Design of 6-link Stephenson type dwell mechanisms

The synthesis of linkage-type dwell mechanisms consists of determining basic four-bar linkages that trace approximate straight-lines or circular arcs, as a part of their coupler curves, and proper output-dyads. Although this method of synthesis is well known, the work done by earlier researchers was primarily graphical in nature and lacked completeness. Stephenson linkages provide a means to create an approximate dwell mechanism without the use of cams. The dwell cycle is created by first choosing of designing a four-bar linkage that contains a coupler curve with a near circular segment. An external dyad is attached to the coupler point such that the center of the floating link of the dyad coincides with the center of the circular portion of the coupler curve. This connection produces a dwell in the external dyad as the four-bar linkage traverses through the circular portion of the coupler curve. The objective of this research is to generate a computer program for designing Stephenson linkage dwell mechanisms, only by defining the link lengths of the basic four bar mechanism, which is already existing in the completed part of the designed machine, the duration of dwell and the swing angle desired. This program will save time and effort and gives more accurate results as well as generating a series of probable mechanisms enabling the designer to select a mechanism which suits other design objectives, like overall size of mechanism, places for pivot, transmission angle characteristics and velocity distribution.