HK1024665B - Apparatus and method for moulding an opening device on a packaging sheet - Google Patents

Description

Apparatus and method for molding opening devices on packaging sheet material

Technical Field

The present invention relates to an apparatus and a method for injection moulding opening devices of plastics material directly at the holes of a packaging sheet. The term "opening device" as used herein refers to a variety of opening devices used for pouring liquid contents from a container, and also includes opening devices that can be used for filling a container.

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 fixed to the wall portion, for example by means of an adhesive, surrounding the hole by the periphery of the base, the cover element being hinged to the base. 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.

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.

In US-4725213, the injection channel extends from the injection head, which extends a considerable distance along one surface of the web, up to one end of the mould cavity, thus forming an opening device, which has a number of disadvantages. Because the injection channel enters the mold cavity at one end, it is difficult to completely fill the mold cavity with heated thermoplastic material, and the injection molding of the portion of the mold cavity remote from the injection channel is extremely inefficient. Furthermore, if the injection channel extends too long along one side of the sheet, filling of the mould cavity is made very difficult and extremely inefficient, and therefore the apparatus and method are limited to moulding the opening device substantially only close to the edge of the sheet, where the injection head is positioned. Furthermore, forming the band of plastic material inside the injection channel necessitates the addition of a further step in order to eliminate such band, thereby reducing productivity and leading to the possibility of damaging the opening devices due to the necessity of eliminating such band. Further complicating the surface treatment of the sheet of packaging material is that it is generally very little rigid and resistant to the elevated pressures and temperatures of the thermoplastic material injected into the injection channel.

The above-mentioned difficulties in completely filling the mould cavity may lead to the situation that the plastic material will not flow to all parts of the mould cavity, as a result of which the opening edge cannot be effectively sealed by the opening arrangement of the plastic material. The packaging sheet 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 to form the surface in contact with the contents. Other possible material layers such as ink layers, composite layers and aluminum foil layers may be disposed between the paper layer and the outer 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, and unless this edge is suitably sealed by an opening device of injection moulded thermoplastic material, the packaged contents may come into contact with the inner layer of the packaging sheet, causing them to be damaged. Furthermore, when it is desired to have increased time for each molding operation in which the heated thermoplastic material is injected, in order to ensure proper filling of the mold cavity, the overall efficiency of the apparatus and method is reduced.

In US-4725213, the die consists of a pair of dies which can move in an opening and closing direction, the direction of movement of which is perpendicular to the direction of extension of the sheet. This mechanism substantially limits the adaptability of the forming die to the forming of different shapes of opening devices, since the die cannot encounter any part of the opening device projecting in a direction perpendicular to the direction of movement of the die. The injection moulded opening device of US-4725213 does comprise a pull tab extending in a direction perpendicular to the sheet material, for which long extension the grip of the user is facilitated. Such an extended protruding pull tab has disadvantages for storage and transport of packaging containers with opening devices of this type.

It is particularly desirable to have an opening device having a base portion that connects the openings of the sheet material and a lid portion that is located slightly above the plane of the base portion and the packaging sheet material. These lid portions have edges or lips parallel to the plane of extension of the packaging sheet for the user to grip and open the opening device. The apparatus of US-4725213 cannot form this type of opening device because of the opening movement of its mould.

There is also a need for an apparatus and method that enables injection moulding of an opening device of thermoplastic material on a packaging sheet material, which ensures a high efficiency and good results in the moulding of the opening device.

Summary of The Invention

According to a preferred aspect of the present invention, there is provided an opening device moulding apparatus for injection moulding an opening device of plastics material at a hole in a packaging sheet material, comprising: a molding station of an opening device; at least one first mold positionable in a closed position to contact the first side of the sheet positioned at the molding station of the opening device and positionable in an open position to be positioned away from the first side of the sheet positioned at the molding station of the opening device; at least one second mold, which can be set in a closed position so as to be in contact with the second side of the sheet positioned at the molding station of the opening device, and which can be set in an open position so as to be positioned away from the first side of the sheet positioned at the molding station of the opening device; wherein in the closed position of the first and second molds a mold cavity is formed between the first and second molds for at least partially receiving the aperture edge of the sheet material positioned at the molding station of the opening device; an injection channel for injecting heated thermoplastic material into said mold cavity, wherein said injection channel extends in at least one of said first and second molds such that thermoplastic material is injected directly into the mold cavity at an injection point of the mold cavity, said injection point being located away from an aperture edge of a sheet material received in the mold cavity; a drive mechanism selectively movable between open and closed positions for moving the first and second molds; at least one of the first and second molds comprises a pair of mold halves; it is characterized in that the driving mechanism comprises: a drive for simultaneously driving the half moulds to move from the open position to the closed position, or vice versa, so that between the open and closed position, the direction of movement of each half mould comprises a component of direction parallel to the plane of extension of the sheet and a component of direction perpendicular to the plane of extension of the sheet, the directions of movement of the half moulds being tangential to each other in the vicinity of the closed position.

Because the injection point is located away from the edge of the hole, it is advantageous for the heated thermoplastic material to enter the mold cavity at this injection point, which makes the filling of the mold cavity with good effect and high efficiency. The heated plastic material will initially flow smoothly and evenly from the injection point away from the edge of the hole, which enables a continuous filling of the mould cavity so that the heated plastic material comes into contact with the edge of the hole at the end of the injection process. The efficiency of the molding operation of the opening device is improved due to the reduction in time required for each injection process.

According to a most preferred aspect of the invention, the injection point is arranged in a cover-forming part of the mould cavity, which is in a substantially central position with respect to a base-forming part of the mould cavity, and the injection channel extends in one of the moulds in a direction substantially perpendicular to the direction of extension of the cover-forming part in the mould cavity. For this configuration, the efficiency of the material flow is greatly improved, the material flow initially flows away from the orifice edge in a symmetrical and uniform manner from the injection point and can continuously fill the base molding portion of the mold cavity. This configuration also avoids the flow of heated thermoplastic material, which can adversely affect the surface of the sheet.

Due to the construction of the drive mechanism, it is possible to obtain good results with directly moulded opening devices having various shapes, including, in particular, a part projecting in a plane and an extended part, the plane being parallel to the plane of extension of the sheet. Furthermore, this particular configuration of the drive mechanism allows the half-moulds to be brought into contact with each other in the closed position, which is positioned close to each other, so as to reduce the wear of the half-moulds. According to the most preferred embodiment, the drive mechanism is constructed so that the movement direction of the mould halves between the open and closed position varies tangentially along a circular trajectory, so that the space required for the moulding equipment of the opening device can be reduced, thereby reducing the wear of the mould halves.

According to another aspect of the present invention there is provided a method of injection moulding an opening arrangement of plastics material directly at a hole in a packaging sheet material, the hole having a hole edge, comprising the steps of: moving at least one first mould from an open to a closed position into contact with a first side of the packaging sheet and at least one second mould from an open to a closed position into contact with a second side of the packaging sheet, thereby forming a mould cavity between the first and second moulds in such a way that at least a part of the edge of said aperture is located inside the mould cavity; injecting a plastic material into the mold cavity so as to form an opening device for the plastic material, wherein the plastic material is injected directly into the mold cavity at an injection point of the mold cavity, the injection point being located away from the portion of the aperture edge; the method includes providing a pair of half molds defining at least first and second molds; it is characterized by comprising: moving the half-moulds to define, between an open position and a closed position, a direction of movement of each half-mould comprising a component of direction parallel to the plane of extension of the sheet and a component of direction perpendicular to the plane of extension of the sheet, the directions of movement of the half-moulds being tangential to each other in the vicinity of the closed position. 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.

Fig. 1 is a schematic view of feeding a packaging sheet in a packaging machine comprising a moulding station of an opening arrangement according to a preferred embodiment of the invention.

Fig. 2 is a perspective view of the first preferred embodiment of the present invention showing the lower portion of the molding station of the opening device.

Fig. 3 is a partial side sectional view of the opening device of the molding station of fig. 2 with the mold in an open position.

Fig. 4 is a partial side sectional view of the opening device shown in fig. 3 at a molding station with the mold in a closed position.

FIG. 4a is an enlarged fragmentary view of the detail of the sheet between the molds of FIG. 4, with the molds in a closed position, forming the mold cavities, ready for injection of the heated thermoplastic into the molds.

Fig. 5 is a partial side sectional view of an opening device at a molding station with a mold in an open position in a second preferred embodiment of the present invention.

Fig. 6 is a partial side sectional view of the opening device shown in fig. 5 at a molding station with the mold in a closed position.

FIG. 6a is an enlarged fragmentary view of the detail of the sheet shown in FIG. 6 between the molds, with the molds in a closed position, forming the mold cavities, ready for injection of the heated thermoplastic into the molds.

Best mode for carrying out the invention

Referring initially to figure 1 which shows an apparatus 2 according to the present invention, reference numeral 18 indicates a packaging apparatus for forming packaging containers from a sheet 4 of packaging material. It will be appreciated that the apparatus 2 may be incorporated in the packaging or filling apparatus 18, or that the apparatus 2 may be provided upstream of such an apparatus. The sheet 4 is fed through the packaging device 2 in a feed direction 8 by means of suitable drive means 6 a-e. The driving devices 6a-e are adapted to intermittently feed the sheet 4 at the intermittent feed portion 2a of the apparatus 2, and to continuously feed the sheet 4 at the continuous in-feed portion 2b and the continuous out-feed portion 2c, which are disposed upstream and downstream of the intermittent feed portion 2a, respectively, with respect to a feeding direction 8 of the sheet.

In the intermittent feeding section 2a, there are provided a punching station 12 for punching holes in the sheet 4, and a molding station 10 for injection molding an opening device of thermoplastic material at the holes of the sheet 4. The drive means 6a-e are adapted to intermittently feed the sheet 4 through the punching station 12 so that the sheet 4 is stopped appropriately and stops in the correct position at the punching station 12 for a sufficient time to punch a hole in the sheet 4. The drive means 6a-e are also adapted to intermittently feed the sheet 4 through the moulding station 10 of the opening device so that the holes in the sheet 4 are suitably positioned at the moulding station 10 of the opening device at a standstill for a sufficient time to mould the opening device at the holes punched in the preceding punching station 12.

The driving means 6a-e comprise continuously feeding rollers 6b and 6c, which are arranged in the continuous infeed section 2b and the continuous outfeed section 2c, respectively, for unwinding and feeding the web 4 from a roll 14 of packaging material web, and for continuously feeding the web 4 with moulded opening devices 16 to a container forming station 18, for forming the web 4 into containers and for sealing and filling the containers with contents.

The drive means 6a-e further comprise an intermittent feed roller 6a, a tension roller 6d and an idler roller 6e of the intermittent feed section 2a, which together cooperate so that the tension of the sheet 4 is kept substantially constant at the stop position at the intermittent feed section 2a, so that the operation of the die perforation and die opening devices can be performed with sufficient accuracy. Further, the special structure of the driving devices 6a-e forms a feed buffer storage section 20 and a feed buffer storage section 22. The infeed buffer storage section 20 includes a varying infeed sheet length 4b extending between the tension roller 6d and the continuous infeed roller 6b and moving vertically in direction 20' to vary the size of the infeed sheet length 4b, as shown in phantom in FIG. 1, to compensate appropriately at the interface between the intermittent feed section 2a and the continuous infeed section 2 b. Also, the outfeed buffer storage section 22 includes a varying outfeed sheet length 4c extending between the intermittent drive roller 6a and the continuous feed roller 6c and moving vertically in the direction 22' to vary the size of the outfeed sheet 4c, as shown by the dashed line in fig. 1, to compensate appropriately at the intersection between the intermittent feed section 2a and the continuous infeed section 2 c. In this manner, the supply of sheet material 4 is continuous at the roll 14 and container forming station 18. Whereas the feeding of the sheet 4 is intermittent at the punching station 12 and the moulding station 10 of the opening device.

In fig. 1, 3 punching stations 12 and 3 molding stations 10 of the opening device are depicted. Thus, in the intermittent stop position of each sheet 4, 3 holes are punched in the sheet 4 and 3 opening devices are moulded in the sheet 4. The particular number of punching stations 12 and moulding stations 10 of the opening device can be varied as desired. Furthermore, the punching station 12 and the moulding station 10 of the opening device can be moved relative to each other along the feeding extension of the sheet 4 in directions 12a and 10a, respectively, so that the holes provided in the sheet and the opening devices can be spaced relative to each other in different positions, so that packaging containers of different sizes can be formed.

In the manner described above, apparatus and methods for feeding sheet 4, punching holes in sheet 4, forming and sealing containers from sheet 4 and filling the containers with contents are well known, one example being TBA/19-SYSTEM manufactured by TETRA BRIK, Inc. of MODENA, Italy.

The location of the moulding station 10 provided with opening devices in combination with the packaging machine 2 has the advantage of providing an efficient apparatus and a continuous method for moulding opening devices continuously on a web of material supplied from a roll and for forming, sealing and filling packaging containers sequentially on the same compact production line. As is performed by existing conventional apparatus, the bonding of the separately formed and fed opening devices to the sheet material is eliminated, thereby providing an apparatus and method that saves time and costs relative to separately producing, storing and transporting the separately formed opening devices. Whilst the moulding station 10 of the opening device is particularly advantageous for the reasons described above, it is envisaged that the moulding station 10 of the opening device may operate in different ways, for example moulding the opening device on a supplied sheet and then rolling it into a roll of sheet material for later use, or for example moulding the opening device on a sheet of any type and shape of packaging material, such as a blank of packaging material, a raised flap of packaging material, etc. In addition, the packaging device 2 may also be provided in other forms, so that the roll of sheet material 14 is already provided with pre-punched perforations, so that the perforation punching station 10 is eliminated and/or the drive for the entire sheet material 4 is operated intermittently. Also, the container forming station 18 may have any number of forming and sealing packages of different sizes and shapes, as well as filling with different products to form packages.

Fig. 2-4a show a first preferred embodiment of a moulding station 10' of the opening arrangement. The molding station 10 'of the opening device comprises a first mold 20 and a second mold 22, which first mold 20 and second mold 22 are arranged in their closed position with respect to the sheet 4 so that they contact a first side 24 of the sheet 4 and a second side 26 of the sheet 4, respectively, when the sheet 4 is in the stop position of the molding station 10' of the opening device. The first die 20 and the second die 22 are arranged in their open positions with respect to the sheet 4 so as to be positioned away from the first side 24 and the second side 26 of the sheet, respectively, as shown in fig. 3, so that the sheet 4 can be fed intermittently in the direction 8.

In this particular embodiment shown, the first mold 20 comprises a single inner mold 20 that is in a fixed position during operation. The second mold 22 comprises a pair of outer mold halves 22a and 22b which are driven relative to each other between positions of opening and closing by a drive mechanism described below and relative to the sheet 4 and the inner mold 20. The inner mould 20 is arranged in contact with a first side 24 of the sheet, which first side 24 is the inside of the packaging container formed from the sheet 4, and the outer moulds 22a and 22b are arranged in contact with a second side 26, which second side 26 is the outside of the packaging container formed from the sheet 4.

With particular reference to FIG. 4a, in the closed position of inner mold 20 and outer mold halves 22a and 22b, a mold cavity 28 is formed between inner mold 20 and outer mold halves 22a and 22 b. The hole edge 30 of the hole 32 of the sheet 4, correctly positioned at the moulding station 10' of the opening device, is located within the mould cavity 28.

In this embodiment, the mould cavity 28 comprises a portion 28a for forming a lid portion of the opening device 16, a portion 28b forming a base portion of the opening device 16 for connecting said base portion with the sheet 4, and a connecting portion 28c forming a tearable edge portion of the opening device 16 of reduced thickness which helps to separate the lid portion and the base portion from each other. The disclosed construction involves many special ways in which the opening arrangement is moulded on the sheet 4 at the hole edge 30, while the opening arrangement 16 may have any different shape.

In this embodiment, the perimeter of the aperture edge 30 completely surrounds the aperture of the sheet 4, and preferably, prior to injection molding, the entire aperture edge 30 is disposed inside the base-forming portion 28b of the mold cavity 28, with the base-forming portion 28b having a perimeter dimension sufficient to completely surround the aperture edge 30. Preferably, the hole edge 30, the base-forming portion 28b and the connecting portion 28c are oval-ring-shaped in longitudinal cross-section substantially parallel to the direction of extension of the sheet 4. While the cover portion 28a is oval-shaped disc-shaped in longitudinal cross section in a longitudinal cross section substantially parallel to the extending direction of the sheet 4. In addition, at the closed molding station, a gap 34 is formed between upper and lower molds 20 and 22, preferably with the width dimension of gap 34 being less than the thickness of packaging sheet 4, whereby the molds compress sheet 4 inside gap 34 and form an effective seal to prevent any heated thermoplastic material from leaking outside of mold cavity 28.

The molding station 10' of the opening device also comprises an injection channel 36 for injecting heated thermoplastic material into the mold cavity 28. The heated thermoplastic material may be injected through the injection passage 36 using conventional methods and apparatus known to those of ordinary skill in the art.

In a preferred particular embodiment of the invention, the injection channel 36 extends in the stationary inner mold 20, the injection channel 36 being shaped such that the thermoplastic material is injected directly into the mold cavity 28 at an injection point 38 of the mold cavity 28, said injection point 38 being remote from the orifice edge 30.

Due to the provision of the injection point 38 remote from the orifice edge 30, it is advantageous for the heated thermoplastic material to enter the mold cavity at a location where the filling operation of the mold cavity is performed in a highly efficient and reliable manner. The heated plastic material initially flows smoothly and uniformly away from the orifice edge 30 from the injection point 38 and may continuously fill the base molding portion 28b of the mold cavity 28 so that the heated plastic material contacts the orifice edge 30 when the injection process is complete. The time required for each injection molding process is reduced, thereby improving the efficiency of molding the opening device.

In a particular embodiment, the injection point 38 is provided on the cover molding portion 28a of the mold cavity 28, which is located substantially centrally with respect to the base molding portion 28 b. This configuration substantially increases the flow efficiency of the material that initially flows uniformly symmetrically away from the orifice edge 30 from the injection point 38 and sequentially fills the base molding portion 28b of the mold cavity 28.

Furthermore, the direction of extension of the injection channel 36 within the inner mould 20 is substantially perpendicular to the direction of extension of the cover-forming portion 28c of the mould cavity 28, so as to avoid completely that the surface of the sheet 4 first touches the flowing heated thermoplastic material.

Between the open and closed positions, the inner mold 20 and the outer mold halves 22a and 22b are driven by the drive mechanism 40 to move relative to each other and relative to the sheet 4 and the inner mold 20. The drive mechanism 40 cooperates with the drive means 6a-e for feeding the sheet 4 and with the punching station and the station for injecting the heated thermoplastic material through the injection channel 36, so as to continuously produce the opening devices 16 moulded on the sheet 4.

The drive mechanism 40 comprises a support structure 42 which supports the outer mould halves 22a and 22b so that, in the open position, the outer mould halves 22a and 22b are spaced apart from each other along a plane of extension which is substantially parallel to the plane of extension of the sheet 4, as shown in figure 3. In the closed position, the outer mold halves 22a and 22b are positioned in contact with each other and with the second side 26 of the sheet, as shown in FIGS. 4-4 a. The drive mechanism 40 also comprises a drive 44 to move the outer half moulds 22a and 22b from the open position to the closed position, or vice versa, so that the direction of movement of the outer half moulds 22a and 22b between the open position and the closed position comprises a direction component extending parallel to the plane of extension of the sheet 4 and a direction component extending perpendicular to the plane of extension of the sheet 4.

The particular configuration of the drive mechanism 40 causes the half-shells 22a and 22b to move in the direction in which they move between the open position and the closed position, so that it is possible to effectively form opening devices of various shapes, comprising particular portions which project and extend along a plane parallel to the plane of extension of the sheet 4.

Furthermore, the particular structure of the drive mechanism 40 allows the half-shells 22a and 22b to meet and come into contact with each other from a precisely approached manner in the closed position, since the movement of each half-shell 22a and 22b may comprise a directional component parallel to the extension plane direction of the sheet 4, the movement time of which is reduced, while, in the closed position, the shells are in contact with each other. Such exact proximity of the half outer dies 22a and 22b advantageously ensures that wear of the half outer dies 22a and 22b is reduced.

In the most preferred embodiment, as shown in FIGS. 2-4, the drive mechanism 40 is configured such that the direction of movement of the outer mold halves 22a and 22b between the open and closed positions varies tangentially along a circular path. In this way, the component of the directional movement parallel to the plane of extension of the sheet 4 of the half-outer moulds 22a and 22b is reduced practically to zero in the approaching and parting phase closest to the closed position, while the component of the directional movement parallel to the plane of extension of the sheet 4 can be rapidly increased in the phase away from the closed position, so as to reduce the space required by the moulding station 10' of the opening devices, thus reducing the wear of the half-outer moulds 22a and 22b, while still maintaining the flexibility of forming opening devices for different shapes.

The support structure 42 includes a fixed bracket having a horizontal base 46 and a pair of support arms 48a-c, which support arms 48a-c extend vertically upward from the base 46. The supporting structure further comprises a pair of horizontal links 50 and 52, which are rotatably connected between lateral supporting arms 48a and 48c, respectively, and the outer mould halves 22a and 22b can be pivoted about a pivot axis which is substantially parallel to the direction of the plane of extension of the sheet 4.

The support structure 42 further includes a horizontal slide plate 54 having slots 54a with bolts 54b connecting the respective outer mold halves 22a and 22b, respectively, the bolts 54b being slidably received in the slots 54 a. The slot 54a extends within the slide plate 54 so that each of the outer mold halves 22a and 22b is slidably supported on the slide plate 54 with its sliding direction parallel to the sheet feeding direction 8.

The driving means 44 comprise a fluid-driven pressure cylinder 55 having an extending rod which is slidably passed through the fixed base 46 and connected to the slide plate 54 for reciprocating the slide plate 54 in a vertical direction, the direction of movement of which is perpendicular to the direction of extension of the sheet 4.

This particular configuration of the drive mechanism 40 causes the outer mold halves 22a and 22b to move between the open and closed positions along a circular path centered about the pivot axes of the pairs of links 50 and 52 and the side support arms 48a and 48c, respectively.

The dimensions of the outer mold halves 22a and 22b at the side support arms 48a, 48c and the pairs of tie bars 50, 52 are such that when the outer mold halves 22a and 22b are in contact engagement in the closed position, the contact force generated between the mating surfaces of the outer mold halves 22a and 22b creates a sufficiently suitable seal against the mold cavity 28 such that the heated thermoplastic material cannot leak outside of the mold cavity 28 at the location where the mating surfaces of the outer mold halves 22a and 22b are located. In accordance with another aspect of the present invention, adjustable biasing means are provided for adjustably determining the contact force between the outer mold halves 22a and 22b in the closed position.

For this purpose, the side support arms 48a and 48c are provided with through holes 56 which allow the side support arms 48a and 48c to be considerably flexible in a direction parallel to the feeding direction 8 of the sheet. A pair of tie rods 58 connect the side support arms 48a and 48 c. A pull rod 58 is slidably disposed within the central support arm 48b and an adjustment nut 58a is threadably adjustable at the end of the pull rod 58.

FIG. 4 shows that when the outer mold halves 22a and 22b are in the closed contact position, with the side support arms 48a and 48c flexed outwardly, the adjustment nut 58a will be appropriately selected in the closed position to have the desired contact force between the outer mold halves 22a and 22 b.

The structure of the support structure 42 is such that, in the closed position of the outer mould halves 22a and 22b, as shown in figure 4, the portion of the sheet 4 in contact with the outer mould halves 22a and 22b extends in a plane whose contact plane is remote from the normal extension plane of the sheet 4 when the outer mould halves 22a and 22b are in the open position, as shown in figure 3. In this way, sheet 4 is subjected to additional tension at a location spaced from the normally extended position, which helps to separate sheet 4 and molded opening devices 16 from molds 20 and 22 as molds 20 and 22 move from the closed position to the open position.

Fig. 5-6a show a second preferred embodiment of the moulding station 10 "of the opening arrangement. The molding station 10 "of the opening device comprises a first mold 20 'and a second mold 22' which are reciprocally associated in a closed position with respect to the sheet 4, the first mold 20 'and the second mold 22' being in contact with a first side 24 and a second side 26, respectively, of the sheet 4 when the sheet 4 is in a stop position in the molding station 10" of the opening device, as shown in figures 6, 6 a. The first die 20 'and the second die 22' are also cooperatively disposed relative to the sheet 4 in an open position so as to be positioned away from the first side 24 and the second side 26 of the sheet 4, respectively, as shown in fig. 5, so that the sheet 4 can be intermittently fed in the feeding direction 8. The first mold 20 'includes a separate inner mold 20' which moves in a vertical direction. The second mold 22 ' includes a pair of side outer molds 22a ' and 22b ' which are movable in vertical and horizontal directions, respectively. The inner mold 20 ' and the lateral outer molds 22a ' and 22b ' are driven by a drive mechanism described below to move relative to each other between open and closed positions relative to the sheet 4.

Referring to fig. 6a, at the closed molding station of the inner mold 20 ' and the lateral outer molds 22a ', 22b ', a mold cavity 28 ' is formed between the inner mold 20 ' and the lateral outer molds 22a ', 22b ', a hole edge 30 of a hole 32 of the sheet 4 correctly positioned at the molding station 10 ″ of the opening device being received in the mold cavity 28. The mould cavity 28 'comprises a portion 28 a' so as to form a cover portion of the opening device 16; and a portion 28b 'forming a base portion of opening device 16 connected to sheet 4, and a connecting portion 28 c' forming a tearable edge of reduced thickness of opening device 16, so as to facilitate separation of the cover portion from the base portion.

Preferably, the entire aperture edge 30 is positioned inside the base forming portion 28b 'prior to injection molding, while the perimeter of the base forming portion 28 b' is of sufficient size so that it completely encloses the aperture edge 30. Preferably, the base forming portion 28b 'and the connecting portion 28 c' are ovoid-shaped in their longitudinal cross-section, which is substantially parallel to the extension of the sheet 4. The cover forming portion 28 a' has an oval plate-like shape whose longitudinal cross section is substantially parallel to the extending direction of the sheet 4. In addition, at the closed molding station, a gap 34 ' is formed between upper and lower molds 20 ', 22 ', preferably having a width dimension less than the thickness of packaging sheet 4, thereby compressing sheet 4 inside gap 34 ' to form an adequate seal against leakage of heated thermoplastic material to the outside of mold cavity 28 '.

The molding station 10 "of the opening device also includes an injection channel 36 'for injecting the heated thermoplastic material into the mold cavity 28'. The injection channel 36 'extends within a stationary injection head 60, which has an upper end portion 60a that forms part of the second mold 22', as shown in fig. 6 a. Thus, the side outer molds 22a ' and 22b ' can be moved in a prescribed manner relative to the fixed upper end portion 60a to form the mold cavity 28 ' at the closed molding station.

The configuration of the injection channel 36 'enables the thermoplastic material to be injected directly into the mold cavity 28' at an injection point 38 'of the mold cavity 28', said injection point 38 'being located away from the orifice edge 30, whereby excellent results can be obtained as in the first embodiment of the molding station 10' of the opening device described above. Furthermore, an injection channel 36 'extends inside the outer mould tool 22' in a direction substantially perpendicular to the direction of extension of the cover-forming portion 28c 'of the mould cavity 28' and away from the surface of the sheet 4.

Between the open and closed positions, the drive mechanism driving the inner mold 20 ' and the side outer molds 22a ', 22b ' comprises a movable support bracket 62, which is peripherally disposed around the fixed injection head 60 and is movable in a vertical direction. The fixed support frame 64 supports fluid-actuated pressure cylinders 66a, 66b and 68 having rods 66a ', 66 b' and 68 ', respectively, which connect the movable support frame 62 and the inner mold 20', respectively, for reciprocating the above elements in the vertical direction. The drive mechanism also includes fluid-driven pressure cylinders 70a and 70b having rods 70a 'and 70 b', respectively, and rods 70a 'and 70 b' are connected to the side outer molds 22a 'and 22 b', respectively, to reciprocate the elements in a horizontal direction.

The cylinders 66a, 66b, 68, 70a and 70b cooperate with the driving means 6a-e for feeding the web 4, with the punching station 10, and with the station for injecting the heated thermoplastic material through the injection channel 36', so as to perform a continuous production, molding the opening devices 16 on the web 4.

Claims (7)

1. An opening device moulding apparatus (2) for injection moulding an opening device (16) of plastics material at a hole in a packaging sheet (4), comprising:

a moulding station (10) of opening devices;

at least one first mould (20) which can be set in a closed position so as to be in contact with a first side (24) of the sheet (4) positioned at the moulding station (10) of the opening device, and which can be set in an open position so as to be positioned away from the first side (24) of the sheet (4) positioned at the moulding station (10) of the opening device;

at least one second mold (22) which can be set in a closed position so as to be in contact with the second side (26) of the sheet (4) positioned at the molding station (10) of the opening device, and can be set in an open position so as to be positioned away from the first side (26) of the sheet (4) positioned at the molding station (10) of the opening device;

wherein, in the closed position of the first and second moulds (20, 22), a mould cavity (28) is formed between the first and second moulds for at least partially receiving a hole edge (30) of the sheet (4) positioned at the moulding station (10) of the opening device;

an injection channel (36) for injecting heated thermoplastic material into said mold cavity (28), wherein said injection channel (36) extends in at least one of said first and second molds such that thermoplastic material is injected directly into the mold cavity (28) at an injection point (38) of the mold cavity located away from a hole edge (30) of a sheet material received within the mold cavity (28);

a drive mechanism (40) selectively movable between open and closed positions for moving the first mold (20) and the second mold (22);

at least one of the first and second molds (20, 22) comprises a pair of half molds (22a, 22 b);

it is characterized in that the driving mechanism comprises: -a drive (44) for simultaneously driving the half moulds (22a, 22b) to move from the open position to the closed position, or vice versa, so that between the open and closed position the direction of movement of each half mould (22a, 22b) comprises a component of direction parallel to the plane of extension of the sheet (4) and a component of direction perpendicular to the plane of extension of the sheet (4), the directions of movement of the half moulds (22a, 22b) being tangential to each other in the vicinity of the closed position.

2. The apparatus of claim 1, wherein: the drive mechanism is configured such that each mold half (22a, 22b) follows a circular path trajectory between open and closed positions.

3. The apparatus of claim 1 or 2, wherein: the drive mechanism (40) includes: -a support structure (42) supporting the half-moulds (22a, 22b) so that, in the open position, the half-moulds (22a, 22b) are spaced apart from each other along a plane extending parallel to the extension plane of the sheet (4), and, in the closed position, said half-moulds (22a, 22b) are in contact with each other and with the second side (26) of the sheet.

4. The apparatus of claim 3, wherein: in the closed position, the sheet (4) extends in a plane which is remote from the plane of extension of the sheet (4) in the open position.

5. The apparatus of claim 3, wherein: adjustable biasing means (48a, 48c, 58, 58a) are also provided to adjust the contact force between the mold halves (22a, 22b) in the closed position.

6. A method of injection moulding an opening device (16) of plastic material directly at a hole in a packaging sheet (4), the hole having a hole edge (30), comprising the steps of:

-moving at least one first mould (20) from an open to a closed position in contact with a first side (24) of the packaging sheet, and moving at least one second mould (22) from an open to a closed position in contact with a second side (26) of the packaging sheet, thereby forming a mould cavity (28) between the first and second moulds (20, 22) in such a way that at least a part of said aperture edge (30) is located inside the mould cavity (28);

injecting plastics material into the mould cavity (28) so as to form an opening arrangement (16) of plastics material, wherein the plastics material is injected directly into the mould cavity (28) at an injection point (38) of the mould cavity (28), the injection point being located away from the portion of the aperture edge;

the method includes providing a pair of mold halves (22a, 22b) defining at least first and second molds;

it is characterized by comprising: -moving said half-moulds (22a, 22b) so as to define, between an open position and a closed position, a direction of movement of each half-mould (22a, 22b) comprising a component of direction parallel to the plane of extension of the sheet (4) and a component of direction perpendicular to the plane of extension of said sheet (4), the directions of movement of said half-moulds (22a, 22b) being tangent to each other in the vicinity of the closed position.

7. The method of claim 6, wherein: the movement of each half-mould (22a, 22b) between the open and closed positions is a circular path trajectory.