Title of Invention	DEVICE FOR THE EXTRUSION OF PREFORMS IN WEB OR STRIP FORM FROM THERMOPLATIC MATERIAL AND METHOD FOR THE EXTRUSION OF SUCH A PREFORM
Abstract	Device for the extrusion of preforms 1 in web or strip form from thermoplastic material with an extrusion die head, the melt outlet of which is formed as a die gap which can be adjusted perpendicularly to the direction of extrusion and extends in a straight line. The device is distinguished by the fact that the die gap 6 is bounded at least on one side directly by a number of segments 9 which can be adjusted perpendicularly to the direction of extrusion independently of one another and make it possible for the width of the die gap 6 to be adjusted in stages or steps.

Title of Invention

DEVICE FOR THE EXTRUSION OF PREFORMS IN WEB OR STRIP FORM FROM THERMOPLATIC MATERIAL AND METHOD FOR THE EXTRUSION OF SUCH A PREFORM

Abstract

Device for the extrusion of preforms 1 in web or strip form from thermoplastic material with an extrusion die head, the melt outlet of which is formed as a die gap which can be adjusted perpendicularly to the direction of extrusion and extends in a straight line. The device is distinguished by the fact that the die gap 6 is bounded at least on one side directly by a number of segments 9 which can be adjusted perpendicularly to the direction of extrusion independently of one another and make it possible for the width of the die gap 6 to be adjusted in stages or steps.

Full Text	Device for the extrusion of preforms in web or strip form from thermoplastic material and method for the extrusion of such a preform The invention relates to a device for the extrusion of preforms in web or strip form from thermoplastic material with an extrusion die head, the melt outlet of which is formed as a die gap which can be adjusted perpendicularly to the direction of extrusion and extends in a straight line. The invention also relates to a method for the extrusion of a preform in web or strip form from thermoplastic material, preferably using the device. A device of the type mentioned at the beginning is known for example from the utility model DE 20 2006 013 751. Utility model DE 20 2006 013 751 describes a molding tool for producing preforms in strip form, comprising a number of channels which respectively have an inlet opening in the form of a segment of a ring and an elongate outlet opening, the inlet openings in the form of segments of a ring being arranged on a common radius such that they are distributed over the circumference and spaced apart from one another by radially running cutting edges. To be able to set a wall thickness profile for the plastic moldings in web form produced by means of such a molding tool, DE 20 2006 013 751 proposes a wall thickness control device with which the wall thickness of the preform can be changed over its entire width. In addition, a wavy profile over the entire length or at defined points over the width can be set for the preform in strip form by means of the wall thickness control device proposed there. For this purpose, it is proposed to adjust the die gap of the slot die used for the extrusion by means of an adjusting element which acts over the entire width of the die and also to superpose on this adjustment an adjustment by means of an adjusting element in the form of an adjusting bar of elastic spring steel. A number of adjusting drives may act on the adjusting bar in such a way that the width of the outlet gap of the slot die can change partially over the length of the preform, so that, according to requirements, a portion of a greater wall thickness can be created and a smaller wall thickness can be created in a neighboring portion of the preform. This makes it possible for the contour of the preform to be adapted well to the requirements of the semifinished or end product to be produced from it. However, with the known device there are limits to the variability of the difference in wall thickness over the width of the preform, for example the absolute width of the preform cannot be influenced. There are also limits to the creation of individual sharp projections over the width and length of the preform in web form, since only a limited thickness variation of the preform is possible because of the lack of flexibility of the adjusting bar. The invention is therefore based on the object of improving a device of the type mentioned at the beginning in these respects. The invention is also based on the object of providing a method which avoids the disadvantages described above. The object is achieved in the first instance by a device of the type mentioned at the beginning which is distinguished by the fact that the die gap is bounded at least on one side directly by a number of segments which can be adjusted perpendicularly to the direction of extrusion independently of one another and make it possible for the width of the die gap to be adjusted in stages or steps. It has surprisingly been found that a staged formation of the inner contour of the die gap does not have any adverse influence on the flow behavior of the melt. The fact that the segments can be respectively adjusted independently of one another also allows relatively great wall thickness variations of the preform to be achieved, even to the extent of accumulations of material that can be described as a step change in wall thickness. In this way, an optimum distribution of material over the length and width of the preform can be achieved, which in the production of relatively large components is accompanied by a considerable saving of material. In particular if the preforms to be produced are to be formed and re-formed within a blow molding tool by applying internal positive pressure or a vacuum to give a finished product, a favorable distribution of accumulations of material, thick points and thin points over the length and width of the preform is desirable, in particular also to allow for the different stretching and extending behavior of the component to be made to expand in the tool. One particular advantage of the device according to the invention can be seen in that not only can the width of the die gap be partially influenced, but the die gap can also be set in its width. For this purpose, it is particularly expedient that the segments are respectively formed as slides which can be adjusted transversely to the direction of melt flow by means of individual actuators. The seglnents may, for example, be dynamically adjustable during the extrusion, to be precise on the basis of a prescribed wall thickness program. This may, for example, bring about the continuous adjustment of the actuators by means of a controller, so that the desired profile is set for the preform. It is particularly expedient if no basic adjustment of the gap width of the die gap is provided by means of a separate component that acts over the entire width of the die gap. It is advantageous if the segments are of different widths, so that they contribute to different extents to bounding the die gap; in particular, if the outer segments are narrower than the segments lying in between, a staged reduction in the width of the die gap can be achieved particularly favorably, so that for example even constricted or drawn-in or waisted preforms in web form can be produced. In the case of the preferred variant, it is provided that the segments are respectively adjustable between a completely open and neutral position, in which the die gap has the maximum width in the region concerned, and a position completely closing the die gap in this region. In the case of a preferred variant of the device according to the invention, it is provided that the die gap is bounded by adjustable segments on both sides, i.e. on both longitudinal sides, transversely to the direction of extrusion. This allows a still greater thickness variation over the width and length of the preform to be achieved. The die gap is preferably formed in a neutral position of the segments as a cross-sectionally rectangular slot, the length of which is much greater than its width. The length or width of the slot corresponds to the width of the preform, whereas the width of the slot defines the thickness of the preform. The object on which the invention is based is also achieved by a method for the extrusion of a preform in strip or web form from thermoplastic material, comprising the following method steps: plasticating thermoplastic material in an extruder, feeding the plasticated material to a die gap of an extrusion die head, the die gap having an elongate, approximately rectangular cross section, adjusting the gap width of the die gap in portions by means of adjustable segments directly bounding the die gap, the adjustment taking place dynamically during the extrusion and a wall thickness profile over the length and/or width being set thereby for the preform. According to a further aspect of the method according to the invention, it is provided that the length of the die gap is dynamically varied during the extrusion. This makes it possible for example to obtain waisted preforms. In particular if blow-molded articles, which are for example made up of shells that complement one another, are to be produced in a multipart tool, a considerable saving in material is achieved by this measure. The size of the pinched-off excess material (flash) can be reduced in this way. In the case of the method according to the invention, it is provided that the plasticated material from the extruder is initially brought into the form of a tube¬like melt stream in the extrusion die head and said stream is deflected within the extrusion die head into at least one, preferably two, web-like melt streams. For this purpose, the extrusion die head may be formed in a known way as an axially gating head or radially gating head, the melt stream emerging from the extruder flowing axially or radially around the mandrel or the pin. The melt stream may then be deflected within the extrusion die head by appropriately formed flow channels. It may be provided here that a number of melt streams arranged on the radius in the form of a circular .ring (multilayered preforms) are cut or divided up by means of cutting devices and emerge through a number of elongate, straight die gaps as preforms in sheet or web form. In the case of a further advantageous method step, it is provided that the extrudate emerging from the die gap is further processed within a multipart molding tool in the first heat by using gas pressure and/or a vacuum to form a plastic article. The invention is explained below on the basis of an exemplary embodiment that is represented in the drawings, in which: Figure 1 shows a schematic view of an extrusion device according to the invention and a multipart molding tool arranged underneath the extrusion device. Figure 2 shows a section along the lines II-II in Figure 1, Figure 3 shows a section along the lines III-III in Figure 2, Figure 3 illustrating a first exemplary embodiment of the device according to the invention. Figure 4 shows a view corresponding to Figure 3 with the adjusting devices actuated during extrusion. Figure 5 shows a view corresponding approximately to Figures 3 and 4 on the basis of a second exemplary embodiment according to the invention, Figure 6 shows a greatly exaggerated representation of a preform emerging from the device according to the invention, Figures 7a to 7c show possible cross-sectional profiles of a preform obtained by the device on the basis of the first exemplary embodiment of the invention and Figure 8 shows a possible cross-sectional profile of a preform obtained by the device on the basis of the second exemplary embodiment of the invention. In Figure 1, part of the method for producing an extrusion blow molded article from preforms 1 in web form is schematically represented. The preforms 1 are extruded in a suspended manner from two slot dies 2. The slot dies 2 are part of an extrusion die head (not represented), which is charged with molten thermoplastic material from an extruder in a known way. As represented for example in Figure 1, the preforms 1 in the form of webs or sheets can be extruded between the opened parts of a molding tool 3. The molding tool 3 comprises two outer molds and a center mold 3b. The outer molds 3a respectively form part-cavities, into which the preforms 1 are drawn or pressed and which respectively determine the later outer contour of the finished article. The production of the article may take place for example by the preforms 1 first being respectively extruded between the opened outer molds 3a and the center mold 3b. Then the outer molds 3a are closed against the center mold 3b and the preforms 1 are formed in the part-cavities 4a, 4b by applying either gas pressure or a vacuum. The center mold 3b comprises extendable and retractable component holders 5, by means of which it is possible during or after the forming of the preforms 1 to introduce built-in parts into the article to be produced as a hollow body. Then the center mold 3b is made to move between the outer molds 3a transversely to the direction of extrusion, either into the plane of the drawing or out of it. The outer molds 3a, 3b are moved toward one another in the sense of a closing movement, so that the shell-shaped semifinished products contained in them are welded to form a container with a peripheral seam. The preforms 1 may be respectively provided as a multilayered co-extrudate. The part-cavities 4a, 4b and the geometry of the outer molds 3a are greatly simplified in the exemplary embodiments represented. Depending on the article to be produced, both part-cavities 4a, 4b may have a highly fissured contour. In addition, the outer molds 3a do not necessarily have to have an approximately rectangular cross section, as represented in Figure 2. Consequently, it is desirable to be able to vary the width of the preforms over their length. In addition, it is likewise desirable to set a wall thickness profile for the preforms 1, since, depending on the topography of the part-cavities 4a, 4b, the material made to expand in the latter undergoes a greater or lesser degree of extension or stretching. On the one hand, excessive accumulations of material in the wall of the finished article are to be avoided, on the other hand, however, it may also be desirable to provide accumulations of material at certain points. For this purpose, it is provided according to the invention that the die gap 6 of the slots dies 2 is adjustable both in its width and in its length. As can be seen in particular from the sectional views in Figures 3 to 5, the die gap 6 is formed as a cross-sectionally rectangular slot, the length of which is a multiple of its width. In the case of the exemplary embodiment represented in Figures 3 and 4, the die gap 6 is bounded on the one hand by a rigid wall portion 7 of the die body 8 and on the other hand by a number of segments in the form of slides 9. The wall portion 7 and the slides 9 respectively bound longitudinal sides of the die gap 6. The slides 9 are respectively adjustable transversely to the direction of extrusion by means of adjusting devices 10, to be precise independently of one another, so that an approximately stepped or staged profile can be set for the preform 1 concerned. Although the cross section of the die gap is consequently staged, it has surprisingly been found that the plasticated material has such a flow behavior that these stages or discontinuous changes in wall thickness are not reproduced on the preform as sharp transitions. As already mentioned above, the adjustment of the slides 9 by means of the adjusting devices is influenced during the extrusion, i.e. dynamically, so that a profile changing over the length of the preforms (changing thickness over the width) can be set for the preforms 1. The slides 9 are represented for example in Figure 3 in the completely open and neutral position, whereas for example in Figure 4 the slides 9 defining the outer narrow sides of the die gap 6 are in their completely closed end position. In this way, the length of the die gap 6 can similarly be influenced, so that, as represented for example in Figure 6 in an exaggerated form, preforms 1 which are waisted, or have drawn-in portions (B), can be created. The preform 1 shown in Figure 6 has with respect to the length three successive portions A, B, C, whereas the portion B has a smaller width, or is drawn in, with respect to the portions A, C. It should be mentioned once again at this point that the slot dies 2 according to the invention do not have any superposed or separate basic gap adjustment that acts over the entire width of the die gap 6. The slides 9 can all be actuated independently of one another. Finally represented in Figure 5 is a variant of the slot die 2 according to the invention in which slides 9 directly bound both longitudinal sides of the die gap 6, so that a wall thickness profile can be set for the preform 1 in such a way that it has two profiled outer sides, as represented for example in the sectional view in Figure 8. In this way it is possible particularly advantageously to create a preform which can be produced with a complex topography varying over the length and width on both its large outer surfaces. In addition, as represented in Figure 5, the length of the die gap 6 can also be set, to be precise the slides 9 can be moved in portions toward one another from the outside inward, so that it is also possible for the device according to Figure 5 to produce a preform as represented in Figure 6. List of designations: 1 preforms 2 slot dies 3 molding tool 3a outer molds 3b center mold 4a, 4b part-cavities 5 component holders 6 die gap 7 wall portion 8 die body 9 slides 10 adjusting devices Patent claims 1. A device for the extrusion of preforms (1) in web or strip form from thermoplastic material with an extrusion die head, the melt outlet of which is formed as a die gap which can be adjusted perpendicularly to the direction of extrusion and extends in a straight line, characterized in that the die gap (6) is bounded at least on one side directly by a number of segments (9) which can be adjusted perpendicularly to the direction of extrusion independently of one another and make it possible for the width of the die gap (6) to be adjusted in stages or steps. 2. The device as claimed in claim 1, characterized in that the segments are respectively formed as slides (9) which can be adjusted transversely to the direction of melt flow by means of individual adjusting devices (10). 3. The device as claimed in either of claims 1 and 2, characterized in that the segments (9) are dynamically adjustable during the extrusion. 4. The device as claimed in one of claims 1 to 3, characterized in that no basic adjustment of the gap width of the die gap (6) is provided by means of a component that acts over the entire width of the die gap (6). 5. The device as claimed in one of claims 1 to 4, characterized in that the segments are of different widths, so that they contribute to different extents to bounding the die gap (5). 6. The device as claimed in claim 5, characterized in that the outer segments are narrower than the segments arranged in between. 7. The device as claimed in one of claims 1 to 5, characterized in that the segments are respectively adjustable between a completely open and neutral position, in which the die gap (6) has the maximum width in the region concerned, and a position completely closing the die gap (6) in this region. 8. The device as claimed in one of claims 1 to 7, characterized in that the die gap (6) is bounded by adjustable segments on both longitudinal sides transversely to the direction of extrusion. 9. A method for the extrusion of a preform in strip or web form from thermoplastic material, comprising the following method steps: plasticating thermoplastic material in an extruder, feeding the plasticated material to a die gap of an extrusion die head, the die gap having an elongate, approximately rectangular cross section, adjusting the gap width of the die gap in portions by means of adjustable segments directly bounding the die gap, the adjustment taking place dynamically during the extrusion and a wall thickness profile over the length and/or width being set thereby for the preform, 10. The method as claimed in claim 9, characterized in that the length of the die gap is dynamically varied during the extrusion. 11. The method as claimed in either of claims 9 and 10, characterized in that the plasticated material from the extruder is initially brought into the form of a tube-like melt stream in the extrusion die head and said stream is deflected within the extrusion die head into at least one, preferably two, web¬like melt streams. 12. The method as claimed in one of claims 9 to 11, characterized in that the extrudate emerging from the die gap is further processed within a multipart molding tool in the first heat by using gas pressure and/or a vacuum to form a plastic article.

Full Text

Device for the extrusion of preforms in web or strip
form from thermoplastic material and method for the
extrusion of such a preform
The invention relates to a device for the extrusion of preforms in web or strip form from thermoplastic material with an extrusion die head, the melt outlet of which is formed as a die gap which can be adjusted perpendicularly to the direction of extrusion and extends in a straight line.
The invention also relates to a method for the extrusion of a preform in web or strip form from thermoplastic material, preferably using the device.
A device of the type mentioned at the beginning is known for example from the utility model DE 20 2006 013 751. Utility model DE 20 2006 013 751 describes a molding tool for producing preforms in strip form, comprising a number of channels which respectively have an inlet opening in the form of a segment of a ring and an elongate outlet opening, the inlet openings in the form of segments of a ring being arranged on a common radius such that they are distributed over the circumference and spaced apart from one another by radially running cutting edges.
To be able to set a wall thickness profile for the plastic moldings in web form produced by means of such a molding tool, DE 20 2006 013 751 proposes a wall thickness control device with which the wall thickness of the preform can be changed over its entire width. In addition, a wavy profile over the entire length or at defined points over the width can be set for the preform in strip form by means of the wall thickness control device proposed there. For this purpose, it is proposed to adjust the die gap of the slot die used for the extrusion by means of an adjusting element which acts over the entire width of the die and also to

superpose on this adjustment an adjustment by means of an adjusting element in the form of an adjusting bar of elastic spring steel. A number of adjusting drives may act on the adjusting bar in such a way that the width of the outlet gap of the slot die can change partially over the length of the preform, so that, according to requirements, a portion of a greater wall thickness can be created and a smaller wall thickness can be created in a neighboring portion of the preform. This makes it possible for the contour of the preform to be adapted well to the requirements of the semifinished or end product to be produced from it.
However, with the known device there are limits to the variability of the difference in wall thickness over the width of the preform, for example the absolute width of the preform cannot be influenced. There are also limits to the creation of individual sharp projections over the width and length of the preform in web form, since only a limited thickness variation of the preform is possible because of the lack of flexibility of the adjusting bar.
The invention is therefore based on the object of improving a device of the type mentioned at the beginning in these respects.
The invention is also based on the object of providing a method which avoids the disadvantages described above.
The object is achieved in the first instance by a device of the type mentioned at the beginning which is distinguished by the fact that the die gap is bounded at least on one side directly by a number of segments which can be adjusted perpendicularly to the direction of extrusion independently of one another and make it possible for the width of the die gap to be adjusted in stages or steps.

It has surprisingly been found that a staged formation of the inner contour of the die gap does not have any adverse influence on the flow behavior of the melt. The fact that the segments can be respectively adjusted independently of one another also allows relatively great wall thickness variations of the preform to be achieved, even to the extent of accumulations of material that can be described as a step change in wall thickness. In this way, an optimum distribution of material over the length and width of the preform can be achieved, which in the production of relatively large components is accompanied by a considerable saving of material.
In particular if the preforms to be produced are to be formed and re-formed within a blow molding tool by applying internal positive pressure or a vacuum to give a finished product, a favorable distribution of accumulations of material, thick points and thin points over the length and width of the preform is desirable, in particular also to allow for the different stretching and extending behavior of the component to be made to expand in the tool.
One particular advantage of the device according to the
invention can be seen in that not only can the width of
the die gap be partially influenced, but the die gap
can also be set in its width.
For this purpose, it is particularly expedient that the segments are respectively formed as slides which can be adjusted transversely to the direction of melt flow by means of individual actuators.
The seglnents may, for example, be dynamically adjustable during the extrusion, to be precise on the basis of a prescribed wall thickness program. This may, for example, bring about the continuous adjustment

of the actuators by means of a controller, so that the desired profile is set for the preform.
It is particularly expedient if no basic adjustment of
the gap width of the die gap is provided by means of a
separate component that acts over the entire width of
the die gap.
It is advantageous if the segments are of different widths, so that they contribute to different extents to bounding the die gap; in particular, if the outer segments are narrower than the segments lying in between, a staged reduction in the width of the die gap can be achieved particularly favorably, so that for example even constricted or drawn-in or waisted preforms in web form can be produced.
In the case of the preferred variant, it is provided that the segments are respectively adjustable between a completely open and neutral position, in which the die gap has the maximum width in the region concerned, and a position completely closing the die gap in this region.
In the case of a preferred variant of the device
according to the invention, it is provided that the die
gap is bounded by adjustable segments on both sides,
i.e. on both longitudinal sides, transversely to the
direction of extrusion. This allows a still greater
thickness variation over the width and length of the
preform to be achieved.
The die gap is preferably formed in a neutral position of the segments as a cross-sectionally rectangular slot, the length of which is much greater than its width. The length or width of the slot corresponds to the width of the preform, whereas the width of the slot defines the thickness of the preform.

The object on which the invention is based is also achieved by a method for the extrusion of a preform in strip or web form from thermoplastic material, comprising the following method steps:
plasticating thermoplastic material in an extruder,
feeding the plasticated material to a die gap of an extrusion die head, the die gap having an elongate, approximately rectangular cross section,
adjusting the gap width of the die gap in portions by means of adjustable segments directly bounding the die gap,
the adjustment taking place dynamically during the
extrusion and a wall thickness profile over the
length and/or width being set thereby for the
preform.
According to a further aspect of the method according to the invention, it is provided that the length of the die gap is dynamically varied during the extrusion. This makes it possible for example to obtain waisted preforms. In particular if blow-molded articles, which are for example made up of shells that complement one another, are to be produced in a multipart tool, a considerable saving in material is achieved by this measure. The size of the pinched-off excess material (flash) can be reduced in this way.
In the case of the method according to the invention, it is provided that the plasticated material from the extruder is initially brought into the form of a tube¬like melt stream in the extrusion die head and said stream is deflected within the extrusion die head into at least one, preferably two, web-like melt streams. For this purpose, the extrusion die head may be formed in a known way as an axially gating head or radially

gating head, the melt stream emerging from the extruder flowing axially or radially around the mandrel or the pin. The melt stream may then be deflected within the extrusion die head by appropriately formed flow channels. It may be provided here that a number of melt streams arranged on the radius in the form of a circular .ring (multilayered preforms) are cut or divided up by means of cutting devices and emerge through a number of elongate, straight die gaps as preforms in sheet or web form.
In the case of a further advantageous method step, it is provided that the extrudate emerging from the die gap is further processed within a multipart molding tool in the first heat by using gas pressure and/or a vacuum to form a plastic article.
The invention is explained below on the basis of an exemplary embodiment that is represented in the drawings, in which:
Figure 1 shows a schematic view of an extrusion device according to the invention and a multipart molding tool arranged underneath the extrusion device.
Figure 2 shows a section along the lines II-II in Figure 1,
Figure 3 shows a section along the lines III-III in Figure 2, Figure 3 illustrating a first exemplary embodiment of the device according to the invention.
Figure 4 shows a view corresponding to Figure 3 with the adjusting devices actuated during extrusion.

Figure 5 shows a view corresponding approximately to Figures 3 and 4 on the basis of a second exemplary embodiment according to the invention,
Figure 6 shows a greatly exaggerated representation of a preform emerging from the device according to the invention,
Figures 7a
to 7c show possible cross-sectional profiles of a preform obtained by the device on the basis of the first exemplary embodiment of the invention and
Figure 8 shows a possible cross-sectional profile of a preform obtained by the device on the basis of the second exemplary embodiment of the invention.
In Figure 1, part of the method for producing an extrusion blow molded article from preforms 1 in web form is schematically represented. The preforms 1 are extruded in a suspended manner from two slot dies 2. The slot dies 2 are part of an extrusion die head (not represented), which is charged with molten thermoplastic material from an extruder in a known way.
As represented for example in Figure 1, the preforms 1 in the form of webs or sheets can be extruded between the opened parts of a molding tool 3.
The molding tool 3 comprises two outer molds and a center mold 3b. The outer molds 3a respectively form part-cavities, into which the preforms 1 are drawn or pressed and which respectively determine the later outer contour of the finished article. The production of the article may take place for example by the preforms 1 first being respectively extruded between

the opened outer molds 3a and the center mold 3b. Then the outer molds 3a are closed against the center mold 3b and the preforms 1 are formed in the part-cavities 4a, 4b by applying either gas pressure or a vacuum. The center mold 3b comprises extendable and retractable component holders 5, by means of which it is possible during or after the forming of the preforms 1 to introduce built-in parts into the article to be produced as a hollow body. Then the center mold 3b is made to move between the outer molds 3a transversely to the direction of extrusion, either into the plane of the drawing or out of it. The outer molds 3a, 3b are moved toward one another in the sense of a closing movement, so that the shell-shaped semifinished products contained in them are welded to form a container with a peripheral seam.
The preforms 1 may be respectively provided as a multilayered co-extrudate.
The part-cavities 4a, 4b and the geometry of the outer molds 3a are greatly simplified in the exemplary embodiments represented. Depending on the article to be produced, both part-cavities 4a, 4b may have a highly fissured contour. In addition, the outer molds 3a do not necessarily have to have an approximately rectangular cross section, as represented in Figure 2. Consequently, it is desirable to be able to vary the width of the preforms over their length.
In addition, it is likewise desirable to set a wall thickness profile for the preforms 1, since, depending on the topography of the part-cavities 4a, 4b, the material made to expand in the latter undergoes a greater or lesser degree of extension or stretching. On the one hand, excessive accumulations of material in the wall of the finished article are to be avoided, on the other hand, however, it may also be desirable to provide accumulations of material at certain points.

For this purpose, it is provided according to the invention that the die gap 6 of the slots dies 2 is adjustable both in its width and in its length. As can be seen in particular from the sectional views in Figures 3 to 5, the die gap 6 is formed as a cross-sectionally rectangular slot, the length of which is a multiple of its width.
In the case of the exemplary embodiment represented in Figures 3 and 4, the die gap 6 is bounded on the one hand by a rigid wall portion 7 of the die body 8 and on the other hand by a number of segments in the form of slides 9.
The wall portion 7 and the slides 9 respectively bound longitudinal sides of the die gap 6. The slides 9 are respectively adjustable transversely to the direction of extrusion by means of adjusting devices 10, to be precise independently of one another, so that an approximately stepped or staged profile can be set for the preform 1 concerned.
Although the cross section of the die gap is consequently staged, it has surprisingly been found that the plasticated material has such a flow behavior that these stages or discontinuous changes in wall thickness are not reproduced on the preform as sharp transitions.
As already mentioned above, the adjustment of the slides 9 by means of the adjusting devices is influenced during the extrusion, i.e. dynamically, so that a profile changing over the length of the preforms (changing thickness over the width) can be set for the preforms 1.
The slides 9 are represented for example in Figure 3 in the completely open and neutral position, whereas for

example in Figure 4 the slides 9 defining the outer narrow sides of the die gap 6 are in their completely closed end position. In this way, the length of the die gap 6 can similarly be influenced, so that, as represented for example in Figure 6 in an exaggerated form, preforms 1 which are waisted, or have drawn-in portions (B), can be created.
The preform 1 shown in Figure 6 has with respect to the length three successive portions A, B, C, whereas the portion B has a smaller width, or is drawn in, with respect to the portions A, C.
It should be mentioned once again at this point that the slot dies 2 according to the invention do not have any superposed or separate basic gap adjustment that acts over the entire width of the die gap 6. The slides 9 can all be actuated independently of one another.
Finally represented in Figure 5 is a variant of the slot die 2 according to the invention in which slides 9 directly bound both longitudinal sides of the die gap 6, so that a wall thickness profile can be set for the preform 1 in such a way that it has two profiled outer sides, as represented for example in the sectional view in Figure 8. In this way it is possible particularly advantageously to create a preform which can be produced with a complex topography varying over the length and width on both its large outer surfaces. In addition, as represented in Figure 5, the length of the die gap 6 can also be set, to be precise the slides 9 can be moved in portions toward one another from the outside inward, so that it is also possible for the device according to Figure 5 to produce a preform as represented in Figure 6.

List of designations:
1 preforms
2 slot dies
3 molding tool
3a outer molds
3b center mold
4a,
4b part-cavities
5 component holders
6 die gap
7 wall portion
8 die body
9 slides
10 adjusting devices

Patent claims
1. A device for the extrusion of preforms (1) in web or strip form from thermoplastic material with an extrusion die head, the melt outlet of which is formed as a die gap which can be adjusted perpendicularly to the direction of extrusion and extends in a straight line, characterized in that the die gap (6) is bounded at least on one side directly by a number of segments (9) which can be adjusted perpendicularly to the direction of extrusion independently of one another and make it possible for the width of the die gap (6) to be adjusted in stages or steps.
2. The device as claimed in claim 1, characterized in that the segments are respectively formed as slides (9) which can be adjusted transversely to the direction of melt flow by means of individual adjusting devices (10).
3. The device as claimed in either of claims 1 and 2, characterized in that the segments (9) are dynamically adjustable during the extrusion.
4. The device as claimed in one of claims 1 to 3, characterized in that no basic adjustment of the gap width of the die gap (6) is provided by means of a component that acts over the entire width of the die gap (6).
5. The device as claimed in one of claims 1 to 4, characterized in that the segments are of different widths, so that they contribute to different extents to bounding the die gap (5).
6. The device as claimed in claim 5, characterized in that the outer segments are narrower than the segments arranged in between.

7. The device as claimed in one of claims 1 to 5, characterized in that the segments are respectively adjustable between a completely open and neutral position, in which the die gap (6) has the maximum width in the region concerned, and a position completely closing the die gap (6) in this region.
8. The device as claimed in one of claims 1 to 7, characterized in that the die gap (6) is bounded by adjustable segments on both longitudinal sides transversely to the direction of extrusion.
9. A method for the extrusion of a preform in strip or web form from thermoplastic material, comprising the following method steps:
plasticating thermoplastic material in an extruder,
feeding the plasticated material to a die gap of an extrusion die head, the die gap having an elongate, approximately rectangular cross section,
adjusting the gap width of the die gap in portions by means of adjustable segments directly bounding the die gap,
the adjustment taking place dynamically during the
extrusion and a wall thickness profile over the
length and/or width being set thereby for the
preform,
10. The method as claimed in claim 9, characterized in that the length of the die gap is dynamically varied during the extrusion.
11. The method as claimed in either of claims 9 and 10, characterized in that the plasticated material from the extruder is initially brought into the form of

a tube-like melt stream in the extrusion die head and said stream is deflected within the extrusion die head into at least one, preferably two, web¬like melt streams.
12. The method as claimed in one of claims 9 to 11, characterized in that the extrudate emerging from the die gap is further processed within a multipart molding tool in the first heat by using gas pressure and/or a vacuum to form a plastic article.

Documents:

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Patent Number

272615

Indian Patent Application Number

7010/CHENP/2009

PG Journal Number

16/2016

Publication Date

15-Apr-2016

Grant Date

12-Apr-2016

Date of Filing

27-Nov-2009

Name of Patentee

KAUTEX TEXTRON GMBH & CO. KG

Applicant Address

KAUTEXSTR. 52, 53229 BONN

Inventors:

#	Inventor's Name	Inventor's Address
1	ECKHARDT, JOACHIM	FINKENWEG 38, 53229 BONN
2	FRANKE-MAINTZ, MATTHIAS	DAMBROICHER STR. 75, 53773 HENNEF
3	FROITZHEIM, THOMAS	ALBERT-SONNTAG-STRASSE 1, 53757 ST. AUGUSTIN
4	WOLTER, GERD	LONGENBURGER STRASSE 37, 53639 KONIGSWINTER

PCT International Classification Number

B29C47/16

PCT International Application Number

PCT/EP08/02914

PCT International Filing date

2008-04-12

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10 2007 025 296.1	2007-05-30	Germany