A manual wheelchair system comprising of a pair of lever arms positioned on each side of the chair that actuate a propulsion system located entirely under the seat of the wheelchair. Both the push and pull stroke of the levers, unlimited by stroke angle, provides unidirectional forward propulsion to the rear wheels of the chair. This is accomplished through drive gears fitted with one-way clutches and idler gears intermeshing with them. A sprocket is attached to one drive gear, and connects to an internal shifting hub using a chain or belt. This hub could optionally be a manual or automatic unit, with the automatic shifting unit relying on sensory feedback from the rear drive wheel to determine the most efficient ratio of operation. The hub connects to the rear drive axle through another sprocket and chain combination and drives the rear wheel as the levers are manipulated. The rear axle has a disconnecting clutch so that the entire drive propulsion system can disengaged from the chair. This allows the operator to use the wheelchair in a conventional manner (by hand directly at the wheel handrails).
Inventors: Schaeffer, Jon Eric; (Beaverton, OR) ; Schaeffer, Jerome Edwin; (Beaverton, OR)
Correspondence Name and Address: JON SCHAEFFER
11791 SW CRATER LP
Serial No.: 977424
Series Code: 09
Filed: October 15, 2001
U.S. Current Class: 280/248; 280/250.1
U.S. Class at Publication: 280/248; 280/250.1
Intern'l Class: B62M 001/14
What we claim as our invention and desire to be secured by Letters of Patent is:
1. A wheelchair in combination with a propulsion system comprising, in combination: a. said propulsion system using pivotably connected lever arms that act in both the forward and reverse stoke ("push" and "pull"), and b. drive gears fitted with one-way clutches or one-way ratcheting mechanisms, and c. idler gears intermeshing with said drive gears, whereby said wheelchair in combination with said propulsion system will produce unidirectional forward motion to the rear wheels.
2. A wheelchair set forth in claim 1 comprising, in combination: a. footrests that swing up, aiding in user accessibility, and b. seat of said wheelchair that adjusts forward or back to change the effective center of gravity and aid in user accessibility, and c. said seat is removable for easy storage and transportation, and d. separation of said wheelchair at or near the center for easy storage and transportation, and e. independent suspension on each of the wheels to aid in traction control and stability, and f. a roller, disk or caliper brake actuated by a hand operated brake lever to aid in stopping and steering.
3. A wheelchair in combination with a propulsion system comprising, in combination: a. said propulsion system located entirely under the seat of the wheelchair, and b. internal shifting hubs (either automatic or manual in nature) to change gear ratios for various terrain and speeds, and c. lever arms that are not limited by possible stroke angle, whereby said wheelchair in combination with said propulsion system will produce an efficient means of transportation.
4. A wheelchair in combination with a propulsion system comprising, in combination: a. a disengaging means for the rear axle to disengage it from said propulsion system, and b. said disengaging means having a two-spring system (one in compression, one in tension) to aid in disengaging clutch and said propulsion system of the wheelchair, whereby said disengaging system allows the user to reverse the wheelchair and operate it by hand at the wheel handrails in very tight quarters (such as indoor operation).
1 CROSS-REFERENCE TO RELATED APPLICATIONS 287,789 November 1883 Arbogast 297/376 3,666,292 May 1972 Bartos 280/234 3,994,509 November 1976 Schaeffer 280/242 WC 4,506,900 March 1985 Korosue 280/242 WC 4,560,181 12/24 Herron 280/242 WC 4,811,964 March 1989 Horn et al. 280/250.1 5,007,655 April 1991 Hanna 280/250.1 5,263,729 November 1993 Watwood 280/246 5,632,499 May 1997 Hutcherson et al. 280/246 5,865,455 February 1999 Taylor 280/250.1 6,158,757 December 2000 Tidcomb 280/250.1 6,234,504 B1 May 2001 Taylor 280/250.1
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
 Not Applicable
BACKGROUND OF THE INVENTION
 1. Field of Invention
 This invention relates to a manually propelled wheelchair. In particular, this invention encompasses the chair as a system using two levers that the user stokes, in a rowing motion, forward and backward with. Both the "push" and "pull" stroke of these lever arms provide forward propulsion to the rear wheels. The two levers are mounted on each side of the chair while the remaining components (gears, shafts, bearings, clutches, internal shifting hubs, sprockets and chains) are located entirely under the seat of the chair. For reversing and indoor operation, the propulsion system can be disengaged. This allows the chair to be used in a conventional manner (by hand directly at the wheel handrails). An automatic shifting hub option is available that relies on sensory feedback from the rear wheels to intelligently determine which ratio of gears is best suited for terrain and speed.
 2. Description of Prior Art
 For persons having disabilities making walking impossible or difficult, chairs with wheels attached have traditionally been the standard means of transportation. These chairs typically have two small caster wheels on the front that can turn 360 degrees, and two larger wheels on the back for propulsion. The larger rear wheels have handrails attached to them that the user grasps and pushes forward repeatedly. This requires wrist and shoulder strength and often results in chronic stress injuries after extended use due to the poor ergonomics. In order to turn these wheelchairs, the operator grasps one wheel while pushing the other forward. Stopping is similarly done by grasping both rear wheels at the handrails. Thick leather gloves are often used in this grasp and release motion to aid in grip, and protect the user's hands from injury. In addition, climbing hills can be nearly impossible, as the user must remove his or her hands from the rim on each subsequent stroke. This creates an inefficient system and loss of work as the force from gravity pulls backward on the chair.
 Employing handles to aid in the propulsion of wheelchairs dates back to before the turn of the century. For example, U.S. Pat. No. 287,789 granted to Arbogast on Nov. 6, 1883, utilizes a wheelchair hand crank system in which the ground wheels of a wheelchair are driven by a chain which is also connected to the hand crank. The chain provides a smooth linkage between the hand crank and the ground wheel. However, to attain the leverage needed for easy operation, the hand crank must be extended to an awkward length.
 U.S. Pat. No. 3,666,292 utilizes two lever arms that turn a crank mechanism attached to the rear wheels of the wheelchair. Steering is accomplished by individually turning the lever arms, which translates this motion to the front caster wheels with cables. This chair provides no means of gearing for various speed or terrain conditions. Also, since the steering is done with the front wheels, the turning radius is extremely large and not practical for indoor operation.
 U.S. Pat. No. 3,994,509 includes two lever arm drive assemblies mounted on the outside of the chair. Each propulsion drive system utilizes one way clutches with idler sprockets to transmit unidirectional rotation to the ground wheel in both the push and pull stroke. This system uses a cable chain capable of reverse bending to wrap around the idler sprockets. The entire propulsion system adds to the overall width of the wheelchair. The complex reverse bending chain also makes maintenance and assembly very difficult. In addition, the need for a reversible-shifting hub, not currently available on the market, makes the design proposition extremely expensive to manufacture.
 U.S. Pat. No. 4,506,900 focuses on utilizing a single lever arm to propel the wheelchair with one hand (either the right or left side is possible). It provides a forward, reverse and neutral lever position to aid in maneuverability. It, however, offers no means of gearing, and can only be turned by placing the lever in a neutral position and manipulating the wheelchair by hand at the wheels.
 U.S. Pat. No. 4,560,181 contains two lever arms that drive a ratchet wheel located on the rear wheel axle in both the forward and reverse stroke. The forward stroke engages one ratchet while the other is disengaged and reverses this action for the return stroke. By changing where the ratchet wheel is connected to the lever arm, a continuously variable gear ratio is possible. However, this adjustment can not be made while the chair is in motion, and it also will either increase or decrease the length of possible stroke available to the lever arm.
 U.S. Pat. No. 4,811,964 uses a single lever arm located between the operator's legs. This drives two separate sprockets on one rear axle which employ ratcheting mechanisms with chains attached to cables. The cable is run through an idler pulley such that both the push and pull stroke transmits power to the rear wheels with no loss of work. Due to the single rear axle, conventional wheelchair turning (braking one wheel while powering the other) cannot be used. Instead, the lever arm acts as the turning mechanism through a pivoting universal joint. This increases the overall turning radius of the chair making it impractical for tight corners or indoor use. There are also no provisions for gearing or gaining mechanical advantage through other means to adjust the speed.
 U.S. Pat. No. 5,007,655 uses a pair of lever arms on each side of the chair, each of which is connected to a sprocket on the rear drive wheels through a rack-and-pinion engagement. A one-way clutch is used to effectively drive the sprocket during the power stroke. After the power stroke is complete, the lever arm is retracted as the one-way clutch disengages from the rear drive wheel. This produces a wasted return stroke and loss of work for the user. The wheelchair has provisions for changing the leverage applied to the sprocket by moving where the lever arm attaches to the rack-and-pinion engagement. It does not, however, provide a means of easily changing this lever advantage while pumping the lever arms.
 U.S. Pat. No. 5,263,729 uses a structure mounted to an existing wheelchair frame. A lever extends from the inside of the rear wheel axles up to the user. It contains a prawl that has teeth on it and extends over the tire of the wheel. These teeth provide positive contact with the tire during the pushing stroke and release during the return stroke. This invention has the disadvantage of a lost return stroke with no work generated, and also no means of gearing or gaining mechanical advantage are provided.
 U.S. Pat. No. 5,632,499 is a wheelchair system using a pair of lever arms that drive self contained planetary gears. These gears are designed such that both the forward and reverse stroke drive the rear wheel in the forward direction. There are, however, no provisions made for dynamically gearing the system, and the complexities of the small, planetary gears make service and maintenance difficult.
 U.S. Pat. No. 5,865,455 is a wheelchair using two push levers as its propulsion system. This chair employs standard bicycle sprocket clusters mounted on the rear axles with chains connecting to the front push lever drive system. A standard bicycle derailer is mounted on each axle to change gear ratios and thus speeds. This system uses a ratchet mechanism in the push levers to change between forward, neutral and reverse directions. It does not provide a means of using both the push and pull stroke to transmit unidirectional motion to the rear wheels. Therefore, one stroke, either the push or pull is a wasted return stroke and loss of work.
 U.S. Pat. No. 6,158,757 uses a flexible motion conversion, such as a cable, to transmit the lever's pushing power directly to a drum attached to the rear wheel. This reduces complexity in gearing, chains and sprockets, but only transmits power during the pushing stroke. Again, the disadvantage to this system is a wasted return stroke with loss of work. Also, the only provisions made for changing mechanical advantage is by lengthening or shortening the lever arm. No changeable gears or hubs are used to adapt the chair to various speeds or terrain.
 U.S. Pat. No. 6,234,504 B1 is a continuation of U.S. Pat. No. 5,865,455 described above. It employs the same principal, but has further descriptions and drawings of the invention.
BREIF SUMMARY OF THE INVENTION
 We have invented a manual wheelchair that comprises a propulsion system located entirely under the seat of the chair. Two lever arms, positioned on the side of the chair, actuate the propulsion system and provide forward motion with both the push and pull stroke. This is accomplished using drive and idler gears fitted with one-way clutches or ratcheting mechanisms that transmit the power to the rear wheel through sprockets and chains.
 The drive gears are linked to an internal shifting hub that is either manual or automatic in nature. The manual shifting option uses conventional bicycle shifting levers to change gears during operation. The automatic shifting hub option contains sensory feedback from the rear wheel, a shifting motor, and a central processing unit to automatically determine the most efficient gear available for terrain and speed.
 A disconnecting clutch is located on the rear axle to disengage the entire propulsion system from the chair. This enables the user to reverse the chair, and also use it as a conventional wheelchair in very tight quarters (such as indoor operation). The disconnecting clutch employs two springs, one in compression and one in tension, to aid the user in disengaging the propulsion system under load.
 Using quick release draw clamps, the entire chair is easily separated into three pieces comprising of; the seat, the right half propulsion system and the left half propulsion system. This makes transportation in vehicles practical. Also, the seat of the wheelchair can be moved forward or backward to accommodate getting into and out of the chair, as well as moving the effective center of gravity for stability and traction control.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
 FIG. 1 is a right side elevation view of the wheelchair constructed in accordance with the present invention.
 FIG. 2 is a front elevation view of the wheelchair.
 FIG. 3 is a cross sectional view of the wheelchair showing the propulsion system (gears, shafts, bearings, internal shifting hubs, rear drive axles).
 FIG. 4 is an enlarged view of the drive and idler gears along with the lever arm and disconnecting clutch cable with tension spring.
 FIG. 5 is an enlarged view of a single drive gear with a press fit, one way clutch or ratcheting mechanism
 FIG. 5a is a cross sectional view of the single gear shown in FIG. 5.
 FIG. 6 is an enlarged view of the planetary idler gear assembly.
 FIG. 7 is an enlarged view of the quick release draw clamps used to separate the chair.
DETAILED DESCRIPTION OF THE INVENTION
 Reference will now be made to the preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. As required, detailed embodiments of the invention are disclosed herein; however, details to the function and structure are not meant to be interpreted as limiting, but rather a basis for the claims of the invention and educate one skilled in the art to employ the invention in virtually any structure.
 Referring now to FIG. 1, there is illustrated the wheelchair (1) with two large rear wheels (2) on the right and left side of the chair, and two smaller front casters (3) constructed in accordance with the present invention. Wheelchair (1) includes a frame (4) that may be formed of tubular metal, plastics, or any other sufficient materials able to support the chair. A seat (5) is connected to the tubular frame in order to provide a suitable position for the user to operate the wheelchair. This seat (5) can be moved forward or backward at the seats connection point (10) in relationship to the rear wheels (2) and front wheels (3), effectively changing the center of gravity of the wheelchair. This moveable seat (5) aids the user in traction control and also getting into and out of the chair. In addition, the seat angle is adjustable to various positions using an adjusting plate (14).
 Two lever arms (6) are located on the outside of the chair which are pivotally connected to a shaft (7) near the front of the wheelchair. These lever arms (6) have attached brake levers (12) and disconnecting buttons (11) conveniently located for accessibility by the user during operation. A sprocket (19) connects the shaft (7) to an internal hub (16) using a conventional bicycle chain or belt (17). This internal hub (16) may be either automatic or manual in nature, and offers several different gear ratios to accommodate various speeds and terrain. The internal hub connects to the rear axle (15) using a standard bicycle chain or belt (18). The combination of these components on the propulsion system allow the reciprocating motion of lever arms to be converted into unidirectional rotary motion at the rear wheel.
 Independent suspension (20, 43) allow for a smoother ride and improved traction control as the wheels of the wheelchair can track rough terrain better than conventional fixed wheels. The footrests (8) can be swung up at position (36) to aid the user in getting into and out of the wheelchair. These footrests include straps (9) to keep the user's feet secure while operating the wheelchair.
 Referring to FIG. 2, there is illustrated the wheelchair (1) in a front elevation view. Handrails (13) are shown and enable the user to operate the chair in a conventional manner while the disconnecting button (11) is pulled. The front portion of the propulsion system is clearly visible in this front elevation view. Two drive gears (21) fitted with one-way clutches allow both the forward and reverse stroke of levers (6) to provide forward propulsion to the rear wheels (2). The planetary idler gears (22) allow the transmission of unidirectional rotation to the sprocket (19) which transmits power to the rear wheel (2).
 The seat of the chair (5) is removable at the upper chair frame (10) to assist in transportation. In addition, the two propulsion halves of the wheelchair separate near the centerline of the wheelchair using quick release clamps (23).
 Referring to FIG. 3, there is illustrated the wheelchair (1) in a top cross-sectional view. This view gives a clear representation of one way that the propulsion system components might be constructed. The lever arms (6) are pivotally connected to a shaft (7) that is supported with bearings (38) near the front of the wheelchair. This shaft (7) actuates two drive gears (21) fitted with one-way clutches or ratcheting mechanisms (see FIG. 5). Idler gears (22) transmit the reciprocating motion of the lever arm into unidirectional motion in the sprocket (19). This sprocket (19) is secured to one of the drive gears (21) and connects to an internal shifting hub mechanism (16) with a chain or belt (17).
 The internal shifting hub (16) is designed to handle various gear ratios, and may be automatic or manual in nature. The automatic internal shifting hub option uses a shifting motor (26), central processing unit (35), and sensory feedback (34) from the rear wheel to dynamically determine optimal gear ratios for terrain and speed. The manual internal shifting hub option (not shown) would use conventional bicycle shifting levers to actuate the internal shifting hub cable (26). The internal shifting hub (16) has a second drive sprocket (33) attached to it with a chain or belt (18) transmitting the power to the rear sprocket (30) which is attached to the rear axle (15). This rear axle (15) is attached to, and drives the rear wheel (2) of the wheelchair. A disconnecting clutch (31) allows the user to disconnect the entire propulsion system from the chair, and operate the wheelchair in a conventional manner (by hand on the rear wheel handrails (13)). A compression spring (32) causes the propulsion system disconnecting clutch (31) to engage when not disconnected by means of the disengaging button (11).
 A disk or roller brake (28) is attached to the internal shifting hub (16) and is actuated by a cable (25) that connects to the hand operated brake lever (12). A secondary brake option (not shown) using conventional bicycle caliper brakes directly at the wheelchair rims may also be used.
 Referring to FIG. 4, FIG. 5, FIG. 5a and FIG. 5, there is illustrated an enlarged view of one of the drive gear clusters. The two gears (21) include ratcheting mechanisms or one-way clutches (39) that allow the reciprocating motion of the lever arm (6) to transmit unidirectional rotation through the idler gears (22) to the main driving sprocket (19).
 Internal to the lever arm (6), a tension spring (37) is shown. This spring (37) attaches to the disconnecting button (11) and disconnecting cable (29) to aid the user in disengaging the propulsion system of the chair when under load.
 Referring to FIG. 6, there is illustrated an enlarged view of the quick release draw clamp (23). This draw clamp is located near the centerline of the wheelchair (1), and allows the chair to be separated for ease in transportation.