GB1564885A

GB1564885A - Apparatus for and method of interlacing continuous filaments

Info

Publication number: GB1564885A
Application number: GB572378A
Authority: GB
Original assignee: SNIA Viscosa SpA
Current assignee: SNIA Viscosa SpA
Priority date: 1977-02-23
Filing date: 1978-02-13
Publication date: 1980-04-16
Also published as: DE2807410A1; BR7801080A; ES466948A1; FR2381846A1; AR213890A1; JPS53119343A; IE46563B1; IT1075661B; FR2381846B1; IE780393L

Description

(54) APPARATUS FOR AND METHOD OF INTERLACING CONTINUOUS FILAMENTS (71) We, SNIA VISCOSA Societa Nazionale Industria Applicazioni Viscosa S.p.A., an Italian company, of 18 Via Montebello, Milan, Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an improved process and device for interlacing continuous filaments, in particular synthetic fibres.

It is known to effect the interlacing of continuous filaments, in particular synthetic fibres, by pneumatic means, viz. by projecting a transversal air stream on to bundles of parallel continuous filaments, while the bundles pass in the vicinity of or in contact with suitably formed solid surfaces. In a method and device of such a type, which is the object of previous Italian patents of the applicant, No. 700,695 and No. 1,007,563, the interlacing is effected by passing the bundle of continuous filaments in the vicinity of an essentially cylindrical surface and by projecting on the bundle a jet of air issuing from a nozzle the axis of which is preferably perpendicular both to the direction of travel of the filaments and to the axis of the cylindrical surface.In another process and device for the same purpose (Italian patents Nos. 623,506 and 657,666) the yarn (by which word is meant herein the bundle of parallel or nearly parallel filaments) is passed through a substantially cylindrical channel and the air jet is introduced into the channel substantially in the direction of a diameter thereof.

In any case, overlappings and intertwinings of the individual adjacent continuous filaments are produced by these processes and devices, whereby a coherency is imparted to the filament bundle which is sufficient to permit of employing it in textile processings without the need of twisting it.

Therefore the interlaced filament bundle is normally without twist or is possessed of a very low twist. The fibres preferably employed for this purpose are polyamide fibres, cellulose acetate or viscose rayon.

The degree of coherency thus imparted to the filament bundle is measured by the number of so-called "knots" or more properly "pseudo-knots", and standardized methods for measuring said quantities are set forth in the previously mentioned patents and will be further recalled, for the sake of clarity, in the present description.

Obviously the main cost of the interlacing operation derives from the use of compressed air, and this cost is sufficiently relevant to the general economy of the process. In the known processes and devices such cost is relatively high.

It is a purpose of the invention to provide a process and device which reduce the consumption of compressed air and the cost related thereto, the efficiency of the interlacing of the filament bundles being unimpaired.

Considering that, as has been said, every process for the pneumatic interlacing of filament bundles involves passing the bundle in the vicinity of or in contact with suitable solid surfaces, while it is subjected to the action of a compressed gas, practically air, jet, a distinction will be made, for the sake of clarity, in the following description, between two parts of the device, viz. the nozzle from which the compressed air issues, and what will be defined as the "guide and contact member" which is constituted by the remaining part of the device, having any known shape, within which or in the vicinity of which the filament bundle passes and with which it comes into intermittent contact, with the result that "pseudo-knots" are formed and the bundle is rendered coherent.From the view point of the process, it is possible separately to consider the operation of feeding compressed air to the zone through which the yarn passes, the deflection and control of the fed air jet in the zone through which the yarn passes, and finally the control and limitation of the motion of the filaments themselves by means of the guide and contact member.

The invention relates essentially to the compressed air feeding phase and correspondingly to the feed nozzle. The remaining phases of the process and correspondingly the yarn guide and contact member, may be of any kind. Although a particular device will be described for illustrative purposes, and consequently the stages of guiding the fed compressed air and the yarn will be carried out, in the illustrative examples, in a way which is in agreement with the structure of the guide and contact member thereof, these do not constitute a limitation of the invention, since any known guide and contact member may be used and correspondingly the operations of guiding the fed air and the yarn may be carried out in any known way and/or in any manner which is in agreement with the known means employed.

The invention is characterized in that the compressed air is accelerated in the vicinity of the point at which it is fed to the yarn passage zone, in such a way as to reach a supersonic speed and preferably a speed in the order of magnitude of 1-2 to 1-8 Mach.

From the viewpoint of the device, the invention is characterized in that the nozzle through which the air is fed to the yarn passage zone, comprises an inner passage way which in its end portion has a crosssection which increases from a constriction or throat having a minimum cross-section to the outflow cross-section.

Thus, according to the present invention, there is provided a method of interlacing artificial or synthetic filament bundles having low or no twist, which comprises causing a gas stream having its direction of flow perpendicular on average to the direction of travel of the filament bundle to impinge on the filament bundle while the filament bundle is caused to progress through an interlacing zone wherein its freedom of movement in a plane transverse to its direction of travel is limited and wherein the gas stream is deflected, the gas stream being led to the interlacing zone at supersonic speed.

The present invention also provides an apparatus suitable for use in the interlacing of artificial or synthetic filaments in bundles, having low or no twist, the apparatus comprising a feed device for producing a gas stream and including a nozzle having an axis perpendicular or substantially perpendicular to the intended direction of travel of a bundle of filaments and means for feeding compressed gas to the nozzle; and a contact and guide means comprising an open channel for limiting the freedom of motion of the filament bundle in a plane transverse to its intended direction of travel and for deflecting the gas stream emerging from the nozzle; wherein the nozzle has a throat and downstream thereof an outlet, the throat having a cross-sectional area smaller than that of the outlet, whereby the nozzle is adapted to accelerate gas fed thereto to supersonic speed.

Preferably, the cross-section of the nozzle passageway also increases through a certain distance towards the inside and consequently the end cavity of the nozzle is ideally constituted by two frusto-cones joined at their small bases or has a conformation which approximates said ideal conformation, including optional modifications or connections suggested by constructional convenience. When using the nozzle according to the invention, the air is fed with such a pressure as to have a sonic speed in the cited minimum cross-section or throat, whereas the flow is further accelerated and becomes supersonic in the divergent portion of the nozzle passageway which goes from the throat to its opening.

Preferably the dimensional and operative parameters of the device and of the process according to the invention are chosen in such a way that the pressure of the air at the nozzle outlet, viz. the discharge pressure of the compressed air, is substantially equal to the pressure of the surrounding environment, which is normally atmospheric pressure, instead of being significantly higher than the same as invariably occurs in the known devices and processes.

It has been found that the present invention attains the surprising result of permitting to employ amounts of air which are much lower, the coherency factor of the yarn being equal, viz. the number of "pseudo-knots" of the same being equal.

For a better understanding of the invention, reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 schematically illustrates an embodiment of the invention, the nozzle being shown in view and the yarn guide and contact member being shown in cross-section along the axis of the yarn, for illustrative reasons; Figure 2 is a cross-section of Fig. 1 taken along the nozzle axis; Figure 3 represents a part of Fig. 2, and precisely the nozzle, on a larger scale for the purpose of illustrating the dimensional parameters of the -embodiment; Figure 4 illustrates a conventional nozzle for comparative purposes, in a manner analogous to Fig. 3;; Figure 5 is a diagram which shows the flow rates of a nozzle according to Fig. 3 compared to those of a nozzle according to Fig. 4, the outlet cross-sections being the same, as a function of the relative pressure applied to the nozzle; and Figure 6 is a diagram which comparatively illustrates the coherency, expressed as the number of "pseudo-knots", achieved on the same yarn, as a function of the flow rate, employing the nozzles of Fig. 3 and of Fig. 4.

With reference now to the drawings, numeral 10 indicates the nozzle and numeral 11 indicates the contact and guide member for the yarn 12. In this particular embodiment, as is clearly seen in Fig. 2, the yarn guide and contact member has an approximately semicircular configuration and defines a semicircular channel through which the yarn passes, but as has been said, any different guide and contact member can be used, such as those illustrated in the patents hereinbefore mentioned or in the other numerous patents which concern this subject.

As is better seen in Fig. 3, nozzle 10 has a cylindrical body 16 which ends with a cross-section the diameter of which is indicated in the drawing by da. In the embodiment illustrated, the nozzle passageway tapers inwardly from this point thus defining a frusto-conical surface having a conicity angle p, until it reaches the minimum diameter in the throat 13 wherein the said diameter is indicated as dl. The frustoconical surface in question is indicated by 14. From throat 13 on, the inner surface of the nozzle has a frusto-conical configuration with increasing cross-section, in the zone indicated by 15, and with a conicity angle a, until it attains the outlet diameter d2.

Preferably, according to the invention, angle a has value lower than 10 degrees, and angle p has values from 10 degrees and 45 degrees. The ratio dt/da is from 0-2 and 0 7. The preferred pressure employed for feeding the nozzle is from 2-1 to 6-0 ab- volute atmospheres. In practical cases the diameter d1 is from 0-6 to 20 mm.

Figure 4 illustrates a nozzle of a known type, which is in normal industrial use and which may be considered typical of the known nozzles as to efficiency and general characteristics. The nozzle itself, generally indicated at 20, has a cylindrical portion 21, a short more or less conical tapered zone 22 and a cylindrical zone 23 having a constant diameter which extends to the nozzle outlet.

Figure 5 illustrates the comparative behaviour of the two nozzles according to Fig.

3 and Fig. 4 respectively, said nozzles having equal outlet cross-sections. The relative pressures Pr applied to the nozzle, expressed in relative atmospheres, are marked in the abscissae, and the flow rates Q expressed in normal litres per hour are marked in the ordinates. Curve A indicates the flow rate of the nozzle of Pig. 3 and curve B the flow rates of the nozzle of Fig. 4. As it is seen, the pressure and the outlet cross-section been equal, the flow rates of this latter, are much higher and consequently the amount of air consumed is higher.

The difference in the industrial result is evidenced by Fig. 6, wherein the flow rates in normal litres per hour are marked in the abscissae and the number of "pseudoknots", expressing the degree of coherency, are marked in the ordinates. The curve indicated by I defines the number of pseudoknots obtained by means of the nozzle of Fig. 3 and the curve II the pseudo-knots obtained by means of the nozzle of Fig. 4, which may be considered typical of con ventional nozzles. As it is seen, the pseudo knots being equal, there is a considerable reduction of flow rate with the nozzle according to the invention and consequently a considerable economy is achieved.

The pseudo-knots are measured by the method described in the cited Italian patent No. 657,666, page 4, from line 73 to 97.

The tests which have permitted to draw the curve of Fig. 6 have been carried out with the following parameters: Yarn: Polyamide 6 (polycapronamide), count 40 deniers 12 filaments, glossy polymer having a triangular cross-section- Speed of yarn feed to the nozzle zone: 500 metres per minute- Tension of the yarn in said zone: 15-20 gr.

The nozzles used in the tests had the fol- lowing specific dimensions and characteristics: for the nozzle according to the invention (Fig. 3) the ratio between the area of the throat (in correspondence to the diameter dE) and the area of the outlet crosssection (in correspondence to the diameter d2) was 0-845. The nozzle was calculated to operate with an applied pressure of 3 absolute atmospheres and an outlet stream speed of 1-5 Mach. These conditions correspond therefore approximately to the highest point of the curve A.The angle a was 5 and the angle p was 20 . The distance measured parallel to the nozzle axis from the throat (cross-section dl) to the outlet opening (cross-section d2) was 0-4 mm and the diameter d3 was 3 0 mm. The diameter of throat d1 was 0-8 mm. The nozzle according to the state of the art had equal outlet cross-section and maximum inner diameter equal to d3, viz. 3 0 mm.

In general the preferred ratios of the area of the throat to the area of the outlet crosssection are from 0-69 to 0-98 and the pre ferred ratios of the area of the throat to the maximum cross-sectional area of the nozzle cavity (in correspondence of the diameter d3) are from 0 04 to 0-49.

Claims

WHAT WE CLAIM IS:

1. A method of interlacing artificial or synthetic filament bundles having low or no twist, which comprises causing a gas stream having its direction of flow perpendicular on average to the direction of travel of the filament bundle to impinge on the filament bundle while the filament bundle is caused to progress through an interlacing zone wherein its freedom of movement in a plane transverse to its direction of travel is limited and wherein the gas stream is deflected, the gas stream being fed to the interlacing zone at supersonic speed.

2. A method according to claim 1, wherein the speed with which the gas stream is fed to the interlacing zone is in the range from 1-2 to 1-8 Mach.

3. A method according to claim 1 or 2, wherein the pressure of the gas at the point at which it is fed to the interlacing zone is approximately ambient pressure.

4. A method according to claim 1, 2 or 3 wherein the gas is supplied to a feed device having a nozzle provided with a throat which has a minimum cross-section and which precedes the outlet of the nozzle, the gas being accelerated to the supersonic speed at which it is fed to the interlacing zone in that portion of the nozzle between the throat and the outlet.

5. A method according to claim 4, wherein the pressure of the gas being supplied to the nozzle is in the range from 2'1 to 60 atmospheres absolute.

6. A method according to any preceding claim, wherein the limitation of the freedom of movement of the filament bundle and the deviation of the gas stream are produced by a contact and guide means having a concave surface in the form of part of a cylindrical surface having an axis parallel to the direction of travel of the filament bundle, the filament bundle being caused to progress through the space at least partially defined by the concave surface.

7. An apparatus suitable for use in the interlacing of artificial or synthetic filaments in bundles, having low or no twist, the apparatus comprising a feed device for producing a gas stream and including a nozzle having an axis perpendicular or substantially perpendicular to the intended direction of travel of a bundle of filaments and means for feeding compressed gas to the nozzle; and a contact and guide means comprising an open channel for limiting the freedom of motion of the filament bundle in a plane transverse to its intended direction of travel and for deflecting the gas stream emerging from the nozzle; wherein the nozzle has a throat and downstream thereof an outlet, the throat having a cross-sectional area smaller than that of the outlet, whereby the nozzle is adapted to accelerate gas fed thereto to supersonic speed.

8. An apparatus according to claim 7, wherein the ratio of the cross-sectional area of the throat to the cross-sectional area of the outlet is in the range from 0-69: 1 to 0-98: 1.

9. An apparatus according to claim 7 or 8, wherein the interior of the nozzle has a substantially frusto-conical inner surface between the throat and the outlet, the conic angle being less than 10 .

10. An apparatus according to claim 7, 8 or 9, wherein the interior of the nozzle has a region having a substantially frusto-conical inner surface, the cross-section of which increases in a direction opposite to intended direction of flow of the gas, and which is located immediately upstream (in terms of intended gas flow direction) of the throat, the conic angle of this inner surface being in the range from 10 to 45 degrees.

11. An apparatus according to any one of claims 7 to 10, wherein the contact and guide means has a cavity having the shape of a cylindrical segment with an axis parallel to the intended direction of travel of the filament bundle and provision for the introduction of the gas stream into the cavity and perpendicularly to its axis.

12. An apparatus according to any one of claims 7 to 11, wherein the ratio of the cross-sectional area of the throat to the maximum cross-sectional area of the interior of the nozzle is in the range from 0-04:1 to49:1.

13. An apparatus according to any one of claims 7 to 12, wherein the means for feeding compressed gas is capable of feeding the gas at a sufficient rate, and the conformation and dimensions of the apparatus are such, that the apparatus may be effected for carrying out the method according to claim 1, 2, 3 or 5.

14. An apparatus according to claim 7, substantially as hereinbefore described with reference to, and as illustrated in, Figures 1, 2 and 3 of the accompanying drawings.

15. A method according to claim 1, whenever effected in an apparatus as claimed in any one of claims 7 to 14.