FI56639C - CONTAINER FOR THE CONDUCT OF BIAXIAL STRAECKNING AV ETT ROER AV STRAECKBART KONSTAEMNE - Google Patents

Description

----- r_, .... ADVERTISEMENT rre · \ n danger · M (^ 1) UTLAGGNINGSSKRIFT 56639 c Pnter.tti myör; n * 'tiy 10 03 1930 (45) Patent neddelnt ^ (51) Kv.ik . '/ Int.ci. " B 29 D 23/0 * FINLAND - FINLAND (11) p * t «nttlh» k * mu * - Ptt * ntin * öknlng 3638/73 (22) Htk «ml» pllvt - Aniöknlngtdig 26.11.73 (23) AikupUvi - Giltlghättdag 26.11.73 (41) Gotten stuck - Bllvlt offantHg 30.05.71+

Patent and Registration Office NlhtMkslpeion. kuUL | ulk * un pvm.-

Patent and registration authorities Anteku utlagd och utl.tkmcm publicurad 30.11.79 (32) (33) (31) Pyy *** y «uelkeut — Begird priorlut 29.11.72 02.i2.72 Greece-Greece (GR) 803 / 7/53, 837/7/87, Ο9.Ο3.73 Federal Republic of Germany- Förbundsrepubliken Tyskland (DE) P 2311732.0 Proven-Styrkt (71) George Aristovoulos Petzetakis, Deliyanni 103, Kifissia, Athens, Greece-Grekland (GR) (72) ) Aristovoulos George Petzetakis, Greece-Grekland (GR) (71 *) Oy Kolster Ab (5I +) Method and apparatus for biaxial stretching of a stretchable active tube - Förfarande och anläggning för biaxial sträekning av ett rör av sträekbart constant

The invention relates to a method for biaxially stretching a tube of stretchable active material, in particular thermoplastic synthetic material, in which the tube is extruded as a seemingly flowable blank in a high viscosity state from a die-headed die head and then to a fixed tube, whereby a hydraulic lubricant is further introduced between the tube and the stretching mandrel. The invention further relates to an apparatus for carrying out the method. - Within the scope of the invention, the term pipe also includes hoses, which pipes may have a circular or even a seemingly circular cross-section. By seemingly flowable preform is meant the fluid space of the active material coming from the injection head, which is already preformed into a tubular shape, in which case, however, this extrudate 56639 is not yet able to receive internal and external compressive forces.

In the known method, U.S. Patent No. 2,708,772, the inch diameter of the nozzle or injection head is significantly larger than the diameter of the tube.

Besides, air is brought in through the boreholes. This requires an air cushion, in addition to the work, the introduced air requires an air cushion, which prevents contact with the stretching mandrel. Thus, the towing flow has not materialized. It does not arise either.

The towing flow would require a medium in which, on the one hand, the viscosity, on the other hand, the thrust-stress conditions allow the towing flow to occur. But this is not possible when using air. But also when a hydraulic lubricant (lubricant) is simultaneously introduced through the boreholes. As a result, the specified stress conditions cannot be achieved for circumferential stretching and axial stretching. In fact, in the context of the known method, no axial stretching of the manufactured tube has been considered. This is also due to the fact that the substances mentioned in this context can hardly be considered as stretching agents. Significant degrees of stretching comprising a defined stretch cannot be achieved by the known method in the circumferential direction nor in the axial direction.

In other similar known operations, which remain in the test stage, the tube is first calibrated after cooling, in which the tube leaves a seemingly fluid state, and the calibration is performed externally, after which the tube is passed through a tempering bath which is stretched to below the crystalline melting temperature. on a stretching mandrel of the described structure suspended by a rope on the mandrel of the spray head and arranged at a considerable distance from the spray head in front of the pipe removal machine. The conical extension of the stretching part then determines the degree of stretching in the circumferential direction, the difference between the extrusion speed and the higher discharge rate relative thereto, the degree of axial stretching. This causes difficulties at least when desirable of considerable degrees of stretching. Strong fluctuations in the degree of stretching, both in the circumferential direction and in the axial direction, are often observed and, moreover, the stretching is not sufficiently defined and is not sufficiently homogeneous (in layers). The inner surface of the tube is often damaged by sliding friction when stretched.

The object of the invention is to provide a method and a simple apparatus with which a well-defined stretch in both the circumferential direction and also in the axial direction can be achieved even in connection with considerable degrees of stretching.

3 S6639

The invention firstly relates to a method for hiaxially stretching a tube of stretchable active material, wherein the tube is extruded as a seemingly flowing blank in a high viscosity state from a die head with a nozzle mandrel, tempered to a stretching temperature and extruded further, a hydraulic lubricant is introduced between the tube and the stretching mandrel. The invention is to work by means of a stretching mandrel with a conical extension part, a receiving part substantially in diameter corresponding to the mouthpiece mandrel, that a hydraulic lubricant is brought to the beginning of the receiving part without pressure and that the pipe carries the lubricant with the convex part on which the lubricant layer thins wedge-like in the region of the expansion part and the removal part under the effect of radial forces.

The invention is based on the knowledge that a defined stretch also requires a certain temperature distribution in the stretchable pipe wall. According to a preferred embodiment, a homogeneous temperature is maintained in the stretchable pipe wall, which can be achieved in a simple manner, e.g. by tempering the stretching temperature inside and outside the area of the extended receiving part. The internal tempering takes place in such a way that a heat exchange medium having a suitable temperature is passed through the receiving part of the stretching mandrel. The external tempering takes place in such a way that the entire pipe is passed through a suitable bath, whereby the tank for the bath can be divided into several chambers adapted for different temperatures. The additional towing flow of the lubricant according to the invention further promotes heat transfer between the receiving cylinder and the inner wall of the tube. At the same time, it is achieved that all the volume elements of the stretchable tube move at the same speed (without internal metabolism), which supports the defined temperature distribution and its maintenance in the stretchable tube. According to the defined and preferred embodiment of the invention, the tube thus produced with a homogeneous temperature distribution now stretches practically without sliding friction between the inner wall of the tube and the stretching mandrel, because here according to the invention the movement always takes place with a lubricant towing flow under radial forces. Surprisingly, however, take the tube with this lubricant towing wedge, taking care not to cause the expansion and associated cooling to occur too suddenly. In 66639 longitudinal section, the towing wedge forms a sloping plane and a hydraulic cushion. It must be prevented that the towing wedge does not break in the transition area between the cylindrical receiving part and the conical extension part, while the pipe wall there is detached from the stretching mandrel. The fold between the cylindrical receiving portion and the conical extension portion should be prevented and replaced by an arcuate displacement. The towing flow itself continues even up to the cylindrical outlet of the stretching mandrel. At the point of entry, the hydraulic lubricant must be depressurized. This applies in particular to imports in the region of a seemingly flowing blank. The hydraulic lubricant is thus towed with it, but is not squeezed between the pipe and the stretching mandrel. This does not preclude the lubricant from being introduced by pressure into the respective feed channels _ to overcome the friction losses in the feed channels. The effect of the hydraulic lubricant is hydrodynamic but not hydrostatic as described within the scope of the invention.

According to a preferred embodiment of the invention, the tempering takes place - but not necessarily - internally and externally in the region of the extended receiving part. The receiving section is so long that this tempering is achieved up to a sufficiently defined or homogeneous temperature distribution. In the area of the conical expansion part, the tube is practically exposed only to immobile air.

Otherwise, the pipe can be cooled strongly in the area of the discharge part, so that the thickness of the lubricant-towing wedge is considerably reduced. This cooling causes a strong shrinkage of the pipe. The shrinkage acts as a plug here and prevents the stretched tube from still carrying a significant amount of lubricant.

The advantages achieved can be seen above all in that, according to the method of the invention, the thermoplastic active tubes can be stretched biaxially with precisely predetermined and also very high degrees of stretching.

At the same time, a very precise calibration of the inner diameter of the expanded tube is achieved by stretching, as will be explained in connection with the figures, which at the same time—- show an apparatus for carrying out the method according to the invention, characterized by what is stated in claim 3.

In the schematic representation, Fig. 1 shows a longitudinal section of the apparatus for carrying out the method according to the invention, Fig. 2 an enlarged section A of Fig. 1, Fig. 3 an enlarged section B of Fig. 1, Fig. K a pressure distribution in the region, S 66639 Fig. 5 are tensile tensile stresses of a thermoplastic synthetic rod, Fig. 6 further schematically shows the surface conditions of the inner surface of a pipe to be stretched during stretching and Fig. 7 the velocity conditions in one part of a lubricating tow wedge

The apparatus shown in Fig. 1 acts for the axial stretching of a stretchable active tube 1, the tube 1 being extruded as a seemingly fluid in a high viscosity state out of a die head 2 provided with a nozzle mandrel 3, tempered and pulled by a cylindrical receiving portion U, a conical extension on the mandrel U, 5 »6 and is cooled from the outside and then hardened to a solid tube. Connected to the front of the nozzle head 2 is an artificial spiral press (not shown). According to the invention, the receiving part k is connected to the melt-cap end mandrel 3 (and thus considerably extended backwards towards the stxulate head 2 with respect to known embodiments) and provided with a device 7 for supplying hydraulic lubricant between the pipe 1 and the stretching core U, 5, 6. According to the invention, in the region of the extended receiving part U there is further a receiving bath U, 5> 6 for receiving the stretching mandrel 1, 5 and 6 and thus a tempering bath 8 for tempering the tube 1 to the stretching temperature, while the stretching inch 1+, 5 » A cooling bath 9 is arranged in the region of the discharge part 6. In the embodiment and according to a preferred embodiment of the invention, the device 7 for supplying hydraulic lubricant consists of a groove 7 into which the lubricant introduction holes 10 in the nozzle end 2 open, this groove 7 joining conically in the discharge direction. to the U-surface. The tempering bath is placed in a tempering tank 8 comprising a plurality of tempering chambers 11, whereby the tempering chambers 11 can be adjusted to a different tempering temperature while the correspondingly heated tempering liquid is introduced into these chambers 11.

Correspondingly, the cooling bath is arranged in the region of the cylindrical outlet part 6 in the cooling tank 9 »which may likewise have several cooling chambers 12. The conical expansion part 5 is made as conical as possible to prevent slippage in the transition area between the cylindrical receiving part U and the conical extension part 5 at 13 towing flow 1U interrupted. The largest diameter of the cone determines the degree of stretch in the circumferential direction. According to a preferred embodiment, the stretching mandrel U, 5 * 6 as a whole has the smoothest possible surface. Here the bend between the parts 1 *, 5 can be replaced by an arc. The ejector, 56639 6 15 works in this transition area. Its speed is practically equivalent to the extrusion speed. The speed difference between this discharge device 15 and the trailed discharge device 17 determines the degree of stretch in the axial direction. As a result, the tube 1 is tapped back to the nozzle end 2 in the region of the extended receiving section 1+ to the stretching temperature, that in the region of the seemingly fluid at point 7 between the tube 1 and the receiving section 1+ a hydraulic lubricant is fed to form a lubricant towing flow 1U with a flow il * on the receiving part U, the conical extension part 5 and the outlet part 6, whereby in the region of the expansion part 5 and the outlet part 6 the lubricant towing vi rt axis under the influence of radial forces formed or produced by expansion and cooling forms a lubricant towing wedge . This is shown in Figures 1-3. The hydrodynamic conditions in the lubricant towing flow and the lubricant towing wedge 16, respectively, are again described in connection with Figures U-7.

The curve 18 in Fig. H shows, at the expansion part 5 and the discharge part 6, the pressures which must act against the inner surface of the stretched and stretched tube 1, respectively, in order to compensate for the stresses which arise when the tube 1 expands. In this case, there is no substantial cooling in the region of the expansion part 5. In this connection, cooling takes place in the cooling bath 9, so that in addition there are shrinkage stresses which must be received. This causes the curve 18 to rise further in this area. As a result, the thickness of the lubricant towing wedge 16 decreases, and as the thickness decreases, higher hydrostatic pressures develop that compensate for the explained forces. Thus, it is clear that the stretching takes place with the sliding tow wedge 16 and no longer in direct or direct contact with the stretching inch 1 +, 5.6. Fig. U shows, on the one hand, a decreasing gap between the extension part 5 of the stretching inch U, 5, 6 and, on the other hand, the pipe wall 1. Figure 5 shows how, in the case of a thermoplastic active material, such as hard PVC, the tension shown by curve 19 changes with rotation, whereby the stretching temperature is assumed to be e.g. 93 ° C. These conditions have been taken into account in drawing the curve according to Figure U. Figure 6 shows that there are irregularities 20 in the inner surface of the tube 1 to be stretched. During the stretching, these irregularities decrease, so that the end result is a tube 1 with a very smooth inner surface. This is an additional advantage of the stretching according to the invention. In addition, no defects can occur on the inner surface. Despite the formation of the irregularities 20, the lubricant towing wedge 16 travels as already shown to the end of the removal part 6 of the stretching mandrel U, 5, 6. There, rapid cooling causes shrinkage, which at the same time acts as a plug. The required hydraulic pressure is generated for the towing flow 1L, 16 τ 56639. This is shown once again in Figure 7 ·

It shows the velocity profile 21 of the towing flow 16 and the wedge shape determining angle 22. This angle 22 can change in the longitudinal direction of the lubricant towing wedge 16. Despite the varying temperatures, the required back pressure can always be achieved in the lubricant towing wedge 16 and also in the lubricant towing flow 1U by means of hydrodynamic effects. The viscosity of the lubricant must be less than the viscosity of the apparent fluid as it exits the nozzle head 2. It is important that the lubricant does not corrode the surface of the active material to be made into a tube. Conventional mineral lubricants are generally suitable. If the viscosity of the lubricant is very low, the conical extension 5 must be very long, so that it must have a relatively small conicity. On the other hand, if a lubricant having a relatively high viscosity is used, the conicity of the conical extension portion 5 may be greater. In any case, however, the already explained improvement is also achieved - an improvement of the inner surface in that the surface becomes smooth. At the beginning of the manufacture, the tube must first be pulled onto the discharge device 17, e.g. by means of an expandable sleeve which can be pulled over the stretching inch U, 5, 6. Conical extension 5. can also be changed to provide different degrees of stretching.

Claims (5)

66639 A method for biaxially stretching a tube of stretchable active material, wherein the tube (1) is extruded as a seemingly flowing preform in a high viscosity state from a die head provided with a nozzle mandrel (3), tempered to a stretching temperature and pulled (4, 5, 6) and is cooled from above and then hardened to a solid tube, whereby a hydraulic lubricant is further introduced between the tube (1) and the stretching mandrel (1, 5, 6), characterized in that the stretching mandrel (L, 5 , 6) with a receiving part (li) substantially in diameter corresponding to the nozzle mandrel, connected to the conical expansion part, that the hydraulic lubricant is introduced to the beginning of the receiving part without pressure and that the tube (l) carries the lubricant with the receiving part (li) , on the conical extension part (5) and on the removal part (6), whereby the lubricant layer thins the wedge-shaped in the region of the expansion part and the removal part under the influence of radial forces. Method according to Claim 1, characterized in that the tube (1) is cooled in a manner known per se in the region of the receiving part from the inside and the outside to the stretching temperature. Apparatus for carrying out the method according to claims 1 and 2, the apparatus comprising an artificial spiral press having an extruder and a mandrel (3) thereof and a stretching mandrel (li, 5, 6) connected thereto, comprising a cylindrical receiving part (li), a conical expansion part (5) and a cylindrical discharge part (6), characterized in that the receiving part (li) is connected to the nozzle head mandrel (3) and provided with a device (T) for introducing a hydraulic lubricant into the tube (1) and the stretching mandrel (li, 5, 6) and that in the region of the receiving part (li) - a per se known tempering bath (8) is arranged to temperature the tube (1) to the stretching temperature and in the region of the outlet part (6) a per se known cooling bath (9) is arranged. - li. Apparatus according to claim 3, characterized in that the device for introducing a hydraulic lubricant between the pipe (1) and the stretching mandrel (1, 5, 6) comprises a groove (T) with lubricating bore holes (10) and a groove (T) in the extruder mandrel (3). conically joins the surface of the receiving part (li). Apparatus according to Claims 3 and 11, characterized in that the conical extension part (5) with low conicity is made so long that the lubricant flow is not interrupted in the transition area between the cylindrical receiving part (H) and the conical extension part (5).