FR2638674A1 - TOOL FOR SCRAPING PAPER OR CARDBOARD SHEETS - Google Patents

Abstract

Tool for grooving (scoring) sheets 8 of paper or cardboard, of the type comprising: - a pressure plate 1 made from a hard material; - grooving (scoring) threads (ribs) 3 integral with the said pressure plate 1; - a counterpressure plate 5, also made from a hard material, on which the sheet 8 to be grooved (scored) rests through the effect of the approach of the pressure plate 1, characterised in that the front face 7 of the counterpressure plate 5, arranged opposite the threads (ribs) 3, is covered with a layer 6 made from a hard resilient material.

Description

TOOL FOR SCRAPING PAPER OR CARDBOARD SHEETS
The invention relates to a tool for creasing sheets of paper or cardboard, in particular on a platen press or on a rotary press.

As is known, most generally, the creasing of a carton is carried out on a platen or rotary press consisting essentially
- a pressure plate made of a hard material such as steel
- grooving threads integral with said pressure plate, the end of which has a rounded part
- a backpressure plate, also made of a hard material such as steel, on which are arranged creasing counterparts placed opposite the creasing threads, and on which the sheet to be creased under the effect of the approximation of the pressure plate.

 If more generally, the back pressure plate is animated with a movement relative to that of pressure, the reverse is also possible. In practice, the threads are arranged in a plywood plate secured to the press tool, the threads being supported on the pressure plate proper.

This creasing technique, although very widespread, still has many disadvantages. We can cite
- the need to manufacture counterparts of a precise shape adapted to each creasing net and to the type of cardboard to be creased;
- the need to manufacture a counterpart fitting tool
- the need to carry out very precisely the installation of counterparts vis-à-vis the rowing nets
- the need to control the permanence of the adjustment of the counterparts vis-à-vis the grooving nets
- the change in shape of the counterparts and their wear, due to the numerous successive passages of the sheets to be creased
- only partial delamination of the cardboard during creasing, both in the direction of the thickness of the cardboard and in its plane
- damage to the cardboard in the tight area between the edges of the creasing net and the upper corners of the counterpart: cracking on the front and back, breakage of the interior fibers
- the high resistance of the grooves to folding.

 The invention overcomes these drawbacks. It targets a creasing tool which significantly improves the quality of this operation and eliminates the delicate and tedious operations of setting up and controlling the positioning of counterparties.

The tool according to the invention for creasing sheets of paper or cardboard of the type comprising
- a pressure plate made of hard material
- rowing nets, integral with said pressure plate,
- a back pressure plate, also made of a hard material, on which the sheet to be creased rests under the effect of the approximation of the pressure plate, is characterized in that the front face of the back pressure plate, arranged facing the nets, is covered with a layer of a hard elastic or pseudo-elastic material.

 In other words, the invention consists in placing in the creasing tool between the threads and the back-pressure plate a layer of a hard elastic or pseudo-elastic material on which the sheet to be creased rests.

 In the description and in the claims, “elastic or pseudo-elastic material” means a material which can undergo large deformations under a given force, but which returns almost instantaneously, when this constraint is removed, to its original form and that, without significant and permanent modification of its essential characteristics or its molecular constitution.

 In practice, this material must also be hard and resistant to wear under the action of the net (hardness of at least 50 Shores).

 Advantageously, as hard, elastic material, use is made of natural or synthetic rubber, cellular foams or complex materials. It has been found that good results are obtained with a double-sided coated fabric, the textile support of which consists of a warp and weft fabric in extensible multifilament yarns; the coating is advantageously made of any suitable elastomeric material, such as in particular chloroprene or latex. The thickness of the layer of elastic material must be greater than the positioning tolerances of the plates, counter-plates and threads. As in practice, this tolerance is of the order of a tenth of a millimeter, the thickness of the characteristic elastic layer must be at least 0.2 millimeter and advantageously of the order of a millimeter.

 The characteristic of the invention lies essentially in the interposition between the thread and the plywood of a layer of a hard, elastic material. The interposition of this characteristic hard, elastic material not only provides a significant improvement in the quality of creasing, but above all implements different functions since, as we will see, creasing, which consists in fact of the association of a Phenomenon of delamination of the cardboard and of a folding phase of the cardboard, is no longer carried out essentially by shearing, but by lateral traction, from which new and advantageous results ensue.

 The manner in which the invention can be implemented and the advantages which result therefrom will emerge more clearly from the following exemplary embodiments, given by way of non-limiting example, in support of the appended figures, in which, to facilitate understanding, the proportions have not been met.

 Figure 1 is a summary sectional view of a creasing tool according to the invention.

 Figures 2 and 3 schematically show the main phases of the creasing process according to the invention.

 The platen press equipped in accordance with the invention essentially comprises a fixed pressure plate (1) of steel, on which is fixed a plywood plate (2) which carries the grooving threads (3) of steel. The bottom (4) of these threads is supported on the pressure plate (1). The back pressure plate (5) made of hard steel, capable of being moved up and down as indicated by the arrow F, is, according to the characteristic of the invention, covered with a layer (6 ) in a hard elastic material such as for example a warp and weft fabric in elastic textured multifilament yarns, covered on both sides with a coating of chloroprene, the assembly having a thickness of 1.0 millimeter.

 According to the characteristic of the invention, the front face (7) of the counterpressipn plate (5) is covered with this characteristic layer (6), which in turn receives the cardboard sheet (8) to be creased, of which the front (9) is directed towards the net (3) and the back (10) towards the characteristic elastic layer (6).

 The layer of elastic or pseudo-elastic material (6) is held on the back-pressure plate (5) by any suitable means. Advantageously, it is removable.

 When the net (3) comes into contact with the cardboard sheet (8) (Figure 2), it exerts pressure on the layer of hard elastic material (6), which is pushed back, then stretched on both sides. 'an axis parallel to the longitudinal axis of the crease net. The successive layers of the cardboard opposite the creasing net (3) are then delaminated, and this gradually from the face (10) of the cardboard in contact with the layer of hard elastic material (6) to the face (9) cardboard in contact with the crease net (3). This delamination is also carried out gradually from the part of the cardboard located under the central part of the creasing net (3) to the part of the cardboard located under the edges of the creasing net (3).

 Then the crease net (3) rises (Figure 3) and the layer of elastic hard material (6) returns to its original shape.

 Thus, unlike the current creasing technique in which the creasing of the sheet is carried out by shearing, in the method according to the invention, the creasing is carried out essentially by lateral traction caused by the entrainment of the material and more precisely from the back (12) of the sheet (10).

The creasing technique according to the invention has many advantages compared to the technique used until now. We can cite
- its simplicity,
- its ease of implementation,
- the fact that there is no longer any need to make "bets" to recover the level differences and the flatness defects between the threads and the plates, resulting in a considerable saving of specialized personnel and at least on the other hand, the possibility of using nets of lower tolerance
- delamination of all the layers of the cardboard and over the entire width of the groove
- the reduction in the folding resistance of the creased cardboard
- finally, the ease of fitting and replacing the characteristic layer of hard and elastic material.

 In this way, this creasing tool can be used advantageously for creasing paper and cardboard in the most diverse formats and shapes.

Claims (4)

 1 / Tool for creasing sheets (8) of paper or cardboard, of the type comprising  - a pressure plate (1) made of a hard material  - creasing threads (3) integral with said pressure plate (1);  - a back pressure plate (5), also made of a hard material, on which rests the sheet (8) to be grooved under the effect of the approximation of the pressure plate (1), characterized in that the front face ( 7) of the back-pressure plate (5), arranged opposite the threads (3) is covered with a layer (6) of a hard elastic material.  2 / creasing tool according to claim 1, characterized in that the layer (6) of elastic material has a thickness greater than the positioning tolerances of the pressure plates (1), back pressure (5) and the threads ( 3).  3 / creasing tool according to one of claims 1 and 2, characterized in that the layer (6) of elastic hard material has a hardness of at least 50 shores.  4 / creasing tool according to one of claims 1 to 3, characterized in that the elastic layer (6) consists of a warp and weft fabric in extensible multifilament yarns coated on both sides with a hard elastic material.