| 摘要 |
In the electrically heated continuous flow heater another electric switching element (26) having an open and a closed switching position is electrically connected in series to the thermostat (12), it being always closed in the brewing process while it can be opened and closed again in the keepwarm process by a control circuit (11). Said control circuit (11) comprises a temperature sensor (21) which is in good heat contact with the infusion beverage. When in the initial phase of the keep-warm process the sensor temperature is in excess of a definable switching temperature, the control circuit (11) keeps the switching element (26) in its open position for as long as the sensor temperature remains higher than the switching temperature in the course of the consequently occurring cooling of the infusion beverage. When the sensor temperature is below or equal to the temperature of the switching element (26) in the keep-warm process, the control circuit (11) keeps the switching element (26) in its closed position for a predefinable first time interval (heating cycle) irrespective of the sensor temperatures produced during the heating cycle. The heating cycle is rated to be so short that the temperature of the thermostat (12) always remains below said's opening temperature. Upon termination of the heating cycle, the control circuit (11) opens the switching element (26) irrespective of the temperature measured by the temperature sensor (21) at the end of the cycle and keeps it open for a definable dead time. It is accomplished thereby that, on the one hand, the continuous flow heater (1) furnishes its full heating power in the brewing process, and that, on the other hand, this power is controlled in the keep-warm process such that the temperature variations of the warming plate (10) and hence those of the infusion beverage are minimized to the greatest possible extent. |
