Abstract:
The present invention relates to improvements in the design of a rear-steer collapsible, in particular the invention relates to a number of safety enhancing features that provide a safer and more versatile rear steer portable wheelchair.

Description:
FIELD OF THE INVENTION 
     The present invention relates to improvements in the design of a rear steer portable wheelchair. The portable wheelchair is collapsible for ease of deployment, handling and transport, while also providing a strong and manoeuvrable wheelchair. 
     CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage application (under 35 U.S.C. §371) of PCT/NZ2013/000169, filed Sep. 18, 2013, which claims benefit of New Zealand applications 602506, filed Sep. 18, 2012 and 606618, filed Feb. 4, 2013. 
     BACKGROUND OF THE INVENTION 
     Portable and collapsible wheelchairs have been developed in the past and one such wheelchair is described in U.S. Pat. No. 5,857,688. However no rear steer wheelchairs have been described that provide a lightweight and portable wheelchair with an ability to be maneuvered over moderately rough terrain. 
     It is therefore an object of the invention to provide the public with a useful choice or to at least provide the public with a useful alternative. 
     SUMMARY OF THE INVENTION 
     The present invention provides a rear steer portable and collapsible wheelchair having;
         (a) a pair of side frame assemblies each having an upper tube member and a lower tube member and forward and aft sections; and   (b) a scissor hinge assembly mounted on the side frame assemblies, which hinge extends centrally between the side frame assemblies, which hinge assembly is foldable from between an in-use position to a collapsed position;   (c) a pair of front wheels with each wheel being attached to the forward section of the side frame assemblies,   (d) a pair of rear steer wheels with each wheel being attached to the aft section of the side frame assemblies,   (e) a pair of collapsible pushing arms that are attached to the side frame assemblies,   (f) a pair of arm rests that are attached to the side frame assemblies,   (g) a back support means, which is attached to the aft section of at least one of the side frame assemblies; and   (h) a seat support that extends above the scissor hinge and between the side frame assemblies;
 
wherein in use the wheelchair is deployed by (i) spreading the side frame assemblies apart to pull the scissor hinge into a locked position and (ii) putting the pair of collapsible pushing arms into a locked in-use position and further wherein in use the wheelchair is collapsed by (i) pulling a handle proximate the central position of the scissor hinge to release the locked position of the scissor hinge to pull the side frames assemblies together, and (ii) collapsing the collapsible arms from their in-use locked position to a folded out of use position into a compact, readily lifted and transportable configuration.
       

     In one embodiment, the scissor hinge includes a pair of geared hinge linkages. 
     In one embodiment the back support means is secured on a pair of back support arms, each back support arm being attached to the aft section of the proximate side frame assembly. 
     In another embodiment the rear wheel is biased by way of a biasing member to keep the rear steer wheel aligned in a substantially straight ahead manner. 
     In another embodiment the pair of collapsible pusher arms include ergonomically angled handles. 
     In another embodiment the pair of collapsible pusher arms include a brake lever that activates a front wheel brake in at least one of the front wheels. 
     In another embodiment the wheelchair is collapsible into a size no greater than about 800 mm in length ×about 350 mm in width ×about 700 mm in height. 
     In one embodiment the wheelchair includes a pair of foot rests that are secured to the forward section of the side frame assembly. Preferably the foot rests can pivot through about 90 degrees relative to the side frame assembly. In another embodiment each foot rest is designed to rotate upwardly against the side frame assembly. More preferably each foot rest is designed to rotate upwardly against the side frame assembly and then to rotate towards the seat support. In an alternative embodiment each foot rest is designed to rotate towards the seat support and then to rotate upwardly against the side frame assembly. In another embodiment the foot rest includes a foot restraint. 
     In another embodiment the wheelchair further includes a lap safety belt for use by an occupant. 
     In another embodiment the wheel chair includes at least one hand brake that acts upon at least one of the front wheels. 
     In another embodiment the handle of the wheelchair that in use is pulled to break the scissor hinge upon collapse of the wheelchair is also adapted in size and shape to provide a carry handle for the wheelchair in its collapsed configuration. 
     The foregoing brief summary broadly describes the features and technical advantages of certain embodiments of the present invention. Further technical advantages will be described in the detailed description of the invention that follows. Novel features which are believed to be characteristic of the invention will be better understood from the detailed description of the invention when considered in connection with any accompanying figures and examples. However, the figures and examples provided herein are intended to help illustrate the invention or assist with developing an understanding of the invention, and are not intended to be definitions of the invention&#39;s scope. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective view of one embodiment of a wheelchair. 
         FIG. 2  shows a perspective view of the wheelchair shown in  FIG. 1  without the seat and back rest in place. 
         FIG. 3  shows a side view of the wheelchair shown in  FIG. 1 . 
         FIG. 4( a )  shows a top view of the wheelchair in  FIG. 1  in a collapsed state. 
         FIG. 4( b )  shows a side view of the wheelchair in  FIG. 1  in a collapsed state. 
         FIG. 4( c )  shows a bottom view of the wheelchair in  FIG. 1  in a collapsed state. 
         FIG. 4( d )  shows a front view of the wheelchair in  FIG. 1  in a collapsed state. 
         FIG. 5  shows a perspective view of the wheelchair in  FIG. 1  in a collapsed state. 
         FIG. 6( a )  shows a side view of the right side frame assembly of the wheelchair. 
         FIG. 6( b )  shows a top perspective view of the side frame assembly shown in  FIG. 6( a ) . 
         FIG. 6( c )  shows a bottom perspective view of the side frame assembly shown in  FIG. 1  in a collapsed state. 
         FIG. 7( a )  shows a scissor hinge of the present invention as it would appear in a wheelchair ready for use. 
         FIG. 7( b )  shows a scissor hinge of the present invention as it would appear in a wheelchair that has been collapsed for transport. 
         FIG. 8( a )  shows the mounting of a front wheel to the forward section of the side frame assembly. 
         FIG. 8( b )  shows the mounting of a front wheel hand brake proximate the forward section of the side frame assembly. 
         FIG. 8( c )  shows the mounting of a front hub disc brake between the front wheel and the side frame assembly and also the components that allow for the mounting of the front wheel hand brake shown in  FIG. 8( b ) . 
         FIG. 9( a )  shows a side view of the relationship between the handle, arm rest and the upper tube of the side frame assembly in the position when the wheelchair is in deployment mode. 
         FIG. 9( b )  shows a side view of the detail from section c of  FIG. 9( a ) . 
         FIG. 9( c )  shows a side view of the relationship between the handle, arm rest and the upper tube of the side frame assembly when the wheelchair is in a partially collapsed mode. 
         FIG. 9( d )  shows a side view of the relationship between the handle, arm rest and the upper tube of the side frame assembly when the wheelchair is in collapsed mode. 
         FIG. 10( a )  shows a side view of the rear wheel connection to the aft section of the side frame assembly where the rear wheel is being propelled in a straight ahead direction. 
         FIG. 10( b )  shows a side view of the rear wheel connection to the aft section of the side frame assembly where the wheel is being turned. 
         FIG. 10( c )  shows a perspective exploded view of the components of the rear wheel mounting connection to the side frame assembly. 
         FIG. 10( d )  shows a side view of the rear wheel showing the trail of the hub of the wheel relative to the centre of the pivot mount of the wheel to the side frame. 
         FIG. 11  shows the top and bottom perspective views of a rigid moulded plastics seat for use in the wheelchair of the invention. 
         FIGS. 12( a ) to 12( c )  show the dual rotation feature of a footrest of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Prior to setting forth the invention in detail, it may be helpful to provide definitions of certain terms to be used herein. 
     The term “about” as used herein in connection with a referenced numeric indication means the referenced numeric indication plus or minus up to 10% of that referenced numeric indication. For example, the language “about 50” units covers the range of 45 units to 55 units. 
     With reference to  FIGS. 1 to 3  a wheelchair  1  of one embodiment of the invention is shown. The wheelchair includes a pair of side frame assemblies,  2  and  3  respectively. The side frame assemblies  2  and  3  are equivalent in configuration, shape and dimensions except for the fact that each assembly is a mirror image of the other. The wheelchair  1  has a right side frame assembly  2  and a left side frame assembly  3  when looking at the wheelchair from the back of the chair to the front of the chair. The shape and configuration of the right hand side frame assembly  3  is shown in particular detail in  FIGS. 6( a ) to 6( c ) . The side frame assemblies are constructed from metal tubing, having a round, elliptical or square cross section. The tubing is preferably made from aluminum or some other metal preferably light weight metal of about 25 mm-32 mm (1 inch- 11/4  inch) in diameter or cross sectional width and depth. The side frame assembly includes an upper tube member  4  and a lower tube member  5 . The upper and lower tube members are shaped by bending around formers into the desired shape. The upper tube member  4  is connected to the lower tube section in both the forward section  6  and aft section  7 . The lower and upper tube members are joined together at their respective forward and aft sections by welds. The upper tube member  4  of the side frame assembly also provides an arm rest link  8  that is connected by a bolt and bracket system to the upper tube  4 . With reference to  FIGS. 6( a ) to 6( c )  the side frame assemblies include an aft upper tube bracket  9  that is used to connect to a back support arm  10  as shown in  FIGS. 2 and 9 ( a ). The aft section  7  of the side frame assembly also includes a rear wheel mounting bracket  11 . The forward section  6  of the lower tube member  5  provides a mount  12  for a front wheel  13  (as shown in  FIG. 8 ) The forward section of the upper tube member  4  is adapted to provide means to mount a foot rest  14  (as shown in  FIG. 1 ) and also means for mounting a mount  15  for a front wheel hand brake  16 . The foot rest  13  in this embodiment is a standard off the shelf hinged foot rest constructed from a light plastics material. Preferably the foot rest is pivotable through about  90  degrees relative to the side frame to ease occupant ingress. The height of the footrests may be positioned at a plurality of heights along the upper side frame  4  to suit the occupant as required. As shown in the foot rest embodiment in  FIGS. 12( a ) to 12( c )  a dual rotation foot rest mechanism is illustrated. The foot rest  14  is first rotatable about 90 degrees towards the side frame as shown in  FIG. 12( c )  about a first axle or pivot  121 . The folded footrest  14  is then further rotatable towards the seat of the wheelchair about a second pivot point  122 . The footrest when folded about the second pivot point  122  (as shown in  FIG. 12( c )  shows the foot rest folded against the side frame and out of the space through which a user must step to get into or out of the seat. In one embodiment the foot rest may include a foot restraint, such as but not limited to a foot strap that would go over the foot of the wheelchair occupant and where the strap can be tightened to secure the occupant&#39;s foot to the foot rest. 
     The front and rear wheels  13  and  17  respectively may optionally include mudguards to protect the chair occupant from splashes or dirt and dust flicking of the wheels. The front wheel  13  is preferably between 8-20 inches in diameter (more preferably around 16 inch) and includes preferably plastic or metal spoked rims, or the front wheel is a composite wheel, which by way of example is, constructed from plastic spokes and an aluminum rim. The front wheel preferably has either an inflatable pneumatic tyre or polyurethane foam filled rubber tyre. The size of the rear wheel is a 12.5 inch wheel but it is envisaged that a range of wheel size from 6 inch to 14 inch would be suitable. The rear wheel preferably includes plastic or metal spoked rims, or the rear wheel is a composite wheel, which by way of example is, constructed from plastic spokes and an aluminum rim. The rear wheel preferably has either an inflatable pneumatic tyre or polyurethane foam filled rubber tyre. It is also preferred that the front and optionally the rear wheels are removable from their axle mounts by a quick release axle, that is a hub push button release system or spring clip. It is also preferred that the front wheel includes an internal expanding shoe drum brake  18  as shown in  FIG. 8( c )  that is cable operated. With reference to  FIG. 1 , the cable (not shown) for the brake  18  runs through to the pushing handle  19  proximate which a brake handle  20  is provided to activate the brake. In one embodiment it is also envisaged that it may be desirable to have the two front brakes activated by a single brake lever that may activate both front wheel drum brakes  18  simultaneously. 
     The collapsibility of the wheelchair is achieved by a scissor hinge assembly  21  as shown in  FIGS. 7( a ) and 7( b ) . The scissor hinge assembly is mounted to the pair of side frames by way of a pair of hinge mounts  22  and  23  respectively that are positioned between the upper and lower tube members of the side frame assemblies  2  and  3 . The hinge mounts  22  and  23  are located substantially centrally along the length of the upper and lower tube members of the side frame assemblies as shown in  FIGS. 6( a ) to 6( c ) . The hinge mounts span between the upper and lower tube members. With reference to  FIG. 7( a )  the scissor hinge includes a pair of geared hinge units  24  and  25  respectively. Each geared hinge unit includes an upper hinge linkage (upper hinge linkages ( 26  and  28 ) respectively and lower hinge linkages ( 27  and  29 )) respectively. However, it is to be appreciated that these hinge units  24  and  25  could be rotated 90 degrees to provide a front and rear/aft facing linkage. The hinge linkage rotates about a pivot point through a pair of involute sector spur gears  30  and  31  that positively engage with each other and lead to a locked hinge arrangement when the wheel chair is deployed for use. The gears  30  and  31  maintain the correct relative positions of the linkages. In use, the arrangement of the hinge linkages is such that you can achieve a locking action brought about by an over centre arrangement/geometry of the linkages. Preferably the scissor hinge assembly would include a positive stop on the upper and lower linkages that prevents the linkages from clashing around the central pivot section  32 . In use, when the wheelchair  1  is being collapsed, the hinge linkages are broken by pulling on a handle  33  attached to the upper pair of linkages  26  and  28  at the central pivot section  32 . With reference to  FIGS. 1 and 5  the handle  33  is pulled to extend through the seat base  34  and collapsed back rest  35  to bring the side frame assemblies  2  and  3  of the wheelchair  1  together. It is to be appreciated that the hinge linkages may be made out of a lightweight metal (such as aluminum, titanium or pressed steel) or a rigid plastics material or a composite or plastic and metal. 
     With reference to  FIGS. 1 and 2 , the pair of side frame assemblies  2  and  3  also support a pair of arm rests  36  by way of an arm rest link  8  (see  FIG. 6( a )-6( c )  by a bolt and bracket system. A pair of conventional arm rests  36  are provided and are shown in the embodiment exemplified. It is to be appreciated that unconventional or modified arm rests may be provided where an occupant&#39;s specific needs require a modified arm rest. With reference to  FIG. 9 ( a )  and section c as shown expanded in  FIG. 9( b )  the rear of the arm rest  36  is mounted partway along the length of the pushing handle and the back rest upright  10 . It can be seen from  FIG. 9( a )  that there is a four bar linkage hinge between the collapsible pushing arms  37  and the arm rest  36 . As shown in  FIG. 9( b )  the bracket for the aft section of the arm rest  36  also mounts the bracket or link  38  for the collapsible pushing arm  37 . The pushing arm  37  at its lower end is pivotally attached to the side frame assembly  2  by an arm rest link  8 . The arm rest link  8  is a folded plate, die cast or extrusion linkage which also connects to an arm rest linkage  44 . The connection between the pushing arm  37  and the pushing arm link  40  is controlled by a releasable or retractable locking pin  41  that is mounted on the lower part of the pushing arm  37 . The locking pin  41  prevents the rotation of the pushing handle  37  relative to the pushing arm link  40 . The locking pin  41  slides in a sleeve  42  mounted on the pushing arm  37 . The locking pin  41  can be retracted clear of the pushing handle link  40  by retracting the pin into the sleeve  41  by an actuating means  43 . The pushing arm  37  at its upper end is shaped and dimensioned to provide an ergonomically positioned handle  19 . The pushing handle  19  also supports a brake lever  20  that controls in this example front wheel brakes and optionally other controls such as, rear brakes and rear wheel pivot limiters or the like. 
     The brake levers  20  also preferably include a locking pin (not shown) so that the brakes can be engaged on a permanent basis until selectively disengaged. 
     With reference to  FIG. 1 , the back rest uprights  10  may optionally include a support link between the back rest uprights. The back rest  35  and seat support  34  may be made from a wear resistant fabric, such as an acrylic canvas or a nylon canvas. Alternatively the back rest and or seat support may be a solidly contoured detachable insert that is put in place as required. A suitable shaped seat support is shown in  FIG. 11 . The molded plastic fibreglass or plastics seat base  45  would clip onto the side frame and would optionally include a foam pad on the seat pad to provide cushioning for the occupant. The back rest may also include a molded plastic or fibreglass support that slides over the back rest uprights. The back rest may be adapted to include pockets or fixtures to secure water bottles and/or to provide a head support for the occupant. Similarly the back rest or the seat base may be adapted to provide fixtures to secure or contain a catheter bag or other medical devices required by the wheelchair occupant. 
     With reference to  FIGS. 10( a ) to 10( d )  each rear wheel  17  is mounted to the side frame assembly by a leg  45  sliding into a rear wheel mounting bracket  11 . It is also envisaged that a quick release mechanism provided by a depressible pin that fits into a complimentary hole on the leg  46  would allow for the rear wheel  17  and leg  46  to be quickly removed for compact transport reasons. To enhance the stability of the rear steer wheelchair, the connection of the rear wheel  17  to the side frame assembly  2  has been achieved by using a biasing swivel connection assembly such that when the chair is being propelled forward the wheel trails behind the leg by a trail distance of around 50-60 mm. This is achieved by using a biased swivel connection  47  to (i) keep the wheel in a trailing position and discourage the wheel from turning and becoming unstable and (ii) to hold the wheel in a forward facing position when the wheel chair is collapsed and folded up into a packed position. The biasing may be by spring  48  and face cam  49 ,  50  as shown in  FIGS. 10( a )-10( c ) , but it is to be appreciated that other biasing means may be employed. One such biasing means would be the use of a detent system or a pin system that biases the wheel into the desirable position. 
     In the embodiment illustrated the angle of the side frame extending to the leg relative to the normal of the ground is about 4 to 8 degrees. In the embodiment shown in  FIG. 10( d )  the trail  51  of the wheel is about 57 mm. 
     It is to be appreciated that the overall centre of gravity of the chair, and therefore stability of the chair, can be modified by moving the side frames forward or back relative to the wheels of the chair. Similarly adjustments in the height of the seat relative to the wheels will also affect the overall centre of gravity of the chair. 
     Use of the Wheelchair 
     The wheelchair is expected to be used as any other standard wheelchair would be used. However, with the rear steer aspect and ease of deployment and collapsibility it is anticipated that this wheelchair will appeal to those wheelchair users who like getting out and going places. Furthermore with the use of larger front wheels with wider pneumatic tyres the wheelchair has the ability to go over rougher terrain with ease. Traditional wheelchairs will stop if their small front wheels hit a pebble or some other imperfection in the ground surface. It is hoped that people associated with wheelchair users will be more inclined to take the wheelchair to places that might not have been suitable for more traditional style wheelchairs. 
     In use, the wheelchair can be easily deployed by pulling the side frames of the wheelchair apart to lock the scissor hinge in a locked position. The pushing arms of the wheelchair can be readily pulled back into a locked position. When the occupant is positioned in the chair and secured by an optional lap belt, the chair is ready for use. Once the chair has been used and needs to be transported say in a vehicle the pushing arms of the wheelchair can be folded down towards the seat of the chair, the handle that brakes the locked scissor hinge configuration is pulled and passed through the seat of the chair to collapse the scissor hinge and thereby bring the side frames of the chair closer together. The scissor hinge handle can then be used as a carry handle to carry the wheelchair in its collapsed configuration. Various views of the collapsed wheelchair are shown in  FIGS. 4( a ) to 4( c )  and  FIG. 5 . 
     The present invention and its embodiments have been described in detail. However, the scope of the present invention is not intended to be limited to the particular embodiments of the invention described in the specification. Various modifications, substitutions, and variations can be made to the disclosed material without departing from the spirit and/or essential characteristics of the present invention. Accordingly, one of ordinary skill in the art will readily appreciate from the disclosure that later modifications, substitutions, and/or variations performing substantially the same function or achieving substantially the same result as embodiments described herein may be utilized according to such related embodiments of the present invention. Thus, the following claims are intended to encompass within their scope modifications, substitutions, and variations to the embodiments of the invention disclosed herein.