Abstract:
A combined chain guide and chain ring protector for a bicycle for off-road use having a lower bracket sleeve, a chain ring around which a drive chain extends and a chain ring outer radius. The protector includes a mounting bracket secured at the lower bracket sleeve and a guard mounted thereto. An outer edge of the guard extends beyond the outer radius of the chain ring, thereby protecting a portion of the chain ring from inadvertent impacts. The chain guide extends from the mounting bracket along a path of the drive chain, and preferably includes an upper guide having an inner barrier positioned inboard of the bicycle chain an outer barrier positioned outboard of the inner barrier and an upper barrier positioned above the bicycle chain for preventing the chain from derailing from the chain ring in an upward direction.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates generally to devices for preventing damage to the chain ring, chain, crank and bottom bracket of a bicycle and devices that maintain the chain safely on the teeth of the chain ring. Specifically, the invention improves upon the prior art by uniquely integrating a chain guide with an improved chain ring protector. 
         [0003]    2. Description of the Related Art 
         [0004]    The forward portion of the bicycle drivetrain, consisting of the bottom bracket bearings, crank, chain ring, and chain is vulnerable to damage from underside impacts with rocks, stumps and other road and trail obstacles. The need to protect this part of the bicycle from such impacts, particularly during off-road cycling, has been addressed with round plates of metal or plastic that rotate with the chain ring and also with appliances that attach to the bicycle&#39;s lower frame tubes and act as a protective undercarriage. 
         [0005]    An even more practical device is disclosed in U.S. Pat. No. 7,066,856, which is incorporated herein by reference, and which is assigned to the assignee of the current application. It consists of a bracket portion that mounts to the bottom bracket shell of the bicycle frame and a semi-circumferential guard portion that extends from the bracket to below the chain ring. The guard portion deflects trail obstacles that otherwise would damage the chain ring or other forward drivetrain components. 
         [0006]    In addition to a device for protecting the chain ring from impacts, it is advantageous for the bicycle to be equipped with a device for maintaining the chain securely on the chain ring. The same rough terrain that presents underside obstacles capable of damaging the drivetrain can, when struck by the bicycle&#39;s wheels, jar the entire bicycle, thereby causing the chain to shake violently enough to derail it from the chain ring. A derailed chain can result in damage to mechanical components as well as inconvenience and even physical danger to the rider. 
         [0007]    The need exists for a chain guide and chain ring protector. Other novel advantages of the combined device will become apparent in the following specification. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    A mounting bracket is preferably affixed to the bottom bracket shell of the bicycle. An upper chain guide is affixed to an upper extension of the bracket, and the upper guide preferably contains the chain on three sides of the chain: inner, outer and upper. A lower guide retains the chain on an idler pulley, forms a barrier against derailment during backpedaling and is attached to the mounting bracket. A guard with a portion extends downwardly from the mounting bracket past the chain ring and a relatively straight portion of the guard extends rearwardly along the lower chainline. The rearward bracket extension that provides the point of attachment for the lower guide also reinforces the structural integrity of the guard. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0009]      FIG. 1   a  is a side view illustrating a bicycle frame showing portions of the downtube, seat tube, right chainstay, and bottom bracket shell with integral bosses for chainguide attachment. 
           [0010]      FIG. 1   b  is a side view illustrating the bracket of the present invention in its preferred embodiment, attached to the bosses of the bottom bracket shell. 
           [0011]      FIG. 2   a  is a side view illustrating the bracket and guard. 
           [0012]      FIG. 2   b  is a side view illustrating the bracket with guard and inner members of upper and lower chain guides. 
           [0013]      FIG. 2   c  is a side view illustrating the bracket with guard and upper and lower guides complete. 
           [0014]      FIG. 3  is a side view illustrating the device with crank, chain ring, and chain. 
           [0015]      FIGS. 4   a  and  b  are front views illustrating the device with crank, chain ring, and chain. 
           [0016]      FIGS. 5   a  and  b  are rear views illustrating the device with crank, chain ring, and chain. 
       
    
    
       [0017]    In describing the preferred embodiment of the invention which is illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited to the specific term so selected and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. For example, the word connected or terms similar thereto are often used. They are not limited to direct connection, but include connection through other elements where such connection is recognized as being equivalent by those skilled in the art. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0018]      FIG. 1   a  shows a portion of a conventional bicycle frame  1  consisting of the seat tube  2 , the downtube  3 , and the right chainstay  4 . The tubes join at the bottom bracket shell  5 , which contains radial tabs, such as the bosses  11 , for attachment of a chain guide, and through which a conventional crank rotatably extends. The terms “bottom bracket shell” and “lower bracket sleeve” are interchangeable. 
         [0019]    Referring to  FIG. 1   b,  the preferred embodiment of the mounting bracket  20  of the present invention is shown mounted in its operable position to the bottom bracket shell  5  by the screws  31  inserted through the arcuate slots  24  formed at spaced locations on the bracket  20 , preferably aligned at International Standard Chain Guide (ISCG) mounting locations, for mounting to the bosses  11  on the bottom bracket shell  5  at ISCG positions. Although it is preferred for the slots  24  to be formed at ISCG locations, it should be noted that there may be other standards, including but not limited to the known ISCG 05 standard, which dictate the locations of mounting slots or other apertures, and may require fasteners, mounting devices or components thereof. Such standards are known to the skilled artisan to require alternative slot or aperture locations and/or mounting components, and such alternatives are substitutes for the preferred embodiment. Although it is preferred to mount the mounting bracket to the bottom bracket shell using screws or other fasteners, it is contemplated to clamp the mounting bracket in place against, or in close proximity to, the bottom bracket shell as described in U.S. Pat. No. 7,066,856, and particularly at column 4, lines 3-16, such as by a lip on the mounting bracket that is compressed between the bottom bracket cup and the bottom bracket shell of the frame. 
         [0020]    Radial tabs with threaded apertures (the bosses  11 ) are shown formed at spaced locations around the bottom bracket shell  5  in  FIG. 1   a  in accordance with the ISCG and ISCG 05 standards. However, it is also known to substitute for such radial tabs a wider shoulder (not illustrated), such as by forming a thicker shell wall or by merely extending the width of the radial tabs around the shell&#39;s entire periphery to form a contiguous radial lip, around the bottom bracket shell with threaded apertures at similarly spaced locations. Other alternatives are also known. The skilled person will recognize the modifications that are necessary to fasten the components of the invention to the alternative structures. 
         [0021]    The upper extension  25  of the bracket defines the attachment slot  26  for attaching the upper guide of the chain guide, as discussed in more detail below. The lower extension  28  of the bracket defines the attachment slot  29  for attaching the lower guide of the chain guide. The bracket  20  further defines, on its perimeter, the lugs  21  with the holes  23  for attaching the guard  50 . 
         [0022]    Referring to  FIG. 2   a , the cup of the bottom bracket bearing set  40  is shown installed to the bicycle frame  1  within the inner diameter of the bracket  20 . The guard  50  is also secured at its semi-circumferential portion  53  to the lugs  21  of the bracket by the screws  61  extending through the holes  23  to attach to conventional nuts (not shown). Extending rearward from the semi-circumferential portion  53  of the guard is the straight portion  55 , containing at its rearmost extremity the attachment slot  59 . Preferably, the semi-circumferential portion  53  is integral with the straight portion  55 . The guard  50  is preferably made of a tough, strong material, such as aluminum or polycarbonate. 
         [0023]    Referring to  FIG. 2   b , the inboard upper guide  70  contains the attachment hole  73 , and the guide  70  is secured to the upward extension  25  of the bracket by a fastener, such as a screw, extending through the hole  73  and the slot  26 . The idler pulley  82  likewise contains the hole  83  and the pulley  82  is rotatably mounted to the guard  50  and bracket  20  by extending a fastener, such as a screw, through the slots  29  and  59  and the hole  83 . 
         [0024]    Referring to  FIG. 2   c , the outboard upper guide  72  is attached to both the inboard upper guide  70  and the bracket upper extension  25  by means of the screw, which preferably extends through the hole  73  and slot  26 , and the nut  79  (not visible). The lower guide  80  is attached with the idler pulley (not visible in  FIG. 2   c ) to both the guard  50  and bracket lower extension  28  by means of the screw, which preferably extends through the hole  83 , the slot  59  and the slot  29 , and the nut  89  (not visible). 
         [0025]    Referring to  FIG. 3 , the device is seen fully mounted to cooperate with the crank  100 , the chain ring  120 , and the chain  150 . The outboard upper guide  72  is positioned where the chain  150  engages the top of the chain ring  120  and is most vulnerable to shaking motion that could derail the chain from the chain ring. The lower guide  80  is positioned where the pulley  82  aligns with the teeth of the chain ring where the chain exits from the teeth of the chain ring during forward pedaling. Due to its position, the lower guide  80  ensures that the chain remains engaged with the chain ring over a larger part of the chain ring&#39;s perimeter than if the chain merely extended from the chain ring at the lowest point of the chain ring. The lower guide  80  also serves to prevent derailment, especially during backpedaling. 
         [0026]    Still referring to  FIG. 3 , the semi-circumferential portion  53  of the guard  50  extends radially downwardly and outwardly past the chain ring along that portion of the chain ring most likely otherwise to suffer damage from underside impacts with obstacles as the bicycle moves forward. Preferably, the configuration of this portion of the apparatus is consistent with the configuration in U.S. Pat. No. 7,066,856, which is incorporated herein by reference. The straight portion  55  of the guard additionally protects the portion of the chain and chain ring that extends just rearward of the vertical centerline of the bottom bracket. The straight portion  55  of the guard further protects the lower guide  80  from damage from underside impacts. 
         [0027]    Still referring to  FIG. 3 , the screw-and-nut  89  that attaches the lower guide and idler pulley (not visible in  FIG. 3 ) to the bracket  20  also attaches the guard  50  to the bracket  20 , providing support to the straight portion  55  of the guard and adding strength, rigidity and structural integrity to the assembly as a whole. 
         [0028]    Referring to  FIG. 4   a  and magnified view  FIG. 4   b , the device is seen from the front with crank  100 , chain ring  120 , and chain  150 , which are moving parts that make up the drivetrain, along with the bottom bracket spindle and any other moving, bicycle-propelling components. The inboard upper guide  70  forms an inner barrier to prevent the chain  150  from derailing toward the bicycle frame  1 . The outboard upper guide  72  forms an outer barrier that prevents the chain from derailing away from the bicycle frame  1 . Additionally, the two guides  70  and  72  combined form an upper barrier to prevent the chain from being dislodged upwardly off the chain ring even if the chain is violently shaken. 
         [0029]    Referring to  FIG. 5   a  and magnified view  FIG. 5   b , the device is seen from the back with crank  100 , chain ring  120 , and chain  150 . The chain  150  wraps up and over the idler pulley  82 , outboard of which is the lower guide  80  and inboard of which are the straight portion  55  of the guard  50  and the lower extension  28  of the bracket  20 . The lower guide  80  forms an outer barrier against chain derailment. The chain tends to be retained and tensioned by the idler pulley  82 , in addition to which the lower guide  80  forms a barrier to prevent the chain from derailing outboard away from the frame  1 . It can also be seen that the straight portion  55  of the guard extends below the idler pulley  82 , the chain  150  and the lower guide  80 , thereby protecting these parts from damage from underside impacts. 
         [0030]    Therefore, the bracket  20  is attached to the bottom bracket shell by mounting to the bosses  11  as described herein. This attachment forms an extremely strong structure that mounts the bracket  20  where it preferably makes no contact with drivetrain components. This is preferred so that the bracket  20  does not negatively impact bicycle operation, whether the bracket  20  is attached to the bosses  11  or by any of the alternative attachment structures. The guard  50  is attached to the bracket  20  at the perimeter lugs  21  and the lower extension  28 . This configuration mounts the guard  50  to the bracket  20  with a very strong attachment, and extends the guard  50  rearwardly from the leading edge of the chain ring to significantly behind the chain ring to protect the lower chain guide components and chain. Such protection of the rearward components is extremely advantageous, and because of the cooperation between the guard components and the integrated guide components, this forms a stronger and more protective device. Thus, the invention is lighter, stronger and more protective of the bicycle components than the prior art devices or combinations of the prior art. 
         [0031]    This detailed description in connection with the drawings is intended principally as a description of the presently preferred embodiments of the invention, and is not intended to represent the only form in which the present invention may be constructed or utilized. The description sets forth the designs, functions, means, and methods of implementing the invention in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and features may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention and that various modifications may be adopted without departing from the invention or scope of the following claims.