Abstract: For the double chainstitch machine, the multiple spatial motion of the looper is realized by a spatial linkage with two degrees of freedom in the traditional way. Because of two spherical joints included in it, there are some problems, such as complicated manufacture process, wearing, and so on. Based on the analysis of the motion properties of the multiple spatial motion, two new types of spatial mechanisms are presented with spatial RCCC linkage. Hence, the design of the double chainstitch machine is converted into a function synthesis of spatial RCCC mechanism. The dimensions of spatial RCCC mechanism are obtained using the approach of adaptive curve fitting for spatial mechanism. In the new double chainstitch machine, not only the number of linkages but also the space of the machine are decreased.

Key words: Double chainstitch machine, Function generation, Spatial mechanisms