This is a combination of cam and bevel gear differential mechanisms. The bevel gears have the same tooth number.
Input is the orange spur gear shaft to which a cam is fixed. The cam’s profile is a symmetric double Archimedes curve. The green spur gear shaft and the green bevel gear are fixed together.
Transmission ratio of the spur gear drive is 4.
The yellow bevel gear idly rotates on the pink arm carrying the red roller.
The blue output bevel gear has four dwells in one revolution of the green and blue bevel gears.