Method for producing a container from thermoplastic material

Abstract

The invention relates to a method for producing a container from thermoplastic material having a connection element (5) passing through the wall thereof. The method comprises making available at least one plate-shaped or shell-shaped or tube-shaped preform (3) made of plasticized thermoplastic material, introducing the preform (3) into a multipart molding tool (1) having cavities defining at least one molding recess, molding and final shaping of the preform (3) within the molding tool (1) using differential pressure, piercing of the still warm-plastic preform (3) from the tool side by means of a mandrel (9) in order to produce an opening (6) in the preform (3), insertion from the molding recess side of a connection element (5) into the opening (6) produced by the mandrel (9), and connection of the connection element (5) to the preform (3).

Claims

1. A method for producing a container from thermoplastic material having a connection element passing through a wall thereof, comprising: heating thermoplastic material, making at least one preform from the heated thermoplastic material, introducing the at least one preform of the heated thermoplastic material into a multipart molding tool having at least one cavity defining at least one molding recess, wherein the heated thermoplastic material has a tool side which faces the at least one cavity and a molding recess side opposite the tool side, molding the at least one preform with the multipart molding tool using differential pressure to form shell intermediates, joining the shell intermediates to form a hollow body, wherein the shell intermediates are welded to one another, piercing the heated thermoplastic material from the tool side by a mandrel to produce an opening in the heated thermoplastic material, inserting a connection element into the opening formed in the heated thermoplastic material from the molding recess side, and connecting the connection element to the heated thermoplastic material, wherein the opening produced by the mandrel is sized before or during the insertion of the connection element into the opening, and wherein the sizing is carried out by at least one sizing sleeve inserted into the opening from the tool side.

2. The method as claimed in claim 1, wherein the connection element is inserted into the opening by a connection stub inserted into the sizing sleeve situated in the opening, whereupon the sizing sleeve is withdrawn from the opening and, during the withdrawal of the sizing sleeve or subsequently, the connection element is connected to the heated thermoplastic material by a collar provided on the connection element.

3. The method as claimed in claim 2, wherein the connection element is connected on the molding recess side of the heated thermoplastic material to a venting device arrangeable in the container.

4. The method as claimed in claim 3, characterized in that wherein a pressure equalization of a volume of the venting device is established via the connection element during a pressurization of the at least one molding recess.

5. The method as claimed in claim 4, wherein the pressure equalization is accomplished by the mandrel.

6. The method as claimed in claim 5, wherein the pressure equalization is carried out while the sizing sleeve is in the opening.

7. The method as claimed in claim 1, wherein the at least one mandrel is arranged coaxially with the at least one sizing sleeve, which is adjustable relative to the mandrel.

8. The method as claimed in claim 7, wherein the mandrel comprises a hollow needle having at least one opening through which media is flowable and is connected to a pressure medium source for pressurizing the molding recess.

9. The method as claimed in claim 1, wherein connecting the connection element to the heated thermoplastic material is performed before forming the hollow body.

Description

(1) The invention is explained below by means of an illustrative embodiment shown in the drawings, in which:

(2) FIG. 1 shows a schematic simplified view of part of a molding tool having a preform inserted into the latter and having a perforation device according to the invention, before the piercing of the preform,

(3) FIG. 2 shows a view corresponding to FIG. 1 during the piercing of the preform,

(4) FIG. 3 shows a view corresponding to FIG. 1 during the sizing of the opening,

(5) FIG. 4 shows a view corresponding to FIG. 3 with the mandrel retracted,

(6) FIG. 5 shows a view corresponding to FIG. 4, which illustrates the insertion of the connection element into the opening,

(7) FIG. 6 shows a view corresponding to the previous figures after the welding of the connection element to the preform.

(8) In the figures, the size ratios of the molding tool 1 and of the perforation device 2 are not shown in proportion. The depiction serves only to illustrate the method and, in other respects, is highly simplified.

(9) Only part of a wall 2 of the molding tool 1 is shown in FIG. 1. The complete molding tool and, where present, one or more associated extrusion devices, comprising an extruder and at least one extrusion head, a removal device and the like, are not shown for the sake of simplification.

(10) The molding tool 1 can be designed as a blow molding tool, for example, comprising at least two outer molds and a central mold, wherein the individual parts of the blow molding tool are mounted in a conventional manner on mold clamping plates, which are arranged so as to be movable within a closing frame. The outer molds can be moved away from one another and toward one another to produce an opening and closing movement of the blow molding tool. The central mold can be moved transversely to the opening and closing movement. The central mold comprises pneumatically adjustable or movable component holders, for example, by means of which internal fittings can be positioned in the container to be produced. The container according to the invention is expediently designed as a plastic container extruded in multiple layers from a thermoplastic material based on HDPE.

(11) The method explained below with reference to the illustrative embodiment comprises the ejection of web-shaped preforms 3 from at least one extrusion head, wherein the preforms 3 are cut to length between the abovementioned outer molds and the central mold of the molding tool.

(12) In a first method step, the outer molds are closed against a central mold or against a tool divider, the preforms 3 are pulled or pushed into the partial cavities 4 of the molding tool 1, which are formed by the outer molds, by the application of gas pressure and/or by means of an externally applied vacuum. Although a plurality of partial cavities 4 is mentioned here, only one side of the molding tool 1 with one partial cavity 4 is illustrated in the figures.

(13) In the partial cavity 4, the preforms 3 initially adopt the contour of the molding tool 1 predetermined by the partial cavity 4 after initial molding. In a further method step, provision is made to join internal fittings to the preforms 3 on the molding recess side, i.e. on the side of the preforms 3 which faces away from the partial cavities 4. This joining can be accomplished by welding and/or in situ riveting, for example. According to the method, provision is made, for example, to introduce a container with an internal venting device comprising vent lines, at least one bubble section and intercommunicating vent lines.

(14) By means of a connection element 5, which will be described below, the vent line arrangement including valves and at least one bubble section is provided with a connection through the subsequent container wall, namely in the form of the connection element 5 (see FIG. 5, for example). For this purpose, the connection element 5 is inserted into a previously produced opening 6 in the preform 3.

(15) For this purpose, reference is made first of all to FIG. 1, which shows part of the wall 2 of the molding tool 1 with a preform 3 inserted. In this state, the preform 3 is at melting temperature and is warm-plastic. Provided in the wall 2 of the molding tool 1, at that point of the preform 3 which is to be perforated, is an aperture 7, behind which a perforation device 8 according to the invention is provided on the tool side.

(16) The perforation device 8 comprises a mandrel 9, which is designed as a hollow needle, and a sizing sleeve 10, which is arranged concentrically and coaxially with the mandrel 9. The mandrel 9 and the sizing sleeve 10 are provided with a first and a second feed device 11 and 12, by means of which the mandrel 9 and the sizing sleeve 10 are arranged in such a way as to be movable jointly and relative to one another. The feed devices 11, 12 can have pneumatic cylinders and a corresponding actuating mechanism, for example. As an alternative, these can, for example, also be designed as electric drives, e.g. in the form of stepping motors. The feed devices 11, 12 can likewise be driven hydraulically.

(17) The mandrel 9 and the sizing sleeve 10 can be moved into the partial cavity 4 through the aperture 7 in the wall 2 of the molding tool 1.

(18) In the method according to the invention, it is envisaged that pre-shaping or placing of the preforms 3 in the partial cavities 4 of the molding tool 1 is followed by the production of an opening 6 by means of the perforation device 8 to accommodate the connection element 5, at least in the case of one preform 3. In this process, the mandrel 9 is first of all driven or pushed through the aperture 7 into the partial cavity 4, piercing the preform 3. The mandrel 9 is designed as a hollow needle with a needle tip 13 which has a plurality of media passages, e.g. in the form of holes.

(19) The process of driving in the mandrel 9 is illustrated in FIG. 2. This does not involve any punching of material out of the preform 3 but only piercing the preform 3. This has the advantage, in particular, that no material is separated from the preform 3, which would stray within the finished container in some circumstances.

(20) After the driving in of the mandrel 9, the sizing sleeve 10 is also pushed, by means of the feed device 12, into the opening 6 thus produced, wherein the sizing sleeve 10 has a larger diameter than the mandrel 9 and is provided at its leading end with an encircling outward-beveled rim 15. The sizing sleeve 10 displaces the material of the preform 3 in order to produce the opening 6 with a defined outside diameter (see FIG. 3).

(21) After the sizing of the opening 6 in the preform 3, the mandrel 9 is pulled back relative to the sizing sleeve 10, and the sizing sleeve 10 remains in the opening 6 of the preform 3 (see FIG. 4).

(22) The connection element 5 is then inserted by means of a connection stub 16 into the opening 6 of the preform 3 by means of a component holder (not shown), which is arranged on the molding recess side, i.e. on the side of the preform which faces away from the wall 2 of the molding tool 1 (see FIG. 5).

(23) The connection element 5 is designed as a 2-component part in the form of a nipple, which has a firtree profile 17 on the molding recess side and which, on the opposite side, comprises a connection stub 16 projecting from the subsequent container. In the figures, the connection stub 16 is formed as a smooth stub but it could likewise have a firtree profile. The connection stub 16 and the firtree profile 17 of the connection element 8 are designed as a tubular polyamide main body which allows a through flow. The connection element 5 furthermore comprises an encircling collar 18, which is provided with a welding flange 19. The welding flange 19 is preferably composed of an HDPE which is compatible with the HDPE of the preform 13 so as to allow welding.

(24) On the molding recess side, a vent line of a vent valve arrangement is mounted on the firtree profile 17 of the connection element 5. With the vent line pre-fitted, the connection element 5 is pushed into the opening 6 of the preform 3 until the welding flange 19 comes into contact with the preform 3 on the molding recess side. In this process, the connection element 5 is welded to the preform, which is still at melting temperature, in the region of the welding flange 19.

(25) While the sizing sleeve 10 is still in the opening 6 of the preform 3 (after the insertion of the connection element 5 in FIG. 5 and before the retraction of the perforation device 8 in FIG. 6), the central mold is removed from between the outer molds, the outer molds are closed against one another in order to finish the blow-molding of the container to be produced by applying a blowing pressure of about 4 to 7 bar. For this purpose, one or more blowing mandrels are driven into the preform 3. These blowing mandrels are not shown.

(26) The blowing mandrels are supplied with a gaseous pressure medium, e.g. with air, in a conventional manner. The mandrel 9, which is designed as a hollow needle through which media can flow, communicates in such a way with a pressure medium line for applying blowing pressure that some of the pressure medium is introduced via the mandrel 9 into the connection element 5 and into the venting device volumes connected thereto, thereby establishing a pressure equalization with the venting device, such that the final application of blowing pressure cannot cause compression of the volumes or partial volumes of the venting device.

(27) After the final blowing, the perforation device is withdrawn completely from the container or from the preform 3 into the molding tool 1, as illustrated in FIG. 6.

REFERENCE SIGNS

(28) 1 molding tool 2 wall of the molding tool 3 preform 4 partial cavities 5 connection element 6 opening 7 aperture 8 perforation device 9 mandrel 10 sizing sleeve 11 feed device 12 feed device 13 needle tip 14 media passages 15 rim 16 connection stub 17 firtree profile 18 collar 19 welding flange