Endless belt power transmission systems or components – Pulley with expansible rim means or pulleys with alternately... – Structure for variably adjusting radius of rim section
Reexamination Certificate
1999-07-01
2001-02-06
Wright, Dirk (Department: 3681)
Endless belt power transmission systems or components
Pulley with expansible rim means or pulleys with alternately...
Structure for variably adjusting radius of rim section
Reexamination Certificate
active
06183385
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
This invention relates generally to variable-ratio belt-driven transmissions and more specificially to belt-driven transmissions for which the ratio of belt velocity to the angular velocity of the transmission output is continuously variable.
A belt-driven transmission converts power supplied by an endless belt to rotary power. It is desirable for many applications that the transmission ratio, the ratio of the linear velocity of the belt to the angular velocity of the transmission output, be not only variable but continuously variable.
Perhaps the oldest and simplest variable-ratio transmission is an assembly of pulleys of different diameters on a common hub. The transmission ratio is changed by shifting the belt from one pulley to another.
A variable-ratio transmission for use with V-belts consists of a pulley split into two halves with a means for varying the separation of the two halves. Since the cross section of the split-pulley belt channel is V-shaped to match the sides of the V-belt, the distance of the V-belt from the axis of rotation and the transmission ratio is proportional to the separation of the pulley halves. The split-pulley approach has the advantage of having a transmission ratio that is continuously variable. Unfortunately, the torque available from such a transmission is limited since the torque depends on the frictional force that maintains the V-belt in contact with the pulley.
In order to obtain higher torques, it is necessary to use corrugated belts and pulleys (or chains and sprockets) that provide positive, non-slip engagements. A transmission with a continuously-variable transmission ratio and based on the use of a corrugated belt and a matching corrugated pulley implies a pulley having a continuously-variable diameter and a constant rib pitch. Such a pulley tends to be very complex. A need exists for a simple continuously-variable transmission that is suitable for high-torque applications.
BRIEF SUMMARY OF THE INVENTION
The invention is a variable-ratio transmission comprising a base having an axis of rotation to which an object can be attached and a plurality of pulley assemblies slideably attached to the base along radials. Each pulley assembly comprises one or more pulleys, a pulley shaft, and a pulley transport. The pulleys of a pulley assembly are rotatably attached to the pulley shaft and are rotatable in only one direction about the pulley shaft. The pulley shaft is attached to the pulley transport. The pulley transport is slideably attached to the base along a radial. The pulley assemblies are so arranged that the plurality of pulleys can engage at least one encircling belt or chain. An actuating system applies radial forces to the plurality of pulley transports for the purpose of maintaining the pulley assemblies in fixed radial positions or moving the pulley assemblies to other radial positions. The actuating system is controlled by an external entity.
REFERENCES:
patent: 4740190 (1988-04-01), Pike
patent: 4874351 (1989-10-01), Jackson
patent: 5104357 (1992-04-01), Leonard et al.
patent: 5290206 (1994-03-01), Graham
patent: 5476422 (1995-12-01), Schendel
patent: 55-86948 (1980-01-01), None
Malm Robert E.
Wright Dirk
LandOfFree
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