US3152313A - Elastic heater for compound curves - Google Patents

Description

Oct. 6, 1964 n. R. BARBOUR ETAL 3,152,313

ELASTIC HEATER FOR COMPOUND CURVES Filed NOV. 28, 1958 vi I y t m w Z 9 nBC A 3,152,313 ELASTIC HEATER FOR COMPOUND CURVES Donald R. Barbour, Coxsackie, and Robert V. Cahlll, Catskill, N.Y., assignors to General Electric Company, a corporation of New York Filed Nov. 28, 1958, Ser. No. 777,101 1 Claim. (Cl. 338-214) This invention relates to an elastic heater to be used for compound curves and, more particularly, to an insulated heater device constructed so that it has elasticity in all directions to thereby conform to the compound curvature of a surface.

In many present day installations requiring the use of heaters, such as heaters used to temperature cure aircraft bonded structures and the like, some of the surfaces to which the heat is to be applied are composed of a variety of simple and compound curves. In those instances in which the heat must be applied to a compound curvature it is generally necessary to tailor that portion of the heating device to specifically conform to such compound curve. As will be readily apparent, this special tailoring of a portion of the heating device necessarily increases the cost of the heater, while at the same time rendering the heating device relatively ineffective for other installations. Also, due to the special tailoring of such heating devices, any change which may later be made in the compound curve for which the heating device was specifically designed, will cause the heating device to be less effective in such installation, if not completely useless therefor.

There are presently available today heating devices which are flexible and can thereby adjust to simple curves, but such heating devices do not have the necessary elasticity to conform to compound curves. That is, these heating devices do not have elasticity in all directions so as to be able to conform to a compound curve. There are also available some heating devices which are made of an elastic material. In these elastic heating devices, the elastic insulating material is capable of stretching or of elasticity in all directions. However, the heater wire patterns of these elastic insulated heaters are so formed that they are incapable of stretching in more than one direction. Therefore, while these elastic insulated heating devices are capable of conforming to simple curves they lack the necessary overall elasticity to conform to compound curves. From the above it can be seen that there is presently a need in the heating art for a simple and relatively inexpensive heating device which will be able to readily conform to compound curves, without the necessity of specifically designing or tailoring such heating devices to the exact curvature of the surfaces to which it is to be applied.

It is, therefore, an object of this invention to provide a heating device which will be elastic so as to stretch in all directions to readily conform to a compound curvature of a surface to which it is to be applied.

A further object of this invention is to provide a heating device having the necessary elasticity to be useful in installations having compound curvatures, the heating device having sufficient elasticity to readily meet any changes in the designs of the compound curvature to 'which it is originally applied.

It is a further object of this invention to provide a simple and inexpensive heating device having high temperature capabilities and being provided with the necessary elasticity to readily conform to any curvatures on the surface to which it is to be applied.

In carrying out this invention in one form a heating device is provided in which the pattern of the heater wire is so constructed and arranged as to be stretchable in all on United States Patent 3,152,313 Patented Oct. 6, 1964 ice directions, the patterned heater wire being imbedded in an elastic insulation means having elasticity in all directions, to thereby enable the heater device to stretch in all directions so as to conform to any compound curves.

This invention, and the manner in which its objectives and advantages are obtained will be better understood from the following description taken in connection with the accompanying drawing in which:

FIGURE 1 is a plan view of one form of a heater wire pattern which may be utilized in the practice of this invention;

FIGURE 2 is a sectional view, taken on the line 2--2 of FIGURE 1, of a heating device formed in accordance with this invention; and

FIGURE 3 is a perspective view of a heating device, made in accordance with this invention, as applied to a surface having a compound curvature, the heater wire pattern being shown in full lines.

Referring now to the drawing in which like numerals are used to indicate like parts throughout, and in particular with reference to FIGURE 1, this invention is shown in a preferred form as a heating device 10 which is comprised of an elastic insulation 12 and a patterned heater wire 14. As shown in FIGURE 1 the heating device 10 is in the form of a flat thin heater which may for example be applied to a metallic surface, such as for example, by bonding, to apply heat to such surface. In those instances in which the surface to which the heater device 10 is to be applied contains a compound curve, it is desired that the heating device 10 closely conform to such compound curve. In order that the heating device 10 conform to such compound curve the wire carrying, electrical insulation 12 is formed of an elastic material, such as for example, a natural or synthetic rubber. Where the heating device 10 is required to generate very high temperatures for heating, the elastic material 12 may for example, be silicone rubber, which is well known for its ability to withstand high temperatures without deterioration. The heater wire 14, which is imbedded in the wire carrier 12, is patterned in a manner as shown in FIGURE 1 so as to provide the desired stretchability in all directions. Present heating devices which are provided with an elastic insulation are unable to conform to compound curves because the pattern of the heater wire carried in such heating devices has elasticity in generally only one direction. To overcome this defect, the heater wire 14 is patterned so that the runs 13 of the heater wire in the direction of the double headed arrow 16 are made in an undulated form so as to be stretchable, or have elasticity in the direction of the double headed arrow 16. The various connecting runs 15 in the direction of the double headed arrow 18, which form the connection between the various runs in the direction of the double headed arrow 16, are also patterned in an undulating form, so as to have a desired elasticity in the general direction of the double headed arrow 18. Thus, the heating device 10 would have elasticity in all directions and therefore, would be able to closely conform to any compound curvature on the surface to which it was to be applied. While the runs 13 and 15 are shown as being substantially perpendicular to each other it will be understood that they may bepatterned in any desired configuration.

In constructing the heating device of this invention, a sheet or layer of elastic insulation, such as for example silicone rubber, is provided with a number of pins or other means placed on the layer in the shape of the desired pattern. The heater wire 14 is then wound on these pins so as to assume the desired shape, such as for example, the pattern shown in FIGURE 1. A second layer of elastic insulation, for example silicone rubber, is then cemented to the first layer so as to form the desired heating device and maintain the heater wire in its position between the two layers. When the layers have been cemented together the pins may then be removed and the heater wire will be held in the desired position. Of course, in order to provide the desired current to the heater wire connections 202 are .provided at opposite ends of the heater wire 14, as shown in FIGURE 1. An appropriate source of electrical current may be attached to the connections 2tl2tl, for supplying electrical energy to the heating device ltl. The construction according to that set forth above is shown in FIGURE 2 where the heater wire 14 is shown as being firmly held in place between the elastic installation 12, which is formed of the layers 22 and 24- cemented together along the line 26.

Of course, it will be understood by those skilled in the art, that it is not necessary that the elastic material be formed of two layers cemented together. For example, it is possible to suspend the heater wire at a desired height within a mold, and then to form a one piece elastic insulation about the heater wire by filling the mold with the liquid form of an elastic insulation, and then setting or curing the insulation. The heater wire could be suspended on rods or other devices within the mold which could be removed after the curing of the insulation, thereby giving a one piece construction which would be substantially the same as the two layer construction, but would not be liable to any limitations which might be imposed by existing adhesive material.

FIGURE 3 shows the application of a heating device formed in accordance with this invention to a compound curved surface, such as for example, the nose cone of a missile. In FIGURE 3 the heating device 10' is comprised of an elastic insulating material 12, having imbedded therein a patterned heater wire 14. The heating element 10 is formed in a large sheet, such as that shown in FIGURE 1, and is then wrapped about the conical surface. As shown, the conical surface has a small end 28 and a large end 36. In wrapping the heating device 10 about the conical surface one end of the heating device 11? is not required to stretch as it is wrapped around the smaller end 28, however, the end of the heating device Til which is Wrapped around the end 30 is required to stretch a considerable amount. This stretching is indicated by the very small amplitude of the undulations in the heater wire 14 at that end of the conical surface. Of course, it will be understood that if applied to a flat surface having a compound curvature therein, that the heating device 10' would merely be required to stretch over the portion of the surface composed of the compound curvature, thereby closely conforming to such compound curvature. It will be understood by those skilled in the art that the pattern of the heater wire 14' may be in any desired shape so long as it is enabled to stretch in all directions within the heating element. While there has been shown and described the present preferred embodiment of the invention, various modifications may be made by those skilled in the art to which this pertains. Therefore, the spirit and scope of this invention including all such modifications is set forth in the appended claim.

What is claimed as new and which is desired to be secured by Letters Patent of the United States is:

A heating device capable of use in high temperature application and adapted to conform to compound curves comprising, a silicone rubber insulation material, a heater wire embedded within said silicone rubber insulation, said heater wire being formed in a pattern of a series of undulations in one direction and a series of undulations in a substantially perpendicular direction to said one direction, and connector means connected to the ends of said heater wire and adapted to provide electrical current to said heater wire.

References Cited in the file of this patent UNITED STATES PATENTS 2,284,673 Munschak June 2, 1942 2,412,843 Spraragen Dec. 17, 1946 2,423,196 MacKendrick July 1, 1947 2,460,795 Warrick Feb. 1, 1949 2,584,302 Stein Feb. 5, 1952 2,631,219 Suchy Mar. 10, 1953 2,674,683 Rand Apr. 6, 1954 2,718,584 Hariu Sept. 20, 1955

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