Injection-molding device for producing multi component moldings and method for producing multi-component moldings

Abstract

The invention relates to an injection-molding device for producing multi-component moldings from a thermoplastic molding compound, comprising a mold, forming a first article cavity, comprising means for filling the first article cavity with the thermoplastic molding compound, comprising an injection device for injecting a fluid against a projectile to be driven, wherein the injection device comprises a projectile carrier with at least one injection nozzle and with at least one projectile receptacle for a projectile as a displacer for the molding compound. The injection-molding device also comprises a mold insert, which forms a continuation of the first article cavity and encloses the projectile carrier, wherein the projectile carrier forms with the mold insert a second article cavity that can be filled with the molding compound, wherein the mold insert has a separate sprue and wherein the second article cavity of the mold insert can be sealed off for a time with respect to the first article cavity by means of movable mold parts. The invention also relates to a method for producing multi-component moldings by using the injection-molding device.

Claims

1. A method for producing a plastic article, comprising: a) providing an injection-molding device comprising a mold having a first article cavity, an injection device to inject fluid into the first article cavity, a mold core, a mold insert, wherein the mold insert forms an appendage of the first article cavity and which encloses the mold core, wherein at least the mold core and the mold insert form a second article cavity; b) sealing the second article cavity by movable mold parts; c) at least partially filling the second article cavity with a second article molding compound; d) opening the mold parts after the second article molding compound has at least partially solidified; e) moving the mold insert and the mold core along an advancement path that is formed by the opening of the mold parts; f) at least partially filling the first article cavity with a first article molding compound, wherein the first article molding compound is different from the second article molding compound, and the first article molding compound and the second article molding compound are compatible in molecular terms, and wherein the first article molding compound connects to the second article molding compound; g) introducing a fluid into the first article cavity with the injection device such that the fluid displaces a portion of the first article molding compound from the first article cavity to provide the plastic article having a hollow body; and i) demolding the article.

2. The method as claimed in claim 1, wherein the injection device comprises a projectile carrier, which is provided as the mold core, and the method further comprises: j) providing a projectile; k) equipping the projectile carrier with the projectile, wherein moving the mold insert into the advancement path that is formed by the mold parts is performed conjointly with the projectile carrier, and wherein the fluid drives the projectile through at least a portion of the first article cavity while displacing a portion of the first article molding compound in such a manner that the projectile configures the hollow body.

3. The method as claimed in claim 1, wherein: the first article molding compound and the second article molding component each comprise at least one thermoplastic material which is selected from a group comprising high-density polyethylene, polyamide, polyamide 6, polyamide 12, polyurethane, polycarbonate, acrylonitrile-butadiene-styrene copolymer, polyketone, polystyrene, olefin-based thermoplastic elastomers, cross-linked thermoplastic olefin-based elastomers, thermoplastic urethane-based elastomers, thermoplastic polyester elastomers, and thermoplastic copolymers.

4. The method as claimed in claim 1, wherein: the second article molding compound is thermoplastic material which is a thermoplastic elastomer and the first article molding compound is a thermoplastic material which is not a thermoplastic elastomer.

5. The method as claimed in claim 1, wherein at least partially filling the second article cavity with a second article molding compound further comprises: at least partially filling the second article cavity with a second article molding compound through a second article cavity sprue.

6. The method as claimed in claim 5, wherein: the second article cavity sprue opens into the second article cavity.

7. The method as claimed in claim 5, wherein: the second article cavity sprue is disposed in the mold insert.

8. The method as claimed in claim 1, wherein sealing the second article cavity by movable mold parts further comprises: sealing the second article cavity by movable mold parts which bear against the mold core.

9. The method as claimed in claim 1, wherein: the movable mold parts comprise at least one slide.

10. The method as claimed in claim 1, wherein: the movable mold parts form a portion of the second article cavity with the mold core and the mold insert.

11. The method as claimed in claim 1, wherein: the movable mold parts each have an end face having an undercut or step-shaped profile.

12. The method as claimed in claim 1, wherein at least partially filling the first article cavity with a first article molding compound further comprises: at least partially filling the first article cavity with a first article molding compound through a first article cavity sprue.

13. The method as claimed in claim 12, wherein: the first article cavity sprue opens into the first article cavity.

14. The method as claimed in claim 1, wherein: the mold insert is movable relative to the mold, from a first position which is sealed in relation to the movable mold parts to a second position which seals the first article cavity of the mold.

15. The method as claimed in claim 1, wherein: the second article cavity is configured as an annular space.

16. The method as claimed in claim 1, wherein: the mold insert and the mold core are conjointly advanceable in a direction towards the first article cavity and conjointly retractable in a direction away from the first article cavity.

17. The method as claimed in claim 1, wherein moving the mold insert and the mold core along an advancement path that is formed by the opening of the mold parts further comprises: moving the mold insert and the mold core along an advancement path that is formed by the opening of the mold parts such that the second article molding compound which at least partially fills the second article cavity enters a portion of the first article cavity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be explained hereunder by means of an exemplary embodiment illustrated in the drawings in which:

(2) FIG. 1 shows a schematic partial sectional view of an injection-molding mold according to a first exemplary embodiment of the invention, in a first position of the mold insert;

(3) FIG. 2 shows a view corresponding to that of FIG. 1, in which the mold insert is located in a second position; and

(4) FIG. 3 shows a schematic partial sectional view of an injection-molding mold according to a second exemplary embodiment of the invention.

DETAILED DESCRIPTION

(5) The figures in a simplified manner show parts of an injection-molding device 1 according to the invention. Devices for extruding the thermoplastic molding compound are not illustrated for reasons of simplification. The injection-molding device 1 comprises a mold 2 which is composed, for example, of two mold halves which define a first article cavity 3. The first article cavity 3 can be configured, for example, in the form of a tube (3D tube) that is curved multiple times in space. The mold 2 comprises a plurality of movable components in the form of slides and the like, and at least one secondary cavity. The secondary cavity is capable of being blocked in relation to the first article cavity 3 by means of slides. These details are likewise not illustrated in the drawings for reasons of simplification.

(6) FIGS. 1 and 2 show an end of the first article cavity 3 in the region of an end of the tube to be molded as the article, for example. The mold 2 comprises a first sprue 4 which opens into the first article cavity. Furthermore, an injection device 12 having a projectile carrier 5 is disposed so as to be adjacent to the mold 2. The projectile carrier 5 penetrates a movable mold insert 6 which is configured in one or multiple parts and which is part of the injection-molding device.

(7) The mold insert 6 forms an appendage of the first article cavity 3. The internal diameter of the mold insert 6 corresponds to the internal diameter of the first article cavity 3. The appendage thus formed is disposed so as to be aligned with and coaxial with the first article cavity 3.

(8) As has already been mentioned above, the mold insert 6 conjointly with the projectile carrier 5 is re-adjustable in the direction of the arrow indicated in FIG. 1, that is to say in the direction of the longitudinal axis of the first article cavity 3. The projectile carrier 5 is penetrated by a fluid duct 7 which on the free end of the projectile carrier 5 configures an injection nozzle 8.

(9) The projectile carrier 5 which is configured as a mandrel, on the free end of said projectile carrier 5 receives a projectile 9 which is configured as a plastics material cap.

(10) The projectile carrier 5 comprises a shank portion 10, the diameter being smaller than the internal diameter of the mold insert 6 by the dimension of the wall thickness of the article to be fabricated. The projectile carrier 5 conjointly with the mold insert 6 forms a second article cavity 11 in the shank portion 10, said article cavity 11 being capable of being filled with a thermoplastic molding compound by way of a second sprue 13.

(11) The second article cavity 11 that is formed between the projectile carrier 5 and the mold insert 6 by way of two movable mold parts in the form of separation slides 14 is capable of being blocked in relation to the first article cavity 3.

(12) FIG. 1 shows the mold insert 6 in a first retracted position in which the separation slides 14 in each case by way of a sealing face 15 bear on the shank portion 10 of the profile carrier 5. The projectile carrier, the first article cavity 3, and the second article cavity 11 have in each case a toroidal cross-section. The sealing faces 15 of the separation slides 14 are configured in the shape of a circular segment and encompass the shank portion 10 of the projectile carrier 5 such that the second article cavity 11 is completely sealed by way of the separation slides 14.

(13) FIG. 1 shows the second article cavity 11 in a state in which the latter is filled with a thermoplastic molding compound. FIG. 2 shows the assembly drawn in FIG. 1, wherein the separation slides 14 therein are open such that the sealing faces 15 no longer bear on the shank portion 10 of the profile carrier 5. Moreover, the mold insert 6 is shown in a position advanced in the direction toward the first article cavity 3, in which position the second article cavity 11 communicates with the first article cavity 3, and the first article cavity 3 is sealed by way of the mold insert 6. When the separation slides 14 are repositioned to the opened position illustrated in FIG. 2, said separation slides 14 release an advancement path for the mold insert 6.

(14) The state of the injection-molding device 1 in which the first article cavity 3 is also filled with a thermoplastic molding compound is illustrated in FIG. 2.

(15) The method according to the invention will now be explained hereunder with reference to FIGS. 1 and 2.

(16) The method initially provides that the mold 2 which, for example, is composed of two mold halves is open. In this method step, the mold insert 6 is disposed relative to the mold halves in the position illustrated in FIG. 1. The projectile carrier 5 thereafter, at the leading end thereof, is equipped with a projectile 9. The mold halves of the mold 2 are closed and kept shut.

(17) In a next method step, a first thermoplastic molding compound having a first thermoplastic component is filled into the second article cavity 11 that is formed between the projectile carrier 5 and the mold insert 6. The second article cavity 11 is sealed by way of the separation slides 14. The separation slides 14 have in each case end faces having a step-shaped profile such that an end face of the preform molded in the second article cavity 11 has a corresponding staged contour in a step-shaped manner.

(18) Once the preform/injection-molded part thus produced has at least partially solidified, the separation slides 14 are opened, that is to say repositioned to the position illustrated in FIG. 2 in which said separation slides 14 form an advancement path for the mold insert 6. The mold insert 6 thereafter is advanced in the direction toward the first article cavity 3 such that the now exposed end side of the preform partially protrudes into the first article cavity 3. The mold insert 6 in this position assumes sealing of the first article cavity 3.

(19) In a next method step, a second thermoplastic molding compound having a second thermoplastic component is filled into the first article cavity 3 by way of the first sprue 4. As is commonplace in injection-molding, filling can be performed completely or partially.

(20) Slides which connect the secondary cavity to the first article cavity 3 (not illustrated) are opened in a further method step. The fluid duct 7 thereafter is impinged with a pressurized fluid, for example with water. Pressurized fluid exits the injection nozzle 8 and drives the projectile 9 through the first article cavity 3, and herein displaces a liquid core of the thermoplastic molding compound that has been injected into the first article cavity 3 into the secondary cavity, on account of which a tubular article from a thermoplastic plastics material having a defined residual wall thickness and a comparatively defined internal diameter is created.

(21) A thermoplastic elastomer is preferably injected by way of the second sprue 13 of the mold insert as the first thermoplastic molding compound; a non-thermoplastic component which is compatible with the thermoplastic elastomer can be provided as the second thermoplastic molding compound which can be injected into the first article cavity 3 by way of the first sprue 4.

(22) After the mold 2 has been opened, the multi-component molding in the form of an integral tube thus produced from thermoplastic plastics material can be retrieved.

(23) FIG. 3 shows a second exemplary embodiment of an injection-molding device 1 according to the invention. In the case of the exemplary embodiment illustrated in FIG. 3, components which correspond to those of the first exemplary embodiment are provided with the same reference signs.

(24) The injection-molding device 1 according to FIG. 3 is configured for carrying out the method according to the invention in which a pressurized fluid is introduced directly into the article cavity 3 (water injection technology/WIT). Accordingly, the injection-molding device 1 according to FIG. 3 differs from that according to FIGS. 1 and 2 in that the mold insert 6 comprises an injection nozzle 8 which is configured as a simple mold core and which does not receive any projectile.

(25) The mold insert 6 otherwise corresponds to that according to FIGS. 1 and 2. The method carried out by the injection-molding device 1 according to FIG. 3 differs from the method that is carried out by the injection-molding device according to FIGS. 1 and 2 in that no projectile is provided which while displacing part of the molding compound is driven through the first article cavity 3.

(26) FIG. 3 shows the mold insert 6 in a position in which the latter forms a second article cavity 11 which is capable of being filled with the molding compound, wherein the second article cavity 11 is sealed in relation to the first article cavity 3 by means of the separation slides 14. The filling of the second article cavity 11 with the plasticized molding compound is subsequently performed by way of the second sprue 13.

(27) When the molding compound has at least partially solidified, the separation slides 14 are opened and the mold insert 6 in a manner corresponding to the assembly in FIG. 2, is advanced in the direction toward the first article cavity 3 such that the now exposed end side of the preform/injection-molded part thus produced protrudes into the first article cavity. The mold insert 6 in this position assumes the sealing of the first article cavity 3.

(28) In a next method step, a second thermoplastic molding compound, or a second thermoplastic component, respectively, is filled into the first article cavity 3 by way of the first sprue 4. Also in the case of the exemplary embodiment according to FIG. 3, filling can be performed completely or partially.

(29) In a further method step, slides which connect the secondary cavity to the first article cavity 3 are opened (not illustrated). The fluid duct 7 is thereafter impinged with a pressurized fluid, for example with water. The pressurized fluid exits the injection nozzle 8 and herein displaces directly a liquid core of the thermoplastic molding compound that has been injected into the article cavity 3 into the secondary cavity. In order for a displacement of the as yet plastic molding compound to be caused across the largest area possible, the injection nozzle 8 is provided with a port 16 that is widened in the manner of a diffuser.

(30) The separation slides 14 according to the exemplary embodiment illustrated in FIG. 3 differ from the separation slides 14 according to the exemplary embodiment illustrated in FIGS. 1 and 2 in that the end faces of said separation slides 14 have a profile which generates an undercut on the preform, into which undercut the second component of the thermoplastic plastics material that is injected into the second article cavity 3 can engage such that the portions of the article thus generated engage in one another in a materially integral as well as a form-fitting manner

(31) The multi-component molding produced by the method according to the invention can be configured, for example, as a filler pipe of a fluid container of a motor vehicle, said filler pipe potentially having a first portion from a thermoplastic polymer and a second portion from HDPE or, for example, a polyamide.

LIST OF REFERENCE SIGNS

(32) 1. Injection-molding device 2. Mold 3. First article cavity 4. First sprue 5. Projectile carrier 6. Mold insert 7. Fluid duct 8. Injection nozzle 9. Projectile 10. Shank portion of the projectile carrier 11. Second article cavity 12. Injection device 13. Second sprue 14. Separation slide 15. Sealing face 16. Port of the injection nozzle 8 (FIG. 3 only)