METHOD, SYSTEM AND BLOW MOLDING MACHINE FOR BLOW MOLDING A CONTAINER

Description

[0001] The present invention relates to a method for blow molding a container, a system comprising a gripper and a head plate of a blow molding tool for carrying out the method, and a blow molding machine comprising such a system according to the preamble of the independent claims.

[0002] Various containers for holding liquids are known from the state of the art. For example, glass bottles or plastic bottles for holding beverages have become well-known. Containers made of fiber-based materials have also been proposed.

[0003] A fiber-based container was proposed in WO 2012 / 139590 A1. To produce this container, so-called pulp is introduced into a mold and pressed against a corresponding wall using a flexible balloon in this mold, thereby compressing it accordingly.

[0004] Pulp is a mixture of fibers and water, especially natural fibers such as hemp fibers, cellulose fibers, or flax fibers, or a mixture thereof. The pulp may contain additives, as known, for example, from PCT / EP2019 / 076839, which, for example, improve the hardening of the compressed pulp, influence its final appearance, or generally change the properties of the pulp or the final container.

[0005] With these containers, there is a risk that they will soften due to liquid stored in the container and, for example, become leaky or that substances from the container will diffuse into the liquid.

[0006] It has been proposed to provide such fiber-based containers with an inner plastic layer, in particular by arranging a plastic bottle within the fiber-based container, which can assume corresponding barrier functions. The fiber-based container thus merely provides a shell for a thin-walled plastic container. Such a combination is known from WO 2018 / 167192 A1. Another such combination is known from US 2015 / 308050 A1.

[0007] Typically, a fiber-based shell is provided into which a plastic layer or a plastic lining is introduced. This typically occurs in such a way that in a first step the fiber-based shell is provided and in a second step a preform is inserted into this shell. This preform is then inflated within the fiber-based shell until it touches an inner contour of the fiber-based shell or is in contact with the inner contour of the fiber-based shell. This inflation process typically takes place in a blow mold whose cavity corresponds to the outer contour of the fiber-based shell. Since, in contrast to conventional blow molding processes, two separate elements have to be handled, this type of process is much more complicated because the preform has to be positioned and held relative to the fiber-based shell and this in turn has to be positioned and held within the blow mold.

[0008] An exemplary process is described, for example, in EP 3 375 593 A1. EP 3 375 593 A1 describes a preform for producing a container. The preform has extensions in its neck area that can be brought into engagement with a corresponding fiber-based casing, with the aim of ensuring that the casing and the preform remain connected to one another. However, it has been found that this type of connection is prone to errors, since the inner contour or the inner surface of the casing is subject to varying degrees of deviation depending on the specific properties of the pulp from which the casing is formed. This is particularly disadvantageous in the neck area, since a suitable clearance is required for clean pressing between the preform or the fiber-based casing.its extensions and the fiber-based casing, certain tolerance limits must be maintained, but this is not always possible due to the different process parameters and the possibly changing nature of the pulp.

[0009] The object of the invention is to remedy one or more disadvantages of the prior art. In particular, a method and / or system comprising a gripper and a head plate of a blow mold for blow molding a container is to be provided, which simplifies production and increases process reliability.

[0010] This object is achieved by the methods and devices described in the independent patent claims. Further advantageous embodiments emerge from the dependent patent claims.

[0011] A method according to the invention for blow molding a container with a fiber-based shell comprises the steps: Providing a fiber-based shell Inserting a preform into the fiber-based shell to produce a semi-finished product Gripping the semi-finished product with a gripper Transferring the semi-finished product into a blow mold and blowing the container.

[0012] The gripper presses an inner wall of the fiber-based shell onto an outer surface of the preform. The outer surface of the preform can be located on the neck of the preform, but it is also possible for the outer surface to be located on an extension of the neck of the preform.

[0013] In this context, a semi-finished product is understood to be the combination of a fiber-based shell and a preform positioned relative to this fiber-based shell. This relative positioning already represents the final position of a preform neck relative to the fiber-based shell.

[0014] With regard to axes and / or directions, a longitudinal axis or an axial direction corresponds to the direction extending from a base of the preform or container to the opening of the preform or container. The radial direction is also defined from this axis. The axial direction thus also lies essentially in a plane of the blow mold parting surfaces.

[0015] By pressing an inner wall of the fiber-based sleeve onto an outer surface of the preform with the gripper, a force is induced between these two surfaces, correspondingly increasing the frictional force between them. In other words, by positioning a gripper on an outer surface of the fiber-based sleeve, the sleeve can be securely held together with the preform. The semi-finished product consisting of the preform and fiber-based sleeve can be easily and safely manipulated, in particular, it can be easily and safely transferred into a blow mold.

[0016] It is preferably provided that from the first gripping of the semi-finished product with the gripper until it is introduced into the blow mold, a uniform pressure is applied to the fiber-based casing so that it is pressed essentially constantly onto the preform.

[0017] This can further increase process reliability.

[0018] In addition, it can be provided that the gripper continuously grips the semi-finished product during the blow molding process.

[0019] By continuously gripping a part of the blow mold during the blow molding process, the gripper can also perform a positioning function. The gripper can therefore be used as a means of holding and positioning the semi-finished product within the blow mold and / or during blow molding.

[0020] Additionally or alternatively, it can be provided that the gripper is in contact with the blow molding tool during the blow molding process, in particular in contact with a head plate of the blow molding tool.

[0021] The gripper can thus be supported on the blow molding tool, or on a head plate of the blow molding tool, and thus transfer axial forces acting on the gripper or on the semi-finished product to the blow mold.

[0022] Preforms typically have so-called support rings to facilitate handling. Such a support ring is also described, for example, for the preform in EP 3 375 593 A1.

[0023] The support ring divides a preform and, accordingly, a container into two sections. In particular, the support ring separates a closure area of the container from the rest of the container. As can be seen, for example, from the aforementioned EP application, the fiber-based sleeve is arranged below the support ring. The method as described here typically comprises a gripper that grips the semi-finished product below the support ring and presses the fiber-based sleeve onto an outer surface of the preform below this support ring.

[0024] However, it can also be provided that the gripper grips the semi-finished product both below the support ring and above the support ring of the preform.

[0025] For this purpose, the gripper in the area of the support ring can be designed to be essentially C-shaped in cross section.

[0026] By gripping the semi-finished product both below and above the support ring, axial displacement of the semi-finished product can be reliably prevented or the semi-finished product can be adjusted to a specific position in relation to its axial position.

[0027] For this purpose, the gripper can be provided with a first gripping jaw and a second gripping jaw which are spaced apart from one another in the axial direction.

[0028] It may be provided that when the preform is inserted into the fiber-based shell, an upper end of the fiber-based shell is brought into contact with the support ring.

[0029] This allows for relative positioning of the preform with respect to the fiber-based shell. It is particularly advantageous if the fiber-based shell has been cut to the appropriate length prior to preparation.

[0030] Preferably, the gripper grips the semi-finished product from at least two sides and also clamps the semi-finished product from at least two sides.

[0031] By clamping the semi-finished product from two sides, it can be positioned centrally in the gripper. The gripper can be provided with two legs for gripping the semi-finished product from at least two sides, which are arranged opposite each other with respect to the longitudinal axis.

[0032] Typically, after the semi-finished product has been transferred to the blow mold, the blow mold is closed. Blow molds typically have two mold halves that can be joined together along a parting line. After the container has been blown, the blow mold is opened, and the now completely blown container is removed from the blow mold using the gripper and transferred, for example, to a conveyor system for further processing.

[0033] Another aspect of the invention relates to a system comprising a gripper and a head plate of a blow molding tool for carrying out the method described here. The gripper has a first gripping jaw with a height, and the head plate has a recess with a depth corresponding to the height of the gripping jaw. Alternatively, the head plate can have a projection with a height corresponding to the height of the gripping jaw.

[0034] By providing a recess with the same height as the gripping jaw, the gripping jaw can be inserted into the recess within the head plate, with an upper edge of the gripping jaw lying essentially in the same plane as an upper edge of the head plate. In other words, by means of a corresponding recess in the head plate in conjunction with the gripping jaw, an essentially continuous, co-planar surface can be provided on which, for example, a support ring of the preform can be evenly supported. If corresponding projections are provided on the head plate, these are arranged in such a way that they fill a free space towards the gripping jaw in such a way that an essentially continuous, co-planar surface is also provided.

[0035] The recess may have an outer contour that essentially corresponds to an outer contour of the gripping jaw.

[0036] This allows the gripper jaw to be inserted precisely into the recess, preventing lateral displacement. Appropriate radial stops allow the gripper jaw to be positioned reliably and precisely relative to the longitudinal axis.

[0037] The gripper can have a second gripping jaw spaced apart from the first gripping jaw such that a support ring can be inserted between the first and second gripping jaws. The first gripping jaw is thus axially spaced apart from the second gripping jaw. The first and second gripping jaws together form an approximately C-shaped cross-section.

[0038] This means that the gripper can grip the semi-finished product both below the support ring and above the support ring of the preform.

[0039] By gripping the semi-finished product both below and above the support ring, axial displacement of the semi-finished product can be reliably prevented or the semi-finished product can be adjusted to a specific position in relation to its axial position.

[0040] It can be provided that the gripper has a first leg and a second leg, wherein a first gripping jaw is arranged on each leg.

[0041] These two legs are arranged opposite each other in an end position, i.e. during the gripping process when the semi-finished product is clamped in the gripper.

[0042] This arrangement allows the gripper to clamp the semi-finished product from at least two sides.

[0043] By clamping two sides, the semi-finished product can be positioned centrally in the gripper.

[0044] It can be provided that a second gripping jaw is arranged on at least one, preferably on each, leg.

[0045] As already explained, this enables the exact axial positioning of the semi-finished product within the gripper and thus also relative to the blow mold during the blow molding process.

[0046] It can be provided that the first gripping jaw and / or each first gripping jaw has a gripping surface that extends along a circular ring over an angle of at least 30°. This ensures, on the one hand, that the semi-finished product is gripped over a minimal area, and, on the other hand, that the gripping force is distributed over a specific minimum area, thus ensuring that the compression of the fiber-based casing onto the preform does not exceed a limit.

[0047] Likewise, the second gripping jaw and / or every second gripping jaw can have a gripping surface that extends along a circular ring over an angle of at least 30°. This ensures, on the one hand, that the semi-finished product is gripped over a minimal area, and, on the other hand, that the gripping force is distributed over a specific minimum area, thus ensuring that the compression of the preform does not exceed a limit.

[0048] The first gripping surface and the second gripping surface can be offset from one another in a radial direction, in particular by an offset corresponding to the wall thickness of the fiber-based casing. The second gripping surface, i.e., the gripping surface located above the support ring, is arranged closer to the longitudinal axis than the first gripping surface, which is located below the support ring.

[0049] In this configuration, the pressure is evenly distributed on the preform above the support ring and on the combination of preform and fiber-based shell below the support ring.

[0050] Another aspect of the present invention relates to a blow molding machine comprising a system as described herein.

[0051] This enables the provision of a complete production unit with all coordinated elements. The invention is explained below using exemplary embodiments based on schematic figures. It shows: Figure 1: a perspective view of a leg of a gripper; Figure 2: a preform; Figure 3: a perspective view of a fiber-based sleeve; Figure 4: a cross-section through a semi-finished product during gripping; Figure 5: a perspective view of a blow mold before closing; Figure 6: a detailed view of the blow mold from the Figure 5after closing.

[0052] The Figure 1 shows a perspective view of a leg 41 of a gripper 40 (see Figure 5 ). The leg 41 has a first gripping jaw 43 and a second gripping jaw 44. A gripping surface 431 is arranged on the first gripping jaw 43 and a gripping surface 441 on the second gripping jaw 44. The gripping surfaces 441 and 431 each extend along a circular ring over an angle of 30°. The first gripping jaw 43 is axially spaced from the second gripping jaw 44. In cross section, the first gripping jaw 43 forms a substantially C-shaped cross section with the second gripping jaw 44. This C-shaped cross section is formed around a corresponding support ring 32 (see Figure 2 ). In relation to the second gripping jaw 44, the first gripping jaw 43 is offset radially outwards (see also the Figure 4 ).

[0053] In particular, contours can be formed on the gripping surface 431 of the first gripping jaw 43 which improve the friction between this gripping surface 431 and a fiber-based sheath 20 to be gripped.

[0054] The Figure 2 shows a preform 30. The preform 30 has an elongated body with a preform base. A support ring 32 is arranged on the preform 30, which divides the preform 30. In the present illustration, a closure region 33 is arranged above the support ring 32. In the present illustration, below the support ring 32, the preform body has four projections 34, each of which has an outer surface 31 formed thereon. For the sake of clarity, only one of the projections 34 and one of the outer surfaces 31 is provided with reference numerals.

[0055] The Figure 3shows a perspective view of a fiber-based sheath 20. The fiber-based sheath 20 has an upper end 22 that is essentially hollow-cylindrical. An inner wall 21 is formed at this upper end.

[0056] The Figure 4 shows a cross-section through a semi-finished product 60 during gripping. In the illustration according to the Figure 4 is therefore a Preform 30 (see Figure 2 ) into a fiber-based shell 20 (see Figure 3 ) is introduced. The fiber-based sleeve 20 has a wall with a wall thickness W, wherein this wall has an inner wall 21 and an outer wall 23. The fiber-based sleeve 20 is in contact with an outer surface 31 of the preform 30 with its inner wall 21. The outer surface 31 is formed on a projection 34. A clamping effect already takes place between the preform 30 and the fiber-based sleeve 20. In the Figure 4is also a first leg 41 of a gripper 40 (see Figure 5) is visible. The leg 41 has a first gripping jaw 43 and a second gripping jaw 44. The first gripping jaw 43, with its gripping surface 431, is just in contact with the outer wall 23 of the fiber-based sleeve 20. Figure 4 shows that at this time the second gripping jaw 44 is spaced apart by the distance A from an outer surface 35 of the closure region 33. To fix the fiber-based sleeve 20 to the preform 30, the leg 41 is moved towards the preform 30 until the distance A disappears. In the process, the wall thickness W of the fiber-based sleeve 20 is compressed by the distance A and pressed accordingly onto the projection 34. The distance A is smaller than the wall thickness W and in this case is approximately half the wall thickness W. The gripping surface 431 of the first gripping jaw 43 is here radially spaced from the gripping surface 441 of the second gripping jaw 44.The distance is the difference between the wall thickness W and the distance A plus the height of the projection 34, i.e., the distance between the outer surface 31 and the outer surface 35 of the closure region 33. It is understood that a second leg 42 is arranged opposite the leg 41, which is not shown for the sake of simplicity. The second leg 42 is configured in the present case like the first leg 41.

[0057] As in the Figure 4 As can also be seen, the first gripping jaw 43 is offset radially outward relative to the second gripping jaw 44. In this case, the offset amounts to the height of the projection 34 relative to the outer surface 35 of the closure area plus approximately half the wall thickness W.

[0058] Also shown is the height H of the first gripping jaw 43.

[0059] The Figure 5shows a perspective view of a blow mold 50 before closing. A semifinished product 60 is introduced into an open blow mold 50 by means of a gripper 40 having a first leg 41 and a second leg 42. The two legs 41 and 42 of the gripper 40 are arranged on two gripper arms (not shown here), which can be pivoted together into and out of the blow mold 50.

[0060] The blow mold 50 has two blow mold halves (not designated in more detail), with one half of a head plate 51 being arranged on each blow mold half. On the head plate 51, an elevation is formed on which a projection 52 is formed. The projection 52 has a height equal to the height H of the first gripping jaw 43 (see Figure 4 ) corresponds.

[0061] The Figure 6 shows a detailed view of the blow mold 50 after closing. The support ring 32 now rests on the projections 52 (see Figure 5) of the head plate 51. The legs 41 and 42 rest essentially on the head plate 51 between the projections 52. By resting the legs 41 and 42 on the head plate, they are precisely positioned in the axial direction. In this illustration, the support ring rests only on the projections 52. Alternatively, the projections 52 can be aligned with a surface of the respective first gripping jaws 43 (see Figure 4 ) form a common surface for supporting the support ring 32. It is also possible that the legs 41 and 42 in the Figure 6 In the position shown, they are still slightly spaced from the head plate 51 to prevent excessive friction when assembling the blow mold 50. The legs 41 and 42 can be pressed onto the head plate 51 during the blowing process, which accordingly forms a counterbearing.

Claims

1. A method for blow molding a container having a fiber-based shell (20), comprising the steps of - providing a fiber-based shell (20) - introducing a preform (30) into the fiber-based shell (20) in order to produce a semi-finished product (60) - gripping the semi-finished product (60) by means of a gripper (40) - transferring the semi-finished product (60) into a blow molding tool (50) and - blowing the container characterized in that the gripper (40) presses an inner wall (21) of the fiber-based shell (20) onto an outer surface (31) of the preform (30).

2. The method according to claim 1, characterized in that the gripper (40) surrounds the semi-finished product (60) continuously during the blowing process.

3. The method according to claim 1 or 2, characterized in that the gripper (40) is in contact with the blow molding tool (50), in particular with a head plate (51) of the blow molding tool (50), during the blowing process.

4. The method according to any one of claims 1 to 3, characterized in that the gripper (40) grips the semi-finished product (60) both below a support ring (32) of the preform (30) and above the support ring (32).

5. The method according to claim 4, characterized in that, as the preform (30) is introduced into the fiber-based shell (20), an upper end (22) of the fiber-based shell (20) is brought into contact with the support ring (32).

6. The method according to any one of claims 1 to 5, characterized in that the gripper (40) grips and clamps the semi-finished product (60) from at least two sides.

7. A system composed of a gripper (40) and a head plate (51) of a blow molding tool (50) for carrying out the method according to any one of claims 1 to 6, characterized in that the gripper (40) has a first gripping jaw (43) with a height (H) and the head plate (51) has a recess with a depth corresponding to the height (H) or has a projection (52) with the height (H).

8. The system according to claim 7, characterized in that the recess has an outer contour which substantially corresponds to an outer contour of the gripping jaw (43).

9. The system according to claim 7 or 8, characterized in that the gripper (40) has a second gripping jaw (44), which is spaced apart from the first gripping jaw (43) in such a way that a support ring can be introduced between the first gripping jaw (43) and the second gripping jaw (44).

10. The system according to any one of the claims 7 to 9, characterized in that the gripper (40) has a first member (41) and a second member (42), on each of which members (41, 42) a first gripping jaw (43) is arranged.

11. The system according to claim 9 and 10, characterized in that a second gripping jaw (44) is arranged at least on one, preferably on each, member (41, 42).

12. The system according to any one of claims 7 to 11, characterized in that the first gripping jaw (43) has a gripping surface (431) which extends along a circular ring over an angle of at least 30°.

13. The system according to any one of claims 9 to 12, characterized in that the second gripping jaw (44) has a gripping surface (441) which extends along a circular ring over an angle of at least 30°.

14. The system according to any one of claims 9 to 13, characterized in that the first gripping surface (431) and the second gripping surface (441) are offset relative to one another in a radial direction, in particular by a wall thickness (W) of the fiber-based shell.

15. A blow molding machine comprising a system according to any one of claims 7 to 14.