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WO1997022524A1 - A method and device at a longitudinal joint sealing of a package blank - Google Patents

A method and device at a longitudinal joint sealing of a package blank Download PDF

Info

Publication number
WO1997022524A1
WO1997022524A1 PCT/SE1996/001704 SE9601704W WO9722524A1 WO 1997022524 A1 WO1997022524 A1 WO 1997022524A1 SE 9601704 W SE9601704 W SE 9601704W WO 9722524 A1 WO9722524 A1 WO 9722524A1
Authority
WO
WIPO (PCT)
Prior art keywords
inductor
longitudinal joint
lower member
packaging blank
joint
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/SE1996/001704
Other languages
French (fr)
Inventor
Anders Hilmersson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Tetra Laval Holdings and Finance SA
Original Assignee
Tetra Laval Holdings and Finance SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tetra Laval Holdings and Finance SA filed Critical Tetra Laval Holdings and Finance SA
Priority to AU12187/97A priority Critical patent/AU1218797A/en
Publication of WO1997022524A1 publication Critical patent/WO1997022524A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/72—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined
    • B29C66/723—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered
    • B29C66/7232—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered comprising a non-plastics layer
    • B29C66/72321—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered comprising a non-plastics layer consisting of metals or their alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/36—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction
    • B29C65/3604—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the type of elements heated by induction which remain in the joint
    • B29C65/3644—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the type of elements heated by induction which remain in the joint being a ribbon, band or strip
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/36—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction
    • B29C65/3604—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the type of elements heated by induction which remain in the joint
    • B29C65/3656—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the type of elements heated by induction which remain in the joint being a layer of a multilayer part to be joined, e.g. for joining plastic-metal laminates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/36—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction
    • B29C65/3668—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the means for supplying heat to said heated elements which remain in the join, e.g. special induction coils
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/36—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction
    • B29C65/3672—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the composition of the elements heated by induction which remain in the joint
    • B29C65/3676—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the composition of the elements heated by induction which remain in the joint being metallic
    • B29C65/368—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the composition of the elements heated by induction which remain in the joint being metallic with a polymer coating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/01—General aspects dealing with the joint area or with the area to be joined
    • B29C66/05—Particular design of joint configurations
    • B29C66/10—Particular design of joint configurations particular design of the joint cross-sections
    • B29C66/11—Joint cross-sections comprising a single joint-segment, i.e. one of the parts to be joined comprising a single joint-segment in the joint cross-section
    • B29C66/112—Single lapped joints
    • B29C66/1122—Single lap to lap joints, i.e. overlap joints
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/40—General aspects of joining substantially flat articles, e.g. plates, sheets or web-like materials; Making flat seams in tubular or hollow articles; Joining single elements to substantially flat surfaces
    • B29C66/41—Joining substantially flat articles ; Making flat seams in tubular or hollow articles
    • B29C66/43—Joining a relatively small portion of the surface of said articles
    • B29C66/432—Joining a relatively small portion of the surface of said articles for making tubular articles or closed loops, e.g. by joining several sheets ; for making hollow articles or hollow preforms
    • B29C66/4322—Joining a relatively small portion of the surface of said articles for making tubular articles or closed loops, e.g. by joining several sheets ; for making hollow articles or hollow preforms by joining a single sheet to itself
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/40—General aspects of joining substantially flat articles, e.g. plates, sheets or web-like materials; Making flat seams in tubular or hollow articles; Joining single elements to substantially flat surfaces
    • B29C66/49—Internally supporting the, e.g. tubular, article during joining
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2795/00—Printing on articles made from plastics or substances in a plastic state
    • B29C2795/002—Printing on articles made from plastics or substances in a plastic state before shaping
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C53/00—Shaping by bending, folding, twisting, straightening or flattening; Apparatus therefor
    • B29C53/36—Bending and joining, e.g. for making hollow articles
    • B29C53/38—Bending and joining, e.g. for making hollow articles by bending sheets or strips at right angles to the longitudinal axis of the article being formed and joining the edges
    • B29C53/40—Bending and joining, e.g. for making hollow articles by bending sheets or strips at right angles to the longitudinal axis of the article being formed and joining the edges for articles of definite length, i.e. discrete articles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/71—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the composition of the plastics material of the parts to be joined
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/80—General aspects of machine operations or constructions and parts thereof
    • B29C66/83—General aspects of machine operations or constructions and parts thereof characterised by the movement of the joining or pressing tools
    • B29C66/832—Reciprocating joining or pressing tools
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/712—Containers; Packaging elements or accessories, Packages

Definitions

  • the present invention relates to a method and a device at a longitudinal joint sealing with induction heat of a packaging blank or the like of polymer lined metal plate, wherein an inductor is applied against a joint, formed of an upper member and a lower member.
  • a problem at such a longitudinal joint sealing of an overlapping joint with induction heat is that the heat is developped in the metal layer or member which is closest to the inductor, i e the upper member. This means that a for example about 5 mm wide burnt zone is formed on the upper member, where it otherwise would have been desireable to have a decoration, which should extend around the packaging without interruption.
  • FIG. 1 in perspective illustrates the cooperation between a packaging blank with frusto-conical shape and an inductor beam for accomplishing a longitudinal joint in the packaging blank
  • Fig 2 is a side view, namely from the right, of the arrangement shown in Fig 1 with an inductor according to the invention
  • Fig 3 is a plan view of the device according to Fig 2,
  • Fig 4 is an end view from the left of the device according to Fig 3 ,
  • Fig 5 is a simplified section along the line V-V in Fig 3
  • Fig 6 is a plan view to a reduced scale of a mandrel for use together with the inductor beam shown in Figs 1 - 5.
  • a frusto-conical packaging blank 1 shall - starting from a planar sheet - be given the conical shape shown in the drawings and be provided with a longitudinal joint in the way defined by the invention, whereupon it can be equipped with a bottom and a cover in a way not further shown or described here .
  • the packaging blank 1 is preferably made of aluminium with a thickness of 50 - 300 ⁇ m, for example 85 ⁇ m.
  • the aluminium surface is at least on one side lined with a sealable polymer, for example a polyester, but often on both sides.
  • a sealable polymer for example a polyester
  • an inductor beam 2 is used and as dolly a mandrel 3 indicated in Fig 6 and for example made of fabric reinforced bakelite.
  • Special problems are encountered at sealing compara ⁇ tively thick polymer lined aluminium with induction heat, above all due to the low resistance and high heat conduc ⁇ ting ability of the material.
  • the current in the inductor and accompanying matching transformer becomes unacceptably high with normal inductors having only one turn.
  • the problem is further complicated at longitudinal joints, where the induced current shall follow the edge of the material as far as possible and then promptly turn.
  • use is instead made of an inductor having several windings, prefe ⁇ rably an inductor with five turns .
  • a litz wire contains a large number of conductors isolated from each other, in the present case about 400 conductors within a total diame ⁇ ter of 2 mm, and thus accomplishes an even distribution of the current in the wire.
  • the I-beam shape is chosen for enabling the applica- tion of the pressure on the joint necessary for the sea ⁇ ling, and the litz wires 5 are laid in the web of the I- beam for concentrating the current and accomplishing the heat necessary for rapid melting and sealing.
  • the I-beam 4 with its litz wires 5 is laid into a ferritic mass for con- centrating the current. At a sealing of 85 ⁇ m aluminium sealing times of 30 - 300 ms can be accomplished.
  • All the return conductors of litz wire 5 (to the left in Figs 4 and 5) are laid next to each other under a copper plate 6 in the inner surface of the inductor beam for the purpose of distributing the current.
  • the inductor beam 2 can be provided with screw holes 2' for its mounting at the machine (not shown) for the sea ⁇ ling.
  • the heat is normally developped in the metal layer closest to the inductor.
  • This zone must then be free from decoration in the same way as at steel cans and the like with welded longitudinal joint. If the members of the longitudinal joint however are laid in the way which appears from Figs 4 and 5, i e if the member on which the return litz wires 5 and the copper plate 6 are applied is laid lowest in the joint, both the sealing current and the return current will pass through the lower member, which means that the heat will be con ⁇ centrated to the lower plate layer.
  • a copper strip 7 (Fig 6) is arranged on the mandrel or dolly 3 at the back side of the packaging blank 1 in the vicinity of the place where the current turns.
  • a strip 7 is in its longitudinal direc ⁇ tion displaced a few mm inside the end of the longitudinal joint. It will take care of the turning current and will relieve the joint.
  • Such a strip 7 is normally arranged at each end of the longitudinal joint. It can however also occur that the packaging is provided with a cover before the longitudinal joint, and in such case it suffices with one strip 7 at the free end of the joint.
  • Another way of accomplishing the desired effect with current concentration and pressure application ability is to use an inductor in the form of a number, for example five, next to each other standing but from each other iso ⁇ lated copper rods, each with a height of 4 - 5 mm and a thickness of 0.8 mm. In the return conducting phase these copper rods can be turned 90° and be placed at a certain distance from each other.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Package Closures (AREA)
  • Closing Of Containers (AREA)
  • Lining Or Joining Of Plastics Or The Like (AREA)
  • General Induction Heating (AREA)

Abstract

A longitudinal joint sealing with induction heat of a packaging blank (1) of polymer lined metal plate is accomplished by means of an inductor (2) for application against a joint, formed by an upper member and a lower member. For obviating burning of decoration on the upper member the return current of the inductor is conducted via the lower member.

Description

A METHOD AND DEVICE AT A LONGITUDINAL JOINT SEALING OF A PACKAGE BLANK
Technical Field
The present invention relates to a method and a device at a longitudinal joint sealing with induction heat of a packaging blank or the like of polymer lined metal plate, wherein an inductor is applied against a joint, formed of an upper member and a lower member. Background of the Invention
A problem at such a longitudinal joint sealing of an overlapping joint with induction heat is that the heat is developped in the metal layer or member which is closest to the inductor, i e the upper member. This means that a for example about 5 mm wide burnt zone is formed on the upper member, where it otherwise would have been desireable to have a decoration, which should extend around the packaging without interruption. The Invention
The problem can according to the invention be solved in the way which is defined in the attended claims, namely in that the return current of the inductor is conducted via the lower member of the packaging blank. This means that the lower member becomes heated and that the upper member is heated indirectly from below, whereby the decoration on its upper side is not burnt. Brief Description of the Drawings
The invention shall be further described below under reference to the accompanying drawings, in which
Fig 1 in perspective illustrates the cooperation between a packaging blank with frusto-conical shape and an inductor beam for accomplishing a longitudinal joint in the packaging blank, Fig 2 is a side view, namely from the right, of the arrangement shown in Fig 1 with an inductor according to the invention,
Fig 3 is a plan view of the device according to Fig 2,
Fig 4 is an end view from the left of the device according to Fig 3 ,
Fig 5 is a simplified section along the line V-V in Fig 3 , and Fig 6 is a plan view to a reduced scale of a mandrel for use together with the inductor beam shown in Figs 1 - 5.
Detailed Description of Preferred Embodiments
A frusto-conical packaging blank 1 shall - starting from a planar sheet - be given the conical shape shown in the drawings and be provided with a longitudinal joint in the way defined by the invention, whereupon it can be equipped with a bottom and a cover in a way not further shown or described here . The packaging blank 1 is preferably made of aluminium with a thickness of 50 - 300 μm, for example 85 μm. The aluminium surface is at least on one side lined with a sealable polymer, for example a polyester, but often on both sides. For accomplishing a longitudinal joint in the packa¬ ging blank 1 the technique with induction heat is utilized. For this purpose an inductor beam 2 is used and as dolly a mandrel 3 indicated in Fig 6 and for example made of fabric reinforced bakelite. Special problems are encountered at sealing compara¬ tively thick polymer lined aluminium with induction heat, above all due to the low resistance and high heat conduc¬ ting ability of the material. The current in the inductor and accompanying matching transformer becomes unacceptably high with normal inductors having only one turn. The problem is further complicated at longitudinal joints, where the induced current shall follow the edge of the material as far as possible and then promptly turn. At the method according to the invention use is instead made of an inductor having several windings, prefe¬ rably an inductor with five turns . In the shown case one turn at the place where the longitudinal joint shall be accomplished is formed as an I-beam 4, whereas the other turns are constituted of litz wire 5. A litz wire contains a large number of conductors isolated from each other, in the present case about 400 conductors within a total diame¬ ter of 2 mm, and thus accomplishes an even distribution of the current in the wire.
The I-beam shape is chosen for enabling the applica- tion of the pressure on the joint necessary for the sea¬ ling, and the litz wires 5 are laid in the web of the I- beam for concentrating the current and accomplishing the heat necessary for rapid melting and sealing. The I-beam 4 with its litz wires 5 is laid into a ferritic mass for con- centrating the current. At a sealing of 85 μm aluminium sealing times of 30 - 300 ms can be accomplished.
All the return conductors of litz wire 5 (to the left in Figs 4 and 5) are laid next to each other under a copper plate 6 in the inner surface of the inductor beam for the purpose of distributing the current.
The inductor beam 2 can be provided with screw holes 2' for its mounting at the machine (not shown) for the sea¬ ling.
At overlapping joints, with which the present inven- tion is concerned, the heat is normally developped in the metal layer closest to the inductor. This means that a for example about 5 mm wide burnt zone can be formed on the surface of the packaging material. This zone must then be free from decoration in the same way as at steel cans and the like with welded longitudinal joint. If the members of the longitudinal joint however are laid in the way which appears from Figs 4 and 5, i e if the member on which the return litz wires 5 and the copper plate 6 are applied is laid lowest in the joint, both the sealing current and the return current will pass through the lower member, which means that the heat will be con¬ centrated to the lower plate layer. The heating of the upper plate layer will hereby occur from below, and the upper printed decorated layer is not damaged. Where the current turns at the outer ends of the longitudinal joint, the current density becomes so great that the material in the packaging blank is damaged. This problem can be obviated in that a copper strip 7 (Fig 6) is arranged on the mandrel or dolly 3 at the back side of the packaging blank 1 in the vicinity of the place where the current turns. Such a strip 7 is in its longitudinal direc¬ tion displaced a few mm inside the end of the longitudinal joint. It will take care of the turning current and will relieve the joint. Such a strip 7 is normally arranged at each end of the longitudinal joint. It can however also occur that the packaging is provided with a cover before the longitudinal joint, and in such case it suffices with one strip 7 at the free end of the joint.
As a modification to the embodiment described above and shown in the drawings with an I-beam, it is also pos¬ sible to make use of other profiles, such as a U- or T- beam, and the number of litz wires can for example be in the area 3 - 7.
Another way of accomplishing the desired effect with current concentration and pressure application ability is to use an inductor in the form of a number, for example five, next to each other standing but from each other iso¬ lated copper rods, each with a height of 4 - 5 mm and a thickness of 0.8 mm. In the return conducting phase these copper rods can be turned 90° and be placed at a certain distance from each other.

Claims

1. A method at a longitudinal joint sealing with in¬ duction heat of a packaging blank (1) or the like of poly¬ mer lined metal plate, wherein an inductor (4, 5) is applied against a joint, formed of an upper member and a lower member, c h a r a c t e r i z e d in that the return current of the inductor (4, 5} is conducted via the lower member of the packaging blank (1) .
2. A device at a longitudinal joint sealing with induction heat of a packaging blank (1) or the like of polymer lined metal plate with an inductor (4, 5) for application against a joint, formed of an upper member and a lower member, c h a r a c t e r i z e d in that the return current conductors of the inductor (4, 5) are arranged in the vicinity of the lower member of the packa¬ ging blank.
3. A device according to claim 2, c h a r a c t e r¬ i z e d in that the inductor is constituted of four litz wires (4) arranged in the web of an I-beam (5), which forms a fifth conductor, and in that the return conductors of litz wire are laid next to each other at a distance from the inductor winding in the vicinity of the lower member of the packaging blank (1) .
PCT/SE1996/001704 1995-12-20 1996-12-19 A method and device at a longitudinal joint sealing of a package blank Ceased WO1997022524A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU12187/97A AU1218797A (en) 1995-12-20 1996-12-19 A method and device at a longitudinal joint sealing of a package blank

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9504566-2 1995-12-20
SE9504566A SE505571C2 (en) 1995-12-20 1995-12-20 Methods and apparatus for longitudinal joint sealing with induction heat of a packaging material of polymer coated metal sheet

Publications (1)

Publication Number Publication Date
WO1997022524A1 true WO1997022524A1 (en) 1997-06-26

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1996/001704 Ceased WO1997022524A1 (en) 1995-12-20 1996-12-19 A method and device at a longitudinal joint sealing of a package blank

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AU (1) AU1218797A (en)
SE (1) SE505571C2 (en)
WO (1) WO1997022524A1 (en)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2785263A (en) * 1952-03-28 1957-03-12 Philips Corp Method for the local heating of metallic work-pieces by inductive hf-heating and hf-inductor
SE338424B (en) * 1969-06-23 1971-09-06 Spiess C F & Sohn
DE2653753A1 (en) * 1976-11-26 1978-06-01 Bosch Gmbh Robert DEVICE FOR MANUFACTURING A PACKAGING TUBE FROM A PACKAGING STRIP BY WELDING THE EDGE AREAS
US4230923A (en) * 1977-06-20 1980-10-28 Ab Akerlund & Rausing Device for induction welding
US5260535A (en) * 1990-10-11 1993-11-09 Tetra Alfa Holdings S.A. Apparatus for induction welding

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2785263A (en) * 1952-03-28 1957-03-12 Philips Corp Method for the local heating of metallic work-pieces by inductive hf-heating and hf-inductor
SE338424B (en) * 1969-06-23 1971-09-06 Spiess C F & Sohn
DE2653753A1 (en) * 1976-11-26 1978-06-01 Bosch Gmbh Robert DEVICE FOR MANUFACTURING A PACKAGING TUBE FROM A PACKAGING STRIP BY WELDING THE EDGE AREAS
US4230923A (en) * 1977-06-20 1980-10-28 Ab Akerlund & Rausing Device for induction welding
US5260535A (en) * 1990-10-11 1993-11-09 Tetra Alfa Holdings S.A. Apparatus for induction welding

Also Published As

Publication number Publication date
SE9504566L (en) 1997-06-21
SE9504566D0 (en) 1995-12-20
SE505571C2 (en) 1997-09-15
AU1218797A (en) 1997-07-14

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