Method for top sealing a cardboard tray lined with a plastic foil and cardboard tray therefor

Abstract

The invention relates to a method for top sealing a cardboard tray lined with a plastic foil. The method includes the steps of providing a cardboard tray having a bottom, upstanding walls arranged along the periphery of the bottom and a horizontal flange arranged along the upper edges of the upstanding walls, wherein the inside of the cardboard tray is lined with a plast foil, which plastic foil extends at least onto the horizontal flange; arranging the cardboard tray in a lower sealing tool member having a compressible support edge, wherein at least the horizontal flange is supported by the compressible support edge of the lower sealing tool member; arranging a cover foil over the cardboard tray arranged in the lower sealing tool member to cover the opening of the tray defined by the upper edges of the upstanding walls; and pressing a heated upper sealing tool member onto the lower sealing tool member, wherein the cover foil, the plastic foil liner and the horizontal flange are pressed together to seal the cover foil onto the plastic foil liner along the horizontal flange. The overlapping area of the plastic foil liner, the cover foil, and the compressible support edge extends at least partially outside of the area of the horizontal flange.

Claims

1. A method for top sealing a cardboard tray lined with a plastic foil, which method comprises the steps of: providing a cardboard tray having a bottom, upstanding walls arranged along the periphery of the bottom and a horizontal flange arranged along the upper edges of the upstanding walls, wherein the inside of the cardboard tray is lined with a plastic foil, which plastic foil extends at least onto the horizontal flange; arranging the cardboard tray in a lower sealing tool member having a compressible support edge, wherein at least the horizontal flange is supported by the compressible support edge of the lower sealing tool member; arranging a cover foil over the cardboard tray arranged in the lower sealing tool member to cover the opening of the tray defined by the upper edges of the upstanding walls; and pressing a heated upper sealing tool member onto the lower sealing tool member, wherein the cover foil, the plastic foil and the horizontal flange are pressed together to seal the cover foil onto the plastic foil along the horizontal flange, wherein in view of the pressing direction, the overlapping area of the plastic foil, the cover foil and the compressible support edge of the lower sealing member extends at least partially outside of the area of the horizontal flange, the compressible support edge being configured to press directly against both the plastic foil and the horizontal flange during performance of the pressing step.

2. The method according to claim 1, wherein the compressible support edge of the lower sealing tool is a compressible rubber or plastic band.

3. The method according to claim 2, wherein, when the upper sealing tool member is pressed onto the lower sealing tool member, the compressible rubber or plastic band abuts against the plastic foil where, in view of the pressing direction, the overlapping area of the plastic foil, the cover foil and the compressible support edge extends at least partially outside of the area of the horizontal flange.

4. The method according to claim 1, wherein the compressible support edge is positioned to extend at least partially outside the area of the horizontal flange and at least partially underneath the horizontal flange when viewed in the pressing direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other features of the invention will be elucidated in conjunction with the accompanying drawings.

(2) FIGS. 1A-1C show schematically the steps of an embodiment of the method according to the invention.

(3) FIGS. 2A and 2B show respectively a perspective view and a cross-section of a first embodiment of a cardboard tray according to the invention.

(4) FIGS. 3A and 3B show respectively a perspective view and a cross-section of a second embodiment of a cardboard tray according to the invention.

(5) FIGS. 4A and 4B show respectively a perspective view and a cross-section of a third embodiment of a cardboard tray according to the invention.

DESCRIPTION OF THE INVENTION

(6) FIG. 1A shows a first step of an embodiment of the method according to the invention. In this step a cardboard tray 1 is provided. The cardboard tray 1 has a bottom 2, upstanding walls 3 and a horizontal flange 4 arranged on the upper edges of the upstanding walls 3.

(7) The inside of the tray 1 is lined with a plastic foil 5, which runs over the bottom 2, the upstanding walls 3, the horizontal flange 4 and extends beyond the outer edge of the horizontal flange 4.

(8) In FIG. 1B the cardboard tray 1 is supported with the horizontal flange 4 on a lower sealing tool member 6, which is provided with a compressible support edge 7 made out of a compressible rubber band.

(9) In this step a cover foil 8 is arranged over the cardboard tray 1 and a heated upper sealing tool member 9 is positioned there above.

(10) In FIG. 1C the next step of the method according to the invention is shown. The heated upper sealing tool member 9 is pressed down onto the cover foil 8, the plastic foil liner 5, the horizontal flange 4 and the lower sealing tool member 6.

(11) Due to the pressure exerted by the upper sealing tool member 9 the compressible rubber band 7 will deform and ensure that the part of the plastic foil liner 5 extending beyond the outer edge of the horizontal flange 4 is also pressed against the cover foil 8, such that a reliable seal is obtained between the plastic foil liner 5 and the cover foil 8.

(12) FIG. 2A shows a perspective view of a first embodiment of a cardboard tray 20 according to the invention, which is folded out of a cardboard blank. The tray 20 has a bottom 21 with upstanding walls 22, 23 arranged along the periphery 24 of the bottom 21.

(13) A horizontal flange 25, 26 is composed out of horizontal flange portions 25, 26, which are arranged to the upper edge of a respective upstanding wall 22, 23.

(14) The upstanding wall 22 is provided with a flap 27, which has an opening 28. The flap 27 overlaps and abuts with the adjacent upstanding wall 23.

(15) FIG. 2B shows a cross-section of the cardboard tray 20 arranged in a sealing tool with a heated upper sealing tool member 9 and a lower sealing tool member 6 with a compressible rubber band 7, such as disclosed in FIGS. 1A-1C.

(16) The cardboard tray 20 is lined on the inside with a plastic foil 29, which extends over the horizontal flange part 25 and beyond the outer edge thereof. Due to the compressible rubber band 7, the plastic foil 24 is support also outside of the horizontal flange 25, such that a reliable seal with the cover foil 30 is obtained.

(17) FIG. 3A shows a perspective view of a second embodiment of a cardboard tray 40 according to the invention. The tray 40 is folded from a cardboard blank and has a bottom 41, upstanding walls 42 and horizontal flange parts 43, similar to the embodiment of FIGS. 2A and 2B.

(18) At the transition 44 of adjacent horizontal flange parts 43, an opening 45 is provided. As shown in FIG. 3B this opening 45 is covered by a plastic foil liner 46, which extends from the bottom 41, over the upstanding walls 42 and the horizontal flange 43.

(19) When the cardboard tray 40 is compressed together with a cover foil 47 between the lower and upper sealing tool members 6, 9, the compressible rubber band 7 deforms into the opening 45, such that also the part of the plastic foil liner 46 covering the hole 45 is sufficiently supported to obtain a reliable seal with the cover foil 47.

(20) FIG. 4A shows a perspective view of a third embodiment of a cardboard tray 50 according to the invention. The cardboard tray 50 has an octagonal shaped bottom 51 with along its periphery 52 upstanding walls 53, 54, 55. At the upper edge 56, 58 of the upstanding walls 53, 55 respectively a horizontal flange part 59, 60 is arranged.

(21) The upstanding wall 54, arranged adjacent to both the upstanding walls 53, 55 does not have a horizontal flange part, such that an opening 63 is formed.

(22) The upstanding wall 53 has a flap 61 with opening 62, which overlaps and abuts with the upstanding wall 54. As shown in FIG. 4B, the inside of the tray 50 is lined with a plastic foil 64, which also runs over the flap 61 and adheres via the opening 62 to the underlying upstanding wall 54, such that the folded cardboard retains its shape.

(23) When the cardboard tray 50 is positioned in a sealing tool having a heated upper sealing tool member 9 and a lower sealing tool member 6 with a compressible rubber band 7, the rubber band 7 will deform into the opening 63. As a result the deformed rubber band 7 will also support the plastic foil liner 64 extending over the opening 63, such also at this position a good seal with the cover foil 65 is obtained.