The lengths of the links comply with the conditions: A͞D=D͞C, A͞B=B͞C, A͞E=E͞F=E͞H and C͞G=G͞F. Figure ABCD is a rhomboid linkage. Link 1 turns about fixed axis A and is connected by turning pairs B and E to links 3 and 5. Link 4 turns about fixed axis D and is connected by turning pairs C and G to links 3 and 2. Links 2 and 5 are connected by turning pair F. When link 1 turns about axis A, point F describes straight line Aa which is perpendicular to AD, and point H describes straight line Ab which coincides with AD. Points of link 5 describe ellipses. Angle ∠ AEF is always equal to angle ∠ FGC. Angle ∠ FCB equals 90°.
$708$LW,GI$