A mold and a tool for the mold

Abstract

The present invention provides an inner mold (10) forming part of a mold (30) to be used in the injection molding process of a plastic article, such as a plastic top for liquid food packaging. The inner mold (10) comprises an outer surface (16) defining the inner surface of the plastic article to be produced, wherein a longitudinal end of the inner mold (10) is provided with a bushing (40) having a flat surface (42), the flat surface (42) defining the longitudinal end of the inner mold (10) and configured to contact a matching outer mold (20) during injection molding. The bushing (40) is provided with a side wall (44) extending from the flat surface (42), the side wall (44) forming part of the outer surface (16) of the inner mold (10).

Description

Technical Field

[0001] The present invention relates to a mould, in particular to a mould for injection moulding and also to a tool forming a part of the mould. Background Art

[0002] Injection molding is a well-known method for manufacturing articles by injecting molten material into a mold and allowing the material to harden before being removed from the mold. In recent years, injection molding technology has become popular in the packaging industry, where it can be used to produce packaging containers having plastic parts injection-molded onto a cardboard-based sleeve.

[0003] Such packaging combines the environmental benefits of paperboard-based packaging with the structural benefits of a plastic top and has been particularly successful for packaging storing liquid foods. Packaging and its various shapes is one such example.

[0004] To produce this packaging, an open-ended sleeve made of cardboard-based material is placed on a mandrel. One end of the mandrel, extending axially from the end of the sleeve, forms the inner mold during the injection molding of the plastic top. Two outer molds are moved toward the inner molds to form a cavity in the shape of the plastic top to be produced. Once the outer molds have reached their operating position relative to the inner molds, injection molding is performed, thereby producing the plastic top directly onto the cardboard-based sleeve. Once the outer molds have been separated and moved away from the inner molds, the cardboard-based sleeve can be removed from the mandrel. At this point, the open-ended sleeve is provided with the plastic top, which is in turn sealed with, for example, a threaded cap. The packaging can then be filled through the open bottom end before the bottom end is sealed and formed into a suitable, usually flat shape.

[0005] When the spindle carrying the inner mold rotates towards its injection position, the outer mold moves in one plane towards the inner mold. In this position, the spindle is arranged vertically, which means that the outer mold moves upwards and horizontally towards the inner mold to reach its working position. In order to produce a plastic top with the required dimensions, the outer mold must be aligned with the inner mold in the vertical direction and in the horizontal plane. For alignment in the vertical plane, the upper part of the inner mold is provided with a bushing, which comes into contact with the outer mold and thus provides vertical guidance for the outer mold. Figure 1 As shown, the entire cover forming unit can achieve horizontal alignment between the inner mold and the outer mold.

[0006] The above-mentioned packages are typically manufactured in high-speed filling machines; the entire injection molding process for one plastic top is completed in about 1.5 seconds. Due to the high-speed application, the mold needs to be cooled very quickly, so the outer mold is usually made of aluminum. Any misalignment between the outer mold and the bushing of the inner mold will cause wear on the outer mold, which will eventually cause the injection molded material to leak out of the expected size of the plastic top. Injection molding failure will produce burrs on the upper end of the plastic top (i.e., the edge of the pouring spout of the package). Since the edge of the pouring spout is in direct contact with the consumer's lips, it is very important to avoid burrs, especially for smaller packages.

[0007] One solution is to replace the outer mold more frequently before wear introduces burrs. However, it would be more desirable to provide an improved mold that reduces the risk of burrs, thereby extending the life of the mold and increasing the safety of consumers consuming food directly from packaging having paperboard laminates and injection molded parts. Summary of the Invention

[0008] It is an object of the present invention to at least partially overcome one or more of the above-mentioned limitations of the prior art.

[0009] To achieve these objectives, an inner mold is provided. The inner mold forms part of a mold to be used during the injection molding of a plastic article, such as a plastic top for liquid food packaging. The inner mold includes an outer surface that defines the inner surface of the plastic article to be produced, wherein a longitudinal end of the inner mold is provided with a bushing having a flat surface that defines the longitudinal end of the inner mold and is configured to contact a mating outer mold during the injection molding process. The bushing is provided with a sidewall extending from the flat surface, the sidewall forming part of the outer surface of the inner mold.

[0010] The bushing may have a cylindrical shape, which is advantageous because the entire circumference of the bushing may be used to define the article to be injection moulded.

[0011] The bushing may be supported by at least one spring biasing the bushing into a longitudinally extended position. This reduces the risk of wear on the outer mould as the contact area between the bushing and the outer mould is increased and the contact occurs only in a horizontal plane.

[0012] The inner mould may comprise a neck and a nozzle portion, wherein the side walls of the bushing form the longitudinal ends of the nozzle portion. Thus, the bushing terminates the cavity of the mould, thereby reducing the risk of burrs appearing at the spout of the package.

[0013] The bushing may protrude longitudinally from the body of the inner mould, and the radius of the bushing may be smaller than the radius of the body.The bushing may thereby be movable inside the body, which means that the bushing is guided by the body during movement of the body.

[0014] The bushing can be attached to the body of the inner mould by means of one or more screws. This allows for a secure fixation of the bushing.

[0015] According to a second aspect, a mold for use during injection molding of a plastic article, such as a plastic top for liquid food packaging, is provided. The mold includes an inner mold and at least two outer molds, which together define a cavity to receive molten plastic material during injection molding. A bushing is provided at a longitudinal end of the inner mold, the bushing having a flat surface that defines the longitudinal end of the inner mold and is configured to contact a mating outer mold during the injection molding process. The bushing has sidewalls extending from the flat surface, the sidewalls being arranged to be spaced apart from the outer mold during the injection molding process.

[0016] The distance between the side wall of the bushing and the outer mould may form part of the cavity of the injection moulding, which is advantageous since no part of the side wall of the bushing serves as a guide surface for the outer mould.

[0017] The inner mold can be arranged on a mandrel configured to receive a sleeve of packaging material, onto which the plastic product to be injection molded is placed, wherein the outer mold is configured to contact the outer surface of the sleeve during the injection molding process. This allows for efficient and reliable guidance of the outer mold.

[0018] The outer mould can be guided in a first direction by the flat surface of the bushing and in a second direction by the outer surface of the bushing. This provides adequate guidance for the outer mould in all necessary directions.

[0019] According to a third aspect, a method for injection molding a plastic article onto a sleeve of packaging material is provided. The method includes placing the sleeve of packaging material onto a mandrel, moving two outer molds toward an inner mold disposed on the mandrel, pressing the outer molds toward the inner mold so that the outer molds are guided in a first direction by a flat surface of a bushing provided on the inner mold and in a second direction only by an outer surface of the sleeve, and injecting molten plastic material into a cavity formed between the inner and outer molds.

[0020] The first guiding direction can be arranged perpendicular to the second guiding direction, which provides for effective and reliable guidance of the outer mould in all required dimensions.

[0021] The outer mould may be pressed against the inner mould such that the bushing is pushed towards the sleeve of packaging material in the longitudinal direction of the sleeve.

[0022] Other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Embodiments of the present invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which

[0024] Figure 1 Isometric view of the injection molding station of a filling machine.

[0025] Figure 2 yes Figure 1 An isometric view of two parallel molds of an injection molding station is shown.

[0026] Figure 3 is a perspective view of various parts of a mold according to one embodiment.

[0027] Figure 4 is a cross-sectional view of a mold according to one embodiment.

[0028] Figures 5a to 5d is a cross-sectional view of the mold in a closing sequence showing the outer mold moving toward the inner mold to define the injection mold cavity; and

[0029] Figure 6 is a schematic diagram of a method according to one embodiment. DETAILED DESCRIPTION

[0030] exist Figure 1 , a non-limiting example of an injection molding station 1 is shown, which can be incorporated into a filling machine (not shown). The term "filling machine" is used to characterize a machine configured to receive a laminate of paperboard-based packaging material in the form of a roll or individual blanks, to perform the necessary operations to form sleeves or packaging containers for containing food products under certain hygienic requirements, and finally to seal the packaging containers for further distribution.

[0031] In the present case, the filling machine is typically configured to produce individual consumer packages enclosing liquid food products, while the injection molding station 1 is configured to mold plastic tops onto sleeves made of cardboard-based packaging material as well as plastic tops.

[0032] Two parallel mandrel wheels 2 are arranged in the upper right part of the injection molding station 1. Each mandrel wheel 2 carries four mandrels 4, which are 90° apart in the same plane. Each mandrel has a longitudinal extension in the radial direction of the relevant mandrel wheel 2 and ends in the inner mold 10. During operation, the mandrel wheel 2 rotates. In one position, for example, the position in which the mandrel 4 points to the right in the figure (indicated by the reference symbol PA), a sleeve of packaging material is fed to the mandrel 4. As the mandrel wheel 2 rotates clockwise, the next position of the mandrel 4 is the injection molding position, as shown in FIG. Figure 2 Further shown.

[0033] At the next sequential position, the injection-moulded article can be cooled, whereupon the sleeve (and its associated plastic top) can be withdrawn from the mandrel 4 .

[0034] Now go to Figure 2 , forming a mold 30 at the injection molding position. Each mold 30 includes an inner mold 10 (i.e., the longitudinal end of the mandrel 4) and two movable outer molds 20.

[0035] exist Figure 2 In the injection molding position shown, the outer mold 20 is arranged against the inner mold 10 so that a cavity is formed between them for receiving the molten plastic material according to the available injection molding technology.

[0036] exist Figure 3 , mold 30 is shown in cross-section, with one outer mold 20 omitted for ease of understanding. As described above, inner mold 10 is positioned at the longitudinal end of mandrel 4. Mandrel 4 has a rectangular cross-section, but with rounded corners to define the shape of the cardboard-based package. Inner mold 10 has a neck 12 that extends into a nozzle portion 14. The distal end of nozzle portion 14 is formed by a sleeve 40. Sleeve 40 is provided with a sidewall 44, thereby forming the longitudinal end of nozzle portion 14.

[0037] The inner mold 10 includes an outer surface 16 that defines the inner surface of the plastic article to be produced (i.e., the plastic top in the embodiment described). A bushing 40 has a flat surface 42 that defines the longitudinal ends of the inner mold 10 and extends between side walls 44. During injection molding, the flat surface 42 contacts the mating outer mold 20.

[0038] Now go to Figure 4 , showing the mold 30 in cross section. A cavity 50 is formed inside the mold 30, which defines the shape of the article to be produced. In this embodiment, the cavity has a circular cross-section to define the neck and nozzle of the plastic top. The cavity 50 has a bottom portion 52, which forms the interface to the sleeve 60 of the paperboard-based packaging material, and is only Figure 4 . The cavity 50 extends above the neck portion 12 of the inner mold 10 and the nozzle portion 14 of the inner mold 10. The upper end 54 of the cavity 50 is circular or annular and terminates at the flat surface 42 of the bushing 40, so that the side wall 44 of the bushing also forms a boundary of the cavity 50. The side wall 44 of the bushing 40 thus forms a portion of the outer surface 16 of the inner mold 10.

[0039] The bushing 40 has a cylindrical shape and is downward (at the Figure 4 The bushing 40 extends in a T-shape (in the direction opposite to the direction of the axis BD in FIG. 1 ). One benefit of the T-shape is that the longitudinal guidance of the bushing 40 is improved. However, we would like to point out here that the bushing 40 can also work without the T-shape. Figure 4As shown, a plurality of springs 70 are arranged below the bushing 40 to support the bushing 40 relative to the body 18 of the inner mold 10. In this exemplary embodiment, six compression springs 70 are distributed at equal angular distances (60°) from each other. However, it will be readily understood that a different number of compression springs 70 and other types of springs (leaf springs, etc.) may be used.

[0040] The spring 70 biases the bushing 40 in the longitudinal direction BD away from the spindle 4 to the longitudinally extended position. Figures 5a to 5d This longitudinally extended position and the movement of the bushing 40 are shown in FIG.

[0041] Figures 5a to 5d The sequence of the outer mold 20 moving from the remote position to the injection position is shown. In order to fully understand the complex movement of the inner mold 10 and the outer mold 20, refer again to Figure 1 and Figure 2 . The outer molds 20 move towards their operating positions; during this movement, the inner mold 10 also moves towards the injection position by a rotational movement. This means that the outer molds 20 cannot move in a linear manner, they must be separated from the inner mold 10 in the horizontal direction and in the longitudinal direction to allow the inner mold 10 to rotate to its desired position. To achieve this, the movement of the outer molds 20 can be controlled by means of a belt drive 80, such as described in WO2004050327 by the same applicant. The belt drive 80 is thus configured to open and close the mold 30 by moving the outer molds 20 in a first direction radial to the hub of the spindle wheel 2 and in a second direction perpendicular to the first direction and pointing towards the plane of the circumferential movement of the inner mold 10. Preferably, the outer molds 20 are moved so that their center axes coincide throughout the entire movement. The movement in the first direction and the second direction preferably takes place simultaneously.

[0042] exist Figure 5a In FIG, the outer mold 20 is positioned away from the inner mold 10; the position shown corresponds to when the inner mold 10 has reached its injection molding position, but the outer mold 20 still has a certain travel distance.

[0043] exist Figure 5b , the outer mold 20 has reached the inner mold 10 so that the flat surface 42 of the bushing 40 is in contact with the matching flat surface 22 of the corresponding outer mold 20. As these flat surfaces 42, 22 are in contact with each other, no cavity is formed between them.

[0044] exist Figure 5c 5 , the outer dies 20 have been moved further towards each other in the second direction, i.e. in the horizontal direction, so that the vertical end faces of the outer dies 20 are pressed towards each other (interface denoted by reference numeral MT in FIG. 5 ). During the movement towards its horizontal end position, each outer die 20 is guided by a sleeve 60 (see FIG. Figure 4 ). This also means that the vertical surface of the bushing 40 (ie the side wall 44) does not come into contact with the vertical surface of the outer mold 20; this is particularly advantageous for the purpose of reducing wear on the outer mold 20. Figure 5c During the step in , the polymer material intended to form the top of the packaging container is injected into the cavity 50 between the inner mould 10 and the outer mould 20 .

[0045] exist Figure 5d , the final position of the outer mold 20 is shown. Here, the outer mold 20 has moved in the vertical direction, thereby pushing the bushing 40 upwards and compressing the spring 70. In this final step of the molding process, the polymer melt that has been injected into the cavity 50 between the inner mold 10 and the outer mold 20 is squeezed between the inner mold and the outer mold by the movement of the outer mold 20 relative to the fixed inner mold 10. The maximum longitudinal distance moved by the bushing 40 is in the range of 0.2 mm to 0.7 mm, for example 0.5 mm. Figure 5d As shown, the radius of the bushing 40 is smaller than the radius of the main body 18 of the inner mold 10. The bushing 40 is thereby slidably guided by the main body 18 in its reciprocating movement.

[0046] The bushing 40 is attached to the body 18 of the inner mold 10 by means of one or more screws 46. This attachment allows a secure connection while still enabling movement of the bushing 40. The screws 46 are therefore not threaded to the bushing but merely determine the final axial position of the bushing 40 (end stop).

[0047] A cover 48 may be provided to cover the screws 46 .

[0048] Now turn Figure 6 , schematically shows a method 100 for injection molding a plastic article onto a sleeve of packaging material. The method 100 comprises a first step 102 of arranging the sleeve of packaging material on a mandrel, and a second step 104 of moving two outer molds toward an inner mold arranged on the mandrel. In a step 106, when the two outer molds have come into contact with each other, molten polymer material is injected into the cavity formed between the inner mold and the outer mold. Finally, in a step 108, the outer mold is pressed against the inner mold, whereby the outer mold is guided in a first direction by the flat surface of a bushing provided on the inner mold and in a second direction only by the outer surface of the sleeve. In this step 108, the molten polymer material is pressed into the cavity formed between the inner mold and the outer mold by moving the outer mold against the inner mold.

[0049] Although various embodiments of the invention have been described and shown according to the above description, the invention is not restricted thereto, but may also be embodied in other ways within the scope of the subject matter defined in the appended claims.

Claims

1. An inner mould (10) forming part of a mould (30) to be used in an injection moulding process for a plastic article, wherein The inner mold (10) comprises an outer surface (16) defining the inner surface of the plastic article to be produced, wherein a bushing (40) is provided at a longitudinal end of the inner mold (10), the bushing (40) having a flat surface (42) defining the longitudinal end of the inner mold (10) and configured to contact a matching outer mold (20) during injection molding, the bushing (40) being provided with a side wall (44) extending from the flat surface (42), the side wall (44) forming a portion of the outer surface (16) of the inner mold (10), Its characteristics are: The inner mold (10) includes a neck (12) and a nozzle portion (14), wherein the side wall (44) of the bushing (40) forms a longitudinal end of the nozzle portion (14).

2. The inner mold (10) according to claim 1, wherein The bushing (40) is supported by at least one spring (70) that biases the bushing (40) to a longitudinally extended position.

3. The inner mold (10) according to claim 2, wherein The bushing (40) protrudes longitudinally from the main body (18) of the inner mold (10), and wherein a radius of the bushing (40) is smaller than a radius of the main body (18).

4. The inner mold (10) according to claim 3, wherein The bushing (40) is attached to the body (18) of the inner mold (10) by one or more fastening means (46).

5. The inner mold (10) according to claim 1, wherein The bushing (40) has a cylindrical shape.

6. The inner mold (10) according to claim 1, wherein The plastic product is a plastic top for liquid food packaging.

7. A mold (30) for use in an injection molding process of a plastic product, the mold (30) comprising an inner mold (10) according to any one of claims 1 to 6 and at least two outer molds (20), the inner mold (10) and the at least two outer molds (20) together defining a cavity (50) for receiving molten plastic material during the injection molding process, wherein a bushing (40) is provided at a longitudinal end of the inner mold (10), the bushing having a flat surface (42) defining the longitudinal end of the inner mold (10) and configured to contact the matching outer mold (20) during the injection molding process, characterized in that The bushing (40) is provided with a side wall (44) extending from the flat surface (42), the side wall (44) being arranged at a distance from the outer mold (20) during the injection molding process.

8. The mold (30) according to claim 7, wherein The distance between the side wall (44) of the bushing (40) and the outer mold (20) forms a part of the cavity (50) of the injection molding.

9. The mold (30) according to claim 7 or 8, wherein The inner mold (10) is arranged on a mandrel (4), and the mandrel (4) is configured to accommodate a sleeve (60) of packaging material on which the plastic article to be injection molded is placed, wherein the outer mold (20) is configured to contact the outer surface of the sleeve (60) during the injection molding process.

10. The mold (30) according to claim 9, wherein The outer mold (20) is guided in a first direction by the flat surface (42) of the bushing (40), and in a second direction by the outer surface of the sleeve (60).

11. The mold (30) according to claim 7, wherein The plastic product is a plastic top for liquid food packaging.

12. A method for injection molding a plastic article onto a sleeve of a packaging material, comprising: placing said sleeve of packaging material on a mandrel, moving two outer molds toward an inner mold arranged on the mandrel until the two outer molds come into contact with each other, injecting molten plastic material into the cavity formed between the inner mold and the outer mold, The outer mold is pressed toward the inner mold, thereby pressing the injected molten plastic material into the cavity formed between the inner mold and the outer mold, so that the outer mold is guided in a first direction by the flat surface of the bushing provided on the inner mold and in a second direction only by the outer surface of the sleeve, wherein the bushing is provided with a side wall extending from the flat surface, the side wall forming a part of the outer surface of the inner mold.

13. The method according to claim 12, wherein: The first guiding direction is arranged perpendicular to the second guiding direction.

14. The method according to claim 12 or 13, wherein: The outer mould is pressed towards the inner mould so that the bushing is pushed towards the sleeve of packaging material in the longitudinal direction of the sleeve.

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