GB2040322A - Yarn stapling - Google Patents

Abstract

Apparatus for drawing newly- spun and dressed glass filaments from a bushing includes a cutter operable to cut the filaments whilst wet into staple fibres, the cutter comprising a first roll having a plurality of generally radially directed blades projecting a relatively short distance (i.e. less than 1.5 mms) from its surface, and a second, back-up roll having a resilient surface, said first and second rolls being mounted with their axes substantially parallel so that the projecting portions of said blades engage the resilient surface so as to be fully embedded therein at the region of contact between the rolls, said region of contact constituting the working zone of the cutter.

Description

SPECIFICATION Improvements in or relating to the production of glass fibres Technical field of the invention This invention relates to the manufacture of staple glass fibres by cutting of newly-formed filaments drawn directly from a bushing.

The prior art Glass filaments are produced by rapid attenuation of cones of molten glass formed at the orifices of a heated bushing. It is usual to produce a relatively large number of filaments simultaneously; these are drawn off, treated with an aqueous dressing/size which may contain up to 10% by weight of solids and then collected by winding as a bundle into a package. This package may then be converted into staple fibres, in a separate operation, by unwinding the filaments and passing them through a cutter.

This is a dry or partially dry cutting process because the dressing/size applied to the newly-spun filaments facilitate winding and handling is usually at least partly dry by the time the material reaches the cutter. The filaments may, however, be converted to staple fibres in a rather different manner, by cutting directly from the bushing, without any intermediate winding step. In this case, the cutter may be used to draw/attenuate the filaments from the bushing.

Because the dressing/size composition is applied to the filaments just before they reach the cutter, the cutting operation is necessarily carried out wet.

Because of this, the filament bundle tends to slip on the cutter blades. Furthermore, this effect is accentuated by the fact that the filaments are not stuck together; they are in a highly "split" or dispersed state. One wet cutting process and apparatus is described in US Patent 3,869,286; another arrange mentis described in US Patent 3,815,461. Common to both of these and indeed to other glass fibre staple cutters is the use of a rotary cutter comprising a first rollerwith radially-directed blades projecting from its surface with a second, back-up roller provided with a resilient surface. The two rollers are mounted with their axes parallel and with the tips of the blades in contact with the resilient surface of the back-up roll.It is common practice for the cutter roll to be driven, the back-up roll being freely rotatable and driven only through contact with the blades and the filaments being cut.

Description ofthe invention According to the present invention, apparatus for drawing newly-spun and dressed glass filaments from a bushing includes a cutter operable to cut the filaments whilst wet into staple fibres, the cutter comprising a first roll having a plurality of generally radially directed blades projecting a relatively short distance from its surface and a second, back-up roll having a resilient surface, said first and second rolls being mounted with their axes substantially parallel so that the projecting portions of said blades engage the resilient surface so as to be fully embedded therein at the region of contact between the rolls, said region of contact constituting the working zone of the cutter.

Contrary to previous practice in this regard, the wet filaments are gripped between the tips of the blades and the back-up roll and also between the first roll and the back-up roll in the working zone.

This is made possible by the fact that the blades only project a relatively short distance from the surface of the first roll. In this context, a relatively short distance means that the blades project no more than 1.5mm from the roll surface and preferably no more than 0.5mm. The minimum projection practicable is of the order of 0.1 25mm for satisfactory cutting.

Hitherto, blade projections in the range 3mm to 9mm have been used, effectively preventing the blades from being fully embedded in the resilient surface because of the wear that would inevitably result. Because of this, the major load on the cutter has been on the tips of the blades, which have not only exerted a pulling load on the filaments, but also on the back-up roll.

It has been found that the use of a relatively short blade projection in accordance with the invention has significant advantages. Because the filaments are more positively gripped, the cutting action is also more positive, having a stretch-breaking characteristic, as opposed to simple cutting. Furthermore, because the working zone is completely cushioned in that the projecting portions of the blades are fully embedded in the resilient surface of the back-up roll, the noise level generated by cutting is reduced. A further, but related reduction in noise occurs because of the short distance by which the blades project from the first roll; it is the projecting portions of the blades which cause air movement and associated resonance effects, depending on the rotational speed of the first roll.Whilst the resonance effect is still present, its amplitude is significantly reduced because the blades project less and therefore tend to displace less air.

Surprisingly, despite the blades being fully embedded in the back-up roll in the region of contact, blade wear is apparently reduced relative to conventional blade projections, although some dulling of the cutting edge occurs. Most of the operational wear occurs in the resilient surface of the back-up roll and it is relatively simple and inexpensive to replace this surface as necessary. However, it has also been found that this operational wear can be made more even over the whole surface of the back-up roll by arranging for the axis of rotation of one or other of the two rolls to be slightly tilted relative to the other, so that although the line of contact between the rolls is parallel to both oftheir axes of rotation in one plane, it is at a slight angle to one of them in a plane normal to the first plane.In this way, the blades do not tend to repeatedly engage the same parts of the back-up roll and the wear is evened out somewhat. Furthermore, because the whole length of a blade does not strike the resilient surface at the same instant, the impact noise is reduced in amplitude.

Description ofa preferred embodiment In order that the invention be better understood, one preferred embodiment of it will now be de scribed by way of example with reference to the accompanying drawings in which Figure I is a diagrammatic end view of a first roll provided with a plurality of generally radially directed cutter blades projecting therefrom, Figure2 is a section through the roll of Figure 1, taken on the line A-A thereof and further showing a drive shaft and bearings therefor, and Figure 3 is a schematic view taken in the direction of Figure 1 and showing the first roll in operative relation to a second, back-up roll for cutting a plurality of glass filaments into staple fibres, in accordance with the invention.

As far as practicable like parts in all three figures bear the same numerical designations. Referring to the figures a roll 4, (the "blade roll") carries a plurality of radially directed cutter blades 5, retained by end caps 6 and associated machine screws 7. In this particular example, 50 blades were used. The blades are seated in grooves in a central boss 8 which is supported by a drive spindle 9 to which it is attached by a locknut 10. The spindle 9 is journalled in a bearing 11 which is supported by a tube 12. The rest of the spindle 9, its associated drive means and the tube 12 are conventional and are not shown as they need not be discussed in further detail in the present context.

Referring in particular to Figure 3, the roll 4 is mounted with its axis parallel to the axis of rotation of a freely-rotatably mounted back-up roll 13 having a resilient surface layer 14. The spacing between the axes of rotation of the two rolls 4 and 13 is adjusted so that the exposed tips 15 of the blades 5 are fully embedded in the resilient surface layer 14 at the point of contact (the working zone) 16 (in plan view, this is of course a line of contact constituting a nip between the rolls.) To facilitate this, the back-up roll is adjustably mounted for movement in a line through the centres of the two rolls and through the point of contact 16.

In operation, a plurality of continuous glass filaments 21 is fed from a bushing (not shown) to the cutter assembly around a guide 17. This guide 17 is supported by a traverse mechanism (not shown) which causes itto reciprocate in a path parallel to the axis of the back-up roll so as to distribute the filaments over at least a major part of the width of the nip 16, thereby evening out wear on the cutter. In the working zone, the filaments are gripped both by the blades and between the surfaces of the two rolls.

The back-up roll is of course driven only through contact with the blade roll. From the working zone, a stream 19 of staple fibres falls for collection in the usual way. The assembly is partly enclosed by a cover, 20 in the interests of safety and of reducing noise.

In the embodiment shown, a conventional ancillary press roll 18 is provided to hold the filaments against the resilient surface layer 14 of the back-up roll as they progress towards the working zone. This roll is freely-rotatable and driven only through surface contact with the back-up roll. It should be noted that the use of this press roll is optional and in fact it is preferred to omit it. Although such press rolls have been used previously to improve the pulling effect of the back-up roll on the continuous filaments, the use of the technique of the present invention renders a conventional press roll unnecessary in most instances. This is a further advantage of the invention.

Claims (7)

1. Apparatus for drawing newly-spun and dressed glass filaments from a bushing including a cutter operable to cut the filaments whilst wet into staple fibres, the cutter comprising a first roll having a plurality of generally radially directed blades project; ing a relatively short distance from its surface and a second, back-up roll having a resilient surface, said first and second rolls being mounted with their axes, substantially parallel so that the projecting protions of sàid blades engage the resilient surface so as to be fully embedded therein at the region of contact between the rolls, said region of contact constituting the working zone of the cutter.

2. Apparatus according to claim 1 wherein said blades project no more than about 1.5mm from the surface of the blade roll.

3. Apparatus according to claim 1 wherein said blades project no more than about 0.5mm from the surface of the blade roll.

4. Apparatus according to any preceding claim wherein the blades project from the surface of the blade roll a distance in the range of from 0.125mm to 0.5mm.

5. Apparatus according to any preceding claim wherein the axial spacing between the blade roll and the back-up roll is adjustable.

6. Apparatus according to any preceding claim wherein the axis of rotation of one of said rolls is slightly tilted relative to the axis of the other roll, so that the line of contact between them is parallel to both axes in one plane, it is at a slight angle to one of said axes in a plane normal to the first plane.

7. Apparatus according to any preceding claim further including an ancillary press roll mounted in running contact with the back-up roll and disposed so as to hold filaments against said back-up roll as they are carried thereby to the working zone of the cutter.