1.straight bevel gears
2.spiral bevel gears
Bevel gears are gears where the axes of the two shafts intersect and the tooth-bearing faces of the gears themselves are conically shaped.
1.Straight bevel gear
spiral bevel gears are use when the direction of the rotational shafts is required. these type of gears are mainly applicable in differential.design of the teeth are modified in the helical form.the teeth are curve so the engagement of the teeth are much gradual.this mostly reduces the noise and vibration in the system.however the design of the spiral gear is similar as the helical gears but the they have different functioning
When the shaft s neither parallel nor intersecting …is known as skew shafts. 1.Worm gears
Advantages of Worm Gears
- Worm gear drives operate silently and smoothly.
- They are self-locking.
- They occupy less space.
- They have good meshing effectiveness.
- They can be used for reducing speed and increasing torque.
- High velocity ratio of the order of 100 can be obtained in a single step.
Disadvantages of Worm Gears
- Worm gear materials are expensive.
- Worm drives have high power losses and low transmission efficiency.
- They produce a lot of heat.
Applications of Worm Gear Drives:
Worm drives are used in:
- Steering system and Gate control mechanisms
- Hoisting machines
- Automobile steering mechanisms
there are some basic components
The flexspline is made of special steel with a higher resistance to fatigue. these are also elastically deformable ring type gears which either has inner or outer teeth.it adopt the elliptical shape of the wave generator. these are externally engage with the circular or dynamic spline.
circular spline has internal teeth.the difference between circular and flex spline is that circular spline is circular and the shape of the flex spline is elliptical.the circular spline keep two gear more than the flex spline.
The Dynamic Spline is an internally toothed ring gear with the same number of teeth as the Flexspline. This component rotates in the same direction and with the same speed as the Flexspline and is used as output element when the gear is used as a speed reducer.
principle of operation
in this operation the wave generator acts as input element.because we know that the shape of the wave generator is elliptical so it deforms the flex spline into the elliptical shape and so this is engage with both circular and dynamic spline.in above moving image you can understand that as the planets are rotate in the clockwise direction then it press the elastical deformable flexspline into the tooth of the fixed circular spline.
Because the Flexspline possesses two teeth less than the Circular Spline, for each 180° clockwise movement of the Wave Generator, the Flexspline moves counterclockwise by one tooth relative to the Circular Spline. Each complete clockwise rotation of the Wave Generator results in the Flexspline moving counterclockwise by two teeth from its previous position relative to the Circular Spline. The Dynamic Spline rotates in the same direction and with the same speed as the Flexspline and is used as the output element.
Characteristic of the wave gear system
1.there is no backlash
2 .it light in weight
3.they are more efficient.The mating portion of each tooth is subjected to very little slide motion. Therefore, motion loss due to friction is reduced substantially. This is why the Harmonic Drive can maintain a high level of efficiency, allowing for the down sizing of driving motors as a result.
4.they have high torque capability
5.high gear reduction is possible in low volume space.
6.coaxial input and output shafts.
7. excellent repeatability when repositioning inertial loads.
8.small numbers of components and ease of assembly.
9 .Vibration free operation. With the Harmonic Drive, quiet and vibration-free operations are possible because the teeth do not come into rolling contact with one another, and since the circumferential speed of each tooth is low, the teeth provide a well-balanced force.
disavantage of the wave gear system
during the lower torque region it include a tendency for “Wind up”.
Application of the harmonic drive
Harmonic Drives offer robot manufacturers many benefits including zero backlash, high positional accuracy, low vibration and a compact design. They can be used in any of the robot axes and their light weight design contributes minimal weight to the robotic arm which increases robot payload capacity.
- Machine Tools
Harmonic drives allow accurate control of the motions for axis positioning and for tool changing.
Applications using harmonic drives include patient beds, rehabilitation equipment, and MRI / Cat scan gantries.
- Military Aerospace
The Harmonic Drives are used to accurately rotate and tilt the antennas and arrays. They are also used for driving lunar vehicle motions and positioning aerials and telescopes e.g. Harmonic drives are used in the Hubble Telescope.
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