The lengths of the links comply with the conditions: A͞B<C͞D<B͞C<A͞D and A͞B+B͞C<A͞D+D͞C. Link 1 is the crank and has complete rotation through 360°. Link 3 is the rocker arm which oscillates through the angle α. Any point of link 2 describes a connecting-rod curve. The angles of forward and reverse oscillation of rocker arm CD correspond to angles 180°+θ and 180°-θ of rotation of crank AB.
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