US2792324A - Method of manufacturing hollow articles composed of resin impregnated yarn windings - Google Patents

Description

May 14, 1957 H. s. DALEY ET AL METHOD OF MANUFACTURING HOLLOW ARTICLES COMPOSTO OF RESIN IMPREGNATED YARN WINDINGS Filed NOV. 24, 1954 INVENTORS BY Horace SDa/ey IHETHOD F MANUFACTURING HOLLOW ARTI- CLES COMPOSED 0F RESIN IMPREGNATED YARN WINDINGS Horace S. Daley, Clifton, and Edward A. Wentz, Mont clamN. J., assignors to Specialties Development Corporation, Belleville, N.v J., a corporation of New Jersey Application November 24, 1954, Serial No. 471,022

' 1 claim. (ci. 154-83) The present invention relates to a method of and apparatus for manufacturing hollow articles partially composed of resin impregnated yarn windings, and, more particularly, to the conditioning and handling of the yarn preliminary to -its application as a winding in the manufacture of receptacles, such as cylinders or spheres and tubes or conduits, for confining uid medium under high pressure.

It has been proposed to manufacture receptacles of the foregoing character by applying windings of resin impregnated yarn on an inner shell or a form, and curing 'the resin to provide a Wall consisting of resin and yarn and having a thickness to withstand high pressure. Such receptacles are much lighter in weight than similar receptacles formed of metal, but, heretofore, difficulty has been encountered in producing such receptacles which can safely withstand the high pressures at which it is desired to confine the medium and which can survive the pressure fluctuations to which such receptacles are subjected in the normal use thereof. The difficulties which have rbeen most pronounced are that the bursting strength of such receptacles-is well below that desired and that the wall composition fatigues too quickly whensubjected to fthe pressure fluctuations the yreceptacles are required to withstand under present safety regulations. In accordance with the present invention, it has now -been discovered that localized stresses caused by small imperfections in the winding are instrumental in greatly weakening such receptacles. It has been found that uneven dryness and tensioning of the yarn or strands of yarn and uneven impregnation thereof primarily arethe cause of the aforementioned diiiiculties; and rthat uneven impregnation is induced by uneven dryness and uneven tensioning, and that uneven dryness affects proper tensioning.

Accordingly, an object of the present invention is to provide `a method of and apparatus for producing high pressure medium` confining receptacles having greater bursting strength and greater'fatigue resistance than receptacles of comparable wall thickness heretofore produced.

Another object is to provide such method and apparatus which condition the lwindings in a manner to uniformly tension and impregnate the same, whereby localized weaknesses in the resulting receptacles are greatly minimized or entirely eliminated.

A yfurther object is to provide such method and apparatus which are simple, practical and economical and do not slow down production.

Other and `further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claim, and various advantages not referred to herein will occur to one skilled in the art upon employment ofthe invention in practice.

A preferred embodiment of the invention has been chosen for purposes of illustration and description, and

was at@ ice is shown in the accompanying drawing, forming a part of the specification, wherein:

means and steps utilized in carrying out the present invention.

Fig. 2 is a schematic plan View lillustrating apparatus in accordance with the invention.

As shownin Fig. l of the drawing, theA essential means of the apparatus for performing the steps of the method utilized in connection with practicing the present invention comprise a creel 10 for supplying strands of yarn including means for uniformly tensioning the strands, means 1l for drying the strands, means 12 for resin impregnating t-he strands, means 13 for grouping together the strands, means 14 for removing excess resin lfrom the strands, and means 1S for finally applying the resin impregnated strands as windings to produce the wall structure of hollow receptacles. The order of arrangement of certain of these means and the corresponding -method steps performed thereby can be varied, whereby the present invention is in no Way to be lirnited by the illustrative embodiment herein. For example, the strands may be dried prior to tensioning the same, and the strands may be grouped together after removing the excess resin therefrom.

ln Fig. 2, the aforementioned means arev illustrated schematically, and, as shown therein, the creel includes a plurality of yarn packages 20 each adapted to Supply a strand or end of yarn S. Four of such packages are shown by way of example, although any suitable number greater than four may be utilized depending on yarn size and the ltype of winding to be applied. Such a creel may be of any conventional design and need not be illustrated in detail.

I-f desired, the yarn drying means 11 may be associated with the creel by providing an enclosure 21 for the creel having an inlet 22 and an outlet 23 for heated air acting as a drying medium, and having a slit 24 through which The impregnating means 12 or the zone in which im-A pregnation takes place may include a receptacle 26 containing liquid resin and suitable rolls 27 forpassing the strands, through the resin or applying the resin to the strands by coming in contact therewith., Such impregnating `devicesare well known and need not he illustrated or described in detail. y v

in order to assure uniform impregnation of the strands and the individual laments or fibers of which the strands may be composed, the strands are maintained out of contact with each other while in the impregnating zone. This may be accomplished by passing the strands between sets of spaced apart pins or a pair of combs 28 and 29 at each end of the impregnating bath.

The excess resin removing means 14 may be a blade or wiper 3d over which the strands pass in contact therewith, or, alternatively conventional squeeze rolls could be used for this purpose. If desired, the strands are maintained in the aforementioned spaced apart relation to provide for uniform resin impregnation of the strands `after the excess is removed by the comb 29 at the incoming side of the means 14 and a comb 30 at the outgoing side. Preferably, the amount of resin permitted to remain on the yarn is just about sufficient to coat the individual fibers or filaments thereof with a film adapted to prevent abrasion therebetween and between strands Patented May 14, 19.574.

o f yarn. This amount of resin is effective to bondY they yarn upon curing of the resin and to produce a composition having a strength., Y Y v The strand grouping means; 13, may beaguide 32 ysuch as a pair of pins, a ring, kor.converging tube for bringing thev strands together,"and may include a hanged pulley or wheel 33 for arranging the strands into a ribbon-like bandv adapted tov be passed through a guide 34 and applied as the winding.

The` strand applying means .15 is illustrated herein as a Winder for applying a hoop Winding on a cylindrical surface ofa receptacle R,.although such means could be winders for applyingA hoop and/or end-over-end windings, on. cylinders or great circle windings on spheres.

The Winder shown herein comprises a spindle 35 on which the receptacle is mounted for rotation about its longitudinal axis, and a'yarn traverse 36 including a guide 37 forxpositioning the winding on the: receptacle. The winder'serves to withdrawthe strands from the creel and to draw the same through the impregnating bath and the grouping means.

, After the winding is applied to provide` a wall of desired y thickness, the resin is cured by placing the receptable in an oven for atleast about 4 hours, maintained at a temperature of about212 F., whereby a solid wall structure composed of yarn and resin is produced. By conditioning the yarn in the manner described herein, it Was found that the wall structure consisted of between 80% to 85% yarn and 20% to 15% resin. Cylinders having a capacity of about 500 cubic inches were constructed of such yarn-resin composition and were found toV safely;

withstand: internal pressures of about 3000 pounds per square inch in service and G00 pounds per square inch under test, and exhibited no signs of fatigue after being alternately pressurized from 0 to 3000 pounds per square inch through 5000 cycles in about 24 hours.

The term yarn is used herein in a broad sense and is intended to include yarns formed of natural or synthetic fibers or filaments suitable for impregnation. Fiber glass yarn is preferred because of its high tensile strength and resistance to heat, although other types of high tenacity yarns may be usedto good advantage, for example, multiiilament yarns formed of materials such as nylon, vinylidene chloride, polyester and exible metal.

Fiber glass yarn has a tensile strength ofbetween about 300,000 pounds per square inch, a specic gravity of about 2.57, and is available'in various sizes. For example, sixteen. strands of size 140 (14,000 yards per pound, 204 filaments) fiber glass yarn, impregnated and grouped together in accordance with the method of the present invention, provide an excellent winding.

A wide variety of thermosetting or thermoplastic resins' may be utilized, for example, epoxy or modied epoxy resins, polyester typev resins and acrylic resins which are available in liquid form. Also, silicone resins andl phenolic resins modied with a solvent may be used. A suitable wetting agent may be admixed in the resin to expedite impregnation of the yarn. Such resins upon curing are converted into a solid mass having a tensile high yarn content and high structurat 15% by weight of. the impregnated strands upon curing l of the resin which amount is sufficient to coat the indi# strength on the order of about 5000 to 8000 pounds per` square inch.

A specic example of practicing the method in ac cordance with present invention comprises supplying sixteen strands of size 140 ber glass yarn which have been uniformly dried and tensioned to' about l0 grams, passing the strands through Vliquid epoxy resin while maing, taining the strands apart to assure uniform impregna? tion thereof, removing excess resin from the strands, grouping the strands together in a ribbon-like band, applying the band to a shell as a winding under a tension' of about 3 to l0 pounds, and curing the resin to produce a wall structure surrounding the shell composed of` about 85% fiber glass and 15% insoluble resin. r 1

From the foregoing description it will b e seen that the present invention providesV a simple,practical and economical method of and apparatus for producing strong and durable wall structures for receptacles consisting of yarn and resin.

As various changes may be made in the form, con` struction and arrangement of the partsV herein, 'without departing from the spirit and scope of the invention andl without sacrificing any ofy its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in any limiting sense.

We claim:

The method of manufacturing hollow articles for confming afiuid medium under pressure, which method comprises simultaneously exposing a plurality of strands composed of yarn filaments to a drying atmosphere to uni-v formly remove moisture therefrom, individually tension-V ing the strands'. to place the same under substantially con# stant uniform tension on the order of about 5 to l5 grams, individually impregnating the strands` immediately after l tensioning of the same by simultaneously applying a liquid resin thereto from a common .,source, removing resinfrom the strands to leave an amount of resin of about vidual laments and prevent abrasion therebetween, grouping together the impregnated strands into a ribbonlike band, applying the band as a winding of a plurality of layers to form a hollow article, and curing the winding to provide a wall for the hollow article having a yarn content of about 85% by weight, the wall of the hollow article being characterized in that it canV safely withstand internal pressure of about 5000 p. s. i. and exhibits no sign of fatigue after being alternately pressurized from 0' to 3000 p. s. i, through 5000 cycles in about.

twenty-four hours.

References Cited in the le of this patent UNITED STATES PATENTS

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