Abstract:
An improvement relating to an infinitely variable ratio transmission having a pair of oppositely oriented conical torque input and output members is disclosed wherein the conical members include multi-angled conical surfaces. Further the conical members include longitudinal floating sprocket bars which combined with the multi angled conical surfaces compensate for the effect of an inextensible drive belt as the drive belt is axially moved along the longitudinal length of the torque input and output members.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention generally relates to a power transmission whereby the input speed, from a constant velocity, prime mover, such as an automotive engine, or any other suitable power source, may be reduced to a desired output speed by the internal workings of the transmission.  
           [0002]    More specifically the present invention relates to an infinitely variable ratio drive mechanism, of the endless belt type, having a pair of rotating conical members configured to have parallel longitudinal axis with the smaller diameter of one conical member adjacent to the larger diameter of the other. An endless, inextensible, belt encircles and drivingly engages both conical members whereby power may be transmitted from one conical member to the other. A variable speed reduction, between the conical members, is obtained by selectively moving the endless belt along the longitudinal axis of the conical members during power transmission.  
           [0003]    It has been well known to use opposing conical members as the driving member and the driven member in power transmissions as evidenced by the following U.S. Pat. Nos. 944,585; 2,801,547; 3,021,717; 3,906,809; 4,842,569; and 5,226,854.  
           [0004]    All of the above references employ conical members having a single fixed, conical angle. However, as the belt or chain moves axially away from the longitudinal center, where the cone diameters are equal, the total required peripheral belt length encircling the conical members increases as a function of the axial distance from the longitudinal center. Therefore, either the belt must be elastic or some other means must be employed to accommodate the inherent peripheral variation. Providing an elastic belt results in losses of power transmission efficiencies. Therefore, some other mechanical solution is preferred.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention relieves the belt length problem by providing conical members having, at least, two conical angles. A first cone angle is employed from the large diameter end of the conical member to its mid longitudinal position, and a second, slightly larger cone angle is employed from the mid point of the conical member to its small diameter end. Alternatively the conical surface of the conical members may be replaced with a curved surface whereby the peripheral length of the drive belt is constant for all positions along the longitudinal length of the drive members.  
           [0006]    Further the present invention teaches novel, free floating sprocket bars spaced about the periphery of the conical members and extending longitudinally (axially) along the surface thereof. The sprocket bars generally parallel the surface of the conical members. However, the sprocket bars may take any other convenient shape, such as a convex configuration, as described further below. By being free floating, the sprocket bars freely move diametrically and circumferentially whereby they may fully engage a beaded or other suitably configured and generally inelastic, inextensible drive chain.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 presents a schematic view of the primary elements of my new and improved transmission.  
         [0008]    [0008]FIG. 2 is an isolated schematic view of one of the conical members of the transmission as shown in FIG. 1.  
         [0009]    [0009]FIG. 3 is a crossectional view taken along line  3 - 3  in FIG. 2.  
         [0010]    [0010]FIG. 4 is an enlarged view of the circled area in FIG. 3.  
         [0011]    [0011]FIG. 4A presents an alternate embodiment of the circled area in FIG. 3.  
         [0012]    [0012]FIG. 5 presents a crossectional view taken along line  5 - 5  in FIG. 1.  
         [0013]    [0013]FIG. 6 is an enlarged view of the circled area in FIG. 5.  
         [0014]    [0014]FIG. 7 present a crossectional view taken along line  7 - 7  in FIG. 1.  
         [0015]    [0015]FIG. 8 presents a schematic view of an alternate embodiment for the conical members illustrated in FIG. 1, illustrating the dual conical angle profile.  
         [0016]    [0016]FIG. 9 presents an alternate embodiment for the drive chain as shown in FIGS. 1 and 7.  
         [0017]    [0017]FIG. 10 presents a diagrammatic, crossectional view of the drive belt at the longitudinal midpoint of the conical members.  
         [0018]    [0018]FIG. 11 presents a diagrammatic, crossectional view of the drive belt at a longitudinal location, on the conical members, other than the midpoint.  
         [0019]    [0019]FIG. 12 presents a view taken along line  12 - 12  in FIG. 9.  
         [0020]    [0020]FIG. 13 presents an alternate embodiment, of my invention, wherein the beaded drive chain includes floating beads.  
         [0021]    [0021]FIG. 14 presents a schematic view of an alternate embodiment wherein a conical member has convexly configured sprocket bars.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    Referring now to FIGS. 1 through 4, FIG. 1 presents a diagrammatic view of the basic elements of my invention. A pair of rotatable, elongated, conical sprocket wheel assemblies  12  and  14  are positioned on parallel axis  16  and  18 .  
         [0023]    Since the structure of sprocket wheel assemblies  12  and  14  are identical, a detailed description of sprocket wheel assembly  12  will generally follow with the understanding that both sprocket wheel assemblies  12  and  14  are, in fact, identical in structure and function, and generally interchangeable. Sprocket wheel assembly  12  generally comprises a truncated cone  20 , which may be hollow or solid depending upon end use and/or application.  
         [0024]    Generally, power input to the system will be through a primary or driving sprocket wheel  12  and transmitted to the secondary driven sprocket wheel  14  by way of an endless belt (preferably a notched belt) or beaded chain assembly type of element  22  encircling both the driving sprocket wheel  12  and the driven sprocket wheel  14  as illustrated in FIG. 1.  
         [0025]    Sprocket wheels  12  and  14  include axially directed groove like channels  25  receiving therein elongated sprocket bars or cogs  26 . Channels  25  are circumferentially wider than sprocket bars  26  thereby permitting circumferential movement of sprocket bar  26  within channel  25  as will be discussed further below. Further, sprocket bars  26  are resiliently received within channels  25  by action of compression spring  28 , or any other suitable elastic element, positioned between sprocket bar  26  and the bottom of channel  25 . Thereby biasing sprocket bar  26  radially outward whereby, as illustrated in FIG. 6, compression spring  28  forces sprocket bars  26  radially outward into groove  38  of ring gear  32  thereby causing sprocket bar  26  to be self centering when not engaged with drive chain  22 .  
         [0026]    With reference to FIGS. 5 and 6 sprocket wheels  12  and  14  include, at each axial end thereof ring gears  32  and  34  each having circumscribing gear teeth  36  thereabout. Each ring gear circumscribes its associated sprocket wheel and is rigidly affixed thereto whereby driving torque is transmitted between the ring gear and its associated sprocket wheel. Each ring gear includes “V” shaped grooves  38  aligned with and receiving therein each sprocket bar  26  thereby retaining each sprocket bar within its associated channel  25  and acting to center sprocket bar  26 , within channel  25 , as the sprocket bar is thrust upward into the groove. The ring gears may be appropriately geared to other internal workings of the transmission whereby input torque may be input to the transmission and output torque delivered from the transmission. Alternatively sprocket wheels  12  and  14  may be directly affixed to the transmission input and output shaft of the transmission.  
         [0027]    Alternatively, channels  25  may be shaped as an inverted “T” and sprocket bars  26  provided a complimentary “T” shape whereby the channel configuration  25 A would retain sprocket bar  26 A therein as shown in FIG. 4A. Similarly, any other type of known complimentary configurations might be used for retaining sprocket bars  26  within channels  25  such as a wedge shaped configuration (not shown).  
         [0028]    Sprocket bars  26  may be configured, as illustrated in FIG. 4, with a wedge shaped top having straight, or flat surfaces  27  or, as illustrated in FIG. 4A, having scalloped surfaces  29 . The exact configuration of the sprocket bars will necessarily vary depending upon the application for which they are being used. Shoulder  23  of sprocket bar  26  preferably extends a distance x above the surface  24  of the sprocket wheel, as illustrated in FIG. 4. In operation, beads  35  will rest upon shoulder  23  when engaging the sprocket bar. The floatability of the sprocket bar, in the radial direction, may also compensate for the excess length of the drive chain, as the chain moves away from the sprocket wheel midpoint, by floating the drive chain above the surface  24  of the sprocket wheel.  
         [0029]    Referring now to FIGS. 1 and 7. It is assumed for the following operational discussion that sprocket wheel  12  is the driving wheel and sprocket wheel  14  is the driven wheel. Driving torque is transferred from the transmission input means (not shown) to ring gears  32  and  34  on sprocket wheel  12 . By chain drive the driving torque is transferred to sprocket wheel  14  through beaded drive chain  22 . The output torque is then transferred to the transmission output shaft (not shown) by way of ring gears  32  and  34  on the driven sprocket wheel  14 . When drive chain  22  is at the exact mid point of sprocket wheels  12  and  14  the gear ratio between sprocket wheel  12  and  14  will be 1 to 1.  
         [0030]    However when drive chain  22  is shifted to the right, as viewed in FIG. 1, the gear ratio between sprocket wheel  12  and sprocket wheel  14  will be less than 1, with the exact ratio being dependent upon the given axial location of drive chain  22 . Thus sprocket wheel  14  will be turning at a faster RPM than sprocket wheel  12 .  
         [0031]    Similarly, if drive chain  22  is moved to the left, as viewed in FIG. 1, the gear ratio between sprocket wheel  12  and sprocket wheel  14  will be greater than one, depending upon the specific axial location of drive chain  22 . Any convenient apparatus may be used to longitudinally move drive belt  22 . For example see U.S. Pat. No. 3,021,717.  
         [0032]    Except for the floating sprocket bars, many prior patents teach the above basic principle. For example see U.S. Pat. Nos. 944,585; 2,801,547; 3,021,717; 4,842,569; 5,226,864; and 6,135,907.  
         [0033]    However, as drive chain  22  moves axially away from the axial mid point, the required length of drive chain  22  increases and is dependent upon the specific axial location of drive chan  22 . Namely, the length of drive chain  22  necessary to wrap about sprocket wheel  12  and  14 , plus bridge the gap between the sprocket wheels is a function of axial location. Prior art patents generally teach using an elastic drive belt of some type to accommodate this problem.  
         [0034]    For an explanation of this phenomena consider FIGS. 10 and 11. FIG. 10 illustrates drive belt  22  positioned at the longitudinal midpoint of sprocket wheel  12  and  14 . At the longitudinal midpoint belt  22  wraps about sprocket wheels  12  and  14  a full 180 degrees. Thus the length of drive belt  22  is equal to the circumference of one sprocket wheel plus twice the axial offset L. However, as drive belt  22  is moved away from the longitudinal midpoint, as illustrated in FIG. 11, belt  22  wraps sprocket wheel  12  180 degrees plus twice angle C. However, on sprocket wheel  14 , belt  22  wraps the wheel 180 degrees minus twice angle D. Radius r1 and r2 are parallel since they are perpendicular, by definition, to belt  22 ; and radius r1′ and r2′ are also parallel since they are perpendicular to belt  22  in FIG. 10. Therefore, angles C and D are equal as they are formed by a pair of intersecting parallel lines.  
         [0035]    Thus for belt  22  to encircle sprocket wheels  12  and  14 , belt  22  must change in length. The length of arc  16  and  18  is equal to a constant times the radius r1 and r2 respectively, where the constant is a function of the arc&#39;s angle (C and/or D). However, since angle C equals angle D the constant is identical. Therefore arcs  16  and  18  are a function of, and differ only by the difference of radius r1 and r2. Thus it is apparent that arc  16  is larger than arc  18 . Therefore the length of belt  22  must increase by the difference in the lengths of arc  16  and  18 . As drive belt  22  moves from the longitudinal midpoint to either extreme longitudinal location the difference between arc  16  and  18  progressively increases.  
         [0036]    By experimentation I have found that an inextensible, beaded chain, as illustrated in FIGS. 1 and 7, may be successfully used if the sprocket bars  26 , as illustrated herein, are free to move, or float, within channels  25  in both the radial and the circumferential direction and dual angled conical members are employed as described below.  
         [0037]    Referring to FIG. 7, when using a beaded chain as illustrated, wherein a given gap  30  separates beads  35  one may not be certain that as chain  22  wraps around the sprocket wheel  12  or  14  that the sprocket bars will always be positioned between two adjacent beads. However, by permitting the sprocket bar  26  to move radially inward and/or shift cirumferentially, if a bead  35  impinges upon a sprocket bar as chain  22  wraps about the sprocket wheel, sprocket bar  26  may move to accommodate the fixed position of the bead, as illustrated in FIG. 7, and thereby transmit torque to chain  22 . Although the drive chain embodiment illustrated herein comprises a beaded chain, other inextensible chain, and/or belt, configurations are feasible. For example, FIG. 9 illustrates an alternate embodiment for drive chain  22  wherein a portion of linked chain  50  is illustrated having hinged, or pivoting links  52 . Each link  52  includes a spherical portion  54  for engagement with sprocket bars  26 .  
         [0038]    Further I have discovered that it is desirable that sprocket wheels  12  and  14  are configured with a double cone angle as illustrated in FIG. 8. Referring to FIG. 8, sprocket wheel  40  includes a first conical angle A from the smaller diameter  46  to mid point  44  and a smaller conical angle B from mid point  44  to the large diameter  42 . By this technique the difference between arc  14  and arc  18  (FIG. 11) may be lessened and combined with the movable sprocket bars, as taught above, will provide for matching a pair of sprocket wheels that will function with and/or accommodate an inextensible drive belt. Further, it is conceivable that a multiple number (three or more) of cone angles may be employed from one end  46 .  
         [0039]    Although four equally spaced sprocket bars are illustrated for teaching my invention herein any number of sprocket bars may be used. Further it may be advantageous, in some applications, to space sprocket bars  26  unevenly about the circumference of the sprocket wheels. Also, for particular end uses, it may be desirable to have different sprocket bar arrangements for each conical surface of the sprocket wheel.  
         [0040]    I have constructed and successfully tested a prototype unit (see FIG. 8) having two sprocket wheels wherein the longitudinal length x of each sprocket wheel is 25.4 cm. (10 inches) and wherein the small end diameter y1 equals 5.08 cm. (2 inches) and the large diameter end y2 equals 9.89 cm. (3.89 inches). The midpoint diameter y3 is 7.62 cm. (3 inches). Thus cone angle A is approximately 11.333 degrees and cone angle B is approximately 10.66 degrees. Eight equally spaced sprocket bars, of the design as illustrated in FIGS. 4 and 6, were used along with a beaded chain similar to that of a typical electric lamp “pull chain.” The chain is comprised of {fraction (3/16)}th inch beads spaced ¼ inches apart. Channels  25  are approximately 9 mm. wide and 6 mm. deep, with sprocket bars approximately 6 mm. wide and 6 mm. high.  
         [0041]    Although a double cone configuration was used to construct the prototype unit described above it is also conceivable that for a given end use application, a smooth geometric curve may be developed for use from the longitudinal midpoint of each sprocket wheel to either the large diameter end, or the small diameter end, or both, or one continuous curve might be developed extending from the small diameter end of each sprocket wheel to the large diameter end.  
         [0042]    [0042]FIG. 14 presents an additional alternate embodiment wherein a free floating, convexly configured sprocket bar  26   a  is illustrated. Although no testing of this alternate embodiment has been carried out, it is believed that use of a, free floating sprocket bar having a convex configuration, as illustrated in FIG. 14, may duplicate the affect of the multi tapered cone taught above. The high point  39  of the convexity would be located at the midpoint of the conical drive wheel  12 .  
         [0043]    Although the embodiment as taught above is believed to be the most preferred embodiment of the invention, FIG. 13 schematically illustrates an alternate embodiment wherein the drive chain  22 A includes movable beads  35 A slidingly received on a continuous, inextensible, runner, band or cable,  30 A. Positioned upon runner  30   a  are equally spaced hard stops  33  rigidly affixed to runner  30 A. A locating spring, or any other suitable resilient means,  31  positions beads  35 A midway between the hard stops. Thus both the sprocket bar  26  and movable bead  35 A may cooperatingly shift circumferentally to accommodate the fixed, inextensible length of drive chain  30 .  
         [0044]    A further alternate embodiment may comprise a flexible drive chain as taught immediately above, wherein sprocket bar  26 , having only one degree of freedom, is free to move radially, but not circumferentially whereby the free float of beads  35 A accommodate the fixed inextensible drive chain length.  
         [0045]    Similar to the free floating beads  35 A, as taught immediately above, the spherical portion  54  of chain link  50 , in FIGS. 9 and 12, may be modified to be free floating within link  50 .  
         [0046]    While I have described above the principles of my invention in connection with specific embodiments, it is to be clearly understood that this description is made only by way of example and not as a limitation of the scope of my invention as set forth in the accompanying claims.