Current Technology: Toothed-wheel Gears and Worm Gears
Toothed-wheel drives have been in use for several hundred years. For a long time it was enough to make sure that the teeth on the two wheels do not clash; this has been achieved by using identical separation and non-interfering shapes for the teeth on the two wheels. Later the need has arisen to keep the angular velocity of the two wheels constant in time; this has been achieved by using specially shaped tooth profiles such as evolvents and cycloids. A typical evolvent profile is shown in the figure below.
However, the surfaces of the two coupling teeth keep sliding on one another - except in the position when the contact point between the two teeth just touches on the line connecting the centres of the two wheels. In the case of twisted-teeth gears and also of screw gears and worm gears, the teeth are not only sliding on one another radially but also axially i.e. along their length. This introduces very strong friction between the teeth reducing significantly the energy efficiency and also causing overheating and abrasion and ultimately reduced lifetime. The figure below depicts a worm gear arrangement.
Another major disadvantage of the conventional toothed-wheel drives is that back-lash cannot be eliminated completely or it is very difficult to do. Unlike in the case of roller gears pushing the wheels against each other does not work because that would jam the teeth and the wheels and seize movements. This is simply impossible to do in conventional gears due to their very basic geometry and structure.
New Technology: Roller Gears
In our new patent-protected roller gearing and transmission mechanism we use rollers to couple the motion of the driving and the driven bodies. The rollers are embraced by two corresponding grooves developed onto the surfaces of the two bodies and as the driving body moves the rollers pass the force on and transmit the movement to the driven body. The rollers simultaneously roll along the grooves of the two bodies while travelling along a well-defined path, the roller coupling path, in the space between the two bodies. It is important to note that the rollers carry out pure rolling motion in this system without any sliding. As the rollers travel along the roller coupling path they reach the end of the path and exit from coupling. Then they are guided back to the beginning of the path where they enter the roller coupling path again and introduce coupling between the two bodies again.
The main fundamental feature of this mechanism is that the conditions for pure rolling motion for the rollers are strictly satisfied at any time and all the time. This is true to none of the currently existing conventional gears and drives - with the only exception of the ball-screw drives. In the case of ball-screw drives, however, the movement transmission is strictly collinear, i.e. very restrictive, while in the case of the roller gearing mechanism it is completely general, as it is apparent in the example shown in the figure below.
The roller gearing and transmission mechanism can be universally applied to any shaft geometries and arrangements including shafts with evading and intersecting axes of any angles and also including parallel shafts. In addition, the mechanism can also be applied to internally and externally coupled wheels, to planetary drive arrangements as well as to gear rack arrangements with both parallel and perpendicular axes. A summary of the possible arrangements is shown here.
The mechanism shows remarkable flexibility in terms of design specifications and corresponding geometries, namely, the designer has a great liberty to choose from various alternative design geometries and arrangements yet keeping the same gearing specifications. This is not the case for toothed-wheel drives. There, for example, the ratio of the wheel diameters determines the gearing ratio uniquely, while here, the wheel diameters can be varied across a very wide range while maintaining the same gearing ratio. The gearing ratio is maintained by adjusting other parameters of the system such as the shapes and geometries of the grooves for example. Also, the relative direction of rotation of the wheels can be varied flexibly in the case of the roller gearing mechanism by simply changing again the shape and geometries of the grooves while in the case of toothed-while drives an extra wheel is needed to be put in - causing all kinds of problems such as additional frictional energy losses etc.
In this mechanism the driving and driven bodies can be coupled by ten or twenty or even more rollers simultaneously while in the case of conventional toothed-wheel drives the so called engagement factor is typically only 1.5 and can be a maximum of three only. This has far reaching consequences in terms of design and operational features as listed above.
Potential Advantages Summarised
Summarising some of the main technical advantages of the roller gearing and transmission mechanism as compared against the conventional toothed-wheel drives we see that
- frictional losses are much smaller resulting in lower operating costs
- engagement factor is much larger allowing for a smaller overall size, much more precise movements and greater reliability
- back-lash is eliminated through flexible pre-stressing and thus movements are much more precise
- high gear-up ratio can be achieved in a less complex drive arrangement
- actuating torque is significantly smaller
Potential Applications Summarised
These advantages suggest numerous potential applications for this technology such as these below
|due to lower operating costs, smaller size and greater reliability|
|car and truck gearboxes, truck rare-axle differential drives, steering
gears; same for ships, locomotives and aircrafts, as well as for motor
bikes and bicycles; all advantages above apply|
|due especially to smaller actuating torque|
|due to no back-lash; instead of having a very long ball-screw drive
that often resonates due to its length it is much better to apply a
perpendicular-axis gear rack drive to avoid resonances|
|high energy efficiency, high gear-up ratio and backlash-free adjustments|
|all advantages above apply|