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
1988-07-15
1990-08-07
Bui, Thuy M.
Endless belt power transmission systems or components
Control for variable input to output speed-ratio
Including belt shiftable axially from one to another surface...
192142R, 280238, F16H 722, F16H 900
Patent
active
049464256
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The invention relates to an electromechanical bicycle gear shift mechanism of the type defined in the generic clause of patent claim 1.
Described in U.S. Pat. No. 39 19 891 is an embodiment of an electromechanical gear shift mechanism of this type, in which one end of a telescopically extensible three-sided housing is secured to the vehicle frame, the other end being operatively connected to an actuator member by a pin. Mounted within the housing is a drive member in the form of a threaded spindle driven by an electric motor for retracting and extending the outer housing portion relative to the fixed housing portion in a direction parallel to the wheel axis. In an actuating mechanism of this type the distance between the actuator member and the wheel axis remains constant, in contrast to the customary cinematics of known derailleur gear shift mechanisms employing a parallelogram linkage, in which the shift actuator member is moved parallel to itself and in addition along an arcuate path. In the case of this gear shift mechanism known from U.S. Pat. No. 39 19 891 it is difficult to accurately engage the individual gears with the chain correctly positioned on the respective sprocket, because the reaction forces of the chain, travel-induced shocks and vibrations, and the gear shift forces result in excessive loads acting on the relatively movable housing portions, resulting in rapid wear and thus impairing the gear shift accuracy.
In a further electromechanical bicycle gear shift mechanism of another type known from U.S. Pat. No. 40 41 788, an electric motor is operable to move a lever arm carrying a floating gear adapted to assume two engagement positions with respect to a spindle drive mechanism for moving a shift actuator member in opposite directions along an axis extending parallel to the rear wheel axis. The rotation of the spindle drive mechanism is derived from the chain movement. Associated to the chain tensioning lever and to the lever arm carrying the floating gear are a plurality of positioning wiper contacts included in the electrical circuit for controlling the electric motor and serving for accurately positioning the shift actuator member in respective gear engagement positions by reversing the electric motor controlling the gear shift operation when the tensioning lever reaches the accurate gear engagement position to thereby disengage the floating gear at an accurately timed instant.
Known from FR Patents 10 03 373 and 12 77 691 are purely mechanical bicycle gear shift mechanisms in which the carrier of the shift actuator member formed as a chain tensioning lever or a deflector sprocket is guided in a housing in a simple sliding guide assembly, any rotation of the carrier being prevented by a guide pin engaging a longitudinal groove or by a non-circular cross-section of the carrier.
In an electromechanical bicycle gear shift mechanism known from FR-PS 22 33 220, the carrier simultaneously acts as the shift actuator member freely guided in a transverse guide slot and threadedly engaged with a spindle connected to an electric motor. The electric control circuit of the motor contains series-connected reed switches and simple change-over switches with control relais and diodes.
In an electromechanical bicycle gear shift mechanism known from FR-PS 25 87 079, the embodiment comprising a shift actuator member displaceable parallel to the wheel axis, the actuator member is inadequately guided on an exposed transverse guide bar. The control circuit for the electric motor comprises printed circuit components and a plurality of wiper contacts highly sensitive to wear and contamination.
From GB-PS 004 05 09 there is finally known a linear motor of the stepped-motion type in which the position of the movable motor component is monitored by an electro-optical sensing device comprising fotocells, receiving elements and a longitudinally extending scale and operating to generate countable signals indicative of the position of the movable motor component.
It is an object of the invention to provid
REFERENCES:
patent: 3863512 (1975-02-01), Crawley
patent: 3919891 (1975-11-01), Stuhlmuller et al.
patent: 4041788 (1977-08-01), Nininger, Jr.
patent: 4143557 (1979-03-01), Wakebe et al.
patent: 4605240 (1986-08-01), Clem et al.
Bui Thuy M.
Villiger Sohne AG Cigarrenfabriken
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