Couplings are mechanical elements that ‘couples’ two drive elements which enables motion to be transferred from one element to another. The drive elements are normally shafts. We tend to see lot of applications of the couplings mainly in the automobiles, for example the drive shaft which connects the engine and the rear axle in a bus or any automobile is connected by means of a universal joint.

In order to transmit torque between two shafts that either tend to lie in the same line or slightly misaligned, a coupling is used. Based on the area of applications there are various types of coupling available. But they are generally categorised in the following varieties

1. Rigid Couplings

2. Flexible or Compensating Couplings

3. Clutches to are a type of Coupling – We will the dealing on them separately.

RIGID COUPLINGS

Rigid Couplings are mainly used in areas where the two shafts are coaxial to each other. There are many types of couplings that fall under the rigid couplings category. They are

· Rigid Sleeve or Muff Couplings- This is the basic type of coupling. This 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 in 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. The photo shows a type of the rigid sleeve or muff coupling.

 Flanged Coupling – The coupling basically consists of two flanged end pieces as shown in the figure. A spigot and recess is provided in the flanges to provide location between them. The flanges are connected firmly by means of fitted bolts which are tightened accordingly to the torque to be transmitted.

FLEXIBLE OR COMPENSATING COUPLINGS

Flexible couplings are normally used in areas where the coaxiallity between the connecting shafts is not always assured and in areas where there is a possibility of occurrence of shocks in the transmission is applicable. They are also called as Elastic Couplings. By construction these couplings tend to have a elastic member in between the two connecting entities. The different types of flexible couplings are

1. Flanged Pin Bush Couplings

2. Bibbly Coupling

3. Gear Tooth Coupling

4. Tyre couplings

5. Elastomeric Couplings – This consists of jaw type and S-flex couplings.

6. Oldhams Coupling

7. Universal Coupling or Hooke’s Coupling

8. Bellows Coupling

Each of the above couplings are quite unique in their construction and we can deal in detail on their constructional and working aspects in separate articles.