Abstract:
A collapsible frame comprises a plurality of frame members joined together by a flexible tension cable. In one embodiment, the individual frame members are also joined together by an elastic cord o facilitate assembly. The tensioning member includes an arcuate cable track and is rotatably connected to the frame. Relative rotation of the frame and tensioning member in a first direction tightens the tension cable, while relative rotation of the frame and tensioning member in a second direction loosens the tension cable.

Description:
BACKGROUND  
       [0001]     The present invention relates generally collapsible frame structures, and more particularly to collapsible frame structures comprising a plurality of separable frame members held together by an internal cord or cable.  
         [0002]     Collapsible frame structures comprising a plurality of frame members that are joined end-to-end and held together by a flexible cord or cable are known. For example, U.S. Pat. Nos. 6,557,572; 4,827,958; 4,706,696 disclose tent poles comprising pole sections held together by an elastic cord. The individual pole sections can be separated and folded over to form a compact bundle for storage. The elastic cord pulls the individual frame members together to facilitate assembly. Similar frame systems may be found in other types of devices as shown by U.S. Pat. No. 6,038,802 (portable displays); U.S. Pat. No. 4,215,877 (folding utility carts); and U.S. Pat. No. 6,062,648 (folding chairs). Frame structures that rely on an elastic cord to hold the individual sections together are easily assembled but limited in the loads that can be supported.  
         [0003]     It is also known to use an inelastic cable, such as a steel cable, to tension a multi-part frame structure as shown in U.S. Pat. Nos. 5,930,971 and 4,167,354. In these patents, a tension cable runs interiorly through individual frame members joined end-to-end and is tightened by means of a tensioning device after the frame is assembled to strengthen the frame. Frames that use an inelastic tension cable can support greater loads, but are not as easily assembled. Further, the tensioning devices tend to be cumbersome to operate.  
         [0004]     Accordingly, there is a need for a collapsible frame structure that can support relatively heavy loads, and yet remain easy to assemble.  
       SUMMARY  
       [0005]     The present invention relates to a collapsible frame structure comprising a plurality of frame members that are connected end-to-end and held together by a flexible member. One aspect of the invention comprises the use of first and second flexible members to interconnect a plurality of frame members. The first flexible member comprises an elastic cord that facilitates assembly by pulling together the individual frame members. The second flexible member comprises an inelastic cable that is tensioned during assembly of the frame to add strength to the frame. Another aspect of the invention comprises the design of the tensioning member. The tensioning member includes an arcuate cable track and is rotatably connected to the frame. Relative rotation of the frame and tensioning member in a first direction tensions the cable, while relative rotation of the frame section and tensioning member in a second direction loosens said cable. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a perspective view of a collapsible frame structure in an unfolded position.  
         [0007]      FIG. 2  illustrates the collapsible frame structure folded with the joints separated.  
         [0008]      FIGS. 3A-3C  illustrate exemplary straight joints between frame members.  
         [0009]      FIG. 4  illustrates a first exemplary corner joint between frame members.  
         [0010]      FIGS. 5 and 6  illustrate a second exemplary corner joint between frame members.  
         [0011]      FIGS. 7 and 8  are perspective views of a tensioning device comprising two tensioning members in the unfolded and folded positions respectively.  
         [0012]      FIG. 9  is a perspective view of one tensioning member for the tensioning device shown in  FIGS. 7 and 8 .  
         [0013]      FIG. 10  is a top view of the tensioning device in an unfolded position.  
         [0014]      FIG. 11  is a section view of the tensioning device in the unfolded position taken through line  11 - 11  of  FIG. 10 .  
         [0015]      FIG. 12  is an end view of the tensioning device in a folded position.  
         [0016]      FIG. 13  is a section view of the tensioning device in the folded position taken through line  13 - 13  of  FIG. 12 .  
         [0017]      FIG. 14  is perspective view showing the frame collapsed.  
         [0018]      FIG. 15  is a perspective view of a second embodiment of a collapsible frame structure.  
         [0019]      FIG. 16  is a perspective view of a third embodiment of a collapsible frame structure. 
     
    
     DETAILED DESCRIPTION  
       [0020]     Referring now to the drawings,  FIG. 1  illustrates an exemplary frame structure indicated generally by the numeral  10 . Frame structure  10  comprises twelve tubular frame members indicated generally by the numerals  12 ,  14  and  16 , four corner connectors  24 , and two tensioning devices  50 . Two frame members  12  are connected to each tensioning device  50  and extend outwardly from the tensioning device  50  in opposite directions. Frame members  14  connect in end-to-end fashion with the frame members  12  to form the sides of the frame structure  10 . Two frame members  16  join end-to-end to form each end of the frame structure  10 . Frame members  16  are connected at a 90 degree angle to respective frame members  14  by the corner connectors  24 .  
         [0021]     In one exemplary embodiment of the invention, the frame structure  10  comprises two u-shaped frame sections labeled as respectively as frame section A and frame section B. In other embodiments, the frame may be divided in more than two sections. For example, the frame  10  could be divided into four sections. In the illustrated embodiment, the two frame sections are pivotally connected to one another so as to pivot about an axis X. Each frame section comprises two frame members  12 , two frame members  14  and two frame members  16 . For convenience, letter suffixes a and b are used in the following description to distinguish similar components in different sections of the frame structure  10  where needed for clarity. For example, frame member  12  for frame section A may be referred to as frame member  12   a  when needed to distinguish it from the frame members  12  in frame section B. The letter suffix is not used when referring generally to components of a particular type and it is not necessary to distinguish components in frame section A from components in frame section B.  
         [0022]     The frame members  12 ,  14  and  16  in each frame section are held together by one or more flexible members. In the exemplary embodiment, each frame section has two flexible members; an elastic cord  30  and a tension cable  32 . The elastic cord  30  and tension cable  32  extend interiorly through the frame members  12 ,  14  and  16 . The opposing ends of the elastic cord  30  and tension cable  32  for each section are connected to respective tensioning devices  50 . There is one elastic cord  30  and one tension cable  32  for each frame section. The elastic cord  30  and tension cable  32  may be bound together at selected points by ties (not shown) such that the elastic cord  30  helps pull the tension cable  30  from the tensioning devices  50  when the frame  10  is collapsed.  
         [0023]     As will be described in more detail below, the elastic cord  30  facilitates assembly of the frame structure  10  by pulling the frame members  12 ,  14  and  16  together. However, the elastic cord  30  does not impart sufficient strength to the frame structure  10  for load bearing structures. The tension cable  32  is a flexible and generally non-elastic cable, such as a steel or carbon fiber cable, that is tensioned during assembly of the frame structure  10  to impart added strength to the frame structure needed for load bearing structures. The elastic cord  30  and tension cable  32  also hold the frame sections  12 ,  14  and  16  loosely together when the frame structure  10  is disassembled or collapsed so that the parts will not be separated and lost.  
         [0024]      FIG. 2  illustrates the frame structure  10  folded in half with the joints separated. As will be described in more detail below, the act of folding the frame structure  10  in half creates slack in the tension cable  32 , allowing the joints of the frame to be separated. Once the joints are separated, the entire frame structure can be collapsed to form a bundle, as shown in  FIG. 12 . Those skilled in the art will appreciate that separating the joints stretches the elastic cord  30 .  
         [0025]      FIGS. 3A-3C  illustrate exemplary straight joints  18  between frame members  12  and  14 . The same joint  18  may be used to join two frame members  16  at each end of the frame structure  10 . A sleeve  20  is fixed at the end of frame member  14 . The sleeve  20  extends from the end of frame member  14  and inserts into the end of frame member  12 . Alternatively, the sleeve  20  could be fixed to frame member  12  and insert into the end of frame member  14 . The ends of the frame members  12  and  14  may be cut at an angle as shown in  FIG. 3B  to prevent relative rotation between frame members  12  and  14 . Elastic cord  30  and tension cable  32  pass through the connection between frame members  12  and  14 . When the frame structure  10  is disassembled for storage, the frame members  12  and  14  are pulled apart and folded side by side. The sleeve  20  may have a cut-out or slot  21  formed therein as shown in  FIG. 3C . The presence of the slot  21  reduces the amount of slack that needs to be created to collapse the frame structure  10 .  
         [0026]      FIG. 4  illustrates an exemplary corner joint  22  connecting frame members  14  and  16 . A corner connector  24  is fixed to the end of frame section  14 . Corner connector  24  includes a sleeve  26  that inserts into the end of frame section  16 . Alternatively, sleeve  26  could be fixed to frame member  16  and insert into the end of frame member  16 . Elastic cord  30  and tension cable  32  pass through the connection between the corner connector  24  and frame member  16 . The corner connector  24  may include a guide pulley  28  to guide the tension cable  32  through the corner connector  24 .  
         [0027]      FIGS. 5 and 6  illustrate an alternative design for the corner connector  24 . In this design, the corner connectors  24  comprise first and second sections that are pivotally connected by a pivot  25 .  FIG. 5  illustrates the corner connector  24  in an unfolded position. When the frame structure  10  is collapsed, the first and second sections fold inward as shown in  FIG. 6 .  
         [0028]      FIGS. 7 and 8  illustrate the tensioning device  50 . Tensioning device  50  tightens the tension cable  32  in each frame section during assembly of the frame structure  10  to add strength to the frame structure  10 . The tensioning device  50  comprises two tensioning members  52   a  and  52   b  that are pivotally connected. The tensioning members  52   a  and  52   b  rotate about a pivot member  53  between an unfolded position shown in  FIG. 7  and a folded position shown in  FIG. 8 . Frame member  12   a  connects to tensioning member  52   b  and frame member  12   b  connects to tensioning member  12   a . Thus, tensioning member  52   a  rotates relative to frame member  12   a  and tensioning member  52   b  rotates relative to frame member  12   b.    
         [0029]      FIG. 9  is a perspective view illustrating one tensioning member  52 . Tensioning member  52  comprises a rotatable housing  54  including a connector  62  for connecting the tensioning member  52  to a respective frame member  12 . The housing  54  may be a unitary member formed of thermoplastic, metal, or metal alloy. The rotatable housing  54  is generally circular in shape and includes a hub  55 , an inner wall  56  and outer wall  58 . The inner wall  56  and outer wall  58  define a circular cable track  60  to accommodate a tension cable  32 . An opening  57  in the inner wall  56  receives the end of the tensioning cable  32  to secure the tension cable  32  to the tensioning member  52 . A guide pulley  64  may be provided to guide the tension cable  32  into the cable track  60  of the mating tensioning member  52  to reduce friction and wear.  
         [0030]      FIGS. 10 and 11  illustrate the tensioning device  50  in an unfolded position.  FIGS. 12 and 13  illustrate the tensioning device  50  in a folded position. Tension cable  32   a  for frame section A enters the connector  62   b  of tensioning member  52   b , crosses over into tensioning member  52   a , and passes around the cable track  60   a  of tensioning member  52   a . The end of tension cable  32   a  passes through opening  57  in the inner wall  56  of tensioning member  52   a  and is secured to the tensioning member  52   a . Similarly, tension cable  32   b  enters the connector  62   a  of tensioning member  52   a , crosses over into tensioning member  52   b , and passes around the cable track  60   b  of tensioning member  52   b . The end of tension cable  32   b  is secured to the tensioning member  52   b  in a similar manner. The cross-over of the cables from one tensioning member  52  to another is shown best in  FIG. 10 .  
         [0031]     When the tensioning members  52  are in the disassembled or folded position shown in  FIG. 11 , the tension cables  32  travel only a small distance around the cable tracks  60  of respective tensioning members  52 . When the tensioning members  52  are in the assembled or unfolded position shown in  FIG. 10 , the tension cables  32  travel more than 180 degrees around the cable tracks  60  of respective tensioning members  52  removing slack from the tension cable  32 . Thus, rotation of the tensioning devices  52  in a first direction tightens the cables  32 , while rotation in the opposite direction slackens or loosens the cables.  
         [0032]      FIG. 12  illustrates a disassembled frame structure  10 . When disassembled, the components of the frame structure  10  can be folded to form a bundle as shown in  FIG. 2 . To disassemble the frame structure  10 , the frame structure  10  is first folded in half along the transverse axis X of the frame structure  10  as shown in  FIG. 2 . The act of folding the frame structure  10  loosens the tension cables  32 . After the frame structure is folded in half, the frame members  12 ,  14  and  16  can then be pulled apart and arranged side-by-side to make a bundle. The disassembled frame structure  10  can be secured with strap, or placed in a bag. The process is reversed to assemble the frame structure  10 .  
         [0033]     To assemble the frame, the individual frame members  12 ,  14 , and  16  are arranged as shown in  FIG. 2 . The elastic cord  30  will then pull the frame members  12 ,  14 , and  16  together. Once the frame members are pulled together, the two frame sections can be moved to the open position shown in  FIG. 1 . Moving the frame sections to the open position shown in  FIG. 1  removes the slack from the tension cable  32 . A latch or other locking mechanism may be used to lock the frame sections in the open position.  
         [0034]     In the illustrated embodiment, each frame section includes a separate tension cable  32  and elastic cord  30 . In other embodiments, a single elastic cord  30  and tension cable  32  for both frame sections could be used. The ends of the elastic cord  30  and tension cable  32  do not necessarily need to be fixed to the tensioning member  52 . Instead, the end of either the elastic cord  30  or tensioning cable  32  could be terminated in one of the frame members  12 ,  14 , or  16 .  
         [0035]     Those skilled in the art will recognize that the frame structure described above represents only one exemplary embodiment and that many variations thereof may be used. For example, the frame structure  10  may have more than two folding frame sections.  FIG. 13  illustrates a frame structure  10  including three frames sections, which may be used, for example, in a chair or stroller. Also, some of the frame members  12 ,  14 , and  16  may be pivotally connected. In  FIG. 14  illustrates an embodiment wherein the frame members  16  at either end of the frame structure  10  are connected by a hinge  19 . Also, the number of elastic cords  30  and tension cables  32  can be varied. For example, four elastic cords  30  and four tension cables  32  may be used in the embodiment shown in  FIG. 14 .  
         [0036]     The frame structure  10  can be used in an almost endless variety of structures such as tents and canopies, chairs and tables, strollers, luggage carriers, utility carts, beds and cots, displays, canes and walkers.  
         [0037]     The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.