US3407437A - Spinning head for high pressure melt spinning - Google Patents

Description

United States Patent "ice 3,407,437 SPINNING HEAD FOR HIGH PRESSURE MELT SPINNING Erich Lenk, Remscheid-Lennep, Germany, assiguor to Barmer Maschinenfabrik Aktiengesellschaft, Wuppertal- Oberbarmen, Germany Filed July 11, 1966, Ser. No. 564,154 Claims priority, application Ggrmany, July 15, 1965,

5 Claims. (c1. 18-8) ABSTRACT OF THE DISCLOSURE This invention relates to a spinning head adapted to be inserted in a heating element. The spinning head consists of a housing which contains filter, distributor and nozzle elements in a packaged assembly which is held in the housing by means of screw threads. The melt entry comprises an opening at the base of the housing. The spinning head is used in the production of single and multiple synthetic fibers and threads under high pressure extrusion.

Such spinning heads are used for the melt spinning of synthetic threads, for instance those of thermoplastic polymers. As is generally known, this process involves feed of hot melt at a high pressure to the spinning heads. Gear pumps and/ or extruders are used to transfer the material, and therefore special attention has to be directed to the sealing methods. Disc-shaped filter, distributor, and nozzle elements are usually inserted in the cylindrical housing of the spinning head and the seal rings are inserted between these elements. The entire package is fitted in the housing to resist the pressure of the melt. On the other hand, it is also known to use arrangements wherein the pressure of the melt presses the elements of the package together. Finally it has also been sug ested that the gap between two spinning head elements be sealed by a seal ring that deforms under the pressure of the melt. The distributor and the filter element is supported against the nozzle element in such an arrangement, whereby the entire pressure of the melt is borne by the mounting of the nozzle element. The magnitude of the existing or possible pressures impose such high unit area pressures on the supporting and sealing surfaces of the spinning head elements and the nozzle plate itself that the useful spinning area for the nozzles becomes too small because of the necessary enlargement of the supporting surface. Also, the diameter of the spinning head housing has to be increasd considerably.

All the constructions having a large portion of the housing under a high radial pressure require a heavy wall thickness for the spinning head housing. This results in high weights which make the manufacture of these items expensive and makes the item difficult to handle.

This invention provides a spinning head-consisting of a housing enclosing a nozzle plate and a distribuator plate which is supporting a filter-which can stand pressures of more than 1000 kg./cm. during the extrusion of textile and technical synthetic fibers and threads and is also light 3,407,437 Patented Oct. 29, 1968 in weight for easy handling and is of relatively low cost. The basic concept of this invention is the protection of the inside of the housing from the radial forces caused by the melt pressure and the reduction of the stress on the supporting surface for the nozzle element.

According to this invention, the spinning head is made in such a way that the first inserted distributor element rests tightly on the housing base. A relief in the face of this distributor element may contain and hold a filter. The nozzle element which is the next part in the assembly of the head rests tightly against the distributor element. A self-sealing gasket ring is between housing base and distributor element and another of the same kind is between the distributor element and the nozzle element. The gaskets are self-sealing when the melt pressure acts against them. One of these gasket rings supports itself with its faces against the distributor element and the housing base without exerting a radial load against the housing wall. The gasket ring between the housing base and the distributor element and the one between the distributor element and the nozzle bear against these elements in such a way that the housing wall receives practically only an axial tensile force. One or both faces of the distributor element and the face of the nozzle elements opposite the distributor element may have reliefs in such a way that the gasket ring faces are supported on the circumference of these reliefs. Also the surface of the base of the housing may have a conical surface which intercepts at its center the radial and/or axial melt feed passage in the base. The spinning head of this invention differs from the generally known type in several aspects. Generally known spinning heads consist of a nozzle plate which also carries the filter elements or the distributor plates with the filter elements. These elements bear the full force of the melt pressure, and a large portion of the inside wall of the housing is subjected to the radial pressure of the melt. The invention provides a relief in the face of the distributor plate for mounting the filter package, whereas the generally known arrangement has filter elements extending up to the inside of the housing wall. The latter arrangement allows entry of the melt over the entire filter height and therefore permits a pressure load on the housing wall over a corresponding height.

The invention as described in this application transmits the axial force as generated by the throttling effect of the filter to the distributor plate and from this distributor plate through its thread to the supporting surface of the housing which, in this case, is the inside thread of the housing. The use of very fine filters such as sieves of tight mesh construction and the use of melts of high viscosities cause a high force load on the filter element. The melt pressure can be in extreme cases 1000 kg./cm. Such pressures exert high forces on the supporting surfaces such as were used in the conventional spinning head designs. The supporting face in such designs is very narrow, and this narrow shoulder transmitted the load from the nozzle plate to the housing wall. This results in very high loads on the supporting surface, and the designer is forced to increase its area by making the housing diameter larger. At an equal effective nozzle area, this larger housing diameter in turn results in higher forces against the supporting ring-surface, which stress the seals. Stronger housing wall thicknesses are required, and the result is a larger and heavier spinning head.

The main stress caused by a pressure inside of a container of cylindrical shape is a tensile stress in the circumferential direction, whereas the axial stress caused by the pressure against the base of the cylindrical container amounts to one-half of the stress in the tangential direction. The generally known melt spinning head-s receive the forces from the melt pressure on their entire height. It is necessary to make them with thick walls because of these stresses in several directions, resulting in a spinning head of relatively heavy weight. The invention herein prevents the immediate load against the circumferential wall of the housing. The highest stress on the housing is in the area of the gasket ring between housing 'base and distributor plate at the intersection of the cylindrical side wall to the base wall. The axial forces, caused by the pressure of the melt on the filter carrier and the nozzle plate, are highest in this area. Additionally, the force generated by the pressure against the inner circumference of the seal is transmitted to the housing wall at said intersection. The wall thickness of the spinning head housing can be reduced from the generally known type, because the diameter' to be considered for a calculation of the pressure load is equal to the diameter on the inside of the gasket ring. The forces caused by the melt pressure against the inside of the gasket ring are transmitted to the housing only by half their original amount because these tangential stresses are reduced by the invention to such an extent that the tangential stress in the housing wall is only a fraction of what it is when the pressure of the melt acts against the full circumference against the housing wall. The tangential stress in the side wall of a cylindrical container is as mentioned above more than twice the stress caused by the same pressure against bottom, which results in a stress in the axial direction. The arrangement suggested in this invention reduces the tangential stress in the housing by a considerable amount and allows reduction of the wall thickness and thus the weight of the housing.

The spinning heads shown in the drawing are about 50% lighter in weight than conventional heads. Below the critical cross section" as mentioned above and in the area of the distributor piece, there are axial stresses only. They are the result of the force of the melt against the filter element. They are half the magnitude of the tangential stresses and'are transmitted via the thread to the housing wall. This holds true for the nozzle element also. However one has to consider that 50% of the melt pressure is lost in the filter element so that relatively small tensile stresses act against the wall of the housing in the area of the seal between nozzle element and distributor element. i

The advantage of the suggested arrangement can be seen in the saving of material and a weight reduction of 50% as compard with the generally known design. This is also true when this type spinning head is used at very high pressures. Another advantage in addition to the lower material and thus manufacturing cost is the easy handling during the exchange of the spinning heads.

As a further development of the invention, the spinning head may be mounted in the heating element in such a way that, in order to assure a positive connection of the melt feed line from the pump to the spinning head container bottom, the heating element is of cylindrical or box shape to receive the spinning head with the melt inlet near the housing bottom. This inlet can be pressed against a gasket ring which is between heating element and spinning head housing. The spinning head housing can be pressed against this gasket ring by means of a screw thread in the heating element.

The drawing shows the invention in two preferred embodiments of the invention.

In the drawing:

FIG. 1 is a diametric cross-section of the spinning head in the heating element.

FIG. 2 shows the same spinning head in a modified form. r

The spinning head in FIG. 1 consists of a housing 1. A distributor plate 2 is mounted by screw threads in this housing. A filter package 3 is mounted in a relief or recess 4 of the distributor plate. A nozzle plate is mounted in the mounting ring 7 in the annular recess 8. Nozzle plate 6 is mounted by screw threads 9 in the downstream end of cavity of housing 1. Ring gaskets 11 and 12 are inserted between the base 13 of the housing 1 and the distributor plate 2 and between the distributor plate 2 and the nozzle plate 6, respectively. These gasket rings consist of a softer metallic material than the above mentioned parts of the spinning head. The melt passage 14 extends radially through the base 13 of the housing 1. It connects with the apex of a concentric, conical wall 15 of base 13. Wall 15 is the base wall of the cavity in housing 1.

The spinning head has a shoulder 16 around the circumference of the cylindrical housing 1 which is supported in the bore 17 of the heating element 18 by the ring shoulder 19. The spinning head 'is' fastened in theheating element 18 by a bolt 20 which is threaded through the wall of the heating element 18 and seats in the spinninghead in recess 21. Bolt 20 assures a positive seal between the melt line 21 which comes from the pump 22 and passage 14 by compression of the gasket ring 23. The heating element can be heated by electric heating elements or by steam or other hot fluid which can enter and leave jacket 26 through the ports 24 and 25.

FIG. 2 is a modified embodiment wherein the distributor plate 2 and the nozzle plate 6 on the side facing the distributor plate 2 have frusto-conical faces 27, 28and 29 serving as seats for the radially tapered, self-sealing rings 30 and 31.

The invention herein disclosed provides spinning heads which are capable of handling pressures of 1000 kg./cm. and more, and which are lighter in weight by about 50% as compared with previously known spinning heads.

Thus, the invention provides a spinning head 1 for spinning polymer melts, which head is adapted to be inserted in a heating element 18. The spinning head housing has a cavity with screw-threaded cylindrical walls 33 and 34 and a base wall 13 at one end thereof. Said base wall has a melt feed passage 14 therein opening into said cavity. A distributor element 2 is screw threaded in said cavity adjacent to said base wall. This element has a plurality of axial melt passages 35 therethrough. A sealing ring 11 is compressed between said element and said base wall. The nozzle member including a nozzle plate 6 with axial nozzle passages 36 therein is screw threaded in said cavity next to said distributor element. A sealing ring12 is compressed between said nozzle member and said distributor element, A melt-filtering element is provided in said cavity. The spinning head is characterized by lack of radial force against said cylindrical walls by said sealing rings and by pressure of the melt as it passes under pressure through said spinning head.

Preferably, the face of said distributor element opposite said base wall has a recess 4 therein, and said filter element is mounted in said recess. The inner face of said base wall opposite said distributor elementpreferably is conical in shape, and said melt feed passage opens into said cavity at the apex of said conical face,

The spinning head 1 may be mounted in a bore of a heating element 18 which surrounds said spinning head. A bolt 20 is threaded in and .projects through said heating element against a side of said spinning head..The heating element has a melt feed passage 24 extending through its Wall diametrically opposite said bolt. The melt feed passage 14 in saidbase wall extends radially therein, and said melt feed-passagesare aligned. There is a ring gasket 23between contiguous ends of said passages, whereby said ring gasket is compressed by tighteningsaid bolt against said side of said spinning head. h

Thev invention is hereby claimed as follows;

1. A spinning head'for spinning polymer-melts and adapted to be inserted in a heating element comprising a spinning head housing having a.-;heavy;end wall and a hollow,- cylindrical shell projecting therefrom,..the inner wall of saidshell having screwzthreads thereon, the inner face of said end .wall being concavely conical in. shape, said base wall having a melt feed passage 'therethrough with the discharge opening thereof-at the apexof said conical, inner face, a distributor element screw threaded in said cavity adjacent to said base wall, said element having a plurality of axial melt passages therethrough, a first sealing ring having a sloping face matingly seated against the outer peripheral portion of said conical inner face and compressed between an end of said distributor element and said conical, inner face, a nozzle member including a nozzle plate with axial nozzle passages therein, said nozzle member being screw threaded in said cavity next to said distributor element, and a second sealing ring compressed between opposing faces of said nozzle member and said distributor element, said spinning head being characterized by distribution of pressure forces exerted against said housing by polymer melt pumped through said spinning head into axial and radial forces against said heavy end wall and into essentially axial forces on said screw threads of said housing with substantially no radial pressure being exerted against said hollow, cylindrical shell.

2. A spinning head as claimed in claim 6, the face of said distributor element opposite said base wall having a recess therein, and a filter element being mounted in said recess.

3. A spinning head as claimed in claim 6, the peripheral portion of said end of said distributor element having a concavely frusto-conical face, and said first sealing ring being a radially tapered, self-sealing ring compressed between said conical and frusto-conical faces.

4. A spinning head as claimed in claim 6, peripheral portions of said opposing faces of said nozzle member and said distributor plate respectively being concavely frustoconical faces, and said second sealing ring being a radially tapered, self-sealing ring compressed between said lastmentioned faces.

5. The spinning head of claim 6 mounted in a bore of a heating element which surrounds said spinning head, a bolt threaded in and projecting through said heating element against a side of said spinning head, a melt feed passage extending through said heating element diametrically opposite said bolt, said melt feed passage in said base wall extending radially therein and said melt feed passages being aligned, and a ring gasket between contiguous ends of said passages, whereby said ring gasket is compressed by tightening said bolt against said side of said spinning head.

References Cited UNITED STATES PATENTS 2,589,870 3/1952 Sale et al 18-8 2,792,122 5/ 1957 Munch et a1 188 XR 2,932,062 4/1960 Speakman et a1 18-8 3,050,774 8/1962 Tait 18-8 3,123,858 3/1964 McDerrnott 18-8 3,259,938 7/1966 Martin 18-8 3,299,470 I/ 1967 Stockbridge 188 FOREIGN PATENTS 779,787 7/ 7 Great Britain. 780,743 8/1957 Great Britain.

WILLIAM J. STEPHENSON, Primary Examiner.

U.S. DEPARTMENT OF COMMERCE PATENT OFFICE Washington, D.C. 20231 UNITED STATES PATENT OFFICE CERTIFICATE ()FICORRECTION Patent No. 3,407,437 October 29, 1968 Erich Lenk It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 69, "distribuator" should read distributor Column 5, lines 20, 24 and 29 and colunm 6, line 4, the claim reference numeral "6", each occurrence, should read l Signed and sealed this 31st day of March 1970.

(SEAL) Attest:

? WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

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