US3439381A

US3439381A - Spinneret

Info

Publication number: US3439381A
Application number: US599796A
Authority: US
Inventors: Hermanus Plomp
Original assignee: Algemene Kunstzijde Unie NV
Current assignee: Akzo NV
Priority date: 1965-12-10
Filing date: 1966-12-07
Publication date: 1969-04-22
Anticipated expiration: 1986-04-22
Also published as: BE690704A; FR1503306A; GB1166830A; DE1660169A1; ES334340A1; ES334336A1; LU52553A1; NL6516064A

Description

H. PLOMP April 22, 1969 SPINNERET Filed Dec. 7, 1966 sheet cfa FIG.3

FIG. 2

INVENroR HERMANUS PLOMP Aprilzz, 1969v HPLOMP 3,439,331

` SPIVNNERET .filed Dec. v. 1966A 3 sheet 3 of" 3 HERMANUSPLOMP( 3 ymmmfw ATTORNEYS vApril 22, 1969 vH PLOMF 3,439,381

SPINNBRET n Filed Dec. v, 196e` j sheet 3 bf s INVENTOR HERMANUS PLoMP United States Patent O 3,439,381 SPINNERET Hermanus Plomp, Rijswijk, South Holland, Netherlands, assigner to Algemene Kunstzijde Unie, N.V., Arnhem, Netherlands, a corporation of the Netherlands Filed Dec. 7, 1966, Ser. No. 599,796 Claims priority, application Netherlands, Dec. 10, 1965, 6516064 Int. Cl. D01d 5/00 U.S. Cl. 18-8 9 Claims ABSTRACT F THE DISCLOSURE Spinneret structure is provided for the manufacture of profiled filaments of dumbbell, Y-shaped or star-shaped cross sections by the extrusion of synthetic masses, in which a profiled spinning `channel is afforded consisting of a thin-walled tube the outlet zone of which is profiled both internally and externally and which is preferably supported in a bore of the spinneret only along strips of its circumferential surface. The thin-walled tube is formed by squeezing the outward end thereof in a special tool provided with jaws that are movable with great accuracy in a truly radial direction, the number of jaws corresponding to the number of desired indentations between the arms of the cross section of the thin-walled tube, the jaws being smoothly rounded in order that the transition from the non-profiled portion of the thin-walled tube to the profiled portion thereof shall be gradual.

The invention relates to a spinneret for the manufacture from synthetic masses of profiled filaments; and more particularly filaments having dumbbell, Y-shaped or starshaped cross sections, and to a method for the manufacture of a spinning channel of such a spinneret.

For the manufacture of a profiled filament the spinning channel must, at the outlet end, have a cross-sectional shape that substantially corresponds to that of the filament. A spinning channel in a spinneret must satisfy high demands as far as the material of the channel wall and the manufacturing technique are concerned, because the wall must be capable of resisting the temperature, the pressure and the aggressive action of the extruded synthetic masses for the filaments for a reasonably long time. The materials of which the spinnerets are made are therefore difficult to machine, so that the spinnerets obtained are very expensive.

For this reason the spinnerets are often made of a less high-grade material and are provided with simple, cylindrical or slightly conical bores, in which there are fixed inserts of high-grade material, each of which contains a spinning channel.

A spinning channel for the production of round filaments mostly consists of a wide inlet zone having a more or less cylindrical wall, an outlet zone having a cylindrical wall of a smaller diameter and a slightly conical intermediate zone providing transition between the inlet zone and the outlet zone. An insert provided with such a channel is manufactured, for instance, by depositing metal on a core having the desired channel shape, removing the core by chemical means and grinding the insert to fit the bore in the spinneret. ln this way it is possible, by starting from a core having the desired shape, to give a channel any cross-sectional shape. However, the manufacture of such inserts remains very laborious and costly.

The present invention, in the first instance, has for its object to provide a spinneret of a fundamentally very simple character which is equipped with a number of bores, the programmed manufacture of which is simple and rapid. According to the present invention, the wall of a profiled spinning channel consists of a thin-walled ice tube, the outlet zone of which is profiled `both internally and externally and is preferably supported in the bore only along strips of its circumferential surface.

According to the present invention, the wall of the spinning channel is preferably formed by a thin-walled tube which fits a bore in a spinneret and which is, for

part of its length, supported in the bore over its entire circumferential surface, and of which the profiled outlet zone is supported in the bore only along strips or portions of its circumferential surface.

According to the present invention, the actual circumference and the wall thickness of the profiled outlet zone of said tube are practically equal to the circumference and the wall thickness of the non-profiled zone.

With a different embodiment according to the present invention, the spinneret is on its lower face provided with a projecting tube, which is coaxial with a spinning channel, and of which the outlet zone is profiled both internally and externally and is supported only along strips of its circumferential surface preferably in a bore provided in a member surrounding the projecting tube.

Preferably, the strips of the circumferential surface of the profiled outlet zone are straight, but if it is desired to have a helically profiled channel, they may follow helical paths.

In order to ensure that the exit of the profiled outlet zone is not cracked or burred and is truly perpendicular to the axis of the spinning channel, it is, according to the present invention, advantageous to conically bevel the end of the thin-walled tube on the outside thereof before the profile is applied. On account of the smaller wall thickness the bevelled end can be deformed more easily, without being cracked or developing irregular edges. In View of the end being bevelled, grinding and polishing of the edges, which is a very difficult process, then becomes unnecessary.

A channel cross section having sharp angles, however, is difficult to realize, and if the filament cross section is still to have sharp-angled tips, it is, according to the present invention, possible to connect to the profiled outlet zone of the channel a separate, constricted passage of -which the diameter is smaller than that of the circle circumscribed about the arms of the profiled channel. This constricted passage, which may be formed by a ring placed in the bore of the spinneret, covers the rounded tips of the arms of the profiled channel. Said ring `may also form part of the member surrounding a tube projecting from the spinneret.

According to the present invention, a profiled spinning channel is manufactured Iby the following method. The thinwalled tube is placed, with its end that is to be de formed to the outlet zone, in a special tool provided with a number of jaws which are movable with a particularly great accuracy, in truly radial direction and the inner wall of the tube is, from the outside and without being additionally supported, given the desired shape. The number of jaws corresponds to the number of indentations between the arms of the cross-section, and the jaws are smoothly rounded in order that the transition to the tube zone that is not to be profiled may be gradual.

The present invention will now be further described with reference to the accompanying drawings, which show. by way of example, embodiments according to the invention.

FIGURE 1 is a cross-sectional view of a non-deformed tube with a channel therethrough; p

FIG. 2 is a cross-sectional view of a partly deformed tube;

FIG. 3 is a cross-sectional view of a tube deformed to show the desired profile:

FIG. 4 shows, in longitudinal section, a bore in a spinneret, in which there is provided a member shown in side elevation to provide a spinneret construction and arrangement according to the present invention;

FIG. 5 is a longitudinal sectional view of a spinneret bore in which a thin-walled tube with a helically profiled outlet zone is provided;

FIG. 6 is a sectional view of another arrangement similar to FIGS. 4 and 5, but with a profiled tubular spinning channel which is of reduced diameter in the outlet zone;

FIG. 7 is a cross-sectional view taken on line 7 7 of FIG. 6;

FIG. 8 is a sectional view of a modification of the bore of a spinneret for producing sharp-angled tips on the arms of the filament cross section, and is taken along line 8-8 of FIG. 9;

FIG. 9 is a cross-sectional view taken along line 9 9 of FIG. 8;

FIG. 10 is a sectional view of still another modification in which the deformed spinning channel is integral with the spinneret and is supported by a removable ring, and is taken along line 10-10 of FIG. 11; and

FIG. 1l is a cross-sectional view taken along line 11-11 of FIG. l0.

The manufacture of a profiled outlet zone in a spinning channel of a spinneret for the melt spinning or extrusion from a synthetic mass of a filament having a Y-shaped cross section is started from a tube 1 of which, as can be seen in FIG. 1, the wall thickness is small with respect to the diameter.

Around the tube 1 there is provided a special tool provided with a number of jaws, which can deform the tube wall to the desired shape in that the jaws are simultaneously movable in a radial direction with particularly great accuracy. The provision of the Y-shaped cross section, as described here, requires three jaws, which are schematically indicated in the drawings by arrows 2.

It will be clear that the provision of a dumbbell cross section will require two jaws and the provision of an X-shaped cross section will require four jaws.

The jaws exert pressure in the directions indicated by the arrows 2 as a result of which the tube 1 is deformed, the speed of deformation being, of course, adapted as desired to the properties of the tube material. If necessary or desired, the deformation may take place while the tube material is being heated.

FIG. 2 shows a. remarkable stage in the deformation of the tube in that the movement of the jaws has reduced the original circular shape to a triangular shape with straight sides and rounded tips 3. The total length Of the circumference has not changed, because during the deformation the parts of the circle that are intermediate between the jaws are not supported. Consequently, the shaped tips 3 project somewhat from the original circular circumference 4 of the tube 1 (indicated by the dashed line in FIG. 2).

During the further deformation to the shape represented in FIG. 3 the straight sides of the triangle are pressed inwardly still further, as a result of which the channel is given its desired Y-shaped cross section. The tips 3 are now back again on the circle 4, and the arcs form, as it were, the inwardly buckled parts of the original circular shape, without the length of the circumference and the wall thickness of the tube having been changed. The tube 1 is profiled in this way only along a part of its length, there being a gradual transition to the non-profiled zone as best shown in FIG. 4.

For a given channel cross section, the diameter of the tubular member and its wall thickness must be correlated to each other.

FIG. 4 shows such a tube 1 provided in a bore 5 of spinneret 6. The bore 5 is a simple, cylindrical or very slightly conical bore which, however, need by no means satisfy the high demands normally made on a spinning channel. The tube 1 is pressed into the bore 5 or cemented therein, but it can readily be removed again and be replaced by another tube, as is the case with the known inserts.

According to the present invention, the tube 1 is deformed and profiled in the above-described manner for about one-third of its length to form the outlet zone 7. The entire outer surface of the non-deformed zone bears against the bore 5, and the zone 7 only bears against the bore along strips that correspond to the tips 3 of the cross section shown in FIG. 3. At its top end the bore 5 is chamfered and the tube 1 is bent over in the chamfer to form a conical flared portion or bead 8, which seals off any space left between the bore and the tube. The conical iiared portion or bead 8 also serves to facilitate the iniiow of the synthetic mass undergoing processing.

The bottom edge of the outlet zone 7 is provided with a bevel 9. Before being deformed, the tube 1 is conically bevelled on the outside so that the wall thickness decreases towards the edge. As a result, deformation during the shaping operation does not give rise to high stresses in the edge, which could lead to cracking. Moreover, the bottom edge remains more truly perpendicular to the channel axis, so that grinding and polishing as the final step of the process is not necessary. This is a considerable advantage because grinding the edge perpendicular, without the formation of burrs, is extremely difficult, and burrs lead to irregularities in the filaments produced.

When a synthetic mass to be spun into profiled filaments is passed under high pressure through the spinning channel, the wall of the channel (the wall of the tube 1) is pressed against the bore 5. As the wall thickness of the tube 1 is relatively small, the axial pressure of the synthetic mass on the annular cross section will be smaller than the friction between the bore 5 and the tube 1, which acts on a far greater cylindrical surface and is dependent on the radial pressure of the synthetic mass. The nonprofiled zone of the tube will therefore stick in the bore under any and all spinning conditions. The synthetic mass which ows through the channel at a decreasing pressure passes through the region of gradual transition, and finally reaches the profiled outlet zone 7, where the pressure of the mass will tend to remove the profile. However, as the tips 3 of the tube bear against the bore 5, and the interto buckle from the positions of FIG. 3 through the straight mediate arcs are tensioned, it is impossible for said arcs positions shown in FIG. 2, so that the profiled cross section of the tube 1 is maintained during spinning in spite of the small wall thickness of the tube.

As indicated above, the transition from the non-profiled to the profiled zone of the tube is gradual in order not only to prevent the ymaterial of the tube from being overloaded during the deformation and the channel surface from getting rough, but also to keep the resistance to the passage of the synthetic `mass as low as possible. To this end the jaws with the aid of which the tube 1 is pressed inwardly to the desired cross-sectional shape are provided with gradual transitions and are moved in such a manner that the tube will not show abrupt transitions at any point.

The bore 5 is preferably longer than the entire tube 1, as a result of which the latter is supported along its full length and the profiled outlet zone 7, which preferably extends for not more than one-third of the total length, does not project from the bore 5.

FIG. 5 shows a thin-walled tubular spinning channel or tube 1 with a helically profiled outlet zone 7a, whose rounded tips 3a are supported by the bore 5 of the spinneret 6.

With thin-armed profiles of a tube 1b such as shown in FIGS. 6 and 7, the actual circumference of the profiled outlet zone 7b may be long with respect to the diameter of the circle on which the tips are to be located. In that case the tips 3b are on a circle 5a the diameter of which is smaller than that of the original circle 5 of the tube 1b. The bore 5 in the spinneret is then given a stepped shape in order that the tips 3b may bear against the bore wall 5a on a circle of the appropriate, smaller diameter.

If it is desired to produce a filament the cross section of which shows sharp-angled edges of the arm tips, the tube 1 would have to be provided with -shar-p angles when it is being deformed. This may lead to overloading and cracking of the material of the tube and present difficulties with respect to the gradual transition from the round cross section to the profiled cross section. In order still to obtain a sharp-angled cross section the bore 5 may, under the outlet zone 7, be provided with a constriction of a smaller inside diameter so that the rounded tips 3 of the arms of the profiled channel are just covered and separated off sharply. The constriction may a'lso be realized by providing a ring 12 in a counterbore 14 in the outlet end of bore 5 as seen in FIGS. 8 and 9. Ring 12 is provided With a circular hole 16 which is smaller in diameter than bore 5 and intersects the rounded tips 3 of the outlet zone 7, thus providing a spinning channel with sharpedged arms as indicated at 3c. Ring 12 is retained in counterbore 14 by means of plate 18 suitably secured to spinneret 6. Said plate is provided with an aperture 20 larger than hole 16, so that there is no interference with the emerging profiled filament. The resistance offered by the small portions of the ring 12 that cover the tips of the rounded profile is absorbed by plate 18. It should be added that the ring 12 must be formed to snugly fit the bevel 9 to prevent lagging and other disturbances.

With a still different embodiment according to the present invention, use is not made of an insert in the form of a tube 1 mounted in a bore 5, but rather (see FIGS. 10 an'd 1l) the spinneret 26 is provided with a spinning channel which now satisfies all the demands to be made on such a channel, and extends into a coaxial tubular member 21 projecting from the lower face of the spinneret. The projecting tube has a cross section similar to that shown in FIG. 1 and is deformed-in the same way to the filament profiling zone 27 (or, if desired, to a different dumb-bell or star-shaped cross section), Moreover, the gradual transition from a round to a proled cross section is provided in the yprojecting tube 21. Around the projecting tube 21 there is provided a bored member 29, which supports the tips 23, and may be attached to the spinneret 26. In general the member 29 may be a removable `ring. However, this particular spinneret con struction has the disadvantages that the spinneret must be made entirely of high-grade material and that when the spinning channel has been damaged, the spinneret must be removed and repaired or a damaged spinning channel must be plugged until the spinneret is exchanged. Because they are absent, exchange of inserts is impossible unless the projecting tube with its non-profiled zone is itself removably attached to the spinneret and is exchangeable. It should be added that there may be circumstances in which there are exerted on the profiled zone of the projecting tube 21 such small forces that the projecting tube, because it forms part of the spinneret or is attached thereto, is supported by the spinneret, an'd is thus given sufficient rigidity to prevent the profiled surface from buckling back to a cylindrical surface, as a result of which the provision of the retaining ring 29 may not be necessary. However, if, as described above, it is desired to have a cross section with sharp angles, then the ring 29 must be used and may at its bottom end be provided with a constriction providing the lament cross section with the sharp angles. in the manner described above 4in connection with other embodiments of the invention.

While specific examples of preferred methods and articles embodying the present invention have been set forth above, it will be understood that many changes and modifications may be made in the methods of procedure and in the articles without departing from the spirit of the invention. It will therefore be understood that the examples cited, the particular methods of operation and the articles set forth above are intended to be illustrative only, and are not intended to limit the scope of the inventlon.

What is claimed is:

1. A spinneret for the manufacture of profiled filaments from synthetic masses, which spinneret has at least one spinning channel, characterized in that the wall of a profiled spinning channel consists of a thin-walled tube, the outlet zone of which is profiled both internally and externally.

2. A spinneret according to claim 1,` characterized in that the outlet zone of the thin-walled tube is supported in a bore only along strips of its circumferential surface.

3. A spinneret according to claim 1, characterized in that the wall of the spinning channel is rformed by a thinwalled tube which fits ina bore of the spinneret and is, for part of its length, supported in the bore over its entire circumferential surface, and of which the profiled outlet zone is supported in the bore only along strips of its circumferential surface.

4. A spinneret according to claim 2, characterized in that the bore that supports the strips is provided in a member which is connected with thespinneret- 5. A spinneret according to claim 1, characterized in that the actual circumference and the wall thickness of the profiled outlet zone of the tube are substantially equal to the circumference and the wall thickness of the nonproled zone.

6. A spinneret according to claim 1, characterized in that the end of the outlet zone of the tube is bevelled on the outside.

7. A spinneret according to claim 2 for the manufacture of profiled filaments having sharp-,angled tips, characterized in that under the outlet zone the bore is provided with a constriction of which the diameter is smaller than that of the circle circumscribed about the supporting strips of the profiled channel.

8. A spinneret according to the claim 7, characterized in that the constriction is provided in the member.

9. A spinneret according to claim 1, characterized in that the outlet zone of the tube is helically profiled.

References Cited UNITED STATES PATENTS 1,788,660 1/1931 Colombo. 2,759,219 8/1956 Meakin. 3,038,420 6/ 1962 Immohr. 3,174,183 3/1965 Siegel. 3,197,812 8/1965 Dietzsch et al.

OTHER REFERENCES German printed application I (1960), Gold. `German printed application II (1961), Bayer.

WILLIAM I. STEPHENSON, Primary Examiner.

U.S. C1. XR. 76--107 ggo UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 439, 381

Dated April 22, 1969 Invented-5) Hermanus Plomp It is certified that error appears in the above-identified patent and that said Letters Patent are .hereby corrected as shown below:

(SEAL) EdwardMFlelchlIr. Auesting Ofr SIMI Fm SCLE Noz.' s im mmm E. JR. Gomiusioner of Patents