Front derailleur with frame support structure

A bicycle front derailleur that includes a chain guide configured to engage a bicycle chain and a mounting member operatively coupled to the chain guide. The mounting member includes a frame support structure that includes a contact member that is configured to contact the frame of the bicycle, and a support member mounted to the mounting member. The contact member is supported by the support member.

FIELD OF THE INVENTION

The present invention relates to a front derailleur for a bicycle that includes a frame support structure.

BACKGROUND OF THE INVENTION

A bicycle front derailleur is sometimes attached to the seat tube of a bicycle frame by a mounting fixture, which is fastened to the seat tube of the frame by welding, threaded fasteners or the like. This mounting fixture is sometimes called a direct-mounting seat or braze-on seat. Since such mounting fixtures are fastened to the seat tube beforehand, the chain guide of the derailleur cannot be disposed in a parallel position directly above the front sprocket in the case of systems in which a band is formed as an integral part of the front derailleur, unless the orientation is adjusted about an axis parallel to the seat tube following mounting.

US 2007/0117666A1, which is incorporated by reference in its entirety herein, teaches a bicycle front derailleur which is capable of adjustment. However, a need exists for an improved front derailleur with adjustment capabilities. The present invention relates to a front derailleur which is fastened to a bicycle frame and which can be attached to a mounting fixture having a circular arcuate surface so that fine adjustments can be made by rotation about a first axis.

SUMMARY OF THE PREFERRED EMBODIMENTS

In accordance with a first aspect of the present invention there is provided a bicycle front derailleur that includes a chain guide configured to engage a bicycle chain and a mounting member operatively coupled to the chain guide. The mounting member includes a frame support structure that includes a contact member that is configured to contact the frame of the bicycle, and a support member mounted to the mounting member. The contact member is supported by the support member.

In a preferred embodiment, the contact member is movably connected to the support member. In a preferred embodiment, the contact member includes a support plate and a resilient cover that covers the support plate and the resilient cover is movably connected to the support member. The resilient cover includes a recess for receiving the support member. In a preferred embodiment, the support member includes an end portion that has a semi-globular shape that is received in the recess of the resilient cover. In a preferred embodiment, the support member extends through an opening defined in the mounting member and the support member is movable with respect to the mounting member and within the opening. In a preferred embodiment, the contact member has an arcuate shape and when the derailleur is mounted on a seat tube of a bicycle, the contact member has a different diameter than the seat tube.

The invention, together with additional features and advantages thereof, may be best understood by reference to the following description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It will be appreciated that terms such as “front,” “back,” “top,” “bottom,” “side,” “short,” “long,” “up,” “down,” and “below” used herein are merely for ease of description and refer to the orientation of the components as shown in the figures. It should be understood that any orientation of the components described herein is within the scope of the present invention.

Referring now to the drawings, which are for purposes of illustrating the present invention and not for purposes of limiting the same,FIGS. 1-6show a front derailleur10for a bicycle. In a preferred embodiment, as shown inFIGS. 4-6, the front derailleur10is mounted on the seat tube100of a bicycle. However, this is not a limitation on the present invention, and the front derailleur can be affixed to or mounted on other parts of a bicycle.

As shown inFIG. 1the front derailleur10is a downswing-type derailleur. The front derailleur10preferably includes the main body or mounting member40, a chain guide41, an inner link42and an outer link43. The mounting member40is mounted on the seat tube100and the chain guide41is configured to move between a retracted position and an extended position relative to the mounting member40. It will be understood that inFIGS. 2-6, the chain guide41, inner and outer links42and43and associated components have been omitted for ease of viewing of the remaining components.

As shown inFIG. 4the front derailleur10is mounted to the seat tube100using a mounting fixture102of the bicycle frame (not shown) to support the front derailleur10in a desired angular orientation. The mounting fixture102is fastened to the seat tube100by fastening means such as welding, fastener (bolt) or the like. The mounting fixture102has a bicycle frame fastening part102athat can be fastened to the seat tube100, a front derailleur mounting part102bthat is disposed on the bicycle frame fastening part102aand that secures or fastens the front derailleur10in place.

The front derailleur mounting part102bsecures the front derailleur10in position so that adjustment is possible about a first adjustment axis X1, which is generally parallel to the seat tube100and is disposed at a distance from the seat tube100. The front derailleur mounting part102bis formed by bending a long plate-form member in the vertical direction about the first adjustment axis X1and includes circular arcuate surfaces102cand102dthat are centered substantially on the first adjustment axis X1. Moreover, a slot (not shown) which is used to fasten the front derailleur10so that adjustment is possible in the vertical direction is formed in the front derailleur mounting part102b. The slot allows a first fastening bolt33, which is used to fasten the front derailleur10, to pass through from a first fastening direction that runs along a second mounting axis X2orthogonal to the first adjustment axis X1. The width of the slot is a dimension that is considerably larger than the external diameter of the first fastening bolt33, so that the first fastening bolt33can pass through at an inclination. In another embodiment, the slot can be omitted and replaced by a circular opening, thus eliminating adjustment in the vertical direction.

The bicycle frame fastening part102ahas a size that allows mounting on the outer circumferential surface equal to approximately a quarter circle of the seat tube100. The circumference of the bicycle frame fastening part102ais welded to the seat tube100. In the case of such a construction, the position of the mounting fixture102cannot be later adjusted and the orientation of the front derailleur10is therefore adjusted by the front derailleur mounting part102b.

The mounting member40of the front derailleur10is secured to the mounting fixture102, while the chain guide41is free to move in the gear shift direction toward or away from the mounting member40via the inner and outer links42and43which are disposed generally parallel to each other and rotatably connect the mounting member40and the chain guide41.

The fixing part45of the mounting member40is formed in a generally semi-circular arcuate shape as seen in a plan view (such asFIG. 4) so as to conform to the circular arcuate surface102cof the front derailleur mounting part102b. A screw hole (not shown) is formed in the fixing part of the mounting member40for threadedly receiving the first fastening bolt33.

The chain guide41guides the chain (not shown) to either of the at least two front chain rings (not shown) by moving corresponding shift positions that include a low shift position disposed over the small diameter or inside chain ring, and a top shift position disposed over the large diameter or outside chain ring. The chain guide41is connected to the outer ends of the inner link42and the outer link43so as to move between the retracted position and the extended position relative to the mounting member40. The inner link42and the outer link43are pivotally coupled at their inner ends to the mounting member40and pivotally coupled at their outer ends to the chain guide41. The inner link42and the outer link43are arranged so as to be generally parallel to each other. Thus, the inner and outer links42and43form a four bar linkage assembly with the mounting member40and the chain guide41in order to move the chain guide41between the retracted position and the extended position. In the present embodiment, the chain guide41has an outer plate41aand an inner plate41bthat define a chain receiving slot therebetween. The outer plate41ais disposed on the outside (the side distant from the seat tube100), and the inner plate41bis disposed on the inside.

As shown inFIG. 1, the inner link42is disposed, beneath the mounting member40in a state in which the mounting member40is mounted on the seat tube100, and both ends of this link are connected to the mounting member40and chain guide41in a manner that allows the link to pivot freely. One end of the inner link42is connected to the mounting member40so that the inner link42can swing freely. The chain guide41is connected to the other end of the inner link42so that the chain guide can swing freely.

The outer link43is a link which is disposed generally parallel to the inner link42and in which both ends of the link are connected to the mounting member40and the chain guide41in positions that are more distant from the mounting member40than the inner link42is, so that outer link43can pivot freely. A cable anchoring arm44is provided on the outer link43. A cable anchoring part44afor bolting down the inner cable of the gear shift cable (not shown) is disposed on the extended distal end of the cable anchoring arm44.

As shown inFIGS. 5-6, a screw hole (not shown) that is used for fastening by the first fastening bolt33in the direction of the axis X2orthogonal to the first adjustment axis X1is formed in the mounting member40, and a screw hole40dis formed along a third displacement axis X3that is orthogonal to the first adjustment axis X1, but not orthogonal to the second mounting axis X2. A support member23, that is preferably threaded with a recessed hexagonal socket is mounted in the screw hole40dso that the support member23is free to advance and retract. A hexagonal recessed socket that can be turned by an Allen key is formed in the base end of the support member23, and the distal end portion23ahas a semi-spherical or globular shape. Mounted on the distal end23aof the support member23is a contact member25that contacts the outer circumferential surface of the seat tube100, as shown inFIGS. 4-6.

As shown inFIGS. 2-3, in a preferred embodiment, the contact member25comprises a resilient support plate cover27that houses a support plate28and that includes a receiver member29that has a recess29adefined therein for receiving the distal end23aof the support member23. In another embodiment, the contact member25can comprise a single resilient member. In other words, the support plate28can be omitted. Preferably, the support plate cover27and support plate28have an arcuate shape. As shown inFIGS. 5 and 6, in a preferred embodiment, opening29aextends through the back surface of the support plate cover and support plate28includes an indentation28ain the back surface thereof, which receives and seats the distal end23aof the support member23. It will be understood that, in this embodiment, the distal end portion23ais movably supported within opening29aand that distal end portion23aand opening29a(together with indentation28) form a “ball joint” arrangement. In a preferred embodiment, the resilient support plate cover28is made of a resilient material, such as a resin or the like, and the support plate28is made of a metal. However, this is not a limitation on the present invention. As shown inFIGS. 4-6, although the arcuate shape of the contact member25and the components thereof (the support plate cover27and support plate28) has a different diameter than that of the seat tube100, it is preferred that the contact member and the seat tube can have a similar diameter so that the entire front surface of the contact member is flush against the seat tube.

An example of how the front derailleur10of the present invention can be adjusted will now be described. Initially, the first fastening bolt33is positioned in a lightly tightened state, so that the vertical position can be adjusted and adjustment about the first adjustment axis X1is possible. The vertical position is then adjusted so that the gap between the addendum circle of the large-diameter sprocket and the lower edge part of the outer plate is approximately 1 to 3 mm, and the orientation about the first adjustment axis X1is adjusted so that the outer plate is disposed in a position directly above the smaller-diameter sprocket and parallel to the smaller-diameter sprocket. When the adjustments are completed, the first fastening bolt33is tightened. In cases where the contact member25does not contact the seat tube100, a wrench is placed in the recessed, hexagonal socket in the support member23via an opening in the outer link43and the support member23and contact member25are advanced until the contact member25(the resilient cover27) comes into contact with the seat tube100. It will be appreciated by those skilled in the art that the chain guide41is more stably supported by the contact member25when the chain guide41is in the extended position compared to a derailleur without the contact member15.

As is shown inFIG. 5, the support member23(and the third axis X3) are arranged such that they form an angle with the second axis X2between about 78° to about 86°.FIG. 5also shows an access opening46so that a tool/wrench can be passed through the axis opening46to access the support member23.