Types of Gears PDF

TYPES OF GEARS GEARS The function of a gear is to transmit motion from one rotating shaft to another. Gears are often used to increase or reduce speed or change the direction of motion from one shaft to the other. ADVANTAGES OF GEAR DRIVES Advantages 1. It transmits exact velocity...

TYPES OF GEARS GEARS The function of a gear is to transmit motion from one rotating shaft to another. Gears are often used to increase or reduce speed or change the direction of motion from one shaft to the other. ADVANTAGES OF GEAR DRIVES Advantages 1. It transmits exact velocity ratio. 2. It may be used to transmit large power. 3. It may be used for small center distances of shafts. 4. It has high efficiency. 5. It has reliable service. 6. It has compact layout DISADVANTAGES OF GEAR DRIVES Disadvantages 1. Since the manufacture of gears require special tools and equipment, therefore it is costlier than other drives. 2. The error in cutting teeth may cause vibrations and noise during operation. 3. It requires suitable lubricant and reliable method of applying it, for the proper operation of gear drives. TYPES OF GEARS 1. Spur gears are simplest and, hence ,the most common type of gear. The teeth of a spur gear are parallel to the axis of rotation. Spur gears are used to transmit motion between parallel shafts, which encompasses the majority of applications. TYPES OF GEARS 2. A rack is a special case of spur gear where the teeth of the rack are not formed around a circle, but laid flat. The rack can be perceived as a spur gear with an infinitely large diameter. When the rack mates with a spur gear, translating motion is produced. TYPES OF GEARS 3. Internal or annular gears have the teeth formed on the inner surface of a circle. When mating with a spur gear, the internal gear has the advantage of reducing the distance between the gear centers for a given speed variation. TYPES OF GEARS 4. Helical gears are similar to spur gears, but the teeth of a helical gear are inclined to the axis of rotation. The angle of inclination is termed the helix angle φ. This angle provides a more gradual engagement of the teeth during meshing and produces less impact and noise. Because of this smoother action, helical gears are preferred in high-speed applications. However, the helix angle produces thrust forces and bending couples, which are not generated in spur gears. TYPES OF GEARS 5. Herringbone gears are used in the same applications as spur gears and helical gears. In fact, they are also referred to as double helical gears. The herringbone gear appears as two opposite-hand helical gears butted against each other. This complex configuration counterbalances the thrust force of a helical gear. TYPES OF GEARS 6. Bevel gears have teeth formed on a conical surface and are used to transmit motion between non-parallel shafts. bevel gears can also be used in applications that require shaft angles that are both larger and smaller than 90°. As bevel gears mesh, their cones have a common apex. However, the actual cone angle of each gear depends on the gear ratio of the mating gears. TYPES OF GEARS 7. Miter gears are a special case of bevel gears where the gears are of equal size and the shaft angle is 90°. TYPES OF GEARS 8. A worm and worm gear is used to transmit motion between non-parallel and non-intersecting shafts. The worm has one tooth that is formed in a spiral around a pitch cylinder. This one tooth is also referred to as the thread because it resembles a screw thread. In most applications, the worm drives the worm gear to produce great speed reductions. Generally, a worm gear drive is not reversible.