Patent Publication Number: US-2004055803-A1

Title: Variable speed transmission for scooter

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
     [0001] This application claims the benefit of U.S. Provisional Patent Application No. 60/413,319, filed Sep. 24, 2002, incorporated herein by reference. 
    
    
     
       STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT  
       [0002] Not Applicable  
       Reference to a “Sequence Listing,” a Table, or a Computer Program Listing Appendix Submitted on a Compact Disk.  
       [0003] Not Applicable  
       [0004] This invention relates to small, motor-driven vehicles, such as scooters and go-carts. More particularly, a driven shaft from the vehicle motor for driving a driven wheel has an adjustable diameter. When the driven shaft is adjusted to have a small diameter, the small, motor-driven vehicle is propelled at low speed and high torque. When the driven shaft is adjusted to have a larger diameter, the small, motor-driven vehicle is propelled at higher speed and lower torque. Accordingly, the adjustable diameter of the driven shaft permits optimization of vehicle torque and speed.  
       BACKGROUND OF THE INVENTION  
       [0005] Go-carts and scooters powered by motors are known. By way of example, see Patmont, U.S. Pat. 6,095,274, entitled Engine Drive for Scooter, in which the rider of a scooter stands upon a scooter platform and directs a foreword steered wheel while applying motor power through a throttle mechanism to a rear driven wheel. In this disclosure, the throttle mechanism includes an engine mounted on a pivot arm offset from the axis of rotation of the rear driven wheel of the scooter. This engine has a protruding driven shaft overlying the driven wheel for moving into and out of contact with the periphery of the driven wheel. Through offset mounting of the engine pivot relative to the point of rear wheel rotation and the periphery of the driven wheel, the driving shaft can be brought into and out of contact with the rear driven wheel for controlled propulsion of the scooter.  
       [0006] In this particular driving arrangement, the torque and speed applied to the rear driven wheel is a function of two parameters. First, the driven shaft must be in contact with the periphery of the driven wheel. Second, the torque and speed of the motor is transmitted through the driven shaft and directly transferred to the driven wheel. As the torque and speed of the engine varies, the torque and speed of the driven vehicle wheel varies.  
       [0007] Small, motor-driven vehicles, such as the scooter illustrated in the Patmont &#39;274 patent, are used on surfaces having variable slopes and variable resistance to vehicle passage. It is common for such small, motor-driven vehicles to proceed uphill, on the level, and downhill. Further, it is common for such small, motor-driven vehicles to be used on an all-terrain basis on rough, sandy, or marshy ground where the resistance to the foreword passage of the small, motor-driven vehicle is highly variable. Given a driven shaft of constant diameter, the only variation of torque and speed will be the variation of torque and speed of the driving motor. This is not necessarily in the best interest of efficient small, motor-driven vehicle propulsion.  
       [0008] Variable speed and torque transmissions are known. However, virtually none of these is suitable for the simple environment of a small, motor-driven vehicle, such as a scooter. Simply stated, between the motor and driven wheel, there is no room for mechanical complication. Simplicity is required in all these transmissions.  
       BRIEF SUMMARY OF THE INVENTION  
       [0009] A small, motor-driven vehicle has at least one steered wheel and at least one motor-driven wheel with the rider supported between the wheels. The rider directs the steered wheel while applying motor power through a throttle mechanism to the driven wheel. The throttle mechanism includes a driven shaft from the motor contacting the periphery of the driven wheel. This driven shaft has an adjustable diameter. When the driven shaft is adjusted to have a small diameter, the small, motor-driven vehicle is propelled at low speed and high torque with optimum power transmission for proceeding either uphill or over terrain presenting higher resistance to vehicle passage. When the driven shaft is adjusted to have a larger diameter, the small, motor-driven vehicle is propelled at higher speed and lower torque, on the level, downhill or over terrain presenting lower resistance to vehicle passage. Accordingly, the adjustable diameter of the driven shaft permits optimization of scooter torque and speed for proceeding with optimum motor efficiency. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0010]FIG. 1 is a side elevation view of a small, motor-driven vehicle, here shown as a scooter, illustrating the front steered wheel, the rear driven-wheel, and the rider supporting platform supported between the two wheels;  
     [0011]FIG. 2 is an enlarged side elevation similar to FIG. 1 illustrating the throttle mechanism of the Patmont &#39;274 patent with the invention of this disclosure schematically shown in broken lines;  
     [0012]FIG. 3 is a first schematic of the drive mechanism shown in FIG. 2 illustrating the driven shaft with a small diameter for driving the driven wheel with high torque and low speed;  
     [0013]FIG. 4 is a second schematic of the drive mechanism shown in FIG. 2 illustrating the driven shaft with a larger diameter for driving the driven wheel with lower torque and higher speed;  
     [0014]FIGS. 5A and 5B are first and second views of a mechanism having opposed interlocking parts for producing a variable diameter driven shaft with FIG. 5A illustrating the mechanism having a small diameter when fully expanded with one interlocking part away from the other interlocking part, and FIG. 5B illustrating the mechanism having a larger diameter when contracted with one interlocking part moved toward the other interlocking part; and,  
     [0015]FIGS. 6A and 6B are first and second views of an inflatable variable diameter driven shaft with FIG. 6A illustrating the mechanism having a small diameter when deflated and FIG. 6B illustrating the mechanism having a larger diameter when inflated. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0016] Referring to FIG. 1, the small, motor-driven vehicle is shown as scooter S. Scooter S can be easily understood. Scooter S includes standing platform P, front steered wheel F and rear driven wheel R. Engine E drives rear driven wheel R in the apparatus disclosed herein.  
     [0017] Scooter S includes steering handle  14 , which rotates on head tube H. The single structural member of the scooter chassis is main structural tube T. Main structural tube T connects to head tube H at the front, supports standing platform P in the middle via couplings  28  and  29  and terminates at rear tire mounting section  32 . Referring specifically to FIG. 2, it will be seen that main structural tube T has side-displacing section  30  followed by rear tire mounting section  32 . Rear tire mounting section  32  supports rear driven-wheel R via axle  34 .  
     [0018] Having generally set forth the construction of scooter S, attention will be given first to the physical mounting of engine E to main structural tube T and, second, to the mechanics of the driving of rear driven wheel R.  
     [0019] Referring to FIG. 2, engine E is mounted on pivot V. As can be seen in FIG. 4, engine E has a protruding driving shaft D, which here rotates at the same speed as engine E. Protruding driving shaft D directly contacts peripheral surface  40  of rear driven wheel R. It will be understood that when protruding driving shaft D is in contact with ground contact surface  40  and engine E is operating, scooter S will be driven.  
     [0020] Attention will now be devoted to the drive schematic of FIG. 3. Rear driven wheel R turns on axle  34 . To understand the physics of this invention, note that radial  44  has been drawn from protruding driving shaft D and its contact point on the periphery  40  of rear driven wheel R.  
     [0021] Pivot V is offset with respect to this radial  44 .  
     [0022] Specifically, pivot V should have an angle of 10° to 40° relative to the point of contact between protruding driving shaft D and peripheral surface  40 . This range can be narrowed to be between 15° and 30°, and more optimally is 20°.  
     [0023] Further, the length of pivot arm  48  is preferably less than the length of radial  44  by a ratio of about 60% to 90% in a broad range, 70% to 80% in a medium range, and about 75% as shown in the preferred embodiment.  
     [0024] It will further be noticed that protruding driving shaft D swings in an arc  50 . Arc  50  will be seen to intersect the periphery  40  of rear driven wheel R at an acute angle alpha.  
     [0025] Having set forth this construction, the interaction of protruding driving shaft D and rear driven wheel R during vehicle operation can now be set forth.  
     [0026] Specifically, and as illustrated in FIG. 3, rear driven wheel R turns counterclockwise. Protruding driving shaft D turns clockwise. Taking the reactive force from protruding driving shaft D, it will be understood that engine E on pivot arm  48  drives protruding shaft D counterclockwise and into contact with the periphery  40  of rear driven wheel R.  
     [0027] Given the position of pivot V, it will be understood that protruding driving shaft D moves along arc  50 . This arc  50  contacts peripheral surface  40  of the driven wheel at a shallow (acute) angle. As a result of this motion, firm driving contact takes place—even in the absence of any other biasing forces present.  
     [0028] In the preferred embodiment, two biasing forces are present. One is the weight of engine E. The remaining force is supplied by tension from coil spring  52 , which extends from the distal end of main structural tube T to engine E.  
     [0029] Referring to FIGS. 1 and 3, it will be understood that the motion of engine E and protruding driving shaft D into rear driven wheel R at peripheral surface  40  must be controlled. Precise control of this motion gives corresponding precise control of the motion of scooter S. This being the case, a cable control lever, such as derailleur cable ratchet  54  acting on cable  56 , limits such contact., By the simple expedient of tensioning cable  56  through cable control lever  54 , precision control of the scooter driving force occurs.  
     [0030] It should be understood that the drive here disclosed does not appreciably affect the placement of fender  58 , which hinges to the chassis. Likewise, a conventional scooter brake  58  can be utilized.  
     [0031] It will be understood that where scooter S is used off road, it is possible to completely disengage engine E from rear driven wheel R. In this case, pushing or coasting of scooter S can occur in a conventional manner.  
     [0032] Thus far, the transmission of this invention has not been differentiated from that transmission set forth in the Patmont &#39;274 patent, although it will be understood that the embodiments of FIGS. 1, 2,  3 , and  4  all incorporate this invention. Comparing driven shaft D′ of FIG. 4 to driven shaft D of FIG. 3, the principle on which this invention operates can be readily understood.  
     [0033] The size of driven shaft D′ is larger in diameter than driven shaft D of FIG. 3. Accordingly, rotation of driven shaft D′ wheel drives the driven wheel R at a higher speed and lower torque from engine E. Understanding this much, what is needed is a mechanism for changing the diameter of rotating shaft D from its small diameter shown in FIG. 3 to the larger diameter shown in FIG. 4.  
     [0034] Before moving on to an explanation of these mechanisms, it is important to note with respect to FIG. 4, and the drive swinging axis there illustrated, that the larger diameter of driven shaft D′ does not interfere with the operation of the transmission thus far described. The only consequence of the larger diameter driven shaft is that the engagement of the driven shaft with the periphery of driven wheel R occurs at a different angular interval of the engine E on the drive pivot position.  
     [0035] As of the writing of this Provisional Patent Application, the optimum mechanism for expanding and contracting the diameter of driven shaft D to driven shaft D′ is being selected. At present, two mechanisms are shown for accomplishing this purpose. The mechanism of FIGS. 5A and 5B, illustrates opposed conical splines. The mechanism of FIGS. 6A and 6B, illustrates an inflatable driven shaft. Using either alternative, the objectives sought by this disclosure can be realized.  
     [0036] Referring to FIG. 5A opposed conical spline sections  70 A and  70 B are illustrated. Each spline section fastens to a cylindrical base  72  and has tapering, alternating, conical splines concentric about axis  74  of engine E rotation. In the view of FIG. 5A, spline sections  70 A and  70 B are remote one from another. In the view of FIG. 5B, spline sections  70 A and  70 B have been moved toward one another. Such movement is urged by wire  76  concentric to the rotating conical spline sections  70 A and  70 B. The reader will appreciate that if tension is not exerted by wire  76  drawing the respective splines sections towards one another, the natural tendency of the spline sections will be to move away, one from the other.  
     [0037] Control of the mechanisms of FIGS. 5A and 5B can be easily understood. Specifically, derailleur cable ratchet (not shown) acting on wire  76  can produce, through the tension on the wire, the desired driven shaft diameter. At the same time, the respective conical spline sections will provide the requisite traction to the driven wheel R.  
     [0038] Referring to FIGS. 6A and 6B, an even simpler mechanism is illustrated. In this mechanism, driven shaft D is given an inflatable exterior  80 . In FIG. 6A, inflatable exterior  80  is deflated through inflation conduit  82 . As a result, driven shaft D has a small diameter and drives driven wheel R at low speed and high torque.  
     [0039] Referring to FIG. 6B, inflatable exterior  80  of driven shaft D′ is inflated through inflation conduit  82 . As a result, driven shaft D′ has a large diameter and drives driven wheel R at high speed and lower torque.  
     [0040] The reader will understand that this Provisional Patent Application is intended to cover any mechanism which provides for the convenient expansion and contraction of the driven shaft D, D′. It is anticipated that other preferred embodiments of this mechanism will be identified by the time a non-provisional patent application is filed.