Endless belt power transmission systems or components – Pulley with expansible rim means or pulleys with alternately... – Structure for variably adjusting radius of rim section
Patent
1987-11-30
1992-02-11
Bui, Thuy M.
Endless belt power transmission systems or components
Pulley with expansible rim means or pulleys with alternately...
Structure for variably adjusting radius of rim section
474 52, F16H 5552
Patent
active
050872249
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Gears for speed changing, namely devices used to vary the speed of transmission between a drive shaft and a driven shaft, are well known.
Speed variation may be made by mating cog wheels fitted with differing numbers of cogs, or by friction systems such as moving transmission belts over bevel gears.
In the first case a high level of efficiency, and high degree of precision are obtained as only rolling friction is determined, but variation is uneven and needs compensating devices such as the clutch in automobile vehicles.
In the second case, as a consequence of the sliding friction necessary between driving and driven parts, much efficiency is lost, parts wear out quickly and operation is irregular.
Specifically in the field of cycles and motorcycles, speed change is made by moving the transmission chain over from one cog wheel to another, using devices which are both complex and delicate.
The types of speed change devices with gears inside the hub have complex structures and are therefore both bulky and costly.
SUMMARY OF THE INVENTION
The above invention eliminates these drawbacks and offers considerable advantages as will be described below.
Subject of the invention is a continuous speed change gear applicable to two-wheeled vehicles in particular, comprising a pair of cog wheels, means for continuous variation, as desired, of their center distances accompanied by a radial translation of the cog of at least one of the pairs of wheels in relation to said variation, means for allowing the two wheels to mesh practically with one cog only, and at least with one cog at a time, on the wheel with translatable cogs.
Therefore, by varying the pitch circle of at least one of the two wheels of each pair, it is possible to obtain continuous variation of their ratio of transmission to the desired value.
The wheel with fixed cogs is placed inside the toothing, facing towards its center, of the wheel with translatable cogs.
In one type of execution the means for varying the center distance between the two wheels of each pair comprise a cylindrical support, translatable in the direction of one of its diameters, around which the wheel with fixed cogs can turn freely.
A circular coaxial cam is fixed to the translatable cylindrical support of the wheel with fixed cogs, having a diameter greater than the external circumference of said wheel but having a lower portion of the circumference, with a smaller radius, passing in the base of the groove between the cogs of said wheel, the beginning of said lower portion being marked by a step then continuing by a join portion to regain the maximum circumference.
The maximum diameter zone of the cam prevents meshing between the two wheels of each pair while the lower zone, when a cog on the wheel with translatable cogs presents itself, permits quick meshing with a groove in the wheel of fixed cogs followed by expulsion of the translatable cog to allow the following one to mesh.
In one kind of execution cogs on the wheel with fixed cogs are saw type.
In one kind of execution the wheel with translatable cogs consists of a disk in which there are radial slots and along these sliders move, having outwardly projecting cogs pushed towards the center of the wheel by elastic means.
The invention includes means for automatically varying the ratio of transmission with variation of the load.
Said means essentially consist of movement mechanisms for setting up components of forces generated by the load opposing the forces of reaction set up by the elastic means.
Therefore, as the load varies, according to whether said components overcome the forces of reaction or are overcome by them, a gradual variation takes place in the center distance between the wheels of each pair such as will respectively reduce or multiply the ratio of transmission.
In one type of execution the wheel with translatable cogs is fixed to the back wheel of a bicycle, or similar vehicle, while the chain that transmits pedal crank movement is applied to a sprocket wheel fixed to the wheel with f
REFERENCES:
patent: 3956944 (1976-05-01), Tompkins
patent: 3995508 (1976-12-01), Newell
patent: 4342559 (1982-08-01), Williams
patent: 4608034 (1986-08-01), Reswick
Dore Dario
Stranieri Maria
Bui Thuy M.
Josif Albert
Modiano Guido
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