US3757083A

US3757083A - Connector for high output quick response radiant heater

Info

Publication number: US3757083A
Application number: US00228091A
Authority: US
Inventors: G Dietz; N Hager
Original assignee: Armstrong Cork Co
Current assignee: Armstrong World Industries Inc
Priority date: 1972-02-22
Filing date: 1972-02-22
Publication date: 1973-09-04
Anticipated expiration: 1990-09-04

Abstract

A high intensity, quick response, electrical resistance foil radiant heater is described as having a heating element in the form of a corrugated metal foil ribbon adapted to be heated by electricity to a temperature in the range of about 1,200* to 1,800* F. The heating element is backed by a thermally insulating backing preferably of a ceramic material. A particular connector structure is provided on each end of the foil ribbon to provide a means to fasten power supply leads to the foil ribbon. The connecting means also functions as a means for fastening the ends of the foil ribbon to the backing. The connector structure is composed of two parts, one part constituting a means for receiving electrical leads while the other part constitutes a means for holding the connector in position.

Description

United States Patent 1 [111 3,757,083 Dietz et a1. Sept. 4, 1973 [54] CONNECTOR FOR HIGH OUTPUT, QUICK 1,563,211 11/1925 Maclnnes 338/312 X RESPONSE, RADIANT HEATER 1,565,539 12/1925 Woodson.... 219/542 X 3,223,775 12/1965 Nugent 219/345 UX Inventors George C-D1etZ;NathanlelE- g 3,684,859 8/1972 Desloge 219/354 Jr., both of Lancaster, Pa. [73] Assignee: Armstrong Cork Company, Primary 'f f Lancaster, Pa. Att0rneyCllfford B. Price 1 PP N05 228,091 A high intensity, quick response, electrical resistance foil radiant heater is described as having a heating ele- 52 us. Cl 219/356 219/345 219/357 in the a meta ribbm 2I9/464 219/467 219541 338/313 338/322 adapted to be heated by electricity to a temperature in 51 In. o the range Of about 1,200 to 1,800 The heating ele- [58] Field of Search 219/2f3 345 356 is backed by a thermally insulating backing Pref 219/357 463 464 467 468 erably of a ceramic material. A particular connector 338/206 L structure is provided on each end of the foil ribbon to provide a means to fasten power supply leads to the foil ribbon. The connecting means also functions as a [56] References Cited means for fastening the ends of the foil ribbon to the backing. The connector structure is composed of two UNITED STATES PATENTS parts, one part constituting a means for receiving elecg 8? 219/ 345 X trical leads while the other part constitutes a means for 1 579 732 411926 0:21:12: 13151311 holding the connector in position 2,857,499 10/1958 Feam 219/357 5 Claims, 3 Drawing Figures CONNECTOR FOR HIGH OUTPUT, QUICK RESPONSE, RADIANT HEATER BACKGROUND OF THE INVENTION Metallic foil heaters on a backing are known as is illustrated in U. S. Pat. No. 2,682,596, Cox et al. Such laminated heaters, however, cannot function at the relatively high temperatures contemplated for use by the heaters of the present invention. High temperature heaters, particularly those having a relatively broad heated radiating surface, as compared with the surface of a resistant wire, are normally made by imbedding wire heating elements or rod heating elements in a thick plate in order to achieve the requisite temperature in the thick plate. Other resistance heaters designed to function at high temperatures are made of relatively thick bars or bands which glow when electricity is passed through the resistance heating element. All such heaters have large thermal inertia in that they cool slowly when turned off or heat up slowly when turned on. When such heaters are used to heat objects on a moving line, such as the waxed paper on a paper backing, filled bottles on a bottling line, or thermoplastics, troublesome difficulties occur when the line must be stopped due to a malfunction somewhere along the production line. Stoppage of the objects to be heated in front of such heaters causes the objects to be overheated, resulting in fires, scorched products, or exploded bottles, depending upon the nature of the objects being heated. These high temperature, large mass heaters cannot cool sufficiently fast when the power is cut ofi' to prevent ruination of the objects being heated when those objects are brought to a sudden stop in front of the heater.

While foil heaters are known to have low thermal inertia, high output foil heaters have not been used due to the difficulty of maintaining the structural integrity of the heaters. The backing of the heater must be such to resist thermal expansion and contraction stresses produced by on-and-off operation at the high temperatures. Conductivity of the backing must be sufficiently low that heat loss is minimized through the backing and so the structure for holding the backing is protected. Even worse, the mounting for the high temperature, metallic foil heating element must be such that hot spots are not created. Such hot spots unduly shorten the life of an already fragile heating element. Additionally, the mounting means themselves easily bum out. The support problem can be overcome by the use of metallic mounting means for the heating element which conduct heat away from the heating element and radiate the heat out the back of the backing on which the heating element ribbon is mounted. The mounting means themselves are kept strong by such cooling.

U. S. Pat. No. 3,525,850, I-Iager, has gone a long way to overcome the above deficiencies of the prior art. This patent discloses the use of ends 9 of the ribbon being coated with silver solder or welded between heavier platelets of an oxidation-resistant metal to give good electrical contact and to lower the electrical resistance and thus the heating effect in that portion of the ribbon. Power leads 10 are connected to a suitable source of power and are connected to the ends 9 of the ribbon. Under some circumstances, the connectors of U. S. Pat. No. 3,525,850 have not proved satisfactory for certain operations. Also, these connectors in no way hold the end of the ribbon in position.

It is the principal object herein to provide a connector for the end of the ribbon which will function to hold the ribbon in place, serve as a connecting point for electrical leads, conduct heat away from the hot side of the connector to keep the connection relatively cool, and finally be so positioned that the connector will function very efficiently in certain operating conditions.

SUMMARY OF THE INVENTION A heater is provided having a heating element in the form of a corrugated metallic foil ribbon. The foil is adapted to be heated by the passage of electricity therethrough to a temperature in the range of about 1,200 to 1,800 F. A thermally insulating backing with an area at least substantially coextensive with that of the ribbon heating element is positioned adjacent the heating element. The backing has a thermal conductivity at l,500 F. in the range of about 0.07-0.15 Btu/hrft- F. Metallic mounting means hold the ribbon heating element on the backing. The metallic mounting means are in supporting contact with the ribbon, and they extend to the back of the backing. The mounting means are adapted to convey heat from the ribbon to the cool side of the backing either by passing through the backing or by passing around the edge of the backing to the back'thereof. Connectors are provided on the ends of the ribbon, which connectors extend around to the back side of the board and hook into the board to provide support for the ends of the ribbon. In addition, the connecting elements can receive electrical leads to supply electricity to the ribbon. Finally, the connectors are so positioned that they do not sit entirely on the front 1 planar face of the heater backing, but are mounted substantially to the side or back of the backing member.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a partial tip view of the heater and end connector;

FIG. II is a partial cross-sectional side view of the front view of FIG. I; and

FIG. III is a cross-sectional view of the heater showing the ribbon mounting means.

DESCRIPTION OF THE PREFERRED EMBODIMENT The structure of the heater herein is basically the same A as that in above-mentioned U. S. Pat. No. 3,525,840. The same backing 2 and heating element 1 are used herein as was used in the above-mentioned patent. Referring to FIG. III herein and FIG. III of the above-mentioned patent, there is shown the same basic mounting means for holding the ribbon heater in position at points intermediate of its ends.

Referring to FIG. III herein, the heating ribbon 1 is placed against a backing 2. The heating ribbon l is in the form of a ribbon which is made of a metallic foil. The foil may be made of any metal which stands the rigors of the required heating. It may be, for example, a stainless steel foil of the austenitic type. Other suitable alloys are sold under the known names of Hastelloy, lnconel, Waspalloy, and others of the cobalt-chromiumnickel class of refractory alloys. The foils will have a thickness in the range of about 00005-001 inch and preferably on the order of 0.002 inch. Such foils are readily. attained in various widths, which can be cut to 1-2 inches, which are convenient widths for a variety of applications. corrugations are provided in the foil, and these are necessary to accommodate expansion of the foil due to changes in temperature without losing tension as the heating element cools and heats in response to power input.

The backing 2 could be blocks or sections of insulating brick, such as certain cellular asbestos cement compositions, mineral wool with a clay binder formed into rigid ceramic-like sheets, and glass fiber compositions which can withstand high temperatures. Thickness of the backing may vary, and normally it will run from 0.5-2 inches in thickness. The thermal conductivity of the backing must be in the range of about 0.07-0.15 Btu/hr-ft-F. in order to minimize heat loss out the back.

The heater ribbon intermediate its ends is held relative to the backing by mounting means, as for example, mounting wires 4. These mounting means run from the front part of the heater where they contact the ribbon and hold it in the place to the back side of the ribbon wherein a part 6 of the mounting means is actually positioned in back of the heater. The purpose of having a part 6 of the mounting means extend to the back of the heater backing is to permit the radiation of heat to the back of the backing. If no heat is radiated to the back, the region where the metallic mounting means presses against the heating element 1 will grow hotter until an undue hot spot is created, the hot spot area loses strength and allows the heating element to droop or fall away from the backing 2. The mounting means themselves may burn away unless the heat is radiated out the back. The materials from which the metallic mounting means are constructed will be those materials which will resist high temperatures in air. Several of the stainless steels are suitable, such as the nickel-chrome alloys. A Nichrome wire is particularly useful as a mounting means.

Referring to FIG. I, there is shown the ribbon heater 1, the backing 2 and the power connector 8 which has fastened thereto electrical lead 10. Referring to FIG. ll, there will be shown a front view of the structure of FIG. I with the backing partially cut away. The power connector 8 is basically a two-part structure being composed of one generally J-shaped element 11 and one L-shaped element 12. The J-shaped element is positioned on the back side of the ribbon, and the L-shaped element is positioned on the front side of the ribbon. These two elements are fastened to the ribbon by appropriate electrically conductive contacts such as soldering or spot welding. The L-shaped element It has an electrical terminal 13 to which the electrical lead is fastened. The J-shaped element 112 is used to hold the end of the ribbon heater to the backing. The two parts of the connector element which contain therebetween the ribbon heater are positioned against the side of the backing. Part of the .l-shaped element extends around the back of the backing and the prong end of the J is pressed into the back side of the board to hold the connector in position. This then permits the connector to serve the function of holding the ribbon heater in position adjacent the backing. Part of the L-shaped element extends away from the end of the backing, and it is in a position such that the electrical lead 10 may be connected thereto. Thereby, the power connector functions as the electrical power connector for the heater so that electrical power can be supplied to the ribbon.

Finally, it should be noted that the connector 8 was positioned on the ribbon and positioned relative to the backing so that the portions of the two parts of the connectors which fasten to the ribbon are positioned to the side of the backing and are not directly placed upon the front face of the heater backing. With some applications, it is common to position two heaters opposite each other and facing each other. If the connector was on the front face of the heater, then the connector would be subjected to the heat radiating 011' the opposite heater. By removing the connector from the face of the heater, then it would not be subjected to heat from an opposed heater. This then permits the consideration of less expensive types of materials for forming the connectors and the use of connecting techniques other than spot welding for fastening the connector parts to the heater ribbon.

What is claimed is:

1. In a high intensity, quick response, electrical resistance, foil radiant heater having a heating element in the fonn of a transversely corrugated metallic foil ribbon adapted to be heated by the passage of electricity therethrough to a temperature in the range of about 1,200-l,800 E, a thennally insulating backing for said ribbon, said backing being at least coextensive in area with said ribbon and having a thermal conductivity at 1,500 F. in the range of about 0.070.15 Btu/hr-ft- F., and metallic mounting means intermediate the ends of the ribbon to hold it adjacent said backing, said mounting means generally in supporting contact with said ribbon and being adapted to convey heat from said ribbon to the back of the backing, the improvement comprising a connector on each end of the ribbon, a major portion of said connector being positioned off the plane of the surface of the backing to which the ribbon is fastened and said connector holding said ribbon end in position relative to the backing, said connector being composed of at least two parts which are placed adjacent each other with the foil ribbon therebetween, one part having a portion to which may be connected electrical leads and the other part having a portion which is used in conjunction with the backing to hold the connector and foil ribbon in position.

2. The heater of claim 1 wherein the part of the connector which may have electrical leads connected thereto is of a general L-shape with one leg of the L- shape receiving the electrical leads while the second leg of the L-shape is placed adjacent the end of the heating element.

' 3. The heater of claim 2 wherein the part of the connector which holds the foil ribbon in position is of a general .l-shape with the curved portion of the J-shape being pressed into the back of the backing to hold the connector in place while the other straight portion of the l-shape is placed adjacent the end of the heating element.

l. The heater of claim 3 wherein the second leg of the L-shape connector part and the straight portion of the J -shape connector part are placed on either side of one end of the ribbon of the heating element.

5. In a high intensity, quick response, electrical resistance, foil radiant heater having a heating element in the form of a transversely corrugated metallic foil ribbon adapted to be heated by the passage of electricity therethrough to a temperature in the range of about l,200-l ,800 F., a thermally insulating backing for said ribbon, said backing being at least coextensive in area with said ribbon and having a thermal conductivity at 1,500 F. in the range of about 0.07-0.15 Btu/hr-ft- F and metallic mounting means intermediate the ends of the ribbon to hold it adjacent said backing, said mounting means generally in supporting contact with said ribbon and being adapted to convey heat from said ribbon to the back of the backing, the improvement comprising a connector on each end of the ribbon, a major portion of said connector being positioned off the plane of the surface of the backing to which the ribbon is fastened and said connector holding said ribbon end in position relative to the backing said connector is generally composed of a two-part structure, one part being generally J-shaped and the other part being generally L-shaped, the two parts being fastened to the ribbon with the ribbon therebetween and the J-shaped element being pressed into the back of the backing to hold the connector and ribbon in position and said L-shaped element having means for connecting electrical leads thereto, the two parts are fastened together with one leg of the L-shaped part being placed against the upright leg of the J-shaped part.

Claims

1. In a high intensity, quick response, electrical resistance, foil radiant heater having a heating element in the form of a transversely corrugated metallic foil ribbon adapted to be heated by the passage of electricity therethrough to a temperature in the range of about 1,200*-1,800* F., a thermally insulating backing for said ribbon, said backing being at least coextensive in area with said ribbon and having a thermal conductivity at 1,500* F. in the range of about 0.07-0.15 Btu/hr-ft-* F., and metallic mounting means intermediate the ends of the ribbon to hold it adjacent said backing, said mounting means generally in supporting contact with said ribbon and being adapted to convey heat from said ribbon to the back of the backing, the improvement comprising a connector on each end of the ribbon, a major portion of said connector being positioned off the plane of the surface of the backing to which the ribbon is fastened and said connector holding said ribbon end in position relative to the backing, said connector being composed of at least two parts which are placed adjacent each other with the foil ribbon therebetween, one part having a portion to which may be connected electrical leads and the other part having a portion which is used in conjunction with the backing to hold the connector and foil ribbon in position.

2. The heater of claim 1 wherein the part of the connector which may have electrical leads connected thereto is of a general L-shape with one leg of the L-shape receiving the electrical leads while the second leg of the L-shape is placed adjacent the end of the heating element.

3. The heater of claim 2 wherein the part of the connector which holds the foil ribbon in position is of a general J-shape with the curved portion of the J-shape being pressed into the back of the backing to hold the connector in place while the other straight portion of the J-shape is placed adjacent the end of the heating element.

4. The heater of claim 3 wherein the second leg of the L-shape connector part and the straight portion of the J-shape connector part are placed on either side of one end of the ribbon of the heating element.

5. In a high intensity, quick response, electrical resistance, foil radiant heater having a heating element in the form of a transversely corrugated metallic foil ribbon adapted to be heated by the passage of electricity therethrough to a temperature in the range of about 1,200*-1,800* F., a thermally insulating backing for said ribbon, said backing being at least coextensive in area with said ribbon and having a thermal conductivity at 1, 500* F. in the range of about 0.07-0.15 Btu/hr-fT-* F., and metallic mounting means intermediate the ends of the ribbon to hold it adjacent said backing, said mounting means generally in supporting contact with said ribbon and being adapted to convey heat from said ribbon to the back of the backing, the improvement comprising a connector on each end of the ribbon, a major portion of said connector being positioned off the plane of the surface of the backing to which the ribbon is fastened and said connector holding said ribbon end in position relative to the backing said connector is generally composed of a two-part structure, one part being generally J-shaped and the other part being generally L-shaped, the two parts being fastened to the ribbon with the ribbon therebetween and the J-shaped element being pressed into the back of the backing to hold the connector and ribbon in position and said L-shaped element having means for connecting electrical leads thereto, the two parts are fastened together with one leg of the L-shaped part being placed against the upright leg of the J-shaped part.