DE2712970A1 - Plastic hose extrusion head - with axial mandrel bore, disc channel and distributor sleeve held by offset webs - Google Patents

Abstract

A thermoplastic hose extrusion head includes a mandrel with a central axial bore for the feed, extending into a radial disc channel. The latter extends into annular spaces extending both upwards and downwards, sepd. by a distributor sleeve. The two annular spaces merge into a feed channel for the extrusion nozzle. This requires no flow correction after the plastic flow has been split by the mandrel holder. The new die can be used for plastics with different material constants with little corrections.

Description

Hose head

The invention relates to a hose head for producing a multilayer Hollow strand made of thermoplastic material, consisting of one in the hose head housing held, centrally fed mandrel, and a running in the direction of injection, Ring-shaped and connected to the spray nozzle via channels connected to the material inlet opening open feed channel.

In known hose heads, the thermoplastic is supplied Plastic via continuously or discontinuously conveying extruders, and the material is introduced into the hose head as a full strand in order to then after flowing around a stationary hose head part in the annular feed channel to get and thus to get an annular shape.

During the reshaping of the solid strand into a hollow strand, the material becomes cut open at least once and again after flowing around the fixed part welded. This results in inhomogeneities in the thermoplastic material due to temperature differences between neighboring material particles, due to different Orientation of the molecules mainly due to different flow velocities the material flows to be welded in the feed channel can be caused. The flow velocities depend on the flow paths and the canal cross-sections, which the material flows must pass before they reach the feed channel. Step If there are differences here, the mass flow is hindered and undesirable results arise Wall thickness differences in the preform, which later during the inflation process shows different stretching behavior.

With hose heads with one in the hose head cylinder over Mandrel holder Fixed mandrel, the plasticate flows around the mandrel holder before it Feed channel is fed. To achieve the most even stretching behavior possible during of the inflation process, created the mandrel holder with staggered webs. The centrally fed plastic is divided by the offset bars. The splitting takes place only up to the middle of the hose in order to achieve a better weld of the plastic, because the inner and outer webs are through a Ring connected, which causes a division into two layers. Between Ridges flow partial currents, the outer layers of which have increased dwell times and orientations exhibit. A confluence is created by the obstruction of the mass flow through the webs disturbed below the webs.

This impairment is particularly different due to the long stretches in the channels between inner and outer webs favored. The differences in the path result in different flow speeds and times, this in turn results in temperature differences in the melt streams, from which orientation and develop density changes. One tries to find something that is reasonably satisfactory Flow compensation through exact coordination of the length of the feed channel following the webs and the coordination of the inner and outer channels between the inner and outer webs to reach the mandrel holder.

With such a coordination, the material properties are closed consider. A satisfactory flow balance can only be achieved with plastics work with comparable material values. For processing plastics other material properties, the hose head must be converted by using other web arrangements, Channel cross-sections and lengths must be determined empirically.

According to DT-OS 25 18 649, a hose head with a central flow is used Known mandrel, in the case of the central channel in the upper part of the mandrel fastened in the hose head is arranged.

The part of the mandrel, which is at a distance below, is interposed a mandrel holder middle part by axially extending bolts on the upper part of the mandrel attached.

In this way, two floors are created one below the other Channels, which in turn open into the feed channel via separate ring channels. Seen in a longitudinal section, the image presents itself with several nested one inside the other Bowls, the conically outwardly directed side walls of the annular channel boundaries form. The volistrang coming in from the central channel is partly in the upper one Distributed floor and over the adjoining ring channel as a hose fed to the feed channel. Part of the plastic material migrates through a central bore of the mandrel holder middle part in the lower distribution tier and of its ring channel as well into the feed channel, in which the two converging partial flows become one Hollow strand are welded together.

It should be possible to achieve better mandrel stabilities here.

Because of the rotational symmetry of the Components be simplified. However, there remain flow paths of different lengths Above all, however, distortions of the material flow when passing through the central connecting opening between the distribution floors in the mandrel holder middle part and thus similar disadvantages as with the mandrel holder.

The invention is based on the object of producing a hose head to improve a multilayer preform made of thermoplastic plastic in such a way that that a flow correction occurs behind the dividing zone, whereby the Hose head Even more plastics have different value functions with only minor and simplified post-corrections should be suitable.

These objects are achieved according to the invention in that the end of the central channel running in the axial direction in the mandrel into a single disc-shaped, with the feed channel connected transverse channel opens, with a distance in front of the Inlet into the supply channel of the transverse channel to one up in the axial direction and the annular space extending below is widened, in the interior of which there is a distributor nozzle used in compliance with the wall clearances to the inner wall of the annular space and the outer wall of the sleeve is.

The axial extension of the rotationally symmetrical annulus has equal length from the transverse channel in both directions.

The distances from the wall to the distributor sleeve are also the same.

Because of the channels, which are identical in their dimensions, and because of the same The plasticate adds lengths in the annulus divided by the inner sleeve the splitting takes the same paths back, so that the same orientations and temperatures in the partial flows converging at the end of the single transverse channel behind the annular space to rule. This eliminates differences between the partial flows, see above that a post-correction is unnecessary.

In a further development of the invention, the distributor sleeve can be above and below of the transverse channel through longitudinal webs evenly distributed over the inner circumference of the sleeve be connected to the opposite mandrel wall. The longitudinal webs are advantageous here arranged offset in the upper and lower sleeve part. The one downstream from the bridge side The web-free channel then acts as an ironing zone.

In an embodiment of the invention, the distributor sleeve can by means of their end faces attacking screw bolts attached within the annular space be, according to a further idea of the invention of the screw bolt transverse Wall openings are provided in the distributor sleeve. The breakthroughs serve as flow compensation for the material flow inhibited by the bolts.

Embodiments of the invention are shown in the drawing, for example shown.

1 shows a hose head designed as an extrusion head in longitudinal section with longitudinal web connections, Fig. 2 the section C-D of Fig. 1, Fig. 3 shows the section A-B of FIG. 1, FIG. 4 shows an extrusion head with an enlarged central channel, 5 shows an extrusion head with screw bolt connections in an enlarged section.

In the figures, the cylinder of the extrusion head is indicated by 13, and by 2 the mandrel fastened in the cylinder and with 14 the annular piston guided on the mandrel 2 designated. The annular piston 14 is in the upper position in the exemplary embodiments shown. In the dashed lower setting, the annular piston i4 fills the Memory 15 full.

The plasticate delivered by the extruder 16 arrives at a right angle Deflection into the central channel 1 arranged in the mandrel 2 and from there into the only one Transverse channel 5, which is at a distance before entering the supply channel 4 to an annular space 6 is expanded. The hanging space 6 extends in the axial direction in the same length up and down1 so that the transverse channel 5 the annular space 6 in two divides equal halves. The distributor sleeve 7 is arranged within the annular space 6, in such a way that the annulus is divided cross-sections into the same gap.

In Figs. 1 to 4, the distributor sleeve 7 is through evenly over the inner circumference of the sleeve distributed longitudinal webs 8 with the opposite mandrel wall tied together. As best seen in FIGS. 2 and 3, they are opposed to each other Longitudinal webs 8 on the upper and lower sleeve part are arranged offset from one another.

In the embodiment of FIG. 5, the distributor sleeve 7 is means Screw bolts 9 held in the annulus. Below the screw bolts 9 are found the wall openings 10 in the distributor sleeve 7.

In the extrusion head according to FIG. 4, the central channel 1 is above the extended for most of its length. In this enlarged diameter 11 protrudes Central bolt 12 of smaller diameter into it.

In the dashed lower position of the annular piston 14 (Fig. 1 and 4) After leaving the transverse channel 5, the plasticate arrives via the feed channel 4 into the flow channel 17 located under the annular piston 14 and presses the annular piston i4 upwards, whereby the storage space 15 is released for receiving further material will. By lowering the annular piston 14, the plasticate is removed from the storage space 15 pressed through the annular gap of the nozzle 18 to the outside.

The measure shown in Fig. 4 has the advantage that in the the splitting section li following the central channel 1 has a uniform temperature sets in the plasticate.

The ring-shaped temperature zones that form in the full strand become reduced.

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Claims (7)

patentans # rücre hose head for producing a multilayer Hohistranges made of thermoplastic material, consisting of one in the hose head housing held, centrally fed mandrel and a running in the direction of injection, Ring-shaped and connected to the spray nozzle via channels connected to the material inlet opening towards the open supply channel, which means that the End of the central channel (1) running in the axial direction in the mandrel (2) into a single one disc-shaped transverse channel (5) connected to the feed channel (4) opens, with the transverse channel (5) closed at a distance in front of the inlet into the feed channel (4) an annular space (6) extending upwards and downwards in the axial direction is, in the interior of which a distributor sleeve (7) while maintaining wall clearances is used for the inner wall of the annular space and the outer wall of the sleeve. 2) hose head according to claim 1, d a d u r c h g e k e n n -z e i c h n e t that the axial extension of the rotationally symmetrical annular space (6) from Transverse channel (5) has the same length in both directions and the distance to the wall (7) Distributor sleeve are the same. 3) hose head according to claims 1 and 2, d a d u r c h g e k It is noted that the distributor sleeve (7) is above and below the transverse channel (5) through longitudinal webs (8) evenly distributed over the inner circumference of the sleeve with the opposite mandrel wall is connected. 4) hose head according to claims 1 to 3, d a d u r c h g e k It is noted that the longitudinal webs (8) on the upper and lower sleeve part are arranged offset from one another. 5) hose head according to claims 1 and 2, d a d u r c h S e k It is noted that the distributor sleeve (7) by means of their Fastened screw bolts (9) attacking the end faces within the annular space (6) is. 6) hose head according to claim 5, d a d u r c h e k e n nz e i c h n e t that below the screw bolts (9) transversely extending wall openings (10) are provided in the distributor sleeve (7). 7) hose head according to the preceding claims, g e k e n n z e i c h n e t by enlarging the diameter (ii) over part of the length of the central channel (i), in which a fixed central bolt with a smaller diameter (12) is inserted.