D = The lengths of the links comply with the conditions: CB= = 4.3AC, CF = 2.65AC, FD = 2.1AC, DE = 3.5AC = AE, OB=2AC, AO= 3.6AC,EO= = 3.3AC and FB 4.86AC. Sliding member 3 slides along guide a-a of radius OB, turning through angle a about axis O. When point C of crank / travels along the portions of the circle indicated by heavy continuous lines, point F of connecting rod 4 describes a path of which the portions indicated by heavy continuous lines approximate circular arcs of radius DF. The centres of the arcs are at points D and D. When crank / rotates, link 2 oscillates about fixed axis E and has two dwells when point F is on the portions of its path indicated by heavy continuous lines.