US3275489A

US3275489A - Method and apparatus for producing unwoven fabric

Info

Publication number: US3275489A
Application number: US170605A
Authority: US
Inventors: Talv Harry
Original assignee: Ferro Corp
Current assignee: Vibrantz Corp
Priority date: 1962-02-01
Filing date: 1962-02-01
Publication date: 1966-09-27
Anticipated expiration: 1983-09-27

Description

H. TALV Sept. 27, 1966 METHOD AND APPARATUS FOR PRODUCING UNWOVEN FABRIC 2 SheetsSheet 1 Filed Feb. 1,

INVENTOR. HARP) 774/. V

ATTORNEY) H. TALV Sept. 27, 1966 METHOD AND AIPARATUS FOR PRODUCING UNWOVEN FABRIC Filed Feb. 1, 1962 2 Sheets-Sheet 2 INVENTOR. HARRY :441/ B 2Z- ATTOHI EXJ United States Patent 3,275,489 METHOD AND APPARATUS FOR PRODUCING UNWOVEN FABRIC Harry Talv, Nashville, Tenn., assignor to Ferro Corporation, Cleveland, Ohio, a corporation of Ohio Filed Feb. 1, 1962, Ser. No. 170,605 3 Claims. (Cl. 156-181) This invention relates to improvements in machines and processes for producing nonwoven fabrics. It is particularly useful in the production of nonwoven fabrics from glass fibers but is not limited to such use.

Nonwoven fabrics, especially those made of glass fibers, are widely used as reinforcing materials in molded plastic objects and in many other applications. It is known that such fabrics resist stresses longitudinally of the fibers most strongly when the fibers, or strands of fibers, which may be rovings, bundles of fibers, yarns or cords, are substantially straight. This is true whether the strands of fibers are present in warp or weft. It is therefore desirable that the strands of fibers in both warp and weft be substantially straight in order that the maximum strength in the desired direction may be attained with a minimum of fibers and that when stresses of greater magnitude are anticipated in one direction than in another that a corresponding quantity of strands of fibers may be laid in the desired direction.

It is an object of this invention to provide a process for the manufacture of nonwoven fabrics wherein the fibers in both warp and weft are substantially straight so that each strand may have maximum resistance to stress in its lengthwise direction.

It is another object to provide a process wherein strands of fibers, rovings, yarns or bundles of fibers in both warp and weft are placed in position for joining while under tension and are held in straight condition during a step in which they are bonded together.

Another object is to provide a process for the manufacture of nonwoven fabrics wherein the relative proportions of strands of fibers in warp and weft may be varied at will to produce the desired strength in a longitudinal or transverse direction.

Another object is to provide a process for the manufacture of such nonwoven materials in which warp and weft strands may lie at any desired angle to each other.

Another object is to provide a process for the manufacture of such nonwoven fabrics in which opposed pairs of weft strands may enclose between them a plurality of warp strands in substantially parallel arrangement.

Another object is to provide a novel machine for carrying out the process indicated above.

Another object is to provide a machine which is automatic in operation and requires a minimum of control and attention from an operator.

Another object is to provide a novel machine for carrying out the manufacture of nonwoven fabric in which performance of a preceding step automatically trips a control for initiating a following step.

Other objects, advantages and features of this invention will be apparent to one skilled in the art upon a consideration of the written specification, the attached claims and the annexed drawings.

The term strands will be used in the present application and claims to include single, continuous fibers, discrete bundles of such fibers, rovings or lightly twisted yarns of fibers having sufiicient twist to maintain the fibers in discrete strands and to include sheets of combed fibers or rovings of any desired width and thickness. Strands may be very small in size or relatively large; that is, up to a half inch or so in diameter, such as may be desired for reinforcing heavy building panels and the like.

3,275,489 Patented sept. 27, 1966 Briefly, the process of the present invention includes advancing one or more warp strands intermittently and under tension through a fabric-forming zone. When a single warp strand is used it is preferably a sheet of fibers or rovings in which the fibers or rovings are substantially parallel to each other and in close side-by-side relationship. When more than one warp strand is used these are advanced through the fabric-forming zone in substantially parallel relationship to each other. The warp strands may be impregnated with a thermosetting plastic if desired prior to their introduction into the fabric-forming zone; and if it is desired to impregnate these strands with such plastics, it is preferred that they pass through a heating step in which the plastic is heated sufliciently that it sets prior to entering the fabric-forming zone.

One or more weft strands impregnated with a thermosetting plastic resin is then placed across the warp strands under tension, preferably by advancing the weft strands across the warp, holding the weft strands in position and then applying tension to them. In drawing the weft strands across the warp it is preferred that the weft strands be slightly spaced from the warp strands so that they do not touch, to prevent smearing the warp strands with unset thermosetting plastic and thereby prevent gumming up or clogging the equipment used. Preferably placement of the weft strands across the warp may coincide with. the forward intermittent motion of the warp, but if desired, the placing of the weft strands may occur during an interval while the warp strands are stationary in their intermittent advance through the fabric-forming zone. Also it is preferred that the weft strands be placed across the warp in opposing pairs with one weft strand of each pair located on opposite sides of the warp.

While tension is maintained on both warp and weft, the strands of each are pressed firmly together and the thermosetting plastic is heated to a temperature and for such time as is necessary to set the plastic, thus bonding warp and weft strands together. The weft strands are cut and after the heating is completed the warp strands are moved forward through a selected distance and again stopped in their intermittent advance and other steps of the process just described are repeated.

Although many steps in the process described can be performed manually, such manual operation is ordinarily too slow for commercial production and the use of an automatic machine is greatly preferred. A preferred machine of this type includes means for intermittently advancing the warp strands under tension through the fabtic-forming zone against a resistance applied to the warp at a point opposite to the advancing means. The advancing means preferably includes a reciprocable puller movable toward and away from the fabric-forming zone having a clamp arranged to close and seize the warp strands when at a point adjacent to its maximum limit of travel toward the fabric-forming zone and to release the warp at a point adjacent to its maximum limit of travel away from the said zone.

. border to maintain tension on the warp while the reciprocable pulling means is moving toward the fabricforming zone with its clamp released, a backlash clamp is provided. Thisclamp is stationary and preferably is automatically operated to release the warp substantially at the time the puller clamp closes and to close and seize the warp at the time the puller clamp opens or preferably at an instant just before the puller clamp releases the warp.

Suflicient resistance to advance of the warp is provided by passing the warp strands over suitable rollers or through separators or combing devices located on the side of the fabric-forming zone opposite to the puller to maintain the warp strands in straight condition in the fabricforming zone.

Any desired number of weft strands are placed across the warp under tension at any desired angle by suitable placing means, preferablyv including a reciprocating stripper which has one or more fingers each carrying suitable guides such as a series of wire loops through which a weft strand is threaded. It is preferred that the leading guide in a series project beyond the end of the finger, member somewhat thus accurately, locating an end of the weft strand carried thereby at a point where it may be conveniently seized in a manner described later. The stripper is equipped with a stripper clamp which preferably closes automatically before advance of the.

stripper toward and across the weftso that it draws an additional length of weft strands from spindles mounted in a suitable creel through an impregnating device or saturator where the strands are impregnated with thermo setting plastic.

A suitable anchor clamp isprovided for grasping the ends of the weft strands while; they are at their point of maximum travel in advance across the warp. A control means isarranged to correlate closing ofthe anchor clamp with the maximum advance of the, stripper. A control means, preferably an electric switch actuated by closing;

the anchor clamp actuates the stripper clamp to release the weft, and the stripper is free to move back across entire Width of the fabric-forming zone. The warp strands are thus placed in parallel arrangement and are drawn through a fabric-forming zone below pressure heater 9 by action of a puller designated generally as 10. The

puller .is of reciprocating type havinga clamp 11 disposed to grasp fabric which has been formed in the fabric-v forming zone when advanced toward the fabric-forming zone to its full extent of travel and to release the warp when the puller reaches its limit of travel:in the opposite direction. Travel of puller thus advances the warp 7 through the fabric-forming zone intermittently and under the Warp applying tension to the weft strands as the stationary during a period of its intermittentadvance.

After warp and weft strands are held under pressure by the heater a suitable cutter located between the stripper and the warp is actuated to cut the weft strands between the warp and stripper thus freeing the warp for further advance when heating has been completed, bonding warp and weft strands together.

It is preferred that each of the elements described above may be mounted for automatic movement by any suit-able driving means which may be electrical, pneumatic, hydraulic or mechanical and that these actuating means be controlled by a control system so that each succeeding step in the process, or movement of the machine, .may be initiated by carrying out a prior step or-movement so that all the devices work in harmony with each other as will appear more fully froma consideration of the following detailed description and from the drawings in which:

FIG. 1 is a schematic illustration in plan of one preferred type of machine for carrying out the process of this invention showing a warp consisting of five strands and a stripper disposed to place two opposed pairs of weft strands across the warp at each reciprocation of the pp FIG. 2 is a schematic illustration of one nonwoven fabric formed with the device of FIG. 1;

FIG. 3 is an illustration of a more closely woven fabric of the type ordinarily termed scrim and producible by the machine of FIG. 1;

' FIG. 4 is an elevation of the machine of FIG.1 on line 44, further illustrating one preferred type of automatic control system; and

FIG. 5 is an elevationof the machine on line 5-5.

In FIG. 1, warp strands 6 are illustrated as passing beneath a roller 7 and through a laterally spacing or' combing means illustrated as a series of vertical separating rollers 8 arranged to separate the warp strandsfrom each other by a selected lateral distance which may be shown in ro. 1'

tension due to friction of the warp strands on rollers 7 and 8.

A backlash clamp 12 is provided and is actuated to grasp the fabric at the instant before clamp 11 releases to permit return travel of the puller and ,to be released when clamp 11 has closed atthe end of the return stroke.

, Tension is thus maintained on warp strands in the fabricforming zone at all times with the result, that the .warp strands extendgthrou'gh the fabric-forming :zone, 1 a

straight direction and in parallel relationship.

A' stripper designated. generally as 13 .is mountedfor reciprocating motion across all warp strands at any desired angle, and is based at a side of the fabric-forming zone. V

This stripper comprises any desired number, illustrated as two, of fingers each carrying one or more series of guide members 15 which are preferably wire loops through which weft strands 16 are threaded, Preferably, fingers 14 are arranged in pairs so that weft strands carried by the guide members 15 are placed on opposite sides of the warp strands in opposed position whenthe stripper advances.

Weft strands 16 are drawn from spindle 17 mounted in a' suitable .creel (not shown), according to conventional practice and pass around guide rollers, 18 and over rollers 19 into abath 20 of thermosetting plastic resin, which may be dispersed or-dissolved in a suitable solvent, then over rollers 21 where excess resin is-removed from the strands, around spacing rollers 22 and through the series of guides 15. A weft strand gripping means, illustrated as a stripper clamp 23, carried by theastripperv is arranged to close and grip the Weft strands when the stripper 13 is at itslimit of travel in a direction toward the saturator, 20. Fingers 14 reciprocate atsuch a distance from the warp strands that the weft strands,;when carried across the warp by ,anywherein'the range from substantially zero to the advance of the stripper, do not touch the warp strands thus avoiding gumming up the warp ,witlrunset-thermo setting plastic. When the stripper reaches the limit of its travel across the fabric-forming zone, an anchor clamp,

designated generally as 24, closely and grips ends 25 of the weft strands protruding beyond outermost guides 26.

Stripper clamp 23 then is released and the stripper is moved in its return stroke toward saturator 20.. At the end of the strippers return stroke, heater 9 closes upon the warp and weft strands applying heat and pressure to bond these strands together. After heater 9 closes, a cutter 27 cuts the weft strands at a location between stripper 13 and heater 9. The cutter in closing trips a switch applying power to open it.

Heater 9 remains closed for a period required to bond warp and weft strands together by setting of thethermosetting plastic. Thisperiod may be anywhere from a few 'seconds to 'a minute or more depending uponuthe size of the strands and the heat required to set the particular resin used. The heater, 9 then opens backlash clamp 12 and puller 11 again operates to advance the warp strands and the process is repeated.

A. trimmer, designated generally as 28,is preferably 10- r cated between the fabric-forming zone and puller to. trip protruding ends, 29 and 29a from the finished fabricasithe fabric advances. A suit-able fabric-receiving means, illustrated as roller 31, is provided to receive finished fabric passed on by the puller.

Details'of the above machine and itsoperation will be best understood from the following description of FIGS. 4 and 5 in which one preferred typeof electrical control system is illustrated. For simplicity, only one conducto of each circuit is shown; and it is to be understood that suitable grounds or return lines are provided.

The reciprocating puller, designated generally as 10, has a frame 32 carried by wheels 33 mounted upon a track 34 for recopricating movement thereon. The track 34 and wheels 33 preferably are constructed as cooperable rack and gear wheels so that the sides of the puller will remain in parallel relationship with warp strands 6 during its reciprocating movement.

The frame 32 is attached in driven relationship to a piston rod 35 of a cylinder and piston assembly 36, and is driven in reciprocating motion by a fluid under pres sure admitted to the cylinder by solenoid-operated valve means 37 and 37a arranged to admit and exhaust fluid from a source (not shown) upon application and release of energy from the solenoids, respectively.

Twelve cylinder and piston assemblies of this type in which reciprocation of a piston in the cylinder is controlled by solenoid-operated valves are shown schematically in the particular embodiment illustrated. Details of these devices are omitted for clarity in illustration since such assemblies are readily available on the market and details of construction of these devices is not material to the present invention.

A stripper clamp, designated generally as 11, and having upper and lower opposed jaws 11a and 11b mounted on opposite sides of the warp, is carried on frame 32 by a pivoted arm 38. The arm 38 is disposed to be moved into fabric-grasping position and released therefrom by operation of a second cylinder and piston assembly 39 having solenoid-operated valves 39a and 39b at opposite ends thereof arranged to admit and exhaust fluid under pressure to operate clamp 11. The cylinder and piston assembly 39 is responsive to retraction of the puller to the full extent of its travel in the direction of a fabric-forming zone, designated generally as 40, to close jaws 11a and 11b of clamp 11 upon the fabric 41 to draw warp strands 6 through the fabric-forming zone on advance of the puller.

Warp strands 6 are threaded over roller 42 and pass through a bath of thermosetting plastic 43 and upward through a vertically disposed oven 44 where the warp strands are heated to a temperature suflicient to cure the plastic when it is desired to impregnate the'warp strands with such plastic. The warp strands then pass up over roller 48 and under roller 7 and through the combing or spacing rollers 8 where the warp strands are separated from each other by a desired distance determined by the setting of rollers 8. Frequently it will be unnecessary to impregnate warp strands with plastic; and when it is not desired to do so, the rollers 42, the saturating bath 43 and the oven 44 [and roller 45 may be omitted and the strands may be passed directly across rollers 7 and 8.

When the puller described above advances, it draws the warp strands intermittently into fabric-forming zone 40 against resistance supplied by friction with rollers 7 and 8 and with the series of rollers from 45 to 42 when these are used.

The heater, designated generally as 9, is made up of upper and lower members 9a and 9b, pivoted on a frame at pivots 46 and 46a, respectively, and operatively connected by geared segments 47 and 47a. A cylinder and piston assembly 48 controlled by solenoid valves is disposed to move both members 911 and 9b around their pivots and to bring heating faces into contact with the weft strands in the fabric-forming zone 40 and to exert pressure upon these strands, forcing them into firm contact with the warp strands.

A cutter which may include a knife 27 and a block 49 is disposed .at a side of the fabric-forming zone between the zone and the stripper. The knife 27 and block 49 are reciprocable toward and away from each other by fluidactuated solenoid controlled cylinder and piston assemblies 50 and 50a, respectively, to cut weft strands between the stripper and fabric-forming zone.

A trimmer, illustrated as a pair of shears 51, is disposed downstream of the fabric-forming zone and is actuated to trim weft strands closely at a desired distance from the web by operation of a fluid-actuated cylinder connected thereto controlled by a two-way solenoid valve 53. Backlash clamp 12 is disposed between the puller and the fabric-forming zone in position to grip and release the formed fabric. This backlash clamp also is actuated by a solenoid valve controlled cylinder and piston assembly 54 attached thereto.

The stripper for placing the weft strands comprises a frame 55 carried by wheels 56 upon a suitable track 57 for reciprocating movement back and forth across the warp strands 6 in fabric-forming zone 40. The track 57 and wheels 56 preferably are of rack and gear type, as illustrated, so that the stripper will remain at a desired angle to the warp strands during reciprocating movement thereof.

The stripper 13 has one or more pairs of opposed fingers 14 disposed to move back and forth across warp strands 6 with one finger on one side of the warp and the other finger of'the pair upon the opposite side. A series of guides 15 through which weft strands 16 are threaded is disposed upon each of the fingers 14 in position to hold the weft strands 16 out of contact with warp strands 6 during advance of the stripper across the fabricforming zone 40. A cylinder and piston assembly 58 controlled by solenoid-operated valves is disposed to advance and retract the stripper in reciprocating motion on track 57.

The anchor clamp 24 has opposed upper and lower jaws 59 and 59a pivoted on a suitable frame 60 and disposed to be closed and opened by action of a cylinder and piston assembly 61 controlled by solenoid-operated valves.

The control system is best described in connection with the description of the operation of the machine. A suitable main lead line 62 having a main switch 63 therein is disposed to apply direct current from any suitable source through branch leads to a series of switches to be described in detail later. When it is desired to place the machine in operation, the switch 63 is opened, thus cutting off control power from all the solenoid-operated valves controlling the various piston and cylinder assemblies. Warp strands 6 are then drawn below roller 7 beside the spacing roller 8 through the fabric-forming zone to the puller while the heater, backlash clamp and puller clamp are in open position. The puller clamp is then closed manually upon the warp strands while the puller is either in fully retracted or in a median position. The puller clamp thus holds the warp strands and is ready to apply tension thereto when the puller advances.

Each of weft strands 16 is threaded through a series of guides 15 on the stripper with ends of each strand projecting somewhat beyond the outermost guide member 26. The stripper clamp 68 is then closed manually to grip the weft strands, and the anchor clamp 24 is opened. The machine is now ready to begin its automatic series of operations when the main switch 63 is closed.

Closing the main switch applies control power through branch leads 65 and 66 to a switch 70 which is closed bycontact of heater element 9a in the open position of the heater. Control power from switch 70 is thus applied through control leads 71 and 72 to advance the stripper and to advance the puller. The war-p strands are drawn forward through the fabric-forming zone 40 by advance of the puller, and the stripper places weft strands across the warp at the same time.

When the stripper is fully advanced, contact of frame 55 with switch 73 closes the switch and applies power through control lead 74 to close thejaws 59 and 59a of the anchor clamp by operation of the piston and cylinder assembly 61. The anchor clamp in closing grips the 7 protruding ends 25 of the weft strands firmly and closes a switch 75 thus applying control power through lead 78 to actuate the cylinder and piston assembly 69. to open the stripper clamp 68. Full opening of the stripper clamp 68 brings the clamp into contact with switch 77, and operates a means for breaking a circuit in lead 72, illustrated as a relay having normally closed points 80in control lead 72 anda coil 79 in control lead 78. Switch 77 closes to actuate the piston and cylinder assembly 58 to retract the stripper. The circuit breaking in control lead 72 releases power holding the stripper in advanced position.

It will thus be seen that the arrangement of switches 75 and .77 and their connecting leads insures that the anchor clamp shall be completely closed upon the pro jecting ends of the weft strands. before the stripper clamp is released, thus preventing backlash of-the weft strands.

to a position where they could not be easily grasped by the anchor clamp, and that the stripper clamp will be fully opened to prevent pulling the weft'strands out of the anchor clamp or breaking the strands before the stripper begins its return motion.

Fullretraction of the stripper brings, frame 55 into contact with switch 80 to close circuits through control lead 81 to apply power to the cylinder and piston assembly 48 to close the heater upon the warp and weft strands in the fabric-forming zone, and at the same time through control lead 82 to apply power, to the piston and cylin-' der assembly 69 to open the stripper clamp 68.

During the time the stripper has been advancing and retracting, the puller has reached fully advanced position. Advanceof the puller has moved frame 33 in position to close switch 83,to supply control power."

through control lead 84 to actuate the cylinder and piston assembly 54 to close backlash clamp 12. Switch 83 is set at a position to be closed at a point before the puller.

reaches its extreme advanced position and before puller Y clamp 11 contacts a switch85 to apply power to piston and cylinder assembly 36 to retract the puller, to insure that backlash clamp 12 has been set before tension on warp strands 6 is released. At full advance of the puller, the puller clamp 11 closes switch 85, thus ap: plying control power through control lead 86 to retract the puller. The puller does not begin to move in its reverse travel at this time as power to advance the puller still will be on until heater 9-begins to close with resulting opening of switch 70. The cooperation of switches 70 and 85 thus insures that the puller cannot begin its returnstroke until the heater is closed.

Closing the heater, 9 brings the member 99. into contact with switch 87, thereby closing control circuits through control leads 88, 89, 90 and 91 to open the anchor clamp, to open the puller clamp, to close the cutter and through a timer to apply power to actuate the cylinder and piston assembly 48 to close the heater, respectively. The

timer 92 may be of any of the common commercial types which areconstructed to be set to cause a selected time delay in the passage ofcurrent therethrough. Application of power to close the heater through lead 93 directly to the solenoids controlling cylinder and piston assembly 48 to close the heater would be ineffective since at this time the stripper 13 is still fully retracted and power from switch 80 and control lead 81 is still on to close the heater. A means for breaking the circuit in control lead 81 therefore is provided and is illustrated as a relay having normally closed points in control lead 81 and a coil connected in control lead 93 to open the points when current flows from the timer to the solenoid controlling opening of the heater.

The puller thus moves in its returnstroke during the time that the heater is closed; and upon the puller reach ing its fully retracted position, the frame 32 closes a switch 96 applying control power through control leads 98 and 99, respectively, to close the puller clamp and through a timer to open the backlash clamp 12. The

timerfunctions to delay opening of the backlash clamp until the puller. clamp has closed upon the fabric.

It will be seen that the entire series of operations. described above will be initiated each time the heater 9 beyondthe warp are trimmed off at each edge ofthe fabric, or at any desired distance .from the fabric edges. From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects,

hereinabove set forth; together with other advantages which are obvious'and which are inherent to the apparatus and process. 7

It' will ,be understood thatcertain. features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of ,the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, itis to be understood that all matter herein setforth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what isIclaimed is:

1. The method for producing a nonwoven reinforcing fabric comprising the steps of:

(a) intermittently and alternately advancing and stop-,

ping a band consisting of a single layer of a plurality of fibrous warp strands while ,continually in substantially equal tension, said strands arranged and maintained in generally parallel, side-by-side relationship, said strands having a thermosetting resin on the surface thereof,

(b) disposing individually across the tops of said warp strands single, substantially straight weft parallel strands derived from ,a substantially continuous source thereof, said weft strands disposed in transverse relationship with respect, to each and every said warp strand traversed,

(c) bringing said weft strands, as disposed in step (b), in substantial contact with each said warp strand at the points of juncture of said weft strands with said warp,

said weft strands in step, (b) repeatedly and sequentially receiving each of said weft strands, respectively, each time said warp is stopped, and

(d) while maintaining each said weft strand respec tively in a state of stationary tension during and at the point in space of the initial contacting thereof with said warp str-andsin step (c), and ,while said warp strands are stationary, fixing said weft-strands said warp strands and said source of weft while said 1 weft is in its position inspace as set forth in step (d), following completion of step (f) above, advancing said warp strands a predetermined distance, and, repeating, the.

cycle initiated in step .(b) above, to provide a nonwoven fabric having a single layer of warp and a single layer of weft, wherein the tension in each of said warp strands, is substantially equal, and the tension in each of said weft strands is substantially equal,.when said-warp strands are positioned in parallel, side-by-side relationship; at

the maximum separation permitted by any of said weft strands.

2. The method for producing a nonwoven reinforcing fabric comprising the steps of:

(a) intermittently and alternately advancing and stopping a band consisting of a single layer of a plurality of fibrous warp strands while continually in substantially equal tension, said strands arranged and maintained in generally parallel, side-by-side relationship,

(b) disposing individually across the tops of said warp strands single, substantially straight weft parallel strands derived from a substantially continuous source thereof, said weft strands disposed in transverse relationship with respect to each and every said warp strand traversed, said weft strands having a thermosetting resin on the surface thereof,

(c) bringing said weft strands, as disposed in step (b), in substantial contact with each said warp strand at the points of juncture of said weft strands with said 'P,

said warp strands in step (-b) repeatedly and sequentially receiving each of said weft strands, respectively, each time said warp is stopped, and

((1) while maintaining each said weft strand respectively in a state of stationary tension during and at the point in space of the initial contacting thereof with said warp strands in step (c), and while said warp strands are stationary, fixing said weft strands to each of said warp strands in a substantially permanent union at their respective junctures by applying heat to said junctures,

(e) each said weft strand, respectively, maintained at substantially the same degree of tension during fixing thereof to said warp strands,

(f) severing said fixed weft strand at a point between said warp strands and said source of weft while said weft is in its position in space as set forth in step (d),

following completion of step (f) above, advancing said warp strands a predetermined distance, and repeating the cycle initiated in step (b) above, to provide a nonwoven fabric having a single layer of warp and a single layer of weft strands is substantially equal, when said warp strands is substantially equal, and the tension in each of said weft strands is substantially equal, when said warp strands are positioned in parallel, side-by-side relationship at the maximum separation permitted by any of said weft strands.

3. The method for producing a nonwoven reinforcing fabric comprising the steps of:

(a) intermittently and alternately advancing and stopping a band consisting of a single layer of a plurality of glass fibrous warp strands while continually in substantially equal tension, said strands arranged and maintained in generally parallel, side-by-side relationship, said strands having a thermosetting resin on the surface thereof,

(b) disposing individually across the tops of said warp strands single, substantially straight weft parallel glass strands derived from a substantially continuous source thereof, said weft strands disposed in transverse relationship with respect to each and every said warp strand traversed, said weft strands having a thermosetting resin on the surface thereof,

(c) bringing said weft strands, as disposed in step (b), in substantial contact with each said strand at the points of juncture of said Weft strands with said warp,

said warp strands in step (b) repeatedly and sequentially receiving each of said weft strands, respectively, each time said warp is stopped, and

(d) while maintaining each said weft strand respectively in a state of stationary tension during and at the point in space of the initial contacting thereof with said warp strands in step (c), and while said warp strands are stationary, fixing said weft strands to each of said warp strands in a substantially permanent union at their respective junctures by applying heat to said junctures,

following completion of step (f) above, advancing said warp strands a predetermined distance, and repeating the cycle initiated in step ('b) above, to provide a nonwoven fabric having a single layer of warp and a single layer of weft, wherein the tension in each of said warp strands is substantially equal, and the tension in each of said weft strands is substantially equal, when said warp strands are positioned in parallel, side-by-side relationship at the maximum separation permitted by any of said weft strands.

References Cited by the Examiner UNITED STATES PATENTS 2,919,217 12/ 1959 Bobkowicz 154--46 3,029,179 4/1962 Wilson et a1 156-441 3,041,230 6/1962 Diehl 156-181 X FOREIGN PATENTS 777,734 6/ 1957 Great Britain.

EARL M. BERGERT, Primary Examiner.

HAROLD ANSHER, Examiner.

R. J. CARLSON, J. P. MELOCHE, Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,275,489 September 27, 1966 Harry Talv It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 8, line 49, for "weft" read warp column 9, lines 40 and 41, strike out "weft strands is substantially equal, when said warp strands is substantially equal, and the tension in each of said" and insert instead weft, wherein the tension in each of said warp strands is substantially equal, and the tension in each of said Signed and sealed this 29th day of August 1967.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attestingoffioer Commissioner of Patents

Claims

1. THE METHOD FOR PRODUCING A NONWOVEN REINFORCING FABRIC COMPRISING THE STEPS OF: (A) INTERMITTENTLY AND ALTERNATELY ADVANCING AND STOPPING A BAND CONSISTING OF A SINGLE LAYER OF A PLUARLITY OF FIBROUS WARP STRANDS WHILE CONTINUALLY IN SUBSTANTIALLY EQUAL TENSION, SAID STRANDS ARRANGED AND MAINTAINED IN GENERALLY PARALLEL, SIDE-BY-SIDE RELATIONSHIP, SAID STRANDS HAVING A THERMOSETTING RESIN ON THE SURFACE THEREOF. (B) DISPOSING INDIVIDUALLY ACROSS THE TOPS OF SAID WARP STRANDS SINGLE, SUBSTANTIALLY STRAIGHT WEFT PARALLEL STRANDS DERIVED FROM A SUBSTANTIALLY CONTINUOUS SOURCE THEREOF, SAID WEFT STRANDS DISPOSED IN TRANSVERSE RELATIONSHIP WITH RESPECT TO EACH AND EVERY SAID WARP STRAND TRAVERSED, (C) BRINGING SAID WEFT STRANDS, AS DISPOSED IN STEP (B), IN SUBSTANTIAL CONTACT WITH EACH SAID WARP STRAND AT THE POINTS, OF JUNCTURE OF SAID WEFT STRANDS WITH SAID WARP, SAID WEFT STRANDS IN STEP (B) REPEATEDLY AND SEQUENTIALLY RECEIVING EACH OF SAID WEFT STRANDS, RESPECTIVELY, EACH TIME SAID WARP IS STOPPED, AND (D) WHILE MAINTAINING EACH SAID WEFT STRAND RESPECTIVELY IN A STATE OF STATIONARY TENSION DURING AND AT THE POINT IN SPACE OF THE INITIAL CONTACTING THEREOF WITH SAID WARP STRANDS IN STEP (C), AND WHILE SAID WARP STRANDS ARE STATIONARY, FIXING SAID WEFT STRANDS TO EACH OF SID WARP STRANDS IN A SUBSTANTIALLY PERMANENT UNION AT THEIR RESPECTIVE JUNCTURES, BY APPLYING HEAT TO SAID JUNCTURES, (E) EACH SAID WEFT STRAND, RESPECTIVELY, MAINTAINED AT SUBSTANTIALLY THE SAME DEGREE OF TENSION DURING FIXING THEREOF TO SAID WARP STRANDS, (F) SEVERING SAID FIXED WEFT STRAND AT A POINT BETWEEN SAID WARP STRANDS AND SAID SOURCE OF WEFT WHILE SAID WEFT IS IN ITS POSITION IN SPACE AS SET FORTH IN STEP (D), FOLLOWING COMPLETION OF STEP (F) ABOVE, ADVANCING SAID WARP STRANDS A PREDETERMINED DISTANCE, AND REPEATING THE CYCLE INITIATED IN STEP (B) ABOVE, TO PROVIDE A NONWOVEN FABRIC HAVING A SINGLE LAYER OF WARP AND A SINGLE LAYER OF WEFT, WHEREIN THE TENSION IN EACH OF SAID WARP STRANDS IS SUBSTANTIALLY EQUAL, AND THE TENSION IN EACH OF SAID WEFT STRANDS IS SUBSTANTIALLY EQUAL, WHEN SAID WARP STRANDS ARE POSITIONED IN PARALLEL, SIDE-BY-SIDE RELATIONSHIP AT THE MAXIMUM SEPARATION PERMITTED BY ANY OF SAID WEFT STRANDS.