GB1585059A - Method of creasing sheet pvc and other plastics material - Google Patents

Description

(54) METHOD OF CREASING SHEET PVC AND OTHER PLASTICS MATERIAL (71) We, DRG (UK) LIMITED, a British Company of 1, Redcliffe Street, Bristol, BS99 7QY, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method of creasing sheet PVC and other plastics material.

There are various methods of creasing sheet PVC and Plastics mainly based on pressure and special shaping of the creasing rules. The main problem is that the crease does not retain its properties because of the built in "memory" which causes the material to revert to its near former state. Thus the formation and efficiency of the folds in a PVC carton become impaired and the carton does not erect squarely and satisfactorily. We have found that if the creasing units of the forme are replaced by RF electrodes and the indentation into the sheet material is controlled to a predetermined degree then the structure of the material in the indentation area is altered resulting in a permanent indentation and destruction of the "memory" factor in the material. Following this creasing process normal cutting in accurate register and carton making procedures can be carried out and a carton is produced for either easy hand erection or, if suitably designed, machine packaging.

According to this invention there is provided a method of creasing sheet PVC and other plastics material which comprises applying RF electrodes to the sheet material at the positions where the creases are required and heating to produce indentations of reduced thickness at said positions. The thickness of the indentations may be reduced by 85% of the original thickness. The sheet material may be in the form of separate sheets or a web.

The invention also comprises cartons and other containers made by this method.

One way of carrying out this invention is illustrated in the accompanying drawings wherein: Fig. 1 is a portion of a sheet of PVC creased by the method of the invention; Fig. 2 is a perspective view of a carton made from the sheet of Fig. 1, and Fig. 3 is a cross section of an indentation made by the method of the invention shown to a greatly enlarged scale.

To produce the sheet shown in Fig. 1 a forme is prepared using a system of RF electrodes in place of the creasing rules and omitting the usual cutting rules. A sheet 2 of PVC is applied to the forme and RF heating is applied to the electrodes so as to form crease lines 4 by making indentations in the sheet to such an extent that the thickness of the material is reduced by 85% of the original thickness at the creases. Following this creasing, normal cutting in accurate register is carried out in the places indicated in chain dotted lines 6 in Fig. 1.

Normal carton making procedures follow to produce the carton shown in Fig. 2.

Referring to Fig. 3, it can be seen that the thickness of the PVC has been greatly reduced at the crease line 4. The RF treatment has also altered the structure of the material within the indentation area resulting in the folding properties of the sheet at the crease being retained and the "memory" factor being destroyed.

Instead of working with separate sheets, a web of sheet material, fed from a reel, can be employed. A platen action press would then be a suitable machine to carry the forme.

WHAT WE CLAIM IS: 1. Method of creasing sheet PVC and other plastics material which comprising applying RF electrodes to the sheet material at the positions where the creases are required and heating to produce indentations of reduced thickness at said positions.

2. Method of creasing sheet PVC and other plastics material according to claim 1 wherein the thickness of the indentations are reduced by 85% of the original thickness of the sheet.

3. Method of creasing sheet PVC and other plastics material substantially as described with reference to the accompanying drawings.

4. Sheet material creased by the method claimed in any one of claims 1-3.

5. Carton made from the sheet material of

claim 4.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. (54) METHOD OF CREASING SHEET PVC AND OTHER PLASTICS MATERIAL (71) We, DRG (UK) LIMITED, a British Company of 1, Redcliffe Street, Bristol, BS99 7QY, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method of creasing sheet PVC and other plastics material. There are various methods of creasing sheet PVC and Plastics mainly based on pressure and special shaping of the creasing rules. The main problem is that the crease does not retain its properties because of the built in "memory" which causes the material to revert to its near former state. Thus the formation and efficiency of the folds in a PVC carton become impaired and the carton does not erect squarely and satisfactorily. We have found that if the creasing units of the forme are replaced by RF electrodes and the indentation into the sheet material is controlled to a predetermined degree then the structure of the material in the indentation area is altered resulting in a permanent indentation and destruction of the "memory" factor in the material. Following this creasing process normal cutting in accurate register and carton making procedures can be carried out and a carton is produced for either easy hand erection or, if suitably designed, machine packaging. According to this invention there is provided a method of creasing sheet PVC and other plastics material which comprises applying RF electrodes to the sheet material at the positions where the creases are required and heating to produce indentations of reduced thickness at said positions. The thickness of the indentations may be reduced by 85% of the original thickness. The sheet material may be in the form of separate sheets or a web. The invention also comprises cartons and other containers made by this method. One way of carrying out this invention is illustrated in the accompanying drawings wherein: Fig. 1 is a portion of a sheet of PVC creased by the method of the invention; Fig. 2 is a perspective view of a carton made from the sheet of Fig. 1, and Fig. 3 is a cross section of an indentation made by the method of the invention shown to a greatly enlarged scale. To produce the sheet shown in Fig. 1 a forme is prepared using a system of RF electrodes in place of the creasing rules and omitting the usual cutting rules. A sheet 2 of PVC is applied to the forme and RF heating is applied to the electrodes so as to form crease lines 4 by making indentations in the sheet to such an extent that the thickness of the material is reduced by 85% of the original thickness at the creases. Following this creasing, normal cutting in accurate register is carried out in the places indicated in chain dotted lines 6 in Fig. 1. Normal carton making procedures follow to produce the carton shown in Fig. 2. Referring to Fig. 3, it can be seen that the thickness of the PVC has been greatly reduced at the crease line 4. The RF treatment has also altered the structure of the material within the indentation area resulting in the folding properties of the sheet at the crease being retained and the "memory" factor being destroyed. Instead of working with separate sheets, a web of sheet material, fed from a reel, can be employed. A platen action press would then be a suitable machine to carry the forme. WHAT WE CLAIM IS:

1. Method of creasing sheet PVC and other plastics material which comprising applying RF electrodes to the sheet material at the positions where the creases are required and heating to produce indentations of reduced thickness at said positions.

2. Method of creasing sheet PVC and other plastics material according to claim 1 wherein the thickness of the indentations are reduced by 85% of the original thickness of the sheet.

3. Method of creasing sheet PVC and other plastics material substantially as described with reference to the accompanying drawings.

claim 4.

4. Sheet material creased by the method claimed in any one of claims 1-3.

5. Carton made from the sheet material of