Electric resistance heating devices – Heating devices – Vaporizer
Reexamination Certificate
2000-05-16
2001-11-06
Walberg, Teresa (Department: 3742)
Electric resistance heating devices
Heating devices
Vaporizer
C219S433000
Reexamination Certificate
active
06314237
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to immersion heaters and more specifically to immersion heaters for converting liquids into gas as, for example, by generating steam from water for use in a wide variety of applications.
2. Description of Related Art
Humidifiers, distilling apparatus, water kettles and coffee brewing machines are some devices that use immersion heaters to heat a liquid or to convert a liquid, such as water, into vapor or steam by boiling water. In humidifiers steam mixes with air and disperses throughout a room to increase relative humidity. In a distilling apparatus a condenser receives the steam to produce distilled water. In water kettles the immersion heaters boil or heat cold water to a desired temperature. In many coffee makers, immersion heaters boil water to enable the water to percolate through coffee grounds to produce hot coffee.
Many embodiments immersion heater types exist. However, characteristically over time deposits or residues from the water adhere to the surface of such immersion heaters. These deposits form an insulating layer that impedes the transfer of heat to the water thereby reducing the effectiveness of the immersion heater. Cleaning of these deposits or residues becomes very difficult.
U.S. Pat. No. 5,111,529 (1992) to Glucksman, that is assigned to the same assignee as this invention, discloses one embodiment of an immersion heater used with a portable air humidifier. A housing contains an evaporation chamber in the shape of an inverted cup. The chamber has a steam outlet in its top and an electric heating element positioned a short distance above an open bottom. In this particular humidifier a blower delivers cool air through a duct to communicate with the evaporation chamber through its steam outlet to blow humidified air back into the room. Water from a main compartment or tank transfers to a compartment in a removable tray that allows ready access to the compartments for cleaning.
U.S. Pat. No. 4,818,344 (1989) to Glucksman, that is assigned to the same assignee as this invention, discloses a water distilling apparatus with a vaporization chamber containing an electric coil heating element, a fin tube condenser coil and an electric fan for cooling the surfaces of the condenser coils. An electric coil heating element vaporizes water and the resulting steam travels through the condenser tubing where it reconverts to pure water for delivery to a beaker through a water outlet. It is possible to remove various portions of this device for cleaning sediments and residues.
U.S. Pat. No. 5,835,680 (1998) to Glucksman et al., that is assigned to the same assignee as this invention, discloses an immersible heater with an annular collar that spaces a heating element above a bottom wall of the structure. The collar acts as an insulator thereby to limit the heat transferred to the bottom wall that is typically formed of a plastic material. In addition, a thermostat monitors the temperature of the heater. When the water is nearly evaporated, the thermostat or a backup thermofuse turns off the heater. This occurs while water still surrounds at least the collar and therefore prevents damage from overheating.
In another humidifier sold by Slant Fin, a stainless steel cup holds water to be boiled. A heating coil attaches to the exterior of the cup and heats the water in the cup to the boiling point. It is easier to clean the interior of this cup as compared to prior cups. However, like the other devices described above, during cleaning it is necessary to handle an entire base unit. However, such base units generally contain electrical components. Such base units generally can not be immersed in water or be cleaned in a dishwasher.
Each of the foregoing patents discloses a heating element that, like other heating elements of the prior art, becomes difficult to clean. As known, water available through various municipal and other supplies contains minerals that do not evaporate along with the water. Certain of these minerals, especially lime, adhere to the heat transfer area, namely to the outer surface of the heating element. As this residue accumulates, the heat transfer rate to the water decreases with two adverse effects. First, the process by which the boiling occurs becomes less efficient. Secondly, the heating coils will operate at a higher temperature. Moreover, as also known, the residue becomes more difficult to remove as it accumulates over time. Although a stainless steel cup reduces any cleaning effort, a requirement to carry an entire humidifier base to a sink for cleaning remains.
SUMMARY
Therefore it is an object of this invention to provide an immersion heater that is easy to clean.
Another object of this invention is to provide an immersion heater that inhibits the permanent build-up of residue coatings during operation while maintaining an efficient transfer of heat to liquid being boiled.
Still another object of this invention is to provide a steam generator with a heating element that is easy to clean.
Yet another object of this invention is to provide a heating module for boiling water that is inexpensive to manufacture and that is simple to clean.
In accordance with one aspect of this invention, an immersion heater for elevating the temperature of a liquid has a first body having a cavity formed therein and an exterior surface. A second body overlies the first body. An electrical heating element has a portion disposed in the cavity.
In accordance with another aspect of this invention, a steam generator converts water into steam and comprises a container for water. A heating module for immersion in the water includes an aluminum semispherical body defining a cavity and a stainless steel body having a first, semispherical portion overlying the aluminum body. Extensions of the first portion form an annular flange spaced from the aluminum body. A seal lies intermediate the flange and the container. An electrical heater is attached to the aluminum in the cavity. Electrical connectors provide a connection to an electrical source.
In accordance with another aspect of this invention, an immersible heater module converts water in a container into steam. The container has a bottom opening. The heater module includes a base having electrical connections adapted for attachment to a power source and a first body of material selected for its high heat transfer coefficient. The first body is formed with a cavity. A second body of material that resists the adhesion of residue on the material overlies the first body. An electrical heating element attaches to the first body in the cavity. A sealing structure produces a water-tight seal between the heating module and the container. Portions of the heating element extend exteriorally from the cavity and connect to electrical connections in the base.
REFERENCES:
patent: 4818344 (1989-04-01), Glucksman
patent: 5111529 (1992-05-01), Glucksman
patent: 5835680 (1998-11-01), Glucksman et al.
Appliance Development Corporation
Fastovsky L.
Herbster George A.
Walberg Teresa
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