United States Patent [191 Wightman et a1.

1 1 OPEN COIL ELECTRIC HEATER [75] Inventors: Lawrence W. Wightman, St. Louis;

Howard C. Gebhart, Chesterfield; Nick Tichy, Affton, all of Mo.

[73] Assignee: Emerson Electric Co., St. Louis, Mo. [22] Filed: Nov. 12, 1973 [21] Appl. No.: 415,007

[52] US. Cl 219/532, 174/138 J, 219/536, 338/317 [51] Int. Cl. H051) 3/06 [58] Field of Search 219/532, 536,537,550; 338/299, 304, 317; 174/138 J, 154

[56] References Cited UNlTED STATES PATENTS 1,419,309 6/1972 Russell 219/532 1,911,383 5/1933 Noble .219/532 2,856,500 10/1958 Hartman.... 219/536 2,921,172 l/l960 Hackman 219/532 3,016,441 l/1962 Hackman et a1 219/532 3,102,940 9/1963 Stone 219/550 X 3,641,312 2/1972 Ammerman et al. 219/532 3,697,727 10/1972 Neuman et a1. 219/532 Nov. 5, 1974 Primary Examiner-Volodymyr Y. Mayewsky Attorney, Agent, or Firm-Polster and Polster [57] ABSTRACT An open coil electric heater is provided having an improved coil supporting means and associated supporting structure. The supporting structure includes a single beam which is configured in various embodiments to carry an open coil heater element above, below or both above and below the beam. The coil supporting means is mounted to the beam structure and includes a coil holder designed so that the coil heater element may be inserted easily in the coil holder. The same construction, however, prevents coil heater element removal and inhibits heater element movement after insertion. The coil holder also functions as a heat fin radiator for the coil heater element. An insulator is mounted to the beam by a spring lock arrangement. Various embodiments of the insulator provide for carrying one or more coil heater elements from a single insulator by having the coil holder mounted on the ends of the insulator, thereby permitting use of the coil holder as a radiator while simultaneously insulating the support structure from the coil element.

15 Claims, 6 Drawing Figures PATENTEDHUY 51914 3.848.619

SHEET 20$ 2 FIG.3.

FIG.4.

FIG.6.

FIG.5.

1 OPEN COIL ELECTRIC HEATER BACKGROUND OF THE INVENTION This invention relates to electrical heater construction and in particular to open coil heaters having an electric heater coil carried by an insulator-frame structure.

Open coil heaters are known in the art. In general, this form of electrical heating device has a coil or coils mounted within a suitable metallic enclosure. The coil must be supported within and insulated from the metallic enclosure. The most common prior art devices utilize a circular or cylindrical form of insulator which is carried by a supporting beam structure. The insulators are designed so that the electric heater coils are strung through them. Because the insulator must be assembled in the enclosure according to some predetermined working configuration, the manufacturing process of stringing the heater coils through the insulators is one of the more time consuming and inefficient manufacturing procedures. While this form of heater works well for its intended purposes, it possesses additional heretofore unremedied disadvantages. As indicated above, the heater coil of the open coil heater must be supported reliably. It also must be adequately insulated from the supporting frame with minimal engagement of the coil so as to leave the major portion of the coil exposed to the air. The cylindrical form of insulator commonly used in the prior art devices inherently prevents maximum coil exposure because the insulator necessarily must be of a sufficient axial length to support the coil adequately. The axial length of this form of insulator in fact, is longer than would appear necessary because the heater coil, after some period of operating time, tends to distort or sag due to expansion of the coil. Because the coil is completely surrounded by the insulator heat transfer characteristics are poor and prior art opencoil heaters often fail along the insulator.

Electric heater coil sag during use is a particularly bothersome problem. Prior art means utilized to support the heater coil were not designed to prevent coil movement. The most prevalent insulators used for this purpose can not prevent sag as the coil must pass through the insulator during heater construction. In order to overcome the expansion problem, heater enclosures were oversize. That is, the enclosures merely were of sufficient size so that space for expansion was available. The problem of coil expansion, in certain instances, also restricted heater installation practices. Since there is nothing to restrict coil movement, heater installations that permit a vertical attitude for the coils were not acceptable, as the coils might become distorted physically or malfunction electrically due to contact with the heater enclosure.

This combination of factors generally has made open coil heater unit production relatively expensive, has prohibited automated assembly of the heater, has decreased the heat transfer capability of the heater in use, and has prevented the open coil heater from realizing its greatest commercial potential.

The invention disclosed hereinafter differs from these prior art devices in that a novel insulator device is mounted to a supporting beam structure and the insulator carries a coil retaining clip which may be metallic and arranged to grasp a single turn of the heater coil,

locking the heater coil in position. The clip allows the heater coil to be positioned vertically along individual ones of the clips without the necessitiy of stringing the coil through a plurality of cylindrical insulators. That is, the heater coil can be placed on top of the clip and pushed downwardly to attach the coil to the clip. Because the insulator rather than the clip is mounted to the supporting beam structure of the heater enclosure, the clip is able to serve a dual function as a heat radiator, which significantly increases the heat transfer efficiency of the device. The clip is designed to optimize heat transfer at its interconnection with the heater coil.

One of the objects of this invention is to provide an improved coil carrying structure for an open coil heater.

Another object of this invention is to provide a low cost insulator and clip combination for an open coil heater.

Another object of this invention is to provide an open coil heater wherein the coil carrying clip functions as a heat radiator.

Yet another object of this invention is to provide an insulator and clip combination that permits carrying a heater coil both below and above the supporting beam structure.

Still another object of this invention is to provide a clip for engaging a turn of an electric coil in locking engagement.

Another object of this invention is to provide a clip for engaging an electric coil that prevents movement of the coil.

Other objects will be apparent to those skilled in the art in light of the following description and accompanying drawings.

SUMMARY OF THE INVENTION In accordance with this invention, generally stated, an electrical heating device is provided with clip means for holding an electrical coil and insulator means for insulating the clip and coil combination from the frame of the heating device.

In the preferred open coil heater embodiment, the insulators utilized are one of two forms, which are intended to carry a single or double electrical heater coil, respectively. A plurality of insulator are suspended from a single beam support structure. Various configurations of the beam structures are combined to give a predetermined output rating for the heater. Individual ones of the clip means are attached to individual ones of the insulators along the insulator end. Each clip means has a wall defining a clasp, which is formed by splitting the wall and rotating the edges with respect to one another.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, FIG. I is a view in perspective of an open coil heater employing insulator and clip means of this invention;

FIG. 2 is a front plane view of a first embodiment of an insulator used in conjunction with the open coil heater of FIG. 1;

FIG. 3 is a front plan view of a second embodiment of an insulator utilized in the open coil heater of FIG.

FIG. 4 is a top plan view taken along the line 44 of FIG. I;

FIG. is a sectional view taken along the line 5--5 of FIG. 4; and

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, reference numeral 1 indicates an open coil heater constructed in accordance with the principles of this invention. The heater 1 includes a front face 2, a first pair of oppositely opposed support members 3, a second pair of oppositely opposed support members 4, and aplurality of cross beam support structures 5. For simplicity, only individual ones of the support structures 3 and 4 are shown in the drawings. The opposite side of the heater 1, not shown, is substantially identical to the side shown. The beam support structures 5 have a plurality of insulator means 6 mounted to them. Each insulator 6, in turn, has a clip means 7 attached to and extending upwardly from it. At least one electrical heater coil 8 is mounted to the heater 1 by the clip means 7.

The front face 2 of the heater 1 has a plurality of controls 9 extending through it. The controls 9 are conven tional and are not described in detail, those skilled in the art recognizing that the controls 9 may be interconnected electrically with portions of one or more of the heater coils 8 in order to permit the varying of the heater 1 output. The support members 3, 4, 5 and front face 2 conventionally are constructed from sheet metal. They may be interconnected to one another by any convenient method. A particularly low cost and ef ficient method of connection is disclosed in the copending Wightman et al. US. application, Ser, No. 415,008, filed Nov. 12, 1973. Other connection techniques are compatible with the broader aspects of this invention, and certain of the structural members may be integrally formed with one another if desired.

The insulators 6 are shown more particularly in FIGS. 2 and 3. FIG. 2 represents a double insulator 10 while a single insulator 11 is shown in FIG. 3. It may be observed, with reference to the last mentioned Figure, that the single insulator of FIG. 3 conventionally may comprise approximately half of the double insulator of FIG. 2. It is further observable, in FIG. 1, that a plurality of groups of insulators may be arranged vertically in stacks and attached to the beam support structure 5 to provide a variety of configurations for the heater coils 8 utilized in any particular heater 1. Because of the availability of both double and single insulators, either an even numbered or an odd numbered of stacked heat coil 8 groups are available in designing conventional rating embodiments of the heater 1.

Both the double insulator l0 and the single insulator 11 include a body 12 having an upper part 13. The insulator shown in FIG. 2, however, further has a lower part 14 integrally formed with the upper part 13. For convenience, only the double insulator 10 is described in detail, the insulator 11 being substantially similar with the exception of the lower part 14 addition.

The body 12 is formed from a suitable insulation material and has a central opening 15 formed in it. The opening 15, as later described, is important in mounting the insulator to the support structure 5.

Aflrst end 16 of insulator 10 has a U-shaped notch 17 formed in it. A pair of grooves 18 are formed in the body 12, near the notch 17. The grooves 18 are utilized tomount the clip means 7 to the insulators l0 and 11, as later described in detail.

A second'end 19 of insulator 10 has a notch 20 and a pair of grooves 21 formed in it. The end 19 is substantially similar in purpose and design to the corresponsing formations along the ends 16 of the insulators l0 and 11.

Beam support structure 5 is U-shaped in crosssection and includes a first side wall 22, a second side wall 23 and a top wall 24. Top wall 24 has an opening 25 through it, and the end 16 of the body 12 of the insulators 10 and 11 is sized to fir through the opening 25. One of the side walls 22 and 23 has a protrusion 26 extending upwardly from it, above the top wall 24. The protrusion 26 is forced into the opening 15 of the body 12 to lock the insulators l0 and 11 to the support structure 5, as is best seen in FIG. 5. This type of interconnection is similar to that disclosed in the above reference application to Wightman et al., Ser. No. 415,008, filed Nov. 12, 1973, in that the projection 26 will attempt to return to its original state, spring fashion, thereby locking the insulators l0 and 11 t0 the beam structure 5.

Clip means 7 is rectangular in plan, having a front face 27, a first side 28 a second side 29, and a discontinuous back formed by a part 30 integrally formed with side 28 and a part 31 integrally formed with the side 29.

Front face 27 has a groove 32 formed in it, extending vertically downwardly from a first edge 50 of the clip 7. Face 27 also has a channel 33 formed in it, extending horizontally across the face 27 and communicating with the groove 32. That portion of the front face 27 adjacent the groove 32 and channel 33, on each side of the groove 32, defines a pair of flanges 34 and 35 respectively. Flange 34 has a first end 36 and a second end 37. Flange 35 has a first end 38 and a second end 39. The flanges 34 and 35 are rotated with respect to one another so that their respective ends 37, 39 and 36 and 38 lie in opposite planes. That is, the end 36 of flange 34 is rotated outwardly from the vertical plane of the face 27 while the end 37 of the flange 34 is rotated inwardly from the vertical plane of the face 27. Likewise, the end 38 of the flange 35 is rotated inwardly from the vertical plane of the face 27 while the end 39 of the flange 35 is rotated outwardly from the vertical plane of the face 27. Of course, the direction of flange rotation can be reversed, if desired. Certain embodiments of this invention may accentuate the rotation along a tip 55 of each end- 37 and 39 of the flanges 34 and 35 respectively. The groove 32 is designed so that rotation of the flanges 34 and 35 make the groove 32 larger than the diameter of wire used in the heater coil 8 along the edge 50 of the clip 7, while the ends 37 and 39, and particularly the tips 55 of those ends, is smaller than that wire diameter. Consequently, a wire turn 51 easily will enter the groove 32 along the edge 50, but the flanges 34 and 35 must be forced apart along the ends 37 and 39 to enable the wire turn 51 to enter the channel 33. The flanges 34 and 35 return to their original position, relative to one another, after the wire turn 51 enters the channel 33. This construction is important because it functions as a maze lock that enables the clip means 7 to hold individual wire turns 51 of the heater coil 8, after those wire turns are inserted into the channel 33 through the groove 32.

Each of the sides 28 and 29 have a pair of tabs 40 formed in them. The tabs 40, in conjunction with the grooves 18 and 21 of the insulators l0 and 11, are used to attach the clip means 7 to those insulators. The tabs 40 are directed inwardly from the vertical plane of the walls 28 and 29 and lock between the grooves 18 and the outboard ends of the notch 17. Attachment of clip means 7 to the lower part 14 of the insulator is accomplished in the same manner.

The heater coil 8 conventionally is a coil of electrical resistance wire constructed from a plurality of the wire turns 51 wound about an axis 56. As described above and as may be observed in FIG. 4, a single wire turn 51 of the heater coil 8 is inserted through the groove 32 into the channel 33. When so placed, the coil 8 effectively is locked between the perimeter of the channel 33 and the notch 17. The rotation of the flanges 34 and 35 described prevents disengagement of the individual wire turns 51 from their attachment with the clip means 7, because the geometry of the coil 8 and the rotation of the flanges are sufficient to prevent removal of the coil 8. ln addition, movement of the coil 8 in either direction along the axis 56 is prevented by the face 27 because the flanges 34 and 35 abut successive convolutions of the coil 8, effectively preventing such movement within the distance between successive convolutions.

As thus described, an extremely efficient and effective insulator and locking means for holding a coil in an open coil heater is provided. The coil is insulated completely from the metal structural members of the heater 1. Since the coil 8 contacts the clasp means 7, the clasp functions as a radiating fin for the coil 8, thereby increasing the area available for heat transfer and improving the efflciency of the heater 1. ln addition, a higher precentage of heater coil 8 is exposed for heat transfer because the heater coil 8 is held by the clasp means only along a single wire turn 51, and this too increases heater efficiency. Because of the various structural components disclosed herein, heater 1 manufacture is greatly simplified. In particular, use of the insulator and clip of this invention permits simultaneous and automated placement of a coil run in all of the clip means of an individual layer of the bank of heater coils 8 shown in FIG. 1, rather than the heretofore prevalent procedure requiring threading of the coil through a plurality of cylindrical like structures.

Numerous variations, within the scope of the ap pended claims, will be apparent to those skilled in the art in light of the foregoing description and accompanying drawings. Thus, the method for attaching the insulator to the cross structure 5 may be varied. In like manner, the method of attaching the clip means 7 to the insulator also may be changed. The particular silhouette of both the insulator and clip means may be varied in other embodiments of this invention. These variations are merely illustrative.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. ln an open coil electric heater having at least one heater coil, and a frame containing said heater coil, the improvement comprising insulating means for insulating the frame from said heater coil, and clip means for holding said heater coil, said clip means being insulated from said frame by said insulating means, said clip means including a wall separated to provide a pair of flanges defining a groove therebetween. each of said flanges being rotated oppositely one another, said wall having a channel through it, said channel communicating with the groove defined by said flanges.

2. An open coil electric heater comprising:

a frame structure, said frame structure including at least one beam support having at least one opening through it;

an insulator, said insulator extending through the opening in and being attached to said beam structure;

a pair of coil holders mounted to said insulator both above and below said beam structure, each of said coil holders including a coil retaining wall having means for attaching a wire turn of a heater coil formed in it, and means for inhibiting axial movement of said heater coil; and

a pair of heater coils constructed from a plurality of wire turns spiraled about a coil axis, one each of said heater coils being carried by one each of said coil holders along at least a single wire turn, one of said heater coil pairs being carried above said beam structure and the other of said heater coil pairs being carried below said beam structure.

3. The open coil heater of claim 2 wherein the coil retaining wall of each of said coil holders is separated to provide a pair of flanges defining a groove therebetween, each of said flanges being rotated oppositely one another, said respective pair offlanges defining said wire turn attaching means for said coil holders.

4. The open coil heater of claim 3 wherein said coil retaining wall further has a channel formed through it, said channel communicating with the groove defined by said flanges.

5. In an open coil heater having at least one heater coil, said coil comprising a plurality of wire turns wound about a coil axis, and an enclosure, the improvement comprising means for mounting said coil along said enclosure, said mounting means comprising a support member, an insulator structure mounted to said support member, and a coil holder mounted to said insulator and electrically insulated from said support member by said insulator structure, said coil holder including a coil retaining wall having means formed in it for attaching at least a wire turn of said heater coil to said mounting means, and means for inhibiting axial movement of said heater coil, said axial movement inhibiting means being formed by said coil retaining wall.

6. The improvement of claim 5 wherein said coil holder is metal and functions as a heat transfer fln for said heater coil.

7. The improvement of claim 6 wherein said insulator includes a body portion and a U-shaped upper portion.

said support member by forcing said tab into said open ing so as to engage said tab with said opening perimeter.

10. The improvement of claim 5 wherein said coil holder is further characterized by a first pair of oppositely opposed side walls, said coil retaining wall being positioned between said first side wall pair, said coil retaining wall being separated to provide a pair of flanges defining a groove therebetween, each of said flanges being rotated oppositely one another.

11. The improvement of claim 10 wherein said coil retaining wall further has a channelformed through it, said channel communicating with the groove defined by said flanges. 12. In an open coil electric heater having at least one heater coil, and an enclosure, the improvement comprising means for supporting and insulating said coil from said enclosure, said supporting and insulating means including a beam structure, said beam structure having at least one opening in it, an insulator, said insulator including a first base part and a second upwardly extending part, said insulator extending through the opening in and being attached to said beam structure; and first clip means mounted to said insulator and electrically insulated from said beam structure by said insulator, said first clip means including a wall separated to provide a pair of flanges defining a groove therebetween, each of said flanges being rotated oppositely one another, a portion of said heater coil being carried by said first clip means.

13. The improvement of claim 12 wherein said insulator is further characterized by a third part extending downwardly from said base, and second clip means mounted to said insulator along said third downwardly extending part, said second clip means being electrically insulated from said beam structure by said insulator, said second clip means including a wall separated to define a pair of flanges, each of said flanges being rotated oppositely one another, said heater including a second heater coil, at least a portion of said second heater coil being carried by said second clip means.

14. The improvement of claim 12 wherein the upwardly extending part of said insulator has a U-shape d notch formed in it along an end opposite said base, and the wall of said first clip means has a channel formed in it, communicating with a groove defined by said flanges, and extending in a direction generally perpendicular to said groove.

15. The improvement of claim 14 wherein said base part of said insulator has an opening through it, and said beam structure includes an upwardly extending tab positioned to align with said opening in said first base part of said insulator when said insulator is positioned to extend through the opening in said beam structure.