Abstract:
An auxiliary, removable, modular power drive unit has a pivot point that can be attached to any bicycle or vehicle by way of a quick release clamp system. The power for the drive system may be derived from an internal combustion engine or electric motor. The power developed by the engine or motor is delivered to the rear wheel of a bicycle by a friction drive wheel that presses directly onto the tire of the bicycle. The power unit may utilize a clamp joined to an integrated fuel cell by a pivot point, causing the fuel cell to act as a swing arm and a motor mount. This enables the fuel cell to move up and down to compensate for different tire sizes, variations in road conditions, or movement of a suspension system of the bicycle due to imperfections in terrain.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/293,305, filed Jan. 8, 2010, the contents of which are expressly incorporated herein by reference in its entirety. 
     
    
     FIELD OF INVENTION 
       [0002]    This invention relates to an auxiliary drive system for vehicles, and more particularly to a motor drive for a conventional or suspension-based pedal-operated bicycle. 
       BACKGROUND 
       [0003]    It is well known that bicycles are designed to be driven by the leg power of a rider. The rider actuates a pedal system to transmit motion to the rear wheel of the bicycle by way of a chain drive. In many cases, pedal power is augmented by a transmission that alters the force required on the pedals by shifting the chain drive to sprockets of different size associated with the rear wheel of the bicycle. The sprockets are arranged in a cassette and act to provide the chain drive with different pinion ratios. Some bicycles include front or rear suspensions that provide springs or shock absorbers between the bicycle seat and the wheel, to absorb bumps and dips by allowing the wheel to move with respect to the bicycle seat. 
         [0004]    Auxiliary power drives are known using electric or internal combustion motors to apply power to either the front or rear wheel of a bicycle. These devices often use friction drives to engage the bicycle wheel to provide forward motion of the bicycle without pedaling. Such devices have been proposed for attachment to conventional bicycles. However, prior friction drive units are typically rather large and bulky, occupying significant space around or near the bicycle frame, and offsetting the center of gravity and balance of the bicycle. These drive units are often difficult to engage or disengage from the bicycle. Mounting the unit to the bicycle requires significant time and the use of external tools. Upon reaching a destination, the drive unit cannot be easily removed to store the bicycle. Some drive units are permanently attached to the bicycle frame, limiting the flexibility of use of the bicycle as well as the drive unit. Additionally, these drive units often cannot be used on a bicycle with a rear suspension, as the drive unit components and mounting equipment cannot accommodate movement of the rear tire relative to the bicycle frame. Also, some prior drive units accelerate wear of the bicycle tire, beyond the normal wear caused by the road or ground surface. 
         [0005]    Therefore, there remains a need for a drive unit for a bicycle that is easier to engage and disengage from the bicycle, and that can accommodate a bicycle with a rear suspension, without causing excessive tire wear. 
       SUMMARY OF THE INVENTION 
       [0006]    An auxiliary power assisted drive system according to an embodiment of the invention has an electric motor or an internal combustion engine that can be mounted to or removed from a bicycle seat post via a quick release clamping system, without external tools or special training. The motor may be supported on an arm or bracket that incorporates a fuel source such as a fuel tank. The arm or bracket acts as a beam that attaches the motor to the bicycle and allows for movement up and down about a pivot point attached to the clamping system. This permits the motor to be held against the tire of the bicycle even as a suspension system of the bicycle operates. Power is transferred to the wheel of the bicycle by way of a friction drive system including a spindle that frictionally engages the bicycle tire. 
         [0007]    According to an embodiment, the powered friction-driving device can be used on a bicycle with or without a suspension system and can accommodate wheel movement due to uneven road surfaces. The device can be removed and re-installed to the same or a different bicycle without the use of tools, by way of the detachable quick-release clamping system. This enables the device to be reconfigured easily to conditions of normal riding, maintenance or storage. 
         [0008]    In one embodiment, a power unit is provided for a bicycle having a seat post and a wheel with an axis. The power unit includes a motor having an output shaft configured to drive the wheel, a clamp dimensioned to clamp to the seat post of the bicycle, and a pivotal joint connecting the clamp to the motor. The pivotal joint pivots about a horizontal axis parallel with the axis of the wheel, for movement of the motor with respect to the clamp. 
         [0009]    In one embodiment, a bicycle system having a power unit for driving the bicycle includes a bicycle, where the bicycle has a frame, a wheel coupled to the frame, a seat tube coupled to the frame, and a seat post received by the seat tube. The wheel is configured to rotate about a wheel axis. The system also includes a power unit removably attached to the bicycle. The power unit includes a motor operatively coupled to the wheel to rotate the wheel, a clamp removably clamped to the seat post, and a joint between the motor and the clamp. The joint allowing pivoting movement of the motor with respect to the clamp. 
         [0010]    The above mentioned and other features and advantages of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a side perspective view of an auxiliary power drive unit constructed in accordance with an embodiment of the invention and mounted to a bicycle. 
           [0012]      FIG. 2  is an exploded perspective view of a clamping device of the auxiliary power drive device of  FIG. 1 . 
           [0013]      FIG. 3  is a bottom plan view of the auxiliary power drive device of  FIG. 1  illustrating a friction drive spindle and a quick release clamping system of the device. 
           [0014]      FIG. 4  is a side perspective view of the auxiliary power drive device of  FIG. 1  showing details of a pivot point, support bearing and spring used for tension of the unit against a wheel of a bicycle. 
           [0015]      FIG. 5  is a rear elevational view of the auxiliary power drive device of  FIG. 1  mounted to a bicycle. 
           [0016]      FIG. 6  is a perspective view of brackets that mount to a bicycle frame or axle to connect a tension spring for downward force as seen in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    This invention relates to an auxiliary drive system for vehicles, and more particularly to a motor drive for a conventional or suspension-based pedal-operated bicycle. The drive system includes a motor configured to frictionally drive the rear wheel of the bicycle, and a clamp that attaches to the seat post of the bicycle. A pivotal joint is connected between the clamp and the motor. This joint enables the motor to pivot up and down relative to the clamp, pivoting about a horizontal axis. This pivoting movement enables the drive system to accommodate a bicycle with a rear suspension, which allows the rear wheel to move with respect to the seat post. When the bicycle encounters bumps, dips, or other surface irregularities, the rear suspension enables the rear wheel to move up or down relative to the bicycle seat. To accommodate this suspension, the drive system includes the horizontal joint that allows the motor to move with the rear wheel, relative to the clamp mounted to the bicycle seat post. Additionally, the drive system includes a spindle with a concave surface that frictionally engages the outer tread of the bicycle tire, driving the tire forward while reducing slip and tire wear. In an embodiment, the spindle axis, bicycle wheel axis, and pivotal joint axis are parallel. This configuration enables the spindle to remain in driving engagement with the tire tread throughout any up and down motion of the wheel relative to the bicycle frame. 
         [0018]      FIG. 1  illustrates an exemplary embodiment of a compact, self-contained auxiliary power drive unit mounted to a bicycle frame  20 , and more particularly to a seat post  17  such that it can be removed and re-installed without the use of external tools. The power drive unit has a motor  9  mounted for frictional engagement with a tire  19  of the bicycle. The power drive unit also has a clamp  4  for clamping the unit to the bicycle, and a joint  30  between the motor  9  and the clamp  4 , for pivotal movement of the motor relative to the clamp. 
         [0019]    When an operator wishes to engage the unit, he or she simply attaches the clamp  4  of the unit to the bicycle. In one embodiment, the user attaches the clamp  4  to the seat post  17 . The joint  30  connects the clamp  4  to the motor  9 . The operator then engages a tension spring  10  to draw the device downwardly against the tire. The tension spring is engaged by pulling it in a downward motion and connecting it to the bicycle frame  20 , to the wheel axle, or to a spring bracket  21  installed near the axle of the bicycle wheel. The operator then attaches a throttle control  22  to a handle bar  23  of the bicycle and starts pedaling the bicycle in conventional fashion. This pedaling motion causes a friction drive spindle  13  driven by the motor of the power drive unit to rotate against the wheel  19  of the bicycle, starting the motor  9  of the device. The operator may then ride the bicycle as a conventional motorcycle or motorized bicycle would be ridden. When the operator is finished riding the bicycle in its motorized form, the drive unit can simply be removed by reversing the installation process and can easily be stowed in a normal back pack, placed in a suitable case, or otherwise stored for future use. 
         [0020]    The structure of the power drive unit and its attachment to the bicycle will now be described in greater detail. In one embodiment, the power drive unit is mounted to the seat post  17  of the bicycle. The seat post  17  is received into a bicycle seat tube  25  and adjusted to provide the desired height of the seat  11 . The seat post  17  is used as a mounting point for the auxiliary power drive unit due to its strength and integrity when inserted partially into the bicycle seat tube  25 . Placement of a tube inside another tube of slightly larger diameter essentially doubles the strength of the combination and therefore provides a secure mounting location for the power drive unit. The seat post  17  is held securely in place by a seat post clamp  24  that is u-shaped to surround the seat tube  25  into which the seat post  17  is inserted. A bolt draws the ends of the u-shaped clamp together, tightening the clamp around the seat tube  25  to secure the seat post  17 . In an embodiment, this seat post clamp  24  that clamps the seat post  17  to the seat tube  25  is independent of the power drive unit, and is not directly attached to the power drive unit. 
         [0021]    The auxiliary power drive unit is attached to the seat post  17  above the tube  25  and above the seat post clamp  24  by a quick release clamp system. In one embodiment, the clamp system includes a bracket  32  (see  FIG. 2 ). The bracket  32  includes the clamp  4  at one end and the joint  30  at the opposite end. In particular, the bracket  32  includes a clamp  4  designed to attach to the seat post  17 . The particular clamp of  FIG. 2  uses a pair of quick release camming skewers or levers  6  to force each side of clamp  4  together to achieve clamping pressure sufficient to hold the power assist unit in place on the seat post  17  or frame  20 . In different embodiments, the clamp  4  may attach the power drive unit directly to the seat-post  17  of a bicycle, or to any part of the bicycle frame  20 . In the case where the device is clamped to the seat post  17 , it can be positioned at any point along the seat post. This enables the user to adjust the device to provide sufficient clearance of components despite differences in configuration between different bicycles or different desired orientations of the drive spindle  13 , both fore and aft. 
         [0022]    In the embodiment of  FIG. 2 , the clamp  4  includes two arms that are urged together by the levers  6 . To attach the clamp  4  to the seat post  17 , the seat is removed from the bicycle, and the clamp  4  is passed over the top of the seat post  17  and slid down to the desired location along the seat post  17 . Alternatively, the clamp  4  could be designed to open wide enough to receive the seat post  17  into the opened clamp without removing the bicycle seat. In either case, the seat post  17  is received into the clamp  4 , and the levers  6  are engaged to urge the arms of the clamp toward each other, tightening the clamp around the seat post  17 . 
         [0023]    In one embodiment, the clamping system that enables mounting the power unit to any bicycle is a quick disconnect pinch-type clamp that utilizes a camming quick release skewer or lever to force the clamp to constrict around the bicycles seat post. The clamp may be made from light weight aluminum or alternatively it may be made from steel or composite materials. 
         [0024]    In the embodiment of  FIG. 2 , the joint  30  is located directly behind the clamp  4 . The joint  30  can be integrated into the clamp system, or can be separately coupled between the clamp system and the motor  9 . The joint  30  provides a pivotal connection between the motor  9  and the clamp  4 , enabling the motor to pivot with respect to the claim  4  and thus the bicycle seat post  17  and frame  20 . This freedom of motion of the motor  9  with respect to the clamp  4 , seat post  17 , and frame  20  enables the power drive unit to operate on bicycles with rear suspensions. As the rear suspension allows the rear wheel to move up or down with respect to the bicycle frame and seat, the joint  30  allows the motor to move along with the wheel, without dislodging the clamp or losing contact with the bicycle tire. This enables power to be applied efficiently to the tire of virtually any bicycle, including both bicycles having modern suspension systems and bicycles of the non-suspension type. 
         [0025]    In one embodiment, the joint  30  is formed at the connection of the bracket  32  and the swing arm  7 . In particular, the bracket  32  includes a through-passage  36  for receiving a shaft  5 . The pivot point is made up of a pair of polyurethane bushings  3  with a pivot axle thru shaft  5 , and includes bolts  1  and washers  2  that hold the swing-arm/fuel tank  7  to the bracket  32 . The bracket  32  thus serves as a pivotal attachment of the swing arm  7  (and attached motor  9 ) to the clamp  4 . As mentioned above, this pivot point can be located adjacent the seat post  17 , directly behind the clamp  4 , or it can be coupled further rearward, between the clamp  4  and the motor  9 . 
         [0026]    In one embodiment, a swing arm or bracket  7  connects the motor  9  to the joint  30 . In one embodiment, the swing-arm  7  includes an integrated fuel tank, fuel cell, or battery for powering the motor  9 . That is, a fuel tank, fuel cell, or battery housing may be utilized as the swing arm  7 . In such an instance, the swing arm  7  may also have a fuel filler cap  8  or a bung and cap system for the purpose of refilling with fuel or charging the battery. This swing arm  7  may be made of aluminum but may also be steel or a suitable composite material such as plastic. In the illustrated embodiment, the swing-arm/fuel tank  7  has a mounting point for engaging the joint  30 , thereby attaching the swing arm  7  to the clamping system of  FIG. 2 . The swing arm  7  also includes a mounting point for the motor  9 . The motor  9  may be mounted to the top surface of the swing arm, or to the side wall of the swing arm, or any other suitable mounting arrangement. The swing arm  7  also includes bearing supports  14  for rotatably supporting the friction spindle  13  (described below). 
         [0027]    The motor, which may be of any configuration, is directly mounted to the swing-arm/fuel tank  7  in the illustrated embodiment. In the alternative, the motor may be mounted through bushings or other means of support. A friction drive spindle  13  is mounted directly to the output shaft of the motor. The friction drive spindle  13  is made from steel with a pattern known as knurling (see  FIG. 3 ) cut into its circumference for traction against a bicycle wheel  19 . The spindle  13  may also be manufactured from aluminum or a suitable composite of different materials. The friction drive spindle  13  in this embodiment has an apple core shape, having a concave or depressed outer surface, that allows for self-centering of the power unit while the spindle is in motion. The output shaft of the motor  9  and the friction drive spindle  13  are supported by support bearings  14 , which may be located on both the outboard and inboard/motor side of the swing arm  7 . The inboard and outboard bearings  14  provide support to the spindle  13 , to protect the motor and output shaft from forces that may otherwise occur. In one embodiment, the spindle  13  is mounted to the motor output shaft. Mounting the spindle directly to the motor output shaft provides a simple and robust design, without extra gears or other components. 
         [0028]    The unit is powered by a motor  9 , which may be an internal combustion engine supplied by a fuel tank, or an electric motor powered by batteries or solar panels. The internal combustion engine may be of the type used in a conventional string trimmer or other suitable powered appliance, which may be of either two stroke or four stroke design. As shown in  FIG. 5 , the motor  9  is controlled by way of a cable and lever system  22  not unlike a motorcycle. The lever  22  is mounted to the handlebars  23  of a bicycle using a removable clamp or a strap having a hook and loop attachment system. The user can operate the lever  22  to increase the power supplied to the motor  9 , thereby increasing or decreasing the bicycle&#39;s speed. 
         [0029]    The weight of the motor  9  and swing arm  7  tends to press the spindle  13  against the tire  19 . However, to provide additional friction between the spindle and the tire, in one embodiment, a tension spring  10  (such as a coil spring) is provided to further urge the spindle against the tire. In one embodiment, the spring  10  is attached at one end to the drive unit (such as being attached to the swing arm  7 , either on the motor side or the opposing side) and at the other end to the bicycle wheel axle, or to a spring bracket  21  mounted to the bicycle as illustrated in  FIGS. 1 ,  5 , and  6 . The spring bracket  21  serves to connect the tension spring  10  to the bicycle axle or frame  20  in a universal manner. The spring provides an additional downward force on the friction drive spindle  13  to create an intimate and non-slipping contact between the spindle and the tire. In this way, the force required to drive the bicycle forward is efficiently transmitted to the bicycle tire without loss of motion, and without damaging or adversely affecting the life of the tire. The spindle  13  contacts the tire at the outer tread of the tire, rather than the side wall of the tire. Contact along the outer tread of the tire prevents accelerated wear of the tire, as the contact between the spindle and the tire takes place at the tread, where the tire is designed to sustain contact with the road surface. 
         [0030]    Upon reaching a destination, it is common practice for cyclists to lock bicycles in order to prevent theft. The presence of a power unit on an unattended bicycle could make the bicycle a more attractive target, creating a security issue if the power unit is left on the bicycle when the bicycle is parked. In embodiments as described above, the clamp system  4  enables the power unit to be easily removed and transported away from the bicycle when the bicycle is parked or stored. The power unit can be separately locked or stored away from the bicycle, reducing the risk of theft of the bicycle or the power unit. The power unit can be re-attached to the bicycle when the user is ready to leave, or the bicycle can be subsequently used in a conventional manner, without the power unit attached. The power unit can be safely stored away from the bicycle, and can be used with other, different bicycles as desired. The clamp system  4  and the pivotal joint  30  enable the power unit to be quickly and easily attached to a new bicycle with different dimensions, size, and geometry (including bicycles with or without suspension systems). 
         [0031]    In one embodiment, the joint  30  pivots about a horizontal axis, allowing the swing arm  7  and motor  9  to rotate in a vertical plane. In one embodiment, the rotational axis of the joint, the bicycle wheel axis, and the rotational axis of the spindle  13  are all parallel, and in one embodiment they are all horizontal. Also, in one embodiment, the spindle  13  contacts the bicycle tire at or behind the wheel axle. This geometry, with the swing arm  7  extending from the joint  30  to the spindle  13  at or behind the axis of the bicycle wheel, provides a stable configuration of the motor, swing arm, spindle, and joint as the spindle drives the wheel. The concave shape of the outer surface of the spindle also creates a stable contact of the spindle against the wheel. This design maintains contact between the spindle and the tire, even as the system pivots at joint  30 , thereby reducing losses due to slipping, and reducing inefficient tire wear. 
         [0032]    Although the present invention has been described and illustrated in respect to exemplary embodiments, it is to be understood that it is not to be so limited, since changes and modifications may be made therein which are within the full intended scope of this invention as hereinafter claimed.