kinematic Pair | Link | Definition & Types Explained with Images

What is a kinematic pair?

Before going to the definition of kinematic pair, let us first understand definition of a link.

A resistant body or a group of resistant bodies with rigid connections preventing their relative movement is known as link.

links can be classified on the basis of their ends on which turning pairs can be placed.

Now we can move on to definition of kinematic pair.

A kinematic pair or simply a pair is a joint of two links having relative motion between them.

Types of kinematic pairs

Kinematic pairs can be classified according to following three criteria

1. Nature of contact
2. Nature of mechanical constraint
3. Nature of relative motion

Kinematic pairs according to the nature of contact

1. Lower pair

A pair of links having surface or area contact between its members is called lower pair.

2. Higher pair

A pair of links having line or point contact between its members is called higher pair.

Kinematic pairs according to the nature of mechanical constraint

1. Closed pair

The pair of links in which the contact between the members can be broken by destruction of at least one of the members is called closed pair.

2. Unclosed pair

The pair of links which are in contact either due to gravity or spring action is called unclosed pair.

Kinematic pairs according to the nature of relative motion

1. Sliding pair

Pair of links having sliding motion with respect to each other is called sliding pair.

2. Turning pair

Pair of links having turning or revolving motion with respect to each other is called turning pair.

3. Rolling pair

Pair of links having rolling motion with respect to each other is called rolling pair.

4. Screw pair (helical pair)

Pair of links having turning as well as sliding motion with respect to each other is called screw or helical pair.

5. Spherical pair

When one link in the form of sphere turned inside a fixed link, it is a spherical pair.

Image source for relative motion types