DE2748164C2 - Device for the production of a pipe from a thermoplastic material by means of extrusion - Google Patents

Description

characterized in that in front of the head part (26, _ ^

64) on the dome (9, 59) a heating direction (13, 72) 35 that is present on the tube of the end to form an inner skin is. area of the cathedral formed by a separate headboard.

5. Device according to one of claims 1 to 4, characterized in that the head part (26, 64) and the rest of the dome (9.59) relative to each other are rotatably arranged. 40 is arranged

6. Device according to one of claims 1 to 5, in this way the internal cooling area closes characterized in that the cooling length of the

Head part (26, 64) is larger than a quarter and smaller than four times the wall thickness of the pipe (15). det is that forms the tool-side closure of the internal cooling area and that between the head part and a thermal barrier directly attached to the remaining part of the mandrel to the molding tool, the coolant bringing the mandrel head part to such a temperature cools that the pipe is still inside the mold, where the plastic material from the extrusion pressure is promoted, a solidified inner skin receives, which then receives no more damage. Through the Thermal barrier ensures that none of the material flow disturbing cooling of the rest of the cathedral

50 sin occurs Another advantage is that with considerable higher extrusion speed can be driven. You can also do this inside the mold work at higher temperatures than usual.

The invention relates to a device for producing a pipe from a thermoplastic material by means of extrusion, with a molding tool that has an annular channel delimited on the inside by a mandrel for

Contains the passage of the plastic, in extrusion 55 if the thermal barrier is adjusted accordingly, the direction of the outlet, seen behind the outlet opening of the with the formation of the inner skin in the area of the dome ring channel, is closed at both ends and
Inside cooling area bounded on the outside by the inside of the pipe, the coolant supply line of which goes through the mandrel
runs, as well as a cooled 60
the calibration jacket are available.

With one of the generic DE-QS 25 06 517 * known device begins the internal cooling area

- just like the outer calibration jacket - with ab- _{β a}

stood by the molding tool. The material savings from the molding tool 65, but also a faster pipe exit extruded pipe passes freely through the reconstruction entails.

ambient atmosphere to the tool-side From DE-OS 24 56 386 it is known that the

Closure of the internal cooling area forming the sealing element, a directly adjoining internal cooling

Headboard is ensured. Since the internal cooling area directly adjoins the molding tool, the Device also shorter.

In all of this, the advantage is retained that there are no tensile stresses in the tube material on the inside of the tube. but compressive stresses arise, so that a. Pipe designed for a certain internal pressure can be relatively thin-walled, which is not just one

rich can limit. A targeted formation of the inner skin on the pipe inside the mold is not provided and does not occur inadvertently, since the Here a continuous one-piece mandrel is only cooled on the front side by the refrigerant gas injected in the known case will. Incidentally, greater cooling would result in uncontrolled and material flow in the mold disruptive cooling of the cathedral result.

The thermal barrier is useful formed separate insulating ring. In this way you can use the material of the headboard to achieve the desired cooling effect accordingly and the material of the insulating ring of the required thermal insulation independently choose from each other.

As an alternative to this, the thermal barrier can be formed by a cross-sectional tapering of a cylindrical area be formed of the head part.

It is also advantageous that there is a heating device in front of the head part on the dome. By means of a Such a heating device can possibly occur in spite of the thermal barrier towards the cooled head part Heat loss can be compensated.

Another useful measure is that the head part and the remaining part of the mandrel relative are arranged rotatably to each other. In this way you can with a rotating mandrel with a fixed head part or with a stationary mandrel with a rotating head part. A rotating mandrel can then, for example be advantageous if reinforcing fibers are contained in the plastic material.

Finally, practice has shown that it can be advantageous that the cooling length of the head part is greater than a quarter and less than four times the wall thickness of the pipe is

Embodiments of the invention will now be described with reference to the drawing. It shows

F i g. 1 shows the longitudinal section of an extrusion device in a schematic representation and

F i g. 2 another embodiment of the device also in a longitudinal section.

The pump part 1 of the in F i g. 1 shown extrusion device contains a disk-shaped pump body 2, which is rotatably mounted by means of an axis 3 is and can be driven in any known manner, e.g. B. with the help of a V-belt pulley 4 and a driven V-belt 5.

The pump part 1 is followed by a molding tool 6. This contains an annular channel 7, the outside of an outer wall 8 and is bounded inside by a mandrel 9 and with derr. Pump chamber 10 of the pump part 1. in which the blades 11 of the pump body 2 rotate, The outer wall 8 and the mandrel 9 hold the annular channel 7 with the aid of heating elements 12 or 13 at the desired temperature. A calibration jacket 14 for the Calibration of the outer diameter of the pipe 15 to be produced. Around the calibration jacket 14 water jackets 16 are arranged. The calibration jacket 14 is also provided with bores 17 which serve to that when the extrusion process starts, the first lengths of the tube 15 being formed are good Guide to the calibration jacket 14 can be sucked in by generating a vacuum in the bores 17 will. Seen in the direction of extrusion downstream, the water jacket 16 can be independent connect from this usable further water jacket 18, in which the pipe 15 as a container wall serves

In the exemplary embodiment, the mandrel 9 forms a solid whole with the disk-shaped pump body 2, see above that it rotates with it. The axis 3, the disk-shaped pump body 2 and the mandrel 9 The unit formed is provided with a central bore 40 through which lines concentric to one another are provided through the zv / ei 20 and 21 enter, each a connecting mare 22 and 23 respectively. The line 20 runs concentrically in the mandrel 9, with an insulating material in between 25 containing annular space 24 is present

Downstream, the line 20 continues to the end region of the mandrel 9, where it is at one of the end regions of the mandrel-forming head portion 26 is attached. The head portion 26 is over with the remainder of the mandrel an insulating ring 27 is connected, which can also serve as a centering for the head part 26. The material of the Jisolierring 27 is chosen so that it is at temperatures of about 220 ° C its stiffness or his Maintains load-bearing capacity In addition, it must have good sliding properties because of the rotating mandrel 9, offer little resistance to the plastic pipe passing through and ultimately be workable with dimensional accuracy. Suitable materials that meet these requirements, are known

The line 21 extends approximately to the end of the water jackets 16, 18, as seen in the extrusion direction. in the End of the line 21 holes 28 are attached. At its end, the line 21 is with a Seals having piston 39 connected, which closes the interior of the tube 15

During operation, powdery or granular plastic material enters the pump chamber 10 and becomes there brought into a liquid state by heating means (not shown). The disk-shaped pump body 2 pumps this plastic material into the heated annulus 7, where the liquid mass, on the right Brought temperature, takes the tube shape and the mandrel end, d. H. the head part 26 reached, on which the Dorn is left.

Via the connection piece 23 cooling water is admitted into the line 21, which through the openings 28 in an internal cooling region 30 flows through the wall of the tube 15, the head part 26 of the mandrel 9 and the Piston 29 limits the distance between a head part 26 and the piston 29 is so great that the tube 15 when the piston 29 is reached, it has already hardened sufficiently to allow a caterpillar haul-off without deformation to be able to happen.

The water located in the inner cooling area 30 flows against the head part 26 and cools it to a Temperature at which the processed plastic is at least almost solid. This gives the pipe vcr leaving the head part on the inside a firm one, which can be thin. Immediately after the The pipe with the cooling water flowing through the internal cooling space 10 enters the outlet from the annular space 7 Contact, so that here an extremely intensive cooling of the tube 15 takes place from the inside. Come in addition, preferably a little downstream, the external cooling through the calibration jacket 14 with the water jacket 16. The layers solidifying from the inside and the outside of the pipe meet each other about half the thickness of the pipe wall. Compared to cooling from only one side the cooling time is reduced to «in quarters.

The cooling water that has flowed out of the openings 28 into the internal cooling area 30 is transferred via the between the two Lines 20, 21 located annular space

19 and the connecting piece 22 derived so that heat is exchanged in countercurrent. The pressure of the Cooling water is chosen so that the solidifying pipe 15 is pressed against the calibration jacket 14 in such a way that that the desired outer diameter of the finished pipe is exactly obtained.

The cooling of the pipe wall from the inside results in the finished pipe in the area of the inside Compressive stresses. This has for a pipe that is to transport a pressurized medium to As a result, the wall thickness can be relatively thin. They also make compressive stresses in the area the inner wall coming into contact with the transported medium, the pipe material less sensitive to stress corrosion. is

In the embodiment described above, the head part 26 of the dome 29 is by means of a line

20 kept still, which may be useful in some cases may, in other cases it may be more favorable that the Head part 26 is seated on mandrel 9 in a rotationally fixed manner. It will be understood that in this case the line 20 is rotatable with the Connection 23 must be coupled.

In the embodiment according to FIG. 2, where the molten plastic is better known through an extruder Construction method is promoted, the mandrel stands still. The melt is via a channel 51 in a connector 50 and fed via a pre-distributor 52 into the helical channels 54 of a spiral distributor 53 headed. In such a distributor, the melt becomes flatter in the direction of extrusion Worm threads 55 of the channels gradually distributed over the entire circumference, in such a way that in the annular gap 57 between the housing 56 and the smooth end 73 of the distributor 53 a homogeneous extrudate is present, the mean flow rate in the extrusion direction at each circumferential point of the gap 57 is the same.

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the actual molding tool, which consists of a housing 58 and a mandrel 59. The plastic material comes out of the annular gap 57 via a transition channel 60 to the outlet-side annular channel 61, which essentially extends from the cylindrical inner wall of the housing 62 and the mandrel outer wall 63, which is concentric to this, is limited. The end area of the cathedral is in turn formed by a head part 64 which is attached to the coolant discharge line 65, which in turn screwed tightly to the end piece 68 of the distributor 52, 53 by a nut 66 via a few disc springs 67 will. In this way, the relative length caused by differences in temperature can Line 65 across from the core unit 52,53,59 the disc springs 67 are collected. The head part 64 closes by means of a profile edge 69 to the rest Part of the dome 59, which is provided with a corresponding profile edge 70 for this purpose

In order to reduce the heat transfer between the head part 64 and the remaining part of the mandrel 59, is In this case, the head part is provided with a taper 71 in the cylindrical area, whereby the for the Heat conduction available cross-section is kept small. The head part 64 consists of a heat relatively poorly conductive material, e.g. B. 37% nickel steel The mandrel 59 is with a heating wire 72 is provided, the capacity of which is chosen so that it precisely compensates for the heat dissipation via the taper 7i can.

In this embodiment there is the possibility of the head part 64 being rotatable relative to the rest Run part of the mandrel. In order to determine the axial component of the friction vector between the head part 64 and the To reduce the size of the already hardened inner skin of the pipe, it is useful that the head part 64 rotates.

For this purpose 2 sheets of drawings

Claims (4)

Patent claims: 1. Device for the production of a pipe from a thermoplastic material by means of extrusion, with a molding tool that has an annular channel, which is delimited on the inside by a mandrel, for the passage of the plastic contains, seen in the extrusion direction behind the outlet mouth of the ment over which the pipe is pulled. At the point of this sealing element, the pipe is mainly located on its inside - between the mold and the sealing element, the pipe encloses a standing one and therefore a hot volume of air - still plastic State so that when sliding over the sealing element there is a risk of damage to the inside of the pipe Furthermore, when the pipe slides onto the sealing element, abrasion occurs which is Ring channel collects a closed volume of air that is closed at both ends. Since this sticky abrasion, so to speak and bounded on the outside by the inside of the pipe, adheres to the pipe sliding past, the cooling area, its coolant supply line
runs through the mandrel, as well as one on the outside of the tube it brings further damage to the inside of the pipe with it. In order to remove the abrasion, the operation must the device are interrupted. The inside of the pipe, which is still plastic, also gets there in the internal cooling area in direct contact with the coolant, causing deformation of the inside of the pipe Also, due to the high temperatures in the the tool-side closure of the internal cooling air volume between the mold and the sealing area ßO) , and also the quality of the inside of the pipe Adjacent cooled calibration jacket are available, characterized in that - That to form an inner skin on the pipe (15) the end region of the dome (9, 59) is formed by a separate head part (26, 64) which that between the head part (26, 64) and the remaining part of the dome (9.59) a thermal barrier (27,71) is arranged damaging oxidation of the pipe material occur. Finally, it is also disadvantageous that it is necessary because of the free exit of the extrudate from the molding tool this and the sealing element to a so-called melt fracture, d. H. to a wave-like changing course of the wall can come. Around to avoid this, the extrusion speed must be correspondingly low. Based on this, the object of the present invention is to provide a device of the initially to create the type mentioned, with the help of which you get a pipe with the most perfect inside This object is achieved according to the invention 2. Apparatus according to claim 1, characterized in that the thermal barrier bus a separate Isolating ring (27) is formed 3. Apparatus according to claim 1, characterized in that the thermal barrier is formed by a cross-sectional taper (71) a cylindrical region of the head part (t >> 4) is formed 4. Device according to e / iem di. Claims 1 to 3,