US3061907A - Method of forming a fabric - Google Patents

Description

Nov. 6, 1962 J. NICHOLL 3,

METHOD OF FORMING A FABRIC Filed July 9, 1959 T1 .5. 23 22 INVENTOR ATTORNEY United States Patent .0

3,0619% lt/ETHOD F roar/uni G A FABRIQ Jonathan Ferrell Nichoii, Upper Montciair, NJ, assignor to Chicopee Manufacturing Qorparation, a corporation of Massachusetts Filed .l'uiy 9, 1959, Ser. No. 825,97tl 2 Claims. (El. 2873) The present invention relates to the manufacture in wide widths of relatively open mesh fabrics, more particularly to the manufacture of cloth of this type which normally is useful for insect screens and may be Woven from thermoplastic synthetic or plastic materials or other materials such as glass or metal coated with a thermoplastic material.

In the manufacture of fabrics of this type in conventional widths, a permanent selvage is Woven along each edge of the Warp by employing continuous weft material and continuously looping the weft around groups of warp filaments at each edge of the fabric to provide the selvages. These selvages then may be gripped to hold the fabric out and the warp and weft filaments may be set where they cross over one another. When thermoplastic filaments are employed, setting is accomplished by softening the thermoplastic material until the crossing filaments become fused or adhered to one another and then allowing the material to cool to set the bonds formed.

Considerable savings can be achieved in weaving fabrics of this type in wide widths, since this lowers the cost per unit of area. These savings can best be realized by weaving the fabric with a Wide width automatic shuttleless loom of the type which picks weft material from a stationary weft supply at one side of the loom and draws individual picks through the warp at an extremely rapid rate, i.e., approximately twice as fast as the same width could be woven in a conventional loom employing shuttles carrying their own weft supplies.

In high speed shuttleless looms of the above type, individual weft filament lengths are severed from the weft supply as soon as they are laid in the Warp. Devices have been developed for tucking or turning the ends of individual picks, or lengths of weft material, back into the next shed during weaving, thereby forming a type of looped selvage. However, considerable difiiculty has been experienced in weaving screen cloth from synthetic thermoplastic materials such as saran, and glass or metal filaments coated with a thermoplastic material such as a vinyl plastic, in that slight variations in flexibility, or stiffness, filament size, surface roughness, and the like cause defects in the selvage. Saran is a long-chain copolymer comprising a major proportion, not less than about 70 percent, of vinylidene chloride and a minor proportion, not greater than about 30 percent, of another material such as vinyl chloride. Vinyl chloride and mixtures of vinyl chloride and acrylonitrile commonly have been used in saran screen cloth filaments as the minor component in an amount comprising about to 12 percent of the total copolymer. It appears that, with the tucking devices now available, the weaving of looped selvages of this type will remain a problem for the relatively stiff screening materials normally employed.

Since the widths which are desirable for use normally are considerably narrower than the wide woven widths, it is desirable to weave what are known as internal selvages in the form of stripes extending longitudinally of the fabric intermediate the edges of the fabric. One or more internal selvage stripes of this type may be included. The resulting fabric then is cut or slit along one of the edges of, or through, the internal selvage stripe to divide the wide width fabric into narrower widths which are more suitable for use. When the fabric is Woven with looped tucked external selvages and one or 3,661,907 Patented Nov. 6, 1962 more internal selvages of the type described above and slit along the internal selvage, the resulting narrower widths have selvages which are not symmetrical. This is undesirable from the standpoint of the ultimate user and uneconomical when it is necessary to trim on? the looped selvage to provide a more symmetrical appearing fabric.

According to this invention, an open mesh fabric is formed by first weaving individual weft filament lengths with a warp comprising a wide layer of warp filaments so as to form a wide width structure wherein the weft filament lengths are wider than the warp and spaced substantialiy from one another longitudinally of the warp. The ends of the weft filament lengths are untucked and protruding from each of the longitudinal edges of the warp so as to present a multiplicity of spaced unconnected weft end portions. The weft filaments are drawn through, or laid into, each shed of the warp, either by drawing a length of weft material from a weft supply through the warp and shipping its ends at each edge of the warp or by passing a length of weft material of the desired length through the warp. In either case, the ends of the picks, or weft filaments, are caused to protrude from the edges of the resulting structure, as mentioned above, and are not turned back or tucked into the warp.

The term filament when used herein shall mean an extruded filament or Wire, a yarn comprising twisted fibers, a multifilament strand, a composite yarn or strand consisting of a mixture of any of the above, or the like. The term thermoplastic filament when used herein shall mean an extruded thermoplastic filament, a yarn comprising thermoplastic fibers, a multifilament strand comprising thermoplastic materials or the like, or a yarn, strand, filament or wire of a nonthermoplastic material such as metal, glass or the like coated with a layer of a thermoplastic material such as vinyl resin. The terms heat settable and heat set when used herein shall means, respectively, that property of a fabric or fabric portion according to which its crossing filaments may be adhered or fused together by the application of heat, and the resulting state of being adhered or fused together by the application of heat. In the same way, the terms settable and set when used herein without reference to heat shall have the same meaning as heat settable and heat set except that these terms are not limited to the use of heat to set the crossing filaments.

According to a preferred embodiment of the invention, the warp and weft filaments are interwoven in such a way as to form a wide width structure having a longitudinally extending settable selvage stripe immediately adjacent each of the edges of the structure, with the stripes being alike or at least of like construction. Three or four or more warp ends may be placed very closely together adjacent the edge of the warp to provide a selvage stripe when interwoven with the weft filaments, or as many as eight or ten or more warp filaments may be woven in pairs adjacent the edge of the warp to provide such a selvage stripe. In the stripes there is a greater number of warp yarns so as to provide a higher fabric density. The warp yarns may be crossed around the weft filaments, as in a leno weave, to provide an even more stable structure in the stripes. However, the construction in the stripes normally is such that the crossing filaments must be softened and adhered to one another to provide the desired strength in the stripes. The selvage stripes advantageously may be in the form of an inverted-doup leno weave. If about 3 to 6 pairs of conventional inverted-doup leno ends are used, the stripes may have sufficient stability to withstand tentering before softening or fusing, as described hereinafter. Similarly, the selvage stripe may be formed from a twisted weave in the nature of a leno weave wherein the warp filaments are twisted around the weft lengths using a Warner & Swasey Sulzer weaving machine equipped with a twisted selvage unit. At least one wider additional longitudinally extending settable selvage stripe of like construction to the above-mentioned selvage stripes, in so far as the spacing of the filaments is concerned, is located intermediate the first-mentioned selvage stripes. In order to form symmetrical selvages conveniently with such an arrangement, it is necessary that the internal selvage stripe be about swice as wide as one of the first-mentioned selvage stripes. Preferably, a pair of internal selvage stripes spaced slightly from one another is located intermediate the first-mcntioned selvage stripes. The purpose of this arrangement of internal selvage stripes is to provide from a wide width of open mesh screen cloth more than one narrower width of screen cloth having symmetrical selvages. When a pair of intermediate selvage stripes, as mentioned above, is employed, this is accomplished by cutting between the stripes after the fabric is set to divide the fabric and trimming off the edges of the fabric beyond the outside selvage stripes in a manner which will be described more fully hereinafter, if this is necessary. The pair of intermediate selvage stripes may be located halfway between the first-mentioned selvage stripes or elsewhere, depending upon the widths desired for the narrower fabrics.

It is not practicable to heat set the whole fabric on the loom for various reasons. To accomplish this, it would be necessary to provide an oven or a similar device for each loom; and this would be prohibitively expensive. In addition, it would be necessary to provide a device capable of being heated up and cooled ofi almost instantaneously across the Width of the loom in order to avoid burning or melting the fabric during the numerous loom stoppages which occur in normal operation. 'Screen cloth of this general type normally is heat set after it is removed from the loom by passing it through a heated tenter wherein the longitudinal edges of the fabric are gripped so that the fabric is held fiat, normally under transverse tension, while heat is applied thereto to soften orfuse the thermoplastic component of the filaments so that the filaments are welded together where they contact one another at their crossing points. These welds at the crossing points are hardened as the fabric is cooled to form bond between the crossing filaments. However, if the fabric is woven without a turned selvage, i.e., merely with the picks laid in the warp and protruding from the edges thereof and then rolled up and removed from the loom prior to heat setting, the crossing filaments tend to shift so that the fabric becomes distorted, particularly at the edges of the fabric.

This invention contemplates the setting of the edges of the fabric by the application of heat thereto from a heat source while the warp still is under weaving tension to provide firm external selvages which may be gripped for tentering and which prevent the edges of the fabric from becoming distorted during handling. The application of heat to the edges of the fabric is synchronized with the forward motion of the fabric so that the heat source is instantaneously rendered ineffective to heat said edges to the softening temperature of the filaments or other material positioned at the edges when the forward motion of the structure through the loom is stopped. This may be accomplished by employing electronic sealing means which applies heat inductively only to the surfaces to be sealed together through a dielectric field generated be tween electrodes, as will be described more fully hereinafter. Other means, such as steam or electrically heated rollers or shoes mounted so as to move away from the fabric when the loom stops, may be used. The rollers may be moved toward and away from the fabric by a solenoid controlled device, or the like, synchronized with the forward motion of the fabric. Similarly, hot air jets directed toward the edges of the fabric may be operated by a cutofli device synchronized with the motion of the fabric through the loom so that the jets are instantaneously cut off when the loom stops. With air jets, some sort of pressing device, such as a set of pressure rollers spaced from the jets may be desirable to help bond the crossing filaments and form firm external selvages at the edges of the fabric.

Depending upon the material used, the edges of the fabric also may be set by the application of a solvent along with heat or with a solvent alone. It may be desirable to soften or plasticize a particular material such as nylon, for instance, so that it may be softened for heat setting at a lower temperature by the heat source employed for this purpose. On the other hand, it is possible that other materials may be softened sufiiciently to set the filaments in the fabric or in the selvage stripes merely by the application of a controlled amount of a solvent. Thus, a solvent may be applied to selvage stripes at the edges of the fabric by liquid applicator rollers provided for this purpose. Various other techniques of accomplishing this will suggest themselves to one skilled in the art.

Under certain conditions it may not be necessary to set the selvages at the edges of the fabric prior to removing the fabric from the loom. For instance, if the fabric is dropped immediately through a vertical oven located beneath the floor supporting the loom, the fabric may be heated generally to set its filament crossings and provide durable external selvages without undesirable distortion of the fabric or displacement of the filaments at its edges. This particularly is true if the selvage stripes woven at the edges of the fabric have several pairs of inverted-doup leno woven ends or a similar stable construction.

It is possible that selvages sufiiciently stable for tentering prior to setting of the selvages may be woven without tucking or turning the ends of the picks at the edges of the Warp, although this is not preferred because of the increased costs which may be involved. About 3 to 6, in most instances 5, pairs of adjacent inverted-doup leno ends woven into the fabric by conventional means may sufiice for this purpose.

According to one embodiment of this invention, a length of reinforcing material is progressively heat sealed onto the weft end portions protruding beyond the outside selvage stripes at each edge of the fabric structure while the warp still is under weaving tension to provide firm external selvages. The external selvages formed by the reinforcing material then are gripped, and the structure is held fiat while heat is applied generally thereto to cause the warp and weft filaments to adhere to one another at their crossing points and set the fabric. The warp and weft filaments making up the internal selvage stripes also are adhered to one another so that the internal selvage stripes are set at the same time. Then, the external selvages may be trimmed off the fabric; and the fabric may be divided into two or more narrower widths by cutting between the intermediate internal selvages as described above to provide narrower fabrics having symmetrical selvages at each lengthwise edge.

The reinforcing strip or strips may be applied to the protruding weft end portions of the fabric structure one on top of the other, i.e., one above and one below the fabric; or a single reinforcing strip on one side of the fabric may be used. The reinforcing strip may be in the form of a narrow band or sheet cut from a film of thermoplastic material, or it may be a narrow strip of woven or nonwoven fabric, or one or more thermoplastic yarns or filaments, or the like. Preferably, the reinforcing material is in the form of a strip of sheet material. The exact thickness and width of the strip or strips depends largely upon whether one or two strips is used at each edge 'of the fabric and the type of material. Typically, when the strips are to be placed above and below the fabric, they may be cut in A to inch widths from vinyl film of about 1 to 6 mils in thickness. The strip may be extruded from a vinyl material or it might be slit from a Wider extruded, calendered, or cast vinyl film which may or may not be laminated with some other type of backing material. Various other thermoplastic materials which are capable of forming strong bonds when subjected to electronic heat sealing means or similar heat sealing devices may be employed.

The invention will be understood better from the following drawings of one embodiment of apparatus for performing it wherein:

FIGURE 1 is a schematic view in elevation of this apparatus;

FIG. 2 is a broken-away schematic plan view of a fabric being manufactured according to this invention with part of its structure removed for the purposes of clarity;

FIG. 3 is an enlarged schematic view showing the relationship between one of the reinforcing strips and its respective sealing and guide rollers.

Referring to the drawings, there is shown a heat settable open mesh screen fabric 11 being woven from thermoplastic filaments in accordance with this invention. The fabric is woven in a conventional wide width automatic loom wherein individual filaments are successively laid or woven in their respective sheds in the warp in such a way that the weft filaments are spaced substantially from one another longitudinally of the warp and are unconnected at their ends so as to present a multiplicity of spaced weft end portions 12 protruding from each of the longitudinal edges 13 of the warp. In FIGS. 1 and 2, this weaving operation is represented by that portion of the figures to the right of the fell 14 of the fabric; and since it is conventional, it only is represented schematically and in part. For instance, in FIG. 1 harnesses 15 and 16 are represented by the pair of vertical centerlines passing through the peak of the shed; and a reed 17 and a transversely extending race board 18 are shown schematically to the left of the harnesses to position the fell 14 of the fabric.

The fell 14 of the fabric is restrained at its edges by temples of standard or unique design of which there are many existing types. Illustrated are a pair of narrow horizontal temple rollers 19 at each side of the fabric. These rollers, which may be of a suitable material such as hard rubber or the like, hold the edges of the fabric and prevent them from becoming displaced in or out. One of the temple rollers 19 is shown in phantom at only one side of the fabric in FIG. 2 to locate them transversely of the fabric since the rollers 19 are symmetrically positioned on the fabric. Following the temple rollers is an electronic welding device 21 at each edge of the fabric. Since these devices are identical, they will be described with reference (to only the device 21, shown in FIG. 1, which is located at one side of the fabric. This device seals reinforcing strips 22 of thermoplastic material onto the protruding weft ends 12. One strip 22 is laid on top of the ends and the other is positioned directly underneath the top strip, and the strips then are inductively heated electronically along their inner surfaces to weld them to the thermoplastic weft ends.

Each of the welding devices 21 comprises a pair of discshaped cylindrical electrodes 23, one above and one below each edge of the fabric. Each of the electrodes 23 is mounted on an arm 24 extending from a housing 25 which is connected to a suitable power supply. A pair of guide rollers 26 is positioned one above and one below the fabric between the electrodes 23 and the temple rollers 19. Each of the guide rollers is rotatably mounted at the end of a bracket 27 extending fIom the arm 24 of its respective welding electrode. The strips of reinforcing material 22 are drawn from supply rolls 28 above and below the temple rollers, respectively, around their respective guide rollers 26 and into contact with the top and bottom surfaces of the layer of pick ends 12. The strips 22 then move in contact with the pick ends until they reach the electrodes 23 which inductively heat the surfaces of the strips in contact with the picks to the temperature necessary to weld the strips and the picks together to form firm external selvages which are shown in FIG. 2 between the points A and B on one side of the fabric and A and B on the other side of the fabric. Heating is accomplished by a high frequency dielectric field created between the electrodes. During this operation, the surfaces of the electrodes 23 remain relatively cool so that the fabric cannot be damaged by virtue of its contact with the electrodes during loom stoppages. When the forward motion of the woven structure through the loom stops, a switch, not shown, is immediately tripped to cut ofi power to the electrde housings 25 and eliminate the dielectric field, thereby instantaneously rendering the electrodes ineffective to heat the reinforcing material to its softening temperature.

The relationship between the electrodes 23, the strip of reinforcing material 22 and the guide rollers 26 is shown schematically in FIG. 3. The guide roller has a cylindrical surface 29 which contacts the strip and a flange 38 at each end of the cylinder which positions the strip weftwise of the fabric and the electrodes 23. The disc-shaped electrodes 23 are narrower than the strip 22. This is desirable since it tends to prevent arcing between the electrodes. It may be desirable under certain conditions to provide a pair of additional guide rollers, now shown, similar to the guide rollers 26 or the temple rollers 19 just following the electrodes 23 for keeping the weight of the fabric off the electrodes.

As shown in FIG. 2, a group of four warp filaments are crowded together at each of the edges of the fabric to provide a longitudinally extending heat settable selvage stripe 31 immediately adjacent each edge of the structure. The stripes are of like construction since they each are woven with the same picks in the same way in accordance with conventional practice. A pair of additional longitudinally extending heat settable internal selvage stripes 32 of like construction is located halfway between the outside selvage stripes 31. The additional selvage stripes 32 are spaced from one another to provide a channel 33 between them along which the resulting fabric may be cut to divide it into two narrower widths.

After the reinforcing strips 22 have been heat sealed in position on the protruding pick ends 12 to form the aforementioned external selvages, the fabric is removed, or disconnected, from the loom and heated generally to cause the warp and weft filaments to bond to one another where they cross, as described above. This may be accomplished by running the fabric through a vertical oven or a conventional textile tenter, not shown. The warp and the weft filament crossings in the selvage stripes 31 and 32, as well as those in the body of the fabric, are set at this time. This gives the selvage stripes 31 and 32 sufiicient strength to act as selvages when the fabric is trimmed to the edges of the stripes. Then, the fabric is divided into narrower widths having symmetrical selvages merely by cutting along the centrally located channel 33 and trimming the reinforcing strips 22 and attached pick ends 12 from the outside edges of the original fabric structure.

It is of importance that the fabric structure be maintained as woven and that the edges of the fabric do not become distorted until they are sealed in accordance with this invention. For this reason, it is desirable in most cases that the heat sealing step occur as close to the fell 14 of the fabric as possible and while the warp is still under weaving tension. In FIG. 1, the fabric is shown being drawn over a conventional breast roller 35 to a windup roller, not shown, in such a Way that the desired weaving tension is maintained.

If it is desired to dispense with a turned or tucked selvage in a wide width fabric without employingreinforcing strips at the edges of the fabric as woven, or to divide such a fabric into narrower widths having symmetrical selvages without employing reinforcing strips, a different embodiment of this invention may be employed. This method is similar in almost every respect with that which has just been described in detail with reference to the drawings with the exception that the reinforcing strips are dispensed with and the electrodes at each edge of the fabric are positioned over and under the selvage stripes 31 immediately adjacent each edge of the fabric structure. In this embodiment of the invention, the electrodes heat the Warp and weft filaments in the outer selvage stripes 31 directly and cause them to become Welded together to form a selvage which is strong enough to go through the above-described tentering operation. The electrodes should be treated or coated, as by a layer of polytetrafluoroethylene, or in some way adjusted, to prevent them from arcing through the interstices in the selvage stripe since now they are separated only by the Weave of the selvage stripe and not by this weave plus the reinforcing strips 22, described above.

The components of the electronic sealing device may be units of an electronic sewing machine such as that produced by Union Special Machine Co., of Chicago, Illinois. The automatic wide width loom itself may be a Warner and Swasey Co. Sulzer-type shuttleless loom suitably modified to lay the picks ends straight and conform to the general arrangement at the fell of the fabric described herein. As mentioned hereinbefore, the twisted selvage unit provided with such looms may be employed in carrying out this invention.

Having now described the invention in specific detail and exemplified the manner in which it may be carried into practice, it will be readily apparent to those skilled in the art that innumerable variations, modifications, applications, and extensions of the basic principles involved may be made without departing from its spirit and scope.

The invention claimed is:

l. The method of forming a heat set open mesh fabric which comprises successively weaving thermoplastic weft filaments with a Warp of thermoplastic warp filaments so as to form a wide width structure having a longitudinally extending heat settable selvage stripe immediately adjacent each of the edges of the structure and at least one wider additional longitudinally extending heat settable selvage stripe intermediate the first-mentioned selvage stripes, said additional selvage stripe being of like construction to the first-mentioned selvage stripes in so far as the size and spacing of the filaments are concerned, said weft filaments being spaced substantially from one another longitudinally of the warp and being unconnected at their ends so as to present a multiplicity of spaced weft end portions protruding from each of the longitudinal edges of the warp, progressively heat sealing a length of reinforcing material onto the Weft end portions at each edge of the structure while the warp still is under weaving tension so as to provide firm external selvages therefor, applying heat generally to the structure and setting the Warp and weft filaments where they cross in contact with one another, and trimming the edges including the external selvages from the structure by cutting longitudinally through the weft filaments just inwardly of the external selvages, whereby an open mesh fabric is formed which is adapted to be cut along the additional selvage stripe to provide at least one length of a narrower open mesh screen fabric having symmetrical selvages.

2. The method of forming a stabilized open mesh screen fabric which comprises successively weaving individual Weft filament lengths with a warp comprising a wide layer of warp filaments so as to form a wide width structure having a longitudinally extending settable selvage stripe immediately adjacent each of the edges of the structure and at least one wider additional longitudinally extending ettable selvage stripe intermediate the first-mentioned selvage stripes, said additional selvage stripe being of like construction to the first-mentioned selvage stripes in so far as the size and spacing of the filaments are concerned, said weft filament lengths being Wider than the warp and spaced substantially from one another longitudinally of the warp, the ends of said lengths presenting a multiplicity of spaced untucked Weft end portions protruding from each of the longitudinal edges of the warp, progressively sealing a length of reinforcing material onto the weft end portions of each edge of the structure while the warp still is under Weaving tension so as to provide firm external selvages therefor, gripping the external selvages and holding the structure flat, setting the structure generally by forming bonds between the warp and weft filaments where they cross in contact with one another, and trimming the edges including the external selvages from the structure by cutting longitudinally through the weft filaments just inwardly of the external selvages, whereby an open mesh fabric is formed which is adapted to be out along the additional selvage stripe to provide at least one length of a narrower open mesh fabric having symmetrical selvages.

References Cited in the file of this patent UNITED STATES PATENTS 1,696,155 Davis Dec. 18, 1928 1,792,460 Davis Feb. 10, 1931 1,854,693 Dickie ct al Apr. 19, 1932 1,941,510 Scruggs Jan. 2, 1934 2,072,095 Cohn Mar. 2, 1937 2,319,019 Van Court May 11, 1943 2,659,958 Johnson Nov. 24, 1953 2,757,435 Bihaly Aug. 7, 1956 2,769,222 Southwell Nov. 6, 1956 FOREIGN PATENTS 940,120 France Dec. 3, 1948

Claims (1)

1. THE METHOD OF FORMING A HEAT SET OPEN MESH FABRIC WHICH COMPRISES SUCCESSIVELY WEAVING THERMOPLASTIC WEFT FILAMENTS WITH A WRAP OF THERMOPLASTIC WRAP FILAMENTS SO AS TO FORM A WIDE WIDTH STRUCTURE HAVING A LONGITUDINALLY EXTENDING HEAT SETTABLE SELVAGE STRIPE IMMEDIATELY ADJACENT EACH OF THE EDGES OT THE STRUCTURE AND AT LEAST ONE WIDER ADDITIONAL LONGITUDINALLY EXTENDING HEAT SETTABLE SELVAGE STRIPE INTERMEDIDATE THEFIRST-MENTIONED SELVAGE STRIPES, SAID ADDITIONAL SELVAGE STRIPE BEING OF LIKE CONSTRUCTION TO THE FIRST-MENTIONED SELVAGE STRIPES IN SO FAR AS THE SIZE AND SPACING OF THE FILAMENTS ARE CONNECTED, SAID WEFT FILAMENTS BEING SPACED SUNSTANTIALLY FROM UNCONANOTHER LONGITUDINALLY OF THE WARP AND BEING UNCONNECTED AT THEIR ENDS SO AS TO PRESENT A MULTIPLICITY SPACED WEFT END PORTIONS PROTRUDING FROM EACH OF THE

Images