Abstract:
The invention pertains to wheelchairs, and more particularly, to a wheelchair seat having a seat back member which substantially maintains a constant vertical angle when the seat bottom or rail is pivotably raised and lowered. Accordingly, the angle between a seat back and seat rail is changed during adjustment of the seat rail.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a wheelchair including a seat assembly having an upright leg member which telescopes into and out of an intermediate rear frame member in a substantially vertical manner. The seat assembly also includes a back member which maintains a substantially constant angle with respect to a vertical direction during telescoping of the upright leg member. 
     BACKGROUND OF THE INVENTION 
     The invention pertains to wheelchairs, and more particularly, to a wheelchair seat having a changeable angle between a seat back and seat bottom or rail member. Although the angle therebetween is changeable, during adjustment of the seat bottom, the seat back member substantially maintains a constant vertical angle. 
     Prior art structures utilize a multitude of complex designs and configurations. Although some such arrangements have been commercialized, the industry still seeks a compact, reliable, simple and economical seat assembly. 
     U.S. Pat. No. 5,997,021 relates to an adjustable seat back assembly for a wheelchair of the type having a frame with an upwardly extending rear frame portion and an adjustable angle seat support which includes a pivotable front end and a rear end which is secured to said rear frame portion at any of a plurality of different positions. A seat back support is mounted to a pivot on the seat support from adjacent its rear end. A link connects the seat support to a slider on the rear frame portion to maintain the position of the slider relative to the seat back support pivot as the seat angle is adjusted. A releasable seat back angle adjuster secures the seat back support to the slider at any of a plurality of positions. When the seat back angle adjuster is released, the seat back support may be folded down towards said seat support. 
     U.S. Pat. No. 5,851,018 relates to a lightweight wheelchair having adjustable wheel camber, adjustable toe-in/toe-out positions, and front-to-rear adjustment of the wheel assembly relative to the frame. The wheel camber is changed by removable camber tubes having plugs in opposite ends with different angular relationships. The camber tube is removed from an axle tube, related through one hundred eight degrees, and reinserted to change the wheel camber. The location of the angular recesses in the camber plugs addresses minor toe-in/toe-out adjustments while rotation of an axle tube provided with indicia assures that proper toe-in/toe-out adjustment is provided for larger wheel camber adjustments. The front to rear location of the wheels relative to the frame can be adjusted via a single fastener on each side. Moreover, the track width of the rear wheels can be adjusted in response to the change in wheel camber. 
     SUMMARY OF THE INVENTION 
     Wheelchair users often have different preferences or prescribed requirements for comfortable or proper positioning in a chair. In order to meet these needs, a wheelchair is provided having a seating assembly including a back member and a bottom member with the angle therebetween being adjustable. The seating assembly is designed so that the back member substantially maintains a constant angle with respect to vertical while the angle between the back member and bottom member is adjusted as the seat bottom is lowered. 
     By maintaining the back member at a constant angle, the user&#39;s center of gravity stays substantially the same, and is not allowed to move rearward upon lowering the rear of the seat, or forward upon raising of the seat, or vice versa. Another advantage of the seating assembly of the present invention is that stability and anti-tip forces are maintained even though the seating assembly is adjustable to numerous different positions. That is, if the angle of the back member were allowed to vary substantially upon lowering or raising of the chair, the wheelchair would have a greater likelihood of tipping. 
     Both the back member and bottom or rail member are operably connected to a seat bracket. Attached to the seat bracket is an upright leg member which telescopes downwardly into an intermediate rear frame member in order to change the angle of the seating assembly. Through independent adjustment, the angle of the back member with respect to vertical can also be adjusted. 
     Therefore, it is an object of the present invention to provide a wheelchair with a simple, quickly adjustable seat assembly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the present invention, the a accompanying drawings incorporated in and forming a part of the specification, illustrate several aspects of the present invention, and together with the description, serve to explain the principles of the invention, wherein: 
     FIG. 1 is a perspective view of a manual wheelchair incorporating the adjustable seat assembly of the present invention; 
     FIG. 2 is a side elevational view of selected components of FIG.  1  and particularly illustrating the seat assembly; 
     FIG. 3 is a view somewhat similar to FIG. 2 further illustrating some of the positions in which the seat assembly can be maintained; 
     FIG. 4 is an exploded view of the upright leg member and intermediate rear frame member interface showing that the same can be adjustably positioned in numerous positions with respect to each other; 
     FIG. 5 is a perspective view of a power wheelchair utilizing the seating assembly of the present invention; and 
     FIG. 6 is a rear elevational view of the upright leg member and intermediate rear frame member, both of which contain various holes to allow the seating assembly to be secured in numerous positions. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The drawings are referred to now herein below for the purposes of illustrating the preferred embodiment of the invention only, and not for purposes of limiting the same. It is to be understood that the various aspects and parameters of the present invention can vary within the scope of the teachings herein. 
     While various components described herein below and/or shown in the drawings as located on the left-hand side or the right-hand side of the wheelchair, it is to be understood that such components exist on both sides of the chair and are generally very similar, and are usually either identical or mirror-image. 
     Referring now to FIG. 1, wheelchair  10  is a manual wheelchair having wheels  32  and front caster wheel assembly  18 . Wheelchair  10  contains seat back member  44  and seat bottom member  46 , commonly referred to as a seat rail member, operably connected through seat bracket  50 . Also illustrated in FIG. 1 are optional foot rest  24  and anti-tipping devices  25 . FIG. 1 further shows folding center frame  38  whereby the wheelchair can be folded into a more compact form, such as for easier storage as described in U. S. Pat. No. 4,712,830 hereby fully incorporated by reference. 
     As illustrated in FIGS. 1 and 2, wheelchair  10  includes frame, generally denoted as  12 , which has front portion  14  and rear portion  16 . The front end of frame portion  14  contains front caster wheel assembly  18  so that wheelchair  10  can be readily pivoted and turned in any desirable direction. Front arm  20  of front frame portion  14  has seat rail bracket  22  desirably formed integrally thereon or attached thereto for allowing pivotal movement of seat bottom member  46 . 
     Rear portion  16  of frame  10  includes top member  26  and bottom member  28 . Intermediate rear frame member  30  is located between and attached to the ends of top and bottom members  26  and  28  respectively. 
     As also illustrated in FIG. 3, seat assembly  40  includes seat back member  44  and seat rail member  46 . Back member  44  can be a metal tube or any other suitable article and can have handle  45  which can be used by an individual to push the wheelchair. Likewise, seat rail member  46 , as well as the rest of the wheelchair frame members can be metal tubes or any other suitable materials. Seat  40  can contain upholstery, cushions or other materials secured thereto in order to provide for the comfort or needs of the user. 
     As seen in FIGS. 2,  3 , and  4 , seat bracket  50  is employed to operatively connect seat back member  44  to seat rail member  46 . Seat bracket  50  allows back member  44  to be fixedly secured to the rail member at a number of reclining positions other than 90 degrees (i.e. vertical) with respect to horizontal. This is accomplished through seat bracket aperture  51  and a plurality of partially connected or scalloped apertures  52  and suitable fastening devices such as pins or bolts and nuts (not shown). In order to achieve a different degree of tilt for the back member, the fastening device is selectively placed in one of the partially connected apertures  52  which will then maintain back member  44  at a fixed angle with respect to vertical. Back member  44  can be fixedly positioned generally in a total range from about 20 to about 25 degrees. That is, desirably from about minus 10 or minus 5 degrees (forward) to about plus 10 or plus 15 degrees (rearward), and preferably from about minus 5 to about plus 5 degrees with respect to vertical. 
     Seat back member  44  can be folded down such as in a storage position when the suitable fastening device is removed from seat back member  44  and partially connected apertures  52 , allowing seat back member  44  to pivot around seat back aperture  51 . Seat bottom member  46  is pivotably and operatively attached to front frame arm  20  through seat rail bracket  22 . The other end of seat bottom member  46  is slidably and pivotably attached to seat bracket  50  through slot  53  and is thus also operatively attached to back member  44 . Slot  53  is capable of accepting a fastening device as stated above so as to allow movement in the slot between seat rail member  46  and seat bracket  50 . 
     Upright leg member  42  is fixedly attached to seat bracket  50  as can be seen at least in FIG.  3 . Upright member  42  is substantially vertically aligned and generally extends downward below the seat assembly. As seen in FIG. 3, intermediate rear frame member  30  is desirably hollow, allowing upright leg member  42  to slidably contact the same. Thus, upright leg member  42  telescopes, slidably engages, or is otherwise allowed to move upwardly and downwardly within intermediate member  30 . Upon telescopic movement of upright leg member  42 , seat rail member  46  pivots about rail bracket  22  whereby the rear portion of member  46  moves slightly back and forth and thus slides and pivots within slot  53 . Consequently, the rear portion of seat rail member  46  can be moved up and down changing the distance, i.e. height, between said rear portion and a surface upon which the wheelchair resides, such as a floor. Lettering (a) through (e) in FIG. 3 represent some of the possible positions in which seat rail member  46  can be positioned. Also, the angle between seat back member  44  and seat rail member  46  changes when the upright member  42  is telescoped within intermediate member  30 . 
     As upright leg member  42  telescopes within intermediate member  30 , the angle of seat bottom member  46  ranges generally from about 0 to about 18 degrees desirably from about 0 to about 16 degrees and preferably from about 0 to about 13 degrees with respect to horizontal. 
     FIGS. 4 and 6 show that upright member  42  and intermediate member  30  have apertures or holes  43  and  31  respectively which accept at least one fastener  47  to fix the members in relation to each other. Due to the numerous holes, it is easily seen that the members may be variably positioned to achieve any of numerous desired or needed position for the users of the wheelchair. The distance of the rear portion of the bottom member  46  to the floor can be changed or adjusted utilizing the above noted apertures, generally from about 0 to about 4.0 inches, independently of rear wheelchair wheel adjustment or caster wheel adjustment, by simply telescoping the seat through upright leg member  42  to the desired position. 
     Wheelchair  10  is also shown with a pair of large diameter rear wheels  32  which can be adjustably located at different positions of the rear frame portion  16  via wheel bracket  36  and plurality of holes  34 . Wheelchair  10 , as shown in the drawings, is a folding frame manual wheelchair, but the frame can also be a rigid frame as is commonly known in the art as shown in FIG. 5 having rigid frame  60 . Alternatively, as commonly known in the art, a motor  62  and supporting electronics, such as a motor, and battery  64 , may be utilized to power select wheels of the chair, such as rear wheels, mid wheels, or front wheels. Moreover, the wheelchair may have different wheel sizes or other features commonly known in the art. 
     Obviously, other modification and alterations with respect to the wheelchair exist. 
     In accordance with the patent statutes, the best mode and preferred embodiment have been set forth, and the scope of the present invention is not limited thereto, but rather by the scope of the attached claims.