Brewing unit for a coffee machine
The invention relates to a brewing unit ( 1 ) for a coffee maker for brewing a ground coffee portion ( 10 ), comprising a brewing unit housing ( 2 ), an upper plunger ( 3 ) firmly connected to the brewing unit housing ( 2 ), a holder ( 4 ) for receiving the ground coffee portion ( 10 ), said holder being open at the top and closed at the bottom by a base ( 7 ), and a brewing plunger ( 6 ) for compressing the ground coffee portion ( 10 ) in a brewing chamber ( 5 ). The holder ( 4 ) and the brewing plunger ( 6 ) are disposed movably and pivotally in the brewing unit housing ( 2 ). Mechanical operating elements are provided in the brewing unit housing ( 2 ) for raising, lowering, and pivoting the holder ( 4 ) and the plunger ( 3 ). The brewing plunger ( 6 ) is hydraulically guided displaceably in the holder ( 4 ) relative to the holder ( 4 ). Between the brewing plunger bottom side ( 14 ) and the base ( 7 ) of the holder ( 4 ) a lower chamber space ( 13 ) is provided, into which the hot water supply ( 8 ) opens. The brewing plunger ( 3 ) has a passage ( 11 ) for the hot water, said passage being provided with a valve ( 12 ) and connecting the lower chamber space ( 13 ) to the brewing chamber ( 5 ). When supplying pressurized hot water via the hot water supply ( 8 ) in the lower chamber space ( 13 ), overpressure is created there, by which the brewing plunger ( 6 ) can be hydraulically pressed in the direction of the brewing chamber ( 5 ).
1. A brewing unit for a coffee machine for brewing a coffee powder portion, comprising:
a housing of the brewing unit,
an upper plunger having a beverage outlet, the upper plunger is fixedly connected with the housing of the brewing unit,
a sleeve, open at a top of the sleeve and closed at a bottom of the sleeve by a base, the sleeve configured to receive the coffee powder portion,
a brewing plunger for compressing the coffee powder portion in a brewing chamber, the sleeve and the brewing plunger being movably and pivotally arranged in the housing of the brewing unit,
mechanical actuating members for:
raising and lowering the sleeve and the brewing plunger arranged in the housing of the brewing unit to perform brewing in a brewing position, and
pivoting the sleeve and the brewing plunger arranged in the housing of the brewing unit after the end of the brewing to a cleaning position to perform expulsion of the coffee powder portion after brewing and to a filling position for insertion of the coffee powder portion;
the brewing plunger being mechanically and hydraulically guided in the sleeve so as to displace relative to the sleeve, the upper plunger being maintained stationary relative to the housing of the brewing unit while the sleeve and the brewing plunger move from the filling position to the brewing position and to the cleaning position;
a lower chamber space, where a hot water supply duct ends fixedly connected to the sleeve, said lower chamber space provided in the sleeve between the base of the sleeve and a bottom face of the brewing plunger, the brewing plunger having a plunger duct for hot water, the plunger duct is equipped with an inlet valve and connects the lower chamber space with the brewing chamber, wherein, by supplying pressurised hot water through the supply duct, an overpressure can be created in the lower chamber space and the brewing plunger can be hydraulically pushed in the direction of the brewing chamber until the inlet valve opens and the hot water flows into the brewing chamber;
wherein the upper plunger fixedly connected with the housing of the brewing unit further comprises an outlet valve configured to open when a predetermined pressure is attained in the brewing chamber whereby a brewed beverage can flow out through the outlet only when the outlet valve opens.
2. Brewing unit according to claim 1 wherein the brewing plunger has a convex surface whose radius of curvature corresponds to a pivoting radius of the sleeve.
3. The brewing unit according to claim 2 , wherein the lower chamber space is sealed from the outside in pressure-tight manner by a plunger gasket associated with the brewing plunger and by a plunger rod gasket associated with a plunger rod of the brewing plunger.
4. Brewing unit according to claim 1 , wherein the lower chamber space is sealed from the outside in pressure-tight manner by a plunger gasket associated with the brewing plunger and by a plunger rod gasket associated with a plunger rod of the brewing plunger.
5. A brewing unit for a coffee machine for brewing a beverage using a portion of coffee powder, comprising:
a housing;
an upper plunger having a beverage outlet, the upper plunger is mounted in a fixed manner to the housing to be stationary relative to the housing throughout the brewing of the portion of coffee powder;
a sleeve open at a top end of the sleeve and closed at a bottom end of the sleeve by a base, the sleeve configured to receive the portion of coffee powder;
a lower plunger for compressing the portion of coffee powder in a brewing chamber formed by the sleeve, the upper plunger and the lower plunger, the sleeve and the lower plunger movable in the housing;
mechanical actuators configured to raise and lower the sleeve and the lower plunger in the housing of the brewing unit and to pivot the sleeve and the lower plunger, so that the mechanical actuators move the lower plunger downwards relative to the sleeve and move the sleeve and the lower plunger from a brewing position to a filling position wherein a new portion of coffee powder is received in the sleeve while the upper plunger remains fixedly connected with and stationary relative to the housing of the brewing unit;
a lower chamber connected to a hot water supply duct, the lower chamber provided in the sleeve between the base of the sleeve and a bottom face of the lower plunger, the lower plunger having a plunger duct for hot water;
an inlet valve and an intermediate duct that controls flow of hot water from the lower chamber to the brewing chamber, so that pressure can be developed in the lower chamber before the inlet valve opens; and
an outlet valve associated with the beverage outlet and configured to open when a predetermined pressure is attained in the brewing chamber to thereby allow the beverage to flow out through the outlet.
6. The brewing unit of claim 5 , wherein, the hot water supply duct is fixedly connected to the base of the sleeve.
7. The brewing unit of claim 5 , wherein the sleeve and the lower plunger are configured to be pivoted within the housing from a brewing position to a cleaning position, wherein the portion of coffee powder used for brewing is expelled.