Electric resistance heating devices – Heating devices – Convection space heater
Reexamination Certificate
1995-07-14
2002-02-26
Hoang, Tu Ba (Department: 3742)
Electric resistance heating devices
Heating devices
Convection space heater
C392S373000, C392S375000, C392S383000, C392S422000
Reexamination Certificate
active
06351602
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to portable electric room air heaters and particularly to upright radiant heaters suitable for placement in a corner or any other location in a room while occupying a minimum amount of floor space. As will become apparent to those familiar with the art, aspects of this invention may be used with other types of heaters.
An upright or so-called “tower” heater is relatively tall in relation to its horizontal area or “footprint.” Examples are shown in U.S. Design Pat. No. 111,000, granted Aug. 23, 1938, to C. Knox et al., and U.S. Design Pat. No. 141,834 granted to W. E. Maxson, Jr. on Jul. 10, 1945. These may be contrasted to horizontal heaters that have a relatively low profile, such as shown in U.S. Pat. No. 3,175,550, issued to R. S. Knapp on Mar. 30, 1965, U.S. Pat. No. 3,059,090, granted to R. S. Waters on Oct. 16, 1962, and U.S. Pat. No. 3,610,882, issued to William A. Omohundra on Oct. 5, 1971.
One of the problems encountered in any portable heater is the creation of localized “hot spots” on or adjacent the heater. These are areas that get much hotter than adjacent areas. Hot spots are undesirable because they can present a fire hazard as well as cause discomfort to the user of a heater. Portable electric air heaters sold in the United States at this time must meet testing requirements of Underwriter's Laboratories, Inc. when in actual service, so that the heaters do not present a risk of fire, electric shock or personal injury when operated continuously under abnormal conditions. With many heaters, such tests can only be passed successfully by the use of relatively expensive safety control devices.
SUMMARY OF THE INVENTION
An object of this invention is to provide a portable heater which is inherently designed to avoid the formation of hot spots and therefore, avoid the need for all but basic electrical safety devices.
Another object of the invention is to provide an efficient, upright radiant electric heating appliance which occupies minimal floor space, is easy to operate, and which is capable of heating a room relatively rapidly.
Another object is to provide a thermostatically-controlled room air heater with accurate on-and-off cycling to maintain or increase to desired room temperatures. Ancillary thereto is an object of minimizing, simplifying and reducing cost of the structure for controlling such a thermostat.
Another object of the invention is the provision of such a heater which has exterior housing portions which are relatively cool to the touch, thereby allowing such portions to be produced from thermoplastic molded materials that may readily be manufactured to various different shapes. This enables designers of heaters to design heaters of various aesthetically pleasing designs that may be produced at lower costs than similar heaters which have all metal housings.
An upright radiant electric heating appliance in accordance with this invention has a reflector assembly that includes radiant heat reflective side panels which lie in vertical planes that intersect one another at an included angle of between 90 and 180 degrees, a vertically-extending heating element assembly located near the rear of the reflector assembly that radiates heat energy throughout substantially 360 degrees in a horizontal direction, and a circular open grill at the front of the reflector assembly. Heat energy is directly radiated by the heating element assembly through the open grill or reflected by the reflective side panels through the open grill.
In a preferred embodiment, the heating element assembly is preferably spaced on the order of eight inches or more from the open grill and each reflective side panel is similarly spaced from the opposite side of the open grill. Accordingly, most of the heat energy reaching the open grill has traveled at least eight inches from the heating element assembly or from a reflective side panel. Because the reflective side panels lie at a mutually included angle of 90 degrees or more the reflected heat energy is dispersed across the open grill into the surrounding area. Hot spots are avoided because none of the heat energy is focused. The reflective side panels may be formed with vertical ribs for rigidity and also to create a pleasing visual effect due to the reflection from different planes of the visible light created by the heating element assembly.
Also forming part of the reflector assembly are horizontally extending, reflective top and bottom walls. Heat energy impinging on these walls and exiting from the open grill at the front of the reflector assembly is also dispersed across the open grill into the surrounding area. The horizonal top and bottom walls also avoid any focusing of the heat energy which might produce hot spots.
The reflector assembly may also include a reflective rear panel that connects the side panels and that is located behind the heating element assembly. Heat energy reflected by the rear panel is mostly reflected back to the heating element assembly or to the side panels. The reflective side panels and rear panel preferably are formed from a single piece of sheet metal, preferably tin plated steel. The reflective top and bottom walls can be separately formed from the same material.
Further in accordance with this invention, room air is drawn into the heater from below the reflector assembly and forced upwardly by a motorized fan through an air passage behind the reflector assembly and then through an open control chamber at the top of the heater before passing through ducts positioned along the top front edge of the reflector assembly. As well known, the air temperature at the floor of a room is cooler than the air above the floor and becomes increasingly warmer toward the ceiling of the room. Accordingly, air drawn into the bottom of the heater of this invention is relatively cool. This air is warmed as it rises inside the heater housing because it picks up heat from the backside of the reflective side and rear panels. A thermostatic control is positioned in the inside top portion of the heater. This location, as opposed to the bottom of the heater, is deemed better representative of the room air temperature sought to be obtained because of the warming of the relatively cool air drawn into the bottom of the heater. A thermostat located at the top of the heater tends to cycle on and off more frequently than would be the case if the thermostat were located upstream of the reflector assembly, near the bottom of the heater, but it enhances the ability of the thermostat to so control the heater as to maintain a relatively constant room temperature. In the preferred practice of this invention, baffles are provided to direct the air flow toward the thermostat. In addition, the power switch is also located at the top of the heater and control knobs for both the power switch and the thermostat extend upwardly from the top of the housing for ease of operation.
As a result of the combined effect of the cooling of the heater caused by the air flowing upwardly from the bottom of the heater and the sensitivity and responsiveness of the thermostatic control, a heater in accordance with this invention may have exterior housing parts which are relatively cool to the touch, thereby allowing selected exterior housing parts to be molded from thermoplastic materials which can readily be formed to aesthetically pleasing designs.
Yet another object of this invention is to provide an improved quartz heating element assembly for use in an electric heater and, more particularly, an improved heating element assembly which may be located above a fan blade. Such a heating element assembly in accordance with this invention comprises a pair of quartz heating elements each of which comprises a resistance heater wire inside a heat-radiating quartz tube. The tubes are closed at their ends by ceramic holders. Two cold wires or rods, one at each end of the resistance wire, are spot-welded to the resistance wire in each tube. The ends of the cold rods opposite the ends thereof welded to the re
Chaney David B.
Mills Thomas H.
Smith Barry W.
Dybvig Roger S.
Hoang Tu Ba
The W. B. Marvin Manufacturing Company
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