Patent Application
20130264796
The invention relates to knee, leg or foot rests for chairs and seats. More specifically, the invention relates to adjustable, pivotally moveable footrests that are connected to the chair or seat for relative movement.
Many people suffer from disabilities that affect their life activities. Fortunately, some disabilities can be ameliorated or even alleviated through the use of engineered devices. For example, a cane or walker can help someone with strength or balance problems, while a pacemaker can improve a cardiac patient's quality of life.
One common assistive device that is beneficial to both temporarily- and permanently-disabled individuals is the wheelchair. These are available in a wide range of styles, from light-duty, temporary chairs, to racing and cross-country chairs and fully-powered electric models. Although wheelchairs can be useful in a variety of situations, lower-body and leg injuries are disproportionately common among the difficulties faced by a wheelchair user.
For this reason, many chairs include leg-support structures (generically, “leg rests”) to improve user comfort and convenience. Of course, users' bodies are different sizes and proportions, so it is important for the leg rests (as well as other parts of the chair) to be adjustable, and to be carefully adjusted to fit the user. With respect to leg rests in particular, a problem often encountered is that the rests must be moved, raised and lowered (e.g., to provide suitable ground clearance), and rotated (or swung) up and down (extending the leg) to improve comfort or promote circulation.
A number of mechanisms for adjustable and extensible leg rests are known in the art, but a common problem is that the effective rotation center of many rests is offset from the leg-rotation (extension) center at the user's knee, which causes either the flexed or extended leg-rest length to be wrong. (In other words, a leg rest properly adjusted for length in the flexed position, is too short in the extended position; or vice versa.) Mechanisms designed to address this problem are often complex, heavy or prone to breakage. Furthermore, such existing mechanisms are incompatible with standardized, mass-produced, inexpensive leg-rest components that fit many existing wheelchairs. (
A new wheelchair accessory that can convert a standard wheelchair and universal leg rest into a length-corrected, extendable leg rest may be of significant value to many wheelchair users.
Embodiments of the invention add at least one degree of freedom to the adjustment of a wheelchair leg rest so that the rest can be extended and retracted without requiring a compensating adjustment in length. Many embodiments are designed to work with existing non-extendible leg rests.
Embodiments of the invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean “at least one.”
Embodiments of the invention provide for adjustment of the location of a pivot point where an elevating leg rest attaches to a wheelchair. Adjusting the pivot point to be closer to the user's knee allows the foot support of the leg rest to travel in a similar arc as the user's lower leg and foot, so the foot support remains at a comfortable position, neither too near nor too far from the front of the chair.
The user's thigh is represented by heavy horizontal line 340, while his lower leg and foot are shown as 350 and 355. These lines may be thought of as approximating the location and orientation of the bones of the leg and foot: the femur, tibia/fibula, tarsus, metatarsus and phalanges. Rotation of the lower leg relative to the upper leg occurs at the knee 360.
As shown in
At the left side of
At the right side of the figure, the embodiment's mounting bosses 420 and 430 are visible. These bosses connect the embodiment to the wheelchair (for example, the upper boss 420 fits into, and the lower boss 430 rests against, a vertical tube of the frame of the wheelchair, indicated in this figure by dashed lines 200. Vertical adjustment tube 410 can be secured in place by a locking mechanism 470 (in the embodiment depicted here, the locking mechanism comprises a simple slot 460 in the main body 400 to form a split-flange feature, with a thumb-screw adjustable compression ring 470 to hold tube 410 at a desired position. In use, locking mechanism 470 would be released and tube 410 adjusted vertically to bring pivot 430 near the seated wheelchair user's knee. Then compression ring 470 would be tightened to lock tube 410 and pivot 440 in position.
In some embodiments, other locking mechanisms may be used. For example, a lever and cam “quick release” may substitute for the thumb-screw adjustable compression ring. Alternatively, for more-permanent installations, a set screw or grub screw may secure the sliding tube. If fine adjustability is not necessary, a five- or six-hole captured-pin or shear-pin adjustment, similar to the length adjuster of the leg rest, may be provided. The important capability of the adjuster is that it allow at least vertical movement and positioning of pivot 440, to bring the pivot nearer the wheelchair user's knee.
It is appreciated that, for best results, the pivot point must be both vertically and horizontally near the user's knee when viewed from the side (but need not be near the knee medially). The embodiments shown in
It is appreciated that the two sets of mounting features of an embodiment (the features that connect to the leg rest assembly, and the features that connect to the wheelchair) may be similar (if the embodiment is to be interposed between a leg rest and a wheelchair for which the leg rest is designed); or different (if the embodiment is to be interposed between a leg rest and a different wheelchair, with which the leg rest could not ordinarily be used). In other words, in addition to allowing adjustment of the elevating leg rest pivot point so that the leg rest length need not be adjusted between the elevated and retracted positions, an embodiment can serve as an adapter to allow one type of leg rest to be used with a different type of wheelchair. As an alternative way of describing this property of an embodiment, note that the two sets of mounting features are complementary. In an embodiment designed for use with a leg rest and the wheelchair for which the leg rest is designed, two instances of the embodiment can be connected together because the leg-rest mounting features of one instance will mate properly with the wheelchair mounting features of the other instance. By contrast, in a “heterogeneous” embodiment (designed to fit between a wheelchair and a leg rest designed for a different, incompatible wheelchair), two instances of the heterogeneous embodiment cannot be connected together because the mounting features are not compatible.
The embodiments illustrated in
Embodiments of the present invention have been described largely by reference to specific examples and in terms of particular physical structures to achieve the useful characteristics described. However, those of skill in the art will recognize that adjustable elevating leg rests for wheelchairs can also be constructed using different components and arrangements. Such variations and implementations are understood to be captured according to the following claims.
