Abstract:
A gearless speed reducer or increaser consists of an input shaft, an output shaft, and a motor connected to the input shaft. There is an external race connected to one of the shafts, and an internal race attached to the other shaft. Two ball bearings are disposed between the races and held in place by a finger assist. After the ball bearings have been inserted, the shafts are tilted relative to each other so that the balls become fixed in pockets created between the races and cannot slide within the races.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 USC 119(e) of U.S. Provisional Application Ser. No. 61/906,569, filed on Nov. 20, 2013, the disclosure of which is herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to a gearless speed reducer or increaser. In particular, this invention relates to a device that transmits rotational power from an input shaft to an output shaft, so that the second shaft rotates at a greater or lesser speed than the input shaft, using a set of ball bearings, and without using gears. 
         [0004]    2. The Prior Art 
         [0005]    In traditional devices used to increase or reduce speed, the connection between the input shaft and the output shaft is made through the use of gears. An internal gear on one shaft cooperates with an external gear on the other shaft to transmit the power from one shaft to the other. If the two shafts have different radii, the speed of one shaft will differ from that of the other shaft. 
         [0006]    A problem with this arrangement however, is that it is very difficult to create precisely machined gears that have no play between them. This play leads to inaccuracies in the machine in which the shafts are disposed. With operations that require very precise positioning, such as with jewelry making or circuit board operations, the traditional gear-based speed reducers are not optimal. 
         [0007]    U.S. Pat. No. 8,033,953, the disclosure of which is herein incorporated by reference, provides a gearless speed reducer or increaser which solves these problems. However, it would be desirable to provide a device of this type which does not require precise manufacturing tolerances. 
       SUMMARY OF THE INVENTION 
       [0008]    It is therefore an object of the invention to provide a speed reducer or increaser that can achieve very precise tolerances. It is another object of the invention to provide a speed reducer or increaser that can be easily manufactured with few parts. 
         [0009]    These and other objects are achieved by a gearless speed reducer or increaser comprising an input shaft, an output shaft, and a motor connected to the input shaft. There is an external race connected to one of the shafts, and an internal race attached to the other shaft. Two ball bearings are loosely disposed between the races. After the ball bearings have been inserted, the shafts are tilted relative to each other to form a pocket for the balls so that the balls are held in place, and cannot slide around within the races. The pocket is formed by the tilting of the races, and the curvature of the inner and outer races with respect to each other. The pockets are created by reducing the clearance on either side of the ball via the tilting so that the ball cannot move out of its current position. Rotating one of the shafts thus rotates the other shaft, since the balls do not slip when they are confined within the pocket between the races. Instead, the rotation of the input shaft causes the ball bearings to rotate, which in turn rotate the output shaft in the opposite direction. The ratio of the diameter of the inner race to the outer race is what determines the degree of speed reduction or increase. The greater the size difference between the inner and outer race, the greater the speed reduction (or increase). If the outer race has an inner (contact) diameter of twice the outer (contact) diameter of the inner race, then the speed ratio of the inner race to the outer race will be 2:1. 
         [0010]    The system can be uncoupled merely by pivoting the shafts back into alignment so that the balls can rotate freely within the races. 
         [0011]    The amount of tilt required to engage the shafts with each other depends on the amount of play existing between the races and the balls. The shafts are tilted just enough to capture the balls so that they stay in place. The tilt occurs around an axis running through both of the balls, and through a center of the races. This axis is perpendicular to the longitudinal axis of the shafts. 
         [0012]    The inner race can be mounted on either the input shaft or the output shaft, depending on whether the system is used as a speed increaser or reducer. For speed reduction, the inner race is mounted on the input shaft. For speed increase, the outer race is mounted on the input shaft. Once the proper tilt angle is created, the shafts can be fixed in place to guarantee smooth power transmission. Speed reduction takes place because one rotation of the input shaft causes only a fractional rotation of the output shaft, due to the larger diameter of the outer race. 
         [0013]    A system can be set up using two of the transmission arrangements, arranged on either end of an intermediate shaft. The input shaft transmits power through the first transmission arrangement, which causes the output shaft to rotate. This output shaft forms part of an intermediate shaft and is connected to a second transmission arrangement, which then transmits power to the final output shaft of the second transmission arrangement. By using two transmission arrangements, a maximum amount of speed reduction can be achieved, and the angles of the two transmission arrangements can be set so that the input shaft and the final output shaft are rotating parallel to each other. The intermediate shaft can be constructed as a hollow sleeve into which the output shaft of the first speed reducer is inserted. The input shaft of the second transmission arrangement is inserted into the other end of the sleeve. 
         [0014]    The shafts are held in place in the sleeve against rotation. This can be accomplished in several ways. In one embodiment, the shafts and sleeve are equipped with a series of ball tracks, into which ball bearings are disposed. The ball bearings hold the shaft against rotation in the sleeve. In another embodiment, a keyway is provided. The sleeve can be provided with a longitudinal ridge that slides within a longitudinal groove in the shaft, or vice versa. This also prevents rotation of the shaft within the sleeve. While rotation relative to the sleeve is prevented, the shafts are able to move longitudinally within the sleeve to obtain the proper tension on the speed reducers. This tension is accomplished by springs, which press the shafts and their associated races against the corresponding races in the speed reducers. This ensures that the rotational motion is transmitted through the transmission arrangement, and prevents any slippage by the balls in the transmission arrangement. The sleeve is also preferably equipped with stop elements that prevent excessive axial movement of the shafts within the sleeve. 
         [0015]    In another embodiment, the shafts are supported in a housing, and finger assists are mounted in the housing so as to press the balls into place within the races. The finger assists are rigid projections that extend into the races and press the balls into the proper position. This allows the unit to function well, even if precise manufacturing tolerances are not achieved. The finger assists can have a curved surface that contacts the balls, which gives greater contact with the balls, and/or can have a rubberized coating or pad on the contact surface, which also increases friction with the balls to prevent excessive movement. One finger assist can be provided for each ball. The finger assists can be fixedly connected to the housing, or can be mounted so as to pivot. The pivoting mount allows the finger assists to achieve the greatest amount of contact with the balls. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the invention. 
           [0017]    In the drawings, wherein similar reference characters denote similar elements throughout the several views: 
           [0018]      FIG. 1  shows a top view of the transmission arrangement according to the invention, with the ball bearing shown in dotted lines; 
           [0019]      FIG. 1A  shows a cross-sectional view of the inner and outer races of  FIG. 1 ; 
           [0020]      FIG. 2  shows a side cross-sectional view of the transmission arrangement of  FIG. 1 ; 
           [0021]      FIG. 2A  shows a perspective view of the arrangement shown in  FIG. 2 ; 
           [0022]      FIG. 3  shows a top cross-sectional view of the transmission arrangement of  FIG. 1 ; 
           [0023]      FIG. 4  shows a side cross-sectional view of the transmission system according to the invention; 
           [0024]      FIG. 5  shows a cross-sectional view along lines V-V of  FIG. 4 ; 
           [0025]      FIG. 6  shows a cross-sectional view of an alternative arrangement of the shaft and sleeve; 
           [0026]      FIG. 7  shows a top view of the transmission system according to the invention shown in  FIG. 4 ; 
           [0027]      FIG. 8  shows an interior view of the arrangement having finger assists according to the present invention; and 
           [0028]      FIG. 9  shows another view of the arrangement of  FIG. 8 ; 
           [0029]      FIG. 10  shows another variation of the finger assist; and 
           [0030]      FIGS. 11 and 12  show a further embodiment, in which the finger assist is pivotable. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0031]    Referring now in detail to the drawings,  FIG. 1  shows a top view of the transmission arrangement according to one embodiment of the invention. The transmission arrangement  1  comprises an input shaft  10 , connected to an inner race  15 , and an output shaft  11 , connected to an outer race  16 . Between the two races are two ball bearings  14 , shown in dotted lines in this view. A motor  20  is connected to input shaft  10 . Inner race  15  is disposed angularly offset to outer race  16 , so that ball bearings  14  are held in a pocket between the races with no play. The offset occurs by pivoting one of the races around the y-axis shown in  FIGS. 2-3 . The degree of offset required to hold the balls depends on the curvature of the raceways, the size of the balls, and the amount of play of the balls in the races prior to being offset. This pivoting creates a pocket to accommodate the balls, and reduces the clearance on both sides of each ball  14  to eliminate the ability for the ball to slide along the races. Balls  14  are held in the races 180 degrees apart at all times, and the pivot or offset of the races takes place around an axis created by balls  14 . Rotation of input shaft  10  causes output shaft  11  to rotate, but at a different speed. The speed reduction or increase is directly dependent on the ratio between the diameters of the inner and outer races. 
         [0032]      FIG. 2  shows a side cross-sectional view of transmission arrangement  1  according to the invention, and  FIG. 3  shows a top cross-sectional view, which is the same view shown in  FIG. 1 .  FIG. 2A  shows a perspective view of the transmission element  1 . Here, it is clearly shown that outer race  16  is pivoted with respect to inner race  15 . This pivoting takes place around the Y axis, to form pockets for balls  14 . The twisting of the races cuts off access to the rest of the ball cage, to prevent the balls  14  from sliding around within the races. 
         [0033]      FIG. 1A  shows a detailed view of the speed reduction/increase mechanism. In the views shown in  FIGS. 1-3 , the device is a speed reducer. In this device, inner race  15  is connected to input shaft  10  and outer race  16  is connected to output shaft  11 . Rotation of inner race  15  by motor  20  causes bearings  14  to rotate as well, since they are held within the pocket created between inner race  15  and outer race  16  without any slippage. In turn, rotation of bearings  14  then causes outer race  16  to rotate, and consequently outer shaft  11 , to which it is coupled. The degree of rotation of outer race  16  is less than the degree of rotation of inner race  15 , due to the different diameters of the two races. The greater the difference between outer contact diameter d of inner race  15  and inner contact diameter D of outer race  16 , the greater the degree of speed reduction or increase. The inner and outer contact diameters are based on the diameters of the inner and outer races where each contacts ball bearing  14 . 
         [0034]    Pivoting races  15  and  16  so that shafts  10 ,  11  are parallel to each other releases ball bearings  14  and stops the transmission of power. The system according to the invention has great advantages over conventional gear transmissions, because there is virtually no slippage between the races once the shafts are rotated to capture the balls in place. Furthermore, since there is no slipping or rubbing, wear on the balls and races is minimal. 
         [0035]      FIGS. 4 and 7  show an embodiment of the transmission arrangement in a transmission system having two of the above-described transmission arrangements. In the system, output shaft  11  of one transmission system, which is connected to outer race  16 , is connected via a hollow sleeve  30  to a second transmission system  2 , having an input shaft  39  and an inner race  17 . Inner race  17  is then coupled via ball bearings to an outer race  18  and a second output shaft  40 , as shown in  FIG. 7 . As shown in  FIG. 4  and in the cross-sectional view shown in  FIG. 5 , shafts  11  and  39  are held within sleeve  30  so as not to rotate, by a series of ball bearings  27  that roll within cut-out channels  28  and  29  of shafts  11 ,  39  and sleeve  30 , respectively. This arrangement allows shafts  11 ,  39  to slide axially within sleeve  30  (i.e., along longitudinal axis A) and yet only rotate together with sleeve  30 . As an alternative, channels  28  and  29 , a keyway arrangement can be provided, such as shown in  FIG. 6 . Here, instead of channels and balls, the shafts are held in place against rotation by a ridge  34  connected to sleeve  30 , and a groove  19  cut into shaft  11  or  39 . Ridge  34  slides within groove  19  and allows axial movement, but not rotation relative to sleeve  30 . To prevent excessive axial motion of shafts  11 ,  39 , a stop mechanism formed of protrusions  33 ,  34  is arranged between shafts  11 ,  39  and sleeve  30 . Protrusions  33  limit the motion of shafts  11 ,  39  to the distance between protrusions  33 , as protrusion  34  cannot pass the barrier formed on either side by protrusion  33 . Other methods of limiting the axial motion could also be used. 
         [0036]    Sleeve  30  is held in place by roller bearings  31 ,  32 . Other means for holding sleeve  30  in place may also be used, such as a cage with ball bearings, slide bearings, or any other suitable arrangement that allows sleeve  30  to rotate when motor  20  is running. 
         [0037]    To ensure proper pressure on transmission arrangements  1  and  2 , to keep the races in proper positioning, a spring  25  may be used, as shown in  FIGS. 4 and 7 . Spring  25  acts on races  16  and  17 , to press them against races  15  and  18 , respectively to ensure proper engagement of ball bearings  14 . Spring  25  rests against a stop  42  on sleeve  30 . Other means of ensuring pressure of the races against each other could also be used. 
         [0038]    As shown in  FIG. 7 , by using two transmission arrangements  1 ,  2 , the shafts can be positioned so that second output shaft  40  is parallel to input shaft  10 , thus avoiding any potential complications from having the shafts be set at an angle to each other. The dual transmission arrangement also allows for twice the speed reduction or increase. The system of the present invention provides for very precise rotational motion transmission, with virtually no play between the shafts. This makes the system of the present invention ideal for uses that require very accurate positioning of parts, such as in jewelry making, circuit board manufacturing, and many other industries. Furthermore, the system according to the invention is simpler to construct and does not wear down as quickly as gear-based systems, thus saving cost and maintenance time. 
         [0039]      FIGS. 8 and 9  show another embodiment of the invention. In this embodiment, input shaft  10  and output shaft  11  are rotatably mounted in a housing  30 . Two finger assists  32 , 33  are fixedly mounted to housing  30  so as to press the balls  14  into their proper location between inner race  15  and outer race  16 . In this embodiment, finger assists  32 ,  33  are made of spring steel, but other variations, such as using coil springs or any other suitable method to push the balls into location can be used as well. By using this finger assists  32 , 33 , the unit&#39;s manufacturing tolerances can be looser, which reduces manufacturing expenses. Also the unit will only work in one direction, and allows free spin of balls  14  in the direction opposite of that in which the balls are being pushed. This prevents the unit from being back-driven. The desired location can be defined as the natural pocket that is created by the traction drive. 
         [0040]      FIG. 9  shows input shaft  10  in a tilted position, which engages balls  14  to transmit power to the output shaft. In this embodiment, shaft  10  is rotating in the counter-clockwise direction. Finger  32  will push the ball  14  to the left, and Finger  33  will push the other ball  14  (not shown) to the right. This assists in the engagement of the unit. 
         [0041]      FIGS. 10-12  show another variation of the invention, in which the finger assist  32  is curved to follow the shape of the balls. This increases the stability of the device and reduces stress on the system. In addition, a coating or layer of resilient material  37 , such as viton or rubber can be placed on the interior surface of finger assist  32  to increase the amount of surface area of finger assist  32  that contacts ball  14 . 
         [0042]    In  FIGS. 11-12 , the finger assist is shown in a pivoting mechanism formed by perpendicular base  34  mounted to shaft  35 , which is pivotally positioned in bore  36  in housing  30 . This allows the finger assist  32  to pivot with movement of the system, further reducing tension and wear on the system. As the ball  14  turns clockwise, the pivoting finger assist  32  will try to pivot counter clockwise. This will apply more pressure between the ball  14  and the finger assist  32 . The pivoting finger assist  32  can only pivot slightly because of its radius versus the radius of the pivot point. The rate of pressure increase is determined by the speed of the fluid on the ball pushing the pivoting finger assist and also the shear strength of the lubrication. 
         [0043]    Finger assists  32 ,  33  can be used with any of the variations of the system shown in  FIGS. 1-7  to increase the system&#39;s effectiveness, even when precise manufacturing tolerances have not been met. 
         [0044]    Accordingly, while only a few embodiments of the present invention have been shown and described, it is obvious that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.