The lengths of the links comply with the conditions: E͞B=D͞C and B͞C=E͞D, i.e. figure EBCD is a parallelogram linkage. Rigid triangles ABE,GCB, HDC and FED are respectively similar to triangles AGF, GHA, HFG and FAH. For any configuration of parallelogram linkage EBCD, quadrangle AGHF retains constant angles at its vertices. When link 1 turns about fixed axis A, selected as the centre of similarity, and one of the points, G, H or F, is traced along any arbitrary path, the other two points describe similar paths turned through constant angles. The mechanism has reversibility since any point, A, G, H or F, can be selected as the centre of similarity.
$852$LW,P$