US 2004/0005951 A1Published application

Front derailleur for a bicycle

AssigneeSunRace Sturmey-Archer Inc.

InventorsMing-Chih Tsai, Yan-Long Sheng

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Abstract

The present invention provides a bicycle front derailleur mountable to a seat tube of a bicycle frame for fitting a chain around a selected sprocket of a multiple chainwheel by pushing the chain laterally at a portion thereof advancing into engagement with the chainwheel, the front derailleur comprising: a fixed section fixed to a bicycle frame, a chain guide for contacting a chain to shift the chain, and an actuating arm and a linkage rod disposed between and pivotally connected to the fixed section and the chain guide. In the above construction, the present invention has achieved the intended object of providing an improved bicycle front derailleur capable of reliably effecting a change speed operation with the aid of a sufficient restoring force of the return spring and achieving minimized in operation forces required for various change speeds.

Claims6

Dependent claims

A front derailleur for a bicycle, said bicycle comprising a chain, a chainwheel, a control cable and a seat tube, said front derailleur comprising:

a frame bracket having a pair of lugs disposed at a side thereof close to the chainwheel for connecting with the seat tube;
a chain guide comprising a guide plate overstriding said chain and a pivot joint formed at an opposite side of said guide plate;
a linkage rod having one of its ends pivotally connected to said lug, and the other end thereof pivotally connected to said pivot joint;
and
an actuating arm pivotally connected to said frame bracket using a shaft installed with a return spring, wherein one end of the actuating arm is pivotally connecting to said pivot joint of said chain guide, and a cable connector is installed on the other end thereof for connecting to the control cable;
wherein, the chain guide is drivenable by the control cable for operating between at least a highest speed mole and a lowest speed mode;
wherein, said frame bracket, chain guide, linkage rod and actuating arm are so positioned in such a manner that, while said chain guide of the front derailleur is operating in the highest speed mode, said linkage rod is at a position substantially parallel to said seat tube, so that a restoring force provided by said return spring is equal to an active component force for actually shifting said chain, that is, the restoring force can be utilized fully for down-shifting.

4 more elements

A front derailleur for a bicycle, said bicycle comprising a chain, a chainwheel, a control cable and a seat tube, said front derailleur comprising:

a frame bracket having a pair of lugs disposed at a side thereof close to the chainwheel for connecting with the seat tube;
a chain guide comprising a guide plate overstriding said chain and a pivot joint formed at an opposite side of said guide plate;
a linkage rod having one of its end pivotally connected to said lug, and the other end thereof pivotally connected to said pivot joint;
an actuating arm 2 pivotally connected to said frame bracket using a shaft, wherein one end of the actuating rod is pivotally connecting to said pivot joint of said chain guide, and a cable connector is installed on the other end thereof for connecting to the control cable;
and
an extension spring having one end thereof connected to said lug where connecting with said linkage rod, and the other end thereof connected to said chain guide via a connecting hole located at the upper inward side of said guide plate.
wherein, the chain guide is drivenable by the control cable for operating between at least a highest speed mode and a lowest speed mode;
wherein, said frame bracket, chain guide, linkage rod and actuating arm are so positioned in such a manner that, while said chain guide of the front derailleur is operating in the highest speed mode, said linkage rod is it a position substantially parallel to said seat tube, so that a restoring force provided by said return spring is equal, to an active component force for actually shifting said chain, that is, the restoring force can be utilized fully for down-shifting.

5 more elements

Dependencies are inferred from the claim text.