GB2083089A - Apparatus for drawing-off and depositing continuous strands - Google Patents

Abstract

The apparatus comprises a driven rotor 2 having a vertical axis of rotation and bearing a plurality of oppositely rotated guide rollers 4 whose axes of rotation are at a small angle to the vertical, and means (comprising a passage 3) for directing a continuous strand of material 1 substantially tangentially onto one of the guide rollers 4 and around the apparatus in contact with all the guide rollers 4. In use, the strand passes around the apparatus in contact with each guide roller at least twice and is then allowed to pass off the guide rollers under gravity, and the rotor 2 is driven in a direction opposite to that in which the strand passes around the apparatus and substantially or completely neutralises the rotational speed of the strand. <IMAGE>

Description

SPECIFICATION Drawing-off and depositing continuous strands The invention relates to a method and apparatus for drawing-off and depositing continuous filament, strand or rope material, for example filament yarn, man-made fibres tow, wire, wire rope or string.

Since technological developments have led to ever higher rates of production and, consequently, of delivery or deposition, of continuous strands of material, it has become more and more difficult to achieve satisfactory deposition. At this stage, the material must be slowed down to a speed which allows deposition without causing damage or other undersirable changes in the material. For example, if a filament yarn or a man-made fibre tow is passed into a storage container at a production rate of more than 1800 m/min, impact causes bulging and spreading apart of the individual filaments. As a result, irregularities and, possibly, entanglement are observed during further processing and thus interruptions in production and waste.

If the material is slowed down prior to deposition, folds or loops are formed. Careful deposition which does not result in entanglement and allows subse quent trouble4ree withdrawal of the material from the storage container in which it is deposited, presupposes that the folds or loops are formed in a controlled manner and are regular in shape. A variety of proposals have been made for this purpose; operable systems have been brought into effect but, without exception, these show inadequacies which do not permit an increase in the rate of production, to values above 2400 to 3000 m/min.

Relatively, the most successful systems are those which lay the material in loops, e.g. by winding the material by means of a revolving yarn-guiding device onto a winding body which is stationary or revolves at a speed different from that of the yarnguiding device and is arranged concentrically with the axis of rotation of the yarn-guiding device, conveying elements being mounted in the winding body which convey the coils of material downwardly in an axial direction, the coils being allowed to fall into a storage container. The vertical conveying movement is produced, either by suitably arranged belt or chain conveying elements, or by means of screw or worm conveyors. Systems of this type are described in German Offenlegungsschriften Nos. 2633474, 2747 706 and 2809661.

The disadvantages of these known systems are manifest in the low tensile stress which can be applied to the material entering the arrangement.

Tests have shown that even loads of less than 2N result in disturbances, such as lap formation or interruption of the conveying action; it should be noted that the delivery mechanisms require minimum tensile stresses of about 1 N for satisfactory operation.

The range of variability of operating conditions is thus small, so that trouble-free continuous operation is made correspondingly difficult.

According to the present invention, apparatus for use in the drawing-off and deposition of a continuous strand of material comprises a rotor having a vertical axis of rotation, a plurality of guide rollers whose axes of rotation are inclined slightly to the vertical, and means for directing a continuous strand of material substantially tangentially onto one of the guide rollers and around the apparatus in contact with all the guide rollers.

According to a further aspect of the present invention, a method for drawing-off and depositing a continuous strand of material comprises passing the strand through apparatus of the invention, such that the strand passes around the apparatus in contact with each guide roller at least twice and is then allowed to pass off guide rollers under gravity, in which the rotor is driven in a direction opposite to that in which the strand passes around the apparatus and substantially or completely neutralises the rotational speed of the strand.

In use of the apparatus of the present invention, the material can be supplied at the rate of production and deposited in loops in a controlled manner. By comparison with the systems of the prior art, relatively large tensile stresses can be safely applied in continuous operation. In theory, the tensile stresses may be chosen as high as may be desired, limited solely by the drive imparted through the rotor to the guide rollers, the stability and strength of the com ponentparts, and the breaking strength of the material itself. The apparatus is of simple construction and yet allows deposition at very high rates of production, e.g. 6000 m/min.

It will be appreciated that, in order to ailow the strand which passes round the guide rollers to fall off those rollers under gravity, the rollers are suitably suspended from the rotor. By orienting these rollers at a small angle to the vertical, the strand is guided downwardly along a helical path. Once it passes from the ends of the rollers, the strand falls freely while maintaining its helical line which is, at most, drawn out by acceleration under gravity.

By driving the rotor in a direction opposite to that in which a strand passes around the apparatus, and substantially or, preferably, completely neutralising the circumferential speed of the strand, the strand does not perform any rotational/horizontal, but only downwardly vertical, movement.

The apparatus of the invention will usually be provided in a housing which has an opening to allow the strand to fall into a container positioned beneath the housing. The guide rollers may be caused to rotate by providing a gear on each and a stationary ring gear within the housing, such that each roller is geared to the ring gear. Alternatively, each guide roller may bear, frictionally, against a stationary rolling track. Preferably, each guide roller is in driving contact with a belt which passes through means which prevent the belt, when driven, from travelling vertically, at least to any substantial degree, as a result of contact with the rollers. Thus the belt is prevented from making the downward movement which is The drawing(s) originally filed was/were informal and the print here reproduced is taken from a later filed formal copy.

imparted to the continuous strand of material. The belt is preferably of circular cross-section.

The means for directing the continuous strand of material preferably comprises a passage through which the strand is directed downwardly along the axis of the rotor, and then radially outwardly. The strand may be forced into the passage using compressed air, with the aid of a conventional conveying injector device of the type usually employed for loading draw-off apparatus. Under the influence of centrifugal force, the radially-directed strand strikes against the wall of a housing, preferably at an annular perforated zone in the housing. By using suction means, the stand is sucked against the perforated zone and maintained there until, after a number of turns, it has been wound around the guide rollers.

On interruption of the flow of air, the strand passes along the rollers, downwardly.

There may be only two, but there are preferably at least three, more preferably at least four, and most preferably at least five, guide rollers. The guide rollers are preferably arranged symmetrically around the axis of the rotor. In plan view, the strand of material assumes a race-track or preferably, polygonal configuration (in which the corners of the polygon are replaced by curves determined by the curvature of the rollers). The polygon is preferably regular.

Each looping of the roller polygon by the material strand corresponds to a looping of a single imaginary roller and consequently to a looping angle of 27r radians. An initial tensile stress is produced at the lower end of the guide rollers by inertial forces in interaction with the friction between the rollers and the material, and the draw-off force proper of the apparatus builds up in the upward direction. This draw-off force increases exponentially from winding to winding in the direction opposite to the direction in which the thread runs and reaches its maximum at the point where the strand comes into contact with the guide rollers, e.g. at the exit from a passage as described.The initial tensile stress is produced by the continual radial acceleration to which the nonrotating material on the rotating roller polygon is exposed, in interaction with the friction between the material and the rollers.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a view of an embodiment of apparatus according to the invention from below; Figure 2 is a vertical cross-section of the embodiment shown in Figure 1 along the line A-A in Figure 1; and Figure 3 is a partially cut-away elevational section of a further embodiment of apparatus of the invention.

The principle of the operation of apparatus of the invention will first be described with relation to Fig ures 1 and 2 which show a strand of material 1 pas sing in the direction of the arrow along a passage 3 in a rotor 2, the passage bending radially outwardly at its lower end. The rotor carries six cylindrical guide rollers 4 whose axes are set at the points of a hexagon whose centre is the axis of the rotor 2. The guide rollers 4 are orientated at an angle ato the vertical. The strand 1 is guided via the passage 3 onto the periphery of one of the rollers 4 and from this roller in a helix, downwardly, over the remaining guide rollers. The apparatus is mounted in a housing 5 which is open at its lower end and the strand is allowed to fall freely off the rollers 4.

The rotor 2 is driven via a belt pulley 6 by means of a motor (not shown). The rotation of the rotor is A shown in Figure 7 as being clock-wise. The guide rollers 4 are set in rotation in the opposite direction,' also as shown by an arrow. The complementary rotation of the rotor 2 and the guide rollers 4 is achieved by means of gears 7 fixed on the shaft of the rollers 4, in contact with internal toothing 8 in the upper part 9 of the housing 5. The inclined setting of the rollers 4 is compensated by suitable toothing of the engaging teeth of the gears.

Figure 2 shows an annular perforated member 10 in the wall of the housing 5 surrounded by an annulay zone 13 from which air is drawn off through a duct 12 by suction apparatus (not shown).

Figure 3 shows an alternative embodiment of the invention, in which elements common to Figures 1 and 2 are designated by the same symbols. In the apparatus shown in Figure 3, the rotation of the guide rollers 4 is caused by a belt drive. A cord 14 having a circular cross-section is looped around the polygon of guide rollers 4 in the same way as the strand of material 1. The cord 14, however, is retained at each end in the wall of the housing 5.

Since it should not be allowed to pass downwardly like the strand 1, the cord 14 passes through bearings 15 and 16 which permit rotation of the cord 14 about its longitudinal axis. As a result of the interaction of the vertical movement caused by the guide rollers 4 and the possibility of free rotation ofthe cord 14 and its anchorage in bearings 15 and 16, the cord 14 rolls on the surfaces of the guide rollers 4, constantly performing an upwardly-directed rolling movement about its longitudinal axis.

The following Examples illustrate the invention.

Example 1 Apparatus according to the invention, as shown in Figure 3, having six guide rollers, has the following principal characteristics: Diameter of each guide roller: 50 mm Active length of each guide roller: 115 mm Corner dimension of the roller polygon over the 200 mFn periphery ofthe rollers: 200 mm Installed drive power: 6 kw Maximum rotor speed: 133.3 rpxn Maximum draw-off rate: 81 m/s Number of turns of yarn in contact with rollers: 12 A spun polyester yarn of 204 tex, consisting of 1000 individual filaments, was drawn off by means of this apparatus at a rate of 70 m/s and deposited in a cylindrical storage container which rotated about its vertrical axis below the apparatus. In the process, the yarn tension between the delivery mechanism (repeatedly looped pair of godets) and the deposition apparatus was measured by increasing the yarn tension until it began to stretch; a yarn tension of 6.4 N was measured. The power consumption of the motor was 715W. The progress of the work remained trouble-free. The pile of loops in the storage container showed geometricaliy faultless, cycloidally-shaped loops lying one on top ofthe other like scales. It was thereafter possible to draw off the whole of the yarn, which had a total weight of 53 kg, from the container without any trouble and free from loops.

Example 2 A tow of 2448 tex consisting of 12,000 individual fibrils wa's drawn off by means of the apparatus used in Example 1, under the same conditions as in Example 1. It proved possible to increase the tension of the tow to 55.45 N; the driving motor then reached its maximum permissible power consumption of 6 kW. There was no stretching of the tow. The structure of the deposited pile of loops was faultless and the material could be drawn off without any trouble.

Claims (15)

1. Apparatus for use in the drawing-off and deposition of a continuous strand of material, which comprises a rotor having a vertical axis of rotation and bearing a plurality of guide rollers whose axes of rotation are at a small angle to the vertical, and means for directing a continuous strand of material substantially tangentially onto one of the guide rollers and around the apparatus in contact with all the guide rollers.

2. Apparatus according to claim 1, which additionally comprises means for driving the rotor and the guide rollers in opposite senses, such that a strand of material passing in contact with the guide rollers undergoes no, or substantially no, rotation.

3. Apparatus according to claim 1 or claim 2, in which each guide roller is geared to a stationary ring gear.

4. Apparatus according to claim 1 or claim 2 in which each guide roller bears against a stationary rolling track.

5. Apparatus according to any preceding claim, in which each guide roller is in driving contact with a belt which passes through means which preventthe belt from travelling continuously downwardly vertically, as a result of contact with the rollers, when driven.

6. Apparatus according to claim 5, in which the belt is of circular cross-section.

7. Apparatus according to any preceding claim, in which the material-directing means comprises a passage through which the strand is directed along the axis of the rotor and then radially outwardly.

8. Apparatus according to any preceding claim, in which there are at least three guide rollers.

9. Apparatus according to claim 8, in which there are at least four guide rollers.

10. Apparatus according to claim 8, in which there are at least five guide rollers.

11. Apparatus according to any preceding claim, in which the guide rollers are regularly spaced around the axis of the rotor.

12. Apparatus according to claim 1, substantially as illustrated in Figures 1 and 2 of the accompanying drawings.

13. Apparatus according to claim 1, substantially as illustrated in Figure 3 of the accompanying drawings.

14. A method for drawing off and depositing a continuous strand of material, which comprises passing the strand through apparatus according to any preceding claim, such that the strand passes around the apparatus in contact with each guide roller at least twice and is then allowed to pass off the guide rollers under gravity, in which the rotor is driven in a direction opposite to that in which the strand passes around the apparatus and substantially or completely nullifies the rotational speed of the strand.

15. A method according to claim 14, substantially as described in either Example.