Electric resistance heating devices – Heating devices – Continuous flow type fluid heater
Reexamination Certificate
2001-05-02
2003-03-25
Walberg, Teresa (Department: 3742)
Electric resistance heating devices
Heating devices
Continuous flow type fluid heater
C392S450000, C392S490000
Reexamination Certificate
active
06539173
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to water heaters and more particularly to a compact water heater for very high heating capacity for delivering water at 120-130 degrees F. at flow rates in the range of from 0.5 to 2.0 gallons per minute where heating time is not longer than about 30 seconds.
2. Description of the Related Art
The following art defines the present state of this field:
Flanders, U.S. Pat. No. 3,952,182 describes a miniature electric fluid immersion heater adapted for instantaneously heating relatively small bodies or flow increments of fluid to a predetermined temperature. The heater is particularly adaptable to be mounted immediately in advance of a hot water faucet in a home or building so as to provide a continuous flow of instantaneously heated water and thereby eliminate the standard hot water heater and the entire hot water piping system in the building. The heater comprises a small, cylindrical, thermally insulated pressure vessel having a fluid inlet and outlet as opposite ends. A series of individually actuated electrical heating elements are positioned within the vessel so as to be in intimate physical contact with the flowing fluid. The heating elements are constructed of a heavy gauge resistance element which is thinly coated with a glass or ceramic frit fused into an impervious, chemically resistant, electrically non-conductive coating having negligible thermal insulation and heat storage capabilities. The wire and coating preferably have matched thermal expansion characteristics so as to minimize stress on the coating. A control circuit for selectively activating the individual heating elements delivers electrical energy automatically responsive to demand. A flow sensor prevents the activation of the majority of the heating elements unless there is a flow of fluid through the heater. When a flow is present, the amount of electrical energy transferred to the fluid as it flows through the heater is controlled by automatic separate activation of the respective elements within the heater, the number of activated elements and their periods of activation being just sufficient to maintain a predetermined fluid temperature at the heater outlet.
Eastep, U.S. Pat. No. 4,410,791 describes an electric instant water heater mounted in a cold water line in proximity to a water tap including an elongated core molded from a ceramic material and having a rectangular cross-section water flow passage extending therethrough from a circular inlet connected to a water supply pipe to a circular outlet connected to the water tap. A plurality of parallel, spaced, thin rectangular electrical resistance heating plates are positioned within the passage with one rolled edge of each plate being embedded in the core on one side of the passage way and the opposite rolled edge of each plate extending freely into the passage. A plurality of projections molded integrally with the core extend from the opposite side of the passage into the spaces between the heating plates and terminate short of the one side of the passage to define with the plates a serpentine flow path from the inlet to the outlet to cause water to be heated to flow across each face of the heating plates. The core is thermally insulated and a thermal overheat switch is provided to control energization of the heater plates.
Todd, Jr., U.S. Pat. No. 4,567,350 describes a compact instantaneous-type electric water heater for household and commercial use providing hot water at a rate of at least five gallons per minute and including a plurality of individual heating chambers connected in series flow relationship between a cold water inlet and a hot water outlet. A metallic mixing coil is disposed in series between each adjacent pair of chambers to promote even heating. The chambers are provided with electric heating elements having a combined wattage of at least thirty-thousand (30,000) watts. The heating elements are energized by a flow switch only at the time hot water is demanded and are controlled by an adjustable thermostat which sets the outlet water temperature and by a high temperature safety switch limiting outlet water temperature should the thermostat fail. The heating elements are connected to the electrical utility system by contactor-type relays so that some of the heating elements are connected to the service side of the utility system while the others are connected to the building side of the system. An adjustable regulator is provided to assure that the water flow rate will not exceed the capacity of the heater to heat the water to a minimum acceptable level. The heater is enclosed in a sheet metal casing capable of being accomodated inside a standard wood wall between a pair of adjacent studs thereof.
Takai, et al, U.S. Pat. No. 4,786,782 describes an instantaneous water heater with enhanced temperature control and less variation in output water temperature having an output hot water pipe extending into a heating tank through the top thereof and surrounding a coiled sheath electric heater for heating the water in the tank, the output pipe extending to the tank bottom and provided with an inlet thereat. An inlet pipe for water to be heated extends into the bottom of the tank and is throttled to provide an accelerated flow of incoming water away from the heater and outlet pipe toward an overheat prevention thermostat mounted externally on the top of the tank and connected to the heater. An output hot water temperature sensor located within the output water pipe adjacent the inlet thereof cooperates with a control unit of regulating operation of the heater to maintain the hot water output temperature at a preset level. The inlet to the water output pipe is throttled to insure mixing of the heated water, accurate temperature measurement and the reduction of scale deposition on the temperature sensor.
Sydenstricker, U.S. Pat. No. 5,129,034 describes an on-demand electric water heater including at least one heating chamber having an electric heating element operatively positioned between a cold water inlet and a hot water outlet. The heating elements are controlled by pressure sensing switches activated by water flow initiation or termination. A pressure relief valve is provided as a safety feature in the event the pressure sensing switches fail.
Boyd, Jr. et al, U.S. Pat. No. 5,388,179 describes a device for protecting a heating element in an electric water heater which consists of a sensor for sensing a predetermined amount of water that has entered the electric water heater and an electric circuit with a relay controlled by the sensor, for energizing the heating element when the predetermined amount of water is within the electric water heater and covering the heating element thereby preventing the burn out of the heating element; wherein the sensor has a float with electrical contacts that engage adjustable contacts set at a desired level to energize the heating element at a predetermined water level and includes an expandable seal mounted on the float preventing water from going above the float.
White, Jr. et al, U.S. Pat. No. 5,479,558 describes a very compact tankless water heater which delivers heat in proportion to demand. A flow responsive valve energizing an electrical control system is purely flow responsive, even to minute flow, and consumes no power when dormant. An uncomplicated electronic control system is connected to power by the flow switch, and is substantially deenergized when dormant. Most electronic components of the control system are mounted on the flat front wall of the pressure vessel. Thus, overall dimensions are minimized, cool water serves as a heat sink, and heat generated by electronic controls is captured for heating purposes. In particular, triacs controlling the heating elements are cooled, thus prolonging their life. A preferred embodiment of the novel heater has a maximum electrical consumption of 22 kilowatts, with equivalent heat output, and has overall external dimensions of 24 inches in height, 5.5 inches in width, a
Campbell Thor
Dynamo Aviation, Inc.
Patent Law & Venture Group
Scott Gene
LandOfFree
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