Clutch for medium-size eccentric presses.
The big pulley rotates continuously. For connecting the clutch, step on a pedal (not shown) to pull down the green slider. Then the pink rotary key can rotate (under the red spring’s force) when it meets the slot in the big pulley hole, thus makes the crankshaft rotate.
The green slider goes up to disconnect the clutch.
Keep down the pedal to make the crankshaft rotate continuously.
The small picture shows how the rotary key rotates in round hole between the crankshaft and the big pulley when they are immobile.