Abstract:
The seat of a wheelchair has a back that is deeply contoured to provide lateral support for a user, and which is adjusted to conform to user torsos of various sizes. The seat back has a rigid, curved shell formed by a back panel with separate wings adjustably projecting forward from opposite sides of the back panel. Adjustment of the wings alters the length of curvature of the shell to conform to user torsos of different sizes. A cushion is attached to the shell and has pleated sections which expand and contract as the shell is adjusted.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not Applicable  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not Applicable  
       BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     The present invention relates to wheelchairs, and more particularly to the back for the seat of the wheelchair.  
         [0005]     2. Description of the Related Art  
         [0006]     Wheelchairs are commonly used by people who are unable to walk. The typical wheelchair has tubular metal frame with large rear wheels at each side and smaller front wheels which typically swivel. In its simplest form, the seat of the wheelchair comprises a sheet of material which is hung between two horizontal arms of the frame and a similar vertical sheet of material strung between two vertical posts at the rear of the wheelchair. Such sheets of material are flexible thereby conforming to the contour of the user&#39;s body.  
         [0007]     This simple seat arrangement can aggravate certain medical conditions of some wheelchair users, especially those with spinal abnormalities or injuries. As a consequence, padded seat backs, such as the one in U.S. Pat. No. 5,149,173, have been developed. This type of seat back has a slightly curved rigid back panel attached to the wheelchair frame and a foam cushion is mounted to the panel. The foam cushion forms a curved recess for receiving the back of the person seated in the wheelchair. The curvature of the seat back was relatively shallow in order to accommodate users having torsos of different sizes. The cushion can not be adjusted to conform to the contour of different sized torsos.  
         [0008]     For wheelchair users requiring more lateral support, small bolsters can be attached on each side of the seat back. The attachment mechanism for such bolsters provides some degree of adjustability, both vertically and horizontally, with respect to the seat back cushion.  
         [0009]     Nevertheless, there still exists a need for a more deeply contoured seat back which would provide greater lateral support for the torso of the wheelchair user. However, such a seat back would require a significant degree of adjustability in order to accommodate user torsos of various sizes and contours.  
       SUMMARY OF THE INVENTION  
       [0010]     A seat back for a wheelchair has a rigid, curved shell with a back panel from which two wings extend toward the front of the wheelchair. The first wing is fastened in an adjustable position at one side of the back panel and the second wing fastened in an adjustable position at the other side of back panel. In a preferred embodiment, the back panel comprises a central portion with a first lateral portion extending at a forward angle from one side, and with a second lateral portion extending at a forward angle from another side. The first wing is adjustably fastened to the first lateral portion, and the second wing is adjustably fastened to the second lateral portion.  
         [0011]     A cushion is attached to the shell and has a body of a resilient material, such as a closed cell foam for example. The body comprises a central section adjacent the central portion of the shell, a first lateral section adjacent the first wing, and a second lateral section adjacent the second wing. Preferably, the body has pleated sections which overlap the lateral portions of the shell. The pleated sections allow the width of the cushion to stretch and contract, thereby accommodating variation in the curvature of the shell due to adjustment of the wing positions.  
         [0012]     A fastener arrangement is provided to attach the rigid shell to the wheelchair frame. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is an isometric front view of a wheelchair with a seat back according to the present invention;  
         [0014]      FIG. 2  is a isometric front view of a shell in the seat back;  
         [0015]      FIG. 3  is a rear exploded, isometric view of the shell showing fasteners for securing to the wheelchair frame;  
         [0016]      FIG. 4  is a front view of a cushion body that is incorporated in the seat back; and  
         [0017]      FIG. 5  is a top view of the cushion body.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     With initial reference to  FIG. 1 , a wheelchair  10  has a tubular metal frame  12  that includes a pair of vertical posts  14  and  16  and two horizontal members  19 . A seat  15  of the wheelchair comprises a seat bottom  18  and a seat back  20 . The seat bottom is formed by a sheet of fabric hung between the horizontal frame members  19 .  
         [0019]     The seat back  20  includes a back portion  26  from which two lateral supports  28  extend on each side toward the front of the wheelchair  10 . The back portion  26  and lateral supports  28  form a curved, U-shaped structure within which the wheelchair user can rest and be supported to the rear and both sides. The seat back  20  is fabricated with a rigid, curved plastic shell  22  to which a cushion  24  is attached on the front. The rear of the plastic shell  22  is fastened to the vertical posts  14  and  16  of the frame  12 , as will be described.  
         [0020]     Referring to  FIG. 2 , the shell  22  comprises several pieces  30 ,  38 , and  42  of a rigid plastic, for example, adjustably fastened together by hex socket screws or bolts. Although the shell pieces and their sections are essentially planar, they are angled with respect to one another thereby forming a generally curved shell  22 . Specifically, the shell has a single-piece, back panel  30  formed by a generally planar central portion  32  from one side of which a first lateral portion  34  extends at a forward angle. A second lateral portion  36  projects in a similar manner from the opposite side of the back panel  30 . A first wing  38  of the shell  22  is attached to the first lateral portion  34  and a second wing  42  is secured to the second lateral portion  36 . The first and second wings  38  and  42  each have a pair of elongated apertures  44  through which hex socket screws or bolts  40  extend from the back of the respective lateral portion  38  or  42  and are threaded into a mounting bracket  46  to secure the shell pieces together. The elongated apertures  44  allow the position of each wing  38  and  42  to be adjusted in the horizontal direction. In addition, the first and second lateral portions  34  and  36  have a vertical row of apertures  48  (see  FIG. 3 ) through which the hex socket screws or bolts  40  can selectively extend to adjust the vertical position of each wing  38  and  42 . Such horizontal and vertical adjustment allows the curvature of the shell  22 , and thus the seat back  20  in general, to conform to the torso of different sized wheelchair users.  
         [0021]     With continuing reference to  FIG. 3 , four fasteners  50  are attached to the rear surface of the central portion  32  to secure the seat back  20  to the frame  12  of the wheelchair  10 . Two of those brackets  50  are on each side of the central portion  32  and engage one of the vertical posts  14  and  16  of the wheelchair frame. Each fastener  50  includes an L-shaped bracket  52  that has a long leg  54  with two horizontal slots  56  there through. A pair of hex socket screws or bolts  58  pass through the slots  56  and through two of a plurality of apertures  60  which are aligned in two vertical rows in the shell central portion  32 , as seen in  FIG. 2 . Initially each aperture  60  extends only partially through the central portion  32  from the interior surface which provides a more aesthetically pleasing appearance to the seat back than if all the aperture opened through the rear surface that is exposed to view. When the mounting location for a fastener  50  has been selected, a tool, such as the Allen wrench, is inserted into the appropriate apertures  60  and used to punch the aperture through the rear surface of the central portion  32 . The hex socket screws or bolts  58  engage threaded holes in a mounting plate  62  on the opposite side of the central portion to secure the L-shaped bracket  52  in place.  
         [0022]     A short leg  64  of the L-shaped bracket  52  also has a pair of horizontal slots  66 . A mounting hook  68  is attached to the short leg  64  by another pair of hex socket screws or bolts  72  that pass through the slots  66  and are threaded into apertures in a plate  74 . The mounting hook  68  has a curved portion  70  which snaps around the respective vertical post  14  or  16  on one side of the wheelchair frame  12 .  
         [0023]     The two sets of elongated apertures  56  and  66  enable each fastener  50  to be adjusted along two orthogonal axes. Specifically, the brackets allow the seat back  20  to be moved in both horizontal axes, i.e. left to right and front and back. This adjustability allows the seat back  20  to be mounted on wheelchairs of varying sizes and to be positioned on the wheelchair frame  12  to accommodate the torso of the wheelchair user.  
         [0024]     An strap  76  may be attached by hex socket screws  77  and a mounting plate  78  through apertures  79  in the upper region of the central portion  32 . This provides a place for a hand to grasp the seat back  20  and the wheel chair  10  in general.  
         [0025]     The cushion  24  of the seat back  20  shown in  FIG. 1  has a foam body inside and an outer cover  81 . As shown in detail in  FIG. 4 , the body  80  is fabricated from any one of several well known resilient foam materials, such as a closed cell foam, commonly used in seat cushions. The body  80  is formed initially from a flat piece of that material which is cut into the shape illustrated, so that when bent, the body conforms to the interior curvature of the shell  22 . The body  80  has a central section  82  from which first and second lateral sections  84  and  86  project on opposite sides. The front surface  85  of the central section  82  has a grid of horizontal and vertical channels  88  through which air flows between the body  80  and the cover  81  of the cushion. The horizontal channels  88  continue to extend laterally across the first and second lateral sections  84  and  86 .  
         [0026]     The first and second lateral sections  84  and  86  relatively deep V-shaped grooves  90  extending vertically in their front surfaces and a plurality of similar vertical grooves  92  in their rear surfaces interleaved with the grooves  90  in the front surface. The pattern these vertical grooves  90  and  92  in the lateral sections  94  and  96  form pleated regions  94  and  96  on each side of the body  80 .  
         [0027]     The body  80  is encased in the cover  81  made of a bidirectionally stretchable fabric to form the completed cushion  24 , shown in  FIG. 1 . The rear surface of the cushion cover  81  is formed of a hook material of a standard hook and loop fastening system, such as the type sold under the registered trademark VELCRO. A plurality of patches  98  of the loop component of the fastening system are adhered to the front surfaces of the elements  32 ,  38 , and  42  of the shell  22 , as shown in  FIG. 2 .  
         [0028]     In order to place the cushion  24  into the shell  22 , the cushion is folded so that the first and second lateral sections  84  and  86  of the body  80  are folded over the front surface of the central section  82 . The folded cushion is then placed into the shell so that the central section abuts the central portion  32  of the shell. Once the cushion  24  is pressed against the central portion  32 , the hook and loop material on the abutting surfaces engage to hold the cushion in place. The first and second lateral sections  84  and  86  of the cushion body then are unfolded so that their outer edges align with the outer edges of the two wings  38  and  42  of the shell  22 . This alignment is facilitated by the pleated portions  94  and  96  of the body  80  which allow the cushion to bend in conformity with the curvature of the shell  22 , and the width of the cushion  24  compress or expand. The compressibility and expansibility enable the cushion to accommodate the variable lengths of shell curvature due to adjustment of the wing positions. For example, in the illustrated configuration of the shell  22  shown in  FIG. 2 , the wings  38  and  42  are located at the extreme inward position of adjustment, thereby creating the smallest curvature length from the front edge of first wing  38  to the front edge of the second wing  42 . Alternatively, when the two wings  38  and  42  are located at the extreme outward position, the length of shell curvature is several inches greater. This difference in the distance of curvature, depending upon the adjusted position of the wings  38  and  42 , is accommodated by the expansion and contraction of the cushion  24  that is permitted by the pleated portions  94  and  96  of the body  80 .  
         [0029]     The foregoing description was primarily directed to a preferred embodiment of the invention. Although some attention was given to various alternatives within the scope of the invention, it is anticipated that one skilled in the art will likely realize additional alternatives that are now apparent from disclosure of embodiments of the invention. Accordingly, the scope of the invention should be determined from the following claims and not limited by the above disclosure.