Abstract:
A suspension structure for a wheelchair generally includes movable arm that serve to connect driving wheels with frame of a wheelchair, sliding unit is further provided for enabling the movable arm to movably connect with a front cantilever of the wheelchair. By such arrangements, in case that the wheelchair of the present invention encounters a raised ground, or similar barriers of the like, the front cantilever will work with the movable arm to raise front jockey wheels, whereas the driving wheels firmly catches the ground, such that enables the wheelchair to the pass the barrier smoothly without difficulties.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a suspension structure for a wheelchair, and more particularly to a suspension structure comprised of front cantilever, movable arm and sliding assembly, which are provided between front jockey wheel, driving wheel and frame of a wheelchair.  
         [0003]     2. Description of the Prior Arts  
         [0004]     A conventional wheelchair with suspension structure as shown in  FIGS. 1 and 2  (as disclosed by U.S. Pat. No. 6,199,647), wherein between a frame  10 , driving wheel  11  and front jockey wheel  12  is provided with plural compression springs  13 , the compression springs  13  serve to timely raise or lower down the front jockey wheel  12  and the driving wheel  11  upon encountering a raised ground, or similar barrier of the like, so as to enable the wheelchair to overcome the barrier. However, there are some deficiencies will be found in real operation:  
         [0005]     First, the front jockey wheel  12  and the driving wheel  11  are independently structured, and which are adjusted by the compression springs  13  corresponds to road condition, in this case, upon encountering barrier, the body of the wheelchair will substantially tilt and swing sharply (caused by the compression and expansion of the compression springs), it is unsafe for user to sit on an unstable wheelchair. Moreover, the respective compression springs  13  also have elastic fatigue problem.  
         [0006]     Second, when faced with a barrier and the front jockey wheel  12  is stopped by resistance (when the front jockey wheel abuts against slopping surface of the barrier), since the suspension structures of the front jockey wheel  12  and that of the driving wheel  11  are not interactively connected, the friction of the driving wheel with the road can not be increased correspondingly, in this case, the wheelchair is not easy to roll over the barrier.  
         [0007]     Third, since the compression springs  13  serve as suspension structure for the driving wheel  11  and the front jockey wheel  12 , the suspension structure is very complexly designed as comprising at least a pair of front cantilevers  14 , a pair of drive rods  15 , four pieces of compression spring  13  and shafts  16 , a pair of stop rods  17 . Thus the cost is pretty high.  
         [0008]     The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional suspension structure for a wheelchair.  
       SUMMARY OF THE INVENTION  
       [0009]     The primary object of the present invention is to provide a suspension structure for wheelchair, which generally includes movable arm that serves to connect driving wheels with frame of a wheelchair, sliding unit is further provided for enabling the movable arm to movably connect with a front cantilever of the wheelchair. By such arrangements, upon encountering a raised ground, or similar barriers of the like, the front cantilever will work with the movable arm to raise the front jockey wheel, whereas the driving wheels firmly catches the ground, so as to enable the wheelchair to the pass the barrier smoothly without difficulties.  
         [0010]     The present invention will become more obvious from the following description when taken in connection with the accompanying drawings, which shows, for purpose of illustrations only, the preferred embodiments in accordance with the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is an illustrative view of a wheelchair equipped with conventional suspension structure;  
         [0012]      FIG. 2  is a side view of the wheelchair equipped with conventional suspension structure;  
         [0013]      FIG. 3  is an exploded view of a suspension structure for wheelchair in accordance with the present invention;  
         [0014]      FIG. 4  is a perspective assembly view of a suspension structure for wheelchair in accordance with the present invention;  
         [0015]      FIG. 5  is an operational view of the suspension structure for wheelchair in accordance with the present invention, wherein front jockey wheel rolls against a barrier;  
         [0016]      FIG. 6  is an operational view of the suspension structure for wheelchair in accordance with the present invention, wherein the front jockey wheel rolls on slopping surface of the barrier;  
         [0017]      FIG. 7  is an operational view of the suspension structure for wheelchair in accordance with the present invention, wherein the front jockey wheel rolls over the barrier;  
         [0018]      FIG. 8  is an operational view of the suspension structure for wheelchair in accordance with the present invention, wherein the front jockey wheel and the driving wheel rolled over the barrier;  
         [0019]      FIG. 9  is a perspective view of a suspension structure for wheelchair in accordance with another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     Referring to  FIGS. 3-5 , wherein a suspension structure for wheelchair is shown and comprised of movable arm  30 , front cantilever  40  and a sliding assembly  50  which are respectively provided between frame  20 , driving wheel  31  and front jockey wheel  41 .  
         [0021]     The frame  20  is main body of a wheelchair and serves to carry respective components of the wheelchair. The front side of the frame can be provided with a first ear  21  and a second ear  22 , the rear end of the frame can be equipped with rear wheel  23 .  
         [0022]     The movable arm  30  is swingingly coupled to the first ear  21  of the frame  20 . An end of the movable arm  30  is connected to the driving wheel  31 , the driving wheel  31  is driven by a motor  32  to move the wheelchair.  
         [0023]     The front cantilever  40 , a first end of which is equipped with the front jockey wheel  41  and a second of the front cantilever  40  is fixed to the second ear  22  of the frame, thus the front cantilever  40  is able to swing.  
         [0024]     The sliding assembly  50  includes a pair of slide plates  51  and a shaft  52 . Each of the slide plates  51  is defined with a slot  511 , the slides plates  51  are oppositely arranged in corresponding way and then a pair of bolts  53  are used to make the movable arm  30  slidably connect to the front cantilever  40 , and thus the bolts  52  are able to slide within the slot  511 , the shaft  52  is slidably disposed between the two bolts  52 .  
         [0025]     Based on the above-mentioned structure, the wheelchair in accordance with the present invention is able to roll over barriers  60  easily and smoothly.  
         [0026]     When running on level road, the front jockey wheel  41  and the driving wheel  31  keep contacting the ground. However, as shown in  FIGS. 5 and 6 , initially the front jockey wheel  41  will contact the sloping surface  61  of the barrier  60  upon encountering a barrier  60  and is stopped by the surface  61  (as shown  FIG. 5 ). At this moment, the driving wheel  31  keeps driving the wheelchair to move forward, with the pushing force generated by the driving wheel  31 , the front jockey wheel  41  and the front cantilever  40  will rise upward smoothly. And then, via the sliding assembly  50 , the front cantilever  40  raises an end of the movable arm  30  connecting to the sliding assembly  50 , whereas another end of the movable arm  30  connecting to the driving wheel  31  is lowered accordingly. In other words, with the first ear  21  serving as a fulcrum of the movable arm  30 , an end of the connecting  30  rises and the other end of the same is lowered.  
         [0027]     It will be noted that when the end of the movable arm  30  connecting to the driving wheel  31  is lowered, the friction of the driving wheel  31  on the road will be increased (the driving wheel will abut closely against the road), such that the driving wheel is able to drive the wheelchair efficiently to move it forward, by this way, the front jockey wheel  41  rises continuously and rolls over the sloping surface  61  of the barrier  60 . In real operation, initially the front jockey wheel  41  rises a little smoothly and then followed by a quick rise, so as to roll over the barrier  60 .  
         [0028]     After the front jockey wheel  41  overcome the sloping surface  61  of the barrier  60  (as shown in  FIGS. 7 and 8 ), the height difference between the front jockey wheel  41  and the driving wheel  31  can be adjusted by slide movement of the movable arm  30  and the front cantilever  40  with respect to the sliding assembly  50 . By this way, both the front jockey wheel  41  and the driving wheel  31  are allowed to keep contacting the road. Wherein the shaft  52  is able to make the movable arm  30  and the front cantilever  40  which located in the sliding plates  51  slide smoothly. After rolling over the barrier  60  and roll on level road again, the movable arm  30  and the front cantilever  40  will return to their original position with the help of the sliding assembly  50 . In other words, with the sliding assembly  50  to couple the movable arm  30  with the front cantilever  40  and make them to slide, the suspension structure in accordance with the present invention is able to enable wheelchair to overcome the barrier.  
         [0029]     Referring again to  FIG. 3 , between the movable arm  30  and the frame  20  can be provided with a buffer  70  which can be made of elastic rubber, the buffer  70  serves as a stop piece and a shock-absorber to smooth the swing of the movable arm  30 , and make the ridding comfortable. The buffer  70  is useful but not essential.  
         [0030]     The suspension structure of the present invention is simple but effective as only being comprised of movable arm  30 , front cantilever  40  and sliding assembly  50 , which requires no spring and steel rope, and no worry about elastic fatigue.  
         [0031]     In addition, the rear wheel of the wheelchair in accordance with the present invention is designed as having no suspension device, this design has no influence on the wheelchair in overcoming barrier, but it discomforts the rider. In view of this, the present invention offers a simple shock-absorbing method for reference. Referring to  FIG. 9 , wherein a cantilever  80  is provided on the rear side of the frame  20 , and between the cantilever  80  and the rear side of the frame  20  a shock-absorbing spring is disposed for connecting them together. A first end of the cantilever  80  can be provided with rear wheel  23 , whereas a second end of the same is pivotally connected to the rear side of the frame  20 , such that the cantilever  80  is able to swing pivotally. An ear  81  can be provided on the rear side of the cantilever  80 . The shock-absorbing spring comprises shaft  82  and spring  83 , the spring  82  is mounted onto the shaft  83 . An end of the cantilever  82  is connected to the ear  81  of the cantilever  80 , and another end of the cantilever  82  is connected to mounting bracket  84  on the rear side of the frame  20 , and then a locking pin  85  is used to prevent disengagement of the shaft  82  from the mounting bracket  84 . By this way, the rear wheel  23  can be adjusted precisely corresponds to the real road condition.  
         [0032]     While we have shown and described various embodiments in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.