2. A COLLAPSIBLE FLAMMABLE HYDROCARBON OIL TANK FOR AIRCRAFT HAVING FLEXIBLE WALLS OF VULCANIZEDTOGETHER LAYERS DIFINING AN OIL CONFINING CHAMBER, SAID WALLS INCLUDING AN OIL-RESISTANT SYNTHETIC RUBBER INNER LAYER, A WEAR-RESISTANT SYNTHETIC RUBBER OUTER COVERING LAYER, AN INTERMEDIATE HEAT GENERATING NON-METALLIC ELECTRICALLY CONDUCTIVE RUBBER LAYER EMBEDDED BETWEEN ELECTRICALLY NONCONDUCTIVE RUBBER FURTHER INTERMEDIATE LAYERS AND ELECTRICAL CONDUCTORS CONNECTING WITH OPPOSITE MARGINAL SIDES OF SAID CONDUCTIVE LAYERS WHEREBY CURRENT IS SUPPLIED TO SAID CONDUCTIVE LAYER.
Patented Aug. 19, 1952 UNITED LIQUID CONTAINER Robert E. Workman, Akron, Ohio, assignor to Wingfoot Corporation, Akron, Ohio, a corporation of Delaware Application April 3, 1948, Serial No. 18,810
(Cl. 21S-44) 2 Claims. 1
This invention relates to collapsible hydrocarbon oil tanks or cells for airplanes. The general object of the invention is to maintain oil in such tanks at proper viscosity for proper engine performance or transfer of the oil under sub-normal temperatures. According to the invention this result is accomplished through the provision of heating means adapted to heat the oil so arranged as to reduce to a minimum or eliminate the possibility of igniting the oil. Moreover the heating means is of such character and so arranged as to withstand collapsing and strain and is protected against exposure to wear from sources exteriorly of the tank.
Other objects of the invention will appear hereinafter as the description proceeds, the novel features, arrangements and combinations being clearly pointed out in the specification and in the appended claims.
In the drawings,
Fig. 1 is a perspective view of a representative non-rigid fuel tank for use in an airplane;
Fig. 2 is a representative section, taken along the line 2 2, of the fuel tank shown in Fig. l;
Fig. 3 is a detailed View of a heating element partly broken away to show the details of the construction.
This invention solves these problems by providing heating elements that become an integral part of the collapsible oil tank structure and are able to withstand, Without damage, the severe punishment to which the containers are sometimes subjected by vibrations, flexing and pressures. The heating elements are constructed from an electrically conductive material, such as natural or synthetic rubber, or other plastics and resins such as nylon, cellulose acetate, viscose and Vinylite, which may be compounded and designed to provide the desired temperature for the particular conditions to which the containers Will be subjected.
Except for the heating means, the general construction of the non-rigid tank shown in Figs. l and 2 conforms to usual practice. Such tanks are ordinarily constructed of several layers of material which, because of the irregular shapes of the oil tanks, are usually plied up in the unvulcanized state on a plaster or papier-mch form (not illustrated). In the tank I, the inner layer 2 is a synthetic rubber material which, when vulcanized, is unaliected by the contact with the oil. Adjacent to this inner layer 2, is a backing layer or barrier 3 composed of a synthetic linear polyamide, such as one of the types of nylon manufactured by the E. I. du Pont Nemours Company. This barrier layer 3 serves to reduce the permeation of the oil through the wall structure of the oil tank. A thin insulating layer I of electrically non-conductive rubber or plastic material is applied to the exterior of the barrier layer 3, either in the sheet form or by brushing, spraying, or dipping, so as to provide proper insulation for the electrically conductive rubber heating elements 5 which are applied to the tank I at the previously determined locations. The entire tank I then is provided with an exterior covering 6 of a non-conductive lamination or layer of material which preferably should be of such nature as to impart wear resistance to the surface and suflicient rigidity to prevent the collapse of the tank. The entire assembly after fabrication on the form is then subjected to a temperature suitable for vulcanization, and after Vulcanization the tank is removed from the form.
The details of the construction of a typical vheating element are shown in Fig. 3. 'Ihe sheet I2, of substantially uniform thickness, is rubber of an electrically conducting composition, for example, a rubber compound containing sufficient electrically conducting carbon particles to make the sheet an electrical conductor, or may be a material such as fabric or asbestos coated with a conductive rubber compound. Electric energy is supplied to the conductive rubber element I2 by the spaced parallel conducting wires I3 and I4 connected to a source of electric energy (not shown). The conducting wires I3 and I4 extend along the opposite edges of the element I2 in parallel arrangement and are not insulated in the contact area but are made integral With the element I2 by folding the edges of the element I'2 over the wires and cementing in place or any other means suitable for accomplishing this result. The electric current passes from one conductor to the other through the conductive rubber element I2 which causes the heating of the element I2. The degree of heat generated by the element I 2, is controlled by the amount of conductive compound that is mixed in the rubber compound or by the thickness of the conductive layer or the spacing of the Wires, etc.
The conductive rubber element may be insulated completely by covering it with a layer of non-conductive material such as a sheet of nonconductive rubber or plastic or by brushing, spraying, or dipping it with a non-conductive composition. The construction of conductive rubber heating elements is Well known in the art and any applicable construction may be used to practice this invention.
The position and number of heating elements in the wall structure of any particular container may be varied according to the amount of heat required to properly maintain the liquid at a suitable viscosity or temperature. In some instances, it may not be necessary that the heat be applied to all surfaces of the container. By the application of heat to particular sections of the container, the liquid may be suiiiciently heated and consequently the heating elements may be incorporated into the structure on one or more sides, as required. The heating means for any Wall of the container need not be a unitary heating element but may consist of several smaller heating elements. This method of construction is particularly adaptable to containers with irregularly contoured walls, as it would eliminate the numerous difiiculties encountered in the construction of a unitary heating element for such a Wall. The dotted lines in Fig. 1 illustrate, as an example, the location of the various heating elements in the structure of an oil tank to provide the requisite heating of the oil.
As illustrated in Fig. 1, a heat insulating blanket or cover l5 of a material like asbestos, glass fabric or the like, may be applied to the exterior of the oil tanks to prevent the loss of heat from the heating' elements 5 through the exterior covering 6. I5 also tends to prevent the dissipation of the internal heat through the tank walls. The insulating cover I5 may be incorporated into the original fabrication of the structure or, preferably, may be applied to the cell after vulcanication.
It will be understood that the aforementioned constructions are only illustrative of the application of this invention. There are numerous methods used to fabricate liquid containers and thelike for many diversified uses, and this invention is not limited in its use to any specific construction of such containers other than the necessary limitations for the incorporation of this invention into the container structure. For example, it is possible to build up the illustrated oil tanks of either partially vulcanized or vulcanized components or a combination of these; and also in the usual constructions, adhesives or solvents are sometimes used between the layers to produce better adhesion between them, but such details have not been described as they are well known in the art and are not an essential part of this invention.
Other modifications and changes may be made in the particular construction and arrangement This heat insulating cover of the parts without departing from the spirit of the invention and therefore I do not wish to be limited except as set forth in the appended claims.
Having thus fully described my invention, what I claim and desire to secure by Letters Patent of the United States is:
1. A collapsible flammable hydrocarbon oil tank for aircraft having exible walls of'vulcanizedtogether layers deiining a oil confining chamber. each of said walls including an inner layer of hydrocarbon oil-resistant flexible synthetic rubber, a layer of hydrocarbon oil-impermeable synthetic linear polyamide adjacent to said inner layer, and, exterior of said layers and as an ntegral interior part of said Wall, an electrically insulated heat-generating flexible non-metallic electrically conducting rubber layer, spaced parallel conductors secured to the opposite marginal sides of said conductive layer whereby electric current is supplied to said conductive layer and a wear-resistant outer covering layer of synthetic rubber.
2. A collapsible flammable hydrocarbon oil tank for aircraft having flexible walls. of vulcanizedtogether layers dening an oil confining chamber, said walls including an oil-resistant synthetic rubber inner layer, a wear-resistant synthetic rubber outer covering layer, an intermediate heat generating non-metallic electrically conductive rubber layer embedded between electrically nonconductive rubber further intermediate layers and electrical conductors connecting with opposite marginal sides of said conductive layers whereby current is supplied to said conductive layer.
. ROBERT E. WORKMAN.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,684,942 Carleton Sept. 18, 1928 1,992,593 Whitney 1 Feb. 26, 1935 2,255,376 Bull et al. Sept. 9, 1941 2,321,587 Davie et al June 15, 1943 2,404,736 Marick July 23, 1946 2,430,931 Hershberger Nov. 18, 1947 2,440,965 Merrill et al May 4, 1948 OTHER REFERENCES Synthetic Substances with Rubber-Like Properties, Mechanical Engineering, October, 1938, pages 735-737.