EP0794013A1 - Installation for preparation and delivery of a coating composition to a paper coating head or the like - Google Patents

Abstract

Apparatus for coating paper and similar materials comprises a series of hoppers (T1-T5) with outlet valves (V1-V5) for supplying different ingredients to a premixer (2), whose discharge duct (C2) leads to a main mixer (1) with a high speed agitator (7) which in turn supplies coating mixture via a reservoir (3) to a coating head (5). A detector controls valves (V1-V5) to refill premixer (2) when the level therein falls. Detector (D4) monitors the level in reservoir (3).

Description

Technical area

The invention relates to the field of the paper industry and more specifically to paper coating installations. It relates more precisely to the installation for preparing and dosing the composition intended to supply the coating head.

Prior Techniques

In known manner, in a coating installation, the coating head is supplied with a composition commonly called "coating sauce". This coating sauce is made up of the mixing and mixing of different pigments, fillers and binders intended to give the paper special visual and tactile qualities.

The preparation of this coating sauce is carried out in a mixing unit generally called a "coating kitchen". Two main techniques, different in principle, are generally used to ensure the dosing and feeding of the coating head. Thus, the technique commonly known as "batch" is known, in which the various ingredients of the coating sauce, contained in specific dosing hoppers, are poured in selected quantities into a mixing and storage tank. When the stirring and mixing operation is complete, the quantity of sauce produced is poured into the circuit connected to the coating head. Thus, the operation for preparing the sauce and its injection into the feeding circuit of the coating head are independent, and necessarily consecutive. It follows that the overall operation of the installation is discontinuous, which requires the presence of relatively expensive storage tanks.

Furthermore, there are also known installations seeking to overcome this drawback, operating continuously. Thus, in this solution, the various dosing hoppers pour the coating ingredients directly into the circuit supplying the coating head, undergoing mixing. Although increasing the speed of actuation of the installation, this solution requires extremely precise metering means making it possible to deliver the exact quantity of pigments or binders necessary for the quality of coating coating used. These means of precise dosing increases the overall cost of an installation.

The problem which the invention therefore proposes to solve is to provide a sleeping kitchen allowing flexible operation concerning the feeding of the sleeping head, which delivers a quality sauce strictly constant over time, and which does not require special and high precision dosing means.

Statement of the invention

The invention therefore relates to an installation for the preparation and supply of a coating composition to a coating head for paper or the like, comprising a plurality of hoppers, each intended to receive and deliver an ingredient of the composition.

• un bac prémélangeur alimenté par les différentes trémies, destiné à mélanger et à homogénéiser la composition formée ;
• un bac-réacteur alimenté par le bac prémélangeur, comportant des moyens de cisaillement de la composition ;
• une capacité-tampon, directement et en permanence alimentée par le bac-réacteur, reliée à la tête de couchage ;
• des moyens pour détecter un besoin en composition de la tête de couchage;
• et des moyens de commande reliés auxdits moyens de détection pour alimenter le bac-prémélangeur en ingrédients issus des trémies.

This installation is characterized in that it comprises:

• a premixer tank fed by the various hoppers, intended for mixing and homogenizing the composition formed;
• a reactor-tank fed by the premixer tank, comprising means for shearing the composition;
• a buffer tank, directly and permanently supplied by the reactor vessel, connected to the coating head;
• means for detecting a need for composition of the coating head;
• and control means connected to said detection means for supplying the premixer with ingredients from the hoppers.

In other words, the installation according to the invention comprises means for simultaneously carrying out, on the one hand, the metering and mixing of the different ingredients to obtain the coating sauce, and on the other hand the continuous feeding of the head with the sauce thus prepared. In other words, the installation combines the advantages of precise and independent dosing with those of continuous feeding of the coating head without any interruption.

In a first variant, the premixer comprises a composition level detector, for actuating the means for controlling the supply of ingredients.

In other words, according to a first regulation strategy, the triggering of the dosage results from the monitoring of the level in the premixer. Thus, when the level in this premixer reaches a low threshold, the various dosing hoppers pour part of their content into the premixer.

In an advantageous geometry, the premixer tray marries at its lower end a frustoconical shape in which the level detector and an agitator are arranged.

Advantageously, the installation comprises a drain pump arranged on the circuit between the premixer and the reactor. In this way, the emptying of the premixer is ensured at a regular rate, regardless of the viscosity of the liquid. The flow times are therefore regular.

As already said, the invention consists in carrying out a discontinuous dosage of the various ingredients making up the coating sauce, and at the same time ensuring a continuous supply of the coating head with this sauce. Thus, in an advantageous embodiment, the reactor tank into which the mixture produced in the premixer is periodically poured, comprises a high speed agitator to ensure the dispersion of the composition by shearing.

As already said, after dispersion, the coating sauce is poured into a buffer tank directly connected to the pump located on the circuit in the direction of the coating head.

Advantageously, the buffer capacity has a level detector of the composition for actuating the supply to the reactor vessel. Thus, in this alternative embodiment, the need for coating sauce corresponds to a low threshold in composition in its buffer capacity, which causes, when it is reached, the opening of a valve and the operation of the pump. drain located between the premixer and the reactor.

Advantageously in practice, the supply of the buffer capacity by the reactor tank is effected by means of an overflow.

To ensure, in accordance with the problems posed, a continuity of supply compatible with a discontinuous dosing of the coating sauce, the volume of the buffer capacity is greater than the useful volume of the premixer tank.

In another alternative embodiment, the circuit between the buffer capacity and the coating head comprises a sensor for actuating means for controlling the supply of ingredients to the premixer tank.

In other words, in this other architecture corresponding to a different control strategy, the discontinuous metering corresponding to the supply of the premixer is triggered by flow or level thresholds observed downstream of the actual sleeping kitchen.

In a particular embodiment, the hoppers, the premixer tank, the reactor tank and the buffer tank also have means for supplying and washing water.

Brief description of the drawings

• La figure 1 est un synoptique simplifié général montrant les différents éléments composant une cuisine de couchage conforme à l'invention.
• La figure 2 est un diagramme montrant une première phase de fonctionnement de la cuisine de couchage, dans laquelle la capacité-tampon est remplie.
• La figure 3 est le même diagramme, dans une phase ultérieure pendant laquelle le niveau dans la capacité décroît tandis que le pré-mélangeur se remplit.
• La figure 4 est le même diagramme illustrant la phase suivant la vidange du prémélangeur.

The manner of carrying out the invention, as well as the advantages which ensue therefrom, will emerge clearly from the description of the embodiment which follows, with the support of the appended figures, in which:

• Figure 1 is a general simplified block diagram showing the different elements making up a sleeping kitchen according to the invention.
• Figure 2 is a diagram showing a first operating phase of the sleeping kitchen, in which the buffer capacity is filled.
• FIG. 3 is the same diagram, in a later phase during which the level in the capacity decreases while the premixer is filling.
• FIG. 4 is the same diagram illustrating the phase following the emptying of the premixer.

Way of realizing the invention

In known manner, a sleeping kitchen comprises a plurality of elementary tanks (not shown) containing ingredients necessary for the composition of the sleeping sauce. The various elements and organs composing the sleeping kitchen are intended to ensure the mixing and the production of a sufficient quantity for the supply of the circuit (C4) leading to the sleeping unit (5) proper.

According to the invention, the various storage tanks are linked by all known means, to a plurality of dosing hoppers (T1-T5). For the sake of clarity of the drawings, the number of hoppers shown is five, but it goes without saying that the principle of the invention applies to a much higher number of hoppers. Each of these dosing hoppers (T1-T5) is connected to a circuit (C1) opening into a characteristic premixer (2). Each hopper is equipped with a level sensor (D1) and a valve (V1-V5) allowing the supply of the premixer to be controlled. Each of these hoppers is located at a height greater than that of the premixer, so that the flow in this premixer (2) is effected by gravity.

The premixer (2) notably comprises stirring means (6) and a sensor (D2) capable of determining the quantity of liquid it contains.

This premixer (2) is connected to a high capacity reactor (1), via a circuit (C2) on which are mounted an isolation valve (V6) and a pump (P1), for example of the volumetric type. This reactor (1) comprises means making it possible to ensure the dispersion of the coating sauce by shearing, by rotation at high speed (several thousand revolutions per minute), and this in order to ensure homogenization of the coating sauce. The circuit (C2) allows the introduction of the coating sauce not yet dispersed in the lower part of the reactor. This is equipped with a level detector (D3).

In accordance with an essential characteristic of the invention, the reactor (1) is associated with a buffer capacity (3) in which the coating sauce dispersed by the reactor (1) flows. In a preferred embodiment, this flow takes place via an overflow circuit (C3), connected to the upper part of the reactor (1). In accordance with a fundamental characteristic of the invention, it is important that the volume of this buffer capacity (3) is greater than the useful volume of the premixer (2), and this in order to ensure a continuous supply of the coating head (5) during the dosing phase by filling the premixer (2). This buffer capacity can be achieved by a tank itself or even by a simple diameter pipe making it possible to comply with the volume criterion set out above.

This buffer capacity (3) is connected, via the circuit (C4) to the supply unit (5) of the coating head. A valve (V7), arranged on this circuit (C4), upstream of the transfer pump (4) allows the isolation of the sleeping kitchen from the feeding unit of the sleeping head (5 ).

The operation of the sleeping kitchen according to the invention is as follows.

Thus, Figure 2 illustrates the operating phase during which the reactor (1) has just received a quantity of composition from the premixer (2), not yet dispersed. At this time, the valve (V6) has just closed and the stirring and shearing means (7) perform their dispersing action. The upper zone of the reactor, where the already sheared coating composition is located, flows via the circuit (C3) into the buffer tank (3).

In a second operating phase of the sleeping kitchen illustrated in FIG. 3, the capacity (3) sees its level drop due to the continuous consumption of the sleeping head, via the circuit (C4). At the same time and simultaneously, the low level in the premixer (2), detected by the sensor (D2) causes the valves (V1 to V5) to open for determined times allowing the flow of predetermined and calculated quantities to obtain the chosen dosage. . Thus, the premixer (2) is filled, while the capacity (3) is emptied.

According to an essential characteristic of the invention, the filling time of the premixer must be less than the draining time of the capacity (3). During this second intermediate phase, the level in the reactor drops, which stops the overflow phenomenon.

In the third operating phase of the sleeping kitchen, illustrated in FIG. 4, the valves V1 to V5 are all closed, following the filling of the premixer, controlled by the sensor (D2). After these closings, when the level in the capacity (3) reaches a low threshold detected by the sensor (D4), the valve (V6) is open and the pump (P1) is actuated to drain the premixer (2) in the reactor (1) via the circuit (C2). It follows that the level in the reactor (1) rises and that the overflow circuit (C3) is again traversed by sheared sauce which fills the capacity (3). We then find ourselves in the operating phase corresponding to FIG. 2.

Of course the invention is not limited to this described embodiment but also covers other variants not described in detail in which the sequence of the different operating phases is, for example, provided by a sensor (D5) located on the circuit leading to the coating head supply unit (5).

It emerges from the above that the coating kitchen according to the invention makes it possible to simultaneously ensure a discontinuous metering of the various ingredients of the coating sauce, with a continuous supply of the supply unit of the coating head. It follows that on the one hand, the operation of the latter is essentially continuous, which makes it possible to optimize the times of use, and that on the other hand, the means necessary for the dosage are relatively simple and inexpensive .

Claims (10)

Installation for the preparation and feeding of a coating composition to a coating head for paper or the like, comprising a plurality of hoppers (T1-T5), each intended to receive and deliver an ingredient of the composition, characterized in that it includes: - a premixer tank (2) supplied by the various hoppers (T1-T5), intended to mix and homogenize the composition formed; - A reactor vessel (1) supplied by the premixer vessel (2), comprising means (7) for shearing the composition; - a buffer tank (3) directly and permanently supplied by the reactor vessel (1), connected to the coating head (5); - means for detecting a need for composition of the coating head (5); - And control means connected to said detection means for supplying the premixer tank (2) with ingredients from the hoppers (T1-T5). Installation according to claim 1, characterized in that the premixer tank (2) comprises a level detector (D2) for actuating the means (V1-V5) for controlling the supply of ingredients. Installation according to claim 1, characterized in that the premixer tank (2) follows at its lower end a frustoconical shape in which the level detector (D2) and an agitator (6) are arranged. Installation according to claim 1, characterized in that it comprises a drain pump arranged on the circuit (C2) between the premixer (2) and the reactor (3). Installation according to claim 1, characterized in that the reactor vessel (1) comprises a stirrer (7) at high speed to ensure the dispersion of the composition by shearing. Installation according to claim 1, characterized in that the buffer tank (3) has a level detector (D4) of the composition for actuating the supply to the reactor vessel (1). Installation according to claim 1, characterized in that the supply of the buffer capacity (3) by the reactor vessel (1) is effected by means of an overflow (C3). Installation according to claim 1, characterized in that the volume of the buffer capacity (3) is greater than the useful volume of the premixer tank (2). Installation according to claim 1, characterized in that the circuit (C4) between the buffer capacity (3) and the coating head (5) comprises a sensor (D5) for actuating the control means (V1-V5) the ingredients are fed into the premixer. Installation according to claim 1, characterized in that the hoppers (T1-T5), the premix tank (2), the reactor tank (1) and the buffer tank (3) have supply means (9) and washing with water.

Images