The kinematic pairs are joined in such a way that the last link is connected to the first link, in order to transmit motion in a desired direction. We can say that kinematic chain is a combination of rigid bodies which provides completely or successfully constrained motion.
Relation between number of links (l) and number of pairs (p) in a kinematic chain can be expressed as
l = 2p – 4
Relation between number of joints (j) and number of links (l) in a kinematic chain can be expressed as
j = (3/2)l – 2
Both the above equations are applicable for kinematic chains having lower pairs.
Following types of joints are usually found in a kinematic chain.
(a). Binary joint – In this type, two links are joined at a connection.
(b). Ternary joint – Three links are connected at a connection.
(c). Quatenary joint – Four links are connected at a connection.
There are three types of Kinematic Chains.
(a). Four bar chain – It has four turning pairs.
(b). Single slider crank chain – It has one sliding and three turning pairs.
(c). Double slider crank chain – It has two sliding and two turning pairs.