Abstract:
A continuously variable transmission is disclosed for use in rotationally or linearly powered machines and vehicles. The transmission provides a simple manual shifting method for the user. Further, the practical commercialization of traction roller transmissions requires improvements in the reliability, ease of shifting, function and simplicity of the transmission. The present invention includes a continuously variable transmission that may be employed in connection with any type of machine that is in need of a transmission. For example, the transmission may be used in (i) a motorized vehicle such as an automobile, motorcycle, or watercraft, (ii) a non-motorized vehicle such as a bicycle, tricycle, scooter, exercise equipment or (iii) industrial equipment, such as a drill press, power generating equipment, or textile mill.

Description:
RELATED APPLICATIONS 
     This application is a continuation of and claims priority to U.S. application Ser. No. 10/770,966 filed on Feb. 3, 2004, which issued as U.S. Pat No. 6,949,049 on Sep. 27, 2005, which claims priority from U.S. application Ser. No. 10/134,097 filed on Apr. 25, 2005, which issued as U.S. Pat. No. 6,689,012 on Feb. 2, 2004, which in turn claims priority from U.S. Provisional Application No. 60/286,803, filed Apr. 26, 2001. The entire disclosure of each of those applications is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The field of the invention relates generally to transmissions, and more particularly the invention relates to continuously variable transmissions. 
     2. Description of the Related Art 
     The present invention relates to the field of continuously variable transmissions and includes several novel features and inventive aspects that have been developed and are improvements upon the prior art. In order to provide an infinitely variable transmission, various traction roller transmissions in which power is transmitted through traction rollers supported in a housing between torque input and output disks have been developed. In such transmissions, the traction rollers are mounted on support structures which, when pivoted, cause the engagement of traction rollers with the torque disks in circles of varying diameters depending on the desired transmission ratio. 
     However, the success of these traditional solutions has been limited. For example, in one solution, a driving hub for a vehicle with a variable adjustable transmission ratio is disclosed. This method teaches the use of two iris plates, one on each side of the traction rollers, to tilt the axis of rotation of each of the rollers. However, the use of iris plates can be very complicated due to the large number of parts that are required to adjust the iris plates during transmission shifting. Another difficulty with this transmission is that it has a guide ring that is configured to be predominantly stationary in relation to each of the rollers. Since the guide ring is stationary, shifting the axis of rotation of each of the traction rollers is difficult. 
     One improvement over this earlier design includes a shaft about which a driving member and a driven member rotate. The driving member and driven member are both mounted on the shaft and contact a plurality of power adjusters disposed equidistantly and radially about the shaft. The power adjusters are in frictional contact with both members and transmit power from the driving member to the driven member. A support member located concentrically over the shaft and between the power adjusters applies a force to keep the power adjusters separate so as to make frictional contact against the driving member and the driven member. A limitation of this design is the absence of means for generating an adequate axial force to keep the driving and driven members in sufficient frictional contact against the power adjusters as the torque load on the transmission changes. A further limitation of this design is the difficulty in shifting that results at high torque and very low speed situations as well as insufficient means for disengaging the transmission and coasting. 
     Therefore, there is a need for a continuously variable transmission with an improved power adjuster support and shifting mechanism, means of applying proper axial thrust to the driving and driven members for various torque and power loads, and means of disengaging and reengaging the clutch for coasting. 
     SUMMARY OF THE INVENTION 
     The systems and methods have several features, no single one of which is solely responsible for its desirable attributes. Without limiting the scope as expressed by the claims that follow, its more prominent features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description of the Preferred Embodiments” one will understand how the features of the system and methods provide several advantages over traditional systems and methods. 
     In one aspect, a continuously variable transmission is disclosed having a longitudinal axis, and a plurality of speed adjusters. Each speed adjuster has a tiltable axis of rotation is located radially outward from the longitudinal axis. Also provided are a drive disk that is annularly rotatable about the longitudinal axis and also contacts a first point on each of the speed adjusters and a support member that is also annularly rotatable about the longitudinal axis. A bearing disk is provided that is annularly rotatable about the longitudinal axis as well, and at least two axial force generators. The axial force generators are located between the drive disk and the bearing disk and each axial force generator is configured to apply an axial force to the drive disk. 
     In another aspect, a bearing disk annularly rotatable about the longitudinal axis is disclosed along with a disengagement mechanism. The disengagement mechanism can be positioned between the bearing disk and the drive disk and is adapted to cause the drive disk to disengage the drive disk from the speed adjusters. 
     In yet another aspect, an output disk or rotatable hub shell is disclosed along with a bearing disk that is annularly rotatable about the longitudinal axis of the transmission. A support member is included that is annularly rotatable about the longitudinal axis as well, and is adapted to move toward whichever of the drive disk or the output disk is rotating more slowly. 
     In still another aspect, a linkage subassembly having a hook is disclosed, wherein the hook is attached to either the drive disk or the bearing disk. Included is a latch attached to either the drive disk or and the bearing disk. 
     In another aspect, a plurality of spindles having two ends is disclosed, wherein one spindle is positioned in the bore of each speed adjuster and a plurality of spindle supports having a platform end and spindle end is provided. Each spindle support is operably engaged with one of the two ends of one of the spindles. Also provided is a plurality of spindle support wheels, wherein at least one spindle support wheel is provided for each spindle support. Included are annular first and second stationary supports each having a first side facing the speed adjusters and a second side facing away from the speed adjusters. Each of the first and second stationary supports have a concave surface on the first side and the first stationary support is located adjacent to the drive disk and the second stationary support is located adjacent to the driven disk. 
     Also disclosed is a continuously variable transmission having a coiled spring that is positioned between the bearing disk and the drive disk. 
     In another aspect, a transmission shifting mechanism is disclosed comprising a rod, a worm screw having a set of external threads, a shifting tube having a set of internal threads, wherein a rotation of the shifting tube causes a change in the transmission ratio, a sleeve having a set of internal threads, and a split shaft having a threaded end. 
     In yet another aspect, a remote transmission shifter is disclosed comprising a rotatable handlegrip, a tether having a first end and a second end, wherein the first end is engaged with the handlegrip and the second end is engaged with the shifting tube. The handlegrip is adapted to apply tension to the tether, and the tether is adapted to actuate the shifting tube upon application of tension. 
     These and other improvements will become apparent to those skilled in the art as they read the following detailed description and view the enclosed figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cutaway side view of an embodiment of the transmission. 
         FIG. 2  is a partial end cross-sectional view taken on line II—II of  FIG. 1 . 
         FIG. 3  is a perspective view of a split shaft and two stationary supports of the transmission of  FIG. 1 . 
         FIG. 4  is a schematic cutaway side view of the transmission of  FIG. 1  shifted into low. 
         FIG. 5  is a schematic cutaway side view of the transmission of  FIG. 1  shifted into high. 
         FIG. 6  is a schematic side view of a ramp bearing positioned between two curved ramps of the transmission of  FIG. 1 . 
         FIG. 7  is a schematic side view of a ramp bearing positioned between two curved ramps of the transmission of  FIG. 1 . 
         FIG. 8  is a schematic side view of a ramp bearing positioned between two curved ramps of the transmission of  FIG. 1 . 
         FIG. 9  is a perspective view of the power adjuster sub-assembly of the transmission of  FIG. 1 . 
         FIG. 10  is a cutaway perspective view of the shifting sub-assembly of the transmission of  FIG. 1 . 
         FIG. 11  is a perspective view of a stationary support of the transmission of  FIG. 1 . 
         FIG. 12  is a perspective view of the screw and nut of the transmission of  FIG. 1 . 
         FIG. 13  is a schematic perspective view of the frame support of the transmission of  FIG. 1 . 
         FIG. 14  is a partial cutaway perspective view of the central ramps of the transmission of  FIG. 1 . 
         FIG. 15  is a perspective view of the perimeter ramps of the transmission of  FIG. 1 . 
         FIG. 16  is a perspective view of the linkage sub-assembly of the transmission of  FIG. 1 . 
         FIG. 17  is a perspective view of the disengagement mechanism sub-assembly of the transmission of  FIG. 1 . 
         FIG. 18  is a perspective view of the handlegrip shifter of the transmission of  FIG. 1 . 
         FIG. 19  is a cutaway side view of an alternative embodiment of the transmission of  FIG. 1 . 
         FIG. 20  is a cutaway side view of yet another alternative embodiment of the transmission of  FIG. 1 . 
         FIG. 21  is a perspective view of the transmission of  FIG. 20  depicting a torsional brace. 
         FIG. 22  is a perspective view of an alternative disengagement mechanism of the transmission of  FIG. 1 . 
         FIG. 23  is another perspective view of the alternative disengagement mechanism of  FIG. 22 . 
         FIG. 24  is a view of a sub-assembly of an alternative embodiment of the axial force generators of the transmission of  FIG. 20 . 
         FIG. 25  is a schematic cross sectional view of the splines and grooves of the axial force generators of  FIG. 24 . 
         FIG. 26  is a perspective view of an alternative disengagement mechanism of the transmission of  FIG. 1 . 
         FIG. 27  is a perspective view of the alternative disengagement mechanism of  FIG. 26 . 
         FIG. 28  is a schematic illustration of a transmission as embodied in a turbine application. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Embodiments of the invention will now be described with reference to the accompanying figures, wherein like numerals refer to like elements throughout. The terminology used in the description presented herein is not intended to be interpreted in any limited or restrictive manner simply because it is being utilized in conjunction with a detailed description of certain specific embodiments of the invention. Furthermore, embodiments of the invention may include several novel features, no single one of which is solely responsible for its desirable attributes or which is essential to practicing the inventions herein described. 
     The transmissions described herein are of the type that utilize speed adjuster balls with axes that tilt as described in U.S. patent application Ser. No. 09/695,757, filed on Oct. 24, 2000 and the information disclosed in that application is hereby incorporated by reference for all that it discloses. A drive (input) disk and a driven (output) disk are in contact with the speed adjuster balls. As the balls tilt on their axes, the point of rolling contact on one disk moves toward the pole or axis of the ball, where it contacts the ball at a circle of decreasing diameter, and the point of rolling contact on the other disk moves toward the equator of the ball, thus contacting the disk at a circle of increasing diameter. If the axis of the ball is tilted in the opposite direction, the disks respectively experience the converse situation. In this manner, the ratio of rotational speed of the drive disk to that of the driven disk, or the transmission ratio, can be changed over a wide range by simply tilting the axes of the speed adjuster balls. 
     With reference to the longitudinal axis of embodiments of the transmission, the drive disk and the driven disk can be located radially outward from the speed adjuster balls, with an idler-type generally cylindrical support member located radially inward from the speed adjuster balls, so that each ball makes three-point contact with the inner support member and the outer disks. The drive disk, the driven disk, and the support member can all rotate about the same longitudinal axis. The drive disk and the driven disk can be shaped as simple disks or can be concave, convex, cylindrical or any other shape, depending on the configuration of the input and output desired. The rolling contact surfaces of the disks where they engage the speed adjuster balls can have a flat, concave, convex or other profile, depending on the torque and efficiency requirements of the application. 
     Referring to  FIGS. 1 and 2 , an embodiment of a continuously variable transmission  100  is disclosed. The transmission  100  is shrouded in a hub shell  40 , which functions as an output disk and is desirable in various applications, including those in which a vehicle (such as a bicycle or motorcycle) has the transmission contained within a driven wheel. The hub shell  40  can, in certain embodiments, be covered by a hub cap  67 . At the heart of the transmission  100  are a plurality of speed adjusters  1  that can be spherical in shape and are circumferentially spaced more or less equally or symmetrically around the centerline, or axis of rotation, of the transmission  100 . In the illustrated embodiment, eight speed adjusters  1  are used. However, it should be noted that more or fewer speed adjusters  1  can be used depending on the use of the transmission  100 . For example, the transmission may include 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or more speed adjusters. The provision for more than 3, 4, or 5 speed adjusters can provide certain advantages including, for example, widely distributing the forces exerted on the individual speed adjusters  1  and their points of contact with other components of the transmission  100 . Certain embodiments in applications with low torque but a high transmission ratio can use few speed adjusters  1  but large speed adjusters  1 , while certain embodiments in applications where high torque and a transmission high transmission ratio can use many speed adjusters  1  and large speed adjusters  1 . Other embodiments in applications with high torque and a low transmission ratio can use many speed adjusters  1  and small speed adjusters  1 . Finally, certain embodiments in applications with low torque and a low transmission ratio may use few speed adjusters  1  and small speed adjusters  1 . 
     Spindles  3  are inserted through holes that run through the center of each of the speed adjusters  1  to define an axis of rotation for each of the speed adjusters  1 . The spindles  3  are generally elongated shafts about which the speed adjusters  1  rotate, and have two ends that extend out of either end of the hole through the speed adjusters  1 . Certain embodiments will have cylindrical shaped spindles  3 , though any shape can be used. The speed adjusters  1  are mounted to freely rotate about the spindles  3 . In  FIG. 1 , the axes of rotation of the speed adjusters  1  are shown in an approximately horizontal direction (i.e., parallel to the main axis of the transmission  100 ). 
       FIGS. 1 ,  4  and  5 , can be utilized to describe how the axes of the speed adjusters  1  can be tilted in operation to shift the transmission  100 .  FIG. 4  depicts the transmission  100  shifted into a low transmission ratio, or low, while  FIG. 5  depicts the transmission  100  shifted into a high transmission ratio, or high. Now also referring to  FIGS. 9 and 10 , a plurality of spindle supports  2  are attached to the spindles  3  near each of the ends of the spindles  3  that extend out of the holes bored through the speed adjusters  1 , and extend radially inward from those points of attachment toward the axis of the transmission  100 . In one embodiment, each of the spindle supports  2  has a through bore that receives one end of one of the spindles  3 . The spindles  3  preferably extend through and beyond the spindle supports  2  such that they have an exposed end. In the embodiments illustrated, the spindles  3  advantageously have spindle rollers  4  coaxially and slidingly positioned over the exposed ends of the spindles  3 . The spindle rollers  4  are generally cylindrical wheels fixed axially on the spindles  3  outside of and beyond the spindle supports  2  and rotate freely about the spindles  3 . Referring also to  FIG. 11 , the spindle rollers  4  and the ends of the spindles  3  fit inside grooves  6  that are cut into a pair of stationary supports  5   a ,  5   b.    
     Referring to  FIGS. 4 ,  5  and  11 , the stationary supports  5   a ,  5   b  are generally in the form of parallel disks annularly located about the axis of the transmission on either side of the power adjusters  1 . As the rotational axes of the speed adjusters  1  are changed by moving the spindle supports  2  radially out from the axis of the transmission  100  to tilt the spindles  3 , each spindle roller  4  fits into and follows a groove  6  cut into one of the stationary supports  5   a ,  5   b . Any radial force, not rotational but a transaxial force, the speed adjusters  1  may apply to the spindles  3  is absorbed by the spindles  3 , the spindle rollers  4  and the sides  81  of the grooves  6  in the stationary supports  5   a ,  5   b . The stationary supports  5   a ,  5   b  are mounted on a pair of split shafts  98 ,  99  positioned along the axis of the transmission  100 . The split shafts  98 ,  99  are generally elongated cylinders that define a substantial portion of the axial length of the transmission  100  and can be used to connect the transmission  100  to the object that uses it. Each of the split shafts  98 ,  99  has an inside end near the middle of the transmission  100  and an outside end that extends out of the internal housing of the transmission  100 . The split shafts  98 ,  99  are preferably hollow so as to house other optional components that may be implemented. The stationary supports  5   a ,  5   b , each have a bore  82 , through which the split shafts  98 ,  99  are inserted and rigidly attached to prevent any relative motion between the split shafts  98 ,  99  and the stationary supports  5   a ,  5   b . The stationary supports  5   a ,  5   b  are preferably rigidly attached to the ends of the split shafts  98 ,  99  closest to the center of the transmission  100 . A stationary support nut  90  may be threaded over the split shaft  99  and tightened against the stationary support  5   b  on corresponding threads of the stationary support  5   a ,  5   b . The grooves  6  in the stationary supports  5   a ,  5   b  referred to above, extend from the outer circumference of the stationary supports  5   a ,  5   b  radially inwardly towards the split shafts  98 ,  99 . In most embodiments, the groove sides  81  of the grooves  6  are substantially parallel to allow the spindle rollers  4  to roll up and down the groove sides  81  as the transmission  100  is shifted. Also, in certain embodiments, the depth of the grooves  6  is substantially constant at the circumference  9  of the stationary supports  5   a ,  5   b , but the depth of the grooves  6  becomes shallower at points  7  closer to the split shaft  98 ,  99 , to correspond to the arc described by the ends of the spindles  3  as they are tilted, and to increase the strength of the stationary supports  5   a ,  5   b . As the transmission  100  is shifted to a lower or higher transmission ratio by changing the rotational axes of the speed adjusters  1 , each one of the pairs of spindle rollers  4 , located on the opposite ends of a single spindle  3 , move in opposite directions along their corresponding grooves  6 . 
     Referring to  FIGS. 9 and 11 , stationary support wheels  30  can be attached to the spindle supports  2  with stationary support wheel pins  31  or by any other attachment method. The stationary support wheels  30  are coaxially and slidingly mounted over the stationary support wheel pins  31  and secured with standard fasteners, such as ring clips for example. In certain embodiments, one stationary support wheel  30  is positioned on each side of a spindle  2  with enough clearance to allow the stationary support wheels  30  to roll radially on concave surfaces  84  of the stationary supports  5   a ,  5   b  when the transmission  100  is shifted. In certain embodiments, the concave surfaces  84  are concentric with the center of the speed adjusters  1 . 
     Referring to  FIGS. 2 ,  3 , and  11 , a plurality of elongated spacers  8  are distributed radially about, and extend generally coaxially with, the axis of the transmission. The elongated spacers  8  connect the stationary supports  5   a  to one another to increase the strength and rigidity of the internal structure of the transmission  100 . The spacers  8  are oriented generally parallel to one another, and in some embodiments, each one extends from a point at one stationary support  5   a  near the outer circumference to a corresponding point on the other stationary support  5   b . The spacers  8  can also precisely fix the distance between the stationary supports  5   a ,  5   b , align the grooves  6  of the stationary supports  5   a ,  5   b , ensure that the stationary supports  5   a ,  5   b  are parallel, and form a connection between the split shafts  98 ,  99 . In one embodiment, the spacers  8  are pressed through spacer holes  46  in the stationary supports  5   a ,  5   b . Although eight spacers  8  are illustrated, more or less spacers  8  can be used. In certain embodiments, the spacers  8  are located between two speed adjusters  1 . 
     Referring to  FIGS. 1 ,  3 , and  13 , the stationary support  5   a , in certain embodiments, is rigidly attached to a stationary support sleeve  42  located coaxially around the split shaft  98 , or alternately, is otherwise rigidly attached to or made an integral part of the split shaft  98 . The stationary sleeve  42  extends through the wall of the hub shell  40  and attaches to a frame support  15 . In some embodiments, the frame support  15  fits coaxially over the stationary sleeve  42  and is rigidly attached to the stationary sleeve  42 . The frame support  15  uses a torque lever  43 , in some embodiments, to maintain the stationary position of the stationary sleeve  42 . The torque lever  43  provides rotational stability to the transmission  100  by physically connecting the stationary sleeve  42 , via the frame support  15 , and therefore the rest of the stationary parts to a fixed support member of the item to which the transmission  100  is to be mounted. A torque nut  44  threads onto the outside of the stationary sleeve  42  to hold the torque lever  43  in a position that engages the frame support  15 . In certain embodiments, the frame support  15  is not cylindrical so as to engage the torque lever  43  in a positive manner thereby preventing rotation of the stationary sleeve  42 . 
     For example, the frame support  15  could be a square of thickness equal to the torque lever  43  with sides larger than the stationary sleeve and with a hole cut out of its center so that the square may fit over the stationary sleeve  42 , to which it may then be rigidly attached. Additionally, the torque lever  43  could be a lever arm of thickness equal to that of the frame support  15  with a first end near the frame support  15  and a second end opposite the first. The torque lever  43 , in some embodiments, also has a bore through one of its ends, but this bore is a square and is a slightly larger square than the frame support  15  so the torque lever  43  could slide over the frame support  15  resulting in a rotational engagement of the frame support  15  and the torque lever  43 . Furthermore, the lever arm of the torque lever  43  is oriented so that the second end extends to attach to the frame of the bike, automobile, tractor or other application that the transmission  100  is used upon, thereby countering any torque applied by the transmission  100  through the frame support  15  and the stationary sleeve  42 . A stationary support bearing  48  fits coaxially around the stationary sleeve  42  and axially between the outside edge of the hub shell  40  and the torque lever  43 . The stationary support bearing  48  supports the hub shell  40 , permitting the hub shell  40  to rotate relative to the stationary support sleeve  42 . 
     Referring to  FIGS. 1 and 10 , in some embodiments, shifting is manually activated by rotating a rod  10 , positioned in the hollow split shaft  98 . A worm screw  11 , a set of male threads in some embodiments, is attached to the end of the rod  10  that is in the center of the transmission  100 , while the other end of the rod  10  extends axially to the outside of the transmission  100  and has male threads affixed to its outer surface. In one embodiment, the worm screw  11  is threaded into a coaxial sleeve  19  with mating threads, so that upon rotation of the rod  10  and worm screw  11 , the sleeve  19  moves axially. The sleeve  19  is generally in the shape of a hollow cylinder that fits coaxially around the worm screw  11  and rod  10  and has two ends, one near stationary support  5   a  and one near stationary support  5   b . The sleeve  19  is affixed at each end to a platform  13 ,  14 . The two platforms  13 ,  14  are each generally of the form of an annular ring with an inside diameter, which is large enough to fit over and attach to the sleeve  19 , and is shaped so as to have two sides. The first side is a generally straight surface that dynamically contacts and axially supports the support member  18  via two sets of contact bearings  17   a ,  17   b . The second side of each platform  13 ,  14  is in the form of a convex surface. The platforms  13 ,  14  are each attached to one end of the outside of the sleeve  19  so as to form an annular trough around the circumference of the sleeve  19 . One platform  13  is attached to the side nearest stationary support  5   a  and the other platform  14  is attached to the end nearest stationary support  5   b . The convex surface of the platforms  13 ,  14  act as cams, each contacting and pushing multiple shifting wheels  21 . To perform this camming function, the platforms  13 ,  14  preferably transition into convex curved surfaces  97  near their perimeters (farthest from the split shafts  98 ,  99 ), that may or may not be radii. This curve  97  contacts with the shifting wheels  21  so that as the platforms  13 ,  14  move axially, a shifting wheel  21  rides along the platform  13 ,  14  surface in a generally radial direction forcing the spindle support  2  radially out from, or in toward, the split shaft  98 ,  99 , thereby changing the angle of the spindle  3  and the rotation axis of the associated speed adjuster  1 . In certain embodiments, the shifting wheels  21  fit into slots in the spindle supports  2  at the end nearest the centerline of the transmission  100  and are held in place by wheel axles  22 . 
     Still referring to  FIGS. 1 and 10 , a support member  18  is located in the trough formed between the platforms  13 ,  14  and sleeve  19 , and thus moves in unison with the platforms  13 ,  14  and sleeve  19 . In certain embodiments, the support member  18  is generally of one outside diameter and is generally cylindrical along the center of its inside diameter with a bearing race on each edge of its inside diameter. In other embodiments, the outer diameter of the support member  18  can be non-uniform and can be any shape, such as ramped or curved. The support member  18  has two sides, one near one of the stationary supports  5   a  and one near the other stationary support  5   b . The support member  18  rides on two contact bearings  17   a ,  17   b  to provide rolling contact between the support member  18  and the sleeve  19 . The contact bearings  17   a ,  17   b  are located coaxially around the sleeve  19  where the sleeve  19  intersects the platforms  13 ,  14  allowing the support member  18  to freely rotate about the axis of the transmission  100 . The sleeve  19  is supported axially by the worm screw  11  and the rod  10  and therefore, through this configuration, the sleeve  19  is able to slide axially as the worm screw  11  positions it. When the transmission  100  is shifted, the sleeve  19  moves axially, and the bearings  17   a ,  17   b , support member  18 , and platforms  13 ,  14 , which are all attached either dynamically or statically to the sleeve, move axially in a corresponding manner. 
     In certain embodiments, the rod  10  is attached at its end opposite the worm screw  11  to a shifting tube  50  by a rod nut  51 , and a rod flange  52 . The shifting tube  50  is generally in the shape of a tube with one end open and one end substantially closed. The open end of shifting tube  50  is of a diameter appropriate to fit over the end of the split shaft  98  that extends axially out of the center of the transmission  100 . The substantially closed end of the shifting tube  50  has a small bore through it so that the end of the rod  10  that is opposite of the worm screw  11  can pass through it as the shifting tube  50  is placed over the outside of the split shaft  98 . The substantially closed end of the shifting tube  50  can then be fixed in axial place by the rod nut  51 , which is fastened outside of the shifting tube  50 , and the rod flange  52 , which in turn is fastened inside of the shifting tube&#39;s  50  substantially closed end, respectively. The shifting tube  50  can, in some embodiments, be rotated by a cable  53  attached to the outside of the shifting tube  50 . The cable  53 , in these embodiments, is attached to the shifting tube  50  with a cable clamp  54  and cable screw  56 , and then wrapped around the shifting tube  50  so that when tension is applied to the cable  53  a moment is developed about the center of the axis of the shifting tube  50  causing it to rotate. The rotation of shifting tube  50  may alternately be caused by any other mechanism such as a rod, by hand rotation, a servo-motor or other method contemplated to rotate the rod  10 . In certain embodiments, when the cable  53  is pulled so that the shifting tube  50  rotates clockwise on the split shaft  98 , the worm screw  11  rotates clockwise, pulling the sleeve  19 , support member  18  and platforms  13 ,  14 , axially toward the shifting tube  50  and shifting the transmission  100  towards a low transmission ratio. A worm spring  55 , as illustrated in  FIG. 3 , that can be a conical coiled spring capable of producing compressive and torsional force, attached at the end of the worm screw  11 , is positioned between the stationary support  5   b  and the platform  14  and resists the shifting of the transmission  100 . The worm spring  55  is designed to bias the shifting tube  50  to rotate so as to shift the transmission  100  towards a low transmission ratio in some embodiments and towards a high transmission ratio in other embodiments. 
     Referring to  FIGS. 1 ,  10 , and  11 , axial movement of the platforms  13 ,  14 , define the shifting range of the transmission  100 . Axial movement is limited by inside faces  85  on the stationary supports  5   a ,  5   b , which the platforms  13 ,  14  contact. At an extreme high transmission ratio, platform  14  contacts the inside face  85  on one of the stationary supports  5   a ,  5   b , and at an extreme low transmission ratio, the platform  13  contacts the inside face  85  on the other one of the stationary supports  5   a ,  5   b . In many embodiments, the curvature of the convex radii of the platforms  13 ,  14 , are functionally dependant on the distance from the center of a speed adjuster  1  to the center of the wheel  21 , the radius of the wheel  21 , the distance between the two wheels  21  that are operably attached to each speed adjuster  1 , and the angle of tilt of the speed adjuster  1  axis. 
     Although a left hand threaded worm screw  11  is disclosed, a right hand threaded worm screw  11 , the corresponding right hand wrapped shifting tube  50 , and any other combination of components just described that is can be used to support lateral movement of the support member  18  and platforms  13 ,  14 , can be used. Additionally, the shifting tube  50  can have internal threads that engage with external threads on the outside of the split shaft  98 . By adding this threaded engagement, the shifting tube  50  will move axially as it rotates about the split shaft  98  causing the rod  10  to move axially as well. This can be employed to enhance the axial movement of the sleeve  19  by the worm screw  11  so as to magnify the effects of rotating the worm screw  11  to more rapidly shift the gear ratio or alternatively, to diminish the effects of rotating the worm screw  11  so as to slow the shifting process and produce more accurate adjustments of the transmission  100 . 
     Referring to  FIGS. 10 and 18 , manual shifting may be accomplished by use of a rotating handlegrip  132 , which can be coaxially positioned over a stationary tube, a handlebar  130 , or some other structural member. In certain embodiments, an end of the cable  53  is attached to a cable stop  133 , which is affixed to the rotating handlegrip  132 . In some embodiments, internal forces of the transmission  100  and the conical spring  55  tend to bias the shifting of the transmission towards a lower transmission ratio. As the rotating handlegrip  132  is rotated by the user, the cable  53 , which can be wrapped along a groove around the rotating handlegrip  132 , winds or unwinds depending upon the direction of rotation of the cable  53 , simultaneously rotating the shifting tube  50  and shifting the transmission  100  towards a higher transmission ratio. A set of ratchet teeth  134  can be circumferentially positioned on one of the two sides of the rotating handlegrip  132  to engage a mating set of ratchet teeth on a first side of a ratcheted tube  135 , thereby preventing the rotating handlegrip  132  from rotating in the opposite direction. A tube clamp  136 , which can bean adjustable screw allowing for variable clamping force, secures the ratcheted tube  135  to the handlebar  130 . When shifting in the opposite direction, the rotating handlegrip  132 , is forcibly rotated in the opposite direction toward a lower transmission ratio, causing the tube clamp  136  to rotate in unison with the rotating handlegrip  132 . A handlebar tube  137 , positioned proximate to the ratcheted tube  135 , on a side opposite the ratchet teeth  134 , is rigidly clamped to the handlebar  130  with a tube clamp  138 , thereby preventing disengagement of the ratcheted tube  135  from the ratchet teeth  134 . A non-rotating handlegrip  131  is secured to the handlebar  130  and positioned proximate to the rotating handlegrip  132 , preventing axial movement of the rotating handlegrip  132  and preventing the ratchet teeth  134  from becoming disengaged from the ratcheted tube  135 . 
     Now referring to embodiments illustrated by  FIGS. 1 ,  9 , and  11 , a one or more stationary support rollers  30  can be attached to each spindle support  2  with a roller pin  31  that is inserted through a hole in each spindle support  2 . The roller pins  31  are of the proper size and design to allow the stationary support rollers  30  to rotate freely over each roller pin  31 . The stationary support rollers  30  roll along concave curved surfaces  84  on the sides of the stationary supports  5   a ,  5   b  that face the speed adjusters  1 . The stationary support rollers  30  provide axial support to prevent the spindle supports  2  from moving axially and also to ensure that the spindles  2  tilt easily when the transmission  100  is shifted. 
     Referring to  FIGS. 1 ,  12 ,  14 , and  17 , a three spoked drive disk  34 , located adjacent to the stationary support  5   b , partially encapsulates but generally does not contact the stationary support  5   b . The drive disk  34  may have two or more spokes or may be a solid disk. The spokes reduce weight and aid in assembly of the transmission  100  ine embodiments using them, however a solid disk can be used. The drive disk  34  has two sides, a first side that contacts with the speed adjusters  1 , and a second side that faces opposite of the first side. The drive disk  34  is generally an annular disk that fits coaxially over, and extends radially from, a set of female threads or nut  37  at its inner diameter. The outside diameter of the drive disk  34  is designed to fit within the hub shell  40 , if the hub shell  40  employed is the type that encapsulates the speed adjusters  1  and the drive disk  34 , and engages with the hub cap  67 . The drive disk  34  is rotatably coupled to the speed adjusters  1  along a circumferential bearing surface on the lip of the first side of the drive disk  34 . As mentioned above, some embodiments of the drive disk  34  have a set of female threads  37 , or a nut  37 , at its center, and the nut  37  is threaded over a screw  35 , thereby engaging the drive disk  34  with the screw  35 . The screw  35  is rigidly attached to a set of central screw ramps  90  that are generally a set of raised surfaces on an annular disk that is positioned coaxially over the split shaft  99 . The central screw ramps  90  are driven by a set of central drive shaft ramps  91 , which are similarly formed on a generally annular disk. The ramp surfaces of the central drive ramps  91  and the central screw ramps  90  can be linear, but can be any other shape, and are in operable contact with each other. The central drive shaft ramps  91 , coaxially and rigidly attached to the drive shaft  69 , impart torque and an axial force to the central screw ramps  90  that can then be transferred to the drive disk  34 . A central drive tension member  92 , positioned between the central drive shaft ramps  91  and the central screw ramps  90 , produces torsional and/or compressive force, ensuring that the central ramps  90 ,  91  are in contact with one another. 
     Still referring to  FIGS. 1 ,  12 ,  14 , and  17 , the screw  35 , which is capable of axial movement, can be biased to move axially away from the speed adjusters  1  with an annular thrust bearing  73  that contacts a race on the side of the screw  35  that faces the speed adjusters  1 . An annular thrust washer  72 , coaxially positioned over the split shaft  99 , contacts the thrust bearing  73  and can be pushed by a pin  12  that extends through a slot in the split shaft  99 . A compression member  95  capable of producing a compressive force is positioned in the bore of the hollow split shaft  99  at a first end. The compression member  95 , which may be a spring, contacts the pin  12  on one end, and at a second end contacts the rod  10 . As the rod  10  is shifted towards a higher transmission ratio and moves axially, it contacts the compression member  95 , pushing it against the pin  12 . Internal forces in the transmission  100  will bias the support member  18  to move towards a high transmission ratio position once the transmission ratio goes beyond a 1:1 transmission ratio towards high and the drive disk  34  rotates more slowly than the hub shell  40 . This bias pushes the screw  35  axially so that it either disconnects from the nut  37  and no longer applies an axial force or a torque to the drive disk  34 , or reduces the force that the screw  35  applies to the nut  37 . In this situation, the percentage of axial force applied to the drive disk  34  by the perimeter ramps  61  increases. It should be noted that the internal forces of the transmission  100  will also bias the support member  18  towards low once the support member  18  passes beyond a position for a 1:1 transmission ratio towards low and the hub shell  40  rotates more slowly than the drive disk  34 . This beneficial bias assists shifting as rpm&#39;s drop and torque increases when shifting into low. 
     Still referring to  FIGS. 1 ,  12 ,  14 , and  17 , the drive shaft  69 , which is a generally tubular sleeve having two ends and positioned coaxial to the outside of the split shaft  99 , has at one end the aforementioned central drive shaft ramps  91  attached to it, while the opposite end faces away from the drive disk  34 . In certain embodiments, a bearing disk  60  is attached to and driven by the drive shaft  69 . The bearing disk  60  can be splined to the drive shaft  69 , providing for limited axial movement of the bearing disk  60 , or the bearing disk  60  can be rigidly attached to the drive shaft  69 . The bearing disk  60  is generally a radial disk coaxially mounted over the drive shaft  69  extending radially outward to a radius generally equal to that of the drive disk  34 . The bearing disk  60  is mounted on the drive shaft  69  in a position near the drive disk  34 , but far enough away to allow space for a set of perimeter ramps  61 , associated ramp bearings  62 , and a bearing race  64 , all of which are located between the drive disk  34  and the bearing disk  67 . In certain embodiments, the plurality of perimeter ramps  61  can be concave and are rigidly attached to the bearing disk  60  on the side facing the drive disk  34 . Alternatively, the perimeter ramps  61  can be convex or linear, depending on the use of the transmission  100 . Alternatively, the bearing race  64 , can be replaced by a second set of perimeter ramps  97 , which may also be linear, convex, or concave, and which are rigidly attached to the drive disk  34  on the side facing the bearing disk  60 . The ramp bearings  62  are generally a plurality of bearings matching in number the perimeter ramps  61 . Each one of the plurality of ramp bearings  62  is located between one perimeter ramp  61  and the bearing race  64 , and is held in its place by a compressive force exerted by the ramps  61  and also by a bearing cage  63 . The bearing cage  63  is an annular ring coaxial to the split shaft  99  and located axially between the concave ramps  61  and convex ramps  64 . The bearing cage  63  has a relatively large inner diameter so that the radial thickness of the bearing cage  63  is only slightly larger than the diameter of the ramp bearings  62  to house the ramp bearings  62 . Each of the ramp bearings  62  fits into a hole that is formed in the radial thickness of the bearing cage  63  and these holes, together with the previously mentioned compressive force, hold the ramp bearings  62  in place. The bearing cage  63 , can be guided into position by a flange on the drive disk  34  or the bearing disk  60 , which is slightly smaller than the inside diameter of the bearing cage  63 . 
     Referring to  FIGS. 1 ,  6 ,  7 ,  8 , and  15 , the bearing disk  60 , the perimeter ramps  61 , and a ramp bearing  62  of one embodiment are depicted. Referring specifically to  FIG. 6 , a schematic view shows a ramp bearing  62  contacting a concave perimeter ramp  61 , and a second convex perimeter ramp  97 . Referring specifically to  FIG. 7 , a schematic view shows the ramp bearing  62 , the concave perimeter ramp  61 , and the second convex perimeter ramp  97  of  FIG. 6  at a different torque or transmission ratio. The position of the ramp bearings  62  on the perimeter ramps  61  depicted in  FIG. 7  produces less axial force than the position of the ramp bearings  62  on the perimeter ramps  61  depicted in  FIG. 6 . Referring specifically to  FIG. 8 , a ramp bearing  62  is shown contacting a convex perimeter ramp  61 , and a concave second perimeter ramp  97  in substantially central positions on those respective ramps. It should be noted that changes in the curves of the perimeter ramps  61 ,  97  change the magnitude of the axial force applied to the power adjusters  1  at various transmission ratios, thereby maximizing efficiency in different gear ratios and changes in torque. Depending on the use for the transmission  100 , many combinations of curved or linear perimeter ramps  61 ,  97  can be used. To simplify operation and reduce cost, in some applications one set of perimeter ramps may be eliminated, such as the second set of perimeter tramps  97 , which are then replaced by a bearing race  64 . To further reduce cost, the set of perimeter ramps  61  may have a linear inclination. 
     Referring to  FIG. 1 , a coiled spring  65  having two ends wraps coaxially around the drive shaft  69  and is attached at one end to the bearing disk  60  and at its other end to the drive disk  34 . The coiled spring  65  provides force to keep the drive disk  34  in contact with the speed adjusters  1  and biases the ramp bearings  62  up the perimeter ramps  61 . The coiled spring  65  is designed to minimize the axial space within which it needs to operate and, in certain embodiments, the cross section of the coiled spring  65  is a rectangle with the radial length greater than the axial length. 
     Referring to  FIG. 1 , the bearing disk  60  preferably contacts an outer hub cap bearing  66  on the bearing disk  60  side that faces opposite the concave ramps  61 . The outer hub cap bearing  66  can be an annular set of roller bearings located radially outside of, but coaxial with, the centerline of the transmission  100 . The outer hub cap bearing  66  is located radially at a position where it may contact both the hub cap  67  and the bearing disk  60  to allow their relative motion with respect to one another. The hub cap  67  is generally in the shape of a disk with a hole in the center to fit over the drive shaft  69  and with an outer diameter such that it will fit within the hub shell  40 . The inner diameter of the hub cap engages with an inner hub cap bearing  96  that is positioned between the hub cap  67  and the drive shaft  69  and maintains the radial and axial alignment of the hub cap  67  and the drive shaft  69  with respect to one another. The edge of the hub cap  67  at its outer diameter can be threaded so that the hub cap  67  can be threaded into the hub shell  40  to encapsulate much of the transmission  100 . A sprocket or pulley  38  or other drive train adapter, such as gearing for example, can be rigidly attached to the rotating drive shaft  69  to provide the input rotation. The drive shaft  69  is maintained in its coaxial position about the split shaft  99  by a cone bearing  70 . The cone bearing  70  is an annular bearing mounted coaxially around the split shaft  99  and allows rolling contact between the drive shaft  69  and the split shaft  99 . The cone bearing  70  may be secured in its axial place by a cone nut  71  which threads onto the split shaft  99  or by any other fastening method. 
     In operation of certain embodiments, an input rotation from the sprocket or pulley  38  is transmitted to the drive shaft  69 , which in turn rotates the bearing disk  60  and the plurality of perimeter ramps  61  causing the ramp bearings  62  to roll up the perimeter ramps  61  and press the drive disk  34  against the speed adjusters  1 . The ramp bearings  62  also transmit rotational energy to the drive disk  34  as they are wedged in between, and therefore transmit rotational energy between, the perimeter ramps  61  and the convex ramps  64 . The rotational energy is transferred from the drive disk  34  to the speed adjusters  1 , which in turn rotate the hub shell  40  providing the transmission  100  output rotation and torque. 
     Referring to  FIG. 16 , a latch  115  rigidly attaches to the side of the drive disk  34  that faces the bearing disk  60  and engages a hook  114  that is rigidly attached to a first of two ends of a hook lever  113 . The engaging area under the latch  115  opening is larger than the width of the hook  114  and provides extra room for the hook  114  to move radially, with respect to the axis, within the confines of the latch  114  when the drive disk  34  and the bearing disk  60  move relative to each other. The hook lever  113  is generally a longitudinal support member for the hook  114  and at its second end, the hook lever  113  has an integral hook hinge  116  that engages with a middle hinge  119  via a first hinge pin  111 . The middle hinge  119  is integral with a first end of a drive disk lever  112 , a generally elongated support member having two ends. On its second end, the drive disk lever  112  has an integral drive disk hinge  117 , which engages a hinge brace  110  via the use of a second hinge pin  118 . The hinge brace  110  is generally a base to support the hook  114 , the hook lever  113 , the hook hinge  116 , the first hinge pin  111 , the middle hinge  119 , the drive disk lever  112  the second hinge pin  118 , and the drive disk hinge  117 , and it is rigidly attached to the bearing disk  60  on the side facing the drive disk  34 . When the latch  73  and hook  72  are engaged the ramp bearings  62  are prevented from rolling to an area on the perimeter ramps  61  that does not provide the correct amount of axial force to the drive disk  34 . This ensures that all rotational force applied to the ramp bearings  62  by perimeter ramps  61  is transmitted to the drive disk  34 . 
     Referring to  FIGS. 1 and 17 , a disengagement mechanism for one embodiment of the transmission  100  is described to disengage the drive disk  34  from the speed adjusters  1  in order to coast. On occasions that input rotation to the transmission  100  ceases, the sprocket or pulley  38  stops rotating but the hub shell  40  and the speed adjusters  1  can continue to rotate. This causes the drive disk  34  to rotate so that the set of female threads  37  in the bore of the drive disk  34  wind onto the male threaded screw  35 , thereby moving the drive disk  34  axially away from the speed adjusters  1  until the drive disk  34  no longer contacts the speed adjusters  1 . A toothed rack  126 , rigidly attached to the drive disk  34  on the side facing the bearing disk  60 , has teeth that engage and rotate a toothed wheel  124  as the drive disk  34  winds onto the screw  35  and disengages from the power adjusters  1 . The toothed wheel  124 , has a bore in its center, through which a toothed wheel bushing  121  is located, providing for rotation of the toothed wheel  124 . Clips  125  that are coaxially attached over the toothed wheel bushing  121  secure the toothed wheel  124  in position, although any means of fastening may be used. A preloader  120 , coaxially positioned over and clamped to the central drive shaft ramps  91 , extends in a direction that is radially outward from the center of the transmission  100 . The preloader  120 , of a resilient material capable of returning to its original shape when flexed, has a first end  128  and a second end  127 . The first end of the preloader  128  extends through the toothed wheel bushing  121  and terminates in the bearing cage  63 . The first end of the preloader  128  biases the bearing cage  63  and ramp bearings  62  up the ramps  61 , ensuring contact between the ramp bearings  62  and the ramps  61 , and also biases the toothed wheel  124  against the toothed rack  126 . A pawl  123 , engages the toothed wheel  124 , and in one embodiment engages the toothed wheel  124  on a side substantially opposite the toothed rack  126 . The pawl  123  has a bore through which a pawl bushing  122  passes, allowing for rotation of the pawl  123 . Clips  125 , or other fastening means secure the pawl  123  to the pawl bushing  121 . A pawl spring  122  biases rotation of the pawl  123  to engage the toothed wheel  124 , thereby preventing the toothed wheel  124  from reversing its direction of rotation when the drive disk  34  winds onto the screw  35 . The pawl bushing  121  is positioned over a second end of the preloader  127 , which rotates in unison with the drive shaft  69 . 
     Referring again to  FIG. 1 , a coiled spring  65 , coaxial with and located around the drive shaft  69 , is located axially between and attached by pins or other fasteners (not shown) to both the bearing disk  60  at one end and drive disk  34  at the other end. In certain embodiments, the coiled spring  65  replaces the coiled spring of the prior art so as to provide more force and take less axial space in order to decrease the overall size of the transmission  100 . In some embodiments, the coiled spring  65  is produced from spring steel wire with a rectangular profile that has a radial length or height greater than its axial length or width. During operation of the transmission  100 , the coiled spring  65  ensures contact between the speed adjusters  1  and the drive disk  34 . However, once the drive disk  34  has disengaged from the speed adjusters  1 , the coiled spring  65  is prevented from winding the drive disk  34  so that it again contacts the speed adjusters  1  by the engagement of the toothed wheel  124  and the pawl  123 . When the input sprocket, gear, or pulley  38 , resumes its rotation, the pawl  123  also rotates, allowing the toothed wheel  124  to rotate, thus allowing the drive disk  34  to rotate and unwind from the screw  35  due to the torsional force created by the coiled spring  65 . Relative movement between the pawl  123  and the toothed wheel  124  is provided by the fact that the first end of the preloader  128  rotates at approximately half the speed as the second end of the preloader  127  because the first end of the preloader  128  is attached to the bearing cage  63 . Also, because the ramp bearings  62  are rolling on the perimeter ramps  61  of the bearing disk  60 , the bearing cage  63  will rotate at half the speed as the bearing disk  60 . 
     Referring now to  FIG. 19 , an alternative embodiment of the transmission  100  of  FIG. 1  is disclosed. In this embodiment, an output disk  201  replaces the hub shell  40  of the transmission  100  illustrated in  FIG. 1 . Similar to the drive disk  34 , the output disk  201  contacts, and is rotated by, the speed adjusters  1 . The output disk  201  is supported by an output disk bearing  202  that contacts both the output disk  201  and a stationary case cap  204 . The case cap  204  is rigidly attached to a stationary case  203  with case bolts  205  or any other fasteners. The stationary case  203  can be attached to a non-moving object such as a frame or to the machine for which its use is employed. A gear, sprocket, or pulley  206  is attached coaxially over and rigidly to the output disk  201  outside of the case cap  204  and stationary case  203 . Any other type of output means can be used however, such as gears for example. A torsional brace  207  can be added that rigidly connects the split shaft  98  to the case cap  204  for additional support. 
     Referring now to  FIGS. 20 and 21 , an alternative embodiment of the transmission  100  of  FIG. 1  is disclosed. A stationary support race  302  is added on a side of stationary support  5   a  facing away from the speed adjusters  1  and engages with a stationary support bearing  301  and a rotating hub shell race  303  to maintain correct alignment of the stationary support  5   a  with respect to the rotating hub shell  40 . A torsional brace  304  is rigidly attached to the stationary support  5   a  and can then be rigidly attached to a stationary external component to prevent the stationary supports  5   a ,  5   b  from rotating during operation of the transmission  300 . A drive shaft bearing  306  is positioned at an end of the drive shaft  69  facing the speed adjusters  1  and engages a drive shaft race  307  formed in the same end of the drive shaft  69  and a split shaft race  305  formed on a radially raised portion of the split shaft  99  to provide additional support to the drive shaft  69  and to properly position the drive shaft  69  relative to the stationary supports  5   a ,  5   b.    
     Referring now to  FIGS. 22 and 23 , an alternative disengagement mechanism  400  of the transmission  100  of  FIG. 1  is disclosed. A toothed wheel  402  is coaxially positioned over a wheel bushing  408  and secured in position with a clip  413  or other fastener such that it is capable of rotation. The wheel bushing  408  is coaxially positioned over the first end of a preloader  405  having first and second ends (both not separately identified in  FIGS. 22 , and  23 ). The preloader  405  clamps resiliently around the central drive shaft ramps  91 . The first end of the preloader  405  extends into the bearing cage  63 , biasing the bearing cage  63  up the perimeter ramps  61 . Also positioned over the wheel bushing  408  is a lever  401  that rotates around the wheel bushing  408  and that supports a toothed wheel pawl  411  and a pinion pawl  409 . The toothed wheel pawl  411  engages the toothed wheel  402  to control its rotation, and is positioned over a toothed wheel bushing  414  that is pressed into a bore in the lever  401 . A toothed wheel pawl spring  412  biases the toothed wheel pawl  411  against the toothed wheel  402 . The pinion pawl  409 , positioned substantially opposite the toothed wheel pawl  411  on the lever  401 , is coaxially positioned over a pinion pawl bushing  415  that fits into another bore in the lever  401  and provides for rotational movement of the pinion pawl  409 . A pinion pawl spring  410  biases the pinion pawl  409  against a pinion  403 . 
     Referring now to  FIGS. 1 ,  22  and  23 , the pinion  403  has a bore at its center and is coaxially positioned over a first of two ends of a rod lever  404 . The rod lever is an elongated lever that engages the pinion pawl  409  during coasting until input rotation of the sprocket, pulley, or gear  38  resumes. A bearing disk pin  406  that is affixed to the bearing disk  60  contacts a second end of the rod lever  404 , upon rotation of the bearing disk  60 , thereby pushing the rod lever  404  against a drive disk pin  407 , which is rigidly attached to the drive disk  34 . This action forces the first end of the rod lever  404  to swing away from the toothed wheel  402 , temporarily disconnecting the pinion  403  from the toothed wheel  402 , allowing the toothed wheel  402  to rotate. A lever hook  401  is attached to the lever  401  and contacts a latch (not shown) on the drive disk  34  and is thereby pushed back as the coiled spring  65  biases the drive disk  34  to unwind and contact the speed adjusters  1 . During occasions that the input rotation of the sprocket, pulley, or gear  38  ceases, and the speed adjusters  1  continue to rotate, the drive disk  34  winds onto the screw  35  and disengages from the speed adjusters  1 . As the drive disk  34  rotates, the drive disk pin  407  disengages from the rod lever  404 , which then swings the pinion  403  into contact with the toothed wheel  402 , preventing the drive disk  34  from re-engaging the speed adjusters  1 . 
     Referring to  FIGS. 24 and 25 , a sub-assembly of an alternative set of axial force generators  500  of the transmission  300  of  FIG. 20  is disclosed. When rotated by the input sprocket, gear, or pulley  38 , a splined drive shaft  501  rotates the bearing disk  60 , which may have grooves  505  in its bore to accept and engage the splines  506  of the splined drive shaft  501 . The central drive shaft ramps  508  are rigidly attached to the bearing disk  60  or the splined drive shaft  501  and rotate the central screw ramps  507 , both of which have bores that clear the splines  506  of the splined drive shaft  501 . The central tension member  92  (illustrated in  FIG. 1 ) is positioned between the central drive shaft ramps  508  and the central screw ramps  507 . A grooved screw  502  having a grooved end and a bearing end is rotated by the central screw ramps  90  and has grooves  505  on its bearing end that are wider than the splines  506  on the splined drive shaft  501  to provide a gap between the splines  506  and the grooves  505 . This gap between the splines  506  and the grooves  505  allows for relative movement between the grooved screw  502  and/or bearing disk  60  and the splined drive shaft  501 . On occasions when the grooved screw  502  is not rotated by the central drive shaft ramps  508  and the central screw ramps  507 , the splines  506  of the splined drive shaft  501  contact and rotate the grooves  505  on the grooved screw  502 , thus rotating the grooved screw  502 . An annular screw bearing  503  contacts a race on the bearing end of the grooved screw  502  and is positioned to support the grooved screw  502  and the splined drive shaft  501  relative to the axis of the split shaft  99 . The bore of the grooved screw  502  is slightly larger than the outside diameter of the splined drive shaft  501  to allow axial and rotational relative movement of the grooved screw  502 . A screw cone race  504  contacts and engages the annular screw bearing  503  and has a hole perpendicular to its axis to allow insertion of a pin  12 . The pin  12  engages the rod  10 , which can push on the pin  12  and move the grooved screw  502  axially, causing it to disengage from, or reduce the axial force that it applies to, the nut  37 . 
     Referring to  FIG. 26 , an alternative disengagement means  600  of the disengagement means  400  of  FIGS. 22 and 23  is disclosed. The lever  401  is modified to eliminate the T-shape used to mount both the pinion pawl  409  and the toothed wheel pawl  411  so that the new lever  601  has only the toothed wheel pawl  411  attached to it. A second lever  602 , having a first end and a second end. The pinion pawl  409  is operably attached to the first end of the second lever  602 . The second lever  602  has a first bore through which the first end of the preloader  405  is inserted. The second lever  602  is rotatably mounted over the first end of the preloader  405 . The second lever  602  has a second bore in its second end through which the second end of the preloader  603  is inserted. When rotation of the sprocket, gear, or pulley  38  ceases, the drive disk  34  continues to rotate forward and wind onto the screw  36  until it disengages from the speed adjusters  1 . The first end of the preloader  405  rotates forward causing the pinion pawl  409  to contact and rotate the pinion  403  clockwise. This causes the toothed wheel  402  to rotate counter-clockwise so that the toothed wheel pawl  411  passes over one or more teeth of the toothed wheel  402 , securing the drive disk  34  and preventing it from unwinding off of the screw  36  and contacting the speed adjusters  1 . When rotation of the sprocket, gear, or pulley  38  resumes, the second end of the preloader  603  rotates, contacting the second end of the second lever  602  causing the pinion pawl  409  to swing out and disengage from the pinion  403 , thereby allowing the drive disk  34  to unwind and reengage with the speed adjusters  1 . 
     With this description in place, some of the particular improvements and advantages of the present invention will now be described. Note that not all of these improvements are necessarily found in all embodiments of the invention. 
     Referring to  FIG. 1 , a current improvement in some embodiments includes providing variable axial force to the drive disk  34  to respond to differing loads or uses. This can be accomplished by the use of multiple axial force generators. Axial force production can switch between a screw  35  and a nut  37 , with associated central drive shaft ramps  91  and screw ramps  90 , to perimeter ramps  61 ,  64 . Or the screw  35 , central ramps  90 ,  91 , and perimeter ramps  61 ,  64  can share axial force production. Furthermore, axial force at the perimeter ramps  61 ,  64  can be variable. This can be accomplished by the use of ramps of variable inclination and declination, including concave and convex ramps. Referring to  FIG. 1  and  FIGS. 6–8  and the previous detailed description, an embodiment is disclosed where affixed to the bearing disk  60  is a first set of perimeter ramps  61 , which may be concave, with which the ramp bearings  62  contact. Opposite the first set of perimeter ramps  61  are a second set of perimeter ramps  97  that are attached to the drive disk  34 , which may be convex, and which are in contact with the ramp bearings  62 . The use of concave and convex ramps to contact the ramp bearings  62  allows for non-linear increase or decrease in the axial load upon the drive disk  34  in response to adjustments in the position of the speed adjusters  1  and the support member  18 . 
     Another improvement of certain embodiments includes positively engaging the bearing disk  60  and the drive disk  34  to provide greater rotational transmission and constant axial thrust at certain levels of torque transmission. Referring to an embodiment illustrated in  FIG. 1  as described above, this may be accomplished, for example, by the use of the hook  114  and latch  115  combination where the hook  114  is attached to the bearing cage  63  that houses the ramp bearings  62  between the drive disk  34  and the bearing disk  60 , and the latch  115  is attached to the drive disk  34  that engages with the hook  114  when the ramp bearings  62  reach their respective limit positions on the ramp faces. Although such configuration is provided for example, it should be understood that the hook  114  and the latch  115  may be attached to the opposite component described above or that many other mechanisms may be employed to achieve such positive engagement of the bearing disk  60  and the drive disk  34  at limiting positions of the ramp bearings  62 . 
     A further improvement of certain embodiments over previous designs is a drive disk  34  having radial spokes (not separately identified), reducing weight and aiding in assembly of the transmission  100 . In a certain embodiment, the drive disk  34  has three spokes equidistant from each other that allow access to, among other components, the hook  114  and the latch  115 . 
     Another improvement of certain embodiments includes the use of threads  35 , such as acme threads, to move the drive disk  34  axially when there is relative rotational movement between the drive disk  34  and the bearing disk  60 . Referring to the embodiment illustrated in  FIG. 1 , a threaded male screw  35  may be threaded into a set of female threads  37 , or a nut  37 , in the bore of the drive disk  34 . This allows the drive disk  34  to disengage from the speed adjusters  1  when the drive disk  34  ceases to provide input torque, such as when coasting or rolling in neutral, and also facilitates providing more or less axial force against the speed adjusters  1 . Furthermore, the threaded male screw  35  is also designed to transmit an axial force to the drive disk  34  via the set of female threads  37 . 
     Yet another improvement of certain embodiments over past inventions consists of an improved method of shifting the transmission to higher or lower transmission ratios. Again, referring to the embodiment illustrated in  FIG. 1 , this method can be accomplished by using a threaded rod  10 , including, for example, a left hand threaded worm screw  11  and a corresponding right hand threaded shifting tube  50 , or sleeve, that operates remotely by a cable  53  or remote motor or other remote means. Alternatively, left-handed threads can be used for both the worm screw  11  and the shifting tube, or a non-threaded shifting tube  50  could be used, and any combinations thereof can also be used as appropriate to affect the rate of shifting the transmission  100  with respect to the rate of rotation of the shifting tube  50 . Additionally, a conical spring  55  can be employed to assist the operator in maintaining the appropriate shifting tube  50  position. The worm screw  11  is preferably mated with a threaded sleeve  19  so as to axially align the support member  18  so that when the worm screw  11  is rotated the support member  18  will move axially. 
     Another improvement of some embodiments over past inventions is the disengagement mechanism for the transmission  100 . The disengagement mechanism allows the input sprocket, pulley, or gear  38  to rotate in reverse, and also allows the transmission  100  to coast in neutral by disengaging the drive disk  34  from the speed adjusters  1 . 
       FIG. 28  illustrates one embodiment including a turbine powered system  700  in which the transmission  100  of  FIG. 1  is coupled to a power output  701  of a turbine  702 . In one embodiment, the turbine  702  is coupled to the transmission  100  via the sprocket or pulley  38  of  FIG. 1  or another suitable drive train adapter, such as gearing for example. 
     The foregoing description details certain embodiments of the invention. It will be appreciated, however, that no matter how detailed the foregoing appears in text, the invention can be practiced in many ways. As is also stated above, it should be noted that the use of particular terminology when describing certain features or aspects of the invention should not be taken to imply that the terminology is being re-defined herein to be restricted to including any specific characteristics of the features or aspects of the invention with which that terminology is associated. The scope of the invention should therefore be construed in accordance with the appended claims and any equivalents thereof.