Endless belt power transmission systems or components – Control for variable input to output speed-ratio – Including belt shiftable axially from one to another surface...
Patent
1999-03-03
2000-10-24
Estremsky, Sherry L.
Endless belt power transmission systems or components
Control for variable input to output speed-ratio
Including belt shiftable axially from one to another surface...
474 82, B62M 916
Patent
active
061359033
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a device for tensioning and guiding a chain for a bicycle gearshift.
BACKGROUND OF THE INVENTION
There is known from European application EP-A-95450012.0, a process for gear selection as well as means to practice this process, in the name of the present applicant.
This invention has a high interest because the user has an increased predetermined gear selection, staged as a function of need, from among a much greater number of combinations but in which the redundancies in particular are numerous.
To achieve this high number of combinations, the bicycle is generally provided with several chain rings, secured in rotation with the crank axle, with a front derailleur to select them, gears secured to the rear wheel with a rear derailleur to select them as well as a chain connecting the chain rings and the gears.
SUMMARY OF THE INVENTION
The invention, which consists in selecting and synchronizing the gears, has as a result also limiting the chain crossings by omitting end crossings corresponding to the largest chain ring with the largest gear or the smallest chain ring with the smallest gear. Thus, such combinations are useless because the comparable gears can be obtained with other combinations having less influence on the length on the chain.
To compensate the variations of length of the chain, there is provided a tensioner with a guide in the form of a clevis comprising a pair of freely-rotating wheels one for guiding/derailing, the other for tensioning, provided with teeth adapted to coact with the openings of the chain.
The clevis is generally mounted rotatably at the end of an arm itself mounted rotatably relative to the frame. A return spring is interposed in line with each axis of rotation so as to exert a force having the tendency to cause the arm to pivot forwardly whilst the clevis is urged rearwardly relative to the arm. This mounting permits maximum taking up of the length of the chain in the take-up loop.
This double articulation permits compensating large variations of length of the chain but there can also be envisaged the case of an arm which is no longer movable but fixed. It should be noted that in any case a movable tensioning roller is required.
Between the arm and the clevis, in a known manner is at present interposed a deformable parallelogram which displaces this clevis in translation perpendicular to the plane of the bicycle, so as to guide the chain and to effect its derailing and the passage from one gear to another.
If this type of derailleur gives satisfaction in principle, it is nevertheless true that this element takes up space and reduces the clearance of the ground, rendering it vulnerable particularly for all-terrain usage.
Moreover, one can foresee placing in a casing the assembly of the drive, which is to say the chain, the rear derailleur and the front derailleur.
The casing should be sealed and contain a lubricant which, not only decreases friction and facilitates changing gears, but will protect the fragile members mechanically.
Efficiency will be improved by the fact that during outings or competitions, dirt, water and other particles cannot accumulate in places that might impede the good operation of the transmission.
On the contrary, it will be understood that, in the case of derailleurs of the prior art, the placing in a casing is unrealistic because it would be necessary to provide a volume corresponding to the maximum extension of the clevis.
The present invention overcomes these difficulties of the prior art by providing a tensioning and guiding device for the chain, which permits derailing the chain, but which is of reduced size, which permits placing it in a casing, which is suitable for existing bicycles, requiring only very small modifications, and which increases the ground clearance.
To this end, the tensioning and guidance/derailing device of a chain of a drive system for a set of pinions (a-h) and also a set of chain rings (A, B, C), for a bicycle comprising synchronized selection means of a limit
REFERENCES:
patent: 3748916 (1973-07-01), Morse
patent: 4637808 (1987-01-01), Wakamura
patent: 5213549 (1993-05-01), Blanchard
patent: 5730670 (1998-03-01), Ferrarin
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