The two links or element of a machine when in contact with each other are said to be form of a pair. if the relative motion between them is completely or successfully constrained the pair is called a Kinematics pair.
TYPE OF KINEMATIC PAIR:-
Kinematic pair cab be classified on the basis of
A.Type of Contact
B. Type of Constraint
C. Type of relative motion
1. According to the types of contact between the element.
a. Lower pair:- When the two element of pair have a surface contact when relative motion take place and the the surface of one element slides over the surface of the other. the pair formed is known as a lower pair.
b. Higher pair:- When the two element of a pair have a line or point contact when relative motion take place and motion between the two element is parting turning and parting sliding then the air is known as a higher pair.
2. According to the types of Constraint pair.
a. Closed Pair:- When two element of a pair are connected together mechanically in such a way that only required kind of relative motion occurs it is then as closed pair. the lower pair and is closed pair.
b. Unclosed pair:- When the two element of a pair are connected mechanically but are kept in contact by the acting of external force the pair is said to be a Unclosed pair.
3. According to the types of relative motion between the elements:-
a. Sliding pair:- When the two element of pair are connected in such a way that one can any slide relative to the other the pair is known as a sliding pair. Ex- piston and cylinder,etc.
b. Turning pair:- When two element of there are connected in such a way that one and only turn or revolve about a fixed axis of another link the pair is known as a turning pair.
c. Rolling pair:- When the two elements of a pair are connected in such a way that one roll over another fixed link the pair is known as a rolling pair.
d. Screw pair:- When the two element of a pair are connected in a such a way that one element can turn about the another by screw thread the pair is known as screw pair.
e. Spherical pair:- When the two elements of a pair are connected in such a way that one element turn screw or the other fix element the pair form is called a spherical pair.
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