US3062081A - Apparatus for severing and sorting staple fibre bundles - Google Patents

Description

Nov. 6, 1962 N. J. BOND ETAL 3,

APPARATUS FOR SEVERING AND SORTING STAPLE FIBRE BUNDLES 2 Sheets-Sheet 1 Filed NOV. 30, 1959 .3 m L ,e m mm m n o woH 1 1 3 J M e Nov. 6, 1962 N. J. BOND ETAL APPARATUS FOR SEVERING AND SORTING STAPLE FIBRE BUNDLES Filed NOV. 30, 1959 2 Sheets-Sheet 2 COUNTER PIILsE D PIILsE mAI IPLIEIER- B AMPLIFIER 6 &SHAPER BRO E '7 20 I POWER ELECTRONIC x AMPLIFIER IEW Inventors:

Norman Jo/m Bond, 7 Cl/ve William Hooper United States Patent ()fifice 3,062,081 Patented Nov. 6, 1962 3,062,081 APPARATUS FOR SEVERING AND SORTING STAPLE FIBRE BUNDLES Norman John Bond, Llanrumney, Cardiff, Wales, and Clive Williams Hooper, Newport, England, assignors to British Nylon Spinners Limited, Pontypool, Engand Filed Nov. 30, 1959, Ser. No. 856,065 Claims priority, application Great Britain Dec. 13, 1958 4 Claims. (Cl. 83--79) The present invention relates to apparatus for the manufacture of staple fibre, and more particularly to those apparatuses known as staple fibre cutters.

Staple fibre is defined in Textile Terms and Defininitions published by the Textile Institute in September 1954 as Man-made fibres of length and fineness suitable for conversion into yarn by established methods. Before the discovery of the fully synthetic filaments such as polyamides or polyesters it was already the practice to make staple fibre, which could thus be spun into yarn like natural fibres, by cutting up the continuous filaments of cellulosic artificial silk or rayon. The staple fibre cutters already proposed for this purpose are very numerous indeed. Some, for instance, are described in British specifications Nos. 317,025, 375,356, 384,335, 451,987, 639,466, 725,977 and 726,246. In many cases the cutters have been specially designed to cope with the fully synthetic filaments, e.g. polyhexamethylene adipamide, polyethylene terephthalate, since these tend to present more difficulty on account of their greater toughness as compared with cellulosic artificial silk. Examples of cutters of this nature are to be found in British specifications Nos. 682,473, 688,845 and 720,233. The type of disc cutter described in British specification No. 289,028 is frequently employed. This specification is in the name of Societa Italiana Lavorazioni Meccaniche who were the assignees of A. Beria. Such cutters are consequently often known as Beria cutters and may be defined as apparatuses for cutting a bundle or tow of continuous filaments into staple fibre comprising a rapidly rotating disc having an internal radial channel conveying the continuous filaments, impelled by centrifugal force, from the centre to the periphery of said disc, where a knife, positioned substantially tangentially thereto, cuts the issuing bundle of filaments into tufts of staple fibre. These apparatuses or machines may contain a plurality of channels and/ or knives and many modifications thereof have been proposed (compared, for example, British specifications Nos. 482,976, 506,712, 507,280, 641,262, 679,039, 685,564, 743,943). None of these staple fibre cutters, however, is relevant to the present invention although some are concerned with the avoidance of the occurrence of long fibres in the resulting staple fibre, that is to say, fibres longer than the desired staple length.

The reasons for the occurrence of long fibres may be classified under two heads:

(1) Long Fibres Due to Faults in the Working of the Machine Thus the knife may fail to cut all the filaments in the tow presented to it by the revolving disc. This may arise from the knife becoming blunt; it may also be due to a few of the filaments being blown out of the emergent bundle by the draught and lying back close to the circumference of the disc so that they fail to meet the knife edge squarely and brush past it without being cut.

(2) Long Fibres Due to Faults in the Tow Filaments may be present in the tow which are coiled or folded back upon themselves. It will be clear that this circumstance can lead to the filament severed being over-long.

Whilst long fibres due to faults in the machine are usually a multiple of the correct staple length, those arising from adventitious faults in the tow are of variable length.

Moreover, although the first class of long fibres could theoretically be avoided by perfect adjustment of the machine, conditions under which, assuming the tow to be faultless, no long fibres are produced, are not found to be an economic and/ or practicable proposition in the course of commercial practice. Furthermore, the second class of long fibres is not attributable to the machine, and consequently no adjustment thereof can prevent their occurrence.

Attention has therefore been turned to modifying the cutter by incorporating a device whereby any tufts containing long fibres, or any other predetermined tufts which it is desired to segregate, are automatically separated fromthe main production of the cutter.

For this purpose it is necessary (a) to detect the predetermined fibres, the tufts resulting from which are to be segregrated and (b) to segregate them. Accordingly the device has two parts, viz. (1) the predetermined fibre detector and (2) the tuft sorter.

The tuft sorter of the invention is designed to operate on receipt of an electric signal from the detector of the predetermined fibres. Thus suitable electric control of the sorter enables the tufts to be segregated at will. In the course of manufacture of the filaments intended to be cut up into staple fibre, for example, during the meltspinning of synthetic filaments, such as polyhexamethylene adipamide, it occasionally happens, owing to some maladjustment of the apparatus or defect in the polymer employed, that the quality of the resulting filaments is below the standard required. The fault may be discovered during the melt-spinning or when the filaments are undergoing some subsequent process, e.g. drawing. Provided, however, that arrangements are made to mark the faulty filaments in such a way that the mark can be detected during the cutting up of the filamentary tow into staple fibre, and caused to produce an electrical sig nal, then this signal can be used to operate the tuft sorter so that the tufts made from these predetermined filaments, i.e. the faulty filaments are automatically segregated. Examples of some suitable methods of marking the filaments for this purpose together with the means of detection are listed below:

Means of Detection coumarin Ultraviolet fluorimeter. Magnetic material e.g.

magnetite Pick-up coil.

In addition to tufts containing long fibres, the tuft sorter will thus also segregate tufts cut from faulty continuous filament tow, or other predetermined filaments.

Various forms of detector and sorter can be employed, as can also different types of cutter, for instance the Beria cutter. Rather surprisingly, it has thus been found possible notwithstanding the extremely high speed at which staple fibre cutters norm-ally work, to devise means for rapidly detecting the presence of the predetermined fibres in any cut tuft of staple fibre by causing their presence to generate an electrical or mechanical signal which is conveyedto the tuft sorter so that the latter segregates the oifending tuft, from the stream of severed tufts issuing from the cutter. Numerous conventional techniques may be adapted to this end. For example the predetermined fibres may be strongly illuminated, and in their turn reflect light into a photoelectric cell, producing an electrical signal which, after appropriate amplification, operates a solenoid which moves a vane or shutter in the duct carrying the stream of staple fibre tufts so that the tuft containing the predetermined fibres is diverted from the main stream and so separated from the other tufts.

Accordingly the present invention relates to an apparatus for the manufacture of staple fibre, comprising means for cutting a bundle of continuous filaments into staple fibre, wherein said bundle is fed towards a cutting zone and cut by a knife into tufts of staple fibre, means for detecting the presence of predetermined fibres or filaments, the tufts resulting from which are to be segregated from the main production of the cutter, whereby the presence of such fibres or filaments produces an electrical signal, and means for sorting the tufts of staple fibre, operated by said signal and adapted to segregate any tufts containing the predetermined fibres and separate them from the other tufts.

The means for cutting the continuous filaments may comprise, as already indicated, numerous different types of apparatus, but is preferably a Beria cutter. Such a cutter may work at a speed of 1200-1600 revolutions per minute. Conveniently a travelling knife is employed therewith as described in British specification No. 679,039.

In the drawings, which are schematic:

FIGURE 1 is a side view of a Beria staple fibre cutter;

FIGURE 2 is a front view of the cutter of FIGURE 1;

FIGURE 3 is a fragmentary side view on an enlarged scale of the cutter of FIGURE 1 in a different position;

FIGURE 4 is a block diagram illustrating the electrical circuit for the detector and sorter; and

FIGURE 5 is a view on a reduced scale similar to FIGURE 3 and showing a travelling knife.

In the following description, the predetermined fibres referred to are long fibres, but, as already indicated above, the apparatus of the present invention is also applicable to other sorts of predetermined fibres which it is desired to segregate.

One means of detecting the presence of long fibres, namely, by the reflection of light into a photoelectric cell has already been mentioned. Alternatively there may be employed mutatis mutandis other wavelengths of electromagnetic radiation with corresponding source of radiation and receiver, for example, ultra-violet light produced by a mercury vapour lamp and a photoelectric cell sensitive only to ultra-violet light.

Another detector means comprises an electric capacitor suitably positioned so that any long fibres present alter the capacity thereof thus generating an electric signal. Electrical circuitry adapted to translate the capacity change due to a fibre into an impulse or signal is described in our copending application No. 34657/ 55. Reference is also made in this connection to British specifications Nos. 744,754 and 772,049.

Another detector means comprises a sensitive element such as the protruding electrode of a mechanico-electronic transducer valve (obtainable from the Radio Corporation of America) against which the long fibres, if and when present, strike mechanically, giving rise again to an electric signal. Numerous other electrical devices are known for converting a minute mechanical displacement, such as that occasioned by the long fibre colliding with a suitably positioned anvil, into the desired electrical signal. Such devices are often referred to as transducers. The following articles are cited as descriptive of these devices.

Electronic Engineering, 1952, September, p. 420, A Linear Transducer for the Electrical Measurement of Displacement by M. J. Tucker.

Electronics, 1953, January, p. 105, Measuring Minute Capacitance Changes, by G. W. Cook.

Electronic Engineering, 1953, February, p. 66, A Differential Transformer Gauge and Amplifier for Measuring Small Displacements, by D. T. R. Dighton.

Wireless World, 1954, June, p. 275, Piezo-electric Crystals, by S. Kelly.

Again very sensitive electrical means are available for detecting the presence of an electrostatic charge on a moving thread, and these means can be conveniently applied to register the presence of the undesirable long fibres in the tufts of stable fibre by means of a charge carried thereon. Either the electrostatic charge itself or the field due to the charge can be measured. Details of some of the methods adopted for this purpose are to be found in the following references.

(1) Enka and Brecla Rayon Revue (English Edition) published by International Rayon Trading Co., Arnhem, Holland, 1953, page 8; corresponding to the Dutch edition of 1952, vol. II, page 253Static Electrification of Textile Yarns, by V. E. Gonsalves and B. J. van Dongeren.

(2) Textile Research Journal, 1955, vol. XXV, page 279, Static Electrification of Filaments, by S. P. Hersh and D. J. Montgomery.

(3) British Journal of Applied Physics, 1953, supplement II, Static Electrification, page 47, Two Electrostatic field-meters, by A. S. Cross.

It has to be pointed out that the detector is not necessarily arranged so as to detect the presence of longfibres at the stage when they already form part of a (faulty) tuft. As soon as a tuft has been incompletely severed, for instance, the unsevered filaments exist, and it is these which form long fibres in the next tuft to be cut. Thus, for example, in the case of the Beria cutter, which is fully illustrated below, the knife is intended cleanly to cut off the piece of protruding tow. Any filaments which, for any reason, escape being cut, will be carried round during one more revolution when they, in the form of long filaments, meet the knife again. Now it is convenient to detect the uncut filaments at as early at stage as possible, in order to afford time to segregate the tufts before they break up. It is consequently advantageous to detect uncut filaments, which give rise to tufts with long filaments, shortly after they leave the knife.

The necessity for extremely rapid action, already mentioned in connection with the long fibre detector, applies equally to the sorting means adopted to segregate any tufts of staple fibre containing long fibres. Nevertheless a number of techniques are available for this purpose or capable of adaptation to fulfill the desiderata of the apparatus of the present invention.

The device of a vane or shutter in the staple fibre duct, designed to switch the tufts from one channel to another and operated by a solenoid, has already been alluded to. Many varieties of electro-rnechanical transducers may, however, be employed. The essential condition, that the transducers must satisfy, is that the ratio of torque or thrust to inertia should be sufficiently large to enable the sorter to switch over quickly enough, in view of the usual high rate of travel of the tufts. Such transducers can be described as devices producing a mechanical force between two members in consequence of the inter action of two magnetic fields, at least one of which is determined by the input current, i.e. by the signal from the detector. Examples of these transducers are:

(1') moving coil vibrator, wherein a helical coil is sup ported in the air gap of a magnet and produces an axial force when current passes through the windings of said coil.

(ii) balanced armature torque motor, in which an electric impulse causes the armature to turn the output shaft through a small angle.

(iii) rotary solenoid, in which a rotary motion is imparted to an attracted armature by means of ball bearings running in a helical track. (iv) high torque electromotor, wherein the torque/inertial ratio is large.

A convenient arrangement is one in which the transducer, e.g. a balanced armature torque motor, does not operate the vane or shutter directly, but instead actuates the controlling valve system or a hydraulic servo-mechanism or other amplifier, which itself works the vane or shutter.

Other types of tufts sorter exhibiting suitably rapid action may, however, be mentioned by Way of example, as follows:

(1) electromagnetically controlled pneumatic tuft sorters; (2) electrostatic sorters.

In the case of the pneumatic sorters, the main duct carrying all the tufts may have perforated side walls followed by a bifurcation or division into two ducts, one for the good tufts and one for the bad. The perforated side walls permit a blast of air to be directed in either direction across the main duct, so as to convey the tufts into the desired duct at the bifurcation. The air blast is turned on electromagnetically as a result of the electric signal produced by the detector, as already described above. It must be pointed out, however, that in View of the high velocity with which the tufts usually move, as they come from the cutter, the air blast should be applied over a length of duct amounting to several metres, to enable adequate deflection of the tufts to occur. The necessary deflection may be ca. 3 cms. In this case an air flow across the duct moving at 30 rn./sec. is satisfactory.

The operation of the electrostatic sorters depends on (a) charging the tufts and (b) submitting them to an electorstatic field in order to move the tufts at right angles to the stream thereof coming down the duct from the cutter. The electrostatic field is switched on by the electric signal coming from the detector and is applied to the stream of tufts just before it reaches the bifurcation or division into two ducts. The tufts are accordingly delivered to one duct or the other in obedience to the signal from the detector, and in this way the faulty tufts, i.e. those containing long fibres are separated from the good tufts of staple fibre.

As mentioned Beria staple fibre cutters may run at speeds of 1200-6000 revolutions per minute. It is accordingly preferred that the detector and sorter adopted for use in the present apparatus shall be capable of operating in less than -50 milliseconds.

The following embodiment of the invention is described with reference to the accompanying diagrammatic drawings by way of illustration and not by way of limitation.

FIGURE 1 shows the rotor 1 of a Beria staple fibre cutter in its housing '2 viewed from the side. The speed of the rotor is 2950 revolutions per minute corresponding to a peripheral speed of 70.7 metres per second. Through the funnel 3 there enters a tow, consisting of 80,600 filaments of polyhexamethylene adipamide and having a total denier of 120,900. Thus each filament has a denier of 1 /2. The tow enters the rotor at a speed of 100 meters per minute. The tow is expelled by centrifugal force through the radial channel 4, emerging at the nozzle 5. 6 is the photo-electric cell having a caesiumantimony photocathode with a blue-sensitive spectral response, which produces an electric signal on picking up light from fibres near the tip of the nozzle 5. These fibres are strongly illuminated by rneans of the light source 7, slit system 8 and mirrors 9. It will be observed that the beam of light, which is rectangular in crosssection passes through a correspondingly shaped aperture 10 in the rotor.

FIGURE 2 gives a front view of the rotor and is correspondingly numbered, the arrow indicating the direct3 tion of rotation. In this figure there is also shown the knife 11.

FIGURE 3 illustrates (on a larger scale) the edge of the rotor 1 where the knife 11 is, and shows the arrangement of ducts and light moving vane of aluminum. At 12 are seen the filaments streaming from the nozzle 5 just before severance by the knife 11. The arrow shows the direction of movement of the rotor. The severed tufts of fibres fall into funnel 13 and are directed thence by the moveable vane 14, hinged at 2 1, into the duct 15. With the vane in the other position, shown dotted at 16, the severed tufts are precipitated into the duct 17. The vane 14 is actuated by a moving coil vibrator 18, which operates the driving rod 20, pivoted at 19. As seen in FIGURE 5, the knife may be provided with means for moving the same longitudinally of itself so as to present fresh portions of the cutting edge to the filaments 12' issuing from the nozzle 5' in the disc 1'. The moving means 30 is connected to the knife 11' so as to move the latter in the direction of the arrow 31. After the knife 11' has traversed substantially its own length, the moving means 30 returns it to its starting position.

The mode of operation of the apparatus is as follows. Let it be supposed that the knife 11 in FIGURE 2 fails to cut all the filaments of the tow protruding from the nozzle, when severing a tuft of fibres. The tuft severed will have fibres of correct length but the remaining uncut filaments will then stream from the nozzle 5 as shown at 22 in FIGURE 2, and are detected, in the positionthere shown, by the beam of light and photoelectric cell '6 which forms part of the electrical system, to be described below. As a result the coil vibrator 18 moves vane 14 as shown in FIGURE 3 to position 16. The next tuft cut contains long fibres and accordingly falls into duct 17.

The sensitivity of the detector may be examined by considering the case in which only one filament of denier 1% is left uncut. Using as light source 7 a 24 Watt tungsten filament lamp, and as photomultiplier i.e. the photoelectric cell, a Mazda 27M1 unit, that one 1% denier fila. ment produces millivolts, which is ample after amplification to warm the vane. Larger clumps of uncut filaments may give rise to a signal of 10 volts.

The time available for the detector and sorter to act can be calculated as follows. Since the speed of the rotor is 2,950 revolution per minute, the time of one revolution is 20.34 milliseconds. Now it Will be observed that the nozzle arrives at the detection position after the rotor has turned approximately 45 from the position at which the knife cuts the tuft. The rotor has therefore to revolve a further 315 i.e. A; of a revolution before the next tuft is cut. This takes 17.8 milliseconds.

The transmit time of the vane can be approximately estimated as follows. The effective mass of the vane at the driving pivot 19 (assuming a small angle of rotation) is 50 grams, being 8 /3 times its actual mass of 6.0 grams, since the driving rod 20 operates at the pivot 19 which is two-fifths of the way from the hinge 21 to the centre of inertia of the vane. To be added to this is the mass of the coupling rod 20, namely 2 grams and that of the transducer coil assembly, 8 grams, making a total moving mass of 60 grams. The transducer, supplied with a current of 1.5 amperes, generates a steady force of 600 grams weight so that the acceleration produced, neglecting friction and air resistance and electrical lag (if any), is 600+60=10 times that of gravity. The excursion of the driving rod 20 needed to move the vane from duct 15 to duct 17 is 2.5 mm. The time taken to move the vane under these corditions may accordingly be calculated as 7 millisecon s.

Although the transit time of the vane may be considerably greater that the above estimate owing to air resistance etc., the present tuft sorter is in fact easily capable of sufficiently rapid action for use with a fast rotating Beria cutter.

The block diagram in FIGURE 4 illustrates the electric-al circuit. Here 6 and 14 denote the photoelectric cell and moveable vane, respectively, as previously numbered. The signal or pulse emitted by the photoelectr c cell 6, as and when fibres, giving rise to long fibres in tufts, are detected, is amplified and shaped at 24. The pulse then passes to a modified Schmitt trigger circuit 25, which is used as a coincidence circuit and pulse broadener. It is explained that, by way of excluding adventitious extraneous electrical interference, the Schmitt trigger circuit is adjusted, so as only to operate, when it receives a signal from the photoelectric cell '6 substantially at the same instant as its reception of a pulse originating in a coil 23 placed close to the rotor which bears a small permanent magnet. The latter is so positioned that the first positive pulse from the coil, coincides with the response from the photoelectric cell (if any). When the circuit 25 is triggered, a long positive pulse passes to the pulse amplifier 26, which is a small thyratron, and thence to the electronic latching relay 27. The latter is an Eccles- Jordan bi-stable state circuit. This circuit receives at every revolution of the rotor and at the same time as the pulse coming from the amplifier 26, if any, also a pulse from the coil 23. Now the pulse from the amplifier 26, if present, overrides the pulse from the coil 23, and sets (or retains) the electronic relay in the position which operates the transducer 18 via the amplifier 28 and thus moves the vane to position 16 (see FIGURE 3) so as to switch the faulty tuft into duct 17. If there is no signal from the photoelectric cell, after the next cut, that is to say if at that time all the filaments are severed "(though that particular tuft will contain long fibres) then the pulse from coil 23 operates so as to restore the relay circuit 27 to the other position, whereby the vane returns to its former position 14, and the next tuft cut i.e. a good tuft of correct fibre length falls into duct 15.

At 29 in FIGURE 4 is a counter which registers the pulses coming through from the photoelectric cell 6, that is to say, the number of cases of fibres, giving rise to a tuft with long fibres, which have been detected by the apparatus. After the apparatus has been running for 5 minutes, the proportion of tufts containing long fibres is determined by means of the detector and counter and found to be one tuft in 9% tufts.

The effectiveness of the segregation of tufts containing long fibres !by the apparatus just described is demonstrated by the following data:

Number of long fibres per million fibres out Apparatus Production Discarded bres fibres Beria cutter of prior art (no segregation of 120 bad tufts).

Apparatus of present invention less than 10..-- 1,080

What we claim is:

1. Apparatus for the manufacture of staple fiber from a bundle of continuous filaments comprising: means for cutting the bundle of continuous filaments into tufts of staple fiber filaments, said means including a rotatable disc having an internal radial channel for continuously conveying the continuous filaments radially outwardly and knife means adjacent the periphery of said disc for cutting the filaments issuing from said channel into tufts; means for transmitting electromagnetic radiation across a path which is travelled by filaments issuing from said radial channel, said path being rearwardly of said radial channel in the direction of rotation of said disc, the rotation of said disc causing filaments issuing therefrom to fan rearwardly of said radial channel, said issuing filaments including predetermined filaments which cause interruption of said electromagnetic radiation; means for detecting the interruption of said electromagnetic radiation by the predetermined filaments; means synchronized with said detecting means for sorting the tufts of stable fiber filaments and segregating tufts containing said predetermined filaments from other tufts upon severing thereof.

2. Apparatus as claimed in claim 1 wherein said transmitting means transmits electromagnetic radiation across the path of filaments extending beyond said channel and uncut in the severing of a tuft of staple fiber filaments from the bundle of continuous filaments whereby said uncut filaments constitute the preselected filaments and further wherein said sorting means segregates the next-cut tuft.

3. Apparatus as claimed in claim 1, wherein the means to;l detecting the presence of the fibres is a photoelectric ce 4. Apparatus as claimed in claim 1 wherein the knife is a traveling knife.

References Cited in the file of this patent UNITED STATES PATENTS 2,232,496 Thompson Feb. 18, 1941 2,447,976 Curtis Aug. 24, 1948 2,617,528 Moore Nov. 11, 1952 2,765,035 Tucker Oct. 2, 1956

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