This invention relates to a mechanical power transmission system.
Presently, there are continuously varying transmission systems (CVT) provided in vehicles in which there is no provision for the manual shifting of gears. CVT belts V belts transmit torque from a drive pulley to a driven pulley through their side surface contact friction.
CVT efficiency is very low, especially in city traffic conditions, during which the vehicle undergoes frequent acceleration and deceleration resulting in belt slip and consequent low transmission efficiency accompanied by low fuel efficiency.
This invention seeks to eliminate or at least minimize such drawbacks.
The mechanical power transmission system, according to this invention, comprises an internally expanding drive pulley enabling the segments to circumferentially expand

or contract with speed; a fixed diameter driven pulley; a belt coupling the drive pulley and the driven pulley for transmitting the load by the inner surface of the belt; a belt tensioner; a centrifugal clutch driven by the driven pulley, said clutch becoming operative when the driven pulley exceeds a speed of a predetermined value.
This invention will now be described with reference to the accompanying drawings which illustrate, by way of example, and not by way of limitation, one of various possible embodiments of the mechanical power transmission system proposed herein.
An internally expanding drive pulley PI is provided with a belt B for transmitting the load by the inner surface (not the side surface) of the said belt to a fixed diameter driven pulley P2 . A belt tensioner T is provided for the belt B.

The drive pulley has a plurality of circumferential segments S pivoted to its hub H, by arms A thus enabling the segments to circumferentially expand or contract with speed. Expansion of the segments increases the effective diameter of the drive pulley and, consequently, reduces the belt slip and varies the speed ratio at the same time.
A centrifugal clutch is driven by the driven pulley, said clutch becoming operative when the driven pulley exceeds a speed above a predetermined value.
It will thus be observed that the transmission system described above is highly efficient by reason of its construction and operation.

The terms and expressions herein are of description and not of limitation since the said transmission drive system is not confined to the embodiment described and illustrated, but it is understood that various other embodiments thereof are possible without departing from the scope and ambit of this invention.

We Claim:
1. A mechanical power transmission system comprising an
internally expanding drive pulley provided with a plurality
of circumferential segments pivoted to its hub thus
enabling the segments to circumferentially expand or
contract with speed; a fixed diameter driven pulley; a belt
coupling the drive pulley and the driven pulley for
transmitting the load by the inner surface of the belt; a belt
tensioner; a centrifugal clutch driven by the driven pulley,
said clutch becoming operative when the driven pulley
exceeds a speed of a predetermined value.
2. A mechanical power transmission system substantially as
herein described and illustrated in the accompanying
drawings