Personal mobility vehicle with tiltable seat

The vehicle comprises a base and a seat moveable along a curve having a focal point. The vehicle is adjustable to position an occupant in the seat to achieve a desired position for the center of gravity of the occupant relative to the focal point of the curve. A method for minimizing effort required to tilt the seat of a personal mobility vehicle comprises the steps of providing a personal mobility vehicle having a seat that is adapted to move along an arc having a center of curvature, positioning the seat substantially horizontally, providing an occupant in the seat, and adjusting the position of the vehicle occupant's center of gravity so that the center of gravity is substantially equal to or below the center of curvature of the arc.

BACKGROUND OF INVENTION

This invention relates generally to land vehicles and more particularly to personal mobility vehicles. Most particularly, the invention relates to a personal mobility vehicle having a tiltable seat assembly.

Personal mobility vehicles with tilting seats are well known. Such vehicles are typically used in highly dependent or geriatric care, wherein the ability to reposition a vehicle occupant in various angular positions is beneficial to the occupant's health and daily routine. Tilting a vehicle occupant relieves pressure to the vehicle occupant's ischial tuberosities (i.e., the bony prominence of the buttocks). Continuous pressure to the vehicle occupant's ischial tuberosities, which is applied when the vehicle occupant remains in a single seated position, can cause the development of decubitus ulcers (i.e., pressure sores). For vehicle occupants with severe kyphosis (i.e., curvature of the spine), seated tilting may allow the occupant to look forward and interact with their surroundings. Tilting may also be beneficial to assist with proper respiration and digestion.

Some personal motor vehicle occupants require attendant care, wherein an attendant is responsible for positioning the vehicle seat angle, often changing the angle on a prescribed schedule. The ability to tilt the vehicle occupant offers the occupant a variety of positions that accommodate their daily schedule, including, for example, an anterior tilt for eating at a table and posterior tilt for resting.

Conventional tilting personal mobility vehicles consist of a seat frame that is pivotally mounted to a base frame so that the seat frame tilts to reposition the vehicle occupant. The pivot axis is typically mounted between the base frame and seat frame, towards the rear of the seat and away from the occupant's center of gravity. Tilting the occupant involves lifting or lowering his or her center of gravity and therefore requires effort on the part of the attendant. Mechanisms, such as springs or gas cylinders, are often employed to assist in tilting the occupant. Typically, levers are attached to handles on a seat-tilting vehicle. The levers allow an attendant to release a locking mechanism, change the tilt angle by pushing or pulling on the handles, and engage the locking mechanism, which fixes the tilt angle.

Tilting the seat in conventional tilt personal motor vehicles may invoke a reaction on the part of the occupant who experiences the sensation of being tipped over. The occupant experiences a sensation of being pitched off balance during tilting. Conventional tilt seat designs involve translation of the vehicle occupant's center of gravity during tilting. Significant effort on the part of the attendant may be required to tilt the vehicle occupant when the occupant's mass translates during tilting. Moreover, conventional vehicles with tilt seats require large base frames and anti-tip devices because tilting the chair displaces the occupant's center of gravity fore and aft over the wheelbase, potentially placing the vehicle off balance.

What is needed is a personal mobility vehicle that does not evoke the sensation of being tipped over; that requires minimal effort on the part of the attendant to tilt (i.e., no lifting or lowering of the vehicle occupant's center of gravity should be required to tilt the vehicle seat assembly); does not affect weight distribution between the front and rear wheels; and that is limited to pure rotation (i.e., the only effort required is to overcome friction within the system), thus eliminating the need for springs or gas cylinders to assist tilting.

SUMMARY OF INVENTION

The present invention is directed towards a personal mobility vehicle that overcomes the foregoing deficiencies. The vehicle comprises a base and a seat moveable along a curve having a focal point. The vehicle is adjustable to position an occupant in the seat to achieve a desired position for the center of gravity of the occupant relative to the focal point of the curve.

Another embodiment of the invention is directed to a personal mobility vehicle comprising a personal mobility vehicle having a seat that is supported for movement relative to a radial or quasi radial curve having a center of curvature that is preferably substantially fixed in space. The seat is adjustable with respect to the curve so that the center of gravity of a vehicle occupant is sufficiently coincident with the focal point of the curve so that force required to tilt the seat is minimized.

Another embodiment of the invention is directed to a personal mobility vehicle comprising a base and a seat for support a vehicle occupant. The seat is supported for movement along a curve having a center of curvature. The seat is adapted to support a vehicle occupant having a center of gravity that is adapted to be positioned relative to the center of curvature sufficient to minimize effort required to move the seat with the vehicle occupant therein along the curve.

Another embodiment of the invention is directed to a personal mobility vehicle comprising a base, a plurality of wheels that are adapted to support the base relative to a supporting surface, and a seat for supporting an occupant. The seat is supported relative to the base for movement along an arcuate path with a fixed center of rotation. The seat is adjustable such that the center of gravity of the occupant is adapted to be substantially coincident with the center of rotation.

Another embodiment of the invention is directed to a personal mobility vehicle comprising a base, a plurality of wheels that are adapted to support the base relative to a supporting surface, a seat, one or more tracks having a constant radius arc supporting the seat for movement relative to the base, and a low friction support assembly supported by either the base or the seat or any combination thereof. The support permits an overall tilt angle range of the one or more tracks to be adjusted.

Another embodiment of the invention is directed to a personal mobility vehicle comprising a base, a plurality of wheels that are adapted to support the base relative to a supporting surface, a seat for supporting an occupant, and one or more tracks supporting the seat. The tracks serve as a rolling or sliding surface that allows the seat to rotate with respect to the base. The tracks have a constant or substantially constant radius arc with a focal point that is substantially fixed in space, whereby the location of the center of gravity of the occupant can be adjusted to be coincident or near coincident with the focal point.

Another embodiment of the invention is directed to a method for minimizing effort required to tilt the seat of a personal mobility vehicle. The method comprises the steps of providing a personal mobility vehicle having a seat that is adapted to move along an arc having a center of curvature, positioning the seat substantially horizontally, providing an occupant in the seat, and adjusting the position of the vehicle occupant's center of gravity so that the center of gravity is substantially equal to or below the center of curvature of the arc.

DETAILED DESCRIPTION

Referring now to the drawings, there is illustrated inFIGS. 1 and 2a personal mobility vehicle, as generally indicated at10. The vehicle10has a base12and a seat assembly14supported by the base12. The base12is supported on a supporting surface by wheels, such as the front casters16and the rear wheels18shown. The front wheels16are preferably casters and the rear wheels18are preferably driven wheels, which may be manually driven or power driven. It is noted that the personal motorized vehicle shown is in the form of a wheelchair but the invention is intended to be practiced with other personal mobility vehicles, including but not limited to scooters. Although the wheelchair illustrated is a rear wheel-drive wheelchair, the invention may be practiced with front mid-wheel drive vehicles. The seat assembly14has a seat frame20and a seat back22. The seat frame20includes longitudinally extending frame members, such as tubes, for supporting a seat24, which can be in the form of a semi-rigid or rigid pan, as shown, or a resilient or pliable sling (not shown). The seat24may include adjustable parts, such as the telescopic parts shown, that are longitudinally adjustable relative to one another to permit the length of the seat24to be adjusted. The seat back22preferably includes laterally spaced canes26for supporting a backrest (not shown). The canes26are preferably formed of adjustable parts, such as the telescopic tubes shown, that permit the length of the canes26, and the seat back22, to be adjusted. A handle28may be supported by the canes26. In the illustrated embodiment, the handle28is pivotally coupled to the canes26, preferably by couplings30that are adapted to releasably hold the handle28in a fixed relation to the canes26.

The seat frame20is preferably adapted to support armrests32and footrest assemblies34. The armrests32are preferably releasably attached to the seat frame20and movable in a longitudinal direction relative to the seat frame20. The armrests32are preferably held in fixed relation to the seat frame20in any conventional manner, such as by the tube clamps36shown. The footrest assemblies34are also releasably and movably attached to the seat frame20.

As illustrated inFIGS. 3 and 4, the base12includes a base frame (shown but not referenced), which is comprised of opposing side frame members, such as the tubes40, joined by a pair of longitudinally spaced, laterally extending frame members, such as the tubes42shown. It should be noted that the laterally extending tubes42are preferably of telescopic tubes that are adjustable relative to one another to permit the vehicle10to grow in width. It should further be noted that the position of the laterally extending tubes42is preferably adjusted relative to the side tubes40, for example, via the longitudinally spaced holes and fasteners (not shown).

The seat frame20is similarly comprised of opposing side frame members, such as the tubes44shown, and curved or substantially curved members, such as the tracks or rockers46shown, or a curved rack (not shown), joined by a plurality of longitudinally spaced, laterally extending members such as the tubes48shown. It should be noted that the laterally extending tubes48are preferably in the form of telescopic tubes that are adjustable relative to one another to permit the vehicle10to grow in width. The seat frame20is supported relative to the side tubes40by the rockers46via one or more support assemblies50.

As shown in plain view, the side tubes40can support caster housings52, which in turn are suitable for supporting the caster stems. The rear wheels18can be supported in a fixed relation to the side tubes40by any conventional means, including the axle mounting plate54shown.

The footrest assemblies34can include a member, such as the tube56, that is telescopically received by, or otherwise adjustably related to, the side tubes44. The tube56is preferably adjustable relative to the side tubes44to permit the longitudinal position of the tube56to be located in various fixed positions relative to the side tubes44. This accommodates growth in the vehicle10in a longitudinal direction.

It should be noted that an alternative seat back58is shown inFIGS. 3 and 4, wherein opposing handles60are provided on opposing canes62. The handles60can be telescopically received in or otherwise adjustably related to the canes62. An additional assist handle64can optionally extend rearward from the canes62.

As depicted inFIG. 5, the support assemblies50and axle mounting plates54preferably adjustable in a longitudinal direction. This can be accomplished in any suitable manner. For example, in the illustrated embodiment, the side tubes40can be provided with a series of longitudinally spaced holes66. The support assemblies50and axle mounting plates54can each be provided with holes116,117, and72that are spaced to align with the holes66in the side tubes40. Fasteners (not shown) can be adapted to be secured in the aligned holes to hold the support assemblies50and axle mounting plates54in a substantially fixed relation to the side tubes40. To move the support assemblies50and axle mounting plates54, simply remove the fasteners. The support assemblies50and axle mounting plates54can be moved longitudinally (i.e., in directions to the left and right when viewingFIG. 5). This permits the weight, as depicted at W inFIG. 6, of the vehicle occupant to be adjusted longitudinally with respect to the wheelbase, for example, to optimize steering performance and stability. A preferred weight distribution is about 40 percent to the front casters16and 60 percent to the rear wheels18. Such adjustment also permits the wheelbase to grow longitudinally, for example, to accommodate occupants of varying size.

Continuing withFIG. 6, the arc A preferably has a radius R that is constant or substantially constant. The center of curvature or focal point P of the arc A is preferably coincident with the center of gravity CG of the vehicle occupant. The constant radius arc A and the coincident focal point P and center of gravity CG are preferred so that the center of gravity CG remains fixed or substantially fixed as the seat assembly14is tilted (i.e., as the seat assembly14is displaced in clockwise and counter-clockwise directions when viewingFIG. 6).

InFIG. 7, there are directional arrows (i.e., pointing to the left and right when viewing the drawing) that depict movement of the footrest assemblies34and the seat back canes62, for example, to permit the seating system to be adjusted for different size occupants. The growth capability of these two components in two directions further enable adjustment such that the vehicle occupant's center of gravity is maintained at the center of rotation or focal point P. This can be accomplished in any suitable manner. For example, the tubes56of the footrest assemblies34can be telescopically received by or otherwise adjustable related to the side tubes44and the canes62can have couplings74or other suitable members that are attachable for movement relative to the side tubes44. The tubes56and the couplings74can have holes, which are adapted to align with holes in the side tubes44of the seat frame20, and fasteners (not shown) can be adapted to and secured in the holes.

The couplings74are preferably structured to be adjustable with minimal disassembly. As shown inFIG. 8, the couplings74can include an assembly of plates80and saddles82,84. Upper ends of the plates80can be attached to the bottom of the canes62by cane saddles82. Holes86,88in the plates80and saddles82can align with holes (not shown) in the canes62to receive a fastener90. This fastener90can form a pivot for the canes62to fold downward in the direction D relative to the side tubes44of the seat frame20. Each plate80can have another hole92just below the bottom of the canes62. These plate holes92can align with one another to receive another fastener94. This fastener94can be selectively engaged and disengaged by a piston96that is biased downward by a spring98. A lever100or other suitable control member extending rearward from the piston96can be displaceable to raise the piston96out of engagement with the fastener94to permit the canes62to be folded downward. Lower ends of the plates80can be attached to the side tubes44of the seat frame20by opposing elongate saddles84. The lower ends of the plates80and the elongate saddles84can have aligning holes102,103and104,105for receiving fasteners106,108for securing the plates80and elongate saddles84to the side tubes44of the seat frame20. It should be noted that the elongate saddles84have bosses110extending laterally therefrom. The bosses110are coincident with the rear holes103in the saddles84. The rear holes105of the plates80are preferably sized to receive the bosses110. The upper fasteners90,94hold the plates80together with the bosses110in the holes105. The bosses110function as a pivot for adjusting the angle (e.g., the angle of recline) of the canes62relative to the side tubes44of the base frame20. The lower fasteners106,108are preferably removable to permit the plates80and elongate saddles84, together with the canes62, to move longitudinally relative to the side tubes44of the seat frame20.

As clearly illustrated, the holes102,103in the elongate saddles84are adapted to align with holes111in the side tubes44of the seat frame20. The fasteners106,108can be received in any of the aligned holes, for example, to accommodate growth in the vehicle10in a longitudinal direction and permit a wide range or variation in the positions of the footrest assemblies34and the support assemblies50to permit the vehicle occupant to be positioned with his or her center of gravity CG substantially coincident with the arc A of the focal point P.

InFIG. 8, there are also illustrated tabs112extending downward from the elongate saddles84. The tabs112have holes114extending laterally therethrough. The front holes102in the elongate saddles84and the holes114in the tabs112align with the holes104, which are preferably an arcuate arrangement of scalloped holes, in the plates80. The rear hole105in each plate80is preferably the focal point of the arcuate arrangement. The front lower fastener106is adapted to be received through the front holes102in the elongate saddles80or the holes114in the tabs112and through any one of the scalloped holes104. Alternatively, the front lower fastener106is adapted to be received through the front hole102in the elongate saddles80, and an optional additional fastener (not shown) is adapted to be received through the holes119in the tabs112and through another one of the scalloped holes104. This permits the angle of the canes62to be adjusted relative to the side tubes44of the seat frame20to recline the canes62.

The functionality of coupling74results from the use of elongate saddles84. These saddles84permit angular and longitudinal adjustment of the canes62and plates80with greater ease than conventional coupling systems that perform a similar function. For both angular and longitudinal adjustment, the upper fasteners90,94remain intact with plates80and saddles82.

Angular adjustment of the cane62and plates80relative to the seat tube44of the illustrated coupling74can be accomplished by removing the front lower fastener106and loosening the back lower fastener108to reduce the clamping pressure of the plates80on the saddles84and the side tubes44. The canes62and plates80can then freely rotate coincidentally about the rear plate holes105and rear saddle holes103.

Longitudinal adjustment of the canes62and plates80of the illustrated coupling74can be accomplished by removing only the front and back lower fasteners106,108. No other parts require removal or are free to loosen or drop out during this adjustment because the back lower holes105in the plates80are coincidentally engaged about the bosses110of the saddles84and the plates80maintain a pre-load against the saddles84and side tube44due to the installed clamping force of upper fasteners90,94so that the plates80remain engaged with the saddles84. When the desired longitudinal location of the canes62along side tube44is established, the front and back lower fasteners106,108can be re-installed and secured in place.

It should be noted, that during longitudinal adjustments, pre-established angular settings of the canes62and plates80can be preserved by first removing the back rear fastener108from the holes103,105in the saddles84and plates80and then placing the back rear fastener108completely through the holes114in the saddle tabs114and the scalloped holes104in the plates80. The back rear fastener108is now in a shear mode that maintains the angular position of the cane62and the plates80. Next, by removing front lower fastener106, the entire assembly (i.e., the cane62and the plates80) is free to translate longitudinally along side tube44.

InFIG. 9, there is illustrated an example of a structure for adjusting the angle of the rockers46. It should be appreciated that the structure is provided for illustrative purposes and that other structures could be used for carrying out the invention. The structure shown is supported by the support assemblies50. The support assemblies50may include one or more side plates115, each having a first mounting hole116therein, and a plurality of spaced apart angle adjustment holes117a,117b,117cin spaced relation to the first mounting hole116. The first mounting hole116in combination with one of the angle adjustment holes117a,117b,117csupports the seat assembly14at a fixed or substantially fixed angle relative to the base12and in relation to the other angle adjustment holes117a,117b,117c. For example, the first mounting hole116and a first one of the angle adjustment holes117asupport the support assembly50at an angle α, which is about zero degrees relative to the side tubes40, although other angles may be desired. The first mounting hole116and a second one of the angle adjustment holes117bsupport the support assembly50at an angle β, which is about five degrees relative to the side tubes40. Although other angle may be desired. The first mounting hole116and a third one of the angle adjustment holes117csupport the low-friction support assembly50at an angle γ, which is about ten degrees relative to the side tubes40. It should be clearly understood that these three angular adjustments affect the tilt range of the seat assembly14. It should be understood that the 0, 5 and 10 degree angular adjustments shown are provided for illustrative purposes and that the invention can be practiced with other suitable angular adjustments.

InFIG. 10, there is illustrated a lock assembly130for locking the rockers46in relation to one or more support assemblies50. The lock assembly130can be supported by the inner plate115and can include a protrusion that engages any one of a plurality of recesses in the rockers46. In the illustrated embodiment, a plunger pin132can be biased by a spring134into engagement with any one of a plurality of holes136in rockers46. The plunger pin132and the spring134can be housed in a housing138that is threaded, pressed, or otherwise held in a fixed relation to a hole in the inner plate115of the support assemblies50. The plunger pin132can be actuated by a cable140, which can be controlled by a conventional lever (e.g., the levers154shown inFIG. 12). The lever can be supported on one of the handles60of the seat back58to permit the plunger132to be actuated by an attendant.

An alternative lock assembly142is illustrated inFIG. 11. This lock assembly142would be suitable for use with a track, such as the rocker144shown, which is tubular and round in cross-section. The lock assembly142can include a pair of locking plates146that are held in spaced relation by a spring148. The spring148can be attached for movement relative to the side plate115of one or more of the support assemblies50. The spring148is adapted to bias the locking plates146outward in opposing directions (i.e., in the left and right directions when viewingFIG. 10) and into engagement with the rocker tube144to prevent the rocker tube144from moving relative to the locking plates146. Note that an actuator cable150can extend through the locking plates146and control the locking plates146to move the locking plates146out of engagement with the rocker tube144to permit the rocker tube144to move.

InFIG. 12, there is illustrated a vehicle having handles152with supporting levers154for actuating the cables for controlling the rocker locking assemblies, such as the locking assemblies described above. The handles152can also be provided with handholds156to enable the vehicle occupant to tilt his or herself in the seat assembly14relative to the base12.

InFIG. 13, there is illustrated a sectional view of a side tube40of the base12, a rocker46of the seat assembly14, and a support assembly50supporting the rocker46relative to the side tube40. In accordance with the illustrated embodiment, the side tube40of the base12is situated between the side plates115of the support assembly50. As stated above, the side plates115can be attached to the side tube40by fasteners, such as the bolt160shown, that pass through holes66(also shown inFIG. 5) in the side tube40that align with corresponding holes in the side plates115. A bottom roller162can be supported for movement above the side tubes40by an axle164. The bottom roller162can be supported in spaced relation to the side tubes40. The rocker46can have a contact surface166that engages the bottom roller162. The rocker46and the bottom roller162preferably have mating surfaces, such as the rounded contact surface166of the rockers46and the saddle shaped surface167of the bottom roller162. The rocker46can further have an arcuate shaped relief168in a side thereof. The arc of the relief168preferably has a radius that is constant or substantially constant. A top roller170preferably engages the relief168to trap a portion of the rocker46against the bottom roller162. The top roller170is preferably supported by an adjustable eccentric cam bolt172. It should be appreciated that the relief168and the top roller170can include mating surfaces that engage one another with a force that depends upon the position of the eccentric cam bolt172. It should be appreciated that the instant invention is not intended to be limited to the rocker46and rollers162,170set forth above but can be practiced with other low friction elements, such as but not limited to one or more bearings, slides, skids, pinions, and/or the like.

As shown inFIGS. 14A through 17B, the seat assembly14is adapted to support a variety of seats. For example, the seat174illustrated inFIGS. 14A and 14Bis a drop seat, which is adapted to be supported below the side tubes44of the seat frame20so that the height H1of the seat174is minimized. The seat176illustrated inFIGS. 15A and 15Bis a standard seat, which is adapted to be supported atop the side tubes44of the seat frame20so that the height H2of the seat176is substantially the same as the height of the side tubes44. The seat176illustrated inFIGS. 16A and 16Bis a standard seat, which is adapted to be supported above the side tubes44of the seat frame20by spacers178so as to raise the side tubes40and the seat176to a greater height H3. It should be quite clear that the height H3is dependent on the size and number of spacers178used. The seat176illustrated inFIGS. 17A and 17Bis a standard seat similar to that shown inFIGS. 16A and 16B, further supporting a cushion180, which is elevated to a greater height H4above the side tubes44. The aforementioned seats174,176and spacers178are adapted to be attached in any suitable manner. These and other seats can be supported by the seat assembly14. The importance of the above mentioned seat height adjustments is that it enables vertical positioning of the occupant's center of gravity to be coincident or substantially coincident with center of curvature or focal point P of the rocker46.

InFIGS. 18A and 18B, there is illustrated by example means for adjusting the height of the caster housings52. The adjusting means can be any suitable adjusting means including but not limited to an offset182, as shown at the front end of the side tubes40of the base12. As shown inFIG. 18A, the offset182can be directed up to minimize the height H1of the seat assembly14. InFIG. 18B, the offset182can be directed down to maximize the height H2of the seat assembly14. Also note the change in the position of the axle sleeve184relative to the side tubes40of the base12in the two drawings. The close proximity of the axle sleeve184to the side tubes40lowers the rear of the seat assembly14. The converse holds true if the axle sleeve184is moved down and away from the side tubes40. That is, the rear of the seat assembly14is raised accordingly. The axle sleeve184can be positioned above the side tubes40to further lower the rear of the seat assembly14.

As illustrated inFIGS. 19A and 19B, it is preferable that the seat assembly14be removed from the base12. This can be accomplished in any suitable manner. For example, the support assemblies50can be releasably attached (i.e., preferably readily removable with or without the aid of tools) to the side tubes40of the base12, as shown inFIG. 19A, so that the support assemblies50and thus the seat assembly14can be easily removed from the base12for ease in transporting the vehicle10. Alternatively, the seat assembly14can be releasably attached to the support assemblies50, as shown inFIG. 19B, so that the seat assembly14can be easily removed from the support assemblies50. One of ordinary skill in the art of the invention, without undue experimentation, could provide suitable means for releasably attaching the seat assembly14, including a variety of quick-release fasteners.

It should be noted that the vehicle10can be comprised of two primary parts: the base12and the seat assembly14. The seat assembly14can include the seat frame20, the seat back22,58, and the footrest assembly34, all preferably rigidly or substantially rigidly supported on the rockers46. The support assemblies50can capture the rockers46and constrain the motion of the seat frame20to pure rotation about the rocker's center of curvature (i.e., focal point P).

In a preferred embodiment, four bottom rollers162(i.e., two rollers162per rocker46) preferably support the underside surface of the rockers46. These rollers162are preferably saddle-shaped to position the rockers46along the center of the support assembly50. The rockers46preferably have a similarly shaped profile that fits within the saddle-shaped rollers162. These mating shapes serve to align the rockers46with the rollers162.

Four top rollers170(i.e., two top rollers170per rocker46) preferably contact an upper curved surface of the rockers46, capturing the rockers46and preventing the rockers46from lifting off the base12. The top and bottom rollers162,170allow the seat frame20to rotate with minimal friction about the center of curvature P of the rockers46.

It should further be noted that the holes136, which serve as the engagement features for the spring-loaded plunger pins132, can be equally spaced and arranged in a series, for example, between the upper and lower surfaces of the rockers46, along an arc concentric or substantially concentric with the curvature of the rockers46. The holes136can be spaced discrete angular distances apart, such as one-degree apart, to permit incremental adjustments in the tilt angle of the seat frame20. Multiple pins132could engage multiple holes136of the rockers46to reduce sheer forces encountered by the pins132when locking the rocker46in position. It should be clearly understood that the tilt angle of the seat frame20can be changed, for example, by squeezing levers to release the pins132from the holes136and rotating the seat frame20by pushing or pulling on handles. When the levers are released, the pins132can engage with the closest aligned holes136, locking the seat frame20with respect to the base12at a specific tilt angle.

In order for the vehicle10to function as intended, a vehicle occupant's center of gravity should coincide closely with the center of curvature of the rockers. To this end, the vehicle occupant should be properly positioned at the center of curvature or substantially close to the center of curvature of the rockers. For example, the center of gravity of the vehicle occupant can be above the center of curvature or focal point of the rocker (i.e., when the seat frame is substantially horizontal, as shown inFIG. 20A), though placing the center of gravity of the vehicle occupant too far above the center of curvature could create an inverted pendulum effect, which could create an unbalanced load, causing the seat frame to tend to rotate away from horizontal, which may require substantial force to counteract when moving or tilting the seat frame. This phenomena is illustrated inFIGS. 20A and 20B. The center of gravity of the vehicle occupant can also be below the center of curvature of the rocker (i.e., when the seat frame is substantially horizontal, as shown inFIG. 21A). Though this is generally more suitable than being above the center of curvature, placing the center of gravity of the vehicle occupant too far below the center of curvature could create a pendulum effect, which could cause the seat frame to tend to rotate toward horizontal, which may also require substantial force to counteract when moving or tilting the seat frame. This phenomena is illustrated inFIGS. 21A and 21B. In the most preferred embodiment of the invention, the center of gravity of the vehicle occupant is coincident or substantial coincident with the center of curvature of the rocker, as shown inFIG. 22. This is the most suitable relationship because the seating system is in equilibrium or substantially in equilibrium, thus tilting the seat frame requires little force to overcome friction.

The preferred embodiment of the invention can be summarized as a personal mobility vehicle having a seat or seating system that is supported for movement relative to a radial curve or a quasi radial curve (e.g., via a radially curved track or member, or a substantially radially curved track or member) having a focal point that is preferably substantially fixed in space, wherein the seat or seating system is adjustable (e.g., horizontally, vertically, or both) with respect to the curve so that the center of gravity of the seat is adjusted or the center of gravity of any vehicle occupant is sufficiently coincident with the focal point of the curve so that excessive force, or a significant amount of force, is not required to tilt the seat frame with the occupant therein. In one embodiment of the invention, the center of gravity can be sufficiently vertically aligned with the focal point when the seat or seating system is horizontal.

The relative position of the center of gravity of the vehicle occupant and the center of curvature or focal point obviously depends on the weight of the user, and possibly the physical abilities of the attendant. For example, a near coincident relationship between the center of gravity of the vehicle occupant and the focal point P that requires 50 pounds of force to tilt the seat frame and occupant may be a suitable relationship for some attendants but not others. Generally, the center of gravity is preferably within a one-inch radius about the focal point. Depending on the weight of the occupant, the center of gravity can be within a two and one-half inch radius about the focal point, though this may not be suitable of occupants exceeding certain weight capacities. The center of gravity can even be within a three to four inch radius about the focal point, although this may not be a possible range for very heavy occupants. With these ranges in mind, it is conceivable that center of gravity can even be within a radius about the focal point that is in a preferred range of about four to seven percent of the fore to aft length of the vehicle seat24, or a possible suitable range of about 11 to 17 percent of the fore to aft length of the vehicle seat24.

To establish a desired relationship between the center of gravity of the vehicle occupant and the focal point P of the arc A, the wheelchair10can incorporate several means for adjusting the position of the vehicle occupant to align the occupant's center of gravity CG with or close to the center of curvature of the rockers46. The seat back22,58, the seat24(e.g., a pan, a sling, etc.), and the footrest assemblies34all preferably incorporate fore/aft adjustability with respect to the center of curvature. Couplings that secure the canes26,62and seat24to the seat frame20preferably allow for fore/aft adjustability. The tubes56supporting the footrest assemblies34also preferably have fore/aft adjustability. This adjustability allows proper center of gravity CG alignment for a range of vehicle occupant sizes and accommodates occupant growth.

The center of curvature of the rockers46is a virtual point in space that can preferably reside close to the occupant's abdomen. Because the pivot point in this design is a virtual point in space, and not a physical pivot axis near the abdomen, the vehicle occupant is not confined by hardware or the vehicle structure that surrounds the occupant. The absence of any vehicle structure at this location is advantageous because the seating area remains unconfined. This assists in transferring the occupant in and out of the vehicle.

Proper positioning of the center of gravity CG of a vehicle occupant with respect to the base12is important for stability and maneuverability of the vehicle. Stability is ensured when the center of gravity CG is properly positioned between the front casters16and rear wheels18attached to the base frame12. Increased maneuverability is achieved when the rear wheels18support a larger portion of an occupant's weight. Reducing the weight on the front casters16produces easier steering and facilitates lifting the front end of the vehicle when crossing thresholds. Because the vehicle10is intended to cover a wide range of occupant sizes, the vehicle footprint (i.e., the distance between the front casters16and the rear wheels18) can grow.

The vehicle10incorporates several unique features to maintain stability and maneuverability while accommodating a wide range of occupant sizes. The seat frame20can be adjusted fore/aft with respect to the base12. The seat frame20can be positioned with respect to the base12by moving the support assembly50fore/aft along the base12. The rear wheels18may be positioned fore/aft along the base12as well. This ability to adjust the size of the vehicle footprint and position the occupant's center of gravity CG fore/aft within this footprint allows the vehicle to be properly configured for stability and maneuverability over a wide range of occupant sizes.

The support assembly50can be mounted on the base12in a plurality of different angular positions. These positions allow the range of tilt to be changed to accommodate a particular vehicle occupant's needs. Changing the first position allows the seat assembly14to tilt in a range of about 5° anterior to about 50° posterior. Changing the second position allows the seat assembly14to tilt in a range of about 0° to about 55° posterior. Changing the third position allows the seat assembly14to tilt in a range of about 5° posterior to about 60° posterior. An increased posterior tilt range provides more pressure relief to the ischial tuberosities. An increased anterior tilt range assists in transferring the vehicle occupant in and out of the vehicle10and allows a occupant to foot propel. These tilt ranges allow the tilt range to be customized to a particular occupant's needs.

The rocker144according to an alternative embodiment of the invention can be in the form of a round steel tubing, as partially shown in cross-section inFIG. 11. The rocker144is formed into a curve that preferably has a constant radius or substantially constant radius. This rocker144serves the same function as the rocker46according to the preferred embodiment of the invention. The rocker144is attached to the seat frame20. The rocker144can be secured to the support assembly50, for example, by a plurality of rollers, one or more rollers186above the rocker144and one or more rollers187below. The tilt angle can be fixed by the alternative lock assembly142, which can be located within the support assembly198. The locking plates146have holes192through which the rocker144passes. These holes192are slightly oversized with respect to the diameter of the rocker144. The plates146pivot about their upper ends. The spring148situated between the plates146forces the plates146to pivot away from one another and cam against the rocker144to lock the rocker144in place with respect to side tube40of the base12. This secures the tilt angle of the seat frame20. The plates146oppose one another so that, when the seat frame20is tilted in one direction, the trailing plate in the direction of travel of the rocker144cams against the rocker144and prevents the seat frame20from tilting. The cable150is preferably a lever-operated cable that is secured across the plates146so that, when the lever (not shown) is squeezed, the plates146pivot towards one another. As the plates146pivot toward one another, the axes of the holes192within the plates146align with the arc of the rocker144and release the rocker144to allow the rocker144to slide freely as the seat frame20tilts.

The invention described herein can be easily adapted to a battery-powered motor or actuator that could drive the tilt angle of the seating system. This adaptation could allow the tilt function of the vehicle to be operated by a control device that is accessible to either the attendant or the vehicle occupant. Likewise, the center of gravity seating system described herein could be mounted on a power base so that the wheels of the vehicle can be motor-driven.

The present invention is not intended to be limited to the embodiments shown and described above. The base and seat assembly illustrated and described above are merely provided for illustrative purposes. Other bases and seat frames can be suitable for carrying out the invention. The rockers are also provided for illustrative purposes. It should be understood that one or more tracks, other than the rockers shown and described, having radius curves with a center of curvature that is coincident or substantially coincident with the vehicle occupant's center of gravity may be suitable for carrying out the invention. The tracks can be supported by one of more rollers, slides, or other suitable low-friction members that allow the seat frame to rotate with respect to the base. Seat frame adjustments, including adjustments to the seat, the seat back, and the footrest assemblies, can be carried out in ways other than those set forth above. It should further be understood that the vehicle may or may not accommodate growth and further that growth accommodation may be carried out in a manner other than that described. It should also be appreciated that the seat frame and support assembly can be adjustable in a manner other than that described.

The present invention can achieve a truly stationary center of gravity during tilting. Minimal effort may be required on the part of the attendant or the vehicle occupant when tilting the seat assembly. No lifting or lowering of the occupant's center of gravity may be required to tilt the seat assembly. Because the tilting is preferably limited to pure rotation, the only effort required may be then regulated to overcome friction within the system.

The vehicle occupant should not experience a sensation of being pitched off balance during tilting. The sensation experienced during the center of gravity tilting should be more reassuring to the occupant and less likely to induce inadvertent reactions that could potentially injure the vehicle occupant.

The instant invention may also be advantageous in that the vehicle occupant's center of gravity may remain substantially stationary with respect to the base, thus increasing vehicle stability and allowing for a shorter base length. Having a shorter base frame increases the maneuverability of the vehicle and creates a smaller overall footprint for the vehicle, allowing it to fit within tighter confines.

Lastly, the present invention permits the weight distribution on the front and rear wheels of the vehicle to remain constant while tilting the seat frame20. The well-defined weight distribution assists in controlling and steering of the vehicle.