BACKGROUND OF INVENTION
This invention relates in general to land vehicles and more particularly, to personal mobility vehicles. Most particularly, the invention relates to camber assemblies for wheelchairs.
Frequently, the rear wheels of a wheelchair are cambered, or angled with respect to a vertical plane. A wheelchair with a large camber angle has more responsive turning, and is typically beneficial in sports applications. A wheelchair with little to no camber has a smaller overall width and thus increased maneuverability in tight confines. Wheelchairs with adjustable camber are well known in the art. Adjustable camber allows the user to change the camber angle in order to adapt to a driving environment. A user would typically choose a small camber angle for indoor use, and a large camber angle for outdoor use. Changing camber alters several characteristics of the wheelchair due to the repositioning of the wheels. One undesirable consequence of changing from no camber to a high camber angle is that the rear of the wheelchair is lowered. This lowering not only alters the user's position, but also requires the front casters to be re-squared. Re-squaring the front casters is often a difficult adjustment. Another undesirable result of adjustable camber is that the tops of the rear wheels tend to tilt inward towards the centerline of the wheelchair, which changes the location of the tires and hand rims. To compensate for these changes, the rear axles must displace outward and downward as the camber angle increases. There are several wheelchairs available that offer two or more camber angles while addressing these issues with limited success. One such wheelchair is described in U.S. Pat. No. 6,311,999. In this invention, the height of the rear of the wheelchair changes as the camber angle is changed, requiring that the front casters be re-squared during such adjustment.
What is needed is a wheelchair that offers the user a wide range of camber angles, is quickly and easily adjusted without having to re-square the casters, and that compensates for the change in position of the wheel.
SUMMARY OF INVENTION
The present invention is directed towards an angle adjustable camber assembly that meets the foregoing needs. The assembly is adapted to support the wheel of a wheelchair having a seat, the rear of which is at a rear seat height. The assembly comprises a movable member for supporting the wheel. The movable member is adapted to translate and rotate so as to be able to selectively position the wheel at any one of a variety of camber angles while substantially maintaining the rear seat height and spacing between the top of the wheel and the seat frame.
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.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a side elevational view of an angle adjustable camber assembly according to the invention.
FIG. 2 is a cross-sectional view of the angle adjustable camber assembly taken along the line 2-2 in FIG. 1.
FIG. 3 is an exploded rear perspective view of the angle adjustable camber assembly shown in FIGS. 1 and 2.
DETAILED DESCRIPTION
Referring now to the drawings, there is illustrated in FIGS. 1-3 an angle adjustable camber assembly 10 that is a lightweight means of changing camber, preferably between 0°, 3°, 6° or 9° camber, quickly and easily, and preferably without tools. The assembly 10 is adapted to reposition the rear wheel axles (not shown) of a wheelchair so that the positions of the rear seat height and the handrim of the rear wheels (neither of which are shown) do not change as camber angle changes. The assembly 10 can be an option that mounts to and has substantially the same adjustment features as the axle plate assembly described in copending U.S. Provisional Patent Application No. 60/608,604, filed Sep. 10, 2004, the subject matter of which is incorporated herein by reference. The assembly 10 generally comprises a large diameter camber tube 12 that is adapted to be secured to the axle plate 14 using, for example, large diameter camber tube clamps 16, as shown in FIG. 3. The rear wheel axle is adapted to be attached to, or otherwise supported by an axle slide 18, or other movable member, that assumes a plurality of positions, such as the four positions shown, within the camber tube 12 to establish, for example, the four camber angles described above. As the slide 18 moves from, for example, the 0° to 3° to 6° to 9° positions, the slide 18 translates outward and downward and changes angle in order to maintain a substantially constant rear seat height and wheel handrim position. The slide 18 preferably has two cross-holes 18a (see FIG. 3) that preferably have dowel pins 20 pressed therein so that opposing ends of the dowel pins 20 protrude substantially an equal distance beyond the thickness of the slide 18. A guide assembly preferably includes two guides 22 that are substantially fixed to the sides of the interior of the camber tube. The guides 22 create a cavity where the slide 18 resides. These guides 22 preferably have two arc shaped tracks 22a that capture the ends of the dowel pins 20, and control the path of the slide 18 as the slide 18 moves from one camber angle setting to another. An index pin 24 engages with a groove 18b (see FIG. 2) on the underside of the slide 18. The groove 18b has a series of peaks and valleys 18c (see FIG. 2). The four valleys 18c are positions where the index pin 24 settles when the slide 18 is located at the discrete (i.e., 0°, 3°, 6° or 9°) camber position. The index pin 24 is loaded by a compression spring 26 that biases the index pin 24 into engagement with one of the four valleys 18c. The compression spring 26 is held captive between the index pin 24 on one end, and a set knob 28 on the other end. The set knob 28 is adapted to be loosened to change camber angle, and tightened to lock the assembly 10 into a selected camber angle. The set knob 28 is preferably adapted to be threadably engaged with a pin carriage 30 that is substantially fixed relative to the camber tube 12. The pin carriage 30 has a central bore 30a (see FIG. 3) that may capture the outer diameter of the index pin 24, restricting the index pin 24 to motion along the axis A1 of the index pin 24. When the set knob 28 is tightened, the set knob 28 contacts the lower end of the index pin 24 and pushes the index pin 24 into engagement with one of the valleys 18c. When the set knob 28 is loosened, the index pin 24 remains biased towards engagement with the groove 18b due to the compression force of the spring 26, but has sufficient clearance to rise and fall over the peaks and valleys 18c. To change camber angle position, the user may loosen the set knob 28 and push or pull on the rear wheel or slide 18. An indexed clicking is felt as the index pin 24 settles into the valleys 18c. The user may tighten the set knob 56 to locking the index pin 24 into engagement with a selected valley 18c, thereby taking any play out of the assembly 10.
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.
Patent Grant
7249773
