Abstract:
An eccentric bottom bracket assembly having a body member, at least two wing members, a wedge driver with two wedge members, and at least one spring member altogether forming a tubular, cylindrical assembly to fit within the inner shell of the bottom bracket area of the bicycle frame for adjusting the chain length or tension. The assembly is preferably used for the front and rear bottom brackets of a tandem bicycle for adjusting the chain that is connected to the front and rear driving sprockets. The assembly is also alternatively used in single-rider bicycles and other bicycles with the need for adjusting chain tension. The assembly allows for the wing members and the body member to circumferentially and outwardly expand or inwardly retract by co-acting with the rotation of the wedge driver which laterally displaces the wedge members in a parallel direction relative to the longitudinal axis of the body member.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates to an improved eccentric bottom bracket assembly for bicycles. More specifically, the present invention relates to an eccentric bottom bracket assembly that is used in connection with adjusting the chain of a bicycle. 
       BACKGROUND OF THE INVENTION 
       [0002]    Bicycles generally work when bicyclists manually and rotatably push on pedals attached to cranks which are connected to the rear bottom bracket axle or spindle with front and rear driving brackets coupled by a chain between the two bottom brackets. In order for bicycles to function properly, appropriate tension of the chain has to be maintained. Even though it may be impractical to fine tune the chain length or tension precisely, slight repositioning or adjustment of the chain tension utilizing certain components is highly desired. By repositioning or adjusting a component of a bicycle, chain tension can be optimized for installing and maintaining the chain. It is a well-known and conventional practice to periodically adjust the rotational axis of the front pedal crank spindle or the rear pedal crank spindle, on which the front and rear driving sprockets are mounted. One of the adjusting components for adjusting the chain length or chain tension of a bicycle is an eccentric mount, which is an assembly in which the rotational axis of the spindle is eccentric to a cylindrical casing or a shell that is rotatable for positional adjustment within the shell of the bottom bracket portion of a bicycle frame. 
         [0003]    Typically, the term “eccentric” refers to a wheel that rotates on an axle or spindle bringing about a mechanical motion to operate as a crank or a cam by an attachment to the wheel. This term “eccentric” is commonly used as a cylindrical part for bicycles, particularly for placing the part through the bottom bracket inner shell of a bicycle. The term “bottom bracket” refers to the part of the bicycle frame around which the pedal cranks rotate and also includes other bearings and axle/spindle components such as pedal shafts which run through this bottom bracket inner shell of the bicycle frame. Eccentrics are typically used to adjust the tension of the chain on a bicycle, when the eccentric is rotatably adjusted, the chain is tightened or loosened. An eccentric, positioned in the bottom bracket inner shell, also has an opening or a bore in which the pedal crank assembly or pedal shaft is snugly placed for bicyclists to generate motion by rotatably pushing on the pedals attached to cranks with pedal shafts running through the bore which are securely fastened to the eccentric in the bottom bracket inner shell. 
         [0004]    There are different mechanisms for adjusting the eccentric depending on the design of the shell of the bicycle and the eccentric being used. The first design of adjusting the eccentric is by placing the eccentric into the loose bottom bracket shell of the bicycle frame. In this mechanism, the shell is a split shell. After placing the eccentric into the loose bottom bracket shell, the outer shell can be tightened to close any gap of a split shell by utilizing pinch bolts to tightly engage the eccentric to the inner shell. An easy way to conceptualize this mechanism and assembly is to look at bicycles on which the conventional pinch bolts are used to adjust the height of a seat post by loosening or securing the seat tube with small, movable handles on the frame near the seat tube. The second mechanism of adjusting the eccentric is to use a setscrew whereby a screw can fit around and through the outer portion of the shell to tightly engage the eccentric to the inner shell of the bottom bracket. The first design of using pinch bolts requires designing the bicycle with a split shell which results in higher labor and manufacturing costs. The second design requires bicyclists to prepare for situations whereby chains can become loose or undone in a remote location. To prepare for such events, bicyclists are subject to unnecessarily carrying heavy tools which is not feasible nor preferable, particularly for weight-sensitive bicyclists. 
         [0005]    A bottom bracket assembly mechanism using a wedge bolt is taught in the U.S. Pat. No. 4,808,147 (the “&#39;147 patent”) and U.S. Patent Application Publication No. US2006/0189426 A1 (the “&#39;426 publication”), to Graham and Dodman et al., respectively. Both of these references are directed to an adjustable eccentric bracket assembly for a bicycle using a wedge bolt. Both of these references disclose assemblies limited to particular purposes. 
         [0006]    The &#39;147 patent, for example, is directed to an eccentrically mounted pedal crank spindle that is rotatably adjustable in the inner surface of the shell of the bottom bracket of a bicycle frame. The assembly taught in the &#39;147 patent comprises a body member with a major portion having a circular cylindrical external surface that can fit with the inner surface of the shell. The remainder of the external surface of the body member is a flat wedge surface obliquely oriented to the axis of the cylindrical surface to coextensively adapt to a wedge member. The solid wedge member has a circular external cylindrical surface with the same diameter of the body member and a wedge surface that is complementary to the body member. The &#39;147 patent teaches a drive mechanism of rotatably screwing a wedge driver in which the wedge member is displaced laterally to tighten within the inner surface of the shell of a bicycle frame. Even though this assembly solved the problems mentioned in the prior art, the solid, planar, and cylindrical surface of the body member and the solid wedge surface of the wedge member contribute to overall weight of the assembly. Furthermore, the assembly oftentimes contributes to sticking of the wedge to the single planar, flat wedge surface when the wedge is being loosened to adjust the position of the assembly in order to adjust the chain of a bicycle. 
         [0007]    The &#39;426 publication is directed to a similar bracket assembly with two wedge members with two external surfaces of the body member which is obliquely oriented to the axis of the cylindrical surface rather than using a single wedge member complimentary to the body member. The eccentric body member also has an external outer cylindrical surface that is provided in close fit with the inner surface of the shell of the bicycle frame. The wedge members are provided to co-act with the body member to alternatively tighten or loosen the body member with respect to the inner shell of the bicycle frame. The body member and the wedge members are similarly provided as in the &#39;147 patent with complimentary wedge surfaces. The wedge members are laterally and perpendicularly displaced relative to the body member to tighten or loosen the fit within the inner surface of the shell. Despite the fact that the overall weight of the bracket assembly is somewhat reduced, the assembly taught in this publication is not designed to accommodate the frictional resistance necessary to sustain and prevent slipping from the correctly adjusted position of the bottom bracket assembly to the inner surface of the shell of the bicycle frame. 
         [0008]    Therefore, a design of an eccentric bottom bracket assembly is necessary that further reduces the overall weight of the assembly and provides overall strength and longevity to endure years of wear and tear. A design of an eccentric assembly is also necessary to allow a bicyclist to easily adjust the position of the eccentric bottom bracket assembly when the chain comes undone in a remote location leaving a bicyclist with limited access to tools. An eccentric bottom bracket assembly is also desired that can be universally mounted on any bicycle and utilized from either sides of the bicycle. An eccentric bottom bracket assembly is also desired that is easily adjustable without the jamming of any portion of the assembly within the inner surface of the shell of a bicycle frame. 
         [0009]    The present invention is directed to overcoming the foregoing and other disadvantages. More specifically, the present invention is directed to a new and improved eccentric bottom bracket assembly for a bicycle frame on an eccentrically mounted spindle that is rotatably adjustable. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    According to the present invention, the assembly is easily adjustable, reusable, durable, light-weight, and does not easily stick within the inner surface of the shell of a bicycle frame. Providing an eccentric bottom bracket assembly with improved features enables optimization of adjusting the chain tension and offers numerous advantages over traditional split shell assembly, setscrew assembly, and previously known eccentric bottom bracket assemblies. The advantages stem mostly from the design of the body member engaged with two wing members co-acting with the two wedge members on the wedge driver. The assembly is preferably used for the front and rear bottom brackets of a tandem bicycle for adjusting the chain that is connected to the front and rear driving sprockets. The assembly is also alternatively used in single-rider bicycles and other bicycles with the need for adjusting chain tension. 
         [0011]    According to the present invention, the eccentric bottom bracket assembly includes a body member, two wing members, a wedge driver with two wedge members and at least one spring member altogether forming a tubular, cylindrical assembly to fit within the inner shell of the bottom bracket area of the bicycle frame. The body member is a hollow, tubular, cylindrical shape with protruded portions located on the outer cylindrical portions on the latitudinal axis of the body member provided to fit with the circularly shaped wing members mounted on and around the body member with the internal surfaces of the wing members touching the body member. The wedge driver with two wedge members is also sitting in the interior chamber created between the two wing members and over the body member. The wedge members&#39; flat, bottom surfaces are touching the top of the body member, and the lateral surfaces of the wedge members are touching the internal wedge surfaces of the first and second wing members while snugly fit between the two wing members. In one embodiment of the invention, the entire assembly of the body member, two wing members, and one wedge driver with two wedge members is flexibly and expandably held together by two spring members encircling the body member and the two wing members by way of the slit portions. 
         [0012]    In one embodiment of the invention, the wing surfaces of the first and second wing members pivot or slidably move on the wing surfaces of the body member when the wing members are circumferentially and outwardly expanding or inwardly retracting from the body member. The movement of the first and second wing members at the wing surfaces also co-acts with the rotation of the wedge driver which laterally displaces the two wedge members in a parallel direction relative to the longitudinal axis of the body member with a slight lift from the body member in a perpendicular direction from the body member relative to the longitudinal axis of the body member. 
         [0013]    According to the present invention, the rotation of the wedge driver causes lateral and parallel displacement of the two wedge members away from each other on and around the wedge driver relative to the longitudinal axis of the body member thereby outwardly and circumferentially expanding the wing members away from the body member to tightly engage the eccentric bottom bracket assembly against the inner surface of bottom bracket of the shell. The opposite rotation of the wedge driver causes lateral and parallel displacement of the two wedge members back toward each other relative to the longitudinal axis of the body member to co-act by condensing the two wing members back towards the body member to loosen the tight engagement of the eccentric bottom bracket assembly from the inner shell of the bottom bracket area. After condensing the two wing members back toward the body member, the eccentric bottom bracket assembly is loose from the inner shell of the bicycle frame allowing for rotatable adjustment of the assembly for adjusting the chain tension or length. The design features of using wing members provides a number of advantages. The wing design with recesses not only reduces the overall weight of the eccentric bottom bracket assembly, the circumferential expanding and condensing mechanism is most superior in preventing sticking of the body member and the wing members against the inner surface of the shell of the bicycle frame. 
         [0014]    In one advantageous embodiment of the present invention, the end, perpendicular portions of the wing members have at least one aperture on each wing member for a pin spanner-type tool to fit within one aperture of each wing to rotatably adjust the eccentric bottom bracket assembly in a clockwise or counterclockwise direction in its fully assembled state and retracted position within the shell of a bicycle. Once the assembly is adjusted for the proper chain tension, the wedge driver can be rotated in a clockwise direction to laterally displace the wedge members to co-act for circumferential expansion of the first and second wing members and the body member to tightly engage against the inner surface of the shell. 
         [0015]    The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a side view of an eccentric bottom bracket assembly of the present invention having a first and second wing members mounted on a body member. 
           [0017]      FIG. 2  is a cross-sectional side view of an eccentric bottom bracket assembly of the present invention showing a second wing member mounted on a body member. 
           [0018]      FIG. 3  is a cross-sectional side view of an eccentric bottom bracket assembly of the present invention showing a second wing member mounted on a body member and a wedge driver with two wedge members sitting on top of the body member with the lateral sides of the wedge members closely engaged and touching the wedge surfaces of the second wing member. 
           [0019]      FIG. 4  is a top view of an eccentric bottom bracket assembly of the present invention with the wedge driver with two wedge members positioned in the interior chamber and closely engaged between the two wedge surfaces of a first and second wing members and the two wedge members in a non-laterally displaced and retracted positions. 
           [0020]      FIG. 5  is a top view of an eccentric bottom bracket assembly of the present invention with the wedge driver with two wedge members positioned in the interior chamber and closely engaged between the two wedge surfaces of a first and second wing members and the two wedge members in a laterally displaced and expanded positions. 
           [0021]      FIG. 6  is a front view of an eccentric bottom bracket assembly of the present invention having a body member with a first and second wing members mounted on top of the body member with a wedge driver with two wedge members sitting on top of the body member and between the first and second wing members in the interior chamber with the wedge members engaged between the wedge surfaces of the wing members in a retracted position. 
           [0022]      FIG. 7  is a front view of an eccentric bottom bracket assembly of the present invention having a body member with a first and second wing members mounted on top of the body member with a wedge driver with two wedge members sitting on top of the body member and between the first and second wing members in the interior chamber with the wedge members engaged between the wedge surfaces of the two wing members in an expanded position. 
           [0023]      FIG. 8  is an exploded perspective view of the eccentric bottom bracket assembly showing a body member, a first and second wing members, a wedge driver with two wedge members and spring members prior to assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    The eccentric bottom bracket assembly of the present invention comprises of an adjustable assembly that allows either a bicyclist or any bicycle repairman to adjust the assembly to either tighten or loosen the chain when a chain has come loose or fallen off the chain sprocket.  FIG. 1  illustrates a side view of an eccentric bottom bracket assembly  10  of the present invention with a first wing member  200  and a second wing member  201  (not shown in this figure) mounted on top and over the body member  100  and circularly engaging the body member  100  forming an assembly  10  with a tubular and cylindrical shape. The first wing member  200  has wing surfaces  220  along the longitudinal axis of the body member  100  to fit on the wing surfaces of the body member  110  similarly located on the longitudinal axis of the body member  100 . The wing surfaces  110 ,  111  of the body member are to accommodate the wing surfaces of the first and second wing members  220 ,  221  to provide a fit between the first wing member  200 , the second wing member  201  (on the other side of the first wing member  200  but not shown in this figure) and over the body member  100  to provide a pivotal or movable connection at the wing surfaces  110 ,  111 ,  220 ,  221 . The length of the first wing member  200  is identical to the length of the body member  100  to fit together in providing the eccentric bottom bracket assembly  10 . In one preferred embodiment, the first wing member  200 , the second wing member  201  (on the other side which is not shown in this figure), and the body member  100  are further engageably held together with two spring members  400 ,  401  (not shown in this figure). The spring members fit within the slit portions of the body member  140  and the slit portions of the wing member  240  to provide engageability, expandability and flexibility for the first and second wing members  200 ,  201  to expand outwards by slidably moving on the wing surfaces  110 ,  111  of the body member by lateral displacement of the wedge members and altogether forming a tubular and cylindrical shape of the eccentric bottom bracket assembly  10  to fit within the inner shell of the bottom bracket of the bicycle frame. Expanding the first and second wing members  200 ,  201  away from the body member  100  tightly engages the wing members against the inner shell of the bicycle frame while retracting the first and second wing members  200 ,  201  disengages from the inner surface of the shell. The expandable and retractable moving action of the first and second wing members  200 ,  201  will be more readily shown and understood in other figures. The body member  100  also has an optional recess  120  with a large indentation to provide a lighter weight bottom bracket assembly  10 . The first wing member  200  also has a recess  230  to further lessen the overall weight of the bottom bracket assembly  10  whereby the outer surface of the body member  100  can be seen through the hollow recess  230  of the first wing member  200 . The shape of the recess  230  can be any size as long as the wing members  200 ,  201  can function to provide housing for the wedge driver  300  with the two wedge members  305 ′,  305 ″ and fit with the wing surfaces of the body member  110 ,  111 . The body member  100  and the first and second wing members  200 ,  201  can be made of any suitably hard material that resists wear and breakage, and is capable of being machined, molded, or otherwise fabricated to form a bottom bracket assembly that is light weight. 
         [0025]      FIGS. 2 and 3  illustrate cross-sectional side views of an eccentric bottom bracket assembly  10  of the present invention.  FIG. 2  shows a cross-sectional side view of the eccentric bottom bracket assembly comprising a body member  100 , a first wing member  200  and a second wing member  201 . Referring to  FIGS. 2 and 3 , the first wing member  200  is not shown for the purposes of demonstrating the cross-sectional view of the assembly  10 . The second wing member  201  is mounted on top of the body member  100  and circularly engaging the body member  100 . The body member  100  shows a hollow bore  105  to accommodate the pedal crank spindle or shaft of the bicycle which is not shown in this figure. The body member  100  also contains a recess  120  to provide a lighter weight bottom bracket assembly  10  of the present invention. In one embodiment of the present invention, the second wing member  201  has an internal wedge surface  250  that is concavely shaped with a retaining member  215 ″. A retainer member is a notch with corresponding projections in the shape of a hook to receive the wedge driver  300 . The slit portion of the second wing member  241  is shown for the spring member  400  to be disposed within the slit portion of the first and second wing members to flexibly and engageably hold together the body member  100 , the first wing member  200 , the second wing member  201 , and the wedge driver  300  with the two wedge members  305 . 
         [0026]      FIG. 3  shows a cross-sectional side view of the eccentric bottom bracket assembly  10  with the body member  100  and the second wing member  201  mounted on the body member  100  as shown in  FIG. 2 , further comprising a wedge driver  300  with the two wedge members ( 305 ′ and  305 ″). The cylindrical wedge driver  300  has two wedge members ( 305 ′ and  305 ″) which rotate through and around the wedge driver  300 . For assembly, the two wedge members  305 ′,  305 ″ are rotated through and around the threaded cylindrical portion  301  of the wedge driver  300  to screw on the two wedge members  305 ′,  305 ″ inwardly to the smooth cylindrical portion of the wedge driver  302 . The threaded cylindrical portion  301  is oppositely threaded such that the wedge members  305 ′,  305 ″ can be screwed on inwardly toward each other when rotating the wedge members on and around the wedge driver  300 . Likewise, counterclockwise rotation of the wedge driver  300  also laterally displaces the wedge members  305 ′,  305 ″ outwardly from each other due to the oppositely threaded cylindrical portions  301 . 
         [0027]    The two wedge members  305 ′,  305 ″ have lateral surfaces  350  which engageably fit on the internal wedge surfaces of the first wing member  250  (not shown in this figure) and internal wedge surface of the second wing member  251 . The retaining member  215 ″ from the wedge surface of the second wing member  251  and the retaining member  215 ′ from the wedge surface  250  of the first wing member (not shown in this figure) also hold in place the wedge driver  300 , particularly the projections hugging over and under the smooth cylindrical portion of the wedge driver  302 . The threaded cylindrical portion  301  of the wedge driver  300  is not touching any portion of the first or second wing member  200 ,  201  but sitting in the interior chamber  205  created between the first and second wedge surfaces  250 ,  251  of the first and second wing members  200 ,  201 , while the flat bottom surfaces of the wedge members  360 ′,  360 ″ (not shown) touch the top of the body member  100 . 
         [0028]      FIGS. 4 and 5  illustrate top views of the eccentric bottom bracket assembly  10  of the present invention, comprising a first wing member  200  and a second wing member  201 , sitting on over the body member  100  (not shown in this figure) tightly engaging a wedge driver  300  with the two wedge members  305 ′,  305 ″ in the interior chamber  205  between the first and second wing members  200 ,  201 . In one preferred embodiment, the eccentric bottom bracket assembly  10  is circularly and flexibly held together using round, flexible spring members  400 ,  401  fitting within the slit portions of the second wing member  241 , the slit portions of the body member  140 , and the slit portions of the first wing member  240 , to circulate around the bottom bracket assembly  10 . The bottom bracket assembly  10  in  FIG. 4  shows the cylindrical wedge driver  300  with the two wedge members  305 ′,  305 ″ engaged between the first wing member  200  and the second wing member  201 . The lateral surfaces  350  of the two wedge members  305 ′,  305 ″ are engaged and laterally touching the internal wedge surfaces  250 ,  251  of the first and second wing members  200 ,  201 . The retaining member  215 ′,  215 ″ of the first wing member  200  and the second wing member  201  have a notch with corresponding projections to receive the smooth cylindrical portion  302  of the wedge driver  300 , and also provides some support to hold the wedge driver  300  in place. The flat bottom surfaces  360  of the wedge members  305 ′,  305 ″ sit on top of and touch the body member  100  which is not shown in this view. The hollow wedge driver  300  can be rotated using any type of tool, preferably an allen wrench, through the opening  320  of the wedge driver  300  from either side, causing the oppositely threaded cylindrical portion  301  of the wedge driver  300  to laterally displace the first and second wedge members  305 ′,  305 ″ in opposite direction away from the smooth cylindrical portion  302  of the wedge driver  300 . As the two wedge members  305 ′,  305 ″ are oppositely and laterally displaced from the smooth cylindrical portion  302  due to rotation of the wedge driver  300 , the interior chamber  205  between the first and second wing members  200 ,  201  is widened. The interior chamber  205  between the first and second wing members  200 ,  201  is widened because the wedge members  200 ,  201  are shaped with slightly wider portions toward the smooth cylindrical portion  302  of the wedge driver  300  that are gradually tapered down to narrower portions facing away from the center. The lateral surfaces  350  of the wedge members  305 ′,  305 ″ are laterally and oppositely displaced from each other while moving along the internal wedge surfaces  250 ,  251  of the first and second wing members  200 ,  201 . As a result of the lateral displacement of the first and second wedge members  305 ′,  305 ″ away from each other, particularly the wider portions of the first and second wedge member  305 ′,  305 ″ moving outwardly away from each other causing the widening of the entire interior chamber  205  between the first and second wing members  200 ,  201 . The lateral displacement of the two wedge members  305 ′,  305 ″ further causes the first and second wing members  200 ,  201  to circumferentially expand outwardly away from the body member  100  to tightly engage against the inner shell of the bottom bracket area.  FIG. 5  shows the laterally displaced wedge members  305 ′,  305 ″ in opposite direction from each other with the widened interior chamber  205  which also simultaneously results in circumferential expansion of the two wing members  200 ,  201  away from the body member  100  causing circumferential expansion of the entire assembly  10 . 
         [0029]      FIGS. 6 and 7  illustrate front views of an eccentric bottom bracket assembly  10  of a preferred embodiment of the present invention, comprising a body member  100 , a first wing member  200  and a second wing member  201 , a wedge driver  300 , and a first and second wedge members  305 ′,  305 ″. In  FIG. 6 , the body member  100  has a bore  105  to accommodate the pedal crank spindle or shaft (not shown in this figure) that fits through the bore  105 . The diameter of the bore  105  or the inner circumference of the body member  100  is typically the diameter size of a conventional pedal crank spindle or shaft in the range of 1.0 to 1.8 inches. The outer diameter size of the body member  100  from one wing surface of the body member  110  to the other wing surface of the body member  111  is the diameter size of a conventional eccentric bottom bracket to fit within the inner shell of a bicycle frame (not shown in this figure). The nominal diameter of this outer diameter can be around 2⅛ inches. In a preferred embodiment, the body member  100  has two wing surfaces  110 ,  111  to accommodate the wing surfaces  220 ,  221  of the first and second wing members  200 ,  201  for a pivotal, hinged, movable or slidable connection. In a preferred embodiment, the two wing surfaces of the body member  110 ,  111  are concavely shaped to accommodate the convexly shaped wing surfaces of the wing members  220 ,  221 , however, the present invention is not limited to this particular shape of the wing surfaces of the body member  110 ,  111  or the wing surfaces of the wing members  220 ,  221 . The wing surfaces of the body member  110 ,  111  can be convexly shaped and the wing surfaces of the wing members  220 ,  221  can be concavely shaped to accommodate the wing surfaces of the body member  110 ,  111 . As long as the wing surfaces of the body member  110 ,  111  and the wing surfaces of the wing members  220 ,  221  are connected to provide a slidable movement without being confined, any shape or form can be used for the wing surfaces. 
         [0030]    The first wing member  200  and the second wing member  201  are mounted on top and over the body member  100  while the first and second wing members  200 ,  201  also encase a wedge driver  300  with the first and second wedge members  305 ′,  305 ″ as shown in  FIG. 6 . The first and second wing members  200 ,  211  have internal surfaces that are approximately cylindrical to mount on and over the cylindrical external surface of the body member  100  to complete a larger cylinder assembly  10  to fit within the bottom bracket area. The lateral surfaces of the wedge members  350 ′,  351 ″ are shown to touch the first and second wedge surfaces  250 ,  251  of the wing members  200 ,  201 . In a preferred embodiment, the wedge surfaces of the first and second wing members  250 ,  251  are slightly concavely shaped to fit with the slightly convexly shaped lateral surfaces of the wedge members  350 ′,  350 ″ for easily displacing the wedge members  305 ′,  305 ″ laterally, outwardly and inwardly on the wedge surfaces  250 ,  251  of the first and second wing members  200 ,  201  when the wedge driver  300  is rotated clockwise or counterclockwise (motion more easily understood in  FIGS. 4 and 5 ). However, the shape of the lateral surfaces of the wedge members  350 ′,  350 ″ is not limited to having a slightly convex shape and the wedge surfaces of the wing members  250 ,  251  having a slightly concave shape. The shape of the lateral surfaces of the wedge members  350 ′,  350 ″ and the wedge surfaces of the wing members  220 ,  221  can be modified as long as the wedge surfaces of the wing members  220 ,  221  fit with the lateral surfaces of the wedge members  350 ′,  350 ″. 
         [0031]    The end portion of the wedge driver  300  is shown in  FIGS. 6-7  with the first wing member  200  surrounding the wedge driver  300 . In a preferred embodiment of the present invention, the wedge driver  300  has an opening  320  shaped to accommodate insertion of a portably lightweight piece of tool, such as an allen wrench, to rotate the wedge driver  300 . The opening  320  is not limited to a shape to accommodate an allen wrench but can shaped in any form to be used with other easily portable and lightweight tools. As a tool is used to rotate the wedge driver  300 , the wedge members  305 ′,  305 ″ are laterally and outwardly displaced from the center or each other, enlarging the interior chamber  205  between the first and second wing members  200 ,  201  and the body member  100  in which the wedge driver  300  and the wedge members  305 ′,  305 ″ are positioned. While the two wedge members  305 ′,  305 ″ are laterally displaced, the enlarging of the interior space  150  among the first and second wing members  200 ,  201  and the body member  100  also causes circumferential and outward expansion of the first and second wing members  200 ,  201  away from the body member  100  as shown in  FIG. 7 , allowing the first and second wing members  200 ,  201  to tightly engage against the inner shell of the bottom bracket (not shown in this figure).  FIG. 7  shows the expanded position of the first and second wing members  200 ,  201  and the body member  100 . The expanded position can be shown in  FIG. 7  in which the expansion of the first and second wing members  200 ,  201  have circumferentially lifted up and away from the body member  100  leaving a slight interior space  150 . Rotating the wedge driver  300  by inserting a piece of tool through the opening  320  in the end section in a counterclockwise direction, the expanded first and second wing members  200 ,  201  can adjustably retract back to its previously unexpanded position as shown in  FIG. 6 . The assembly  10  can be unexpanded and retracted in order to loosen the assembly  10 , more particularly, the body member  100  and the first and second wing members  200 ,  201  toward each other and to disengage the assembly  10  to further rotatably adjust the assembly  10  for chain adjustment. 
         [0032]    Furthermore, the first and second wing members  200 ,  201  have end surfaces  260  with at least one aperture  210 ,  211  on each wing member. The first wing member  200  has at least one aperture  210 , and the second wing member  201  has at least one aperture  211 . The two apertures  210  and  211  from the first and second wing members  200 ,  201  are used by a bicyclist to insert a pin-spanner type wrench in each aperture  210 ,  211  from the first and second wing members  200 ,  201  to rotate the eccentric bottom bracket assembly  10  in a clockwise or counterclockwise direction with the bottom bracke assembly  10  in its retracted position as shown in  FIG. 6 . In a preferred embodiment, the first wing member  200  has three apertures  210 ′,  210 ″,  210 ′″ of varying aperture sizes on the end surfaces  260  of the first wing member  200 , and the second wing member  201  also has three apertures  211 ′,  211 ″,  211 ′″ of varying aperture sizes also on the end surfaces  260  of the second wing member  201 . However, each wing member  200  or  201  is not required to have all three apertures. Each wing member can have only one aperture  210  or  211  to accommodate a pin spanner-type wrench for rotatably adjusting the eccentric bottom bracket assembly  10 . Each of the first and second wing members  200 ,  201  can have as many apertures that can fit on the end surfaces  260 . The aperture sizes are preferably shaped to accommodate a conventional pin spanner-type wrench to easily rotate the eccentric bottom bracket assembly  10  either a clockwise or counterclockwise direction to adjust the chain on a bicycle (not shown in this figure). Adjusting the eccentric bottom bracket assembly  10  is performed when the eccentric bottom bracket assembly  10  is in the retracted position as shown in  FIG. 6  since the first and second wing members  200 ,  201  and the body member  100  are not expanded and tightly engaged against the inner shell of the bottom bracket of the bicycle frame. 
         [0033]      FIG. 8  is an exploded view of the eccentric bottom bracket assembly  10  of the present invention in an unassembled state. The body member  100  has a recess  120  in the inner portion of the cylindrical portion on a longitudinal axis for a lighter weight eccentric bottom bracket assembly  10 . The outer portions of the body member  100  on a longitudinal axis has outwardly protruded portions with wing surfaces  110 ,  111  of the body member  100  to fit with the first and second wing members  200 ,  201 . The body member  100  is a hollow cylinder with a bore  105  with internal threaded portions  135  to accommodate a pedal crank spindle or shaft. A typical pedal spindle&#39;s diameter size can range from about 1.0 to 1.8 inches, therefore, the diameter of the bore can be within that range to accommodate the pedal shaft. The nominal diameter of the body member  100  with the first and second wing members  200 ,  201  mounted on and over the body member  100  can be around 2⅛ inches. The body member  100  also has at least one slit portion  140  for the spring member  400  to hold the eccentric bottom bracket assembly  10  altogether. In a preferred embodiment, the first spring member  400  and the second spring member  401  are used to hold the eccentric bottom bracket assembly together, however, the present invention is not limited to having two spring members  400 ,  401 . The eccentric bottom bracket assembly  10  can also be assembled and joined together by using only one spring member  400 . Even though the body member  100 , the first and second wing members  200 ,  201  are made out of aluminum which are anodized, it is contemplated that the assembly  10  may comprise any relatively light-weight alloy, composite, anodized metal, or any suitably hard material having sufficient structural strength to withstand and maintain the assembly  10  in an engaged position to the inner surface of the shell. 
         [0034]    The first and second wing members  200 ,  201  are shown in  FIG. 8  which mount on the cylindrical portion of the body member  100 . The wing surfaces  220 ,  221  of the first and second wing members  200 ,  201  fit with the wing surfaces of the body member  110 ,  111  to allow for a movable or slidable connection. The wing surfaces  220 ,  221  of the wing members  200 ,  201  are touching the wing surfaces of the body member  110 ,  111  while the first and second wing members  200 ,  201  are free to slidably pivot in a latitudinal axis of the body member  100  with the externally inward force provided by the spring members keeping together the wing members  200 ,  201  on the wing surfaces of the body member  110 ,  111 . In a preferred embodiment, the wing surfaces of the body member  110 ,  111  are concavely shaped to fit with the convexly shaped wing surfaces  220 ,  221  of the first and second wing members  200 ,  201 , however, the shape of the wing surfaces  220 ,  221 ,  110 ,  111  is not limited to this design. The wing surfaces of the body member  110 ,  111  can be convexly shaped, straight, curved, hinged or angled in a different manner as long as there is a fit between the wing surfaces of the body member  110 ,  111  and the wing surfaces of the first and second members  220 ,  221 . The first and second wing members  200 ,  201  also have a recess  230  to lessen the overall weight of the eccentric bottom bracket assembly  10 . In a preferred embodiment, the first and second wing members  200 ,  201  also have slit portions  240 ,  241  which align with the slit portions of the body member  140  forming a continuous cylindrical pathway for the spring members  400 ,  401  to encircle and hold together the eccentric bottom bracket assembly  10 . The spring members  400 ,  401  are flexible and expandable so that the first and second wing members  200 ,  201  can flexibly and circumferentially expand out and flexibly retract back in. 
         [0035]      FIG. 8  shows the wedge members  305 ′,  305 ″ already screwed over, through and around the wedge driver  300 . The wedge members  305 ′,  305 ″ can be inwardly screwed and rotated on and around the threaded cylindrical portion  301  of the wedge driver  300  until the wedge members  305 ′,  305 ″ come to a halt at the middle, smooth cylindrical portion  302  of the wedge driver. Once the wedge members  305 ′,  305 ″ are screwed onto the wedge driver  300 , the wedge driver  300  with the wedge members  305 ′,  305 ″ are ready to be further assembled with the rest of the parts of the assembly  10  including the first and second wing members  200 ,  201  and the body member  100 . The wedge driver  300  with the wedge members  305 ′,  305 ″ fits within the interior chamber  205  or between the first and second wing members  200 ,  201  and over the body member  100 . The lateral surfaces of the wedge members  350 ′,  350 ″ are touching the first and second wedge surfaces  250 ,  251  of the first and second wing members  200 ,  201 . The flat bottom surfaces of the wedge members  360  are touching the top of the body member  100  in an unexpanded and assembled state. Even though the retaining member  215 ′,  215 ″ of the first and second wing members  200 ,  201  cannot be seen in this figure, the retaining members  215 ′,  215 ″ provide a notch and corresponding projections to hold the smooth cylindrical portion  302  of the wedge driver  300  in its assembled position with the wedge members. When first and second wing members  200 ,  201  are mounted on the body member  100  with adjoining wing surfaces, the wedge driver  300  with the wedge members  305 ′,  305 ″ is placed between the first and wing members  200 ,  201 , and all the parts can be held altogether using at least one spring member  400  making it the eccentric bottom bracket assembly  10 . In the preferred embodiment, the first and second spring members  400 ,  401  are used to hold the eccentric bottom bracket assembly  10  comprised of the body member  100 , the first and second wing members  200 ,  201 , and the wedge driver  300  with the first and second wedge members  305 ′,  305 ″. In one preferred embodiment, the wedge driver  300  is a hollow structure with a threaded cylindrical portion  301  made out of steel, however, any appropriate screw or device can be used for allowing lateral displacement of the wedge members  305 ′,  305 ″ made of alloy, composite or other materials. 
         [0036]    The present invention can be practiced in this one preferred embodiment when a bicyclist assembles the bottom bracket assembly  10  by joining the body member  100 , the first and second wing members  200 ,  201 , the wedge driver  300  with the first and second wedge members  305 ′,  305 ″, and at least one spring member  400 . The bottom bracket assembly  10  is assembled to be inserted within the bottom bracket of the shell of the bicycle frame. When the bottom bracket assembly  10  is inserted within the bottom bracket of the shell of the bicycle frame, the pedal shaft can be inserted into the bore  105  of the body member  100  and rotated to tighten the pedal crank spindle with pedals against the internal threaded portion  135  of the body member  100 . The chain tension can be adjusted by rotatably adjusting the bottom bracket assembly  10  by inserting a pin spanner type wrench through at least one aperture  210 ,  211  located on the end surfaces  260  of the first and second wing members and rotatably adjusting the bottom bracket assembly  10  until the desired position is found. To keep the desired position of the bottom bracket assembly  10 , a bicyclist can insert a tool through the opening  320  of the wedge driver  300  to rotate the wedge driver  300  in a clockwise direction to tighten the bottom bracket assembly  10  against the inner surface of the shell of a bicycle frame. When the desired position of the bottom bracket assembly  10  is secured and chain tension adjusted, the bicycle is ready for riding. If the chain tension needs readjusting or the chain falls off, a bicyclist can stop and loosen the bottom bracket assembly  10  by inserting a tool through the opening  320  of the wedge driver  300  to rotate the wedge driver  300  in a counterclockwise direction until the entire bottom bracket assembly  10  is loosened from the inner surface of the shell of a bicycle frame. The process of rotatably adjusting the bottom bracket assembly  10  can be repeated to adjust the bottom bracket assembly  10  and to find the desired position for the bottom bracket assembly  10  for optimal chain tension prior to tightening and securing the bottom bracket assembly  10 . 
         [0037]    It can also be appreciated by one skilled in the art that while two spring members are depicted for use in the eccentric bottom bracket assembly  10 , one spring member or multiple spring members may be incorporated in the assembly by varying the slit portions of the assembly. Taking out a spring member or adding on more spring members requires, however, a further modification of the assembly. Consequently, within the scope of the appended claims, it will be appreciated that the invention can be practiced otherwise with many other modifications and variations ascertainable to those of skilled in the art than is specifically described herein.