Heating element compartment for electric dryer applications

Abstract

A heating box for an electric heating element is disposed in a clothes dryer. A substantially rectangular enclosure is opened at a first end and closed at a second end and internally supports one or more heating elements. A surface of the enclosure includes a plurality of holes which allow the heating element along its length to remain in contact with ambient air. The first end is connected to the heating duct of the dryer, and air enters through the plurality of holes and is heated. The air is drawn through the open end of the heating box due to a negative pressure applied to the dryer chamber into the dryer. In accordance with a preferred embodiment, the size of the holes changes along the length of the enclosure.

Description

BACKGROUND OF THE INVENTION

The present invention relates to clothes dryers having electrical heating elements for generating drying air. Specifically, a heating box is disclosed for an electric heating element assembly which increases the heat transfer efficiency of the heating element.

Both home and commercial clothes drying devices require substantial heat generation in order to provide drying air to remove moisture from articles being dried. Drying air is generated either from a gas burner or from an electrical heating element which operates from conventional A/C. In the case of electric heating, drying air is supplied from a plurality of electrical elements which are connected to the electrical service in the facility. A heating box surrounds the heating element, and ambient air enters one end and is drawn through to the second end into a drying chamber of the dryer due to a negative pressure created within the drying chamber from an impeller.

The life of the electric heating elements are finite, and, over time, replacement is necessary. The dryer down time as well as technical support needed to replace the elements is a significant drawback for this type of dryer which competes with the gas dryer.

It has been determined that the life expectancy of the electric heating elements can be improved by improving the heat transfer rate from the heating element to the ambient air being heated for the dryer. As the efficiency goes up, the time of operation of the heating element decreases, prolonging the life of the heating elements. The present invention has been designed in an effort to improve the efficiency of electrically heating drying air and which will produce a longer useful life for the heating element.

SUMMARY OF THE INVENTION

A heating box is provided by an enclosure which encloses a heating element and has an open end which supplies hot air to the dryer drying chamber. Ambient air enters holes along the surface of the enclosure and is heated to a drying temperature. The holes in the surface of the enclosure have a diameter which varies over the length of the enclosure. Ambient air is in contact with the entire length of the heating element creating a more uniform transfer of heat from the heating element to the ambient air.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a heating box in accordance with the present invention implemented in a commercial laundry dryer;

FIG. 1B is an isometric view of the laundry dryer of FIG. 1A;

FIG. 2 illustrates an exploded view of the heating box of FIG. 1;

FIG. 3 illustrates an isometric view of a heating box;

FIG. 4 is an end view showing connections to the heating elements in the heating box and the contactor;

FIG. 5 is a top view of another embodiment of the invention;

FIG. 6 is a front view of the embodiment of FIG. 5;

FIG. 7 is a bottom view of the heating box of the embodiment of FIGS. 5 and 6; and

FIG. 8 illustrates the connection to the heating elements in the heating box.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 1A and 1B, a section view and isometric view of a commercial laundry dryer are shown. The laundry dryer includes a drying drum 12 supported for rotation on bearings 17. An opening 14 to the drying drum 12 is closed by the door 15.

Drying air is provided to the drying drum 12 from a source of electric heating elements within a heating box 19 supported by bracket 21. Air within the heating box 19 enters through a plurality of opening 31 in the surface of the heating box enclosure 19. Heating box 19 supplies hot air through a duct 20 into an opening of drying chamber 12.

The heating box of the preferred embodiment is disclosed more particularly in FIGS. 2, 3 and 4. The enclosure 25 is rectangular and includes a plurality of holes 29, 31 on the top surface thereof as well as 32 and 33 on the side surface thereof. The bottom 23 is shown having no holes. An open end of the heating box includes tabs 26 which engage a surface of the dryer forming the heating duct 20, and the opposite end of the heating box 19 is closed. The holes along the surface of the heating box are evenly spaced and generally sized so that the holes decrease in diameter as the distance from the closed end increases. Thus, the holes 29, 32 near the closed end of the heating box are sized larger than the holes 31, 33 at the open end of the heating box 19. The effect is to uniformly distribute ambient air entering through holes 29, 31, 32 and 33 along the length of the heating element. The result is that heat transfer from the surface of the heating elements is more uniform than in the conventional arrangement where ambient air enters through an open, opposite end of a heating box having no holes along its length. Contactor 24 supplies electrical current to each of the heating elements 27.

In a typical configuration, the heating elements of the prior art would deliver a certain wattage of heat. In the preferred embodiment of the present invention, the element wattage rating can be increased and still allow the same element operating temperatures. Instead of a higher heat output with the larger heat element, the temperature may be lowered for each of the heating elements in order to preserve the life of the heating elements. For instance, a 100° decrease in temperature may double the element life.

A second embodiment of the invention is illustrated with respect to FIGS. 5-8. FIG. 5 represents a top view of a rectangular heating box which includes holes 41, 42 extending across the top surface of the heating box. Holes 41 have a smaller diameter than those identified as 42. Air flows into the holes 41 and 42 and out the exit opening in the box 45 communicating with the hot air duct 20. The opposite end of the box 49 is closed so that all air flow must be through holes in the top, sides and bottom of the heating box.

The side view of FIG. 5 is shown in FIG. 6, and includes a plurality of terminals 47 which connect the electrical heating elements to a contactor 24 which supplies operating current to the heating elements under control of the dryer controller.

The side walls of the heating box include a plurality of channels 48 which support the heating elements in a stacked arrangement with heating box 19. A heating box support 48 is shown to support the closed end of the heating box within the dryer.

FIG. 7 illustrates a bottom view, wherein a plurality of holes 43, 44 are shown along the length of the heating box 19. As in the top surface of the heating box, the bottom surface includes smaller diameter holes at the open end exit 45 and larger holes 44 at the closed end of the heating box 49.

FIG. 8 illustrates terminals 47 which are connected to the heating elements and to the contactor by wires (not shown). In the embodiment shown, it is contemplated that six heating elements would be provided, each pair of heating elements having a common terminal with the remaining end of the heating element connected to one phase of the three phase electrical system.

Using the principles of the foregoing embodiments, the heat distribution over the heat elements is distributed more uniformly, increasing the life of the heating element.

The foregoing description of the invention illustrates and describes the present invention. Additionally, the disclosure shows and describes only the preferred embodiments of the invention in the context of a heating element compartment for electric dryer applications, but, as mentioned above, it is to be understood that the invention is capable of use in various other combinations, modifications, and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein, commensurate with the above teachings and/or the skill or knowledge of the relevant art. The embodiments described hereinabove are further intended to explain best modes known of practicing the invention and to enable others skilled in the art to utilize the invention in such, or other, embodiments and with the various modifications required by the particular applications or uses of the invention. Accordingly, the description is not intended to limit the invention to the form or application disclosed herein. Also, it is intended that the appended claims be construed to include alternative embodiments.

Claims

1. A heating box for an electric heating element comprising:

an enclosure open at a first end supporting a heating element and closed at an opposite end, a surface of said enclosure including a plurality of holes which allow said heating element along its length to remain in contact with ambient air, said first end being open and arranged to deliver heated drying air to a drying chamber of a laundry dryer.

2. The heating box according to claim 1, wherein said holes are evenly spaced along said enclosure surface.

3. The heating box according to claim 2, wherein said holes vary in size from said closed end of said enclosure to the open end of said enclosure.

4. The heating box according to claim 1, wherein said heating box has a rectangular cross section.

5. The heating box according to claim 4, wherein each surface of said heating box includes said holes.

6. The heating box according to claim 4, wherein said plurality of holes vary in size from said open end to said closed end with larger holes being located near said closed end.

7. A method for equalizing the temperature distribution across a heating element comprising:

supporting said beating element in an enclosure, said enclosure being open at one end arranged to deliver heated drying air to a drying chamber of a laundry dryer and closed at an opposite end; and

locating holes along the length of said enclosure having a size which varies from one end to another, whereby the heating element is in contact with the ambient air along substantially along its entire length.

8. The method for equalizing the temperature distribution across a heating element according to claim 7, wherein said holes adjacent an end which delivers hot air are smaller than the holes adjacent the closed end.

9. The method for equalizing the temperature distribution across a heating element according to claim 8, wherein said holes are distributed on each of four surfaces of a rectangular enclosure.