Patent Publication Number: US-6338496-B1

Title: Tilt-in-space wheelchair

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of previously filed co-pending application Ser. No. 09/049,482, filed Mar. 27, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     Tilt-in-space or tilt-and-recline wheelchairs are known. See, for example, the survey article titled “Tilt &amp; Recline: A Balance of Cost and Consumer Need”, which appeared in  Team Rehab Report,  Miramar Communications, Inc., April, 1996 (ISSN 1053-5926). A consensus of opinion in the design of such chairs appears to indicate that cost and mechanical adaptability are key factors needing improvement to satisfy current needs of patients who require such chairs for mobility. 
     Wheelchair bound patients, who spend most of their day in fixed-in-space seating, or in seating having limited ability to recline, can develop body sores, aches and pains and general malaise resulting from the pressure of sitting in a single position for extended periods of time. “Tilt-in-space” is an option that is available on some higher priced wheelchairs that allows the frame and attached seating system to be tilted or rotated in space. This is often needed to better position a patient who is hypotonic by allowing gravity to help keep him/her sitting upright. This feature is also often used in reducing sitting pressures by tilting and thus transferring pressure from the seat surface to the back surface in an effort to prevent decubitus ulcers in patients who cannot otherwise effect weight shifts. 
     Problems associated with current tilt-in-space wheelchairs may include: 
     Inability to fold the wheelchair in the conventional way for transport in a vehicle; 
     High cost; and 
     Weight. 
     Previous efforts have been made to provide wheelchair assemblies having adjustable seating which are also economically feasible, and are described in previous patents. For example, U.S. Pat. No. 5,292,144 describes a conversion kit for standard wheelchairs whereby a wheelchair with a stationary fixed seat can be retrofitted with a tiltable seat having a reclinable back. The seat and back may be separately adjusted by extendible, lockable adjusters and the seat and back apparatus is mountable upon conventional wheelchair constructions. See also the patents described therein. The apparatus of that invention must be removed in order to transport the chair from one site to another, and must be reassembled at the new location. 
     U.S. Pat. No. 4,565,385 discloses a tiltable supporting wheelchair having a tilting mechanism with front support wheels which pivot downwardly and outwardly engaging the floor and raising the front of the wheelchair, thereby tilting it backwardly. The tilting mechanism includes a cross-frame pivotably attached to the frame of the wheelchair and activated by movement of an attached arm. The arm is controlled by a rod leading to a pivotable plate which is connected to a lever on the side of the wheelchair by a linkage. Upon movement of the lever, the linkage rotates the plate, moving the arm and cross-frame to extend or retract the front wheels. A locking mechanism prevents accidental movement of the lever. Rear supports extend behind the wheelchair and engage the floor upon the front wheels being pivoted to their furthest point forward. This device also must be disassembled for transporting it from one site to another. Furthermore, when the tilt feature of this device is activated, the legrests simultaneously elevate, resulting in knee extension which is undesirable in most situations. The general purpose of a “tilt-in-space ” chair is to rotate the patient posteriorly while at the same time maintaining 90 degree angles at the hips and knees. This prior apparatus does not maintain all relative positioning angles of the patient&#39;s body and limbs upon tilting of the chair. 
     SUMMARY OF THE INVENTION 
     An improved, manually propelled, tilt-in-space wheelchair is provided. A patient seated in the wheelchair may be tilted backwardly or forwardly so as to rotate the patient spatially while maintaining all relative positions of the patient&#39;s body and limbs fixed with respect to one another. The wheelchair is of the folding type having an X-brace frame mechanism which permits the unoccupied wheelchair to be folded side-to-side for ease of transport from one site to another. The wheelchair has conventional, large, paired drive wheels, and paired smaller, independently castered front wheels. The patient seating apparatus is supported by a support frame mounted on the axle, and includes seat, back, a headrest, legrests and armrests. 
     In its most general form, the wheelchair of the invention includes means for effecting rotation of the entire patient seating apparatus, including the patient seated thereon, about the axles of the large wheels, while maintaining the drive wheels and the front castered wheels all in fixed spatial relationship, i.e. resting on a fixed ground plane, with respect to each other. The chair also includes means for locking in place the patient seating apparatus at any desired rotation. A key feature of the present invention, and essential to the improvement provided, resides in the fact that the means for rotating the patient and the means for locking the apparatus at the desired rotation do not interfere with nor inhibit the ability of the chair to be folded, side-to-side, for transport. 
     In one embodiment, discussed more fully below, the improved apparatus includes elongate supporting brace members, each having a forward end and a rearward end, the rearward end of each being affixed to the support frame in close proximity to the wheel axle, one adjacent each drive wheel, with the forward end of each having a caster housing which houses one castered front wheel. The tilt-adjusting brace members each act cooperatively with one of the supporting braces, with each tilt-adjusting brace member also being affixed to the support frame at an intermediate position between the forward and rearward ends of its cooperating support brace and in adjacent proximity thereto. Means are provided for effecting relative movement of each tilt-adjusting brace member relative to its cooperating supporting brace so as to effect rotation of the patient seating apparatus about the wheel axles, and for locking the supporting braces in fixed positional relationship with respect to the tilt-adjusting brace members at a desired extent of rotation. 
     The tilt-adjusting brace members may each have arcuate, rearward edges possessing gear-like teeth therein, these arcuate edges being concave with respect to the axle and substantially concentric with respect thereto. The means for locking includes spring-biased tooth engaging means affixed to the supporting braces which releasably engage the gear-like teeth at the desired rotation and effect locking of the patient seating apparatus thereat. 
     In an alternate embodiment, the locking means include cam-actuated means for engaging and disengaging locking at any desired degree of spatial rotation of the chair, also by means of spring-biased tooth-engaging means. 
     The wheelchair may include a manually operated lever control mounted so as to be gripped by an attendant pushing the wheelchair and having flexible cable means mounted on the frame rearwardly of the patient. The cable preferably extends from the lever to the spring-biased tooth engaging locking means, providing manual control of the locking of the seating apparatus at the desired extent of rotation. Additional, independently adjustable means for spatially varying and adjusting each of the seat, back, headrest, legrests and armrests may be provided. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a side elevation, partly broken away, of one embodiment of the improved wheelchair of the invention, with the right-hand wheels (only) and associated mechanical components removed for clarity of illustration, in a tilted-back position; 
     FIG. 2 is a side elevation, partly broken away, of the wheelchair of the invention in an upright position; 
     FIG. 3 is a side elevation similar to that shown in FIG. 1 in a partially tilted-back position; 
     FIG. 4 is a schematic, perspective illustration of one embodiment of the apparatus, which may be attached to an otherwise conventional wheelchair in order to provide the improved wheelchair of the invention, shown in a locked configuration; 
     FIG. 5 shows the apparatus of the invention, which may be attached to an otherwise conventional wheelchair, in an unlocked, rotatable configuration; 
     FIG. 6A is a front elevational view of the wheelchair of the invention illustrating its cross-braces which are segmented, hinged and foldable, enabling the entire chair to be folded side-to-side for transport, which cross-braces do not interfere with the tilt-and-lock mechanisms of the chair; 
     FIG. 6B is a front view of the wheelchair shown in FIG. 6 in its folded configuration; 
     FIG. 7 is a side elevation of a conventional wheelchair; 
     FIG. 8 is a side elevational view, similar to FIG. 1, of an alternate embodiment of the wheelchair of the invention, also shown with the right hand wheels (only) and associated mechanical components removed for illustration clarity, in an upright position; 
     FIG. 9 is a side elevation of the alternate embodiment of the wheelchair shown in FIG. 8 in a tilted-back position; 
     FIG. 10 is an enlarged perspective view of the brackets and an external view of the tilt-and-lock mechanism useful in this alternate embodiment of the chair of the invention; 
     FIG. 11 is a perspective view of a locking pin particularly adapted to be used in the tilt-and-lock mechanism shown in FIG. 10; 
     FIG. 12 is an enlarged elevational view, partly in cross-section, showing the details of the alternate tilt-and-lock mechanism of FIG. 10 in a locked position; and 
     FIG. 13 is an enlarged elevational view, similar to FIG. 12, partly in cross-section, showing the details of the alternate tilt-and-lock mechanism of FIG. 10 in an open, unlocked configuration, permitting the chair to be tilted a desired degree of rotation. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS WITH REFERENCE TO THE DRAWINGS 
     A tilt-in-space wheelchair is provided in which all seating angles are preset to a patient&#39;s needs and the entire seating system may be tilted backwardly or forwardly as a single unit, as desired, to redistribute the patient&#39;s sitting pressures. The apparatus is light in weight and may be installed on conventional, manually propelled folding wheelchairs and, when installed, the chair may still be folded to transport it to a different location. In use, the apparatus allows the sitting patient to be repositioned while maintaining in place all preset relative orientations of the patient&#39;s body and limbs. 
     A detailed description of the invention is best provided with reference to the drawings wherein FIG. 1 shows a side elevation partly broken away of one embodiment of the wheelchair of the invention in a tilted-back position. In this figure, the wheels on the right hand side of the chair are removed for clarity of illustration only. It will be understood that the chair is never used in this configuration. The right and left sides are substantially identical in function. FIG. 1 depicts the frame  12  of the chair to which are affixed the large drive wheels  14  having adjacent hand propelled drive rings  16 . Back support frame  18  is also affixed to frame  12  as shown. The front caster housings  24  which house casters  20  and front castered wheels  22  are attached to the supporting braces  42  at the forward ends thereof. The left support brace  42  is visible in FIG. 1, its rearward end being affixed to frame  12  in close proximity to the axle  39  of wheels  14 , and axle hub  38 . Adjustable footrest  26  is affixed to legrest  28  which, in turn, is affixed to frame  12 . Frame  12  also supports the seat  30  and back rest  32 . Armrest  34  is attached to the back support frame  18  in the conventional manner, as is the handle  36 . 
     The tilt-adjusting brace member  44 , of which there are two with the right one being visible in FIG. 1, acts cooperatively with supporting brace  42 . Brace member  44  is affixed as shown to frame  12  immediately adjacent the support member  42 , and at an intermediate position between the forward end and the rearward (axle) end of support member  42 . The paired tilt-adjusting brace members  44  each have arcuate rearward edges possessing gear teeth  48  and grooves  49  therein, with these arcuate edges being concave with respect to the wheel axle  39  and substantially concentric with respect to the axle. Mounted upon each support member  42  is a gear tooth engaging spring-biased head mechanism having spring-biased head  54  and spaced-apart gear teeth  56  extending from the head  54  and being capable of cooperatively meshing with the grooves  49  in brace member  44 , being forced therein by bias spring  58 . Engaging or disengaging of the teeth  56  at a desired degree of tilt of the chair is controlled by cables  60  which control the tension on the spring  58  by means of cable lever handles  64 , held in position and affixed to the back support frame by cable handle housing  62  and cable guide and support  66 . The spring biased head mechanism  54  provides a means for locking and unlocking the seating apparatus of the chair at a desired degree of rotation about the axle  39 . Compressing lever  64  unlocks the gear teeth  56  from their respective seating grooves  49  in brace members  44  and allows the seating apparatus to be rotated. Releasing lever  64  at the desired tilt permits seating of the teeth  56  into the respective grooves  49  and locking of the frame assembly thereat, all while maintaining drive wheels  14  and castered front wheels  22  in a fixed spatial relationship with respect to each other, i.e. all remaining on the ground plane. In this manner, a patient seated in the chair may be tilted backwardly and forwardly, as needed, so as to rotate the patient spatially while maintaining all relative positions of the patient&#39;s body and limbs fixed with respect to one another. 
     FIG. 2 depicts a side-elevation of the wheelchair of the invention in a fully upright position, showing complete assembly of all component parts, wherein the individual components are as described above in connection with FIG.  1 . 
     FIG. 3 is similar to FIG. 1, but the chair is shown in a partially tilted-back configuration. 
     FIG. 4 shows a schematic perspective view of the hardware assembly  40  of the invention in the embodiment depicted in FIGS. 1 and 3, but with the wheelchair removed for illustration purposes. The right and left-hand assemblies are substantial mirror images of each other. Essential to the tilting and locking functions of the chair are the cooperative operating characteristics of the elongate supporting brace members  42  with their respective tilt-adjusting brace members  44 . At its forward end, each support brace  42  has affixed to it the caster housing  24  which houses caster  20  and front wheel  22 . Affixed to the body of support  42  is spring-biased head mechanism  54  having teeth  56  which mesh with the grooves  49  in brace member  44 . Springs  58 , controlled by hand lever  64  and cables  60 , enable locking and disengagement of the teeth  56  in grooves  49  at any desired tilt rotation of the chair, all controlled by the attendant. Lower stop  50  and upper stop  52  provide safety stops which, respectively, prevent the chair from tilting too far forward or backward. 
     The rearwardly arcuate edges of brace members  44  are substantially concentric with the main axles  39  of the large drive wheels and provide the tilting capability of this chair. Importantly, the rearward end of the support brace  42  should be affixed to the frame  12  of the chair as close as possible to the axle  39  and axle hub  38  to enable tilting and simultaneously maintaining the caster  20  in substantially 90° orientation with respect to the ground surface on which the chair rests. 
     Also shown in FIG. 4 for completeness are the associated hardware components including cable guides and supports  66 , cable handle housing  62  and chair handle  36 . Only one handle  64  is shown controlling both cables  60 , but this is a matter of preference. Independent handles could be employed to control adjustment of right and left tilt, but no particular advantage is seen from this modification. 
     FIG. 5 is virtually identical to FIG. 4 except that handle  64  has been depressed, indicated by the arrow, causing the gear teeth  56  to disengage from the grooves  49 , indicated by the small arrow, thus permitting the chair to be tilted. 
     FIG. 6 is a front elevational view of the wheelchair of the invention showing the cross- or “X”-braces  72  under seat  30  which provide lateral support for this chair, as in conventional chairs. The braces  72  are hinged enabling these brace members to be folded as shown in FIG.  6 A and the entire chair collapsed for transport. The back  32  is generally of a canvas type material which readily folds upon itself as shown in FIG.  6 A. 
     FIG. 7 is a side elevation of a conventional wheelchair which is included for completeness. Like components are designated as above, and no further explanation is deemed necessary. It is to be noted that the tilt-and-lock mechanism described above, and that of the alternate embodiment described below, may be integrated into this conventional wheelchair simply by removing a few nuts and bolts, and securing the tilt-and-lock mechanism in place. Compare, for example, FIGS. 2 and 7. 
     An alternate embodiment of the wheelchair of the invention is depicted in FIG.  8 . Again, like components are numbered as before, and both right hand wheels (only) are omitted for clarity of presentation. Focusing on the alternate tilt-and-lock mechanism, this includes generally horizontal upper brace  80  and lower brace  82  bolted to generally vertical main end brace  86 , which, in turn, is bolted to the frame  12  of the chair. The front ends of these braces  82 ,  84  are bolted to the front caster housing assembly, as shown. When main brace  86  is bolted very near to the hub  38  of drive wheel  14 , the caster assembly and caster wheels  22  are maintained in their generally 90° orientation with respect to the ground surface during tilting of the chair. 
     FIG. 9 depicts the alternate embodiment of the chair shown in FIG. 8 in a tilted-back configuration, again where like components bear like number identification. The right hand components are, generally, mirror images of the left hand components. 
     FIG. 10 shows an enlarged perspective view, partly in cross-section, of the outside appearance of an alternate tilt-and-lock mechanism useful in the chair of the invention. It will be clear to one skilled in the art that various alternatives, other than those depicted herein, may be employed to achieve the tilt-and-lock capability of the chair of the invention. In FIG. 10, the top brace  80  is bolted to main brace  86  to which is affixed, by weld or bolts or other suitable means, outside cam housing  92 . Mating with outside cam housing  92 , as shown, is inside cam housing  94 , held in place thereat by bias spring mechanism  96 . Affixed in cooperative relationship by brackets  90  and  104  is the cable  60 , whose end is attached to bracket  104  and having its own bias spring  102  which tends to keep the cam mechanism of housings  92  and  94  in their closed, mating positions shown in FIG.  10 . Main brace  86  is shown bolted to the chair frame  12 . 
     Extending through the cam housings  92  and  94  and through brace  82  is the connecting pin  88 , shown in FIG.  10  and in perspective in FIG.  11 . Pin  88  has a rectangular cross-section end extending into brace  82  to lock it in position thereat and prevent its rotation. This pin  88  has circular cross-section where it extends through main bracket  86  and outside cam housing  92 , and is free to rotate with respect thereto. Pin  88  has a rectangular cross-section again where it passes through a corresponding rectangular opening in inside cam housing  94 , the rotation of which, caused by applied tension in cable  60 , forces the inside cam housing  94  to separate from the outside cam housing  92 , as is more clearly illustrated by a side-by-side comparison of FIGS. 12 and 13. 
     In the lower portions of FIGS. 12 and 13 may be seen tooth-and-groove means  98  and  100 , which may be cup-shaped in configuration having teeth  99  and grooves  101  in their respective rims. Cup  98  is affixed to outside cam means  92  by weld or bolts or otherwise and cup  100  is affixed similarly inside the inside cam means  94 . The teeth  99  and grooves  101  act cooperatively to lock the cam means  92  and  94  in place in their closed, mating positions. Referring again to FIG. 10 as well as FIG. 12, when there is no tension applied to cable  60 , the cam means  92  and  94  remain in a closed, mating and locked configuration. Referring to FIG. 13, tension has been applied to cable  60  causing rotation of outer cam housing  94  forcing it to separate from complete mating with inside cam housing  92 , and the respective affixed cup means  98  and  100  also separate, thus disengaging their respective teeth and grooves, allowing for rotation of the chair frame  12  freely about the wheel axles, all as depicted by the arrows shown in FIG.  13 . At the desired rotation of the chair and frame, the tension is released in cable  60 , the cam housings again fall into a mating configuration, forced therein by bias spring  96 , as illustrated in FIG. 12, thereby locking the tilt in place by the reengagement of the teeth  99  and grooves  101  at the selected tilt position. 
     While the invention has been disclosed herein in connection with certain embodiments and detailed descriptions, it will be clear to one skilled in the art that modification or variations of such details can be made without deviating from the gist of this invention, and such modifications or variations are considered to be within the scope of the claims hereinbelow.