Types of Couplings Used in Shafts

Couplings are mechanical elements that ‘couples’ two drive elements which enables motion to be transferred from one element to another. The driven elements are normally shafts. Application of couplings are mainly seen in automobiles, for example the drive shaft which connects the engine and the rear axle in an 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. There are various types of coupling available based on the area of application. They are generally categorized in the following varieties

1. Rigid Couplings
2. Flexible or Compensating Couplings
3. Clutches are also a type of Coupling

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

Rigid Coupling - Sleeve or Muff Coupling
Rigid Sleeve or Muff CouplingsSleeve or muff coupling is the simplest type of rigid coupling. It is a hollow cylinder with an inner diameter which will make an engineering fit with the drive shaft and the driven shaft. There is a keyway in the sleeve to couple the drive shaft with the sleeve and to the driven shaft with the help of a gib headed key. And there are some Allen screws are also provided in the sleeve to lock the key in position.

Spline Coupling- As we can see the sleeve coupling with a keyway above, this spline coupling is similar as the sleeve or muff coupling but instead of the keyway, we have a number of slots on the inner diameter of the sleeve as shown in the picture below.

The sleeve inner side and the shaft outer side will have the same profile slots with the same number of them.

Rigid Coupling - Spline Coupling

Rigid Coupling - Flange coupling
 Flange Coupling – A coupling having two separate flange hubs with the keyed fit to the individual shaft. These two flanges will be joined together with the bolted pattern. On one flange there will be projected part called pilot or spigot on the other flange there will be a corresponding recess to make the perfect alignment for both flanges.
This Flange coupling can be helpful to bring the shaft to maintain the alignment and also capable to adopt the heavy loads. so it will be used on the large shafts.

Clamp or split-muff or compression coupling- The above Sleeve or Muff coupling is a single mechanical part. whereas this clamp or compression or Split miff coupling is made into two pieces and bolted together with the mild steel studs or bolts.
There is one advantage over the sleeve or muff coupling is that to install this split muff coupling, no need to change the positions of the drive shaft or the driven shaft.
This coupling can be used for heavy duty and moderate speed applications.
Clamp or split-muff or compression coupling

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

A clutch is a mechanical device which engages and disengages power transmission especially from driving shaft to driven shaft.
In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). In these devices, one shaft is typically attached to an engine or other power unit (the driving member) while the other shaft (the driven member) provides output power for work. While typically the motions involved are rotary, linear clutches are also possible.
In a torque-controlled drill, for instance, one shaft is driven by a motor and the other drives a drill chuck. The clutch connects the two shafts so they may be locked together and spin at the same speed (engaged), locked together but spinning at different speeds (slipping), or unlocked and spinning at different speeds (disengaged).