DE2409020B2 - Method and device for manufacturing thin-walled drainage pipes made of plastic - Google Patents

Description

The invention relates to a method for producing thin-walled drainage pipes made of plastic with a corrugated wall, seen in axial section, in which there are water inlet holes, in which a thermoplastic plastic tube is extruded and corrugated and perforated while it is still hot-deformable will. The invention also relates to an apparatus for carrying out this method.

Drainage pipes of the type mentioned are widely used. The production takes place after known processes mentioned at the beginning (DE-GM

ίο 73 15 345) by first using a plastic tube seen in axial section corrugated wall is produced. The finished plastic pipe is then passed through a the extrusion and molding device downstream punching device, in the holes in the wall of the Pipe to be punched. The disadvantage here is the fact that such a punching process is only finished when cured pipe material can be carried out, so that the punching device must not be connected immediately after the extrusion device.

Furthermore, the accumulation of punched-out waste material is disadvantageous. Finally, the perforated tubes tend to when subjected to stress, tearing at the punched holes.

In another known device, the technical effort is less, since on the complete Completion of the plastic pipe before punching can be dispensed with by the extrusion nozzle Folded pipe production plant on a rod carries a mandrel which is still in the folding tube located in the molding machine Parts should scrape away so that in the outside as There are holes in the pipe parts that appear in the wave troughs. In practice this is the procedure however not feasible as the scraping knives either do not take away enough plastic so that no holes arise, or run onto the form elements of the molding machine, so that the latter and / or the knives are damaged. A setting so precise that just the plastic is taken away, but not the knife on the Start up mold segments of the molding machine, cannot be implemented in practice. Otherwise, holes with tapered edges would result where stress accumulations occur when the pipe is loaded, which promotes the tearing of the holes.

Based on this prior art, the object of the invention is to describe the method and the device mentioned at the beginning To simplify avoidance of cutting hole production.

This object is achieved according to the invention in that the punching by piercing into the still The thermoformable wall of the pipe is achieved compared to the method mentioned at the beginning Simplification lies in the fact that the punching in still thermoformable state takes place, so that it is not more is required to complete the pipe before the holes can be made. Furthermore, there is the advantage that by piercing the holes in the pipe wall, which is still soft, material is not separated but is displaced towards the edges of the hole, so that holes thickened with bead-like shapes Edges are formed where there is no longer any risk of tearing due to the increased wall thickness, when the pipe is subjected to loads.

Although basically the method according to the invention can be carried out in a separate device in which the folded tube If the deformation temperature is heated, this is done

Perforation preferably during the corrugation or immediately after the corrugation of the pipe wall. If the piercing takes place during the corrugation of the pipe wall, it can be done before the corrugation process kick off. The latter is particularly recommended when the process of corrugation does not result in the still plastically deformable pipe string nestling against it superatmospheric pressure is caused inside the pipe string, but by subatmospheric pressure Pressure inside the pipe shape and outside the pipe string. Especially when with superatmospheric Pressure is worked, the piercing is advantageously carried out essentially during the corrugation or immediately after the waves. If the piercing takes place very early, it is advantageous to use the rigid Inside of the mold protruding spikes worked, while a late grooving immediately after the Waving is best done when the spikes can be pulled into the inner surface of the hollow mold, as will be explained later.

The perforation of the pipe wall by piercing can be done in the thermoplastic state of the plastic as well as in a thermoelastic state. It is essential in the method according to the invention an appropriate temperature control; that is, the wall of the pipe must still be warm when piercing to be enough. When removing the spike from the pipe wall, the pipe wall must be cold enough. She muC be at least already cooled to the lower part of the thermoelastic state, so that the hole shape, generated by the piercing is frozen. To get a correct temperature control here the mold segments can be heated at the beginning and then cooled later. The temperature of the Form segments is not too critical when working with rigid spikes, because then the hole process has already largely ended when the plastic material rests against the wall of the hollow mold. If, on the other hand, you work with retractable spikes, which may only be inserted into the form segment to plastic material applied to the wall are pierced, the mold segments must be sufficiently warm be held.

When speaking of stinging, it is intended to indicate a process at which material is pushed aside without cutting, as when an eel is pierced into leather, and not is machined or punched out in the form of a plate.

Even if basically a stinging like this does not appear impossible inside, however, this presents considerable difficulties. Accordingly, this will be Piercing from the outside is preferred. It takes place with the plastic being pushed away to the side. This will the pipe wall thickens a little near the hole, which causes the edges of the hole to tear when the Rohres counteracts

A device with an extruder, which has an annular nozzle, is advantageously used to carry out the process has, one of the annular nozzle downstream Wellvor- & o direction, which is several sequences of shape segments, each running on closed paths possesses, which run parallel to one another and without gaps on part of their orbit and in this area form an inside of the outer shape of the tube to be produced corresponding traveling hollow shape, with a Device for generating a pressure gradient from the inside of the pipe to the outside of the pipe, through which the still thermoformable from the nozzle leaked plastic pipe to the inner surface of the still migrating Hollow shape is nestled, and with a device for perforating the pipe wall

According to the invention, the mold segments have spikes on their inside for piercing Holes in the still thermoformable wall of the pipe. The spikes can both be in the grooves sit on the inside of the mold segments as well as on the back of the ribs provided there, depending after whether the water entry holes in the drainage pipe are on the (seen from the outside) wave back or in the Should sit in the troughs of the waves.

Depending on the desired shape of the holes, the spikes can have a round or a different cross-section to have. To create elongated holes, the cross-section of the spikes should be at least in the foot area be correspondingly long. In this case, the mandrel tip can also be designed in the form of a cutting edge be. In general, however, a point-shaped mandrel tip is preferred. It will be understood that this is sharp should be »so that the piercing of the plastic pipe wall, which is still warmly deformable, is as easy as possible finds little resistance

The side surfaces of the spikes are advantageously on the one hand within cylinder surfaces above the Mandrel foot cross-section, which extend in the direction in which the mold segments at the end of the Hollow form are first moved apart. This ensures that excessive friction of the Thorn wall at the pierced hole or even a subsequent deformation of the hole when moving apart the mold segments, i.e. when the finished pipe is released through the mold and punching device, he follows. Although deviations from this rule are possible, the lower the difference, the better Deviations are. On the other hand, the plastic material, which is still warmly deformable, should be used when the Spikes are loaded into the same as evenly as possible. The boundary condition for this is that the Side surfaces of the piercing spikes also within cylinder surfaces above the mandrel base cross-section are located, which extend towards the center of the hollow mold. This will remove the tip of the mandrel The hole punched in each case when widening up to the cross-section of the mandrel foot should not be too far to the side pushed.

If the spikes are allowed to protrude rigidly from the inner surface of the mold, this brings about a particularly simple and as far as advantageous construction with it. In this case, however, when working with superatmospheric Pressure inside the malleable tubing kept the diameter of the extruder nozzle so small that it will still lie within the clearance that has remained free between the tips of the thorns as a result, the nozzle diameter is undesirably small, so you can use a correspondingly corrugated one here Work exit profile of the extrusion nozzle, which in each case in the path of a row of thorns inwards This has the advantage that the total extent of the extrude thermoplastic Plastic hose is larger than it would be the case with a circular profile. That way will In addition, the reduced nozzle diameter is compensated for again, so that with such a nozzle formation there are no disadvantages due to the reduced diameter. The structural effort for the nozzle will however, one works with a device

with superatmospheric pressure in the hose area inside the mold, this pressure is normally maintained by means of a rod protruding from the nozzle core at or near the end of the migrating hollow shape provides a sealing piston, which the inside width of the generated Filled tube approximately fills and so an excessive outflow of the likewise in the usual way avoids compressed air supplied to the nozzle core. In the case of fixed mandrels, this is provided with a sealing piston corresponding longitudinal grooves in which the inwardly protruding through the plastic pipe wall Parts of the stinging dony the area of the sealing piston can traverse. Hold the sealing piston long enough so that there are always at least two spikes are just in each longitudinal groove of the sealing cap, so as a result, the pressure loss is not increased to a disruptive extent

If you work with suction of the air from the hollow area outside the plastic pipe, so Such measures are not necessary, since the extruder nozzle cannot protrude into the hollow mold and the plastic tube can be guided freely a piece in which the spikes already begin can press into the plastic tube. The sealing piston mentioned above is also here not mandatory.

The spikes can also be designed to be retractable into the inner surface of the hollow mold. Such a one Training is particularly suitable for working with superatmospheric pressure to snuggle up to the still thermoplastic plastic hose to the inner surface of the hollow mold. In this case, take care one ensures that the spikes are still retracted when sliding past the last end of the extension nozzle and are then advanced radially inward. Does the sealing piston have none of the above Longitudinal grooves, so corresponding devices can be provided to also in the area of Retract the spikes.

In order to explain the invention, exemplary embodiments of the same are given below with reference to the schematic Drawings described. It shows

F i g. 1 an axial section (according to the section line I-I in Fig.3) through the extrusion nozzle and part of the Hollow shape of a device according to the invention,

F i g. 2 shows a detail of FIG. 2 on a greatly enlarged scale. 1,

F i g. 3 in opposite to F i g. 1 enlarged compared to FIG. 2 the section I-I on a reduced scale Fig. 1,

FIG. 4 schematically shows a view from above of essential parts of a device according to FIG Invention,

F i g. 5 drawing the spikes into a mold segment,

FIG. 6 shows the section VI-VI from FIG. 6 on a somewhat enlarged scale compared to FIG. 5.

The in F i g. 1, like the device according to FIG. 4, has an extrusion nozzle 1 from which the still warm plastic pipe 2 exits at the nozzle end face Mold segments 3. The circulation of the path is indicated in FIG. 4 by a dashed line. 1 coincides with the end of the extrusion nozzle 1 - in the exemplary embodiments shown, two sequences of shape segments each serve to form the hollow shape - opposing Formseg elements lie against one another. Instead of only two each other zi a closed hollow shape complementary Formseg ment follow but also several, z. B. three or four such sequences can be used. He makes the construction of the device difficult, but has certain advantages in terms of the arrangement of the spikes used according to the invention.

ίο The shape segments shown in Fig. 4 and 6 3 differ from the shape segments 3 according to FIG. 1 to 3 only by the fact that in the former dii Spikes 10 are rigidly attached, while they ii the latter are mounted retractable back into the inner surface of the hollow mold.

In all Ausführungsbeispieien the Formseg elements 3 and 3 'in the usual way inside eil Ribbed groove profile through which the usual plastic drainpipes run in a well-known manner de wall is achieved.

The in F i g. Device shown in the core 1 has ί the mold an air supply pipe 6, through what a "compressed air via the outlet channels 7 in the space in the interior of the extruded tube 2 between the end 'of the extrusion nozzle 1 and the sealing piston J is introduced. The sealing piston 8 is carried in the usual way by a rod 9 which is extended beyond the sealing piston 8 and in the area where the mold segments 3 move apart at the end of the hollow mold, it provides central guidance of the finished folded tube

In the construction according to FIG. 1 to 3 are six rows of fes evenly distributed around the circumference in the form segments 3 seated piercing pins Ii vorgesehea the piercing pins 10 are used here Creation of holes which are larger in the circumferential direction of the pipe 2 produced than in the latter Longitudinal direction. The surface is slightly curved, wii this in particular from FIG. 2 and 3 can be seen

Since the shape segments 3 in FIG. 3 by moving the plane of the drawing towards one another to form a wandering hollow shape and behind the sealing piston i also wander away from one another again by moving in this plane, the spikes U each lie within cylinder surfaces 11, the generators of which are all shown in FIG. 1 and 3 run parallel to the drawing level and from top to bottom. These * cylinder surfaces 11 are indicated in FIG. 3 by the dashed and dotted lines, as in particular FIG. 2 um

3, the spikes 10 are located within cylinder surfaces, the generating straight lines of which, like those of the cylinder surfaces 11, go through the outline of the foot cross-section of the respective piercing pin: 10, but run radially to the center 13 of the hollow shape .

Because of the above-mentioned opening movement of the mold segments 3 at the end of the hollow mold , not all spikes 10 have the same shape. The prongs U are, therefore, because the opening movement of ii Fig.3 Fonnsegments 3 shown, for example, NaCl is done above, in this figure, while the side lying prongs W are symmetrical gebaui unsym metrically, that they slightly upward erfolgend "motion generated from the in Hole pulled out

it can be.

So that the holes created from the inside ii the inside of the tube protruding spike tips do not collide with the sealing piston 8, this has ir

Example shown six longitudinal grooves 15 distributed over the circumference according to the rows of spikes which the aforementioned piercing spike parts can pass through when the mold segments 3 migrate. That I there are constantly several spike tips in each groove, is here by the sealing piston 8 despite the longitudinal grooves 15 a perfect seal of the space to the left of the sealing piston 8 and to the right of the extrusion nozzle 1 achieved, so that in this space the built-up air pressure, which is several atmospheres can be, the extruded tube 2 fits perfectly from the inside to the mold segments 3 and this the spikes 10 through the wall of the tube 2 in the FIG. 1 and in particular from FIG. 2 can be seen Way through. 1 s

As shown in FIG. 1 and in particular FIG. 2, is the outer diameter in the embodiment shown the front nozzle area so much smaller that it is still between the tips of the spikes 10 in the closed hollow form goes freely. Further back the radius of the extrusion nozzle increases, since there the individual Form segments 3 are not yet fully closed.

As in particular from FIG. 2, it expands inside the pipe 2 between the extrusion nozzle 1 and the air pressure located on the sealing piston 8 on the tube 2 and nestles it with an enlarged diameter from the inside to the wandering hollow form. The spikes 10 prick each with their tips through the pipe 2. Nevertheless, the excess air pressure cannot get through the holes here escape because the spikes 10 narrow from the pressureless side to the pressure side and as a result, the air pressure acting on the plastic material has a component which strives to Press plastic material onto the surface of the piercing spikes 10 r>. This way it becomes sufficient Seal achieved.

When moving apart the mold segments 3 in the same way as in Figure 4 behind the Sealing piston 8 is indicated, in the embodiment according to FIGS. 1 to 3, the piercing spikes 10 extend effortlessly out of the sufficiently cooled pipe 2, since the mold segments 3 parallel to themselves radially from be pushed away from each other.

In the construction indicated in FIGS. 4 to 6, the spikes 20 and 20 'are each mounted in the corresponding mold segments 3' such that they can be displaced in their axial direction. For the sake of simplicity, all three spikes 20 and 20 'are arranged parallel to one another, so that they can be displaced perpendicular to the plane of separation w of the hollow mold. They carry spring plates 22, on which springs 23 act, which endeavor to press the spring plates 22 into contact with the lower end face in FIGS. In Fig. 5 and 6 at the top, the springs 23 are each supported on plates 26, which are screwed to the rear of the mold segments 3 'in a manner not shown and have corresponding bores through which the shafts of the piercing spikes 20 protrude outward. The shafts of the spikes 20 protrude loosely through a thin elastic sheet 28, which is stiffened by means of transverse stiffening ribs 29. As a result, the sheet 28 is flexible in the direction of travel of the mold segments 3 ', but not transversely thereto. At its front end 30 in the direction of travel of the shaped segments 3 ', the sheet metal 28 is arched upwards, so that a gap is created between the sheet metal 28 and the plate 26 here. If the sheet 28 is raised, it simultaneously lifts the spikes 20 via their rear heads 31 resting on the sheet 28, as shown in FIG. 5 and 6 can be seen.

Both in the area of the extrusion nozzle 1 and in the area of the sealing piston 8, as shown in FIG. 4 and 6 can be seen, guide rails 35 and 36 attached. These guide rails 35, 36 are not in supported by corresponding arms 37 in the manner shown. They are at their the direction of movement Shape segments 3 'sharpened opposite ends, so that in each case the on the back of the Form segment 3 'located sheet 28 with its bent end over the sharp edge of the Guide rail 36 slides so that the guide rail 36 on the two edges of the plate 28, as shown in FIG. 6th can be seen, engages under this and thus also moves the spikes 20 over the plate 28 so that they are behind the inner surface of the respective mold segment 3 'can be withdrawn. This allows the shape segments 3 'in this state easily slide over the extrusion nozzle 1 and the sealing piston 8. At the end of the guide rails 35 and 36, the springs 23 pull over the spikes 20 and 20 ' the sheet 28 back into the position shown in FIG. 5 position shown on the left.

Instead of a continuous sheet 28, each transverse row of spikes 20 or 20 ', as shown in FIG 6 are shown, wear a separate sheet metal strip, which on its in the direction of travel of the mold segments 3 'front side is bent upwards.

The latter construction has the advantage that with a correspondingly strong design of the springs 23 and jerky end of the guide rails 35, the spikes 20 suddenly return to the full in the interior the shape-directed position occur, so that they abruptly the wall of there already to the Pierce a hollow molded plastic pipe or a plastic pipe that is still deformable. The mass forces that occur here promote the desired effect.

The spikes 20 do not have to be arranged so that they are in the outside as a groove or wave troughs in Pierce the wall parts of the pipe that appear. They can also be arranged that way if desired be that they create holes in the outer corrugation back of the drainage pipe. Such a spike arrangement is shown in Figs. 2 and 3 indicated by dash-dotted lines.

Since the tube 2, which is still plastically deformed and inflated, does not have a cylindrical shape at the beginning of the piercing, but is already fully inflated with its areas further forward in the hollow shape migration direction, while the rear areas have a smaller diameter, the shape of the plastic tube area runs that is being pierced is often conical. In order to favor the piercing conditions, the piercing mandrel tips can - within the conditions indicated above - be inclined somewhat forwards in the hollow shape migration direction. This then not only facilitates the piercing, but also promotes the seal between the pipe wall and the piercing mandrel 20 during the piercing.

For this purpose 2 sheets of drawings

Claims (11)

Patent claims: 1. Process for the production of thin-walled drainage pipes made of plastic with an axial section seen corrugated wall, in which there are water entry holes, in which a thermoplastic plastic pipe is extruded and in still is corrugated and perforated in a thermoformable state, characterized in that the Punching is carried out by piercing the wall of the pipe, which is still warmly deformable 2. The method according to claim 1, characterized in that the piercing takes place from the outside 3. The method according to claim 1 or 2, characterized in that the piercing under the side The plastic is pushed away 4. The method according to any one of claims 1 to 3, characterized in that the piercing before the waves begin 5. The method according to claim 1 to 4, characterized in that the piercing during the Wellens takes place 6. The method according to any one of claims 1 to 3, characterized in that the piercing takes place immediately after the waves 7. Device for performing the method according to one of claims 1 to 6, with a Extruder, which has an annular nozzle, a corrugating device downstream of the annular nozzle, which has several sequences of shape segments, each running on closed paths part of their orbit run parallel to each other without a gap and one inside in this area the outer shape of the tube to be produced corresponding wandering hollow shape with a device for generating a pressure gradient from the inside of the pipe to the outside of the pipe, by means of which the plastic pipe, which is still warmly deformable and which has emerged from the nozzle, is nestled against the inner surface of the moving hollow form, and with a device for perforating the pipe wall, characterized in that the shaped segments (3) have spikes (10) on their inside Wear to pierce holes in the wall of the pipe (2), which is still thermoformable. 8. Apparatus according to claim 7, characterized in that the spikes (10) point or are sharpened in the shape of a cutting edge. 9. Apparatus according to claim 7 or 8, characterized in that the side surfaces of the spikes (10) both within cylinder surfaces (U) lie above the mandrel foot cross-section, which extend in the direction in which the mold segments (3) at the end of the hollow mold initially be moved apart, as well as within cylinder surfaces (U) above the mandrel base cross-section, which extend towards the center of the mold. 10. Device according to one of claims 7 to 9, characterized in that the spikes (10) protrude rigidly from the inner surface of the mold. 11. Device according to one of claims 7 to 9, characterized in that the spikes (10) can be drawn into the inner surface of the hollow mold.