BRPI0612639A2 - device and method for sealing a thermoplastic-coated packing material tube - Google Patents

Abstract

DEVICE AND METHOD FOR TRANSVERSAL SEALING OF A TUBE OF MATERIAL FOR PACKAGING COATED WITH THERMOPLASTIC. A device (10) and a method for cross-sealing a tube (12) of material for packaging coated with thermoplastic are provided. The tube is formed by an overlap joint seal (14) between two mutually opposite edge sections (26, 28) of a sheet of material for packaging. The device includes opposing first and second jaws (16, 18) having first and second main sealing surface (20, 22), respectively. The tube is placed to be extended flat and pressed between these main sealing surfaces to heat the thermoplastic there and obtain a transverse seal along the main sealing line (24) of the tube. The device is characterized by the fact that it is placed to penetrate the outer edge section (28) of the joint overlapping along the main sealing line before sealing to allow the first main sealing surface (20) to contact the edge section internal (26) of the overlap joint.

Description

1

"DEVICE AND METHOD FOR CROSS SEALING OF A THERMOPLASTIC COATED PACKAGING MATERIAL"

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a device and method for transverse sealing a thermoplastic coated packing material tube, the tube being formed by sealing a joint overlapping two mutually opposite edge sections of a sheet of material. packaging. The device includes first and second opposing jaws, having first and second main sealing surfaces, respectively, between which the tube is placed to be flat extended and pressed to heat the thermoplastic between the main sealing surfaces and obtaining a transverse sealing along main pipe sealing line.

ART GROUNDS

In packaging technology, packaging has long been used to package and transport products such as milk, juices and other perishable products. A large group of such packages are made from a laminated packaging material including a core layer of, for example, paper or cardboard and an outer, liquid-tight thermoplastic material coating at least on that side of the core layer which forms the inner part of the packaging. Sometimes the material also includes a gas barrier, for example in the form of an aluminum layer.

Such packaging containers are often produced in the form in which a spool of packaging material is formed in a tube sealing the longitudinal overlapping edges of the spool. The longitudinally sealed tube is continuously fed with a product and formed as pads. The seal is made of separate narrow along, transverse and mutually spaced seal zones. Transverse sealing of the pipe takes place in a manner substantially known per se, with right angles in the longitudinal direction of the pipe and constantly in the same plane. The sealing portions of the pipe thus containing contents are hereinafter separated from the pipe by incisions in these sealing zones.

In a machine known for producing packages such as those described above, the pipe sealing is effected by placing the pipe between two opposing jaws. Each jaw includes a sealing bar, the tube being extended flat and pressed between those sealing bars to heat the thermoplastic material in the sealing zone and obtain the sealing. The area where the longitudinal seal intersects with the transverse seal zone will contain three layers of packing material instead of common number two. So this area will be critical when sealing, especially in connection with some sealing techniques, such as ultrasonic sealing. Suitably, to perform essentially constant pressure throughout the entire transverse sealing zone, and thus a good transverse sealing, the jaw in contact with the intersection between longitudinal sealing and the transverse sealing zone may be constructed to have an opening slightly wider than the width of the longitudinal seal.

When the longitudinal seal is optimally aligned, the opening provides pressure substantially along the transverse seal zone upon receiving the third outer layer of material for packaging the longitudinal seal. On the contrary, if the longitudinal seal is somehow compensated from its optimal alignment, e.g. g. By the pivoting tube, the longitudinal seal may be positioned partially along a portion of the jaw external to the opening during transverse sealing and thus be subjected to much higher pressure. Similarly, the transverse sealing zone outside the longitudinal sealing intersection may be positioned partially along a portion of the jaw within the opening during the transverse sealing and thus be subjected to insufficient pressure. Very high pressure as well as insufficient pressure can negatively affect the transverse seal, a correct alignment of the longitudinal seal with respect to the jaws and is therefore of great importance.

However, to make this correct alignment, precise adjustments need to be made by an operator, which can be both time consuming and cumbersome.

Additionally, as mentioned above, to be able to achieve substantially uniform pressure, the opening must be slightly wider than the longitudinal seal. As shown in the discussion above, the desired pressure is not obtained with an opening being too wide or too narrow. Therefore, the use of a jaw supplied with a fixed width opening is limited to the cross sealing of pipes with a certain longitudinal sealing width. Consequently, in an environment where pipe types with different widths of longitudinal seals must be transversely sealed, grips with openings of different widths must be provided.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a device and method for cross sealing, which device and method at least partially eliminate potential limitations of the prior art. The basic concept of the invention is to penetrate the outermost layer of the three layers at the intersection between the longitudinal seal and the pipe cross sealing area prior to the pipe sealing to obtain the same material thickness, and thus essentially the same quality. in this intersection area as in the rest of the cross sealing area. The device and method for achieving the above objective are defined in the appended claims and discussed below.

A device for transverse sealing a thermoplastic-coated packing material tube, the tube being formed by sealing an overlap joint between two edge sections of a mutually opposing packaging material sheet in accordance with the present invention includes first and opposing second jaws having first and second main sealing surfaces respectively. The tube is placed to be flat extended and pressed between these first and second main sealing surfaces to heat the thermoplastic therein and obtain a transverse seal along the main sealing line of the tube. The device is characterized in that it is placed to penetrate the outer section of the overlap joint along the main sealing line before the seal allows the first main sealing surface to contact the inner edge section of the overlap joint.

By transverse seal is meant to seal through another existing seal, i.e. in the intersection area between two seals.

In the manufacture of packages of the type described above, the joint overlap corresponds to the longitudinal seal, and the main seal line corresponds to the transverse seal zone.

The foil may be included in a spool to form a portion thereof, and the device may be placed for cross sealing of this spool. Such an alternative could be particularly useful in connection with a manufacturing method such as that initially described.

By main sealing line is meant that the transverse line along the flat extended package in which a continuous seal is to be obtained.

By inner edge section is meant the edge section placed to be on the inside of the pipe. Similarly, "outer edge section" means the edge section placed to be outside the pipe.

By penetrating the outer edge section of the overlap joint prior to sealing, the first main sealing surface can transfer power directly to the inner edge section of the overlap joint to obtain a seal between this inner edge section and the opposite pipe wall. extended flat. Thus, the energy need not be transferred first through the outer edge section, and can therefore be used more effectively.

An advantage with the device according to the present invention is that the positioning of the overlap joint with respect to the jaws during sealing becomes less critical since the overlap joints need not be placed in an opening or the like. Another advantage is that the same inventive device can be used in connection with cross sealing of different pipe types with varying widths of overlap joints.

According to one embodiment, the jaws are arranged to interact so as to achieve essentially uniform pressure along the main sealing line when the main sealing surfaces are disposed in parallel. This is possible since penetration of the outer edge section results in the thickness of the material pressed between the jaws being essentially constant along the length of the main sealing line. This configuration resembles a transverse sealing situation of a packing material tube with no overlap joints (longitudinal sealing) where the problems initially described are no longer present.

The device may be constructed to be disposed to penetrate the outer edge section of an overlap joint by cutting it to form a tab of cushioning material which may shift to expose the inner edge section of the overlap joint. to the first main sealing surface. By creating such a tab, material for wrapping the outer edge section which is "on its way" to the first main sealing surface can be moved "out of the way" to effect the transverse seal without being permanently removed from the pipe. This is advantageous since no unnecessary loss will be produced that requires particular control. Instead, the flap will be a part of the final packaging without affecting its performance.

In a configuration as described above, the device may additionally include a receptive space for receiving the flap for uncovering the outer edge section along the main sealing line during sealing. The receiving space may be formed in numerous different ways, for example as a notch along the first main sealing surface. In such a case, the notch should preferably have a length and width slightly greater than the length and width of the flap. Additionally, the receiving space could be placed to be positioned opposite the overlap joint prior to penetration of the outer edge section of the overlap joint. This is advantageous as it can allow automatic reception of the tab in the receiving space in connection with penetration of the outer edge section.

According to one embodiment, the first claw of the inventive device includes penetration devices for penetrating the outer edge section of the overlap joints prior to sealing. The penetration means may be formed in numerous different ways, for example as a tapered part of the first main sealing surface. This configuration is advantageous as it allows relatively less complicated and stable construction of the device. Additionally the penetration device could be placed to be positioned opposite the overlap joints prior to the penetration of the outer edge section of the overlap joint. This is advantageous as it can allow automatic penetration of the outer edge section when the jaws approach each other to press the material for wrapping.

According to one embodiment, the first jaw additionally includes a recess on one side of the main sealing surface, the recess being placed to receive a portion of the one-sided overlap joint corresponding to the main sealing line during penetration and sealing. By this recess, which corresponds to the opening described in the paragraph above entitled Base of Art, the pressure exerted on the overlap joint may be reduced to achieve a defined transverse seal.

The device according to the present invention is applicable in connection with different types of techniques for cross seals, for example, ultrasonic seals and hot sealing. When used in connection with ultrasonic sealing, the first claw is an anvil and the second claw is an ultrasonic comet.

A method for cross sealing a thermoplastic-coated packing material tube, the tube being formed by sealing an overlap joint between two mutually opposing edge sections of a packing material sheet according to the present invention includes pressing the pipe in a flat extended condition between first and second main sealing surface of the first and second opposite jaws, respectively; to heat the thermoplastic between the main sealing surfaces and obtain a transverse seal along the main sealing line of the pipe. The method is characterized by additionally including penetration into the outer edge sections of the overlap joint along the main sealing line before sealing to allow the main sealing surface of the first jaw to contact the inner edge section of the overlap joint.

The features discussed in connection with the cross sealing device are of course transferable to the cross sealing method. Additionally, these features can of course be combined in the same configuration.

BRIEF DESCRIPTION OF DRAWINGS

The invention will now be described in more detail with reference to the accompanying schematic drawings which show an example of a presently preferred limitless embodiment of the present invention.

Fig. 1 is a perspective view of a cross sealing device according to the present invention.

Fig. 2 is a perspective view of a portion of a packaging material tube which should be flat extended and sealed transversely by means of the devices according to fig. 1.

Fig. 3 is a partial cross section of the tube shown in fig. 2 in a flat extended condition.

Fig. 4a is a front view partially showing the anvil of the device according to fig. 1 in more detail.

Fig. 4b is an amplification of the enclosed area in fig. 4th

Fig. 4c is a cross section of the anvil taken along line A-A in fig. 4b.

Fig. 4d is an amplification of the enclosed area in fig. 4c.

Fig. 5 is a cross section illustrating the operation of the device according to fig. 1

Fig. 6 is a front view of a portion of the pipe portion in fig. 2 after cross sealing and separation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Fig. 1 illustrates a device 10 for cross sealing a tube 12 of packaging material, a portion of which is illustrated in FIG. Pipe 12 is formed by longitudinally sealing an overlap joint 14 between two mutually opposite terminating sections of a spool of packing material. The packaging material is of the type initially described, i.e. a laminated packaging material including a core layer of paper coated on both sides with thermoplastic material. Thus, the overlap joint sealing can be achieved by heating the thermoplastic material at the interface between the overlap edge sections according to any suitable sealing technique.

Device 10 is an ultrasonic sealing device working in accordance with well-known principles for transverse sealing of tube 12. This includes two opposing claws serving as an anvil 16 and an ultrasonic comet 18. As will be described in greater detail herein. details below, the tube 12 is placed between the anvil and the comet and locally extended flat and pressed between the main sealing surfaces 20, 22 at regular intervals to obtain transverse seals along the main sealing lines 24. Main sealing is not fixed, but is defined by the location of the main sealing surfaces in relation to the pipe. Thus, the main sealing lines are not printed on the pipe as it would appear in FIG. 2, but only imaginary and drawn there for illustrative purposes.

Fig. 3 illustrates in part the appearance of the pipe cross section along a main seal line where the pipe is extended flat and pressed. As apparent from the figure, the thickness of the material along the cross section is twice the thickness of the wall anywhere except for the area of the joint 14 where the thickness of the material instead is triple the thickness of the wall due to overlap, outer and inner edge sections 26, 28 respectively. As described initially, this triple wall thickness area, or more particularly the transitions between double and triple the wall thickness areas, will be critical when reaching the transverse seal. For this reason, the device is built as described below.

Fig. 4a-d are views illustrating anvil 16 in more detail. Since the device is constructed to produce two transverse seals simultaneously, an upper transverse seal of one package and a lower transverse seal of another package, as is well known in the art, the anvil is constructed accordingly.

Of course, as is the ultrasonic comet which however is not described here in detail. Thus, the anvil 16 includes base surfaces 30, main sealing surfaces 20 being raised above respective base surfaces. The main sealing surfaces 20se continuously extend through essentially the entire length of the anvil with a constant width except at an intermediate part 17 of the anvil where the main sealing surfaces are tapered and have a reduced width. In addition, like the rest of the main sealing surfaces 20, taking part in the tube transverse seals by interacting with the corresponding main sealing surfaces 22 of the ultrasonic comet 18, the tapered parts are arranged to function as penetration devices 32 for cutting outer edge section 28 in connection with cross seal as will be described below.

Additionally, the anvil 16 includes a recess 34 in the intermediate portion 17 of each of the base surfaces 30 for receiving the overlap longitudinal seal in connection with the transverse seal. Additionally, the biome 16 includes sealing sub surfaces 36, also placed on the intermediate part 17 of the biome. The main sealing surfaces 20 are raised above the sealing sub surfaces36, the sub surfaces in turn being raised above the base surfaces 30. When the pipe 12 is extended flat and pressed between the main sealing surfaces 20, 22 to To obtain transverse seals along the main sealing lines 24, the anvil sub-surfaces 36 are arranged to interact with corresponding sealing sub-surfaces 38 (shown in FIG. 5) to the ultrasonic comet 18 to obtain seals along the sub-lines. Imaginary sub-sealing lines are shown in Figure 2. Anvil 16 additionally has notches receiving spaces 42 in the intermediate part 17 of the anvil between the corresponding pair of penetration means 32 and sealing sub-surface 36. The function of these receiving spaces will be described below. Finally, the anvil 16 includes a groove 43 extending along and between the main sealing surfaces 20. A knife 44 (shown in fig. 5) is placed to run in this groove and a corresponding groove 46 in the ultrasonic comet for separate the unsealed portions of the pipe as mentioned initially.

Fig. 5 is a cross-sectional view taken in the area outside the intermediate part 17 of the anvil 16, illustrating the operation of the device 10. Fig. 6 is a front view of an insulated and unsealed portion of the tube 12. The following description is directed to transverse sealing of this part of the tube which is obtained with a "half" of the inventive device. In connection with packaging manufacturing, the continuously longitudinally sealed tube which is filled with the desired product is fed in the direction denoted P along an axis A. The anvil 16 and the ultrasonic comet 18 are placed opposite each other. another with tube 12 between them. At regular intervals the pipe 12 should be transversely sealed by ultrasonic sealing. The anvil 16 and the ultrasonic comet 18 then approach each other to contact the tube along the main sealing surfaces 20,22 and sealing sub surfaces 36,38. As the bigoma and comet move closer together, the tube 12 is extended flat and pressed. The longitudinally overlapping joint 14 is placed directly opposite the anvil intermediate part 17 and received in the recess 34. With continuous pressing, the penetrating device 32 cuts through the outer edge section 28 of the joint 14 along a cutting line 48. and contacts the outer edge section 26 of the joint, whereas sealing sub-surface 36 contacts the outer edge section 28 of the joint. At this time, the main sealing surfaces 20 22 are placed in parallel and they interact to create essentially uniform pressure along the main sealing line 24. This is possible as long as the thickness of the material along the entire main sealing line is constant and equal to twice the wall thickness. The thickness of the material along the sealing subline 40 is three times the wall thickness but this is offset by the distance between the sealing sub surfaces 36, 38 being greater than the distance between the main sealing surfaces 20, 22.

Although not apparent in the figures, the penetration device 32 is wider than the overlap joint 14. However, the cut will stop after penetration of the outer edge section, i. e. when constant material thickness has been obtained between the main sealing surfaces, leaving the remainder of the packaging material undamaged. Because the penetration device is wider, the positioning of the joint relative to the device is less critical. Also, one and the same device with a relatively wide penetration device can be used for cross sealing of pipes with different widths of overlap joints.

Then, in connection with cutting the outer edge section 28, a tab 50 of wrapping material is created. The flap 50 is forced into the corresponding receiving space 42 and out of the way of the main sealing surface 20 which can then produce a continuous transverse seal along the main sealing line by interacting with the main sealing line 22. Simultaneously, the sealing sub-surface 36 produces a continuous sealing along the sealing subline by interaction with the sealing sub-surface 38. Suitably, two essentially parallel seals are formed in the overlap joint area, one through a double layer of material for sealing. wrapping and one through a triple layer of wrapping material. In fact, these two seals are not distinctly formed but mixed together.

Above, transverse seals of a continuous tube formed from a spool of packing material have been described. However, the pipe must not be "infinitely" long, but may be of some length. Especially, the tube may be the tube of a single package, i.e. a so-called blank package.

The settings described above should be considered as examples only. One skilled in the art understands that the discussed configurations can be combined and varied in numerous ways without departing from the scope of the invention.

For example, in the configuration described above, the device is constructed such that the anvil shows inventive characteristics. Of course, the device could also be constructed in an opposite manner so that the ultrasonic comet instead has these characteristics. The tube should then be placed with its overlapping joints facing the ultrasonic comet.

As another example, the invention is not limited to use in connection with ultrasonic sealing. This can also be used with other sealing techniques such as heat sealing.

Additionally, the appearance of the cross seal obtained by the above configuration is only an example. The transverse seal must not be positioned perpendicular to the longitudinal seal. Also, the transverse seal need not extend continuously through the extension of the flat extended tube.

Also, the penetration of the outer edge section need not be affected by the penetration devices included within the anvil devices. For example, the penetration devices could instead be placed as to be separated from the anvil and the comet.

Finally, it should be emphasized that figures are not drawn to scale.

Claims (18)

1. Device (10) for cross sealing a tube (12) of thermoplastic coated packing material, the tube being formed by sealing a gasket (14) between two mutually opposing edge sections (26, 28) of a sheet packing material, including first and second opposing jaws (16,18) having first and second main sealing surfaces (20, 22) respectively, between which the tube is placed to be flat extended and pressed to heat the thermoplastic between main sealing surfaces and obtain a transverse seal along a main sealing line (24) of the pipe, characterized in that it is placed to penetrate the outer edge section (28) of the overlap joints along the sealing line before sealing to allow the first main sealing surface (20) to contact the inner edge section (26) of the overlap joint. Device (10) according to claim 1, characterized in that the jaws (16, 18) are arranged to interact so as to achieve essentially uniform pressure along the main sealing line (24) when the surfaces main sealing rings (20, 22) are placed in parallel. Device (10) according to any one of the preceding claims, characterized in that it is arranged to penetrate the outer edge section (28) of the overlap joint (14) by cutting it to create a flap (50) of material. for packing that can be moved to expose the outer edge section (26) of the overlap gasket to the first main sealing surface (20). Device (10) according to claim 3, characterized in that it further includes a receiving space (42) for receiving the flap (50) for discovering the inner edge section (26) along the main sealing line (24). ) during sealing. Device (10) according to Claim 4, characterized in that the receiving space (42) is formed as a notch along the first main sealing surface (20). Device (10) according to any one of claims 4 to 5, characterized in that the receiving space (42) is arranged to be positioned opposite the overlap joint (14) prior to penetration of the outer edge section ( 28) overlap joint. Device (10) according to any one of the preceding claims, characterized in that the first jaw (16) includes a penetration device (32) for penetrating the outer edge section (28) of the overlapping joint (28). 14) before sealing. Device (10) according to Claim 7, characterized in that the penetration device (32) is formed as a tapered part of the first main sealing surface (20). Device (10) according to any one of claims 7 to 8, characterized in that the penetration device (32) is arranged to be positioned opposite the overlap joint (14) prior to penetration of the outer edge section. (28) of the overlap joint. Device (10) according to any one of the preceding claims, characterized in that the first jaw (16) further includes a recess (34) on one side of the main sealing surface (20), the recess being placed for receiving a portion of the overlap gasket (14) on a corresponding side of the main seal line (24) during penetration and sealing. Device (10) according to any one of the preceding claims, characterized in that it is for use in ultrasonic sealing, the first jaw (16) being an anvil and the second jaw (18) being an ultrasonic comet. . 12. Method for cross sealing a tube (12) of thermoplastic-coated packing material, the tube being formed by sealing an overlap joint (14) between two mutually opposing edge sections (26, 28) of a sheet. packing material, comprising pressing the tube in a flat extended condition between first and second sealing surfaces (20, 22) of the first and second opposing jaws (16, 18), respectively, to heat the thermoplastic between the main sealing surfaces. and obtain a transverse seal along the main sealing line (24) of the pipe, characterized in that it additionally comprises penetration into the outer edge section (28) of the overlap joint along the main sealing line before sealing to allow the sealing surface (20) (26) of the overlap joint of the first jaw (16) to contact the outer edge section A method according to claim 12, further comprising allowing the jaws (16, 18) to interact so as to achieve essentially uniform pressure along the main sealing line (24) when the main sealing surfaces (20, 22) are placed in parallel. Method according to any one of claims 13 to 14, characterized in that it further includes penetration into the outer edge section (28) of the overlap joint (14) by cutting it to form a flap (50) of material for casing that can be moved to expose the inner edge section (26) of the overlap joint (14) to the first main sealing surface (20). A method according to claim 14, characterized in that it further comprises receiving the flap (50) into a receiving space (42) to discover the inner edge section (26) along the main sealing line (24) during seal. Method according to claim 14, characterized in that it further includes positioning of receiving space (42) opposite the overlap joint (14) prior to penetration of the outer edge section (28) of the overlap joint, the receiving space being formed as a notch along the first main sealing surface (20). Method according to any one of claims 12 to 16, characterized in that it further includes positioning of penetration device (32) arranged for penetration of the outer edge section (28) of the overlap joint (14) before to be sealed and included in the first jaw (16) as the tapered portion of the first sealing surface (20) opposite the overlap joint prior to penetration of the outer edge section overlap joint. A method according to any one of claims 12 to 17, characterized in that it is for use in ultrasonic sealing, the first jaw (16) being an anvil and the second jaw (18) being an ultrasonic comet. .