US3835435A

US3835435A - Heating element support

Info

Publication number: US3835435A
Application number: US00316052A
Authority: US
Inventors: J Seel
Original assignee: Individual
Current assignee: EHD Inc
Priority date: 1972-12-18
Filing date: 1972-12-18
Publication date: 1974-09-10
Anticipated expiration: 1991-09-10

Abstract

An electric heating element assembly for a moving air system in which the element is composed of a thin strip of apertured, foillike material. According to the invention, the strip is formed with a series of continuous corrugations which establish a wavy pattern. The corrugated foil is immobilized and supported by a plurality of insulators which are connected to a support rod. The entire length of the resistance material between adjacent insulators is formed as a single, continuous, smoothly curved corrugation and the insulators maintain separation of those corrugations to prevent shorting or arcing. Various connecting arrangements are provided between the support rod and each insulator to prevent axial and rotational movement of each insulator relative to the support rod. The entire length of the resistance material between adjacent insulators is formed as a single, continuous, smoothly curved corrugation and the insulators maintain separation of those corrugations to prevent shorting or arcing. Various connecting arrangements are provided between the support rod and each insulator to prevent axial and rotational movement of each insulator relative to the support rod.

Description

United States Patent [191 Seel [ HEATING ELEMENT SUPPORT [76] Inventor: Jerry Eslie Seel, 595 Meadowbrook Dr., Adrian, Mich. 49221 [22] Filed: Dec. 18, 1972 [21] Appl. No: 316,052

[56] References Cited UNITED STATES PATENTS 977,456 12/1910 Leonard 338/279 X 1,335,483 3/1920 Colby 338/282 X 1,526,843 2/1925 Dominguez 338/317 1,721,910 7/1929 Kemble 338/280 X 2,023,875 12/1935 Drumm 338/318 X 3,102,940 9/1963 Stone 338/317 X 3,651,304 3/1972 Fedor 219/538 X 3,673,387 6/1972 Drugmand et a1. 338/319 X Primary Examiner-A, Bartis Attorney, Agent, or FirmEdward E. Sachs 1451 Sept. 10, 1974 [57] ABSTRACT An electric heating element assembly for a moving air system in which the element is composed of a thin strip of apertured, foil-like material. According to the invention, the strip is formed with a series of continuous corrugations which establish a wavy pattern. The corrugated foil is immobilized and supported by a plurality of insulators which are connected to a support rod. The entire length of the resistance material between adjacent insulators is formed as a single, continuous, smoothly curved corrugation and the insulators maintain separation of those corrugations to prevent shorting or arcing. Various connecting arrangements are provided between the support rod and each insulator to prevent axial and rotational movement of each insulator relative to the support rod. The entire length of the resistance material between adjacent insulators is formed as a single. continuous. smoothly curved corrugation and the insulators maintain separation of those corrugations to prevent shorting or arcing. Various connecting arrangements are provided between the support rod and each insulator to prevent axial and rotational movement of each insulator rela' tive to the support rod.

19 Claims, 14 Drawing Figures ,......c v 0 0 0 o Pmmmszn man SHEET 1 [IF 2 PAIENIEDSEPIOIHH 3.835.435

SHEU 2 BF 2 FIG] FIG. 8

HEATING ELEMENT SUPPORT BACKGROUND OF THE INVENTION The present invention relates generally to an electric resistance heating element and, more particularly, to an electric resistance heating element assembly which includes a thin strip of foil-like material and which is adapted to be employed in moving air systems.

In the prior art, electric resistance heating elements are commonly constructed either by utilizing a flat, self-supporting, expanded metal 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 coiled wire.

The conventional coiled wire construction, however, has a low surface area and a high mass compared to a foil-like material. The high mass leads to a relatively high raw material cost, while the low surface area contributes to reduced heating and cooling efficiency. 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, often well into the red heat range. The operation of the element at the high temperature level has at least two detrimental consequences. The areas of restricted 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.

Prior art self-supporting expanded metal strips which are secured between two supporting membersare subject to excessive sagging at operating temperatures. To overcome these disadvantages found in the prior art, a heating element has been proposed which is composed of corrugations establishing a wavy pattern which provides at least the same electrical characteristics as prior art devices but with a considerable saving in raw material. Such a device is set forth in US. Pat. No. 3,651,304. According to that patent, a foil-like, corrugated heating element is supported internally by a supporting rod having an electrically nonconductive surface which extends through most of the corrugations to structurally support the strip at very short intervals. Since the strip is skewered by the support rod, it has a tendency to rotate about the rod and move axially relative to the rod. Although these tendencies are not detrimental when the element is properly installed, careless handling prior to or during installation may tend to rotationally or axially displace the strip relative to the support rod. Axial displacement may tend to collapse some of the corrugations into contact with an adjacent corrugation, thereby shorting out a portion of the circuit. Any rotational movement of the element relative to the support rod may cause the element to contact the surrounding support structure.

SUMMARY OF THE INVENTION This invention overcomes many of the disadvantages common in the prior art by providing a resistance heating assembly which includes a support rod having a plurality of insulators secured thereto and restrained against rotational and axial movement relative to the support rod. According to the invention, a thin strip of apertured foil-like material formed with a series of continuous corrugations, which establish a wavy pattern, is retained and supported by immobilizing means at each insulator. According to one embodiment of this aspect of the present invention, an immobilizing means comprises a clip extending through the strip to fasten the strip to the insulator. According to another embodiment of this aspect of the present invention, an immobilizing means includes a clamping portion of the insulator which, preferably, does not contact substantial portions of the strip to cause overheating of the insulators and a decrease in efficiency of convective air heating.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a resistance heating assembly according to one aspect'of the invention;

FIG. 2 is a cross sectional view, the plane of the section being indicated by the line 22 in FIG. 1;

FIGS. 3 through 6 are fragmentary perspective views of heating element assemblies according to further aspects of this invention;

FIG. 7 is a perspective view of a connector employed to attach insulators to a support rod according to some aspects of the invention;

FIGS. 8 and 9 are fragmentary perspective views of heating element assemblies according to further aspects of this invention;

FIG. 10 is an exploded, fragmentary perspective view of a heating element assembly according to a further aspect of this invention;

FIG. 11 is a cross sectional view, the plane of the section being indicated by the line lI-Il in FIG. 10;

FIGS. 12 and 13 are fragmentary perspective views of heating element assemblies according to further aspects of this invention; and

FIG. 14 is a fragmentary, cross sectional view, the plane of the section being indicated by the line l4l4 in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, there is shown a foillike strip 10 of commercially available material which has electric resistance characteristics. This material is more fully described in US. Pat. No. 3,651,304, the disclosure of which is incorporated herein by reference. The strip 10 is formed with a series of continuous and generally parallel extending corrugations 12 which establish in their totality a wavy pattern. The corrugations are illustrated as being substantially transverse to the longitudinal axis of the strip. A number of techniques are set forth herein for supporting the strip 10 to maintain a predetermined spacing between corrugations and to prevent rotational displacement of the strip.

According to the embodiment set forth in FIG. 1 of the drawings, the strip 10 is retained and supported by a plurality of insulators 16 which are symmetrically mounted on a support rod means 18. The insulators 16 are preferably made from electrical grade ceramics, such as steatite, and have strip attaching means on either side of the support rod means 18. The strip attaching means includes immobilizing means which in FIGS. 1 and 2 comprise split ring, wire clips 20 extending through apertures in the strip 10 and through apertures 22 in the insulator 16. To facilitate installation of the clips 20 on the insulator l6, grooves 24 may be formed Connecting means are provided between the support the support rod 18, the support rod 18 comprises a pair of

flat bars

28 and 30 which are displaced laterally relative to each other when all of the insulators 16 have been properly located on the support rod. By displacing the

bars

28 and 30 in this manner, the bars are jammed against the ends of each aperture 26 to retain the insulators 16 against axial movement. To aid in this retention, a series of serrations 31 maybe provided along the edges of the bars which contact the aperture ends. Other retention means, such as spaced notches, may be employed. The

bars

28 and 30 are held in their displaced condition by such means as spot welds or rivets (not shown) which tie the

bars

28 and 30 together along their lengths. The

bars

28 and 30 may have flared

end portions

32 and 34, respectively, and those end portions are fixed to a mounting plate 36 by spot welds (not shown) or by rivets 38. Terminal posts 40 are provided on the mounting plate 36 and are electrically connected to the strips by conductors 42 (only one of which is shown in FIG. 1). The other ends of the strips 10 are connected by a conductor 44 to complete the circuit.

The remaining embodiments of the invention are illustrated'fragmentarily for purposes of simplicity. It should be appreciated, however, that a plurality of insulators are mounted on a support rod to immobilize successivestrip corrugations and that each support rod is fixed to a mounting plate.

In FIG. 3 a support rod 102 having a noncircular cross section is provided. An insulator 103 is fixed to the support rod 102 by a connecting means to prevent axial and rotational movement of the insulator relative to the support rod. In FIG. 3, the connecting means comprises a V-shaped clip 104 having a pair of legs 105 which flare outwardly relative to a rectangular portion 106 of the clip. The rectangular portion 106 receives the insulator 103 and the legs 105 have apertures 107 which receive the rod 102. The insulator 103 is mounted on the rod 102 by first mounting the insulator within the rectangular portion 106. The clip 104 may then be positioned at a desired location on the rod 102 by pressing the legs 105 together and inserting the rod through the apertures 107. When the desired location is reached, the legs 105 are released so that they spring back to the position illustrated in FIG. 4, thereby preventing further axial movement of the insulator 103 along the rod. If desired, clip engaging serrations or notches (not shown) may be provided on the support rod 102. Strips 10 may then be fixed to the insulator 103 by employing clips 108 which pass through apertures in the strips 10 and through apertures 109 in the insulator.

Referring now to FIG.'4, there is illustrated a resistance heating assembly which comprises a support rod 117 having a noncircular cross section. An insulator 118 is connected to the rod 1l71by connecting means which comprises a V-shaped clip 119 having a pair of legs which function in a manner similar to the legs (FIG. 3). The insulator 118 includes projections 120 which immobilize the strips 10 by projecting through .apertures in the strips. 7

In FIG. 5, a resistance heating assembly according to another aspect of this invention comprises a support rod 121 having a V-shaped cross section which extends through a V-shaped aperture 122 in an insulator 123. Rotational movement of the insulator 123 relative to the support rod 121 is prevented by the noncircular cross section of the support rod and the noncircular cross section of the aperture 122. To prevent axial movement of the insulator 123 relative to the support rod, a portion 124 of the rod 121 is upset after the insulator has been properly positioned on the rod. A similar upset portion (not shown) is provided on the rod adjacent the opposite face of the insulator. Strips 10 are immobilized relative to the insulator 123 by clips 125 which extend through apertures in the strips 10 and through apertures 126 in the insulator 123 to hold the strips by either a snap-type or twist-lock arrangement.

Referring now to FIGS. 6 and 7, a resistance heating assembly is illustrated which includes an insulator 134 fixed to a support rod 135. The insulator 134 includes a pair of

mating elements

136 and 137 each having rectangular notches which cooperate to form a rectangular aperture 138. The

portions

136 and 137 are joined to each other and connected to the support rod 135 by an apertured clip 139. Asmay be seen more clearly in FIG. 7, the apertured clip comprises a strip of metal which is bent to form a rectangle. The clip has first, second, and third planar faces 140, 141, and 142, respectively, and those faces are provided with cooperating

rectangular apertures

143, 144, and 145, respectively. To assemble each insulator and to mount each insulator on the support rod 135, corrugated portions 12 of the strips 10 are positioned between opposing faces of the

portions

136 and 137 and those portions are held together while the clip 139 is wrapped about the midportion of the insulator 134 so that the

apertures

143, 144, and register with the aperture 138. The insulators 134 are then skewered by then passing the support rod through the apertures in the insulators and in the clips. The insulators are restrained against axial movement relative to the support rod 135 by static frictional engagement therewith.

A more preferred form of this aspect of the invention is illustrated in FIG. 8. As may be seen in FIG. 8, a resistance heating assembly includes an

insulator having portions

151 and 152 which are fastened together and connected to a support rod 153 by an apertured clip (not shown in this Figure but similar to the clip 139). One edge of the portion 152 is provided with projections 154 which register with notches 155 in an opposed edge of the portion 151. The depth of the notches 155 is less than the length of the projections 154 so that a space is provided between the

portions

151 and 152 to minimize heat concentration. The projections 154 tend to immobilize the strips 10 by entering apertures therein.

Referring now to FIG. 9, a resistance heating element according to a further aspect of this invention comprises an insulator 200 which includes a pair of fritcoated rods 201 having bared midportions which are welded to a support rod 202. The frit coatings at the ends of the rod have cooperating saw teeth 203 which pass through apertures in the strips to thereby immobilize the strips relative to the insulators.

Turning now to FIG. 10, there is illustrated a resistance heating assembly which is adapted to immobilize up to four strips of electric resistance material. The assembly includes a support rod 225 having a U-shaped cross bar 226 welded thereto. The cross bar 226 has upstanding legs 227 on which insulators 228 are mounted. Each insulator comprises

mating portions

229 and 230. Each

portion

229 and 230 has a rectangular socket 231 (FIG. 11) and a rectangular projection 232. The projection 232 of the portion 229 is received within the socket 231 of the portion 230 and the

portions

229 and 230 are mounted on a leg 227 by inserting the leg through a rectangular aperture 233 which extends through both portions. To tie the portions together, a pair of clips (not shown but similar to the clip shown in FIG. 7) may be wrapped about the portions with the legs 227 projecting through the clip apertures. Each insulator 228 immobilizes two strips 10 by clamping the strips between end edges 234 of the

portions

229 and 230. lnwardly extending areas 235 of the

portions

229 and 230 are relieved to provide a space between major portions of the insulator 228 and the strip and to thereby prevent excessive heat build-up in immobilized strip portions. A further embodiment of the present invention is illustrated in FIG. 12. The embodiment illustrated in that Figure includes an assembly which is capable of immobilizing a single strip of electric resistance material. The resistance heating assembly includes an insulator 250 having a rectangular aperture therein through which a support rod 252 extends. To prevent axial movement of the insulator 250 relative to the rod 252, a V-shaped clip (not shown) is provided. The V-shaped clip is similar to the clip 104 (FlG. 3). The insulator 250 has a hook-shaped portion 254 which has an end extending through an aperture in the strip 10 to thereby immobilize the strip relative to the insulator.

FIG. 13 illustrates a resistance heating assembly according to a still further aspect of this invention which is capable of supporting a pair of resistance material strips on each side of a support rod. The assembly includes an insulator 270 which is fixed to a support rod 271 by a clip 272 which is similar to the clip illustrated in FIG. 3. To further restrain the clip 274 relative to the support rod 271, the support rod may be provided with serrations 271a which cooperate with the legs of the clip. Strips 10 are immobilized at upper edges of the insulator by clips 273 which extend through apertures in the strips 10 and through upper apertures 274 in the insulator 270. Other strips 10a are immobilized at the lower edges of the insulator 270 by clips 275 which extend through apertures in the strips 10a and through lower apertures 276 in the insulator 270. Thus, each corrugation of the strips 10a forms a mirror image with respect to an opposite corrugation of each strip 10a.

The foregoing embodiments of the invention set forth heating element assemblies wherein the support rods are straight. It should be appreciated, however, that other assemblies may be provided wherein the support rods are curved.

While there have been described what are at present considered to be the preferred embodiments and aspects 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:

l. A resistance heating assembly comprising:

a. support rod means;

b. a plurality of insulators fixed to said support rod means and angularly related thereto;

c. connecting means between said support rod means and each insulator preventing axial and rotational movement of each insulator relative to said support rod means;

d. a thin strip of apertured, foil-like, electric resistance material retained and supported by said insulators at short intervals along the length of said strip, the entire length of the resistance material between adjacent insulators being formed as a single, continuous, smoothly curved corrugation; and

e. immobilizing means retaining the strip relative to each insulator.

2. A resistance heating assembly according to claim 1, wherein said insulators are substantially symmetrically mounted on said support rod and have strip attaching means on either side of the rod.

3. A resistance heating assembly according to claim 1, wherein said immobilizing means comprises aperture means in said insulators and clips extending through said aperture means and clamping said strip to said insulators.

4. A resistance heating assembly according to claim 1, wherein said insulator comprises insulation coated rod means fixed to said support rod.

5. A resistance heating assembly according to claim 4, wherein said insulation coated rod means comprises a pair of rods fixed to said support rod and wherein said strip is clamped between said rods.

6. A resistance heating assembly according to claim 1, wherein said support rod has a noncircular cross section to prevent said rotational movement between said insulator and said support rod.

7. A resistance heating assembly according to claim 6, wherein said connecting means includes deformed portions of the support rod which prevent axial movement of the insulator.

8. A resistance heating assembly according to claim 7, wherein said support rod has a V-shaped cross section.

9. A resistance heating assembly according to claim 1, wherein each of said insulators comprises separable portions which are clamped to said support rod. I

10. A resistance heating assembly according to claim 9, wherein portions of said strip are clamped by and between said separable portions of said insulators.

11. A resistance heating assembly according to claim 1, wherein each of said insulators includes slot means therethrough through which said strip extends.

12. A resistance heating assembly according to claim 11, wherein each of said insulators has projections extending into said slot means and through said strip to provide spaces between each of said insulators and to immobilize said strip relative to said insulators.

13. A resistance heating assembly according to claim 1, wherein said support rod means extends through an aperture in each insulator and wherein said support rod comprises a plurality of juxtaposed rods which are displaced transversely relative to each other to frictionally engage opposite portions of said aperture.

14. A resistance heating assembly according to claim 13, wherein rod portions engaging opposite portions of said aperture are serrated.

15. A resistance heating assembly according to claim 1, wherein said immobilizing means are provided adjacent opposite edges of each of said insulators and wherein a strip of apertured foil-like, electric resistance material is retained and supported by each immobilizing means with each corrugation being formed as 21 mirror image of an opposite corrugation.

16. A resistance heating assembly according to claim 1, wherein said connecting means between said support rod means and each insulator includes aperture means in each insulator through which said support rod means passes.

17. A resistance heating assembly according to claim 16, wherein said insulators are flat, relatively thin blocks, each block having faces parallel to the faces of adjacent blocks and perpendicular to said support rod means, with each said corrugation located between a pair of adjacent blocks.

18. A resistance heating assembly comprising:

a. support rod means; I

d. said support rod means extending through an aperture in each insulator and comprising a plurality of juxtaposed rods which are displaced transversely relative to each other to frictionally engage opposite portions of said aperture;

e. a thin strip of apertured, foil-like, electric resistance material retained and supported by said insulators at short intervals along the lengths of said strip; and

f. immobilizing means retaining the strip relative to each insulator.

19. A resistance heating assembly according to claim 18, wherein rod portions engaging opposite portions of said aperture are serrated.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3:S35:L:'35 Dated September 10, 19711 Inventor(s) Jerry Eslie Sel 5 It is certified Eat error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Title Page: Add

(73)Assignee: Gould Inc., Chicago, Il1inois Signed and sealed this 6th day of May 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3: 35, 35 Dated September 10, 197

Inventor(s) Jerry Slie Seel It is certified tTat error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Title Page: Add

(73)Assignee: Gould Inc., Chicago, Illinois Signed and sealed this 6th day of May 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Arresting Officer and Trademarks

Claims

1. A resistance heating assembly comprising: a. support rod means; b. a plurality of insulators fixed to said support rod means and angularly related thereto; c. connecting means between said support rod means and each insulator preventing axial and rotational movement of each insulator relative to said support rod means; d. a thin strip of apertured, foil-like, electric resistance material retained and supported by said insulators at short intervals along the length of said strip, the entire length of the resistance mAterial between adjacent insulators being formed as a single, continuous, smoothly curved corrugation; and e. immobilizing means retaining the strip relative to each insulator.

9. A resistance heating assembly according to claim 1, wherein each of said insulators comprises separable portions which are clamped to said support rod.

15. A resistance heating assembly according to claim 1, wherein said immobilizing means are provided adjacent opposite edges of each of said insulators and wherein a strip of apertured foil-like, electric resistance material is retained and supported by each immobilizing means with each corrugation being formed as a mirror image of an opposite corrugation.

18. A resistance heating assembly comprising: a. support rod means; b. a plurality of insulators fixed to said support rod means and angularly related thereto; c. connecting means between said support rod means and each insulator preventing axial and rotational movement of each insulator relative to said support rod means; d. said support rod means extending through an aperture in each insulator and comprising a plurality of juxtaposed rods which are dIsplaced transversely relative to each other to frictionally engage opposite portions of said aperture; e. a thin strip of apertured, foil-like, electric resistance material retained and supported by said insulators at short intervals along the lengths of said strip; and f. immobilizing means retaining the strip relative to each insulator.