| 摘要 |
An espresso machine is provided with an infusion piston displaceable inside an infusion cylinder. The infusion piston is force-connected to a spring and to a device for activating the infusion piston and, in a first position, tightly encloses ground coffee inside an infusion chamber of the infusion cylinder between itself and an outlet sieve. A pressurized water inlet is connected to the infusion chamber, the infusion piston is automatically pushed by the pressure of the infusion water flowing into the infusion cylinder and counter to a spring force to a second predetermined position, thereby expanding the infusion chamber, whereupon during a pressure drop inside the infusion chamber the infusion piston is returned automatically to the first position. The infusion piston can essentially be displaced proportional to a pressure increase inside the infusion chamber, caused by the infusion water flowing in, until it reaches a nominal opening pressure for a frothing valve that closes off the infusion chamber in a downstream direction.
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