Patent Application
20130125378
1. Technical Field
This invention relates generally to mechanical devices, and more particularly to a device for selectively attaching a leg rest to a wheelchair.
2. Background Art
Many wheelchairs come with detachable leg and foot rests. To remove a leg rest, a user presses a push-button of a mechanical assembly, which causes a shaft to move laterally along an axis, thereby releasing the leg rest from the wheelchair. The problem with prior art leg rest releases is that the shaft is threaded into the push-button. Repeated use of the push button causes the shaft to unscrew. Once the shaft unscrews, the entire mechanical assembly is rendered inoperative. Accordingly, the leg rests cannot be secured to the wheelchair. As these devices are not replaceable, the entire wheelchair must be replaced.
It would be advantageous to have a more reliable leg rest release.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
Embodiments of the invention are now described in detail. Referring to the drawings, like numbers indicate like parts throughout the views. As used in the description herein and throughout the claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise: the meaning of “a,” “an,” and “the” includes plural reference, the meaning of “in” includes “in” and “on.” Relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, reference designators shown herein in parenthesis indicate components shown in a figure other than the one in discussion. For example, talking about a device (10) while discussing figure A would refer to an element, 10, shown in figure other than figure A.
Embodiments of the present invention provide a release mechanism for use in wheelchairs that offers a far more reliable construction when compared to prior art designs. A shaft-stem assembly is integrally formed with a push-button as a unified component. The shaft-stem assembly is then disposed within a central axis of two cylindrical housings. The cylindrical housings have different diameters, with one being smaller than the other, so that they may couple together in a nested configuration. In one embodiment, the cylindrical housings are threaded such that an overall length of the nested cylindrical housings can be adjusted by rotating one cylindrical housing relative to the other. Embodiments of the present invention do not use a threaded coupling between push-button and shaft. For this reason, the problem of the shaft unscrewing during use, which is present in prior art designs, is obviated in embodiments of the present invention.
Beginning with
To assemble the mechanical assembly 100, one first inserts the spring 105 into the cylindrical member 106. One then inserts the push-button 101 into a first end 107 of the cylindrical member 106. Next, the shaft 102 is inserted into an opposite end 108 of the cylindrical member 106. The threads 104 of the shaft 102 are then screwed into the push-button 101 by rotating the shaft 102, the push-button 101, or both. Prior art designs require the shaft 102 to thread into the push-button so that the length of the push-button-shaft assembly can be adjusted to properly align with a ball-bearing release mechanism (not shown). Without the threaded push-button-shaft assembly, the prior art design cannot be reliably manufactured. The completed mechanical assembly 100 is shown in a ghost view in
The problem with the design of
To remedy this problem, embodiments of the present invention employ a shaft-stem assembly that is integrally formed with the push-button as a unitary component. Accordingly, the shaft is not able to unscrew from the push-button because they are perdurably connected together. In addition to preventing the shaft from separating from the push-button, embodiments of the present invention allow for overall length adjustment by using a novel nested cylindrical housing design.
Turning now to
In one embodiment, the shaft 302, which can be manufactured from metal in one embodiment, is perdurably connected to the push-button 301 by insert molding. Where this is the case, the push-button 301 can be manufactured from a thermoplastic or resin. In an insert molding process, the shaft 302, and optionally the stem 303, are placed into a mold. The thermoplastic or resin is then injected into the mold about the stem 303, thus forming a unitary, perdurably connected component. Where both the shaft 302 and the push-button 301 are manufactured from thermoplastics, they can, of course, be molded as a singular, non-separable component.
In another embodiment, both the push-button 301 and the shaft 302 can be manufactured from metal. Accordingly, the push-button 301 and the shaft 302 can be perdurably connected via a welding process, soldering process, or other metal adhesion process. Similarly, where the stem 303 and shaft 302 are manufactured from separate selections of metal, the stem 303 and shaft 302 can be perdurably connected by welding, soldering or other metal adhesion process. Alternatively, the stem 303 and shaft 302 can be manufactured from a single piece of metal, thereby eliminating any connection point between the two components.
In yet another embodiment, the shaft 302 and push-button 301 can be perdurably connected together by way of epoxy or other permanent adhesive component. In yet another embodiment, the shaft 302 and push-button 301 can be perdurably connected together by pinning, riveting, crimping, or otherwise permanently affixing the two components together. The perdurable connecting methods described are illustrative only, as others will be obvious to those of ordinary skill in the art having the benefit of this disclosure.
A spring 305, which is geometrically configured to be conical in the illustrative embodiment of
A second cylindrical housing 304, which has a diameter that is less than that of the first cylindrical housing 306 in this illustrative embodiment, nests within the first cylindrical housing 306 to form a nested cylindrical housing assembly 311 via a threaded end 313. An axial length 312 of the nested cylindrical housing assembly 311 can be selectively adjusted by rotating the second cylindrical housing 304 into or out of the first cylindrical housing 306. While the second cylindrical housing 304 is shown as having the smaller diameter, note that in another embodiment the opposite could be true, with the first cylindrical housing having 206 having a diameter that is less than that of the second cylindrical housing 304 so as to nest within the second cylindrical housing via a threaded component disposed at the end of the first cylindrical housing 306.
A ball bearing 309 disposed in the second cylindrical housing 304 is selectively allowed to translate into and out of the second cylindrical housing 304 in a direction that is orthogonal to the central axis defined by the first cylindrical housing 306 and the second cylindrical housing 304. Note that while the ball bearing 309 is shown being disposed in the second cylindrical housing 304 in
The central axis of
The “axial length adjustability” of the nested cylindrical housing assembly 311 can be more readily appreciated using the view of
Turning now to
At step 503, the spring 305 is inserted into a second end 509 of the first cylindrical housing 306. The unitary shaft-stem assembly 310 is then inserted into the second end 509 of the first cylindrical housing 306 through an axial center of the spring 305 such that the shaft 302 and stem 303 pass through an interior of the spring 305. In this illustrative embodiment, the second cylindrical housing 304 has been rotated into the first cylindrical housing 306 to a maximum extent such that the axial length 402 of the nested cylindrical housing assembly 311 is at its minimum.
In one embodiment, the minimum of the axial length 402 is less than an axial length 510 of the unitary shaft-stem assembly 310 extending from just below a push surface 511 of the push-button to the end of the stem 303. This is shown at step 504, where the unitary shaft-stem assembly 310 has been fully inserted into the nested cylindrical housing assembly 311, thereby compressing the spring 305 such that the stem 303 protrudes from an end of the nested cylindrical housing assembly 311. Accordingly, the unitary shaft-stem assembly 310 is disposed along an axial center of the nested cylindrical housing assembly 311. This “full insertion” occurs when the minimum of the axial length 402 is less than an axial length 510 of the unitary shaft-stem assembly 310 causes the stem 303 and a portion of the shaft 302 to extend beyond a second end 512 of the second cylindrical housing 304, thereby allowing the ball bearing 309 to be inserted between the walls of the second cylindrical housing 304 and the shaft 302. Said differently, the ball bearing 309 passes by the shaft end of the stem 303 into the second cylindrical housing 304.
When the unitary shaft-stem assembly 310 is released, the spring 305 causes the stem 303 to retract into the second cylindrical housing 304 by biasing the push-button outwardly from the nested cylindrical housing assembly 311, thereby retaining the ball bearing 309 within the second cylindrical housing 304. This is shown in step 505, where the stem 303 retains the ball bearing 309 within the second cylindrical housing 304. Once the unitary shaft-stem assembly 310 is release, the second cylindrical housing 304 can be un-rotated 513 from the first cylindrical housing 306 to adjust the axial length 402 of the nested cylindrical housing assembly 311 to a length appropriate for its application, i.e., for an appropriate length corresponding to the particular wheelchair into which it is to be inserted.
Turning now to
Beginning with
Turning to
Turning to
Turning to
Turning to
As shown, a leg rest 1112 has been attached to a wheelchair 1113. An aperture 1114 is defined between the leg rest 1112 and the wheelchair 1113. The explanatory leg rest release 1100 is configured for insertion into the aperture 1114.
After rotating the first cylindrical housing 1106 relative to the second cylindrical housing 1104 to create the appropriate axial length 1142 of the nested cylindrical housing assembly 1111, a user first presses the push-button 1101 into the explanatory leg rest release 1100, thereby causing the stem 1103 to extend beyond the second cylindrical housing 1104. This permits the ball bearing 1109 to withdraw into the second cylindrical housing 1104. The explanatory leg rest release 1100 is then inserted into the aperture 1114. Once seated, the user may release the push-button 1101, thus retracting the stem 1103 into the second cylindrical housing 1104 due to a loading force of the spring (not shown) disposed in the first cylindrical housing 1106. The ball bearing 1109 is thus forced outwardly from the second cylindrical housing 1104 and engages a détente in the wheelchair 1113, thereby holding the leg rest 1112 securely against the wheelchair 1113.
In the foregoing specification, specific embodiments of the present invention have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Thus, while preferred embodiments of the invention have been illustrated and described, it is clear that the invention is not so limited. Numerous modifications, changes, variations, substitutions, and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as defined by the following claims. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims.
