Patent issued on improved variable diameter pulley CVT

A+CVT VDP is First Positive-Drive, Non-Friction-Dependent VDP

October 19, 2005 – The United States Patent Office this week issued a patent for the first variable diameter pulley (VDP) continuously variable transmission (CVT) that does not depend on friction. The A+CVT VDP (U.S. Patent 6,955,620) is a positive-drive, chain-driven technology. It is designed to be more mechanically-efficient and thus offer greater fuel efficiency than other variable diameter pulley CVTs. (See www.andersoncvt.com.)

The A+CVT VDP is based on the same technology used in the dual cone version of the A+CVT, which was patented in 2003. The dual cone A+CVT utilizes “floating sprocket bars” (FSBs) which are mounted longitudinally in channels around the circumference of each of two parallel cones. A specially-designed chain meshes with the FSBs and is free to slide up and down the entire length of the cones, changing the gear ratio at each point.

Similarly, the variable diameter pulley version of the A+CVT utilizes floating sprocket bars which are mounted in channels on the inner face of each of two pulley flanges. A specially-designed chain winds around the pulleys and meshes with the floating sprocket bars. As the pulley flanges move apart, they permit the chain to slide downward, toward the axis of the pulley. As the flanges move closer together, the chain moves outward, toward the perimeter edge of the pulley. The gear ratio changes as the chain moves up or down on each pulley.

The basic concept of a variable diameter pulley CVT has been known for many years. However, all such CVTs have relied on friction to keep the drive belt from slipping while driving the pulleys. Until recently, such CVTs were limited to use in smaller, lightweight vehicles such as golf carts and riding lawnmowers due to torque limits on the drive belt.

In the past few years, several automakers have used a steel “push chain,” enabling variable diameter pulley CVTs to be used in some larger automobiles and SUVs. However, these CVTs are still dependent on friction, which prevents them from attaining optimum efficiency. All friction-dependant CVTs waste energy. This problem partly negates the fuel-saving benefits which are expected of CVTs.

“The variable diameter pulley A+CVT solves the friction problem inherent in other variable diameter pulleys that are now on the market,” said inventor Larry Anderson. “With A+CVT technology, you don’t need complicated and expensive hydraulic controls to squeeze the pulley flanges against a belt. The chain is driven by floating sprocket bars, not friction. It’s much more efficient, and that will mean greater fuel savings.”

Like the dual cone version of the A+CVT, Anderson says that the variable diameter pulley version is applicable to many types of vehicles and machinery, including automobiles, trucks, farm equipment, airplanes and boat motors. It would be especially useful for bicycles and motorcycles, he says, because of its relatively narrow configuration, similar to conventional pedal-and-sprocket systems. However, he is hopeful that the variable diameter pulley A+CVT will catch on within the automobile industry.

“The variable diameter pulley A+CVT should be easily adaptable to many existing drivetrains,” said Anderson. “The auto companies already have the controls in place to operate this kind of CVT. It should be a simple matter of retrofitting their existing CVT designs, to accommodate floating sprocket bars and the special chain.”

Currently, a prototype exists only of the dual cone version of the A+CVT. Anderson hopes to soon develop a prototype of the variable diameter pulley version, in partnership with either a research institution or a manufacturer.

More information about A+CVT technology is available at www.andersoncvt.com.