Abstract:
A wheelchair that upon folding can become more compact for transporting and storage by enabling the vertical side frames of the wheelchair to move towards each other through the use of a sliding mechanism.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of patent application Ser. No. 11/760,625, filed on Jun. 8, 2007, which claims the benefit of Provisional Application No. 60/812,582, filed Jun. 8, 2006, the disclosure of which is hereby expressly incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    A wheelchair with the ability to become narrower for transportation and storage has several benefits. It allows the wheelchair to fit into a vehicle easier without the need to remove components, such as wheels. It takes less room to store when not in use. When folded it will fit through narrow passageways. However, traditional folding wheelchairs suffer from several problems. 
         [0003]    As non-limiting examples, a typical folding wheelchair with an X-frame style frame, as can be seen in U.S. Pat. Nos. 2,379,566 and 5,328,183, folds very compactly but at the expense of functionality and durability. Other designs fold the frame vertically, as can be seen in U.S. Pat. No. 5,593,173, or laterally, as can be seen in U.S. Pat. Nos. 4,863,181; 6,572,133 and 4,595,212. All of the folding methods require many additional components adding substantial weight and complexity. The added weight makes it much more difficult to self propel and to lift into a vehicle for transport. Due to the many joints and pivots, they also have reduced durability for daily use requiring frequent maintenance. The additional components also increase the cost of manufacture. 
       SUMMARY 
       [0004]    This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
         [0005]    A foldable frame for a wheelchair is provided. The foldable frame includes first and second side frames and a frame structure connecting the first side frame to the second side frame. The frame structure permitting the first side frame and the second frame to selectively move toward each other and away from each other. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0006]    The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
           [0007]    The foregoing aspects and many of the attendant advantages of this invention will become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
           [0008]      FIG. 1  is an isometric view of the complete wheelchair formed in accordance with one embodiment of the present disclosure; 
           [0009]      FIG. 2  is an isometric view of the wheelchair frame; 
           [0010]      FIG. 3  is an isometric view of the complete wheelchair in its folded position with the seat fabric removed for clarity; 
           [0011]      FIG. 4  is a detail side view of the barrel lock assembly in its unlocked or open position; 
           [0012]      FIG. 5  is a detail isometric view of the barrel lock mechanism in its unlocked or open position; 
           [0013]      FIG. 6  is a detail isometric view of the barrel lock assembly in its unlocked or open position; 
           [0014]      FIG. 7  is a detail side view of the barrel lock assembly in its locked position; 
           [0015]      FIG. 8  is a detail isometric view of the barrel lock mechanism in its locked position; 
           [0016]      FIG. 9  is a detail isometric view of the barrel lock assembly in its locked position; and 
           [0017]      FIG. 10  is a detail bottom view of the barrel lock assembly in it&#39;s unlocked position. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    A foldable wheelchair constructed, in accordance with one embodiment of the present disclosure, may be best understood by referring to  FIGS. 1-10 . The foldable wheelchair includes a set of large rear wheels  5 , a set of front smaller wheels or casters  6 . The wheels are connected to two generally vertical side frames  10 ,  20  between which extends interconnecting frame structures  8  connecting the forward ends of the side frames  10 ,  20  and  9  connecting the aft ends of the side frames  10 ,  20 . The seating and backrest fabric  3  and  4  respectively are attached to the side frames. Footrest assemblies  7  are inserted into the side frames  10 ,  20  and can be fixed at a variety of heights depending on the size of the user. 
         [0019]    As may be best seen by referring to  FIG. 2 , the interconnecting structures include sliding joints. In its preferred form, it would include two telescopic cross tubes. The telescopic tubes include an outer sleeve tube  13  fixed to side frame  10  and a slidable inner sleeve tube  23  fixed to side frame  20 . When the side frames  10  and  20  are pulled away from one another such that the seating and backrest fabric  3 ,  4  are pulled tight, the inner and outer tubes can be locked together to form a rigid frame in the open position with the use of a locking mechanism  40 . 
         [0020]    Referring to  FIGS. 2-3 , when the locking mechanism  40  is in its unlocked position the side frames  10 ,  20  can slide toward each other which slides the inner sleeve tube  23  further inside the outer sleeve tube  13  until the outer sleeve tube  13  touches the side frame  20  which represents the wheelchair in its folded position. 
         [0021]    As may best be seen by referring to  FIGS. 1-2 , side frames  10  and  20  are substantially mirror images of each other and will be described together with the few exceptions highlighted. The side frame components are made from hollow structural steel tubing. The side frames are composed of side rails  11 ,  21  which support the mostly horizontally positioned seat fabric  3  and are then bent downward near their midpoint to align with the footrest assembly  7 . Near the forward ends of the side frames  11 ,  21  the castor connects tubes  15 ,  25  are welded to both the side rails  11 ,  21  and the vertically oriented castor tubes  30 . The mostly vertical backrest support frames  12 ,  22  are welded to the aft end of side rails  11 ,  21 . Additionally, the backrest support frames have the substantially horizontal axle mount tubes  33 , passing through them and welded near their lower ends. The axle bolts of the rear wheels  5  pass through the axle mounts  33  and are locked in place. The backrest canes  31  slide into the upper end of the backrest support frames  12 ,  22  and are locked into position. The armrest support tubes  14 ,  24  are welded at their aft ends to the backrest support frames  12 ,  22  they follow a substantially horizontal position on which the armrests  2  are bolted, they then bend downward near their midpoint and continue to the side rails  11 ,  21  where they are welded. 
         [0022]    The interconnecting tube assemblies include the two outer sleeve tubes  13 . The forward tube passes through and is welded to side frame  11  and the second passes through and is welded to backrest support tube  12 . Additionally, there are two inner sleeve tubes  23 . The forward inner sleeve tube  23  passes through and is welded to side frame  21  and the second passes through and is welded to backrest support tube  22 . The inner sleeve tube is of proper outside diameter to fit inside the outer sleeve tube  13  with sufficient clearance to not bind up, but similar enough to allow the outer sleeve tube  13  to be securely clamped around it using clamping assembly  40 . 
         [0023]    As may be best seen by referring to  FIG. 4-10 , the clamping assembly  40  includes the binding tube  45  which is oriented perpendicular the outer sleeve tube  13  and mitered to match the outer diameter of outer sleeve tube  13  and then welded to the under side of it near its end, the barrel lock bolt  43  which passes through the binding tube  45  and adjustment nut  44  which is threaded onto the barrel lock bolt  43 . The cam lock lever  41  is attached to the barrel lock bolt with the cam pin  42 . The barrel lock bolt  43  is mitered near its mid section to match the outer diameter of the inner sleeve tube  23 . This allows the inner sleeve tube  23  to pass through the binding tube  45  and barrel lock bolt  43  without interference. Near the end of the inner sleeve tube  23  there is an inner sleeve tube miter  46  oriented perpendicular to its length and the same diameter as the barrel lock bolt  43 . The inner sleeve tube miter  46  is located such that when lined up with binding tube  45 , a bolt the diameter of the barrel lock bolt  43  could pass through the inner sleeve tube  23  without interference. 
         [0024]    The clamping assembly works in two ways to lock the inner sleeve tube  23  to the outer sleeve tube  13  when the wheelchair is in its open position. The first way the inner and outer sleeve tubes  23 ,  13  are locked together is with a barrel lock. The barrel lock has an open and a locked position. When the barrel lock is in the open position ( FIGS. 4-6 ) the barrel lock bolt  43  is rotated so its mitered section matches the contour of the inner sleeve tube  23 , thus allowing it to pass through the barrel lock bolt  43 . To place the barrel lock in its locked position ( FIGS. 7-9 ) the inner sleeve tube miter  46  is lined up with binding tube  45  and the barrel lock bolt  43  is rotated one hundred eighty degrees, moving its unmitered side into the inner sleeve tube miter  46 , thus preventing the inner sleeve tube  23  from sliding in or out of outer sleeve tube  13  or rotating relative to outer sleeve tube  13 . 
         [0025]    Referring to  FIGS. 4-10 , the second clamping mechanism includes a cam lock. The cam lock utilizes several additional features built into the binding tube  45 , cam lever  41 , adjustment nut  44  and outer sleeve tube  13 . A miter that matches the shape of the cam lever profile when the cam lever  41  is substantially vertically oriented is cut into the end of binding tube  45 . The hole that allows the cam pin  42  to pass through cam lever  41  is slightly offset horizontally relative to the location of the center of the cam lever profile when the cam lever  41  is positioned substantially vertical. Additionally, a slot  47  ( FIG. 10 ) has been cut through the underside the outer sleeve tube  13  and the binding tube  45 . The cam lock has an open and locked position. In the open position ( FIGS. 4-6 ) the cam lever  41  is oriented such that cam lever profile edge with the shortest distance relative to cam pin  42  is along the side of the mitered profile of the binding tube  45 . To place the cam lock in its locked position ( FIGS. 7-10 ) the cam lever  41  is rotated approximately 180 degrees about the cam pin  42 . When the cam lever  41  is rotated, the cam lever profile edge will be the longest distance relative to the cam pin  42  is moved along the side of the mitered profile of the binding tube  45  thus pulling the barrel lock bolt  43  and adjustment nut  44  in the direction of the cam lever  41 . As the barrel lock bolt  43  and adjustment nut  44  are pulled toward the cam lever  41  the adjustment nut pushes against the unmitered end of the binding tube  45  and the cam lever  41  pushes against the mitered end of binding tube  45  partially collapsing the slot  47  and compressing the outer sleeve tube  13  onto the inner sleeve tube  23 . With the addition of the cam lock, any space between the inside of the outer sleeve tube  13  and inner sleeve tube  23  is removed providing a firmly locked joint when used in combination with the barrel lock. 
         [0026]    A foldable wheelchair of the present disclosure includes a set of large rear wheels, a set of front smaller wheels or casters. The wheels are connected to two generally vertical side frames between which extends interconnecting frame structures connecting the two side frames together. The interconnecting frame structures connect the first side frame to the second side frame in a manner permitting the first frame member and the second frame member to be selectively moved toward and away from each other, thereby, permitting the collapse of the wheelchair for storage or transport. The interconnecting structure includes a sliding joint. In its preferred form, it would have two telescopic cross tubes. One telescopic tube connects the forward end of the side frames and the second connects the aft end of the side frames. The telescopic tubes include an outer tube fixed to one side frame and a slidable inner tube fixed to the other side frame. The inner and outer tubes can be locked together to form a rigid frame. The locking mechanism can be readily changed from the locked open wheelchair position to an unlocked position that allows the wheelchair to be folded. 
         [0027]    The sliding interconnecting structure provides a robust and simple folding mechanism. With fewer components and no pivoting joints the system provides a durable, lightweight and lower cost folding system. 
         [0028]    While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.