1. Field of the Invention
This invention relates generally to a height adjustable seat and particularly a height adjustable seat suitable for use in wheelchairs.
2. State of the Prior Art
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.
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's body on the seat, and to provide such capability in a seat suitable for installation in wheelchairs, including folding wheelchairs.
This invention provides a height adjustable or riser seat which is responsive to repositioning of the user's body weight on the seat.
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's body weight from the seat onto a ground surface such that the spring overcomes the user'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.
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'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.
Preferably, the seat is depressed from an elevated to a lowered position when the user's body assumes a relatively reclined position wherein the user's body weight overcomes said urging of said spring. Conversely, the seat may be elevated from a lowered position if the user's body is partially offloaded from said seat onto a ground surface such that said spring overcomes the user'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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
With reference to the accompanying drawings wherein like elements are designated by like numerals,
A telescoping support 18 is mounted between the side frame subassemblies 12a, 12b, 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
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
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
In the embodiment of
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 26a of tubular member 26 into frictional engagement against the inside of tubular member 28. For example, the center of gravity of the user'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.
A friction plate 30 may be welded at the top of the lower tubular member 26 with an inside edge 30a oriented for engaging the inside surface 28a of the upper member 28 so as to enhance frictional engagement as the upper member 28 is urged against the inside edge 30a by the user's body weight on seat 20.
This frictional engagement between the telescoping members 26, 28 can be controlled by adjustment and repositioning of the seated user's body weight on seat 20.
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'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.
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.
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.
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.
In the first embodiment of this invention shown in
For example, as best understood by reference to
A second embodiment of the invention shown in
The telescoping support 18′ is supported firstly at center pivot 16′. Foldable slide braces 36a, 36b 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
It will be noted that in the second embodiment of
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
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.