Endless belt power transmission systems or components – Friction drive belt – Including plural interconnected members each having a drive...
Patent
1983-11-22
1986-04-01
Leppink, James A.
Endless belt power transmission systems or components
Friction drive belt
Including plural interconnected members each having a drive...
474201, F16G 121
Patent
active
045795509
DESCRIPTION:
BRIEF SUMMARY
The present invention provides a linked chain of metal or other hard material, for use in continuously variable ratio transmissions (CVT's) which employ conical, or semi-conical, pulleys whose effective diameters are varied during operation.
THE PRESENT STATE OF THE ART
Continuously variable transmissions which employ a pair of conical, or semi-conical pulleys connected by a flexible belt or a chain, which transmit torque by frictional forces between the sides of the pulleys and the belts, and which vary the ratio of transmission by altering the distance between the opposing internal faces of each pulley, have been known for a considerable time. The most common types employ continuous flexible belts of trapezoi dal cross-section. Other common types employ flexible belts which incorporate more rigid elements of trapezoidal cross-section which are able to sustain greater compression forces from the two sides of the pulleys, and hence transmit more torque and power. All such flexible belts are, of course, limited in their performance by the maximum permissible stresses and temperatures of the materials that they employ.
There have been many proposals for chains, made of metal, which can withstand much higher stresses, and also be cooled by oil. However, all such proposals up to now have used chain links which are relatively long, and which would limit performance of any C.V.T. by imposing high concentrations of stress on the relatively few lines of contact between the chain links and the pulley faces, as well as limiting the rotational speed.
A different approach to steel C.V.T. transmission belts has been developed in the several patents and products of the Van Dooren's Transmissei B.V. They employ relatively slim, trapezoidal metal plates which are held together by laminated steel belts, on which the plates can slide freely. These transmission belts differ from prior C.V.T. transmission belts and chains in that they transmit torque by compression between the metal plates, which are held together and pressed up against the pulley sides by the tensioned laminated belts.
The Van Doorne transmission belts have been incorporated into the only continuously variable transmissions which are sufficiently compact, efficient, silent durable, easy to manufacture and economical as to compete with transmissions presently used in automobiles and machine tools. The main reasons for their high performance are the relatively large number of lines of contact between the belts and the pulleys, which reduce stressconcentrations, noise and wear.
One of their main limitations is that, since the trapezoidal compression plates are held pressed together, and are not joined by any positive links, they cannot be made too long because they tend to twist out of line and produce an unstable set of force between the pulley surfaces. This limits the amount of variation is the transmission ratio and also limits the compression forces between the sides of the pulleys.
According to the present invention, a belt for a continuously variable transmission of the type including two pulleys of variable effective diameter, comprises a plurality of links of substantially trapezoidal form, each link having pulley-engaging traction surfaces at its nonparallel edges and being attached in abutting relationship to its adjacent links by tension-transmitting articulations, each link being further provided with a pair of parallel compression surfaces, each of which abuts a compression surface of an adjacent link when the links are joined in a linear array.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
This invention proposes chains of generally planar trapezoidal elements for use in continuously variable transmissions which are oriented in generally parallel planes and are preferably linked together by pins such that:
(a) the links need be no thicker 150% of the link pin diameters, hence they can be relatively short and closely packed, which reduces stress concentration and noise in comparison with other proposed C.V.T. chains;
(b) the bending and shear str
REFERENCES:
patent: 2403607 (1946-07-01), Ogard
patent: 4303404 (1981-12-01), Moore
Leppink James A.
McKenzie Frank
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