Abstract:
A package operable to provide power assist to a pedal operated vehicle having a rear wheel, the vehicle movable longitudinally, comprises: 
     a) a carrier 
     b) a ground engaging drive wheel supported by the carrier and at least one electric battery and an electric battery operated drive supported by the carrier to rotate the drive wheel, 
     c) the carrier coupled to the vehicle for up and down pivoted movement about a generally lateral axis in close association with the vehicle rear wheel, 
     d) the battery or batteries and at least part of the drive being located vertically above the drive wheel so that the weight of the carrier, the battery or batteries, and at least part of the drive bears downwardly on the drive wheel to urge the wheel into ground engagement.

Description:
This application is a continuation of Ser. No. 09/246,790 filed Feb. 9, 1999, abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to power assist devices for human powered vehicles, such as bicycles; more particularly it concerns a unique power assist package easily connectible to a bicycle and operable to provide power-assist, when needed or wanted. 
     There have been many design approaches for coupling a battery-powered power assist device to a bicycle, but so far to my knowledge none has provided, in a convenient, economical way, a complete system add-on device that one can install quickly onto bicycles having various types of tires, brakes, gears, etc. To avoid the complexity of needing to couple somehow to the bicycle drive system (tires, wheels, sprockets, chain, cranks; components with geometry that vary from bicycle to bicycle) the power assist needs to power its own wheel or wheels. Various sidecars towed units have been developed to provide self-contained, add-on drive of an integrated wheel or wheels, but none to my knowledge have been highly successful in the modern marketplace. 
     The geometry challenge is 1) to have the desired force pressing the wheel to the ground at all times, 2) the device never tangling with the rider&#39;s body, legs, or feet, 3) the device not inhibiting parking in a small space or backing up, 4) the device not preventing the rear bicycle rack from carrying packages, basket, or even a passenger, 5) the device not having a significant affect on the vehicle&#39;s dynamics, 6) the device combining all the batteries, motor, and drive wheel in a package that can be rolled or carried for recharging or storing; and the device avoiding scrubbing. For a practical battery-powered assist, the batteries, motor, and drive wheel should be part of a single unit. 
     SUMMARY OF THE INVENTION 
     It is a major object of the invention to provide an easily operable and reliable power assist package readily connectible to a bicycle or in combination with a bicycle, and overcoming problems and deficiencies as referred to above. 
     Basically, the package includes: 
     a) a carrier; 
     b) a ground engaging drive wheel supported by the carrier, and an electric battery operated drive supported by the carrier to rotate the drive wheel; 
     c) and connecting arm structure associated with the carrier and projecting for connection to the bicycle frame to position the carrier for up and down pivoted movement in close association with and generally parallel to the bicycle rear wheel, with the drive wheel lowermost extent spaced less than six inches to the rear of the lowermost extent of the bicycle rear wheel, so that neither the drive wheel or the carrier will interfere with operation of the bicycle. 
     It is another object to provide a package that is positioned “tightly” adjacent the left side of the rear bicycle wheel, with an arm connecting it to a pivot on the bicycle frame in front of the rear wheel axle. The drive wheel may typically contact the ground at a point between about  350  and  550  down from and rearwardly of the pivot, so that drive wheel thrust force is accompanied by a nearly equivalent down force that adds to the unit&#39;s weight to keep the drive wheel pressed to the ground and not slipping when powered. The body of the system moves around this pivot point to keep the drive wheel touching the ground, whether the bicycle is banked left or right, or if the road slants sideways. 
     A further object is to provide a device package having a portion that is movable up and down, but is constrained against any lateral or twisting movement relative to the bicycle. In a preferred embodiment, such constraint is provided by fingers or tabs that slide in slots, for example one at the upper part of the unit, and one at the lower portion of the unit. 
     Yet another object is to provide for contact of the drive wheel with the ground less than about 6 inches behind the ground contact point of the rear wheel. (If the drive wheel is further back, it tends to scrub as the bicycle turns sharply; and if the drive wheel has a large diameter it projects so far forward as to interfere with the rider&#39;s left heel during pedaling.) Solutions to these two problems of scrubbing (by limiting the drive wheel axis position to be not far behind the bicycle rear wheel axis), and rider heel hitting or striking (by limiting the front of the drive diameter wheel to be positioned only slightly in front of the main wheel axis) require use of a relatively small drive wheel. A large wheel can only be used if its axis is so far back that, to avoid scrubbing, it casters when the bicycle goes around a corner. While provision for castering solves the scrubbing problem, it introduces others, beyond just weight cost and complexity: a castering drive wheel that must operate over a wide speed range tends to wobble unless damped; the drive wheel jackknifes when the bike is pushed backwards; and the drive wheel must be moved further out laterally from the bicycle rear wheel to avoid striking it when the bike turns to the right. Such greater lateral distance means the drive wheel must move further up and down relative to the bike as the bicycle banks—complicating the pivoting limits and lateral constraints. Also, when the bike travels over and down a curb, the drive wheel is abruptly driven upward relative to the bike as the bike wheel descends. 
     A further object is to provide a drive package meeting the following requirements, for use with a standard size bicycle: 
     1) The unit&#39;s weight rests generally on the drive wheel; 
     2) The motion of the drive wheel/motor/battery assembly or package about the pivot at the front of a connecting arm is constrained laterally near the top and bottom of the unit carrier so that movement of the package is always in a plane parallel to the plane of the bike rear wheel; 
     3) The drive wheel contacts the ground less than 5 inches to the left of, and less than 6 inches (preferably less than about 4 ½ inches) behind the ground contact point of the main bicycle wheel, i.e. rear wheel; and 
     4) The front of the drive wheel is less than about 1 inch ahead of the bicycle rear axle. 
     These latter three requirements have associated related specific lengths or dimensions of the bicycle. These are lengths appropriate for an adult bicycle with the rear wheel being of standard dimension, about 26-27 inch diameter. The fore and aft geometric requirements relate more to the distance between the front and rear wheel axes of the bicycle (typically around 42 inches) than they do to the rear wheel diameter. For 16 or 20 inch diameter bicycle wheels, the avoidance of scrubbing of the drive and like wheels during turns and avoidance of heel hitting is comparable to the situation for a 26 inch wheel diameter bicycle, with the same bicycle wheel base. The power assist may alternatively be attached to other pedaled vehicles, such as tricycles, and the term “bicycle” is intended to refer to such. 
     An additional object is to provide, for a standard bicycle a combination wherein: 
     1) the drive wheel axis is less than about 10.5% of the bicycle wheel base behind the bike rear wheel axis; and 
     2) the drive wheel is spaced to the left of the bicycle rear wheel by an amount that leaves less than 19% of the bicycle rear wheel diameter spacing between the adjacent edges of the tires of the drive wheel and the bicycle rear wheel. 
     These features are applicable to a battery-powered electric assist unit that incorporates battery, motor, and wheel in one assembly. That assembly is preferably pivoted to 1) have a pivot position such that in normal operation the drive wheel ground contact point is between 35°-55° down from a horizontal line rearward from the pivot, and 2) permit vertical movement of the package in an upright plane parallel to the upright plane of the bike rear wheel, in the direction of travel. The assembly is also constrained from lateral or roll movements relative to the plane of the rear bicycle wheel. This constraint can be accomplished in various ways. One is the fingers/slots mechanism described above and herein. Another is to employ a bearing on or in application with the above described pivot, that rotates about an axis, parallel to the rear wheel axis and is sufficiently strong as to be able to constrain any motion of the main assembly from moving non-parallel to the plan e of the rear wheel . 
     A yet additional object is to provide features that include a handle affixed to the main assembly near the package top (front, rear, or side), the handle located on a spring-loaded arm, or gravity nested, so that it remain down snug against the assembly box or carrier, or frame, when not in use, but can be lifted up to a height convenient for trundling the unit. Another feature is providing the arm that extends from the main assembly, i.e. carrier, to the pivot to be hinged at the main assembly end, so it can be folded up along the front of the carrier box, whereby it is out of the way when moving or storing the device. Another arm can be provided that extends from the pivot to near the front of the drive wheel, and stabilizes the assembly, and also folds up when not in use. A rain cover top can be provided on the main assembly, the hinged cover keeping rain out, but permitting the flow of cooling air. Louvers on the side of the main assembly box can also permit air flow, but keep out rain. 
     A battery charger can be put into or behind the main assembly box or the cover. The batteries, can easily be lifted out by a strap and charged elsewhere, if desired. Free-wheeling of the drive wheel can also be provided to allow back-up of the unit (and drive wheel reverse rotation in free-wheeling mode). Various controls are usable, such as ON-OFF switches, or a cruise control to maintain bike speed, varying the output of the package to maintain a set speed, and in relation to power of pedaling. Other control objectives are possible such as speed indication. 
     These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following specification and drawings, in which: 
    
    
     DRAWING DESCRIPTION 
     FIG. 1 is a side elevation showing a power assist unit pivotally connected to a bicycle, adjacent the left side of the bicycle rear wheel; 
     FIG. 2 is an opposite side elevation view of the power assist unit; 
     FIG. 3 is an enlarged section taken on lines  3 — 3  of FIG. 2; 
     FIG. 4 is a rear elevation taken on lines  4 — 4  of FIG. 1, but showing interior details of the unit; 
     FIG. 5 is a schematic plan view showing location of wheel to ground contact points in longitudinal and lateral upright planes; and 
     FIG. 6 is a left side view of a bicycle to which the power assist unit is connected. 
    
    
     DETAILED DESCRIPTION 
     In FIGS. 1 and 4, a power assist unit or package  10  is located at the left side of a bicycle  11  having a rear wheel  12  defining a lateral axis  13  of rotation. Wheel contact with the ground is indicated at point  14 . The power assist unit  10  has a drive wheel  15 , much smaller than wheel  12 , and which contacts the ground at point  16 . 
     Points  14  and  16  are also seen in FIGS. 4 and 5, and located in longitudinally extending upright and forward planes  17  and  18  (bisecting the wheels) and in laterally extending upright planes  19  and  20 . Point  14  is also at the ground level intersection of planes  17  and  19 ; and point  16  is also at the ground level intersection of planes  18  and  20 . Plane  19  passes through and contains the bicycle&#39;s rear wheel axis  13 . The spacing between parallel planes  17  and  18  is indicated at “d 1 ” and the spacing between parallel planes  19  and  20  is indicated at “d 2 ”. The forwardmost edge  15   a  of drive wheel is located at a distance “d 3 ” forward of plane  19 . As indicated above, for a bicycle rear wheel about 42 inches in diameter, the dimensions are as follows: 
     d 1  is preferably less than about 5 inches 
     d 2  is less than 6 inches and preferably about 
     4 ½ inches 
     d 3  is preferably less than about ½ inch (but in general is less than 2 inches) 
     d 4  (drive wheel diameter) is less than about 10 inches. 
     The drive wheel  15  has an axle  22  bearing mounted to the lower frame of an upright carrier  23 . The carrier has opposite upright side walls  24  and  25  carried by the frame, and upright end walls  26  and  27 , so that the wheel  15  is located between lower-most extents  24   a  and  25   a  of side walls  24  and  25 , and protrudes forwardly and rearwardly, as well as downwardly, as seen in FIG.  1 . An electric motor  28  is suitably mounted within the carrier interior, above the drive wheel, and drive chains  29  and  29   a  (or gearing) couple the motor to the wheel  15 , as via suitable sprockets  30  and  31 , and step-down sprockets  30   a  and  31   a , whereby desired speed reduction is achieved, as between the RPM of the motor and the RPM of the drive wheel. A variable speed transmission can be used between the motor and drive wheel. 
     An electric battery, or batteries  34  are located within the carrier interior, for example above the motor, so as to be upwardly removable for replacement. A resiliently yieldable cushion, such as foam rubber  35 , or a spring or springs, supports battery or batteries, above a support plate  36 . Damping of the spring or springs may be employed. A suitable cable connection from the battery to the motor is indicated at  37 ; and accessible ON-OFF controls and/or speed controls are provided as at  40 . A transporting handle for the package or unit  10  is seen at  41 , protruding above the carrier. It has legs  42  extending downwardly into suitable channels at the side  24  of the carrier, and the handle can be elevated to an up-position  41   a  for use in manually transporting the unit  10  to and from a bicycle. Suitable stops on a leg  42  and on the carrier frame limit upward elevation of the handle. If desired, the extended handle leg sections  42   a  and  42   b  can be hinged, as at  43 , to allow fold-down to position  42   a  seen in FIG. 4, as is desirable during power assist use. 
     Connecting arm structure is provided in association with the carrier and projecting for pivoted connection to the bicycle frame to position the carrier for up and down pivoted movement in close association with the bicycle rear wheel and generally parallel thereto, with the drive wheel lowermost extent spaced less than six inches to the rear of a lateral axis through the lowermost extent of the bicycle rear wheel, during non-banking travel of the bicycle. 
     Also, the connecting arm structure projects forwardly and upwardly from the carrier, the pivotal connection at  52  located forwardly of upright plane  19  containing the bicycle rear wheel axis. 
     As shown, the connecting arm structure includes two arms,  50  and  51  pivotally connected at  52  to the bicycle frame member  53  that extends between the bicycle rear wheel hub and the pedal hub. The connection  52  allows up-down pivoting of the arms  50  and  51 , which are rigidly attached at  50   a  and  51   a  to the carrier  23 , for example to the carrier frame. Locations  50   a  and  51   a  are spaced apart generally vertically, as shown. These locations may define locked hinge connections to allow unlocking and folding of the arms  50  and  51  back against the side of the carrier, for storage. Traction force generated by rotation of the drive wheel  15  is transmitted from the carrier to the arms  50  and  51 , and forwardly and upwardly by those arms to the bicycle frame. Pivot location  52  is located forwardly of the upright plane  19  containing the bicycle rear wheel axis  13 . 
     The connecting arm structure also constrains the carrier for pivoted movement parallel to upright plane  17  defined by the bicycle rear wheel, and normal to axis  13 , and at a maintained gap or spacing such as referred to at d 1  in FIGS. 4 and 5. For that purpose two additional arms  60  and  61  are preferably employed, to extend between the bicycle frame and the carrier for maintaining carrier up-down movement in a pre-determined vertical plane, such as plane  18  as referred to. Arm  60  has one end rigidly connected or clamped at  60   a  to bicycle lower frame member  53  (see FIG.  2 ); and arm  61  has one end rightly connected or clamped at  61   a  to bicycle upper frame member  63  that extends toward the bicycle seat. The two arms may also have their mid-portions rigidly interconnected as shown at  64 . 
     The opposite ends  60   b  and  61   b  of the arms extend into close proximity to the carrier  23 , as for example adjacent its side  25 , to guide its vertical movement and to block lateral movement of the carrier in the direction of arrows  66  in FIG.  4 . For this purpose, lost motion tongue and groove connections may advantageously be provided between the arm ends  60   b  and  61   b  and the carrier side wall  25 . Elongated rigid strap  67  has its opposite ends connected at  67   a  and  67   b  to flat vertical side  25  of the carrier, and to provide an elongated guide slot or groove  68  between  67  and  25 . The slot closely receives the flat arm end  60   b  (finger) and allows up-down movement of the carrier and strap about pivot  52 , relative to arm end  60   b , as indicated by arrow  69 . A thin slider or wear plate  70  may be attached to  25  to slide against the arm end. Accordingly, arm end  60   b  guides vertical movement of the carrier, and blocks its lateral deviation. See FIG.  3 . 
     Similarly, a lower level elongated rigid strap  71  has its opposite ends connected at  71   a  and  71   b  to side  25  of the carrier, to provide a similar elongated guide slot or groove between  71  and  25 . That slot closely receives the flat arm end  61   b , and allows up-down movement of the carrier and strap, about the pivot  52 , and relative to arm end  61   b , as indicated by arrow  75 . A thin slider or wear plate, like plate  70  may be attached to  25  to slide against the flat arm end  61   b . Accordingly, arm end  61   b  likewise guides vertical movement of the carrier and blocks its lateral deviation. 
     Another function of the pre-positioned arm ends  60   b  and  61   b  is to allow their simple and rapid assembly into the slots under the straps  67  and  71 , when the power assist unit is initially assembled to the stationary bicycle, as in a forward direction indicated by arrow  76 , in FIG.  2 . It is only then necessary to assemble the pivot connection  52  as by means of a simple pin attachment. A parallelogram or other multi-bar linkage may be used to pivotally connect the carrier to the frame. 
     The position of the power assist unit as described, relative to the bicycle, maintains it out of interference with the cyclist&#39;s feet or shoes as during peddling of the bicycle; and the power assist unit is also maintained out of contact with the bicycle rear wheel. At the same time, the closeness of the power assist unit to the bicycle rear wheel prevents impact with nearby objects to the lateral side of the bicycle. Parallel up-down movement of the unit is also maintained during lateral tilting of the bicycle frame, in use. An enlarged bearing (indicated at  52 ′) at pivot location  52  may alternatively, or additionally be used to block lateral direction of the power assist unit. 
     FIG. 4 also shows optional fold-down of the handle  41 , as via a hinge  43  located between sections  42   a  and  42   b  of the handle legs  42 , for handle storage during power assist use. 
     The axle of the drive wheel or motor can have an end extension for power take-off to devices such as tools, whereby the power assist device has extended utility. 
     The drive wheel typically includes an elastomeric tire, having a maximum width of about two inches, for good traction. 
     FIG. 6 shows a two-wheeled bicycle  100  having the package  10  connected in driving relation. Also shown are controls  101  at the bicycle handle bars that have wire connection  102  to the controls  67 , or to the motor or transmission, for controlling operation of the power assist unit. 
     The motor may consist of an internal combustion engine power unit, instead of an electric motor; or, the drive can employ a fuel cell, or other power source. 
     Finally, the drive wheel axis can be tilted relative to the carrier, so that the wheel axis is canted from horizontal. The carrier itself can be positioned just to the rear of the bicycle rear wheel axis so as not to interfere with fasteners or other structure projecting at that axis.