In the paper, the graphic method and the analytic method are applied to analyze the fast back kinematic characteristic of double crank mechanism, in term of which the formula of fast back kinematic characteristic coefficient of double crank mechanism is deduced.

The mechanism offset double crank slider not only has the characteristic of super quick-return (k>3),but also has variety time ratio.

The characteristic of quick-return of radial double crank slider mechanism was analyzed,the result proved that this mechanism not only has the characteristic of super quick-return but also has the characteristic of variety quick-return.

This paper set forth the changeability of quick-return motion and quick-return characteristics in the different extreme positions on double crank mechanism, and expressed them in the form of the line graphics ψ3～θ.

Discussion on quick-return characteristics of planar linkage;

This paper presented an optimization method to the double crank slider six bar mechanism,which had quick-return characteristics,and was used in main drive of gear shaper.

The equal-visual angle theorem and half-angle rotation was described and the method of designing crank-slider mechanism with quick-return characteristics by motion geometry was presented,including drawing method and analytical method.

The larger the speed ratio coefficient of travel and the stronger the quick return characteristics in the unidirectional operated crank-slider mechanism are the higher its working efficiency is.

The quick return characteristics of planar linkage mechanisms have closely relationship with its crank angle θ between the two limiting positions.

According to the graph drawn above, it analysizes the effects of quick-return characteristics on load-transmitting performance in detail, which provides the basis for determining .