US3651304A - Electric resistance heating element - Google Patents

Electric resistance heating element Download PDF

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Publication number
US3651304A
US3651304A US3651304DA US3651304A US 3651304 A US3651304 A US 3651304A US 3651304D A US3651304D A US 3651304DA US 3651304 A US3651304 A US 3651304A
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Prior art keywords
heating element
electric resistance
resistance heating
element according
corrugations
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Expired - Lifetime
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Robert J Fedor
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EHD Inc
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Gould Inc
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    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHTING NOT OTHERWISE PROVIDED FOR
    • H05B3/00Ohmic-resistance heating
    • H05B3/20Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
    • H05B3/22Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible
    • H05B3/32Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor mounted on insulators on a metallic frame
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24HFLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT GENERATING MEANS, IN GENERAL
    • F24H3/00Air heaters having heat generating means
    • F24H3/02Air heaters having heat generating means with forced circulation
    • F24H3/04Air heaters having heat generating means with forced circulation the air being in direct contact with the heating medium, e.g. electric heating element
    • F24H3/0405Air heaters having heat generating means with forced circulation the air being in direct contact with the heating medium, e.g. electric heating element using electric energy supply, e.g. the heating medium being a resistive element; Heating by direct contact, i.e. with resistive elements, electrodes and fins being bonded together without additional element in-between

Abstract

An electric resistance heating element for a moving air system in which the element is composed of a thin strip of apertured, foil-like material formed with a series of continuous and generally parallel extending corrugations which establish a wavy pattern. The foil is supported by a central, longitudinally extending, electrically insulated rod.

Description

United' States Patent Fedor [45] Mar. 21, 1972 [541 ELECTRIC RESISTANCE HEATING ELEMENT r [56] References cued [72] Inventor: Robert J Fedor, Westlake, Ohio UNITED STATES PATENTS [73] Assignee: Gould lne., Chicago, 111. 1,006,655 10/1911 Harris ..338/291 1,860,493 5/1932 Campbell ..338/287 [221 F1|ed= 1971 1,991,935 2/1935 Melsom ..338/333 x [2!] App! Nu; 129,893 3,244,860 4/1966 Lindley ..219/374 m s ti n Data Primary Examiner-C. L. Albritton Att0rney-Edward E. Sachs [63] Continuation-impart of Ser. No. 96,322, Dec. 9, 1970, 1

abandoned. I [57] g ABSTRACT An electric resistance heating element for a moving air system 2 [5 l U 8 CI 9 9 219/375 47 in which the element is composed of a thin strip of apertured, 51 I t Cl "95b foil-like material formed with a series of continuous and E i o'f'seirch 21 9 l 2 3 53 355 generally parallel extending corrugations which establish a "saw wavy pattern. The foil is supported by a central, longitudinally extending, electrically insulated rod.

9 Claims, 3 Drawing Figures ,vaslyiv ELECTRIC RESISTANCE HEATING ELEMENT This application is a continuation in part application of US. Application, Ser. No. 96,322, filed Dec. 9, 1970 and now abandoned.

The present invention relates generally to an electric resistance heating element and, more particularly, to an element which is composed of a thin strip of foil-like material and is adapted to be employed in moving air systems.

In the prior art electric resistance heating elements are commonly constructed by either utilizing a self-supporting expanded meta] strip which is secured between two supporting members, or by using a coiled wire arrangement which is supported at intermediate locations by means of a ceramic bearing mount which surrounds the wire.

The conventional coiled wire construction can be characterized as having a low surface areaand a high mass, or a low surface area to mass ratio. The high mass leads to a relatively high raw material cost, while the low surface area leads to inefficient heating and cooling. As a consequence of the high raw material cost, a constant effort is made to minimize the amount of material used by deliberately operating the element at as high a temperature as possible, usually well into the red heat range. The operation of the element at the high tempera ture level has at least two detrimental consequences. The areas of low air flow (inside the ceramic bushings) become overheated and are prone to failure; secondly, the efficiency of convective air heating is decreased as a significant amount of the energy is spent in radiant heating the solids surrounding the element. The low surface area to mass ratio also causes a slow heat-up and cooling rate.

In the past, considerable experimentation and effort has been expended to produce an element with a high surface area to mass ratio. However, to date, no economical method has been found to provide a system which would have the desired low weight and high surface area without the associated problem of excessive sagging.

It is the primary object of the present invention to provide an electric heating element which overcomes the disadvantages common in the prior art.

It is a further main object of the present invention to provide an electric resistance heating element which is very light weight, yet is supported in a manner that will prevent sagging.

It is a further object of the present invention to provide a heating element having an expanded or otherwise apertured metal foil grid which provides at least the same electrical characteristics as prior art devices; however, with a considerable saving in raw material.

It is another object of the present invention to provide a heating element which lends itself to assembly by automated means.

It is another object of the present invention to provide a heating element in which the support for the heating element is internal rather than external, as is the common practice today.

It is another object of the present invention to provide a heating element which is composed of corrugations establishing a wavy pattern which has the advantage of placing a long length of material in a relatively small area to obtain a relatively high electric resistance.

It is another object of the present invention to provide a heating element in which the heating element establishes a corrugatedand wavy pattern which is supported at very short intervals to prevent, or a least to substantially reduce, creeping or sagging.

An aspect of the present invention resides in the provision of an electric resistance heating element for a moving, or forced air system which includes a thin strip of apertured foillike, electric resistant material which is formed with a series of continuous and generally parallel extending corrugations which establish a wavy pattern. A supporting rod having an electrically non-conductive surface extends through most of the corrugations and is effective to structurally support the strip at very short intervals. A structural frame is provided to connect to the support rod for mounting the assembly of the rod and the strip.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the drawing:

FIG. 1 is a perspective view of a heating element in accordance with this invention;

FIG. 2 is a plan view of the heating element shown in FIG. 1; and

FIG. 3 is an elevational side view of the heating element.

Referring now to the drawing there is shown a foil-like strip 10 of commercially available material which has electric resistance characteristics. As the term foil" is used herein, it is to denote materials having a thickness of between 4 to 16 mils (inch). While the invention is, theoretically, utilizable for strips having a thickness greater than 16 mils (inch), it should be noted, however, that as the thickness of the foil-like strip increases, the weight increases correspondingly and thus becomes, at a given point, uneconomical. Similarly, as the foil thickness decreases below 4 mils, the cost of the raw material increases significantly to the point where the use of the element as an electric resistance member becomes uneconomical. Conventional heating elements, by comparison, usually are composed of wire or sheet material having a thickness of 40 to 60 mils.

The heating element 10, as shown in the drawing, has a diamond shape expanded metal configuration. The expansion of the metal is accomplished by first splitting the solid foil strip intermittently so that the entire sheet has a series of closely spaced parallel cuts, to permit expanding it laterally to form the open screen. However, the invention is not limited to expanded metal elements. For example, the strip or element l0 can be composed of a solid foil which is mechanically perforated by impact, or wherein the apertured foil is electrochemically formed.

While the diamond shape configuration, as shown at 12 in the drawing, is usually made by an expanded metal process, such configuration is not necessarily the most desirable. For instance, it has been found that a rectangular or square-like grid pattern has a more direct current path and thus is preferred from an electrical performance point of view; however, such configuration does present cost and formability problems in the manufacture thereof.

The strip 10 is formed with a series of continuous and generally parallel extending corrugations 14 which establish in their totality a wavy pattern. While there are shown two rows of such heating elements, it will be appreciated that numerous longitudinally extending rows, which are electrically connected in series, can be constructed; all of such rows forming together a continuous loop with one end of the loop being connected to a current terminal 16 and the other end being physically and electrically connected to the other electric terminal 18. The terminals 16 and 18 are suitably mounted to a common plastic insulating mount 20.

In order to support the strip 10, an particularly the individual corrugations 14 thereof, there is provided a longitudinally extending rod 22 which protrudes through the individual corrugations in a skewer-like manner. The rod 22 extends through the corrugations 14 about a central axis to provide maximum support for the corrugations 14 which are also generally symmetrically arranged along and parallel to the longitudinal axis of the rod. The rod 22 has a dielectric strength of at least 2% thousand volts. This is typically accomplished by providing a steel rod coated with ceramic material, although a solid glass or quartz rod may be utilized. Alternatively, a steel rod having a ceramic sleeve has also been found to be satisfactory.

The assembly of the rod 22 and the corrugated strip structure l0, 14 is supported by means of a simple frame which comprises a network of rods 24 connecting at opposite ends to the insulated rods 22 and to a mounting plate 26.

The present invention will be better understood when the operating characteristics are compared with those of the conventional devices. For example, a typical 5,600 watt laundry heating element of standard coiled wire construction has the following characteristics:

Surface Area 69 in. Weight 0.265 Surface Area to Mass Ratio 260 in./# Room Temperature Resistance 9.3 ohms Operating Temperature at 236 volts nominal l600l800 F. Alloy Type C Wire Gage l6=(.0$08") Time to dry 10 load of towels 70 minutes Length of Wire 35.6 ft.

The Type C resistance alloy, with a nominal composition of 6ONi-24Fe-16Cr, is commonly used for this application because it has sufficient oxidation resistance at the operating temperatures with a minimum utilization of expensive nickel. On the other hand, a Type D alloy, with a composition of 35Ni-45Fe-20Cr, would be less expensive because of the lesser amount of nickel; however, its elevated temperature properties are not conducive to a long operating life. Typically, when failure of the wire does occur, the break is in an area where air blockage (such as inside a ceramic bushing) causes the temperature of wire to exceed the temperature capability of the wire.

As a comparative specific example of the operating characteristics of the high surface area to mass ratio heating element in accordance with the invention, the performance data of a 5,600 watt laundry type heating element can be described as:

Surface Area 96 in. Weight 0.100 Surface Area to Mass Ratio 960 in./# Room Temperature Resistance 9.3 ohms Operating Temperature Black to lS50 F.

(236 volt nominal) Alloy Type C Thickness 0.0!2" Pattern Diamond shaped apertures .50 in. in length .20 in. in width .0l8 in. in strand width Length of strip ll ft. Time to dry [0 load of towels 54 min.

shown that the desirable ratio range is approximately 900 to 2,500 in?/# When the upper end of the ratio range is appreciably exceeded, economic considerations such as excessive cost of material and fabricating expenses nullify or depreciate the advantages of a thin foil heating element. Similarly, when the lower end of the ratio range is exceeded, the desired performance characteristics are significantly lost.

In addition, the skewered thin foil construction does not have areas of air blockage analagous to the bushing areas of the coiled wire design. And the operating temperature can be maintained considerably below the upper limit of performance of the Type C alloy, thus permitting the use of less expensive alloys such as, for example, Type D (35Ni-45 Fe-20Cr).

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention and it is aimed, therefore in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. An electric resistance heating element particularly for moving air systems, comprising:

a thin strip of apertured foil-like, electric resistance, material formed as a grid with a series of continuous and generally parallel extending corrugations establishing a wavy pattern;

a support rod with an electrically nonconductive surface extending through most of said corrugations, effective to structurally support said strip at short intervals; and

frame means connecting to said support rod for mounting the assembly of said rod and strip.

2. An electric resistance heating element according to claim 1, wherein said rod extends through said corrugations about a central axis.

3. An electric resistance heating element according to claim 1, wherein said corrugations are generally symmetrical and extend along a longitudinal axis.

4. An electric resistance heating element according to claim 1, wherein said corrugations form a continuous loop of said strip of foil-like material.

5. An electric resistance heating element according to claim 1, wherein the apertures of the foil-like material are symmetrically arrayed.

6. An electric resistance heating element according to claim 1, wherein said material is electrochemically formed.

7. An electric resistance heating element according to claim 1, wherein said material is an expanded metal foil grid.

8. An electric resistance heating element according to claim 1, 'wherein said corrugations are supported on said rod in a skewer-like fashion.

9. An electric resistance heating element according to claim 1, wherein said foil has a thickness approximately in the range of4 to 16 mils inch.

Claims (9)

1. An electric resistance heating element particularly for moving air systems, comprising: a thin strip of apertured foil-like, electric resistance, material formed as a grid with a series of continuous and generally parallel extending corrugations establishing a wavy pattern; a support rod with an electrically nonconductive surface extending through most of said corrugations, effective to structurally support said strip at short intervals; and frame means connecting to said support rod for mounting the assembly of said rod and strip.
2. An electric resistance heating element according to claim 1, wherein said rod extends through said corrugations about a central axis.
3. An electric resistance heating element according to claim 1, wherein said corrugations are generally symmetrical and extend along a longitudinal axis.
4. An electric resistance heating element according to claim 1, wherein said corrugations form a continuous loop of said strip of foil-like material.
5. An electric resistance heating element according to claim 1, wherein the apertures of the foil-like material are symmetrically arrayed.
6. An electric resistance heating element according to claim 1, wherein said material is electrochemically formed.
7. An electric resistance heating element according to claim 1, wherein said material is an expanded metal foil grid.
8. An electric resistance heating element according to claim 1, wherein said corrugations are supported on said rod in a skewer-like fashion.
9. An electric resistance heating element according to claim 1, wherein said foil has a thickness approximately in the range of 4 to 16 mils inch.
US3651304A 1971-03-31 1971-03-31 Electric resistance heating element Expired - Lifetime US3651304A (en)

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Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3775590A (en) * 1971-10-27 1973-11-27 Steiner W Portable space heater
US3798417A (en) * 1973-07-12 1974-03-19 Gould Inc Heating element assembly
US3835435A (en) * 1972-12-18 1974-09-10 J Seel Heating element support
US3852568A (en) * 1973-02-01 1974-12-03 Gould Inc Electric resistance heating element
US3860789A (en) * 1973-03-26 1975-01-14 Gould Inc Heating element assembly
US3898426A (en) * 1973-12-21 1975-08-05 Gould Inc Heating assembly for domestic forced air electric furnace
US4019023A (en) * 1975-06-16 1977-04-19 Whirlpool Corporation Electrically heated dryer
US4025754A (en) * 1975-06-16 1977-05-24 Whirlpool Corporation Electrically heated dryer
US4048472A (en) * 1974-01-29 1977-09-13 Varta Batterie Aktiengesellschaft Vibratory spiral conveyor chute and a resistance heating element
US4100395A (en) * 1976-06-29 1978-07-11 Glenro, Inc. Expanded element radiant heating device
US4151398A (en) * 1975-07-31 1979-04-24 Gould Inc. Clothes dryer heating unit
US4563572A (en) * 1984-08-01 1986-01-07 Armstrong World Industries, Inc. High-efficiency task heater
WO1992007121A2 (en) * 1990-10-17 1992-04-30 Exxon Chemical Patents Inc. Melt-blowing die
WO2003086018A1 (en) * 2002-04-11 2003-10-16 Valeo Climatisation Electric heating device, particularly for a heating or air-conditioning unit in a vehicle
US6694975B2 (en) * 1996-11-21 2004-02-24 Aradigm Corporation Temperature controlling device for aerosol drug delivery
US20040251244A1 (en) * 2003-06-10 2004-12-16 Eiichi Torigoe Heat exchanger for heating, and air conditioner for vehicle use
US20090140066A1 (en) * 2007-12-04 2009-06-04 Hyundai Motor Company Heating device with Cathode Oxygen depletion function for fuel cell vehicle
US20120155840A1 (en) * 2010-12-20 2012-06-21 Hwang Gyu Eob Fan heater applying a carbon fiber ribbon secured in each heating cartridge

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1006655A (en) * 1911-02-18 1911-10-24 Clarke Chapman And Company Ltd Electric resistance.
US1860493A (en) * 1929-01-21 1932-05-31 Cutler Hammer Inc Grid resistance
US1991935A (en) * 1932-03-04 1935-02-19 Expanded Metal Electrical resistance, resistance heater, and the like
US3244860A (en) * 1962-04-26 1966-04-05 Parsons C A & Co Ltd Heaters for gases

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1006655A (en) * 1911-02-18 1911-10-24 Clarke Chapman And Company Ltd Electric resistance.
US1860493A (en) * 1929-01-21 1932-05-31 Cutler Hammer Inc Grid resistance
US1991935A (en) * 1932-03-04 1935-02-19 Expanded Metal Electrical resistance, resistance heater, and the like
US3244860A (en) * 1962-04-26 1966-04-05 Parsons C A & Co Ltd Heaters for gases

Cited By (25)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3775590A (en) * 1971-10-27 1973-11-27 Steiner W Portable space heater
US3835435A (en) * 1972-12-18 1974-09-10 J Seel Heating element support
US3852568A (en) * 1973-02-01 1974-12-03 Gould Inc Electric resistance heating element
US3860789A (en) * 1973-03-26 1975-01-14 Gould Inc Heating element assembly
US3798417A (en) * 1973-07-12 1974-03-19 Gould Inc Heating element assembly
US3898426A (en) * 1973-12-21 1975-08-05 Gould Inc Heating assembly for domestic forced air electric furnace
US4048472A (en) * 1974-01-29 1977-09-13 Varta Batterie Aktiengesellschaft Vibratory spiral conveyor chute and a resistance heating element
US4019023A (en) * 1975-06-16 1977-04-19 Whirlpool Corporation Electrically heated dryer
US4025754A (en) * 1975-06-16 1977-05-24 Whirlpool Corporation Electrically heated dryer
US4151398A (en) * 1975-07-31 1979-04-24 Gould Inc. Clothes dryer heating unit
US4100395A (en) * 1976-06-29 1978-07-11 Glenro, Inc. Expanded element radiant heating device
US4563572A (en) * 1984-08-01 1986-01-07 Armstrong World Industries, Inc. High-efficiency task heater
WO1992007121A3 (en) * 1990-10-17 1992-08-06 Exxon Chemical Patents Inc Melt-blowing die
WO1992007121A2 (en) * 1990-10-17 1992-04-30 Exxon Chemical Patents Inc. Melt-blowing die
US20070062526A1 (en) * 1996-11-21 2007-03-22 Aradigm Corporation Temperature controlling device for aerosol drug delivery
US6694975B2 (en) * 1996-11-21 2004-02-24 Aradigm Corporation Temperature controlling device for aerosol drug delivery
US7143766B2 (en) 1996-11-21 2006-12-05 Aradigm Corporation Temperature controlling device for aerosol drug delivery
FR2838599A1 (en) * 2002-04-11 2003-10-17 Valeo Climatisation Electric heating device, in particular for heating apparatus and or vehicle air conditioning
WO2003086018A1 (en) * 2002-04-11 2003-10-16 Valeo Climatisation Electric heating device, particularly for a heating or air-conditioning unit in a vehicle
US20040251244A1 (en) * 2003-06-10 2004-12-16 Eiichi Torigoe Heat exchanger for heating, and air conditioner for vehicle use
US7009146B2 (en) * 2003-06-10 2006-03-07 Denso Corporation Heat exchanger for heating, and air conditioner for vehicle use
US20090140066A1 (en) * 2007-12-04 2009-06-04 Hyundai Motor Company Heating device with Cathode Oxygen depletion function for fuel cell vehicle
US8807446B2 (en) * 2007-12-04 2014-08-19 Hyundai Motor Company Heating device with cathode oxygen depletion function for fuel cell vehicle
US20120155840A1 (en) * 2010-12-20 2012-06-21 Hwang Gyu Eob Fan heater applying a carbon fiber ribbon secured in each heating cartridge
US8463113B2 (en) * 2010-12-20 2013-06-11 Gyu Eob HWANG Fan heater applying a carbon fiber ribbon secured in each heating cartridge

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