EP1261467B1 - Method and device for producing a straight cylindrical body by molding using a loose hardenable granular material and the utilization thereof for producing a tube - Google Patents

Abstract

The invention relates to molding a right cylindrical body from a settable loose granular composition in a mold cavity, in which a mold cavity ( 4 ) is fed with successive charges of the composition in the loose state and each new charge is thrust by means of thrust surfaces ( 11 ) into the surface S of the molded composition in order to cause the new charge and the molded composition to interpenetrate in such a manner as to densify the molded composition. The invention is applicable to making a pipe, in particular out of a cement composition.

Description

The invention relates to the manufacture by molding of a straight cylindrical body from a composition curable granular material (see eg DE-C-207 943 and DE-C-222 448).

The term "straight cylindrical" designates the generated form by a line called "generator" that moves parallel to itself by following a so-called curve "Director" situated in a plane perpendicular to the right. This director is circular in the case most simple, but the invention is not limited to this profile and extends to any form of director.

The body therefore has a constant cross-section in a plane perpendicular to the direction of the length from the body.

The invention applies in particular to the manufacture by molding a pipe from a composition cement or curable ceramic, but without being limited to this application.

In recent years we have developed curable cementitious compositions consisting of relatively thin and reportable materials very low water / cement weight, especially a ratio weight less than 0.16.

These compositions have characteristics very advantageous mechanical

US-A-5 545 297 discloses the manufacture of a straight cylindrical pipe from a composition cement in which the composition is passed to the pasty state in the molding cavity of an extruder, with an extrusion pressure all the higher as the proportion of water to cement in the composition is weak.

Publication EP-A-0 406 612 describes a technique of manufacturing a straight cylindrical pipe in which one gradually pour a granular cementitious composition in a loose state in a vertical molding cavity having the shape of the pipe to be obtained and put it in the cavity to the action of a vibrating wall generating forces radial and vertical forces directed upwards.

The present invention relates to a technique of industrial manufacture by molding a cylindrical body right, including a pipe, from a composition granular initially loose, not requiring the implementation high pressures or the implementation of a such vibrating wall and which is nevertheless suitable for the molding a curable cementitious composition containing only a very small proportion of water.

According to the invention, a molding cavity is used right cylindrical having dimensions in cross-section of the cross section of the body to be manufactured and fed this cavity with a controlled flow of successive charges loose composition, so that at any time the composition in place in the cavity presents a free surface and that each new charge is deposited on an area of this free surface, and one pushes each new charge in said surface to cause a interpenetration of the new charge and composition underlying said surface, by means of push that one moves on the one hand according to a movement of back and forth directed towards said free surface and in sense reverse and, on the other hand, according to a cyclical movement such that thrust surfaces are moved in the expanse of the free surface, and simultaneously during the molding, a relative displacement of the molded composition is achieved and pushing surfaces so as to maintain substantially constant the distance between the average point of the movement of the back-and-forth movement of the surfaces of thrust and said free surface, said flow of the loads being controlled so that, during each cycle, the material on which the charges are deposited gradually densified in depth by the cumulative interpenetration of the loads, the conditions being adjusted so that in all cycles, the densification is substantially homogeneous throughout the material, and the molded composition is allowed to cure.

Advantageously, the interpenetration is carried out so that that at each elemental blow of a thrust surface, the underlying composition is interpenetrated on a depth at least five times the average diameter of the granular class of the larger constituents of the composition.

If the composition contains fiber or other similar reinforcements, the dimensions of these constituents are not taken into account for the determination of the depth of penetration.

In a preferred embodiment, the depth is limited maximum penetration at ten times this average diameter.

Thus, in the case of a cementitious composition containing grains of sand that make up the biggest component of the composition, the conditions will be preferably adjusted so that the interpenetration is produce on a depth of 5 to 10 times the diameter mean of the grains of sand is for example a depth 1.5 to 3 mm if this average diameter is 0.3 mm.

Preferably, loads of loose material are deposited simultaneously on several non-contiguous areas of the said free surface.

• on utilise pour pousser les charges une pluralité de surfaces de poussée séparées ;
• on introduit les charges entre les surfaces de poussée ;
• ledit mouvement cyclique est un mouvement de rotation ;
• on réalise ledit déplacement relatif en évacuant au travers de la cavité de moulage la composition moulée comme dans une filière, au fur et à mesure du moulage ;
• on réalise ledit déplacement relatif en déplaçant les surfaces de poussée, au fur et à mesure que le niveau de la composition moulée s'élève dans la cavité de moulage ;
• on réalise ledit déplacement relatif en déplaçant simultanément une paroi de la cavité de moulage et les surfaces de poussée ;
• on réalise une pression inférieure à la pression atmosphérique pour dégazer les charges avant de les pousser ;
• on réalise un déphasage entre les mouvements de va-et-vient des différentes surfaces de poussée.

Although the process is preferably carried out continuously, that is to say, by providing the charges continuously, it can also operate discontinuously. In special cases:

• a plurality of separate thrust surfaces are used to push the loads;
• the charges are introduced between the thrust surfaces;
• said cyclic movement is a rotational movement;
• said relative displacement is carried out by evacuating through the molding cavity the molded composition as in a die, as and when molding;
• said relative displacement is effected by moving the thrust surfaces as the level of the molded composition rises in the molding cavity;
• said relative displacement is effected by simultaneously moving a wall of the molding cavity and the thrust surfaces;
• a pressure lower than the atmospheric pressure is made to degas the charges before pushing them;
• there is a phase shift between the back and forth movements of the different thrust surfaces.

The material is allowed to harden before unmolding or after demolding, as appropriate.

When the invention is applied to the manufacture of a body from a cementitious composition, we use preferably a composition consisting of fine powders, for example example, a composition such as the composition of the concrete matrix defined in the publication FR-A-2 707 625.

• un moule qui détermine une cavité de moulage cylindrique droite qui présente une section droite de forme identique à celle du corps à fabriquer et qui s'étend selon un axe perpendiculaire au plan de cette section droite, sur une longueur égale à une fraction ou à la totalité de la longueur du corps à fabriquer ;
• des moyens d'introduction pour introduire un débit contrôlé de charges de la composition lâche en direction de ladite cavité ;
• des moyens de poussée qui déterminent une pluralité de surfaces de poussée séparées réparties autour dudit axe et dirigées vers le plan de la section droite de la cavité de moulage ;
• des moyens de commande pour provoquer un déplacement des surfaces de poussée d'une part selon un mouvement de va-et-vient dirigé selon cet axe et, d'autre part selon un mouvement cyclique autour dudit axe ;
• et des moyens de commande pour réaliser pendant le moulage un déplacement relatif de la composition moulée et des surfaces de poussée, en fonction du débit d'introduction du matériau lâche, de façon à maintenir sensiblement constante la distance entre le point moyen de la course du mouvement de va-et-vient et la surface libre de la composition moulée.

Dans des réalisations préférées :

• les moyens d'introduction sont conçus pour introduire les charges entre les surfaces de poussée ;
• la cavité de moulage constitue une filière à travers laquelle on pousse le matériau moulé ;
• la cavité de moulage est déterminée par un intervalle entre deux parois, l'une de ces parois étant déplaçable avec les surfaces de poussée pour réaliser ledit déplacement relatif ;
• le moule est fixe et les surfaces de poussée sont déplaçables pour réaliser ledit déplacement relatif ;
• les surfaces de poussée sont telles qu'il existe entre elles et les parois qui déterminent la cavité de moulage un intervalle latéral qui permet un dégagement d'une partie du matériau des charges sous l'effet des déplacements des surfaces de poussée ;
• les surfaces de poussée sont précédées dans le sens dudit mouvement cylindrique, par des surfaces inclinées de pré-compactage des charges.

To implement the method of the invention, it is recommended according to the invention to implement a device which comprises:

• a mold which determines a straight cylindrical mold cavity which has a cross-section of shape identical to that of the body to be manufactured and which extends along an axis perpendicular to the plane of this cross-section, over a length equal to a fraction or to the the total length of the body to be manufactured;
• introduction means for introducing a controlled flow rate of charges of the loose composition towards said cavity;
• thrust means which determines a plurality of separate thrust surfaces distributed about said axis and directed towards the plane of the cross section of the mold cavity;
• control means for causing a displacement of the thrust surfaces on the one hand in a reciprocating movement directed along said axis and, on the other hand in a cyclic movement about said axis;
• and control means for performing during molding a relative displacement of the molded composition and the thrust surfaces, as a function of the rate of introduction of the loose material, so as to maintain substantially constant the distance between the midpoint of the stroke of the back and forth movement and the free surface of the molded composition.

In preferred embodiments:

• the introduction means are designed to introduce the charges between the thrust surfaces;
• the molding cavity constitutes a die through which the molded material is pushed;
• the molding cavity is determined by a gap between two walls, one of these walls being movable with the thrust surfaces to achieve said relative displacement;
• the mold is fixed and the pushing surfaces are movable to effect said relative movement;
• the thrust surfaces are such that there is between them and the walls which determine the molding cavity a lateral gap which allows a part of the material of the charges to be released under the effect of displacements of the thrust surfaces;
• the thrust surfaces are preceded in the direction of said cylindrical movement by inclined surfaces of pre-compaction of the charges.

Movements back and forth and moving cyclic thrust surfaces are obtained by choice any conventional means (motorized gears, cams, springs recall, crank / crank systems, etc.) that are well known mechanics and it is not necessary to describe here.

• la figure 1 est une coupe axiale schématique d'un dispositif conforme à l'invention réduit à ses parties essentielles ;
• la figure 2 est un schéma qui montre des détails du dispositif de la figure 1, en coupe axiale ;
• les figures 3 et 4 sont des vues en perspective schématiques qui montrent le dispositif de la figure 2, respectivement vu selon une direction oblique à 45° vers le bas (figure 3) et vu selon une direction oblique à 45° vers le haut (figure 4) en partant de l'oeil de l'observateur.
• les figures 5 à 7 sont des schémas de dispositifs selon différentes réalisations de l'invention.

Embodiments of a device according to the invention applied to the manufacture of a pipe will be described below, with reference to the figures of the attached drawing, in which:

• Figure 1 is a schematic axial section of a device according to the invention reduced to its essential parts;
• Figure 2 is a diagram showing details of the device of Figure 1, in axial section;
• FIGS. 3 and 4 are diagrammatic perspective views which show the device of FIG. 2, respectively seen in a 45 ° downwardly oblique direction (FIG. 3) and seen in a 45 ° oblique direction towards the top (FIG. 4) starting from the eye of the observer.
• Figures 5 to 7 are diagrams of devices according to different embodiments of the invention.

The mold shown in Figure 1, intended for manufacture of straight cylindrical pipe with straight section circular, consists essentially of two walls cylindrical coaxial (1), (3) vertical axis (2), determining between them an annular molding cavity (4) whose transverse dimensions correspond to the transversal dimensions of the pipe to be manufactured.

To the right of this cavity is arranged a rotor (5) which carries a plurality of identical pushing tools (6) between them and separated by constant intervals.

Respective means (not shown) are used to drive the tools respectively according to a movement cyclic around the axis (2) of the molding cavity, in the direction of the arrow (8) and in a reciprocating motion according to the arrow (9) parallel to the axis (2) of the cavity molding.

Means schematized by the arrows (10) are present to introduce between the tools loads of loose material. To guide loads to the surface (S) already molded material, a frustoconical wall (13) is provided above the inner wall of the mold (3).

Figures 2 to 4 show parts of the Figure 1, on a different scale, for better to show the tools, apart from their common support.

The tools are shaped to present one end lower part (6a) which has a face (11) facing towards the down to push the loose material towards the free surface of the material already in place in the mold when the tool is moved down and one face (12) turned in the direction rotation according to the arrow (8), which precedes the face of pushing in the rotary motion of the tool and that is able to precompact the load of loose material.

These two faces contribute to push the material of fillers in the molded material. Preferably, they together form a convex surface. They are themselves flat or curved.

In FIG. 2, the tools are shown in the extreme low (solid lines) and high interrupted) of their movement back and forth.

In practice, moving the surfaces back and forth thrust is preferably set with a frequency of quite high displacement, typically from 5 to 50 goes back and forth per second, even better from 10 to 30 back and forth by second.

Preferably, there is between the tools and the walls of the molding cavity a lateral gap (T).

• dans le cas de la figure 1, la paroi extérieure (1) du moule est fixe et sa paroi intérieure (3) est déplacée vers le haut pendant le moulage en même temps que les outils. Par exemple, le moule comporte un noyau (17) dont la partie inférieure est conformée pour constituer la paroi (3) du moule, ce noyau portant les outils (6) en sorte que ceux-ci puissent tourner autour du noyau (flèche 8) et s'élever ou s'abaisser (flèche 9) ; le noyau lui-même est déplacé vers le haut (flèche 18) pendant le moulage.
• dans le cas de la figure 5, le moule est progressivement éloigné des outils pendant le moulage dans le sens de la flèche (19), les outils restant fixes (sauf bien entendu leurs deux mouvements fonctionnels de va-et-vient et de rotation).
• dans le cas de la figure 6, le moule fonctionne comme une filière et sa paroi de fond (14) est déplacée (flèche 16) pendant le moulage de façon à maintenir sensiblement constante la distance entre le point moyen de la course du mouvement de va-et-vient des outils et la surface libre (S) du matériau moulé.
• dans le cas de la figure 7, le moule est fixe et les outils sont progressivement entraínés vers le haut pendant le moulage (flèche 20).

The figures represent different possibilities for driving the tools and for making a relative displacement between the molded material and the tools as the molded material increases:

• in the case of Figure 1, the outer wall (1) of the mold is fixed and its inner wall (3) is moved upward during molding at the same time as the tools. For example, the mold comprises a core (17) whose lower part is shaped to form the wall (3) of the mold, the core carrying the tools (6) so that they can rotate around the core (arrow 8) and raise or lower (arrow 9); the core itself is moved upward (arrow 18) during molding.
• in the case of Figure 5, the mold is progressively removed from the tools during molding in the direction of the arrow (19), the tools remaining fixed (except of course their two functional movements back and forth and rotation) .
• in the case of Figure 6, the mold operates as a die and its bottom wall (14) is moved (arrow 16) during molding to maintain substantially constant the distance between the average point of the stroke of the movement of tools and the free surface (S) of the molded material.
• in the case of Figure 7, the mold is fixed and the tools are gradually driven up during molding (arrow 20).

Example:

• on prépare un matériau lâche, sec et pulvérulent essentiellement constitué par malaxage des constituants suivants (pour 10kg de matériau) :

• 4,5 kg de sable dont la grosseur de grain est de l'ordre de 0,3mm
• 0,9 kg de quartz broyé à une grosseur de grain de 10 micromètres
• 1 kg de fumée de silice (grosseur de particules 0,5 micron)
• 3,1 kg de ciment Portland (grosseur moyenne 15 micromètres)
• 0,1 kg de superplastifiant (à 30% d'extrait sec)
• 0,4 kg d'eau.

To manufacture a tube made of cementitious material, the following operations are carried out:

• a loose, dry and powdery material consisting essentially of kneading of the following constituents (for 10 kg of material) is prepared:

• 4.5 kg of sand whose grain size is of the order of 0.3 mm
• 0.9 kg of crushed quartz to a grain size of 10 microns
• 1 kg of silica fume (particle size 0.5 microns)
• 3.1 kg of Portland cement (average size 15 micrometers)
• 0.1 kg of superplasticizer (at 30% dry extract)
• 0.4 kg of water.

- on constitue un moule vertical avec deux parois cylindriques coaxiales ayant respectivement des diamètres de 120 et 100 mm et une paroi de fond, en utilisant la paroi centrale du moule pour porter quatre poussoirs conformés selon l'invention ;

- on verse dans le fond du moule une fraction du matériau lâche jusqu'à y constituer un anneau sur une hauteur de quelques millimètres ;

- on anime chaque outil de poussée d'un mouvement vertical alternatif de 15 coups par seconde sur une course verticale de 10 mm, les mouvements alternatifs étant déphasés chacun d'un quart de cycle, et d'un mouvement rotatif de 1 tour par seconde, tout en alimentant la surface libre avec un débit volumique de 0,2 litre par seconde de matériau lâche et tout en soumettant les outils et la paroi centrale du moule à un déplacement vertical de 3cm/seconde. On obtient ainsi à chaque tour une couche de 3 cm d'épaisseur dont la densité est de l'ordre de 2,5.

- On laisse durcir le matériau dans le moule et on démoule.

The density of the loose material is between 1 and 1.5.

a vertical mold is formed with two coaxial cylindrical walls respectively having diameters of 120 and 100 mm and a bottom wall, by using the central wall of the mold to carry four shaped pushpieces according to the invention;

a fraction of the loose material is poured into the bottom of the mold to form a ring over a height of a few millimeters;

each of the pushing tools is animated with a vertical reciprocating movement of 15 strokes per second over a vertical stroke of 10 mm, the reciprocating movements being out of phase each by a quarter of a cycle, and by a rotary movement of 1 revolution per second , while feeding the free surface with a flow rate of 0.2 liters per second of loose material and while subjecting the tools and the central wall of the mold to a vertical displacement of 3cm / second. This gives each turn a 3 cm thick layer whose density is of the order of 2.5.

- The material is allowed to harden in the mold and is demolded.

The invention is not limited to this example or to achievements that have been described.

Claims (22)

1. A method of manufacturing a right cylindrical body by molding a settable loose granular composition in a mold cavity, in which method a right cylindrical mold cavity is used having dimensions in right section equal to the right section of the body to be made, and said cavity is fed with a controlled rate of flow of successive charges of the composition in the loose state, in which said feeding is performed in such a manner that at all times the composition in place in the cavity presents a free surface and each new charge is deposited on a zone of said free surface, and each new charge is thrust into said surface by means of thrust surfaces that are moved both in reciprocating motion directed towards and away from said free surface, and in cyclical motion such that the thrust surfaces are moved over the extent of the free surface, and simultaneously during molding, relative displacement is implemented between the molded composition and the thrust surfaces, the method being characterized in that each new charge is thrust in such a manner that on each individual stroke of a thrust surface, the underlying composition is caused to interpenetrate over a depth that is not less than five times the mean diameter of the grain size of the coarsest ingredients of the composition, in that said relative displacement is performed in such a manner as to maintain a substantially constant distance between said free surface and the mean point of the stroke of the reciprocating motion of the thrust surfaces, and in that the flow rate of said charges is controlled in such a manner that during each cycle the material onto which the charges are deposited becomes progressively densified in depth by the cumulative interpenetration of the charges, conditions being adjusted in such a manner that over all of the cycles, this densification is substantially uniform throughout the material, and the molded composition is allowed to set.
2. A method according to claim 1, in which the maximum penetration depth obtained on each individual stroke of a thrust surface is limited to ten times the mean diameter of the grain size of the coarsest ingredients of the composition.
3. A method according to claim 1 or claim 2, in which charges of loose material are deposited simultaneously on a plurality of non-touching zones of said free surface.
4. A method according to any one of claims 1 to 3, in which the charges are delivered continuously.
5. A method according to any one of claims 1 to 4, in which a plurality of separate thrust surfaces are used.
6. A method according to claim 5, in which the charges are introduced between the thrust surfaces.
7. A method according to any one of claims 1 to 6, in which said relative displacement is performed by delivering the molded composition through the mold cavity as in a die, as molding progresses.
8. A method according to any one of claims 1 to 6, in which said relative displacement is performed by moving the thrust surfaces as the depth of the molded composition increases in the mold cavity.
9. A method according to any one of claims 1 to 6, in which said relative displacement is implemented by moving simultaneously the wall of the mold cavity and the thrust surfaces.
10. A method according to any one of claims 1 to 9, in which a pressure lower than atmospheric pressure is implemented for degassing the charges prior to applying thrust thereto.
11. A method according to any one of claims 1 to 10, in which a phase offset is implemented between the reciprocating motions of the various thrust surfaces.
12. A method according to any one of claims 1 to 11, in which the reciprocating motion of the thrust surfaces is implemented at a frequency of 5 to 50 go-and-return strokes per second.
13. A method according to claim 12, in which said frequency is set to lie in the range 10 to 30 go-and-return strokes per second.
14. A method according to any one of claims 1 to 13, in which said cyclical motion of the thrust surfaces is rotary motion.
15. Apparatus for implementing a method according to any one of claims 1 to 14, the apparatus comprising a mold (1, 3) defining a right cylindrical mold cavity (4) of right section that is identical in shape to the right section of the body to be made and that extends along an axis (2) perpendicular to the plane of said right section over a length that is equal to a fraction or the entire length of the body to be made; introduction means (10) for introducing a controlled flow of charges of the loose composition into said cavity; thrust means (6) defining a plurality of separate thrust surfaces (11) distributed around said axis and directed towards the plane of the right section of the mold cavity, and such as to ensure that there exists a lateral gap between said surfaces and the walls defining the mold cavity, said gap serving to disengage a fraction of the material from the control means in order to cause the thrust surfaces to move; control means for moving the thrust surfaces both with reciprocating motion (9) directed along said axis, and with cyclical motion (8) about said axis, and control means operative during molding to implement relative displacement (18; 19; 16; 20) between the molded composition and the thrust surfaces as a function of the rate at which the loose material is introduced so as to maintain a substantially constant distance between the free surface of the molded composition and the mean point of the stroke of the reciprocating motion.
16. Apparatus according to claim 15, in which the introduction means (10) are designed to introduce the charges between the thrust surfaces.
17. Apparatus according to claim 15 or claim 16, in which the mold cavity (4) constitutes a die.
18. Apparatus according to claim 15 or claim 16, in which the mold cavity (4) is defined by a gap between two walls (1, 3), one of said walls being displaceable together with the thrust surfaces in order to achieve said relative displacement.
19. Apparatus according to claim 15 or claim 16, in which the mold is stationary and the thrust surfaces (11) are displaceable to implement said relative displacement.
20. Apparatus according to any one of claims 15 to 19, in which the thrust surfaces (11) are preceded in the direction of said cylindrical motion by sloping surfaces (12) for precompacting the charges.
21. Apparatus according to claim 20, in which the thrust surface (11) and the precompacting sloping surface (12) together form a bulging surface.
22. Apparatus according to any one of claims 15 to 21, in which the mold has a frustoconical wall (13) for guiding the charges towards said free surface.

Images