DE2409020A1 - Thin-walled plastic corrugated, perforated drain pipes prodn. - by maaking holes -crrrorugations in pipe while stilll plastically deforme - Google Patents

Abstract

Thin-walled plastic drain-pipes with an axially corrugated wall contg. water inlet holes are produced by (a) extruding a thermoplastic tube, (b) corrugating the tube while it is still in a warm deformable state, and (c) making the holes by piercing the corrugated tube while it is still in a warm deformable state. Method provides easy hole formation without damaging the wall of the pipe. Size of the holes can be controlled to give efficient drainage.

Description

Method and apparatus for manufacturing thin-walled drainage pipes from unsstoffr The invention relates to a method and a device for Manufacture of thin-walled drainage pipes made of plastic with seen in axial section corrugated wall in which there are water inlet holes, wherein a thermoplastic plastic tube extruded and in the still warm formable Condition is corrugated and perforated, Such drainpipes are widely used. The production usually takes place, by first using a plastic pipe is made with a corrugated wall seen in axial section. The finished plastic pipe is then made by a punching and forming device downstream of the extrusion and molding device. or cutting device in which holes punched in the wall of the pipe or when forming the tube in its wall provided hollow nipples for the purpose Hole generation are cut off. These known methods are in various Time consuming. They each require, among other things, a separate one that requires maintenance Punching device.

In another known device, the technical effort far less. It consists essentially in the fact that the extrusion nozzle of the folded tube manufacturing plant carries a thorn on a rod, which is still in the Shaping machine located Paltenrohr parts is to scrape away so that in the Holes emerge on the outside as tube parts appearing as wave troughs. In the In practice, this procedure is not feasible because of the scraping knife either do not remove enough plastic so that there are no holes, only wall thinning or grind on the form elements of the forming machine so that the latter and / or the knives are damaged. An attitude that is so precise that just removed the plastic, but not the knife on the Grinding form segments of the forming machine is not possible in practice.

In contrast, the invention creates a method and a device, which is characterized by great simplicity and the cutting hole generation avoids.

The method according to the invention is characterized in that the Punching by piercing the holes in a hot, deformable state in the pipe wall he follows. Even if basically according to the method according to the invention in a separate Device can be carried out in which the folded tube to deformation temperature is heated, the punching is preferably carried out during the corrugation or immediately after corrugating the pipe wall. If the grooving takes place during the corrugation of the Pipe wall, it can begin before the corrugation process. The latter recommends especially when the process of corrugation has not yet been caused by nestling plastically deformable pipe string due to superatnine spherical pressure inside of the pipe string is caused, but by sub-atmospheric pressure within the hollow form and outside of the pipe string. Especially when with superatmospheric Pressure is being used, the piercing is advantageously carried out essentially during of the ripple or immediately after the ripple. If the piercing very early he follows, it is advantageous to work with fixed piercing mandrels, while late piercing then expediently takes place immediately after the corrugation when the mandrels are in the molding dies the molding machine are slidably mounted, as will be explained later.

The perforation of the pipe wall by piercing can be done both in thermoplastic State of the plastic as well as in the thermoelastic state. Essential in the method according to the invention is an expedient temperature control; That means, the wall of the pipe must still be warm enough when piercing. When removing the .Stezedornes from the pipe wall, the pipe wall must be cold enough. She must at least already cooled to the lower part of the thermoelastic state so that the cup created by the piercing is frozen. In order to achieve a correct temperature control here, one can use the molding dies Warm up at the beginning and cool down later. The temperature of the molding dies is when working with fixed mandrels not too critical, since then the piercing process is already largely is finished when the plastic material rests against the wall of the mold. Is working on the other hand, with movable mandrels, which may only be inserted into the die wall applied plastic material are pierced, the matrices must be sufficient be kept warm.

In both cases, a material for the mandrels is advantageous those with the lowest possible thermal conductivity, such as such a steel used. However, other materials also come here, such as those used in technology today Ceramic and corundum materials often used for cutting purposes are also in question, which also have poor thermal conductivity.

It is also important for the material of the spikes that this has a smooth surface. It is advantageous to polish it so that the mandrels can be polished at least in the tip area.

When speaking of stinging here, it is intended to indicate a process become, in which chipless, as when piercing an eel in leather, the material is pushed aside and not machined or punched out in the form of a plate will.

Even if the reason is that it is not impossible to pierce from the inside appears, this presents considerable difficulties. Accordingly, will piercing from the outside is preferred. It takes place while the Plastic. As a result, the pipe wall near the hole is slightly thickened, what a tearing of the hole edges when bending of the pipe counteracts.

To carry out the method according to the invention is advantageous a device with an extruder having an annular nozzle, one of the annular nozzle downstream corrugating device or shaping device, which each have several has circumferential sequences of shape segments on closed paths, which on a Part of their orbit run parallel to one another and without a gap, and so in this one Area a wandering inside corresponding to the outer shape of the pipe to be produced Form a hollow shape, with a device for generating a pressure gradient from the Inside of the pipe to the outside of the pipe, through the soft the still warm plastic from the Nozzle leaked plastic tubing to the inner surface of the still moving hollow form is nestled, and with a device for punching the pipe wall.

According to the invention, the mold segments have spikes on their inside for piercing holes in the plastic wall of the pipe, which can be deformed while it is still warm on. The spikes can both be in the grooves on the inside of the mold segments as well as on the back of the ribs provided there, depending on whether the Water entry holes in the drainage pipe on the back of the wave (seen from the outside) or should sit in the wave troughs. Preferably the spikes sit on the move the ribs on the inside of the mold segments.

Depending on the desired shape of the holes, the mandrels can be round or also have a different cross-section. The cross-section should be the thorns must be correspondingly long, at least in the foot area. In this case, the The mandrel tip can also be designed in the form of a cutting edge. In general, however a punctiform mandrel tip is preferred. It goes without saying that this will be spicy should, so that the piercing of the still warm deformable plastic pipe wall one finds as little resistance as possible.

On the one hand, the side surfaces of the mandrels are advantageously within of cylindrical surfaces over the mandrel root cross-section, which extend in the direction in which the dies or mold segments are initially moved apart at the end of the hollow mold will. This ensures that excessive friction of the mandrel wall on the pierced Hole or even a subsequent deformation of the hole when the Forming segments, that is, when releasing the finished pipe through the forming and punching device If deviations from this rule are possible, the lower the better, the lower it is these deviations are. On the other hand, the plastic material, which can still be deformed while still warm, should be loaded as evenly as possible when piercing the spikes into the same. the The boundary condition for this is that the side faces Thorns are also located within cylinder surfaces above the mandrel base cross-section, which extend towards the center of the cavity. This will remove it from the tip of the mandrel each punched hole is not impermissible when expanding up to the cross-section of the mandrel base pushed far to the side.

The side surfaces or flanks of the mandrels can basically also be arched. However, side surfaces that are created by corresponding movement are preferred of a straight line as generating line, such as straight or inclined conical surfaces.

If you let the mandrels protrude rigidly from the inner surface of the mold, it brings this is a particularly simple and in this respect advantageous construction with it in this case, however, when working with superatmospheric pressure inside of the malleable tubing, the diameter of the extruder nozzle can be kept so small that that it is still within the space that has remained free between the tips of the thorns lies. If the nozzle diameter becomes undesirably small as a result, one can use here work a correspondingly corrugated outlet profile of the nozzle, which in each case is drawn inward in the path of a row of thorns. This has the advantage that the total circumference of the extruded thermoplastic plastic hose is larger than would be the case with a circular profile. In this way will additionally compensated for the reduced nozzle diameter, so that at one No disadvantages arise due to the reduced diameter of the nozzle shape. The structural effort for the nozzle is increased, however. Do you work with a Device with superatmospheric pressure in the hose area within the hollow mold, so this pressure is usually maintained by using one of the A nozzle core protruding rod at or near the end of the traveling hollow form Provides piston which approximates the clear width of the folded tube produced fills and so an excessive outflow of the likewise in the usual way by avoids compressed air supplied to the nozzle core.

In the case of fixed mandrels, this piston is advantageously given corresponding ones Longitudinal grooves in which the inwardly protruding through the plastic pipe wall Parts of the mandrels can traverse the area of the sealing piston. If you hold the Piston long enough so that there are always at least two mandrels in each longitudinal groove of the Pistons are, this does not increase the pressure loss to a disruptive extent.

If you work with suction of the air from the hollow area outside of the plastic pipe, such measures are not necessary because this the extruder nozzle cannot protrude into the hollow mold and the plastic tube cannot Piece can be guided freely, in which the mandrels can already begin to move into the plastic tube. The one above mentioned sealing piston is also not required here.

As mentioned above, the mandrels can also be inserted into the inner surface form the hollow form retractable. Such a training is particularly suitable for working with superatmospheric pressure to nestle the still thermoplastic Plastic tube to the inner surface of the hollow mold. In this case, take care one advantageous for the fact that de mandrels when accompanying past at the last end of the nozzle are still drawn in and then pushed forward radially inwards. Has the sealing piston no longitudinal grooves mentioned above, corresponding devices can be provided be to retract the mandrels also in the area of the sealing piston.

The mandrels can be springs or, for example, pneumatic ones Piston must be pressed radially inwards. In this case, those in the places where the mandrels should be withdrawn, preferably appropriate guides to the inevitable Moving back the mandrels. Are the thorns under external pressure from springs? or pneumatic pistons, corresponding guide rails can also be opened after outside protruding ends of the mandrels act to where to look should protrude inside and stick into the plastic tube to push inwards.

The following are advantageous exemplary embodiments to explain the invention the same described with reference to the schematic notices.

Fig. 1 shows an axial section (according to the section line 1-1 in Fig. 3) through the extrusion nozzle and part of the hollow shape of a device according to of the invention, which with superatmospheric pressure to nestle the plastic hose works on the inner wall of the hollow mold.

FIG. 2 shows, greatly enlarged, a part of FIG. 1, namely that in Fig. 1 upper part of the end of the extrusion nozzle and the exiting into the Hollow form snug plastic tubing.

Fig. 3 shows in comparison to FIG. 1, enlarged compared to FIG.

2 shows the section I-I from FIG. 1 on a reduced scale.

Fig. 4 shows schematically the view from above of the essentials Parts of a device according to the invention, in which guide rails are provided in the area of the nozzle and the sealing piston of the device to withdraw from the interior of the wandering Aoulforrn.

Fig. 5 shows how a guide is just beginning, the spikes in one Draw in the die segment on a scale greatly enlarged compared to FIG. 4.

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

The device according to the invention shown in FIG. 1 also has like the device according to FIG. 4, an extrusion nozzle 1, from which at the nozzle face the tubular or hose-shaped plastic strand 2, which is still warm, emerges. The usual, well-known ways are used to shape the plastic strand several sequences of die segments each revolving on self-contained paths 3. The circulation of the web is indicated in FIG. 4 by a dashed line. At the Beginning of the moving hollow shape, which coincides with the end of the nozzle 1 in FIG. 1 - Two sequences of half matrices each serve in the exemplary embodiments shown the formation of the hollow shape - there are each opposing mold segments to each other. Instead of just two complementing each other to form a closed hollow shape Matrix sequences can, however, also use several, e.g. three or four such sequences will. This complicates the construction of the device, but also has to do with the Arrangement of the spikes used according to the invention have certain advantages.

The mold segments 3 shown in FIGS. 4 and 6 differ from the mold segments according to FIGS. 1 to 3 only in that the piercing spikes in the former are firmly attached, while in the latter they can be withdrawn from the interior of the hollow mold are appropriate.

In all the exemplary embodiments, the die segments 3 or 3 ' in the usual way inside a rib-groove profile, through which in known Way, the bellows shape usual for plastic drainpipes is achieved.

The device shown in Fig. 1 has a core 5 of the die Air supply line 6, through which compressed air via the outlet channels 7 into the room inside the extruded plastic tube between the end of the nozzle 1 and the Seal piston 8 is introduced. The sealing piston 8 is in the usual way of a rod 9 carried, which is advantageously extended beyond the piston 8 also and in the area of the divergence of the mold segments at the end of the hollow mold one causes central guidance of the finished folded tube.

In the construction of FIGS. 1 to 3, six are evenly across the circumference distributed rows of spikes firmly seated in the mold segments 3 10 provided. The piercing spikes are used here to create holes in the circumferential direction of produced plastic pipe are larger than in the longitudinal direction. The surface is slightly curved, as can be seen in particular from FIGS. 2 and 3.

Since the shape segments in Fig. 3 by movement in the plane of the drawing towards each other close to the wandering hollow shape and behind the piston 8 through again Movement away from each other in this plane, the spikes 10 are each within cylinder surfaces, the generatrix of which all in Fig. 1 and 3 parallel to Drawing plane and running from top to bottom. These cylinder surfaces are shown in Fig. 3 indicated by the dash-dotted lines 11. As in particular Fig. 2 and 3 show, the spikes 10 are also located within cylinder surfaces, whose generating straight line as well as that of the cylinder surfaces 11 through the outline of the Go foot cross-section of the respective mandrel, but radially to the center of the hollow form run there. The center of the hollow mold is indicated at 13 in FIG. 3.

Because of the above-mentioned opening movement of the mold segments at the end of the hollow form, not all spikes have the same shape. The spikes 10 are because the opening movement of the segment shown in FIG. 3, for example upwards, built symmetrically in this figure, while those lying on the side Spikes 10 'are unsymmetrical so them at the top ensuing movement can easily be pulled out of the hole he created.

So that the holes created from the inside into the inside of the pipe protruding spike tips do not collide with the sealing piston 8, this has in the example shown 6 distributed over the circumference according to the rows of spikes Longitudinal grooves 15 through which the aforementioned piercing spike parts pass when the mold moves can. Since there are always several spike tips in each groove, here due to the piston, despite the grooves, a perfect seal of the space to the left of the Piston and to the right of the nozzle, so that the air pressure built up in this space, which can be several atmospheres, the extruded plastic pipe 2 properly clings to the mold segments from the inside and the spikes through the wall of the plastic pipe in that shown in FIG. 1 and in particular from FIG Way through.

As can be seen from FIG. 1 and in particular FIG. 2, is shown in FIG Embodiment the outer diameter of the front nozzle area is so much smaller, that it is still free between the tips of the spikes in the closed hollow form goes. The radius of the nozzle increases further to the rear, since this is where the individual mold segments are not yet fully closed are. You will become better known there Way brought together by parallel displacement to each other by means of inclined guide surfaces. According to the same principle, they are separated again behind the sealing piston 8. Other methods of merging known per se are of course also possible and separation of the mold segments possible.

If a precise alignment of the sealing piston 8 on its rod 9 should be avoided with respect to its rotational position, one can use the inlet areas the grooves 15 widen and the piston rotatably so that the piercing mandrel tips bring the piston into the desired correct rotation position yourself.

As can be seen in particular from Fig. 2, the inside of the inflates Plastic pipe located between the nozzle 1 and the piston 8 air pressure that Pipe and nestles it against the migrating one from the inside, expanding its diameter Hollow shape. The spikes 10 pierce with their tips each through the Pipe through. However, the excess air pressure cannot get through the holes here escape as the mandrels narrow from the unpressurized side to the pressure side and thereby the air pressure acting on the plastic material has a component, which strives to press the plastic material against the surface of the spikes. In this way a sufficient seal is achieved.

When moving the segments apart in the same way as in Fig. 4 is indicated behind the sealing piston 8, drag in the execution 1 to 3, the spikes effortlessly out of the sufficiently cooled plastic tube out, as the segments are pushed radially away from each other parallel to themselves will.

In the construction indicated in FIGS. 4 to 6, the spikes are 20 and 20 'each displaceable in their axial direction in the corresponding mold half-segments 3 'stored. For the sake of simplicity, all three spikes 20 and 20 'are parallel arranged to each other so that they can be displaced perpendicular to the plane of separation of the hollow mold are. They wear spring plates 22, on which springs 23 act, which strive to the spring plate 22 in contact with the in Fig. 5 and 6 lower end face of the expanded and the corresponding bores 24 in the mold half-segments which receive the springs to press. In Fig.

5 and 6 above the springs 23 are each supported on plates 26, which are screwed to the rear of the mold half-segments in a manner not shown are and carry corresponding holes through which the shafts of the spikes protrude outwards. The shafts of the spikes protrude loosely through a thin, elastic one Sheet metal 28, which is stiffened by means of stiffening ribs 29 running transversely. As a result, the sheet is flexible in the direction of the die migration, but not transversely For this.

The sheet metal is at its front end 30 in the direction of the die migration arched upwards, so that there is a gap between the plate 28 and the plate 26 is created. If the sheet 28 is raised, it simultaneously lifts the spikes via their rear heads 30 resting on the sheet metal, as shown in FIGS. 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 can be seen from FIG. 4, guide rails 35 and 36 in the one from FIG. 4 attached to 6 apparent ways. These guide rails are not shown in FIG Carried by corresponding arms 37 in a manner. They are at their the direction of movement of the mold half-segments opposite ends are sharpened, so that in each case the the back of the half-segment located sheet 28 with its upturned end Slides over the sharp edge of the rail so that the rail is on the two edges of the plate 28, as can be seen from Fig. 6, engages under this and thus over the Sheet metal also moves the spikes so that they are behind the inner surface of the respective shape segment are withdrawn. This allows the shape segments 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 'aihd the sheet again in the position shown in Fig. 5 on the left.

Instead of a continuous sheet 28, each transverse row can also be used of guide pins, as shown in Fig. 6, a separate sheet metal strip wear, which is bent upwards on its front side in the direction of the segment migration is.

The latter construction has the advantage that when accordingly strong training of the springs 23 and jerky end of the guide rails 35 the Spikes suddenly collapse again into the position that is fully directed into the interior of the mold, so that they at the same time abruptly the wall of there already on the hollow form Pierce the snugly or snugly deformable plastic pipe. The inertial forces that occur here promote the desired effect.

The spikes do not have to be arranged so that they are in the outside Pierce the wall parts of the pipe that appear in the form of grooves or wave troughs. They can also, if desired, be arranged so that they have holes in the outer Create the wave back of the plastic pipe. Such a spike arrangement is shown in FIG 2 and 3 indicated by dash-dotted lines.

In many cases the plastic pipe, which has been plastically deformed and inflated not at the beginning of the piercing Has a cylindrical shape, but rather with its areas further ahead in the direction of the ohlform migration, it is already full is bloated. While the rear areas still have a smaller diameter have, the shape of the plastic pipe area runs into which just pierced becomes, often conical.

In order to favor the piercing conditions, the piercing mandrel tips can be used - within the conditions indicated above - something in the hollow shape migration direction be inclined forward. This not only makes the piercing easier, it also makes it easier also favors the seal between the pipe wall and the piercing spike during the Lochens.

Claims (11)

P a t e n t a n s p r ü c h e Process for the production of thin-walled drainage pipes from plastic with a corrugated wall, seen in axial section, in which there are water inlet holes located, with a thermoplastic plastic tube extruded, in still warm deformable state is corrugated and punched, characterized in that the punching takes place by piercing in a hot deformable state. 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 takes place with lateral displacement of the plastic. 4. The method according to any one of claims 1 to 3, characterized in that that the piercing begins before the waves. 5. The method according to claim 1 to 4, characterized in that the Piercing occurs essentially during the corrugation. 6. The method according to any one of claims 1 to 3, characterized in that that the piercing takes place immediately after the corrugation. 7. Device for performing the method according to one of the claims 1 to 6, with an extruder having an annular nozzle, one downstream of the annular nozzle Corrugating device which follows several open tracks of shape segments that are parallel to one part of their orbit without any gaps run towards each other and in this area an inside of the outer shape of the to be generated Form tube corresponding wandering 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 Plastic tubing that has emerged from the nozzle while still warm to the inner surface the wandering hollow shape is snuggled, and with a device for punching the pipe wall, characterized in that the shape segments on their inside Piercing spikes for piercing holes in the plastic wall, which is still warmly deformable of the pipe. 8. Apparatus according to claim 7, characterized in that the mandrels are sharpened point or blade shape. 9. Apparatus according to claim 7 or 8, characterized in that the side surfaces of the mandrels both within cylinder surfaces above the mandrel foot cross-section which extend in the direction in which the dies end up the hollow mold are first moved apart, as well as within from Cylindrical surfaces over the mandrel base cross-section, which extend towards the center of the hollow mold. 10. Device according to one of claims 7 to 9s, characterized in that that the mandrels protrude rigidly from the inner surface of the mold. 11. Device according to one of claims 7 to 9, characterized in that that the mandrels are retractable on the inner surface of the mold.