Abstract:
A bicycle derailleur comprises a first base member structured to be detachably mounted to a bicycle frame, wherein the first base member has a first abutment; a second base member structured to be mounted to the first base member, wherein the second base member has a second abutment that faces the first abutment of the first base member and the first and second base members define a housing space between them; a drive mechanism at least partially disposed in the housing space; a link mechanism that moves in response to movement of the drive mechanism; a chain guide coupled to the link mechanism for moving a chain among a plurality of sprockets; and a misalignment inhibiting structure disposed between the first base member and the second base member to inhibit misalignment of the drive mechanism as a result of an external force.

Description:
BACKGROUND OF INVENTION  
         [0001]    The present invention is directed to bicycles and, more particularly, to a bicycle derailleur with a structure that inhibits misalignment of a drive mechanism relative to first and second base members.  
           [0002]    Bicycles are used for general transportation as well as for sports and recreation. Such potential uses have resulted in the development of bicycles that are comfortable to ride under a variety of riding conditions and are suitable for a wide variety of riding purposes. Not surprisingly, bicycles that have some provision for the automation of various components to accommodate a particular riding environment have become very popular.  
           [0003]    Most bicycles currently have transmissions that allow the rider to select a suitable gear ratio from among a plurality of available gear ratios as the riding conditions change. Such transmissions may include a derailleur that is detachably secured to the rear end of the bicycle frame and is used to engage a chain with one of a plurality of sprockets that are mounted on the hub axle of the rear wheel. Conventional rear derailleurs comprise a base member mounted on the rear end of the bicycle frame, a four-point link mechanism mounted to the base member, and a chain guide mounted to the four-point link mechanism. During operation of the rear derailleur, the four-point link mechanism moves the chain guide in the direction of the hub axle, and the chain guide switches the chain to a desired one of the plurality of sprockets.  
           [0004]    Recently developed rear derailleurs include a drive mechanism, such as a rotating motor, housed within the base member. More specifically, the base member may comprise a plurality of members that form a housing space, and the drive mechanism may be disposed within the housing space. The four-point link mechanism is controlled by this drive mechanism, thus allowing the rear derailleur to be more easily operated in both automatic and manual shifting modes.  
           [0005]    When such conventional bicycle drive mechanisms are mounted on the rear derailleur, the plurality of base members can become misaligned with each other due to impacts on the base member caused by falls as well as by vibrations and shocks caused by changes in the surface of the road. This also causes the drive mechanism to become misaligned in the housing space between the base members, thus adversely affecting the ability of the derailleur to precisely shift the chain from one sprocket to another.  
         SUMMARY OF INVENTION  
         [0006]    The present invention is directed to various features of a bicycle derailleur. In one embodiment, a bicycle derailleur comprises a first base member structured to be detachably mounted to a bicycle frame, wherein the first base member has a first abutment; a second base member structured to be mounted to the first base member, wherein the second base member has a second abutment that faces the first abutment of the first base member such that the first and second base members define a housing space between them; a drive mechanism at least partially disposed in the housing space; a link mechanism that moves in response to movement of the drive mechanism; a chain guide coupled to the link mechanism for moving a chain among a plurality of sprockets; and a misalignment inhibiting structure disposed between the first base member and the second base member to inhibit misalignment of the drive mechanism as a result of an external force. Additional inventive features will become apparent from the description below, and such features alone or in combination with the above features may form the basis of further inventions as recited in the claims and their equivalents. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0007]    [0007]FIG. 1 is a side view of a particular embodiment of a derailleur;  
         [0008]    [0008]FIG. 2 is a view of a particular embodiment of a drive mechanism disposed between a pair of base members;  
         [0009]    [0009]FIG. 3 is an exploded view of the base members and drive mechanism;  
         [0010]    [0010]FIG. 4 is a view of another embodiment of a drive mechanism disposed between a pair of base members; and  
         [0011]    [0011]FIG. 5 is a view of another embodiment of a drive mechanism disposed between a pair of base members.  
     
    
     DETAILED DESCRIPTION  
       [0012]    [0012]FIG. 1 is a side view of a particular embodiment of a rear derailleur  1 . Rear derailleur  1  comprises a first base member  2  and separate second base member  3 , a drive mechanism  4  disposed between the first and second base members  2  and  3 , a four-point link mechanism  5  pivotably coupled to the first and second base members  2  and  3 , and a chain guide  8  pivotably coupled to the four-point link mechanism  5 .  
         [0013]    As shown in FIGS. 1 and 3, four-point link mechanism  5  comprises link shafts  22  mounted on the drive mechanism  4 , first and second link members  23  and  24  pivotably mounted about the link shafts  22 , a biasing member  25  that biases the first and second link members  23  and  24  in one of the pivoting directions, and a coupler  26  pivotably mounted to the other ends of the first and second link member  23  and  24 . Biasing member  25  is mounted diagonally between the link shaft  22  at the first end of first link member  23  and the link shaft  22  at the second end of second link member  24 .  
         [0014]    As shown in FIG. 1, chain guide  8  comprises a pair of guide frames  28  that rotatably support a pair of guide sprockets  27  such that guide sprockets  27  are sandwiched between the pair of guide frames  28 . Guide frames  28  are mounted to coupler  26  so that one end of each guide frame  28  pivots around an axis parallel to the hub axle  6 .  
         [0015]    First base member  2  is detachably mounted on the rear end of a bicycle frame  9 . As shown in FIG. 3, first base member  2  forms a housing space that opens towards second base member  3 , and an abutment  30   a  is formed on a side of first base member  2  that faces second base member  3 . Threaded openings  10  are formed at an upper portion of first base member  2 , and threaded openings  10   a  are formed at a lower portion of first base member  2 , wherein the threaded openings  10  and  10   a  face second base member  3 . A through hole  12  is formed in the top surface of first base member  2  to allow a control cable  11  to be attached to drive mechanism  4 .  
         [0016]    Second base member  3  forms a housing space that opens towards first base member  2 , and an abutment  30   b  is formed on a side of second base member  3  that faces first base member  2 . Bolt openings  13  are formed at an upper portion of second base member  3 , and bolt openings  13   a  are formed at a lower portion of second base member  3 , wherein the bolt openings  13  and  13   a  face the threaded openings  10  and  10   a,  respectively, in first base member  2 . In this embodiment, abutments  30   a  and  30   b  contact each other when first base member  2  and second base member  3  are assembled together, and a housing space is formed on the inside of first and second base members  2  and  3 .  
         [0017]    A first misalignment-inhibiting or interlocking structure  14   a  is disposed between first base member  2  and second base member  3  at threaded openings  10  and bolt openings  13 . As shown in the upper right portion of FIG. 3, first misalignment-inhibiting structure  14   a  comprises recesses  15  and tubular guides  16 . Recesses  15  are concentrically formed in the mutually opposed faces of first and second base members  2  and  3  at threaded openings  10  and bolt holes  13 . Tubular guides  16  pass through openings  20  in drive mechanism  4  and are disposed in recesses  15  such that the ends of tubular guides  16  contact floors  18  of recesses  15 . Bolts  17  extend through bolt openings  13  and tubular guides  16  and screw into threaded openings  10  in first base member  2 .  
         [0018]    As shown in FIGS. 2 and 3, the shapes of first abutment  30   a  and second abutment  30   b  form a second misalignment-inhibiting or interlocking structure  14   b  at a junction  19  between first base member  2  and second base member  3 . More specifically, first abutment  30   a  includes a substantially straight first abutment portion near the top of first base member  2 , a substantially straight second abutment portion extending at an incline from the first abutment portion, and a substantially straight third abutment portion extending from the second abutment portion. The second abutment portion is inclined relative to the third abutment portion, and the first abutment portion is aligned offset substantially parallel to the third abutment portion. Similarly, second abutment  30   b  includes a substantially straight first abutment portion near the top of second base member  3 , a substantially straight second abutment portion extending at an incline from the first abutment portion, and a substantially straight third abutment portion extending from the second abutment portion. The second abutment portion is inclined relative to the third abutment portion, and the first abutment portion is aligned offset substantially parallel to the third abutment portion.  
         [0019]    Drive mechanism  4  is sandwiched between first base member  2  and second base member  3  and is positioned by the tubular guides  16  that extend through the openings  20  in drive mechanism  20 . A cable attachment component  21  for the control cable  11  is provided on the side of drive mechanism  4  that faces first base member  2 .  
         [0020]    During operation, control signals for controlling drive mechanism  4  according to changes in the riding conditions are received by drive mechanism  4  through cable  11  at cable attachment component  21 . Drive mechanism  4  operates in response to these control signals, and four-point link mechanism  5  mounted on link shafts  22  driven by drive mechanism  4  moves accordingly. When first and second link members  23  and  24  pivot, guide frames  28  move in the direction of the hub axle, and the chain  7  supported by guide sprockets  27  is switched to a desired one of the plurality of sprockets  50 .  
         [0021]    When a conventional derailleur is operated in this manner, first and second base members  2  and  3  can become misaligned if derailleur  1  is subjected to impact during falls or is subjected to vibrations and/or shocks resulting from changes in the road surface. This, in turn, causes misalignment of drive mechanism  4 . Stress resulting from misalignment of first and second base members  2  and  3  also can be transmitted from first and second base members  2  and  3  through the attachment bolts to the drive mechanism  4 . To ensure satisfactory derailleur performance in such circumstances, the stability of the drive mechanism  4  disposed between the first and second base members  2  and  3  must be maintained. In this embodiment, the first misalignment-inhibiting structure  14   a  prevents forces applied to the first and second base members  2  and  3  from being transmitted to the drive mechanism  4  because such forces are communicated through the tubular guides  16  from one base member to the other through the floors  18  in the recesses  15 . In other words, the forces that could potentially be transmitted through the bolts  17  to the drive mechanism  4  is absorbed and buffered by the guides  16 , thus protecting the drive mechanism  4  against such external forces. This makes it possible to maintain and ensure the stability of the drive mechanism  4  disposed between the first and second base members  2  and  3 . The second misalignment-preventing member  14   b  also directly transmits forces between the first and second base members  2  and  3  through junction  19  and also inhibits relative rotation between the first and second base members  2  and  3  in response to external forces on the first and second base members  2  and  3 . This, too, makes it possible to maintain and ensure the stability of the drive mechanism  4  disposed between the first and second base members  2  and  3 .  
         [0022]    While the above is a description of various embodiments of inventive features, further modifications may be employed without departing from the spirit and scope of the present invention. For example, the first and second abutments  30   a  and  30   b  of the second misalignment inhibiting structure  14   b  in the above embodiment had an inclined intermediate portion, but the shape of the abutments can take many forms in order to resist external forces. As shown in FIG. 4, the intermediate portions of the abutments  30   a  and  30   b  may be perpendicular to one or both of the adjacent abutment portions to form a perpendicular abutment  40 . Such an abutment helps to inhibit misalignment caused by shear forces applied to the first and second base members  2  and  3 .  
         [0023]    As shown in FIG. 5, a second misalignment-inhibiting structure  14   b  may include an abutment  40   b  provided at the bottom end of a first base member  2   b  for contacting the entire bottom surface of a second base member  3   b.  In this case as well, it is possible to inhibit misalignment resulting from shear forces applied to the first and second base members  2   a  and  2   b  and to inhibit frictional forces applied to the junction  19 .  
         [0024]    In the previous embodiments, the first base member  2  was directly bolted to the frame  9 , but any attachment method that ensures integrity with the frame  9  may be used. For example, first base member  2  can be integrated with frame  9  by means of a bracket.  
         [0025]    The size, shape, location or orientation of the various components may be changed as desired. Components that are shown directly connected or contacting each other may have intermediate structures disposed between them. The functions of one element may be performed by two, and vice versa. The structures and functions of one embodiment may be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature that is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the scope of the invention should not be limited by the specific structures disclosed or the apparent initial focus or emphasis on a particular structure or feature.