DE4141393A1 - Injection moulding plastic tube extending in more than two direction - where core parts are injected first, then assembled by interlocking and second plastic layer is injected around outside - Google Patents

Abstract

An injection moulding process, for mfg. plastic or elastomeric pipes or containers, involves two stages, the first of which requires the mfr. of tubular or container shaped core components. Each core component can be attached to the next with interlocking male and female connectors and is mfd. in thermoplastic, thermosetting or elastomeric material or alternatively in a low m.pt. alloy. When assembled in the desired profile the core unit is placed in a tool and a further layer of plastic or elastomer is injected around it to form a stable integral prod.. The tube or container core sections have radial flanges on the outer face which are equal in height to the thickness of the second, enclosing layer and act as distance pieces. USE/ADVANTAGE - For mfg. tubes or containers which extend in two or more alternating directions. Avoids the problems of core removal when a second change of direction occurs.

Description

The invention relates to an injection molding process for making a plastic tube as well a plastic made by the process pipe.

Such plastic pipes are used for. B. in the car mobile construction as fuel, brake or hydraulic lik lines used. According to the conventional Injection molding processes can only be straight or Pipes extending in two spatial directions produce. The removal of the spray cores is then in two directions in which the Pipe extends possible. However, a third party comes Add spatial direction or bending direction, so lets the spray core between the first and second tube no longer remove the curvature. If a pipe is desired with even more curvature or Directions of curvature is a manufacture extremely complex. In the past different manufacturing directions for such Pipes known.

From 1977 published DE-PS 25 48 254 a manufacturing method and an apparatus Knows for injection molding of 180 degree elbows. The used device allows pulling out the spray cores by a combination of one Rotary, one lift, one spiral and one tilt  movement with subsequent tipping and forwards of the 180 degree elbow. It is obvious, that a device for such complicated Movements extremely complex and therefore ex is extremely expensive.

From EP-223 754 A3 published in 1987 a bending process and one to be used for it Device known for manufacturing with a tube made of thermoplastic three curves. A pipe is in a straight shape inserted and up to the thermoelastic tempera heated in the mold area. Subsequently is by shifting the start and end areas of the straight shape correspond to tube two en curvatures forced and the shape cooled. The device to be used for this is very open agile and the shape itself required precise work temperature control units.

Furthermore, from the 1989 published DE-OS 37 27 717 a method and an apparatus for Manufacture of thermoplastic pipes material with more than two curvatures. The originally straight thermoplastic pipe section is made on a straight core at room temperature a memory metal alloy that slides on inferring an upper transition temperature of the Memory metal alloy is heated so that the core its original, more than two curves pointing shape and the plastic tube, which is caused by the heating of the alloy thermoelastic area is to the desired Shape bends.  

Removing the core leaves the heat set The shape of the cooled plastic pipe is uneven is pregnant. However, if pipes with multiple elbows measurements of less than 90 degrees removal is without damage the plastic pipe is no longer possible. It is obvious that this way only very thin walled pipes made from a highly elastic art fabric can be made. Even if at place a core with a corresponding curvature having a shape made of a memory metal alloy is used is the procedure for a mass production of plastic pipes not suitable.

Finally, from the 1991 published DE-OS 39 39 352 a method and an apparatus became known with a form that can be divided into two or three spatial directions, d. H. the several has consecutive curvatures. In the open form becomes a thermoplastic Inserted plastic tube clamped and locked. Then the mold is heated. In addition, for better heat transfer to the plastic pipe a hot gaseous or liquid medium filled into the mold. Then there is an Ab cooling and then removing the deformed Plastic pipe from the mold. In this way can be very thin-walled elastic at best Manufacture pipes of inferior quality. Tube made of polyamide filled with glass fiber or mineral would not correspond to one without destruction Have the appropriately designed shape brought in.  

The manufacturing process is also suitable not for mass production of pipes.

It is the object of the present invention a manufacturing process for thermoplastic Propose plastic pipes or containers, the tubes or containers being in two or extend more changing spatial directions, d. H. two or more curves in a row exhibit. A production after a usual Injection molding would not be considered because the removal of the inner mold cores from second curvature is not possible.

The task is accomplished through an injection molding process with the features as described in, ning part of the first claim solved. In the subclaims is a plastic pipe claimed, which according to the method of first claim is made.

In a first stage of manufacture, individual cores pipe parts manufactured and pipe parts to put together each result in a pipe bend. A first curvature is produced on a product produced in this way pointing pipe includes a z. B. with tongue and groove provided additional pipe part, whereby then the second, in a different spatial direction send pipe bend connects. The same way any number of pipe parts can be attached to the first Connect the pipe part so that it is put together core tube extending in many spatial directions is obtained.  

The so put together, in many room rich then extending pipe forms the spray casting core for a correspondingly designed pipe.

The above-mentioned plugged pipe will be afterwards in a specially designed form. To the Outer walls of the core tube parts are advantageous Spacers are molded on for you predetermined distance between the core tube parts and the mold wall, so that the shape around the core tube parts form a cavity.

Then the mold is closed and into the hollow space becomes a in the usual injection molding process Plastic melt injected. Through this The injection molding process will be made of many parts standing pipe over its entire length and its entire circumference evenly with a plastic layer overmolded, creating the respective connection areas of the individual core tube parts be closed metically. So it becomes a completely dense and high pressure-bearing com received positive tube, which is very compact and is extremely robust.

It is very beneficial if the tubular Core or container parts justie at their ends rende clamp or snap fasteners z. B. Tongue or groove have similar elements, because then putting the core parts together is simpler and therefore very precise and light one composed of many parts Core tube is obtained.  

Depending on the intended use, the core parts and / or the cladding layer around the core parts advantageously from a thermo plastic or thermosetting plastic be stand, e.g. B. from a polyamide. If the core parts and the cladding layer from one injection molded elastomer you get an elastic tube called vibra can take up.

A plastic can also advantageously be used (Polyamide) with glass fibers mixed in e.g. B. a length of about 20 to 100 my point, are used, which makes a very robust pipe or a corresponding bend or containers with undercuts is obtained.

It’s also advantageous because it’s cheaper, if only the connection areas of the merged put core parts during the second manufacturing level with a plastic in a corresponding molded form. In one Case can be the tubular or container-shaped core share a thinner one in the connection area Show wall thickness than in the middle area. By overmolding the connection areas in the second stage of production ensures that the connection areas are absolutely pressure-tight and thus the finished pipe both in connection same area in the middle area Has wall thickness.  

Pipes that are elastic in certain areas should be obtained in an advantageous manner if the core parts in this case from one at a right relatively low temperature melting metal z. B. also be manufactured as solid core parts that then together with other plastic core parts put the desired core tube shape. If then in the second stage of manufacture Metal core parts with an elastic plastic or an elastomer and the Me Tallkern melted by heating, d. H. is melted out of the coated tube, is the area from which the core tube parts come out were melted, highly elastic. By an ent speaking choice of wall thickness in the second Spray manufacturing stage around the metal cores elastic plastic layer, is also in this Fall a pipe with one over the entire length of the pipe get uniform wall thickness.

When plastic is injected melt on a shape arises on average Pressure of 400-1000 bar.

Because of this high pressure in an injection molding form was assumed in the past that placed in a mold by the in the pressure prevailing during the injection process be pressed together. However, it was in over surprisingly and unexpectedly represents that the core tube parts despite the high Pressure in the mold during the molding process not merged in the second stage of manufacture were pressed.  

The invention is further illustrated by the drawings explained. In the drawings, pipe parts are ge shows. However, it is obvious that Be container using the same manufacturing process can be made, what is due to the Her position of a spherical container clearly becomes. In such a case, two would be spherical Mige half-shells according to the invention after the be knew injection molding process and with ih injection molded snap locks into one Sphere put together. The ball thus obtained becomes as a spray core in a correspondingly designed spherical shape. Outside on the wall in this case the ball would also have small ab molded footbridges. Then in the cavity between the spherical core and the mold wall in the second stage of production plastic melt injected so that the seams between sealed the spherical core halves and a completely closed, air-bearing sphere is obtained. In the same way, be lovingly designed containers are also the most complicated Create kind in a simple way.

Show it:

Fig. 1 mated core tube parts,

Fig. 2 is an overmolded core tube,

Fig 3 tube parts. A clamping connection of the core,

Fig. 4 is a pinned together, over-molded tube stage in a tool by carrying out the second manufacturing,

Fig. 5 mated core tube parts without Umspritzschicht,

Fig. 6 is a pipe as shown in Fig. 5, but with a Umspritzschicht only in the connecting areas

Fig. 7 is a pipe as shown in Fig. 6 in a mold,

Fig. 8 is a tube with an elastic part.

The tube shown in Fig. 1 is composed of three tubular core parts 1 , 2 and 3 , which are manufactured by the usual injection molding process and inserted into each other, as shown in detail in Fig. 3. By injection molded tongue and groove 4 and 5 it is achieved that the core tube parts can only be put together in the correct position, that is to say only adjustably, in order to ensure a very exact subsequent encapsulation.

FIG. 2 shows a tube that has already been overmolded with a plastic layer 6 . The spacer webs 7 to 10 lie against the mold inner wall and thus ensure an exact positioning of the assembled core tube in the mold and thus a completely uniformly thick plastic layer at all points.

In Fig. 4 is a plan view of a mold 11 shows ge with an already overmolded tube as shown in Fig. 2. The plastic melt is injected into the injection channel 12 via the branch channels 13 and 14 to the injection points 15 and 16 with high pressure. The melt is then distributed evenly around the injection core parts 1 , 2 and 3 and forms the layer 6 after it has cooled. Position holders 17 and 18 are inserted in the pipe ends.

In Fig. 5 core parts 19 , 20 and 21 are shown, which were also put together to form a tube extending in three spatial directions. In this case, however, the entire tube is not extrusion-coated with a layer, but only the connection areas 22 and 23 of the individual tube core parts 19 , 20 and 21 . In Fig. 6, the overmolded in the connecting areas tube is shown, with plastic layers 24 and 25th

In Fig. 7 a tube, as shown in FIG. 5 in a mold 26 prior to extrusion coating of the layers 24 and 25. Through the injection channel 27 , the branch channels 28 , 29 and the injection points 30 and 31 , the hot plastic melt enters the cavities 32 and 33 so that only the connection areas 22 and 23 are extrusion-coated.

In Fig. 8 a further embodiment of the invention He is shown with core tube parts 19 and 20 and a so-called fusible core 37 which has anti-rotation locks, not shown. The melting cores can also be produced in an injection molding process, in which a similarly acting metal, which is already melting at a low temperature, is entered into the injection molding machine instead of the molten plastic. The core tube parts 19 and 20 are plugged onto the melting core. Then the core tube is placed in an injection mold in the same way. The middle region 38 with the fusible core 37 is made with another plastic, which, for. B. may have a high elasticity through the injection channel shown by arrow 35 to inject. In the central area, an elastomer 38 can also be injected, so that it will hold a tube which allows bending in this area 38 without being destroyed.

After the elastomer layer 38 has cooled, the spray core 37 is melted out of the tube by a further targeted heating of this area and the tube is ready for a corresponding use. In this special application, an additional melting process for the core 37 is required, on the other hand, however, a bendable or Vi brations without damage receiving tube is obtained in a very simple manner.

Claims (8)

1. Injection molding process for producing a tube or container made of plastic, the tube or the container has a, in two or three spatial directions extending training that does not allow removal of all the injection molding cores when the tube or the container is manufactured according to conventional injection molding technology is characterized in that the tube or the container in two stages Herge is that in the first manufacturing stage in the injection molding process individual tubular or container-shaped core parts ( 1 , 2 , 3 , 19 , 20 , 21 ) who who that the individual core parts are plugged together to form a core tube or core container extending in two or three spatial directions, that the core tube or the core container is inserted into a corresponding injection mold ( 11 , 26 ) adapted to the core tube or core container, and that in the injection mold arranged core tube or the Kernbe container in a second Herste level with a plastic or elastomer layer ( 6 ) is encapsulated. 2. Plastic pipe manufactured by the method according to claim 1, characterized in that the tubular core or container parts ( 1 , 2 , 3 , 20 , 21 , 22 ) at their ends have adjustable clamping or latching connection elements ( 4 , 5 ). 3. Plastic pipe according to claim 2, characterized in that the tubular or container-shaped core parts ( 1 , 2 , 3 , 20 , 21 , 22 ) have spacers on their outside ( 7 , 8 , 9 , 10 ) and that the height of the Spacers about the thickness that corresponds to the layer ( 6 ) sprayed around the core parts in the second production stage. 4. Plastic pipe according to claims 2 and 3, characterized in that the core parts ( 1 , 2 , 3 , 20 , 21 , 22 ) and / or the sheathing of the core parts forming plastic layer ( 6 ) made of a thermoplastic or thermosetting plastic or an elastomer consists. 5. Plastic pipe according to claims 2 to 4, characterized in that the core parts ( 1 , 2 , 3 , 20 , 21 , 22 ) and / or the sheath-forming layer ( 6 ) consists of glasfaserver reinforced plastic or an elastomer. 6. Plastic pipe according to claims 2 to 5, characterized in that only the connection areas ( 22 , 23 ) of the plugged-together core parts are extrusion-coated in the second manufacturing stage with a plastic or elastomer layer. 7. plastic pipe according to claims 2 to 6, characterized, that the tubular or container-shaped core parts one, melt at a low temperature consist of the metal and as a tubular or mas sive core parts are formed and that in the second stage of production around pieced together core parts sprayed art fabric or elastomer layer as a whole or Be richly from an elastic plastic or There is elastomer. 8. plastic pipe according to claims 1 to 8, characterized, that the wall thickness of the core tube parts about half the thickness of the finished sprayed Tube is.