Patent Abstract:
A variable height telescoping tower includes a base section and a second lower most section nested within the base section and extendable from within the base section. The second lower most section includes a plurality of vertically spaced lock apertures disposed thereon. A lock member is attached to the base section, and includes an engaging portion movable between a disengaged position at which the engaging portion rests outside of the lock apertures and an engaged position at which the engaging portion is engaged within one of the lock apertures of the second lower most section.

Full Description:
BACKGROUND 
     Telescoping lattice towers are generally made up of multiple lattice sections that telescope within each other as shown in  FIG. 1 . The telescoping tower  10  depicted in  FIG. 1  includes a base section  12  and two upper sections  14  and  16 . Section  14  nests into base section  12  and section  16  nests into section  14 . 
     The most common method used to extend and retract the sections  14  and  16  is by means of suspension cables made from wire rope. The base section  12  typically has a hand operated or motorized winch  18  to hoist the second lower most section  14  of the tower. All sections above the second lower most section  14  are cabled in a manner to respond to the movement of the second lower most section  14  relative to the base section  12  resulting in all sections telescoping simultaneously in both the extend and retract motions. 
     In the application of telescoping lattice towers with payloads having large projected wind sail areas, or if it is necessary to maintain stiffness in the extended tower, guy cables are often used. When an extended tower is equipped with guy cables, the result is larger vertical or axial loads from both the initial pre tensioning of the guy cables and resultant vertical loads from elevated wind speeds acting against the wind sail area(s). 
     When axial loads are increased, the loads in the lift or suspension cables also increase. In the case of the upper telescoping sections, multiple lift cables can be installed to increase the axial load capacity of the tower. However, this is not easily accomplished for the main lift cable or the winch cable. 
     In many applications, a lock system is incorporated at the interface of the base section and second lower most section to remove the main lift cable from the axial load path. The locks are typically located to lock the base section and second lower most section when the tower is at full extension. 
       FIG. 2  is a diagram showing a typical prior-art lock arrangement at the interface of the base section  12  and second lower most section  14  to remove the main lift cable from the axial load path. A lock base  20  includes opposed faces  24  each having a horizontal slot  26  and is fixed to each of the vertical members of the base section  12 . A horizontally-oriented plate  28  is coupled to actuating arm  30  and is pivoted about pivot point  32 . 
     To lock the second most lower section  14  to base section  12 , the tower  10  is raised so that the bottom of the second most lower section  14  is positioned above slots  26  and the arm  30  is rotated to move the plate  28  through slots  26  in the opposing faces of the lock base  20  so that plate  28  is positioned under the bottom member  34  of the second most lower section  14 . The tower  10  is then lowered until the bottom member  34  of the second most lower section  14  rests on plate  28 , which then carries the vertical load of all of the upper sections of the tower  10  because it is captured in slots  26 .  FIG. 2  shows the lock plates  26  in the locked position. 
     While this solution addresses the problem when the tower is fully extended, there is a need for a system for locking the base section to the second lower most section at intermediate heights to allow the tower to be guyed at different elevations as opposed to only fully extended. 
     SUMMARY 
     The present invention is a system for locking the base section to the second lower most section provides for locking at incremental heights. Locking at incremental heights allows the main lift cable to be isolated from the axial load path enabling guying of the tower at incremental heights between its fully retracted height and its fully extended height. 
     According to one aspect of the present invention, a variable height telescoping tower includes a base section and a second lower most section nested within the base section and extendable from within the base section. The second lower most section includes a plurality of vertically spaced lock apertures disposed thereon. A lock member is attached to the base section, and includes an engaging portion movable between a disengaged position at which the engaging portion rests outside of the lock apertures and an engaged position at which the engaging portion is engaged within one of the lock apertures of the second lower most section. 
     According to another aspect of the present invention, the second lower most tower section includes a lattice plate member in place of the round bar stock lattice members normally used to secure the tower section legs together. 
    
    
     
       DRAWINGS 
       These and other features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
         FIG. 1  is a drawing depicting a typical prior-art telescoping tower. 
         FIG. 2  is a drawing depicting a lock system incorporated at the interface of the base section and second lower most section to remove the main lift cable from the axial load path when the tower is fully extended. 
         FIG. 3  is diagram depicting an illustrative lattice structure design for the second lower most tower section having multiple lock apertures to allow engagement of a lock mechanism at frequent intervals. 
         FIG. 4  is a diagram depicting an illustrative second lower most tower section incorporating the lattice structure design of  FIG. 3 . 
         FIG. 5  is a diagram depicting a portion of the base section and second lower most section of a telescoping tower showing an illustrative design for locking the base section to the second lower most section at incremental heights. 
         FIG. 6A  and  FIG. 6B  are diagrams showing an illustrative locking mechanism in accordance with the present invention in an unlocked position and a locked position, respectively. 
         FIG. 7A  and  FIG. 7B  are diagrams showing another view of the illustrative locking mechanism of  FIGS. 6A and 6B  in the unlocked position and the locked position, respectively. 
         FIGS. 8A and 8B  are diagrams showing a cross sectional view of one of the illustrative locking mechanism of  FIGS. 6A and 6B  in the unlocked position and the locked position, respectively. 
         FIGS. 9A and 9B  are diagrams showing a top view of the locking mechanisms of  FIGS. 6A and 6B  in the unlocked position and the locked position, respectively. 
         FIG. 10  is a diagram showing a tower including two groups of illustrative lock mechanisms disposed at different heights. 
         FIG. 11  is a diagram depicting a variable height telescoping tower including two sets of lock mechanisms disposed at different heights on the base section. 
     
    
    
     DESCRIPTION 
     Persons of ordinary skill in the art will realize that the following description of the present invention is illustrative only and not in any way limiting. Other embodiments of the invention will readily suggest themselves to such skilled persons. 
     According to one embodiment of the present invention, the design of lattice structure used on the second lower most tower section in the area that overlaps the base tower section when the tower is completely retracted is provided with multiple lock apertures at different heights to allow engagement of a lock mechanism. Typical lattice members are made from shapes such as round bar, tubing or structural shapes. In the present invention, the typical type lattice structure is replaced with a lattice structure having lock apertures to allow engagement of a lock mechanism at frequent intervals. This can be accomplished in a number of ways. The variable height telescoping tower of the present invention may be fabricated from steel, although persons of ordinary skill in the art will appreciate that other materials may be employed. Persons of ordinary skill in the art will observe that, while the embodiments of the invention disclosed herein are described with reference to a triangular tower, the principles of the present invention equally apply to other tower configurations, such as but not limited to towers having a square cross section. 
     Referring now to  FIG. 3 , a diagram depicts an illustrative lattice structure design for the second lower most tower section having multiple lock apertures to allow engagement of a lock mechanism at frequent intervals. Lattice plate  40  is preferably formed from a steel sheet. In one particular embodiment, Lattice plate  40  may be formed from half-inch thick steel plate. 
     As may be seen from an examination of  FIG. 3 , lattice plate  40  may be perforated to decrease the weight of the second lower most tower section using a pattern selected to maintain its structural integrity. In the particular embodiment shown in  FIG. 3 , lattice plate  40  is provided with a series of first apertures, shown in  FIG. 3  as rhombic-shaped apertures (one of which is identified by reference numeral  42 ), formed along its length. Smaller triangular apertures (one of which is identified by reference numeral  44 ) are also formed in lattice plate  40 . Apertures  42  and  44  may be formed by processes such as stamping, flame cutting, plasma cutting, laser cutting or the like. 
     According to an illustrative embodiment of the present invention, apertures  42  and  44  are arranged in a pattern that results in the remaining steel structure of plate  40  (some of which are identified by reference numerals  46 ) resembling the cross bracing rods found in conventional lattice tower structures. As noted, the particular pattern of apertures need not be as shown in  FIG. 3 , but should be designed to provide structural integrity to lattice plate  40  considering the mechanical forces to which it will be subjected in use. 
     Lattice plate  40  also includes a plurality of spaced apart rectangular lock apertures formed along each of its opposing long sides. In one embodiment of the invention, pairs of lock apertures on opposing long sides of lattice plate  40  are in alignment with one another. One such pair of lock apertures is designated by reference numerals  46   a  and  46   b . In one embodiment of the present invention, pairs of lock apertures are separated vertically by a uniform distance as shown in  FIG. 3 . In other embodiments of the invention, pairs of lock apertures may be separated vertically by non-uniform distances. 
     In one embodiment of the present invention, the lattice plate  40  may be formed as a single piece. In other embodiments of the present invention, the lattice plate  40  may have a shorter length and two or more lattice plates  40  may be placed end to end to form a combined lattice plate having a longer length. 
     Referring now to  FIG. 4 , a diagram depicts an illustrative second lower most tower section  50  in accordance with the principles of the present invention. In general, the second lower most tower section  50  includes a plurality of lock apertures  46  on each of its faces. These apertures will engage lock mechanisms to lock the second lower most tower section to the base tower section at various heights as disclosed herein. 
     The embodiment shown in  FIG. 4  incorporates the lattice plate  40  design of  FIG. 3  to provide the plurality of lock apertures  46  to allow engagement of a lock mechanism at frequent intervals. In the particular embodiment illustrated in  FIG. 3 , a lattice plate  40  having lock apertures  46  formed into it is fastened to each leg  52  of the tower, such as by welding to the tubular vertical leg members  52  of the second lower most tower section  50 . Persons of ordinary skill in the art will appreciate that arrangements other than providing a windowed plate may be used to provide lock apertures  46  at different vertical positions along the height of the second lower most tower section  50 . It will be apparent, though that use of a lattice plate  40  simplifies manufacturing costs due to the ease of fabrication. 
     The second lower most section includes vertical tubular members  52  (two of the three are shown) held together in a spaced apart relationship along a portion of the length of the second lower most section  50  by lattice plates  40  to which they are welded as has been shown in  FIG. 4 . While  FIG. 5  shows two plates  40 , persons of ordinary skill in the art will appreciate that a single plate  40  may be employed. Each of plates  40  include multiple lock apertures  46  vertically separated from one another. 
     The tubular members  52  along the remainder of the length of second lower most section  50  are held together in a spaced apart relationship by at least one lattice bar  54  which zig zags between or otherwise spans the distance between tubular members  52 . The at least one lattice bar is welded to tubular members  52  as is known in the art. 
     In the embodiment of the second lower most tower section  50  depicted in  FIG. 4 , the lattice plate  40  extends less than half of the length of the second lower most tower section  50  from slightly above the bottom  54  of second lower most tower section  50 . This is because the operation of the particular illustrative embodiment of the lock mechanism depicted herein requires that the interior space within the second lower most tower section  50  be clear of the other tower sections nested with in the second lower most tower section  50 . In other embodiments of the invention the operation of the lock mechanism does not require that the interior space within the second lower most tower section  50  be clear of the other tower sections nested with in the second lower most tower section  50 . 
     Referring now to  FIG. 5 , a diagram depicts a portion of a base section  60  and second lower most section  50  of a telescoping tower showing an illustrative design for a lock mechanism used for locking the base section  60  to the second lower most section  50  at incremental heights. The base section  60  is formed from vertical tubular members  62  (two of the three are shown) held together in a spaced apart relationship by at least one lattice bar  64 , formed, for example of round steel bar stock, which zig zags between or otherwise spans the distance between tubular members  62 . The at least one lattice bar is welded to tubular members  62  as is known in the art. 
     A plurality of lock mechanisms each include a lock arm  66  having an end  68 . Each lock arm  66  is pivotally mounted on a lock arm mount  70  one of the vertical tubular members  62  of the base section at pivot  72  such that the end  68  engages the lock aperture  46  when the lock arm  66  is pivoted into the lock position and disengages the lock aperture  46  when the lock arm  66  is pivoted into the unlock position to allow the second lower most section to be raised or lowered.  FIG. 5  shows the second lower most section  50  locked to the base section  60  as the end  68  can be seen engaged in the lock aperture  46  on the left side of  FIG. 5 . Persons of ordinary skill in the art will appreciate that a support surface (not shown in  FIG. 5 ) may be provided under each of lock arms  66  to carry the vertical load and prevent the weight of the second lower most tower section from exerting a torque on the pivot  72  of each lock arm  66 . 
     As may be seen from an examination of  FIG. 5 , the vertical dimensions of lock apertures  46  is larger than the vertical dimension of the ends of lock arms  66 . In use, the tower is raised to vertically align the lock apertures  46  with the lock arms  66 , and then the lock arms  66  are rotated into the lock apertures  46  to place the lock mechanisms in the locked position. Once this is done, the tower is lowered until the tops of the lock apertures  46  rest on the top surfaces of the lock arms  66 . To disengage the locks, the tower is raised slightly to disengage the top surfaces of the lock arms  66  from the tops of the lock apertures  46 . The lock arms  66  are then rotated out of the lock apertures  46  to place the lock mechanisms in the unlocked position. 
     Referring now to  FIGS. 6A, 6B, 7A, 7B, 8A, 8B, 9A and 9B  a series of diagrams show several different views of an illustrative locking mechanism in both an unlocked position and a locked position, respectively.  FIGS. 6A and 6B  each show an upper isometric view of the locking mechanism.  FIGS. 7A and 7B  each show a lower isometric view of the locking mechanisms.  FIGS. 8A and 8B  each show a cross sectional view of one of the illustrative locking mechanism of  FIGS. 6A and 6B . Finally,  FIGS. 9A and 9B  each show a top view of the locking mechanisms.  FIGS. 6A, 7A, 8A, and 9A  show the locking mechanism in the unlocked position and  FIGS. 6B, 7B, 8B, and 9B  show the locking mechanism in the locked position. 
     All of  FIGS. 6A, 6B, 7A and 7B  show the second lower most tower section  50  formed from tubular members  52  and lattice plates  40  partially nested within the lower most tower section  60  formed from tubular members  62  and lattice rod  64 . A plurality of lock mechanisms each including a lock arm  66  having a tab  68  extending from an end thereof. Each lock arm  66  is shown mounted on a lock mount  70  on one of the vertical tubular members  62  of the base section at pivot  72 . In the embodiment shown in  FIGS. 6A, 6B, 7A and 7B , the lock mount  70  for each lock arm  66  is mounted to a mounting plate  74  attached (for example by welding) to each of the tubular members  62  and having opposing faces  76 . Each opposing face  76  of each mounting plate  74  has a notch  78  formed therein. 
     The lock arms are actuated by actuator rods  80 . Each actuator rod  80  extends across one face of the tower and is connected between adjacent ones of the lock arms  66 . By using three actuator rods  80  as a mechanical linkage to connect together all of the lock arms  66 , the rods can operate in tension no matter whether the lock arms  66  are being moved to engage or to disengage the lock mechanisms. 
     In the embodiment of the present invention depicted herein, the lock arms are moved by a sheathed push/pull control cable  82  to engage and to disengage the lock mechanisms. Sheathed push/pull control cable mechanisms are well known in the art. A first end of cable  82  is fastened to one of the lock arms  66 . A first end of the sheath  84  surrounding cable  82  is anchored at support  86  to the one of the mounting plates  78  to which the cabled lock arm is mounted. A second end of the sheath  84  is preferably mounted towards the lower end of lower most tower section  62  and the second end of cable  82  is coupled to a lever to move the cable  82  from a first position where it extends out of sheath  84  and the lock mechanism is disengaged to a second position where it is pulled into the sheath  84  to pivot the lock arm  66  and engage the lock mechanism. 
     While the embodiments disclosed herein employ a sheathed push/pull control cable  82  to engage and to disengage the lock mechanisms, the present invention is not limited to lock mechanisms driven by sheathed push/pull control cable arrangements. Persons of ordinary skill in the art will appreciate that other drive mechanisms, such as but not limited to solenoids, motor-driven screw drives, etc. may be used to engage and to disengage the lock mechanisms. 
     When in the locked position as shown in  FIG. 6B , the lock arm passes through the slot  78  on one face  76  of mounting plate  72 , through a lock aperture on a lattice plate  40  on a first face of the second lower most tower section  50 , around the inside of the second lower most tower section  50 , through a lock aperture on a lattice plate  40  on a second face of the second lower most tower section  50  adjacent to the first face, and through the slot  78  on the face  76  of mounting plate  72 . As most easily seen in  FIG. 7B , the bottom surfaces of the slots  78  provide structural support for the lock arms to bear the downward forces exerted by the second lower most tower section  50  when the lock is in the locked position. 
     As with the embodiment depicted in  FIG. 5 , in the embodiments shown in  FIGS. 6A, 6B, 7A, 7B, 8A, 8B, 9A and 9B , the vertical dimensions of lock apertures  46  is larger than the vertical dimension of the ends of lock arms  66 . In use, the tower is raised to vertically align the lock apertures  46  with the lock arms  66 , and then the lock arms  66  are rotated into the lock apertures  46  to place the lock mechanisms in the locked position. Once this is done, the tower is lowered until the tops of the lock apertures  46  rest on the top surfaces of the lock arms  66 . To disengage the locks, the tower is raised slightly to disengage the top surfaces of the lock arms  66  from the tops of the lock apertures  46 . The lock arms  66  are then rotated out of the lock apertures  46  to place the lock mechanisms in the unlocked position. 
     Referring now to  FIG. 10 , a diagram shows an exemplary engagement mechanism including levers  88   a  and  88   b , each one controlling a group of three lock mechanisms as shown in  FIGS. 6A, 6B, 7A, 7B, 9A and 9B . The lever  88   a  is shown in the locked position where the lever  88   a  has pulled cable  82   a  downward through the sheath  84   a  to move the group of locking mechanisms with which it is associated to the locked position. The lever  88   b  is shown in the locked position where its cable (not shown) has been pushed upward through the sheath  84   b  to move the group of locking mechanisms with which it is associated to the unlocked position. A portion of a motor drive unit  90  for raising and lowering the tower is shown in  FIG. 10 . 
     Referring now to  FIG. 11 , a diagram depicts a second lower most tower section  50  partially nested inside a base tower section  60 . Two sets of lock mechanisms  92  and  94  are shown disposed at different heights on the base section  60 . The two sets of lock mechanisms  92  and  94  can be used individually to provide a wider range of positions at which second lower most tower section  50  can be locked to base tower section  60  or together to provide greater support strength. 
     Although the present invention has been discussed in considerable detail with reference to certain preferred embodiments, it would be apparent to those skilled in the art that many more modifications than mentioned above are possible without departing from the inventive concepts herein. Therefore, the scope of the appended claims should not be limited to the description of preferred embodiments contained in this disclosure.

Technology Classification (CPC): 4