Abstract:
The invention describes a variable eccentricity assembly, in which the overall eccentricity of the assembly can be changed while continuing rotation of the assembly. Two types of assemblies to change the eccentricity of the assembly are described. In one type multiple eccentric parts are arranged in series, and a relative rotation between them varies the eccentricity of the assembly and in second type a disc is moved in a direction normal to the shaft to vary the overall eccentricity of the assembly. The variable eccentricity assembly can be used in eccentric gearbox, eccentric gear drives, eccentric clutches and in other various-applications. It can also be used in many applications to compensate wear and tear. Use of variable eccentricity assembly can also save maintenance efforts in some applications.

Description:
BACKGROUND 
       [0001]    Many mechanisms use crank and eccentric parts, mainly for forcing an axis to revolve around a reference axis, which is generally a fixed axis. For example crank pin axis of a crank revolves around the crank axis similarly axis of a circular disc that is used as an eccentric part revolves around its axis of revolution; crank axis and axis of revolution of an eccentric part work as fixed reference axes. In almost all the cases, distance between reference axis and revolving axis is constant and is known as crank radius for a crank and eccentricity for an eccentric part. A crank with some crank radius is kinematically equivalent to an eccentric part with eccentricity equal to the crank radius. 
         [0002]    Present invention suggests mechanisms to give variable eccentricity for an assembly. The invented mechanism can change eccentricity of an assembly called variable eccentricity assembly as needed by a machine or by an apparatus or by a device for its operation. With present invention, it is possible to use some value of eccentricity for some duration and use some other value of eccentricity for some other duration, during operation of a machine. Thus, with present invention it is possible to select any value within two set designed values of eccentricity at any time during operation of a machine that uses such a variable eccentricity assembly. A variable eccentricity assembly is very useful for eccentric gear drives and in many other industrial applications where change in eccentricity is useful. 
       PRIOR ART 
       [0003]    1. U.S. Pat. No. 4,776,156, dated Oct. 11, 1988 titled as “Variable eccentricity mass for mechanical shakers” invented by Galen K. Brown, Henry A. Affeldt, Jr., Thomas A. Esch, and Richard J. Wolthuis. It describes an eccentric mass, which can be moved away from a shaft axis that supports the mass as to incorporate change in the vibration by changing the location of an eccentric mass with respect to the rotating shaft that carries the mass. 
         [0004]    2. U.S. Pat. No. 7,064,655 B2, dated Jun. 20, 2006 titled as “Variable Eccentricity Tactile Generator” invented by Matthew J. Murray, Michael Townsend, Chris Eaton, and Gregory S. Patterson. It describes a tactile generator with an eccentric mass that imparts a vibration as it rotates about a rotational axis. The mass is radially movable with respect to the rotational axis such that the distance between the mass and the axis is variable. Varying the distance of the mass from the axis varies the amount of vibration generated when the mass is rotated. The amount of vibration may be controlled responsive to a detected level of ambient noise. 
       INTRODUCTION 
       [0005]    Different types of machines regularly use cranks and eccentric parts. Few of the important uses of eccentric parts or cranks are found within eccentric gear drive, eccentric gearbox, and in reciprocating piston mechanisms. Eccentric gear drive and eccentric gearbox are characterized to give very high speed-ratio between input and output shafts and are very compact as compared to conventional gear drive and conventional gearbox. Eccentric parts or cranks, used for eccentric gearbox and other machines usually have constant eccentricity. Present mechanism gives provision to change effective eccentricity or overall eccentricity of a variable eccentricity assembly as and when needed for better operation of the machine. 
       Definitions: 
       [0006]    Eccentricity: When an axis revolves around another parallel axis, then eccentricity is the distance between the two axes. When these two axes are aligned, the eccentricity becomes zero. 
         [0007]    Eccentric part: An eccentric part is a part which when rotated about a first axis forces a second axis to revolve around the first axis, the distance between the two axes is the eccentricity of the part. An eccentric part can be a circular disc with a non-concentric hole. A basic eccentric part as a disc has at least a portion of individual external and internal surfaces as surfaces of revolution with their geometric axes parallel to each other; the distance between these two axes is the eccentricity of the eccentric part. A circular disc with a shaft, as an eccentric part, does not have a hole in it but, as the disc rotates about the shaft axis, the distance between the shaft axis (first axis) to the axis of the disc (second axis) is the eccentricity of the disc as an eccentric part. For ease of understanding, internal and external surfaces of eccentric parts are considered cylindrical and their respective axes are called as first axis and second axis. Henceforth an eccentric part is called as an eccentric in singular form and as eccentrics in plural form. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0008]    In most applications, eccentrics experience eccentric loads while revolving around the axis of revolution called as reference axis. Thus, when a variable eccentricity assembly is used, it should be able of withstand the eccentric load while revolving around reference axis and simultaneously maintain overall eccentricity at a desired value or in a changeable state as per the operational requirements of the device. 
         [0009]    To achieve variable eccentricity following arrangements are proposed: 
         [0010]    First arrangement with eccentrics in series: In this arrangement, at least two eccentrics are used in series in such a way that the first axis of one eccentric is aligned to the second axis of another eccentric; while the two eccentrics are free to rotate with respect to each other. Relative rotation of eccentrics in series is controlled by some mechanism and overall eccentricity is governed by relative angular positions of these eccentrics. These multiple eccentrics together in series is called as combination assembly of eccentrics and acts as a single eccentric during usual operation of a machine that uses it. In a combination assembly of eccentrics, eccentricity of individual eccentric is independent of each other. 
         [0011]    Though any number of eccentrics can be arranged in series in a combination assembly of eccentrics, in such a way that an eccentric is allowed to rotate with respect to another eccentric, arrangements with only two eccentrics in series are discussed here to explain the mechanism to give variable eccentricity. A person skilled in the art can easily make out how to put more than two eccentrics in series in a combination assembly of eccentrics to get variable eccentricity from it. Eccentrics arranged in series preferably have parallel axes. 
         [0012]    Second arrangement with transverse movement of disc: In this arrangement, at least one disc, with a portion of external surface as a surface of revolution, is mounted on a reference axis, in such a way that the disc and thus its axis can move in a direction normal to the reference axis. In other words, the disc can move in a radial direction. Disc axis is maintained parallel to the reference axis. This movement of the disc causes variation in overall eccentricity of the assembly, which is the distance from the disc axis to the reference axis. 
         [0013]    Third arrangement as combination of first and second arrangements: This arrangement is a combination of the two arrangements mentioned above and thus not discussed further in detail. A person skilled in the art, can easily find out appropriate ways to use above-mentioned arrangements together for making a single variable eccentricity assembly to give variation in its overall eccentricity. In this arrangement, at least one of the eccentrics or at least one disc can move in a direction normal to the reference axis as in second arrangement and at least one eccentric is mounted in series with it as in first arrangement. Other combinations of above-mentioned arrangements can also be worked out as per the requirements of the device that use the variable eccentricity assembly. 
     
    
     
         [0014]    The invention is explained with the help of following figures: 
           [0015]      FIG. 1 : Schematic representation of two eccentrics in series; for ease of understanding, the eccentrics are displaced along the axis of shaft. 
           [0016]      FIG. 2X ,  FIG. 2Y ,  FIG. 2Z : Schematic views of three different relative angular positions of the two eccentrics in series as shown in  FIG. 1 , when viewed in direction AA. 
           [0017]      FIG. 2X : Schematic view of relative angular positions of two eccentrics in series, as shown in  FIG. 1 , when their individual eccentricities are in phase with each other that give maximum overall eccentricity for the combination of the eccentrics. 
           [0018]      FIG. 2Y : Schematic view of relative angular positions of two eccentrics in series, as shown in  FIG. 1 , when one eccentric is rotated with respect to other. 
           [0019]      FIG. 2Z : Schematic view of relative angular positions of two eccentrics in series, as shown in  FIG. 1 , when their individual eccentricities are out of phase with each other that give minimum overall eccentricity for the combination of the eccentrics. 
           [0020]      FIG. 3 : Schematic representation of a spacer or a fastener made of a combination assembly of eccentrics with two eccentrics, for mounting a device. 
           [0021]      FIG. 4 : Schematic arrangement for a combination assembly of eccentrics to relatively rotate two eccentrics with respect to each other, as to vary overall eccentricity of the assembly. Overall eccentricity is shown at its maximum. 
           [0022]      FIG. 5 : Schematic representation of sectional view taken at BB, of the combination assembly of eccentrics that is shown in  FIG. 4 . 
           [0023]      FIG. 6 : Schematic representation of inner eccentric belonging to the combination assembly of eccentrics that is shown in  FIG. 4 . 
           [0024]      FIG. 7 : Schematic representation of outer eccentric belonging to the combination assembly of eccentrics that is shown in  FIG. 4 . 
           [0025]      FIG. 8 : An alternative schematic arrangement, different from the one shown in  FIG. 4 , for a combination assembly of eccentrics to relatively rotate two eccentrics with respect to each other, as to vary overall eccentricity of the assembly. Overall eccentricity is shown at its minimum. 
           [0026]      FIG. 9 : A schematic view of the combination assembly of eccentrics that is shown in  FIG. 8 , when seen in direction CC. 
           [0027]      FIG. 10 : Schematic representation of the combination assembly of eccentrics as shown in  FIG. 8 , when eccentricities of individual eccentrics are in phase with each other and the overall eccentricity of the assembly is at its maximum. 
           [0028]      FIG. 11 : A schematic view of the combination assembly of eccentrics that is shown in  FIG. 10 , when seen in direction DD. 
           [0029]      FIG. 12 : Schematic representation of inner eccentric belonging to the combination assembly of eccentrics that is shown in  FIG. 8  and  FIG. 10 . 
           [0030]      FIG. 13 : A schematic view of inner eccentric that is shown in  FIG. 12 , when seen in the direction EE. 
           [0031]      FIG. 14 : Schematic representation of outer eccentric belonging to the combination assembly of eccentrics that is shown in  FIG. 8  and  FIG. 10 . 
           [0032]      FIG. 15 : Cross-sectional view of a schematic assembly with an arrangement to move a disc in transverse direction to give variable eccentricity for the assembly. 
           [0033]      FIG. 16 : A schematic view of the assembly that is shown in  FIG. 15 , when seen in direction FF. 
           [0034]      FIG. 17 : A schematic view of the part belonging to the assembly shown in  FIG. 15 , which moves the disc in a direction normal to the shaft axis to vary overall eccentricity for the assembly. 
           [0035]      FIG. 18 : A schematic view of the part that is shown in  FIG. 17 , when seen in direction GG. 
           [0036]      FIG. 19 : Schematic view of the disc that gives variable eccentricity when used in an assembly that is shown in  FIG. 15 . 
           [0037]      FIG. 20 : A schematic view of the disc that is shown in  FIG. 19 , when seen in direction HH. 
           [0038]      FIG. 21 : Cross-sectional view of a schematic assembly with an alternative arrangement, different from the one shown in  FIG. 15 , to move a disc in transverse direction to give variable eccentricity for the assembly. 
           [0039]      FIG. 22 : Schematic view of a part belonging to the arrangement as shown in  FIG. 21  that moves in a direction along the shaft axis. 
           [0040]      FIG. 23 : Schematic view of the arrangement that is shown in  FIG. 21 , when seen in direction JJ. 
           [0041]      FIG. 24 : Sectional view along the two axes of a schematic partial eccentric part with non-cylindrical internal and external surfaces. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0042]      FIG. 1  shows a schematic combination assembly of eccentrics, with two eccentrics  1  and  2  separated from each other along the shaft axis  3 . For ease of understanding, both eccentrics are shown with internal and external surfaces as cylindrical surfaces. Eccentric  1  is fixed to the shaft  4  as to rotate with shaft  4 . Eccentric  2  is mounted in a matching cavity on an output component and is free to rotate with respect to it. The output component that uses the variable eccentricity is not shown in figures. Eccentrics  1  and  2  are mounted in series and are free to rotate with respect to each other. 
         [0043]    Second axis or axis of external surface  5  of eccentric  1  and first axis or axis of internal surface  6  of eccentric  2  are aligned and are represented by axis  7 . Second axis or axis of external surface of eccentric  2  is represented by  8 . First axis of eccentric  1  is the same as the shaft axis  3 . Eccentricity of inner eccentric  1  is the distance between its first axis  3  and second axis  7 , and that of outer eccentric  2  is the distance between its first axis  7  and second axis  8 . Overall eccentricity of the combination assembly is the distance between axes  3  and  8  and can be changed by rotating eccentric  2  with respect to eccentric  1  about axis  7 . By controlling relative rotation of eccentric  2  with respect to eccentric  1 , overall eccentricity of the combination assembly of eccentrics as shown in  FIG. 1  can be controlled. 
         [0044]      FIG. 2X ,  FIG. 2Y ,  FIG. 2Z  show three relative angular positions of eccentrics  1  and  2  in a combination assembly of eccentrics, and overall eccentricity thereof. For this example only two eccentrics with equal eccentricities in series are considered, though there can be more eccentrics in series with their individual eccentricities being independent of each other. 
         [0045]      FIG. 2X  schematically displays relative angular positions of two eccentrics  1  and  2  when both eccentrics are in phase with each other and overall eccentricity that is the distance between axes  3  and  8 , is at its maximum and is represented by 9. In other words the three axes  3 ,  7 , and  8  become co-planer. 
         [0046]      FIG. 2Y  schematically shows relative angular position of eccentric  2 , when rotated with respect to eccentric  1  by an angle represented by 10, from the state as shown in  FIG. 2X . Again overall eccentricity is the distance between axes  3  and  8  and is represented by 11. 
         [0047]      FIG. 2Z  schematically shows relative angular position of eccentric  2 , when rotated with respect to eccentric  1  by 180°, from the state as shown in  FIG. 2X . Again overall eccentricity is the distance between the axes  3  and  8  and is at its minimum; three axes  3 ,  7 , and  8  are co-planer. In present case, as the two individual eccentricities are equal and are out of phase, first axis  3  of eccentric  1  and second axis  8  of eccentric  2  are aligned, and overall eccentricity becomes zero. 
         [0048]    Thus by mounting multiple eccentrics in series, in such a way that eccentrics have relative rotation between them, overall eccentricity can be changed by changing relative angular displacement of the eccentrics. For ease of understanding, henceforth axes of shaft, inner eccentric and outer eccentric are represented by  3 ,  7 , and  8  respectively for a combination assembly of eccentrics with two eccentrics. 
         [0049]      FIG. 3 , schematically displays one probable use of eccentrics mounted in series. Parts  12  and  13  with appropriate holes are to be held together with the help of a threaded bolt  14  and a nut  14 ′. If alignment between  12  and  13  is very poor and if we just put a bolt  14  through  12  and  13 , and tighten the nut  14 ′ on other end, the joint may get excessive stress due to improper alignment. In similar situations, an assembly with multiple eccentrics as shown in  FIG. 3  can be of advantage. As shown in  FIG. 3 , bolt  14  is inserted through inner eccentric  15  that is supported by outer eccentric  16 , which is free to rotate within the hole provided in  13 . By rotating  15  and  16 , axis of the bolt  14  can easily be located anywhere within a cylindrical space of radius equal to the obtainable maximum eccentricity of the combination assembly of eccentrics  15  and  16 , with cylinder axis aligned to the axis of external surface of  16 . Assuming  13  as fixed, axis of external surface of outer eccentric  16  becomes its first axis and axis of its internal surface becomes its second axis. Axis of external surface of inner eccentric  15  becomes its first axis, which is aligned to the second axis of outer eccentric  16  as the two are arranged in series. Thus, improper alignment can be taken care of by use of combination assembly of eccentrics with variable eccentricity. 
         [0050]    Eccentrics are mainly used to maintain distance between two axes while revolving one axis about the other axis. Thus, an assembly that has variable eccentricity should be able to maintain the eccentricity while in revolution. Few configurations are developed and described further to relatively rotate eccentrics in series, and simultaneously maintain their relative angular positions while the assembly revolves. Different configurations that use eccentrics in series for varying overall eccentricity of a combination assembly of eccentrics are described below. 
         [0051]    First configuration to give direct relative rotation of the eccentrics:  FIG. 4  shows a combination assembly of eccentrics with inner eccentric  17  fixed to shaft  18  with a key  19 . Outer eccentric  20  is mounted in series with inner eccentric  17  and is free to rotate with respect to  17 . A projection  21  is located on eccentric  20 , another projection  22  with an opening  23  in it, is located on eccentric  17 . Individual eccentrics  17  and  20  are shown in  FIG. 6  and  FIG. 7  respectively. 
         [0052]      FIG. 5  shows a schematic sectional view of the combination assembly as shown in  FIG. 4 , when viewed in direction BB.  FIG. 5  shows a flexible member or a flexible steel wire  24  of fixed length, with its one end fixed to projection  21 . The flexible wire is routed through opening  23 , with its other end fixed to a ring  25 . Ring  25  is fixed to shaft  18  such that it rotates with the shaft and is free to move in direction along the shaft axis. This is achieved by providing an axial groove on the shaft  18  with a matching projection on ring  25  as to slide it within the groove. Ring  25  is provided with a groove  26  on its outer circumference. A pin  27  that is located in groove  26 , is attached to a crank  28  that revolves around a fixed crank axis  29 . 
         [0053]    To oppose tension in flexible wire  24  and to maintain relative angular positions of the eccentrics, a mechanism that is not shown in figures is employed; though few of such mechanisms are suggested here. A spring can be placed between projections  21  and  22 , or yet another wire can be placed between projections  21  and  22  as to oppose tension in wire  24 . Flexible wire  24 , itself can be routed between projections  21  and  22  in a way that torque experienced by shaft  18  due to eccentric load caused by rotation of the combination assembly opposes tension in flexible wire  24 . Thus with a suitable mechanism to oppose tension in flexible wire  24 , outer eccentric  20  can be maintained in any angular position with respect to the inner eccentric  17 . 
         [0054]    When crank  28  is rotated about axis  29 , pin  27  moves ring  25  in direction  30  along shaft axis  3 . While ring  25  rotates with shaft  18 , pin  27  slides in groove  26 . Independent of the shaft rotation, movement of ring  25  along direction  30 , moves projection  21  in relation with projection  22  and rotates outer eccentric  20  with respect to inner eccentric  17 , with the help of flexible wire  24 . Thus, rotation of crank  28 , through movement of ring  25  determines relative angular position of outer eccentric  20  with respect to the inner eccentric  17 . 
         [0055]    Thus, when crank  28  is locked in a position, ring  25  gets a fixed position on shaft  18 ; outer eccentric  20  gets a fixed position with respect to inner eccentric  17 , through flexible wire  24  and a mechanism to oppose tension in wire  24 . Thus with ring  25  in fixed position, parts  17 ,  20 ,  24 , and  25  revolve with shaft  18  and maintain overall eccentricity of the combination assembly during revolution of shaft  18 . Thus by maintaining position of ring  25  on the shaft, overall eccentricity of the combination assembly can be maintained at any value of eccentricity between maximum and minimum values of eccentricity obtainable from the combination assembly of eccentrics with multiple eccentrics in series. 
         [0056]    Various alternative arrangements of first configuration: An example of variable eccentricity assembly is described above to explain the working principle of first configuration. It is possible to use various arrangements of multiple eccentrics in series with mechanisms, to rotate one eccentric with respect to another one. To name few of the arrangements, a hydraulic actuator, a pneumatic actuator, an electronically operated actuator, or some other type of actuator can be employed to control movement of ring  25  in axial direction  30 , instead of the arrangement with crank  28  and pin  27 . In yet another arrangement, an actuator can be connected directly between two projections  21  and  22  and thus connected directly between the two eccentrics instead of flexible wire  24 , as to directly control relative rotation of eccentrics, without the need of the axially movable ring  25 . 
         [0057]    In yet another combination of the above described configuration, outer eccentric can be fixed to the output component, while the inner eccentric is free to rotate with respect to the shaft. 
         [0058]    In all the arrangements above that use flexible member  24 , one end of the flexible member is fixed to the outer eccentric and other end to the ring while the flexible member is routed through the inner eccentric as shown in  FIG. 4 . On the other hand, in yet other alternative combination, one end of the flexible member can be fixed to. the inner eccentric and other end to the ring while the flexible member is routed through the outer eccentric. For all the combinations with ring  25 , as mentioned above, the ring is movable with respect to the eccentrics along the axis of the shaft, and the ring is made to rotate either with inner eccentric or with outer eccentric or with shaft as per specific requirements of the application. 
         [0059]    In an application where a tendency to change the eccentricity is intended, a stretchable or compressible element like a spring can also be put within the length of the flexible member or in between the two eccentrics. 
         [0060]    A person skilled in the art can work out other arrangements to control relative rotation of eccentrics mounted in series in a combination assembly of eccentrics to vary its overall eccentricity while allowing it to revolve. 
         [0061]    Second configuration to give indirect relative rotation of the eccentrics:  FIG. 8  shows another assembly with inner eccentric  31 , outer eccentric  32 , crank  33  together with freely rotating wheel  34 . Eccentrics  31  is provided with a helical projection  35  and eccentric  32  is provided with helical groove  36  that matches with  35 , and also with a collar  37 . Eccentrics  31  and  32  are respectively shown in  FIG. 12  and  FIG. 14 . A schematic view of inner eccentric  31  when viewed in direction EE, is shown in  FIG. 13 . 
         [0062]    As eccentrics  31  and  32  are assembled together in series, with helical projection on one eccentric matching with helical groove on other eccentric, a relative movement along axial direction between the two eccentrics causes corresponding relative rotation between them. One of the eccentrics  31  and  32  is made movable and other is made fixed in the axial direction for easy control of relative axial movement between them. In present assembly, inner eccentric  31  is fixed on shaft  38  with key  39 , as to rotate with the shaft and does not move in axial direction  40 . Outer eccentric  32  is made movable in the axial direction  40  and is free to rotate with respect to the output component that has a provision for axial movement of  32 . Output component is not shown in figures. Helical groove and matching projection convert relative axial movement between the two eccentrics into corresponding relative rotation between them. 
         [0063]    As shaft  38  together with the two eccentrics revolves, a torque is experienced on the shaft. This torque causes an equal and opposite axial force on the eccentrics, direction and magnitude of which depends on direction of torque experienced by the shaft, and angle and direction of helix of the helical projection and groove. This axial force induces a tendency in the movable eccentric, in this case eccentric  32 , to move along the axial direction. Assuming that in present application, movable outer eccentric  32  has a tendency to move axially downwards, a freely rotating wheel  34  mounted on a crank  33  with crank axis  41  is provided to support eccentric part  32  through collar  37  from below. Thus by rotating crank  33  around fixed axis  41 , freely rotating wheel  34  moves outer eccentric  32  in axial direction and correspondingly rotates it with respect to inner eccentric  31 . Thus by locking crank  33  in a position, any required relative angular position of outer eccentric  32  with respect to inner eccentric  31  can be maintained. As the relative rotation of one eccentric with respect to the other eccentric determine overall eccentricity of the combination assembly of eccentrics; overall eccentricity can be controlled by controlling movement of crank  33  around crank axis  41  while freely rotating wheel  34  allows the assembly to continue rotation for any position of the crank  33 . 
         [0064]    For present combination assembly of eccentrics as shown in  FIG. 8 , eccentricities of the two eccentrics  31  and  32  mounted in series are chosen to be equal.  FIG. 8  and  FIG. 9  show the combination assembly of eccentrics when eccentricities of individual eccentrics are out of phase with each other, thus overall eccentricity is zero.  FIG. 10  and  FIG. 11  show the combination assembly of eccentrics when eccentricities of individual eccentrics are in phase with each other, thus overall eccentricity is at its maximum. 
         [0065]    Various arrangements of second configuration: An example of variable eccentricity assembly is described above to explain the working principle of second configuration. In another arrangement of second configuration, a hydraulic actuator, a pneumatic actuator, an electronically operated actuator or some other actuator can be used, instead of crank  33  and freely rotating wheel  34 , to control the axial movement of eccentric  32 , in direction  40 . In yet another alternative arrangement, a helical projection can be made on outer eccentric with a matching helical groove provided on inner eccentric. 
         [0066]    Different combinations of above-mentioned mechanism with helical projection and groove are possible. The combination should have either inner or outer eccentric movable along shaft axis while, either inner eccentric is made to rotate with the shaft and outer eccentric is free to rotate with respect to the output component, or inner eccentric is free to rotate with respect to the shaft and outer eccentric is made to rotate with the output component. According to the specific combination, suitable mechanism is to be employed to control relative axial movement of the eccentrics. 
         [0067]    Two configurations as mentioned above are variants of arrangements that use two eccentrics in series and the relative rotation between them is used to control overall eccentricity of the combination assembly of eccentrics. In all configurations with two eccentrics in series, use of eccentrics with different individual eccentricities can set obtainable minimum overall eccentricity to a non-zero value. Using the principle stated in above-mentioned examples, more than two eccentrics can be arranged in series with both the configurations. A person skilled in the art can employ a suitable mechanism to control relative rotation of one eccentric with respect to another eccentric in series. 
         [0068]    Configuration to move a disc in a direction normal to the shaft axis: This configuration consists of a disc attached to a shaft in such a way that the disc axis is parallel to the shaft axis and the disc is movable in a direction normal to the shaft axis. Distance between the axis of the shaft and that of the disc is the overall eccentricity of the assembly and thus can be changed by appropriately moving the disc in a direction normal to the shaft axis. In most cases, the disc is restrained from moving along the direction of the shaft axis. The disc mentioned above has external surface as a surface of revolution formed by revolving a curve around an axis, which is the disc axis. 
         [0069]    In some applications, the disc can be moved when the shaft is not rotating, for such applications any mechanism that gives linear motion can be used as after setting overall eccentricity or distance between axis of the shaft and that of the disc, the disc can be appropriately locked in the desired position and the shaft rotation can be resumed. The mechanism should also be able to withstand forces coming onto it and simultaneously maintain the distance between axis of the shaft and that of the disc during rotations of the shaft and the disc. 
         [0070]    Two such possible mechanisms are described below to move the disc in a direction normal to the shaft axis. The mechanisms can move the disc while the assembly continues to revolve around the shaft axis 
         [0071]      FIG. 15  shows a schematic assembly, and  FIG. 16  shows its view when viewed in direction FF, that utilizes above-mentioned configuration for varying overall eccentricity of the assembly. Disc  41  is mounted on an output component, which makes use of varying eccentricity of the assembly, in such a way that it is able to rotate freely with respect to the output component. Shaft  42  has its axis of rotation  43 . An intermediate part  44  is mounted on shaft  42  and is movable in direction along axis  43 . Disc  41  is mounted on the intermediate part  44 . Shaft  42 , disc  41  and intermediate part  44  rotate together without relative rotation between them. To mount intermediate part  44  on the shaft in the said manner, it is possible to make shaft  42  as a splined shaft and make part  44  with matching splines on to it. Part  44  can also be mounted on the shaft with a key  45  fixed to it and providing a matching grove on to the part  44  as schematically shown in  FIG. 15 . 
         [0072]    Intermediate part  44  is schematically shown in  FIG. 17  with another view as seen in direction GG in  FIG. 18 . It has two opposing slant surfaces  46  and  47  and has another two opposing surfaces  48  and  49 . The four surfaces  46 ,  47 ,  48  and  49  are shown as flat surfaces for ease of understanding; while in an application the surfaces need not be flat surfaces. Coaxial to the shaft axis  43  a groove  50 , with a suitable cross-section is provided on an outer circumference of part  44 . 
         [0073]    Schematic disc  41  is shown in  FIG. 19  and it&#39;s another view as seen in direction HH is shown in  FIG. 20 . The disc has two opposing surfaces  51  and  52  that match with surfaces  46  and  47  respectively. The disc also has other two opposing surfaces  53  and  54  that match with the surfaces  48  and  49 . 
         [0074]    In the assembly as shown in  FIG. 15 , disc  41  has no relative rotation with respect to shaft  42  and is restrained to move in direction along the axis of the shaft. The disc surfaces  51 ,  52 ,  53 , and  54  are supported by surfaces  46 ,  47 ,  48  and  49  respectively. As the disc is not allowed to move in axial direction, slant surface pairs  46 ,  51  and  47 ,  52  move disc  41  in direction  55  that is normal to the shaft axis  43 , for a corresponding movement of part  44  in axial direction  56 . Similarly for a movement of part  44  in direction opposite to  56 , disc  41  moves in direction opposite to  55 . Surface pairs  48 ,  53  and  49 ,  54  block any movement of disc  41  in direction normal to  55  in a plane normal to shaft axis. Above-mentioned four surface pairs provide stability to the disc  41  and transfer the load from the disc to the shaft while in operation. As schematically shown in  FIG. 15 , an actuator  57  is provided to move part  44  in the direction along axis  43  through part  58  that slides within the groove  50  and has a matching cross-section. Thus, actuator  57  through part  58  can control movement of part  44  in direction  43  and thus moves disc  41  in a direction normal to the shaft axis as to change the overall eccentricity of the assembly while assembly continues to revolve about axis  43 . 
         [0075]    In another arrangement as shown in  FIG. 21 , disc  59  has controlled movement, in a direction  60  that is normal to the axis  61  of the shaft  62 , through threaded member  63  that is fixed to the disc  59 . Nut  64 , matching with the threaded member  63 , is fixed to shaft  62  in such a way that it rotates with the shaft and has no movement along axes  61  and  60 . Nut  64  is free to rotate about axis  60  and is fixed with a bevel gear  65  at one end. A bevel gear  66  in mesh with bevel gear  65 , is fixed to an assembly  67  that is mounted on shaft  62  such that it is free to rotate with respect to the shaft and does not move in axial direction  61 . Assembly  67  is provided with a helical groove  68 . A part  69  as shown in  FIG. 22  is mounted on shaft  62  with a key and matching groove  70 , such that part  69  can move along axis  61  and rotates with shaft  62 . Part  69  is provided with a projection  71  that matches with groove  68  and slides in it. On an outer circumference of part  69 , a groove  72  is provided. Another part  73  matching with groove  72  is attached to an actuator  74  that moves part  73  along axis  61 . 
         [0076]    Actuator  74  moves part  73 , which slides in groove  72  without affecting rotation of part  69 , and thus moves part  69  in direction  75  along axis  61 . Movement of part  69  in direction  75  rotates assembly  67  about axis  61  through sliding of projection  71  within groove  68 . Rotation of assembly  67  rotates bevel gear  66  that rotates meshing bevel gear  65 . Rotation of gear  65  rotates nut  64  that moves threaded member  63  in direction  60  and thus moves axis  76  of disc  59  with respect to the shaft axis  61 . Axis  61  and axis  76  are parallel to each other. Provisions are made in shaft  62  to block movement of nut  64  in direction  60  and allow it to rotate about axis  60 . Surfaces  77  on disc  59 , together with matching surfaces on shaft  62 , blocks rotation of disc  59  about axis  60  and give support to the disc while allowing it to move along direction  60 . Distance between axis  61  and axis  76  is the overall eccentricity of the assembly. Thus, movement of  73  changes overall eccentricity without affecting rotation of  69 ,  67 ,  64 , and  59  around shaft axis  61 . Holding  73  in one position correspondingly maintains overall eccentricity of the assembly. 
         [0077]    In other arrangement, nut  64  can be fixed to shaft  62 , and threaded part  63  is allowed to rotate about axis  60  without moving along axis  60  with respect to the disc  59 ; bevel gear  65  is mounted on threaded part  63  in such a way that it rotates with threaded part  63  while does not move along axis  60 . Thus, movement of  73  along axis  61  rotates threaded part  63 , and thus moves disc  59  along axis  60  and changes the distance between axes  61  and  76 . 
         [0078]    There can be different arrangements that can move disc  59  along a direction normal to axis  61  of shaft  62  to change distance between axis  61  and axis  76  of disc  59  as to change overall eccentricity of the assembly, while continuing rotation of assembly about shaft axis  61 . 
         [0079]    Various arrangements to move a disc in a direction normal to shaft axis: In above two examples the disc movement in a direction along the shaft axis is blocked, in yet another arrangement where the axial movement of the shaft or disc is allowed appropriate modifications can be incorporated in the arrangements described above. For example, surfaces  46 ,  47 ,  48 , and  49  can be fixed to the shaft and the disc can be moved along the shaft axis with a collar fixed to the disc as in outer eccentric  32  shown in  FIG. 14 . In other words relative movement of a disc along shaft axis with respect to the shaft is converted to relative movement of the disc in direction normal to the shaft axis. In yet another arrangement, actuator  57 , and  74  can be replaced with arrangement with a crank similar to that shown in  FIG. 4  and  FIG. 8  with appropriate design modifications. In other arrangements, an actuator can directly be put between the shaft and the disc as to move the disc with respect to the shaft in a direction normal to the shaft axis without the need of part  44 , or assembly  67  and actuator  57  or  74  to do so. 
         [0080]    Any suitable mechanism other than the above-mentioned mechanisms can also be used to move a disc in a direction normal to the shaft axis as to change the overall eccentricity while continuing rotation of shaft and the disc about shaft axis. Basic requirement of such a mechanism is that it should be able to control the movement of a disc in a direction normal to shaft axis as per the requirements of the output component that use the variable eccentricity assembly. Thus by controlling the movement of the disc in a direction normal to the shaft axis, with respect to the shaft, overall eccentricity of the assembly can be controlled. 
         [0081]    External surface of the disc need not be cylindrical but should be a surface of revolution formed by revolution of a curve around an axis. A typical eccentric with non-cylindrical surfaces  78  and  79 , is shown in  FIG. 24 . Internal surface  78  is formed by revolving a suitable curve around axis  80 , similarly external surface  79  is formed by revolving another suitable curve around axis  81 . The two axes  80  and  81  are axes of revolution for surfaces  78  and  79  respectively and are the first axis and the second axis respectively for the eccentric. Only surfaces  78  and  79  form the basic eccentric and thus are of interest, the eccentric may have some other surfaces but are not considered here. Non-cylindrical external surface  79  can be used as the external surface of disc  41  or disc  59 . 
         [0082]    In all the above arrangements proper use of lubrication and appropriate use of bearings improves performance of the arrangements and can be worked out by a person skilled in the art and thus not discussed here. 
       Advantages of Assembly With Variable Eccentricity: 
       [0083]    1. A variable eccentricity assembly in its basic form with at least two eccentrics in series can be used as a spacer or fastener to help joining two unaligned parts with ease. For an example, this type of spacer can be of much use while mounting a radiator in an automobile as it is to be mounted on the chassis of the vehicle and the mounting holes cannot maintain very accurate positions. 
         [0084]    2. Variable eccentricity assembly finds application in eccentric gear boxes 
         [0085]    3. Variable eccentricity assembly can be used to auto adjust the eccentricity to compensate wear and tear in a device. For example, a device that has one hollow ring inside which a disc of diameter smaller than that of the ring is moving with an eccentric such that disc external surface is rubbing on the internal surface of the ring. For this case, the eccentricity of the eccentric is half the difference between the two diameters. As wear and tear of the rubbing surfaces takes place eccentricity increases, this reduces contact pressure at the rubbing surfaces with a constant eccentricity drive. A variable eccentricity assembly instead of a constant eccentricity eccentric with maximum eccentricity of the assembly set to more than half the difference between the two diameters can be used to compensate for the wear and tear. Arrangement can be made to incorporate a tendency with appropriate magnitude towards increasing eccentricity of the variable eccentricity assembly, as to maintain rubbing pressure until due to wear and tear the difference between the two diameters becomes double the maximum eccentricity of the assembly. 
         [0086]    4. In an eccentric gear drive, engagement and disengagement of the gear with external teeth and gear with internal teeth, or in case of an eccentric clutch, engagement and disengagement of the disc and the ring, can be controlled by varying eccentricity of the assembly. When the eccentricity of the assembly is made maximum the engagement takes place and when the eccentricity is made minimum, the disengagement can take place. If the eccentricity is made zero, then the inner gear with external teeth and the ring gear with internal teeth or the inner disc and the outer ring become coaxial and depending on their individual diameters, can be made to rotate without making contact. 
         [0087]    5. A variable eccentricity assembly can be used in many applications where correction in eccentricity is beneficial. 
         [0088]    6. In most of the applications where eccentrics are used, a variable eccentricity assembly in place of a constant eccentricity eccentric can be used, this will give adjustment of eccentricity to compensate wear of the eccentric itself. This will improve life of the device and improve performance of the device; this may also reduce maintenance cost.