Abstract:
A backrest mounting system provides angular and height adjustment of a backrest shell independent of backrest canes. The backrest mounting system attaches to a centrally located mounting structure on the backrest shell and defines at least two pivot axes that determine the angular position of the backrest shell relative to a wheelchair seat.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 62/247,540, filed Oct. 28, 2015, the disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates in general to wheelchair seating systems and, in particular, to an angle adjustable backrest mounting system. 
         [0003]    Wheelchairs are typically intended to be used by persons having different size, physical constitutions, and impairments. These conditions are accommodated, in one respect, by providing adjustable seating systems that permit the seat and/or seat back to be positioned to the user&#39;s seated body contours. Many known seating systems provide a variety of adjustments but are either bulky or cumbersome to adjust so that the seated user is comfortable. In addition, many adjustable seating systems for manual wheelchairs rely on backrest canes as part of the backrest mounting structure. This adds extra weight and an obstacle for freedom of movement, particularly in light weight or sport wheelchairs. Thus, it would be desirable to provide a seat backrest adjustment mechanism that is easily adjustable, yet light weight and sized so that a variety of seat backs, particularly smaller seat back associated with sport chairs or light weight chairs, can be easily adjusted to a comfortable angular position. 
       SUMMARY OF THE INVENTION 
       [0004]    This invention relates to wheelchair seatback mounting systems. This mounting system eliminates reliance on traditional backrest canes on the sides of the wheelchair to mount and support a backrest. This eliminates the interference between the canes and user&#39;s arms, particularly during propulsion, allowing greater freedom of body (trunk) movement and rotation. Since the backrest mounts are located in the center of the shell, the backrest width is not dependent on wheelchair width and can be smaller or larger than wheelchair. Mounting hardware is located in the center of the back shell and allows adjustment for different height and angular backrest positions. 
         [0005]    Two pivoting axes allow additional height, depth and angle adjustment. This can be an infinite adjustment or incremental with gear/teeth feature on the offset mounts. Two offset mounts are inter-locked with a locking tube and screw connection to eliminate any misalignment in the backrest tubes. 
         [0006]    Various aspects of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a perspective, partially exploded view of a backrest mounting system in accordance with the invention. 
           [0008]      FIGS. 2A-2C  are views showing adjustment points of the backrest mounting system. 
           [0009]      FIG. 3A  is a plan view, partially exploded, of the backrest mounting system of  FIG. 1 . 
           [0010]      FIG. 3B  is an elevational view, partially exploded, of the backrest mounting system of  FIG. 1 . 
           [0011]      FIG. 4  is a perspective view of the backrest mounting system of  FIG. 1 . 
           [0012]      FIGS. 5A and 5B  are enlarged views of an embodiment of a position adjustment feature of the backrest mounting system of  FIG. 4 . 
           [0013]      FIG. 6  is a rear elevational view of a wheelchair including the backrest mounting system of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]    Referring now to the drawings, there is illustrated in  FIG. 1  a wheelchair backrest mounting system, shown generally at  10 . The backrest mounting system  10  attaches a backrest shell  12  to a wheelchair frame (shown at  FIG. 6 ). The backrest mounting system  10  includes a mounting block  14  that is fastened to the backrest shell  12  by attachment pads  16 . The mounting block  14  includes a bore  18  that extends therethrough and includes tapered or beveled receivers  20 . An offset locking tube  22  is configured to extend through and be supported by the bore  18  for rotation. The offset locking tube  22  terminates in locking teeth  24 . The illustrated locking teeth  24  are shown as tube end cutouts that have offset profiles along the tube longitudinal axis. Other tooth arrangements, such as multiple teeth, may be provided if desired. The locking tube  22  maintains spaced-apart offset mounts  26  oriented in alignment relative to each other. The offset mounts  26  include pivot ends  28 , as shown in  FIGS. 5A and 5B . In the illustrated embodiment, the offset mounts  26  are configured such that locking bores  30  in the pivot ends  28  are coaxially aligned. The locking bores  30  include a locking profile  32  that mates with the locking teeth  24  of the offset locking tube  22 . Alternatively, the locking teeth  24  may be multiple teeth distributed around the end perimeter of the offset locking tube  22  in order to permit the offset mounts  26  to be indexed relative to each other. When so indexed, the mounting block  14  may be oriented at an angle relative to the wheelchair frame to accommodate specific user conditions such as lateral spinal curvature issues which cause a tilted seated position. 
         [0015]      FIG. 5A  illustrates the offset mount  26   a  configured for one side, such as a left side of the wheelchair and  FIG. 5B  illustrates the mirror image offset mount  26   b  for mounting on a right side of the wheelchair. Where the offset mounts  26  have locking bores  30  with multiple teeth (not shown) distributed around the locking bore inner diameter, the offset mounts  26   a  and  26   b  may be adjusted to provide a lateral tilt to the backrest shell  12 . In order to provide the lateral angular adjustment described above, one offset mount  26   a  may be rotated in a direction opposite of the other offset mount  26   b.    
         [0016]    Both of the offset mounts will be described relative to one the offset mount  28 . As shown in  FIG. 5A , the pivot end  28  includes a tapered surface or cone-shaped surface  34  that mates with the tapered or beveled receiver  20  of the mounting block  14 . The tapered surface  34  of the offset mount  26  is end loaded or compressed against the tapered receiver  20  to frictionally adjust the angular pivot orientation of the backrest shell  14 , as shown in  FIG. 2B . An adjustable fastener  35 , such as a bolt, screw, or other length-adjustable connector extends through the offset locking tube  22  to end load the tapered surfaces  34  against the tapered receivers  20 . The tapered surface  34  and the mating tapered receiver  20  are shown having smooth profiles to provide a free range of adjustment. Alternatively, this surface may be profiled, such as radially extending surfaces to provide a discrete series of adjustments. In operation, the bolt  35  may be loosened to permit rotation of the backrest shell  12  about the axis defined by the bore  18 , as shown by the arrows of  FIG. 2B . In addition the backrest shell  12  may be moved toward or away from an edge of a wheelchair seat by moving the offset mounts  26   a  and  26   b  together in a clockwise or counterclockwise direction. As shown in  FIG. 2C , the backrest shell  12  may include adjustment slots  12   a  to permit height adjustment of the backrest shell  12  relative to the wheelchair seat of  FIG. 6 . 
         [0017]    Referring again to  FIG. 1 , the offset mount  26  includes a frame mount  36  that engages a saddle  38  that supports the backrest relative to backrest frames or tubes  40 . In one embodiment, the backrest tubes  40  may terminate in a mounting point  40   a  that permits attachment, either removable or permanent, to a wheelchair frame  52  of a wheelchair  50 , as shown in  FIG. 6 . The frame mount  28  may include a mounting face  42  that contacts the saddle  38 . In one embodiment, the mounting face  42  and the contacting face of the saddle  38  are smooth and permit a free range of angular adjustment, as shown by the arrows in  FIG. 2B , of the backrest shell  12  relative to the backrest tubes  40 . Alternatively, the surfaces may be profiled to permit discrete angular adjustment positions. A barrel nut  44  accepts a mounting screw  46 ; that extends through the frame mount  36 , the saddle  38 , and at least a portion of the backrest tube  40 ; to permit the connection to be tightened. In one embodiment, the barrel nut  44  is supported within a cap  48  that fits into an open end of the backrest tube  40 , proximate to the backrest shell  12 . In one adjustment operation, bolt  35  and mounting screws  46  may be loosened to permit the plane of the backrest shell  12  to be moved along a longitudinal axis of the wheelchair. In addition, the backrest shell may be rotated to an angular position relative to a side view of the wheelchair  50 , as shown in  FIG. 2B . 
         [0018]    The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.