personnel must either climb the tower and work on the device in situ or disassemble the device from the tower and lower it to the ground for it to be accessible there.
Tilt-up tower constructions have also been proposed such as in U.S. Pat. No. 4,366,386. However, such towers do not have a multi-step tilt-up system with a leveraged construction which allows easy staged tilting for both placement and maintenance.
Given the above, it therefore would present a great advantage if such a tower could be erected and lowered for service without the need for cranes or workers to climb the tower or relatively high powered winches. The present invention allows these operations to be carried out from the ground and without the need for heavy equipment, only small, low-powered winch devices or the like.
By means of the present invention there is provided a collapsible, tilt-up and pivoting support tower assembly for supporting an elevated device of interest, such as an electric power generating wind turbine, which requires only a small, low-power operating winch to raise and lower the tower providing both ease of raising into place and lowering for disassembly or servicing of associated equipment. The support tower assembly of the invention includes an upper tower section and a tower base section pivotally joined together. In one embodiment, the assembly is based on three-point support in which the tower base section is also pivotally mounted on two legs and has a free leg to provide a third support point. Both the upper tower section and the tower base section are readily raised and lowered using separate cable systems and a mechanized winch. A mounting base system is provided which includes three spaced points of support for receiving the support legs for the base section and includes a pair of spaced pivotal mounts and a fixed leg receiving mount spaced from the pivotal mounts and providing an anchor point for the third leg.
In one illustrative embodiment, the free leg of the pivoting tower base section is a composite strut leg or strut support that includes converging struts. It combines with a pair of base section pivoting support legs having free upper ends and lower ends designed to be received and pivotally attached to a pair of spaced pivotal shaft mounts using openings in the lower ends thereof and pivot pins. An upper tower section is provided which is designed to attach to and pivot about a main pivot shaft connected with the free upper ends of the base section. The upper section support legs are pivotally mounted using bearings so that the upper tower section is able to pivot between an upright raised position and a lowered service or assembly position. The upper tower section includes an extended aspect extending beyond the pivot assembly which compliments the tower base section and provides an extended lever arm for ease of pivoting the upper tower section.
A winching mechanism is provided for selectively pivoting the tower base section and the upper tower section utilizing cables. Pulleys are provided to selectively reduce the cable tension force needed to pivot the upper tower section. Latching systems selectively fix the upper tower section to the tower base section and the free strut leg of the tower base section to the fixed mount to secure the tower in an upright or fully raised position. These may be in the form of removable bolts.
In the fully upright position, the tower of this embodiment assumes a slightly truncated profile on the side described by the pivoting legs. This places the center of balance of the upper tower section slightly beyond the pivot joints and thereby slightly biases the upper section toward pivoting into a lowered position when it is not retained in place. As indicated above, the upper tower section is normally latched in place by being bolted to the tower base section. Cable tension is used to replace the latch bolt when it is desired to lower the upper tower section so that lowering is accomplished by using the winch to play out cable. Thus, the cable system for the upper tower section should be in place when the upper tower section is unlatched.
It should be noted that the number of base points of support or base support configuration may be varied so long as a stable system is provided. A four-leg or four-point support embodiment along with an embodiment with a platform base are also illustrated in the detailed description.
An embodiment having an open-sided pivoting base tower section in combination with a pivoting boom or upper tower section is also described. The upper tower section pivots from the top of the lower tower section on spaced bearing assemblies and is leveraged by a tail section which, when the upper tower section is raised, nests in the open side of the base tower section where the tail is fastened to the lower tower section. The lower tower section may be bolted to a platform. The upper tower section is not truncated and is slightly biased to pivot downward when it is released by mounting the bearing assemblies slightly off center with respect to the upper tower section.
In the drawings wherein like reference characters denote like parts throughout the same:
FIG. 1a is a perspective schematic elevational view of one embodiment of a truss-type support tower assembly constructed in accordance with the invention shown in a fully deployed or elevated position;
FIG. 1b is a side elevational view of the embodiment of FIG. 1a;
FIG. 1c is an enlarged fragmentary schematic detail of pivot mount for a support leg of a support tower assembly;
FIG. 1d is an enlarged fragmentary schematic detail of a pivot assembly between an upper tower section and tower base section;
FIG. 2 is a schematic plan view of a mounting base layout suitable for the support tower assembly of FIGS. 1a and 1b;
FIG. 3 is a schematic drawing of the support tower assembly of FIGS. 1a and 1b fully assembled and pivotally attached to a mounting base, but prior to being raised into an elevated position;
FIG. 4 is a schematic illustration of the support tower assembly of FIG. 3 shown with the tower base section partially raised;
FIG. 5 is a schematic drawing of the support tower assembly of FIG. 3 with the tower base section in a fully upright disposition and the upper tower section slightly raised by a connected cable prior to being fully raised or in a lowered position for service;
FIG. 6a is an enlarged schematic representations of a winch/pulley system as in FIG. 4 for operating the pivot functions of the tower base section shown with the tower base section in the fully raised position as in FIG. 5;
FIG. 6b is an enlarged schematic representation of a winch/pulley system for operating the pivot functions of the upper tower section as in FIG. 5;
FIG. 7 is a perspective schematic elevational view of an alternate embodiment of a truss-type support tower assembly shown in the fully deployed or elevated position;
FIGS. 8a-8f are schematic views that depict the stages of deployment or erection of a support tower of another embodiment of the invention which does not use a truss-type construction;
FIG. 9 is an enlarged fragmentary view of the lower portion of the base tower section at the stage of FIG. 8c;
FIG. 10 is an enlarged fragmentary view that illustrates a method of fixing the lower end of the upper tower section of the embodiment of FIGS. 8a-8f to the base tower section with the support tower fully raised;
FIG. 11 is an enlarged fragmentary view showing a tower pivot bearing arrangement; and
FIG. 12 is an enlarged schematic top view of the base tower section near the pivot points showing the upper tower section position in section.
The detailed description is directed to one or more embodiments of the inventive concepts of the present invention and this material is presented as being representative of these concepts but is not intended to be interpreted as limiting with respect to any aspect of the invention. In view of the above, the embodiments of the drawings will be described. One embodiment is illustrated in FIGS. 1a-6b and alternative embodiments are shown in FIGS. 7 and 8a-12.
FIGS. 1a and 1b illustrate in schematic form perspective and side elevational views of an embodiment of a collapsible, tilt-up support tower assembly shown in the fully deployed or elevated position. The support tower assembly, generally denoted by the reference character 10, includes a lower tower section or tower base section 12 and an upper tower section 14. The upper tower section 14 carries a vertically disposed mast 16 supported from and secured to a support member or tower tube 18. Tower tube 18 and mounting post or mast 16 or other such devices are designed to carry an elevated operating device of interest such as a wind turbine power generating device, radio transmitter, cellular phone relay station, television antennae, or other elevated equipment.
The tower base section 12 includes a pair of spaced pivotally mounted diverging support legs 20 and 22 forming two points of support. A pair of strut members 23 and 24 are connected from the upper portions of the pair of spaced diverging pivotally mounted legs 20 and 22 and converge to form a third point of support at 25. As will be described, the tower base section support legs 20 and 22, together with third point of support 25, provide an anchored, stable three-point support for the tower base section of the fully deployed tower. As best seen in the plan view of FIG. 2, the three points of support are carried on a matching triangular base mounting system which includes respective mounting pads 26, 27 and 28, which are preferably concrete pads or other stable anchored mounting devices and may form an equilateral triangle, the spacing being dependent upon the height and particular use of the tower. The lower ends of support legs 20 and 22 are mounted to pivot at pivot assemblies 30 and 32. Pivot assembly 30 is shown in the enlarged fragmentary view of FIG. 1c. Support leg 20 is pivotally mounted between lugs 34 anchored in mounting pad 26 using a pivot pin or shaft as at 36. Pivot assembly 32 is of similar construction. The free ends of converging struts 23 and 24 at 25 are selectively fixed to mounting lugs 40 anchored in mounting pad 27 as by a pin, bolt or shaft 42 inserted through openings therein when the base section 12 is in the erected position.
The upper tower section 14 is designed to compliment and interlock with tower base section 12 and is mounted to pivot about a pivot shaft 44 on pivot bearing 46 and 48, which are preferable conventional split pillow block assemblies bolted together, as shown in the enlarged fragmentary view of FIG. 1d. The pivot shaft 44 is attached to the upper tower section 14. The lower halves or bases of pillow block bearing assemblies 46 and 48 typically are fixed to the tops of legs 20 and 22 as by welding. The pivot shaft 44 is preferably integral with the upper tower section 14. The pivot joints are secured by pillow block bearing cap bolts 49.
The upper tower section is provided with an extended aspect which includes extended fixed leg 50 and lower converging strut members 52 and 54. Strut members 52 and 54 connect to pivot shaft 44, which is, in turn, disposed to rotate inside of the bearings 46 and 48, and converge with extended leg 50 into a mounting assembly 56 which may be a pair of spaced flange plate members which includes provision to be selectively bolted (i.e., removably fixed) to the tower base section at 57. The pivoting function is accomplished with the assistance of a cable and a pulley system as will be described. A rather small mechanized winch 58 is used to raise both the tower base section 12 and the upper tower section 14. A fixed pulley is shown at 60.
The upper tower section 14 further includes a pair of converging/diverging upper leg members 62 and 64 which match and commonly connect to and pivot shaft 44 with the struts 52 and 54 at the lower ends thereof inside of the aforementioned bearings 46 and 48. The upper portions of leg members 62 and 64 converge with leg 50 to support tower tube 18 at the upper ends thereof. Lateral bracing as at 66 and X-bracing as at 67, if desired, are used to strengthen the tower structure as needed in both the base section 12 and upper tower section 14.
It will be appreciated that the pivoting complimentary sectional construction of the tilt-up support tower assembly of the invention enables greatly facilitated vertical assembly of the structure and lowering for servicing of associated elevated operating devices mounted on the top of the support tower assembly mast. In this manner, the entire tower support structure and any electric wiring cable can be assembled on the ground prior to being raised into position in sections. Generally, the operating device (not shown) will be mounted on the tower mast 16 and necessary electrical or other connections made when the upper tower section is partially raised as depicted in FIG. 5.
The tower erecting or raising assembly steps are illustrated in FIGS. 3-5 of the drawings. FIG. 3 is a side schematic view of the structural support tower of FIGS. 1a and 1b with the pivoting support legs 20 and 22 of the tower base section 12 pivotally mounted to their corresponding mounting pads 26 and 28 using fixed lugs 32 and 34 with shafts or spindles 36 and 38 in a fully lowered position ready to be raised. The combination of strut members 23 and 24 at 25 is fastened to a strand of base raising cable 70, at connection point 72 when the tower base section 12 is in the fully raised position. As shown enlarged in FIG. 6a, the cable 70 extends partially around pulley 60 to a winch mechanism 58.
In accordance with the tower design of the invention, the raising of the support tower assembly structure is a two-step process devised to reduce both the stress on the tower structure itself and the force required to operate associated raising and control cables. As shown in FIG. 3, the tower support structure is assembled together on the ground ready to be raised. The separate cable system for raising the upper tower section has been removed for clarity.
The raising process for the support tower assembly begins with the assembled structure in its fully lowered position with the pivoting legs 20 and 22 attached to the base. The bolt or the fastening device at 57 that connects the upper tower section 14 with the tower base section 12 is removed to allow the two sections to pivot independently and freely relative to each other about shaft 44. A base cable 70 is attached to be operated by winch 58 under pulley 60 and at an attachment point 72 on the base section 12 as depicted in FIG. 6a. The winch 58 is operated to reel in the cable and raise the base section as shown in FIGS. 4 until the base reaches its raised position as shown in FIG. 5. Once the base section is raised to an upright posture, the combined struts at 25 are secured in lugs 40 as by a pin or shaft or bolt 42. The cable 70 can then be disconnected and removed.
As depicted in FIGS. 5 and 6b, a separate cable and pulley system is employed to operate (raise and lower) the upper tower section 14. The illustrated system includes an upper pulley 80 attached to mounting assembly 56 and base pulley 60. The pulleys are strung with cable 82, thereby creating a three-strand pulley system giving winch 58 additional mechanical advantage. Of course, the number of upper and lower pulleys and thus the number of cable strands, may be selectively varied in accordance with the force required to operate the upper tower section and the power of the winch used. The elevated pivot location at shaft 44 also helps to reduce the force needed to raise the upper tower section as the leverage for raising that structure is greatly enhanced by the creation of a long lever arm while, at the same time, the distance from the pivot location to the top of the tower is shortened. Once the upper tower section is raised, the mounting assembly 56 is re-secured to the tower base section 12 using a pin as at 57. With the upper tower section partially raised, as shown in FIG. 5, but with the mast 16 still relatively close to the ground, the operating device of interest (not shown) can readily be mounted on the mast and/or serviced with the upper tower section lowered to that position. This position is stabilized by the tension in the cable 82.
Thus, an important aspect of the present invention involves the leveraged pivot mounting and design of the upper tower section using pivot shaft 44 between sections 12 and 14 which combines with the tilt-up base to allow a rather easy two-step, tilt-up erection process. In this manner, a rather large support tower assembly can be raised and lowered for service or moving by using only a small power winch and pulley system and without the need for a crane or other piece of heavy equipment on site.
As can be seen best in FIGS. 1a and 1b, the configuration of legs 20, 22, 62 and 64 in the fully upright position of the tower is slightly truncated at the pivot points. This produces a slightly off-center balance point in the tower with reference to the pivot joints so that the upper tower section has a modest tendency to tilt toward the lowered position such that, when the member securing the upper tower section to the tower base section locking the upper tower section in place is removed, it produces tension in cable 82. This configuration enables the controlled lowering of the upper tower section to be accomplished by simply playing out cable which is kept under tension after the removal of the securing member, pin 57. This eliminates the need for a separate device to initiate the pivoting of the upper tower section when it is desired for that section to be lowered. In this manner, a small winch or similar device readily accomplishes both the raising and lowering of the collapsible, tilt-up support tower assembly of the invention.
FIG. 7 shows an alternative embodiment of the support tower assembly, generally 110, including tower base section 112 and upper tower section 114 carrying vertically disposed mast 116 supported by tower tube 118. This embodiment is quite similar to that earlier described with the exception that it is a four-legged support configuration system. The tower base section includes a pair of spaced pivotally mounted support legs 120 and 122 and a pair of strut members 123 and 124 which are selectively fixed to mounting lugs as at 125 and 126. Four mounting pads 128, 130, 132 and 134 are also provided. The legs 120 and 122 are pivotally mounted in the same fashion as legs 20 and 22 previously described with regard to FIGS. 1a and 1b in pivot lugs 136 and 138, respectively. The upper tower section 114 is designed to pivot on shaft 140 utilizing pillow block bearings 142 and 144 connected to legs 120 and 122 as has been previously described with regard to the embodiment of FIGS. 1a and 1b. Thus, the upper tower section includes pivoting legs 146 and 148 and is leveraged by extended free legs 150 and 152, the free leg 150 being designed to selectively connect to free strut 123 and the free leg 152 being designed to selectively connect to free leg 124 when the tower 110 is fully deployed. A winch and pulley system is shown at 154. Horizontal and cross bracing is also shown at 156 and 158, respectively. In this embodiment, the winch is generally located on a separate pad 160 in the center between the pads 132 and 134 where the securing mounts are located. Thus, it can be seen that the number of support points can be varied with respect to the collapsible, tilt-up support tower assembly of the invention while remaining well within the scope of the inventive concepts.
Another embodiment of a support tower in accordance with the invention is depicted in FIGS. 8a-8f and 9-12. This embodiment, illustrated generally by 200, also includes a lower or tower base section 202 and a pivotally connected upper tower or boom section 204 connected at pivot points by bearing assemblies, including a pair of pillow block bearings 208 and 210 with associated shafts 212 and 214. One of the pillow blocks is shown in greater detail in FIG. 11, including top cap and lower bearing base sections 216 and 218, respectively, held together by threaded fasteners 220. The bearing base section 218 is fixed to the top of the lower tower section 202. The various stages of deployment and use are depicted in FIGS. 8a-8f and the enlarged fragmentary view of FIG. 9.
FIG. 8a depicts the tower 200 in a fully lowered or initial assembly position. The base tower section is connected to a foundation at one or more base pivot connections as at 230 using pivot lugs and shafts in the manner of earlier described embodiments. The base tower section is also provided with a folding (hinged) or removable leverage strut 232 to provide additional leverage to aid in the pivoting operation making it an easy low-power lift. A lifting cable 234 is connected between the free or top end of the base tower section at 236 and a winch or other force applying device at 238, and using the leverage strut connected at 240.
FIG. 8b represents an initial phase of erecting the base which is continued in FIGS. 8c-8d. The enlarged fragmentary view of FIG. 9 shows the pivoting and fastening scheme of the base tower section and upper tower section in greater detail. The base tower 202 is fixed to a mounting flange device in the form of a base plate or platform 242 which has a series of openings which align with a series of foundation bolts as at 244 used to fix the base tower section to platform.
As seen in FIG. 8e, with the base tower section fully erected, the upper tower or boom section is yet to be raised. As was the case with previously described embodiments, the upper tower or boom section is pivotally leveraged about the bearings as at 210 and is raised using a second cable 250 attached at one end to the lower end or tail section 248 of the boom 204 and to a winch or the like at 254 which may be a different device from the force applying device 238. A pair of idler sprockets or pulleys 256 and 258 are provided to route the cables through the base 202. As shown in the top, partial section view of FIG. 12, the tower base section 202 has an open side to accommodate the tail section 248 which nests therein with the upper tower section or beam 204 fully raised or fully lowered. The pivot line of the upper tower section 204, indicated by 260, is offset somewhat toward the open side of the tower base section such that the distance b<a to bias the upper tower section toward tipping to facilitate lowering of the upper tower section to a height for servicing, without the need for outside forces to initiate tipping, as shown in FIG. 8e, but without the need for a truncated or leaning structure in the manner of previously described embodiments.
The tower is shown fully deployed with cables attached in FIG. 8f. Once the tower is fully raised, as illustrated in FIG. 10, a device for retaining or latching the upper tower section or boom in place, such as a saddle strap 270 retained as by a bolt and nut fastener at 272 may be used. Release of the saddle strap allows the upper tower section to pivot by playing out the cable 250 to lower the upper tower section as desired so that the lowering and raising of the upper tower section may be accomplished easily in the manner of previously described embodiments. The leverage strut 232 may be folded against the tower or removed when the tower base section 202 is fixed in place.
This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use embodiments of the example as required. However, it is to be understood that the invention can be carried out by specifically different devices and that various modifications can be accomplished without departing from the scope of the invention itself.