At http://www.pattakon....takonPatBox.htm it is presented the PatBox CVT wherein an auxiliary thin belt rides around the conventional V-belt and around rollers mounted on a lever.
The displacement of the lever varies the transmission ratio:
1 is a drive shaft (the crankshaft in most cases).
2 is a drive pulley comprising two conical halves.
3 is a driven shaft.
4 is a driven pulley comprising two conical halves.
5 is a V-belt.
6 is an auxiliary belt; it surrounds and abuts on the V-belt at the drive pulley side.
7 is a lever comprising free rollers (12, 13) around which the auxiliary belt runs; a restoring spring (not shown) pulls the lever 7 to the left and keeps the auxiliary belt in tension; the linear speed of the inner side of the auxiliary belt 6 equals the linear speed of the external side of the V-belt 5.
When the lever 7 is free to move, the variator (not shown) controls the transmission ratio conventionally / automatically. The "engine revs vs. vehicle speed" plot can be like:
From p1 to p2 the automatic clutch (not shown) engages.
From p2 to p3 the transmission ratio is constant and short. The revs are not yet adequately high to allow the variator to start reducing the effective diameter of the drive pulley.
From p3 to p4 the variator increase progressively the effective diameter of the drive pulley (as a result, and due to the constant length of the V-belt, the effective diameter of the driven pulley decreases; as another result, the auxiliary belt 6 abuting on the V-belt 5 pulls the free rollers to the left and causes the rotation of the lever 7 for several degrees clockwise). The transmission ratio gets longer and longer (the engine revs remain constant while the vehicle speed increases).
At p4 the transmission ratio is the longest possible (the effective diameter of the drive pulley cannot increase any longer) and remains constant until p5.
In case the rider, by putting his foot on the end 11 of the lever 7 for instance, blocks properly the clockwise motion of the lever 7, the previous plot can change like:
and the vehicle can accelerate faster (because the engine operates at revs wherein more power is provided).
Until the p9 the transmission operates conventionally (as in the first plot).
From p9 to p10 the driver / rider blocks the upwards motion of the end 11 of the lever 7 (and so the clockwise rotation of the lever 7); in order the variator to increase the effective diameter of the drive pulley, it needs also either to increase the length of the auxiliary belt (which is constant) or to displace to the left, through the auxiliary belt, the free rollers and the lever 7 (which is not allowed by the driver). So the transmission ratio remains constant and short.
From p10 to p11 the driver releases progressively the lever 7 so that the revs of the engine to remain constant while the vehicle speed increases.
From p11 to p12 the driver blocks again the upward motion of the end 11 of the lever 7; the transmission ratio remains constant (like having the second gear in a manual gearbox).
From p12 to p13 the driver releases progressively the lever 7 keeping the revs of the engine constant while the vehicle speed increases.
From p13 to p14 the lever 7 is again blocked (like having the third gear in a manual gearbox).
And so on.
It is characteristic that in all the above steps the driver / rider does not provide energy to the PatBox CVT; he just blocks or releases the lever 7; the energy for the motion of the lever 7 comes from the engine (like having a built-in servo).
In the following plot the transmission system operates like a manual gearbox having six distinct gear ratios.
Until the point p27 the transmission operates automatically.
At p27 the driver blocks the lever 7 (and selects this way the first gear); at p28 the driver, by releasing the lever 7 and blocking it again at the point p28, shifts to the second gear; at p30 the driver shifts to the third gear; at p32 the driver shifts to the fourth gear; at p34 the driver shifts to the fifth gear; at p36 the driver shifts to the sixth gear.
It is like shifting gears in a manual gearbox (but without the need of a clutch).
In the following plot the driver keeps the lever 7 blocked from the beginning; the engine revs go high; then the driver releases the lever 7 progressively keeping the revs constant.
If the peak power of the engine is provided at the revs corresponding to the point p16, the acceleration of the vehicle is the fastest possible.
Here is a stereoscopic drawing of the mechanism:
The rider can either vary, "on the fly", the characteristics of the transmission in order to meet the instant needs for acceleration, quiet operation, fuel efficiency, mileage etc, or the driver can leave alone the CVT to operate normally / automatically.
While the PatBox CVT can provide infinite additional modes of operation, it actually adds no friction; on the contrary, with the additional modes of operation, the overall efficiency (the mileage) can be improved.