IL30408A - Apparatus for extruding tubular netting - Google Patents

Description

Apparatus for extrudi g tubular netting OEKERALE AUME TAIRB S.A.

C. 28683 This invention relates to apparatus for continuously extruding a tubular plastic network, and more particularly to a network having a polygonal or lozenge-shaped mesh that facilitates axial deformation of the network.

A tubular network having a lozenge-shaped mesh as distinguished from square or rectangular meshes is ideally suited for packing products of irregular shape, such as potatoes, because of the ability of the lozenge-shaped mesh to deform axially and intimately follow the shape of the packed product.

It is conventional, as exemplified by Israeli Patent No. 17499, to produce tubular networks with square or rectangular meshes. However, networks with lozenge-shaped meshes heretofore have been produced either by separately extruding filaments or strands that were subsequently crossed or superposed at the outlet of the extruding spinneret, or by extruding a planar lozenge-shaped mesh, as exemplified in Israeli patent Mo. 17499» and welding the latter into tubular form. In neither case is the resultant lozenge-shaped mesh tubular network integral. As a consequence, an inherent weakness exists at the junction where the separate fila ments are welded.

It is an object of this invention to provide apparatus for continuously extruding a tubular plastic network which is capable of producing an integral mesh having a polygonal or lozenge-shaped mesh.

Acoording to the invention, there is provided apparatus for continuously extruding a tubular plastic network comprising an extrusion head consisting of two coaxial, relatively displaceable spinnerets, one spinneret being formed of a first pair of cylindrical elements having opposite toothed, spaced apart, edges which define a circumferentially extending serrated slot, the other - 3 - 30408/2 pair of cylindrical elements which interengage with the first pair of elements and are axially spaced from each other so as to define between them a circumferential slot located in a plane perpendicular to the axis of the extrusion head, the second pair of cylindrical elements being connected to each other by axially displaceable means consisting of an axial pin axially guided with respect to the extrusion head and by rods guided in the same extrusion head and connected to the axial pin.

In a preferred embodiment, means are provided for adjusting the width of the circumferential slo;t whereby the thickness of the mesh can be adjusted.

One embodiment of the invention is illustrated by way of example in the accompanying drawings wherein; Fig. 1 is an axial section of an extruding machine according to the present invention; Fig. 2 is an enlarged perspective view, partly cut away, of the two spinnerets showing the serrated slot on one of the spinnerets and the circumferential slot on the other of the spinnerets; Figs. 3 - 5 show various relative positions of the coaxial spinnerets illustrating how the integral mesh is extruded; Fig. 6 is a partial view of a tubular net, showing an enlarged portion^ of one type of mesh obtainable with the apparatus according to the invention, and Figs. 7a and 7b, 8a, 8b, 9a and 9b and 10a and 10b are diagrams of different serrated spinnerets and of the netting - 4 - 30408/2 obtainable by using them.

Referring now to Fig. 1, reference numeral 1 denotes a feed connector adapted to be connected to an eitruder scre (not shown) of a machine for extruding plastic, and which comprises an axial duct 2 through which plastics from the extruder 3 screw passes. Reference numeral ] denotes means for heating the plastics in the feed connector.

The feed connector 1 terminates in a threaded section 5 screwed into the extrusion head 6 which comprises an upper sleeve 7, a middle sleeve 8 and a lower sleeve 9» all of which are hollow and are held together by screws 10 (only one of which is shown) forming a unit which is surrounded by heating means 11· A hollow tube 12, axially mounted in a central bore in upper sleeve 7» has a portion of reduced diameter at its lower end defining an inclined annular shoulder 13, the upper part 14 of which is level with feed duct 2 when feed connector 1 is threaded into the upper sleeve 7. Tube 12 is prevented from rotating in the upper sleeve by means of key 15. The smaller diameter part of tube 12 (i.e., the part under the shoulder 13) cooperates with the bore in upper sleeve 7 to form an annular chamber 16 connected with annular chamber 17 formed between the lower part of tube 12 and the central bore of middle sleeve 8. The central bore in sleeve 8 is defined at its upper end by a conical portion 18 where chamber 16 merges into chamber 17, and at its lower end by a cylindrical portion 19· Chamber 17 is connected via a transverse annular passage 20 between the lower part 21 of tube 12 and abutment 22 of the - 5 - 30408/2 middle sleeve 8, to an annular passage 23 between the lower part of a hollow cylinder 27 received in the bore of tube 12, and one element 24 of a first spinneret that comprises elements 24 and 28. The lower surface of element 24 is formed with corrugations or saw teeth 25 (see Fig. 2). Element 24 has an enlarged abutment 26 at its upper end and is attached to the head by lower 3l©eve 9 which bears against abutment 26.

The lovier part of a hollow cylinder 27 bears the second part or element 28 of the first spinneret which is locked by a pin 29 in a position such that the corrugations or saw teeth 30 (see Fig. 2) on its upper surface mesh, with clearance, into the corresponding corrugations of the first element 24 of the first spinneret define a circumfe^ entially extending serrated slot 31 communicating with passage 23.

The upper part of cylinder 27 extends beyond plate 32 fixed to the extrusion head carrying vertical support 33» only one of which is shown in the drawings. A bracket 34 is fixed to support members 33 by means of screws 34'· The end 35 of cylinder 27 is threaded at 36 to receive a lock nut 37 for rigidly connecting cylinder 27 to the extrusion head and accurately spacing the two elements 24 and 28 of the first spinneret.

A rod 38, axially slidable in cylinder 27, has on its lower endI an element 39 of the second spinneret that comprises elements 39 and 46. Element 39 comprises a cylindrical ring having an axially-tapering lip 40 that is slidably received over the second element 28 of the first spinneret and rigidly - 6 - 30408/2 connected to rod 38 by means of a nut 41 and a matching nut 42 mounted on a rod 43 threaded at 44 into the lower end of rod 38. A gauge 45 is attached to the other end of rod 43.

The second cylindrical element 46 of the second spinneret is slidably received on the first cylindrical member 24 of the first spinneret. Part 46 has a lip 47 that axially tapers towards its front end 48 (see Fig. 2) and a side protuberance 49 which is fixed to a rod slidably mounted in aligned openings 51 and 52 in the sleeves 7-9 and in the opening 53 in plate 32. Rod 50 projects above plate 32, and the end of the rod 54 is rigidly attached to cross-piece 56 by nut 58· threaded onto the threaded end 591 of rod 50.

Cross-piece 51 has opening 60' for receiving the lower end 61' of rod 57 of an hydraulic or pneumatic ram (not shown) which is driven in a known manner so as to make rectilinear, or alternating movements as indicated by the double arrow P. The end 61' of rod 57 is formed with a threaded opening 62' in which the end 63' of rod 38 is screwed. Locking nut 64' threaded on the end 63' of rod 38, presses on ring 65' which in turn presses ring 66' against the lower surface of cross-piece 56. A sealing ring 67* engaged with a shoulder on rod 57 of the hydraulic ram, presses against the upper surface of cross-piece 56. As a result, the end 63' of rod 38 is rigidly attached to cross-piece 56 this producing a movable unit which can be driven by the hydraulic ram. The movable unit comprises cross-piece 5 to which rods 38 and 50 are rigidly attached, and the second spinneret comprising relative elements 39 and 46 which is thus movable *©i©*e to the first - 7 - 30408/2 spinneret comprising elements 24 and 28.

The hydraulic ram may be replaced by any other known pneumatic, mechanical or electrical device which can impart to the movable unit a rectilinear or alternating motion in the direction indicated by the double arrow F.

In operation, the extruded plastic from feed connector 1 passes through feed duct 2 via chambers 16, 17 and 23 into the corrugated gap or serrated slot 31 between the two elements 24 and 28 of the first spinneret Reciprocating axial motion imparted to the second spinneret comprising the elements 39 6 and 4$ kept at a fixed distance from one another by the connection previously described, causes the plastic to be forced through certain regions of the serrated slot as determined by the axial displacement of the second spinneret relative to the first spinneret., When, for example, the circumferential slot between the elements 39 and 46 is positioned adjacent the lower apices of the serrated slot 31 (see Fig. 3), the plastic is extruded into a plurality of separate filaments designated 58, 59 and 60, which filaments extend radially from slot 31» When the second spinneret comprising elements 39 and 46 moves upwardly, as shown in Fig. 4, each of the filaments 58, 59 and 60 is separated by the serrated slot 31 into two separate filaments such as shown at 61 and 62 in Fig. 4. T e latter form the two sides of a lozenge-shaped mesh which is completed when the second spinneret moves downwardly as shown in Fig. · It will be seen that the cross-section of filaments 58, 59 and 60 depend on the shape of the apices of the - 8 - 30408/2 serrated slot 31, the width of the gap between members 39 and 46, and the time during which the gap is level with the apices.

If the serrated slot is of uniform width, the resulting filaments 58, 59 and 60 are each equal in cross-section to the mesh side filaments 61 and 62. Since filaments 8, 59 and 60 form the mesh apices, the apparatus described can be used to manufacture netting in which the sides and connecting points between two meshes have the same cross-section, the connecting points being made of single filaments without soldering or adhesion, as shown more particularly in Fig. 6.

Furthermore, since all the filaments forming apices, e.g. those denoted by 61 and 62, and by 58, 59 and 60, have the same cross-section and each pass through an annular gap formed by members 39 and 46, they are all in the same plane, with the result that the netting is of uniform thickness.

The size of the meshes in the tubular netting extruded by the aforementioned apparatus will iary in dependence on the frequency of oscillation imparted to the movable spinneret head comprising members 39 and 46. Furthermore, the cross-section of the apices and the mesh filaments depends on the distance between elements 24 and 28 of the first spinneret and between elements 39 and 46 of the second spinneret. It is an advantage, therefore, to provide means for adjusting the two slots. In Fig. 1, the gap between members 39 and 46 can be adjusted by nut 41 and matching nut 42.

The invention, of course, also includes the opposite embodiment, in which the spinneret comprising elements 39 and 46 is fixed, and the elements comprising the spinneret with - 9 - 30408/2 the serrated slot are in alternating axial motion.

The invention is not limited to the particular embodiment in which the serrated slot 31 has saw teeth with rounded apices. The slot can be given a different shape, e.g. it can be made sinusoidal or rectangular. In the latter case, the machine can be used to manufacture tubular netting with overlapping rectangular meshes, in which the filaments are parallel and perpendicular respectively to the tubular netting axis.

A spinneret of this type is shown diagrammatically in Pig. 7a, where each element 24 and 28 has matching rectangular corrugations 63 and 64 overlapping into one another so as to form the corrugated opening 65. Reference numeral 66 denotes the circumferential opening of the other spinneret, which is not shown. By moving one and/or the other spinneret in the manner described previously, a network is obtained with rectangular meshes such asthose shown diagrammatically in Fig. 7b. Filaments 67 and 68 are parallel to the axis of elements 24-28, and filaments 69 and 70 are perpendicular to the axis. The heights and widths of the crenellations can be varied so as to alter the dimensions of the rectangular meshes, e.g. so.as to obtain square meshes.; In the embodiment in Fig. ,8a, elements 24 and 28 have a saw tooth opening 71 between two rectangular openings 73 and 72; in this case, the resulting netting (Fig. 8b) comprises a tubular wall section 74 havin lozenge-shaped meshes between two tubular wall sections 75 and 7o having rectangular meshes. - 10 - 30408/2 If, a3 in Fig. ¾» the serratea slot has saw teeth with one side 77 parallel to the axis of elements 24 and 28 of the spinneret, the result (Fig. 9b) is a network comprising straight filaments 78 parallel to one another and to the spinneret axis, and corrugated filaments 79 connecting the filaments 78.

Finally, if elements 24 and 28 have a rectangular opening 80 between two corrugated openings 81 and 82 (Fig. 10a), the resulting netting (Fig. 10b) has a wall section with wide lozenges 83 between two sections with more compact lozenges 84 and 85.

All tie embodiments are given by way of example.

The invention comprises all possible embodiments resulting from all imaginary combinations of different corrugations.

Claims (4)

- 11 - 30408/2 CIAIMS

1. Apparatus for continuously extruding a tubular network comprising two coaxial tubular spinnerets coaxially movable with respect to one another and provided with radially directed circumferential outlet elo1¾ the outlet slot of the inner spinneret having a corrugated saw-toothed or crenellated shape whilst the outlet slot of the outer spinneret is of substantially annular shape, the outlet slots of the two spinnerets being aligned to define a gap whose width is inde- pentently controllable, the spinnerets being displaceable with respect to each other by an axial alternating movement.

2. Apparatus according to Claim 1, wherein the inner spinneret consists of two spinneret parts axially displaceable with respect to one another and the outer spinneret consists of two rings axially displaceable with respect to one another whereby said width can be independently adjusted.

3. Apparatus according to Claim 2, wherein the two rings of the outer spinneret are connected b means of an axial pin, a cross piece and a outer pin slidable in"a guide channel formed by three consecutive axially aligned bores of a fixed support means.

4. Apparatus for continuously extruding a tubular network substantially as described herein with reference to