Patent Publication Number: US-8522511-B2

Title: Methods and apparatus for mast system with enhanced load bearing

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     The present invention was made with government support under Contract No. W31P4Q-09-G-0001 awarded by the U.S. Army Lower Tier Program Office (LTPO) in Huntsville, Ala. The government has certain rights in the invention. 
    
    
     BACKGROUND 
     As is known in the art, mast systems are used to elevate and support a payload. For example, telescoping antennas are widely used for portable communication, radar systems, surveillance systems, etc. In telescoping antennas, a series of mast sections are coaxially aligned to enable capture of each mast section into the next larger section. Telescoping antennas provide a compact stowed configuration, which is also known as a nested length, and an extended deployed configuration. As is well known in the art, the stowed configuration facilitates transport of the telescoping antenna to a desired location at which the antenna can be positioned for transition to the deployed configuration. 
     There are a variety of known mechanisms and structures to manipulate the antenna from the stowed configuration to the deployed configuration in which the antenna mast is fully extended, typically in the vertical direction. Known mechanisms include cables, screw drives, pulley drives, breach loadings, motor actuators, and the like. These mechanisms are generally complex with poor performance in adverse conditions. 
     Telescoping antennas can be located in harsh environmental conditions that can degrade performance. Windy arid locations, such as deserts, can result in sand and other debris damaging the tightly fitted telescoping mast sections. Known mechanisms to combat sand include wipers, sleeves, and the like. However, these mechanisms require continual maintenance and replacement to ensure proper functionality over the life of the mast system. 
     SUMMARY 
     The present invention provides methods and apparatus for a telescoping antenna having structural members, such as ribs, on mast sections to increase load bearing. With this arrangement, an elegant telescoping mechanism is provided for applications requiring an antenna mast. While exemplary embodiments of the invention are shown and described in conjunction with particular communication applications and antenna configurations, it is understood that the invention is applicable to telescoping antennas in general in which it is desirable to bear loads. 
     In one aspect of the invention, a mast system comprises: a telescoping mast having first and second mast sections, the mast having a stowed configuration and a deployed configuration, the first mast section including an inner surface having ribs disposed thereon, and the second mast section including a coupling mechanism to engage the ribs on the first mast section for enabling axial movement of the second mast section with respect to the first mast section. 
     The mast system can further include one or more of the following features: the coupling mechanism includes channels to capture the ribs, the coupling mechanism includes bushings to capture the ribs, the ribs include a bulbous portion extending from a stein extending from an inner surface of the first mast section, a liner disposed in the second mast section, the first and second mast sections have outer surfaces configured to provide a gap, the gap is sized to allow debris to pass through the first and second mast sections, a liner in the second mast section to maintain alignment of the first and section mast sections, the second mast section includes an engagement mechanism to engage a guy wire to stabilize the mast in a deployed configuration and to manipulate the second mast section to the deployed configuration, the engagement mechanism forms part of an end cap extending about an inner surface of an end of the second mast section, the end cap includes apertures for the ribs, and/or the liner has an undulating inner surface. 
     In another aspect of the invention, a method comprises: forming a telescoping mast having first and second mast sections, the mast having a stowed configuration and a deployed configuration, employing ribs on an inner surface of the first mast section to engage a coupling mechanism on the second mast section, and configuring the ribs and the coupling mechanism to enable axial movement of the second mast section with respect to the first mast section. 
     The method can further include one or more of the following features: configuring outer surfaces of the first and second mast sections to form a gap for enabling debris to pass through the gap between the first and second mast sections, securing a liner in the second mast section to maintain alignment of the first and section mast sections, and/or employing an engagement mechanism to engage a guy wire to stabilize the mast in a deployed configuration and to manipulate the second mast section to the deployed configuration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing features of this invention, as well as the invention itself, may be more fully understood from the following description of the drawings in which: 
         FIG. 1  is a schematic representation of a telescoping mast system in accordance with exemplary embodiments of the invention; 
         FIG. 2  is a schematic representation of a further telescoping mast system in accordance with exemplary embodiments of the invention; 
         FIG. 2A  is a pictorial representation of a mobile mast system in accordance with exemplary embodiments of the invention; 
         FIG. 2B  is a pictorial representation of the mast system of  FIG. 2A  shown partially deployed; 
         FIG. 2C  is a pictorial representation of the mast system of  FIG. 2A  in a deployed configuration; 
         FIG. 3  is a schematic representation of a mast section interface in accordance with exemplary embodiments of the invention; 
         FIG. 4A  is a isometric view of a telescoping mast system in accordance with exemplary embodiments of the invention; 
         FIG. 4B  is a top view of the mast system of  FIG. 4A ; 
         FIG. 4C  is a cross-sectional top view of the mast system of  FIG. 4A ; 
         FIG. 4D  is a cross-sectional side view of the mast system of FIG. 
         FIG. 4E  is a cross-sectional view showing further detail for a top portion of the mast system of  FIG. 4D ; 
         FIG. 4F  is a cross-sectional view showing further detail for a bottom portion of the mast system of  FIG. 4D ; 
         FIG. 4G  shows a schematic representation of a portion of an alternative embodiment of a mast system in accordance with exemplary embodiments of the invention; 
         FIG. 4H  is a top view of the mast system of  FIG. 4G ; 
         FIG. 5  is a side view of a mast system with the mast in an extended configuration in accordance with exemplary embodiments of the invention; 
         FIG. 5A  is a side view of a portion of the mast system of  FIG. 5 ; 
         FIGS. 5B ,  5 C,  5 D and  5 E show exemplary dimensions for a mast section for the mast system of  FIG. 5 ; 
         FIG. 6  is a schematic representation of a mast assembly in accordance with exemplary embodiments of the invention; 
         FIGS. 6A and 6B  are top views showing additional detail for the mast assembly of  FIG. 6   
         FIG. 7  is a schematic representation of a portion of a first mast section in accordance with exemplary embodiments of the invention; 
         FIG. 7A  is a top view of the first mast section of  FIG. 7 ; 
         FIG. 8  is a schematic representation of a portion of a second mast section in accordance with exemplary embodiments of the invention; 
         FIG. 8A  is a top view of the second mast section of  FIG. 8 ; 
         FIGS. 8B-8K  are schematic representations of alternative rib embodiments for the mast assembly of  FIG. 6 ; 
         FIG. 9  is a schematic representation of a mast section interface configuration in accordance with exemplary embodiments of the invention; 
         FIGS. 10 ,  10 A, and  10 B show exemplary dimensions for mast sections for a mast system in accordance with exemplary embodiments of the invention; 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is an exemplary telescoping mast system  100  including a guy wire telescoping mechanism  102  having a stabilization structure  104  with a guy wire  106  to support the mast  108  and also to manipulate at least one mast section between stowed and deployed configurations. The guy wire  106  forms a portion of the stabilization structure  104  to support the mast and also telescope the mast  108  so as to provide significant advantages over known systems, such as reduced mast deployment time, reduced manpower for deployment, and reduced complexity and parts count. 
     As is known in the art, a guy wire or guy-rope is a tensioned cable extending from a mast, or other elongate structure, to the stabilization structure, ground, or other anchor point to provide stability. Typically, a number of guy wires are used about a radius from the mast base. Radio towers, for example, typically have a series of guy wires attached at multiple heights to stabilize the tower for preventing tip over. 
     The stabilization structure  104  stabilizes the mast  108  in the deployed configuration. In the illustrated embodiment, the stabilization structure  104  includes a number of outriggers  110  that extend radially from the mast  108  at an angle in the deployed configuration. In the stowed configuration, the outriggers  110  can be generally parallel to the mast or other position to facilitate storage and transport. 
     In one embodiment, a pulley system  150  manipulates the guy wire  106 , which extends from a winch mechanism  154  to an anchor point  156  via the outriggers  110  and antenna mast sections  108 , as described more fully below. 
     A first mast section  108   a , a second mast section  108   b , a third mast section  108   c , a fourth mast section  108   d , and a fifth mast section  108   e , are coaxially aligned to enable capture of the second mast section into the first mast section, the third mast section into the second mast section, and so on. The first mast section  108   a  has a diameter that is slightly larger than a diameter of the second mast section  108   b , which has a diameter slightly larger than the third mast section  108   c , and so on. The mast sections  108  are moved to the deployed configuration by the winch mechanism  154  pulling the guy wire  106 . 
     As the guy wire  106  is pulled, the second mast section  108   b  is pulled out from the base or first mast section  108   b . Similarly, the guy wire  106  pulls the third mast section  108   c  out of the second mast section  108   b , etc. When the mast sections  108  are deployed as desired, as shown for example, in  FIG. 2B , the guy wire  106  can be locked down to maintain tension in the guy to support the extended mast. 
     In an exemplary embodiment, the outriggers are moved manually or automated to a deployed configuration to support the extended mast. Once extended, the winch mechanism  154  can retract the guy wire to deploy/telescope the mast. 
     It is understood that the guy wire can be coupled to the mast section(s) in a variety of configurations that are effective to cause axial movement of the mast section as the guy wire is pulled/retracted. In general, the guy wire can move axially with respect to a mast section to create axial movement of the mast section. The position of the guy wire in relation to the mast section should be maintained while the guy wire moves. 
     It is understood that a variety of stabilization structures that include a guy wire to telescope a mast section can be provided in alternative embodiments.  FIG. 2  shows an exemplary embodiment having a plurality of mast sections  208  manipulated by a guy wire  206  coupled to a pulley system  250  secured to a stabilization structure  204 . A winch mechanism  254  applies a force to the guy wire  206 . An anchor point  256  supports the vertical mast sections  208  and the winch mechanism  254 . 
     An exemplary stowed configuration is shown in  FIG. 2A  and an exemplary deployed configuration is shown in  FIG. 2C .  FIG. 2B  shows the mast system partially deployed with the outriggers extended prior to raising the mast. The telescoping mast can be transported on a flatbed or other vehicle for mobile installation. 
       FIG. 3  shows part of an exemplary mast section  300  having an engagement mechanism  302  to engage the guy wire  304 . A single pulley is shown to facilitate an understanding of the invention. In general, axial movement of the guy wire  304  in a first direction pulls the mast section  300  out of a larger mast section to deploy the mast. Movement of the guy wire  304  in the opposite direction allows the mast section  300  to be captured by the larger mast section in a transition to the stowed configuration. 
     It is understood that a variety of suitable mechanisms can be used to engage the guy wire and the mast section(s) to enable telescoping of the mast section(s). Exemplary motorized, hydraulic, pneumatic, manual winches and handcranks are well known to one of ordinary skill in the art. Suitable winches are available from Ingersoll Rand Corporation and other companies, hand cranks are available from the David Round Company of Streetsboro, Ohio. Come-a-longs are available from Gempler&#39;s of Madison, Wis. 
     It is understood that any practical number of mast sections and outriggers can be used to meet the needs of a particular application. It is further understood that the length of the mast sections, the amount of mast section overlap in the deployed configuration, the pulley tension level, outrigger length and angle, can vary based upon desired parameters. 
       FIGS. 4A-F  show an exemplary telescoping mast  400  system having a plurality of mast sections  402   a - e  each of which is manipulated by a separate guy wire  404   a - d . The second mast section  402   b  is moved axially out of the first mast section  402   a  by a first guy wire  404   a  via a first engagement mechanism  406   a  that enables movement of the guy wire to pull up the mast section. The third mast section  402   c  is moved axially out of the second mast section  402   b  by a second guy wire  404   b . Similarly, the fourth mast section  402   d  and fifth mast section  402   e  are independently manipulated by respective third and fourth guy wires  404   c, d . As shown in the illustrated embodiment, additional guy wires can be secured to the mast sections as desired. 
     It is understood that any practical number of guy wires can be used to meet the needs of a particular application. For example, a single guy wire can manipulate each mast section, with the guy wires extending from a different position for each mast section. For example, looking downward at an extended mast, a first guy wire extends at zero degrees, a second guy wire at 90 degrees, a third guy wire at 180 degrees, and a fourth guy wire at 270 degrees. 
     In an alternative embodiment shown in  FIGS. 4G-H , a cap  410  can include a respective pulley  420   a - d  for each guy wire  404 ′ a - d  for enabling the guy wires to telescope and retract the mast sections  402 ′. The cap  410  on the penultimate mast section  402   c  provides a focus point for the guy wires  404 . In the illustrated embodiment, each of the four guy wires  404   a - d  passes through the cap  410  coupling with an engagement mechanism  406 ′ for the respective mast section  402 . It is understood that the mast cap  410  can be of any suitable geometry to provide a desired path for any number of guy wires. It is further understood that caps can be disposed on any of the mast sections. 
     FIGS.  5  and  5 A-C shows an exemplary telescoping mast system  500  in accordance with exemplary embodiments of the invention having six mast sections  502   a - f . Exemplary dimensions are shown for the mast sections in  FIGS. 5A-5E . It is understood that any number of practical mast sections of any suitable geometry can be used to meet the needs of a particular application. 
     While exemplary embodiments of the invention are primarily shown and described as telescoping masts for antennas, it is understood that the inventive telescoping mast is applicable to any mast application for which it is desirable to elevate a load. 
     In another aspect of the invention, a telescoping mast includes an interface assembly for mast sections that includes a linear movement mechanism. In an exemplary embodiment, the movement mechanism includes a linear bushing  751 . This arrangement enhances the strength of the mast and increases the ability of the mast to withstand harsh environments, such as wind driven sand. 
       FIG. 6  shows an exemplary mast section assembly  700  including first and second telescoping mast sections  702 ,  704 , each having similar structures of differing size since the second mast section  702  is captured in the first mast section  704 . 
     As shown in  FIG. 7 , a first mast section  702  includes a series of longitudinal ribs  706  that extend along at least a portion of an inner surface  708  of the mast section. As shown more clearly in  FIG. 7A , the ribs  706  include a bulbous portion  710  extending from a stem  712  terminating at the inner surface  708 . 
     As shown in  FIG. 8 , the second mast section  704  includes a series of channels  720  extending along an outer surface  722  in alignment with the ribs  706  on the first mast section. The channels  720  are configured to capture the bulbous portion  710  of the ribs while allowing axial movement of the first and section mast sections. 
     In one embodiment, the channel  720  is circular extending more than 180 degrees so as to retain the bulbous portion  710  within the channel. The open portion of the channel  720  allows the stem  712  to travel in a path aligned with the channel while the bulbous portion  710  is retained in the channel  720 . 
     The ribs  706  increase the strength and rigidity of the mast section  702  to enable heavier loads to be supported by the mast as compared to mast sections of similar thickness without ribs. The ribs  706  significantly increase the strength of the mast without requiring an increased thickness about the entire diameter of the section. 
     In an exemplary embodiment, the strength provided by the ribs  706  eliminates the need for outriggers and other stabilization structures. In other embodiments, stabilization structures can be included to further increase the load carrying capability and/or to enable mast installation in more severe environments, such as higher wind speeds. 
     In an exemplary embodiment, the rib  706 /channel  702  structure provides a gap between the surfaces of the first and second mast sections  702 ,  704 . This gap enables debris to easily pass through the mast sections. For example, in desert environments sand can pass through the gap between the first and second mast sections (and other mast section interfaces) without degrading the telescoping performance of the mast. 
     In one particular application, with reference to  FIGS. 6A and 6B , first and second gaps G 1 , G 2  should be greater than a selected size to enable debris to pass. In one embodiment, the first and second gaps G 1 , G 2  are at least 0.04 inch to enable sand to pass through the mast without obstruction. Gaps G 1 , G 2  less than this dimension will degrade performance of the mast due to debris build up. The guide rail to linear bearing interface gap G 3  should be as close to zero as assembly tolerance allows. It is understood that for the second gap G 2 , as shown in  FIGS. 10-10B , a liner  760  can have an undulating surface to form longitudinal gaps between the liner depressions and a surface of the respective mast section for debris passage. 
       FIG. 9  shows first and second mast sections  702 ,  704  with the ribs  706  of the first mast section  702  engaged with the channels  720  of the second mast section  704 . The second mast section  704  includes an engagement mechanism  750 , which can be similar to the engagement mechanism of  FIG. 310  of  FIG. 3 , extending across the mast section. In general, the engagement mechanism  750  is secured to the mast section so as to enable a guy wire to manipulate the mast section, as described above in detail. 
     It is understood that mast sections can include ribs  706  on an inner surface and channels  720  on outer surface to enable movement of the respective mast sections. 
     In the illustrated embodiment, the engagement mechanism  750  forms a part of an end cap  752  extending about the inner surface of an end of the mast section. Apertures/channels  720  in the end cap  752  are provided for the ribs  706 . 
     As shown in  FIGS. 10 ,  10 A, and  10 B, which show exemplary dimensions, the mast section can further include a liner  760  to maintain alignment of the mast section and an enhanced mast section-to-section interface. An end cap  750  is disposed on an end of a first (larger) mast section MS 1 , which captures a second (smaller) mast section MS 2 . The liner  760  increases torsional stiffness and provides a bearing surface. 
     In an exemplary embodiment, the liner includes an outer surface  762  to complement an inner surface of a mast section and an undulating inner surface  764 . The liner inner surface  764  includes thicker portions  766  and thinner portions  768 . This arrangement maintains mast rigidity while providing pathways for debris to pass through the mast sections. The size and shape of the debris pathway is determined by the application design requirements. 
     It is understood that the liner inner surface  764  can have a wide range of geometries to provide a desired amount of contact between the liner and the mast section and shape and volume for the debris pathways. In an exemplary embodiment the mast section ribs  706  are circular in profile allowing for integration of circular (custom, modified, or commercial) linear guides. Other rib cross sectional profiles could be square, T-shaped, or other. The quantity of ribs is determined by the application design requirements. Illustrative alternative rib embodiments are shown in  FIGS. 8B-8K . 
     The liner  760  can be fabricated from suitable high strength materials, including self-lubricating polymers suitable in environmental conditions, such as sand, dust, salt-spray, and extreme temperatures. The liner can be fabricated using pultrusion, extrusion, injection molded, machined, or other fabrication technique. 
     Having described exemplary embodiments of the invention, it will now become apparent to one of ordinary skill in the art that other embodiments incorporating their concepts may also be used. The embodiments contained herein should not be limited to disclosed embodiments but rather should be limited only by the spirit and scope of the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.