Abstract:
A deployable structure comprising a support and at least one structural element is provided. The structural element is mechanically attached to the support. The latching mechanism assembly is adapted to containing the structural element in a non-deployed state until it is remotely activated or de-latched.

Description:
RIGHTS OF THE GOVERNMENT 
   This invention was made with U.S. Government support. 

   BACKGROUND 
   1. Field of Use 
   These teachings relate generally to deployable structures in general and, more particularly, to the storage and remote deployment of folded panel structures. 
   2. Description of Prior Art 
   Deployable panels, such as solar arrays with folding solar panels, are known in the art. A typical solar array of this type has a support, such as the body of the spacecraft, that mounts a remote controlled deployment boom that may be extended outwardly from one side of the support. Attached to the deployment boom is a folding solar panel composed of a number of panel sections hinged edge-to-edge along hinge lines extending normal to an extension axis of the boom. The two end panel sections are attached, respectively, to the support and to a cross-member at the outer end of the boom. In the stowed configuration of the solar array, the deployment boom is retracted to locate the cross-member adjacent the support, and the solar panel sections are folded accordion-fashion into confronting face-to-face relation flat against the side of the support. During deployment, the boom is extended outwardly from the support to unfold the solar panel to a deployed configuration wherein the panel sections are disposed edge-to-edge substantially in a common plane containing the boom. It will be appreciated that such deployment booms are complicated electromechanical devices subject to mechanical or electrical malfunction. It will also be recognized that a disadvantage of such booms is their space and weight requirements, a major consideration in the case of spacecraft and/or portable devices. Typically, such deployment booms deploy solar arrays, which include one or more panels supporting solar cells for generating electrical power for a spacecraft, or they deploy radio frequency antenna for the reception or transmission of radio frequency signals. As such, the deployment boom must be adequately protected to ensure proper and continuous functionality throughout a mission. For example, during the launch of a spacecraft, the deployment boom may be subjected to extreme stresses and vibrations. Likewise, a portable device containing such a deployment boom may be subjected to harsh and damaging handling. 
   Thus, the above suggests a need for the remote deployment of deployable structures without the inherent disadvantages of complicated boom structures. 
   SUMMARY OF THE PREFERRED EMBODIMENTS 
   The foregoing and other problems are overcome, and other advantages are realized, in accordance with the presently preferred embodiments of these teachings. As will be described below, important aspects of the invention reside in the construction and combination of structural elements; structural elements such as torsion springs and remote mechanical de-latching mechanisms. 
   In accordance with one embodiment of the invention a deployable structure having a support and at least one structural element is provided. The structural element is mechanically attached to the support. A latching mechanism assembly is adapted to contain the structural element in a non-deployed state until it is remotely activated or de-latched. 
   In accordance with another embodiment the invention includes a method for constructing and storing a deployable structure. The method includes the steps of determining a deployed rectangular structure size; forming a perimeter shape of the deployed rectangular structure with a continuous structural element; folding the perimeter shape into at least one uniform section; and storing the uniform sections in a supporting device. 
   Another embodiment of the invention is directed towards an improved self-erecting turnstile antenna system. The system comprises a supporting device and a plurality of antenna elements connected to the supporting device. A latching mechanism assembly connected to the supporting device maintains the plurality of antenna elements in a non-deployed state. Remote activation of the latching assembly allows the plurality of antenna elements to deploy to an operating position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other aspects of these teachings are made more evident in the following Detailed Description of the Preferred Embodiments, when read in conjunction with the attached Drawing Figures, wherein: 
       FIG. 1  is an edge on pictorial view showing two deployable structures in collapsed or stowed positions in a rectangular device having a deployable structure on each vertical side of the rectangular device; 
       FIG. 2  is an aerial view of the rectangular device shown in  FIG. 1  showing the deployable structures in deployed positions; 
       FIG. 3  is a wire diagram showing one 90-degree and one 180-degree joint articulation of one of the deployed structure elements shown in FIG.  1  and  FIG. 2 ; 
       FIG. 4  is a pictorial view of one of the 90-degree joints shown in FIG.  2  and  FIG. 3  showing reinforcement of the 90-degree joints; 
       FIG. 5  is a wire diagram of one of the 90-degree joints shown in  FIG. 3 , showing the joint in a 90-degree torsion spring configuration; 
       FIG. 6  is a pictorial view of one of the 180-degree joints shown in FIG.  2  and  FIG. 3  showing reinforcement of the 180-degree joint; 
       FIG. 7  is a wire diagram of one of the 180-degree joints shown in  FIG. 3 , showing the joint in a 180-degree torsion spring configuration; 
       FIG. 8  is pictorial view of a latching mechanism in the latched position and holding the deployable structures of  FIG. 1  in the collapsed or stowed position; 
       FIG. 9  is a pictorial view of the latching mechanism shown in  FIG. 8 , showing a latching pin and strap; 
       FIG. 10  is a pictorial view of the latching mechanism shown in  FIG. 8 , showing the latching mechanism in the de-latched and open circuit position; 
       FIG. 11  is a flow chart of one method showing the steps for constructing and storing the deployable structure shown in  FIG. 1 ; and 
       FIG. 12  is an aerial view of an alternate embodiment of the present invention showing the deployed structure with transducer arrays. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , there is shown a rectangular device  15  incorporating features of the present invention.  FIG. 1  presents an edge on pictorial view showing two deployable structures  11  in collapsed or stowed positions in the rectangular device  15 ; the rectangular device  15  in the preferred embodiment having deployable structures  11  on each vertical side. The device  15  could be any suitable apparatus requiring deployable structures. Exemplary, but not limiting embodiments include: a radio device requiring remote deployment of an antenna structure for the reception and/or transmission of radio frequency signals; a satellite device requiring remote deployment of panels or transducers such as satellite solar panels or radio antennas; or an acoustic processor requiring the remote deployment of acoustic transducer arrays ( FIG. 12 , item  125 ). In an alternate embodiment, device  15  could incorporate both embodiments, e.g., elements  11  could serve as the structural panel-supporting elements, as well as the antenna elements. Exemplary, but not limiting embodiments include a sail used to convert the energy of a moving fluid (e.g., atmospheric wind, solar wind, hydrodynamic motion) to an energy form suitable to power supporting device  15 .  FIG. 1  also shows a latching mechanism assembly  12  and a strapping wire  83  incorporating features of the present invention. Referring also to  FIG. 2  the elements  11  are shown in deployed and working positions. 
     FIG. 11  shows the method steps for forming the rectangular structures shown in FIG.  2 . Step  111  determines the size and shape required for the deployed structure  11 . Step  112  forms a perimeter shape of the deployed structure  11  with a continuous structural element. In the preferred embodiment the continuous structural element also functions as a horizontally polarized radio frequency antenna element. In alternate embodiments the continuous structural element could function as a vertically polarized RF antenna. Also, in alternate embodiments the continuous structural element could be a single non-conductive element such as plastic wire. Step  113  folds the perimeter shape of the deployed structure  11  in to at least one uniform section  11 A,  11 B. The folded uniform sections  11 A,  11 B are then stored in the supporting device  15 , step  114 . 
   Referring also to  FIG. 3  there is shown a wire diagram showing one 90-degree and one 180-degree joint articulation between the uniform sections of one of the deployed structure elements  11  shown in FIG.  1  and FIG.  2 . The structural elements  11  are articulated to satisfy both packaging volume and working horizontal positions.  FIG. 3  further illustrates the articulation of an element between the collapsed and deployed state and the relative angles between the device  15  and subsequent sections of the structural element  11 A,  11 B. In the preferred embodiment the structural elements  11  include a single wire-like element capable of electromagnetic transmission; the single wire is shaped into uniform sections  11 A,  11 B, for efficient storage of the collapsed structural element  11  as shown in FIG.  1 . In addition the uniform section widths are generally shaped to facilitate radio frequency transmission and reception. In general, the width of a section (e.g.,  11 A,  11 B) is one-quarter wavelength of the intended wavelength to be received or transmitted. In an alternate embodiment the single wire may be formed into as many sections as needed to efficiently fit within a predefined space. 
   Referring also to  FIG. 4 , there is shown in the preferred embodiment the joint between the first section  11 A and the device  15 . The wire or structural element  11  is formed into a configuration of two straight wire torsion springs ( FIG. 5 , items  22 ). 
   Referring also to  FIG. 5 , there is shown a wire diagram showing the formation of structural element  11  to form a torsion spring  22  along the width of the section to accomplish 90 degrees of movement. In an alternate embodiment each of the straight wire torsion springs could incorporate a helical wound spring. 
   Referring still to  FIG. 3  it is clear that the middle joint  21  and any subsequent joints of the structural element  11  are capable of articulating 0 to 180 degrees. The effective length of a torsion-like spring should be twice the width of the section  11 A to perform properly and without experiencing permanent deformation of the structural element  11 . Yet, the structural element  11  must still fit efficiently into the space provided by device  15 . Thus, forming the structural element  11  as shown in FIG.  6  and  FIG. 7  allows the formation of two 180-degree articulating joints  75 .  FIG. 7  shows in greater detail the configuration of the structural element wire  11  when forming the 180-degree joint articulations. Effectively, the structural element wire  11  is used as a 90 degree torsion spring for one width of the section, and then doubled back along that same width for the other 90 degrees of movement. Thus, the spring joints  75  bend their fully intended range of 180-degrees without any permanent deformation. In an alternate embodiment each of the straight wire torsion springs  75  could incorporate a helical wound spring. 
   Each element of the structural element  11  is constructed from one continuous piece of wire and joined at the 180-degree bend points of each section with a heat-shrinking polymer tube  71 . In alternate embodiments this could be any suitable tube material for housing and not interfering with the bending of the structural element  11 . 
   In the preferred embodiment the structural element  11  is small diameter drawn wire suited to the transmission and reception of radio frequency signals. Due to the length of the wire in the preferred embodiment, and the low bending stiffness of the small diameter wire, reinforcement tubes  23  are placed on the inboard segments of each section. In the preferred embodiment the reinforcement tubes are {fraction (1/16)}-inch outer diameter metal tubes that house the drawn wire, and increase its bending stiffness. These reinforcing tubes  23  are shown in  FIGS. 2 ,  4 , and  6 . In an alternate embodiment the reinforcing tubes  23  could be any suitable structural elements for reinforcing small diameter wire. 
   Referring also to  FIG. 8  there is shown a pictorial view of the latching mechanism  12  in the latched position and holding the deployable structures of  FIG. 1  in the collapsed or stowed position. Deployment of the structural element  11  is initiated by application of an electrical pulse to the positive connection  86  that then releases the strapping wire  83  and allows the stored energy contained in the torsion joints  21 , 22  to deploy the stored structural elements  11 . 
   Referring also to  FIG. 9  there is shown a pictorial view of the invention incorporating features of the latching mechanism. Strap wire  83  is wrapped around the stored structural elements  11 , with a loop  91  on one end of the strapping wire  83 . The loop  91  slides over strap pin  82  and the other end of the strapping wire  83  is attached to an electronics chassis grounding screw  84 . The stored structural elements  11  exert an outward force due to the tension contained in the 90-degree and 180-degree joints. Thus, when the strapping pin  82  is pulled out of the loop  91 , the strap releases, and allows the spring-loaded structural elements  11  to deploy. The strapping wire  83  is generally constructed of small gauge wire and the strap pin  82  from small tubing. In an alternate embodiment any suitable strapping wire and pin arrangement may be used. 
   In the preferred embodiment the strap pin  82  is actuated or pulled out of the loop by using small gauge nickel-titanium contracting wire  81  which contracts when electrically driven. The wire  81  is anchored by the positive connection  86  and insulated from the chassis at this anchor point. The other end of the contracting wire  81  is attached to the strap pin  82 , which is grounded through the strap wire  83  at the ground screw  84 . In the preferred embodiment the contracting wire may be any suitable thermally actuated shape memory alloy device. 
   A voltage potential is applied to the positive connection  86  and a current flows through the contracting wire  81 . This causes the wire  81  to physically shorten in length, thus pulling the strap pin  82  from the loop  91  of the strapping wire  83 .  FIGS. 8 and 9  illustrate the flow of electrical current as dashed lines. In the preferred embodiment the application of a signal to the positive connection Is via a remote control signal to a relay-like device (not shown), which in turn applies a voltage potential to the positive connection. Remote controlled relays are well known and will not be discussed further. In an alternate embodiment the application of a voltage potential could be any suitable method for applying a voltage potential to the positive connection  86 . For example a timer controlled relay circuit could be employed. In addition, it should be noted that it does not mater which direction current flows through the contracting wire  81 . In an alternate embodiment a negative voltage potential could be applied to the positive connection  86 . Current flow would then be opposite to that shown as dashed lines in  FIGS. 8 and 9 . 
   Referring still to  FIG. 9 , it is dear that the strapping wire  83  completes the electrical circuit; current flows from the positive connection  86 , through the contracting wire  81 , through the strap pin  82  to the strapping wire  83  and finally to chassis ground  84 . Once the strapping wire  83  has been released, the electrical path is disrupted and the circuit is open circuited. 
   In the preferred embodiment, the housing and fixture  85  for the actuating wire-pin assembly is made from nonconductive material. This allows the ground to only be completed by the strap that retains the antennas.  FIG. 10 , exhibits the latch and strap in the open-circuit position after the elements have been erected. Notice the strapping wire  83  and chassis ground is no longer in electrical contact with the strap pin  82 . 
   It should be understood that the foregoing description is only illustrative of the invention. Moreover, it will be readily appreciated that an advantage of the present invention is the use of the antenna elements that are self-articulating through torsion type joints. It will be further appreciated that advantages of the present invention include remote deployment of structural elements without cumbersome and complicated boom devices and that the latching mechanism feature utilizes a unique contracting wire circuit for actuation and automatically deactivates itself after deployment of the elements. Thus, various alternatives and modifications can be devised by those skilled in the art without departing from the invention. For example, the torsion springs could include helical forms in addition to, or in place of the wire form shown, in order to accommodate various articulations. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims.