What is Coupling
Reference to Wikipedia, a coupling is a device used to connect two shafts together at their ends for the purpose of transmitting power. The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end movement or both.
Couplings do not normally allow disconnection of shafts during operation, however there are torque limiting couplings which can slip or disconnect when some torque limit is exceeded.
By careful selection, installation and maintenance of couplings, substantial savings can be made in reduced maintenance costs and downtime.
Types of Coupling
As a type ofaccessories, couplings are commonly used to connect with input shafts or output shafts. Couplings have many different types and are used in machinery for several purposes.
1. Flange Coupling:
The flange coupling has two separate cast iron flanges. Each flange is mounted on the shaft end and keyed to it. The two flanges are coupled together with the help of bolts and nuts. The projected portion of one of the flanges and corresponding recess on the other flange help to bring the shaft into line and to maintain alignment. A flange which is provided with a shroud which shelters the bolts heads and nuts is called protected type flange coupling.
2. Flexible Coupling:
Flexible couplings are used to transmit torque from one shaft to another when the two shafts are slightly misaligned. Flexible couplings can accommodate varying degrees of misalignment up to 3° and some parallel misalignment. In addition, they can also be used for vibration damping or noise reduction. This coupling is used to protect the driving and driven shaft members against harmful effects produce due to misalignment of the shafts, sudden shock loads, shaft expansion or vibrations etc.
3. Gear Coupling:
A gear coupling is a mechanical device for transmitting torque between two shafts that are not collinear. It consists of a flexible joint fixed to each shaft. The two joints are connected by a third shaft, called the spindle.
4. Universal Coupling (Universal Joint):
Universal coupling is a joint or coupling in a rigid rod that allows the rod to ‘bend’ in any direction, and is commonly used in shafts that transmit rotary motion. It consists of a pair of hinges located close together, oriented at 90° to each other, connected by a cross shaft. The universal joint is not a constant velocity joint.
5. Sleeve Coupling:
Sleeve coupling is also known as box coupling, which consists of a pipe whose bore is finished to the required tolerance based on the shaft size. Based on the usage of the coupling a keyway is made in the bore in order to transmit the torque by means of the key. Two threaded holes are provided in order to lock the coupling in position.
There are also some other couplings, such as rigid coupling, beam coupling, diaphragm coupling (disc coupling), fluid coupling, jaw coupling, etc. They have their own advantages and usefulness.