Method for producing a container from thermoplastic material and plastic container produced according to said method

Abstract

The invention relates to a method for producing a tank from thermoplastic material, comprising the following method steps: extruding or providing a hose-like parison composed of plasticized thermoplastic material, and dividing and spreading the parison into two areal extrudate webs, or extruding or providing two parisons in web form, laying-in and molding the parisons in recesses of a multi-part blow-molding tool using differential pressure, wherein the recesses of the blow-molding tool delimit a mold cavity, punching out, or cutting out in a circular shape, at least one opening in at least one shell-like intermediate product, wherein the opening is produced by way of a punching or cutting tool which penetrates through a wall of one of the shell-like intermediate products, wherein in a second separate method step, a first attachment element of a line connection or of a line arrangement is welded, at the mold cavity side, to the wall of the shell-like intermediate product, in such a way that an encircling weld collar of the first attachment element sealingly surrounds the opening, joining the shell-like intermediate products to form a tank, and removing the tank from the blow-molding tool, and connecting a second attachment element, which is complementary to the first attachment element in the context of a plug-type connection, to the first attachment element, wherein the plug-type connection is produced within the contour of the tank as defined by the tank wall.

Claims

1. A method for producing a tank from thermoplastic material, comprising: forming a plurality of parisons of thermoplastic material, laying-in and molding the parisons in recesses of a multi-part blow-molding tool using differential pressure to form a corresponding plurality of shell-like intermediate products, wherein the recesses of the blow-molding tool delimit a mold cavity, punching out or cutting out at least one opening in at least one of the shell-like intermediate products, wherein the opening is produced by a mold-cavity-side punching or cutting tool which penetrates through a wall of the shell-like intermediate product into a tool-side die, wherein the die is closed by a tool-side piston during the laying-in and molding of the parisons, and the die is opened by the piston for producing the opening after the laying-in and molding of the parisons, welding a first attachment element of a line connection or a line arrangement, at the mold cavity side, to the wall of the shell-like intermediate product, such that an encircling weld collar of the first attachment element sealingly surrounds the opening, wherein the first attachment element does not pierce or extend through the wall of the intermediate product, joining the shell-like intermediate products to form a tank, and removing the tank from the blow-molding tool, and connecting a second attachment element, which is complementary to the first attachment element for a plug-type connection, to the first attachment element.

2. The method as claimed in claim 1, wherein the first attachment element has a socket end and the second attachment element has a plug end, wherein the plug end is inserted into the socket end.

3. The method as claimed in claim 1, wherein the first attachment element has a pot-shaped housing which is open at an end side and which has at least one attachment pin which is arranged in said housing and which is accessible from the open end side, wherein the housing is, by the open end side, welded at the mold cavity side to the wall of the shell-like intermediate product, in a manner encircling the opening.

4. The method as claimed in claim 1, wherein the opening is formed into a region of the wall of the intermediate product, said region extending at an angle of greater than 0 to a plane of the shell-like intermediate product, which plane defines the greatest extent of the shell-like intermediate product, such that the plug-type connection can be produced parallel to a top or a bottom of the tank.

5. The method as claimed in claim 1, wherein the blow-molding tool comprises two blow mold halves which each have at least one of the recesses, at least one sealing frame and/or one joining frame which is/are movable transversely with respect to an opening and closing movement of the blow mold halves and which is/are locatable between the blow mold halves.

6. The method as claimed in claim 5, wherein the opening is produced by way of the punching or cutting tool arranged in the sealing frame.

7. The fuel tank as claimed in claim 4, wherein the angle of greater than 0 is approximately 90.

8. The method as claimed in claim 5, further comprising arranging the blow mold halves in an open position, positioning the plurality of parisons of thermoplastic material and the sealing frame between the open blow mold halves, and thereafter closing the blow mold halves against the sealing frame prior to the laying-in and molding of the parisons in the recesses of the blow-molding tool using differential pressure.

9. The method as claimed in claim 8, wherein the punching out or cutting out of at least one opening is performed while the blow mold halves are closed against the sealing frame, and with the punching or cutting tool provided with the sealing frame.

10. The method as claimed in claim 9, further comprising opening the blow mold halves after the punching out or cutting out of the at least one opening, and thereafter removing the sealing frame from between the open blow mold halves.

11. The method as claimed in claim 10, further comprising positioning the joining frame between the open blow mold halves after the removing of the sealing frame from between the open blow mold halves, and thereafter closing the blow mold halves against the joining frame.

12. The method as claimed in claim 11, wherein the welding of the first attachment element of the line connection or the line arrangement is performed while the blow mold halves are closed against the joining frame.

13. The method as claimed in claim 12, further comprising opening the blow mold halves after the welding of the first attachment element of the line connection or the line arrangement, and thereafter removing the joining frame from between the open mold halves.

14. The method as claimed in claim 13, further comprising closing the blow mold halves towards each other to facilitate the joining of the shell-like intermediate products to form a tank.

15. The method as claimed in claim 1, wherein the forming of the plurality of parisons further comprises forming each of the plurality of parisons by extruding each of the plurality of parisons.

16. The method as claimed in claim 1, wherein the forming of the plurality of parisons further comprises forming each of the plurality of parisons in a web form.

17. The method as claimed in claim 1, wherein the forming of the plurality of parisons further comprises forming each of the plurality of parisons in a sheet form.

18. The method as claimed in claim 1, wherein the forming of the plurality of parisons further comprises forming the plurality of parisons from an extrudate.

19. The method as claimed in claim 18, wherein the forming of the plurality of parisons from the extrudate further comprises forming the plurality of parisons from the extrudate by dividing the extrudate into the plurality of parisons.

20. The method as claimed in claim 1, wherein the at least one opening has a circular shape.

Description

(1) The invention will be discussed below on the basis of an exemplary embodiment illustrated in the drawings, in which:

(2) FIGS. 1A to 1C are a schematic illustration of the manufacturing cycle for the production of the tank according to the invention,

(3) FIGS. 2a and 2b each show a perspective view of a first variant of the tank according to the invention,

(4) FIG. 3 shows a perspective view of the first attachment element according to the first exemplary embodiment of the tank according to the invention,

(5) FIG. 4 shows an enlarged partial view of the tank illustrated in FIG. 2a, partially in section, from which the position of the first attachment element in the tank can be seen,

(6) FIG. 5 shows a perspective view of a punching unit arranged on the mold cavity, which punching unit is used in the method according to the invention, directly before the punching of the opening,

(7) FIG. 6 shows a view corresponding to FIG. 5, during the punching of the opening,

(8) FIG. 7 shows a perspective view of the punching device after the punching of the opening, wherein, for the sake of simplicity, the blow-molding tool is not illustrated,

(9) FIG. 8 shows a perspective view of a welding device which is provided on the mold cavity and which serves for the joining and welding of the first attachment element,

(10) FIG. 9 shows a side view of the welding device during the welding of the first attachment element,

(11) FIG. 10 shows an internal view of the tank with the fully installed attachment element,

(12) FIG. 11 shows a perspective view of a tank according to a second variant of the invention,

(13) FIG. 12 shows a perspective view of a first attachment element according to a second variant of the invention, and

(14) FIG. 13 shows a sectional view through the attachment element illustrated in FIG. 12.

(15) Reference is made firstly to FIGS. 1a to 1c, which show a schematic view of a blow-molding tool 1 and of an extrusion head 2 for carrying out the method according to the invention. The blow-molding tool comprises two blow mold halves 3 which are fastened to mold clamping plates and which are movable away from one another and toward one another in an opening and closing movement. Even though the expression blow mold halves has been used here, it falls within the invention for the individual blow mold halves 3, which each have a recess 5, to be of multi-part form. Each of the blow mold halves 3 need not necessarily form half of the blow-molding tool. Also, the parting planes of the blow mold halves need not necessarily form a geometrically halved division of the blow-molding tool.

(16) In the exemplary embodiment illustrated, the mold clamping plates 4 are part of a machine base frame which is not shown in any more detail.

(17) The extrusion head 2 is illustrated in highly simplified form in the drawings, and comprises two wide-slot nozzles, from which in each case sheet-like or web-like parisons 7 which extend rectilinearly into the plane of the drawing are extruded in continuous fashion in a hanging manner, that is to say in the direction of gravitational force. The parisons 7 are preferably composed in each case of an altogether six-layer extrudate comprising a carbon-black-pigmented HPDE layer, a recyclate (regrind) layer based on HDPE, an EVOH barrier layer surrounded on both sides by an adhesion promoter, and a further, non-pigmented HDPE layer. The adhesion promoter layers may for example be based on LDPE.

(18) The blow-molding tool 1 according to the invention comprises not only the machine base frame (not illustrated) but also a machine frame 8 which is movable relative to the machine base frame and transversely with respect to the opening and closing movement of the mold clamping plates 4. A sealing frame 9 and a joining frame 10 are arranged on the machine frame 8 so as to be spaced apart from one another. The sealing frame is equipped with encircling sealing surfaces 11 which define an encircling contour which approximately follows the delimitation of the recesses 5 of the blow mold halves 3.

(19) The joining frame 10 is likewise in the form of a central frame, within which there are arranged individual component receptacles 12 in the form of pneumatic piston-cylinder arrangements with fastening means.

(20) It is basically possible for the structural depth of the sealing frame 9 and that of the joining frame 10 to be approximately equal. The sealing frame 9 may, in the simplest case, be in the form of a simple plate, possibly with means for the pressurization of the recesses 5 with gas. In the variant of the blow-molding tool 1 illustrated in the present exemplary embodiment, the sealing frame 9 accommodates a punching unit 14. A punching unit of said type may additionally or alternatively also be arranged in the joining frame 10.

(21) In the case of the illustrated embodiment, the machine frame 8 with the sealing frame 9 and joining frame 10 arranged thereon is movable relative to the extrusion head 2. Provision may alternatively be made for the sealing frame 9 and the joining frame 10 to be arranged on the machine frame 8 so as to be movable relative to one another. It is likewise possible in the context of the invention for the machine frame 8 to be arranged on the machine frame so as to be movable relative to the extrusion head 2, and for the joining frame 10 and the sealing frame 9 to be arranged on the machine frame so as to be movable relative to one another. Finally, provision may also be made for the machine frame 8 to be arranged positionally fixed relative to the extrusion head 2, and for the blow mold halves 3 to be moved relative to the sealing and joining frames which are arranged positionally fixedly on the machine frame 8.

(22) FIGS. 1A and 1B show the blow-molding tool 1 at the end and at the start of each working cycle. A working cycle of said type comprises initially the extrusion of the parisons continuously to a length which corresponds approximately to the height of the blow mold halves 3, as illustrated in FIG. 1c. The parisons 7 are extruded between the open blow mold halves, specifically in each case between a blow mold half 3 and the sealing frame 9 arranged between the blow mold halves 3. In a further method step which is not illustrated, the blow mold halves close against the sealing frame 9 arranged between them, the parisons 7 are then cut off at the extrusion head 2, specifically with the aid of further tools for cutting the continuously extruded parison. For the sake of simplicity, said tools are not illustrated. Then, the parisons 7 are laid in the recesses 5 of the blow mold halves 3, and molded, using vacuum and/or positive pressure.

(23) In a further method step, by way of the punching unit 14 arranged in the sealing frame 9, an opening 18 is punched in the parison 7 that has been molded to form a shell-like intermediate product. Here, by way of the punching unit 14, the opening 18 is punched out of the parison 7, which has been molded in the respective recess 5 to form a shell-like intermediate product, by way of a punching sleeve 19, wherein a punching sleeve 19 is pushed into a correspondingly shaped die 20 within the recess 5 of the blow-molding tool 1. In the die 20 there is arranged a piston 21 which is preferably subjected to a pneumatic pressure preload and which closes the die 20 and which is displaced by the punching sleeve 19. The piston 21 serves for holding the die 20 closed during the molding of the parisons 7 to form shell-like intermediate products while the blow mold halves are closed against the sealing frame 9, in order to thereby ensure that the tool-side surface of the shell-like intermediate product is not deformed into the die 20.

(24) The blow mold halves 3 are opened, then the joining frame 10 is placed between the open blow mold halves 3. This may be realized either by virtue of the machine base frame (not shown) being moved relative to the positionally fixedly arranged extrusion head 2 or by virtue of the machine frame 8 being moved relative to the blow-molding tool 1, which is arranged positionally fixedly under the extrusion head 2.

(25) In the joining frame 10 there are provided component receptacles 12 with insert components 13 which are intended to be arranged in the interior of the tank to be manufactured.

(26) In this method step, in the open recesses 5 of the blow-molding tool, the shell-like intermediate products are molded whilst still in the hot plastic or warm plastic state.

(27) In the following method step, the insert components 13 are, utilizing the plasticization heat that is still present, joined to the shell-like intermediate products which are still in the warm plastic state, wherein the joining may be performed either cohesively and/or in positively locking fashion. In this context, cohesive joining encompasses the welding of the insert components 13 to the mold-cavity-side wall of the respective shell-like intermediate product.

(28) In the context of the present application, a mold cavity is to be understood to mean the space enclosed by the recesses 5 of the blow mold halves 3. In the context of the present application, the expression mold cavity side refers to that side of the parison or of the shell-like intermediate product which is averted from the respective recess.

(29) For the purposes of joining the insert components in the context of welding these to the wall, which is still in the warm plastic or hot plastic state, of the shell-like intermediate product, the joining frame 10 comprises at least one welding unit 15. The welding unit 15 may have infrared heat radiators or welding mirrors or heating plates of some other design. The insert component 13 to be joined is softened and or heated at the welding surface provided for this purpose, for example by way of IR radiators or welding mirrors, and is then pressed, for example actively by way of the component receptacles 12, against the shell-like intermediate product.

(30) Above, the possibility of providing the component receptacles 12 in the form of pneumatic piston-cylinder arrangements was mentioned; in this case, the insert components 13 are actively joined in the sense that they are moved by way of the component receptacles 12 in the direction of the shell-like intermediate product.

(31) It is alternatively possible and expedient for the component receptacles 12 to be in the form of simple plug receptacles which merely hold and fix the respective insert components 13, with the actual joining process then being realized by way of the closure of the blow mold halves 3 against the joining frame 10 (static joining).

(32) The exemplary embodiment on which the application is based is described with reference to a fuel tank for motor vehicles, in which, for example, the ventilation valves are installed as insert components. The ventilation valves are connected to one another by way of a ventilation line 16; this arrangement is also referred to generally as a so-called spider of lines. To be able to attach the ventilation line 16 to the outside of the fuel tank 17 to be produced, it is necessary for a line leadthrough or opening 18 to be provided in the wall of the fuel tank 17 as the article/tank to be manufactured. As mentioned above, said opening 18 is produced immediately after the molding of the parisons 7 to form shell-like intermediate products, specifically by way of the punching unit 14 arranged in the sealing frame 9. The punching unit 14 is illustrated in FIGS. 5 to 7.

(33) After the closure of the blow-molding tool or of the blow mold halves against the joining frame 10, the welding of an attachment end of the ventilation line 16 to the shell-like intermediate product is realized by way of the welding unit 15, illustrated in FIG. 8, in the region of the opening 18, such that the attachment end of the ventilation line communicates with the opening 18.

(34) At the same time, the welding of the other insert components, for example in the form of the ventilation valves which are connected via the ventilation line 16, is performed. For the purposes of attachment to the parison 7 in the region of the opening 18, the ventilation line 16 is connected to a first attachment element in the form of a welding sleeve 22. The welding sleeve 22 on the ventilation line 16 is illustrated in FIGS. 3 and 10.

(35) As can be seen in particular from FIG. 8, the ventilation line is inserted with its open end and the welding sleeve 22 into the welding unit and, there, is initially placed by way of a welding collar 23 against a heating element 24. When the welding collar, which for example has a material compatible with the parison 7 in terms of weldability, has softened to an adequate extent, the welding sleeve 22 is pressed against the parison 7 or against the shell-like intermediate product that has already previously been molded at this stage of the process, such that the welding sleeve 22 is welded, at the edge of the opening 18, to the parison 7.

(36) Even though the description above refers firstly to the punching of the opening 18 and then the welding, it is expedient and possible in the context of the invention for the insertion of the ventilation line 16 into an article receptacle of the welding unit, and the softening of the welding collar 23, to be performed outside the blow-molding tool immediately before the joining frame 10 is placed between the blow mold halves 3.

(37) FIG. 9 illustrates the process of the joining and welding of the welding sleeve 22 to the wall of the fuel tank 17 within the blow-molding tool 1, wherein the welding sleeve 22 has already been pre-mounted on the ventilation line 16.

(38) FIG. 10 illustrates the completed attachment of the welding sleeve 22 to the wall of the fuel tank 17.

(39) After the joining of the insert components 13 and in particular the attachment of the ventilation line 16 to the opening 18, the blow mold halves 3 are opened, the joining frame 10 is moved out of the closing path of the blow mold halves 3, and the latter are closed against one another, wherein the shell-like intermediate products are joined to form the substantially finished fuel tank 13. The joining is performed in a known manner by way of welding of the shell-like intermediate products or of the parisons 7 at the edges.

(40) Then, the blow mold halves 3 are opened again, and the article in the form of a finished fuel tank 17 is removed.

(41) After said fuel tank has possibly been trimmed, a second attachment element 25 of an external line section 26 is inserted through the outwardly exposed opening 18.

(42) As can be seen from FIGS. 2a and 2b, which show the fuel tank 17 in perspective external views, the opening 18 on the finished fuel tank 17 is arranged so as to extend approximately perpendicular to a top 27 of the fuel tank 17, such that the external line section 26 can be laid parallel to the top 27 without a line bend and substantially without an angle piece.

(43) The plug-type connection can, owing to the configuration described above, be produced within the volume of the fuel tank 17. An alternative embodiment of the fuel tank 17 and of the second attachment element is illustrated in FIGS. 11 to 13. FIG. 12 shows the first attachment element as a plug connector 28 or as a plug end. Said plug connector 28 comprises a cup-like or bowl-like or pot-shaped housing 29, which has an end-side opening 30 and a base 31. Integrally formed on the housing 29 is an attachment pin 32, in the form of a double nipple, which extends through said housing. The attachment pin 32 comprises a plug end which is surrounded by the housing 29, and a plug end which is situated in the interior of the tank in the installed position and onto which the ventilation line 16 is plugged in the interior of the tank. Finally, the opening 30 of the housing 29 is surrounded by a welding collar 23 which, in the above-described manner, is welded to the parison 7 or to the shell-like intermediate product, so as to border or enclose the opening 18, during the production of the fuel tank 17, wherein the housing 29 is situated entirely in the interior of the tank, such that the free plug end of the attachment pin 32 is, as can be seen in FIG. 11, arranged in recessed fashion within the tank contour, such that, in this variant of the fuel tank 17, too, a second attachment element can be connected from the outside to the attachment pin 32 such that the plug-type connection extends within the contour of the fuel tank 17 as defined by the tank wall 33. In this case, the external line section 26 may be plugged either by way of a socket end or else directly onto the attachment pin 32, wherein the attachment direction is approximately normal to the extent of the top 27.

(44) In the exemplary embodiment shown in FIG. 11, the welding collar 23 of the housing 29 extends approximately parallel to the top 27 of the fuel tank 17, but the invention is to be understood as also including a situation in which installation at an angle to the direction of extent of the top 27 is possible, for example perpendicular thereto, such that the external line section 26 can be plugged in or connected approximately parallel to the direction of extent of the top 27 of the fuel tank 17.

(45) In the context of the invention, a plug-type connection is also to be understood to mean a plug-type connection which is or can be produced by way of a detent action.

LIST OF REFERENCE NUMERALS

(46) 1 Blow-molding tool 2 Extrusion head 3 Blow mold halves 4 Mold clamping plate 5 Recesses 6 Wide-slot nozzles 7 Parisons 8 Machine frame 9 Sealing frame 10 Joining frame 11 Sealing surfaces 12 Component receptacles 13 Insert components 14 Punching unit 15 Welding unit 16 Ventilation line 17 Fuel tank 18 Opening 19 Punching sleeve 20 Die 21 Piston 22 Welding sleeve 23 Welding collar 24 Heating element 25 Second attachment element 26 External line section 27 Top 28 Plug connector 29 Housing 30 Opening 31 Base 32 Attachment pin 33 Tank wall