Abstract:
A wheelchair back support assembly is both lightweight and sturdy, is designed to be inexpensively retrofit to an existing wheelchair of tubular frame construction, is designed to comfortably support the back of wheelchair user&#39;s of different sizes and having different physical characteristics and also flexes and moves relative to the wheelchair in response to movements of the back, shoulders and arms of the wheelchair user to thereby provide comfortable dynamic support to the back of the wheelchair user.

Description:
BACKGROUND OF THE INVENTION 
     1) Field of the Invention 
     The present invention pertains to a wheelchair back support assembly that is designed to be retrofit to a wheelchair or to replace an existing back support of a wheelchair. The wheelchair back support assembly has a simple construction that is both lightweight and sturdy and includes a back support panel that can be contoured to match the back of the wheelchair user and springs that permit the back support to comfortably flex in response to movements of the back of the wheelchair user. 
     2) Description of the Related Art 
     Wheelchairs have various different constructions but many are constructed of tubular metal members that are connected together to form a rigid frame of the wheelchair. A wheelchair  10  of this type is shown in FIGS. 1 and 2. The metal construction of the wheelchair tubular members significantly contributes to the overall weight of the wheelchair. As seen in FIGS. 1 and 2, the tubular frame members include two side horizontal frame members  12  and one rear horizontal frame member  14  that are connected together to form a support for the seat of the wheelchair. Many of the connections between the tubular frame members of the wheelchair are telescoping connections where an end of one member is inserted into an end of another member. The connections are then secured by threaded fasteners, by spring biased detents, or by other equivalent means. The seat of the wheelchair shown is a soft “sling” type seat that is constructed of a piece of sturdy fabric  16  stretched across the side horizontal frame members  12  and in front of the rear horizontal frame member  14 . The horizontal frame members  12 ,  14  are supported on the wheels of the wheelchair by a framework  18  of tubular members. The framework includes a pair of rear, lower vertical frame members  20  that are connected to the rear wheels  22  of the wheelchair. The pair of lower vertical frame members  20  are also connected with the side horizontal frame members  12  and the rear horizontal frame member  14  and terminate at their top ends (not shown) adjacent the horizontal frame members. An upper pair of vertical frame members  24  are connected to the top ends of the pair of vertical frame members  20 . 
     The upper pair of vertical frame members  24  extend upwardly from the horizontal frame members  12 ,  14  to bent upper ends  26  of the vertical frame members that function as the handles of the wheelchair. This additional pair of vertical frame members  24  at the rear of the wheelchair are commonly referred to as the “canes” of the wheelchair due to their shape. They support a soft “sling” type back  28  of the wheelchair that is commonly constructed of a piece of sturdy fabric. The pair of vertical canes  24  are often telescopically attached to the upper ends of the lower vertical frame members  20  attached to the wheelchair rear wheels. The canes  24  are secured to the lower vertical frame members  20  by threaded nut and bolt fasteners inserted through aligned holes of the frame members, by spring biased detents or by other equivalent means as discussed above. 
     In many prior art wheelchairs constructed of tubular frames similar to the wheelchair discussed above, there is no adjustability or only limited adjustability of the tubular frame members to accommodate wheelchair users of different physical characteristics, for example different sizes and different weights. In addition, wheelchairs with tubular frame members often have their back supports fixed rigidly to their seat supports, providing no adjustment of the back support to accommodate users of the wheelchair having different physical characteristics. Should a user of a wheelchair desire a specific configuration of a back support on the wheelchair to either accommodate their larger size or to more comfortably support their back, the wheelchair user was often required to purchase an entire new wheelchair that incorporated the specialized options such as a wider back support or a back support that tilts. 
     What is needed to overcome these disadvantages of existing wheelchairs is a back support assembly that is both lightweight and sturdy, is designed to be inexpensively retrofit to an existing wheelchair frame, is designed to comfortably support the back of wheelchair users of different sizes and having different physical characteristics, and also flexes and moves relative to the wheelchair in response to movements of the back, shoulders and arms of the wheelchair user to thereby provide comfortable dynamic support to the back of the wheelchair user. 
     SUMMARY OF THE INVENTION 
     The wheelchair back support assembly of the present invention overcomes the disadvantages associated with rigid, uncomfortable wheelchair back supports of wheelchair&#39;s having tubular frame members by providing a back support assembly that can be inexpensively retrofit to an existing wheelchair frame replacing its original back support and which flexes and moves in response to movements of the wheelchair user. 
     The back support assembly of the invention includes a padded back panel constructed of composite materials or other similar types of materials that can be specifically molded or shaped in different sizes to conform to the back configurations of the wheelchair users of different sizes. The back panel is connected between a pair of side columns that have mounting poles at their bottom ends. The mounting poles are specifically designed to be telescopically received on tubular frame members of an existing wheelchair in place of the back support or canes of the wheelchair. The mounting poles are attached to the side columns of the back support assembly by inclination adjustment mechanisms that permit an adjustment of the angle of inclination of the back panel. In addition, the inclination adjustment mechanisms are connected to the side columns by a pair of spring assemblies that allow the back panel to flex comfortably relative to the mounting poles of the back support assembly. The pair of spring assemblies are mounted to the side columns by connectors that can be adjustably positioned along the lengths of the side columns, thereby adjusting the vertical position of the back panel relative to the wheelchair. In addition, the back panel is provided with a centered manual handle or, alternatively, a pair of manual handles may be attached to the side columns and adjustably positioned along the lengths of the side columns. The side columns are also designed to have additional components such as lateral torso supports and arm rests adjustably attached to the side columns. 
     The wheelchair back support assembly provides an inexpensive back support with a simple construction of only a few component parts that can be easily retrofit to a tubular frame of an existing wheelchair, replacing the wheelchair&#39;s original back support. The back support assembly provides the wheelchair with a back support that can be provided in different sizes for the size and shape of the wheelchair user&#39;s back, that can be adjustably positioned both angularly and vertically relative to the wheelchair, and that flexes as the wheelchair user moves on the wheelchair to comfortably support the wheelchair user. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further objects and features of the present invention are set forth in the following detailed description of the preferred embodiment of the invention and in the drawing figures wherein: 
     FIG. 1 is a front view of a conventional wheelchair having a frame constructed of tubular frame members; 
     FIG. 2 is a side view of the wheelchair of FIG. 1; 
     FIG. 3 is a partial view of the wheelchair back assembly of the present invention; 
     FIG. 4 is a partial left side view of the wheelchair back assembly, the right side view being a mirror image of FIG. 4; 
     FIG. 5 is a view of the back panel of the wheelchair assembly with mounting posts and their clasps removed; 
     FIG. 6 is a top view of the back panel of FIG. 5; 
     FIG. 7 is a front view of the back panel of FIG. 5; 
     FIG. 8 is a bottom view of the back panel of FIG. 5; 
     FIG. 9 is a side elevation view of the right side mounting clamp and mounting post of the wheelchair assembly removed from the back panel; 
     FIG.  10 . is a view of the mounting clamp and mounting post of FIG. 9 turned 180° and with the mounting clamp removed from the mounting post; 
     FIG. 11 is a front view of the mounting post of FIG. 9; and 
     FIG. 12 is a rear view of the mounting post of FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 3 is a view from the back of the wheelchair back support assembly  32  of the invention. FIG. 4 is a left hand side view of the back support assembly. The back support assembly  32  is basically comprised of a back panel  34 , a pair of side columns  36  with side blocks  38  attached to the back panel, a pair of clasps  42  that are attached to the side blocks, a pair of angle adjustment assemblies  44  that attach to the clasps, and a pair of mounting posts  46  that are connected to the angle adjustment assemblies  44  and are adapted for attachment to a wheelchair in place of the vertical frame members or canes  24  of the wheelchair. Each of the basic component parts of the wheelchair back support assembly listed above are preferably constructed of a lightweight yet strong material, for example composite materials such as fiberglass or Twintex®, a material manufactured by Vetrotex France, plastic resins or extruded or stamped aluminum. 
     The back panel  34  is preferably constructed of a composite material, however other similar materials may be used. The panel is formed with vertically opposite top  48  and bottom  52  edges and horizontally opposite side edges  54 ,  56 . As seen in FIGS. 6 and 8, the panel  34  is formed with a curved contour with a front surface  58  being concave and a back surface  62  being convex. With the panel being formed by compression molding of a composite material or an other similar process it can be given a specific contoured or curved configuration designed to match and shape and size of a particular user of the wheelchair. Alternatively, the shape and size of the back panel  34  could be specifically designed to fit particular age groups, for example adult, young adult and children, or could be designed to fit particular size and weight groups of wheelchair user&#39;s. As seen in FIGS. 5 and 7, the back panel  34  is formed with an opening  64  that defines a handle  66  at the top of the panel, thus eliminating the need to provide separate handles or canes for use with the back support assembly  32 . The panel is also formed with pluralities of horizontally oblong openings  68  adjacent the horizontally opposite side edges  54 ,  56  of the panel. The oblong openings  68  are employed in attaching the pair of side columns  68  to the horizontally opposite side edges  54 ,  56  of the back panel  34 . Although not shown, in use the back panel  34  could have some type of cushion, for example a foam cushion or air cell cushion secured to its front surface  58 . 
     In the embodiment shown the side columns  36  are attached to the rear surface  62  of the back panel by set screws with enlarged heads  72  that pass through the oblong opening  68  of the panel and are screw threaded into complementary internally threaded holes (not shown) in the side columns. The oblong opening  68  enable the side columns  36  to be horizontally adjustably positioned relative to each other and relative to the back panel  34  by moving the set screws  72  of the columns horizontally in the oblong openings, thus enabling adjustment of the side columns to accommodate the wheelchair back assembly  34  to fit the vertical cane supports of various different wheelchairs as will be described. In the preferred embodiment the side columns  36  are formed of extruded aluminum, although other materials may be employed. The columns  36  are formed with side grooves  76  and rear grooves  78  that have general t-shaped cross sections that extend along the vertical lengths of the columns as seen in FIGS. 4 through 6 and  8 . The rear grooves  78  are employed in attaching the pair of side blocks  38  to the side columns and the side grooves  76  may be employed in attaching arm rests, lateral torso supports or other similar accessories to the wheelchair in the same manner as the side blocks to be described. 
     The side blocks  38  are preferably constructed of a rigid, plastic material, although other materials may be employed. Each side block  38  is attached to one of the side columns  36  for vertical adjustable positioning of the side blocks by internally threaded washers (not shown) that are screw threaded on to pairs of set screws  82  on each side block. The internally threaded washers (not shown) are inserted into the rear grooves  78  of the side columns  36 , thereby attaching the side blocks  38  to the side columns  36  in a manner that enables the side blocks to slide along the rear grooves  78  to a desired vertically adjusted position of the side blocks  38  relative to the side columns  36 . Tightening the set screws  82  of the side blocks  38  secures them in their adjusted positions relative to the side columns  36 . This enables a vertical adjustment of the position of the back panel  34  relative to the mounting posts  46 . Each of the side blocks  38  is also provided with an attachment post  84  that is used in removeably attaching the back panel  34  to the mounting posts as will be explained. The attachment posts  84  project horizontally outwardly from the two side blocks  38 . Each of the side blocks  38  also has a slide pin  86  that is mounted in a horizontal hole (not shown) toward the top of each side block for horizontally reciprocating movement of the slide pin between extended positions shown in dashed lines in FIG.  6  and retracted positions shown in solid lines in FIG.  6 . The side blocks  38  have oblong horizontal slots  88  in their rear surfaces that communicate with the horizontal holes of the slide pins  86 . Levers  92  extend through the horizontal slots  88  and are secured to the slide pins  86 . The levers  92  are used in manually sliding the slide pins  86  between their extended and retracted positions. In the preferred embodiment, a small coil spring (not shown) is also provided in the horizontal hole of the slide pins and biases the slide pins  86  toward their retracted positions. 
     The clasps  42 , the angle adjustment assemblies  44  and the mounting posts  46  make up the mounting members of the wheelchair back support assembly. In FIGS. 9-12 only the right side mounting member is shown. The left side mounting member is a mirror image of the right side mounting member and therefore only the right side mounting member will be described. 
     In the preferred embodiment the clasps  42  are molded of a rigid plastic material, although other similar materials may be employed. The clasps  42  each have a main body  96  that has the same general configuration of the side columns  36 . Each clasp is formed with an angled slot  98  toward the bottom end of the clasp body  96  and a shallow groove  98  with a recessed hole  102  toward the top of the clasp body. A small but powerful permanent magnet  104  is secured in the recesses groove  102  of the clasp. A connector portion  104  of the clasp projects outwardly from the bottom of the main body  96  and an arcuate web or arm  108  connects the connector portion  102  to the top of the clasp main body  96 . The connector portion  106  has an internally threaded hole  112  that extends partially through the connector portion and is employed in securing the clasp  96  to the angle adjustment assembly  44  as will be explained. A curved hole  114  is also formed in the bottom surface of the clasp connector portion  106 . 
     In the preferred embodiment the angle adjustment assemblies  44  are molded of a rigid plastic material such as that of the clasps  42 , although other similar materials may be employed. The adjustment assemblies  44  are formed with a substantially flat bottom surface  118  and with a pair of lobes  122 ,  124  projecting upwardly from the bottom surface. A small circular hole  126  is recessed into the bottom surface  118 . A first one of the lobes  122  shown to the left in FIG.  9  and to the right in FIG. 10 has a hole  128  passing through its center. The hole receives a set screw  132  with an enlarged head that is screw threaded into the internally threaded hole  112  of the clasp connector, thereby attaching the clasp  42  to the angle adjustment assembly  44 . The second of the two lobes  124  shown to the right in FIG.  9  and to the left in FIG. 10 also has a hole (not shown) passing through the center of the lobe. The hole of the second lobe  128  receives a pivot pin in pivotally attaching the angle adjustment assembly  44  to the mounting posts  46  as will be explained. In referring to FIG. 10, the angle adjustment assembly  44  also has an elongate, narrow set screw  134  that is screw threaded transversely through a cylindrical key  136 . The right hand end of the set screw  134  passes through a hole in the second lobe  24  of the angle adjustment assembly and the left end of the set screw  134  has an enlarged head received in a recess (not shown) of the angle adjustment assembly. This mounting of the elongate set screw  134  enables it to be rotated in the hole through the second lobe  124  of the adjustment assembly but prevents the set screw from moving axially when rotated. However, rotation of the elongate set screw  134  will cause the cylindrical key  136  to move axially along the length of the set screw. When the clasp  42  is attached to the angle adjustment assembly  44  by the set screw  132  that passes through the first lobe hole  128  and into the internally threaded hole  112  of the clasp, the cylindrical key  136  is received in the hole  124  recessed into the bottom surface of the clasp. Thus, by rotating the elongate set screw  134  in opposite directions the cylindrical key  136  is caused to move in opposite directions axially along the set screw and in turn causes the clasp  142  to pivot about the first lobe hole set screw  132  and thereby adjusts the angle of inclination of the clasp  42  relative to the angle adjustment assembly  44 . This enables an adjustment in the angle of inclination of the back panel  34  mounted on the clasps  42  relative to the mounting posts  46  that are mounted to a wheelchair, thus enabling an adjustment of the angle of inclination of the back panel  34  relative to the wheelchair. 
     Each of the mounting posts  46  has opposite top  138  and bottom  140  ends and in the preferred embodiment are formed from cylindrical tubes of aluminum, although other materials may be employed. The exterior dimension of the mounting post  46  is preferably dimensioned to be received inside the vertical frame members  20  of the wheelchair in place of the canes of the wheelchair. The mounting posts are provided with pluralities of openings  142  along their lengths that are aligned with openings of the wheelchair vertical frame members  20  and through which threaded fasteners are passed to mount the mounting posts in vertically adjusted positions on the wheelchair frame members, in the same manner that the canes  24  are mounted to the wheelchair frame. Alternative mechanisms for attaching the mounting posts  46  to the wheelchair could also be employed. In addition, each mounting post could be constructed of two sections that are screw threaded together. The bottom sections could be selectively attached to the top sections or removed to adapt the mounting posts for use with wheelchairs having lower vertical frame members  20  of different lengths. 
     A base of rigid plastic or other similar material is secured to the top end  138  of the mounting posts. The base is formed with a projection having a base surface  146  that opposes the bottom surface  118  of the angle adjustment assembly  44 . The base surface  146  has a small circular recess  148  that opposes the circular recess  126  in the adjustment assembly bottom surface  118 . Adjacent the base surface  146  the base  144  has a pair of horizontally spaced prongs  152  that project upwardly from the base. The prongs  152  have horizontally aligned center holes  154 . The angle adjustment assembly second lobe  124  is received between the prongs  152  with the center hole (not shown) of the second lobe aligned with the base prong center holes  154 . A pivot pin  156  is inserted through the aligned holes, thereby mounting the angle adjustment assembly  44  to the base  144  for pivoting movement of the angle adjustment assembly relative to the base. As seen in FIG. 9, the angle adjustment assembly  44  and the attached clasp  42  and the back panel  34  of the wheelchair back assembly can pivot relative to the base  44  and the mounting post  46  between a first, forward position shown in FIG. 9 where the right hand end of the adjustment assembly bottom surface  118  contacts with the right hand end of the base surface  146 , and a second rearward position relative to the base and mounting posts where the adjustment assembly bottom surface  118  is substantially parallel with the base surface  146 . 
     A spring  158  is positioned between the adjustment assembly bottom surface  118  and the base surface  146 . In the preferred embodiment the spring  158  is a coil spring, however other types of springs may be employed. The spring  158  is received in the hole recessed in the adjustment assembly bottom surface  126  and the hole recessed in the base surface  148 . The spring  158  biases the adjustment assembly  44 , the clasp  42  and the back panel  34  attached thereto to their forward position shown in FIG.  9 . Movement of the angle adjustment assembly  44 , the clasp  42  and the back panel  34  to their rearward position acts against the bias of the spring  158  and compresses the spring between the adjustment assembly bottom surface and the base surface  146 . Thus, the spring  158  enables the horizontally opposite side edges  54  of the back panel  34  to flex and pivot relative to the mounting posts  46  independently of each other as a wheelchair user&#39;s arms and shoulders move about the user&#39;s torso in operating the wheelchair. 
     The wheelchair back assembly of the invention is assembled to the vertical frame members  70  of a wheelchair by inserting the mounting posts  46  into the frame members to a desired vertically adjusted position and then inserting threaded fasteners through aligned holes of the wheelchair vertical frame members  20  and the openings  142  of the mounting posts. Next, the back panel  34  is inserted between the clasps  42  of the mounting members with the side blocks  34  positioned between the clasps. The back panel  34  and side columns  38  are moved downwardly causing the attachment posts  84  of the side blocks to move into the angled grooves  98  of the clasps. With the attachment posts  84  bottomed out in the clasp grooves  98 , the installer moves the slide pin levers  92  of the side blocks  38  toward each other causing the slide pins  86  to be retracted into their holes. The side blocks  38  are then moved between the clasps  42  and the installer releases the levers  92  causing the magnets  104  in the recessed holes  102  of the clasps to draw the slide pins  86  out of their holes and into the magnet holes  102 , thereby releasably attaching the back panel  34  to the wheelchair mounting members. 
     The wheelchair back support assembly described above provides an inexpensive back support with a simple construction of only a few component parts that can be easily retrofit to a tubular frame of an existing wheelchair, replacing the wheelchair&#39;s original back support. The back support assembly provides the wheelchair with a back support that can be provided in different sizes for the size and shape of the wheelchair user&#39;s back, that can be adjustably positioned both angularly, horizontally and vertically relative to the wheelchair, and that flexes as the wheelchair user moves on the wheelchair to comfortably support the back of the wheelchair user. 
     While the present invention has been described by reference to specific embodiments, it should be understood that modifications and variations of the invention may be constructed without departing from the scope of the invention defined in the following claims.