Abstract:
A continuously variable speed transmission and steering differential having a central drive axle, two pairs of sheaves and two shift arms. The drive axel is driven by an external power source. The two pairs of sheaves, left and right, are mounted to the drive axel. Each pair of sheaves includes a fixed drive sheave and a movable drive sheave. Each movable drive sheave is positioned by a shift arm. Shifting the shift arms left or right varies the gear ratio between the left and right pair of sheaves thereby providing steering control. Narrowing the distance between the shaft arms increases the gear ratio and consequently puts the transmission into a higher gear, thereby providing speed control.

Description:
[0001]    This application claims priority from previously filed provisional application no. 62/003,199 titled CONTINUOUSLY VARIABLE SPEED TRANSMISSION AND STEERING DIFFERENTIAL under the name Shawn Watling on May 27, 2014. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present concept relates to continuously variable transmissions and more specifically relates to a continuously variable speed transmission combined with a steering differential. 
       SUMMARY OF THE INVENTION 
       [0003]    A continuously variable speed transmission and steering differential having a central drive axle, two pairs of sheaves and two shift arms. The drive axel is driven by an external power source. The two pairs of sheaves, left and right, are mounted to the drive axel. Each pair of sheaves includes a fixed drive sheave and a movable drive sheave. Each movable drive sheave is positioned by a shift arm. Shifting the shift arms left or right varies the gear ratio between the left and right pair of sheaves thereby providing steering control. Narrowing the distance between the shaft arms increases the gear ratio and consequently puts the transmission into a higher gear, thereby providing speed control. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    The present concept will be described by way of example only with reference to the following drawings in which: 
           [0005]      FIG. 1  is a schematic cross plan view of the continuously variable speed transmission and steering differential with the steering shown in the straight position. 
           [0006]      FIG. 2  is a schematic cross plan view of the continuously variable speed transmission and steering differential with the steering shown in the right turned position. 
           [0007]      FIG. 3  is a schematic cross plan view of the continuously variable speed transmission and steering differential with the steering shown in the left turned position. 
           [0008]      FIG. 4  is a schematic cross plan view of the continuously variable speed transmission and steering differential shown in the lowest gear position. 
           [0009]      FIG. 5  is a schematic cross plan view of the continuously variable speed transmission and steering differential shown in a medium gear position. 
           [0010]      FIG. 6  is a schematic cross plan view of the continuously variable speed transmission and steering differential shown in the highest gear position. 
           [0011]      FIG. 7  is a schematic top plan view of the continuously variable speed transmission and steering differential shown together with the driven pulleys mounted on the driven axles as well as the ball screw actuator for moving the floating arms relative to each other. 
           [0012]      FIG. 8  is a schematic back plan view of another embodiment of a continuously variable speed transmission and steering differential shown together with drive sheaves and driven sheaves, shown in low gear. 
           [0013]      FIG. 9  is a partial top schematic cross sectional view of the embodiment shown in  FIG. 8  taken through the drive axle showing the drive sheaves, the shifting mechanism, and the differential mechanism. 
           [0014]      FIG. 10  is a top plan view of the embodiment shown in  FIG. 8 . 
           [0015]      FIG. 11  is a schematic back plan view of the embodiment in  FIG. 8  shown in high gear. 
           [0016]      FIG. 12  is a schematic back plan view of the embodiment in  FIG. 8  showing a maximum differential left turn. 
           [0017]      FIG. 13  is a schematic back perspective view of the embodiment shown in  FIG. 8 . 
           [0018]      FIG. 14  is a front schematic perspective view of the embodiment shown in  FIG. 8 . 
           [0019]      FIG. 15  is a top plan view of the continuously variable speed transmission and steering differential together with a propulsion motor and handle bars. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    The present concept a continuously the continually variable speed transmission and steering differential shown generally as  100  in  FIGS. 1 through 7  and includes the following major components. 
         [0021]    The major frame members  101  include the centre chassis support  102  having mounted on each side thereof a right floating arm  104  and a left floating arm  106 . Mounted near the rear section  103  of continuously variable speed transmission and steering differential  100  is drive axle  108  which has mounted thereon left fixed drive sheave  110 , left floating drive sheave  114 , right fixed drive sheave  112 , and right floating drive sheave  116 . 
         [0022]    Not shown in  FIGS. 1 to 6  however shown in  FIG. 7  is drive sprocket  202  which is mounted onto drive axle  108  which receives power from for example an internal combustion engine and/or from an electric engine and transmits that power to the drive axle  108  through drive sprocket  102 . In other words power is received from an external power source such as an internal combustion engine or an electric engine via drive sprocket  202  which drives drive axle  108 . The reader will note that the left and right drive sheaves are connected to a common drive axle  108  which is mounted with bearings to centre chassis support  102  as well as right floating arm  104  and left floating arm  106 . 
         [0023]    Looking now to forward section  105  of continuously variable speed transmission and steering differential  100  there are two half shafts mounted onto the centre chassis support  102  and right and left floating arms  104  and  106  namely right driven axle  118  and left driven axle  120 . Right driven axle  118  is mounted onto right finger  111  of centre chassis support  102  and also onto right floating arm  104  using bearings typically known in the art. 
         [0024]    Similarly left driven axle  120  is mounted onto left finger  113  of centre chassis support  102  as well as onto left floating arm  106  again using bearings typically used in the art. 
         [0025]    Right driven axle  118  and left driven axle  120  rotate independently of each other. It is the difference in speed of the rotation between right driven axle  118  and left driven axle  120  which provides steering response. 
         [0026]    The gap or the distance between right floating arm  104  and left floating arm  106  is controlled and actuated by rear ball screw shaft  134  which is attached to rear ball screw nut  136  and front ball screw shaft  130  which is attached to front ball screw nut  132 . The biasing means shown in the diagrams is a ball screw type advancing and retraction means however other biasing means for regulating the gap or the distance between right floating arm  104  and left floating arm  106  could for example be carried out with hydraulic or pneumatic cylinders or other mechanical advancement and retraction means which are known in the art. The absolute gap between right floating arm  104  and left floating arm  106  controls the gear position or the speed at which the right driven axle  118  and the left driven axle  120  are driven at. 
         [0027]    Right driven axle  118  includes right floating driven sheave  128  and right fixed driven sheave  124 . Left driven axle  120  includes left fixed driven sheave  122  and left floating driven sheave  126 . 
         [0028]    The position of centre chassis support  102  relative to both the right floating arm  104  and the left floating arm  106  is controlled by moving differential bell crank  142  which in turn moves differential rocker  138  which in turn urges differential rocker link  140  thereby varying the relative gap between firstly right floating arm  104  and centre chassis support  102  and secondly between left floating arm  106  and centre chassis support  102 . Steering push rod  150  which is connected at one end to a steering wheel and/or handle bar is not shown and is connected at the other end to differential bell crank  142  which pivots about bell crank pivot point  144  thereby actuating differential rocker links  140  which in turn move right floating arm  104  and left floating arm  106  in opposite directions relative to centre chassis support  102 . 
         [0029]    Referring now to  FIG. 7  you will note that  2  additional pulleys are shown which are not depicted in  FIGS. 1 through 6  namely right driven pulley  208  mounted onto right driven axle  118  and left driven pulley  210  mounted on left driven axle  120 . Right and left driven pulleys  208  and  210  would ultimately be connected via belts or chains or other known means to for example the drive wheels or the drive track of a vehicle. It is contemplated that the vehicle would have separately or independently driven left and right wheels or tracks. In this way the speed of the vehicle is controlled by the rate of rotation of right driven pulley  208  and left driven pulley  210  and steering is accomplished by varying the relative rate of rotation of right driven pulley  208  relative to left driven pulley  210 . For example by driving right driven pulley  208  faster than left driven pulley  210  one can accomplish a left turn. By driving left driven pulley  210  more quickly than right driven pulley  208  one can accomplish a right turn. 
         [0030]    Additionally an example of an actuation method for activating rear ball screw shafts  134  and front ball screw shafts  130  is shown. Namely a ball screw actuator  204  which could be in the form of a stepper motor or other known method of activation in the industry would be connected by a sprocket and chain to front ball screw sprocket  212  and a rear ball screw sprocket  214  to rotateably urge rear ball screw shaft  134  and front ball screw shaft  130  thereby varying the gap or the relative distance between right floating arm  104  and left floating arm  106 . 
         [0031]      FIG. 7  also shows a belt  206  in position mounted onto right driven sheaves  124  and  128  as well as onto left drive sheaves  112  and  116 . Additionally there is a front ball screw chain  216  and a rear ball screw chain  217 , belt tensioners  250 , and belt tensioner springs  252 . Ball screw actuator  204  through a gearbox  254  drives front and rear ball screw chains  216  and  217 . 
         [0032]    In  FIG. 7  for example the rear section  103  drive sheaves are shown in open position whereas the forward section driven sheaves  128  and  118  are shown in a relatively closed position. This would correspond to a low gear position of the continuously variable speed transmission. 
         [0033]    Referring now to  FIGS. 1 ,  2  and  3  which show three example positions for steering. 
         [0034]    Referring now to  FIG. 1  the centre chassis support is centred relative to both the right floating arm  104  and the left floating arm  106 . In this position both the left and the right driven sheaves are turning at approximately the same rate of rotation and therefore the steering of the vehicle is approximately straight. 
         [0035]    Referring now to  FIG. 2  the reader will note that by rotation of differential bell crank  142  which in turn urges differential rocker links  140  to displace right floating arm  104  closer to centre chassis support  102  and displaces left floating arm  106  further away from centre chassis support  102  thereby causing the various sheaves to open and close relative together as shown in the drawings thereby creating a right turn condition. 
         [0036]      FIG. 3  shows the positioning of the centre chassis support  102  relative to right floating arm  104  and left floating arm  106  creating a left turn condition. 
         [0037]    In this manner the reader will note that by pivoting differential bell crank  142  with for example a steering push rod  150  one can accomplish a straight steering condition or a right turn steering condition and/or a left turn steering condition by simply moving the right floating arm  104  and the left floating arm  106  relative to the centre chassis support  102  thereby altering the gap between the sheaves of both the rear section  103  and the forward section  105  as shown in drawings  1 ,  2  and  3 . 
         [0038]    Referring now to  FIG. 4  gear selection is accomplished by altering the gap and/or the relative distance between the right floating arm and the left floating arm  106 . 
         [0039]    For example in  FIG. 4  there is a minimal gap between right floating arm  104  and left floating arm  106  and this is accomplished by turning rear ball screw shaft  134  and front ball screw shaft  130  such that the right floating arm  104  and the left floating arm  106  come in as close as possible in proximity to each other. This would represent a low gear position in that the rear section  103  drive sheaves are as open as possible whereas the forward section  105  driven sheaves are in as closed position as possible thereby creating a lowest gear or slow position. 
         [0040]    Referring now to  FIG. 5  the rear ball screw shaft  134  and the front ball screw shaft  130  have been advanced such there is now a greater gap and/or relative distance between right floating arm  104  and left floating arm  106  thereby closing the gap between the rear section  103  drive sheaves and simultaneously slightly opening the gap between the forward section  105  driven sheaves thereby creating a greater rotational speed at both the right driven axle  118  and the left driven axle  120  which are ultimately connected to the drive wheels and/or tracks of the vehicle. 
         [0041]    Referring now to  FIG. 6  once again the rear ball screw shaft  134  and front ball screw shaft  130  are actuated to increase the relative distance or the gap between the right floating arm  104  and the left floating arm  106  to a maximum position which represents the highest gear wherein the gap between the rear section  103  drive sheaves is minimized and the gap between the forward section  105 , driven sheaves is maximized thereby creating the greatest rotational speed of the right driven axle  118  and the left driven axle  120 . This would be the highest gear position to produce the maximum speed condition. 
         [0042]    Another embodiment of the present concept that a continuously variable speed transmission and steering differential is shown general as  300  includes the following major components namely; drive axle  302  which is fixed to the chassis and rotates on bearings. 
         [0043]    Drive axle  302  has mounted thereon left and right moveable drive sheaves  304 , left and right fixed drive sheaves  306 , left and right shift arms  308  and cog pulley  310 . 
         [0044]    Cog pulley  310  receives a cog belt from a motor not shown in  FIGS. 8 and 9  which drives drive axle  302 . 
         [0045]    Continuously variable speed transmission and steering differential  300  includes two major mechanisms namely shift mechanism  303  and differential mechanism  305 . 
         [0046]    First of all shift mechanism  303  includes speed change motor  320 , chain  324 , sprockets  322 , motor sprockets  326  shift arm cap  362  and shift arm base  363 . 
         [0047]    Speed change motor  320  receives signals from an operator to rotate motor sprocket  326  which in turn moves chain  324  and sprockets  322  which in turn rotate ball screw shafts  311  which in turn moves simultaneously shift arms  308  together thereby controlling the width or the spacing between the moveable drive sheaves  304  and the fixed drive sheaves  306  thereby effecting gear changes. 
         [0048]    The reader will note that there are two moveable drive sheaves  304  on both the right and left side of the continuously variable speed transmission and steering differential  300 . 
         [0049]    By bringing shift arms  308  in closer proximity to each other by turning ball screw shafts  311  one can narrow the width between the moveable drive sheave and the fixed drive sheave  306  thereby increasing the gear ratio between the drive axle  302  and the right and left driven axles  340  and  342 . 
         [0050]    One can lower the gear ratio by reversing the direction of rotation of speed change motor  320  which in turn separate the left and right shift arms  308  thereby increasing the distance between the moveable drive sheaves  304  and the fixed drive sheaves  306 . Low gear for example is shown in  FIG. 8  and high gear is shown in  FIG. 9 . 
         [0051]    The reader will note that during the speed change operation shift mechanism  303  simultaneously moves both the left and right shift arms in unison in other words the separation between the moveable drive sheaves  304  and the fixed drive sheaves  306  on both the left and right side remains the same. The amount of speed change will be the same on both the right driven axle  340  and the left driven axle  342 . 
         [0052]    A differential mechanism shown generally as  305  includes the following major components namely a differential arm  312  which is connected to a link arm  314  at the link arm pivot  318  which in turn is connected to left and right differential links  316  which in turn is connected to shift arms  308 . Differential arms  312  are connected to a differential arm shaft  319  and rotate in unison. 
         [0053]    By rotating differential arm shaft  319  either clockwise or counter clockwise this in turn will move shift arms  308  either to the left and/or to the right thereby increasing the distance between the moveable drive sheave  304  and the fixed drive sheave  306  on one side for example the right side and decreasing the distance between moveable drive sheave  304  and fixed drive sheave  306  on the other side namely the left side of the transmission. 
         [0054]    Differential drive shaft  319  which are in turn connected to front and back differential arms  312  as rotated at steering link point  321  through a series of links which ultimately is connected to either a set of handle bars and/or steering wheel. 
         [0055]    On the driven side of the continuously variable speed transmission and steering differential  300  there is a right driven axle  340 , a left driven axel  342 , a right fixed driven sheave  344 , a right moveable driven sheave  348 , a left fixed driven sheave  346  and a left moveable driven sheave  350  having a V-belt  352  mounted thereon. 
         [0056]      FIG. 8  for example shows maximum separation between the fixed drive sheave  306  and the moveable drive sheave  304  which would correspond to the lowest gear possible whereas the right fixed driven sheave  344  and right moveable driven sheave  348  are shown in the closest spacing possible again corresponding to the lowest gear ratio. In other words  FIG. 8  shows the shift mechanism  303  in the lowest gear ratio.  FIG. 11  shows the sheaves  304  and  306  as close as possible and in a high gear position. 
         [0057]      FIG. 8  also shows that the two sets of drive sheaves namely the right and left moveable drive sheaves  304  and fixed drive sheaves  306  are equally spaced meaning that there is no differential or steering input and therefore the differentials in the neutral are straight ahead position. In order to input steering one would urge steering link point  321  either left or right which in turn would turn differential arm shaft  319  which in turn would turn differential arms  312  which in turn would move shift arms  308  either to the right or to the left thereby inputting steering function.  FIG. 12  shows maximum left turn differential input. 
         [0058]    There is further anti-rotation and suspension axles  332  which have a double function first of all provide for attachments to the rear suspension and also prevent rotation of the continuously variable speed transmission and steering differential structure. 
         [0059]    Referring now to  FIG. 9  which is a partial schematic cross-sectional view taken through the centre of drive axle  302  which shows that moveable drive sheave  304  is attached to drive axle  302  with a keyed torque hub  374  which includes hub rollers  360 . 
         [0060]    Drive axle  302  is mounted onto drive axle bearing  331  and also bearings  330  on each end of the shaft. Sliding bushings  370  are mounted onto drive axle  302  and slide longitudinally along drive axle  302  as required. 
         [0061]    Ball screw shafts  311  are mounted on to shift arms  308  with ball screw bearings  313 . 
         [0062]    Additionally drive axle  302  is also supported by centrally located drive axle bearings  372 . 
         [0063]    It should be apparent to persons skilled in the arts that various modifications and adaptation of this structure described above are possible without departure from the spirit of the invention the scope of which defined in the appended claim.