Cafina Ag

Hermann Meier

Jean-Paul Franzolin

The invention provides a piston-cyclinder-assembly for a coffee brewing apparatus, the assembly comprising a cylindric cavity serving as a brewing chamber, a closing member mounted on the cylindric cavity at one end thereof, and a piston which can be displaced into and retracted from the brewing chamber at the other end. The piston is equipped with internal brewing water channels leading to the front face of the piston and connected to a brewing water connector. The closing member has plate-like shape and is fixed against movement in axial direction of the brewing chamber but is pivotally mounted near the cylindric cavity. To drive the piston into the cavity and to retract it, and to pivot the closing member, first and second stepping motors, respectively, are provided which are operatively connected to a control unit. Another embodiment is provided with a normal electric motor to drive the piston and with a pressure sensor. As soon as the piston exerts a preselected pressure on the coffee powder in the brewing chamber, the displacement of the piston is stopped.

Piston-cylinder-assembly for a coffee brewing apparatus and a method of

In a coffee brewing apparatus, a milling assembly produces coffee powder which is filled into a brewing chamber. Then the brewing chamber is closed by a displaceable piston in order to exert a preselected pressure on the coffee powder in the brewing chamber, and hot water is forced through the compressed coffee powder. If it is recognized after several subsequent preparation cycles that too much or too less coffee powder has been filled into the brewing chamber, the operation period of the milling assembly is shortened or extended automatically under the influence of a programmed control unit. Simultaneously or additionally, a flow rate detector measures the amount of water flowing through the compressed coffee powder and the control unit measures the time required by the water to pass through the coffee powder in the brewing chamber. If a deviation of the measured time from a reference value is detected, the milling rate is adjusted to produce finer or coarser coffee powder in one of the subsequent preparation cycles. Minor deviations within normal tolerances are ignored.

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Dottingen, Switzerland

Hermann Meier