Abstract:
A caster assembly for a wheelchair comprises a stem having a frame clamp at a first end and a fork clamp at a second end, the frame clamp configured to form a frame joint with at least one rotational degree of freedom with a frame portion of the wheelchair, a tightening of the frame clamp securing the stem to the frame portion, the frame joint having a frame rotational axis. A fork unit has a fork portion and a caster rotatably supported by the fork portion, the fork unit having swivel mechanism, and a joint portion forming a rotational joint with the fork clamp of the stem, a tightening of the fork clamp blocking rotation of the rotational joint, the rotational joint having a fork rotational axis. A vector of the fork rotational axis is normal to a fork rotational plane in which the fork rotates relative to the stem, and further wherein the frame rotational axis is not parallel to the fork rotational plane.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority on U.S. Patent Application Ser. No. 62/301,939, filed on Mar. 1, 2016, and on U.S. Patent Application Ser. No. 62/310,036, filed on Mar. 18, 2016, the content of both of which is inserted herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present application relates to wheelchairs and, more particularly, to various components of a wheelchair assembly. 
       BACKGROUND ART 
       [0003]    Wheelchairs have evolved over the years to become increasingly ergonomic, lightweight, easy to maneuver and to use. However, there remains room for improvement to add additional adjustment possibilities to wheelchairs, and to render them even more convenient to use, notably in the maneuverability, stiffness, balance, but also for moving into or out of the wheelchair, and folding or unfolding the wheelchair for storage. 
       SUMMARY 
       [0004]    It is an aim of the present disclosure to provide a novel wheelchair caster assembly. 
         [0005]    Therefore, in accordance with the present disclosure, there is provided a caster assembly for a wheelchair comprising: a stem having a frame clamp at a first end and a fork clamp at a second end, the frame clamp configured to form a frame joint with at least one rotational degree of freedom with a frame portion of the wheelchair, a tightening of the frame clamp securing the stem to the frame portion, the frame joint having a frame rotational axis, and a fork unit having a fork portion and a caster rotatably supported by the fork portion, the fork unit having swivel mechanism, and a joint portion forming a rotational joint with the fork clamp of the stem, a tightening of the fork clamp blocking rotation of the rotational joint, the rotational joint having a fork rotational axis, wherein a vector of the fork rotational axis is normal to a fork rotational plane in which the fork rotates relative to the stem, and further wherein the frame rotational axis is not parallel to the fork rotational plane. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0006]    The present application relates to wheelchairs and, more particularly, to various components of a wheelchair assembly. 
           [0007]      FIG. 1  is a perspective view of a wheelchair assembly with a pair of caster assemblies in accordance with the present disclosure; 
           [0008]      FIG. 2  is a side view of one of the caster assemblies of  FIG. 1 ; 
           [0009]      FIG. 3  is a front view of one of the caster assemblies of  FIG. 1 ; 
           [0010]      FIG. 4  is an enlarged perspective view of a stem of one of the caster assemblies of  FIG. 1 ; and 
           [0011]      FIG. 5  is a sectional view of the stem of  FIG. 4  showing a clamping ring for footrest thereof. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring to the drawings and more particularly to  FIG. 1 , there is illustrated a wheelchair assembly at  10 , also simply referred to as wheelchair. The wheelchair assembly  10  is of the type having a plurality of other components, including a seat frame  20 , a pair of front caster assemblies  30 , a footrest  40 , a backrest frame  50 , bracket assemblies  60  and rear wheel units  70 . 
         [0013]    The seat frame  20  forms the structure of the wheelchair assembly  20 . The seat frame  20  has a pair of tube assemblies  21 , a right-side tube assembly and a left-side tube assembly, for instance mirror images of one another. The tube assemblies  21  are shown as having a L-shape. The L-shape is one possible embodiment of the tube assemblies  21 , and other shapes include a generally polygonal shape, a U-shape, etc. Although the expression “L-shape” is used, the tube assemblies  21  may appear to be a L rotated by  90  degrees clockwise or counterclockwise, depending on the point of view of the observer of the wheelchair  10  of  FIG. 1 . Moreover, although a right-angle bend is shown in  FIG. 1 , other angles may be used. 
         [0014]    The tube assemblies  21  may include a tubular member made in any appropriate material, such as carbon fiber, composites, metals (e.g., aluminum, titanium, steel, etc), and combinations thereof. According to an embodiment, the tubular member is a monolithic tube. The tubular member may have a first portion  21 A and a second portion  21 B. The first portion  21 A is generally horizontal when the wheelchair  10  is on its wheels, as in  FIG. 1 . The expression “generally horizontal” is well depicted in  FIG. 1 , in that the first portion  21 A may or may not be substantially parallel to the ground. It is observed that the first portion  21 A is in the seating zone of the wheelchair  10 , and may even support a seat of the wheelchair  10 , as described hereinafter. The first portion  21 A may also support the bracket assemblies  60  and the rear wheel units  70 . The second portion  21 B is generally vertical or generally upright when the wheelchair  10  is on its wheels, as in  FIG. 1 . The expression “generally vertical” is also well depicted in  FIG. 1 , in that the second portion  21 B may or may not be substantially perpendicular to the ground. The second portion  21 B is in the bottom front zone of the wheelchair  10 , and may even support the front caster assemblies  30  and the footrest  40 , as described hereinafter. The sectional shape of the second portion  21 B may be circular as in  FIG. 1 . 
         [0015]    Referring to  FIGS. 2-5 , one of the front caster assemblies  30  is shown. The front caster assembly  30  may also be known as a front wheel assembly, front caster unit, front roller unit, etc. However, for consistency, reference is made herein to “front caster assembly”. The front caster assemblies  30  are generally mirror images of another other, whereby a single one of the front caster assemblies  30  is herein described for simplicity. Each of the front caster assembly  30  has a stem  31 , by which it is connected to a respective one of the tubes  21 , at a bottom of the second portion  21 B. The stem  31  has a clamp  31 A at a first end. The clamp  31 A may be referred to a frame clamp as it clamps the caster assembly  30  to the frame  20  of the wheelchair  10 . The clamp  31 A may be a C-shaped clamp, emulating the shape of a C. The clamp  31 A may have a pair of rings  31 B or a single ring  31 B (also known as prongs), that may be tightened by tightening assemblies, for instance bolts  31 C and nuts (such as threaded bore in the opposed end of the clamp  31 A). When loosened, the clamps  31 A therefore enable a translation and rotation of the stem  31  relative to the tubes  21 . For reference, the joint formed between the clamps  31 A and the second portions  21 B of the tubes  21  may be regarded as a frame joint, with the stem  31  moving along and rotating about frame rotational axis Y 1  ( FIG. 3 ). 
         [0016]    An opposite end of the stem  31  defines another clamp  31 D that may be tightened in similar fashion to the clamp  31 A. The clamp  31 D may be regarded as a fork clamp as it serves to clamp a rotation of the fork unit  32  relative to the stem  31 . The clamp  31 D forms a cylindrical receptacle  31 E, by which a fork unit  32  may be operatively connected to the stem  31 . The fork unit  32  has a joint portion, namely a cylindrical member  32 A, also known as a barrel  32 A at its top end, the barrel  32 A received in the circular receptacle  31 E. Therefore, the barrel  32 A may rotate in the circular receptacle  31 E, unless the clamp  31 D is tightened to block a rotation of the barrel  32 A. The rotational axis may be referred to as fork rotational axis and a vector thereof (i.e., superposed on the fork rotational axis) is normal to a plane of the page in  FIG. 2 , with a rotational arrow showing its movement. The plane of the page in  FIG. 2  may be referred to as fork rotational plane as it is in this plane that the fork unit  32  moves in rotational when the rotational joint formed by the cylindrical receptable  31 E and the barrel  32 A is not blocked by the clamp  31 D. As an alternative embodiment, not shown, the clamp is on the fork unit  32  while the cylindrical joint portion is on the stem  31 . 
         [0017]    A fork portion  32 B projects downwardly from the barrel  32 A. A spirit level  32 C (e.g., bubble level, level, numerical level, etc) may be mounted to the barrel  32 A or to the fork portion  32 B, and is perpendicularly aligned with the axis Y and/or with the orientation of the fork portion  32 B, to allow an adjustment of the orientation of the Y axis, for instance to reach perpendicularity relative to the ground in the sagittal plane of the wheelchair assembly (see  FIG. 2 ), before tightening the clamp  31 D. A wheel  33  (a.k.a., roller, caster, castor, etc) is rotatably held by the fork portion  32 B of the fork unit  32 . The fork portion  32 B is in a swivel arrangement relative to the barrel  32 A, so as to rotate about axis Y, by way of a swivel mechanism. Hence, axis Y may be regarded as a swivel rotational axis. In an embodiment, the swivel rotational axis is parallel to the plane of the page of  FIG. 2  and thus to the fork rotational plane. According to an embodiment, the fork portion  32 B incorporates one of more bearings in its housing  32 D, and the barrel  32 A has a bolt or shaft  32 E rotatably supported by the bearing. In  FIG. 2 , the shaft  32 E is shown as having a nut thereon, for the fork portion  32 B to be held captive and in rotating engagement with the shaft  32 E. 
         [0018]    Referring to  FIG. 3 , it is shown that the axis Y of the fork unit  32 , as defined by the correlation between the stem  31  and the fork unit  32 , is not parallel to axis Y 1  between the stem  31  and the portion  21 A of the tube  21 . Moreover, it is also shown in  FIG. 3 , that the frame rotational axis Y 1  is not parallel to the fork rotational plane, in which the axis Y lies. Stated differently, the frame rotational axis Y 1  intersects the fork rotational plane. Accordingly, by rotating the stem  31  about the tube  21 , it is possible to reach perpendicularity of the Y axis relative to the ground in the frontal plane of the wheelchair assembly  10 . Wth the Y axis being perpendicular to the ground in both the sagittal plane ( FIG. 2 ) and the frontal plane ( FIG. 3 ), the Y axis is normal to a plane of the ground, and the impact of gravity on the swivelling motion may be lessened. The stem  31  has a three-dimensional geometry to allow this. According to an embodiment, the stem  31  may be a forged  3 D hollow piece, with an arcuate shape to the stem  31 . The stem  31  may have a monocoque construction, with the exception of the tightening assemblies for the clamps  31 A and  31 D. Also, the gaps of the clamps  31 A and  31 D, which gaps serve to tighten or loosen the clamps  31 A and  31 D, may be sized relative to the diameters of the tube  21  and of the barrel  32 A, respectively, for the clamps  31 A and  31 D to remain in elastic deformation when tightened. A native gap size (in normal unloaded state) is large enough to allow movement of the stem  31  along and about the tube  21 , or rotation of barrel  32 A. 
         [0019]    Referring concurrently to  FIGS. 1, and 5 , one of many contemplated configurations of the footrest (a.k.a., footplate) is shown at  40 . The footrest  40  is shown as a monolithic tubular assembly, but other configurations are considered. For example, the footrest  40  may be a combination of tubes with a footplate, etc. In the illustrated, the footrest  40  therefore has a pair of upwardly-oriented tube portions  40 A, by which it is connected to the seat frame  20 . In an embodiment, the tube portions  40 A are small enough to be inserted in open ends of the second portions  21 B of the tubes  21  of the seat frame  20 , as illustrated in  FIGS. 4 and 5 . In this embodiment, a clamping ring  41  may have a cylindrical connector portion  41 A inserted in the open end of the second portions  21 B of each of the tubes  21 , in axial alignment with a lower one of the rings  31 B of the clamp  31 A, in stem  31 . The camping ring  41  may therefore rotate relative to the frame tube  21 , due to the complementary cylindrical shapes. The cylindrical connector portion  41 A may further include an interface sleeve  41 B that is configured for sliding engagement with the tube portions  40 A. The interface sleeve  41 B may also elastically deform to apply pressure against the tube portion  40 A to prevent its axial movement. In that way, a clamping of the ring  31 B may apply pressure to the tube portion  40 A, via clamping ring  41 , to lock the footrest  40  in position. Stated differently, the stem  31  of the front caster assembly  30  may additionally or optionally serve the function of allowing a height adjustment for the footrest  40 . To assist in the clamping, a slot may be defined in the second portion  21 B of the tube  21 , upward from the open end of the tube  21 . The slot assists in the elastic deformation of the bottom end of the tube  21  to press against the tube portion  40 A so as to block its movement. 
         [0020]    As observed in  FIG. 4 , the clamping ring  41  may have a flange head  41 C with a hole  42 , provided to receive the tube portion  40 A. The hole  42  is aligned and rotates with the cylindrical connector portion  41 A and/or interface sleeve  41 B, such that the tube portion  40 A is received therein when slid into the hole  42 . The hole  42  may be eccentrically positioned relative a circular body of the flange head  41 C and/or to the cylindrical connector portion  41 A of the clamping ring  41 . This eccentric position is a feature provided to enable a tapering relation between the tubes  21 . The clamping ring  41  may rotate as the tube portions  40  are slid thereinto, to adjust to a spacing between the tube portions  40 A. Indeed, by rotating either or both of the clamping rings  41 , a distance between the holes  42  is adjusted. Once a suitable depth of insertion is reached, the clamps  31 A may lock the footrest  40  to the frame  20 . 
         [0021]    Accordingly, during assembly, both of the clamps  31 A and  31 D are loosened, to respectively allow a rotation of the stem  31  relative to the tube  21 , and of the fork unit  32  relative to the stem  31 . A triangular square may be used when rotating the stem  31  to ensure that the fork portion  32 B is perpendicular to the ground, as in  FIG. 3 , at which point the clamp  31 A may be tightened. The rotation of the fork unit  32  may be guided by the spirit level  32 C to reach the arrangement of  FIG. 2 . The adjustment mentioned above may be done sequentially, in any order, etc.