Among the many benefits of a harmonic drive may be the insufficient backlash because of the unique design. However, the actual fact that they are lightweight and extremely compact can be important.
High gear reduction ratios as high as 30 situations that achieved with planetary gears are feasible in the same space.
C W Musser designed strain wave gearing back in 1957 and by 1960 he was already selling licenses so that industry giants could use his patented item.
harmonic drive assembled The harmonic drive is a kind of gear arrangement often referred to as a strain wave gear due to just how it works. It is a kind of reduction equipment mechanism comprising at the least three main parts. These elements interact in a way that allows for very high precision decrease ratios that could otherwise require a lot more complicated and voluminous mechanisms.
As something, the harmonic drive was invented by the American engineer Clarence Walton Musser in 1957, and it quickly conquered the industry with the countless advantages that it taken to the desk. Musser discovered the potential of his invention at an early stage and in 1960 began selling licenses to producers so they could use his patented product. Nowadays, there are only a small number of manufacturers in america, Germany, and Japan who are holding the license to produce harmonic drives, doing so at their top-notch services and creating ultimate quality strain gears for the whole world.
harmonic drive exploded viewThe workings of a harmonic drive
The rotational movement comes from an input shaft that can be a servo engine axis for example. This is linked to an element called “wave generation” which has an elliptical shape and is certainly encircled by an elliptical ball bearing. As the shaft rotates, the edges transformation position, so that it appears like it really is generating a movement wave. This part is inserted inside a flex spline that is made out of a torsionally stiff however flexible materials. The material occupies this wavy motion by flexing according to the rotation of the input shaft and also creates an elliptical shape. The outer edge of this flex spline features equipment teeth that are ideal for transferring high loads with no problem. To transfer these loads, the flex spline is fitted within the circular spline which is a round equipment featuring internal teeth. This outer band is normally rigid and its internal size is marginally larger than the major axis of the ellipse created by the flex spline. This means that the circular spline will not assume the elliptical shape of the additional two parts, but rather, it simply meshes its inner teeth with those of the outer flex spline part, resulting in the rotation of the flex spline.
The rate of rotation is dependent on the rotation of the input shaft and the difference in the amount of teeth between your flex spline and the circular spline. The flex spline has fewer teeth than the circular spline, so that it can rotate at a very much decreased ratio and in the opposite direction than that of the input shaft. The reduction ration is given by: (amount of flex spline teeth – number of circular spline tooth) / number of flex spline teeth. So for example, if the flex spline has 100 teeth and the circular spline has 105, the decrease ratio is (100 – 105) / 100 = -0.05 which means that the flex spline ration is -5/100 (minus indicates the contrary direction of spin). The difference in the amount of teeth can be changed to accommodate different decrease ratios and thus different specialized needs and requirements.
Achieving reduction ratios of 1/100 or more to even 1/300 by simply using such a compact light arrangement of gears cannot be matched simply by any various other gear type.
The harmonic drive may be the only gear arrangement that doesn’t feature any backlash or recoil effect, or at least they are negligible used. That is mainly thanks to the elliptical bearing installed on the outer rim of the insight shaft allowing the free rotation of the flex spline.
The positional accuracy of harmonic drives even at an extreme number of repetitions is extraordinary.
Harmonic drives can accommodate both forward and backward rotation without necessity to change anything, plus they wthhold the same positional accuracy in both spin directions.
The efficiency of the harmonic drive measured on real shaft to shaft studies by the manufacturer goes up to 90%. There are very few mechanical engineering components that may claim this operational effectiveness level.
Uses for a harmonic drive
In short a harmonic drive can be utilized “in virtually any gear reduction program where little size, low weight, zero backlash, very high precision and high reliability are required”. Examples include aerospace applications, robotics, electric automobiles, medical x-ray and stereotactic devices, milling and lathe devices, flexo-printing devices, semiconductor tools, optical measuring machines, woodworking machines and camera head pans and tilt axes. The most known examples of harmonic drive applications include the wheels of the Apollo Lunar Rover and the winches of the Skylab space station.