GB2231344A

GB2231344A - Method and apparatus for forming non-woven fabric

Info

Publication number: GB2231344A
Application number: GB8908927A
Authority: GB
Inventors: Paul Cooper
Original assignee: James Dewhurst Ltd
Current assignee: James Dewhurst Ltd
Priority date: 1989-04-20
Filing date: 1989-04-20
Publication date: 1990-11-14
Anticipated expiration: 2009-04-20
Also published as: GB8908927D0; GB2231344B

Abstract

A non-woven fabric of the kind in which the warp threads and weft threads adhere to each other where they cross is formed by sinuously traversing a weft yarn between a pair of moving parallel conveyors, cutting the ends off the traversed weft yarn to form a series of separate weft threads and bringing the weft threads into bending contact with a substrate comprising the warp threads. The weft thread spacings ("picks" per metre) is selected by selecting the longitudinal speed of the substate relatively to the speed of forward travel of the conveyors. In the illustrated embodiment, a weft yarn (22) is traversed between parallel conveyors (20) each comprising a double helical coil, the ends of the yarn is cut by a disc (38), and the weft threads so formed fed by double belts (30, 32) to a few of rollers (14, 16) where work thread sheets (10, 12) are applied followed by an adhesive. <IMAGE>

Description

"Method and apparatus for forming non-woven fabric." This invention relates to the production of non-woven fabric of the kind in which there are warp threads and weft threads, the weft threads extending across and lying on one face of the sheet of warp threads (rather than being interlaced therewith as in weaving), the warp and weft threads being caused to adhere to each other where they cross. References to the threads adhering to each other are to be construed so as to include fusion of the threads as well as use of adhesive.

Warp threads are threads which extend mainly or wholly in the longitudinal direction of the fabric and weft threads are threads which extend mainly or wholly in the weftwise direction (i.e. at right angles to the longitudinal direction of the fabric).

Thus, the fabric is distinguished from non-woven fabrics in which "weft" threads are traversed from side-to-side but also moved longitudinally, so that the threads form overlapping zig-zag arrays in which each thread traverses the width of the fabric but is inclined to the longitudinal direction, so that it is not a true weft and there is no warp. A fabric having warp and weft is stronger in both the warpwise and weftwise directions than one in which there is only "weft" in the zig-zag formation.

The invention also relates to a method of fabric production in which a weft array is formed by traversing the weft yarns between a pair of parallel conveyors which carry the weft yarns forwardly. A known method employs helical coils each rotating about its own longitudinal axis as the conveyors, but the invention is not restricted to the use of helical cloils as the conveyors.

According to a first aspect of the invention a method of producing a non-woven fabric of the kind having both warp and weft threads, comprises forming an array of weft threads by reciprocating one or more threads between a pair of rectilinear conveyors and engaging the loops at the ends of the weft space with the conveyors and then bringing the array of weft threads so formed into face-to-face contact with a sheet of warp threads; cutting the ends of the weft threads, so that each weft thread is completely separated from adjacent weft threads, and preselecting the weft thread spacings ("picks" per metre) by selecting the longitudinal speed of the warp sheet relative to the speed of forward travel of the conveyors.It is known to form non-woven fabrics, by means of weft arrays brought into face-to-face contact with a sheet of warp threads, but with all the known methods of producing non-woven fabric in this way, it is not possible to vary the weft thread spacings, without completely altering the weft array forming mechanism. By virtue of the fact that the weft threads are completely separated from each other by the cutting action, it is possible to adjust the weft spacings, by the simple expedient of changing the rate of forward motion of the weft array and the warp sheet.

Preferably the weft threads are cut in advance of the position at which they are bought-into contact with the warp sheet. It is further preferred that the weft array is physically controlled from a position in advance of that where it is cut to at least a position adjacent to where it is brought into contact with the warp sheet.

According to other preferred features of this aspect of the invention, the loops at the ends of adjacent weft threads are cut off and removed by pneumatic means; adhesive is applied to the warp threads and/or weft threads before the array of weft threads is brought into contact with the warp sheet, and cutting of the weft threads is carried out whilst the weft threads are still engaged by the conveyors.

According to a second aspect of the invention apparatus for producing non-woven fabric having both warp and weft threads comprises: a pair of laterally spaced rectilinear conveyors which define a weft space between them; weft laying apparatus for traversing one or more weft supplies across the weft space and for engaging the ends of the weft threads with each of the two conveyors; cutting means for cutting the ends of weft threads adjacent to each of the conveyors and within the length of the conveyors; means for feeding at least one warp sheet longitudinally; means for bringing the warp sheet and an array of weft threads formed across the weft space into contact with each other and a variable speed device for varying the relationship between the speed of advance of the weft array and the speed of advance of the warp sheet.

Weft array control apparatus is preferably provided for controlling the orientation and spacing of the weft threads between the cutting means and the means bringing the warp sheet and array of weft threads into contact with each other. The control apparatus may comprise travelling clamping means, and in a preferred construction, it comprises parallel travelling nipping means extending at least partly across the weft space.

In a specific embodiment, the control means comprises a pair of endless belts, the inside runs of which lie closely adjacent to each other to provide nipping means for weft threads extending across the weft space.

The invention is particularly applicable to non-woven fabric producing apparatus in which the rectilinear conveyors comprise helical elements (similar to coil springs) rotating about their own longitudinal axes to provide a means for traversing the ends of weft threads looped around parts of the helix.

The construction of a non-woven fabric producing machine and its method of operation will now be described by way of examples of both aspects of the invention, and with reference to the accompanying drawing, which is a diagrammatic representation of the part of the machine in which a weft array is brought into contact with two sheets of warp threads.

For present purposes, it is assumed that the fabrics to be produced are all scrims, that is to say fabrics in which there are spaces between adjacent warp threads and spaces between adjacent weft threads, thereby producing rectangular, or square, interstices between the threads. Such fabrics are frequently used as reinforcing fabrics in sheet materials, for instance in wrapping paper, plastics sheets as used in the construction industry and in roofing felt. Some fabrics require larger interstices than others, and whilst it is relatively easy to adjust the spacing between the warp threads, it is not so easy to adjust the weft thread spacing. However, by using the machine herein described, the spacing between adjacent weft threads can be adjusted (within limits) at will.

The machine illustrated is used to produce a fabric in which weft yarns are sandwiched between two warp sheets - rather than being interlaced with the individual threads of a warp sheet as in conventional weaving. It is to be understood however, that a machine of the kind herein described could equally be used to produce a fabric in which the weft threads are laid on one face of a single sheet of warp threads.

The machine is provided with creels or warp beams (not shown) from which two warp thread sheets 10 and 12 are delivered respectively to a pair of front nip rollers 14 and 16. Hence, as the rollers 14 and 16 are rotated in the direction of the arrows, the two warp sheets 10 and 12 are brought together.

From the front nip rollers 14 and 16, the warp sheets travel along a horizontal path indicated at 18 to a take-up device (not shown).

The apparatus for producing the weft array which is sandwiched between the two warp sheets 10 and 12 will now be described. At each side of the weft space (corresponding to the width of the warp sheets 10 and 12) here is a double helical coil 20, made of metal, which is adapted for rotation about its own horizontal longitudinal axis. This longitudinal axis is aligned with the plane of the tangent to both the front warp feed rollers 14 and 16, i.e.

the tangent to the nip of the two front feed rollers 14 and 16. There is also provided a weft supply mechanism (not shown) which is of a known type comprising one or more weft guide tubes, the or each weft guide tube having a radially extending arm leading to an axially extending outlet nozzle. The weft supply tube(s) is or are mounted for rotation about a horizontal axis coaxial with the tangential plane to the front feed rollers 14 and 16, and central of the width of the weft space. Moreover, the arrangement of the weft supply mechanism is such that as the weft supply tube(s) is or are rotated, a weft thread issuing from each weft supply tube is carried over and around the outside of each of the double helical coils 20 which are provided at the sides of the weft space.Consequently, when the weft thread paid out by the weft supply tube(s) is drawn taut, it is engaged in the coils 20 at each side of the weft space, and each weft thread becomes looped around the outsides of two adjacent coils. For example, a single weft thread 22 has a loop which engages around an outside portion 24 of one helical coil. Since the two helical coils 20 are each rotated about their own longitudinal axes, the weft threads thus laid across the weft space are carried forwardly by the helical coils 20, the weft threads lying in the horizontal plane which is an extension of the tangent to the nip of the front rollers 14 and 16.

The method of forming an array of weft threads looped around axial conveyors such as the double helical coils 20 illustrated in the drawing, by means of a rotating weft supply tube, is now well known.

A machine of this type is described for example in the specification of United Kingdom Patent 1 472 207.

It is to be understood however, that the present invention is not restricted to any specific method of producing the array of weft threads, nor to any particular form of conveyor for the weft threads. It is necessary however that there should be some mechanism for producing the array of weft threads, and for conveying the weft thread array towards the nip of the front rollers 14 and 16.

For the purpose of the present invention, it is necessary to control the weft array from a position where it is being formed on the conveyors 20, to the nip of the front feed rollers 14 and 16. For this purpose, a control arrangement comprising top and bottom control belts 30 and 32 is provided closely adjacent to the insides of the conveyor coils 20 at each side of the weft space. It is to be understood, that the conveyor belts 30 and 32 may be quite narrow, and indeed they may be of circular cross-section. The belts are made of elastomeric material, and the top belt 30 extends around a roller coaxial with the front feed roller 14, and a driven roller 34 which is located alongside the helical coil 20 at that side of the weft space.Similarly, the bottom control belt 32 extends around a roller coaxial with the bottom front roller 16 and a driven roller 36 which is also adjacent to one of the helical coils 20, the arrangement of the rollers 34 and 36 being such as to produce an effective nip between them. It will be appreciated, that as the weft threads formed into the array by the weft supply mechanism and the helical conveyors 20 travel in the forward direction, the threads of that weft array become nipped between the inside runs of the belts 30 and 32 at each side of the weft space. In other words, from the nip of the rollers 34 and 36, control of the weft threads is taken over from the helical coils 20, to the nips of the belts 30 and 32 at each side of the weft space.Consequently, the weft threads are then carried forward by the nipping inside runs of the belts 30 and 32, to the nip of the front feed rollers 14 and 16, where the weft threads are delivered between the warp sheets 10 and 12, to produce the sandwich of weft and warp threads which is characteristic of the material being produced on the machine.

A weft cutting disc 38 is provided at each side of the weft space, and each of these discs is quite thin, and is located between the outside of the belts 30 and 32, and the inside of the adjacent helical coil 20 at that side of the machine. As is illustrated, the cutting disc 38 is located mainly on the bottom side of the horizontal path of travel of the weft array, but its top edge passes through that horizontal plane, so that as the weft threads are carried passed the cutters 38, they are severed by the cutters. This has the effect of cutting off the loops which are formed around the parts of the double helical coils 20 from the main laterally stretched portions of the weft threads.However, because by that stage, the weft threads are being controlled by the nip of the belts 30 and 32, the cutting off of the loops at the ends of the weft threads does not affect the lateral orientation of those threads. In other words, the weft threads are maintained in their proper weftwise orientation across the weft space as they travel beyond the cutting disc 38, towards the feed rollers 14 and 16.

The cutting discs 38 may be of the kind which are power driven, and rotate at very high speed to carry out the cutting operation. Alternatively, they may be of the type which engage with a cutting anvil, so that the weft threads are forced to pass between the disc and the anvil, thereby ensuring that severing of the loops from the remainder of the weft takes place.

Just in front of each of the weft cutters 38, there is a pneumatic suction nozzle 40 to suck away the loose ends of the weft threads which are cut off by the cutters 38. Instead of using a suction nozzle, there may be an exit nozzle, with a pneumatic jet for blowing the cut off ends of weft into the exit nozzle. Pneumatic removal of severed portions of threads is well known in the textile industry, and needs no further explanation.

After leaving the front rollers 14 and 16, the combined warp and weft threads 18 pass through a bath of adhesive, so that the warp and weft threads are caused to adhere to each other. The fabric may then be subjected to known drying methods, such as blowing hot air over the material, before it is wound up on a cloth roller. As this part of the operation forms no part of the invention, it is not described in detail.

It will be appreciated, that as the weft array is formed on the conveyors 20, the spacing of the weft threads is determined by the pitch of the coils of the conveyors, and consequently, the weft threads are fed towards the warp threads at a constant rate ("picks" per metre). However, the speed of the feed rollers 14 and 16 can be varied with respect to the speed of rotation of the conveyor coils 20, so that for example, the increment ofwarp thread fed between the rollers 14 and 16 during the time interval between the forward travel of two successive weft threads, may be varied. Thus, as illustrated in the drawing, whilst the weft threads have a relatively small spacing as they leave the conveyors 20, they have a much greater spacing where they leave the feed rollers 14 and 16.

This is because each weft thread can be pulled forwardly by the nipping action of the two warp sheets, without disturbing the following weft threads, since each weft thread lying across the weft space and held by the belts 30 and 32 is completely independent of the following weft threads. This is turn is arrived at by cutting the loops at the ends of the weft threads away from the remainder of the weft threads whilst the weft array is under the control of the belts 30 and 32. In practice, the machine may be equipped with a variable ratio gear box between the driving mechanism to the double helical coil conveyors 20 and the feed rollers 14 and 16, so that it is possible to vary the surface speed of the rollers 14 and 16 with respect to the horizontal travel of the weft array produced by the conveyors 20. It is this facility for varying the spacing between the weft threads without having to alter the conveyors 20, which distinguishes the machine of the present invention from previous machines of this kind. It will be appreciated, that it enables scrim fabrics to be produced with a wide variety of spacings between the weft threads, with no alteration to the machine itself other than adjustment of the variable ratio gear drive.

Claims

CLAIMS:

1. A method of producing a non-woven fabric of the kind having a substrate and weft threads5 comprises forming an array of weft threads between a pair of rectilinear conveyors and engaging loops of the weft threads at the ends of the weft space with the conveyors and then bringing the array of weft threads so formed into face-to-face contact with the substrate; cutting the ends of the weft threads, so that each weft thread is completely separated from adjacent weft threads, and preselecting the weft thread spacings ("picks" per metre) by selecting the longitudinal speed of the substrate relatively to the speed of forward travel of the conveyors.

2. A method of producing a non-woven fabric as claimed in Claim 1, in which the substrate is a sheet of warp threads.

3. A method of producing a non-woven fabric as claimed in Claim 1 or Claim 2, in which the weft threads are cut in advance of the position at which they are brought into contact with the substrate.

4. A method of producing a non-woven fabric as claimed in any one of Claims 1 to 3, in which the weft array is physically controlled from a position in advance of that where it is cut to at least a position adjacent to where it is brought into contact with the substrate.

5. A method of producing a non-woven fabric as claimed in any one of Claims 1 to 4, in which the loops at the ends of adjacent weft threads are cut off and removed by pneumatic means; adhesive is applied to the substrate and/or weft threads before the array of weft threads is brought into contact with the substrate, and cutting of the weft threads is carried out whilst the weft threads are still engaged by the conveyors.

6. Apparatus for producing non-woven fabric having a substrate and weft threads comprising: a pair of laterally spaced rectilinear conveyors which define a weft space between; weft laying apparatus for laying one or more weft supplies across the weft space and for engaging the ends of the weft threads with each of the two conveyors; cutting means for cutting the ends of weft threads adjacent to each of the conveyors and within the length of the conveyors; means for feeding at least one substrate longitudinally; means for bringing the substrate and an array of weft threads formed across the weft space into contact with each other and a variable speed device for varying the relationship between the speed of advance of the weft array and the speed of advance of the substrate.

7. Apparatus for producing a non-woven fabric as claimed in Claim 6, in which weft array control apparatus is provided for controlling the orientation and spacing of the weft threads between the cutting means and the means bringing the substrate and array of weft threads into contact with each other.

8. Apparatus as claimed in Claim 7, in which the control apparatus comprises travelling clamping means.

9. Apparatus as claimed in Claim 7, in which the control apparatus comprises parallel travelling nipping means extending at least partly across the weft space.

10. Apparatus as claimed in Claim 9, in which the control means comprises a pair of endless belts, the inside runs of which lie closely adjacent to each other to provide nipping means for weft threads extending across the weft space.

11. Apparatus as claimed in any one of Claims 6 to 10, in which the rectilinear conveyors comprise helical elements (similar to coil springs) rotating about their own longitudinal axes to provide a means for traversing the ends of the weft threads looped around parts of the helix.

12. A method of producing a non-woven fabric substantially as herein described with reference to the accompanying drawing.

13. Apparatus for producing non-woven fabric constructed and arranged substantially as herein described with reference to the accompanying drawing.