The lengths of the links comply with the conditions: P͞D=D͞A=P͞E=E͞B=c, P͞A=P͞B=2c and 0͞D=0͞E=b. Figure ODPE is a rhomboid linkage. Links 1 and 7, turning about fixed axis 0 , are connected by turning pairs E and D to links 6 and 5. Links 5 and 6 are connected together by turning pair P, and are connected by turning pairs A and B to sliders 3 and 4 which move along cross-piece a-a of T-shaped link 2. Link 2 turns about fixed axis C. Point P describes a conic section with the equation ρ=p/(1+e*cos(ϕ)) where ρ=0͞P, p=(b²-c²)/0͞C, e=0͞G/C͞F, ϕ = polar angle between vector ρ and the polar axis Ox. Point P describes an ellipse when e<1, a parabola when e=1 and a hyperbola when e>1.
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