1. Field of the Invention
This invention generally relates to a front derailleur for a bicycle. More specifically, the present invention relates a front derailleur for a bicycle that has a fixed member with a wide support flange and a wide support link allowing reliable movement of the chain guide.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One part of the bicycle that has been extensively redesigned is the front derailleur. A front derailleur is typically mounted onto the bicycle frame adjacent to the front sprockets.
Generally, a front derailleur includes a fixed member non-movably secured to a bicycle frame, and a movable section supported to be movable relative to the fixed member. Typically, the fixed member is a tubular clamping member that is secured to the seat tube. Alternatively, the fixed member is sometimes coupled to the bottom bracket. In either case, the fixed member preferably has a curved surface designed to contact a curved seat tube portion of the frame. The movable section has a chain guide with a pair of cage plates for contacting and moving a chain between the front sprockets.
The movable section is movable relative to the fixed member by pulling a shift control cable. In particular, the movable section and fixed member usually are interconnected through pivotal links. The control cable is connected to one of the pivotal links to apply a torque thereto, thereby causing the links to move the movable section. The control cable is fixedly coupled to the link in such a position that an operating force is applied to the control cable. This force on the cable is converted into a link swinging torque. Depending on the arrangement and locations of the cable guides, the cable attachment member of the front derailleur may need to be configured differently for different types of frames.
In any case, the linkage assembly of a typical front derailleur is usually constructed of several small plates coupled together. The plates are typically narrow plates located close together to move the chain guide between the various positions. One problem with the typical front derailleur is that the plates experience a variety of forces from the control element (wire), links and chain (resistance). These forces can cause flexing of the links and the chain guide. Thus, smooth shifting can be adversely affected. Additionally, the typical front derailleur can become clogged with mud, dirt or debris. If the derailleur becomes clogged with debris, smooth shifting can again be adversely affected. These prior art derailleurs are often relatively heavy. Moreover, these prior art derailleurs can be complicated and expensive to manufacture and assemble.
In view of the above, there exists a need for a front derailleur for a bicycle, which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.