Abstract:
A muscle-powered continuously variable drive system, and apparatus having same, is disclosed. The system employs dual actuator levers pivoted at one end. The free pedal ends of the levers reciprocate through an arcuate range of motion via application of muscle power by the user, rather than cycling through complete revolutions of a small-radius circle, such as is common for conventional bicycles. The reciprocating motion of the levers initiated by the user generates a force that is translated into rotational motion of a drive wheel via a drive tether. The drive tether is attached to the actuator levers and runs around three idler pulleys mounted to the apparatus&#39; frame. Two chain segments of the tether engage respective dual sprockets at the hub of the drive wheel. The geometry of the transmission enables a light, simple, system of continuously-variable torque multiplication, which eliminates the need for conventional derailleurs and multiple sprockets, or internal gear hubs.

Description:
CLAIM OF PRIORITY  
       [0001]     This application claims priority under 35 USC § 119(e) from U.S. Provisional Patent Application No. 60/651,483, filed on Sep. 13, 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to muscle-powered drive systems and apparatus having same.  
       BACKGROUND ART  
       [0003]     There are a number of transportation devices such as bicycles that rely on muscle-power drive systems. Conventional bicycles, for example, have a front chain wheel (“chain ring”) to which pedals are attached. The pedals are arranged to allow a user to drive the front chain wheel by pedaling in cyclical fashion with their feet while sitting atop the bicycle. The front chain ring is mechanically coupled to a rear freewheel by a chain. The rear freewheel is operably arranged at the hub of the rear wheel of the bicycle, and typically has multiple sprockets so that the user can select between different gears. In operation, the user causes his or her legs to exert a downward force on the pedals to initiate a cycling motion. The force is transferred from the chain ring to a sprocket on the rear freewheel to drive the bicycle forward. Front and rear derailleurs allow the user to change gears by shifting the chain between the multiple sprockets at the rear freewheel and/or the front chain ring.  
         [0004]     There have been numerous attempts to design other types of muscle-powered drive systems with the object of improving efficiency, such as described in the following U.S. patents: U.S. Pat. No. 6,648,355 B2 to Ridenhour; U.S. Pat. No. 6,554,309 to Thir; U.S. Pat. No. 5,785,337 to Ming; U.S. Pat. No. 5,690,345 to Kiser; U.S. Pat. No. 5,335,927 to Islas; U.S. Pat. No. 4,953,882 to Craig, Jr.; U.S. Pat. No. 4,857,035 to Anderson; U.S. Pat. No. 4,630,839 to Seol; U.S. Pat. No. 4,574,649 to Seol; U.S. Pat. No. 4,272,096 to Efros; U.S. Pat. No. 4,133,550 to Brown; U.S. Pat. No. 4,077,648 to Seol; and U.S. Pat. No. 4,019,230 to Pollard.  
         [0005]     Unfortunately, the prior art muscle-power drive systems suffer from excess mechanical complexity, incurring both weight and mechanical efficiency penalties.  
       SUMMARY OF THE INVENTION  
       [0006]     The invention is directed to a light-weight, mechanically simple, ergonomically efficient muscle-power drive system suitable for use in limb-driven human-powered apparatus and machinery such as bicycles, tricycles, wheel chairs, etc. The ergonomic improvement is achieved in the present invention through a reciprocating-motion design. When used in a bicycle, the drive system of the present invention is believed to make better use of leg muscle power as compared to conventional rotary cranking motion drive systems such as used in a conventional bicycle.  
         [0007]     The invention enables the complete elimination of the conventional rotary-pedal bicycle&#39;s front, or crank, hub and bearings, with attendant simplification of the frame design and substantial weight savings. The invention also allows for partial-stroke propulsion (i.e., continuous application of power using less-than-full-length strokes), and mass centralization due to the continuously-side-by-side positioning of the rider&#39;s legs. Both of these features are particularly advantageous in off-road riding.  
         [0008]     Because of the mechanical simplicity of the invention, manufacturing costs are expected to be significantly less than for conventional designs.  
         [0009]     An aspect of the invention is a muscle-powered drive system that utilizes right and left pivotable actuator levers. The levers run horizontally along the sides of a frame, which supports a drive wheel. The drive wheel includes an axle and a hub having two mirror-image but otherwise conventional freewheel devices on its right and left sides, incorporating identical right and left drive sprockets. One end of each actuator lever is pivotably mounted to the frame at or near the rear axle, or to the rear axle itself. A tether with two chain sections and three cable sections is attached at respective ends to coupling points along the length of the actuator levers. The location of the coupling points is changeable (movable) via sliding members (“sliders”) that move within respective channels formed along the length of the actuator levers. The tether runs through idler pulleys attached to the frame and also over the right and left sprockets. The idler pulleys are arranged to convert the force associated with alternating up-and-down strokes of the actuator levers into alternating forward rotational forces on the wheel via engagement of the drive tether with the sprockets of the drive wheel.  
         [0010]     The actuator levers are pivotably mounted to the frame at or near the axle of the drive wheel. The actuator levers have moveable ends (the pedals, in the preferred embodiment) that travel over a small segment (e.g., about 25 degrees) of a large-radius circular arc, rather than through complete revolutions of a small-radius circle as with conventional rotary-pedal bicycles. When the user engages the levers and moves them in reciprocal fashion, the two levers alternately pull on the two ends of the cable-and-chain tether. The tether runs through the system of idler pulleys and acts alternately on right and left sprockets on the drive wheel hub to power the drive wheel. In an example embodiment, the inertia of the reciprocating mass in the system is captured and returned to the system by torsion springs arranged between the frame and the actuator levers. In an example embodiment, the torsion springs provide a natural period of 70-90 cycles/minute, depending on the user&#39;s preference.  
         [0011]     The respective positions of the coupling points is adjustable and can range from close to the pivot end of the actuator lever, to close to the pedal surfaces at the end opposite the pivot end. The geometry of the tether and the idler pulleys thereby provides continuously variable lever-travel-to-wheel-travel ratios over a useful range. This eliminates the need for multiple sprockets and derailleur mechanisms, or internal gear hubs, as used on conventional rotary-pedal bicycles.  
         [0012]     These and other aspects of the invention are discussed in greater detail below. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a side elevational view of an example embodiment of the drive system as incorporated into a bicycle;  
         [0014]      FIG. 2  is a perspective view of an example embodiment of the complete drive system operably coupled to a drive wheel, wherein the Figure omits portions of the frame for ease of illustration;  
         [0015]      FIG. 3  is a side elevational close-up view of one of the actuator levers, showing the adjustable slider and control cables, as well as a twist-grip controller mounted to the handlebars;  
         [0016]      FIG. 4  is a cross-sectional view of the actuator lever of  FIG. 3 , taken along the line I-I′, and showing the upper and lower channels formed with the actuator lever that support the control cable and the slider.  
         [0017]      FIG. 5  is a side elevational close-up view of the lower portion of the frame, showing the attachment of the lower idler pulleys to the frame.  
         [0018]      FIG. 6  is an exploded view of the drive hub, including segments of the frame and the actuator levers, illustrating the torsion springs employed between the frame and the actuator levers so that energy can be stored in the torsion springs and returned to the drive system as the actuator levers are reciprocally operated by a user. 
     
    
       [0019]     The various elements depicted in the drawings are merely representational and are not necessarily drawn to scale. Certain proportions thereof may be exaggerated, while others may be minimized. The drawings are intended to illustrate various implementations of the invention, which can be understood and appropriately carried out by those of ordinary skill in the art.  
         [0020]     Also, where an element in the Figures has first and second counterparts, and one is hidden by the other, the notation “XA, B” is used. For example, in  FIG. 1 , the seat stay lower ends  27 A and  27 B are indicated by “ 27 A, B” where seat stay  27 B is hidden by seat stay  27 A.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0021]      FIG. 1  is a side elevational view of an example embodiment of a muscle-powered drive system (“the drive system”)  18  of the present invention as incorporated into a bicycle  20 . An X-Y-Z Cartesian coordinate system is shown in for the sake of reference, wherein “vertical” is in the Y-direction, and horizontal is in the Z- and X-directions. Also, “front” is associated with the +X direction, the “back” is associated with the −X direction, the “top” or “up” is associated with the +Y direction, the “bottom” or “down” is associated with the −Y direction, the right-hand side is associated with the +Z direction, and the left-hand side is associated with the −Z direction. Also, “horizontal” means in or substantially in the X-Z plane, while “vertical” means in or substantially in the Y-Z plane. Thus, “vertical” and “horizontal” are intended to generally indicate relative orientations.  
         [0000]     The Frame  
         [0022]     Bicycle  20  has a frame  22  that is aligned substantially in the X-Y plane. Bicycle frame  22  is similar to a conventional bicycle frame, e.g., it has a front fork  4  that holds a front wheel  6 , and has handlebars  8  that allow for steering the front wheel to guide the bicycle in a desired direction. However, frame  22  includes some modifications as described below.  
         [0023]     With continuing reference to  FIG. 1  (and also to  FIG. 6 , discussed below), frame  22  includes seat stays  27 A and  27 B that have corresponding lower ends  28 A,  28 B and upper ends  29 A,  29 B, and chain stays  23 A and  23 B that have corresponding back ends  24 A and  24 B, and front ends  25 A and  25 B. Seat stay lower ends  27 A and  27 B and chain stay back ends  24 A and  24 B are respectively fixed to axle brackets  26 A and  26 B, adapted to engage an axle  30  ( FIG. 3 ) of a rear hub  34  of a spoked drive wheel  36  that lies substantially in the X-Y plane. Drive wheel  36  has a front end  37 , which remains fixed relative to the frame even when the drive wheel is rotating.  
         [0024]     Axle  30  has opposing ends  32 A and  32 B, arranged on opposite sides of the wheel. Bicycle frame  22  also includes a substantially vertical seat tube  40  having a top end  42  and a bottom end  44 . A seat  46  is attached to seat tube top end  42 . Seat stay upper ends  29 A and  29 B are fixed to seat tube  40  at or near top end  42 . Chain stay front ends  25 A and  25 B are fixed to the bottom end  44  of seat tube  40 . Frame  22  also includes a top tube  48  having a rearward end  50  and a front end  51 . Rearward end  50  is attached to seat tube  40  at or near top end  42 . Frame  22  also has a down tube  52  having a front end  53  and rearward end  54  attached at or near the bottom end  44  of seat tube  40 . Top tube  48  and down tube  52  are also attached at their respective front ends to a steering head  55 , which allows for handlebars  8  to be operably coupled to fork  4  to allow for steering.  
         [0000]     The Drive System  
         [0025]      FIG. 2  is a perspective view of the drive system  18  of  FIG. 1 .  FIG. 2  omits portions of the bicycle frame  22  for ease of illustration. The drive system  18  includes the aforementioned rear hub  34 , wherein the hub includes left and right mirror-image freewheels  62 A and  62 B. Two identical left and right sprockets  66 A and  66 B are affixed to the corresponding left and right freewheels  62 A and  62 B. Sprockets  66 A and  66 B are adapted to engage the links of a chain. In an example embodiment, rear hub  34  is fabricated according to one of the industry&#39;s standard designs, but is adapted to accommodate two mirror-image freewheels and two sprockets, instead of one of each.  
         [0026]     The drive system  18  also includes left and right actuator levers  70 A and  70 B. The actuator levers have corresponding first ends  72 A and  72 B each pivotably mounted to frame  22  at or near respective axle brackets  26 A and  26 B, or alternatively, to axle  30  at or near respective axle ends  32 A and  32 B. In either embodiment, actuator levers  70 A and  70 B run from their attachment points essentially in the +X direction on either side of the frame. Actuator levers  70 A and  70 B also have corresponding movable pedal ends  74 A and  74 B located at opposite respective pivot ends  72 A and  72 B.  
         [0027]     In an example embodiment, pedal ends  74 A and  74 B include respective pedals  80 A and  80 B (e.g., step-in bindings) adapted to accommodate the respective left and right feet of a user (not shown) of the bicycle when the user sits on seat  46 . Thus, in an example embodiment, pedal surfaces  80 A and  80 B occupy approximately the same location as the pedals of a conventional rotary-pedal bicycle, when such pedals are at their forwardmost position of rotation. In an example embodiment, actuator levers  70 A and  70 B are curved. Actuator levers  70 A and  70 B are discussed in greater detail below.  
         [0028]     The drive system further includes two upper idler pulleys  100 A and  100 B attached to frame  22 , e.g., to respective seat stays  27 A and  27 B at or near ends  29 A and  29 B so that the idler pulleys reside above the corresponding actuator levers  70 A and  70 B and substantially parallel to the X-Y plane with their corresponding actuator levers and sprockets  66 A and  66 B. The Idler pulleys  100 A and  100 B themselves are arranged to operate substantially parallel to the X-Y plane.  
         [0029]     With reference also to  FIG. 5 , the drive system also includes a center idler pulley  110  attached below chain stay front ends  25 A and  25 B near the bottom end  44  of seat tube  40 , which operates substantially parallel to the X-Z plane. A threaded adjuster/spring tensioner  111  (shown in  FIG. 5 ) is incorporated in the mounting for idler pulley  110 , to ensure constant tension and to adjust out any slack in the tether system.  
         [0030]     The drive system also includes a drive tether  120  that mechanically couples actuator levers  70  to sprockets  66 . In an example embodiment, drive tether  120  is contiguous and includes a first end  122 , a first cable section  123 , a first chain section  124 , a second cable section  125 , a second chain section  126 , a third cable section  127  and a second end  128 . In an example embodiment, the cable sections  123 ,  125  and  127  are fabricated of stranded round steel cable, and are connected to the first and second chain section, e.g., via swaged devises (not shown).  
         [0031]     First tether end  122  is coupled to actuator lever  70 A at an adjustable coupling point P 1 A in between actuator lever ends  72 A and  74 A. The adjustability of coupling point P 1 A (and corresponding point P 1 B on the other actuator lever) is discussed in greater detail below. The first cable section  123  of the tether then runs up from point P 1 A to and over the top of idler pulley  100 A from front to back. The tether then runs down around the corresponding sprocket  66 A so that the first chain section  124  engages the back side of this sprocket. The second cable section  125  of the tether  120  then runs forward to center idler pulley  110  along one side of the wheel, around the front part of the center idler pulley, and then back along the other side of the wheel to sprocket  66 B, where the second chain section  126  engages the back side of this sprocket. The third cable section  127  then runs back up to the remaining idler pulley  100 B, passes over this pulley from back to front, and then extends down to the remaining actuator lever, where the second tether end  128  is fixed at an adjustable point P 1 B corresponding to adjustable point P 1 A on the other actuator lever. As discussed above, tensioner  111  is used to provide constant tension and to remove slack in the tether system.  
         [0032]     In an example embodiment, the drive system further includes a lever idler pulley  150  rotatably and pivotably fixed to the frame near the bottom end  44  of seat tube  40  (see  FIG. 5 ). In an example embodiment, lever (or “lower”) idler pulley  150  is positioned below and between the two actuator levers and is oriented substantially parallel to the Y-Z plane. A coupling tether  160  is operatively engaged with pulley  150  and has respective ends  162 A and  162 B fixed to respective positions P 2 A and P 2 B on the respective actuator levers  70 A and  70 B. Tether  160  runs around the bottom side of lever idler pulley  150  through or under the bottom portion of the frame so as to mechanically couple actuator levers  70 A and  70 B. In an example embodiment, actuator levers  70 A and  70 B each include an upward extension  170 A and  170 B to provide for elevated attachment points P 2 A and P 2 B for ends  162 A and  162 B of coupling tether  160 . Elevated attachment points P 2 A and P 2 B allow lever idler pulley  150  to be positioned to provide adequate ground clearance. In an example embodiment, travel-limiting stops  164 A and  164 B are affixed to tether  160  and positioned to mechanically limit the range of motion of the actuator levers to ergonomically appropriate parameters.  
         [0000]     Method of Operation  
         [0033]     In the operation of example drive system  18  in propelling bicycle  20 , a user first positions himself or herself on seat  46  of the bicycle and engages their feet with pedal step-in bindings  80 A and  80 B. Using their leg muscles, the user applies a downward force to one of the pedal surfaces—say, pedal  80 A. This downward force causes actuator lever  70 A to rotate downwardly about pivot ends  72 A and  72 B, which pulls the drive tether end  122  downward. This causes the first chain section  124  to drive sprocket  66 A in the clockwise direction, which causes wheel  36  to rotate and move bicycle  20  forward. During the downward motion of actuator lever  70 A, actuator lever  70 B moves upward and into position for the user to apply a downward force thereto.  
         [0034]     When actuator lever  70 A reaches its limit of motion established by travel-limiting stop  164 A, the user applies a downward force to pedal  80 B with the opposite leg, causing actuator lever  70 B to move downwardly, which pulls the drive tether end  128  downward. This causes the second chain section  126  to drive sprocket  66 B in the clockwise direction, which causes wheel  36  to rotate and move bicycle  20  forward. During the downward motion of actuator lever  70 B, actuator lever  70 A moves upward and into position for the user to apply a downward force thereto.  
         [0035]     The process of sequentially applying downward force to pedals  80 A and  80 B is repeated to provide continual drive power to the drive wheel. Through the use of industry-standard step-in (or “clipless”) binding-type pedals, which removably couple the user&#39;s footwear to the actuator levers, power may also be applied on the upward stroke of each actuator lever in combination with the downward stroke on the opposite lever. This is because coupling tether  160  and lever idler pulley serve to couple the upward motion of one actuator lever with the downward motion of the other actuator lever.  
         [0036]     It will be observed that the operator need not fully depress the pedal levers to their limits of travel established by stops  164 A and  164 B, but may instead choose to reverse their directions of travel after only partial strokes. Partial strokes may be useful, for instance, to avoid contact of the pedals with obstacles on the ground, or when performing a banked turn, while maintaining the continuous application of power to the drive wheel.  
         [0000]     Continuously Variable Transmission  
         [0037]     The range of motion of first and second chain segments  124  and  126  around corresponding sprockets  66 A and  66 B relative to the reciprocating motion of the actuator levers can be changed over a continuous range, depending on how far away adjustable coupling points P 1 A and P 1 B are from respective pivot ends  72 A and  72 B of respective actuator levers  70 A and  70 B. If points P 1 A and P 1 B are relatively close to corresponding pivot ends  72 A and  72 B, the drive system is in a ‘low gear’ due to the torque multiplication over the actuator levers&#39; length. Low gears are typically used when a user wishes to exert more force per unit of distance traveled, such as for hill climbing. If points P 1 A and P 1 B are moved farther from pivot ends  72 A and  72 B and more toward pedals  74 A and  74 B, the drive system is in a ‘high gear’ and the user can provide more force to the drive wheel, such when the user desires higher-speed riding. Of course, in the present invention, there is no quantized changing of discrete gears, as in a conventional bicycle. Rather, the “gear change” is accomplished along a continuum, by changing the leverage applied to the sprockets through the drive tether. This constitutes a continuously variable transmission for the drive system.  
         [0038]      FIG. 3  is a close-up side elevational view of an example embodiment of actuator lever  70 A. Also shown in  FIG. 3  is first cable section  123  of drive tether  120 , and twistgrip controller  300  located, for example, on handlebars  8 .  FIG. 4  is a cross-sectional view of actuator lever  70 A of  FIG. 3  taken along the line I-I′. Actuator lever  70 A includes an inside surface  76 A and an outside surface  78 A. Formed on the inside surface  76 A is an upper channel  202 A that has a lip  204 A, and a lower channel  210 A with a lip  212 A. Channels  202 A and  210 A run along the length of actuator lever  70 A from pivot end  72 A to a point  220 A near pedal end  74 A. A ball-bearing end pulley  226 A is located at point  220 A and has a diameter roughly that of the separation between the upper and lower channels.  
         [0039]     Attached to drive tether end  122  is a slider  240 A sized to fit within channel  202 A and slide therein. In an example embodiment, slider  240 A includes a wheel or other type of rolling member. Lip  204 A holds slider  240 A within channel  202 A. Coupled to the slider is a first push-pull control cable  250 A that resides within channel  202 A. Also coupled to slider  240 A is a second push-pull control cable  254 A that resides within channel  210 , passes over end pulley  226 A and connects up with the slider in channel  202 A. First push-pull cable  250 A is coupled to channel  202 A at pivot end  72 A, and second push-pull cable  254 A is coupled to channel  210 A also at pivot end  72 A using standard adjustable threaded cable couplers  260 A. A twistgrip hand controller  300  is operably coupled to the push-pull cables  250 A and  254 A and is adapted to control the length of the control cables via a twisting motion initiated by the user.  
         [0040]     In operation, push-pull cables  250 A and  254 A are adjusted simultaneously with corresponding cables  250 B and  254 B via the user using twistgrip controller  300  to move the sliders  240 A and  240 B to a desired pair of coupling positions P 1 A and P 1 B along the length of actuator levers  70 A and  70 B. In an example embodiment, actuator lever  70 A and upper and lower channels  250 A and  254 A are curved so that slider  240 A travels over an arc, the center of which is located at or near upper idler pulley  110 A. Aside from the twistgrip controller  300 , the entire drive system  18 , including the above-described gearing system and method, is bilaterally symmetric. Threaded adjusters  260 A facilitate installation of the control cables and eliminate slack. End pulley  226 A minimizes friction when moving slider  240  to change gear ratios.  
         [0041]     Thus, the ‘gearing’ or lever-motion-to-wheel-motion ratio of the drive system is continuously adjustable over a useful range without the need for internal gear hubs, derailleurs and/or multiple-sprocket systems.  
         [0000]     Torsion Spring Embodiment  
         [0042]      FIG. 6  is an expanded perspective view of the rear-wheel hub  34 , sprockets  66 A and  66 B, freewheel devices  62 A and  62 B, pedal levers  70 A and  70 B, and the lower, rear sections of the frame:  24 A,  26 A,  28 A, and  24 B and  28 B ( 26 B not shown).  FIG. 6  also an example embodiment that includes torsion springs  270 A and  270 B. Torsion springs  270 A and  270 B have respective coiled sections  272 A,  272 B, and respective linear extensions  274 A,  276 A and  276 A,  276 B that extend from opposite ends of each coiled section. The linear extensions for each torsion spring form an angle roughly equal to the angle formed by the seat stays  27 A,  27 B and chain stays  23 A and  23 B at the point where seat stay ends  28 A,  28 B intersect respective chain stay ends  24 A,  24 B.  
         [0043]     Respective grooves  280 A and  280 B sized to accommodate a portion of respective coiled sections  272 A,  272 B and respective extensions  276 A,  276 B are formed in the inner surfaces  76 A and  76 B of respective actuator levers  70 A and  70 B at or near respective actuator lever ends  72 A and  72 B. Also, seat stays  27 A and  27 B include respective engaging members  290 A and  290 B formed at respective seat stay ends  28 A and  28 B. Engaging members  290 A and  290 B are adapted to engage a portion of respective torsion spring extensions  274 A and  274 B. T  
         [0044]     When torsion springs  270 A and  270 B are properly situated in respective grooves  280 A and  280 B and also held by engaging members  290 A and  290 B, they are able to store energy when actuator levers  70 A and  70 B move so as to reduce the angle between torsion spring extensions  274 A and  276 A, thus compressing the torsion springs. Energy is returned to the drive system as the direction of travel for each actuator lever is reversed and releases the compression on the respective torsion spring, thus providing additional drive power.  
         [0045]     It will be understood by those skilled in the art that alternative configurations of frame, seat, wheels, and mounting points for the actuator levers may be accommodated through placement of pulleys in addition to those shown and described in the above preferred embodiment, and that many other apparatus from boats to potter&#39;s wheels may advantageously be powered by similar means.  
         [0046]     Accordingly, in the foregoing Detailed Description, various features are grouped together in various example embodiments, or shown separately, for ease of understanding. The many features and advantages of the present invention are apparent from the detailed specification, and, thus, it is intended by the appended claims to cover all such features and advantages of the described apparatus that follow the true spirit and scope of the invention. Furthermore, since numerous modifications and changes will readily occur to those of skill in the art, it is not desired to limit the invention to the exact construction and operation described herein. Accordingly, other embodiments are within the scope of the appended claims.