GB2118581A - Air nozzle for interlacing multifilament yarn - Google Patents

Abstract

An air nozzle for interlacing a multifilament yarn comprising a yarn passage which gradually expands from a central portion thereof towards an inlet opening forming a conical portion, and which has a narrow cylindrical portion from the central portion towards an outlet opening. Two jets are opened just at the border between the conical portion and the cylindrical portion. Fluid streams ejected by the jets generate primary vortices in the cylindrical portion and also secondary vortices in the conical portion. Accordingly a multifilament yarn passed through the yarn passage is at first opened by the secondary vortices and then entangled by the primary vortices. So a satisfactorily interlaced yarn is obtained using less air volume. An apex angle of the conical portion theta 1 and a cross angle between the jet and the yarn passage theta 2 are preferably in the range of 15 DEG to 60 DEG and 60 DEG to 90 DEG , respectively. <IMAGE>

Description

SPECIFICATION Air nozzle for interlacing multifilament yarn Field of the Invention This invention relates to an improved air nozzle for interlacing a multifilament yarn.

Description of the Prior Art A multifilament yarn such as a continuous synthetic fiber yarn is in general produced by means of a drawtwisting machine or a draw winder without any substantial twists being imparted to compact and unify the component individual filaments. The zero-twist yarn is unsuitable for treatment in may of the common textile operations, such as winding, weaving and knitting due to the looseness of the structure which permits individual filaments to separate and break out forming fluff balls, wraps, or similar defects.

To improve the above-mentioned defects, a system for interlacing a multifilament yarn was provided in U.S.P. No. 2985995 by W. W. Bunting Jr et al, in which vortices of fluid streams are exerted to the zero-twist multifilament yarn midway in the yarn passage and interlace the individual filaments so that they become collectively twisted, intertwined, and entangled in a random manner.

Based upon the above-mentioned interlacing system, a plurality of air nozzles generating vortices have been proposed. In general, the conventional air nozzles comprise a yarn passage in a form of a narrow tube, on an inner wall of which are provided jets for ejecting fluid streams.

Since the fluid stream is mainly effective in the confined area within the yarn passage, the resulting interlaced yarn tends to have an undesirable structure, in which entangled portions are unevenly distributed among non-entangled portions.

The present inventors proposed in Japanese Unexamined Utility Model Publication No.

55-46655, an air nozzle comprising a yarn passage 1 partially in a form of a narrow tube, on an inner wall of which are provided jets 2a', 2b' for ejecting fluid streams, said nozzle characterized in that the yarn passage 1 has a conical portion A gradually expanding toward an inlet opening 5, and at both sides of the inner wall of the conical portion A are opened the jets 2a', 2b' as shown in Fig. 3. According to the nozzle, a yarn structure having evenly distributed entangled portions can be successively obtained. However, more volume of the jetted fluid is required to develop a strength of entanglement in the resulting yarn compared to the conventional nozzle, because the fluid can easily escape through the conical inlet opening.

Summary of the Invention It is an object of the present invention to provide a novel air nozzle for interlacing a multifilament yarn improved in air consumption. Another object of the present invention is to provide an air nozzle able to impart a uniform structure of entanglement to a multifilament yarn with less volume of fluid jetted.

Further objects, features, and advantates of the present invention will appear more fully in the following description, referring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING Figure 1 shows a plan view of an air nozzle according to the present invention.

Figure 2 shows a frontal view of the air nozzle illustrated in Fig. 1, and Figure 3 shows a plan view of a prior air nozzle described in Japanese Unexamined Utility Model Publication 55-46655.

DETAILED DESCRIPTION OF THE INVENTION In Figs. 1 and 2, an embodiment of the air nozzle according to the present invention has a yarn passage 1 through its body 3. A slit 4 for inserting yarn to be treated into the yarn passage 1 is slotted on the upper side of the body 3 along the yarn passage 1. At the front half of a central portion 7, the yarn passage 1 expands gradually towards an inlet opening 5 to form a conical portion A. At the rear half of the central portion 7, the yarn passage 1 is straightened towards an outlet opening 6 keeping a narrow cylindrical shape to form a tubular portion B.

Two jets 2a and 2b are symmetrically pierced through the body 3 relative to a plane including an axis of the yarn passage 1, and are opened into the yarn passage 1 at the central portion 7 just on a border of the conical portion A and the tubular portion B of the yarn passage 1. The jets 2a and 2b are connected to a high pressure fluid source, such as a compressed air tank (not shown).

An angle B, between the axis of the yarn passage 1 towards the outlet opening 6 and the axes of the jets 2a or 2b is selected preferably from 60 to 90', and an apex angle O2 of the conical portion B is selected preferably from 15 to 60'. S and O2 selected within the above-mentioned ranges result in the best outcome. On the other hand, dimensions for the diameter and length of the tubular portion A are suitably selected from 1 mm to 3 mm and from 4 mm to 8 mm, respectively.

The multifilament yarn to be treated is introduced into the yarn passage 1, and fluid streams are applied from the jets 2a and 2b.

Since the fluid stream impinging on the yarn passage 1 immediately flows towards the inlet opening 5 due to the ejecting direction of the fluid stream and due to the shape of the conical portion B, secondary vortices in the vicinity of the inlet opening 5 arise. The yarn already introduced into the inlet opening 5 is at first separated in individual filaments by the secondary vortices and simultaneoulsy the relative positions of the individual filaments stagger each other.

Then, the yarn is subjected to primary vortices caused by a direct impingement of the fluid streams ejected from the jets 2a and 2b, and is fully separated and entangled in the narrow area of the tubular portion A.

According to the present invention, it is very important that the jets be placed just on the border of the conical portion and the tubular portion. If the jets are opened at the conical portion, the primary vortices become weaker and unable to fully entangle the individual filaments with each other. If the jets are opened at the cylindrical portion, the secondary vortices become weaker and unable to fully open the individual filaments with each other.

As stated above, the present invention is very advantageous in the textile industry, since an interlaced yarn having entangled portions uniformly along its length can be obtained with less fluid volume compared to the conventional nozzle.

Features and advantages of the invention are more clearly apparent by the following example showing characteristics of the yarns obtained by means of the above-mentioned embodiment.

In the example, two kinds of tests were adopted for evaluating the degree of interlacing; one is a "hook-drop test" described in the afore-said U.S.P. No. 2985995, and the other is a "floating on water test" (referring to F.O.W. test hereafter) proposed by the present inventors.

Hook Drop Test A sample of yarn approximately 100 cm long is clamped at one end in a vertical position under the tension provided by a weight in grams which is 0.20 times the yarn denier (but not greater than 100 grams). A weighed hook, having a total weight in grams numerically equal to the mean denier per filament of the yarn (but weighing not more than 10 grams) is inserted through the yarn bundle and lowered at a rate of 1 to 2 cm/second until the weight of the hook is supported by the yarn. The distance which the hook has traveled through the yarn characterizes the extent of filament entanglement. The test is repeated 100 times, and the mean value of the distance is expressed as a "coherency factor" which is defined as 100 divided by the mean value in centimeters.

F.O.W. Test A sample of yarn 100 cm long is put on a water surface at room temperature in tensionless state. The individual filaments of the sample are completely separated from each other in one minute in the tensionless state due to the surface tension of oil having been imparted to the surface of the yarn during the production, and only the really entangled portions remain unseparated. The number of the residual entangled portions is counted. The test is repeated 100 times and the mean value is calculated, which is representative of the evenness in the yarn structure.

Example: Filament yarn of cellulose diacetate (bright 75d/21f, oil content 2.0%) was prepared as a starting material. The yai-n was interlaced by means of the air noule according to the present invention shown in Figs. 1 and 2 at the rate of 950 m/min. and under the tension of 5 g at the inlet of the nozzle. The test was repeated three times (No. 1, 2, and 3) varying the pressure of air ejected from the jets. As the comparative, the same test was run four times utilizing the conventional nozzle shown in Fig. 3 (No. 4, 5, 6, and 7).

Characteristics of the yarns thus obtained are given in the table, in which D, and D2 indicate diameters of the yarn passage 1 and the jets 2a, 2b or 2a', 2b' respectively, I" 12, and 13 indicate lengths of the conical portion, cylindrical portion, and the distance between the central portion 7 and the jets 2a' or 2b' of the conventional nozzle, respectively, as shown in Figs. 1 and 3.

TABLE Coherency Factor (number / m) #1 #2 D1 D2 l1 l2 l3 Pressure of No. (degree) (degree) (mm) (mm) (mm) (mm) (mm) Air (kg/cm) Hook-Drop F.O.W.

1 85 38 2.5 0.5 7.5 7.5 - 2.0 12 0 2 " " " " " " - 3.0 18 2 3 " " " " " - 4.0 20 3 4 " " " 0.8 " 1.0 3.0 12 1 5 " " " " " " 4.0 25 3 6 " " 0.5 " " " 3.0 5 0 7 " " " " " " " 4.0 9 0 It is clearly apparent that according to the present invention, less air volume is required to obtain the same level of entanglement in the yarn structure compared to the conventional nozzle.

Claims (4)

1. An air nozzle for interlacing a multifilament yarn comprising a yarn passage, a rear half of which is a straight narrow cylinder forming a tubular portion and a front half of which gradually expands towards an inlet opening forming a conical portion, said nozzle characterized in that two jets for ejecting fluid stream into the yarn passage are provided just on a border between the tubular portion and the conical portion.

2. An air nozzle according to claim 1, in which an apex angle of the conical portion is within a range of 15 to 60 .

3. An air nozzle according to claim 1 or 2, in which a cross angle of the axis of the jet and the axis of the yarn passage directing towards the outlet opening is within a range of 60' to 90'.

4. An air nozzle for interlacing a multifilament yarn substantially as described herein with reference to Figs. 1 and 2 of the accompanying drawings.