An Artobolevski’s invention: combination of planetary gear drive and double parallelogram mechanism.
Lengths of blue bars are equal.
Lengths of green bars are equal.
Lengths of orange and violet bars and center distance of green bar fixed pivots are equal.
Pitch radius of the internal gear: R
Pitch radius of the external gear: r
R = 2r (Cardano circles)
Length of pink crank: r
Length of yellow crank (fixed to the external gear): r
The orange bar translates linearly.
The violet bar translates circularly.