IL29916A - Method of and apparatus for producing a continuous tape - Google Patents

Description

η*3*ί cnb iis'l? tpn i no'w A method of and apparatus for producing a continuous tape UNITED AIRCRAFT CORPORATION C: -28309 This invention relates to a method of producing a continuous tape* and to apparatus for carrying out the method* ' - :.

According to the invention! there is provided a method of producing a continuous tape : comprising the steps of continuously applying threads o both sides of a flat continuously movin endless hand so as to extend generally parallel with the edges of the band, wrapping filaments transversely around the band, successive turns of the filaments being in non-overlapping relationship, bonding the filaments to the threads to form a continuous tape, cutting the filaments in a direction generally parallel to an edge of the band, and removin the continuous tape from the band, the completed tape having transverse tensile strength at least one hundred times greater than its longitudinal tensile strength.

According to the invention, there is also provided a machine for producing a continuous tape, comprising an endless band, means for driving the band in a direction longitudinally thereof, spool means for continuously applying adhesive-coated threads to opposite sides of the band so as to extend generally parallel to the edges of the band, a winding platform for continuously wrapping filaments transversely around the band and over the threads, bondin means for bonding the filaments to the threads to form a tape, and cutting means for severing the filaments In a direction generally parallel to the threads whereby the tape may be removed from the band.

As used herein the term "tape" describes a elonated narrow material of x w continuously wound into a reinforced plastics pipe to provide longitudinal reinforoement. The tape is substantially cheaper than woven or filament sheets, has strength only in the direction required, provides efficient and economical utilization of the material of the tape and greatly simplifies the fabrication process.

The tape manufactured is subsequently used to - produce a reinforced plastios pipe having longitudinal reinforcement according to the method described herein below.

In the published literature, various procedures are described for producing a non-woven fabric consistin of longitudinally extending warp strands and of weft strands extending transverse thereto.

The U.S. patent Wo. 3,041,230 discloses for example a method and machine for producing a multi-ply non- woven fabric by using a pair of spaced .apart conveying elements passing alon opposite sides of a stationary table, This composite sheet is not formed by wrapping filaments around a continuous band but around a stationary table and the conveyin elements function only to transport the fabric mat formed on the table. This patent merely shows the application of fabric to one side of the table with the result that in the end produc the filament applied both above and below table are bonded to the fabric and to each other.. In this patent, it will be difficult to maintain the alignment of filaments with respect to the table against, the friotional forces acting between the filaments and the table. The proposed method and machine of the present invention differ from the teachin of this U.S* aten in that the flat mvabl and u filamentB and the member about which they are formed and providing for separation of the filaments on opposite sides of the member. The application of the longitudinal extending filaments at a point prior to the overlapping of the longitudinal filaments with the transverse filaments permits the adhesive coated longitudinal filaments to be completely covered, thereby substantially reducing any problems associated with the filaments adhering to rollers which are used to bond the filaments to each other. The requirement that bonding be completed prior to removal from the mandrel also eliminates problems associated with maintaining filament orientation of unbonded filaments.

The British patent No. 961,716 describes a. method and apparatus for forming strand reinforcement consisting in wrapping filaments around a movable conveyor and cutting them. This requires some gripping means to hold the loose ends of the filaments so that they can be transported from the cutting station to the station at which they are later bonded to the other components of the band. The subject invention, however, proposes a method and machine in which the problem of transporting cut lengths of loose filaments has been overcome by; bondin the transverse filaments to the tacking threads while they are on the band and by cutting them only after the bond between the transverse filaments and the tacking threads has been formed.

The British patent No..1,066,814 discloses a method and apparatus fo making non-woven fabrics consisting of longitudinally extending' warp strands bonded to transversely extending weft strands. A stationary mandrel is used for mandrel b an appropriate driving means, Beside the complex mechanisms to la the warp strands around the mandrel and to apply the weft strands therearound and the meohanisms to kee the formed structure moving through the different stations of the apparatus, friction problems will also occur in this apparatus between the stationary mandrel and the filaments.

This problem has been easily overcome In the present invention by using a double endless moving belt serving both as a mandrel and conveyor. The prior art machine also seems to require some preliminary work to start the production of non-woven tapes whereas the proposed machine of the subject invention is not only quite simple in its construction but also very easily to run without requiring specially trained workers,.

These and other features of this invention will be readily apparent from the following description of the invention with reference to the accompa.nying drawings wherein: Figure 1 is a plan view of a portion of a tape according to this invention and Figure 2 is an enlarged side sectional view of a portion of the tape of Figure 1.

Figure 3 is an enlarged front view of a portion of the tape of Figure 1.

Figure 4 is a front elevation partly in section of a machine for fabricating such tape, Figure 5 is a side elevation iew of a portion of the machine of Figure 4.

Figure 6 is a side elevation of another portion of the machine of Figure 4. ' Figure 7 is a schematic representation of the fabrication of pipe according to this invention.

Figure 9 is a cross section through the wall of another embodiment of the pipe according to this invention.

Referring now to Figures 1, 2, and 3, the tape 1 according to this invention consists of a plurality of parallel longitudinally extending tacking threads 2 haying a multiplicity of transverse high strength filaments 3 bonded to the tacking threads 2 at the points of intersection therewith by adhesive 40, As can be seen more clearly in Figures 2 and 3, the transverse filaments 3 each consist of a band comprising a multiplicity of individual monofilaments 4.

In the filament winding art, the terms "single end filament" and "multiple end filament" describe filaments comprised of a plurality of individual monofilaments. A "single end filament" is a filament comprised of a multiplicity of monofilaments obtained from one bushing in the manufacturing process whereas "multiple end filaments" or "roving" described a filament comprising a multiplicity of monofilaments obtained from a plurality of bushings. As used herein the term "filament band" describes a filament comprising a multiplicity of generally parallel monofilaments and includes both single end and multiple end filaments as well as a multiplicity of generally parallel braided monofilaments.

The function of the tacking threads is merely to support the transverse filaments and not to supply strength to the finished product. Accordingly, the threads 2 can be made from any fiber, filament, or thread such as cotton, nylon, glass, or rayon, for example. The number of such threads is preferrably maintained as low as ossible consistent with ro er of the tape may range from 2 to 10 in number with four being adequate in most situations. The transverse filaments may be any high tensile strength material such as glass filaments, metal wire or filaments, or filaments of synthetic materials such as nylon, rayon or acrylic polymers. Glass fiber is the preferred material, however> because of its high strength, availability and corrosion resistance.

It should be emphasized that the function of the longitudinal tacking strands is merely to hold the trans* verse filaments in proper orientation and not to contribute any structural hoo strength in reinforced plastic bodies fabricated from the tape. Accordingly, the total number of transverse filaments is substantially greater than the number of longitudinal filaments whereby a longitudinal portion of this tape equal in length to the width of the tape will have a transverse tensile strength substantially higher, i.e. at least two orders of magnitude higher, than the longitudinal tensile strength. When this condition is met, the longitudinal strength can be disregarded in the design of pipe according to this invention.

A representative tape manufactured according to this invention is 19 cm (7-½ inches) wide, employs three tacking threads, each tacking thread comprising a single end glass filament of about 120 monofilaments and has approximately three (eight) transverse multiple end glass filaments per running cm (inch), each multiple end filament containing about 2000 monofilaments. The transverse tensile strength of a 19 cm (7-½") length of such a tape is over 300 times greater than the using fewer or smaller tacking threads or by substituting cotton thread for the glass tacking thread. When cotton is used, for example, the transverse tensile strength can be over 1000 times greater than the longitudinal strength.

Referring now to Figures 4, 5, and 6, a machine for fabricating the tape of this invention is shown. The machine comprises a vertical support frame 1 carrying rota-table wheels 2 and 3 and idler wheel 4 over which continuous band 5 is passed. Band 5 is preferrably formed of two band elements 5a and 5b of similar width and aligned with each other so that bands 5a and 5b may be separated by passing over separator roller 6 to facilitate cutting and removal of the tape from the band 5 as will be more fully explained below.

Bands 5a and 5b may also be joined together along one edge in those instances where cutting of the tape on one side is desired. The external faces of band 5 are preferably coated with a release agent such as Teflon to facilitate removal of the tape.

Spools 7 of the tacking thread are mounted on suitable supports attached to frame 1 and the tacking threads 8 are passed through guide eyelets 9 into glue pots 10 and out the bottom thereof through orifices 11 whereby the threads 8 are cpated with an adhesive. A horizontal toroidal table 12 is mounted for rotation about its vertical axis on suitably supported rollers 36 and ir". intained in axial alignment with belt 5 by guide rollers 34 engaging a peripheral groove 35 in the surface of the dependent hollow cylindrical base of said table. A ring gear 13 is formed about the periphery of said base which rotates said table about its vertical axis, by means of gear 14, shaft 15, and gear boxes 16 and 17 driven by motor 18. Motor 18 also drives wheel 2 by means of gear box 19 which supplies power to gear means on the reverse side of the support which turns a shaft and gear which engages a ring gear on the reverse side of wheel 2.

A toroidal horizontal eyelet support table 20 is mounted above table 12 for rotation therewith by means of rods 21. Spools 22 of hightensile strength filaments are supported on table 12 and the filament bands 23 are guided into proper closely vertically spaced position for wrapping around belt 5 by eyelets 24 on table 20. It should be noted that the vertical band width of the filaments 23 above table 20 and eyelets 24 has been exaggerated in Figures 4 and 5 for clarity in illustration. A heating chamber 25 is mounted below table 12 which is supplied with hot air from heaters 26. A series of rollers 27 are mounted within heating chamber 25 which are adapted to firmly press filaments 23 onto tacking threads 8 while the adhesive is being set in heating chamber 25. Rotary cutter blades 28 driven by motors 29 are located adjacent to the opposite edge of belt 5 at a point below separation roller 6 and near guide roller 30. The finished tape 31 is removed from belt 5 and reeled onto takeup reels 32 and 33 which are driven by motors (not shown). In the embodiment shown cutters are employed at opposite edges of the belt 5 to produce two tapes 31. However, one cutter could In operation, wheels 2 and 3 and tape 12 are all rotated in counter-clockwise direction with the gearing being such that during one rotation of table 12 belt 5 is advanced a distance equal to the total vertical band width of filament bands 23 to produce successive turns of nonoverlapping filament bands on belt 5. While for ease of illustration three filament bands are shown as being applied, it is apparent that more or fewer filament bands may be utilized.

As belt 5 advances tacking threads 8 are continuously drawn from spools 7 through glue pots 10 and onto band 5 where they are overwrapped by filaments 23. The filament wrapped belt then passes into heating chamber 25 between rollers 27 which press filaments 23 firmly onto tacking threads 8 while the adhesive is setting. The belt then carries the filaments to cutters 28 where they are cut longitudinally and the finished tape removed from the belts by takeup -reels 32 and 33. Separation element 6 facilitates the cutting step by providing a spacing between the edge of belts 5a and 5b within which the cutter blade may be inserted.

A tape can be manufactured in varying widths according to this invention by appropriate selection of the width of belt 5. Additional variation in width can be obtained by using either one or two cutters or by subsequent longitudinal cutting of the tape after it has been removed from belt 5. The final width of the tape is selected such that it may be conveniently used in the winding process hereinafter described. plastic pipe. Such pipe has a wall structure composed of annularly disposed high strength filaments such as glass, metal wire or whiskers, or various high strength synthetic fibers such as nylon, for example, bonded together by a matrix of a cured resin such as, for example, polyester or epoxy resin as is known to the art. Particulate material may also be incorporated in the wall structure as is more fully described in the aforementioned patent applications.

As shown schematically in Figure 7, the reinforced plastic pipe may be fabricated by coating a rotating mandrel 50 with a gel coat of a resin 51 over which may be applied a layer of veil cloth 52. The continuous tape 53 of transverse filaments is then wound around the mandrel in such a manner that successive turns are partially overlapped and the tape is impregnated with the resin of the gel coat. Resin coated high strength filaments such as glass filaments 54 are then wound around and along the mandrel to build up the desired wall thickness. Depending upon the use to which the pipe is to be put, particulate material may be applied over the filament as described in the above noted copending patent application. Another layer of transverse reinforcing tape is applied over the filaments in partially overlapping manner near the outer surface of the pipe. Generally sufficient resin will be on the winding surface to impregnate the tape or the tape may be coated with additional resin. This layer may be followed by another layer of hoop filaments and particles. The resin is then cured and the pipe removed from the mandrel. Wall structures of pipes produced according to with spacing between the various elements being exaggerated for clarity.

Referring now to Figure 8 a cross section through a wall of one embodiment of pipe is shown i The wall comprises an inner surface of a gel coat of resin 51 followed by a layer of veil cloth 52, a layer of transverse tape 53 partially overlapped as shown, successive alternate layers of hoop wound high tensile strength filaments 54 and particles 55» another layer 53 of partially overlapping transverse tape*, a layer of hoop wound filaments 54 and a layer of particles 55. The whole structure is bonded together by the cured resin matrix which permeates around, between and through the various layers. The matrix has not been hatched for clarity. In Figure 8 the wall has substantial thickness and in such walls the longitudinal bending stress are concentrated at the inner and outer surfaces. Thus for maximum utilization of the transverse filament reinforcing tape the tape layers 53 should be located in proximity to the inner and outer surfaces rather than the center of the wall .

However, as shown in Figure 9 where a relatively thin walled pipe consists of resinoue matrix 60 bonding layers of hoop filaments 54 and overlapped transverse tape 53, a layer of tape 53 may be employed within the wall structure. 29916/2

Claims (4)

1. , A method of producing a continuous tape, comprising the steps of continuously applying threads to both sides of a flat continuously moving endless band so as to extend, generally parallel with the edges of the band, wrapping filaments transversely around the band, successive turns of the filaments being in non-overlapping relationship bonding the filaments to the threads to form a continuous tape, cutting the filaments in a direction generally parallel to an edge of the bandj and removing the continuous tape from the band, the completed tape havin a transverse tensile, strength at least one hundred times greater than its longitudinal tensile strength.

2. A method of producing a continuous tape, substantially as herein described with reference to Figures 1 to 6 of the accompanying drawings.

3. * A machine for producing a continuous tape, comprising an endless band, means for driving the band in a direction longitudinally thereof, means for continuously applyin adheeive-kcoated threads to opposite sides of the band so as to extend generally parallel to the edges of the band, a windin platform for continuously wrapping filaments transversely around the band and over the threads, bonding means for bonding the filaments to the threads to form a tape, and cutting means for severing the filaments in a direction generally parallel to the threads whereby the tape may be removed from the band.

4. A machine according to Claim 3, wherein the band is formed by two superimposed band elements which are separable to facilitate cutting and removal of the tape from the band. 17, A method according to Claim 16 and including the additional steps of depositing particulate material between the layers of filaments inding at least one layer of resin-coated filaments around the last mentioned layer of the tape and depositing a layer of particulate material over the last mentioned layer filaments. 18, Δ method of manufacturing a composite reinforced plastics pipe,; substantially as herein described with reference to Figures 7 to 9 of the accompanying drawings. : 19, composite reinforced pipe made by the method according to any of Claims 16 to 18. 20, A pipe according to Claim 19» and including an annular longitudinally extending wall comprising a matrix of cured resin and containing a plurality of layers of annularly extending filaments and a layer of longitudinally oriented filaments annularly disposed within the matrix, the longitudinally oriented filaments comprising a plurality, of lengths of filaments having overlapping ends. 21, A pipe according to Claim 20, wherein the wall comprises a plurality of layers of longitudinally disposed filaments, at least one of the layers being located adjacent the inner surface of the wall and a least one of the layers being located adjacent the external surface of the wall, 22, A pipe according to any one of Claims.19 to 21, and including additional layers of particulate material disposed between the layers of annularly extending filaments. 23, ' A composite reinforced plastics pipe, substantially as hereinbefore described with reference to, and as Illustrated in, Figures 7 to 9 of the accompanying drawings.