Ours is a very basic manual model. The grape bunches are fed into the hopper on top and then pass through rollers where the berries are crushed and fall onto a stainless steel screen. There the stems are removed by beaters and the berries and juice fall through the screen while the stems are ejected.
Below is the hopper with the rollers at the bottom. The 'paddles' on top rotate and distribute the bunches evenly across the rollers and push them down onto them..
From underneath the crusher you can see the beaters which rotate above the screen (removed for this pic) and destem the crushed grapes. The beater axle is set at an angle which allows the movement of the bunches along the screen, where the grapes all eventually fall through. The now bare stems are ejected through the large hole at the end (top of pic).
Above is the stainless steel screen removed from the crusher.
The crusher with the stainless steel screen in place.