This type of Grashof linkage is obtained when the shortest link is the output link (r4). The output link has full motion. The input link has a limited range of motion that is defined as follows:
lower limit: theta2 = theta1 + theta2'
upper limit: theta2 = theta1 + theta2''
where theta2' = acos [ ( r1^2 + r2^2 - ( r3 - r4 )^2 ) / ( 2 * r1 * r2 ) ]
and
theta2'' = acos [ ( r1^2 + r2^2 - ( r3 + r4 )^2 ) / ( 2 * r1 * r2 ) ]
To see animations of this linkage select the links below: