Patent Application
20120286552
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1. Field of the Invention
The present invention relates generally to seat assemblies and more particularly to seat assemblies for use with wheelchairs.
2. Background of the Related Art
Individuals who must remain seated for prolonged periods of time confront a myriad of problems. One significant concern is the development of pressure sores. Pressure sores, also referred to as contact necrosis, are a painful affliction that develop rapidly in response to various factors, including restricted blood flow due to lack of physical movement and sustained moisture due to insufficient circulation of air around the body surfaces that remain in contact with the seating surface. In particular, wheelchair users and their caregivers must remain vigilant in their efforts to avoid the development of pressure sores. When these sores do develop, the affliction must be treated promptly for fear that it may become exacerbated.
One conventional method for reducing or preventing the development of pressure sores is the use of seating cushions composed of various materials, including foam, gel, fluid and thixotropic materials. Seat cushions are intended to alleviate the pressure loads endured by sensitive areas of the skin while maintaining support at surfaces less likely to develop pressure sores. While these solutions offer varying degrees of success in alleviating the pressure load on sensitive areas of the skin, they invariably have several disadvantages. These disadvantages include insufficient weight distribution, poor shear and tension properties, inconsistent weight distribution between uses, and discouraging good seating posture.
Furthermore, the cushion solution does nothing to address, and even exacerbates, the retention of moisture on skin surfaces. Typically, the materials within and surrounding a cushion are not breathable. As they tend to conform to the body surfaces they support, they actually increase the skin surface area that remains in constant contact with the seating surface. As a result, moisture from natural perspiration and any other sources develops more quickly and natural evaporation of this moisture is inhibited when individuals sit on a cushion for any duration.
Another problem encountered with the use of seat cushions is the addition of significant bulk and weight to wheelchairs. Increased volume makes disassembly and transport of wheelchairs much more cumbersome task. Similarly, added weight significantly impairs the mobility of all wheelchair-bound individuals. This is especially true for individuals with decreased upper body strength and self-propelled wheelchairs.
Further, these cushion solutions do not address another significant concern surrounding long term use of wheelchair seats. Seating surfaces must be cleaned regularly to maintain adequate levels of hygiene. They must be cleaned promptly if soiled due to incidents of incontinence or in the course of normal use. In addition, prolonged contact with seating surfaces leads to the accumulation of residue that is unsanitary and can become an irritant. The components of seat cushions, such as foams and cloth covers, are often absorptive, making them very difficult to keep clean using conventional cleansing methods. When seat cushions do become soiled, it may be impractical to clean them, thus requiring costly replacement.
Another strategy for avoiding the development of pressure sores is the use of segmented and articulating seats that incorporate mechanical or pneumatic apparatuses into the seating assembly. Such apparatuses relieve pressure by selectively withdrawing portions of the seat from contact with the seated wheelchair occupant. A related strategy uses pneumatic or hydraulic systems to adjust cushion pressure. Both of these solutions have several disadvantages. The incorporation of such an apparatus significantly increases the weight of the wheelchair. This is especially important where the wheelchair is self-propelled or the occupant has impaired upper body strength. Further, such apparatuses necessarily increase the cost of the wheelchair, require significant maintenance beyond that already required for a wheelchair and introduce an additional opportunity for mechanical failure. These are all practical considerations for individuals already faced with significant healthcare costs. Finally, this approach does not decrease the retention of moisture, nor does it improve the ease of maintaining the seating surface in a hygienic state.
Another approach to wheelchair seats uses a seating surface formed by a latticework of spaced inelastic straps attached to each other or to the support rails of the wheelchair itself. This solution attempts to address the problem of moisture retention by increasing the opportunity for the circulation of air at the seating surface. While air circulation may be increased, the straps at the periphery of the seating surface as well as the wheelchair rails used to support the latticework create hard edges at the forward, rear and side regions of the seating surface. Significant pressure points occur where the wheelchair user's body comes into contact with these hard edges. The circulation of blood at these points is restricted or prevented entirely causing additional damage at these points and in more distant parts of the body supplied with blood through these regions.
Every attempt to address the development of pressure sores in wheelchair seats suffers from a number of disadvantages. Accordingly, it remains desirable to provide a seat assembly that discourages the development of pressure sores while eliminating the disadvantages encountered by previous designs.
Another significant problem encountered by users of wheelchairs is the need for a suspension system. Traditionally, suspension systems are used in wheeled vehicles to improve handling and to isolate occupants from injury or discomfort from bumps and vibration while traversing uneven surfaces. This same benefit could be realized in a wheelchair. Previous attempts to address the need for suspension have borrowed from the automotive and bicycle industries. These solution involved the incorporation of additional components to a wheelchair, such as coils, shocks or cushioned inserts. All of these attempts necessarily add additional weight to the wheelchair, which is a significant disadvantage in self-propelled wheelchairs and for individuals with decreased upper-body strength. Accordingly, it remains desirable to provide a solution that provides a system of suspension for wheelchairs without increasing the weight of the wheelchair itself.
It is, therefore, an object of this invention to provide a wheelchair seat which discourages the development of pressure sores. Another object of this invention is to provide a wheelchair seat which allows pressure to be more evenly distributed across its seating surface. A further object of this invention is to provide a wheelchair seat which can be adjusted to suit individual occupants' preferences and needs. Still another object of this invention is to provide a wheelchair seat that facilitates the circulation of moisture and air surrounding the seating surface. An additional object of this invention is to provide a wheelchair seat that encourages the circulation of blood where a wheelchair user's bodies meets the seating surface. A further object of this invention is to provide a wheelchair seat which is easily sanitized to maintain hygiene. It is also an object of this invention to provide a wheelchair seat that does not significantly contribute to the weight of a wheelchair. Another object of this invention is to provide a wheelchair seat which does not discourage or prevent the transportation of a wheelchair. An additional object of this invention is to provide a wheelchair seat that incorporates a system of suspension.
Accordingly, the present invention contemplates a new and improved seat, and more particularly, a wheelchair seat assembly. The invention eliminates the above-discussed and other drawbacks of the currently employed wheelchair seating solutions.
The invention solves the problem of pressure sore development by providing a seating surface with improved and adjustable pressure distribution. The problem of heavy and cumbersome seat cushioning options is solved by providing a seat assembly that is both lightweight and sturdy. The invention solves the problem of ease of transporting a wheelchair seat by providing a seat assembly that is detachable from a wheelchair. The problem of maintaining hygienic standards is solved by providing a seating surface that is easily removed and cleaned.
In one embodiment, the invention provides a seating assembly with no rigid points of contact near the front and rear regions of the seating surface. In another embodiment of the invention, the seat assembly is provided with an elastomeric seating surface extending between side members of a frame that are situated higher than the front and rear members. In yet another embodiment of the invention, the side members of the frame are angled away from the plane formed by the front and rear members and the side members are curved away from the longitudinal axis of the assembly. In a further embodiment of the invention, the tension across the seating surface of the seating assembly can be altered by adjusting the width of the seating assembly. In still another embodiment of the invention, the tension across the seating surface of the seating assembly can be altered by independently adjusting the front and rear widths of the seating assembly.
The invention may take physical form in certain parts and arrangements of parts, a preferred embodiment of which will be described in detail in this specification. Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the accompanying drawing, in which:
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings that are herein described in detail. It should be understood, however, that the description herein to specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. It will of course be appreciated that in the development of any such actual embodiment, numerous decisions specific to any particular implementation must be made to achieve the developers' goals, such as compliance with regulatory and medical constraints, which will vary from one implementation to another. In the interest of clarity, not all features of an actual implementation are described in this specification. Moreover, it will be appreciated that such development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
As used herein, rigid point of contact refers to the interface between any firm component of the invention and the user's body, such that increased levels of pressure would be exerted on the user's body at the interface. Such rigid points of contact are liable to promote the development of pressure sores and the myriad medical problems accompanying pressures sores.
As used herein, elastomeric refers to any material which, upon application of a force to its relaxed, initial length can stretch or elongate in at least one direction and will substantially recover back to approximately its original length upon release of the applied force.
The frame components discussed herein may be composed of any of a number of sufficiently strong materials and may be formed or constructed by any of a number of processes. Nothing in the descriptions of the embodiments below is intended to be a limitation in the possible materials to be used in constructing any form of this invention.
Rotation of front threaded member 110 in one direction is a tightening rotation causing the front end members 111 and 112 to move closer together. Rotation of front threaded member 110 in the opposite direction is a loosening rotation causing the front end member 111 and 112 to move further apart. Flattened region 116 accepts use of a lever, such as a specialized key or standard wrench, to facilitate rotation of front threaded member 110.
Rotation of rear threaded member 120 in one direction is a tightening rotation causing the rear end members 121 and 122 to move closer together. Rotation of rear threaded member 120 in the opposite direction is a loosening rotation causing the rear end members 121 and 122 to move farther apart. Flattened region 126 accepts use of a lever, such as a specialized key or standard wrench, to facilitate rotation of rear threaded member 120.
Cushioning material 140 is layered across and secured to the inner peripheries and upper surfaces of side members 131 and 132. Flanges 150 project from seat frame 100. Clasps 160 are pivotally attached to seat frame 100. Seat frame 100 typically attaches to longitudinally oriented bars of a standard wheelchair frame. Such frame bars are oriented approximately parallel to longitudinal axis 101 and approximately perpendicular the front and rear members 110 and 120. Seat frame 100 is supported on wheelchair frame bars by flanges 150.
When a seating surface is attached to the seat frame, the only portion of the frame with which a seated user's body would come in contact with the frame is along the inner peripheries and upper surfaces of the side members 131 and 132. These are also the only firm edges which a user's body might encounter. The cushioning material 140 is present across the entirety of these surfaces to mitigate this contact and distribute any potential pressure points along this interface.
Seat frame 100 is secured to wheelchair frame bars by using clasps 160. Inner circumference of clasps (161) approximates the outer circumference of wheelchair frame bars. To secure seat frame 100, clasps 160 are pivoted down onto wheelchair frame bars and snapped into place around the wheelchair frame bars with the application of pressure. Seat frame 100 is held in place on wheelchair frame bars by the tension exerted around the frame bars at the inner circumference of clasps 161 and by the downward force exerted at flanges 150 by the weight of the user on seat frame 100.
As indicated in
Side member 231 is pivotally attached to front end member 211 and rear end member 221 by fasteners 270. Side member 232 is pivotally attached to front end member 212 and rear end member 222 by fasteners 270. The ability of end members and side members to pivot relative to one another permits the distance between front end members and the distance between rear end members to be set independently. By rotating threaded members 210 and 220 separately, a user or an assistant would be able to customize the tension across the seating surface to the user's preferences.
For example, a user may prefer a very firm seating surface near the rear and a softer seating surface near the front. This could be accomplished by increasing the width across the rear members and decreasing the width across the front members. This variation in widths corresponds to variation in the degree to which different regions of a seating surface are stretched, in the amount of tension across seating surface regions, and the firmness experienced by the user.
Left recessed region 412 is narrower in diameter than immediately adjacent portions of and left member 410. Right recessed region 422 is narrower in diameter than immediately adjacent portion of right member 420. The lengths of left recessed region 412 and right recessed region 422 are at last as long as the width of strap 431.
Ratchet 432 is loosened to adjust the length of strap 431 and, as a result, the length of cross member 430. Ratchet 432 is tightened to set the length of strap 431 and set the length of cross member 430. Wheelchair frame bars to which left member 410 and right member 420 are secured correspond to the axis of rotation for member, respectively. The weight of a person on a seating surface secured to the left member 410 and right member 420 exerts a force pulling left upper region 411 and right upper region 421 closer together. As a result of the axis of rotation, this corresponds to a force moving left recessed region 412 and right recessed region 422 farther apart. Cross member 430 limits the separation of the recessed regions based on the length of cross member. Thereby, the adjusted length of cross member 430 determines the distance between left upper region 411 and right upper region 421 and the corresponding tension across an elastomeric seating surface attached thereto.
Cross member 530 includes left threaded member 531, right threaded member 532 and center member 533. Left threaded member 531 is pivotally attached to left frame member 510. Right threaded member 532 is pivotally attached to right frame member 520.
Left threaded member 531 and right threaded member 532 are threaded in reverse orientation to each other. Center member 533 has a first end with a bore threaded to accept the thread of left threaded member 531 and a second end with a bore threaded to accept the thread of the right threaded member 532. Left threaded member 531 is threadedly attached to center member 533 at the first end. Right threaded member 532 is threadedly attached to center member 533 at second end. Clasps 560 are attached to the left frame member 510 and the right frame member 520. Inner circumference of clasps (561) approximates the outer circumference of bars of a wheelchair frame. Seat frame 500 is secured to a wheelchair frame by snapping clasps 560 onto bars of a wheelchair frame with the application of downward pressure.
Rotation of center member 533 in one direction is a tightening rotation causing left threaded member 531 and right threaded member 532 to move closer together. Rotation of center member 533 in the opposite direction is a loosening rotation causing left threaded member 531 and right threaded member 532 to move farther apart.
When the seat frame 500 has been secured to a wheelchair frame and a tightening rotation is applied to the center member 533, the reduction in distance between the left threaded member 531 and the right threaded member 532 is accompanied by the rotation of the left frame member 510 and the right frame member 520, the axis of rotation being the wheelchair frame bars to which each is secured with clasps 560. As a result of a tightening rotation, left upper region 511 and right upper region 521 are moved farther apart, thereby increasing the tension across an elastomeric seating surface secured thereto. Upon applying a loosening rotation to the center member 533, the increase in distance between the left threaded member 531 and the right threaded member 532 is accompanied by a reduction in the distance between left upper region 511 and right upper region 521 and a decrease in the tension across an elastomeric seating surface secured thereto.
The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention.
While a preferred form and various embodiments of the invention have been shown in the drawings and described, since variations in the preferred form will be apparent to those skilled in the art, the invention should not be construed as limited to the specific form shown and described, but instead as set forth in the following claims.
