Device and method for inductive sealing of a plurality of plies of a laminate

Abstract

A device for inductive sealing of a plurality of plies of a laminate which comprises a carrier layer made of electrically non-conductive material, a sealing layer made of thermoplastic material and a metal layer disposed between the sealing layer and the carrier layer, includes two compressible sealing jaws, each fitted with an inductor embedded in a block of the sealing jaw. The block of each sealing jaw consists of a metallic material. A concentrator of each sealing jaw is composed of a plurality of partial pieces, wherein each partial piece consists of a material suitable for magnetic field concentration and all the partial pieces are electrically insulated from one another and with respect to the metal block. The inductor is disposed in a groove in the concentrator.

Claims

1. A device for inductive sealing of a plurality of plies of a laminate, the laminate including a carrier layer made of electrically non-conductive material, a sealing layer made of thermoplastic material, and a metal layer disposed between the sealing layer and the carrier layer, the device comprising: a first sealing jaw and a second sealing jaw, wherein the first sealing jaw and the second sealing jaw are movable relative to one another, the first sealing jaw and the second sealing jaw defining a sealing gap therebetween configured to receive a plurality of plies of the laminate, a drive configured to impart relative movement of the first sealing jaw and the second sealing jaw to open and close the sealing gap and to build up a pressing force on the plurality of plies of the laminate in the sealing gap, each of the first sealing jaw and the second sealing jaw comprises a block consisting of a metallic material and a concentrator fastened to the block, wherein the concentrator includes a groove having a groove opening facing the sealing gap, the concentrator includes a plurality of partial pieces, each of the partial pieces consists of a material capable of magnetic field concentration, and each of the partial pieces are electrically insulated with respect to one another and with respect to the block, and an inductor received in the groove and configured to heat the metal layer in the laminate to weld together adjacent thermoplastic layers of the plurality of plies of the laminate when the pressing force is applied to the plurality of plies by the first sealing jaw and the second sealing jaw, wherein the inductor has an upper strand and a lower strand, the upper strand and the lower strand are connected to one another by lateral bends of the inductor, at least a first partial piece of the partial pieces of the concentrator receives exclusively the upper strand in the groove, and at least a second partial piece of the partial pieces of the concentrator receives exclusively the lower strand in the groove.

2. The device of claim 1, wherein the partial pieces of the concentrator are electrically insulated from each other by at least one gap.

3. The device of claim 2, further comprising an insulating material of polyimide disposed in each the at least one gap.

4. The device of claim 1, wherein at least two of the partial pieces of the concentrator have a different permeability.

5. The device of claim 1, wherein at least one of the partial pieces of the concentrator has sections with different permeability.

6. The device of claim 1, further comprising a cover disposed on a side of each of the first sealing jaw and the second sealing jaw facing the sealing gap.

7. The device of claim 1, further comprising an insulator insulating all the partial pieces of the concentrator with respect to the metal block, which has a high thermal conductivity of at least 20 W/mK and a high specific electrical resistance of at least 1012 mm2/m.

8. The device of claim 7, wherein the insulator has a high thermal conductivity of at least 100 W/mK.

9. The device of claim 7, wherein the insulator consists of a ceramic material aluminium nitride (AIN).

10. The device of claim 1, wherein the inductor comprises a hollow conductor configured to pass therethrough a cooling medium.

11. The device of claim 1, wherein at least one cooling channel is disposed in the block of the each of the first sealing jaw and the second sealing jaw.

12. The device of claim 1, wherein the each of the first sealing jaw and the second sealing jaw has a first section and a second section offset in a longitudinal direction of the each of the first sealing jaw and the second sealing jaw, the inductor is disposed exclusively in the first section of the each of the first sealing jaw and the second sealing jaw, and an after-pressing and cooling region is located between the opposite second sections of the first sealing jaw and the second sealing jaw.

13. The device of claim 12, further comprising at least one cooling channel disposed in the block of the each of the first sealing jaw and the second sealing jaw, wherein the at least one cooling channel extends through the first section and the second section of the each of the first sealing jaw and the second sealing jaw, whereby cooling medium can flow through both the first section and the second section.

14. The device of claim 13, wherein connections of the cooling channel for the cooling medium are disposed on the second section.

15. A method for inductive sealing of a plurality of plies of a laminate of a packaging using a device including a first sealing jaw and a second sealing jaw, wherein the first sealing jaw and the second sealing jaw are movable relative to one another and the first sealing jaw and the second sealing jaw define a sealing gap therebetween configured to receive a plurality of plies of the laminate, a drive configured to impart relative movement of the first sealing jaw and the second sealing jaw to open and close the sealing gap and to build up a pressing force on the plurality of plies of the laminate in the sealing gap, each of the first sealing jaw and the second sealing jaw includes a block consisting of a metallic material and a concentrator fastened to the block, wherein the concentrator includes a groove having a groove opening facing the sealing gap, the concentrator includes a plurality of partial pieces, each of the partial pieces consists of a material capable of magnetic field concentration, and each of the partial pieces are electrically insulated with respect to one another and with respect to the block, and an inductor received in the groove and configured to heat the metal layer in the laminate to weld together adjacent thermoplastic layers of the plurality of plies of the laminate when the pressing force is applied to the plurality of plies by the first sealing jaw and the second sealing jaw, wherein the each of the first sealing jaw and the second sealing jaw has a first section and a second section offset in a longitudinal direction of the each of the first sealing jaw and the second sealing jaw, the inductor is disposed exclusively in the first section of the each of the first sealing jaw and the second sealing jaw, and an after-pressing and cooling region is located between the opposite second sections of the first sealing jaw and the second sealing jaw, the method comprising the steps: conveying the plies of the laminate to be sealed into the opened sealing gap between the first sections of the first sealing jaw and the second sealing jaw when the sealing gap is opened, sealing the plies of the laminate in the sealing gap between the first sections of the first sealing jaw and the second sealing jaw, opening the sealing gap, conveying, after the step of opening, the sealed plies of the laminate in the opened sealing gap from the first sections to the second sections of the first sealing jaw and the second sealing jaw, the first sections and the second sections being offset in the longitudinal direction of the sealing jaws, building up a pressing force onto the sealed plies of the laminate in the after-pressing and cooling region of the sealing gap between the second sections and cooling the laminate, and opening the sealing gap and conveying the cooled plies of the laminate out of the sealing gap.

16. The method according to claim 15, wherein the step of sealing is performed in an aseptic working area of a filling machine for liquid foodstuffs and the step of building up the pressing force and cooling of the laminate is performed in the after-pressing and cooling region outside of the aseptic working area.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in detail hereinafter with reference to the figures. In the figures

(2) FIG. 1 is a schematic side view of a device according to an embodiment of the invention for inductive sealing of a plurality of plies of a laminate of a gable package,

(3) FIG. 2a, b are detailed views of a multi-part concentrator of a device according to FIG. 1,

(4) FIG. 3 is a schematic perspective view of a sealing jaw of the device according to FIG. 1,

(5) FIG. 4 is a front view of the sealing jaw according to FIG. 3,

(6) FIG. 4A is a section along the line A-A in a first section of the sealing jaw in FIG. 4,

(7) FIG. 4B is a section along the line B-B in a second section of the sealing jaw in FIG. 4,

(8) FIG. 5 is a schematic perspective view of another embodiment of a sealing jaw,

(9) FIG. 6 is a front view of the sealing jaw according to FIG. 5,

(10) FIG. 6A is a section along the line A-A in FIG. 6, and

(11) FIG. 6B is a section along the line B-B FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(12) FIG. 1 shows a device (1) for inductive sealing of a plurality of plies of a laminate (2) of a gable package (6) comprising a first sealing jaw (3a) and a second sealing jaw (3b), a sealing gap (4) disposed between the first and second sealing jaw (3a, 3b) for receiving the plurality of plies of the laminate (2) as well as a drive (20) for producing: a relative movement of the sealing jaws (3a, 3b) with respect to one another and for building up a pressing force on the piles of the laminate (2) in the sealing gap (4).

(13) In the exemplary embodiment shown, the sealing jaw (3a) is held in a fixed position whereas the sealing jaw (3b) is movable to and fro in the direction of the sealing jaw (3a) with the aid of the drive. The direction of movement (5) of the sealing jaw (3a) is at right angles to the pressing surfaces of the two sealing jaws (3a, 3b). For example, a piston-cylinder unit can be considered as drive. Both sealing jaws (3a, 3b) comprise a block (7) of metal material which in the exemplary embodiment shown has a square cross-section. Naturally the block can have a different cross-section if the geometrical relationships and the installation situation of the device require this. A concentrator (8) is fastened to the block (7) in which a groove (9) having a groove opening (9a) pointing in the direction of the sealing gap (4) is introduced.

(14) An inductor (10) configured as an induction loop is let into the groove (9), where the inductor (10) has an upper strand (10a) with connections (10b) for connection of the inductor to a high-frequency alternating voltage. The lower strand (10c) is connected via lateral bends (10d) to the upper strand (10a). In the embodiment according to FIGS. 3, 4, 4A, and 4B the inductor (10) is designed as a solid conductor and is indirectly cooled. In the embodiment according to FIGS. 5, 6, the inductor (10) is designed as a hollow conductor through which a cooling medium can flow, which is supplied to the hollow conductor at the connections (10b) for the electrical high-frequency voltage or removed from the hollow conductor.

(15) FIGS. 2a, b illustrate the structure of the concentrator (8). In the exemplary embodiment shown, the concentrator consists of a total of four partial pieces (8a, b, c, d). FIG. 2b shows the separated partial pieces (8a, b, c, d) whereas FIG. 2a shows the partial pieces (8a, b, c, d) combined to form the concentrator (8).

(16) The upper strand (10a) as well as the bends (10b) of the inductor (10) are let into the groove (9) in the partial pieces (8c, d) and the lower strand (10c) of the inductor (10) is let into the groove (9) in the partial pieces (8a, b) of the concentrator (8). All the partial pieces (8a, b, c, d) are electrically insulated from one another in order to avoid electrical flash-overs between the upper and the lower strand (10a, c) which can adversely affect the structure of the magnetic field over the entire length of the inductor (10) and therefore jeopardize the sealing result. The partial pieces (8a, b, c, d) are electrically insulated from one another by a horizontal gap (11a) and a vertical gap (11b). In order to improve the insulation between the partial pieces (8a-d), a polyimide film (12) is introduced in the horizontal and vertical gap (11a, 11b). The polyimide film (12) can be loaded in permanent use for temperatures up to 230 C. and briefly up to 400 c.

(17) As can be seen in particular from FIGS. 3 to 6B, each sealing jaw (3a, 3h) has a first section (13a) and a second section (13b) offset in the longitudinal direction (14) of the sealing jaw (3a, 3b). The inductor (10) is located exclusively in the first section (13a). Located between the opposite second sections (13b) of the first and second sealing jaw (3a, 3b) is an after-pressing and cooling region (15) for the plies of the laminate (2) sealed in the first section (13a). On the side of each sealing jaw (3a, 3b) facing the sealing gap (4), a cover (16) is disposed in the region of the first section (13a) which protects the inductor (9) exposed towards the sealing gap (14) in the groove (9) from mechanical damage. The plate-shaped cover (16) is designed as stepped in cross-section. In the region of the lower strand (10c) of the inductor (10), the plate-shaped cover (16) is thinner than in the section (16b) covering the upper strand (10a). The gradation of the cover (16) is adapted to the different number of plies of the laminate (2) to be sealed in the sealing gap (4). Four or five plies of the laminate (2) are located in the lower section (16a) of the sealing gap (4) whereas only two plies of the laminate (2) to be sealed are located in the upper section (16b). In the lower section (16a) of the cover the metal layer of the laminate (2) responsible for the heating lies closer to the lower strand (10c) so that as a result of the shorter distance the inductor (10) inputs a higher energy into the four plies than into the two plies in the region of the upper section (16b).

(18) In order to avoid electrical flashover between the strands (10a, 10c) of the inductor (10) through the block (7) and an adverse effect on the energy irradiation, a plate-shaped insulator (17) made of a ceramic material is disposed behind the concentrator (8). The ceramic material comprises in particular aluminium nitride, having a high thermal conductivity with at the same time high specific electrical resistance. The high thermal conductivity is in particular of decisive importance in an embodiment of the device with indirect cooling of the inductor (10) according to FIGS. 3, 4, 4A, and 4B.

(19) For indirect cooling, a cooling channel (18) with an intake (18a) and a return (18b) is located in the block (7) of each sealing jaw (3a, 3b). The intake and return extends from the connections (18c) in the longitudinal direction (14) of the sealing jaw (3a, 3b). The connections (18c) are located on the front side of the sealing jaw (3a, b) in the second section (13b).

(20) In the exemplary embodiment according to FIGS. 5, 6A, and 5B with an internally cooled inductor (10), the cooling channel (18) is located exclusively in the second section (13b). The connections (18c) for the cooling medium are also located on the front side of the sealing jaw (3a, 3b) in the second section (13b). In principle however, it is also possible in one embodiment of the device with internally cooled inductor (10) to provide additional cooling channels in the first section (13a) in order to improve the cooling capacity.

(21) The previously described device (1) for the inductive sealing of a plurality of plies of a laminate (2) of a gable package (6) operates as follows:

(22) The plies of the laminate (2) of the gable package (6) to be sealed are conveyed by means of conveyor, not shown, which operates in a clocked manner, into the opened sealing gap (4) between the first sections (13a) of the two sealing jaws (3a, b). Then with the aid of the drive not shown, sealing jaws (3a, b) are moved towards one another and the adjacent thermoplastic layers of the plurality of plies of the laminate (2) are compressed and sealed with one another by induction of an eddy current in the metal layer of the laminate (2).

(23) The sealing gap (4) is then opened again and the sealed gable package (6) is conveyed in the longitudinal direction (14) between the second sections (13b) of the sealing jaws (3a, b). As soon as the sealed plies of the laminate (2) are located in the after-pressing and cooling region (15), a pressing force on the already sealed plies of the laminate in the sealing gap (4) is built up by movement of the sealing jaw (3a). At the same time, the sealed plies of the laminate (2) are cooled. The sealing gap (4) is then opened and the gable package (6) is conveyed in the longitudinal direction (14) out from the sealing gap. During the after-pressing and cooling in the second section (13b), the next gable package (6) conveyed by the conveyor into the opened sealing gap (4) is already sealed in the first section (13a).

(24) In a filling plant for liquid foodstuffs with an aseptic working area, the sealing jaws (3a, 3b) are disposed parallel to the conveying direction of the gable packages (6) through the aseptic working area. In this case, the first section (13a) is located in the aseptic working area whereas the second section (13b) is located outside the working area. The connections (18c) for the cooling medium on the front side of the second section (13b) prevent any leaking cooling medium from being able to enter into the aseptic working area.

(25) In a further embodiment of the invention, the length of the sealing jaw (3a, b) and of the lower and upper strand (10a, 10c) of the inductor (10) is dimensioned in such a manner that on both sides of the connections (10b) the sealing region of a gable package (6) can be sealed simultaneously in each case.

(26) The length of the after-pressing and cooling region (15) in the second section is also dimensioned in such a manner that the sealing regions of two gable packages (6) can be simultaneously after-pressed and cooled.

LIST OF REFERENCES

(27) List of References

(28) TABLE-US-00001 No. Designation 1. Device 2. Laminate 3a. Sealing jaw 3b. Sealing jaw 4. Sealing gap 5. Movement direction 6. Gable package 7. Metal block 8. Concentrator 8a. Partial piece 8b. Partial piece 8c. Partial piece 8d. Partial piece 9. Groove 9a. Groove opening 10. Inductor 10a. Upper strand 10b. Connections 10c. Lower strand 10d. Bend 11a. Horizontal gap 11b. Vertical gap 12 Polyimide film 13a. First section 13b. Second section 14. Longitudinal direction 15. After-pressing and cooling region 16. Cover 16a. Lower section 16b. Upper section 17. Insulator 18. Cooling channel 18a. Intake 18b. Return 18c. Connections 20. Drive