Machine Design
Gears
Machine Drives : A machine drive is defined as a mechanism which is intended to transmit mechanical power over a certain distance usually involving a change in speed and torque.
Mechanical drives are classified into two group according to the principle of operation. The two groups are :
- mechanical drives that transmits power by means of friction e.g. Belt drive.
- Mechanical drives that transmits power by means of engagement e.g. Chain drive and gear drive.
Gear Drives : Gear is defined as the toothed wheels which transmits power and motion from one shaft to another by means of successive engagement of teeth.
Classification of gears :
The gears are broadly classified into following groups :
- Spur gear: Spur gears or straight-cut gears are the simplest type of gear. They consist of a cylinder or disk with teeth projecting radially.
- Helical gear: Helical or "dry fixed" gears offer a refinement over spur gears. The leading edges of the teeth are not parallel to the axis of rotation, but are set at an angle. Since the gear is curved, this angling makes the tooth shape a segment of a helix. Helical gears can be meshed in parallel or crossed orientations.
- Bevel gear: Bevel gears are gears where the axes of the two shafts intersect and the tooth-bearing faces of the gears themselves are conically shaped. Bevel gears are most often mounted on shafts that are 90 degrees apart, but can be designed to work at other angles as well.
- Herringbone gear: Herringbone gears, also called double helical gearsA herringbone gear, a specific type of double helical gear, is a special type of gear that is a side to side (not face to face) combination of two helical gears of opposite hands
- Worm gear.
A worm drive is a gear arrangement in which a worm meshes with a worm gear The two elements are also called the worm screw and worm wheel.
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