Beverage brewing apparatus with constant temperature water reservoir

Abstract

A beverage brewing apparatus includes a hot water reservoir from which heated water is dispensed in predetermined serving volumes through a beverage filter to a serving beaker. A volume of cold water equal to a predetermined serving volume is admitted to a lower inlet zone of the reservoir, heated by an electric resistance heating element within the reservoir and dispensed in a volume equal to the serving volume from an upper outlet zone of the reservoir coincident with the introduction of cold water into the inlet zone. The reservoir has a volume greater than twice the predetermined serving volume so that a volume of resident heated water is contained in the central brew zone thereof. A temperature sensing element, e.g., thermistor, is disposed within the lumen of a hollow heat conductive tubing extending to a predetermined location in the brew zone at or near the center of the reservoir and produces a temperature control signal continuously indicative only of the temperature of the water in the brew zone. An electronic control circuit varies the duty cycle of the heating element over recurring timing intervals in response to the control signal to maintain the water in the brew zone at a predetermined temperature. The inlet and outlet zones correspond to the lower one-fourth and the upper one-fourth volumes, respectively, of the reservoir.