DE102011002313A9 - Extrusion tool for the production of flat preforms from a plastic melt - Google Patents

Abstract

The invention relates to an extrusion tool for producing flat preforms which are formed from a plastic melt and are fed to a blow molding plant in the thermoplastic state. The extrusion tool comprises a die body (1) which has at least one melt channel (2) with an inlet area (3) and a subsequent die zone (4) with a die gap that narrows towards the exit to form a flat preform. The die gap is limited in the die zone by die elements (6, 7). The gap width of the die gap can be changed by program-controlled infeed movements of at least one die element (7) during the extrusion of a preform. At least one end of the nozzle elements (6, 7) has a head piece (8) which fills the nozzle gap between the nozzle elements (6, 7) and can be adjusted axially during the extrusion of a preform along the nozzle elements for the purpose of adjusting the extrusion width of the nozzle gap is.

Description

The invention relates to an extrusion tool for producing flat preforms which are formed from a plastic melt and are fed to a blow molding plant in the thermoplastic state.

The extrusion tool comprises a nozzle body which has at least one melt channel with an inlet area and a nozzle zone connected thereto with a nozzle gap that narrows towards the outlet for the formation of a flat preform. The die gap in the die zone is limited by die elements. Its gap width can be changed by program-controlled infeed movements of at least one of the nozzle elements during the extrusion of a preform.

An extrusion tool with the features described is, for example, from DE 20 2007 008 132 U1 known. Using one or more of these extrusion tools, flat preforms are produced from plasticized plastic, which are fed to a blow molding plant and, while still in the thermoplastic state, are formed together into a hollow body within a multi-part tool forming a mold cavity. In order for the blow-molded hollow bodies to have a constant wall thickness or a desired wall-thickness distribution, it is necessary to produce preforms which have a changing wall-thickness profile at least in the direction of extrusion. In order to produce a desired wall thickness profile, the gap width of the die gap is changed during the extrusion of each preform by program-controlled infeed movements of at least one of the die elements.

The preforms emerging from the extrusion die sag due to gravity. A middle portion of the preform sheets is advanced. A constriction occurs in the upper area of the preforms, ie the width of the preforms is reduced. In addition, there are rheological effects that affect the contour of the emerging preform. In order to ensure that the preforms cover the cavity of the blow mold and that the surfaces of the preforms to be joined are welded all the way around during the blow molding process, the preforms must be extruded with a correspondingly greater width. This creates unnecessary waste in the blow molding process.

Out of WO 2009/019301 discloses an extrusion die for producing flat preforms, with which it is possible to change the extrusion width of the preforms during extrusion. By changing the extrusion width, the aforementioned effects can be compensated and flat preforms can be manufactured in such a way that they cover the cavity of the blow mold with sufficient contour accuracy. At the nozzle exit, the melt channel of the extrusion tool has flow guide elements or screens on both longitudinal sides of the channel, which can be pivoted about an axis for the purpose of adjusting the extrusion width. However, the structural design does not allow changing the gap width of the nozzle gap in the working area of the pivotable flow guide elements. An optimal thickness distribution of the preforms up to their edge area is therefore not possible with the known extrusion tool.

The DE 10 2007 025 296 A1 describes an extrusion tool for the production of flat preforms, the die gap of which is delimited at least on one side by a number of independently adjustable segments. By adjusting the segments, the gap width of the nozzle gap can be changed locally and, if necessary, also closed. The segments enable the gap width and/or the extrusion width of the die gap to be adjusted in steps or steps. A continuous change of the extrusion width is not possible. The strip surfaces forming segments generate flow vortices in the melt flow, the z. B. in the production of a multi-layer preform, an impermissible mixing of the layers can result.

The DE 10 2005 031 698 A1 relates to an extrusion die whose die gap is delimited by lip elements in the die zone. In order to change the extrusion width of a material web emerging from the extrusion nozzle, adjusting slides are provided in the edge areas of the lip elements, which can be actuated individually and close the nozzle gap in edge areas by an infeed movement. This extrusion tool also enables the extrusion width of the die gap to be adjusted in steps or steps and has the disadvantages described above.

The invention is based on the object of specifying an extrusion die for the production of flat preforms, with which it is possible to regulate the width of the preforms during extrusion in such a way that the influence of sagging is compensated and at the same time an optimal wall thickness distribution can be achieved.

Based on an extrusion tool with the features described above, the object is achieved in that at least one end of the nozzle elements Head piece is provided, which fills the die gap between the die elements and is adjustable during the extrusion of a preform along the die elements for the purpose of adjusting the extrusion width of the die gap in the axial direction. The head piece is adjusted in the longitudinal direction of the nozzle elements. The nozzle gap in the nozzle zone forms a flow channel that is closed in the circumferential direction, which tapers towards the nozzle outlet gap and is delimited by the nozzle elements and the head piece arranged at the end of the nozzle elements. The head piece is designed in such a way that the adjustment of the width of the nozzle gap is not impeded by a corresponding infeed movement of at least one nozzle element. The head piece seals the edge of the flow channel and can be steplessly adjusted transversely to the direction of flow. Program-controlled actuators can be used for the adjustment. Irrespective of this, the width of the die gap can be changed by moving the die elements relative to one another over the entire width of the preform during extrusion. Strips can also be used as nozzle elements, which are deformable at least in a section between the head pieces that is not covered by the working area of the head pieces. The deformation of the nozzle elements can be set statically by adjusting means or changed dynamically by program-controlled actuators even during the extrusion of the preforms. It is essential for the device according to the invention that both the extrusion width of the die gap in the die zone and the gap width of the die gap can be continuously changed during extrusion. The device designed according to the invention avoids dead zones in the flow channel. Between the inlet area of the melt channel and the nozzle zone adjoining it, a step-free and essentially continuous course of the wall surface delimiting the flow channel is ensured over the entire working area of the head element. The geometry of the melt channel can be adjusted accordingly in the inlet area, e.g. B. by means of slides that can be inserted from the side and have a wedge-shaped or profiled contour to limit the melt channel. Adjustable, in particular pivotable, flow guide elements can also be used to adapt the melt channel geometry.

An advantageous embodiment of the extrusion tool provides that the die gap is delimited by a first die element that is fixed in the die body and a second die element that is pivotably mounted about a longitudinal axis, and that the head piece is slidably guided on the stationary first die element or in the die body. The head piece can have a rotary feedthrough for the nozzle element. The rotary leadthrough expediently consists of a disk which is rotatably mounted on the head piece and has a recess for receiving the second nozzle element.

The recess of the rotary feedthrough preferably encloses the second nozzle element in a U-shape, with the nozzle element bearing sealingly on a peripheral section that protrudes or is essentially flush with the rotary feedthrough on a sealing strip. The sealing surfaces on the sealing strip and the corresponding peripheral section of the nozzle element are curved in the shape of a circular arc, so that a sealing effect is always ensured regardless of the angle of rotation.

It is not mandatory that the headpiece encloses the rotatable sealing element and has a rotary feedthrough for the sealing element. A likewise advantageous constructional embodiment provides that the head piece only fills the nozzle gap between the nozzle elements and has a contact surface that lies against the circumference of the rotatable nozzle element. The rotatably mounted nozzle element can have a slotted sleeve that contains a receiving slot in the longitudinal direction for a nozzle bar that delimits the nozzle gap. To seal the rotatably mounted nozzle element, a sealing strip is provided, against which the sleeve rests directly or with the interposition of a further sealing body, which is inserted, for example, in a window on the casing side of the sleeve.

In both of the above-described embodiments, the first nozzle element, which is arranged in a stationary manner, is in sealing contact with a sealing strip. The headpiece expediently has a recess through which the nozzle element is in contact with the sealing strip.

In an embodiment of the extrusion die described below, the die gap is also delimited by a first die element that is fixedly arranged in the die body and a second die element that is pivotably mounted about a longitudinal axis. The second nozzle element has a round profile that can be rotated about its longitudinal axis and a leg that protrudes on the circumference and forms a wall surface of the melt channel in the nozzle zone. A head piece is provided for the lateral delimitation of the flow channel, which can be adjusted in the axial direction during the extrusion of a preform along the nozzle elements for the purpose of adjusting the extrusion width. With a pivoting movement of the round profile, gaps open up on the head piece below and above the leg, which are sealed Need to become. Therefore, at least one end of the round profile, a lower sealing element is guided displaceably along the round profile, which delimits the melt channel at the end and seals the flow area below the leg. Furthermore, according to a preferred embodiment of the invention, a movable disc element is arranged on the head piece, which can be pivoted together with a rotation of the nozzle element and seals a gap between the head piece and the leg. The lower sealing element and the disk element are connected to a transmission element which is axially slidably connected to and rotatable with the second nozzle element, the transmission element and the disk element being axially fixedly connected to the slidable head piece. The transmission element preferably has a guide strip, which is slidably arranged in a guide recess of the round profile. In the embodiment described, the disc element is moved synchronously with a rotary movement of the round profile on the same axis of rotation. The coupling of the movement of the disk element to the movement of the rotatable nozzle element allows the flow channel to be almost completely sealed over the entire pivoting range.

According to a preferred embodiment of the invention, headers are provided at both ends of the nozzle members. The nozzle elements are expediently supported on surfaces of the nozzle body at least in a section between the head pieces that defines an unchangeable minimum extrusion width of the nozzle gap.

If the extrusion width of the die gap in the die zone is reduced, the flow channel wall must also be adjusted in the inlet area so that a smooth transition from the inlet area to the die zone is guaranteed and vortices in the melt flow are avoided. To adapt the melt channel geometry, the melt channel can have a flow guide element for lateral flow channel delimitation on at least one longitudinal side of the channel in the inlet area, which is articulated to the head piece and aligns itself according to the position of the head piece, which can be adjusted to change the extrusion width of the die gap. The flow guide element is arranged on the flow inlet side of the inlet area so that it can pivot about a stationary bearing point. The articulated mounting is expediently designed there in such a way that the flow guide element can perform both a pivoting movement and a linear compensating movement.

The head piece arranged at at least one end of the nozzle elements can also consist of a slide plate, which has a cross section adapted to the nozzle gap in the nozzle zone and is arranged to be displaceable transversely to the flow direction for the purpose of adjusting the extrusion width and has a sliding surface for a second nozzle element, which is arranged to be displaceable in the nozzle body in order to change the width of the nozzle gap and executes program-controlled positioning movements during the extrusion of a preform. The second nozzle element is vertically displaceable or can perform adjusting movements directed obliquely downwards.

A further advantageous embodiment of the invention provides that the slide plate is designed in two parts and has a slide base body and a slide end piece that can be adjusted relative to this. The slide body is linearly movable transversely to the direction of flow of the melt on the first nozzle element or in the nozzle body in the direction of the extrusion width and has a sliding surface lying against the second nozzle element. The slider end piece is guided on the adjustable second nozzle element so that it can move linearly transversely to the direction of flow of the melt in the direction of the extrusion width and has a sliding surface that rests against the first nozzle element. The embodiment described ensures lateral sealing of the nozzle gap over the entire adjustment path of the vertically adjustable second nozzle element.

The first nozzle element can consist of a stationary arranged shaped body. There is also the possibility of designing the first nozzle element with a deformable section. The deformable section can in particular consist of a flexible strip. The profile of the preform emerging from the die gap can be changed by adjusting and/or deforming the deformable section. In this way, thick and thin points can be produced in a targeted manner in zones of the flat preform.

Irrespective of whether the slide plate is designed in one piece or has a vertically adjustable slide end piece as a two-part design, the slide plate preferably has a wedge surface on the edge at its rear end, which bears against a sliding surface of the nozzle body. At least the first nozzle element, with which the slide plate is movably connected, is arranged in the nozzle body so that it can be displaced vertically and, when the slide plate is advanced along the sliding surface of the nozzle body, performs a coupled vertical offset movement together with the slide plate. Adjusting the extrusion width during extrusion results in the This design inevitably leads to a height adjustment of the slide plate, with the wedge surface formed on the rear end of the slide plate guiding the melt flow in the edge zones of the flow channel steplessly from the inlet area into the nozzle zone. The maximum infeed path of the slide plate is determined by the dimensions of the wedge surface.

According to a preferred embodiment of the extrusion tool, the second nozzle element, which performs program-controlled vertical infeed movements for the purpose of setting the nozzle gap width during the extrusion of a preform, is arranged in an adjustable manner in a receiving element which is guided in the nozzle body so that it can move vertically. During the infeed movement of the slide plate, the receiving element, together with the first nozzle element, performs a lifting movement that compensates for the vertical offset of the slide plate.

In the device according to the invention, the nozzle gap can also be delimited by a stationary first nozzle element and a second nozzle element, with the second nozzle element being guided in a horizontally adjustable manner in a stationary arranged receiving body. In this embodiment, the head piece expediently consists of a two-part slide which has a slide main body guided horizontally on the first nozzle element or in the nozzle body and a slide end piece guided horizontally on the second nozzle element. The slider end piece rests against a sliding surface of the slider body and can be moved relative to the slider body with an adjusting movement of the second nozzle element. The nozzle gap adjustment can be achieved by horizontal displacement of the second nozzle element, which can extend over the entire width of the nozzle body. The movable nozzle element is guided in the receiving body and reliably supported. The flow channel is laterally delimited by means of the two-part slide described. Since the nozzle elements are not part of an adjustment movement, additional sealing strips are not necessary.

The invention also relates to the use of the extrusion tools described above to produce a flat preform formed from a plastic melt, which is fed to a blow molding plant in the thermoplastic state and formed into a three-dimensionally shaped body in a blow mold. It is essential for the method according to the invention that a wall thickness profile of the preform that changes in the longitudinal direction of the preform is generated by program-controlled adjusting movements of a movable nozzle element of the extrusion die that delimits the die gap, and that program-controlled adjusting movements of at least one head element arranged at the end of the die elements, which fills the die gap and during which Extrusion of the parison is axially adjusted along the nozzle elements, the width of the parison is changed. The width of the cyclically shaped preforms is controlled during their extrusion in such a way that the influence of sagging of the preform is compensated and at the same time the wall thickness distribution is sufficiently influenced.

If necessary, two or more of the devices described can also be operated in parallel, with the preforms produced by means of the devices being fed to a blow mold and a hollow body being manufactured from these preforms. Both the web width of the preforms and their wall thickness profile can be individually controlled and optimized by the devices.

• 1 ein Extrusionswerkzeug mit Einrichtungen zur Verstellung der Spaltbreite des Düsenspaltes sowie der Extrusionsbreite des Düsenspaltes,
• 2 eine Ansicht auf die Stirnseite des in 1 dargestellten Extrusionswerkzeuges,
• 3 eine Ansicht auf die Längsseite des in 1 dargestellten Extrusionswerkzeuges,
• 4 ein Kopfstück des in 1 dargestellten Extrusionswerkzeuges,
• 5a und 5b Einrichtungen zur Veränderung der Flusskanalgeometrie im Einlaufbereich des Extrusionswerkzeuges,
• 6 das Zusammenwirken des in 4 dargestellten Kopfstückes mit einer Einrichtung gemäß 5a oder 5b,
• 7 eine Modifikation des in 1 dargestellten Extrusionswerkzeuges,
• 8 einen Schnitt durch den in 7 dargestellten Gegenstand,
• 9 eine alternative, konstruktive Ausführungsform des Extrusionswerkzeuges,
• 10a und 10b einen Querschnitt durch das in 9 dargestellte Extrusionswerkzeug in der Schnittebene A-A in verschiedenen Funktionsstellungen,
• 11 einen Längsschnitt durch den Gegenstand der 9,
• 12 die Einzelteilzeichnung eines Schiebers aus dem in 9 dargestellten Werkzeug,
• 13a und 13b eine weitere Ausgestaltung des in 9 dargestellten Extrusionswerkzeuges in verschiedenen Funktionsstellungen,
• 13c und 13d weitere Ausgestaltungen des Extrusionswerkzeuges, jeweils in einem Schnitt durch einen Randbereich des Fließkanals, in dem ein Schieber zur Verstellung der Extrusionsbreite angeordnet ist,
• 14 eine weitere konstruktive Ausgestaltung des Extrusionswerkzeuges,
• 15 im Schnitt eine weitere alternative Ausgestaltung des Extrusionswerkzeuges, welche an das in den 7 und 8 dargestellte Funktionsprinzip ausschließt,
• 16a und 16b perspektivische Darstellungen zu dem in 15 dargestellten Extrusionswerkzeug.

The invention is explained below using exemplary embodiments. They show schematically:

• 1 an extrusion tool with devices for adjusting the gap width of the die gap and the extrusion width of the die gap,
• 2 a view of the front of the in 1 shown extrusion tool,
• 3 a view of the long side of the in 1 shown extrusion tool,
• 4 a header of the in 1 shown extrusion tool,
• 5a and 5b Devices for changing the flow channel geometry in the inlet area of the extrusion die,
• 6 the interaction of the in 4 illustrated headpiece with a device according to 5a or 5b ,
• 7 a modification of the in 1 shown extrusion tool,
• 8th a cut through the in 7 represented object,
• 9 an alternative, constructive embodiment of the extrusion tool,
• 10a and 10b a cross section through the in 9 represented extrusion tool in the cutting plane AA in different functional positions,
• 11 a longitudinal section through the subject of 9 ,
• 12 the individual drawing of a slider from the in 9 shown tool,
• 13a and 13b another embodiment of the in 9 represented extrusion tool in different functional positions,
• 13c and 13d Further configurations of the extrusion tool, each in a section through an edge area of the flow channel in which a slider for adjusting the extrusion width is arranged,
• 14 a further constructive design of the extrusion tool,
• 15 in section, another alternative embodiment of the extrusion tool, which in the 7 and 8th excludes the functional principle shown,
• 16a and 16b perspective representations of the in 15 shown extrusion tool.

The extrusion tools shown in the figures are used to produce flat preforms, which are fed to a blow molding plant in the thermoplastic state. The extrusion dies comprise a nozzle body 1, which has at least one melt channel 2 with an inlet area 3 and a subsequent nozzle zone 4 with a nozzle gap 5 that narrows toward the outlet for the formation of a flat preform. In the nozzle zone 4, the nozzle gap 5 is delimited by two nozzle elements 6,7. The gap width of the die gap 5 can be changed during the extrusion of a preform by program-controlled infeed movements of at least one of the die elements. The gap width corresponds to the short sides of the outlet cross section and determines the thickness of the parison to be extruded.

In all of the extrusion tools shown in the exemplary embodiments, a head piece 8 is provided at least at one end of the nozzle elements, which fills the nozzle gap 5 between the nozzle elements 6, 7 and during the extrusion of a preform along the nozzle elements 6, 7 for the purpose of adjusting the extrusion width of the nozzle gap 5 is axially adjustable. “Extrusion width” means the long side of the die gap 5. It determines the web width or horizontal width of the preform emerging from the die gap orthogonally to the extrusion length.

in the in 1 illustrated embodiment, the head piece 8 is slidably guided on a first nozzle element 6 fixedly arranged in the nozzle body 1 . The head piece 8 has a rotary feedthrough 9 for a second nozzle element 7, which is arranged such that it can be rotated about its longitudinal axis for the purpose of adjusting the width of the nozzle gap. The rotary feedthrough 9 consists of a disk 10 rotatably mounted on the head piece 8 and having a recess for receiving the second nozzle element 7. The recess of the rotary feedthrough encloses the second nozzle element in a U-shape. In particular from 2 shows that the nozzle element 7 is in sealing contact with a peripheral section that protrudes from the recess or is essentially flush with the rotary feedthrough on a sealing strip 11 that extends over the entire length of the nozzle element 7 . The sealing strip 11 and the corresponding peripheral section of the nozzle element 7 have sealing surfaces curved in the shape of a circular arc, so that a seal on the upper side of the melt channel is ensured regardless of the angle of rotation of the nozzle element 7 . The nozzle element 6 arranged in a stationary manner is in sealing contact with a sealing strip 12 which also extends over the entire length of the nozzle element 6 . From the presentation in 4 shows that the head piece 8 has a recess 13 through which the nozzle element 6 is in contact with the sealing strip in the working or positioning area of the head piece 8 . In the exemplary embodiment, head pieces 8 are provided at both ends of the nozzle elements. In a section between the head pieces 8, which defines an unchangeable minimum extrusion width of the die gap, the rotatably mounted die element 7 is supported on a surface 14 of the die body. A corresponding support is expediently also provided below the stationary sealing element 6 .

If the extrusion width of the die gap 5 is changed by adjusting the head pieces 8, the geometry of the melt channel 2 in the inlet area 3 must also be adjusted. The channel geometry in the inlet area 3 is adjusted in such a way that the wall of the melt channel 2 adjoins the nozzle zone 4 without a step, regardless of the position of the head piece 8 . A device for adjusting the channel geometry in the inlet area is in 3 shown. To explain the function and arrangement of this device is also on the 5a , 5b and 6 referenced. The illustrations show that the melt channel 2 in the inlet area 3 has a flow guide element 15 on at least one longitudinal side of the channel for lateral flow channel delimitation, which is articulated to the head piece 8 and is aligned according to the position of the head piece 8, which can be adjusted to change the extrusion width of the die gap . The flow guide element 15 is arranged on the flow inlet side of the inlet area 3 around a stationary bearing point 16 so that it can swivel, the articulated Storage 16 as shown in the 5a and 5b is designed on the inlet side so that the flow guide element 15 can perform both a pivoting movement and a linear compensating movement. In the embodiment of 5a the linear compensatory movement is achieved through a slot 17. According to the illustration in 5b the flow guide element 15 is designed as a telescopic element.

The 7 and 8th show a modification of the extrusion tool described above. In this embodiment too, the nozzle gap 5 is delimited by a first nozzle element 6 which is fixedly arranged in the nozzle body and a second nozzle element 7 which is mounted pivotably about a longitudinal axis. The head piece 8 'is slidably guided on the stationary arranged first nozzle element 6 and fills the nozzle gap 5 between the nozzle elements 6, 7 from. The head piece 8 ′ has a contact surface 18 which rests on the circumference of the rotatable nozzle element 7 . The illustration also shows that the rotatably mounted nozzle element 7 has a slotted sleeve 19 which contains a receiving slot for a nozzle bar 20 delimiting the nozzle gap 5 in the longitudinal direction. To seal the rotatably mounted nozzle element 7, a sealing strip 11' is provided, against which the sleeve 19 bears directly or with the interposition of a further sealing body which can be inserted into a window on the casing side of the sleeve.

The 9 shows an alternative structural embodiment of the extrusion tool. The head piece consists of a slide plate 21, which has a cross section adapted to the die gap in die zone 4 and is arranged to be displaceable transversely to the direction of flow for the purpose of adjusting the extrusion width and has a sliding surface 23 for a second die element 24, which is used to change the die gap width in the Nozzle body 1 is arranged adjustable and performs program-controlled adjustment movements during the extrusion of a preform. When the second nozzle element has its in 10a occupies the position shown, the die gap is closed or has a minimum gap width. By a lifting movement in the in 10b shown position, the nozzle gap 5 is opened and the gap width increased. From the sectional views in the 10a and 10b shows that the flow channel in the nozzle zone 4 is essentially sealed laterally. A lateral gap can only be seen at the nozzle exit when the nozzle gap is opened. However, since the melt pressure at the nozzle outlet is low, only a minimal cross-flow can be expected. This transverse flow does not result in any negative influences and therefore has no negative effects on the extrusion of the preforms.

At the in the 10a and 10b illustrated embodiment of the extrusion tool, the second nozzle element 24 is vertically adjustable. According to another, in 13c In the embodiment variant shown, the second nozzle element 24 is arranged such that it can be displaced at an acute angle α to the melt channel and executes actuating movements directed obliquely downwards.

At the in 13c illustrated embodiment, the first nozzle element 22 consists of a stationary arranged molded body. According to a 13d In the embodiment variant shown, the first nozzle element 22 can have a deformable section 46, through the adjustment or deformation of which thick points and thin points can be produced in zones of the flat preform. The deformable section has a locally adjustable or deformable flexible strip 47 in the transverse direction to the flow channel, which is movably held in a receptacle 48 connected to the first nozzle element 22 . The adjustability and deformability of the deformable section can be limited to the middle area of the flow channel, which is not covered by the slide plate 21 . The deformable flexible bar can also be integrated into the movable nozzle element 24 .

In particular from 11 shows that the slide plate 21 has a wedge surface 25 on the edge at its rear end, which bears against a sliding surface of the nozzle body 1 . When slide plate 21 is advanced into the position shown in dashed lines, wedge surface 25 forms a wall surface delimiting the flow channel, which reduces the larger channel width in the inlet area to the smaller channel width in nozzle zone 4 while avoiding a disruptive step. Insofar as the slide plate fulfills the shape of a reduction piece at the same time and ensures the adaptation of the channel geometry explained at the outset.

The slide plate 21 'in the 13a and 13b The extrusion tool shown is formed in two parts and has a slide base body 26 and a slide end piece 27 that can be adjusted vertically relative to this. The slide base body 26 is guided in a linearly movable manner on the first nozzle element 22 in the direction of the extrusion width and has a sliding surface 23 ′ resting on the second nozzle element 24 . The slide end piece 27 is guided on the vertically adjustable second nozzle element 24 so that it can move linearly in the direction of the extrusion width and has a sliding surface 28 that rests on the first nozzle element 22 . The movement of the slide end piece 27 is coupled to the movement of the vertically adjustable second nozzle element 24 . Since the slide end piece 27 is integrated in the slide body 26, it automatically moves with the latter when the extrusion width is adjusted. A comparative view of 13a and 13b It can be seen that the slide end piece 27 moves automatically with the vertical adjustment of the second nozzle element 24 due to the forced guidance and this embodiment achieves a complete sealing of the flow channel through the head piece over the entire working stroke of the vertically adjustable second nozzle element 24. Due to the lateral covering of the slide body 26, no melt can get into the guides of the slide plate 21'.

The second nozzle element 24, which performs program-controlled vertical adjusting movements for the purpose of setting the nozzle gap width during the extrusion of a preform, is arranged in an adjustable manner in a receiving element 29, which is also guided in the nozzle body 1 so that it can move vertically. When the slide plate 21' is advanced, the receiving element 29, together with the first nozzle element 22, performs a lifting movement that compensates for the vertical offset of the slide plate 21'.

At the in 14 In the illustrated embodiment of the extrusion tool, the die gap 5 is delimited by a stationary first die element 30 and a second die element 31, which is guided in a horizontally adjustable manner in a receiving body 32 arranged in a stationary manner. The head piece for the lateral delimitation of the flow channel consists of a two-part slide which has a slide body 33 guided horizontally on the first nozzle element 30 and a slide end piece 34 guided horizontally on the second nozzle element 31 . The slide end piece 34 rests against a horizontal sliding surface 35 of the slide base body 33 and can be moved relative to the slide base body 33 with an adjusting movement of the second nozzle element 31 . Since the nozzle element 30 and the receiving body 32 are not part of an adjustment movement, additional sealing strips are required for the in 14 shown version of the device is not required.

In another, in the 15 16a and 16b, the nozzle gap 5 is delimited by a first nozzle element 36 fixedly arranged in the nozzle body and a pivotably mounted second nozzle element 37. The second nozzle element 37 has a rotatable round profile 38 and a leg 39 protruding on the peripheral side, which forms a wall surface of the melt channel in the nozzle zone. A lower sealing element 40 is guided displaceably along the round profile 38 at at least one end of the round profile 38 . The sealing element 40 delimits the melt channel at the end and seals the flow area below the leg 39 . To delimit the melt channel, an axially movable head piece 8 is also provided, to which a movable disc element 41 is connected. The disk member 41 pivots along with rotation of the movable nozzle member 37 and seals a gap between the head piece 8 and the leg 39 . The disk element 41 is moved synchronously with a rotational movement of the round profile 38 on the same axis of rotation. The coupling of the movement of the disc element 41 to the movement of the rotatable nozzle element allows the flow channel to be almost completely sealed over the entire pivoting range. The disk element is connected via a connecting element 45 to a transmission element 42, which is connected to the second nozzle element by means of a guide strip 43 and can be rotated with it. The guide bar 43 is slidably arranged in a guide recess 44 of the round profile 38 . The disk element and the transmission element 42 are connected to the displaceable head piece 8 in an axially fixed manner via the connecting element. The representations in particular in the 16a and 16 b It can be seen that a rod-shaped connecting element 45 is provided for connecting the disk element to the transmission element 42 and extends through an elongated hole in the head piece 8 . The section of the connecting element 45 that directly adjoins the transmission element 42 has a larger diameter than the bore of the elongated hole in the head piece 8. The head piece 8 is thus fixed between the connecting element 45 and the disk element in such a way that a synchronous movement of the head piece 8 and disk element 41 is guaranteed in the direction of the flow channel. Without the use of the disc element 41, a gap depending on the set nozzle gap and the length of the leg 39 would result from the rotary movement of the nozzle element 37 between the head piece 8 and the leg 39 of the nozzle element. To avoid this gap, the disc element is provided as a lateral channel delimitation. Together with the head piece 8, the disc element enables the flow channel to be almost completely sealed off in any position.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 202007008132 U1 [0003]
• WO 2009019301 [0005]
• DE 102007025296 A1 [0006]
• DE 102005031698 A1 [0007]

Claims (29)

Extrusion tool for the production of flat preforms formed from a plastic melt and fed to a blow molding plant in the thermoplastic state, having a nozzle body (1) which has at least one melt channel (2) with an inlet area (3) and a nozzle zone (4) connected thereto with a has a die gap (5) that tapers towards the exit to form a flat preform, the die gap (5) being delimited in the die zone (4) by die elements (6, 7; 22, 24) and the gap width of the die gap (5) being program-controlled infeed movements of at least one of the nozzle elements (7) can be changed during the extrusion of a preform, characterized in that a head piece (8, 8'; 21, 21') is provided at at least one end of the nozzle elements (6, 7; 22, 24). is, which fills the die gap (5) between the die elements (6, 7) and during the extrusion of a parison along the die elements for the purpose of a verse position of the extrusion width of the die gap (5) is adjustable in the axial direction. extrusion tool claim 1 , characterized in that the geometry of the melt channel (2) in the inlet area (3) can be adjusted in such a way that if the extrusion width of the die gap (5) changes, there is a transition from the inlet area (3) to the die gap (5) without a pronounced step at the edge is guaranteed. extrusion tool claim 1 or 2 , characterized in that the nozzle gap (5) is delimited by a first nozzle element (6) fixedly arranged in the nozzle body (1) and a second nozzle element (7) pivotably mounted about a longitudinal axis and in that the head piece (8, 8') is mounted on the stationary arranged first nozzle element (6) or in the nozzle body (1) is slidably guided. extrusion tool claim 3 , characterized in that the head piece (8) has a rotary feedthrough (9) for the second nozzle element (7). extrusion tool claim 4 , characterized in that the rotary feedthrough (9) has a disc (10) which is rotatably mounted on the head piece (8) and has a recess for receiving the second nozzle element (7). extrusion tool claim 5 , characterized in that the recess of the rotary feedthrough (9) encloses the second nozzle element (7) in a U-shape and in that the nozzle element (7) on a circumferential section that protrudes or ends essentially flush with the rotary feedthrough (9) on a sealing strip (11) sealing. extrusion tool claim 6 , characterized in that the sealing strip (11) and the corresponding peripheral section of the nozzle element (7) has sealing surfaces curved in the shape of a circular arc. extrusion tool claim 3 , characterized in that the head piece (8') has a contact surface (18) resting on the circumference of the rotatable nozzle element (7). extrusion tool claim 8 , characterized in that the rotatably mounted nozzle element (7) has a slotted sleeve (19) which contains a receiving slot for a nozzle bar (20) delimiting the nozzle gap (5) in the longitudinal direction. extrusion tool claim 8 or 9 , characterized in that for sealing the rotatably mounted nozzle element (7) a sealing strip (11') is provided, against which the sleeve (19) rests directly or with the interposition of a further sealing body which is inserted into a casing-side window of the sleeve. Extrusion tool according to one of claims 3 until 10 , characterized in that the stationary arranged first nozzle element (6) bears sealingly against a sealing strip (12), and that the head piece (8, 8') has a recess through which the nozzle element (6) with the sealing strip (12) in the contact is established. Extrusion tool according to one of Claims 1 until 3 , characterized in that the nozzle gap (5) is delimited by a first nozzle element fixedly arranged in the nozzle body and a pivotably mounted second nozzle element (37), the second nozzle element (37) having a round profile (38) rotatable about its longitudinal axis and a peripherally projecting profile leg (39) forming a wall surface of the melt channel in the nozzle zone. extrusion tool claim 12 , characterized in that at least one end of the round profile (38) a lower sealing element is guided displaceably along the round profile (38), which limits the melt channel at the end and seals the flow area below the leg (39). extrusion tool claim 12 or 13 , characterized in that a movable disc element (41) is arranged on the head piece (8), which can be pivoted together with a rotation of the second nozzle element (37) and seals a gap between the head piece (8) and the leg (39). extrusion tool Claim 14 , characterized in that the lower sealing element (40) and the disc element (41) are connected to a transmission element (42) which, when connected to the second nozzle element (37) in an axially displaceable manner, can be rotated therewith, the transmission element (42) and the disc element (41) (42) are axially fixed to the movable head piece (8). extrusion tool claim 15 , characterized in that the transmission element (42) has a guide strip (43) which is displaceably arranged in a guide recess (44) of the round profile (38). extrusion tool claim 1 or 2 , characterized in that the head piece consists of a slide plate (21, 21'), which has a cross-section adapted to the die gap (5) in the die zone (4) and is arranged to be displaceable transversely to the direction of flow for the purpose of adjusting the extrusion width and a has a sliding surface (23, 23') for a second nozzle element (24), which is arranged to be displaceable in the nozzle body (1) in order to change the width of the nozzle gap and which executes program-controlled adjusting movements during the extrusion of a preform. extrusion tool Claim 17 , characterized in that the second nozzle element (24) is arranged to be displaceable vertically or at an acute angle (a) to the melt channel. extrusion tool Claim 17 or 18 , characterized in that the slide plate (21') is constructed in two parts and has a slide base body (26) and a slide end piece (27) which can be adjusted relative thereto, the slide base body (26) on the first nozzle element (22) or in the nozzle body (1) is guided so that it can move linearly in the direction of the extrusion width and has a sliding surface (23') that rests against the second nozzle element (24), and wherein the slide end piece (27) is guided so that it can move linearly on the adjustable second nozzle element (24) in the direction of the extrusion width and one on the first nozzle element (22) abutting sliding surface (28). Extrusion tool according to one of claims 17 until 19 , characterized in that the first nozzle element (22) consists of a stationary arranged shaped body. Extrusion tool according to one of claims 17 until 19 , characterized in that the first nozzle element (22) has a deformable portion. Extrusion tool according to one of claims 17 until 21 , characterized in that the slide plate (21, 21') has at its rear end a peripheral wedge surface (25) which rests against a sliding surface of the nozzle body (1) and that at least the first nozzle element (22) with which the slide plate ( 21, 21') is movably connected, is arranged in the nozzle body (1) so that it can be displaced vertically and when the slide plate (21, 21') moves forward along the sliding surface of the nozzle body (1) together with the slide plate (21, 21'), a vertical one performs offset movement. extrusion tool Claim 22 , characterized in that the second nozzle element (24), which performs program-controlled vertical infeed movements for the purpose of setting the nozzle gap width during the extrusion of a preform, is arranged in an adjustable manner in a receiving element (29) which is guided in the nozzle body (1) so that it can move vertically , wherein the receiving element (29) performs a stroke movement compensating for the vertical offset of the slide plate (21, 21') during an infeed movement of the slide plate (21, 21') together with the first nozzle element (22). extrusion tool claim 1 or 2 , characterized in that the nozzle gap (5) is delimited by a stationary first nozzle element (30) and a second nozzle element (31), the second nozzle element (31) being guided in a horizontally adjustable manner in a stationarily arranged receiving body (32), that the The head piece consists of a two-part slide which has a slide base body (33) guided horizontally on the first nozzle element (30) or in the nozzle body (1) and a slide end piece (34) guided horizontally on the second nozzle element (31), the slide end piece (34) rests against a sliding surface (35) of the slide body (33) and can be moved relative to the slide body (33) with an adjusting movement of the second nozzle element (31). Extrusion tool according to one of Claims 1 until 24 , characterized in that the melt channel (2) in the inlet area (3) on at least one longitudinal side of the channel a flow guide element (15) for lateral flow channel delimitation which is articulated to the head piece (8, 8') and aligns itself in accordance with the position of the head piece (8, 8'), which can be adjusted to change the extrusion width of the die gap. extrusion tool Claim 25 , characterized in that the flow guide element (15) is arranged on the flow inlet side of the inlet region (3) so as to be pivotable about a fixed bearing point (16). extrusion tool Claim 26 , characterized in that the articulated mounting of the flow guide element (15) is designed on the inlet side so that the flow guide element (15) can perform both a pivoting movement and a linear compensating movement. Extrusion tool according to one of Claims 1 until 27 , characterized in that head pieces (8, 8') are provided at both ends of the nozzle elements (6, 7) and that the nozzle elements are at least in a section between the head pieces (8, 8') which defines an unchangeable minimum extrusion width of the nozzle gap , Are supported on surfaces (14) of the nozzle body (1). Use of an extrusion tool according to one of Claims 1 until 28 for the production of a flat preform formed from a plastic melt, which is fed to a blow molding plant in the thermoplastic state and formed into a three-dimensionally shaped body in a blow mold, with the program-controlled movement of a movable nozzle element (7, 24) of the extrusion tool limiting the nozzle gap (5). wall thickness profile of the preform that changes in the longitudinal direction of the preform is produced, and with program-controlled adjusting movements of at least one head element (8, 8'; 21, 21') arranged at the end of the nozzle elements, which fills the nozzle gap (5), and during the extrusion of the preform along the nozzle elements is axially adjusted, the width of the preform is changed.

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