Abstract:
Angle adjustable backrest made of a lightweight, durable, adjustable, backrest for ultralight manual wheelchairs. Light-weight material can include composites for a rigid backrest for promotion of healthier and functional interface. Angle adjustment can be any desired range such as a range from −5 degree to 55 degrees (i.e. 85 degrees to 145 degree with respect to horizontal with the seat). No tools are necessary for any of the angle adjustments. The backrest has a horizontal adjustment (fore-aft) that can be any desired range such as 1 inch. The height selection depends on the length of the wheelchair frame tubes. The present invention improves the ease and simplicity of adjusting the backrest by or for the user, as well as enhances the aesthetic appearance and adds features necessary for achieving commercial readiness. The present invention can be retro fit onto a wide range for ultralight wheelchairs.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is related generally to the field of angle adjustable backrests, and in particular to wheelchair angle adjustable backrests. 
       BACKGROUND OF THE INVENTION 
       [0002]    In the United States, about 21.2 million people currently have limitations in basic physical activities, such as walking, climbing stairs, carrying, or lifting. Over 100 million people with physical disabilities use wheelchairs for their primary mobility in the world, and yet less than one percent of these people have access to a wheelchair. The use of wheelchairs has increased for several reasons: birth defects, accidents, debilitating diseases, and advanced age. Based on the report of World Health Organization, more than 29,000 people annually have unexpected injuries. An estimated 250,000 to 400,000 people have spinal cord injuries or spinal dysfunction. Therefore, experts anticipate that the need for wheelchairs worldwide will continue to increase, up to 22 percent over the next 10 years. 
         [0003]    While the number of wheelchair usage in increasing, it has created an increased demand for wheelchairs has led to an expanded market that continually offers better wheelchairs and seating systems. Based on innovations in technology, people are living longer, and are participating at higher rates. The demand to maintain an active lifestyle is also presented among people with disabilities. Wheelchair technology is integral to maintaining on active life style for individuals with a disability. Wheelchairs allow people with disabilities to have enhanced function, improved independence, and access to home and community. The lack of wheelchair is the main cause of limited participation to people with spinal cord injuries, so the wheelchairs are most important mobility of them. After their injury, wheelchair users accept their disabilities and consider a wheelchair as an extended body. Wheelchairs are critical components to meet users&#39; expectations, preferences, physical needs, and functional requirements. 
         [0004]    Different types of wheelchairs have different comfort and ergonomic ratings, as the different wheelchairs have different qualities. A wheelchair having more adjustability received higher ratings on comfort and ergonomics compared to a wheelchair with minimal adjustability. Since most wheelchair users spend half of the day sitting. Therefore, as the supply of manual wheelchairs increases, the demand of making them safer, more effective, and more readily available is necessary with wheelchair users&#39; needs/adjustability. 
         [0005]    Secondary injuries (e.g., repetitive strain injuries, pressure sores and so on) are of particular concern for those who use wheelchairs as their primary means of mobility. Since a wheelchair is an extension of the user&#39;s body, even the best fit wheelchair may not prevent the secondary injury. Pressure ulcer is one of the secondary injuries. The pressure sore occurs higher when people stay in a confined chair, have inability to move, have poor nutrition, and have lowered mental awareness. People with disabilities have difficulty changing positions and altered sensation, so they are at risk of pressure sores when they are not provided by adequate pressure-relieving mechanisms. Products and services need to be available to prevent or delay these conditions as they provide demands. 
         [0006]    It is a challenge to recommend a particular wheelchair because wheelchair configuration influences wheelchair users&#39; comfort, possibilities of transfer, efficient propulsion and so on. Wheelchairs usually have adjustability with axle position, seat depth, height of the footrests, tilting angle and reclining angle. Among those of adjustability, changing height of the footrests or changing backrest angles is only trial and error to avoid pressure sores as prevention of a secondary condition. According to the study of effect with changing tilt and seat-to-backrest angles by shoulder during wheelchair propulsion, seat angle could be standard for the user comfort and pressure modulation without risk of overuse shoulder injuries for alleviating pressure. As the backrest provides pressure relief, it is an essential part of wheelchair configuration. 
         [0007]    Differences in postural alignment and shoulder flexion range are observed between wheelchairs with standard configurations and wheelchairs with posterior seat inclination and a low backrest which was set perpendicular to the floor. The wheelchairs with posterior seat inclination and low backrest set perpendicular to the floor give significantly more active upper extremities&#39; flexion. The backrest does support the lumbar spine for maintenance of anterior pelvic tilting. And, the angle of backrest gives the wheelchair users spaces for posterior tilting. 
         [0008]    In addition, the backrest protects and supports the spine which is one of the most important structural parts in the body. Because the weight of the upper body is sustained through the spine to transfer into the limbs, the spine is an imperative structural component. Therefore, the protection or support of the spine is essential. In many cases, wheelchair users have insufficient muscle strength to support and control the spine, so the spine tends to be bent and deformities of the spine are caused by forces of gravity. When the wheelchair backrest does not provide proper postural supports to a wheelchair user, the problems of lordosis, kyphosis, scoliosis or some combinations of these postures may be developed. 
         [0009]    Pelvic stability affects shoulder mobility which gives wheelchair users weight-bearing and movement. Wheelchair users have to perform tasks during the day in a seated posture and the seating for each task performance is not same all day long. Therefore, seating should allow for changes of posture. 
         [0010]    An adjustable backrest is an important feature in different conditions to provide adequate trunk support. While propelling a wheelchair uphill or downhill on a ramp, the wheelchair user should lean into the ramp to minimize the risks of injury or feelings of instability. The adjustment of backrest angle will help to open the hip angle to make users dress easily in the wheelchairs. Also, people could have their own preference for the postures in daily activities. Based on the increasing number of wheelchair users, providing an adjustable backrest is necessary because of the importance of seating position and appropriate trunk support. 
         [0011]    A backrest has different characteristics according to height, shape, stiffness, weight, adjustability and so on. Based on the height of the backrest, wheelchair users have different support and functions. Low backrest provides freedom of movement, but less stable. On the other hand, high backrest provides more support, but limits mobility for propulsion. The rest of characteristics are different from types of backrests. Manual wheelchairs are commonly fitted with one of three types of backrest: sling upholstery backrest, rigid backrest, and custom molded backrest. Most manual wheelchairs come with sling upholstery for the backrest. The sling upholstery backrest is made of fabric or leather. The rigid backrest is one of the most recommended backrest to support user&#39;s posture as a combination of a back cushion on a rigid frame. The custom molded backrest is an individualized backrest for a person who has particular deformity. Each has different perspectives which could be advantages or disadvantages. 
         [0012]    The sling upholstery backrest has a rectangular shape based of frames of wheelchair s tubes. The materials of sling backrest which are fabric or leather are stretched out wheelchair backrest. Because of features of materials, it has adjustability, contours to the shape of spine, and is lightweight. An advantage of this type of backrest is that it can be used by a wide range of people because it conforms based on the back shape and posture, and thus it is common and useful. The flexibility of this backrest also makes it ideal for folding wheelchair which is easily transportable. A primary drawback to the sling backrest is that it does not provide a stable base of support for the posture. 
         [0013]    The rigid backrest has different features contrast to the sling backrest. The rigid frame of backrest has the contour of back, so it looks a trapezoid from seeing upside. Even though there is cushion on the backrest, the frame is firm and has additional weight. Therefore, it is generally not adjustable and is sensitive to the user&#39;s body size. However, it provides a solid base of support for appropriate posture, so it is most appropriate for users without a postural deformity. 
         [0014]    The individualized contour backrest is shaped individually, but usually looks big and bulky. This type of backrest covers whole spine and fills spaces to support deformity of spine. It is very individual product, so it requires intensive labor. The quality of the custom molded backrest depends on clinicians&#39; skills. 
         [0015]    Among the three types of the backrests, the standard sling upholstery for the backrest has been used for most wheelchair manufacturers and wheelchair users. As mentioned earlier, the sling upholstery has a flexibility and adjustability of tension, so wheelchair users can make periodically suitable. However, it provides less postural support. In addition, it would not be enough to support wheelchair users&#39; back while being in dynamic functions such as up and down ramps, various surfaces and over obstacles. 
         [0016]    There is a need for a lightweight, sturdy, user-adjustable, easily set-up and ergonomic backrest support for ultralight wheelchairs to satisfy the needs of wheelchair users by maximizing functionality and improving ease of use. An angle adjustable backrest provides necessary postural support and a variety of positions to easy dressing, propulsion, and seated comfort. 
       SUMMARY OF THE INVENTION 
       [0017]    The present invention is a lightweight, durable, adjustable, backrest for ultralight manual wheelchairs. Light weight material can include composites for a rigid backrest for promotion of healthier and functional interface. Angle adjustment can be any desired range such as a range from −5 degree to 55 degrees (i.e. 85 degrees to 145 degree with respect to horizontal with the seat). No tools are necessary for any of the angle adjustments. The backrest has a horizontal adjustment (fore-aft) that can be any desired range such as 1 inch. The height selection depends on the length of the wheelchair frame tubes. 
         [0018]    The present invention improves the ease and simplicity of adjusting the backrest by or for the user, as well as enhance the aesthetic appearance and add features necessary for achieving commercial readiness. The present invention can be retro fit onto a wide range for ultralight wheelchairs. 
         [0019]    For a better understanding of the present invention, together with other and further objects thereof, reference is made to the accompanying drawings and detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The present invention is illustratively shown and described in reference to the accompanying drawings, in which: 
           [0021]      FIG. 1  is a pictorial illustration of one embodiment of the present invention with the covers in a closed or locked position; 
           [0022]      FIG. 2  is a pictorial illustration of the embodiment of the present invention of  FIG. 1  with the covers in an opened or released; 
           [0023]      FIG. 3  is a pictorial illustration of a J-shaped bracket of the angle adjustment mechanism of  FIG. 1 ; 
           [0024]      FIG. 4  is a pictorial illustration of an exemplary pivot bar of the present invention of  FIG. 1 ; 
           [0025]      FIG. 5  is a pictorial illustration of the right angle adjustment mechanism and wheel chair mounting attachments with right cover in closed or locked position; 
           [0026]      FIG. 6A  is a pictorial illustration of an exemplary cover of the present invention of  FIG. 1 ; 
           [0027]      FIGS. 6B-E  are an internal, side, and top views of the exemplary cover of  FIG. 6A ; 
           [0028]      FIG. 7  is a pictorial illustration of the right angle adjustment mechanism and wheel chair mounting attachments without right cover; 
           [0029]      FIG. 8  is a pictorial illustration of an exemplary hex rod of the present invention of  FIG. 1 ; 
           [0030]      FIG. 9  is a pictorial illustration of an exemplary cover of the present invention of  FIG. 1  in an opened or released position in 0° or centered position; 
           [0031]      FIG. 10  is a pictorial illustration of the present invention of  FIG. 1  adjusted backward to angle Ø 
           [0032]      FIG. 11  is a pictorial illustration of the present invention of  FIG. 1  adjusted forward to angle Ω; 
           [0033]      FIG. 12  is a graphical representation of an exemplary angular rotation of the backrest relative to wheelchair tubing; 
           [0034]      FIG. 13  is pictorial illustration of the degrees of motion of the angle adjustment mechanism of  FIG. 1 ; 
           [0035]      FIG. 14  is a pictorial illustration of a magnification of  FIG. 13  without cover to illustrate the assembly of the gear relative to the pivot bar and the tubing attachment brackets; 
           [0036]      FIG. 15  is a pictorial illustration of an exemplary embodiment of an outer gear of the present invention of  FIG. 1 ; 
           [0037]      FIG. 16  is a pictorial illustration of an exemplary embodiment of an inner gear of the present invention of  FIG. 1 ; 
           [0038]      FIG. 17  is a pictorial illustration of an exemplary embodiment of a tubing attachment bracket of the present invention of  FIG. 1 ; 
           [0039]      FIG. 18  is a pictorial illustration of an exemplary embodiment of the pivot bar and inner gear of the present invention of  FIG. 1 ; 
           [0040]      FIG. 19  is a pictorial illustration of an alternative pivot bar of the present invention; 
           [0041]      FIG. 20  is a pictorial illustration of another embodiment of the present invention having only a single backrest adjustment mechanism incorporated on to a wheelchair with only one wheelchair tubing; 
           [0042]      FIGS. 21A and 21B  are pictorial illustrations of an exemplary remote control mechanism for the present invention to actuate the release mechanism to disengage the locked gears and to engage the gears free to rotate in a relative thereto; 
           [0043]      FIGS. 22A-C  are pictorial illustrations of tapered gears of another embodiment of the present invention, 
           [0044]      FIG. 23  is a pictorial illustration of the remote control cable disengaging the covers with actuation of the remote control mechanism of  FIGS. 21A and 21B ; 
           [0045]      FIGS. 24A-E  are pictorial illustrations of an alternative semi-circular embodiment of the gears of the present invention, and 
           [0046]      FIG. 25  is an exploded view of the embodiment of the present invention of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0047]    As used herein in the specification and claims, including as used in the examples and unless otherwise expressly specified, all numbers may be read as if prefaced by the word “about”, even if the term does not expressly appear. Also, any numerical range recited herein is intended to include all sub-ranges subsumed therein. 
         [0048]    One embodiment of the present invention is illustrated as an exploded view in  FIG. 25  and discussed in detail below. 
         [0049]    Now turning to  FIGS. 1-3  illustrating one embodiment of the present invention including a mechanism  2 A,  2 B of adjusting angular position of backrest  26 . J-shaped brackets  22 A,  22 B,  24 A,  24 B shown in  FIG. 3  are connected to backrest  26 . J-shaped brackets  22 A,  22 B,  24 A,  24 B have slots  28  so that it can be adjustably attached to backrest  26  for positioning of backrest  26  with wheelchair tubing  14 ,  16  to accommodate varying widths between wheelchair tubings  14 ,  16 . J-shaped brackets  22 A,  22 B,  24 A,  24 B have a tapped hole  30  to receive a screw (not shown) for adjustably attaching J-shaped brackets  22 A,  22 B,  24 A,  24 B to slots  32  of pivot bars  10 ,  12  for fore-aft adjustment of backrest  26 . 
         [0050]    Now turning to  FIG. 4  further illustrating pivots bar  10 ,  12 . As shown in  FIGS. 1 and 2 , pivot bars  10 ,  12  are disposed between two J-shaped brackets  22 A,  22 B,  24 A,  24 B and tubing attachment brackets  18 ,  20 . Pivot bars  10 ,  12  include two slots  32   a ,  32 B at ends  64 A,  64 B of each side of the wheelchair for horizontal (fore-aft) adjustment and hex nut hole  54  at center  66  of pivot bars  10 ,  12  for placement of round insert  78  t receive therein hex rod  40 . Pivot bars  10 ,  12  will pivot on the outer surface  41  of round insert  39 . Four (4) holes are positioned around hex nut hole  54  to receive screws that hold inner gear  38 . The shape of pivot bars  10 ,  12  are substantially rectangular with circular shaped center portion  68  to contour to the shape of gears  36 ,  38  and covers  6 ,  8  to prevent dust from entering the gear compartment. 
         [0051]      FIGS. 24A-E  illustrate alternative gears can are less than 360° circumference or full-circle. Though any semi-circular angle is acceptable, examples of acceptable segments can be an outer gear  36 C and/or inner gear  38 C being 180° ( FIG. 24A ) or being 60° ( FIG. 24B ).  FIGS. 24C and 24D  illustrate relation rotational movement of inner gear  38 C (180°) with outer gear  36 C (60°) as limit pin  70  of inner gear  38 C travels within angular position slot  52  of outer gear  36 C.  FIG. 24E  is an illustration of inner gear  38 C (180°) with outer gear  36 C (60°) assembled in mechanism  2 .  FIG. 24F  is an illustration of outer gear  36 C (180°) with inner gear  38 C (60°) assembled in mechanism  2 . 
         [0052]    Now turning to  FIG. 5  illustrating the right angle adjustment mechanism  2 B and wheel chair mounting attachments with right cover  8  in closed or locked position to fix backrest  26  position.  FIGS. 6A-E  illustrate covers  6 ,  8  include internal female gears  42  that slide over and mesh with male gears of outer gear  36  and inner gear  38  when gears  36 ,  38  are aligned ( FIG. 7 ), rotationally constraining these gears. Covers  6 ,  8  include threaded hole  44  that is screwed on to release screw  34  whereby covers  6 ,  8  travel with release screw  34  along common longitudinal axis X when release screw  34  is pulled outward away from outer gear  36  and inner gear  38  to disconnect inner gear  38 . Covers  6 ,  8  also can be designed (as shown in  FIG. 6E ) with a bevel  43  at opening edge  45  of the gear which helps align gears  36 ,  38 . Outer gear  36  and inner gear  38  are not rotationally constrained to each other when cover  6 ,  8  are in opened or released position Bracket  20  is attached to wheelchair tubing  16 . J-shaped bracket  24 A,  24 B are connections between pivot bar  12  and backrest  26  to secure pivot bar  12  to backrest  26 . 
         [0053]    Now turning to  FIG. 7 , outer gear  36  and inner gear  38  are positioned adjacent to one side of pivot bar  12 . Inner gear  38  is fixedly attached to pivot bar  12  and outer gear  36  is connected to hex rod  40  and fixedly attached to tubing attachment bracket  20 . Whereby, inner gear  38  moves or rotates with pivot bar  12  about common longitudinal axis X and outer gear  36  is static relative to tubing attachment bracket  20 . To set backrest  26  in one position, covers  6 ,  8  lock outer gear  36  and inner gear  38  moving relative to the other when at least one male gear tooth of the outer gear  36  and inner gear  38  align and the female gear teeth of covers  6 ,  8  mesh over the male gear teeth of the outer gear  36  and inner gear  38 . 
         [0054]    An alternative embodiment of the present invention does not include outer gear  38  and only relies on covers  6 ,  8  female internal gears to carry operational loads and being attachable to attachment brackets  18 ,  20 . 
         [0055]    As shown in  FIG. 9 , cover  8  slides outward relative to outer gear  36  and inner gear  38  to disengage inner gear  38  relative to outer gear  36  while cover  8  still engages outer gear  36  such that backrest  26  can pivot backward ( FIG. 10 ) or forward ( FIG. 11 ) together with inner gear  38  and pivot bar  12 . Covers  6 ,  8  are pulled inward towards the other cover in opposing directions Z 1 , Z 2  simultaneously for disengaging gears, as shown in  FIG. 2 . For one hand manipulation, covers  6 ,  8  are connected by a pull string or rope  4 . One embodiment of pull string  4  can be polyester rope with 3/32 inch diameter. The gears are repeatedly disengaged and engaged by pulling and releasing pull string or rope  4 . Biasing devices, for example springs  46  integral with hex rod  40 , can biases covers  6 ,  8  back to their original positions. Only one hand can be used for quick release without a certain amount of strength. Pulling pull string or rope  4  also could be done by gross movement or a single actuation in a vertical direction Y 1  or Y 2  at any position along length of pull string  4 . As a result, dexterity is not required to adjust the backrest angle. Therefore, the position of body might be stable when wheelchair users recline. 
         [0056]    Release screw  34  can be integral to hex rod  40  as shown in  FIG. 8 . Internal spring  46  is compressed against shoulder  48  by screw head  50  when release screw  34  is pulled in direction A by pull string  4  to release outer gear  36  and inner gear  38 . Once tension on pull string  4  is removed, then compressed internal spring  46  is decompressed to return to its original position moving covers  6 ,  8  into closed or locked position interconnecting outer gear  36  and inner gear  38 . 
         [0057]    Now turning to  FIGS. 9-12  illustrating the angular adjustment of backrest  26  relative to wheelchair tubing  16 .  FIG. 9  is a pictorial view of an exemplary cover  8  of the present invention of  FIG. 1  in an opened or released position in 0° or centered position.  FIG. 10  is a pictorial view of the present invention of  FIG. 1  adjusted backward.  FIG. 11  is a pictorial view of the present invention of  FIG. 1  adjusted forward.  FIG. 12  is a graphical representation of an exemplary angular rotation of the backrest relative to wheelchair tubing ranging, for example, from an incline of Ω (for example, −5°) to a recline of Ø (for example, +55°). However, an incline angle and recline angle is within the contemplation of this invention. 
         [0058]      FIG. 13  illustrates the degrees of motion of one embodiment of the angle adjustment mechanism. Pivot bars  10 ,  12  rotate in direction C to adjust the angle of backrest  26  (attached to J-shaped brackets  22 A,  22 B,  24 A,  24 B). J-shaped brackets  22 A,  22 B,  24 A,  24 B traverse in direction B within pivot bar slot  32 A,  32 B relative to pivot bars  10 ,  12  to set a horizontal (fore-aft) position of backrest  26 . Tubing attachment brackets  18 ,  20  traverse in direction D relative to wheelchair tubing  14 ,  16  to set vertical height of backrest  26 . 
         [0059]      FIG. 14  is a magnified view of  FIG. 13  without covers  6 ,  8  to illustrate the assembly of outer gear  36  and inner gear  38  to pivot bar  10 ,  12  and tubing attachment brackets  18 ,  20 . 
         [0060]    Now turning to  FIGS. 15 and 16  for a discussion of outer gear  36  and inner gear  38 . Outer gear  36  includes hex rod hole  54  sized to receive hex rod  40  and angular position limit slots  52  sized to freely receive limit pin  70  in inner gear  38 . Hex rod  40  is secured to outer gear  36  by conventional securing mechanisms including but not limited to welding or interference fit with the hex rod hole  54 . Round insert  78  ( FIG. 25 ) with hex shaped hole is received into insert hole  47 . Inner gear  38  is free to rotate in direction C until stopped by limit pins  70 . Though gears  36 ,  38  are illustrated as straight, non-tapered gears in this application, other gear designs such as an angle tapered spline or tapered straight gears, such as outer tapered gear  36 T, inner tapered gear  38 T (see  FIGS. 22A-C ) are also within the contemplation of the invention. 
         [0061]      FIGS. 22A and 22B  are illustrates outer tapered gear  36 T angular position slot  52  aligned adjacent inner tapered gear  38 T. Figure is an illustration of tapered gears  36 T,  38 T assembled in mechanism  2 . One embodiment of mechanism  2  allows for automatic adjustment between covers  6 ,  8  and inner tapered gear  38 T to maintain tightness of fit therebetween. Either there is a gap between inner tapered gear  38 T and pivot bars  10 ,  12  to accommodate cover female internal gear wear as the covers  6 ,  8  move inward toward the outer and inner gears due to the spring load to form a tighter fit with the outer and inner gears, or the initial/new fit between covers  6 ,  8  to inner tapered gear  38 T is that female internal gear teeth  42  of covers  6 ,  8  do not engage the entire depth or width W of the male gear teeth of inner tapered gear  38 T. In the latter case, covers  6 ,  8  will progressive move over the entire depth or width of the male gear teeth of inner tapered gear  38 T as the female internal gear teeth  42  of covers  6 ,  8  wear. 
         [0062]    Now turning to  FIGS. 17  and to illustrate the assembly of present invention. Square insert  74  is inserted into hole  76  of tubing attachment bracket  20  and hex rod  40  is secured into hole  74  of square insert  76  to form a static subassembly  77  either before or after tubing attachment bracket  20  is attached to wheelchair tubing  16 . 
         [0063]    Now turning to  FIG. 18  to illustrate the assembly of pivot bar  12  and inner gear  38  to tubing attachment bracket  20 . Inner gear  38  include round insert  78  in its center hole  80 . Inner gear  38  is fixedly attached to pivot arm  10  to form a rotatable subassembly  82 . The outer gear  36  is fitted onto hex rod  40 . Round insert  78  allows rotatable subassembly  82  to rotate independently relative to static subassembly  77 . 
         [0064]    Now returning to  FIG. 7  to illustrate the further assembly of outer gear  36  to subassembly  77 . Outer gear  36  is secured to hex rod  40  by conventional attachment techniques including but not limited to welding or interference fit between outer surface  84  of hex rod  40  and center hole  86  of outer gear  36 . Cover  8  ( FIG. 5 ) is now screwed onto release screw  34  through threaded hole  44  and pull string  4  is attached to a nut  88  ( FIG. 5 ) screwed onto screw  34  ( FIG. 7 ) to actuate covers  6 ,  8  along a common longitudinal axis X, such that pivoting components (pivot bars  10 ,  12 ; inner gear  38 ) and static components (tubing attachment bracket  18 ,  20 ; outer gears  36 ; covers  6 ,  8 ) adjacent to pivoting components of the completed backrest adjustment mechanism  2  rotates about or is positioned along the same common axis X. The independent backrest adjustment mechanism  2 A,  2 B act in unison with only a single pull of pull string  4 . Therefore, backrest  26  can be angle adjusted by only a single actuation of the actuation mechanism, for example a pull string  4 . 
         [0065]    Another embodiment of the present invention only includes a single backrest adjustment mechanism  2  when there is only one wheelchair tubing  17  to hold backrest  26  as shown in  FIG. 20 . Single backrest adjustment mechanism  2  includes cable or pull string  208  attached to handle  204 . When handle  204  is pulled in a direction substantially along common longitudinal axis X, then mechanism  2  is released as described above. 
         [0066]    Another embodiment of the present invention can include a quick-release mechanism for taking a part of backrest for folding wheelchair users. Quick release mechanism will improve transportability when the backrest is removed quickly instead of having to loosen the mounting screws. 
         [0067]    Another embodiment of the present invention can include a remote control  200  or push buttons for angle adjustment. For the angle adjustment, the mechanism  2  is on the back side of backrest  26  using a string  4  to pull in direction Y 2  for release mechanism  2  ( FIG. 23 ). In addition to placing the angle adjustment actuation mechanism, e.g. pull string  4 , on the back side of backrest  26 , a remote control  200  with lever  206  ( FIGS. 21A and 21B ), similar to a bicycle brake cable, can be adapted to actuate cable  202  attached to pull string  4 , which is attached to covers  6 ,  8  to draw covers  6 ,  8  toward each other (Z 1 , Z 2 ) to release the gears  36 ,  38 .  FIG. 21A  illustrates remote control  200  in locked position.  FIG. 21B  illustrates that cable  202  is drawn into remote control  200  when lever  206  is rotated in direction F. When lever  206  is released, lever  206  will return automatically to the locked position ( FIG. 221 ) because spring  46  decompresses thereby closing covers  6 ,  8  and pulling cable  202  back to its original position ( FIG. 23 ). 
         [0068]    Another embodiment of the remote control can be adapted to select a pre-set angle. For example, angles can range from −5° to 55° with 72 teeth in the gears at 5° increments, so there are 12 different angle positions. Another embodiment includes 6 positions at 10° increments. Pre-set angles can also be customized to users&#39; preference. The pre-sets would be perfect position for usual, reclined position for rest or dressing, forward position for working on tables and so on. 
         [0069]    An alternative pivot bar  110  is illustrated in  FIG. 19 . Pivot bar  110  has several slots and holes for different purposes. From the center of pivot bar  110 , there are two symmetrical slots  112 A,  112 B at the each end  114 A,  114 B of pivot bar  110  for screws (not shown) to attach to tubing attachment brackets (not shown). There is one hole  116  in the center  118  for pivot point. There are two fanwise slots  120  near center hole  116  to limit the angle of recline. 
         [0070]    As discuss above, there is a choice of desired height to attach brackets  18 ,  20  to wheelchair tubes  14 ,  16 . For the backrest height selection, screws (not shown) are loosened, height adjusted, and screws are tightened by anyone without special skills or training. Also discussed above is the horizontal adjustment (fore-aft) whereby the pivot bar slots  112 A,  112 B are moveably connected to the J-shaped brackets. One embodiment of pivot bar slots  112 A,  112 B can be 1 inch length, which means the adjustment is one inch of horizontal adjustment. 
         [0071]    In use for the present invention is in clinics as an evaluation tool for setting a comfortable position for other wheelchairs not equip with the angle adjustable backrest. It would be to determine suitable angle of the backrest during client evaluation in the seating clinic. At the seating clinics, as the clients are selecting the suitable chair, clinicians would have a tool that will allow them to decide on an appropriate angle for the backrest. 
         [0072]    One of the advantages of the angle adjustable backrest is for periodic changes in angles to help with pressure relief while seated. 
         [0073]    While the disclosure has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the embodiments. Thus, it is intended that the present disclosure cover the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.