EP0024980B1 - 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 FR-A-2 416 777 (EP-AZ-0 003 705, publication date: 22.8.79) to constitute the front and rear side walls of the tank using two plates, and its side walls using movable bands which run like the casting floor and which bear 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 above-mentioned application, jets submerged but causing agitation 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, insofar as the front and rear plates are vibrated, there is no deposit which can lead to solidification and the casting device, also called the pouring head below, 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 good adjustment or, failing this, periodic cleaning of the rear 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.

It is also known from US Pat. No. 2,230,074, which reveals the characteristics of the preamble of claim 1, a device for forming a sticky and viscous material having a horizontal forming sole with vertical edges, movable in translation and a forming blade at some distance above the forming sole, associated with a system for supplying the mixture to be formed, consisting of a hopper each vertical wall of which is lined with a moving vertical conveyor belt, to facilitate and regulate the progress of the mixture from top to bottom, up to the forming device. But these vertical conveyor belts do not belong to the forming device, they are arranged above said device at a certain distance from it and they can only play their role if they line all the walls of the hopper and if they all move up and down in the same way. This system is suitable for supplying the forming device from top to bottom with viscous material, but because of its spaced arrangement with respect to the forming sole, because of its need to have identical mats operating in the same way on all the walls. of the hopper, it cannot be used to treat a liquid product which would escape through the space reserved between it and the forming sole, and it cannot itself constitute a pouring device because the idendic belts in vertical movement on all its sides would disturb the flow and prevent the supply of new liquid mixture, in the horizontal direction.

The present invention aims to remedy the drawbacks of prior devices.

In order to be able to possibly dispense with the vibration in the device of: FR-A-2 416 777, the invention proposes to renew the rear wall of the tank placed on the casting hearth, while maintaining the seal necessary for the treatment of a liquid product, without disturbing the flow or agitation.

The invention, in a first embodiment, provides a casting device on a casting hearth movable in translation, of a liquid mixture, plaster and water essentially, from a bottomless tank placed on said hearth pouring, containing the mixture to be poured, the side walls of which are formed by endless bands, provided with a pouring slot adjacent to the pouring bottom under the front wall of the tank, device in which the rear wall of the tank is a portion of a flat plate which is flush with the pouring hearth and which is held pressed against the side walls of the tank, having at least a dimension twice that of the rear wall of the tank, mounted slidingly with respect to said tank in a direction such that by sliding, the flat plate portion facing the tank and which acts as the rear wall, can be put out of service and simultaneously replaced by the plate portion which is juxtaposed to it, the out of service portion being cleaned.

The invention in a second embodiment proposes a casting device on a casting hearth movable in translation, of a liquid mixture, plaster and water essentially, from a bottomless tank placed on said hearth casting, containing the mixture to be poured, the side walls of which consist of endless bands movable in the same direction and at the same speed as the casting hearth, and provided with a casting slot adjacent to the casting hearth under the front wall of the tank, a device in which the rear wall of the tank is a portion of the side surface of a cylinder in contact with the side walls of the casting tank, flush with the casting bed, said cylinder being rotated so as to to present an ever different portion in contact with the mixture in the tank, the out of service portions being cleaned.

In a first variant according to the second embodiment, the cylinder has a vertical axis, with its side wall in contact with the side walls of the casting tank.

In a second variant according to the second embodiment, the cylinder has its horizontal axis, perpendicular to the direction of translation of the casting hearth, and it is in contact with the side walls of the reservoir through its bases.

Advantageously, in this second variant, the surface portion of the cylinder which has come out of contact with the mixture of the reservoir, is cleaned by a reinforcement intended to be introduced into the product produced, said reinforcement rubbing against the surface of the cylinder to be cleaned.

Advantageously, in combination with the rear wall of the tank of the first or second embodiment, the invention proposes to give the front plate of the tank a domed shape with horizontal bending axis perpendicular to the direction of advance of the casting hearth , and to introduce a reinforcement inside said tank, pressing on this curved surface to clean it.

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

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

• - Figure 1: a casting head with sliding rear plate,
• - Figure 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 FIG. 4,
• FIG. 6: a variant of the casting head of FIGS. 4 and 5 equipped with a sealing member,
• - Figure 7: Another curved front plate variant for the introduction of a reinforcement,
• -Figure 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. 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 with its two generators diametrically opposite with the side bands 2 and 3 and it has a seal 13 on its underside which seals with the casting sole 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 rotary 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 arrangement 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 casting tank can be curved so that the energy per unit volume of mixture contained in said tank, supplied by the jets through the supply tubes 21, is 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 a slide so that their spacing can be adjusted relative to the front plate and is 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 diameter large enough 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. Advantageously during the introduction of a reinforcement into 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 roll 29 for storing the reinforcement 30 which 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 against the surface of said front plate 6.

Advantageously, when the reinforcement 30 is too thick and 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 holes 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 progressively progress 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 a distance from the casting floor equal to 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 the supply flow rate for the mixture is fixed in order to manufacture plate products of a given thickness at the chosen speed of the casting hearth, the number of supply tubes liable to be determined is determined. to produce agitation over the entire width of the casting head, the cross-section of the feed tubes and pipes is determined upstream so that the speed of the mixture prevents deposits, that is to say 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 casting tank, a stable mixing level and supply jets submerged. 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 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 carried out 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 reservoir between the front plate and the roller or the rear drum by using a curved front plate, it is arranged so that the reinforcement is stretched from its storage roller 29 rubs over the entire front plate surface in contact with the mixture.

Insofar as one uses, to reinforce the plasterboards, an assembly made up 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 consist of orthogonal wires welded to each other, with all the "warp" wires entirely on one side of the grid midplane, and all the "weft" wires entirely on 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 promote cleaning of this wall.

Insofar as the reinforcement introduced in contact with the front plate becomes too thick and may disturb 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 (15)

1. Apparatus for pouring a liquid mixture comprising essentially plaster and water onto a displaceable casting plate from a bottomless reservoir located on the said casting plate and containing the mixture to be poured, the lateral walls of which reservoir are formed by endless belts (2 and 3) displaceable in the same direction and at the same speed as the casting plate (1), and provided with a pouring orifice adjacent to the casting plate (1) under the front wall (6) of the reservoir, characterised in that the rear wall of the reservoir is a portion of a flat plate (7) which projects above the casting plate (1) which is maintained pressed against the lateral walls (2 and 3) of the reservoir, which has at least one dimension double that of the rear wall of the reservoir, and which is mounted slidably with respect to the said reservoir in such a direction that by sliding, the portion (7a and 7b) of the flat plate facing the reservoir and which acts as the rear wall, can be taken out of operation and simultaneously replaced by the portion of the plate (7a and 7b) next to it, the portion (7a and 7b) taken out of operation being cleaned.

2. Apparatus for pouring a liquid mixture comprising essentially plaster and water onto a displaceable casting plate (1) from a bottomless reservoir located on the said casting plate (1) and containing the mixture to be poured, the lateral walls of which reservoir are comprised by endless belts (2 and 3) displaceable in the same direction and at the same speed as the casting plate (1), and provided with an orifice adjacent to the casting plate under the front wall (6) or the reservoir, characterised in that the rear wall of the reservoir is part of the lateral surface of a cylinder (11 or 22) in contact with the lateral walls (2 and 3) of the pouring reservoir and projects above the casting plate (1), the said cylinder (11 or 22) being rotatably drivable so as to bring into contact with the mixture in the reservoir a continuously changing portion of it, the portions which are out of operation being cleaned.

3. Apparatus according to Claim 2, characterised in that the cylinder (11) has a vertical axis (12), its lateral wall being in contact with the lateral walls (2 and 3) of the puring reservoir.

4. Apparatus according to Claim 3, characterised in that the diameter of the cylinder (11) is the width of the pouring plate (1). ).

5. Apparatus according to Claim 3, characterised in that the diameter of the cylinder (11) is greater than the width of the pouring plate (1).

6. Apparatus according to Claim 2, characterised in that the axis (23) of the cylinder (22) is horizontal and perpendicular to the direction of displacement of the pouring plate (1), the said cylinder (22) being in contact with the lateral walls (2 and 3) of the reservoir by ends.

7. Apparatus according to Claim 6, characterised in that a reinforcement (31} which is to be introduced into the product being manufactured and has the same width as the pouring plate (1), rubs over the lateral surface of the cylinder (22) which is out of contact with the mixture in the reservoir, in order to clean it.

8. Apparatus according to Claim 7, characterised in that the reinforcement (31) envelops at least one quarter of the cylinder (22).

9. Apparatus according to any one of the preceding claims, characterised in that a motor (16, 26) connected to the surface which provides the rear wall of the container, causes its displacement.

10. Apparatus according to Claim 9, characterised in that the motor (16, 26) is a motor which displaces the surface by one of the following methods: continuous displacement, sequential displacement.

11. Apparatus according to any one of Claims 1 to 10, characterised in that the front wall, (6) of the reservoir is curved, with a horizontal axis of curvature perpendicular to the direction of motion of the casting plate (1).

12. Apparatus according to Claim 11, characterised in that a reinforcement (30) which is to reinforce the manufactured product is arranged so that it presses on the lower edge of the said front plate (6) and rubs on the curved surface.

13. Apparatus according to either of claims 11 or 12, characterised in that a distributor (35) for fresh mixture connected to supply means for the mixture, and provided with orifices (36) for discharging the mixture directed towards the rear of the apparatus, is arranged transversely in relation to the casting plate (1) and inside the bottomless reservoir.

14. Apparatus according to Claim 13, characterised in that the distributor (35) is arranged at such a height, with respect to the casting plate (1) that the jets which it delivers are immersed in the mass of mixture already contained in the reservoir.

15. Apparatus according to Claim 13, characterised in that the distributor (35) is arranged at such a height with reference to the casting plate (1) that it is above the surface of the mixture contained in the reservoir, the outlet orifices (36) for the mixture being slightly downwardly inclined in such a manner that the jets of mixture which they deliver penetrate immediately into the mixture already present in the reservoir.

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