Abstract:
A wheelchair includes an anti-wobbling roller mounted at a front portion of a seat frame and spanning across a center of the front portion in such a manner that the roller is capable of balancing the wheelchair in case the roller collides with an obstacle during forward movement of the wheelchair.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a wheelchair, more particularly to a wheelchair which includes an anti-wobbling roller for balancing the wheelchair in case the roller collides with an obstacle during forward movement of the wheelchair.  
           [0003]    2. Description of the Related Art  
           [0004]    Referring to FIG. 1, a conventional wheelchair  20  is shown to include a seat frame  10 , a pair of drive wheels  13  (only one is shown), a pair of ground-engaging castor-type idler wheels  15  (only one is shown), a pair of forward idler wheels  32  (only one is shown), and a resilient suspension unit  33 .  
           [0005]    As illustrated, the seat frame  10  has opposing front and rear frame portions  12 ,  16 , left and right frame portions  14  (only one is visible) interconnecting the front and rear frame portions  12 ,  16 , and a bottom side. The drive wheels  13  are mounted on the left and right frame portions  14  between the front and rear frame portions  12 ,  16 , and are rotatable about a first axis. The idler wheels  15  are mounted on the rear frame portion  16  of the seat frame  10 , and are rotatable about a second axis parallel to the first axis, and further about a vertical axis which is transverse to the first and second axes during left and right turning movement of the wheelchair  20 . The forward idler wheels  32  are mounted on the front frame portion  12  via a transverse rod  30  that extends in a direction parallel to the first axis. The resilient suspension unit  33  includes left and right suspension springs disposed between left and right sides of the front frame portion  12  and the idler wheels  32  for absorbing shocks.  
           [0006]    One drawback of the aforementioned conventional wheelchair  20  resides in that during forward movement of the wheelchair  20  and in case only one of the forward idler wheels  32  collides with an obstacle which is higher than the ground surface, the vibration resulting from said collision will be transmitted to the seat frame  10  to the largest extent, since the vibration is not shared by the other suspension spring which is away from the colliding idler wheel  32 .  
         SUMMARY OF THE INVENTION  
         [0007]    Therefore, the object of this invention is to provide a wheelchair which includes an anti-wobbling roller mounted on a front frame portion of the wheelchair in order to avoid the occurrence of the aforesaid drawback that generally results during use of the conventional wheelchair.  
           [0008]    Accordingly, a wheelchair of the present invention includes a seat frame, a pair of drive wheels, a pair of ground-engaging castor-type idler wheels, an elongated anti-wobbling roller, and shock-absorbing means. The seat frame has opposing front and rear frame portions, left and right frame portion interconnecting the front and rear frame portions, and a bottom side. The front frame portion has left and right ends. The front and rear frame portions cooperatively define a center line that passes through centers of the front and rear frame portions. The drive wheels are mounted on the left and right frame portions between the front and rear frame portions, and are rotatable about a first axis. Each of the drive wheels has a lowermost end for contacting a ground surface. The ground-engaging castor-type idler wheels are mounted on the rear frame portion, and are rotatable about a second axis parallel to said first axis and further about a vertical axis which is transverse to the first and second axes. The anti-wobbling roller is disposed below the bottom side of the seat frame adjacent to the front frame portion, extends between the left and right frame portions, crosses the center line, and has a lowermost end disposed at an elevation which is higher than the lowermost ends of the drive wheels. The shock-absorbing means is interposed between and connects the anti-wobbling roller and the seat frame for absorbing shock that results when the roller collides with an obstacle during forward movement of the wheelchair. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    Other features and advantages of this invention will become more apparent in the following detailed description of the preferred embodiment of this invention, with reference to the accompanying drawings, in which:  
         [0010]    [0010]FIG. 1 is a schematic side view of a conventional wheelchair;  
         [0011]    [0011]FIG. 2 is a partly exploded, perspective view of a preferred embodiment of a wheelchair of the present invention, in which a seat is removed from a seat frame for the sake of clarity;  
         [0012]    [0012]FIG. 3 is an assembled perspective view of the preferred embodiment of the present invention;  
         [0013]    [0013]FIG. 4 is a side view of the preferred embodiment, illustrating how an anti-wobbling roller is mounted thereto; and  
         [0014]    [0014]FIG. 5 is a front view of the preferred embodiment shown in FIG. 2. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]    Referring to FIGS. 2, 3 and  4 , the preferred embodiment of a wheelchair of the present invention is shown to include a seat frame  40 , a pair of drive wheels  431 , a pair of ground-engaging castor-type idler wheels  421 , an elongated anti-wobbling roller  60 , and shock-absorbing means  52 .  
         [0016]    As illustrated, the seat frame  40  has opposing front and rear frame portions  41 ,  42 , left and right frame portion  43  which interconnect the front and rear frame portions  41 ,  42 , and a bottom side  45 . The front frame portion  41  has left and right ends. The front and rear frame portions  41 ,  42  cooperatively define a center line (X) that passes through centers of the front and rear frame portions  41 ,  42 .  
         [0017]    The drive wheels  431  are mounted on the left and right frame portions  43  between the front and rear frame portions  41 ,  42 , and are rotatable about a first axis. Each of the drive wheels  431  has a lowermost end for contacting a ground surface.  
         [0018]    The idler wheels  421  are mounted on the rear frame portion  42 , and are rotatable about a second axis parallel to the first axis, and further about a vertical axis which is transverse to the first and second axes.  
         [0019]    The anti-wobbling roller  60  is disposed below the bottom side  45  of the seat frame  40  adjacent to the front frame portion  41 , extends between the left and right frame portions  43 , and crosses the center line (X) defined by the front and rear frame portions  41 ,  42 . The roller  60  has a lowermost end disposed at an elevation which is higher than the lowermost ends of the drive wheels  431  (see FIG. 4).  
         [0020]    The shock-absorbing means  52  is interposed between and connects the anti-wobbling roller  60  and the seat frame  40  for absorbing shock that results when the roller  60  collides with an obstacle during forward movement of the wheelchair.  
         [0021]    The seat frame  40  further has a pair of left and right legs  413  extending downwardly from the left and right ends of the front frame portion  41 , and a pair of connecting rods  51  that extend frontwardly from the left and right legs  413  in a direction parallel to the center line (X) and that have rear ends  511  pivoted respectively to the left and right legs  413  via brackets  412 , and front ends  513  between which the roller  60  is journalled. The seat frame  40  further has a pair of upright posts  414  that extend from the left and right ends of the front frame portion  41  in directions opposite to the left and right legs  413 , respectively. The shock-absorbing means  52  includes a pair of shock-absorbing cylinders respectively having two opposite ends  521 ,  522 , each of which is pivoted to a respective one of the connecting rods  51  and a respective one of the upright posts  414  via a bracket  411 .  
         [0022]    Since vibrations that result from collision between the roller  60  and the obstacle during forward movement of the wheelchair of the present invention can be uniformly absorbed by the cylinders, a large extent of the vibrations is not transmitted to the seat frame  40 . In addition, a large surface area of the roller  60  contacts the obstacle so as to enhance balancing of the seat frame  40 . Since the features of the present invention do not reside in the specific structure of a seat and mounting of the same on the seat frame  40 , a detailed description thereof is omitted herein for the sake of brevity.  
         [0023]    With this invention thus explained, it is apparent that numerous modifications and variations can be made without departing from the scope and spirit of this invention. It is therefore intended that the invention be limited only as indicated in the appended claims.