NL1009244C1 - Device and method for injection molding a workpiece from at least two different material components. - Google Patents

Description

Device and method for injection molding a workpiece from at least two different material components.

5

The invention relates to an apparatus for injection molding a workpiece from at least two different material components, with a spray nozzle comprising a first inlet for the first material component, a second inlet for the second material component and an outlet in which a first insert is movable arranged to close the first inlet in a first position and to communicate with the outlet in a second position, a channel leading to the outlet being formed in the first insert and a second insert being movable such that the second insert 15 closes the channel in a first position and opens it in a second position, as well as a method for injection molding a workpiece from at least two different material components using such a device.

Such an apparatus and method are known from German patent DE

23 42 789 C2, in which a device and a method for manufacturing rotating bodies with a multi-layer construction are described. The device described therein provides a spray head with a first insert in the form of a sleeve movably arranged therein and a second insert in the form of a needle movably arranged in this sleeve, the sleeve and the needle being provided with the aid of a piston-cylinder units can be moved back and forth. The reciprocating movement of the needle is dependent on the sleeve to the extent that the needle is automatically carried along during movement of the sleeve from the closed position to the open position. Namely, the needle is provided with a laterally projecting arm at the rear, which runs against the rear of the sleeve when the sleeve is returned from its closed position to the open position. In the closed position, the sleeve closes off a first channel for the first material component as well as a second channel for the second material component. In the open position, the sleeve connects the first channel for the first material component to an outlet through a channel formed on the outside of the sleeve, so that the first material component from the first channel is passed through the outside of 1009244-2. sleeve formed channel and a subsequent annular space can flow to the outlet. Simultaneously, in the open position, the sleeve connects yet another channel which is formed in the wall of the sleeve as a passage opening to the second channel for the second material component, whereby the second material component from the second channel is formed by the insertion in the wall of the sleeve other channel in an annular space between the sleeve and the needle and, when the needle is in the open position, can flow through this annular space to the outlet.

10

In this known nozzle, the second material flow can admittedly be added to the first material flow, so that optionally either only the first material component is dispensed, or both material components are simultaneously injected as a common plastic strand; however, the second material flow cannot be controlled completely independently of the first material flow. The construction of the known nozzle allows the pressing of the second material component only either simultaneously with the first material component or, if in doubt, also immediately afterwards, when the first material component 20 is completely used up. However, delivery of only the second material component is completely independent of the first material component or even for delivery of the first material component is not possible.

This circumstance results in that the known device is complicated and inflexible and, in particular, entails problems when exchanging material components, because first of all it is necessary to pay attention which of the two material components must first be sprayed, and then this first material component 30 with the dose the desired amount to be squeezed out exactly.

The object of the invention is to improve an apparatus and method of the prior art in such a way that a flexible and uncomplicated operation is possible, such that both material flows can be controlled independently of each other and without observing a certain sequence.

This problem is solved in that in the aforementioned device the 1009244-3 channel in the first insert is formed such that the second inlet is connected to the channel in the first position of the first insert and closed in the second position of the first insert. .

The construction according to the invention allows a flexible and therefore uncomplicated control and a precise dosing of both material flows completely independently of each other by an actually completely independently controllable reciprocating movement of both inserts. In the arrangement according to the invention 10, it is therefore no longer necessary to pay attention to which inlet which material component must be connected. Furthermore, the construction according to the invention enables a precise dosing of the delivery of the first material component through the first inlet because it can be closed again at any time by the first insert without thereby influencing the optional opening and closing of the second inlet. , which is achieved in closing by the controlled movement of the second insert.

As a result, with the aid of the construction according to the invention, it is possible to spray two different material components optionally successively into the mold one after the other, whereby a multilayer shaped part, in particular a flat part, with sandwich construction is created because the second material component is the back of the first material component is sprayed and thus injected through the first material component without having to open the mold and / or the device.

A further advantage of the invention consists in that the spray nozzle is easier to maintain before closing, because on the one hand the inlets and the outlet are opened and closed correspondingly by the movement of the inserts, so that an additional closing mechanism is not required and, on the other hand, a produces a self-cleaning effect, since the movement of the first and second inserts towards the outlet simultaneously squeezes at least most of the remainder of 35 material components through the outlet that would otherwise remain in the spray nozzle.

A particularly effective self-cleaning effect occurs with an embodiment, 1009244-4, in which the first insert extends in its first position to the outlet and / or the second insert in its first position extends to the outlet.

At least a first molded part and a second molded part are provided in a usual manner, which spaced apart from the first molded part forms an intermediate space in which the outlet of the spray nozzle opens, wherein the molded parts are movable relative to each other, and preferably between a minimum distance corresponding to the desired thickness of a first part of the workpiece to be injection-molded from one of the material components and a maximum distance corresponding to the total thickness of the workpiece to be injection-molded. In this way it is possible to subsequently only form a first part of the workpiece by means of injection molding of one material component and subsequently to form a second part by injection molding of the other material component on this formed first part while the distance between the two molded parts are enlarged to the thickness of the second part to be molded.

This embodiment is particularly suitable for the injection molding of flat resp. flat objects such as trays made of two layers of different material components with different properties. In the case of a tray to be formed, the first and bottom layers may, for example, be of a harder material to give the entire tray a greater rigidity, while the second and top layer may be of a softer rubber-like material to provide a smoother surface. to provide items to be placed thereon.

In a further development of this embodiment, the distance between the first and the second molded part can be essentially constant along their length if the production of flat objects with an essentially uniform thickness, as is the case with trays in the example, is desired. .

For efficiency, one molded part is stationary and the other molded part is movable.

For the automatic operation of the device, a control device is preferably provided which controls the mutual movement of the mold parts 1009244 - 5 - and the spray nozzle in such a way that in a first operational phase the mold parts are set at a minimum distance from each other and the first insert of the spray nozzle is in its second position and in a second operational phase the molded parts are set at the maximum distance from each other and the first insert is in its first position and the second insert of the spray nozzle is in its second position.

For efficiency, the outlet may contain a first outlet opening portion and a second outlet opening portion, the first insert in its first position connects the first inlet to the first outlet opening portion and the channel in the first insert leads to the second outlet opening portion, preferably for an optimum self-cleaning action the first insert extends in its first position into the first outlet opening portion and / or the second insert extends into its second position into the second outlet opening portion. This constructional measure further contributes to the fact that no undesired mixing of remnants of the various material components occurs.

From the viewpoint of space, it is advantageous to arrange the first outlet opening part 20 concentrically around the second outlet opening part. Preferably, in this embodiment, the first outlet opening portion is delimited on the one hand by the outer surface of the second insert and, on the other hand, by the inner surface of a first cavity formed in the spray nozzle in which the first insert 25 is movably mounted and the second outlet opening portion by an inner cavity. first cavity formed second cavity, in which the second insert is movably disposed, so that no intermediate walls are required for separating the two outlet opening parts. In case the part of the workpiece to be injection-molded from the second material component is to be formed on the side remote from the outlet of the spray nozzle, it is preferable to provide a movable element which is arranged in a first position in the intermediate space and here it rests against the second insert and is removed from the intermediate space in a second position. To this end, the control device can expediently control the movable element such that it is in its first position in the first operational phase and in its second position in the second operational phase. From a space viewpoint, it is advantageous if the movable element is arranged in one of the molded parts 1009244-6. A structurally particularly simple further development is characterized in that the movable element is designed as a pin which is arranged in the longitudinal direction and which rests with its free end against the second insert.

5

In a presently preferred embodiment, the first insert is in the form of a sleeve which seals a hole provided in the spray nozzle and which can be slid in the longitudinal direction and whose wall has an opening which, in the first position of the first insert with the second inlet 10 and in the second position of the second insert communicates with the channel and the second insert is in the form of a needle which is sealed in the hole of the sleeve-shaped first insert that forms the channel and can be displaced in its longitudinal direction. In order to achieve a particularly compact construction, the needle-shaped second insert 15 must be arranged concentrically in the sleeve-shaped first insert.

Finally, the first inlet must be located between the second inlet and the outlet.

Furthermore, the above-mentioned problem is solved in that a method for the aforementioned technique is carried out using the above-described device with the following steps, 25 I. the first insert is moved in its second position, the second insert in its first position remains, II. the first material component is forced through the first inlet into the spray nozzle, 30 III. the first insert is returned to its first position, IV. the second insert is brought into its second position, 35 V. the second material component is forced through the second inlet into the spray nozzle, and VI. the second insert is returned to its first position.

1009244 - 7 -

Using the method according to the invention using the device according to the invention, a two-component injection molded part can now be manufactured in a single continuous production phase without interruptions, which leads to a high efficiency in the manufacture of such injection molded parts and therefore to low production costs.

When using movable molded parts, they must be adjusted to the minimum distance from each other before step II and after the step II and before step V to the maximum distance from each other.

When using a movable element of the type described above and forming first and second outlet opening parts in the exhaust, the movable element must be in its first position during steps I and II, before step V in its second position and after step V to be brought back to its first position.

In a further development of this embodiment, the movable element must be moved back into the molded part after step II and before step V such that the free end of the movable element lies substantially flush with the molded part, thereby creating the required free space for the second material component and otherwise damage to the shape of the workpiece to be injection-molded is avoided.

A preferred embodiment of the invention will be explained in more detail below with reference to the annexed figures.

Figure 1 schematically shows a cross-section of a device for injection molding a flat workpiece 30 of two plastic components;

Figure 2 shows an enlarged detail of the front view of Figure 1 showing the construction of the spray nozzle with a sleeve movably disposed therein and a needle movably disposed in the sleeve and the arrangement of the nozzle in a fixed die as well as a movable partridge for detail. in which both the sleeve and the needle of the spray nozzle as well as the movable partridge are each in their first position;

Figure 3 shows the front view of Figure 2 with the sleeve 5 in its second position;

Figures 4 and 5 show the front view of Figure 2 with the needle of the spray nozzle and the movable partridge in a second position; and 10

Figure 6 shows the same front view as Figure 2, with the movable partridge in its second position.

In the figures shown, a device is shown by means of which a flat workpiece can be manufactured from two different plastic components by injection molding. The illustrated device is particularly suitable for the manufacture of substantially flat trays, the core of which consists of hard plastic with a layer of softer plastic on the top thereof to increase the resistance of objects placed thereon against slipping; such trays are therefore also referred to as "Anti-Slip Trays". For the sake of completeness it should already be mentioned here that the device shown can of course also be adapted in such a way that it is also suitable for the production of not only flat but also other workpieces, for example convex or concave shaped, from two different plastics by means of injection molding.

The depicted device is provided with a frame 1 on which a spray nozzle 2 is mounted, provided with a first inlet 4 and a second inlet 6. Through the first inlet 4 a first plastic component is formed and through the second inlet 6 a second plastic component in the spray nozzle 2 pressed.

The spray nozzle 2 is arranged at its front in a fixed die 8 fixed to the frame 1, so that a common outlet 10 of the spray nozzle 2 is flatly closed with the shaping surface 8a of the fixed die 8. The shaping surface 8a of the fixed die 8 is adjacent on one side to an intermediate space 12 into which 1009244 S '- 9 - the plastic components for the formation of the workpiece are injected through the outlet 10 of spray nozzle 2. On the opposite side of the die 8, the spacing 12 is bounded by the shaping surface 14a of a partridge 14 affixed to the frame 5. In the illustrated embodiment, the spaced-apart shaping surfaces 8a and 14a of mold 8 and partridge 14 run substantially parallel to each other, thereby providing injection molding workpiece substantially obtains a flat rectangular shape corresponding to the shape of the intermediate space 12 thus formed. However, it is also conceivable to form the shaping surfaces 8a and 14a of mold 8 and partridge 14 such that workpieces with other, for example, convex or concave shapes.

Partridge 14 is movably disposed, so that optionally the distance from mold 8 and thus the depth of spacing 12 can be changed in a manner to be described in more detail below. In the illustrated embodiment, partridge 14 is movable substantially at right angles to shaping surface 14a, respectively. with respect to the molding plane 8a of mold 8. The movement stroke of partridge 14 is effected by means of a slider 16 which is movable on frame 1 and which is movable on frame 1, against which the movable partridge 14 has its rear face 14b. In the same manner as the corresponding plane 16a of the slider 16, this rear surface 14b is slightly inclined relative to its direction of movement, as shown in Figure 25, whereby the movement of slider 16 is converted into a lifting of the movable partridge 14. Slider 16 is driven hydraulically, only the adjacent part of the hydraulic cylinder 18 of which is shown in Figure 1.

As further shown in Figure 1, there is correspondingly provided a cylindrical pin 20 which seals a hole included in the movable partitions 14 (not shown in the figures in detail) and which is arranged in a longitudinal direction and whose front end 20a is opposite outlet 10 of the spray nozzle is located. The direction of movement of pin 35 20 is the same as that of the movable partridge 14. The opposite end 20b of pin 20 is slidably engaged with a guide groove 22 formed in an insert 24 located in an abutment 16a side. recess provided with slide 16. The 1009244-10 guide groove 22 is inclined with respect to the direction of movement of the slide 16 at a greater angle than that of the rear face 14b of the movable partridge 14, respectively. the contact surface 16a of the slide 16, as shown in figure 1. The greater inclination of guide groove 22 relative to the contact surface 16a of slide 16, respectively. the rear face 14b of the movable partridge 14 effects a greater stroke of movement of the pin 20 relative to the movable partridge 14, which will be explained in more detail below.

10 Figure 2 shows the construction of spray nozzle 2 separately.

Spray nozzle 2 essentially forms a rotationally symmetrical body, the axis of which is in the direction of movement of the movable partridge 14 and of the pin 20 and as such is perpendicular to the molding surfaces 8a and 14a of mold 8 and partridge 14. In a spray nozzle 2 according to the hole provided, a cylindrical sleeve 30 is sealed and slidably arranged in the longitudinal direction. The end 30a of the sleeve 30, which faces the outlet 10 of the spray nozzle 2, has a smaller diameter than the rest of the sleeve 30 and is connected thereto over a conical part 30b; correspondingly, the hole receiving sleeve 30 is also formed in spray nozzle 2. A through hole 32 is formed in the wall of sleeve 30, which in the first position of sleeve 30 shown in Figure 2, in which it closes flat with the front end 30a against the shaping surface 8a of the fixed mold 8, with which the second inlet 6 for the second plastic component. 25

The hole of sleeve 30, on the other hand, is sealed by a cylindrical needle 34 which is slidably arranged in the longitudinal direction. In the first position shown in Figure 2, needle 34 extends to outlet 10 of nozzle 2 so that the front end 34a of needle 34 also closes flat against the molding surface 8a of the fixed die 8.

Pin 20, sleeve 30 and needle 34 are arranged concentrically with respect to each other as well as to the axis of spray nozzle 20 (not shown in more detail in the Figures).

In the first position shown in Figure 2, the movable partridge 14 is set at a minimum distance X from fixed mold 8.

1009244 - 11 -

The pin 20 movably mounted in partridge 14 is in the first position shown in Figure 2 with its front end 20a against the front end 34a of needle 34 of the nozzle 2, so that pin 20 with its front end 20a is the distance X from the molding face 14a of 5 partridge 14.

The first and second inlets 4 and 6 for the various plastic components, referred to below as "A" and "B", each terminate in the cavity of spray nozzle 2 in which sleeve 30 is received, as can be seen in Figure 2 In the first position of sleeve 30 shown in Figure 2, however, the first inlet 4 is closed by sleeve 30 so that the first inlet 4 does not communicate with outlet 10 of spray nozzle 2. Passage opening 32 in sleeve 30 is in communication with the second inlet 6, as shown in Figure 2, but the passage opening 32 is closed by the needle 34 in its first position, so that passage opening 32 and thus the second inlet 6 is not communicates with outlet 10. Thus, both inlets 4 and 6 are closed in the position shown in Figure 2, so that neither plastic component can be injected through outlet 10 into the cavity 12.

In order to now spray the first plastic component A from the first inlet 4 via spray nozzle 2 through its outlet 10 into intermediate space 12, sleeve 30 in the second position shown in Figure 3 is reduced so far that an annular first outlet opening part 10a is formed at outlet 10 of spray nozzle 2. which surrounds the front end 34a of the needle 34 further in its first position and additionally releases the first inlet 4 and in this way connects between the first inlet by the now released part 36 of the cavity formed in spray nozzle 2 4 and the first outlet opening portion 10a of outlet 10 is established. In addition, the movable partridge 14 and also the movable pin 20 are in their first position, so that the movable partridge 14 is further adjusted to the minimum distance Y with respect to the mold and pin 20 with its front end 20a against the front end 34a of the needle 34.

Now the first plastic component A can be injected through inlet 4 via the part of the hollow space 36 from outlet 10 of spray nozzle 2 into intermediate space 12 1009244-12 between mold 8 and partridge 14, whereby the first layer 40 of the workpiece to be formed is produced. wherein the pin 20, which is placed against needle 34, forms an annular casting.

5 After the injection molding of the first plastic component A has ended

the first inlet 4 is closed again by returning the sleeve 30 to its first position (already shown in Figure 2). Thereby, the sleeve 30 with its front end 30a presses the remainder of the first plastic component A, which is still in the part of the hollow space 36 (see Figure 3), through outlet 10 of spray nozzle 2 in intermediate space 12, whereby a self-cleaning effect is created. In the first position, the cavity in spray nozzle 2 is completely closed again by the sleeve 30 and the sleeve 30 with its front end 30a lies flat against the shaping surface 8a of mold 8, as can be seen in Figure 4.

15

The movable partridge 14 is then brought back by a distance Y, so that the movable partridge 14 is now at a maximum distance X + Y from mold 8. In this way a new gap 12 'is formed with the thickness of dimension Y between the already sprayed layer 40 and the shaping face 14a of partridge 14. Simultaneously, the pin 20 is brought back in a second position so far that it now has its front end 20a closes flat against shaping face 14a of partridge 14, as shown in Figure 4. The movement stroke of the pin 20 is thus X greater than that of the movable partridge 14, which is effected by the different slopes of the rear surfaces 14b of the movable partridge 14, respectively. the contact surfaces 16a of slide 16 on the one hand and the guide groove 22 in the insert 24 on the other (see Figure 1), because the return of partridge 14 and pin 20 takes place simultaneously by a corresponding adjustment of slide 18.

30

Finally, the needle 34 in the sleeve 30 of the spray nozzle 2 is returned to a second position shown in Figure 4 such that a circular second outlet opening portion 10b of outlet 10 is in the hole 38 of the sleeve 30 and a further portion of this hole 38 located behind it. as well as the passage opening 32 in the wall of the sleeve 30 are exposed. In this way a connection is made between the second inlet 6 via passage opening 32, hole 38 and the second outlet opening part 10b of the outlet 10 by the annular molding 41 1009244-13 formed by the pin 20 with the newly formed intermediate space 12 '.

As a result of the connection thus formed, the second plastic component B is injected into the new intermediate space 12 ', as a result of which a second layer 42 of the second plastic component is formed on the first layer 40, 5 consisting of the first plastic component, as shown in Figure 5.

Subsequently, the needle 34 in the spray nozzle 2 is brought back into its first position, so that it closes with its front end 34a flat against the shaping surface 8a of fixed mold 8. The remainder of the second plastic component B, which is still there, is pressed out of the hole 38 of sleeve 30 through outlet 10, so that spray nozzle 2 is also cleaned of remnants of the second plastic component. This situation is shown in Figure 6.

15

Finally, the workpiece W made from both layers 40 and 42 can be taken out, for which purpose the movable partridge 14 is preferably returned over a further distance through the fixed mold 8.

For the manufacture of a new workpiece, the injection molding process can then be repeated in the manner described above, without measures having to be taken for cleaning or otherwise shutting down the device.

The above-described movement pattern of the movable partridge 14 of pin 20, sleeve 30 and needle 34 is preferably automatically controlled by a control device which is not shown in the Figures.

1009244

Claims (23)

An apparatus for injection molding a workpiece (W) from at least two different material components (A, B), with a spray nozzle (2) provided with a first inlet (4) for the first material component (A), a second inlet (6) for the second material component (B) and an outlet (10) in which a first insert (30) is movably mounted to close the first inlet (4) in a first position and in a second position with the outlet ( 10), wherein in the first insert (30) a channel (32, 38) leading to the outlet (10) is formed and a second insert (34) is movably arranged such that the second insert (34) the channel (32, 38) closes in a first position and opens in a second position, characterized in that the channel (32, 38) in the first insert (30) is formed such that the second inlet (6) in the first position of the first insert (30) to the channel (32, 38) and in the second position of the first insert (30) is closed. 20 Device according to claim 1, characterized in that the first insert (30) extends in its first position up to the outlet (10) and / or the second insert (34) extends in its first position up to the outlet (10). 25 Device according to claim 1 or 2, with at least a first molded part (8) and a second molded part (14) which is arranged at a distance from the first molded part (8), whereby an intermediate space (12) is created in which the outlet (10) of the spray nozzle opens, characterized in that the molded parts (8, 14) are mutually movable. Device according to claim 3, characterized in that the distance between the first and second mold parts (8, 14) is substantially constant along their length. 35 Device according to claims 3 or 4, characterized in that one molded part (8) is fixed and the other molded part (14) is movably arranged. 1009244 - 15 - Device according to at least one of claims 3 to 5, characterized in that the first and second molded parts (8, 14) are between a minimum distance (X) corresponding to the desired thickness of the one of the material components (A) first part (40) of the workpiece (W) to be injection molded and a maximum distance (X + Y), which corresponds to the joint thickness of the workpiece (W) to be injection molded, are mutually movable. Device according to claim 6, characterized in that a control device which controls the mutual movement of the first and second mold parts (8, 14) and the spray nozzle in such a way that in a first operational phase the mold parts (8, 14) move on are the minimum distance (X) from each other and the first insert (30) of the spray nozzle (2) is in its second position and in a second operational phase the first 15 and second mold parts (8, 14) are arranged at the maximum distance from each other and the first insert (30) is in its first position and the second insert (34) of the spray nozzle (2) is in its second position. Device according to at least one of claims 1 to 7, characterized in that the outlet (10) has a first and a second discharge opening part (10a, 10b) and the first insert (30) in its second position has the first inlet ( 4) to the first discharge opening portion (10a) and feed the channel (38) in the first insert (30) to the second discharge opening portion (10b). 9. Device according to claims 2-8, characterized in that the first insert (30) extends in its first position into the first discharge opening part (10a) and / or the second insert (34) extends in its second position into the second discharge opening part (10b). Device according to claims 8 or 9, characterized in that the first discharge opening part (10a) preferably surrounds the second discharge opening part (10b) concentrically. 35 Device according to claim 10, characterized in that the first discharge opening part (10a) is delimited on the one hand by the outer surface of the second insert (34) and on the other hand by the inner surface of a first cavity (369244 - 16) spray nozzle (36). ) in which the first insert (30) is movably mounted and the second discharge opening portion (10b) is delimited by the inner surface of a second cavity (38) formed in the first insert (30) in which the second insert (34) is movably arranged. 12. Device according to claims 3-11, characterized in that a movable element (20) which is located in a first position in the intermediate space (12) abuts against a second insert (34) and in a second position. removed from the gap (12). Device according to claims 7-12, characterized in that the control device (16, 22, 24) controls the movable element (20) in such a way that the latter is in its first position in the first operational phase and in the second operational phase is in its second position. Device according to claims 12 or 13, characterized in that the movable element (20) is arranged in one of the molded parts (14). 15 II. passing the first material component (A) through the first inlet (4) into the spray nozzle, III. return the first insert (30) to its first position, Device according to at least one of claims 12 to 14, characterized in that the movable element (20) is designed as a pin which is arranged in a longitudinally movable manner and with its free end (20a) against the second insert (34). can be constructed. Device according to at least one of claims 1-15, characterized in that the first insert (30) is designed as a sleeve which seals and longitudinally displaces a hole (36) arranged in the spray nozzle (2) and of which the wall has an opening (32) which communicates with the second inlet (6) in the first position of the first insert (30) and additionally communicates with the channel in the second position of the second insert (34) (38). Device according to at least one of claims 1 to 16, characterized in that the second insert (34) is designed as a needle which seals the hole 35 of the first insert (30) forming the channel (38) and in the longitudinal direction is slidable. Device according to claims 16 and 17, characterized in that the 1009244-17 needle-shaped second insert (34) is placed concentrically in the sleeve-shaped first insert (30). Device according to at least one of claims 1-18, characterized in that the first inlet (4) lies between the second inlet (6) and the outlet (10). 20 IV. bringing the second insert (34) into its second position, V. feeding the second material component (B) through the second inlet (6) into the spray nozzle (2), VI. return the second insert (34) to its first position. 20. Method for injection molding a workpiece (W) from at least two different material components (A, B) using an apparatus according to claim 1, with the following steps, I. putting the first insert (30) in its second position moving with the second insert (34) remaining in its first position, Method according to claim 20 using a device according to claims 6 or 7, characterized in that the molded parts 30 (8,14) before step II at the minimum distance from each other and after step II and before step V at the maximum distance of are adjusted. Method according to claims 20 or 21 using a device according to claims 12 or 13, characterized in that the movable element (20) is in its first position during steps I and II, before step V in its second position and is returned to its first position after step V. 1009244 - 18 - A method according to claim 22 using a device according to claim 14, characterized in that after step II and before step V the movable element (20) is brought back into the molding (14) so far that the free end (20a) of the movable element (20) closes substantially flat with respect to the molding (14). 1009244