EP2619011B1 - Embossing machine including a platen press - Google Patents

Description

The present invention relates to a stamping machine comprising a platen press.

It is known to print texts and / or patterns by stamping, that is to say to deposit by pressure on a sheet-like support, colored or metallized film from one or more strips to be stamped. commonly referred to as metallized strips. In the industry, such a transfer operation is usually carried out by means of a vertical platen press, in which the printing media are introduced sheet-by-sheet, while the feeding of strips to be stamped takes place keep on going.

In a standard platen press, the stamping takes place between a fixed platen extending horizontally, and a platen movably mounted in displacement in a vertical reciprocating motion. This type of press being generally automated, means of transport are provided to bring one by one each sheet between the plates. In practice, it is usually a series of gripper bars, each of which in turn seizes a sheet at its front edge, before pulling it between the two plates of the press when the latter are sufficiently apart .

A stamping strip is schematically composed of a polyester-type support film, on which a pigmented layer is secured by means of a layer of wax. The outer face of this pigmented layer is coated with a hot melt adhesive layer. As in the case of leaves, the diet of the press Punching tapes are traditionally automated, in this case by means of a drive system able to unroll and circulate each of said tapes along a well defined travel path, which passes in particular through the platen press. Generally, such a tape drive system combines a series of cross bars that are located all along the scroll path to guide the tape movement, with several advance trees positioned downstream of said scroll path for respectively driving each of said bands in displacement.

In the industry, stamping is carried out on specialized automatic machines. There are different types of machine construction, the most common of which are vertical platen presses that work with vertical back and forth motion, cylinder presses and rotary presses.

The invention relates exclusively to the field of machines operating with a platen press. In these machines, the movement back and forth is printed on the movable plate by a set of members forming knee and commonly called knee joint cooperating with a drive mechanism type crankshaft and connecting rods. When the crankshaft describes a rotary movement, the knee pads move back and forth to the movable stage.

In these machines the quality of the deposit depends on several parameters. The first is the stamping force. The stamping force is obtained by vertically displacing the movable plate and its movement mechanism, by means of adjustment keys, with respect to a vertical position in which is flush with the surface of the fixed plate. A displacement of a few tenths of a millimeter is enough to precisely adjust the stamping force which can be considerable. Typically this displacement is between one tenth of a millimeter and less than three millimeters.

The stamping force contributes to the regular adhesion of the stamping sheet to the substrate. If the stamping force is too weak, the bond between the substrate and the deposit does not provide sufficient scratch resistance. It may even happen that the deposit is not attached to the substrate, or that there is no removal. Conversely, if the stamping force is too high, stamping too deep may occur, with a deterioration of the substrate that may lead to breakage by cutting, or a deterioration of the deposit or both. For example when using metallized strips, there is frequently a loss of the brightness of the varnish deposit when the stamping force is too high. Nevertheless, for the users of these machines, the stamping force that the machine can support is the essential characteristic of the machine.

Temperature is another crucial parameter to obtain a good quality of removal. The temperature is generally between 90 ° C and 130 ° C and it provides a dual function. Its first function is to soften the layer of wax that binds the layer or layers to be deposited (for example a metallized layer and a layer of pigmented varnish) to the polyester strip. The temperature must therefore be higher than the melting point of the wax. The second function of the temperature is to activate the sticky adhesive which will ensure the connection between the support and the deposit. Different formulations are adapted to different media. For example, for a paper or cardboard support, the adhesive contains polymers compatible with cellulose. For a polypropylene support, it will be composed of polymers compatible with polypropylene. The larger the amount of adhesive, the stronger the bonding. On the other hand, less adhesive makes it possible to obtain a better definition of the details of the stamping. Too low a temperature will not provide these two functions. Conversely, too high a temperature may burn the tape or make the adhesive too liquid and overflow the area to be stamped by deteriorating the quality of the perimeter of the pattern.

In general, the higher the temperature and the higher the stamping force, the higher the production rate can be.

To achieve high production rates, these two parameters have been gradually increased until the limits of the materials used. Thus the rate is often limited only because of the characteristics of the materials.

The document US 2004/0103799 describes a main drive mechanism in a platen press for cutting and gilding. The mechanism includes a base, a movable platen, and four sets forming knee pads. Four rollers present at the knee joint cooperate with four sets of cams of a drive shaft.

Also, the technical problem to be solved by the object of the present invention is to provide a stamping machine with a platen press that allow to achieve higher rates than existing machines.

The solution to the technical problem posed is, according to the present invention, in that the machine comprises in combination the features defined by claim 1.

The present invention also relates to advantageous optional features which will become apparent in the course of the description which follows, and which will have to be considered in isolation or according to their technical combinations defined by the dependent claim 2.

• La Figure 1 illustre une machine d'estampage selon l'art antérieur.
• Les Figures 2a et 2b illustrent le fonctionnement du système à vilebrequin et bielles de la machine selon l'art antérieur.
• Les figures 3a et 3b représentent la presse à platine d'une machine selon l'invention.
• La figure 4 compare les courbes des positions verticales des platines mobiles d'une machine selon l'art antérieur et d'une machine selon l'invention
• La figure 5 représente un exemple de came d'une machine selon l'invention.

This description is intended to better understand what the invention is and how it can be done. The description is further given with reference to the accompanying drawings in which:

• The Figure 1 illustrates a stamping machine according to the prior art.
• The Figures 2a and 2b illustrate the operation of the crankshaft system and connecting rods of the machine according to the prior art.
• The figures 3a and 3b represent the platen press of a machine according to the invention.
• The figure 4 compares the curves of the vertical positions of the moving plates of a machine according to the prior art and of a machine according to the invention
• The figure 5 represents an example of a cam of a machine according to the invention.

For the sake of clarity, the same elements have been designated by identical references. Likewise, only the essential elements for understanding the invention have been represented, and this without regard to the scale and in a schematic manner.

The Figure 1 represents a printing machine 1 which is intended for the customization of cardboard packaging for the luxury industry. Commonly called gilding machine, this printing machine 1 is conventionally composed of several work stations 100, 200, 300, 400, 500 which are juxtaposed but interdependent one by one to form a unitary unit able to process a succession of supports leaf-shaped. There is thus a feeder 100, a margin table 200, a stamping station 300, a feed and recovery station 400, and a receiving station 500. A transport device 600 is also provided for moving each sheet individually from the output of the margin table 200 to the receiving station 500, including through the stamping station 300.

The different parts 100, 200, 300, 400, 500, 600 of the printing machine 1 being perfectly known from the state of the art, they will not be described in detail here, both in terms of their structure and their operation.

In this particular embodiment, selected solely by way of example, the feeder 100 is supplied by means of a succession of pallets on each of which are stacked a plurality of cardboard sheets. The latter are successively removed from the top of the stack by a gripping member which transports them to the margin table 200 directly adjacent.

At the level of the margin table 200, the sheets are laid by the gripping member, that is to say placed one after the other so as to overlap partially. The entire web is then moved along a platen toward the embossing station 300 by means of a belt conveyor mechanism. At the end of the web, the head sheet is systematically positioned accurately, for example by means of front and side cleats.

The workstation located immediately after the margin table 200 is therefore the stamping station 300. The latter has the function of depositing on each sheet, by hot stamping, the film which is issued from a stamping strip 410. It uses for this a platen press 310 within which the stamping operation operates classically between a heated upper plate 320 which is fixed, and a bottom plate 330 which is mounted movably in displacement in a back and forth vertical movement.

Downstream of the stamping station 300 is the tape feed and recovery station 400. As the name suggests, this station plays a dual role since it is responsible for ensuring both the feeding the machine belt stamping 410, and the evacuation of the same band once it used.

In this particular exemplary embodiment, the strip 410 is conventionally stored in a wound form, around a supply reel 420 rotatably mounted. After passing through the platen press 310, the band 410 is evacuated by a recovery device 430.

The process of processing the sheets in the printing machine 1 is completed in the receiving station 500 whose main function is to repackage the previously treated sheets. For this, the transport device 600 is arranged to automatically release each sheet when the latter is found at the right of this new battery. The sheet then falls squarely on the top of the stack.

In a very conventional manner, the transport device 600 implements a series of gripper bars 610 which are movably mounted in transverse translation by means of two feed trains. chain 620 arranged laterally on each side of the stamping machine 1. Each chain train 620 traverses a loop which allows the gripper bars 610 to follow a path passing successively through the stamping station 300, the feed station and 400 and the receiving station 500.

The movable stage 330 is supported by several articulated members forming a toggle joint 340. Each articulated organ forming a toggle joint 340 is composed of two segments: one has an end rotatably mounted relative to the movable stage, the other segment at one end rotatably mounted. relative to a support carried by an adjustment key. The other two end segments are articulated relative to each other via an axis; around which is also articulated a connecting rod 350 connected to the crankshaft 360.

The adjustment keys 370 are in the shape of a wedge, and can move in translation. The movement of a key 370 causes a displacement. vertical of the articulated member forming the toggle joint 340 that it supports, as well as the movable plate 330. The stamping force is precisely adjusted thanks to these keys 370.

The Figures 2a and 2b show in more detail the principle of operation of the mechanism that prints the movement back and forth to the movable plate 330 in the platen press 310 of a stamping machine according to the prior art. The Figure 2a represents the position of the articulated members forming the toggle joint 340 and connecting rods 350 when the movable stage 330 is in the low position. The Figure 2b represents the position of these same members when the movable plate 330 is in the high position.

In a way similar to Figure 2a and 2b , the Figures 3a and 3b represent the operating principle of the mechanism that prints the movement, back and forth to the movable plate 330 in the platen press 310 of a stamping machine according to the invention. The Figure 3a represents the position of the articulated members forming the toggle joint 340 when the movable stage 330 is in the low position. The Figure 3b represents the position of these same members when the movable plate 330 is in the high position.

The stamping machine according to the invention does not include a crankshaft or rods as the stamping machine according to the prior art. On the other hand, it comprises a camshaft 380 carrying at least one cam 385 per articulated member forming a toggle joint 340.

According to the conventional definition, a cam 385 is a mechanical member that renders a movement synchronously with the rotational movement of the cam shaft 380 which carries it. The cam 385 is, in a conventional manner, a cylinder of variable radius between a minimum radius and a maximum radius and the restored movement is defined by its outer profile.

According to the invention, each articulated member forming a toggle joint 340 comprises a connecting member 390 which cooperates with a cam 385 carried by the camshaft 380. By following the external profile of the cam 385, the linking member 390 will restore the movement corresponding to this outer profile, and the articulated member forming the toggle joint 340 will print a reciprocating movement to the movable plate 330.

In order to better realize the difference between the operation of a machine according to the invention and that of a machine according to the prior art, the Figure 4 represents the curve of positions occupied by the movable platen 330 during a back-and-forth movement, which also corresponds to a machine cycle, for a machine according to the prior art with the curve C1 and for a machine according to the invention with the curve C2. The curves C1 and C2 of the Figure 4 correspond to the positions of the plate when there is no contact with the fixed plate 320 but a simple outcrop of the work surfaces. In both cases, the stamping force is zero. The flush with the fixed platen occurs in the upper parts of the two curves C1 and C2.

In both cases, to apply a stamping force, it will be necessary to move the adjustment keys 370. It is immediately realized that in the machines according to the prior art the stamping force obtained will not be constant, and that the strength stamping will be important, the less it will be constant. So much so that when the rate increases, and it is necessary to apply a very important stamping force, two phenomena occur: the stamping force is very important over a relatively short period of time, and the movable plate 330 enters into contact with the fixed plate 320 with a high speed of displacement. The impact may then damage the materials, as well as the maximum stamping force.

On the other hand, we immediately see with the Figure 4 that in a machine according to the invention, the stamping force will be substantially constant throughout the period of contact between the movable plate 330 and the fixed plate 320.

However, contrary to the prejudices of the users of the stamping machines, it is much more efficient to apply a lower stamping pressure over a relatively long duration, that to apply a very important stamping force over a very short time. Therefore, the machines according to the invention can perform work at a high rate, applying a much lower stamping force.

According to experimental results, for a given work, the stamping force decreases between 20% and 50%, with an average greater than 35% relative to the maximum stamping force applied by a machine according to the prior art. On the other hand only 7% of the work can be carried out with a machine according to the prior art, whereas the proportion increases to more than 90% with a machine according to the invention. And for a given job, the pace increases between 10% and more than 65%, with an average of about 40%. The importance of the invention is measured in terms of increasing the productivity of the machines.

Moreover, Figure 4 highlights another advantage provided by the invention. In the machines according to the prior art, the movable plate 330 makes a significant displacement when it moves away from the fixed plate 320. As a result, the mobile plate 330 requires more free space to perform its movement of movement. back and forth and, above all, because of this important displacement of strong turbulences appear at high rates and these turbulences can disturb the behavior of the elements in the form of sheets and bands to be stamped. On the other hand, the lower displacements effected by the mobile stage 330 of a machine according to the invention make it possible to greatly reduce this turbulence at a very high rate.

Preferably, a machine according to the invention comprises four articulated members forming knee pad 340. The Figure 5 is a camshaft 380 adapted for this preferred embodiment, with four cams 385 forming two pairs, intended to cooperate with the four connecting members 390 of the four articulated members toggle 340.

Advantageously, each cam 385 has a sector of at least 5 ° radius substantially equal to the maximum radius of the cam. The maximum radius of the cam corresponds to the most taut position of the articulated members forming toggles 340, therefore to the highest stamping force. This sector therefore makes it possible to have a substantially constant stamping force. Preferably, this sector is at least 25 °, which reduces the stamping force applied, giving a significant application time.

Of course, the invention relates to any stamping machine 1 comprising a platen press 310, as defined by claim 1. In particular, the movable platen 330. can perfectly be the upper platen, and the fixed platen 320 platinum lower. Similarly, the plates do not necessarily have to be positioned horizontally, etc.

Claims (2)

1. Stamping machine of a stamping strip (410) on a support in sheet form, comprising a platen press (310) comprising:

   - a fixed platen (320),

   - a moving platen (330), effecting a reciprocating movement perpendicular to the plane of the platens (320, 330),

   - at least two articulated members forming toggle joints (340), imparting the reciprocating movement to the moving platen (330), and

   - a camshaft (380), bearing at least one cam (385) per articulated member forming a toggle joint (340), each articulated member forming a toggle joint (340) comprising a connecting member (390) collaborating with the cam (385) borne by the camshaft (380),
   characterized in that each cam (385) comprises a sector of at least 25° radius equal to the maximum radius of the cam (385).
2. Stamping machine according to claim 1, characterized in that the machine comprises four articulated members forming toggle joints (340).

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