EXTENSION BRACKET FOR BICYCLE REAR DERAILLEUR

Abstract: Extension bracket for lowering the rear derailleur assembly of a bicycle so that an oversized, high torque gear can be added to the rear gear cluster of the bicycle. With reference to Fig. 3 of the drawing, said bracket includes a plate (10) provided with a pair of elongated, parallel slots (14 and 16). The bicycle's rear axle stud (36) and nut (38) adjustably engage an upper portion of the wider slot (14), and a nut and bolt (18) adjustably attach the bicycle's rear derailleur assembly (40) to a lower portion of the wider slot (14). Narrow slot (16) provides supplemental adjustable attachment of the plate (10) to the bicycle's frame (32) and rear derailleur assembly (40) by means of a pair of fasteners (20 and 22). When the extension bracket is in place an oversized gear (46) can be accommodated by the extended derailleur assembly. The gear (46) greatly increases the torque that can be developed at the rear wheel and thus enhances the hill climbing capabilities of the bicycle.

Description: Dgscription Extension Bracket for Bicvcle Rear Derailleur Technical. Field My invention relates to bicycle accessories and more particularly to accessories which improve the performance of a bicycle's powering mechanism. With the type of bicycle having at least one crank gear, a cluster of gears coupled to the rear wheel axle, a drive chain engaged with the crank gear, and a rear derailleur mechanism for selectively engaging the drive chain with one of the rear cluster of gears, a bicyclist can produce the greatest amount of rear wheel torque when the largest gear of the rear cluster is engaged. Thus the maximum torque developed at the rear wheel has heretofore been limited by the largest gear a standard rear derailleur can accomodate, which is a 38 tooth alpine gear. Unfortunately, even with a 38 tooth gear insufficient torque is produced to climb some very steep grades. Background Art Prior to this invention a bicycle's rear cluster of gears could not include a gear with more than 38 teeth unless a standard rear derailleur mechanism were modified to accomodate it. Modifying a derailleur mechanism has many disadvantages including decreased reliability of the mechanism, and the non-reversibility of such modifi¬ cations. Disclosure of the Invention In accordance with the present invention, I provide a rear derailleur 'extension bracket comprising an elongated plate provided with a pair of spaced, parallel slots, the bracket being associated with fasteners which OMPI attach the bracket between the rear axle assembly and the rear derailleur mechanism. The extension bracket lowers the derailleur so that it can accomodate an oversized gear added to the rear cluster of gears. My extension bracket is advantageous in that it is simple in structure, and does not impair the performance nor does it modify the construction of the bicycle's original rear derailleur. Since the rear derailleur is radially extended from its normal position, much larger rear gears can be used with a resultant enhancement of the bicycle's hill climbing capabilities. Furthermore, the slotted structure of the bracket allows it to be used with virtually any make of bicycle, and to be adusted as perfectly as possible to a particular bicycle. grief Description of the Drawings The details of my invention will be described in connection with the accompanying drawing, in which Fig. 1 is an elevational view; Fig. 2 is a cross-sectional view along line 2-2 of Fig. 1; and Fig. 3 is an elevational view of the bracket operationally attached to a bicycle. Best Mode for Carrying Out the Invention Referring to the drawing, a rear derailleur extension bracket 10 includes a plate 12 provided with a pair of elongated, linear, parallel slots 14 and 16. The bracket is associated with a number of fasteners including a nut and bolt 18 and screws 20 and 22. Plate 10 is quadrilateral with two parallel sides 24 and 26, and a side 28 substantially perpendicular the parallel sides. The remaining side 30 meets side 24 at an acute angle and side 26 at an obtuse angle. The corners of the bracket are rounded for safety. Slots 14 and 16 are preferably formed parallel to sides 24 and 26. Slot 14 is wider than slot 16 so that it can accomodate the shafts of larger bolts and studs. The bracket is preferably constructed from a strong, lightweight material such as aluminum, stainless steel, platic, or any of the numerous alloys known to the bicycle trade. It may be formed by stamping, casting, molding, machining, or any other suitable process. Referring more particularly to Fig. 3, bracket 10 is attached to a bicycle including: a frame 32; a rear axle assembly having a rear cluster 34, an axle stud 36, and an axle nut 38; a rear derailleur 40; and a chain 42. The axle stud is positioned within slot 14 and is affixed to the bracket by axle nut 38. The rear derailleur assembly is attached to slot 14 of the bracket by nut and bolt 18. Screw 20 is disposed through slot 16 and engages the bicycle's frame, and screw 22 is likewise disposed through slot 16 and engages the rear derailleur assembly. The bracket can be easily removed to return the bicycle to its original condition. It will be noted that side 30 is designed to match the contours of that portion of the bicycle's frame to which it attaches. While this is an aesthetically pleasing feature, it is not a necessity because it has been found that the extension bracket works equally well when inverted on some makes of bicycles. It will also be noted that while the derailleur is shown to be attached to the rear of bracket 12, it could equally well be attached to the front of the bracket in many cases. Should axial positioning of the derailleur become necessary, spacer ' s such as washers 44 can be disposed around the shafts of the nuts and bolts. An oversized gear 46 has been added to the rear cluster to illustrate the use of the present device. The bracket assembly allows the derailleur to be displaced downwardly from the rear axle of the bicycle so that chain 42 can be dropped around the oversized gear. Without the extension provided by the present bracket this would not be possible. OMP The bracket is slotted so that it might be fitted to a wide variety of bicycles and so that it can be adjusted to fit any particular bicycle as perfectly as possible. However, the bracket might be provided with only one slot, or even just some bore holes, should that be all that was necessary to fit the bracket to a particular bicycle. The foregoing and other advantages are obvious to those skilled in the art of bicycle design. OMPI

Claims: Claims 1. In a bicycle including a frame, a rear derailleur assembly, and a rear axle assembly; a rear derailleur extension bracket characterized by: a plate provided with a first elongated, substantially vertically oriented slot having an upper portion adapted to adjustably engage said rear axle assembly; and first means for adjustably engaging said rear derailleur assembly with a lower portion of said first slot, whereby said derailleur assembly is radially displaced from said rear axle assembly. 2. The extension bracket of claim 1 further characterized by means for axially spacing said plate from said rear axle assembly. 3. The extension bracket of claim 1 further characterized by means for axially spacing said plate from said rear derailleur assembly. 4. The extension bracket of claim 1 wherein said plate is further provided with a second elongated slot spaced from and substantially parallel to said first slot. 5. The extension bracket of claim 4 further characterized by second means for adjustably engaging said frame with an upper portion of said second slot, and third means for adjustably engaging said said rear derailleur assembly with a lower portion of said second slot. 6. The extension bracket of -claim 4 wherein the lateral dimension of said first slot is greater than the lateral dimension of said second slot. O PI 7. The extension bracket of claim 4 wherein said plate is quadrilaterial with two of its sides parallel to said first slot and said second slot. O PI IPO

Inventors: BYTHEWAY R
Applicants: BYTHEWAY R
Application year: 1981
Main classification: B61L13
IPC codes: B62M9