Electric resistance heating devices – Heating devices – Fluid-in-circuit type heater
Reexamination Certificate
2001-02-22
2003-02-18
Walberg, Teresa (Department: 3742)
Electric resistance heating devices
Heating devices
Fluid-in-circuit type heater
C222S251000
Reexamination Certificate
active
06522834
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to liquid heaters for brewing beverage products, for reconstituting dried food products by supplying heated water thereto and for heating liquid food products. More specifically, the present invention relates to liquid heaters utilizing direct electrical resistance (DER) heating devices.
BACKGROUND OF THE INVENTION
Conventional beverage makers such as coffee brewing machines have water storage tanks, commonly made of stainless steel, to hold water and heating rods with which to heat the water in the water storage tanks. The heating rods include tubes packed with sand and heat generating filaments. Heat generated by the filament is transferred to the sand and, then, to the water in the water tank, thereby heating the water.
Other conventional beverage makers include water boilers similar to the hot water storage tanks except that these boilers are held under pressure enabling the water to be heated to a higher temperature.
These conventional beverage makers, however, suffer from a number of drawbacks. For instance, they require a lengthy cold start period during which a cold water tank, or a boiler, filled with unheated water is heated. They also require a long recovery time when heated water is dispensed and, then, replenished with unheated water. In addition, the water quality tends to degrade over time when kept at a high temperature for prolonged periods of time.
In an effort to alleviate the above drawbacks, some of the conventional coffee brewing machines include on-demand water heating devices. These conventional on-demand water heating devices heat water only when requested. Conventional on-demand heating devices that produce small quantities of heated water include indirect electrical resistance heaters which are bonded to a water pipe. On the other hand, conventional on-demand heating devices that produce larger quantities of heated water include heating blocks which contain a coiled water tube and a coiled heating rod encased in a block of metal. The heating block is a thermal energy storage device to heat water on-demand as unheated water passes through the heating block. This requires a constant supply of electrical power to the heating block in order to maintain it at a certain temperature, thereby wasting electrical energy and losing thermal energy to its environment. In general, the conventional on-demand water heaters are inefficient, among other reasons, because they utilize the indirect resistance heating method.
In addition, due to the drawbacks described above, the conventional heating devices cannot produce heated water at a stable temperature which is a desirable feature in brewing some high quality beverages.
Instead of the conventional water heating method described above, direct electrical resistance (DER) heating methods have been developed for industrial uses. The DER method is also known as electroheating, in-line heating or ohmic heating. A conventional DER device includes a pair of electrodes and an electric power supplier for applying a high power to the electrodes. As an electrically conductive medium, such as meat or other food products, passes between the electrodes, electric currents flow through the medium which generate heat therein. The medium generates heat since it acts as a resistor.
Several references disclose the DER methods for heating different types of electrically conductive medium. For instance, U.K. Patent Application No. GB-A-2304263 (the “'263 application”) discloses an electroheating, processing, pasteurizing and cooking liquid egg. In this electroheating method, liquid egg is pasteurized when it passes through a pair of electrodes while electric power is applied between the electrodes. This method, however, heats only one type of electrically conductive medium, the liquid egg, in a controlled production line. In addition, this method, as with other conventional DER heating methods, requires a high power electrical power supplier among other industrial strength parts, which tend to be relatively expensive for nonindustrial use.
SUMMARY OF THE INVENTION
Accordingly, a general purpose liquid heater using a DER heating device is provided in the present invention, which does not have the drawbacks of the conventional DER heating devices described above.
First of all, the DER heating device of the present invention draws its electrical power from electrical power outlets commonly supplied to homes, offices, restaurants or food servicing facilities. The DER heating device of the present invention is also adaptable to varying electrical conductivity of different types of liquid. Further, electrodes of the DER heating device of the present invention are made of rigid, relatively insert, electrically conductive material tolerant of wear, e.g., graphite. Other advantages over the conventional water heaters are also described in detail below.
In addition, since the heating device of the present invention utilizes a DER heating device, it is capable of rapid and efficient transfer of the electrical energy into the water as thermal energy while reducing the energy loss associated with the indirect heating methods of the conventional beverage makers discussed above.
More specifically, the liquid heater of the present invention includes a first electrode having an electrically conducting surface and a second electrode having a first electrically conducting surface disposed spaced apart from the electrically conducting surface of the first electrode. The liquid heater also includes a first heating passage defined, at least in part, by the electrically conducting surfaces of the first and the second electrodes, the first heating passage including a first opening configured to receive liquid into the heating passage. Electrical power to the liquid heater is provided by an electrical power supplier configured to draw an alternating electrical current having a frequency lower than or substantially equal to 60 Hz and supply an alternating electrical voltage having a frequency substantially equal to or higher than 50 Hz across the first and second electrodes. In this configuration, the first and second electrodes are arranged to make electrical contacts with liquid received into the heating passage, and the liquid in the heating passage generates heat when an electric current flows between the first and second electrodes and through the liquid. It should also be noted that the alternating electrical voltage to be supplied across the electrodes can have a frequency between 20 KHz and 200 KHz.
Advantageously, the electrical power supplier may include an AC/DC converter configured to convert the alternating electrical current to a direct electrical current, a voltage level controller configured to adjust a voltage level of the converted direct electrical current, and a DC/AC converter configured to generate the alternating electrical voltage to be supplied across the electrodes based on the adjusted voltage level of the converted direct electrical current. The electrical power supplier can further include a transformer coupled to the electrodes and the DC/AC converter, the transformer configured to increase electrical power of the alternating electrical voltage to be supplied across the electrodes. If desired the voltage level controller can further include a pulse width modulated signal generator configured to produce a plurality of pulses each of which having a respective pulse width, a duty cycle switch configured to multiply the plurality of pulses with the direct electrical current from the AC/DC converter, and a filter to generate the adjusted voltage level of the converted direct electrical current. Also, if desired, the second electrode can have a pattern on its electrically conducting surface. The patterns can be a number of arcuate grooves.
In order to control the heated liquid production more efficiently, the liquid heater of the present invention can also include a temperature sensor configured to measure the temperature of the heated liquid, a current meter configured to measure
Clyde Gene F.
Herrick James P.
Sastry Sudhir
Wedral Elaine R.
Campbell Thor
Nestec S.A.
Walberg Teresa
Winston & Strawn
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