Patent Publication Number: US-8985618-B2

Title: Wheelchair comprising a height-adjustable and incline-adjustable seat

Description:
TECHNICAL FIELD 
     The invention relates to a wheelchair having an underframe on which front steering wheels and rear drive wheels are fastened at a spacing to one another, a seat frame which is fastened on the underframe so as to be height-adjustable, is mounted so as to be pivotable about a pivot axis and is adjustable in its inclination with regard to the horizontal and in its height, and a backrest frame which is connected to the seat frame which consists of two oppositely situated longitudinal tubes and at least one transverse tube which connects the longitudinal tubes together, wherein the seat frame is connected to the underframe by means of at least two telescopic tubes which are formed from a bottom and a top tube each, and the bottom ends of the bottom tubes are fastened in a rigid manner to the underframe. 
     BACKGROUND 
     Such a wheelchair is known, for example, from U.S. Pat. No. 5,884,928 A. 
     DE 10 2009 049 536 A1 makes known a wheelchair where the seat is adjustable in height and inclination. The seat frame serves for receiving the seat shells or orthopedic seats (which are to be understood as synonymous in the following text) and together with said seat shells forms the seat system for persons who are unable to sit independently as a result of a disability. Seat shells and orthopedic seats are produced individually for said persons because, as a rule, they have serious physical limitations. The seat system is to compensate possibly for existing deformations of the skeleton (for example aligning the pelvis horizontally). As in the case of all sitting persons, the body weight is absorbed to a great extent in the ischium region. In the case of persons with movement limitations, the continual pressure load can result in decubitus. To reduce the risk of decubitus, the body weight has to be distributed over a larger support surface. This is achieved as a result of the inclination of the seat system, the inclination of the seat system being adjusted as a result of an inclination of the seat frame. 
     In particular when the adjustable region of the inclination is large, for example up to 50°, and the weight of the person utilizing the seat system is heavy, it is necessary for the actuating forces in the case of a change in inclination to be low in order to make the optimum adjustment easier for a carer. The simplest way to reduce the actuating forces is to displace the rotational axis into the common center of gravity of the seat system and the user (patient). 
     In the case of the wheelchair known from US 2009/0045599 A1, the rotational axis of the seat system is provided in the vicinity of the center of gravity of the user in order to realize angles of inclination of the seat system of up to 50°. Said wheelchair is structurally very expensive. The adjustability of the seat system or of the seat frame can certainly be made easier by means of a telescopic cylinder, the mechanism connected thereto makes the wheelchair more expensive, increases its weight, as a result of which the handling characteristics are impaired, and it is additionally susceptible to faults. 
     DE 89 08 374 makes known an interchangeable device for a seat which can be connected to an underframe. Said underframe can be a baby-stroller or a wheelchair for children. To this end, the seat is mountable so as to be rotated by 180° such that the line of vision of the person received by the seat is either directed forward or rearward. The seat is fastened on the underframe by means of an adjustable safety lock. 
     U.S. Pat. No. 2,986,200 discloses a wheelchair where the seat is able to be pivoted from a vertical into a horizontal position in order to be able to transport disabled persons not only sitting but also lying. The seat can assume the function of a bed in the horizontal position. 
     DE 10 2004 045 388 B4 makes known an electric wheelchair where the seat is adjustable automatically in its inclination such that the seat always remains in the horizontal even when going up and down. Two guide rails, which are mounted in each case in four rollers which are fixed to the chassis, are fastened to the driver&#39;s seat for this purpose. If the vehicle travels uphill, the seat is pivoted about a virtual pivot point which is situated in the vicinity of the mass pivot point of a person sitting on the seat. 
     SUMMARY 
     Proceeding from said problem definition, the wheelchair described in the introduction is to be improved such that it is not only constructed in a simple manner and comprises a low weight, but also makes it easy to adjust the inclination of the seat system. 
     For solving the problem, a generic wheelchair is distinguished in that the top ends of the top tubes are connected to the seat frame in the rotational axis and a latching plate which is connected to the top tubes is fastened on each of the longitudinal tubes for adjusting the inclination of the seat frame, and that the rotational axis is provided above the seat frame. 
     As a result of the two telescopic tubes, the height of the seat frame is easily adjustable—and in particular is also easily manually adjustable. As a result of the top tubes being connected to the seat frame in the rotational axis, the pivot point of the seat frame lies above its center of gravity, as a result of which it becomes possible to place the pivot axis of the seat system into the vicinity of the overall center of gravity, which is formed from the center of gravity of the seat system and from the center of gravity of the user. The inclination can be adjusted as a result of the latching plate which preferably comprises a latching means which extends in an arcuate manner with a radius which corresponds to the effective spacing between the latching bolt and the rotational axis. In order to be able to adjust the inclination in steps, the latching plates comprise a latching means. The spacing between the latching bores themselves determines the steps of the adjustability. 
     An upwardly projecting seat bracket is preferably mounted on each longitudinal tube so as to be displaceable in the longitudinal direction, the top end of which seat bracket is connected to the top tube in the rotational axis. 
     In order to facilitate the adjustability of the seat bracket and consequently the displaceability of the center of gravity in the horizontal position, the seat brackets are preferably mounted on the longitudinal tubes so as to be steplessly displaceable. The seat brackets are preferably clampable in a positive locking manner with the longitudnal tubes for fixing. 
     In order to be able to adapt the stability of the wheelchair to the change in the position of the overall center of gravity, the spacing between the steering wheels and the drive wheels (wheel base) is in particular steplessly adjustable. 
     In a preferred manner, the telescopic tubes can be telescoped in steps. 
     In order to be able to adapt the seat frame to the width of the seat shell or of the seat, the at least one transverse tube is realized so it can be telescoped. 
     The seat shell (or the seat) which, together with the seat frame and the backrest frame, forms a seat system, is insertable into the seat frame. The overall center of gravity, which is composed of the center of gravity of the seat system and the center of gravity of a person sitting in the seat system, lies at least in the direct vicinity of, preferably on the rotational axis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the invention is to be described in more detail by means of a drawing, in which: 
         FIG. 1  shows the perspective representation of the wheelchair without a seat system; 
         FIG. 2  shows another perspective representation of the wheelchair according to  FIG. 1 ; 
         FIG. 3  shows a part representation of the wheelchair according to  FIG. 1 ; 
         FIG. 4  shows a perspective exploded drawing of the wheelchair; 
         FIG. 5  shows a part representation of the wheelchair according to  FIG. 4 ; 
         FIG. 6  shows a detail from  FIG. 5 ; 
         FIG. 7  shows a further part representation of the wheelchair; 
         FIG. 7   a  shows a detail to illustrate the locking means according to  FIG. 7 ; 
         FIG. 8  shows a part exploded drawing of the wheelchair; 
         FIG. 9  shows a detail from  FIG. 8 ; 
         FIG. 10  shows an exploded drawing of a detail; 
         FIG. 11  shows the wheelchair with the seat system and user; 
         FIG. 12  shows an exploded drawing of a detail of the wheelchair; 
         FIG. 13  shows the section along the line XIII-XIII according to  FIG. 1  to illustrate the adjustment mechanism for the seat inclination; 
         FIG. 14  shows the representation according to  FIG. 13  in the inclined position (unlocked adjustment mechanism); 
         FIG. 15  shows a side view of the wheelchair; 
         FIG. 16  shows an enlarged representation from  FIG. 13  (locked adjustment mechanism); 
         FIG. 17  shows an enlarged representation from  FIG. 14 ; 
         FIG. 18  shows the representation of the seat fastening. 
     
    
    
     DETAILED DESCRIPTION 
     The wheelchair consists of the underframe  1  and the seat frame  3 , which is connected by means of the telescopic tubes  2  and into which the seat shell  4  is inserted. The two front steering wheels  6  and the two rear drive wheels  7  are fastened on tubes  5  of the underframe  1  which extend in the longitudinal direction L. The drive wheels  7  are fastened on the tubes  5  by means of clamping lugs  8  and the spacing in the longitudinal direction L between a steering wheel  6  and a drive wheel  7 , that is the wheel base, is steplessly adjustable by the clamping lug  8  being released and displaced in the desired direction on the tube  5  and retightened again (cf.  FIG. 6 ). 
     The seat frame  3  consists of the two oppositely situated longitudinal tubes  9  and the two transverse tubes  10  which extend at right angles transversely with respect to said longitudinal tubes and connect the longitudinal tubes  9  together. The transverse tubes  10  consist of the outer tubes  10   b , which are welded to the longitudinal tubes  9  and into which an inner tube  10   a  can be inserted and screw connected. Bottom transverse tubes  10  connect the bottom longitudinal tubes  5  of the underframe  1  in the same manner. Two seat lugs  11  are fastened on the longitudinal tubes  9  so as to be steplessly adjustable. The seat lugs  11  extend vertically upward and receive the arm rests  12  at their top end. The top tube  2   a  of the telescopic tubes  2  is fastened on the top end of the seat lug  11  above the seat frame  3  so as to be pivotable in the rotational axis D. The bottom tube  2   b  of the telescopic tubes  2  is connected rigidly to the longitudinal tubes  5  of the underframe  1 . The seat  4  is fastened on the seat tubes  9  by means of lugs  30 ,  31  (cf.  FIG. 18 ). The lugs  30 ,  31  are screw-connected to the under surface of the seat  4 . Their ends facing the longitudinal tubes  9  are bent downward at right angles. The ends fastened to the seat comprise elongated holes  32 ,  33  such that the lugs  30 ,  31  are able to be adapted in their relative position in a stepless manner to the longitudinal tubes  9 . Seats  4  which are individually adapted to the user can consequently be adapted simply to the seat frame  3  and fastened to the same. In the usual manner, the seat  4  consists of the seat surface  4   a , on which the user sits, and the seat back  4   b  which supports his back. For lateral support, side wings can be provided on the seat surface  4   a  and the seat back  4   b  (cf.  FIG. 11 ). The rotational axis D is consequently situated above the seat surface  4   a.    
     A latching plate  14 , which comprises a latching means  15  which extends in an arcuate manner, is provided on each of the longitudinal tubes  9  of the seat frame  3 . The latching plates  14  are steplessly displaceable in the longitudinal direction L together with the seat lugs  11  on the longitudinal tubes  9  and are clampable thereon in a positive locking manner. The radius R of the circular arc of the bores  15   a , which are spaced apart from one another and form the latching means  15 , corresponds to the effective spacing between the rotational axis D and the latching bolt  21  which is fastened on the top tube  2   a  and interacts with the latching means  15 . The back rest frame, which is formed from the two tubes  18 , on the top end of which push handles  19  are provided, is provided at the rear end of the seat frame  3 . The foot supports  20  are fastened at the front on the longitudinal tubes  9 . 
     The bottom tubes  2   b  of the telescopic tubes  2  are provided laterally with a plurality of bores  2 ′ which are spaced apart from one another in parallel. The top tubes  2   a  comprise lateral bores  2 ″. The length of the telescopic tubes  2  and consequently the height of the seat frame  2  can be adjusted by means of the bores  2 ′,  2 ″ by means of a releasable screw connection. 
     The adjusting of the angle of inclination α of the seat frame  3  is effected as follows: 
     A tube  17 , which comprises a spring-loaded latching bolt  21  in the region of each of its two outer ends (cf.  FIGS. 7 ,  7   a ), is arranged below the front transverse rod  10 . The latching bolts  21  are displaceable against the force of the spring  22  in the direction of the arrow. To adjust the inclination of the seat there is provided a release pedal  23 , which is actuatable by the operating person and is connected to the flange  25  by means of a lifting mechanism  24 , by means of which flange the movement is transferred to the locking device which is shown in detail in  FIG. 12 . When the release pedal  23  is stepped on, the locking bolt  21  is displaced against the force of the spring  22  and is moved out of the bore  15   a  of the latching plate  14 . It is then possible to adjust the inclination of the seat  4 . When the actuating pedal  23  is released, the latching bolt  21  springs back into its original position and, once it moves into coincidence with the desired bore  15   a , latches into place again, and the seat  4  is fixed in its inclination at the desired angle α. 
     The transverse tubes  10  of the seat frame  3  can be telescoped for adjusting the width. The outer tubes  10   b  are screw-connected to the inner tube  10   a . The backrest frame is formed by the two tubes  18  which are connected to the longitudinal tubes  9  of the seat frame  3 . 
     List Of References
           1  Underframe     2  Telescopic tube     2   a  Top tube     2   b  Bottom tube     2 ′ Bore     2 ″ Bore     3  Seat frame     4  Seat shell/seat     4   a  Seat surface     4   b  Seat back     5  Longitudinal tube     6  Steering wheel     7  Drive wheel     8  Clamping lug     9  Longitudinal tube     10   a  Inner tube     10   b  Outer tube     10 ′ Bore     11  Seat bracket     12  Armrest     14  Latching plate     15  Latching means     15   a  Bore     17  Tube     18  Tube     19  Push handle     20  Foot support     21  Latching bolt     22  Compression spring     23  Release pedal     24  Lifting mechanism     25  Flange     30  Lug     31  Lug     32  Elongated hole     33  Elongated hole   D Rotational axis   H Horizontal   L Longitudinal direction   R Radius   α Angle of inclination