Abstract: A modular wheelchair assembly is adapted to be reconfigured between a fixed angle of tilt, a dynamically adjustable tilt-in-space configuration with the tilt axis being near the user's knees and a dynamically adjustable tilt-in-space configuration with the tilt axis being near the user's center of gravity. The reconfiguration is achieved by modifying a limited number of selectively removable components of the support assembly or the pivot assembly of the wheelchair.

Abstract: A power assist apparatus for powering a manual wheelchair may include one or more wheels, one or more motors that drives the one or more wheels, a remote operable to control the one or more motors, and a connector operable to attach to the manual wheelchair. The power assist apparatus may be quickly and easily attached to, and removed from a manual wheelchair.

Abstract: A wheelchair safety device comprises a brake lever, four link levers, an upper brake plate, a brake wheel, a lower brake plate, a parking wheel, and an angularly adjustable mounting plate. One end of the first, the second and the third link levers is respectively articulated at the brake lever, another end of the first and the second link levers are articulated with one end of the fourth link lever. Another end of the fourth link lever is articulated at the upper brake plate and another end of the third link lever is articulated at the lower brake plate. One end of the upper and the lower brake plates is respectively articulated at the angularly adjustable mounting plate, and another end thereof is mounted with the brake wheel and the parking wheel, respectively. The brake wheel and the parking wheel respectively act on the wheelchair.

Abstract: A wheelchair that has the ability to change quickly and easily the front casters of the wheelchair to another set of front casters intended for a different usage. This usage includes: an ‘everyday’ chair set up that uses narrower rear tires and smaller front casters; a snow chair set up with wide rear tires and larger front casters (or skis in place of casters); a beach set up with extremely wide rear tires and balloon front casters placed forward of the front of the frame; a hiking set up with mountain bike rear tires and over sized youth mountain bike front casters set); or a beach set up with extremely wide rear tires and balloon front casters placed forward of the front of the frame. A user may also mix and match front casters and rear wheels to form a different combination not listed above.

Abstract: A sensor arrangement for a wheelchair wheel that has a running wheel with a hub and a hand rim includes a running wheel fastening arrangement that is fastened to the running wheel, a hand rim fastening arrangement that is fastened to the hand rim and at least one sensor that detects a movement of the hand rim fastening arrangement relative to the running wheel fastening arrangement. Two restoring elements are provided on the running wheel fastening arrangement and rest against the hand rim arrangement with a prestressing force at least in the zero position. Both restoring elements rest against at least one stop of the running wheel fastening arrangement in the zero position of the sensor arrangement.

Abstract: A modular wheelchair assembly is adapted to be reconfigured between a fixed angle of tilt, a dynamically adjustable tilt-in-space configuration with the tilt axis being near the user's knees and a dynamically adjustable tilt-in-space configuration with the tilt axis being near the user's center of gravity. The reconfiguration is achieved by modifying a limited number of selectively removable components of the support assembly or the pivot assembly of the wheelchair.

Abstract: A wheelchair comprises a base frame, a backrest frame and a hinge assembly. The base frame has first and second side frame members. The hinge assembly connects the backrest frame to a portion of the base frame for selective pivotal movement. The hinge assembly includes a locking mechanism configured to provide selective discrete locking positions of the backrest relative to the base frame. The locking mechanism includes a locking pin and a plurality of cooperating locking apertures. The locking pin is adapted to selectively engage one of the plurality of locking apertures to define a backrest angle relative to the base frame. One or more plugs are adapted to engage one or more of the plurality of locking apertures to prevent the locking pin from cooperating with the plugged locking aperture.

Abstract: A mobility chair is arranged for a high degree of maneuverability, and is particularly useful for handicapped individuals in need of a highly stable and maneuverable carriage. The mobility chair may be particularly useful for children, and includes a seat positioned between first and second wheels of a first wheel set, wherein the axial spacing dimension of the first and second wheels is greater than the axle height. The mobility chair is arranged for pivotability about the first wheel set axle to permit the user to freely pivot forward while in the seat of the chair, with the pivoting being limited in both circumaxial directions about the axle axis.

Abstract: A vehicle convoy system for use in connection with a vehicle, wherein the vehicle includes at least one drive mechanism to impart drive to the vehicle, includes at least a first processor that is adapted to be placed in operative or communicative connection with the drive mechanism to effect control of the drive mechanism based upon data of the position of a leading vehicle in front of the vehicle so that the vehicle moves to follow movement of the leading vehicle. The vehicle can, for example, be a self-propelled wheelchair.

Abstract: A wheelchair having a tiltable and translatable seat for compensating for shifting of the center of gravity of an occupant during tilting is provided. Such a wheelchair includes a frame, a first actuator, a seat assembly, and a first rigid link. The first actuator includes opposing front and rear ends coupled to the frame, a rod that extends between the front and rear ends, and a connector that is capable of translating in response to actuation of the rod. The seat assembly is directly coupled to the connector of the first actuator. The first rigid link has a front end and a rear end. The link front end is pivotably coupled to the frame, and the link rear end is pivotably coupled to the seat assembly. The link may be oriented such that as the connector translates, the first link impels the chair to tilt.

Abstract: A mobile chair and method for exercising in the chair include a mobile chair that includes a seat portion, an undercarriage coupled to and supporting the seat portion, the undercarriage including a frame, a rocking mechanism coupling the seat portion to the frame and movable relative to the frame, and a set of rolling wheels coupled to the frame, and at least one exercise handle mechanically coupled to the frame and shaped to extend above a lower portion of the seat portion. The method includes sitting in the seat portion and applying a sufficient force to the at least one handle to cause the seat portion to move in a substantially lateral direction relative to the frame.

Abstract: A mobile patient chair and method of transferring a patient include providing a mobile patient chair with a seat portion and an undercarriage supporting the seat portion, where the undercarriage includes a set of four wheels providing mobility to the patient chair, a left wheelchair-type wheel coupling member, a right wheelchair-type wheel coupling member, and a pair of levers operable to move the wheelchair-type wheel coupling members away from a flooring surface upon which the patient chair is supported. The method includes manipulating each of the levers in a first direction, coupling wheelchair-type wheels to the wheelchair-type wheel coupling members, manipulating the levers in a second direction, and manipulating the coupled wheelchair-type wheel to cause the mobile patient chair to move.

Abstract: A mobile patient chair includes a seat portion and an undercarriage coupled to and supporting the seat portion, where the undercarriage includes a frame having a set of rollers and a rocking mechanism coupling the seat portion to the frame. The chair has a rolling mode, whereby the set of rollers rotate and allow the mobile patient chair to move from a first location to a second location and a rocking mode, whereby the rocking mechanism is operable to move the seat in a substantially forward and backward translating movement relative to the frame. A lockout member renders the rolling mode and the rocking mode mutually exclusive.

Abstract: In some embodiments, a transport chair includes a base frame, a seat assembly pivotally mounted to the base, and a footrest assembly pivotally mounted to the base frame, the footrest assembly being associated with the seat assembly so as to pivot in unison with the seat assembly until the seat assembly is pivoted forward to an extent at which the footrest assembly contacts the floor or ground, at which point the footrest assembly does not pivot further upon further forward pivoting of the seat assembly.

Abstract: A method and apparatus for wheelchair control. The position and distance of a touch point on a touch pad is used to set speed and wheel differential control. The two major wheels of the wheelchair are controlled according to these set quantities. Exceeding either of two horizontal accelerations measured by an accelerometer limits the set speed. Wheelchair control is shut down upon exceeding a vertical acceleration limit.

Abstract: Each wheel (10, 14/20, 24) of the wheelchair (1) is fixed to a suspension arm (11,15/21, 25). A force transmitting device, for example a spring and damper of the wheelchair unit, directly connects two suspension arms situated on the same side of the wheeled conveyance, so that forces exerted on one of the wheels are transmitted to the other wheel. In this way, obstacles can more conveniently be overcome. A further advantage of the wheelchair is that it can be easily upscaled and driving properties can be adjusted according to a user's preferences.

Abstract: A seat supporting assembly (24) for supporting a seat (18), the assembly comprising a base (25) including a substantially elongated guiding rod (58), a seat support (36), a seat support-to-base linking member (56) pivotally coupled to the seat support (36) and sliding on the base guiding rod (58), a substantially elongated tilting member (60) having a guiding groove (66) and being pivotally attached to the seat support (36) and to the base (25). An actuating assembly (44) is coupled to the base (25) and includes a motion transmitting member (68) mounted within the guiding groove (60).

Abstract: A wheelchair comprises a hub-enclosing open ring engaging a hub disposed in a wheel rotatably, bars extending from two ends of the hub-enclosing open ring, an crescent-shaped cap member fixed to the bars above the tube portion, a power handle engaging the crescent-shaped cap member rotatably through an L-shaped end of the power handle, a wheel-holding plate fixed to the power handle with an angle and covered by the crescent-shaped cap member. The wheel-holding plate comprises a holding edge for pressing down on and holding the wheel. The hub-enclosing open ring, the bars, and the cap member are fixed to one another and configured to rotate about the hub, and the holding edge of the wheel-holding pate is configured to be pressed down on and engaged firmly to the wheel such that the wheel rotates about the hub by pushing and pulling the power handle.

Abstract: According to an embodiment of the invention, a customized wheelchair comprises a frame, a plurality of wheels, and a pair of adjustable armrests. The armrests are coupled to the frame. At least a first armrest of the pair of adjustable armrests comprises a horizontal tubular section that is adapted to be (i) maintained at a first predetermined height when placed in a first operating state and (ii) maintained at a second predetermined height higher than the first predetermined height when placed in a second operating state. To customize the wheelchair, an accessory is provided that can be removably coupled to the horizontal tubular section of the first armrest of the pair of adjustable armrests.

Abstract: A wheelchair includes a frame, a seat, a pair of wheels, and a locking mechanism. The seat is disposed on the frame. The pair of wheels is rotatably supported on the frame. At least one of the pair of wheels includes a removable section that is configured to form a part of an outer circumference of the wheel and to be removable when the wheel is at a predetermined angular position, and a remaining section that is configured to form the outer circumference of the wheel together with the removable section. The locking mechanism is configured to lock the wheel at the predetermined angular position. Under the condition where the wheel is locked, the removable section is separated from the remaining section to facilitate a person to get on and off the seat.

Abstract: A wheelchair frame assembly comprises a frame member having a first leg adapted to support a seat and a second leg configured to support a caster wheel. An axle mounting assembly connects an axle tube to the frame member. The axle mounting assembly includes an axle tube mount, a frame mount, and a spacer. The spacer is configured to alter the distance between the frame member and the axle tube and transfer longitudinal forces between the axle tube mount and the frame mount.

Abstract: A caster mount assembly for a front caster of a wheelchair. The assembly includes a first rotatable body having a first plurality of non-uniformly spaced apart apertures and a second rotatable body having a second plurality of non-uniformly spaced apart apertures. The first and second rotatable bodies may be rotated relative to one another along a common axis of rotation to align a selected one of the first apertures with a selected one of the second apertures. The first rotatable body is non-rotatably coupled to the second rotatable body by a first coupler after the selected first aperture and second aperture have been aligned. A bearing fork assembly is non-rotatably coupled to the second rotatable body for rotation therewith. The second rotatable body may be rotated to orient an upright pivot pin of the bearing fork assembly substantially perpendicular to a support surface.

Abstract: A motorized apparatus that produces either rocking or gliding motion, includes a gear motor with a drive shaft; a drive mechanism to functionally connect to a device to be rocked; the drive mechanism being either an actuating linkage or an eccentric that is rotatably coupled to both said drive shaft and said device to be rocked or glided translating rotary motion of the drive shaft when powered to said drive mechanism, that translates the motion to said device to be rocked or glided providing continuously smooth rocking motion to any device that is enhanced by being able to be rocked or glided, such as a cradle, rocker, or wheel chair.

Abstract: Gentle and substantially linear vertical motion of a wheelchair foot support is expected to assist lower limb circulation for a user with limited leg mobility, reducing risks of clotting or blockage within peripheral blood vessels. Additionally, to whatever extent limb atrophy may be reduced by imposed motion, motion of the foot support may help in maintaining muscle mass and flexibility of ligaments. Accordingly, a circulation assisting wheelchair includes a foot support movably connected to the wheelchair frame by a movable foot support assembly. The movable foot support assembly is connected to a rear wheel of the wheelchair via a drive train, so that normal operation of the wheelchair drives substantially linear vertical oscillating motion of the foot support.

Abstract: Stem (12) is secured to fork (6). Head (27), bearing surface (28), recessed portions (29 and 21), and bearing surface (31) successively engage the interior of housing (13), comprising first bearing (14), laterally movable locking ring (18) and second bearing (15). Locking ring (18) is repelled to the left in diametral direction against spring means urging ring (18). When shoulder (20) has arrived at the height of rim portion (32) of ring (18) the spring means are released. Ring (18) displaces to the right and portion (32) engages groove (29) thus locking the stem in the axial direction. Due to the side location of the button 9, the device can easily be handled using the palm of a hand.

Abstract: A device that detachably mounts to the front side of a wheelchair frame, or similar vehicle, to manually lift or otherwise manipulate an occupied wheelchair up and/or down stairs. The manual wheelchair lift attachment comprises a wheelchair attachment portion and a handhold member for lifting that is connected by connecting arms. The wheelchair lift attachment apparatus may be adjustable to be configured with different sized wheelchairs. The invention also relates to a wheelchair having a permanent wheelchair frame that operably accepts a lifting mechanism apparatus. The invention also relates to a method of using the foregoing attachment and permanent configuration to transport an occupied wheelchair up and/or down stairs or otherwise maneuver the occupied wheelchair about other similar obstacles.

Abstract: A wheelchair is provided for positioning and transporting patients. An exemplary embodiment of the wheelchair includes a tiltable seat frame portion and a base frame portion. The seat frame portion is generally configured to tilt relative to the base frame portion. An arcuate track adjustment portion generally permits pivotal adjustment of the focus about which the seat frame portion rotates. A seat frame adjustment portion generally permits pivotal adjustment of the seat frame portion relative to the base frame portion such that the seat frame portion maintains proper orientation with the base frame portion upon adjustment of the focus about which the seat frame portion rotates.

Abstract: A walker device including a walking aid and a lifting arm attached to, and extending in an approximate vertical direction from, the walking aid. The walking aid may include two front legs and two back legs. The walking aid may include two or more wheels attached to the bottom of the two front legs and/or two back legs. The walking aid may be a multiple-legged cane. The walking aid may be a wheeled mobility device. The lifting arm may include a gripping handle positioned at its approximate distal end.

Abstract: An asymmetric wheelchair is disclosed having a forward wheel assembly with a forward wheel support on one side of the wheelchair leaving an opening for ease of access on the other side.

Abstract: An asymmetric wheelchair is disclosed having a forward wheel assembly with a forward wheel support on one side of the wheelchair leaving an opening for ease of access on the other side. The asymmetric wheelchair can, in some embodiments, be formed by connecting an asymmetric forward wheel support to the frame of an existing symmetric wheelchair.

Abstract: An electric wheelchair that enables users suffering from impairment of the lower extremities due to paralysis or weakness caused by aging to manage their daily lives independently for social rehabilitation by allowing them to raise and lower the seat of the wheelchair between squatting and standing positions, to support their body weight at any position by stopping the chair, and to operate the movement of the wheel chair by using their arms or elbows pressed on either the inner or outer surfaces of the armrests even if both hands are occupied or impaired.

Abstract: The limb elevating accessory can attach itself onto an existing wheelchair and provide a means to support and elevate a limb of an end user seated therein. The limb elevating accessory includes a base support that attaches onto the frame of the wheelchair, and also attaches to an upper support. The upper support has a plurality of holes from which a stirrup or support attaches to support an arm or a leg thereon. The base support also includes an adjustable hook that hooks at a second location to the frame of the wheelchair in order to further stabilize the accessory upon the wheelchair.

Abstract: Wheeled carts, such as a wheel chair and similar devices have a steering wheel, with the steering wheel having a housing to receive the globular wheel, with a seal movably holding the globular wheel in the housing; and a series of friction-reducing bearings being positioned between the globular wheel and the interior of the housing, and held within the housing by the seal in combination with the globular wheel.

Abstract: A center footrest apparatus for use on an existing wheelchair comprises a foot resting plate arranged in a sling-like manner and attached to each side of the chair frame. The apparatus is further provided in a second embodiment comprising a rigidly mounted and height adjustable center footrest portion supported by a T-bar that attaches to the chair frame. The center footrest allows a person to be moved around in tight quarters without interference caused by conventional folding dual footrests.

Abstract: A wheelchair has two central wheels that can be separately driven by a motor. In order to allow the wheelchair to turn around in narrow spaces, the central wheels can be driven in opposite directions of rotation. When the wheelchair is turned around, the front wheels and rear wheels do not constitute a hindrance because they are kept at a distance from the ground by the swiveling wheel. All three wheels are coupled together on each side by a chain. When the front wheels run against an obstacle, the wheelchair climbs over the obstacle with the driven front wheels. This causes the fork of the swiveling wheel to swivel about the rotational axis in the direction of arrow, against the force of a spring, bringing the rear wheels in contact with the ground and also driving the wheelchair's rear wheels. This all-wheel drive allows the wheelchair to overcome relatively high obstacles both forwards and backwards, even when driving slowly and without losing its maneuverability.

Abstract: A wheelchair includes a seat, one or more wheels and a seat weight sensing mechanism. The wheel includes a brake for stopping the wheel. The seat weight sensing mechanism is placed below the seat and is connected to the brake. When the seat is loaded by a weight more than a predetermined value, the seat weight sensing mechanism releases the brake to free the wheel. When the seat is not loaded by a weight more than a predetermined value, the brake stops the wheel.

Abstract: A device that detachably mounts to the front side of a wheelchair frame, or similar vehicle, to manually lift or otherwise manipulate an occupied wheelchair p and/or down stairs. The manual wheelchair lift attachment comprises a wheelchair attachment portion and a handhold member for lifting that is connected by connecting arms. The wheelchair lift attachment apparatus may be adjustable to be configured with different sized wheelchairs. The invention also relates to a wheelchair having a permanent wheelchair frame that operably accepts a lifting mechanism apparatus. The invention also relates to a method of using the foregoing attachment and permanent configuration to transport an occupied wheelchair up and/or down stairs or otherwise maneuver the occupied wheelchair about other similar obstacles.

Abstract: A wheelchair includes a pivoting drive assembly having a drive wheel, a motor drive connected to the drive wheel, and a first pivoting linkage fixedly attached to the motor drive. The pivoting drive assembly is pivotally coupled to a frame at a first frame pivot axis such that the drive wheel, motor drive, and first pivoting linkage pivot about the first frame pivot axis as a unit. The wheelchair further includes a second pivoting linkage and a front caster assembly. The second pivoting linkage is pivotally coupled to the frame at a second frame pivot axis. The first pivoting linkage is pivotally coupled to the front caster assembly at a first front caster pivot axis and the second pivoting linkage is pivotally coupled to the front caster assembly at a second front caster pivot axis.

Abstract: A personal mobility device comprising a frame having a front structure, a rear structure, and two side structures. In one embodiment, main mobility wheels are coupled to ones of the side structures, the main mobility wheels configured to contact a surface upon which the mobility device is designed to move. In this embodiment, the mobility device further includes a knee rest rotatably coupled to the front structure, the knee rest being adjustable from a first substantially-vertical position to a second rearwardly and downwardly-angled position.

Abstract: A modular wheelchair assembly is adapted to be reconfigured between a fixed angle of tilt, a dynamically adjustable tilt-in-space configuration with the tilt axis being near the user's knees and a dynamically adjustable tilt-in-space configuration with the tilt axis being near the user's center of gravity. The reconfiguration is achieved by modifying a limited number of selectively removable components of the support assembly or the pivot assembly of the wheelchair.

Abstract: Seat cushions that prevent a seated handicapped individual from sliding forward on the seat, while preventing the occurrence of decubitus ulcers. The seat a seat cushion includes a resilient body having a generally rectangular-cuboid-shape. The resilient body includes a frontal portion having a front end and a rear end, and which is fabricated from materials having a first density, and a rear portion having a front end and a rear end, and is fabricated from materials having a second density. The first density is substantially higher than the second density. Preferably, the resilient body is fabricated out of a sturdy foam material. Preferably, the seat cushion further includes a protective cover wrapping the resilient body.

Abstract: A toilet adaptable wheelchair comprising a wheelchair including a set of standard features comprising a back rest, a seat, a pair of arm rests, a pair of wheels, a set of foot bars, a set of foot rests, a plurality of side bars and a pair of side panels. The toilet adaptable wheel chair further comprises a cutout within a central portion of the seat beneath where a person sits, a plurality of lifts coordinating with the plurality of side bars, where the plurality of lifts raise and lower the seat, a control panel to activate the plurality of lifts; and a chute secured beneath the cutout, wherein the chute directs substances which pass through the cutout into a toilet to enable the person to use the toilet without leaving the toilet adaptable wheelchair.

Abstract: In accordance with one aspect of the present invention, an alarm assembly for a wheel chair is disclosed. A pair of mounting brackets is combined to the frame underneath the seat of the wheel chair. A removable and extendable switch-bar selectively combines to the mounting brackets. The switch-bar is adjustable in length to accommodate chairs of various widths and selectively positionable on the mounting brackets to change the distance between the seat and switch. The switch on the switch-bar senses the presence of a patient and in response to the absence of a patient communicates an alarm signal to the alarm.

Abstract: A handicapped accessible seat that classifies functionally as an aircraft seat is configured for maneuvering within an aircraft and docking to an aircraft floor using a typical track member having a longitudinal flange like extension and counterbores for mating with a shear plug of an aircraft seat. A bracket or track above the typical track member and containing inwardly-extending longitudinal flanges allows mating association with a plug or plunger on the wheel/caster or bottom seat structure of the handicapped accessible seat (94). A flange-like extension along the bottom portion of the track, having a planar portion along the floor of the aircraft and an outer, upward portion, could run the entire length of an aircraft or in only specific portions thereof and may also be used to guide the wheels into a locking position.

Abstract: A motion control system for lever propulsion of a wheelchair enables a number of different manipulations at the hand grip of the lever. In some embodiments, as many as five user-controlled operations may be performed without need to remove a hand from the hand grip. A user applies force to the hand grip to initiate the motion lever in its forward and rearward strokes. In addition, the hand grip may be pivoted relative to the lever in order to control a brake. A parking brake mechanism may be provided at the hand grip to apply constant brake force. The direction shifter at the top of the hand grip may be used to shift between forward, neutral and rearward modes of operation. In some embodiments, steering of a front caster wheel is possible by rotating the hand grip. Further along the lever, the power applied per lever stroke is adjustable.

Abstract: A drive assistance device for a wheelchair includes a drive motor, a running wheel and a sensor device which is adapted to determine a driving force manually induced into the running wheel; and a control unit which is adapted to control the drive motor for driving the running wheel depending on the driving force manually induced by the user into the running wheel. The control unit of the drive assistance device includes a user force analysis operational mode which is adapted to determine data concerning physical efficiency and capacity of the user. These include a maximum force of the user as well as the maximum speed which can be reached with purely manual drive.

Abstract: A modular wheelchair assembly is adapted to be reconfigured between a fixed angle of tilt, a dynamically adjustable tilt-in-space configuration with the tilt axis being near the user's knees and a dynamically adjustable tilt-in-space configuration with the tilt axis being near the user's center of gravity. The reconfiguration is achieved by modifying a limited number of selectively removable components of the support assembly or the pivot assembly of the wheelchair.

Abstract: The vehicle, for example a stand-up wheelchair, comprises a frame (11) and, arranged on the latter, a seat device (19). On each side of the frame (11), the central wheel (13), which can be driven by a motor (27), and the front wheel (15) are operatively connected to each other by an endless chain (45). The frame (11) has a front part (21) and a rear part (23), which are connected to each other in an articulated manner by way of a joint (25). In the sitting position, the front wheels (15) are not in contact with the ground, which means that they do not obstruct the manoeuvring of the vehicle in a confined space. In the standing position, the front wheels (15) are in contact with the ground, but the central wheels (13) are not. The user, in the standing position, is thus able to turn about the axis of the vehicle, without the central wheels (13) having a blocking action.

Abstract: A wheelchair has a car body of which rear and bottom wall portion are opened, a seat to be divided into right and left portions, a device for moving the right or left portion of the seat, and a holding plate provided on the car body for holding the device for moving the portion of the seat. The device has a link for connecting the seat portion to the car body, and an operation rod for operating the link so that the seat portion is moved between an opened position and a closed position, respectively. Wheels for supporting the car body, brake for the wheel, a brake operation device for operating the brake, a device is provided for synchronously driving the seat moving device and the brake operation device.

Abstract: A personal mobility vehicle includes an base unit having a frame and front and rear pivot arms pivotally mounted at respective front and rear pivot points. The front and rear pivot arms support casters. A drive unit having a ground engaging mid-wheel drive wheel is connected to the frame. A linkage connects the front and rear pivot arms to each other in a manner such that an upward or downward rotation of one of the pivot arms about its pivot point causes rotation of the other pivot arm about its pivot point in an opposite rotational direction. The base unit may also include a drive unit that is pivotally supported on the base unit by a torque arm and a suspension system that includes a suspension stop. The torque arm selectively disengages the suspension stop to allow movement of the front caster wheel in response to the terrain traversed.