Apparatus for preparing coffee

An apparatus for the preparing of coffee in an automatic coffee-percolator, including a scalding cylinder intended for receipt of ground coffee, including further a first and a second piston and piston rods belonging thereto, which pistons are allocated to said cylinder and are movable relative to each other along the axis of said cylinder and operative to define a scalding chamber and to compress ground coffee filled thereinto, which first piston closes off one of the ends of the cylinder and which second piston is movable between a working piston inside said cylinder and a working position outside of latter such to clear the other end of said cylinder allowing said first piston to push the used ground coffee out, including further means for feeding water or steam and for discharging the coffee prepared, said apparatus comprising a driving device operative to move said scalding cylinder back and forth between predetermined positions in a controlled manner along at least one longitudinal guide along its axis, which cylinder moves in the one of the directions of movement over the substantially resting second piston and positively carries thereby the first piston along until the filled in ground coffee is compressed under a predetermined force between the two pistons, and moves off said second piston when moving in the opposite directions of movement and clears the corresponding end of said cylinder and shifts relative to said first piston locked in a predetermined position such that it urges the used portion of ground coffee out of the free end of the cylinder.