US1763586A - Gas container for aircraft - Google Patents

Description

Patented June 10, 1930 UNITED STATES PATENT OFFICE KARI- HUERTTLE, OF AKRON, OHIO, ASSIGNOB TO GOODYEAR-ZEPPELIN CORPORATION, OF AKRON, OHIO, A CORPORATION OF DELAWARE ens con'ramnn ron amcaarr No Drawing.

My invention relates to gas containers for lighter-than-aircraft and ithas particular relation to methods of treatin fabric for such containers whereby to ren er them impermeable to inflating gases. I

More specifically the invention has for one of its objects the provision of a material for coating gas cell fabric which is highly impermeable to gases, relatively inexpensive to manufacture, and Which is extremely durable.

It is customar in the construction of the gas containers or lighter-than-aircraft to apply an impermeable film to the surface of the fabric in order to prevent diffusion of the gas. Heretofore, the most satisfactory material for this purpose has been gold beaters skin, a thin membrane taken from the intestines of animals. However, this material is relatively expensive and it is also obtained in the form of small sheets which must be trimmed and which require a great amount of labor to apply, when extensive surfaces are to be coated therewith.

Rubber cements have, also, been employed as gas proofing media. These cements are comparatively inexpensive and may be readily applied to the fabric b mechanical means such as ordinary ca ender rolls. However, coating films formed of rubber have a much higher degree of permeability than gold beaters skin and are, therefore, objectionable due to the relatively high loss of inflating gas by diffusion.

Numerous substitutes for gold beaters skin and for rubber films have, heretofore, been suggested. Among the materials proposed are gelatin and various cellulose derivatives such as nitrocellulose, cellulose acetate and other compounds of this class. Coatings formed of these materials have proved unsatisfactory for various reasons, some of them being unduly permeable to the inflating gas while others are stifl? and do not adhere readily to the fabrics. They, therefore, quickly crack "and peel from the fabric when placed in service.

This invention consists in the discovery that fabrics coated with solutions or varnishes of phenyl resin, more commonly Application filed January 27, 1928. Serial No. 250,071.

known as bakelite, when suitably treated and applied to as cells, produce coating films which are highly resistant to the diffusion of gases, durable, flexible and which may be obtained and applied to the fabrics at small expense.

In the practice of this invention, a bakelite varnish is mixed with a. suitable softener such as castor oil, tricresyl phosphate, triphenyl phosphate, or other'suitable softening agent. If desired, it may also be mixed with a thinning agent such as acetone. It is then applied to a fabric by means of a spray, or by painting, or by calendering it upon fabric. The latter should be light in Weight, but of a strong closely woven texture. Special grades of cotton fabric are usually employed for this purpose, although silk and linen may be employed in certaln cases.

The coated fabric is stretched and dried while it is heated, preferably by training it about slowly moving rollers within a drying oven. The temperature of this oven should be maintained at 90 to 100 0., although these limits may under certain cir-' cumstances be varied. The fabric should remain in the drying oven for a period of from one to two hours.

The proportions of the various ingredients may vary within relatively wide limits, but the following are examples of formulae which are found to give excellent results:

I (1) 100 grams of bakelite varnish, 15 grams of castor oil and 225 cc. of acetone.

(2) 50 grams of varnish, 10 grams of tricresyl phosphate and 200 cc. of acetone.

(3) 50 grams of bakelite varnish, 5 grams of tricresyl phosphate, 10 grams of castor oil and 200 cc. of acetone.

(4:) 50 grams of bakelite varnish, 15 grams of tricresyl phosphate and 200 cc. of. acetone.

The bakelite varnish employed in these formulae was of the grade known as N o. 1 clear, prepared by the Bakelite Company, Perth Amboy, N. J. It is to be understood that any good grade of bakelite varnish or lacquer may be used.

As previously stated, the castor oil and 10 tricres l phos hate are added to the bakelite varnis in or er to render the finished prodin order that it ma uct tough and flexible. The acetone is added for the pur of thinning the varnish be spread thinly an evenly upon the fa ric. The proportions of the thmnin agent may of course be varied at will. f it is desired to coat the fabric with a sin le film, the proportion of acetone should relativel small so that a comparatively thick coatlng may be applied comprising a fabric coated with bakelite containing castor oil.

In witness whereof, I have hereunto signed my name.

Signed at Akro mit and State of day of anua'ry, 1

at a single application. If it is desired that I the coating should consist of a plurality of thin films of varnish, the latter shoul be first thinned with a relatively large quantity of acetone, in order that it may be spread with suflicient thinness upon the fabric to ofthe secon coating, the probab1 ty of a so permit the application of a relatively lar number of coats without rendering the pro uct unduly heavy.

'The application of a plurality of thin coats is, 1nmany respects, preferable to the application of a single thick coating; because during the evaporation of the ba elite solvent, small bubbles may esca leaving pores andopenings in the coating. If a number of films are applied, each preceding coating bein dried before-the ap lication number of interstices or o ningscoming into alignment with each ot er is relatively slight. Although acetone has been specified as a thinning agent, other suitable bakelite solvents are the equivalent thereof and the invention is, therefore, not limited to that.

particular compound.

After the fabric has been'coated and dried it is cut into pieces of suitable shape and the pieces are then fastened together by cement or other convenient means in order to form gas containers of the desired shape and s1ze.

Although I have described in detail only the preferred embodiments of the invention,

it will be. apparent to those skilled in the art that it isnot so limited, but that various minor modifications may be made therein without, departing from the s irit of the invention or from the scope o the appended claims. What I claim is:

1. A gas cell for lighter-than-aircraft n, in the county of Sum- S(32150, U. S. A., this 26th K'ABL HUERTTLE.