Positive Clutch – Applications, Advantages and Disadvantages

The positive clutches are used when positive (no slip) drives are required. These clutches transmit power from the drive shaft to the driven shaft by the interlocking of jaws or teeth. They are rarely used as compared to friction clutch.
E.g. jaw clutch, claw clutch, toothed clutch.

 
 
Fig. 1 shows a jaw clutch; that is the simplest form of a positive clutch. Jaw clutch consists of two halves; one of them permanently fastened to the driver shaft. The other half is movable and is attached to the driven shaft. It can freely slide axially on the shaft, but cannot turn due to feather key. They can transmit power in both directions; they are used when it is not necessary to engage or disengage under load.

Spiral jaw clutches (Fig. 2) are used when it needs to transmit power only in one direction; it may be left handed or right handed. They are used when engaging and disengaging while in motion is necessary.

Application of positive clutch

They have very limited use. However, they have some application where the synchronous drive is required.

Advantages and disadvantages of positive clutch

Advantages

1. They do not slip.
2. They can transmit large torque.
3. Develop no heat during engagement and disengagement because of rigid interlocking (no friction).

Disadvantages

1. Engagement of clutch cannot be possible at high speed.
2. While starting some relative motion may be required to engage.

Extra:
What are positive drives?
The positive drive means there is no slip, i.e. the input and output have the same speeds under any conditions.

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