US3436524A - Heat energy receptor-radiator wall - Google Patents

Description

April 1, 1969 E. A. PAULS mm ENERGY RECEPTOR-RADIATOR WALL Fi led June 5, 1967 Sheet I of 2 FIG. 2

R 5 mm H J m a r m T m A a z April 1, 1969 E. A. PAULS HEAT ENERGY RECEPTOR-RADIATOR WALL Filed June 5, 1967 INVENTOR. Edd/46D A 9404.5

A rroex/er s United States Patent 3,436,524 HEAT ENERGY RECEPTOR-RADIATOR WALL Edward A. Pauls, Excelsior, Minn., assignor to Research, Incorporated, Minneapolis, Minn., a corporation of Minnesota Filed June 5, 1967, Ser. No. 643,629 Int. Cl. Hb 3/40, 1/00 U.S. Cl. 219-347 9 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND AND OBJECTS In heating devices utilizing radiant heaters, the radiant heaters are normally positioned to radiate directly against the work which may be positioned in or passed through a heating zone. Some of the heat inevitably radiates in directions so as not to impinge upon the work and is lost. To overcome this loss and improve efliciency reflectors for reflecting, or refractory surfaces for re-radiating, the heat rays have been used. Reflectors become dirty or oxidized and lose their reflective efliciency and they are expensive to make and maintain. Prior refractory walls herein referred to as a heat energy receptor-radiator wall which operate on the theory that they become hot and re-radiate the heat energy, have been used, but known constructions are fragile and diflicult to maintain.

This invention relates to refractory heat receptorradiator wall constructions and overcomes prior difliculties of lack of ruggedness and strength, and high cost of construction and maintenance and declining efiiciency of the prior constructions. The objects of the invention are to provide improved heat receptor-radiator composite wall constructions having good heat re-radiation properties which do not appreciably decline during the long life of the construction and are economical to make and install and to maintain. The invention provides advantages in allowing adequate support of the radiant heaters, especially of the tungsten filament-quartz tube type, and it is an object of the invention to provide such devices.

Other and further objects are those inherent in the invention herein illustrated, described and claimed ant" will be apparent as the description proceeds.

The invention is illustrated by the drawings wherein:

FIGURE 1 is an isometric view of an exemplary form of the invention;

FIGURE 2 is a sectional view taken at a right plane through the device of FIGURE 1 at line and arrows 22;

FIGURE 3 is an isometric view, partially broken away and partially in section of another embodiment of the invention; and

FIGURE 4 is a fragmentary isometric view partially broken away, of the upper left portion of the device shown in FIGURE 3.

According to the present invention, there is provided as a wall construction constituting all or part of the heating device, a refractory surface which is adhesively attached to a supporting sheet of heat conductive material, the supporting sheet in turn being positioned so that its outer surface is exposed so that it is cooled by convection and radiation. Depending upon the working temperature to which the entire heating device is put, the support- 3,436,524 Patented Apr. 1, 1969 ing sheet may be composed of sheet metal, fiber glass, high temperature plastics and even glass or similar materials. For most purposes a metal sheet is preferred since it is rugged, easily worked, it has high heat conductivity, and it is not unduly expensive. Even in operations where the device may produce temperatures on the surface of the refractory of several thousands of degrees Fahrenheit, the support sheet may still be metal, such as aluminum. The refractory material is preferably composed of cellular fused amorphous silica ceramic in block or sheet form. Thus Glass Rock 25 (trademark) by the Glass Rock Products Company may be used, or Type N 20 refractory produced by Mexico Refractories Company is suitable. These materials have a weight in the range of twenty to twenty-five pounds per cubic foot, they are light cream or tan color, they are cellular, soft and can be cut by sawing or shaping. The material is substantially opaque to heat radiations, and has a very low coefficient of heat conductivity. Accordingly, a refractor surface of this type, when exposed to heat radiations from a radiant energy source, such as a tungsten filament quartz tube line heater, will quickly receive the energy radiated by the heat source, and the surface temperature of the refractory will rapidly increase, and if the input of heat energy is maintained, the refractory material will reach a higher and higher temperature and will become incandescent and will even fuse to a glassy surface if the heat energy applied is suiiiciently strong and prolonged. Yet, by using a refractory thickness of, for example, one-half to two inch thickness, the heat flow through the layer of refractory material is very slow, and only a relatively small percentage of the total heat input is lost through conduction through the refractory layer.

According to the invention, the refractory layer is bonded to the support layer by means of an elastomer which is capable of enduring the temperatures reached under operating conditions. This elastomer should be capable of deforming under stress and, of course, must be adhesive in respect to the support sheet and the refractory layer which are bonded together by means of the elastomer. As suitable elastomers for accomplishing this purpose, there may be mentioned the product put out by General Electric Company and designated RTV 106 silicone rubber or the Dow Corning Company product Sylistic (trademark) Nos. 106 and 116. These elastomers are high temperature enduring silicone rubber elastomers. They remain permanently elastic in the sense that they will deform when stressed. Other elastomers having the aforesaid characteristics may be used.

With the refractory layer adhesively bonded to the (heat conductive supporting sheet, the following takes place: The heat radiated by the radiant energy heat source(s), or at least some portion which radiates out in an unwanted direction (away from the work which is undergoing treatment) will, at least in part, impinge upon the adjacent refractory layer, which accordingly becomes heated very quickly and begins to re-radiate in the direction of the work. Some small portion of the heat will be conducted through the refractory layer, but due to the low heat conductivity of the refractory layer, only a small amount of heat flows out this way. The heat which does flow through the refractory will, of course, reach the elastomer, which is consequently heated, but since the elastomer is also bonded to the heat conductive supporting sheet, the heat flow is carried outwardly by the supporting sheet, which being exposed on the exterior, is cooled both by convection and radiation and this main tains the elastomer sufliciently cool so that it is not destroyed. The supporting sheet is preferably provided with a dull dark color (coating) on its exterior such as by means of a dull black paint, and this enhances the radiation, and hence the cooling, of the supporting sheet and the elastomer or, if desired, may be provided with a water jacket or cooling coils heat-bonded onto the outer surface of the support sheet, with water or other coolant circulated therethrough for cooling the support sheet. Since the refractory is highly opaque to heat radiations, practically no heat radiations, as such, will pass through the refractory layer onto the elastomer layer.

In the course of heating and cooling, the refractory layer and the supporting sheet will expand and contract at different rates, and during the course of use, the refractory layer will develop random cracks extending completely through the refractory layer from that surface which is exposed to the heat source, back to the surface which is bonded to the supporting sheet. It has been discovered that these random cracks, which in effect segment the refractory layer into a plurality of blocks of irregular dimensions, will actually do no harm, since each block is individually secured by the elastomer and bonded to the supporting sheet.

Referring to the drawings, in FIGURE 1, the supporting sheet is made in any form suitable for the particular shape of heating device undergoing construction, and is here in the form of a sheet metal channel having the side flanges 11 and 12. On these flanges there are outwardly extending supporting tabs 13-13- and 114--14, these being apertured at 13A and 14A to provide for mounting. Within the channel, and on the web or base portion 15, there is placed a refractory layer 16 which in this instance is made of two strips 16A and 16B running the length of the channel. The refractory layer 16 may have a width dimension so as to provide clearance spaces at 17-417 adjacent the flanges 11 and 12 of the channel. The refractory layer 16 is adhesively secured to the web by means of a layer 18 of elastomer which is capable of enduring the temperature of operation of the device, and of deforming under stress, and can be a silicone rubber adhesive, such as previously described. It will be noted that in this instance the channel is composed of a relatively thin piece of sheet metal, such as a piece of sheet aluminum of A to 4 inch thickness or even thicker. The entire channel 11, 12 and 15 is made suficiently strong to carry the load that it is intended to carry and the exact thickness of the metal of the sheet of which it is composed, is of no particular consequence. Therefore, a sheet metal thick enough to stand the weight over the required span is provided. Above the refractory layer 16, and adjacent each side flange -11 and 12 of the channel, there is placed another strip of refractory as at 19 and 20, each being appropriately secured adhesively to its adjacent flange by an adhesive layer as at 21 for the refractory 19 and at 22 for the refractory 20, said adhesive layers being of the same type and quality as used at 18 and previously described. In use, in heating and cooling, the refractory layer 16 will slightly expand into the clearance spaces 17, and random cracking may occur, but this is of no particular disadvantage, since the entire faces of the refractory layer 16 and of the refractories 19 and 20, which are directed towards the web '15 of the flanges 11 and 12, respectively, are adhesively secured by the elastomers 18 and 21-22, respectively.

Within the structure thus formed there are positioned by means not shown, two heat radiating elements 24-24 having filaments 2525 which are heated to a high degree of temperature. The heat which is radiated in a direction other than toward the work, i.e. the radiations toward the channel will be received by the refractory layer 16 and 19 and 20, and the surfaces of these refractories which face the heat sources 24, 25 will become heated. These heated surfaces at 168, 198 and 208, will soon reach a temperature at which they re-radiate heat outwardly from the channel formation and against the work which is spaced outwardly from heaters adjacent and facing the channel.

Referring to FIGURE 3, there is illustrated an embodiment of the invention similar to that shown in FIGURES 4 l-2. Referring to FIGURE 3, there is provided a channel generally designated 30 having a web 31 and a side flange 32 which is uppermost in FIGURE 3 and a bottom flange 34 which is lowermost. These flanges terminate along the lines 32A-32B for the upper flange and at 34A-34B for the lower flange. The web 31 is provided with rearwardly extending flanges at 31A and 3113 which are secured by screws or rivets to the end boxes 35 and 36, the end boxes being in turn secured and bridged by the rear struts 37 at the upper portion and 38 at the lower portion, so as to secure the end boxes together for mounting. The struts 37 and 38 are in the form of channels, which allow easy bolting to adjacent structures.

The channel formation 30 is composed of sheet metal such as sheet aluminum, for example sheet aluminum 4 to of an inch thick. Within the channel format-ion, between the lines 32A-32B (and 34A34B) there are placed the following refractory layers: Against the lower flange 34 there is placed a layer of refractory 40 and against upper flange 32 there is placed a layer of refractory 41, the refractory layers in each instance being several times as thick (for example, one-half inch) as the thickness of the adjacent flanges (34 or 32), to which such refractory layers are adhesively secured by means of a deformable elastomer of the same type as hereinbefore described and exemplified. Then, against the web 31 of channel 30 and filling the space between refractory layers 40 and 41, there is placed a rear refractory layer 42 which is preferably made considerably thicker (for example, 1.5 inch to 2.0 inch thick) than the layers 40 and 41, and the layer 42 of refractory is likewise adhesively secured to the web 31 by means of an elastomer of the type hereinbefore described and exemplified. These layers of refractory 40, 41 and 42 extend along the length of the channel, but terminate as at 41A and 41B for the upper refractory, and similarly at 40A and 40B for the lower refractory, and at 42A and 42B for the refractory 42. Thus, there is provided at each end of the channel 40, a space of the same dimension at each end of the channel, this space being the distance between the line 32A and 41A, or between the line 32B and 41B. Into this space at each end of the channel there is placed a piece of refractory which fills out the distance from the adjacent faces of the refractories 40, 41 and 42 out to the ends of the channel at lines 32A to 32B and lines 34A to 34B. The piece of refractory at 45 at the right end in FIGURE 3, is provided with semicircular notches as at 45A which extend across the front face of the refractory. Similarly the refractory piece 46, at the left end of FIGURE 3, there are similar semi-circular notches at 46A. These notches 45A and 46A are spaced outwardly from the front face of the refractory 42 by the amount of dimension S. As will be observed, the end box 36 has a top, rear and bottom, but it is exposed on its outer face and at the front. The end boxes have front edges at 36A for the box at the left end, and at 35A for the box 35 at the right end in FIGURE 3. Box 36 is then covered by a removable cover in the form of a sheet metal angle 47 at the left end and the box 35 is covered by angle 48. Angle 47 is attached on the studs 47C, 47C at the left end, and held in place by means of the wing nut 49, see FIGURE 4. Angle 48 is held similarly. Angle cover 47 is lined with a sheet of temperature resistance insulation at 43 and angle cover 48 is similarly lined. Angle 47 has a front flange 47A and a side flange 47B, the front flange being spaced forwardly sufficiently so as to provide a space for a block of refractory material 50. Angle 48 similarly provides a space for refractory 51 at the right end. These blocks of refractory 50 and 51 having a vertical dimension so that they cover the front edges of the refractories 45 and 46. On the inner surfaces of the refractories blocks 50 and 51 there are provided a series of half-cylindrical notches, one such being illustrated at 50A. The notches are spaced to match notches 45A and 46A, and extending outwardly beyond the face 46B of the clock 46, and similarly for the block 45. These notches align with and correspond to and cooperate with the notches 45A and 46A, and thus form circular apertures through which the end portions of the heating elements H are loosely retained, but it will be noted that the end terminals of the heating elements are "exposed to the rear faces of the refractories 50 and 51.

The heating elements H are standard articles of manufacture and have one terminal wire connector HC at each end which can then extend back and can be fastened by means of a screw as at 52 to a terminal strip 54. Two terminal strips 54 and 55 are provided at each end being supported on insulated supports 54A and 55A within the block structure 36. These terminal strips 54 and 55 are provided with as many screw connections as are needed for individually connecting the connection terminal wires HC of all of the lamps in the bank of lamps. The two terminal strips 54 and 55 are connected to the same supply wire 56 by means of the connection at 57 and 58, so they are at the same polarity. The structure at the right end of FIGURE 3 is exactly similar and provides power from the other line wire. The refractory strips 50 and 51 are, respectively, adhesively secured to the angle cover pieces 47 and 48 by means of the same elastomer as previously described and illustrated. Thus the cover 47 and its refractory 50 may readily be removed by removing only two wing nuts 49 from the studs 48. This exposes the ends of the heating elements for replacement or repair. When the cover arrangement 4750 is then replaced, the ends of the heating elements are loosely confined and supported and adequately protected electrically. The sheet metal which the angle cover pieces 47 and 48 are composed of, may preferably be of the same kind and thickness of sheet metal as used for the channel 30.

In use the large number of heating elements H-H-H, set parallel to each other and spaced by dimension S, slightly forwardly and parallel to the front surface of the refractory 42, will, of course, radiate an intense amount of heat toward the work. However, the heat which radiates against the front surface of refractory 42 and against the adjacent inner surfaces of the refractories 40 and 41, and refractories 45-51 and 46-50 will cause all of these surfaces rapidly to increase in temperature, and will soon reach a temperature at which re-radiation of the heat will occur in a direction toward the work, which faces the entire heating unit. However, the heat conductivity through the layers of refractory 40, 41 and 42, and through the refractories 4551 and 4650 are very low and these refractories are substantially opaque to the transmission of radiant heat energy, and consequently the surfaces of such refractories by which they are adhesively secured to their respective supports, .are not unduly heated, and such sheet metal supporting surfaces, being exposed on the exteriors to cooling by convection or radiation, are kept at a temperature sufficiently low that the body of the supporting sheet metal of the channel 30 and of the end covers 47 and 48, will not reach temperatures sufficiently high so as to be destructive of the elastomer by which the refractories are bonded. Consequently, the refractories are securely held to the sheet metal supporting elements even though, during use, the refractories may develop line cracks, by which they are separated into various irregularly shaped blocks but since each block is individually secured by the elastomer to its supporting surface, it will not dislodge.

As many widely apparently different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments disclosed herein.

What is claimed is:

1. A heat receptor-radiator wall for a heating device wherein heat from a radiant heater element is generally directed toward a heated zone adjacent said radiant heater, said wall being adjacent the heater and on a side opposite said zone, said wall comprising a support sheet of heat conductive material, said sheet being sufficiently strong so as to form a support, said sheet being an outer surface, a layer of refractory material supported on said sheet and on the side thereof facing said heater, said refractory layer having a high degree of opacity in respect to heat radiations emanated by the radiant heater and having low thermal conductivity, .and bonding layer of elastomer capable of deforming under stress, said elastomer layer being between the support sheet and refractory layer and adhesively securing the layer of refractory material to the support sheet for supporting the refractory rnaterial on the sheet.

2. The device of claim 1 further characterized in that the support sheet is made of metal, glass, fiber glass or high temperature plastic.

3. The device of claim 1 further characterized in that the layer of refractory material is composed of cellular, fused, amorphous silica ceramic.

4. The device of claim 1 further characterized in that the bonding layer of elastomer is a silicone rubber elastomer.

5. The device of claim 1 further characterized in that the support sheet is made of aluminum.

6. The device of claim 1 further characterized in that the surface of the support sheet opposite that surface which is bonded to the layer of refractory is colored a dark dull color to increase heat radiation therefrom.

7. The device of claim 1 further characterized in that elongated electric heater elements are provided extending across and slightly beyond opposite edges of said refractory surface, and edge flanges of refractory material are provided at said opposite edges of the refractory surface, said flanges being apertured for loosely receiving the ends of said heater elements where they extend beyond said surface for supporting them spaced from and substantially parallel to said refractory surface.

8. The device of claim 7 further characterized in that said edge flanges are composed of separable portions in abutment along a plane common to said apertures, one separable portion of each flange being adjacent opposite side edges of said refractory surface and bonded to the support sheet by a bonding layer of elastomer and the other separable portion being bonded by means of a layer of said elastomer to a separable edge flange of the heat conductive sheet material which is removably attached to the support sheet.

9. The device of claim 1 further characterized in that the refractory material is substantially thicker than the support sheet.

References Cited UNITED STATES PATENTS 1,507,142 9/1924 Schoenfield 219-347 1,705,094 3/1929 Owen 219-546 FOREIGN PATENTS 83 3,392 3/1952 Germany.

RICHARD M. WOOD, Primary Examiner. M. C. FLIESLER, Assistant Examiner.

US. Cl. X.R. 13-22; -136; 219-343, 461, 531; 263-50

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