Patent Publication Number: US-7909354-B2

Title: Wheel chair

Description:
BACKGROUND TO THE INVENTION 
     This invention relates to a wheelchair. 
     Motorised wheelchairs are well known. They have particular application with very impaired mobility users. To provide optimum assistance to such users it is desirable that the seat height of the wheelchair be adjustable through a range from below normal ride height to above normal ride height. The latter, for example, enables the user to achieve an elevated height for say location of the user at a table or bench height. 
     One problem that can arise from such adjustability is that the stability of the wheelchair can become compromised due to changes in centre of gravity leading to off balance loads that can either make the user think or feel that the wheelchair is unstable or render the wheelchair unstable. 
     SUMMARY OF THE INVENTION 
     It is thus an object of the present invention to provide a wheelchair particularly suited for very limited mobility users whereby a user can raise and lower the seat of the wheelchair from its normal ride height and not compromise the stability of the wheelchair. 
     Wheelchair users can spend a considerable amount of time in a wheelchair and thus comfort becomes an issue. Thus during travel about in the wheelchair shocks can be transmitted through to the seat of the wheelchair and hence to the user. Also if the wheelchair does not feel stable when traversing uneven or rough ground, the ride quality experienced or perceived by the user can be less than ideal. 
     It is a further object of the present invention to provide a wheelchair of a construction that provides improved ride quality for the user. 
     Broadly according to one aspect of the invention there is provided a wheelchair including a chassis, rear and front wheels mounted to the chassis, a support means pivotally coupled to the chassis and a seat mount, moving means to selectively move the support means relative to the chassis to cause the seat mount to be moved between raised and lowered positions, and a clearance provided between one or more of power supply units and suspension mounts to enable the support means to move therein during movement of the seat mount to and from the lowered position. 
     In a preferred form of the invention the wheelchair includes a pair of batteries power pack mounts whereby a pair of batteries or power packs can be mounted in a spaced apart array. 
     In a preferred form of the invention there are two front wheels, each front wheel is coupled to an arm one end of which is coupled to a mount located to one side of the clearance. 
     According to a preferred form of the invention the pair of batteries or power packs are located below a seat, mounted by the seat mount, when the seat is in a normal ride position. 
     According to a second broad aspect of the invention there is provided a wheelchair including a chassis, a seat mount carried by the chassis, rear wheels independently sprung by suspension means, front wheels each front wheel being coupled to an arm which is pivotally coupled to the chassis, shock absorbing means coupled between the arms and operable to permit the arm of one front wheel to move about its pivot coupling independent of the arm of the other front wheel upon a shock loading being applied to said one wheel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following more detailed description of a preferred embodiment of the invention, reference will be made to the accompanying drawings in which: 
         FIG. 1  is a perspective view from above showing the wheelchair in its normal operative configuration, 
         FIG. 2  is a side elevation view with bodywork and one rear wheel removed in the interests of clarity, the wheelchair being shown in the normal operative configuration, 
         FIG. 3  is a view similar to  FIG. 2  but showing the wheelchair in a configuration where the chair has been lowered to its lowermost position, 
         FIG. 4  is a further perspective view with bodywork and the chair removed, 
         FIG. 5  is detailed B of  FIG. 4 , 
         FIG. 6  is a side elevation view of the wheelchair in the form depicted in  FIG. 4 , 
         FIG. 7  is detailed A of  FIG. 6 , 
         FIG. 8  is a front elevation view, with seat removed, showing how the front arms to which the front wheels are mounted are able to move relative to the chassis and the rear wheels, 
         FIG. 9  is a view similar to  FIG. 8  but with bodywork, batteries and seat removed and showing a different extended movement of the front arms relative to the chassis, 
         FIG. 10  is a side elevation view showing the extent of lowering of the seat, 
         FIG. 11  is a side elevation view showing the extent of normal raising of the seat, 
         FIG. 12  is a side elevation view of showing the extent of extended raising of the seat, 
         FIG. 13  is a pictorial front perspective view of the wheelchair with the seat mount shown in its fully raised position (Position  3  as hereinafter described), and 
         FIG. 14  is a similar pictorial view from the rear and with the seat mount in its normal use position (Position  2  as herein described). 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
     According to the present invention the wheelchair is of a construction, as will hereinafter be described, whereby a user can lower a seat mounted by the seat mount right to the floor or ground level and raise the seat above a normal in-use position. This raising and lowering motion is achieved in a two stage motion, as will herein be described. 
     A wheelchair according to one embodiment of the invention, as described herein, provides a four-wheel wheelchair with suspension that includes independent rear suspension and front suspension capable of allowing one front wheel to move independent of the other under shock loading. This leads to improved ride quality for the user. 
     As shown in  FIG. 10 , the wheelchair according to the present invention has the ability to raise and lower the seat between a Position  1 , where the seat is located at ground level and a Position  2 , which is where the user will have the seat located, when travelling around in the wheelchair, at full speed or near full speed. As will be apparent from the construction, shown in the drawings and disclosed herein, the seat when moving from Position  1  to Position  2  rotates about a pivot and moves upwards and backwards yet still maintains the correct orientation for the comfort and safety of the user. Therefore, there is not a simple linear up/down motion. As a consequence of the seat rotation during movements between Positions  1  and  2 , it is possible to obtain the desired positioning of the seat at Position  1  yet have the chair in Position  2  located in a stable position where the centre of gravity is substantially in the centre of the front and rear wheels. 
     As will hereinafter be described, the seat moves up vertically in order to move from Position  2  to Position  3 . The movement to Position  3  will occur when the user wishes to be at a higher position e.g. to reach something in a cupboard or work at a bench both of which are higher than reasonably accessible to a user when in Position  2 . 
     The wheelchair  10  has a chassis  11  suitably constructed to provide anchor points for moving elements, a pair of electric motors M, a platform  12  for a pair of batteries  13  and suspension mountings. A space  14  is provided between the batteries  13  and also pivot mounts  15  to which arms  16  are pivotally attached via suitable bushes. The arms  16  can thus rotate about axis of rotation A. At the distal ends of the arms  16  are wheel mounts  17  to which front wheels  18  are rotatably mounted in a jockey wheel fashion to the arms  16 . 
     In the drawings there is shown a seat construction  19 . As will be known to those skilled in the art, the seat of a wheelchair of this nature will generally be of a construction suitable for the needs of the actual user of the chair. Therefore, the seat  19 , as shown in the drawings, is simply for illustrative purposes. 
     The seat  19  includes a footplate or support  20  that is pivoted about pivot  21  to an arm  22  pivotally coupled via pivot  23  to the underside of the base  24  of the seat  19 . To complete a parallelogram type linkage, a second link  25  is pivotally coupled at  26  to the underside of base  24  of chair  19 . This link  25  is coupled to an element  27  that extends from the underside of the foot support  20 . 
     Thus, in Positions  2  and  3  the foot support  20  takes its normal position. However, as the seat  19  is moved towards Position  1 , the underside of the foot support  20  comes in contact with the ground surface and, as a result, relative movement between the foot support  20  and the base  24  occurs until the foot support extends outwardly and just below the level of the base  24  as shown in  FIG. 3  (“Position  1 ”). 
     The back  28  of the seat  19  is coupled to a rotating seat support arm  29  via a pivot bearing  20  coupled to the back  28 . The other end of the seat support arm  29  is pivotally coupled between a pair of spaced apart chassis members  11   a  (of a sub-chassis) at pivot bearing  31 . An electric actuator  32  is pivotally coupled about axis A′ to the sub-chassis  11 . 
     As can be seen in  FIG. 2 , the chassis  11  has mounted thereto by a suitable support or mounting arrangement two pairs of guides  35 . W each pair of guides  35  a rail  34  is slidingly mounted. To each rail  34  is attached a chassis member  11   a . This arrangement is, as shown in the drawings, adjacent to but forward of the axis of the rear wheels  40 . 
     An electric actuator  33  is mounted between the chassis  11  and the sub-chassis arrangement of the chassis members′  11   a  and rails  34 . As the actuator  33  is extended and retracted, the chassis members  11   a  and rails  34  slidingly move in mounts  35 . 
     As a result chassis mounters  11   a  move up and down and carry with them the support arm  29 . The actuator  32  also moves up and down as a unit with the sub-chassis. This enables the seat  19  to be moved up and down between Positions  2  and  3 . The actuator  33  is thus only used for vertical up and down motion between Positions  2  and  3 . 
     Returning now to actuator  32 , it is apparent from the drawings that the piston rod  36  is pivotally coupled by pivot  37  to the rotating seat support arm  29 . The electric actuator  32  can thus be operated to move the seat  19  between Positions  1  and  2 . As can be seen in  FIG. 3  the actuator  32  is fully retracted into the cylinder body when the seat  19  is in Position  1 . 
     A further actuator  38  is pivotally coupled by pivot  39  to a lower part of a seat mount  39  attachable to the back  28  of the seat  19 . It is also pivotally coupled to rotate about axis A″ to the sub-chassis. This actuator thus moves as a unit with the sub-chassis. The actuator  38  is operable so as to tilt the seat  19 . This enables the user to achieve a comfortable sitting angle when the chair is at any height in the range from Position  1  to Position  3 . 
     The actuator  38  does not affect the lowering of the seat by actuator  32  because when actuator  32  operates, the actuator  38  only acts as a fixed length support. 
     The space  14  that exists between the batteries  13  in the battery mounts and platform  12  and the suspension mounts  15  for the front arms  16  provides the necessary clearance or cavity for movement of the rotating seats support arm  29  and actuator  38 . The relationship of these components and the space  14  is readily apparent from  FIG. 1 .  FIG. 1  also shows the inclusion of battery covers C and a rear cover C′ that covers the motors M and other componentry, as well as provide a form of mudguard G that provides partial covering the upper portion of the rear wheels  40 . These covers are also apparent in  FIGS. 11 and 12 . 
     A further cover C″ is coupled to the raising and lowering mechanism i.e. the sub-chassis, the chassis members  11   a , rails  14  and actuator  33 . This cover C″ thus moves as the raising and lowering effected by actuator  33  between Positions  2  and  3  occurs (see  FIGS. 11 and 12 ). 
     According to one aspect of the invention there is, therefore, provided a wheelchair whereby the seat  19  can be moved from its normal “ride” position (the so-called Position  2 ) to an elevated or extended height (Position  3 ) as shown in  FIG. 11 , and a fully lowered position (Position  1 ) as shown in  FIG. 3 . 
     The movement from Position  2  to Position  1  has the feature of the seat  19  rotating forward and downwardly so that not only is a full downward movement possible but also the seat clears the batteries  13  which, as shown in the drawings, are located directly under the seat when the seat is in Position  2 . Therefore, ideal weight distribution is achieved in Position  2  and, as a result, the wheelchair is stable as the chair travels at full speed or near full speed. 
     The space or cavity  14  that provides clearance between the batteries  13 , as previously described, is possible because the pivot axes for the front suspension is actually two separate axes set far enough apart so that the actuator  38  and seat support arm  29  can lower down between the two axes (see  FIG. 1 ). 
     According to a second invention embodied in the wheelchair there is provided independent suspension as will hereinafter be apparent. 
     As already described, and as can be seen in the drawings, the front wheels  18  carried by arms  16  are suspended independent from the rear wheels  40 . Also each rear wheel  40  is suspended independent from the other. Furthermore, the arms  16  are able to each move about a pivot axis defined by mount  15  but only move independent of each other under a shock loading on one wheel  18 . 
     According to the preferred form of the wheelchair, the front/front independence only occurs under shock loading conditions (i.e. the user drives one front wheel over a stone, low curb or the like). This front/front independence is achieved by having a pretensioned shock  41  (see  FIG. 9 ) that is pivotally coupled at  42  to each of a pair of levers  43  that extend downwardly from each of the pivot mounts  15  of the front arms  16 . The shock  41  acts as a solid link when the normal weight of the user is in the seat  19 . 
     However, if one of the front arms  16  is shock loaded, the link “breaks” i.e. the pretensioned spring  44  of shock  41  compresses or stretches depending on the direction of shock load on the front wheel. As shown in  FIG. 9  one lever  43  is coupled to the body of shock  41  while the other is coupled to a “piston” in the body and engaged by spring  44 . As a consequence the shock load is dissipated into the pretensioned spring  44  inside the link  41 . This means that the shock load is not transferred back up through the seat  19  to the user. 
     Thus, while the front wheels  18  are freely independent from the rear wheels  40 , the front wheels  18  are independent from each other under shock loading conditions. Under normal conditions, however, the front wheels  18  are linked via shock link  41  so that on uneven ground etc., the front wheels  18  can “track” the ground surface as shown, for example in  FIG. 8 . In this way an even weight distribution on all four wheels is achieved therefore leading to better stability of the wheelchair and a resultant ride quality for the user. 
     As stated above the weight of the user sitting statically in the seat  19  is not sufficient to break the shock link  41 . If the shock link does “break” this effectively results in a lowering of the seat position. It will therefore be appreciated that if the shock link  41  were to break open when a user sits in the seat  19  the chair&#39;s ride height would consequently be lower than when a user is not in the seat. This would have undesirable side effects. 
     For example, if a very limited mobility user were to lower the seat  19  to exactly the height of a toilet then slide off the seat and onto the toilet seat the wheelchair would be without the weight of the user. This would result in the seat springing up to a higher level which would then prevent, or lead to difficulties in the user sliding back from the toilet seat to the now higher wheelchair seat. However, with the construction, according to the present invention, the seat remains at the same height irrespective of whether the user is in or off the seat  19 . 
     The independent rear suspension (see  FIGS. 4 to 7 ) is provided by a double clevis type support strut  48  that mounts on one end to the gearbox  46  (from which projects the drive shaft and wheel mount  47 ) and the other to a rubber supported square shaft (not readily visible but indicated by numeral  49 ) that mounts onto the chassis  11 . The rubber supported square shaft  49  applies the reactive torque force for the operation of the rear suspension. 
     This independent rear suspension thus further improves the ride quality for the user. Consequently in addition to the fully adjustable nature of the seat  19  the present invention provides a stable wheelchair and one which exhibits better ride quality for the user.