Model 36: step-dwell mechanism


Kinematic scheme:



The mechanism consists of a superposition of a crank-slider mechanism and a planetary gear pair. The coupler AB and the planet wheel (radius r=AB) are part of the same body. The rotation centre of the sun wheel coincides with the crank rotation centre A0.

For certain dimensions this mechanism will make a continuous stepping motion of the sun gear. The usual application is to drive a belt with intermittent motion, as sometimes required in production machinery. The (infinitesimal) dwell is short, but the motion is very smooth, see the graph below.




The output step b of the sun gear can be a whole division n>1 of one revolution of the input crank angle a. In the model n=6, so the output step is 60 deg.

For a given value of the sun gear radius R0 the other dimensions are determined as follows:

Planet gear radius r = R0*(n - 1) / n 

Crank length a = R0 - r






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