This invention relates in general to land vehicles and more particularly to wheelchairs and side frames therefor. Most particularly, the invention relates to a side frame for a foldable wheelchair.
A conventional wheelchair typically has a pair of side frames that includes front and rear side frame members and upper and lower side frame members arranged to form a generally rectangular frame structure, which is typically oriented in a substantially vertical orientation.
The left and right side frames may be connected together by two or more cross braces to allow the wheelchair to fold such that the left and right side frames move together to create a narrow folded structure. Each cross brace typically has a lower pivot that pivots about or near a lower side frame member of a corresponding one of the left and right side frames. The cross braces cross one another at a cross brace pivot point and pivot with respect to one another about a central longitudinal pivot axis.
In order to control the folding kinematics of the wheelchair, two cross brace linkages are typically employed. The cross brace linkages have upper ends that pivot about longitudinal axes at or near the upper side frame members. Lower ends pivot about longitudinal pivot axes on the cross braces. The cross braces linkages restrict folding motion to a single degree of freedom, making it easy to fold the wheelchair in a single motion. The resulting folding kinematics is such that the left and right wheelchair side frames remain parallel when the wheelchair is unfolded and are generally parallel when the wheelchair is folded.
Left and right seat frame members are typically supported by upper ends of the cross braces so that the seat frame members reside next to and substantially parallel to the upper side frame members when the wheelchair is unfolded. Typically, an upholstery seat sling is secured between the left and right seat frame members to form a seat surface for supporting a wheelchair occupant. In addition, left and right backrest frame members are typically secured to the side frames and flexible backrest upholstery is secured between these backrest frame members. This upholstery forms a backrest surface for supporting the occupant's back.
Generally, the side frames are supported by drive wheels, usually located at the rear of the wheelchair, and by casters, usually located at the front of the wheelchair. To achieve this, the lower frame members typically extend longitudinally from the drive wheels to the casters. Optionally, connecting members may connect the lower frame members to the drive wheels or casters.
Mounting assemblies are commonly employed for mounting the drive wheels and the casters on the side frames. Such assemblies typically incorporate a number of adjustments that allow the wheelchair occupant to customize the wheelchair to his or her anthropometry or driving condition. Some mounting assemblies are adjustable to allow the height of the drive wheels and the casters to be varied. Mounting assemblies provide the ability to adjust the camber of the drive wheels (i.e., the angle of the drive wheels with respect to a vertical plane). For example, a wheelchair with a large camber angle has more responsive turning while a wheelchair with a little or no camber angle has a smaller overall width and thus greater maneuverability in tight confines. Mounting assemblies also provide the ability to adjust the fore and aft positions of the drive wheels with respect to the wheelchair frame. Such adjustment is known as a center-of-gravity adjustment. For example, moving the drive wheels rearward produces a more stable wheelchair that is less likely to tip backwards while moving the drive wheels forward makes the wheelchair easier to balance on the drive wheels. This helps with maneuverability over obstacles, such as curbs, where the wheelchair occupant must lift the casters off the ground in order to traverse the obstacle. Further, mounting assemblies permit the drive wheels to be adjusted laterally with respect to the side frames. Such adjustment allows the wheels to be properly spaced as close as possible to the side frame, while still providing clearance to accommodate optional accessories, such as side guards or armrests. Having the wheels spaced closer to the side frame creates a narrower overall width, allowing the occupant to enter narrow confines.
There are several problems associated with conventional wheelchairs. For example, conventional foldable wheelchairs often have flimsy frames. To help stiffen the frame, thicker walled tubing is often used. Tight tolerance of the folding pivot joints may also be required. However, these requirements add to the weight and the cost of the wheelchair and may make the wheelchair more difficult to fold.
As another example, foldable wheelchairs often have side frames that do not remain parallel throughout the folding motion of the wheelchair. When the wheelchair is nearing the completely unfolded condition, the upper side frame members are further apart than the lower side frame members. This non-parallel arrangement has the effect of causing upper ends of the backrest members to separate wider than the overall width of the unfolded wheelchair. This, in turn, causes the backrest upholstery to overstretch beyond the width of the wheelchair. Providing additional slack in the backrest upholstery to accommodate this condition is undesirable because the backrest upholstery should be taut when the wheelchair is unfolded. This overstretching of the backrest upholstery makes it difficult to fold and unfold the wheelchair, and tends to overstress components of the wheelchair that support the folding pivot axes. As a result, certain components are reinforced and made heavier to deal with this stress, which further adds to the weight and the cost of the wheelchair.
As yet another example, foldable wheelchairs typically have upper and lower side frame members that which contribute to the overall height of the side frames. The height of such wheelchairs is typically so tall that it is difficult to transfer the folded wheelchair over the user's lap when loading and unloading the wheelchair into and out of a car when the user is sitting in the driver's seat.
Still another example of problems associated with wheelchairs is with regard to the cambered drive wheels, which encounter a change in camber axes when the height of the drive wheels or casters is varied. This causes the drive wheels to toe in or toe out. That is to say, the drive wheels become misaligned with respect to the plane of a supporting surface. This misalignment is undesirable because it increases rolling friction. If the drive wheels are raised or the casters are lowered, the drive wheels will toe out. Conversely, if the drive wheels are lowered or the casters are raised, the drive wheels will toe in. This occurs because the axis of the camber is no longer aligned horizontally. To correct this, the mounting assemblies that attach the drive wheels to the side frames must allow the axles of the drive wheels to rotate in order to re-align the camber angle with respect to horizontal.
While some foldable wheelchairs provide height, lateral, camber toe in and toe out and center-of-gravity adjustability of the drive wheels to address the forgoing problems, there is strong demand for a design that offers user-friendly adjustment and is lightweight. There are major challenges in designing foldable wheelchairs with a structure that is sufficiently rigid. Other factors to consider include the type and amount of material used, the number and intricacy of the component parts, and the overall weight of the wheelchair. It would be advantageous to have a wheelchair that required less material or had less intricate members, and is lightweight. It would be advantageous to have a wheelchair that has a shorter overall package size when folded.
The present invention relates to a foldable wheelchair comprising a substantially horizontally extending upper side frame member. An upper end of an axle plate is secured to the upper side frame member. An axle housing is secured to the axle plate. A cross brace is pivotally secured directly to the axle plate at the lower end of the axle plate.
Another foldable wheelchair comprises a substantially horizontally extending upper side frame member. An upper end of an axle plate is secured to the upper side frame member. An axle housing is secured to the axle plate. A cross brace hinge is secured directly to the axle plate so that the axle housing and the cross brace hinge are substantially equidistant from the upper side frame member. A cross brace has a lower end that is secured to the axle plate via the cross brace hinge. The cross brace hinge is operable to pivot the cross brace with respect to the axle plate.
Another foldable wheelchair comprises an upper side frame member. An axle plate has an upper end secured to the upper side frame member. A wheel axle is secured to the axle plate. A cross brace is secured to the axle plate. The cross brace is operable to pivot with respect to the axle plate.
Another foldable wheelchair comprises an axle plate, a wheel mount extension secured to, and adapted to be substantially vertically adjustable with respect to the axle plate, and an axle sleeve mount secured to, and adapted to be substantially horizontally adjustable with respect to the wheel mount extension. An axle sleeve is secured to the axle sleeve mount. The axle sleeve has an axle bore that is angled with respect to horizontal to provide camber to a wheel. The axle sleeve is rotationally adjustable with respect to the axle sleeve mount about a lateral axis for the purpose of making camber toe in and toe out adjustment.
A wheel mount assembly according to the invention comprises an axle sleeve mount having an internal thread. An axle sleeve has an external thread that is in threaded engagement with the internal thread of the axle sleeve mount. The axle sleeve has an internal bore that accepts a wheel axle. The internal bore is angled with respect to the axis of the external threads to provide camber to a wheel. The axle sleeve is adapted to provide lateral adjustment to the wheel by rotating the axle sleeve within the axle sleeve mount any number of complete revolutions. Moreover, the axle sleeve is adapted to provide toe in and toe out adjustment to a cambered wheel by rotating the axle sleeve within the axle sleeve mount a fraction of a complete revolution.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.
For the purpose of simplicity, the description that follows refers to wheelchairs that are left or right, or laterally, symmetric. As such, the description in most cases refers to features on one side of the wheelchair, with the understanding that a substantially identical feature may resides on the opposite side of the wheelchair. Further, similar components of the various embodiment described herein may use the same name and reference number.
Referring now to the drawings, there is shown in
The wheelchair 10 is generally longitudinally symmetrical, with the right side substantially being the mirror image of the left. Except when otherwise discussed, when a part or component is described on one side, it is to be understood that the wheelchair 10 has similar structure on the opposite side. For example, the wheelchair 10 further includes a pair of seat frame members, such as a left seat frame member 16a and a right seat frame member 16b, and a pair of backrest frame members, such as a left backrest frame member 32a and a right backrest frame member 32b.
The seat frame members 16a and 16b are adapted to be supported by upper side frame members 14a and 14b, respectively. Preferably, the upper side frame members 14a and 14b are provided with couplings, such as the saddles 17a and 17b, shown in
The backrest frame members 32a and 32b may be secured to the upper side frame members 14a and 14b by brackets 33a and 33b, respectively. A seat back 36 extends substantially vertically between the backrest frame members 32a and 32b and is secured to the backrest frame members 32a and 32b by a plurality of straps 35a and 35b. However, the backrest frame members 32a and 32b and the seat back 36 may be secured in any suitable manner. Optionally, the seat back 36 can be adjustable in elevation by raising and lowering the seat back 36 relative to the backrest frame members 32a and 32b. Upper ends of the backrest frame members 32a and 32b may be provided with optional attendant handles 34a and 34b to aid an attendant in maneuvering the wheelchair 10.
Drive wheels 52a and 52b support the rear end of the wheelchair 10. The drive wheels 52a and 52b are adapted to be driven by the wheelchair occupant to propel and maneuver the wheelchair 10. In accordance with the preferred embodiment of the present invention, axle housings 54a and 54b are provided for mounting the drive wheels 52a and 52b to the axle plates 12a and 12b, respectively, as will be described below.
As shown in the drawings, the upper side frame members 14a and 14b are preferably adapted to support wheel guard assemblies 38a and 38b, respectively. The wheel guard assemblies 38a and 38b are secured to the upper side frame members 14a and 14b and to the backrest frame members 32a and 32b preferably by a plurality of threaded fasteners 39a and 39b, and the wheel guard assemblies 38a and 38b are preferably configured to act as armrests, side guards, and wheel guards. The wheel guard assemblies 38a and 38b are sufficiently low to permit a wheelchair occupant to gain access to the drive wheels 52a and 52b, which will be described herein below. The wheel guard assemblies 38a and 38b are provided for support of an occupant's arms, and may also include or incorporate an optional clothing protector, as shown, to protect the wheelchair occupant's person or apparel from being caught in the spokes of the drive wheels 52a and 52b.
Extending from the front of the wheelchair 10 is a footrest assembly 44. The footrest assembly 44 may include extension frame members 46a and 46b and a footplate 48. The extension frame members 46a and 46b extend forwardly and downwardly from the upper side frame members 14a and 14b, respectively. The footplate 48 is attached to the lower ends of the extension frame members 46a and 46b. Preferably, the footplate 48 is attached to the right extension frame member 46b by a pivotal connection, indicated generally at 47, and the footplate 48 is attached to the left extension frame member 46a by a selectively engageable support connection, indicated generally at 49. Thus, the footplate 48 may be engaged when the wheelchair 10 is to be in normal use and the footplate 48 may be disengaged when the wheelchair 10 is to be folded. Alternatively, separate or independent lateral leg supports (not shown) can also be supported by the extension frame members 46a and 46b.
Casters 50a and 50b support the front end of the wheelchair 10 relative to a supporting surface. The casters 50a and 50b may be affixed to the wheelchair 10 in any suitable manner. For example, as shown, the casters 50a and 50b are preferably joined to the upper side frame members 14a and 14b, by caster housings 51a and 51b, respectively, that are secured to the lower front ends of the upper side frame members 14a and 14b, respectively. Bearings within the caster housings 51a and 51b enable the casters 50a and 50b to swivel about vertical axes for maneuverability of the wheelchair 10.
Each axle plate 12a and 12b includes a front axle plate member 61a and 61b, respectively, and a rear axle plate member 63a and 63b, respectively. As shown, the front axle plate members 61a and 61b, and the rear axle plate members 63a and 63b have a rectangular cross-sectional shape. It must be understood, however, that the front axle plate members 61a and 61b and the rear axle plate members 63a and 63b can have any suitable cross-sectional shape, such as, square, round, oval or any other suitable shape.
The axle plates 12a and 12b are joined to opposite seat frame tubes or members 16b and 16a, respectively, by respective cross brace members 22a and 22b. Lower ends of the cross brace members 22a and 22b are pivotally connected to the front axle plate members 61a and 61b and the rear axle plate members 63a and 63b of the axle plates 12a and 12b by respective hinge assemblies, indicated generally at 65a and 65b. Upper ends of the cross brace members 22a and 22b are connected to opposite seat frame members 16b and 16a, preferably by threaded fasteners 67a and 67b. The seat frame members 16b and 16a preferably include a plurality of discretely spaced threaded bores 69a and 69b, as shown in
The cross brace members 22a and 22b are pivotally connected to each other by a pivot pin 71 at approximately the middle of the cross brace members 22a and 22b. The cross brace members 22a and 22b are foldable to permit the wheelchair 10 to be folded into a compact form. The wheelchair 10 is foldable into a compact form to permit the wheelchair 10 to be easily transported and stored.
As shown, the hinge assemblies 65a and 65b are laterally aligned (i.e., positioned and oriented in similar forward to rearward placement and directions). The cross brace members 22a and 22b are also laterally aligned at their respective connections to the seat frame members 16b and 16a and their respective connections to the hinge assemblies 65a and 65b. However, the cross brace members 22a and 22b are preferably curved, or offset forwardly and rearwardly (i.e., longitudinally), as shown in
As best seen in
The clamp 73a includes an outer flange 75a and an inner flange 77a. Preferably, the flanges 75a and 77a are formed integrally to the front axle plate member 61a and the rear axle plate member 63a. The flanges 75a and 77a form a saddle 79a in the clamp 73a. The saddle 79a is suitable to receive the left upper side frame member 14a. The clamp 73a may further include a pair of threaded fasteners 81a to secure the two flanges 75a and 77a together. The left upper side frame member 14a is disposed in the saddle 79a and the two flanges 75a and 77a surround the left upper side frame member 14a and are secured to each other by the threaded fasteners 81a. Thus, the left axle plate 12a is secured to the left upper side frame member 14a by the clamp 73a. The clamp 73a allows for adjustment in the longitudinal position of the left axle plate 12a. It must be understood, however, that the front axle plate member 61a and the rear axle plate member 63a may be secured to the left upper side frame member 14a in any suitable manner, such as by direct welding or nut and bolt fasteners.
The axle housing 54a preferably includes an axle tube 83a suitable to receive the axle of the left drive wheel 52a. The front and rear axle plate members 61a and 63a may include a plurality of discretely spaced threaded bores 85a and 87a. A front groove or slot 89a and a rear groove or slot 91a may be formed in the axle housing 54a to receive the front axle plate member 61a and the rear axle plate member 63a, respectively, as shown in
When the axle housing 54a is positioned at the bottom end of the front axle plate members 61a and 63a, as shown in
Further, while the left axle plate 12a has been described as having the axle housing 54a and the hinge assembly 65a positioned either at the bottom end of the front axle plate members 61a and 63a, as shown in
The left axle plate 12a is joined to the cross brace 22a by the hinge 65a. Generally, hinges include two leaves, or wings, with one leaf pivoting with respect to the other leaf about a common axis of rotation, or pin. Each leaf may include one or more fingers or brackets which serve to connect the leaf to an object, or part, which is to pivot with the leaf with respect to the other leaf and another object, or part, connected to the other leaf. As shown in
As shown in
Although the hinge 65a has been described as including substantially longitudinal hinge pin 105a, it must be understood however that the hinge pin 105a may be oriented in any suitable manner. For example, if the pivot pin 71 is oriented vertically, and the cross braces 22a and 22b are suitably connected to the seat frame members 16a and 16b, the hinge pin 105a may be a vertically oriented hinge pin.
Now with reference to
The side frames 121 may include a frame structure 128, which may support a caster 123, the footrest assembly 124, and an axle plate 129. The frame structure 128 may be comprised of a front side frame member 130 and an upper side frame member 131. The axle plate 129 is preferably adjustable fore and aft with respect to the frame structure 128. Such adjustment may be used to achieve course center-of-gravity adjustment of the rear wheels 122.
Attached to the axle plate 129 is a drive wheel mounting assembly 132. As shown in
As depicted in
Also depicted in
The axle sleeve 136 is preferably in threaded engagement with the axle sleeve mount 135. External threads 136a on the major diameter of the axle sleeve 136 may mate with internal threads 135b in the major bore 135c of the axle sleeve mount 135. A drive wheel axle 141 may reside within a bore 136b in the axle sleeve 136. This bore may be oriented at some angle θ, as shown in
The lower end of the axle plate 129 is preferably pivotally connected to the lower end of the folding cross brace 126 at a pivot point 126a. The two cross braces 126 are positioned longitudinally with respect to one another and are pivotally connected to one another about a generally longitudinal axis at cross brace pivot point 126c. A cross brace link 143 is pivotally connected at one end at a pivot point 143a to the cross brace 126 and at the opposite end at a pivot point 143b preferably to some mid-height region of the axle plate 129. All of these pivot points 126a, 126c, 143a, 143b have pivot axes that are aligned parallel to the upper side frame member 131. This arrangement of linkages and corresponding pivot axis locations is designed such that the left and right side frames remain parallel when the wheelchair is completely unfolded and completely folded. This arrangement is also designed such that the left and right side frames remain substantially parallel as the wheelchair approaches the unfolded position. Such an arrangement has several advantages. By allowing the two side frames to remain substantially parallel as the wheelchair 120 approaches the unfolded condition, the backrest frame members 125 also remain substantially parallel so that the backrest upholstery does not become overstretched. Also, by repositioning the cross brace linkage pivot point 143b near the mid-height region of the axle plate 129, instead of coaxial or near the upper side frame member 131, as is done on conventional foldable wheelchairs, the lower pivot point 126a of the axle plate 129 may be raised closer to the upper side frame member 131. This arrangement has the advantage of creating a shorter side frame that is more easily transportable, for example, into and out of a car.
The seat frame member 127 may be secured to the cross brace 126 using two bolts 144 and two nuts 145. The seat frame member 127 may be adjustable with respect to the cross brace 126 by aligning the holes in the cross brace 126 with a selected pair of holes in a series of holes 127a in the seat frame member 127. This adjustment allows the seat frame member 127 to be repositioned when the axle plate 129 is moved fore and aft for course center of gravity adjustment. The fact that the seat frame member 127 is secured to the cross brace 126 using fasteners makes it practical to interchange the seat frame member 127 with seat frame members of various lengths on the present wheelchair. Such interchangeability is advantageous because the wheelchair is adaptable for seat depth growth. This growth in seat depth may correspond to growth in backrest depth (not shown) by allowing the backrest to be telescopically adjustable in the longitudinal direction with respect to the upper side frame member 121.
As shown in
While the feature described above includes a cradle with a notch secured to the upper side frame member 131, and a mating protrusion in the seat frame member 127, it is understood that other arrangements are possible that achieve the same end result. For example, the mounting location of the cradle and protrusion can be reversed, so that the cradle is inverted and is secured to the seat frame member 127, while the protrusion is secured to the upper side frame member 131. The notch need not be formed in the cradle, but could be formed in the upper side frame member 131. This relation could also be reversed so that the notch could be formed in the seat frame member 127, and the protrusion could be formed in the upper side frame members 131. Any permutation and/or combination of the above relationships that achieves the desired end result of prohibiting relative translation of the seat frame member 127 with respect to the upper side frame member 131 when the wheelchair 120 is unfolded is considered to be within the scope of this invention.
While the invention described thus far includes a wheelchair with no lower side frame, the structure and arrangement of the wheelchair frame can be modified to include a lower side frame 150, as depicted in
It should be understood that the present invention is not intended to be limited to the wheelchairs and component parts described above. For example, as shown in
As another example, cross brace links 230 may employ a methodology, as shown in
Wheel mounting assemblies 232 may include an axle sleeve 234 that is held with respect to an axle sleeve mount 236 by clamping configuration 238, as shown in
As shown in
An alternative axle plate 260 is shown in
The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.
This application claims the benefit of U.S. Provisional Patent Application No. 60/539,033, filed on Jan. 23, 2004, International Patent Application No. US2005/002088, filed Jan. 24, 2005, and U.S. Provisional Patent Application No. 60/621,489, filed on Oct. 22, 2004.
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