Input: green shaft of two long pins rotating regularly.
Output: pink cam shaft of two crossed helical grooves oscillating with dwells at its stroke ends. Oscillating angle: 180 deg.
The arcs of the input are for keeping the output immobile during its dwells.
Pay attention to the ellipse section of the pins which helps the output rotate stably when the pins are at the crossed place of helical grooves.
Long axis of the pin section ellipse is in the direction of the groove along which the pin moves.