The lengths of the links comply with the conditions: B͞C²-K͞C² =B͞D²D͞K²=A͞B². Link 1 turns about fixed axis A. Links 2 and 3 are connected by turning pairs B to link 1 and by turning pairs C and D to sliders 7 and 6 which move along fixed guides. Links 4 and 5 are connected by turning pair K to each other and by turning pairs C and D to links 2 and 3. When link 1 turns about axis A, point K describes a Cassinian oval with the equation (x²+y²+a²)²-4a²x²-4a²r²=0 where a=O͞A and r=A͞B. Points K and B lie on a straight line perpendicular to axis Ay.
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