Abstract:
Aspects of the invention relate to telescoping mast assemblies (telescoping “towers”), polygonal sided masts for use in such assemblies, methods of fabricating polygonal sided masts, methods and apparatus for sequentially actuating and deactuating hold-down and locking mechanisms in telescoping towers, and such other aspects as will be understood from the present descriptions and drawings. Telescopic towers are usable for supporting and raising to a height any type of communications payload, including, for example, radio antennas, television antennas, any type of surveillance and/or sensor payloads, including, for example, microphones, cameras, flood lights, and the like.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/000,949 filed Oct. 29, 2007, which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    Aspects of the invention relate to telescoping mast assemblies (telescoping “towers”), polygonal sided masts for use in such assemblies, methods of fabricating polygonal sided masts, methods and apparatus for sequentially actuating and deactuating hold-down and locking mechanisms in telescoping towers, and such other aspects as will be understood from the present descriptions and drawings. Telescopic towers are usable for supporting and raising to a height any type of communications payload, including, for example, radio antennas, television antennas, any type of surveillance and/or sensor payloads, including, for example, microphones, cameras, flood lights, and the like. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0003]    The figures are not to scale. 
           [0004]      FIG. 1A  is a perspective view of a telescoping tower embodying aspects of the present invention. The tower is shown in its fully-nested condition. 
           [0005]      FIG. 1B  is a side elevation view of a telescoping tower embodying aspects of the present invention. The tower is shown in its fully-nested condition. 
           [0006]      FIG. 1C  is a side elevation view of a telescoping tower embodying aspects of the present invention. The tower is shown in its fully-extended condition. 
           [0007]      FIG. 2A  is a perspective cutaway view of a telescoping tower embodying aspects of the present invention. The tower is shown in its fully-nested condition. 
           [0008]      FIG. 2B  is an enlarged perspective cutaway view of a top portion of the telescoping tower shown in  FIG. 2A . 
           [0009]      FIG. 2C  is an enlarged perspective cutaway view of a bottom portion of the telescoping tower shown in  FIG. 2A . 
           [0010]      FIG. 2D  is an enlarged side elevation cutaway view of a bottom portion of the telescopic tower shown in  FIG. 2A . 
           [0011]      FIG. 2E  is an enlarged side elevation cutaway view of a top portion of the telescopic tower shown in  FIG. 2A . 
           [0012]      FIG. 3A  is a perspective view of a telescoping interior tube that may be employed in a telescoping tower according to aspects of the present invention. The tube is shown with a portion removed or broken away to reduce space on the drawing. Sections shown in  FIGS. 10 and 11  are taken along section lines  10 - 10  and  11 - 11 . 
           [0013]      FIG. 3B  is a side elevation view of the broken-away tube of  FIG. 3A . 
           [0014]      FIG. 3C  is a top plan view of the tube of  FIG. 3A . 
           [0015]      FIG. 3D  is a bottom plan view of the tube of  FIG. 3A . 
           [0016]      FIG. 4  is a perspective view of three nested tubes of a telescopic tower embodying aspects of the present invention. The three tubes may be the three innermost tubes of a telescoping tower such as shown in  FIG. 1A . 
           [0017]      FIG. 5  is a perspective view of two nested tubes of a telescopic tower embodying aspects of the present invention. The three tubes may be the two outer tubes of the three tubes shown in  FIG. 4 . 
           [0018]      FIG. 6A  is an exploded perspective view showing the elements of a hold-down mechanism aspect of the present invention. 
           [0019]      FIG. 6B  is a perspective view showing the elements of the hold-down mechanism of  FIG. 6A  in an assembled and operating position. The tubes on which the elements are mounted are not shown in this view for clarity. 
           [0020]      FIG. 7A  is an exploded perspective view showing the elements of a locking mechanism aspect of the present invention. 
           [0021]      FIG. 7B  is a perspective view showing the elements of the locking mechanism of  FIG. 7A  in an assembled and operating position. The tubes on which the elements are mounted are not shown in this view for clarity. 
           [0022]      FIGS. 8A-8Q  and companion  FIGS. 9A-9Q  (i.e.,  FIG. 8A  is a companion of  FIG. 9A , etc.) are cut-away side-elevation views showing the sequence of operation of the hold-down and locking mechanisms as three adjacent tubes in a tower embodying aspects of the present invention are extended and retracted. Each cut-away side-elevation view is at ninety degrees to its companion so that the respective companion views are cut through the locking mechanism elements ( FIGS. 8A-Q ) and through the hold-down mechanism elements ( FIGS. 9A-Q ). 
           [0023]      FIGS. 10A-10K  and companion  FIGS. 11A-11K  are also companions to  FIGS. 8A-8K  and  9 A- 9 K (i.e.,  FIG. 10A  is a companion of  FIG. 1A  and of  FIGS. 8A and 9A , etc.) are cut-away side-elevation views of both the upper and lower portions of a tower showing the sequence of operation of the hold-down and locking mechanisms as three adjacent tubes in a tower embodying aspects of the present invention are extended and retracted. Each cut-away side-elevation view is at ninety degrees to its companion so that the respective companion views are cut through the locking mechanism elements ( FIGS. 10A-K ) and through the hold-down mechanism elements ( FIGS. 11A-K ). 
           [0024]      FIG. 12A  is a perspective cross section of the drive nut assembly for a telescoping tube. 
           [0025]      FIG. 12B  is an exploded view of the major elements of the drive nut assembly of  FIG. 12A . 
           [0026]      FIG. 12C  is a side elevational cross sectional view of the drive nut assembly of  FIGS. 12A and 12B . 
           [0027]      FIG. 12D  is a side elevational cross sectional view of a variation of the drive nut assembly of  FIGS. 12A and 12B . 
           [0028]      FIG. 13A  a cut-away top plan view of the drive gear box portion of a telescoping tower according to aspects of the present invention. 
           [0029]      FIG. 13B  is a side elevation cross section along the sections lines  13 B of  FIG. 13A . 
           [0030]      FIG. 13C  is a side elevation cross section along the sections lines  13 C of  FIG. 1A . 
           [0031]      FIG. 14  is a perspective view of a portion of a polygonal tube according to aspects of the invention, which tube is useful as a tube in a telescoping tower 
           [0032]      FIG. 15  is a top plan view of the polygonal tube portion of  FIG. 14 . 
           [0033]      FIG. 16A  is a top plan view showing a way in which a polygonal tube portion may be formed from a flat rectangular sheet of metal. 
           [0034]      FIG. 16B  is a top plan view showing the manner in which two portions of polygonal tube as in  FIGS. 12 and 13  may be joined together to form a polygonal tube. 
           [0035]      FIG. 17  show steps in making a faceted cylinder (polygonal tube) in accordance with aspects of the present invention. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0036]    Turning now to the drawings in which like reference characters identify the same elements in several views,  FIGS. 1A ,  1 B and  1 C show a telescoping mast assembly (telescoping “tower”)  10  embodying various aspects of the present invention. In  FIGS. 1A and 1B , the telescoping mast assembly  10  is shown in its fully “nested” condition—each of the multiple mast sections (“tubes”)  11 - 18  of the assembly  10  is in its fully retracted position. In  FIG. 1C , the telescoping mast assembly is shown in its fully extended position—each of the multiple mast sections  11 - 18  of the assembly  10  is fully extended. An axial drive screw mechanism (not seen in  FIGS. 1A-1C ) drives the extension and retraction of the tubes in a predetermined self-actuated sequence. The drive screw mechanism has a drive screw controllably rotated in either of two directions by a gear train (not shown in  FIGS. 1A-1C ) within a gear box  19 , powered by a drive motor  20  or, alternatively, powered manually by a hand crank (not shown) that engages a hand crank receptacle  21 . The gear box  19  also functions as a base for the telescoping mast assembly  10  that may be affixed to a fixed or movable support. Gear box  19  includes an anti-backdrive brake that facilitates stopping an extension of the tower sections at any point and that obviates the need to lock that last inner section to the outer section when the tower is raised to its maximum extension. 
         [0037]    One aspect of the present invention is the use of cylindrical tubular mast sections having a polygonal cross section rather than a circular cross section. Although the various figures herein show such polygonal mast sections, it will be understood that certain aspects of the invention are not limited to mast sections having a polygonal cross section. Although a deca-hexagonal (16 sided) polygon cross section is employed in various examples herein because it closely approximates the wind characteristics of a circular cross section mast section, other sided polygons may be employed. Whether polygonal or circular in cross section, the tube sections are close fitting and progressively smaller in diameter. In practical implementations, the tubes may each have, for example, lengths in the order of five to twelve feet. 
         [0038]    The top of each of all but the top one of the mast sections of  FIGS. 1A-1C  is shown encircled and capped by a respective annular assembly  22 - 28  that includes elements of mast section hold-down and mast section locking assemblies as are described in detail below. Hold-down assemblies prevent premature extension of mast sections. Lock assemblies positively lock the mast against retraction as each section is fully extended. The hold-down assemblies and lock assemblies according to aspects of the present invention are configured to cause a self-sequencing in which the hold-down and locking operations are performed separately and sequentially so as to assure proper extension and retraction of the mast sections. 
         [0039]    Refer now to a cutaway view of the nested mast sections as shown in  FIG. 2A  and enlarged details thereof in  FIGS. 2B-2E . A drive screw  30  is shown extending upward from the gear box  19  through the nested mast sections to a point near the top of the innermost mast section. An annular support assembly  31  (best seen in  FIGS. 2B and 2E ) affixed to near the top of the innermost mast section provides support for the top of the drive screw, particular during shipment. Each of the inner mast sections has a respective drive nut assembly  32 - 38  (best seen in  FIGS. 2C ,  2 D, and  12 A-D). 
         [0040]    The drive screw  30  is threaded along its length except at a bottom portion  30   a  (best seen in FIG.  2 D—the slightly narrowed diameter of the drive screw) and a top portion (best seen in FIG.  2 B—the slightly narrowed diameter of the drive screw)  30   b . Threads are shown in  FIGS. 8A-Q ,  9 A-Q,  10 A-K and  11 A-K. In the nested condition, only one drive nut assembly, that of the innermost mast section, is on the threads of the drive screw. 
         [0041]    The drive screw may have a one inch lead with ten individual starts and may employ an acme thread. A nut going on or coming off the drive screws thus has ten possibilities for each rotation: ten within a tenth of an inch. There is a 100/1000 th  inch linear travel from one lead to another. All of the nuts are spring loaded with an allowance of about 125/1000 th  inch. The springs work in both an upward and downward direction. Nuts have a cone shape and the end of the top end of the drive screw has a semi-spherical end to facilitate a nut coming onto the drive screw. 
         [0042]      FIG. 2A  shows a bracket  39  for affixing the telescoping mast assembly  10  to a structure, such as a building. Also seen in  FIG. 2A  is an enclosure  40  for control circuitry for turning the drive motor on and off and for selecting the direction in which it rotates.  FIG. 2A  also shows an upper optical limit assembly  41  (best seen in  FIG. 2D ) for detecting full extension of the mast sections and a lower optical limit assembly  42  (best seen in  FIG. 2C ) for detecting full retraction of the mast sections. Each optical limit assembly includes a housing  41   a  ( 42   a ), a combination light source and sensor  41   b  ( 42   b ), a series of holes  41   c  through the seven outermost mast sections (not seen in the  FIG. 2C  view) and a mirror in the innermost mast section (not seen in the  FIG. 2C  view), aligned with the series of holes. When the mast sections are fully nested, optical limit assembly  41  detects the fully nested condition and provides a signal that is used to turn off the motor in order to stop the drive screw. Similarly, when the mast sections are fully extended, assembly optical limit assembly  42  detects the fully extended condition and provides a signal that is used to turn off the motor in order to stop the drive screw. Of course, the motor may be manually turned off at any time in order to place the telescoping mast assembly in a condition somewhere between fully nested and fully extended. Alternatively or in addition, automatic turn off of the motor may also be accomplished by counting revolutions of the drive screw. Fail safe mechanical stops may also be provided to provide a forced mechanical stop of extension or retraction in the event that the automatic sensing malfunctions. 
         [0043]      FIGS. 2B and 2E  show the ring assemblies  22 - 28  in greater detail. The ring assemblies each include in their annular encircling portions elements of multiple hold-down assemblies and elements of multiple lock assemblies. In addition, each ring assembly includes an upper flange cap that caps the respective mast section. The various hold-down and lock assemblies and flange caps are staggered in their angular orientation in order to sequentially operate as is explained below. Details of the hold-down assemblies and locks and their operation as the telescopic mast assembly is extended and retracted are set forth below. 
         [0044]    Although  FIGS. 1A-C  and  2 A-E show eight mast sections, polygonal and circular cross-sectioned mast sections in accordance with aspects of the invention may, in principle, be used in telescopic mast assemblies with more than eight and as few as three mast sections. For simplicity in explanation, hold-down and locking mechanism aspects of the present invention will be described with examples employing three mast sections, it being understood that the same principles apply to telescopic mast assemblies employing more than three mast sections by applying the teachings to consecutive triads of mast sections. 
         [0045]      FIGS. 3A-3D  show an example of an intermediate (middle) mast section  50  of a mast section triad (the three masts may be all or some of the masts of a telescopic mast assembly). The mast section may be a generally-cylindrically-shaped polygon tube formed from two halves  50   a  and  50   b  fastened together at overlaps  51   a  and  51   b  with rivets  52  or some other suitable securing method. A deca-hexagon (16 sided) polygon mast is shown in this example. Low friction pads or slides  53  are shown around the bottom periphery for spacing the mast section  50  from the slightly larger mast section (not shown) in which it nests and extends and for facilitating the relative movement of those adjoining mast sections. Similarly, low friction pads or slides  54  are located around the inside of the top of mast section  50  for the same reasons with respect to the slightly smaller mast section (not shown) that nests and extends within mast section  50 . A hole  55  for cooperating with an optical limit switch is provided in the wall of the mast section  50 . 
         [0046]    Elements of two hold-down mechanisms and two lock mechanisms are shown in  FIGS. 3A-3D . As will be explained below, each hold-down mechanism and each lock mechanism employs three main elements, each located on one of three consecutive mast sections (a triad of mast sections). The elements of a hold-down mechanism and a lock mechanism in accordance with aspects of the present invention will be described in greater detail below, as will their operation. Two hold-down actuator pads  56  and  57  are seen in  FIGS. 3A and 3B . Each is secured to the outer wall of the mast section. Two lock actuator pads  58  and  59  are also affixed to the outer wall of the mast section  50 . The mast section annular encircling portion of a ring assembly  60  at the top of mast section  50  holds a pair of hold-down housings  61  and  62 , from each of which extends through a respective slot in the wall of the mast section  50  a portion of the hold-down housing from which a pivoting hold-down extends. The mast section annular encircling portion of ring assembly  60  also holds a pair of lock housings  63  and  64 , from each of which extends through a respective slot in the wall of the mast section  50  a portion of the lock housing from which a pivoting lock extends. 
         [0047]    Nut assemblies  66  of  FIGS. 3A-3D  are described below in connection with  FIGS. 12A-D . 
         [0048]    Depending on the number of mast sections in a telescopic mast assembly, each mast section may have two hold-downs and two locks or two hold-downs and four locks (four locks may be used, for example, for the lower mast sections that must support a higher load than higher, smaller mast sections). As in the example of  FIGS. 3A-3D , locks and hold-downs should be spaced apart from each other and alternated to the extent possible, such as having the pairs of hold-downs and locks opposite each other and spaced by 90 degrees. 
         [0049]      FIG. 4  shows three consecutive mast sections (a triad) nested. In this example, an inner mast section  70  is shown nested within an intermediate mast section  72  which is, in turn, nested within an outer mast section  74 . The main portion of intermediate mast  72  is hidden in this figure (see  FIG. 5 ). The outer mast may be further nested within another mast section (not shown). Inner mast section  70  has no top ring assembly. However, the top ring assemblies of mast sections  72  and  74  are shown. The top ring assembly of intermediate mast section  72  has an upper flange cap  76  which is fastened, as by screws passing through screw holes  78 , to the annular encircling portion of the top ring assembly, which is, in turn, fastened to the top portion of mast section  72  in a suitable way such as by rivets  80 . The upper flange cap  76  has slotted tongues into each of which a lock may extend and into each of which an upper beak portion of a hold-down actuator pad may extend so that shoulders of the hold-down actuator pad engage the upper flange cap to cause the mast section to extend in order that the mast section picks up the drive shaft with its nut. This operation is explained further below.  FIG. 4  also shows a hold-down housing  82  on mast section  72 , a hold-down post  84  on mast section  74 , lock housings  86  and  88  on mast section  72 , lock posts  90  and  92  on mast section  74 , a lock housing  94  and a hold-down housing  96  on mast section  74 . 
         [0050]      FIG. 5  shows the outer two mast sections of the  FIG. 4  depiction—the innermost mast section  70  is not present. The upper flange cap  76  is also not present. The view of  FIG. 5  reveals the intermediate mast section  72  and a second hold-down housing  82   a.    
         [0051]      FIG. 6A  shows the elements of a hold-down assembly in accordance with aspects of the present invention. The hold-down assembly includes a hold-down housing  102 , a pin  104  that functions as a spring rest, a hold-down  106  that is rotatably held within housing  102  and which rotates on the axis of its pin  108 , first and second springs  110  and  112 , a hold-down actuator pad  114  and a hold-down post  116 .  FIG. 6B  shows the hold-down assembly elements in an operating position. Pin  104  passes through a hole  106   a  in the hold-down  106  and the holes  102   a  in the hold-down housing  102 , allowing the hold-down to rotate along the axis of pin  104 . Springs  110  and  112 , working against spring rest pin  108 , urge the hold-down into its engaged position as shown in  FIG. 6B . Hold-down  106  has an extending hook portion  106   b  that engages a mating hook  116   a  extending from the hold-down post  116 . The hold-down actuator pad has an upward extending “beak” or lip portion  114   a  having a beveled top portion  114   b . When the hold-down actuator pad  114  moves upward with respect to the hold-down  106 , its upper beak or lip engages the upper lip  106   c  of the hold-down  106 , causing it to rotate clockwise and disengage the mating hooks  106   b  and  116   a . The lower lip  106   d  of the hold-down is engaged by the beak or lip portion  114   a  of the hold-down actuator pad when it moves downward with respect to the hold-down. With respect to three consecutive mast sections, the hold-down actuator pad  114  is carried by the innermost mast section, the hold-down housing  102  (carrying the hold-down  106 ) by the intermediate mast section, and the hold-down post  116  by the outer mast section. In the hold-down engaged condition shown in  FIG. 6B , the intermediate mast section cannot be extended with respect to the outer mast section. The operation of the hold-down assembly is explained in further detail below. 
         [0052]      FIG. 7A  shows the elements of a lock assembly in accordance with aspects of the present invention. The lock assembly includes a lock pad  120 , a lock housing  122 , a pivot pin  124 , a lock  126 , first and second springs  128  and  130 , and a lock actuator post  132 . The lock  126  has a pin  134  that functions both as a spring retainer and a lock stop.  FIG. 7B  shows the hold-down assembly elements in an operating position. Pivot pin  124  passes through a hole  126   a  in the lock  126  and the holes  122   a  in the hold-down housing  122 , allowing the lock to rotate along the axis of pin  124 . Springs  128  and  130 , working against spring rest pin  134 , urge the lock into its locked position as shown in  FIG. 7B . Lock  126  has an extending latch portion  126   b  that engages the bottom side of the lock pad  120 . The lock actuator post has an upward extending U-shaped member  132   a  having a slot  132   b  that engages lock stop pin  134  of the rotating lock. When the pin is at the bottom of the slot, the lock is open; when the pin is at the top of the slot, the lock is locked. With respect to three consecutive mast sections, the lock pad  120  is carried by the innermost mast section, the lock housing  122  (carrying the lock  126 ) by the intermediate mast section, and the lock actuator post  132  by the outer mast section. The slot in the lock actuator post forces the lock into position even though the lock is spring loaded in the locking position. This results in a positive locking operation. In the locked condition shown in  FIG. 7B , the inner mast section cannot be retracted with respect to the intermediate mast section. The operation of the hold-down assembly is explained in further detail below. 
         [0053]    The following table describes further the operation of the hold-down and locking mechanisms with respect to extension and retraction of the tower sections. 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
               
               
                 FIGS. 
                 Steps 
                 Narrative 
                 Status 
               
               
                   
               
             
             
               
                 FIGS. 1A, 1B, 2A, 
                 Starting condition. 
                 Tubes fully retracted 
                 Hold-downs 
               
               
                 2B, 2C, 2D, 2E, 8A, 
                 Tower fully nested. 
                 as determined by 
                 engaged 
               
               
                 9A, 10A and 11A. 
                   
                 electrical stop or by 
                 Locks unlocked 
               
               
                   
                   
                 fail-safe mechanical 
                 Inner tube&#39;s nut 
               
               
                   
                   
                 stop. Only one nut 
                 on lead screw 
               
               
                   
                   
                 (inner tube&#39;s nut) is 
               
               
                   
                   
                 on the lead screw; the 
               
               
                   
                   
                 other nuts are on the 
               
               
                   
                   
                 lower unthreaded 
               
               
                   
                   
                 portion of the lead 
               
               
                   
                   
                 screw. All hold- 
               
               
                   
                   
                 downs are engaged 
               
               
                   
                   
                 (the outermost tube 
               
               
                   
                   
                 has no hold-down - it 
               
               
                   
                   
                 is secured to the 
               
               
                   
                   
                 tower base. All locks 
               
               
                   
                   
                 are unlocked 
               
               
                   
                   
                 (allowing inner tube 
               
               
                   
                   
                 to move vis-à-vis the 
               
               
                   
                   
                 intermediate tube). 
               
               
                   
                   
                 Top of lead screw is 
               
               
                   
                   
                 supported by a lead 
               
               
                   
                   
                 screw-supporting 
               
               
                   
                   
                 member 31 (FIGS. 
               
               
                   
                   
                 2B, 2E). 
               
               
                   
                 Extension of inner 
                 Drive motor rotates 
                 Inner tube extends 
               
               
                   
                 tube begins. 
                 lead screw in 
                 out of 
               
               
                   
                   
                 direction that causes 
                 intermediate tube 
               
               
                   
                   
                 the inner tube to 
               
               
                   
                   
                 extend out of the 
               
               
                   
                   
                 intermediate tube that 
               
               
                   
                   
                 is held down to the 
               
               
                   
                   
                 outer tube by the 
               
               
                   
                   
                 hold-down 
               
               
                   
                   
                 mechanisms. The 
               
               
                   
                   
                 locking mechanisms 
               
               
                   
                   
                 are not locked. 
               
               
                 FIGS. 8B, 9B, 10B 
                 Inner tube nears its 
                 Hold-downs remain 
               
               
                 and 11B. 
                 full extension. 
                 actuated, keeping the 
               
               
                   
                   
                 intermediate tube 
               
               
                   
                   
                 from moving. Locks 
               
               
                   
                   
                 remain unlocked. 
               
               
                   
                   
                 Hold-down actuator 
               
               
                   
                   
                 pads approach hold- 
               
               
                   
                   
                 downs. Lock pads 
               
               
                   
                   
                 approach lock. 
               
               
                 FIGS. 8C, 9C, 10C 
                 Inner tube continues 
                 Hold-downs remain 
               
               
                 and 11C. 
                 upward toward its 
                 actuated, keeping the 
               
               
                   
                 full extension. 
                 intermediate tube 
               
               
                   
                   
                 from moving. Locks 
               
               
                   
                   
                 remain unlocked. 
               
               
                   
                   
                 Hold-down actuator 
               
               
                   
                   
                 pads more closely 
               
               
                   
                   
                 approach hold-downs. 
               
               
                   
                   
                 Lock pads are passing 
               
               
                   
                   
                 lock. 
               
               
                 FIGS. 8D, 9D, 10C 
                 Inner tube continues 
                 Hold-downs remain 
               
               
                 and 11C. 
                 further upward 
                 actuated, keeping the 
               
               
                   
                 toward its full 
                 intermediate tube 
               
               
                   
                 extension. 
                 from moving. Locks 
               
               
                   
                   
                 remain unlocked. 
               
               
                   
                   
                 Hold-down actuator 
               
               
                   
                   
                 pads begins to engage 
               
               
                   
                   
                 the hold-downs 
               
               
                   
                   
                 (upper lip of hold- 
               
               
                   
                   
                 downs). Lock pads 
               
               
                   
                   
                 continue to pass lock. 
               
               
                 FIGS. 8E, 9E, 10E 
                 Inner tube continues 
                 Hold-downs remain 
               
               
                 and 11E. 
                 further upward 
                 actuated, keeping the 
               
               
                   
                 toward its full 
                 intermediate tube 
               
               
                   
                 extension. 
                 from moving. Locks 
               
               
                   
                   
                 remain unlocked. 
               
               
                   
                   
                 Hold-down actuator 
               
               
                   
                   
                 pads begin to rotate 
               
               
                   
                   
                 the hold-downs 
               
               
                   
                   
                 toward 
               
               
                   
                   
                 disengagement. Lock 
               
               
                   
                   
                 pads continue to pass 
               
               
                   
                   
                 by the lock. 
               
               
                 FIGS. 8F, 9F, 10F 
                 As inner tube 
                 Hold-downs 
                 Hold-downs 
               
               
                 and 11F 
                 continues further 
                 disengage, allowing 
                 disengaged 
               
               
                   
                 upward toward its 
                 the intermediate tube 
                 Stops engaged 
               
               
                   
                 full extension, the 
                 to move with respect 
                 Intermediate tube 
               
               
                   
                 hold-downs 
                 to the outer tube (top 
                 extends out of 
               
               
                   
                 disengage and stops 
                 lip of the hold-down 
                 outer tube along 
               
               
                   
                 on the intermediate 
                 actuator on inner tube 
                 with inner tube 
               
               
                   
                 tube are engaged so 
                 engages the hold- 
               
               
                   
                 that the intermediate 
                 down on the 
               
               
                   
                 tube is carried by the 
                 intermediate tube, 
               
               
                   
                 inner tube. 
                 causing it to release 
               
               
                   
                   
                 from the hold-down 
               
               
                   
                   
                 post hook on the 
               
               
                   
                   
                 outer tube). As the 
               
               
                   
                   
                 hold-down clears the 
               
               
                   
                   
                 hold-down post hook, 
               
               
                   
                   
                 the shoulders of the 
               
               
                   
                   
                 hold-down actuator 
               
               
                   
                   
                 pads engage the stop 
               
               
                   
                   
                 provided by the upper 
               
               
                   
                   
                 flange cap. The inner 
               
               
                   
                   
                 tube carries the 
               
               
                   
                   
                 intermediate tube 
               
               
                   
                   
                 along with it (the 
               
               
                   
                   
                 inner tube&#39;s nut is 
               
               
                   
                   
                 still on the lead 
               
               
                   
                   
                 screw; the 
               
               
                   
                   
                 intermediate tube&#39;s 
               
               
                   
                   
                 nut is not yet on the 
               
               
                   
                   
                 lead screw). The 
               
               
                   
                   
                 locks remain 
               
               
                   
                   
                 unlocked. Lock pads 
               
               
                   
                   
                 are now above the 
               
               
                   
                   
                 lock so that the lock 
               
               
                   
                   
                 can be rotated in 
               
               
                   
                   
                 order to engage the 
               
               
                   
                   
                 bottom of the lock 
               
               
                   
                   
                 pad (it is not yet 
               
               
                   
                   
                 rotated). The overlap 
               
               
                   
                   
                 between the inner and 
               
               
                   
                   
                 intermediate tube is 
               
               
                   
                   
                 determined by the 
               
               
                   
                   
                 relative locations of 
               
               
                   
                   
                 the hold-down pads 
               
               
                   
                   
                 and the lock pads. 
               
               
                 FIGS. 8G, 9G, 10G 
                 As inner tube 
                 Because the outer 
                 Locks begin to 
               
               
                 and 11G. 
                 continues further 
                 tube cannot move (if 
                 engage 
               
               
                   
                 upward, carrying the 
                 it is the ultimate outer 
               
               
                   
                 intermediate tube 
                 tube, it is fixed to the 
               
               
                   
                 with it, the locks 
                 base, otherwise it is 
               
               
                   
                 begin to engage. 
                 held down by hold- 
               
               
                   
                   
                 down mechanisms), 
               
               
                   
                   
                 the lock pin on the 
               
               
                   
                   
                 lock rides up in the 
               
               
                   
                   
                 lock post slot (carried 
               
               
                   
                   
                 by the outer tube) as 
               
               
                   
                   
                 the intermediate tube 
               
               
                   
                   
                 extends (it is carried 
               
               
                   
                   
                 up by the inner tube&#39;s 
               
               
                   
                   
                 engagement of the 
               
               
                   
                   
                 stop), causing the 
               
               
                   
                   
                 lock to begin rotating 
               
               
                   
                   
                 under the lock pad. 
               
               
                 FIGS. 8H, 9H, 10G 
                 The inner tube 
                 The lock pin on the 
                 Locks fully 
               
               
                 and 11G. 
                 continues further 
                 lock rides up in the 
                 engaged 
               
               
                   
                 upward, carrying the 
                 lock post slot to the 
               
               
                   
                 intermediate tube 
                 top of the slot, 
               
               
                   
                 with it. The locks 
                 rotating the lock into 
               
               
                   
                 fully engage into 
                 its fully engaged 
               
               
                   
                 their locked positions 
                 locked position under 
               
               
                   
                 (but there is still a 
                 the lock pads (the 
               
               
                   
                 gap). 
                 intermediate tube is 
               
               
                   
                   
                 still carried by the 
               
               
                   
                   
                 inner tube-there is a 
               
               
                   
                   
                 slight gap between 
               
               
                   
                   
                 the lock and the 
               
               
                   
                   
                 bottom of the lock 
               
               
                   
                   
                 pad; the intermediate 
               
               
                   
                   
                 tube&#39;s nut is not yet 
               
               
                   
                   
                 on the lead screw). In 
               
               
                   
                   
                 its fully rotated 
               
               
                   
                   
                 position, the lock also 
               
               
                   
                   
                 engages a lock stop in 
               
               
                   
                   
                 the lock housing. 
               
               
                 FIGS. 8I, 9I, 10I 
                 Intermediate tube&#39;s 
                 The inner and 
                 Both nuts on the 
               
               
                 and 11I. 
                 nut goes on lead 
                 intermediate tubes 
                 lead screw (inner 
               
               
                   
                 screw 
                 continue upward 
                 and intermediate) 
               
               
                   
                   
                 together (the 
               
               
                   
                   
                 intermediate tube is 
               
               
                   
                   
                 carried by the inner 
               
               
                   
                   
                 tube) causing the 
               
               
                   
                   
                 intermediate tube&#39;s 
               
               
                   
                   
                 nut to engage a thread 
               
               
                   
                   
                 on the lead screw. 
               
               
                   
                   
                 The upper movement 
               
               
                   
                   
                 of the intermediate 
               
               
                   
                   
                 tube causes the 
               
               
                   
                   
                 intermediate tube&#39;s 
               
               
                   
                   
                 nut to engage the lead 
               
               
                   
                   
                 screw, maintaining 
               
               
                   
                   
                 the position of the 
               
               
                   
                   
                 lock pad constant 
               
               
                   
                   
                 with respect to the 
               
               
                   
                   
                 lock housing as the 
               
               
                   
                   
                 inner tube and 
               
               
                   
                   
                 intermediate tube 
               
               
                   
                   
                 move upward (the 
               
               
                   
                   
                 nuts of both tubes are 
               
               
                   
                   
                 on a lead screw 
               
               
                   
                   
                 thread). 
               
               
                 FIGS. 10J and 11J 
                 Inner tube&#39;s nut 
                 The inner and 
                 Inner tube&#39;s nut 
               
               
                   
                 comes off lead screw 
                 intermediate tubes 
                 goes off top of 
               
               
                   
                 threads 
                 continue upward 
                 threaded portion 
               
               
                   
                   
                 together (the 
                 of lead screw; gap 
               
               
                   
                   
                 intermediate tube&#39;s 
                 between lock and 
               
               
                   
                   
                 and inner tube&#39;s nuts 
                 bottom of lock 
               
               
                   
                   
                 are both on the lead 
                 pad goes away; 
               
               
                   
                   
                 screw) causing the 
                 intermediate nut is 
               
               
                   
                   
                 inner tube&#39;s nut to go 
                 on the lead screw. 
               
               
                   
                   
                 off the threads at the 
                 Intermediate 
               
               
                   
                   
                 top of the lead screw. 
                 tube&#39;s nut is on 
               
               
                   
                   
                 The inner tube then 
                 the lead screw. 
               
               
                   
                   
                 seats on the lock of 
               
               
                   
                   
                 the intermediate tube, 
               
               
                   
                   
                 causing the gap to go 
               
               
                   
                   
                 away. The inner tube 
               
               
                   
                   
                 then goes up along 
               
               
                   
                   
                 with the intermediate 
               
               
                   
                   
                 tube. 
               
               
                 FIGS. 10K and 
                 Inner tube&#39;s nut 
                 As the inner tube 
                 Inner tube&#39;s nut 
               
               
                 11K. 
                 comes off lead screw 
                 continues upward 
                 goes off top of 
               
               
                   
                 completely 
                 along with the 
                 lead screw 
               
               
                   
                   
                 intermediate tube, it 
                 completely 
               
               
                   
                   
                 eventually goes off 
                 Intermediate 
               
               
                   
                   
                 the top of the lead 
                 tube&#39;s nut remains 
               
               
                   
                   
                 screw completely (the 
                 on the lead screw. 
               
               
                   
                   
                 topmost portion of the 
               
               
                   
                   
                 lead screw is 
               
               
                   
                   
                 unthreaded). As the 
               
               
                   
                   
                 intermediate tube 
               
               
                   
                   
                 extends it reaches the 
               
               
                   
                   
                 next set of hold-down 
               
               
                   
                   
                 mechanisms and lock 
               
               
                   
                   
                 mechanisms and the 
               
               
                   
                   
                 cycle repeats. Note 
               
               
                   
                   
                 however that the 
               
               
                   
                   
                 intermediate tube is 
               
               
                   
                   
                 not locked to the 
               
               
                   
                   
                 bottom outer tube 
               
               
                   
                   
                 when there is only 
               
               
                   
                   
                 one three tube triad - 
               
               
                   
                   
                 the next to the outside 
               
               
                   
                   
                 tube always has its 
               
               
                   
                   
                 nut on a thread when 
               
               
                   
                   
                 the tower is fully 
               
               
                   
                   
                 extended and that is 
               
               
                   
                   
                 sufficient without 
               
               
                   
                   
                 otherwise locking that 
               
               
                   
                   
                 tube section. 
               
               
                   
                 Begin retraction 
                 Rotate lead screw in 
                 Intermediate 
               
               
                   
                 Inner tube&#39;s nut 
                 direction to cause 
                 tube&#39;s nut is on 
               
               
                   
                 comes onto lead 
                 intermediate tube to 
                 the lead screw. 
               
               
                   
                 screw. 
                 retract. The inner 
                 Inner tube&#39;s nut 
               
               
                   
                   
                 tube, resting on the 
                 comes onto the 
               
               
                   
                   
                 locks, moves along 
                 lead screw. 
               
               
                   
                   
                 with the intermediate 
               
               
                   
                   
                 tube and the inner 
               
               
                   
                   
                 tube&#39;s nut engages a 
               
               
                   
                   
                 thread on the top of 
               
               
                   
                   
                 the lead screw. 
               
               
                   
                 Intermediate tube&#39;s 
                 The inner tube and 
                 Intermediate 
               
               
                   
                 nut comes off the 
                 intermediate tube 
                 tube&#39;s nut comes 
               
               
                   
                 lead screw 
                 continue to retract 
                 off the lead screw. 
               
               
                   
                   
                 together. The nut of 
                 Inner tube&#39;s nut is 
               
               
                   
                   
                 the lower tube, the 
                 on lead screw, 
               
               
                   
                   
                 intermediate tube 
                 unloading the 
               
               
                   
                   
                 comes off the lead 
                 locks. Gap 
               
               
                   
                   
                 screw threads, 
                 reappears. 
               
               
                   
                   
                 shifting the load of 
               
               
                   
                   
                 the lower tube to the 
               
               
                   
                   
                 shoulders of the hold- 
               
               
                   
                   
                 down actuator pads 
               
               
                   
                   
                 that are engaging the 
               
               
                   
                   
                 upper flange cap. 
               
               
                   
                   
                 The inner tube&#39;s nut 
               
               
                   
                   
                 remains on the lead 
               
               
                   
                   
                 screw, taking the load 
               
               
                   
                   
                 of both tubes and 
               
               
                   
                   
                 unloading the locks. 
               
               
                 FIGS. 8J and 9J 
                 Begin unlocking 
                 The inner and 
                 Lock pin enters 
               
               
                   
                 sequence 
                 intermediate tubes 
                 lock post slot. 
               
               
                   
                   
                 continue to move 
               
               
                   
                   
                 together. The lock 
               
               
                   
                   
                 pin enters the lock 
               
               
                   
                   
                 post slot (carried by 
               
               
                   
                   
                 the non-moving outer 
               
               
                   
                   
                 tube). 
               
               
                 FIGS. 8K and 9K 
                 Continue unlocking 
                 The inner and 
                 Lock pin 
               
               
                   
                 sequence 
                 intermediate tubes 
                 continues along 
               
               
                   
                   
                 continue to move 
                 slot, rotating lock. 
               
               
                   
                   
                 together. The lock 
               
               
                   
                   
                 pin continues through 
               
               
                   
                   
                 the lock post slot 
               
               
                   
                   
                 causing rotation of 
               
               
                   
                   
                 the lock. 
               
               
                 FIGS. 9L and 9L 
                 Unlocking sequence 
                 The inner and 
                 Lock pin reaches 
               
               
                   
                 completed. 
                 intermediate tubes 
                 bottom of slot; 
               
               
                   
                   
                 continue to move 
                 lock is unlocked. 
               
               
                   
                   
                 together. The lock 
               
               
                   
                   
                 pin continues to the 
               
               
                   
                   
                 bottom of the lock 
               
               
                   
                   
                 post slot causing full 
               
               
                   
                   
                 rotation of the lock, 
               
               
                   
                   
                 opening the lock. 
               
               
                   
                   
                 Note that the relative 
               
               
                   
                   
                 locations of the lock 
               
               
                   
                   
                 pads/locks and hold- 
               
               
                   
                   
                 down pads/hold- 
               
               
                   
                   
                 downs does not 
               
               
                   
                   
                 change through FIGS. 
               
               
                   
                   
                 8I/9I through 8K/9K 
               
               
                   
                   
                 because the 
               
               
                   
                   
                 intermediate tube is 
               
               
                   
                   
                 hanging from the 
               
               
                   
                   
                 inner tube. 
               
               
                 FIGS. 2A, 2B 
                 Intermediate tube 
                 Inner tube moves 
               
               
                   
                 reaches its nested 
                 down while 
               
               
                   
                 position 
                 intermediate tube 
               
               
                   
                   
                 remains stationary its 
               
               
                   
                   
                 nested position 
               
               
                 FIGS. 8M and 9M 
                 Begin hold-down 
                 Beak of hold-down 
               
               
                   
                 activation sequence 
                 actuator pad engages 
               
               
                   
                   
                 lower lip of hold- 
               
               
                   
                   
                 down, beginning to 
               
               
                   
                   
                 rotate it. 
               
               
                 FIGS. 8N and 9N 
                 Continue hold-down 
                 Jaws of hold-down 
               
               
                   
                 activation sequence 
                 begin to engage hook 
               
               
                   
                   
                 of hold-down post. 
               
               
                 FIGS. 8O and 9O 
                 Hold-down 
                 Beak of hold-down 
                 Hold-down 
               
               
                   
                 activation sequence 
                 actuator pad pushes 
                 engaged. 
               
               
                   
                 completed. 
                 lower lip of hold- 
               
               
                   
                   
                 down to fully engage 
               
               
                   
                   
                 hook of hold-down 
               
               
                   
                   
                 post 
               
               
                 FIGS. 8P and 9P 
                   
                 Lock pads and hold- 
               
               
                   
                   
                 down actuator pads 
               
               
                   
                   
                 below the respective 
               
               
                   
                   
                 locks and hold- 
               
               
                   
                   
                 downs. Inner tube 
               
               
                   
                   
                 continues retraction. 
               
               
                 FIGS. 8Q and 9Q 
                 Return to fully 
                 All tubes fully nested 
                 Hold-downs 
               
               
                   
                 nested condition. 
                   
                 engaged, locks 
               
               
                   
                   
                   
                 unlocked. 
               
               
                   
               
             
          
         
       
     
         [0054]      FIGS. 12A-12C  show a nut assembly  32 - 38  ( FIGS. 2C ,  2 D) in greater detail.  FIG. 12D  shows a variation on the nut assembly of  FIGS. 12A-12C . Referring first to the nut assembly of  FIGS. 12A-12C , a flange  140  adapted for attachment to a tube section has a base  142  having screw holes  142   a  and an annular neck portion  144  for captively holding a threaded drive nut  146 , a wavy ring-shaped metal spring  148 , a retaining ring  150  and a snap ring  152 . The drive nut  152  has a collar  154  for cooperating with the retaining ring and snap ring to capture the wavy spring. Collar  154  has a gap to allow a pin  156  to interfere with the free rotation of the drive nut within the flange. The wavy spring&#39;s vertical “play” and the collar gap&#39;s slight rotational “play” permit the nut to more readily engage the threaded drive screw. 
         [0055]    Referring now to the variation shown in  FIG. 12D , an elastomer (a natural or synthetic rubber), preferably moldable or castable, such as polyurethane or some other suitable material is used instead of a wavy metal washer is employed. The springiness of the polyurethane provides not only vertical and rotational “play” but also provides some cushioning as mast sections are retracted. One way to implement such an arrangement is to provide a ribbed surface area inside the flange collar  144  onto which a castable elastomer such as polyurethane is cast in place. The polyurethane contacts the captive nut and a slight gap is provided between the nut and the flange collar to as to allow some movement of the nut. A metal washer underneath the polyurethane prevents wear of the polyurethane with respect to a retaining ring  160 . 
         [0056]    Suitable materials other than an elastomer may include other thermoset plastics, carbon-fiber and carbon-fiber impregnated thermoset plastics, fiberglass and fiberglass impregnated thermosets, cork, or composites of some or all of the materials mentioned in this paragraph. 
         [0057]      FIG. 13A  is a plan view of the gear box  19  with its cover removed. 
         [0058]      FIG. 13B  is a cross sectional view along section lines  13 B- 13 B of  FIG. 13A . 
         [0059]      FIG. 13C  is a cross sectional view along section lines  13 C- 13 C of  FIG. 13A . 
         [0060]    A polygon mast according to aspects of the present invention may be fabricated from metal sheets, for example aluminum sheet or stainless steel sheet. The sections can be manufactured from nearly any material that is available in sheets that can be formed, including, for example, aluminum, stainless steel, galvanized steel, and any other suitable material. One may start with a flat metal sheet. Such sheets commonly have a width of 96 inches and a length of as much as 14 feet. A 100 foot tower may employ 14 foot mast sections. Shorter sheets and shorter sections may be employed depending on the desired product height. Automated computer numerically controlled (CNC) may be employed to punch holes, cut slots, etc. in a sheet prior to forming into a “half shell”  170  such as shown in  FIGS. 14 and 15 . The polygonal mast may be formed from more than two pieces. A single piece cannot be easily fabricated. 
         [0061]    A flat sheet may be formed into a half shell by applying a series of bends along its length, such as 22.5 degree bends when a sixteen-sided mast cylinder is desired. The bends may be applied in any suitable way to a metal sheet  171  using either manually-controlled or computer-controlled devices.  FIG. 16A  shows the application of such bends using an elongated two-piece die punch  172   a ,  172   b . A stop  173  may be used for aligning the metal sheet with the die.  FIG. 16B  shows two half shells  170   a  and  170   b  mated and fastened together along two overlapping seams  174   a  and  174   b . Rivets or other suitable fasteners may be employed. The end of each of the half shells  170   a  and  170   b  may be offset as shown in order to facilitate the overlap and securing together of the half shells. 
         [0062]    An example of steps useful for fabricating a polygonal mast section is shown in  FIG. 17 . 
         [0063]    Polygon mast section “shells” may also be formed from thermoset plastics or from composites by any of various suitable methods, including, for example, pultrusion, filament winding or layup (using fiberglass or carbon fiber, for example) over a mandrill. Shells formed in any of such manners may provide excellent strength to weight ratios. 
         [0064]    Whether the polygonal sections are formed from metal or other material, as shown in the examples of  FIGS. 3A and 3B , for example, corners of the polygon may be used to hold slides and/or to mount elements of the hold-down or locking mechanisms. 
         [0065]    Polygon mast sections according the teaching herein may be fabricated with very tight clearances, for example as little as 5 to 6/1000 inch. Such tolerances result in a very “tight” tower. 
         [0066]    Although aspects of the invention are not limited to a mast having the cross section of a sixteen-sided polygon, that number of sides is useful because the resulting wind coefficient of the tower is essentially the same as that formed from mast sections having a circular cross section. 
         [0067]    The manufacture of polygonal masts and towers has several advantages. Generic metal sheets can be stocked, usable for various different mast and tower configurations. In addition, manufacturing lead time is very short—there is no need to extrude aluminum parts, for example. 
       INCORPORATION BY REFERENCE 
       [0068]    U.S. Pat. No. 5,163,650 is hereby incorporated by reference in its entirety.