DE1187361B - Device and method for calibrating a pipe made of thermoplastic material emerging from an extrusion press - Google Patents

Description

Apparatus and method for calibrating one of an extrusion press Exiting pipe made of thermoplastic material For the production of pipes from polyamides and superpolyamides one usually uses extrusion presses, from their Mouthpiece made of plastic about 240 "C warm in the form of a viscous sticky liquid exit. This freshly drawn pipe must then be quickly immersed in cold water, so that it solidifies there, whereupon it is stretched and in special devices is rolled up.

Here, however, the round cross-section of the pipe, which is usually is maintained by a slight excess gas pressure inside the pipe, and the exact dimensions in terms of diameter and wall thickness are difficult to match required accuracy, and the achievable diameter will be very soon limited by irregularities in dimensions. Because of this, has Up to now, polyamides have only been used to produce pipes with a small diameter.

When manufacturing pipes made of thermoplastic material (e.g. B. made of polyvinyl chloride or polyethylene), which from the mouthpiece in paste-like non-adhesive form, it is common today to use a "cold nozzle" for molding to use, which consists of a metal pipe cooled from the outside with water that the pipe made of still hot plastic slides, that by inflation is pressed against the inner wall of the cooled metal pipe.

However, such a procedure cannot be used with polyamides, because they are still flowable and very sticky at the exit of the mouthpiece.

Some materials, e.g. B. polytetrafluoroethylene or monochloro-trifluoroethylene, show both good heat resistance and good heat resistance at the processing temperature non-adhesive properties and the ability to cope with sufficient mechanical Deform accuracy.

However, these materials have the disadvantage of being poor heat conductors so that cooling from the outside is not sufficient during the deformation.

According to the present invention there is an apparatus and a method for calibrating a thermoplastic pipe emerging from an extrusion press Plastic, in particular a polyamide, provided, this device consists of a sleeve with perforations through which water of lesser amounts Pressure than prevails inside the pipe to be calibrated, directly with the wall of the tube comes into contact, the device being characterized in that the inner surface of the sleeve is provided with a plurality of flow paths, wherein, as is known per se, the sleeve has the same cross section over its entire length and tightly encloses the pipe to be calibrated.

In particular, the following advantages are achieved by the invention: Great simplicity of execution, especially with smaller diameters; increase the cooling capacity; the possibility of printing on the outside of the extruded Adjust the pipe to the desired value in the course of the solidification process.

According to one embodiment, flow paths are in the wall of the sleeve (For example, grooves or grooves) cut with such a small cross-section that the to The cooling material is not exposed to the influence of the internal pressure, albeit a low one can get stuck in it, which keeps the tube inflated when in these flow paths water is introduced under sufficient pressure. Apart from its cooling effect the water also contributes to the lubrication of the sleeve and prevents it from sticking of the pipe on the wall.

The claimed device is in contrast to known devices the following advantages at the same time: a) the highest possible continuous calibration and b) the contact of the pipe emerging from the extruder with water.

Advantage a) thus becomes constant over its entire length with the help of a Cross-section possessing sleeve (known per se) achieved on the inside flat flow paths (Troughs), which can be helical, the turns of which are close to one another, can be arranged so that the pipe material can not penetrate, or the can also be formed by a series of plates with vertical spaces between them or form parallel passages to the interior of the sleeve. Generally used one in practice for the production of narrow pipes spiral-shaped gutters and for wide ones Tubes plates.

But in order to make the constant calibration as precise as possible, must be an externally acting force over the whole of the pipe during the solidification Act on the material surface of the device. Advantage b) is therefore preferred achieved so that the sleeve when it is put into operation in a vacuum The vessel containing water is located and the inside of the tube is atmospheric pressure prevails. At the same time, the pipe becomes intense in direct contact with water chilled. Such intensive cooling cannot take place through sleeves with cooling jackets. So negative pressure and cooling always come in the same place, i. H. here about the entire length of the device for action, the passage of the tube through the device requires the time for excellent cooling and calibration necessary is.

The water keeps the surfaces of the pipe shiny and prevents it Sticking.

Known methods and devices require the generation of a Overpressure inside the pipe. However, polyamides in particular are against overpressure sensitive, and caused by the overpressure applied inside such a pipe Bloating, if not a tearing of the pipe.

This is particularly the case with fluctuations in the difference in the pressures within and outside the pipe the case. For this reason, one needs in known devices for the precise regulation of the overpressure a device for supplying a measurable Amount of a gas (generally nitrogen) that is blown in under pressure.

Instead of maintaining an overpressure of a few Torr inside the pipe, According to the invention, atmospheric pressure prevails inside the tube, while the cooling liquid is held at negative pressure. It avoids gas leakage and it is easy to keep the pressure difference constant. As mentioned, occur when working in this Do not show any inflation of the pipe or other disturbances. That under atmospheric pressure A standing pipe can be read after it has passed through the sleeve without disturbing the calibration saw up.

When working with known devices and with known methods does not take place at the same time as negative pressure and direct contact with water instead of. Thus, a form in which the warm plastic material moves is known. The part the surface of the mold, which is in a container, is perforated. So it is only provided there for cooling with water.

They are also known to be arranged at a distance from one another for shaping Plates that are deliberately made with only part of the surface of the hollow body to be molded stand in touch. The plates are so far apart that the pipe inflates between the individual plates. With the help of such a device a calibration that is as precise as that according to the invention will by no means take place is possible.

The sleeve can be in the form of a hollow cylinder or any have different cross-sections to tubular hollow bodies of any cross-sectional shape to manufacture, e.g. B. in cross-section elliptical, square and rectangular tubes.

As already indicated, the sleeve can consist of one piece or be formed by several side by side arranged items to either to facilitate the operation or start-up of pipe production.

It can also be in the open air or in a container with cooling water be arranged.

The dimensions of the inner cross-section of the sleeve depend on the masses of the pipe to be produced, taking into account the possible during cooling Shrinkage and deformation.

The extrusion die not forming part of the present invention can be designed in any way. Its dimensions at the outlet end that with those match the sleeve according to the invention, are based in particular on Art the material to be extruded, the extrusion speed, the operating temperature, the distance between the beginning of the sleeve and the exit end of the extrusion die, the shape of the pipe to be produced, etc.

The sleeve must be long enough that the pipe from it is in a solid state and are not deformed by the pressure inside them can. If necessary, several identical sleeve elements can be set joint-tight or not joint-tight to one another, their position to one another invariable in the longitudinal direction or can be regulated.

According to another embodiment, the sleeve is designed so that they have several immediate ones over part of their length or over their entire length Has flow paths for water through their walls. For example, you can consist of a tube that is pierced at numerous points or by a Metal mesh is formed, which is arranged along a cylinder jacket and advantageous is even woven cylindrically or, even more appropriately, from one or more threads or wires that are helically wound and held in place and immersed in the cooling liquid.

The thread or wire can be made of any material that can suitable for contact with the plastic in the extrusion press. He can z. B. off Polyamide, polytetrafluoroethylene or made of metal. The experience has shown that in the case of a metal wire, e.g. B. made of copper, by the abundant Lubrication that is due to the fluid in which the very permeable Sleeve dips, the sticking of the plastic sliding through at the wall prevented and the heat is better dissipated.

Another, also already indicated embodiment of the sleeve is characterized by an arrangement of the items, in which these together so are connected that they together form the wall of the sleeve, with between them recesses remain free, which direct contact with the coolant with the pipe to be cooled.

In this way one achieves numerous advantages in terms of Ease of performing the calibration, the ability to adapt to really any cross-section, the rigidity and non-deformability of the pipe, these latter properties are particularly important when it comes to the Manufacture of large diameter pipes.

The individual parts are in the direction of movement of the pipe to be calibrated arranged one behind the other. They wesien openings, the circumferences of which have the cross-sections of the sleeve.

The items are often arranged so that one edge of each of them forms a surface line of the sleeve channel, the spaces between the individual parts then also follow the surface lines.

The individual parts can be plates or rings or rods.

The invention is useful for processing all plastics, where rapid cooling is important or which is not harmful (e.g. for polyamides, polyethylene, etc.).

The further description of individual items given on the basis of the drawings Embodiments of the invention make the device and its application more understandable.

F i g. 1 is an axial section through an embodiment of the invention; F i g. Fig. 2 is a section along the line II-II; F i g. 3 shows on a larger scale a section through a groove which is provided in the inner wall of the sleeve; F i g. Figure 4 is a longitudinal section of an embodiment having a helically wound one Wire; F i g. Fig. 5 is a cross section along the line V-V; F i g. 6 and 7 are partial longitudinal sections of two embodiments, with respect to the shape of the helically rolled up Wire are modified; F i g. 8 to 10 relate to embodiments that are modified with respect to the structure of the sleeve; F i g. 11 is a cross section by a sleeve, which is built up from mutually parallel plates, which transversely are arranged to the axis of the aisle; F i g. 12 is a longitudinal section along FIG Line XII-XII of Figure 11; F i g. 13 shows a partial section on a larger scale a plate and the rounded edge of its window; F i g. 14 and 15 are analogous Views of a somewhat different embodiment in which the plates are parallel to the Axis of the sleeve are arranged.

In the case of the in FIG. 1 to 3 illustrated embodiment, 1 is the Extrusion die, which has an annular passage 2 from which the plastic Existing pipe 3 exits, as well as a central channel 4, through which one under atmospheric pressure a gas, e.g. B. nitrogen, blows into the interior of the tube 3 to make it inflated to hate. The sleeve is located at a certain distance from the mouthpiece 1 5, the cylindrical channel 6 of which has the same inner diameter as the outer diameter of the finished pipe should be. This tube, made by the pressure of nitrogen is pressed against the channel 6 is by known means in the direction of the arrow 7 drawn. The sleeve 5 is advantageously made of polytetrafluoroethylene or one similar material.

A screw groove 8 is cut into the wall of the channel 6, in the example shown here, clockwise over one part of the bore and runs counterclockwise over the other part, these two parts of the groove meet at a common point 9, from which it is preferably tangential a passage 10 extends through which cooling water flows. The flowing through the groove 8 Water runs off at ii at the ends of the groove. It enables immediate cooling of the plastic pipe 3 and at the same time a kind of lubrication between the pipe and the wall of the sleeve, thereby reducing the non-adhesive properties of the sleeve 5 used plastic can be improved. Channel 6 is of course so long that the pipe emerges from it in a solid state no longer deformable.

The groove 8 preferably has approximately a profile as in FIG. 3 shown it has a sharp edge 8 a on the side on which the extruded tube arrives, and an opposite edge 8b with a stronger bevel through which the movement and distribution of a thin layer of water between the pipe 3 and the Channel 6 is facilitated.

In the described Aufsührungsform allows between the End of the mouthpiece 1 and the entry into the sleeve 5 existing distance as a result the flowable nature of the mass emerging from the mouthpiece the use a sleeve with a cross-section that differs from that of the mouthpiece. One can So with one and the same mouthpiece by suitable cross-sectional dimensioning of the sleeve Manufacture pipes of any cross-section.

In the case of the in FIG. 4 embodiment shown is the sleeve, which in this example has a circular cross-section and in which that from the Mouth piece coming plastic tube 3 slides, formed by a metal wire 20, which is rolled up helically with almost tight spiral joints, with the inner diameter the spiral corresponds to the outer diameter of the tube 3. The spiral is between Longitudinal rails 21 held, which are expediently on the standing with the spiral in contact Side is provided with a type of toothing 22 with rounded notches, in which fit the turns of the spiral that way well at the desired spacing being held. The rails 21 are in turn held by retaining rings 23, to which they can be soldered. The arrangement thus formed can be placed in a container be immersed, which contains the cooling liquid and its walls through holes are perforated, which allow the passage of the extruded pipe to be cooled.

As shown in Figs. 4 and 5, the one from the spiral and the parts 21 and 23 existing structure but also lie in a cylinder 24, which is set up for a circulation of cooling liquid is. This liquid enters the cylinder through a pipe 25, flows between the Rails 21 along the spiral, is constant between the turns of the spiral 21 with the pipe 3 to be cooled and then exits through the pipe 26.

The rails 21 are expediently provided with lugs 27 through which they are centered at the same time with the spiral on the inner wall of the cylinder 24.

This is closed at both ends by screwed-in floors 28, which are provided with holes 29 in which the ends of the screw are centered and through which the pipe 3 to be cooled slides. The spiral can of course also pass through the floors 28 protrude and need not cut off with the outer surfaces of these floors, as shown in the drawing.

The wire forming the spiral can also be used instead of the circular wire Cross-section have any other cross-section, for example an oval (Fig. 6) or rectangular (Fig. 7) cross-section.

In Figure 8, an embodiment is shown in which the sleeve for the spiral forming the extruded tube only at both ends in the bottoms 28 is held, but for which it must be sufficiently stiff. The floors have this a kind of thread 32, which corresponds to the increase in the spiral and in which this can be screwed in. The left bottom is screwed into the cylinder 24 itself. It first picks up the spiral, the end of which is inserted into its thread 32. Of the right bottom has a smooth cylindrical wall 33. You screw it onto the spiral to hold it in the cylinder 24 and hold it by a clamping screw 34 fixed.

The embodiment according to FIG. 9 allows the action of different Negative pressures or different temperatures along the path that the Tube has to go through inside the channel formed by the spiral. The order the spiral 20 of the cylinder 24 and the bottoms 28 is the same as in FIG The interior of the cylinder 24 is here, however, in three chambers cl, ce and c8 by the Winch 35 divided. Each of these chambers receives from the containers bl, bs, b3 coming Cooling liquid and then releases it into the container b1 ,, b2 ,, b3 ', all these containers have a constant liquid level. In the example according to the drawing, the containers are shown lying below the device, the circulation is determined by the height difference between the liquid levels caused, which is here designated with hl ', h2', h8 '. In the three chambers there is a pressure that is below atmospheric pressure.

The negative pressure in these chambers corresponds to the height of the lower plates hl, h2, ht is the liquid level and the feed losses. This negative pressure due to the great permeability of the channel formed by the spiral the outer wall of the extruded tube allows a close fit of the tube on the inner wall of the channel without inflating the Pipe to a pressure above atmospheric pressure is required.

The effect of the negative pressure can if there is an important reason the aim is to use one or more pumps, preferably piston pumps, or by some method of aspirating liquid. the Characteristic values of this Vorcht are depending on the required Suppress and the to be achieved Select and adjust services.

In FIG. 9, the cylinder 24 is also immersed in a container 36 shown, which is filled with liquid up to a certain height 37. The pipe moves through the openings 38 in the walls of the container 36, and through Liquid emerging from these openings is collected in drainage lines 39.

The embodiment of FIG. 10 is suitable for installation replaceable To allow spirals of different diameters in the same cylinder. the Bottoms 28 of the cylinder 24 have an opening 40 of a diameter that is larger is than the diameter of the largest spiral in question. This opening 40 is threaded and can accommodate intermediate rings 41, which themselves again are suitable for receiving the respective spirals. A retaining screw 42 is used to secure the intermediate ring 41 against rotation after its use.

Instead of a circular cross-section, the geometric cylinder, around which the spiral is wrapped, also have an oval or other cross-section, whereby one is able to produce pipes in it by cooling and solidification, which have an oval or other cross-section.

To produce such a spiral, it is sufficient to pass the wire through which it is formed to wrap a mandrel with an oval or similar cross-section, which you then pull out. You can also make spirals like this for the manufacture of pipes with a square or rectangular cross-section, etc. are suitable.

In each case one chooses the diameter of the one forming the spiral Wire as well as the spaces between the turns (which, by the way, are can also change from one end of the spiral to the other) depending on of the dimensions in question, e.g. B. depending on the diameter of the to be molded Pipe and its wall thickness.

In the case of the in FIG. 11 to 13 illustrated embodiment is the Sleeve formed by an arrangement of metal plates 50 which are parallel to each other one behind the other in the direction of movement of the pipe to be cooled (arrow f in Fig. 12), d. H. are arranged transversely to the surface lines of the channel. the end each of these plates is e.g. B. punched out a window 52 that exactly matches the shape of the has the outer cross-section of the pipe to be produced. The drawing shows such Windows that are in the shape of a rectangle; however, they can of course also have any other shape, so that the arrangement can have any cross-sectional shape of the pipe can be adjusted. As in Fig. 13, the edges are the Windows preferably rounded off by a special treatment so that no sharp ones Edges occur that damage the surface quality of the pipe to be cooled could.

The plates are arranged in relation to one another so that their windows S1 are aligned are aligned and that still between two consecutive plates there is always an intermediate space 52 which allows the cooling liquid to move freely between the panels allows to the outer surface of the successive To rinse the window running pipe to be cooled. With such a arrangement in the overlying plates located holes 54 and spacers 55 go through, which establish the desired distances between the plates. The whole is located in a container 56 which contains the cooling liquid and is provided with inlets 57 for the inflow and outflow of this liquid. The end faces of the container, which run parallel to the plates, are of course suitable for and the outlet of the pipe to be cooled is provided with the same windows as the plates.

In the drawing, plates are shown that are the same size like the containers have to center the said plates well in the horizontal plane to be able to, however, have a slightly lower height to between the lower and top edges of the panels and the bottom as well as the top of the container To leave passages 58 so that all spaces between the plates are immediate are in communication with the supply and discharge of the liquid. Foot parts 59, which form a whole with the plates and rest on the bottom of the container, are used to center the panels in terms of height.

In the embodiment according to FIG. 14 and 15 are plates 50 not transversely to the direction of movement of the pipe to be cooled, but parallel to it Web attached in such a way that its edges 60 have a straight surface line of that of Form the pipe traversing path. It is easy to see that one is on this Way sleeves obtained with any cross-section adapted to the shape of the pipe can. In this embodiment, the edges 60 of the plates 50 on which the Running along the pipe, leaving their mark on the wall of the pipe, so that you can receives a corrugated tube. The plates 50 can be used in the manner desired Keep a distance from one another so that their ends engage in grooves 61 in two end plates 62 which are connected to one another by bolts 63 are provided.

The whole thing is allocated in a container through which the cooling liquid flows. Holes 64 can also be provided to facilitate the circulation of this liquid be provided in the plates.

Apart from the fact that the plates form a rigid sleeve, making it possible to create sleeve channels of any shape and size, one of the advantages of the embodiments shown in FIGS. 11 to 15 is that that the plates if they are made of a material that conducts heat well, for discharge of heat from the wall of the pipe and to distribute this heat throughout Circumference of the pipe in which they contribute to the surrounding liquid.

As in Fig. 5 to 10 sleeves described are also suitable the sleeves according to FIGS. 11 to 15 for generating negative pressure on the outside of the Tube, so that it is pressed sufficiently strongly against the wall of the channel.

Of course, it also falls within the scope of the invention if panels are made from several interconnected pieces. The plates can also in the embodiment of FIG. 11 and 12 on a ring shape and at that of the F i g. 14 and 15 may be limited to straight rods.

Instead of being made up of separate, interconnected parts, the plates can be made from one solid piece.

Claims: 1. Device for calibrating one of an extrusion press exiting pipe made of thermoplastic material, in particular a polyamide, this device consists of a sleeve with perforations through which Water at a lower pressure than inside the pipe to be calibrated, comes directly into contact with the wall of the tube, characterized in that the inner surface of the sleeve (5, 20, 50) with a plurality of flow paths (8, 52) is provided, wherein, as is known per se, the sleeve over its entire length Has the same cross-section and tightly encloses the pipe (3) to be calibrated.

Claims (1)

2. Apparatus according to claim 1, characterized in that the flow paths on the inner surface of the sleeve (5, 20, 50) are grooves (8), which are preferably helical run on the inner surface. 3. Apparatus according to claim 2, characterized in that the channel (8) on the front side, seen in the direction of movement of the pipe to be cooled, a sharp edge (8a) and on the opposite side a beveled edge (8b) has. 4. Apparatus according to claim 1, characterized in that the sleeve (5, 20, 50) consists of a non-adhesive plastic. 5. Apparatus according to claim 4, characterized in that the sleeve (20) is formed by one or more wires wound helically are. 6. Apparatus according to claim 1 and 5, characterized in that the sleeve (20) lies in a container (36) containing the cooling liquid and Rails and retaining rings (21, 23) are provided through which the sleeve (20) in this Container (36) with inlet and outlet openings (25, 26) for the cooling liquid is provided, is attached. 7. Apparatus according to claim 6, characterized in that the order the container (36) arranged in the sleeve (20) is divided into several compartments, can absorb the coolant in different states (temperature, pressure). 8. Apparatus according to claim 1 and 6, characterized in that the sleeve (20, 50) is formed by an arrangement of individual parts, the such are interconnected that they successively form the wall of the sleeve while between them recesses remain free, the flow paths (52) for the cooling liquid form, and that the items in the direction of movement of the pipe to be calibrated are arranged one behind the other, these individual parts having openings (51), the circumferences of which form the cross-sections of the sleeve. 9. Apparatus according to claim 8, characterized in that the individual parts are arranged so that an edge (60) of each of these individual parts has a surface line of the sleeve channel forms. 10. Method for calibrating an exiting extruder Thermoplastic pipe in which the pipe to be calibrated goes through a calibration pipe, while the outer surface of the pipe to be calibrated directly with oil is applied and an overpressure inside the pipe to be calibrated is maintained against the pressure acting on its outside, thereby characterized in that the inside of the pipe to be calibrated is atmospheric pressure is maintained. Considered publications: German patent application B 19282 XII / 39a (published March 17, 1955); British Patent No. 647479; french U.S. Patent No. 436,895; U.S. Patent No. 2,423,260; Swiss patent specification No. 308 956.