HK1024664B - Method and injection moulding apparatus for injection moulding a plastics material part in a hole of a packaging sheet material - Google Patents

Description

Method and mould for injection moulding plastic material parts at packaging sheet material holes

Technical Field

The present invention relates to a method of injection moulding a plastic material part at a hole in a packaging sheet material, and a mould in an injection moulding apparatus. In particular, the disclosed method and mould are used for injection moulding opening devices of synthetic plastics material on a packaging sheet.

Technical Field

Different types of opening devices are provided on packaging containers made of sheet packaging material, which are suitable for packaging articles, such as food products, in particular for packaging liquid beverages, such as fruit juices, water, milk, wine, etc., are known.

In an example of such an opening device, it comprises an aperture at the top of the packaging container, and a lid device of plastic material secured to the top wall portion, which in a closed state covers the aperture. The cover device comprises a peripheral base which is fixed to the wall portion, for example by means of an adhesive, surrounding the hole by the periphery of the base, with which the cover element is hinged. Once the cover member is opened, the opening is forcibly opened so that the contents of the packaging container can be dispensed from the container.

Another known opening arrangement comprises an opening provided in the top wall of the packaging container, and a lid arrangement of plastics material, similar to that described above, which in the closed condition is secured to the top wall of the container, covering the lid of the opening. The sealing member may be an aluminium pull tab which is attached to a wall portion of the container so as to cover the opening, and once the lid member is opened, the sealing member is removed to expose the opening for dispensing the contents of the packaging container.

The method for providing the above-mentioned opening arrangement on the packaging container may comprise feeding a continuous sheet of packaging material to a first station, at which station perforations or openings are provided in the sheet; the sheet material is then advanced to a second station where a cover member is secured to the sheet material to cover the perforations or openings. If an aluminum tab is required to cover the opening, it is secured in an intermediate step. After the opening device has been secured to the web, the packaging container is formed from the web, filled with contents, sealed and placed on the finished packaging container for use. One example of an apparatus for forming, filling and sealing packaging containers is the TB8 filling apparatus manufactured by TETRA BRIK packaging system of MODENA, italy.

As another opening device, a cover device of already molded plastic material is provided to the packaging sheet. US-4725213 (the disclosure of which is incorporated herein by reference) discloses an opening arrangement of plastic material, wherein the opening arrangement is injection moulded directly onto the packaging sheet. In particular, a pair of dies is moved to a pre-punched hole around the sheet, and heated thermoplastic is injected through an injection passage extending along the surface of the sheet between one of the dies and one surface of the sheet to form an opening device at the pre-punched hole. The die formed opening device includes a pair of peripheral flange portions secured to the edges of the pre-punched hole on opposite sides of the surface of the sheet material, thereby securing the opening device to the sheet material.

Although the method and apparatus for providing opening devices of the latter type are fully feasible, there is still a need for improvement in the field of opening devices for injection moulding of thermoplastic materials.

It has been found that there are problems, for example, in controlling the flow of injection moulded thermoplastic material into the mould cavity formed by the mould in order to provide the sheet portion with a suitable position relative to the opening arrangement adjacent the pre-punched opening. The portion of the packaging sheet material adjacent the opening is typically of very low stiffness and is exposed to elevated pressure and temperature thermoplastic material during the injection molding process. As a result, portions of the sheet adjacent the opening are undesirably bent, and the injection molded opening device is eventually attached at random locations. There is a need to provide a method for injection moulding an opening device of thermoplastic material onto a packaging sheet in order to obtain a uniform and reliable configuration with respect to the opening device in the correct position of the sheet.

The above-mentioned uncontrollable, possibly curved sheet portion adjacent to the opening can result in a structure in which, during injection moulding of the thermoplastic, the edge of the opening of the sheet is substantially in contact with one of the moulds, whereafter the plastic material does not flow between the mould and the surface of the sheet portion in contact therewith. The sealing of the edge of such an opening is therefore not as good as the way in which the plastic material of the opening device extends at least along the edge of the opening extending adjacent to the surface of the sheet of material of the opening. A packaging sheet material is generally composed of several layers of material, including an inner paper layer, two outer cover layers of synthetic plastic material, one of which is designated the contact surface of the object to be packaged. Other possible material layers, such as ink layers, composite layers and aluminum foil, may be arranged between the paper layer and the cover layer. When punching an opening in a packaging sheet, the inner layer of the packaging sheet is exposed at the edge of the opening, unless such edge is suitably sealed by an injection moulded opening device of thermoplastic material, which may be damaged if the packaged item comes into contact with the inner layer of the packaging sheet. It is therefore desirable to provide a method for injection moulding a thermoplastic opening arrangement in a packaging sheet which ensures that a suitable seal is obtained by injection moulding the opening arrangement around the edges of the hole formed in the packaging sheet.

Summary of The Invention

According to a preferred aspect of the present invention there is provided a method of injection moulding a component of plastics material at an aperture in a packaging sheet material, comprising providing a first mould tool and a second mould tool in contact with opposite sides of the packaging sheet material to form a mould cavity, locating an aperture edge of the sheet material within the mould cavity, biasing the aperture edge and the packaging sheet material adjacent the aperture edge away from the second mould tool, injecting plastics material into the mould cavity to form the component of plastics material, whereby the biasing of the sheet material portion away from the second mould tool assists in forming a formation of the plastics material on a portion of the second side of the sheet material portion; and arranging the first and second dies such that the portion of the packaging sheet in contact with the first and second dies is under pressure relative to the portion of the packaging sheet arranged within the die cavity.

The biasing of the packaging material away from the second mould contributes to a reliable formation of the plastic material on a portion of the second side of the packaging sheet adjacent to the edge of the hole, which can be consistent and reliable for correct positioning of the sheet in relation to the opening arrangement. Furthermore, if or when the second side of the packaging sheet is designated as the food-contact surface of the finished packaging container, the shaping of the plastic material at the second side portion near the aperture edge can form an excellent seal at the aperture edge and the second side, which helps to ensure that the contents do not come into contact with the inner layer of the sheet.

According to another preferred aspect of the invention, there is provided first and second moulds, the moulding stations of which are arranged in co-operation with respect to the packaging sheet so that the packaging sheet is sealingly arranged between the first and second moulds and forms a mould cavity formed by the first and second moulds, in which mould cavity at least a portion of the aperture edge of the packaging sheet is located, wherein at the moulding stations the first and second moulds have a moulding configuration so that the portion of the packaging sheet adjacent the aperture edge is biased away from the second mould, thereby facilitating moulding of the plastics material on a portion of the second side of the packaging sheet, which is located adjacent the aperture edge portion.

In another preferred embodiment the moulding configuration of the first and second moulds in the moulding station comprises the edge of the first mould contacting the first side of the packaging sheet at a first line of contact and the edge of the second mould contacting the second side of the packaging sheet at a second line of contact, whereby the first line of contact is arranged at a greater distance from the edge of the aperture than the second line of contact. The moulding configuration further comprises a void formed between the first and second moulds for receiving the packaging sheet in a sealed manner, wherein the width dimension of the void is smaller than the average thickness of the packaging sheet, whereby, at the moulding station, the packaging sheet in said void is under compression. This particular configuration allows the packaging sheet adjacent the edge of the aperture to be bent at an angle relative to the plane in which the packaging sheet extends substantially outside the mould cavity, thereby obtaining a beneficial biasing effect on the sheet.

According to another preferred embodiment of the invention the moulding configuration of the first and second moulds comprises a void formed between the first and second moulds which accommodates the packaging sheet, wherein the void has an extension in the plane of which extends at an angle into the mould cavity in a direction extending away from the second mould, whereby a beneficial biasing effect on the sheet is obtained.

The invention also provides apparatus for injection moulding a plastics material part into an aperture in a packaging sheet, the aperture defining an aperture edge of the packaging sheet, comprising first and second moulds arranged to co-operate with one another at a moulding station relative to the packaging sheet such that the packaging sheet is sealingly disposed between the first and second moulds and forms a mould cavity formed by the first and second moulds in which at least a portion of the aperture edge of the packaging sheet is located, wherein at the moulding station the first and second moulds have a moulding formation such that the aperture edge and a portion of the packaging sheet adjacent the aperture edge are biased away from the second mould to assist in moulding of the plastics material on a portion of the second side of the sheet portion and at the moulding station the moulding formation comprises a void formed between the first and second moulds to receive the packaging sheet in sealed form, wherein the width dimension of the void is smaller than the thickness of the packaging sheet, whereby, at the moulding station, the packaging sheet in said void is under compression.

Several preferred embodiments, which are non-limiting examples, are described in detail below with reference to the accompanying drawings. The technical features and advantages of the present invention will be clearly understood by those of ordinary skill in the art. Like reference numerals in the drawings denote like elements.

Brief description of the drawings

Fig. 1 is a side sectional view showing the contour of a mold for injection molding an opening device of thermoplastic material onto a packaging sheet according to a preferred embodiment of the invention.

FIG. 2 is an enlarged detailed side sectional view of region A of FIG. 1 showing the portion of the sheet adjacent the hole in the sheet that is disposed inside the mold cavity formed by the mold prior to injection of the thermoplastic material.

Fig. 3 is an enlarged detailed side sectional view similar to fig. 2 showing the sheet material disposed within the mold cavity after injection molding the opening device of thermoplastic material.

FIG. 4 is an enlarged detailed side sectional view similar to FIG. 2 showing another preferred embodiment of the invention with the sheet material disposed inside the mold cavity formed by the mold prior to injection of the thermoplastic material.

Fig. 5 is an enlarged detailed side sectional view similar to fig. 4 showing the sheet material disposed within the mold cavity after injection molding the opening device of thermoplastic material.

FIG. 6 is an enlarged detailed side sectional view similar to FIG. 5 showing another preferred embodiment of the invention, the mold forming a mold cavity relative to the sheet material with the injected thermoplastic material on both sides of the sheet material.

Best mode for carrying out the invention

Referring to fig. 1, in a moulding station the inner mould 2 and the pair of outer moulds 4 and 6 cooperate with each other with respect to a packaging sheet 8, such that the packaging sheet is arranged between the inner mould 2 and the pair of outer moulds 4 and 6, while a mould cavity 10 is formed by the moulds, and an edge 12 of a hole provided in the sheet 8 is placed in the mould cavity 10. The mould is provided with an injection head 14 of thermoplastic material for feeding heated thermoplastic material into the mould cavity 10 through a passage 16 in the injection head 14 for product shaping and then cooling the heated thermoplastic material, the shaped opening means being attached at the hole edge 12 in the sheet 8.

The packaging sheet 8 may be of any type or shape. For example, the web 8 may be a continuous sheet of wrapping material, or a blank of wrapping material, or an extended flap of wrapping material. In a preferred embodiment, the sheet 8 consists of a paper carrier material covered with a synthetic plastic.

In this embodiment the mould cavity 10 comprises a portion 10a forming a lid portion in the opening device, a portion 10b forming a base portion of the opening device connecting the sheets 8, and a portion 10c forming a tearable edge of reduced thickness in the opening device, which facilitates separation of the lid portion from the base portion. The disclosed arrangement is associated with a particular manner in which the opening device is fixed at the hole edge 12 of the sheet 8, while the opening device may have any different shape.

In this embodiment, the aperture edge 12 completely encloses the aperture of the sheet 8 along the periphery, preferably, the aperture edge 12 is positioned completely inside the base portion 10b of the mold cavity 10 prior to injection molding, the base portion 10b also having a peripheral contour of a size sufficient to completely surround the aperture edge 12. Preferably, the hole edge 12, the base portion 10b and the connecting portion 10c are formed in an oval ring shape whose longitudinal cross section extends in a direction substantially parallel to the extending direction of the sheet, and the lid portion 10a is formed in an oval ring shape whose longitudinal cross section extends in a direction substantially parallel to the extending direction of the sheet. In addition, at the molding station, a gap 18 is formed between the molds, preferably with the width dimension of gap 18 being less than the thickness of the packaging sheet 8, so that the molds compress sheet 8 inside gap 18 to form an effective seal against any heated thermoplastic material leaking outside of mold cavity 10.

One of ordinary skill in the art will appreciate that the molded orientation shown in FIG. 1 may be achieved in a number of ways. For example, the inner mold 2 may reciprocate up and down in the vertical direction of the arrow B. And the outer molds 4 and 6 may reciprocate up and down in the vertical direction or reciprocate up and down in the horizontal direction in accordance with the directions of arrows C and D, respectively. At the same time, the injector head 14 remains substantially in a fixed position. When the mould is in the fully open position, the packaging sheet is fed intermittently in direction E into the correct position so that the hole edges 12 are properly aligned, the mould is moved into the corresponding fully closed position shown in figure 1, heated thermoplastic material is fed through the channel 16 of the injection head 14 to fill the mould cavity 10 and form the opening device in the sheet. The mould is released and the sheet 8 is fed again in direction E, leaving the other aperture edge 12 in position to receive the opening device. After the opening devices are provided on the sheet, the packaging sheet is formed into packaging containers, filled with product, and sealed in a subsequent process. Feeding the packaging sheet 8, punching holes 12 in the sheet, moving the mould, injecting the heated thermoplastic material, and moulding, filling are performed. Sealed packaging containers are well known to those of ordinary skill in the art.

Fig. 2 shows the molding configuration 20 for the respective inner and outer molds of the molding station of fig. 1. The inner mould 2 is arranged in contact with the inner side 22 of the sheet 8, while the outer mould 4 is arranged in contact with the outer side 24 of the sheet 8. The moulding formations 20 of the inner and outer moulds bias a portion of the packaging sheet 8 adjacent the edge of the aperture away from the inner mould 2. Once the biasing of sheet 8 is complete, heated thermoplastic material is injected into mold cavity 10 to form opening device 26 secured to sheet 8 at hole edge 12, as shown in fig. 3. Biasing the sheet 8 away from the inner mould ensures that a portion 28 of plastics material is formed on a portion 30 of the inner side 22 of the sheet 8 which is located adjacent the aperture edge 12.

Since the sheet is correctly clamped during the injection process with the hole edges in the offset position, the offset of the sheet 8 and the reliable shaping of the plastic material portion 28 in the mould cavity 10 provide consistency and reliability in the correct position of the sheet 8 relative to the opening arrangement 26. Furthermore, the shaping of the plastic material portion 28 in the vicinity of the hole edge 12, at the portion 30 on the inside of the sheet, provides an excellent seal at the hole edge and on the inside of the sheet, which contributes very well to ensuring that the contents do not come into contact with the inner layer of the sheet when this is designated as the food-contact surface of the finished packaging container.

The moulding profiles 20 of the inner mould 2 and the outer mould 4 comprise the edge of the outer mould 4 which is in contact with the outer side 24 of the packaging sheet 8 at a first contact line 32, and the edge of the inner mould 2 is in contact with the inner side 22 of the packaging sheet 8 at a second contact line 34, whereby the first contact line 32 is arranged further away from the hole edge 12 than the second contact line 34. The sheet 18 is pressed inside the thin space 18 formed between the outer and inner dies, the spatial arrangement of the first contact line 32 and the second contact line 34 causing the portion 8a of the sheet 8 adjacent to the hole edge 12 to bend at an angle relative to the plane of extension of the sheet, which is arranged substantially outside the die cavity 10, thereby biasing the portion 8a of the sheet away from the inner die 2.

Fig. 2 shows that at the molding station, the molding contours 20 of the inner and outer molds are such that the hole edges 12 of the sheet 8 substantially contact the outer mold 4. In this way, during the injection of the thermoplastic plastic material, the plastic material is not moulded on the outer surface 24 of the sheet 8, as shown in fig. 3. However, it is possible to shape the outer mould tool 4 such that the hole edges 12 do not contact the outer mould tool 4 even when the sheet portion 8a is biased away from the underlying inner mould tool 2. In this case, the opening device formed by the step of injection moulding of thermoplastic plastic material comprises portions of plastic material covering the inner and outer surfaces of the sheet adjacent the edges of the aperture. Fig. 3 also shows that a small plastic material portion of the opening arrangement 26 is formed in the interspace 18 between the inner mould 2 and the inner side 22 of the sheet 8, and that it is generally moulded in a high-pressure injection moulding step. However, the sheet material 8 in the compression gap 18 is sufficient to form an effective seal, which is sufficient to prevent significant leakage of heated thermoplastic material through the gap 18 to the outside of the mold cavity 10.

In the embodiment shown in fig. 1-3, the sheet portion 8a is biased away from the inner mould 2, while it is conceivable that the sheet portion 8a can be biased away from the outer mould 4 by changing the relative position between the contact lines 32 and 34, i.e. if desired, the first contact line 32 can be located closer to the location where the second contact line 34 is located from the hole edge 12. The particular relative spacing of the lines of contact that determine the extent and direction of bending of the sheet portion 8a, with respect to the edge of the hole in the sheet, and the particular profile of the mould cavity formed by the mould thus determine the moulding position of the plastic material, which will determine the particular position of the sheet portion 8a in the mould cavity at the moulding station, thus ensuring that the required connection and positioning between the opening device and the sheet is effectively obtained.

FIG. 4 illustrates another embodiment of the present invention which includes molding configurations 120 of inner mold 102 and outer mold 104 disposed at the molding station such that inner mold 102 contacts inner side 22 of sheet 8 and outer mold 104 contacts outer side 24 of sheet 8 to compress sheet 8 in the mold-defined thin void 118 and to seat hole edge 12 in the mold cavity 110 defined by the inner and outer molds. In the moulding configuration 120 formed by inner mould 102 and outer mould 104 of the moulding station, the portion 8a of the packaging sheet 8 adjacent to the hole edge 12 is also biased away from the inner mould 102. Once the biasing of sheet 8 is complete, the heated thermoplastic material is injected into mold cavity 110 to form opening device 126 secured at hole edge 12 of sheet 8, as shown in fig. 5. The sheet portion 8a is offset, away from the inner mould, which ensures that the plastic material portion 128 is moulded over the portion 30 of the inner side 22 of the sheet portion 8a adjacent the hole edge 12. Since the sheet material is correctly clamped during the injection process, the sheet material portion 8a is offset within the mould cavity 110 and the reliable shaping of the plastic material portion 128 provides consistency and reliability with respect to the correct position of the sheet material 8 with respect to the opening arrangement 26. The shaping of the portion 128 of plastics material at the hole edge 12 at the portion 30 of the inner side of the sheet in the vicinity of the hole edge 12 provides an excellent seal at the inner side of the sheet and at the hole edge of the inner side of the sheet, which helps to ensure that the contents do not come into contact with the inner layer of the sheet when this is designated as the food-contact surface of the finished packaging container.

In the void 118 of the moulding formation 120 formed between the inner mould tool 102 and the outer mould tool 104 there is an extension which lies in a plane which is angled to the direction of extension of the mould cavity and away from the inner mould tool 102 so as to cause the sheet portion 8a to be biased sufficiently away from the inner mould tool 102 that a portion of plastics material is reliably formed in the inner portion 30 of the sheet. In the embodiment shown in fig. 4 and 5, the contact lines, i.e. the edges of the inner and outer mould contact surfaces of the sheet 8, are arranged substantially opposite each other, so that no bending of the sheet portion 8a relative to the interspace 118 occurs. Rather, the extension of void 118 itself effectively biases sheet portion 8a away from inner mold 102, ensuring that opening device 126 is attached and positioned as desired on sheet 8. It is also conceivable to combine the bending action of the sheet portion 8a, which can be obtained in the manner described in connection with the embodiment of fig. 1-3, by forming lines of contact spaced apart from each other between the edges of the inner and outer mould tools and between the inner and outer surfaces of the sheet, using an angularly extending configuration of the sheet portion 8a in the mould cavity 110, which is formed by an extension of the void 118, such combination of bending actions of the sheet portion 8a will form a biasing action on the sheet portion 8a in the mould cavity, thereby obtaining the desired positioning of the opening device on the sheet.

Fig. 4 shows that at the molding station, the hole edges 12 of the sheet 8 are slightly removed from the outer mold 104 located above it. However, this slight space ensures that the heated thermoplastic material entering the mold cavity 110 pushes the sheet portion 8a into contact with the outer mold during the injection molding stage, and therefore, the plastic material is not molded on the upper side of the sheet 8.

Fig. 6 shows a variation of the embodiment of fig. 4 and 5, in which the inner mold 202 and the outer mold 204 form a molded configuration 220 that includes angularly extending voids 218 to bias the sheet portion 8a away from the inner mold 202 in the mold cavity 210, the space between the sheet portion 8a and the outer mold 2004 being sufficiently large to form, after the stage of injecting the thermoplastic material, an opening device 226 that includes a plastic material portion 236 disposed on an outer side 238 of the sheet portion 8a, and a plastic material portion 228 disposed on an inner side 230 of the sheet portion 8 a.

In the embodiment shown in fig. 4-6, the sheet portion 8a is biased away from the inner mold, while it is envisioned that the sheet portion 8a could be biased away from the outer mold by changing the direction of the extension of the molded configuration void, if desired. The particular extension of the void of the moulding configuration thus determines the direction of extension of the sheet portion, the particular profile of the mould cavity formed by the mould relative to the edge of the hole in the sheet determines the portion of plastic material to be shaped and the particular position of the sheet portion in the mould cavity at the moulding station, thus ensuring that the final effective attachment and positioning of the opening device on the sheet is obtained.

Claims (5)

1. A method of injection moulding a plastics material part at a hole in a packaging sheet material, the hole defining a hole edge of the packaging sheet material, comprising the steps of:

providing at least one first mould tool contacting a first side of the packaging sheet and at least one second mould tool contacting a second side of the packaging sheet, thereby forming a mould cavity between the first and second mould tools in such a way that the aperture edge is located inside the mould cavity and that the aperture edge and a part of the packaging sheet adjacent to said aperture edge are biased away from the second mould tool;

injecting a plastic material into the mold cavity to form the plastic material part, whereby the biasing of the sheet portion away from the second mold facilitates forming a structure of the plastic material on a portion of the second side of the sheet portion; and

the first and second dies are arranged such that the portion of the packaging sheet in contact with the first and second dies is under pressure relative to the portion of the packaging sheet arranged in the die cavity.

2. The method of claim 1 including forming a mold cavity having:

a first line of contact spaced from the edge of the aperture at which the edge of the first die contacts the first side of the packaging sheet;

a second line of contact spaced from the edge of the aperture at which the edge of the second die contacts the second side of the packaging sheet;

wherein the first contact line is arranged at a greater distance from the edge of the hole than the second contact line, thereby biasing the sheet portion away from the second die.

3. An apparatus for injection moulding a plastics material part into an aperture in a packaging sheet, the aperture defining an aperture edge of the packaging sheet, comprising first and second moulds arranged to co-operate with one another at a moulding station relative to the packaging sheet such that the packaging sheet is sealingly disposed between the first and second moulds and forms a mould cavity formed by the first and second moulds in which at least a portion of the aperture edge of the packaging sheet is located, wherein at the moulding station the first and second moulds have a moulding formation such that the aperture edge and a portion of the packaging sheet adjacent the aperture edge are biased away from the second mould to assist moulding of the plastics material on a portion of the second side of the sheet portion and at the moulding station the moulding formation comprises a void formed between the first and second moulds to receive the packaging sheet in sealed form, wherein the width dimension of the void is smaller than the thickness of the packaging sheet, whereby, at the moulding station, the packaging sheet in said void is under compression.

4. The apparatus of claim 3, wherein: the molding configuration of the first and second molds in the molding station includes: an edge of the first die contacting the first side of the packaging sheet at a first contact line spaced from the edge of the hole, and an edge of the second die contacting the second side of the packaging sheet at a second contact line spaced from the edge of the hole, such that the first contact line is arranged at a greater distance from the edge of the hole than the second contact line, thereby biasing the sheet portion away from the second die.

5. The apparatus of claim 4, wherein: the space formed between the first and second dies has an extension for compressing the packaging sheet, which plane extends at an angle into the die cavity in a direction extending away from the second die.