Cardboard tray

Abstract

A cardboard tray folded from an unfolded sheet of cardboard includes: a bottom wall with a circumferential edge formed out of an even number of straight edges; wall parts each arranged to a straight edge of the bottom wall; and first flange parts alternately arranged to subsequent wall parts along the circumferential edge. The first flange parts include at least a first, a second, and a third elongate flange part section, which are connected parallel and along an elongate edge to each other. The first elongate flange part section is arranged to the respective wall part, the third elongate flange part section is connected parallel and along an elongate edge to the second elongate flange part section, the third elongate flange part section is adhered to the outside of the respective wall part, and the second flange part section is double folded against the first flange part section.

Claims

1. A method for arranging a top seal foil on a cardboard tray, which method comprises the steps of: providing a top sealer; providing a cardboard tray folded from an unfolded sheet of cardboard, the cardboard tray comprising: a bottom wall with a circumferential edge composed out of an even number of straight edges; wall parts each arranged to a straight edge of the bottom wall; first flange parts alternately arranged to subsequent wall parts along the circumferential edge, which flange parts are arranged to an edge of said wall part opposite of the respective straight edge of the bottom wall; wherein the first flange parts comprise at least a first, a second, and a third elongate flange part section, which are connected parallel and along an elongate edge to each other, wherein the first elongate flange part section is arranged to the respective wall part, wherein the third elongate flange part section is connected parallel and along an elongate edge to the second elongate flange part section, wherein the third elongate flange part section is adhered to the outside of the respective wall part, and wherein the second flange part section is double folded against the first flange part section, and wherein the first elongate flange part section slopes downward towards the outer edge of the flange part; arranging the cardboard tray in the top sealer such that the first elongate flange part is pressed to an horizontal position; providing a top seal foil over the cardboard tray; and sealing the top seal foil to the flange parts.

2. A method for arranging a top seal foil on a cardboard tray, which method comprises the steps of: providing a top sealer; providing a cardboard tray folded from an unfolded sheet of cardboard, the cardboard tray comprising: a bottom wall with a circumferential edge composed out of an even number of straight edges; wall parts each arranged to a straight edge of the bottom wall; first and second flange parts alternately arranged to subsequent wall parts along the circumferential edge, which flange parts are arranged to an edge of said wall part opposite of the respective straight edge of the bottom wall; wherein the first flange parts comprise at least a first and a second elongate flange part section, which are connected parallel and along an elongate edge to each other, wherein the first elongate flange part section is arranged to the respective wall part, wherein the second flange part section is double folded against the first flange part section, and wherein the second flange part section extends in longitudinal direction on both ends beyond the first flange part section and overlaps with the second flange parts of adjacent wall parts, and wherein the first elongate flange part section slopes downward towards the outer edge of the flange part; arranging the cardboard tray in the top sealer such that the first elongate flange part is pressed to an horizontal position; providing a top seal foil over the cardboard tray; and sealing the top seal foil to the flange parts.

3. The method of claim 1, wherein the first and second flange parts are arranged to an edge of said wall part opposite of and parallel to the respective straight edge of the bottom wall.

4. The method of claim 2, wherein the first and second flange parts are arranged to an edge of said wall part opposite of and parallel to the respective straight edge of the bottom wall.

Description

BRIEF DESCRIPTION OF THE DRAWING(S)

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

(2) FIG. 1 shows a top view of an unfolded sheet for a cardboard tray.

(3) FIG. 2 shows in perspective view the unfolded sheet of FIG. 1 folded to a cardboard tray.

(4) FIGS. 3A and 3B show a schematic cross-sectional view of the folding of the first flange part.

(5) FIG. 4 shows a cross-sectional view along the line IV-IV in FIG. 2.

(6) FIGS. 5A-5C show schematic cross-sectional views of the method.

(7) FIG. 6 shows a top view of an unfolded sheet for a second embodiment of a cardboard tray.

(8) FIG. 7 shows a top view of an unfolded sheet for a third embodiment of a cardboard tray.

DESCRIPTION OF THE INVENTION

(9) FIG. 1 shows an unfolded sheet 1 for a cardboard tray. The unfolded sheet 1 has a bottom wall 2 with a circumferential edge composed out of straight edges 3.

(10) Wall parts 4 are arranged to each straight edge 3. The wall parts 4 are provided with glue flaps 5 to connect adjacent wall parts 4 together.

(11) The wall parts 4 are alternately provided with either first flange parts 6 or second flange parts 7. The second flange parts 7 are composed out of a single section, while the first flange parts 6 have a first flange part section 8 arranged to the respective wall part 4, a second flange part section 9 and a third flange part section 10.

(12) FIG. 2 shows in perspective view an embodiment of a cardboard tray 20 folded from the unfolded sheet 1 shown in FIG. 1.

(13) The wall parts 4 are folded up and connected via glue flaps 5. The first flange part 6 has the second flange part section 9 double folded against the bottom surface of the first flange part section 8, while the third flange part section 10 is adhered to the respective wall part 4.

(14) The second flange part section 9 has on both ends extending portions 21, which extend in longitudinal direction beyond the first flange part section 8. The extending portions 21 overlap with the ends of the second flange part 7.

(15) Preferably, the overlapping parts of the second flange part section 9 and the second flange part 7 are coated with a heat seal coating, such that the overlapping parts can be adhered to each other with a top sealer.

(16) FIG. 3A shows how the first flange part 8, 9, 10 is folded using a conical erector device or conical gluing system, for example sold by the company Heiber and Schröder. The first, second and third flange part sections are folded into a Z-shape and the third flange part section is adhered to the respective wall part 4.

(17) After the adhesive is set, the first and second flange part sections are bend towards a horizontal position. However, due to the width difference between the width w.sub.1 of the first flange part section and the width w.sub.2 of the second flange part section, the first flange part section remains sloping downwards towards the outside of the tray 20.

(18) FIG. 4 shows a cross-sectional view along the line IV-IV in FIG. 2. The second flange part 7 is in line with the respective wall part 4. It is further clear that the extending portions 21 extend beyond the first flange part section 8, such that the second flange part 7 can be folded onto these extending portions 21 and that a circumferential flange is provided composed out of the second flange parts 7 and the first flange part sections 8.

(19) FIG. 5A shows a first step of an embodiment of a method. A cardboard tray 20 as shown in FIG. 2, is arranged in a top sealer having a lower ring 22 and a top ring 23. Either or both rings 22, 23 are heated. A top seal foil 24 is furthermore provided over the tray 20.

(20) The first flange part section 8 slopes downward, because the width of the first flange part section 8 is larger than the second flange part section 9, such that when the third flange part section 10 is adhered to the outside of wall 4, the first flange part section 8 is urged into a downward sloping position.

(21) In FIG. 5B, both rings 22, 23 are pressed together, such that the first flange part 8, 9, 10 and the second flange part 7, as well as the top seal foil 24 are pressed together. This pressing action causes the first flange part 8, 9, 10, which generally slopes downward, to a horizontal position and the respective wall part 4 to bulge outwardly.

(22) After sealing the top foil 24 to the first flange part section 8 and the second flange part 7, and after sealing the overlapping parts of the flange parts 6, 7, the tray 20 is removed as well as the pressure by the rings 22, 23. As a result, the bulging wall part 4 will straighten and the second flange part section 9 and the overlapping second flange part 7 will return to the downward sloping position, such that the top seal foil 8 is further tensioned, such that cardboard trays 20 can be stacked.

(23) FIG. 6 shows a second embodiment 30 of an unfolded sheet, which can be folded into a box. The sheet 30 is similar to the sheet 1 as shown in FIG. 1 and similar features are designated with the same reference signs.

(24) The unfolded sheet 30 has instead of glue flaps 5, corner parts 31 arranged between each of two adjacent wall parts 4 and the bottom wall 2. The corner parts 31 each comprise a folding line 32, which extends from the bottom 2. This allows for the corner part 31 to be folded double and against one of the adjacent walls 4.

(25) As a result of the corner parts 31, a leak-tight tray is provided, when the unfolded sheet 30 is folded. Preferably, a foil 33 is laminated to at least the wall parts 4, the bottom wall 2 and the corner parts 31, such that even an airtight tray can be obtained.

(26) The flanges 6, 7 are folded and adhered in the same way as with the unfolded sheet 1 and as explained with regard to FIGS. 1-5.

(27) With the corner parts 31 a strong tray can be provided which allows for packaging a cake, which can be baked while being arranged in the tray. The strong walls due to the corner parts prevent bulging, such that a well-shaped cake will be obtained.

(28) FIG. 7 shows a top view of an unfolded sheet 50 for a third embodiment of a cardboard tray, which unfolded sheet can be folded into a box.

(29) The unfolded sheet 50 has a bottom wall 51 with a circumferential edge composed out of straight edges 52. Wall parts 53, 54 are arranged to each straight edge 52. The wall parts 54 are provided with glue flaps 55 to connect adjacent wall parts 53 together.

(30) The opposite positioned wall parts 54, which are provided with the glue flaps 55, are also provided with first, second and third flange part sections 56, 57, 58.

(31) When folding the unfolded sheet 50 to a box, the second flange part section 57 will be double folded against the first flange part section 56, while the third flange part section 58 will be folded against and adhered to the wall part 54.

(32) The wall parts 53 are provided with a single flange 59, which will border the rounded ends of the first and second flange part sections 56, 57, when the sheet 50 is folded into a box. As a result, the single flanges 59 and the first flange part sections 56 will form a peripheral horizontal flange around the opening of the formed box.

(33) When a top foil is sealed onto this peripheral horizontal flange, the flange part sections 56, 57, 58 will ensure that the foil is provided with tension, as described above, while the arrangement of the foil on the full peripheral horizontal flange will provide additional rigidity to the box. The adhering of the foil to the single flanges 59 further contributes to the rigidity of the sealed box. However, the single flanges 59 could also be left out, resulting in a box, which has less rigidity, but still has a tensioned foil.