Abstract:
An adjustable height seat for a wheelchair has a seat supported on a telescoping support. The seat rises and lowers in response to repositioning of the user&#39;s body weight on the seat. A spring normally urges the seat towards an elevated condition. The seat is depressed when the user&#39;s body assumes a relatively reclined position to overcome upward urging of the spring. Conversely, the seat rises when the user&#39;s body weight is partially rested on a ground surface allowing the spring to lift the seated user&#39;s remaining body weight. The telescoping support is frictionally arrested in a generally upright or forward leaning position of the seated user. The adjustable height seat can be installed in a wheelchair frame either permanently or interchangeably with a conventional wheelchair seat.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates generally to a height adjustable seat and particularly a height adjustable seat suitable for use in wheelchairs.  
         [0003]     2. State of the Prior Art  
         [0004]     Various efforts have been made towards providing seats which can assist feeble person in rising from and sitting down on the seat. It is also known to provide wheelchairs with a mechanism designed to help the user rise from a seated position to a standing position.  
         [0005]     A need exists for a seat capable of raising a seated user to a more convenient height to facilitate certain tasks, such as reaching for merchandise on store shelving while shopping or working on a kitchen counter top, for example. It is especially desirable to provide such a height adjustable seat which is responsive to repositioning of the user&#39;s body on the seat, and to provide such capability in a seat suitable for installation in wheelchairs, including folding wheelchairs.  
       SUMMARY OF THE INVENTION  
       [0006]     This invention provides a height adjustable or riser seat which is responsive to repositioning of the user&#39;s body weight on the seat.  
         [0007]     The adjustable height seat has a chair frame, a seat supported on a movable member slidable relatively to a stationary member on the frame, a spring normally urging the movable member towards an elevated condition, the movable member and the stationary member being arranged and configured such that the movable member is arrested against movement relative to the stationary member in a generally normal upright or forward leaning seated position of the user such that the seat remains at a selected position relative to the frame, and the body weight of the user overcomes the urging of the spring in a relatively reclining position of the user thereby to depress the movable member for lowering the seat on the frame, and the seat can be raised on the frame by partially offloading the user&#39;s body weight from the seat onto a ground surface such that the spring overcomes the user&#39;s remaining body weight on the seat thereby elevating the movable member and the seat. The movable member and the stationary member may be assembled in telescoping relationship to provide a telescoping support in which the movable member can be arrested by frictional engagement with a stationary member.  
         [0008]     The adjustable height seat of this invention may be also understood as having a chair frame, a telescoping support mounted to the chair frame, a seat supported on the telescoping support, a spring normally urging said telescoping support towards an elevated condition, the telescoping support being operative for raising and lowering the seat relative to the chair frame responsive to repositioning of a user&#39;s body weight on the seat. The chair frame may be of any suitable design, and may be a wheelchair frame including a folding wheelchair frame. In the case of a folding wheelchair frame, one or both of the movable and stationary members may be removable from the chair frame to permit folding of the chair frame.  
         [0009]     Preferably, the seat is depressed from an elevated to a lowered position when the user&#39;s body assumes a relatively reclined position wherein the user&#39;s body weight overcomes said urging of said spring. Conversely, the seat may be elevated from a lowered position if the user&#39;s body is partially offloaded from said seat onto a ground surface such that said spring overcomes the user&#39;s remaining body weight on said seat and causes telescoping extension of said telescoping support for raising said seat relative to said frame. The telescoping support is frictionally arrested against substantial telescoping movement in a generally upright or forward leaning seated position of the user on said seat for holding the seat at a desired position.  
         [0010]     In one form of the invention the telescoping support is inclined away from the vertical. In the case where the chair frame has a back, a front and two sides, the telescoping support may be inclined towards the front between the sides.  
         [0011]     In one possible configuration the telescoping support has an upper member telescopically slidable relative to a lower member, and the seat is mounted on the upper member. The upper and lower members may be tubular members of rectangular cross section telescopically slidable relative each other, for example, the upper member slidable within the lower member. The spring, such as a gas spring, may be contained in the tubular upper and lower members.  
         [0012]     In one embodiment of the invention the adjustable height or riser seat is installed in a folding wheelchair of the type generally comprising a wheel chair frame having left and right frame subassemblies, a scissor arrangement including a center pivot interconnecting the frame subassemblies for movement towards and away from each other between a deployed condition and a folded condition of the wheel chair. The telescoping support and seat are mounted between the frame subassemblies.  
         [0013]     In one form of the invention the telescoping support is mounted in a riser seat frame which is removably suspended from the wheelchair frame. The riser seat frame is removed from the wheelchair frame to permit folding of the wheelchair frame or to install a non-rising seat as a replacement for the riser seat.  
         [0014]     In another form of the invention a lower member of the telescoping support is permanently mounted to the wheelchair frame, and the seat attached to an upper member of the telescoping support is removable from the permanently mounted lower member to allow folding of the wheelchair.  
         [0015]     The height adjustable seat can be installed in a folding wheelchair frame of the type having a folding scissor arrangement with cross braces for interconnecting two side frame subassemblies. In such case the telescoping support may be supported at the center pivot of the scissor arrangement, and a second support point may be provided by foldable slide braces included in the scissor arrangement thereby to hold the telescoping support upright between the frame subassemblies.  
         [0016]     In an alternate form of the invention suitable for folding and non-folding wheel chair frames, the telescoping support is mounted on a removable riser seat frame adapted to be suspended between the frame subassemblies of the wheel chair and to be removed for folding of the wheel chair frame or for replacing the riser seat with a non-rising seat. The removable riser seat frame can be installed in a wheel chair frame as a replacement for a conventional wheelchair seat. The riser seat frame may be of adjustable width to fit wheel chair frames of different width.  
         [0017]     The removable riser seat frame may have a pair of transverse supports connected by a pair of longitudinal beams, with the telescoping support being mounted between the longitudinal beams. Hanger brackets may be provided on each of the transverse supports for suspending the riser seat frame from the left and right frame subassemblies of the wheelchair frame. The transverse supports are of telescoping length for adjusting the spacing between the hanger brackets thereby to fit wheel chair frames of different width, and fasteners may be provided for fixing the length of the transverse supports.  
         [0018]     These and other improvements, advantages and features of this invention will be better understood by reference to the detailed description of the preferred embodiments set forth below, taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  is a right side elevational view of a wheel chair with a height adjustable riser seat on a removable riser seat frame;  
         [0020]      FIG. 2  is a fragmentary front view of the riser seat and frame of  FIG. 1  supported on the wheel chair&#39;s side frames;  
         [0021]      FIG. 3  is a perspective view of the removable riser seat frame of  FIG. 1  with the seat and upper telescoping member removed to show the upper end of the gas spring extending from the stationary lower member of the telescoping support;  
         [0022]      FIG. 4  is a vertical cross section of the telescoping support of  FIG. 1  shown in fully retracted condition and the seat in fully depressed position;  
         [0023]      FIG. 5  is a front elevational view of the scissor arrangement of a folding wheel chair frame equipped with a height adjustable riser seat;  
         [0024]      FIG. 6  shows the scissor arrangement of  FIG. 5  in folded condition;  
         [0025]      FIG. 7  is a section taken along line  7 - 7  in  FIG. 5 ;  
         [0026]      FIG. 8  is a section taken along line  8 - 8  in  FIG. 5 ;  
         [0027]      FIG. 9  is a section taken along line  9 - 9  in  FIG. 5 ; and  
         [0028]      FIG. 10  is a section taken along line  10 - 10  in  FIG. 5 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]     With reference to the accompanying drawings wherein like elements are designated by like numerals,  FIG. 1  shows a wheel chair generally designated by numeral  10  which has a non-folding wheel chair frame  12  having left and right side frames  12   a ,  12   b . Each side frame has two legs, including a front leg  11   a  and a rear leg  11   b , two horizontal cross members  13   a ,  13   b  and an arm rest  21  between the front and rear leg. A bottom runner  11   c  connects the lower ends of front and rear legs  11   a , 11   b . The rear leg  11   a  has an extended upper portion which supports one side of a back rest  17  and terminates in a handle  19 . A castor wheel  23  is attached to the front leg  11   a  and a larger wheel  27  is mounted to rear leg  11   b  on axle  27   a . The two side frames  12   a ,  12   b  are interconnected by cross members  23   a , 23   b  joined at their intersection by a center fastener  16 .  
         [0030]     A telescoping support  18  is mounted between the side frame subassemblies  12   a ,  12   b , and a seat  20  is supported on an upper end of the telescoping support  18  for movement between a lowered and an elevated condition, shown in solid and phantom lining, respectively, in  FIG. 1 .  
         [0031]     The telescoping support  18  has two tubular members  26 ,  28  which may be steel tubes of rectangular cross section, assembled in sliding telescoping relationship as best seen in  FIG. 4 . The lower, outer tubular member  28  has a closed bottom  25  and an upper end  29 . The upper, inner member  26  is telescopically slidable into and out of outer member  28 . The outside cross section of inner member  26  is slightly undersized to the internal cross section of outer member  26 . The upper end  32  of upper member  26  is closed by a plate  31  which supports the seat  20  at the upper end of the telescoping support  18 . A gas spring  22  is contained in compression between closed bottom  25  and plate  31  for normally urging the telescoping support  18  towards extension and the seat  20  towards an elevated condition. The gas spring  22  has a gas cylinder  22   a  and a piston rod  22   b  driven upwardly against the underside of seat  20  by the gas compressed in the gas cylinder  22   a.    
         [0032]     In general, the adjustable height seat of this invention has a seat  20  supported on a movable member  26  slidable relatively to a stationary member  28  supported on the frame  12 , such as wheel chair frame  12  in  FIG. 1 , a spring such as gas spring  22  normally urging the movable member  26  towards an elevated condition, the movable member  26  and the stationary member  28  being arranged and configured such that the movable member  26  is arrested against movement relative to the stationary member  28  in a generally normal upright or forward leaning seated position of a user on seat  20  such that the seat  20  remains at a selected position relative to the frame  12 , and the body weight of the user overcomes the urging of the spring  22  in a relatively reclining position of the user thereby to depress the movable member  26  for lowering the seat on the frame  12 , and the seat  20  can be raised on the frame  12  by partially offloading the user&#39;s body weight from the seat  20  onto a ground surface G such that the spring  22  overcomes the user&#39;s remaining body weight on the seat  20  thereby elevating the movable member  26  and the seat  20 . The movable member  26  and the stationary member  28  may be assembled in telescoping relationship to provide a telescoping support  18  in which the movable member  26  can be arrested by frictional engagement with a stationary member  28 .  
         [0033]     In the embodiment of  FIGS. 1 through 4  the telescoping support  18  is mounted at an inclined angle θ such as about 15 degrees to the vertical within a vertical plane contained between and generally parallel to the side frame subassemblies  12   a ,  12   b . The support  18  is inclined towards the front of the chair frame  12  in  FIG. 1 .  
         [0034]     The seat  20  is located in relation to the telescoping support  18  so that the center of gravity of the user while in a generally upright or slightly forward leaning seated position applies a substantial transverse force to the upper end of slidable inner member  26 , forcing the forward side  26   a  of tubular member  26  into frictional engagement against the inside of tubular member  28 . For example, the center of gravity of the user&#39;s body weight may be located just forward of the top end  32  of telescoping support  18  when the user is seated in that position. This frictional engagement operates as a brake to arrest the tubular members  26 ,  28  against relative telescoping displacement and to thereby hold seat  20  at a selected elevated position relative to the wheel chair frame  12 .  
         [0035]     A friction plate  30  may be welded at the top of the lower tubular member  26  with an inside edge  30   a  oriented for engaging the inside surface  28   a  of the upper member  28  so as to enhance frictional engagement as the upper member  28  is urged against the inside edge  30   a  by the user&#39;s body weight on seat  20 .  
         [0036]     This frictional engagement between the telescoping members  26 ,  28  can be controlled by adjustment and repositioning of the seated user&#39;s body weight on seat  20 .  
         [0037]     The user on seat  20  can reduce the frictional braking force between the telescoping members  26 ,  28  by leaning back or reclining on seat  20 , thereby shifting the center of gravity of his or her body weight rearwards of the top end  32  of the telescoping support, thereby reducing the transverse force component and consequently the frictional engagement between the telescoping members. Such shift in body weight frees the tubular members  26 ,  28  for sliding telescoping displacement relative to each other, and allows the body weight of the seated user to overcome the upward urging of the gas spring  22 . The gas spring is chosen to have a spring force appropriate to the body weight of the user so as to allow the user&#39;s body weight to compress the gas spring in this manner. Normally, the gas spring is chosen to have a spring force lesser than the body weight of the user for this reason.  
         [0038]     Conversely, the seated user is able to elevate seat  20  to a convenient height by partially offloading his or her body weight from seat  20  sufficiently to allow the upward force of spring  20  to overcome the remaining body weight on seat  20  to be lifted along with the seat by the spring force. The user can accomplish this offloading by placing his or her feet on the ground G in front of the wheelchair  10  and resting part of his or her body weight onto the ground surface G, thereby reducing the body weight bearing down seat  20  until the spring force overcomes the remaining body weight, causing extension of the telescoping support and raising the seat  20 .  
         [0039]     The user can stop the seat at an elevated position by assuming the aforementioned upright or slightly forward leaning seated position on seat  20 , thereby again causing the inner member  26  to bear against the friction plate  30  thereby arresting further telescoping displacement between the telescoping members  26 ,  28 .  
         [0040]     The user can assist in changing the elevation of the seat both up and down by pushing down or pulling up on the armrests  21  of the wheelchair  10 .  
         [0041]     In the first embodiment of this invention shown in  FIGS. 1 through 4 , the telescoping support  18  with seat  20  is mounted on a removable riser seat frame  40  which can be installed in a wheelchair having either a folding or non-folding wheelchair frame such as frame  12 . In this first embodiment telescoping support  18  is mounted on a riser seat frame  40  adapted to be removably suspended between side frame subassemblies  12   a ,  12   b  of the wheel chair frame  12 . The removable frame  40  is preferably of adjustable width so as to fit wheel chairs having different widths between frame subassemblies  12 ,  12   b . The frame can be lifted away from the frame  12  and carried or stored separately, while wheelchair frame  12  can be folded for storage or transport.  
         [0042]     For example, as best understood by reference to  FIG. 3  the riser seat frame  40  has a pair of transverse supports  42   a ,  42   b  connected by a pair of longitudinal beams  44   a ,  44   b , with the telescoping support  18  mounted between the longitudinal beams  44   a ,  44   b . The top end  29  of the outer tubular member  28  is suspended from friction plate  30  which spans cross beams  44   a ,  44   b . Hanger brackets  46  are provided on each of the transverse supports  42   a ,  42   b  for suspending frame  40  from frame subassemblies  12   a ,  12   b  of the wheelchair frame  12 . The transverse supports  42   a ,  42   b  may have telescoping ends  43  for adjusting the spacing between the hanger brackets and thereby effectively adjust the width of frame  40 . Fasteners  52  may be provided for fixing the length of the transverse supports at a desired width of frame  40 . In  FIG. 3  the seat  20  together with the inner tubular member  26  have been removed from the telescoping support  18  for clarity of illustration, allowing the piston rod  22   b  of the gas spring  22  to extend from the open upper end  29  of the outer tubular member  28 .  
         [0043]     A second embodiment of the invention shown in  FIGS. 5 through 10  is a height adjustable seat installed in an otherwise conventional folding frame wheelchair. The folding wheel chair frame has left and right side frame subassemblies  12 ′ a ,  12 ′ b  similar to those shown in  FIG. 1  but interconnected by a scissor arrangement which folds as shown in  FIG. 6  to bring together the side frames. The seat and backrest may be foldable slings or are removable from the frame prior to folding.  
         [0044]      FIG. 5  shows a scissor arrangement  14  such as used in some existing folding wheel chair frames. The scissor arrangement  14  includes diagonal cross braces  34   a ,  34   b  interconnecting side frame subassemblies  12 ′ a ,  12 ′ b  and joined for scissor movement at center pivot  16 ′. The lower ends of cross braces  34   a ,  34   b  are fastened to sleeves  82  rotatable about lower cross member  84  of frame  12 ′. The upper ends of the cross braces  34   a ,  34   b  are pivotably attached to cross member  13 ′ a  which itself is supported on sliding sleeves  86 . Sleeves  86  are slidable up and down along front and rear legs  11 ′ a ,  11 ′ b , between the deployed position of  FIG. 5  and the folded position of  FIG. 6 .  
         [0045]     The telescoping support  18 ′ is supported firstly at center pivot  16 ′. Foldable slide braces  36   a ,  36   b  provide a second support point for the telescoping support  18 ′ in a deployed condition of the scissor assembly  14  to maintain the telescoping support  18 ′ upright on the wheelchair frame  12 ′. The upper member  26  of the telescoping support is removable together with seat  20  from the lower member  28  to allow folding of the wheel chair frame  12 ′ as in  FIG. 6 .  
         [0046]     It will be noted that in the second embodiment of  FIGS. 5 and 6  the telescoping support  18 ′ is generally vertical and is not inclined away from the vertical as in the first embodiment of  FIGS. 1-4 . Nevertheless the telescoping support  18 ′ operates substantially as described in connection with telescoping support  18  of the first embodiment. This is because there is some play between the telescoping members sufficient to allow the internal member to tilt at a slight angle inside the external tubular member in response to a forward shift of the center of gravity of the seated user&#39;s body weight. This tilting brings the inside member into frictional engagement with a front top edge of the outside member, while the bottom end of the inside member is torqued in an opposite direction into frictional engagement against a rear inside surface of the outside member. The frictional engagement and consequent arresting or braking of the telescoping displacement is controlled by repositioning of the user&#39;s body weight on the seat  20  in a manner analogous to the operation described in connection with the telescoping support  18  of the first embodiment of  FIGS. 1-4 .  
         [0047]      FIGS. 7 through 10  are detail cross sections showing certain aspects of the scissor assembly of the folding wheelchair frame.  
         [0048]      FIG. 7  illustrates the center pivot  16 ′ at which cross members  34   a ,  34   b  pivot about a common pivot bolt  50  which passes through aligned diametric holes in each of the cross members. A nut  52  retains the cross members on bolt  50 . A washer  54  is placed on the bolt  50  between the cross members. A spacer sleeve  56  on bolt  50  keeps the cross members away from bolt head  58 . The bolt head  58  is welded to outer tubular member  28  of the telescoping support  18 ′ and provides a first point of support for telescoping support  18 .  
         [0049]      FIG. 8  shows how the sliding braces  36   a ,  36   b  are connected at their inner ends by a bolt  60  which passes through slots  62  in the sliding braces. The braces are retained on the bolt by a nut  64  and washer  66 . The bolt head  68  of bolt  60  is welded to outer tubular member  28  of the telescoping support  18 ′ and provides a second point of support for telescoping support  18 ′.  
         [0050]      FIGS. 9 and 10  show how the outer ends of slide braces  36   a ,  36   b  are pivoted to cross members  34   a ,  34   b  respectively on pin shafts  72   a ,  72   b  of pivot pins  70   a ,  70   b  respectively. Each pin shaft passes through a mounting sleeve  74   a ,  74   b . Each sleeve  74   a ,  74   b  passes through a diametric hole  76  in cross members  34   a ,  34   b  respectively. The slide braces  36   a ,  36   b  are captive on the respective pin shafts between the sleeves  74   a ,  74   b  and pin head  78 .  
         [0051]     The adjustable height seat described in connection with the foregoing first and second embodiments can be also implemented in chair frames or installations other than wheelchairs. The telescoping supports  18 ,  18 ′ can be mounted in any suitable manner on stationary frames for use as a stationary seat of adjustable height. For example, the riser seat frame  40  of  FIG. 3  can be fitted with legs or otherwise supported at a convenient height on a ground surface. In such case the operation of the adjustable height seat by a user is analogous to that described in connection with the wheelchair mounted embodiments above.  
         [0052]     Preferred embodiments of the invention have been described and illustrated for purposes of clarity and example. However, it must be understood that many changes, modifications and substitutions to the described embodiments will be apparent to those having only ordinary skill in the art without thereby departing from the scope of this invention, which is defined by the following claims.