EP0024980A1 - Self-cleaning apparatus for moulding plaster - Google Patents

Abstract

The present invention concerns the manufacture of objects made of plaster, essentially in the form of boards and, specifically, the pouring onto a moving conveyor of a mixture of plaster and water into a reservoir with an open bottom installed on top of said conveyor. It proposes to integrate the upstream rear wall of the reservoir within a surface of greater dimensions than the rear wall, and displacing said continuously, with the purpose of presenting a different portion of the surface as the upstream rear wall. The invention allows continuous cleaning of the upstream rear wall without disturbing the pouring process.

Description

The present invention relates to the manufacture of plaster objects, essentially in the form of a plate, and more specifically to the casting on a pouring floor movable in translation of a mixture of plaster and water contained in a bottomless tank. placed on said casting hearth.

It is known from the publication of French patent FR 2416 777 to constitute the front and rear side walls of the tank using two plates, and its side walls using mobile bands which run like the casting floor and which are supported on the ends of the front and rear plates. The tank is supplied by tubes passing through the front plate, opening into the tank and producing approximately horizontal mixing jets directed against the direction of advancement of the casting hearth. The front plate is slightly raised so as to provide a casting slot between its lower edge and the casting hearth. To avoid solidification within the product contained in the tank and on the walls of said tank, the mixture is introduced through the supply tubes with a certain speed, so as to create agitation in the tank and is vibrated the front and rear plates using vibrators mounted on the plates themselves; when reinforcements must be placed inside the products that we manufacture, in some cases we arrange to introduce said reinforcements by rubbing them on the lower edge of one and / or the other of the front plates and rear of the tank. Insofar as the height of the feed tubes is adjusted, the speed of arrival of the mixture, the spacing between the two front and rear plates of the tank, so as to have, as described in the aforementioned application, submerged jets but causing stirring lines performing at least one outward path from the front plate to the rear plate and a return path returning to the front plate, forming contiguous loops covering the entire surface of the tank, since the front and rear plates are vibrated, no deposit occurs which can lead to solidification and the pouring device , also called the pouring head thereafter, operates without intervention. However, if the casting head is not adjusted to the best, there is some splashing and it can form, mainly on the back plate, near the free surface of the mixture, in particular between the stirring loops and in the angles of the tank, deposits which require a certain cleaning, without however obligation to stop the casting, this all the more frequently as the setting is less good, for example every two or three hours. Despite this drawback of requiring a good adjustment or, failing this, periodic cleaning of the back plate, pouring heads sixty centimeters wide are satisfactory. But when the dimensions increase, the main difficulty is to keep the plates in vibration, in particular the back plate on which the deposits are mainly made.

In order to be able to do without vibration, the invention proposes to renew the rear wall, preferably continuously, without disturbing the pouring or the agitation. One solution to achieve this is to integrate it into a larger surface that is moved, periodically or continuously, so as to present a portion of different surface area in front of the tank, while the portion taken out of service is cleaned in waiting to be represented in front of the tank to play again the role of rear wall.

In one embodiment, this surface is materialized by a flat plate which is made to slide facing the casting tank; in other embodiments, the surface is curved and it is rotated to present a different portion facing the reservoir. This curved surface can be a rotating drum with a vertical axis, either of a diameter equal to the width of the casting hearth and then bearing on the lateral bands during their journey, or of a larger diameter and taking then press only on the ends of the side bands.

In the prior art, it has also been proposed, to reinforce the products produced, to introduce upstream of the tank or into said tank a reinforcement guided by a reinforcement introducer having the form of either a curved flap or a rounded bead. This reinforcement introducer may be integral with the base of the rear plate of the tank, or independently fixed upstream of the tank.

In a preferred embodiment of the invention, the operations of renewing the rear plate, cleaning the rear plate and guiding the reinforcement are combined, constituting the curved surface of which the rear plate is a portion by a cylindrical roller. , of horizontal axis perpendicular to the direction of advancement of the casting hearth, and of width equal to that of this casting hearth. This cylinder is rotated, the reinforcement that one wishes to have in the poured product, introduced in support on its lower portion, rubs on it and cleans it. Preferably, the cylinder is rotated in the opposite direction to the direction of progression of the reinforcement driven by the cast product. The speed of rotation of the roller, or possibly the frequency and the angle of the rotation when it is discontinuous, are such that a point on its surface which comes into contact with the liquid mixture of plaster and water is put out of contact of the mixture and cleaned in a sufficiently short time so that the plaster deposited at this point does not have time to set.

On the other hand, insofar as a reinforcement can be introduced inside the tank, the front plate is given a domed shape with horizontal bending axis perpendicular to the direction of advance of the casting hearth and we introduce this reinforcement resting on this curved surface. Advantageously, the tubes for supplying new product are then independent of the front plate; the feed is done by a feed ramp arranged between the two front and rear plates as close as possible to the front plate.

• Fig. 1 : Une tête de coulée avec plaque arrière coulissante,
• Fig. 2 : Une vue de dessus d'une tête de coulée à plaque arrière tournante,
• Fig. 3 : Une vue de dessus d'une seconde variante selon l'invention,
• Fig. 4 : Une vue de dessus d'une forme préférée de réalisation d'une tête de coulée selon l'invention,
• Fig. 5 : Une vue de côté de la tête de coulée montrée sur la figure 4
• Fig. 6 : Une variante de la tête de coulée des figures 4 et 5 équipée d'un organe d'étanchéité,
• Fig. 7 : Une autre variante avec plaque avant bombée pour l'introduction d'un renfort,
• Fig. 8 : Une tête de rampe d'alimentation indépendante.

The invention will now be described in more detail with reference to the drawings which represent:

• Fig. 1: A casting head with sliding back plate,
• Fig. 2: A top view of a casting head with a rotating back plate,
• Fig. 3: A top view of a second variant according to the invention,
• Fig. 4: A top view of a preferred embodiment of a casting head according to the invention,
• Fig. 5: A side view of the casting head shown in Figure 4
• Fig. 6: A variant of the pouring head of FIGS. 4 and 5 equipped with a sealing member,
• Fig. 7: Another variant with curved front plate for the introduction of a reinforcement,
• Fig. 8: An independent feed ramp head.

Figure 1 shows an installation for pouring a liquid mixture based on plaster and water. Although this mixture may contain other substances such as accelerators or retarders, reinforcing elements such as cut fibers, fillers, surfactants, thinners, resins, foams, etc. ., which will not be mentioned later, it will simply be called a mixture of plaster and water.

The casting installation comprises a horizontal casting hearth 1, movable in translation in the direction of arrow F, two lateral strips 2 and 3 each rotating around two rollers 4 and 5 and forming vertical edges at the casting hearth, a front wall 6 in the form of a vertical plate perpendicular to the direction of advancement of the floor 1 and a rear plate 7 parallel to the front wall 6, bearing on the ends of the lateral bands 2 and 3.

According to the invention, the rear plate 7 has a length sufficient to form at least two portions 7a and 7b arranged side by side, each capable of forming the rear wall of the casting tank e. It is slidably mounted on two vertical slides 8 and 9. Periodically, the plate 7 is slid in these slides so as to deactivate the portion which closed the tank, for example the portion 7a, and to replace it with the other, in this case the portion 7b. The portion 7a is then cleaned and it is ready to be put into service again in place of the portion 7b. Advantageously, the slides are high enough to allow the height positions of the plate 7 to be adjusted.

The plate 7 may have its lower edge covered by a bead 10, or may carry a curved flap, directed outside the tank to guide the introduction of a reinforcement in the product that is manufactured.

FIG. 2 shows a pouring head of the same type but in which the rear wall of the tank is a cylindrical drum 11 with a vertical axis 12, the diameter of which is equal to the width of the casting sole 1. The axis 12 of this cylinder 11 is arranged so that the front of the cylinder, which acts as the rear wall of the casting tank, rests on the floor 1. The cylinder 11 is in contact by its two generators diametrically opposite with the side bands 2 and 3 and it has on its underside a seal 13 which seals with the casting hearth, 1. The axis 12 of the cylinder 11 is equipped with a pinion 14 connected by a chain 15 to a motor 16 for the rotation drive. Means for cleaning the surface of the cylinder 11, such as a scraper 17 and / or a water sprinkler 18 rid the cylinder of plaster deposits. Preferably, these means are placed so as to act on the portion of cylinder wet with plaster which has just left the reservoir, that is to say near the side shown in the figure when the cylinder rotates in the direction of arrow I. Advantageously, this cylinder is suspended by its axis, and it can then be entirely located above the movable casting hearth. In addition, this advantageous assembly makes it possible to introduce a reinforcement into the product, near the lower surface, by causing it to arrive under the drum 11. For this purpose, as said in the publication already cited, a reinforcement introducer 19, independent, in the form of a horizontal and transverse bar, or curved shutter, will be arranged at the rear of the drum 11.

As also explained in this document, the front plate 6 is surmounted by a vibrator 20 and it is crossed by tubes 21 for supplying the mixture. With this type of drum, as soon as the reinforcement must be located in the thickness of the product, that is to say elsewhere than in the immediate vicinity of the underside, it will be preferable to introduce it either inside of the tank, either downstream of the tank.

As can be seen in FIG. 2, the front wall 6 of the pouring tank can be curved so that the energy per unit volume of mixture contained in the tank, supplied by the jets through the supply tubes 21, s _' oit substantially the same in the center and on the edges of the tank. We can also obtain the same energy balance, without bending the front wall 6 but keeping it flat, if we increase the section or the number of supply tubes 21 towards the edges of said plate.

In a variant shown in Figure 3, the drum 11 is supported on the ends of the side bands 2 and 3 and it is of larger diameter allowing to have a tank of practically rectangular surface, better agitated by the supply jets than the tank previous to two pointed corners, adjacent to the drum.

In these two variants, the drums 11 are of thickness substantially equal to the height of the front plate, and at least sufficiently thick to contain the mixture without overflowing. They are mounted on slide so that their distance from the front plate can be adjusted and located at such a distance from the latter that the adjustments made in the case of a fixed and flat rear plate are not modified. The explanation of these settings will be given later.

In both variants, the cylinder 11 is rotated, either continuously or discontinuously, at a speed such that a point on its surface in contact with the plaster mixture at a given time either removed from the tank and cleaned by the cleaning means 17 and 18 before the plaster which has deposited there has had time to set, or times of the order of 2 min for a plaster without setting modifier.

In a more advantageous embodiment of the invention, shown in FIGS. 4 to 6, the curved surface of which a portion forms the rear wall of the casting tank is a cylindrical roller 22 with horizontal axis 23, of length equal to the distance between the side bands 2 and 3 so that the seal between said bands and the cylinder is obtained. The shaft of this cylinder rotates in bearings 24 mounted on a support with two slides 25, one vertical, the other horizontal so as to allow the height adjustment and the adjustment of the distance relative to the front plate. The axis of this roller 22 is connected to a motor 26 capable of driving it in rotation. In addition, as shown in FIG. 6, a sealing shoe 27 having substantially the shape of a prism but the upper surface of which is concave can be placed at the rear of the roller 22. This sealing shoe 27 is mounted on horizontal slides 28 allowing its correct positioning. The roller 22 has a sufficiently large diameter so that its axis can pass over the side bands 2 and 3, so as to be supported and driven by the motor 26. A diameter of the order of 30 cm will be common. It may be a roll of cast iron, steel, plastic, etc., preferably a material which is not very porous and hard.

As shown in FIG. 7, the front plate can be given a domed shape with horizontal generatrixes perpendicular to the direction of advance of the casting hearth. Advantageous during the introduction of a reinforcement by the casting tank, this convex shape of the front plate can be envisaged with all the variants of rear wall: flat wall, drum wall with vertical axis or roll wall with horizontal axis . In this case, the roller 29 of storage of the reinforcement 30 that is introduced inside the tank is disposed in front of the front plate or at least vertically above it so that said reinforcement 30 rubs on the surface of said front plate 6. 1

Advantageously, when the reinforcement 30 is too thick and that it risks disturbing the supply of mixture, preventing agitation in the bucket, it is preferable to feed said bucket by a ramp 35 independent of the front plate 6. The ramp 35 is a tube of length equal to the width of the casting head, provided with a row of orifices 36, connected in the middle of its length, by a tube 37, to the means producing the mixture of plaster and water. This ramp is disposed between the two front and rear plates of the bucket, parallel to said plates, as close as possible to the front plate, is immersed in the mixture so that the jets of mixture which it delivers through orifices 36 are submerged like the jets delivered by the tubes 21 through the front plate in the other embodiments, or placed immediately above the free surface of the liquid, with orifices 36 slightly inclined downwards so that the jets , while rapidly penetrating into the mixture, produce the necessary agitation. The orifices 36 are distributed like the supply tubes 21 which pass through the front plate in the other embodiments. Advantageously, so that the energies of all the jets exiting the ramp are identical, the sections of the orifices are growing from the middle of the ramp towards its ends.

To adjust a casting head such as that shown in FIGS. 4 to 8, the procedure is as follows. First, the height of the roller 22 is adjusted relative to the casting floor 1 by adjusting the position of the bearings 24 on the vertical slides 25. The lower generator of the roller 22 must be at an equal distance from the casting floor at the height at which you want to position the reinforcement in the thickness of the product.

To adjust the distance between the rear drum 11 or the rear roller 22 and the front plate 6, the procedure is as if it were a flat and fixed rear plate; that is to say that once fixed the feed rate of the mixture for manufacturing products in plates of a given thickness at the chosen speed of the casting hearth, the number of feed tubes capable of producing agitation over the entire width of the head is determined casting, we determine the section of the supply tubes and pipes upstream so that the speed of mixing prohibits deposits, that is to say, is greater than 10 cm / s, we create the casting slot under the front plate 6, we adjust the distance from the front plate to the roller or rear drum so as to have, in the pouring tank, a stable mixing level and- submerged supply jets. Distances between the front plate and the front generator of the roller of the order of 10 cm will frequently be encountered.

The reinforcements are then introduced by dispersing their storage rollers so that the reinforcements well sweep the surfaces which they are responsible for cleaning. Thus, a reinforcement 31 is passed under the roller 22 and then under the front plate 6. The reinforcement, driven by the casting, stretches. The storage roller 32 of the reinforcement 31 is placed so that the reinforcement 31 winds at least a quarter and preferably a third of the rear roller 22. Thus in the most remote position possible of the storage roller 32, the reinforcement 31 will descend vertically until contact with roller 22.

If the rear roller 22 is spaced from the casting bed and if a mixture leak occurs, the sealing part 27 will be advanced under the roller 22 to stop this leak. It can be seen that with a roller 22 30 cm in diameter, spaced 6 mm from the casting hearth, under which passes a mat of entangled continuous wires 2.5 mm thick in the free state, with speeds from the 1.50 m to 3 m / min casting bottom, there is no leakage. The leak only appears if the space is increased by 1 or 2 mm.

The speed of rotation of the roller 22 or of the drum 11 is then adjusted, so that a point on the roller does not remain in the plaster or covered with plaster without being cleaned for more than a time of the order of 2 min. , corresponding to the time necessary for the plaster to start setting. Thus, for a rear roller 30 cm in diameter, a mixing height of approximately 15 mm in the tank, a peripheral speed between 1 cm / min and 10 cm / min will be suitable, and a speed of the order of 3 cm will be commonly chosen. The rotation speed should not be too high, so as not to disturb the casting. If the rotation is sequential, rotations will be made approximately every minute, at an angle such that the constraints already stated are respected.

Then, in the same way, if it is desired to introduce an additional reinforcement 30 inside the tank between the front plate and the roller or the rear drum by using a curved front plate, it is arranged so that the reinforcement stretched from its storage roller 29 rubs over the entire surface of the front plate in contact with the mixture.

Insofar as one uses, to reinforce the plasterboards, a set consisting of a mat of continuous glass threads, entangled, enclosed between two grids of glass threads with large mesh, 0.5 mm for example , it is only one of the glass wire grids that we will choose to introduce in contact with the curved front plate. Thus, due to the large size of the meshes, the supply by the tubes 21 and the agitation in the tank will not be disturbed. In addition, if these grids are made up of orthogonal wires welded to each other, with all of the "warp" wires entirely on one side of the grid mid-plane, and all of the "weft" wires entirely of the other side of this same plane, we will choose to put in contact with the curved front wall those of the wires which will be the most transverse to the direction of travel of said grids, or in other words most parallel to the plane of the casting hearth, to favor cleaning this wall.

Insofar as the reinforcement introduced in contact with the front plate becomes too thick and risks disturbing the feeding and agitation and where it is preferred to use a feeding by a ramp 35 independent of the front plate, if the ramp is submerged, it may require a slight cleaning every 2 or 3 hours of operation; if it is not submerged it obviously does not get dirty. With such a ramp, the determinations of flow rates, sections of the orifices, will be made in the same way as if they were tubes 21 through the front plate.

These casting devices have been described by taking a plaster-based mixture as an example, but they can also be used for pouring evolutionary products other than plaster and a fortiori less evolutive or non-evolutive products.

Claims (19)

1 - Pouring device, on a casting hearth movable in translation, of a liquid mixture essentially consisting of plaster and water, to. from a bottomless tank placed on said pouring floor, containing the mixture to be poured, leaving under its front wall a pouring slot adjacent to the pouring floor and continuously supplied with new mixture, characterized in that the rear wall of the tank is formed by a portion of a larger surface, movable relative to the tank, this portion can thus be replaced by displacement of said surface. 2 - Device according to claim 1, characterized in that the larger surface is a flat plate having at least a dimension twice that of the rear wall of the tank, kept pressed against the side walls of the tank, slidingly mounted relative to said reservoir in a direction such that by sliding the portion of the flat plate facing the reservoir, and which plays the role of the rear wall, can be put out of service and simultaneously replaced by the portion of plate which is juxtaposed to it. 3 - Device according to claim 1, characterized in that the larger surface is the lateral surface of a cylinder in contact with the side walls of the casting tank. 4 - Device according to claim 3, characterized in that the cylinder has a vertical axis, its side wall being supported on the side walls of the tank. 5 - Device according to claim 4, characterized in that the cylinder has as diameter the width of the casting hearth. 6 - Device according to claim 4, characterized in that the cylinder has a diameter greater than the width of the casting hearth. 7 - Device according to claim 3, characterized in that the cylinder has its horizontal axis, perpendicular to the direction of translation of the casting hearth, said cylinder being in contact with the side walls of the tank by its bases. 8 - Device according to claim 7, characterized in that ^j- a reinforcement intended to reinforce the manufactured product is disposed over the entire width of the casting hearth, in contact with a part of the lateral surface of the cylinder leaving the reservoir. 9 - Device according to claim 8, characterized in that the reinforcement winds at least 1/4 of the cylinder. 10 - Device according to any one of claims 7 to 9, characterized in that the cylinder is mounted rotating in displaceable bearings on double vertical and horizontal slides. 11 - Device according to any one of claims 7 to 10, characterized in that a sealing shoe having the shape of a prism with the concave upper surface slides behind the cylinder and under it, for avoid any mixture leakage. 12 - Device according to any one of the preceding claims, characterized in that a motor connected to the surface to which belongs the rear wall of the tank causes it to move. 13 - Device according to claim 12, characterized in that the motor is a motor driving the surfaces according to one of the following modes: continuous drive, sequential drive. 14 - Pouring device, on a casting hearth movable in translation, of a liquid mixture of plaster and water, essentially from a bottomless tank placed on said casting hearth, containing the mixture to be poured and provided a casting slot adjacent to the casting hearth under the front wall of the tank, characterized in that the front wall of the tank is curved with a horizontal bending axis perpendicular to the direction of advance of the casting hearth. 15 - Device according to any one of claims 1 to 13, characterized in that the front wall of the tank is curved, with a horizontal bending axis perpendicular to the direction of advance of the casting hearth. 16 - Device according to any one of claims 14 or 15, characterized in that a reinforcement intended to reinforce the manufactured product is arranged so as to bear on the lower edge of said front plate and to rub on its curved surface . 17 - Device according to any one of claims 14 to 16, characterized in that a ramp for supplying a new mixture, connected to the means which supply the mixture, provided with outlet ports for the mixture directed towards the rear of the device is arranged transversely to the casting hearth, inside the bottomless tank. 18 - Device according to claim 17, characterized in that the ramp is arranged at a height such, relative to the casting hearth, that the jets that it delivers are immersed in the mass of the mixture already contained in the tank. 19 - Device according to claim 17, characterized in that the ramp is arranged at a height relative to the casting hearth, such that it is above the free surface of the mixture contained in the tank, the outlet ports of the mixture being slightly inclined downwards so that the mixing jets they deliver immediately penetrate the mixture initially contained in the tank.

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