Single-loop foldable 8R mechanisms with multiple modes

Abstract

This paper deals with single-loop foldable 8R (revolute joint) mechanisms with multiple modes, which can be folded into either the same folded state in different ways or different folded states. Two types of mechanisms are discussed. The first type is constructed by integrating two spherical 4R linkages, and the second type is built by combining one spherical 4R linkage with one planar 4R linkage. Variations of the second type are presented for improving the foldability of the mechanisms. The multiple-mode mechanisms are featured by the motion modes of spherical and planar 4R linkage as well as the motion mode of spatial 8R linkage. These mechanisms can be easily fabricated since all the links of the mechanism can be spread on a plane or several parallel planes to which all the joint axes of the R joints are either parallel or perpendicular.