MARINE ENGINEERING, COUPLING

COUPLING

A coupling is a device which is used to connect two shafts together at the ends for transmitting power. While it is permitting some degree of misalignment or end movement . Flexible coupling also used for vibration damper or noise reduction this also offer protection against over loads while reducing the transmission of shock load from one shaft to another unlike the clutch the coupling transmission is not designed to engage or disengage on normal operation.

Purpose of shaft couplings:-

1. To provide for the connection of shafts of units that are manufactured separately such as a motor and a generator, and to provide disconnection for repairs or alterations.
2. To provide for misalignment of the shafts or to introduce mechanical flexibility.
3. To reduce transmission shock loads from one shaft to another.
4. To introduce protection against overloads.
5. To alter the vibration characteristics of rotating units.

Shaft couplings will be used under the following conditions:-

1. With shafts having collinear axes, that is, axes in the same straight line. Rigid or flexible couplings of various form used here.

2. With shafts having intersecting axes. Universal Coupling is employed.
3. With shafts whose axes are parallel and at a relatively small distance apart. Here the double slider crank principle of  mechanism is used.

A shaft coupling should have the following requirements:-

1. It should be easy to connect or disconnect.

2. It should transmit the full power of the shaft.
3. it should hold the shafts in perfect alignment.
4. It should have no projecting parts.

Difference between coupling and clutch 


A coupling is device used to make permanent or semi-permanent connection
 where as a clutch permits rapid connection or disconnection to the operator.