US2917616A

US2917616A - Electric heating devices

Info

Publication number: US2917616A
Application number: US575993A
Authority: US
Inventors: William L Thomson
Original assignee: Edwin L Wiegand Co
Current assignee: Edwin L Wiegand Co
Priority date: 1956-04-04
Filing date: 1956-04-04
Publication date: 1959-12-15
Anticipated expiration: 1976-12-15

Description

W. L. THOMSON ELECTRIC HEATING DEVICES Dec. 15, 1959 4 Sheets-Sheet 1 Filed April 4. 1956 JNVENTDR. WI LLIAM L. THOMSON Ar'rouinnY Dec. 15, 1959 w. L. THOMSON 2,917,616

ELECTRIC HEATING DEVICES Filed April 4, 1956 4 Sheets-Sheet 2 6 6 .5 7 5 7 I)? 5; 6' I... A8 I g 56 29 7 2 7 I 8 27 INVENTOR.

WILLIAM L. THOMSON ATTORNEY 1366- 1959 w. L. THOMSON ELECTRIC HEATING DEVICES 4 Sheets-Sheet 3 N m M o A Wmwm 1 WA L M mi L H m w 4" 1 n d e m Dec. 1-5, 1959 w. L. THOMSON 2,917,616

ELECTRIC HEATING DEVICES Filed April 4, 1956 4 Sheets-Sheet 4 IN V EN TOR.

WILLIAM L. THOMSON WWW .ATTORNIY United States Patent ELECTRIC HEATING DEVICES William L. Thomson, Pittsburgh, Pa., assignor to Edwin L. Wiegand Company Application April 4, 1956, Serial No. 575,993

6 Claims. (Cl. 219-34) My invention relates to infrared heating devices, more particularly to devices of this type utilizing a sheathed electric heating element as a source of infrared rays, and the principal object of my invention is to provide new and improved heating devices of this character.

My improved construction enables a user to easily vary the amount of heat radiated by the element or to vary the pattern of the heat radiated, and thus permits the device to be adapted for a multitude of uses with a minimum expenditure for equipment and at low labor cost.

In the drawings accompanying this specification and forming a part of this application, there is shown, for purposes of illustration, an embodiment which this invention may assume, and in these drawings:

Figure 1 is a perspective view of a radiant heating device illustrating a presently preferred embodiment of my invention,

a Figure 2 is an enlarged fragmentary perspective view of one end of the device shown in Figure 1,

Figure 3 is a fragmentary longitudinal sectional view taken at one end of the device,

Figure 4 is a broken elevational view illustrating a central portion of the device,

Figure 5 is a fragmentary separated perspective view of details of construction, and

Figures 6 through 11 illustrate various heating patterns which may be provided through use of my invention.

The embodiment of the invention herein disclosed comprises an elongated support or housing 20 having a longitudinally extending channel. The support 20 is preferably formed from extruded aluminum, and has a head portion formed by a pair of longitudinally extending ribs 21-21 and a portion 22 providing a longitudinally extending concavity of generally parabolic crosssection. Each edge 23 of the portion 22 provides a longitudinally extending ledge 24.

Preferably, the concave face of the support 20 is overlaid by a thin sheet 25 which desirably provides an exposed surface having high reflecting qualities. The sheet may be sprung into the concavity of the support to generally assume the shape thereof and may be held in position by having its side marginal edges engaged behind the ledges 24.

The support may be of the type as shown in United States Letters Patent No. 2,627,014 issued to Joseph E. Kolb and assigned to the present assignee. As shown in said patent, a series of supports 20 may be joined together in side-to-side relationship by means of keys (not herein disclosed) fitting within grooves 26 formed in the edge portions 23 of respective supports.

Thus, as shown diagrammatically in Figures 6 through 11, a plurality of supports 20 may be joined in side-toside relationship to form a heat radiating pattern of desired extent. Further, as disclosed in said patent, the joined supports may lie in a common plane or may be arched to direct heat rays in a selected manner. In

2,917,616 Patented Dec. 15, 1959 Figures 6 through 11, the supports 20 are of the same length although it will be appreciated that various lengths may be used. From a manufacturing standpoint, it is preferable to form the supports 20 of one or more standard lengths to avoid the stocking of a great many indiscriminate lengths.

In infrared heating devices of previous manufacture, and as shown in the Kolb patent, it was the practice to provide a single, rectilinear, sheathed heating element, and to support such element from its opposite ends in proper relation within the cavity of the support 20. Such construction had certain merits since the manufacture of the heating element was relatively simple and uniformity of heat distribution lengthwise of the cavity was not a material problem. However, expansion and contraction of the heating element presented serious problems and accordingly provision had to be made to accommodate for such change in length of the element. Ordinarily, at least one end of the element was supported for sliding movement and such construction did not provide the rigidity normally required in heaters of such type. In the case of relatively long heaters, sagging of the heating element also provided a problem and heretofore sagging was attempted to be solved by placing one or more supports intermediate the ends of the heating element.

In my improved construction, the disadvantages of the prior art heating devices have been largely overcome. Referring particularly to Figures 1 and 2 of the drawings, the heating element 27 of my preferred embodiment is of hairpin formation, as shown.

The heating element 27 may be of any suitable type. For example, a rectilinear metal tube, containing a resistor having terminal pins connected to its ends, may be filled with electric-insulating heat-conducting material, such as powdered refractory material. The sheath may be rolled or pressed to change the cross-section of the sheath and laterally compress the powdered refractory material. In the form herein illustrated, the sheath of the heating element 27 has been side pressed from a round cross-section to a generally triangular or heartshape cross-section shown by the dotted lines 28 in Figure 5. The ends of the sheath may or may not be pressed, and as here shown, such ends remain round, or generally so, for a short distance inwardly of each extremity of the element.

The rectilinear heating element may then be bent in any suitable manner to hairpin formation to provide a bight portion 29 and generally parallel legs 30-30 which preferably are of equal length. The sheath of the heating element may then be again side pressed to again redensify the refractory material and fill any voids caused by bending, or the side pressing before mentioned may be accomplished after bending of the heating element.

In any event, it is preferable to provide spaced ribs 31-31 (see Figure 5) on at least one of the legs 30 adjacent to its extremity, for a purpose later to be explained. As seen in Figures 2 and 5, the terminal pins 32 extend outwardly from the open extremity of each leg 30 and a terminal clip 33 is mechanically and electrically secured to each pin 32 for connection to a source of electrical energy.

Referring particularly to Figures 2 and 5, a mounting member 34 preferably of dielectric material, is provided for holding the heating element 27 in position within the cavity of the support 20. In the embodiment illustrated, the mounting member comprises a base part 35 and a cap part 36. The base part 35 has its inner surface shaped generally complementary to the cross-sectional shape of the cavity in the support 20, and its outer surface is formed with two spaced grooves 37-37.

The outer surface, intermediate the grooves 37, is also formed with an undercut 38, generally rectilinear in cross-section, for the purpose of receiving a key portion 39 formed on the inner surface of the cap part 36. The part 36 may also be formed with grooves 4il40 on opposite sides of the key portion 39 and in general alignment with the grooves 37-37 formed in the base part 35.

An aperture 41 extends through the base part 35 and cap part 36 for the purpose of passing a bolt 42. As best seen in Figure 3, the center portion of the inner surface of the base part 35 is provided with a recess 43 so that the head 44 of the bolt 42 is clear of engagement with the sheet 25 which lines the cavity of support 2%. The outer surface of the cap part 36 may also be recessed, as shown at 45, to receive a nut 46 which is threaded on the bolt 42 for the purpose of holding the base and cap parts assembled.

A holding clip 47 is provided for holding the mounting member 34 in fixed position longitudinally of the cavity of the support 20. The clip 47 has an apertured portion 48 which passes the bolt 42 and is clamped between the bolt head 44 and the adjacent inner surface of the base part 35.

The clip 47 also has an upwardly off-set apertured portion 4% which passes a bolt 50. The bolt 59 also passes through

aligned apertures

51 and 52, respectively in the sheet 25 and the support 29. In the construction shown in Figure 3, the bolt head 53 bears against the clip portion 4; and a nut 54 bears against the outwardly directed surface of the support 20.

The method of assembly of the heating element 27 with the mounting member 34, and of the latter With the support, is relatively simple. With the base part 35 and cap part 36 of the mounting member 34 separated, the ends of the legs 30 of the heating element 27 are laid within the grooves 37 of the base part 35. The ribs 31-31 are spaced an amount approximately equal to the width of the base part 35 and engage with opposite sides thereof to locate the heating element 27 with the mounting member 34.

The cap part 36 is then placed over the base part 35 with the key portion 39 fitting within the recess 38 and the grooves tl40 receiving that portion of the legs of the heating element which extends above the upper surface of the base part 35. The bolt 42 is then passed through the apertured portion 48 of the clip 4-7 and through the aperture 41 in the base and

cap parts

35 and 36 and the nut 4-6 is threaded onto the bolt sufiiciently to hold the element in position.

The assembly thus formed may be mounted in position on the support 20 by passing the bolt 50 through the apertured portion 49 of the clip 47 and through the

apertures

51 and 52, respectively in the sheet 25 and support 2b.

In some cases, as where the heating element is relatively short, no further support for the heating element need be provided. However, if further support is desirable, a supporting device 55 may be utilized. The device, as herein shown, comprises two pieces of sheetmetal 5656 secured together over their central portions and having their ends 57 wedge-shaped and diverging, the ends being adapted to be snapped into position wherein they are held within the grooves defined by the ledges 24 but may be slidably moved along the cavity of the support 2%. The pieces 56 have openings to receive dielectric bushings 5858 which freely receive the legs 29 of the heating element 27. in assembly, the device 55 is first disposed over the legs of the heating element before the latter is assembled with the mounting member 34.

In Figure 1, two hairpin type heating elements are shown mounted at opposite ends of the support 2% with bight portions facing each other. The construction of the elements and their mounting is desirably identical and like reference numerals have been applied to indicate like parts. A cover member 59, shown in full lines in Figure 1 and in dotted lines in Figure 3, may be applied over the outer face of the cap part 36 to provide a trim ap pearance. Such cover member may be removably held in place by a nut 60 threaded on the bolt 42.

In order to provide uniform heat radiation between the facing bight portions of the heating elements, it is desirable to space such portions with a certain degree of accuracy. As seen in Figure 4, the spacing is preferably of such amount that were each bight portion cut at its center along the dotted line 61, and each half of the bight portion straightened, as shown by dotted lines 62, the straightened portions of aligned legs 30 would touch.

In Figure 1, the heating elements 27 are shown of equal length and, since such lengths cover many normal uses of the heating device, the

apertures

51 and 52, respectively in the sheet 25 and support 20 (see Figure 3) may be formed at the factory during manufacture of the device.

However, it is contemplated that one or the other of the two heating elements may be shifted longitudinally of the cavity provided by the support 20 or that heating elements of different lengths may be used to replace the elements shown in Figure 1.

For example, Figure 11 shows heating elements 27 wh ch are longer than the elements shown in Figure 1 and all of which are mounted at one end of the joined supports Zil. Figure 8 shows long elements mounted at the opposite end of the joined supports 20, but spaced slightly inwardly of such end.

Figure 7 shows heating elements 27 in facing relationship as in Figure 1, but with shorter elements. Figures 6, 9, and 10 show a combination of long and short elements.

Each individual heating element 27, its mounting member 34 and its supporting device 55 (if used) may be shifted to any desired position along the cavity provided by the support 23, when the fastening bolt 59 is removed. Therefore, it is merely necessary for a user to determine the desired location of the heating element (or elements) and drill new holes through the sheet 25 and the support 20, to receive fastening bolt 50.

Since it is desirable to maintain the spacing between facing bight portions when two heating elements are disposed in the channel, the manufacturer may supply a chart providing dimensions between holes for the bolts 5% for fastening elements in positions other than provided for by the holes 51.-52 formed at the factory. The chart may also show the location of the holes formed at the factory to provide for location of other holes to be drilled by the subsequent user. The chart may be used to determine the locations of heating elements in the various desired patterns such, for example, the patterns disclosed in Figures 6 through 11.

The heating device provided by my invention has great flexibility from a heating standpoint and accordingly is particularly useful to a small manufacturer who requires various heat patterns periodically. My invention also reduces the number of parts required to be manufactured and stocked in order to produce the various heat patterns. To increase the length of a heat pattern, it is merely necessary to move a series of connected supports end-to-end with another series of connected supports. This may be best illustrated by reference to Figures 6 and 7 if it is assumed that the two figures are moved together to eliminate the space therebetween and it is further assumed that a pair of heating elements are disposed in the combined channels thus produced with the elements having their bight portions in facing relation.

The hairpin type elements herein provided not only reduce the great care heretofore required to allow for expansion and contraction but also increase the watts per lineal inch of the heater, since two heating legs are provided in place of the single length heretofore used.

In view of the foregoing it will be apparent to those ill skilled in the art that I have accomplished at least the principal object of my invention and it will also be apparent to those skilled in the art that the embodiment herein described may be variously changed and modified, without departing from the spirit of the invention, and that the invention is capable of uses and has advantages not herein specifically described, hence it will be appreciated that the herein disclosed embodiment is illustrative only, and that my invention is not limited thereto.

I claim:

1. In a radiant heating device, a support having a longitudinally extending channel, a sheathed electric heating element of the hairpin type, means for holding said element in position to extend longitudinally of said channel and comprising a two part mounting member formed of dielectric material, said member having facing surfaces at least one of which has a pair of grooves for receiving portions of the respective legs of said hairpin element, said mounting member having an aperture extending therethrough and transversely of said facing surfaces, a fastening screw passing through said aperture for holding the parts of said mounting member in assembled relation and for clamping said leg portions within said grooves, and means connected to said fastening screw for securing said mounting member to said support.

2. In a radiant heating device, a support having a longitudinally extending channel, a sheathed electric heating element of the hairpin type, means for holding said element in position to extend longitudinally of said channel and comprising a two part mounting member formed of dielectric material and disposed within said channel, said mounting member having facing surfaces at least one of which has a pair of grooves for receiving portions of the respective legs of said hairpin element, said mounting member also having an aperture extending therethrough and transversely of said facing surfaces, a fastening screw passing through said aperture for holding the parts of said mounting member in assembled relation and for clamping said leg portions within said grooves, said fastening screw having a head at the innermost part of said mounting member and a nut threaded on said screw and bearing against the outermost part of said mounting member, a holding clip having a portion clamped between the head of said screw and said innermost part and also having a spaced apertured portion, and a screw passing through the aperture of said clip portion and into an aligned aperture in said support for holding said mounting member assembled with said support.

3. In a radiant heating device, a support providing a longitudinally extending trough, a sheathed electric heating element having a bight portion from which extend a pair of legs in side-by-side relation, the free ends of said legs having terminal connector portions and the leg portions adjacent said bight portion providing for the generation of heat when current is passed through said element, a pair of axially spaced shoulders carried by the free end of one of said legs and extending radially of such leg, and a heat resistant mounting member securable within said trough and to which the free ends of the legs of said element are adapted to be secured to dispose said element longitudinally within said trough and with said bight portion on one side of said mounting member and said terminal connector portions on the other side of said mounting member thereby shielding said terminal connector portions from the heat radiating from said element, said mounting member being apertured to loosely pass the free ends of said legs and said axially spaced shoulders cooperating with respective adjoining portions of said mounting means to locate the latter along said legs and resist relative movement therebetween 1ongitudinally of said legs, said mounting member comprising separable parts which in assembled relation cooperate to provide opposed, aperture defining marginal portions restricting movement of said element transversely of its legs and which in disassembled relation provide for ready assembly of said element with said mounting member by movement of said element transversely of its legs, said mounting member having a marginal portion configurated for close fitting engagement with a defining margin of said trough to minimize convective heat flow between the latter and said mounting member to thereby protect said terminal connector portions from excessive heat and said mounting member being securable at various places along said trough to variously position said element therealong.

4. In a radiant heating device, a support providing a longitudinally extending trough, a sheathed electric heating element having a bight portion from which extend a pair of elongated legs in spaced, side-by-side relation, and a mounting member secured within said trough for supporting said element and having spaced apertures through which respective free ends of said element legs extend, one of said element legs being held against longitudinal movement relative to said mounting member to accurately locate and maintain said element longitudinally of said trough and said other element leg being free to move longitudinally relative to said mounting member to provide for expansion and contraction of said element during temperature changes.

5. In the radiant heating art, the combination of a plurality of standard length elongated supports, each having a longitudinally extending channel, with a plurality of similar hair-pin type sheathed electric heating elements, some heating elements being long and of a length greater than half the length of said channel and other heating elements being short and of a length less than half the length of said channel, mounting means for each of said heating elements and connected to the terminal portion of the legs of a respective element, securing means for connecting said mounting means at selected positions lengthwise of the channel of a respective support, whereby a long heating element may be secured in a support channel in selected longitudinal position, or shorter heating elements may be secured in a support channel in selected relative positions.

6. The construction of claim 5, and further including means connecting elongated supports side-to-side with channels facing in the same direction, and long and short heating elements secured in said channels.

References Cited in the file of this patent UNITED STATES PATENTS 911,864 Ball Feb. 9, 1909 1,695,874 Woodson Dec. 18, 1928 1,760,065 Hynes May 27, 1930 1,806,115 Parsons May 19, 1931 2,088,728 Stranszky Aug. 3, 1937 2,599,029 Turner et al Aug. 3, 1952 2,627,014 Kolb Jan. 27, 1953 2,667,563 McOrlly Jan. 26, 1954 2,668,896 Husaczka et a1. Feb. 9, 1954 2,688,685 Goodell Sept. 7, 1954 2,733,049 Carter Jan. 31, 1956 FOREIGN PATENTS 364,541 Great Britain Dec. 28, 1931 485,104 Great Britain May 13, 1938 775,757 France Oct. 15, 1934 816,720 Germany Oct. 11, 1951