US3773453A

US3773453A - Apparatus for the manufacture of crimped bulky filaments

Info

Publication number: US3773453A
Application number: US00127330A
Authority: US
Inventors: H Hino; M Saki; Y Maezawa; T Nakamura; N Takahashi
Original assignee: Teijin Ltd
Current assignee: Teijin Ltd
Priority date: 1971-03-23
Filing date: 1971-03-23
Publication date: 1973-11-20
Anticipated expiration: 1990-11-20

Abstract

Improved apparatus by which a variety of crimped bulky filaments of uniform quality having desired crimp characteristics can be prepared with great operational advantages regardless of variations of the amount of the shrinkage of the filaments that cannot be avoided during the operation, by making it possible to fix in a stationary manner the point of separating crimped filaments from the screen at a desired and optional point without necessitating any performance of operational controls which are practically difficult or impossible, and various disadvantages in respect of the quality of the product and of the process operation that are inevitable in the known process because of the variations of the amount of the shrinkage of the filaments can be overcome.

Description

United States Patent 11 1 Hino et al.

[ Nov. 20, 1973 APPARATUS FOR THE MANUFACTURE OF CRIMPED BULKY FILAMENTS Inventors: Hazime Hino, Osaka; Magoichi I Saki, Itami; Yoshihiko Maezawa,

Kyoto; Tsutomu Nakamura, Minohara; Nobuo Takahashi,both of Osaka, all of Japan [73] Assignee: Teijin Limited,Osaka,Japan [22] Filed: Mar. 23, 1971 [21] Appl. No.: 127,330

Related US. Application Data [62] Division of Ser. No. 5,224, Jan. 23, 1970, abandoned.

52 US. (:1. 425/223, 28/1.4, 57/157 F, 425/224 51 1m. (:1. D02g 1/16 [58] Field 1 Search 425/84, 223, 224; 28/1.6, 1.4, 72.12; 57/157 F [56] References Cited UNITED STATES PATENTS 3,143,784 8/1964 Scott 29/l.4 X

Primary ExaminerRobert L. Spicer, Jr. AttorneySherman and Shalloway [5 7 ABSTRACT Improved apparatus by which a variety of crimped bulky filaments of uniform quality having desired crimp characteristics can be prepared with great operational advantages regardless of variations of the amount of the shrinkage of the filaments that cannot be avoided during the operation, by making it possible to fix in a stationary manner the point of separating crimped filaments from the screen at a desired and optional point without necessitating any performance of operational controls which are practically difficult or impossible, and various disadvantages in respect of the quality of the product and of the process operation that are inevitable in the known process because of the variations of the amount of the shrinkage of the filaments can be overcome.

12 Claims, 18 Drawing Figures PATENTEUNUV 20 I973 SHEET 2 OF 3 APPARATUS FOR THE MANUFACTURE OF CRIMPED BULKY FILAMENTS RELATED U.S. APPLICATION This application is a division of U.S. Pat. application Ser. No. 5,224, filed Jan. 23,- 1970, now abandoned.

This invention relates to apparatus for improving a known process for preparing crimped bulky filaments by impinging thermoplastic synthetic continuous filaments in a heated jet stream upon a moving screen having numerous perforations, passing the stream through the screen while leaving the filaments on the screen to thereby form crimps in the filaments and separating from the screen the crimped filaments which have been cooled according to the movement of the screen, which apparatus can provide excellent crimped bulky filaments of uniform quality having desired crimp properties with great operational advantages regardless of variations of the amount of the shrinkage of the filaments that cannot be avoided during the operation, wherein the point of separating the crimped filaments can be fixed in a stationary manner at a desired and optional point, whereby various disadvantages in respect of the quality of the product and of the process operation that are inevitable in the above known process because of the variations of the amount of the shrinkage of the filaments can be overcome without necessitating any performance of controlling the feed rate of the filaments, the velocity of impinging the filaments in a heated jet stream upon a moving screen and the velocity of separating and collecting the crimped filaments from the screen according to the variations of the amount of the shrinkage of the filaments, such controls being, from a practical standpoint, difficult or impossible.

More specifically, this invention relates to an improvernent of the above known process, characterized in that at the point where the crimped filaments are separated from the screen means is provided to push the filaments on the screen to thereby fix the separating point in a stationary manner.

There has been known a process for the preparation of crimped bulky filaments which comprises projecting thermoplastic synthetic continuous filaments such as continuous filaments of polyamides and of polyesters from a nozzle together with a heated stream of compressible fluid, impinging the projected thermoplastic "synthetic continuous filaments in a heated jet stream upon a moving foraminous surface such as a rotating screen disk or a screened endless belt, passing the stream through the foraminous surface while leaving thereon the continuous filaments plasticized by the heated fluid, which is generally heated air or other heated gas, forming crimps in the filaments by the impingement of the filaments in a plasticized condition upon the foraminous surface, and taking up from the foraminous surface the crimped filaments which have been cooled according to the movement of the surface (see U.S. Pat. No. 3,156,028 and Canadian Pat. No. 636,056).

It is "easily understood that in the preparation of crimped bulky filaments of this type, unless the force retaining on the screen crimped bulky filaments formed 'byimpingement of thermoplastic synthetic continuous filaments in a heated 'jet stream and in a plasticized conditionis kept substantially constant,-'even when the separation of the filaments from the screen is-effected roll side. The force retaining the filaments on the,

screen is influenced by various factors such as the configuration and perforation ratio of the screen, the kind of the filaments, the number and denier of the monofilaments, the total denier of the filaments, the rate of feeding the filaments to the jet, the temperature of the jet stream, the rate at which the filaments in a heated jet stream impinge against the screen, and the moving velocity of the screen. If these factors be kept substantially constant, it would be possible to keep constant the filament-retaining force, with the result that the point at which the filaments are separated from the surface of the screen would not vary if the take-up of the filaments is effected at a constant rate and under a constant tension.

However, in practical operation, even if the operation is carried out while controlling the above factors so as to prevent the change of the separating point, it is impossible to substantially avoid the change of the separating point, though the change differs in degree to some extent according to circumstances, and it is impossible to foresee occurrence of the change at all. This unavoidable and unforeseeable change of the filamentseparating point is a great cause for variations in the quality of the product. Indeed, it would be easy to say that such change could be overcome by conducting the continuous operation while changing the take-up tension according to the change in the force of retaining the filaments on screen. However, in the actual operation it is extremely difficult to provide such control, because it is impossible to foresee occurrence of such change in the filament-retaining force.

As a result of various research made with a view to solving the above technical problem, we have found that even when the abovementioned various factors are conditions, and even when these factors are made constant during the preparation of starting filaments, the variation of the amount of the shrinkage is observed among monofilarnents. Particularly in the filaments wound up onto a bobbin after the drawing, the amount of the shrinkage is apparently different between filaments in an inner layer of the pim and those in an outer layer of the pim. The difference of the temperature between the upper and lower limits of the prescribed temperature range gives a considerable variation to the amount of the shrinkage. Although it is highly desirable to:avoid such variation of the amount of the shrinkable in the filaments-as much as possible, various technical and economical limitations are imposed on attainment of such trial in the actual operation. And, we have finally found that it is quite unreasonable to try to provide starting filaments in which the change or variation of the amount of the shrinkage might be reduced to a negligible extent, in the preparation of crimped bulky filaments of the type intended in this invention.

Accordingly, we have furthered our research with a view to overcoming various disadvantages in respect of the quality of the product and of the process operation by fixing the above-mentioned point of separating the filaments from the screen by other means which may be industrially applicable, and to our great surprise it has been discovered that crimped bulky filaments of a uniform quality having desired crimp characteristics can be obtained regardless of the unforeseeable variation of the amount of the shrinkage in filaments by utilizing extremely simple means that have neither been conventionally adopted in the preparation of crimped bulky filaments of this type nor suggested to result in great industrial advantages.

Further, a high speed processing operation is made possible by adopting said means. In the conventional process and apparatus, in case the take-up rate reaches, for instance, 500 m/min or more, since the take-up point comes nearer the projecting point of the nozzle, the time for fixing crimps becomes insufficient, with the result that the operation becomes substantially impossible. In contrast, in accordance with the process and apparatus of this invention, such high speed operation is made possible and the separation of the filaments can be effected at a desired and optional point stationarily.

Still further, in the conventional process and apparatus, in case filaments are fed at a constant rate and taken up at a constant rate, the variation of the amount of the shrinkage in the filaments results inevitably in the shift of the point at which the filaments are recovered from the screen and hence in the change of the distance along which the filaments are cooled (the cooling time). Accordingly, in the conventional process and apparatus it is necessary to excessively prolong the distance for cooling in expectation of occurrence of such change or variation. It has been also found, however, that such disadvantage can be overcome by adopting said simple means in accordance with the apparatus of this invention.

Still in addition, it has been found that in accordance with this invention it is possible to overcome another disadvantage of the conventional process and apparatus that since the shift of the separating point changes the time required for cooling and solidifying the filaments crimped by impingement on the screen, if the operation is effected while maintaining the stretching tension at a constant level at the take-up point, the filaments are stretched under different temperature conditions and hence, unevenness of the percentage crimp is caused to appear along the filament length.

Still further, in accordance with the apparatus of this invention, since the point at which the filaments are separated from the screen surface can be made stationary at a desired and optional point, it is possible to vary the stretching tension at the take-up point within a broad range and hence provide crimped filaments rich in variety with improved uniformity and operability at low costs, which the conventional process and apparatus fail to provide.

Accordingly, a primary object of this invention is to provide improved apparatus by which a variety of crimped bulky filaments of uniform quality having desired crimp characteristics can be prepared with great operational advantages regardless of variations of the amount of the shrinkage of the filaments that cannot be avoided during the operation, by making it possible to fix in a stationary manner the point of separating crimped filaments from the screen at a desired and optional point without necessitating any performance of operational controls which are difficult or impossible from a practical standpoint, and various disadvantages in respect of the quality of the product and of the process operation that are inevitable in the known process because of the variations of the amount of the shrinkage of the filaments can be overcome.

Another objects and advantages of this invention will be apparent from the description given hereinbelow.

The above object of this invention can be achieved by the feature that in conducting the above known process, at the point where the crimped filaments are separated from the screen an action of pushing the filaments on the screen is given to the filaments to thereby fix the said separating point in a stationary manner.

For better illustration, the process and apparatus of this invention will be now detailed by referring to the accompanying drawings wherein;

FIG. l-A is a broken perspective of apparatus for preparing crimped bulky filaments utilizing a rotary screen disc;

FIG. 1-8 is a broken perspective of apparatus for preparing crimped bulky filaments utilizing an endless screen belt;

FIG. l-C is a broken side elevation of apparatus for preparing crimped bulky filaments utilizing a suction device for maintaining the filament separation point stationary;

FIG. 2 is a top plan view of the rotary disc and conical pressing roll apparatus of FIG. l-A;

FIG. 3-A is a side elevation in section of a nozzle for use with the apparatus of the present invention;

FIG. 3-8 is a side elevation in section of a conventional nozzle producing turbulent flow;

FIG. 4-A is a diagrammatic illustration of the assembly screen of the present invention;

FIG. 4-8 is a diagrammatic illustration of the operation of conventional screens;

FIGS. S-A and S-B are top plan views of assembly screens for use with the present invention;

FIG. 6-A is a side elevation in section of an assembly screen disc for use with the apparatus of FIG. l-A;

FIGS. 6-B and 6-B' are elevations of support structure for an assembly screen in accordance with the apparatus of FIG. l-B;

FIGS. 7-A, 7-B and 7-C are broken side elevations in section of nozzles for use with the apparatus of the present invention;

FIG. 8-A is a side elevation of an additional nozzle for use with the apparatus of FIG. 1-8; and

FIG. 8-B is a bottom plan view of the projecting outlet of the additional nozzle of FIG. 8-A.

There has been well known an operation of preparing crimped bulky filaments which comprises impinging thermoplastic synthetic continuous filaments in a heated jet stream upon a moving screen such as a rotary screen disk, an endless screen belt or a screen drum, passing the stream through the screen perforations while leaving the filaments on the screen to thereby form crimps in the filaments, and separating from the screen the crimped filaments which have been cooled according to the movement of the screen.

As the typical example of the above known operation, embodiments using a rotary screen disk and an endless screen belt are illustrated in FIGS. l-A and l-B. In these embodiments, at the separating point an action of pushingcrimped filaments on the screen is given to the filaments by means of a pressing roll 1 in accordance with this invention, and the separating point is fixed.

In FIG. l-A, filaments f are fed at a constant rate to a jet 6 via, for instance, a guide 5 by means of feed rolls 3,4. The filaments are accompanied by a heated jet stream projected from the jet 6 and are impinged upon a screen disk 7. The stream passes through the screen, while the filaments, which have been impinged on the screen in a plasticized condition, are left on the screen. Thus, crimps are formed in the filaments. According to the rotation of the disk (the rotation direction is indicated by an arrow in the Figure), the filaments are cooled and the separating point is fixed at a suitable point on the screen by means of the pressing roll 1. The filaments are taken up from the screen surface at the fixed separating point via, for instance, a guide 5 by means of delivery rolls. (not shown) similar to feed rolls 3,4.

In case a screen of the type shown in FIG. l-A is used, it is important to use a pressing roll 1 of a conical configuration, a plan view of which is shown in FIG. 2, because a smooth rotation cannot be attained by a pressing roll of a cylindrical configuration. In the case of a screen of the above type, the filaments move on a locus of the circle of a radius indicated as rf in FIG. 2 according to the rotation of the screen while they are being cooled. In order for the conical pressing roll to rotate smoothly at the prescribed, filament-separating point according to the rotation of the screen, it is essential that among maximum diameter D and minimum diameter D of the pressing roll, and distance r, from the center of the screen to the point of said maximum diameter and distance r, from the center of the screen to the point of said minimum diameter, there be established a relation meeting the equation of D /R, D /r Thus, the screen and pressing roll can be rotated with- ;out causing any slip.

The pressing roll may be positively driven and rotated, or a free roll may be adopted as the pressing roll. .In short, any means can be adopted in this invention, as "far as they may impart an action of pushing filaments on the screen (not by an excessive force but preferably,

'a force as mild as possible) to the filaments at the separating point. For instance, an apron roll, a pressing rod (snubbing rod an air suction pump 23 disposed on the .side of the screen opposite the take-up roll, as shown ,in FIG. l-C and the like may be used in addition to-the jabove mentioned pressing roll. In the case of an air suction pump, an action of pushing the filaments on the .screen can be imparted by causing a force of sucking the filaments on the screen downwardly via the screen.

FIG. l-B illustrates a similar embodiment where the operation is conducted in the same manner as above iexcept'that a screen of an end-less belt type is used in- ,stead of the above screen disk (feed rolls are not shown). The screen 7 spread onto

rolls

8,8 rotated by [suitable means is moved by the rotation of the

rolls

8,8

(the rotation direction is indicated by an arrow in the Figure), and filaments are fed and impinged upon the screen to be crimped in the manner as above. Then, they are cooled according to the movement of the screen and taken up from the screen at the prescribed separating point fixed by a pressing roll 1 in the same manner as in the embodiment shown in FIG. l-A.

.In the embodiment illustrated in FIG. I-C, a suction device 23 is disposed beneath screen 7 at the separa tion point for the filaments f, the suction device receiving air under pressure at an inlet port 24 and expelling the air at an outlet port 25 to create suction at a suction port 26. The suction port 26 is disposed on the side of the screen 7 opposite the take-up roll 27 for the filaments in order to hold the filaments against the screen at the separation point.

In this invention, the position at which the separating point is made stationary can be freely changed by changing the position at which means for imparting the pushing action to the filaments are placed, whereby various modifications may be optionally devised. In addition, the configuration of crimps once formed in the filaments on the screen may be also changed by varying the pushing action, the force of driving the pressing roll, the take-up rate, the take-up tension, etc., with the result that it is possible to obtain filaments whose crimp characteristics are variant in a broad range.

In short, in this invention, since the point at which the crimped filaments are separated from the screen can be made stationary, the time during which the filaments are cooled according to the movement of the screen can be also made constant, and a suitable take-up tension may be freely selected. Therefore, it is possible to obtain a product of uniform quality at a high speed operation. It becomes also possible to attain high productivity by projecting filaments on one screen from a plurality of jets.

As described above, the take-up tension may be changed optionally in this invention. However, in case the take-up tension is very high, there is a tendency that while crimps are made latent under the tension, some of monofilaments constituting continuous filaments slacken and rise at some points of the filament bundle along the length thereof. Accordingly, when it is intended to apply the product in an untwisted condition directly to a knitting, weaving or tufting operation, such slack in the monofilaments are likely to cause such operational troubles as yarn breakages and entanglements. In such case it is preferable that the take-up tension is adjusted to below 0.1 g/d when the crimped filaments are separated and taken up from the screen surface. By controlling the take-up tension as above, it is possible to prevent occurrence of slack in the monofilaments, and a product which may be applied directly in an untwisted condition to a knitting, weaving or tufting operation can be obtained advantageously. The above upper limit of the take-up tension may be preferably determined depending on the denier of the filaments. For instance, in the case of filaments of a high denier such as in filaments for carpets, it is recommendable to adjust the take-up tension to below 0.05 g/d.

In this invention it is preferable to use a jet of a type capable of projecting a heated and compressed gaseous fluid accompanying thermoplastic synthetic continuous filaments in a laminar flow without forming a turbulent flow and of impinging the filaments in the heated jet stream against the screen in the state of parallel bundles. The use of a jet of such preferred type prevents the filaments impinged against the screen from scattering at random, and is effective for not only imparting uniform crimps to the filaments but also improviing the percentage crimp, which will be defined below, while increasing the impinging effect. Further, the use of a jet of such type is helpful to reduce the variation in the force of retaining the filaments on the screen.

FIG. 3-A illustrates the section of a typical example of the jet meeting the above requirements, and FIG. 3-B illustrates the section of an example of a conventional jet which forms a turbulent flow therein.

The jet illustrated in FIG. 3-A comprises a housing 13 including a space 2 in which a heated and compressed gaseous fluid is filled, and a passage 2 connected with said space 2 for projecting the fluid; an inlet 14 provided for feeding the fluid to said space 2 in the housing 13; and a guide needle is for the filaments provided coaxially with said passage 2' to penetrate said housing 13, said guide needle 15 running through said space 2 and extending in the passage 2 at a length of less than one-half of the whole length of said passage 2 to form an annular passage 2" for the fluid between said needle 15 and the inner wall of said passage 2'.

In FIG. 3-A, filaments which have been fed through a filament passage provided in the guide needle 15 from a filament inlet 15' are projected from the nozzle end in a plasticized condition together with a heated jet stream which has been passed through the annular fluid passage 2" and the projection passage 2'. With the use of a jet of the above structure, it is made possible to impinge a heated jet stream accompanying thermoplastic synthetic continuous filaments on the screen in the laminar flow state without forming a turbulent flow that is generally caused when a conventional crimping nozzle is used.

In FIG. 3-A the guide needle 15 is composed of one member, but it can be easily understood that the guide needle may be composed of two members corresponding to the thinner tubular portion and the block-like upper portion in the Figure, respectively. The connection of the guide needle 15 and housing 13 may be effected by insertion, hinging or any other means capable of combining them in a substantially air-tight manner.

The end point of the guide needle 15 extends into the projection passage 2' and reaches the intermediate point of the passage 2' while forming the annular passage 2". This feature promotes an action of separating and opening individual nionofilaments constituting the continuous filaments and directing them to the screen without causing a turbulent flow, namely without forming any substantial disorders or entanglements. The extending length of the guide needle 15 (indicated as AL in the Figure) is shorter than one-half of the whole length of the projection passage 2. In case the length AL is longer than the above limit, though the effect of directing the filaments to the screen is heightened, it is likely that an action of sucking cool open air from the filament inlet 15' to the filament passage in the guide needle is too strong. In constrast, in case this extending portion is not provided, a backward flow of the heated and compressed gaseous fluid into the filament passage of the guide needle is likely to be too conspicuous. In short, it is preferable to adjust the length of the extending portion of the guide needle so that a light backward flow of the gaseous fluid may be allowed to occur. In

general, the length AL of the extending portion is shorter than one-half of the whole length of the passage 2' (inclusive of the length of the passage 2"), preferably shorter than 1.5 mm.

The introduction of the outer air into a nozzle by suction generally results in weakening the effect of heightening the temperature of filaments and bringing about other causes for unevenness in the filaments. Such temperature or heating unevenness results finally in the dyeing unevenness. Accordingly, it is preferable to conduct the operation in a manner such that a little backward flow may be allowed to occur. This backward flow may be not only utilized for pre-heating the filaments but also helpful to reducing the temperature or heating unevenness to thereby attain a uniform dyeability in the product filaments.

FIG. 3-B illustrates an example of the conventional nozzle (for instance, a taslan nozzle) that causes inevitably a turbulent flow. In case such nozzle is used as a jet, filaments introduced from the filament inlet 15 un dergo a violent turbulent action under the influence of the fluid introduced from the fluid inlet 14, and they are convoluted to scatter randomly at the impingement on the screen surface, with the result that the impinging effect is much lowered, the percentage crimp of the product yarn is bad and a uniform processing effect cannot be expected.

In this invention, it is possible and preferable to use an assembly screen previously proposed by some of the co-inventors of this invention US. application Ser. No. 847,548 filed on Aug. 5, I969 while effecting the fixation of the separating point according to this invention.

More specifically, it is recommendable to impinge the filaments in a heated jet stream on an assembly screen comprising at least two adjacent layers of screens and passing said stream through portions of perforations of the lower screen overlapping each perforation of the uppermost screen under a resistance greater than that given when the stream has passed through the uppermost screen.

Although this type of an assembly screen is explained in detail in the above mentioned patent application, a brief description will be now given thereto in this specification.

The above assembly screen can cause an action like that of a stuffing crimper in the screen depth through which the fluid passes, and can impart to the filaments crimps of a high percentage crimp, say, about 40 percent, which value could never be obtained by the conventional process, without substantial increase of a disadvantageous reflection of the jet stream from the uppermost screen.

The above type of an assembly screen comprises at least two adjacent layers of screens wherein a plane perforation area of each portion of the lower screen overlapping each perforation of the uppermost screen is smaller than the plane area of each perforation of the uppermost screen and said portion of the lower screen overlapping each perforation of the uppermost screen has an open space sufficient for the jet stream to pass through said portion and freely escape from the assembly screen. It is preferable that the spacing or degree of adjacency of the screen layers is in the range of from the state where the screen layers are in contact with each other to the state where a distance of about 2 mm is formed between the screen layers, and that the perforation ratio of the assembly screen is in the range of from 30 to 70 percent.

FIG. 4-A is a diagram illustrating the principle of the operational effect attained by the use of such assembly screenfFIG. 4-B is a similar diagram illustrating the principle of the conventional process. FIGS. S-A' and S-B illustrate diagrammatically planes of two embodiments of the assembly screen. Other modifications are explained in detail in the above-mentioned prior application Ser. No. 847,548.

A section of an assembly screen comprising two adjacent layers of screens is shown in FIG. 4-A. A portion of the upper screen composed of

metallic wires

16,16 l6, and a portion of the lower screen composed of

metallic wires

17,17 17 are shown in the Figure. Jet stream projected in the direction indicated by arrows in the Figure impinges against the screen and passes through it while leaving filaments in a plasticized condition in the assembly screen. In this case, the jet stream which has passed through, for instance, the perforation between two

neighbouring wires

16,16 of the upper screen, is obstructed by wire 17 of the lower screen at a portion of the lower screen overlapping the perforation between

wires

16,16 of the upper screen (said portion corresponds to an area indicated by a in the Figure). As a result, the jet stream passes through the lower screen under a resistance greater than that imposed thereon at the upper screen. However, the jet stream can pass through said lower screen easily only with an increased resistance being imposed thereon. Accordingly, the passage of the jet stream through the assembly screen causes a crimping action in the screen depth. It is as if a stuffing crimper of a small size were provided, Such crimper-like space is formed with respect to each perforation of the upper screen. The assembly screen acts as if it were constructed with numerous small crimpers. Thus, the filaments undergo numerous folding crimping actions, and numerous folded crimps are formed in the filaments as shown by dotted lines in the Figure.

On the other hand, in accordance with the conventional process, the principle of which is illustrated in FIG. 4-B, such a multiple-crimper action is not caused to occur, and only coarse crimps shown by dotted lines in the Figure are formed in the filaments.

In an embodiment shown in FIG. 5-A, the upper screen (indicated by solid lines: same in the following description) and the lower screen (indicated by broken lines: same in the following description) have the same .dimensions and planar perforation configuration. The

two screens are overlapped in a manner such that each of wire crossing points of the lower screen is positioned almost at the center of the perforation of the upper screen. FIG. S-B illustrates an embodiment where a screen having a smaller mesh perforation than that of the upper screen is used as a lower screen.

It is preferable to design a screen, particularly in the case of an assembly screen, in a manner such that the fluid which has'passed through the screen can escape therefrom freely without any hindrance. For instance, it is preferable to adopt a structure, the section of which is illustrated in FIG. 6-A, in which the moving screen is composed of an assembly screen disk supported and fixed to a rotary shaft 1 l by means of a supporting member from which the jet stream which has passed through the screen'can freely escape. In the em bodiment shown in FIG. 6-A, numerous

small holes

9,9

. are perforated through a part of a frame 10 confronting the back of a screen 7 hung on the frame and said part is supported and fixed to the head of shaft 11, or a projecting part of the side wall of the frame 10 may be supported and fixed to the head of the shaft 11 by means of a plurality of arms.

In the case of an endless belt type screen such as shown in FIG. l-B, it is important to avoid the vertical movement of the screen surface at the impingement of the jet stream. This may be attained by impinging the jet stream against a roller 8, but this would not allow the stream to pass through the screen. In such case, it is recommendable to adopt modifications such as shown in FIGS. 6-H and 6-B, which have been already detailed in the above-mentioned prior application Ser. No. 847,548. r

In short, it is recommendable to adopt a structure where the moving screen is an endless belt of an assembly screen and an outlet for projecting the heated jet stream is disposed at the position confronting a groove provided on a rotary roll driving the assembly screen belt to allow the jet stream which has passed through the screen to freely escape; or where the moving screen is an endless belt of an assembly screen and an outlet for projecting the heated jet stream is disposed at the position confronting an arm space formed between two rotary disks driving the assembly screen belt to allow the jet stream which has passed through the screen to freely escape.

As is shown in FIG. 6-B, a circular groove is provided on a part of the roller 8 in the longitudinal direction thereof to thereby form a space 9 and to arrange the jet 6 in a manner such that the jet stream from the jet 6 will impinge against the screen at a position confronting the groove. Although the jet may be arranged in an optional position confronting the circular groove on the roller, it is preferred to arrange the jet 6 so as to confront a portion of the groove that is still in contact with the assembly screen 7 but just before the portion at which the assembly screen 7 is released from the contact with the roller 8. No special restriction is given to said circular groove with respect to configuration,

depth and the like. In short, any type of the groove is applicable as far as it allows the jet stream to freely escape along the groove. If desired, a roller comprising a circular die connected therewith concentrically and having a diameter smaller than that of the roller may be used. Further, it is possible to use two dies 8A,8A fixed to each other by means of a plurality of arms (see FIG. 6-B' wherein the numerical reference 12 represents an arm and the screen is not shown). It is sufficient that at least three arms are disposed. In case three arms are used, they are disposed in a manner such that each of the bases of the arms is a vertex of an equilateral triangle. Of course, it is possible to dispose 4 or more arms in a polygonal pattern.

It is also recommendable in this invention to use as the feed roll for feeding thermoplastic synthetic continuous filaments to the jeta roll in which the surface of the portion on the filament-introducing side has a greater coefficient of friction and the surface of the portion on the side forwarding the filaments from the roller for feeding them to the jet as a smaller coefficient of friction.

In the feed roll 3 shown in FIG. l-A, the dotted portion of the roll 3 has a surface of a smaller coefficient of friction and the plain portion has a surface of a greater coefficient of friction. In case such feed roll is used, since the portion of a smaller coefficient of friction is utilized for feeding filaments to the jet, the separation of the filaments from the roll may be effected easily and smoothly. Thus, the feeding of the filaments to the jet can be accomplished very smoothly. Further, since the filaments undergo a pre-shrinkage in this portion of a smaller coefficient of friction, the shrinkage of the filaments in the jet can be controlled. At the same time, since the portion of a greater coefficient of friction maintains the filaments stably, variations of the tension on the filaments can be prevented between the feed roll and jet. Accordingly, the use of such feed roll is effective to keep the filament shrinkage constant during the operation.

In the crimping process to which this invention is directed, the feeding of filaments into a jet (or suction of filaments by a jet) depends mainly on the fluid friction between the filaments and heated jet stream. In this case, the sucking tension is generally low. For instance, in the case of nylon of 210 d/34 fil, the total tension is lower than about 4 g. Since the filament tension is so low as described above when the filaments pass through the jet, the shrinkage of the filaments is naturally effected in the almost relaxed state. For this reason, the shrinkage takes a form of a thermal shrinkage in which variations are likely caused to occur (though an extremely violent thermal condition being also one reason). Further, under such low filament tension the separation of filaments from the feed roll cannot be accomplished smoothly. Therefore, a balance between the frictional force of the roll and filaments and the filament sucking force is easily put into disorder, and variations are caused in the tension of the filaments being introduced into the jet. Since the shrinkage of the filaments in the jet is likely to be varied as mentioned above, such variations in the filament tension cause great influences on the shrinkage of the filaments in the jet, with the result that a deviation of the heat treatment effect is brought about and an undesirable dyeing unevenness is likely imparted to resulting crimped bulky filaments. This disadvantageous variation of the tension of the filaments being introduced into the jet is multiplied by the shrinkage of the filaments by the preheating.

The use of the above feed roll can exert the preheating effect sufficiently and prevent the above undesirable variation of the filament tension and its multiplication by the pre-heating. On the other hand, the use of a feed roll, the entire surface of which exhibits the same coefficient of friction, cannot exhibit any effect of preventing the abovementioned variation of the filament tension or its multiplication, though it may exhibit a pre-heating effect.

FIG. l-A illustrates an embodiment of the feed roll 3 where the coefficient of surface friction of the portion on the filament-feeding side is different from that of the portion on the filament-forwarding side. Of course, it is possible to use a feed roll in which the coefficient of surface friction is different among three or more portions.

It is sufficient in such feed roll that a greater coefficient of friction is such as will not cause slips of filaments. With respect to the number of turns of the filaments on such roll, we have found that it is sufficient to turn the filaments on the portion of a greater coefficient of friction to such an extent as will not cause slips of filaments is dependent on the kind and monofilament denier of M the filaments, the total denier of the filaments, the diameter of the feed roll and the like, it is difiicult to specify the range numerically. But generally the coefficient of friction of the surface of the filamentintroducing side is 0.3 to 0.4 and that of the surface of the filament-forwarding side is 0.15 to 0.2. It is preferable that the ratio of the coefficient of friction of the surface on the filament-forwarding side to that of the surface on the filament-introducing side is less than 0.5. As a specific example of such feed roll there may be cited a roll which consists of a portion of a greater coefficient of friction having a surface plated with hard chromium (a coefficient of friction of 0.4) and a portion of a smaller coefficient of friction having a sand blasted metal (a coefficient of friction of 0.2).

It is general to dispose the end point of the jet nozzle at a position approximating considerably to the screen surface. The distance between the end point of the jet nozzle and the screen surface is usually vern small and up to 10 mm, for instance, in an order of 1 mm to 7 mm, or 1.5 mm to 5 mm. This distance becomes frequently almost equal to the height of the deposit of the crimped filaments. This height is variant depending on the processing conditions such as nozzle temperature, nozzle pressure, speed of the moving screen and feed rate (overfeed amount), and the denier of the fila-- ments, but it is generally about 1 to 3 mm in the filaments of less than 500 denier and about 2 to 5 mm in the filaments of 500 to 3,000 denier. Therefore, there is a danger that filaments fall in contact with the end point of the jet nozzle. In the case of a jet having a naked end point of a processed metal such as shown in section in FIG. 7-A, when the distance between the nozzle end and the screen surface is made smaller, a chance of a contact of the filaments with the outer wall of the jet is increased, and occurrence of yarn breakages or fuzzings increases. Further, filaments which have once adhered to the nozzle end melt to form fused dregs which are not easily separated from the nozzle end and, the presence of such dregs increases the chance of a contact of the filaments with the nozzle.

In order to attain an easy separation of such dregs from the vicinity of the nozzle hole, we have tried to apply to the outer wall of the jet nozzle a silicone oil type separating agent used in the customary melt spinning method for preventing solidification and agglomeration of dregs formed in the vicinity of spinning nozzles. However, the above trial could not result in sufficient effects in the crimp processing process intended in this invention. On the contrary, since the formation of such a thin film of a liquid on the outer wall of the nozzle shows a tendency to heighten the thermal conduction of the filaments and quicken the fusion of the filaments adherent to the nozzle wall, the abovementioned trial only promotes the occurrence of the abovementioned undesirable phenomenon.

In order to overcome such disadvantage, it is preferable in this invention that at least an end portion of the jet nozzle is composed of, or coated with, a material of a thermal conductivity of less than 3.0 X cal/cm.sec.C. As such material there may be cited polytetrafluoroethylene and ceramics which are resistant to temperatureshigher than 200C. and have a thermal conductivity of less than 3.0 X 10 cal/cm.sec.C.

FIGS. 7-B and 7-C illustrate the sections of nozzle ends, similar to that shown in FIG. 7-A, which are composed of, or coated with, such material of a low thermal conductivity. In the Figures, the numerical reference 18 represents a metallic material constituting the nozzle, and the numerical reference 19 represents a material of a thermal-conductivity of lower than 3.0 X 10 cal/cm.sec.C.

As is illustrated in FIG. l-B, in this invention it is possible to provide an additional jet 20 for projecting a heated jet stream to the filaments on the moving screen while they are on the filament passage moving according to the movement of the screen and within a distance where the filaments are maintained at a temperature above the glass transition point thereof. The section of an example of the additional jet 20 is shown in FIG. 8-A in which the reference 21 represents an inlet for a heated and compressed gaseous fluid, usually, heated and compressed air, and the reference 22 represents an outlet for projecting said fluid. It is preferable that the configuration of the projecting outlet 22, as is shown in FIG. 8-B, is of a rectangular form extending in the direction (indicated by an arrow) of the filaments moving according to the movement of the screen.

As described hereinabove with respect to the improvement of the feed roll 3 for feeding filaments to the jet 6, the variations of the shrinkage of the filaments in the jet or on the screen caused by the variations of the tension'of the filaments being introduced into the jet from the feeding roll result in the formation of dyeing unevenness of the resulting crimped bulky filaments. Accordingly, if the variations of the shrinkage are not caused to occur, the problem of the dyeing unevenness should naturally be solved at the same time. For attaining this purpose it is recommendable to adopt means for projecting an additional heated jet stream to the filaments deposited on the screen and having in this state variations of the shrinkage, while they are maintained at a temperature above the glass transition point (second transition point) thereof, namely they are still in the fluid state. When such additional heated jet stream is projected to the filaments, the portion of a smaller shrinkage is further shrunk preferentially, and the uneven shrinkage is corrected so that the shrinkage will be substantially the same along the filament axis, with the consequence that it is possible to obtain easily crimped bulky filaments exhibiting hardly any dyeing unevenness.

This invention will be now described by referring to examples.

The percentage crimp referred to examples is a value measured and calculated in the following manner:

A sample of crimped filaments is dipped in boiling water for minutes in the relaxed state to develop crimps. Then, the sample is taken from water and it is allowed to stand still for 24 hours so as to dry it naturally. A load of 0.1 g/d is imposed on the sample and the length thereof is measured (1 Then, the load is removed from the sample and a load of 2 mg/d is imposed on the sample and the length thereof is measured (1 The value of the percentage crimp is calculated from the following formula:

Percentage crimp (1 1,), X 100 EXAMPLE 1 Runs of preparing crimped bulky filaments from filaments indicated in Table 1 below were carried out under conditions indicated also in Table l. The results are shown in Table 1.

As is apparent from the results shown in Table I, an assembly screen of two screen layers exerts a greater force of retaining the filaments thereon because of improved effects of leaving and depositing the filaments by small spaces formed among screen wires, as compared with a single screen. Therefore, in the case of the assembly screen, the effect attained by the pressing roll is conspicuous. Still further, as is also apparent from the results of Table l, the use of an assembly screen results in crimped filaments excellent in crimp characteristics.

Notes 1. NDS is Nylon semidull.

2. TSD is Tetron semidull (Tradename of polyester filament produced by TEIJIN LIMITED).

3. NB is Nylon bright.

4. In each run using NSD filaments, the filament take-up rate was 520 m/min. and the take-up tension was l5i2g.

S. In each run using TSD filaments, the filament takeup rate was 820 m/min. and the take-up tension was 7 i 2 g.

6. In each run using NB filaments, the filament takeup rate was 320 m/min. and the take-up tensionwas i 10 g.

'7. As the screen of the disk type there shown in FIG. l-A.

8. As the screen of the endless belt type there was used that shown in FIG. l-B.

9. The value given in parentheses in column screen mesh is the value of the perforation ratio of the screen used.

was used that EXAMPLE 2 In this example there was used the apparatus shown in FIG. l-B Nylon-6 continuous filaments of 2 d] 1 36 fil were heated by a feed roll maintained at C. and fed at a rate of 500 m/min. into a jet nozzle maintained at a temperature of 230C. at a compressed air pressure of 5 Kg/cm (gauge). The filaments were projected from the nozzle together with the heated and compressed air and impinged continuously against an endless belt of a metal wire of 10 X 15 mesh moving at a rate of 50 m/min. On the moving belt they were cooled and wound up at a rate of 400 m/min. while adjusting the take-up tension to 0.03 g/d when they were separated from the pressing roll. In this run, the point of separating the filaments was fixed at the point pressed by the pressing roll and the operation could be carried out very stably.

When the resulting filaments were subjected to the tufting operation as they were prepared without being twisted, the tufting could be effected smoothly without entanglements of filaments with guides or needles. The mechanical efficiency of the tufting operation was 80 85 percent. The mechanical efficiency of the tufting is a measure for evaluating the easiness of the tufting operation and expressed in the terms of the ratio of the time during which the tufting machine is actually operated to the total of said time and the time during which the tufting machine is stopped. in the usual tufting operation, mechanical efficiency of the tufting is in the range of about 70 to about 90 percent.

EXAMPLE 3 In this example there was used the apparatus shown in FIG. l-B. Polyethylene terephthalate filaments of 75 d/36 fil were fed at a rate of 1,000 m/min. by means of a feed roll maintained at 170C. which acted also as a preheating roll and passed through a nozzle containing a heated compressed air of 260C. and 5 Kg/cm (gauge) having an action as a laminar flow. Then, they were impinged together with the heated compressed air against an assembly screen of 40 X 40 mesh and crimped thereon. Then, they were cooled and wound up to obtain crimped bulky filaments.

The above run was repeated in the same manner as above except that an additional jet was provided 5 cm after the above cimping nozzle for projecting a heated compressed jet stream, and an additional heated compressed air of 270C. and 3 Kg/cm (gauge) was projected therefrom. As a result there were obtained crimped bulky filaments having a percentage crimp of 25 percent and a dyeing uneveness evaluation of 4.5.

In the above runs, because the pressing roll 1 was used, the operation was effected very smoothly. But, if the runs were conducted without using the pressing roll 1, the variations of the take-up point were extreme and the continuous operation was impossible.

The evaluation of the dyeing unevenness was based on 5 grades. In case the dyeing unevenness is permissible in the practical use, the dyeing unevenness evaluation was determined to 3. In case the dyeing unevenness was too great, the evaluation was determined to be 1, while in case the dyeing unevenness was scarcely or not observed, the evaluation was determined to be 5.

EXAMPLE 4 In this example there was used the apparatus shown in FIG. l-A. Polyamide filaments of 210 d/34 fil were fed at a rate of 700 m/min. by means of a feed roller maintained at 130C. which acted also as a preheating roll and passed through a nozzle of a heated compressed air of 250C. and 5 Kg/cm (gauge) having an action as a laminar flow. Then, they were impinged against an assembly screen consisting two layers of screens of 30 40 mesh, and crimped thereon. They were then cooled and wound up to give crimped filaments.

As the pre-heating roll there was used a roller consisting of a filament-introducing portion having a chromium-plated surface of a coefficient of friction of 0.4 and a filament-forwarding portion having an aventurine surface of a coefiicient of friction of 0.2. Results are shown below.

Percent Thermal shrinkage Thermal Evaluation during Shrinkage shrinkage of dyeing Pre-heatlng roll operation by nozzle on roll Criiups unevenness Chromium plated surface (3 turns) Aventurine surface (9 turns) 13 S 30 5 In the above run, the use of the pressing roll 1 made The chrimp-processing operation was carried outby it .possible to effect the operation very stably, while when the above run was repeated without using the pressing roll 1, the point of separating the filaments from the screen was greatly varied and the continuous operation was impossible. Thus, it is understood that this invention has made it possible for the first time to succeed in the actual'preparation of crimped filaments by utilizing hot air, which the prior art fails to practice in an industrial scale.

EXAMPLE 5 In this example there was used the apparatus shown in FIG. l-A. Polyethylene terephthalate continuous filaments of 75 d/36-fil were fed at a rate of 1,000 m/min. by a feed roll maintained at 170C. to a nozzle maintained at 260C. and a compressed air pressure of 5 .Kg/cm (gauge). They were continuously projected together with the compressed air on a disk wire screen rotating at a peripheral speed of 60 m/min. to form crimped filaments. In this example, the nozzle having an end portion such as shown in FIG. 7-B was used, wherein a polytetrafluoroethylene resin of a thermal conductivity of 0.01 X -l0.' 'cal/cm.sec.C. was coated on the nozzle .zproper composed of brass of a thermal temperature at 260C. As a result there were obtained crimped bulky filaments having very excellent properties.

The use of the pressing roll 1 in these runs made it possible to conduct the'continuous operation very stably ata high producibility, while when the pressing roll 1 was not used, the variation of the yarn-take-up point was extreme and the continuous operation was impossible.

EXAMPLE 6.

In this example was used a nozzle such as shown in FIG. 3-A, in which the projecting opening diameter was 1.8 mm, the projection nozzle length was 30 mm, the inner diameter of the guide needle was 1.0 mm and the outer diameter thereof was 1.4 mm. When the operation was effected at a nozzle temperature of 250C. and a compressed air pressure of 5 Kg/cm while passing polyamide filaments of 210 d/34 fil through the nozzle, it was found that a good balance was established between the sucking force and the force of the backward flow when the extending length AL of the guide needle was 1.2 mm. Thus, a desirable weak backward flow was attained. lt was confirmed by a stroboscopic photograph that the filaments were projected linearly.

maintaining the nozzle at the above-mentioned state" and impinging polyamide filaments indispensable 210 d/34 fil fed at of 700 m/ min. and pre-heated at the nozzle maintained at 250C., onto a rotating, airpermeable assembly screen consisting of two screen layers of 30 mesh and 40 mesh. As a result, there were obtained crimped bulky filaments of a percentage crimp of 30 percent, while the operation was conducted very stably.

It was found that even under such conditions as above where the filaments were projected linearly, it was indispensable to use the pressing roll 1 such as shown in FIG. l-A in order to conduct the continuous operation in the stable condition, and that when the operation was conducted without using such pressing roll, the yam-take-uppoint shifted extremely and the continuous operation was impossible.

We claim: W

1. In apparatus for preparing crimped bulky filaments including a feed roll for feeding thermoplastic synthetic continuous filaments to a nozzle for projecting a heated jet stream accompanying the filaments fed to said nozzle, a moving screen upon which the heated jet stream impinges and which allows the heated jet stream to pass through while leaving the filaments of said screen, and a take-up roll for separating the crimped filaments from said screen at a separation point, the crimped filaments having been cooled according to movement of the screen between the impingement point and the separation point, the improvement comprising means holding the filaments on said screen at the separation point to prevent movement of the separation point.

2. The apparatus described in claim 1 wherein said nozzle includes a housing having a chamber defined therein to receive a heated and compressed gaseous fluid and a tubular passage communicating with said chamber for projecting the fluid; and a hollow guide needle for receiving the filaments, said guide needle being disposed coaxially with said passage to penetrate said housing, said guide needle extending through said chamber and extending into said passage a distance less than one-half of the entire length of said passage to form an annular passage for the fluid between said needle and the inner wall of said passage.

3. The apparatus described in claim 1 wherein said means for preventing movement of the separation point includes a conical pressing roll contacting said screen at the separation point.

4. The apparatus described in claim 1 wherein said moving screen is an assembly screen including at least a perforated upper screen and a perforated lower screen, the plane perforation area of each portion of said lower screen overlapping each perforation of said upper screen being smaller than the plane area of each perforation of said upper screen, said portion of said lower screen having an open space sufficient for the jet stream to pass through said portion and freely escape from the assembly screen.

5. The apparatus described in claim 4 wherein said upper and lower screens are spaced by a distance of up to 2mm. and said assembly screen has a perforation ratio of from to 70 percent.

6. The apparatus described in claim 1 wherein said feed roll for feeding the thermoplastic synthetic continuous filaments is a roller having a first portion receiving the filaments and a second portion feeding the filaments to said jet, said first portion having a surface with a coefficient of friction of at least 0.3 and said second portion having a surface with a coefficient of friction of less than 0.2.

7. The apparatus described in claim 6 wherein said first portion has a surface with a coefficient of friction in the range of 0.3 to 0.4 and said second portion has a surface with a coefficient of friction in the range of 0.15 to 0.2, and the ratio of the latter coefficient to the former coefficient is less than 0.5.

8. The apparatus described in claim 1 wherein said nozzle has an end portion composed of, or coated with. a material having a thermal conductivity of less than 3.0 X 10 cal/cm. sec. C.

9. The apparatus described in claim 8 wherein said material is selected from the group consisting of polytetrafluoroethylene resins and ceramics.

10. The apparatus described in claim 1 and further comprising an additional nozzle projecting a heated jet stream on the filaments on said moving screen at a position where the filaments are maintained at a temperature above the glass transition temperature of a polymer constituting the filaments.

11. The apparatus described in claim 1 wherein said means for preventing movement of the separation point includes a cylindrical pressing roll contacting said screen at the separation point.

12. The apparatus described in claim 1 wherein said means for preventing movement of the separation point includes suction means disposed on a side of said screen opposite the take-up roll.

Claims

5. The apparatus described in claim 4 wherein said upper and lower screens are sPaced by a distance of up to 2mm. and said assembly screen has a perforation ratio of from 20 to 70 percent.

8. The apparatus described in claim 1 wherein said nozzle has an end portion composed of, or coated with, a material having a thermal conductivity of less than 3.0 X 10 2 cal/cm. sec. * C.