Patent Application
20090111624
The present invention relates to derailleur, and particularly to a front speed change device which has a greater rigidity without any interference. Thus no wear and no noise generate in speed change.
In U.S. Pat. No. 7,081,058, a bicycle front derailleur is disclosed. The derailleur comprises a base member configured to be coupled to a bicycle frame; a movable member having a front end, a rear end and a chain guide portion configured to be moved between first and second positions; a first link member including a first coupling portion pivotally coupled to said base member and a second coupling portion pivotally coupled to said movable member about a first pivot axis, said first coupling portion of said first link having a first forwardmost surface and a first rearwardmost surface, and said second coupling portion of said first link having a second forwardmost surface and a second rearwardmost surface; a second link member including a first coupling portion pivotally coupled to said base member and a second coupling portion pivotally coupled to said movable member about a second pivot axis; and a biasing member disposed on said first pivot axis to normally bias said movable member to said first position relative to said base member, said biasing member being at least partially located in front of said first forwardmost surface of said first coupling portion of said first link member relative to said movable member when said front derailleur is mounted to the bicycle frame in a normal operating position, and said biasing member being located completely in front of said second forward most surface of said second coupling portion of said first link relative to said movable member when said front derailleur is mounted to the bicycle frame in the normal operating position, the normal operating position being defined as a position where said chain guide portion extends longitudinally on a right side of the bicycle frame such that the front end of said movable member is located closer to a handlebar mounting portion of the frame than the rear end of said movable member, said first and second forwardmost surfaces facing substantially forward toward the handlebar mounting portion of the frame and said first and second rearwardmost surfaces facing substantially rearwardly away from the handlebar mounting portion of the frame when said front derailleur is mounted to the bicycle frame in the normal operating position. Although the prior art derailleur can increase the rigidity of the structure with a reduced stress and deformation. However, when the chain is engaged to a small teethed ring and a small size sprocket, the chain is shifted so that the chain will interfere the derailleur. Thus noise generates and the derailleur will wear.
In treading a bicycle, the chain suffers from a great extension. In change of speed, when the chain changes to different engagement, the derailleur will suffer from a great stress. Thus there is a demand for a novel design which can improve all above said defects.
Accordingly, the primary object of the present invention is to provide a front speed change device, wherein has a greater rigidity without any interference. Thus no wear and no noise generate in speed change.
To achieve above objects, the present invention provides a front speed change device, comprising: a body includes a base, a first linking rod, a second linking rod and a chain guide unit; wherein the body serves to fix the body to a seat tube; the first linking rod has one end pivoted to the base and another end thereof is pivoted to the chain guide unit; the second linking rod has one end pivoted to the base and another end thereof is pivoted to the chain guide unit; the chain guide unit includes an outer guide sheet and an inner guide sheet; two ends of the outer guide sheet are connected to the two ends of the inner guide sheet; a receiving body is formed between the outer guide sheet and the inner guide sheet for receiving a chain; the outer guide sheet is formed with a first end surface, a second end surface, and a third end surface; and the first end surface is at a front end of the chain guide unit; the second end surface is at a lower side of the first end surface and behind a front part of the first end surface; and is reduced from and parallel to the first end surface; the third end surface is connected to the second end surface; the fourth end surface is connected to the teethed ring set; the second end surface expanded from the first end surface to a rear side thereof; the inner guide sheet 442 is a straight surface.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing.
In order that those skilled in the art can further understand the present invention, a description will be provided in the following in details. However, these descriptions and the appended drawings are only used to cause those skilled in the art to understand the objects, features, and characteristics of the present invention, but not to be used to confine the scope and spirit of the present invention defined in the appended claims.
Referring to
Referring to
A body 40 includes a base 41, a first linking rod 42, a second linking rod 43 and a chain guide unit 44.
The body 40 serves to fix the body 40 to a seat tube 10.
The first linking rod 42 has one end pivoted to the base 41 and another end thereof is pivoted to the chain guide unit 44.
The second linking rod 43 has one end pivoted to the base 41 and another end thereof is pivoted to the chain guide unit 44.
The chain guide unit 44 includes an outer guide sheet 441 and an inner guide sheet 442. Two ends of the outer guide sheet 441 are connected to the two ends of the inner guide sheet 442. A receiving body 45 is formed between the outer guide sheet 441 and the inner guide sheet 442 for receiving a chain 20. The outer guide sheet 441 is formed with a first end surface 4410, a second end surface 4411, a third end surface 4412 and a fourth end surface 4413. The first end surface 4410 is at a front end of the chain guide unit 44. The second end surface 4411 is at a lower side of the first end surface 4410 and is reduced from and parallel to the first end surface 4410. The third end surface 4412 is connected to the second end surface 4411. The second end surface 4411 expanded from the first end surface 4410 to the fourth end surface 4413 so that the second end surface 4411 is formed as an inclined surface. The outer guide sheet 441 is made of aluminum alloy or carbon fiber so as to have a strong structure. The inner guide sheet 442 is a straight surface as illustrated in
In the present invention, the base 41, first linking rod 42, second linking rod 43 and chain guide unit 44 are formed as a four linking structure. When the speed is changed to a lower value, the second end surface 4411 of the outer guide sheet 441 will be in contact with and resist against with the chain 20. Generally, the pitch of the chain 20 is about 1 centimeter. When a width of the outer chain plate with the inner chain plate is three times of the pitch, it is preferable to assure that the second end surface 4411 will in contact with the outer guide sheet 441. Thus it is preferable that the second end surface 4411 has a length about 1 to 3 centimeters. The third end surface 4412 will guide the chain 20 to move inwards. The chain 20 can be changed from the large teethed ring 311 to the small teethed ring 312 successfully. When the chain 20 is at the small teethed ring 312 or the small size sprocket 323, the chain 20 is shifted at a maximum value. The second end surface 4411 is parallel to the chain 20 at this state so as to assure that no interference generates and thus no wear generates. However, the length of the second end surface 4411 is limited, preferably to be between 2 to 5 centimeters so as to avoid the chain guide unit 44 to hurt the crank or ankle of the driver.
The present invention is thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
