Motion of Open Curves
"Since these curves are not closed, one pair cannot be used for continuous motion; but a pair of such curves may be well adapted to sectional wheels requiring a varying angular velocity." This figure shows an example of the process.
Peter Schwamb, S.B. And Allyne L. Merrill, S.B. Elements of Mechanism (New York, NY: John Wiley & Sons, Inc., 1904)
Courtesy the private collection of Roy Winkelman