Monday 22 July 2013

ALL ABOUT GEARS

Gears are Power transmission elements. It is the Gears that decides the torque, speed and direction of rotation of all the driven machine elements. Broadly speaking, Gear types may be grouped into five major categories. They are Spur, Helical, Bevel, Hypoid, and Worm. A lot of intricacies are there in the different types of gears. Actually The choice of gear type is not a very easy process. It is dependent on a number of considerations. Factors that go into it are physical space and shaft arrangement, gear ratio, load, accuracy and quality level.

Types of Gears

A number of gears are manufactured using different materials and with different performance specifications depending on the industrial application. These gears are available in a range of capacities, sizes and speed ratios, but the main function is to convert the input of a prime mover into an output with high torque and low RPM. These range of gears find use in almost every industry right from agriculture to aerospace, from mining to paper and pulp industry. Some of the popular types of gears in use are :

Spur Gears

Spur gears are by far the most common type of gear and with the exceptions of the "cog" the type of gear that has been around the longest. Spur gears have teeth that run perpendicular to the face of the gear.

Helical Gears

Helical gears are very similar to spur gears except the teeth are not perpendicular to the face. The teeth are at an angle to the face giving helical gears more tooth contact in the same area.

Helical gears can also be used on non-parallel shafts to transmit motion. Helical gears tend to run quieter and smoother than spur gears due to the increased number of teeth in constant contact at any one period of time.

Herringbone Gears

Herringbone gears resemble two helical gears that have been placed side by side. They are often referred to as "double helicals".

One benefit of herringbone gears is that it helps to avoid issues related to side thrust created with the use of helical gears.

Bevel / Miter Gears

Bevel gears are used mostly in situations that require power to be transmitted at right angles (or applications that are not parallel). Bevel gears can have different angles of application but tend to be 90°.

Worm Gears

Worm gears are used to transmit power at 90° and where high reductions are required. The worm resembles a thread that rides in concaved or helical teeth.

Internal Gears

Internal gears typically resemble inverted spur gears but are occasionally cut as helical gears.

Racks

A rack is basically a straight gear used to transmit power and motion in a linear movement.

Face Gears

Face gears transmit power at (usually) right angles in a circular motion. Face gears are not very common in industrial application.

Involute Splines

Splined shafts and hubs are usually used as connectors in many different types of applications. One of the most common applications is to connect motors to gear reducers. They may also be used in transmissions.Involute splines resemble spur gears, but tend to have different pressure angles