EP2275240A1 - Method for moulding production of an element made up of a die with a hydraulic socket and system for implementing same - Google Patents

Abstract

The method involves depressurizing a sealed mold (4), and degassing a hydraulically setting matrix e.g. fiber reinforced concrete. The hydraulically setting matrix is injected in the mold, though an injection orifice (9) in a lower portion of the mold, at the pressure ranging between 0.4 and 0.7 bar. The hydraulically setting matrix placed inside the mold is compressed. The orifice of the mold is closed. An element formed in the mold is removed. An independent claim is also included for a system for fabricating an element by molding.

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a method and a device for manufacturing by molding a shaped element in a hydraulic setting die.

STATE OF THE ART

The invention relates more particularly to the elements used in the construction which are obtained by molding a hydraulic setting matrix such as a cement matrix. These molded elements are commonly used for façade cladding, creating sun breezes, making moucharabieh, producing architectural elements, etc. Nowadays, these elements are commonly used because of their mechanical strength, their low cost and the stylistic possibilities they offer.

Currently, there are many manufacturing processes by molding such parts.

In particular, there are methods for casting a cement matrix into a mold and then vibrating the cement matrix when it is placed in the mold in order to obtain a homogeneous compactness of the matrix. However, despite the vibrating operations, the parts thus obtained have a relatively large porosity and insufficient mechanical characteristics. However, it is known that the porosity of an object formed of a cement matrix is partly responsible for the shrinkage, the premature aging of the object, its low flexural strength and its dimensional variation during hardening.

Furthermore, another molding process is also described in the international patent application W02005 / 032780 . In this process, it is intended to inject the cement matrix into a mold, to vacuum the mold during injection to extract the mixing water and then unmold the fresh part. If this method makes it possible to obtain elements having a lower porosity than those obtained by the method described above, the porosity nevertheless remains important. In addition, when the element is demolded, there remains a "carrot" at the injection nozzle of the matrix in the mold. This core must then be removed which results in additional labor and sometimes unsatisfactory finish quality at the injection nozzle.

OBJECT OF THE INVENTION

The aim of the invention is to remedy these problems by proposing a method and a system for manufacturing a member formed of a hydraulically-setting matrix making it possible to obtain an element having a low porosity and whose surface quality is substantially homogenous on all its surface.

1. a) une étape de mise en dépression d'un moule étanche ;
2. b) une étape d'injection dans ledit moule maintenu en dépression, de la matrice à prise hydraulique, via au moins un orifice d'injection formé dans une portion inférieure dudit moule ;
3. c) une étape de post compression lors de laquelle on comprime la matrice à prise hydraulique disposée à l'intérieur du moule et l'on obture l'orifice d'injection du moule ; et
4. d) une étape de démoulage de l'élément ainsi réalisé.

For this purpose, and according to a first aspect, the invention proposes a method of manufacturing by molding a member formed of a hydraulic setting die comprising at least:

1. a) a step of depression of a sealed mold;
2. b) a step of injection into said mold held in depression, of the hydraulic setting die, via at least one injection orifice formed in a lower portion of said mold;
3. c) a post-compression step in which the hydraulic-setting die disposed inside the mold is compressed and the injection port of the mold is closed; and
4. d) a demolding step of the element thus produced.

The injection of the hydraulically setting die into a mold maintained in depression combined with a post-compression step makes it possible to obtain a material having a very low porosity, and consequently good mechanical characteristics.

On the one hand, when the matrix is injected into a mold under pressure reduced, the entrained air can be more easily removed to ensure a cavity-free molded product. Indeed, because of the reduced pressure inside the mold, the air flowing along the fibers or trapped between the aggregates of the matrix is more easily eliminated. Thus, the cohesion between the aggregates, the binder and the fibers is considerably increased, thereby increasing the mechanical strength of the element.

In addition, the injection into a sealed mold maintained in depression advantageously allows to obtain identical crystallization on each of the faces of the element.

On the other hand, when performing a post-compression step, the structure of the molded product becomes even more dense which increases the cohesion of the matrix.

Advantageously, during the post-compression step, a core of matrix is moved towards the mold beyond the injection orifice so as to compress the matrix inside the mold. Thus, the method also makes it possible to eliminate the presence of an unsightly carrot.

Advantageously, a pressure of 0.5 to 5 bars absolute is applied during the post-compression step. Thus, the pressure is sufficient to provide satisfactory density and porosity of the manufactured member.

Preferably, the hydraulic setting die is degassed before being injected into the mold. This step limits the amount of air entrained in the mold with the matrix.

In a preferred embodiment, the hydraulic setting die is a fiber reinforced cement. This type of material is totally suitable for the applications envisaged since it makes it possible to obtain high mechanical performances which allow the production of thin elements, possibly perforated, and consequently lighter.

Advantageously, the injection orifice is located at the lower end of the mold. It is indeed important that the filling of the mold is from bottom to top, preferably relatively slowly, to avoid turbulence in the matrix that would have the effect of retaining air bubbles in the material.

Advantageously, the injection pressure is between 0.4 and 0.9 bar relative. This pressure range is appropriate to the intended application since it allows to drive the matrix relatively slowly so as to avoid turbulence.

Advantageously, the vacuum applied in the sealed mold is between 0.1 and 0.3 bar absolute. This range of depression is a good compromise between the means to be implemented for maintaining depression, the speed of entrainment of the matrix in the mold and the absence of formation of air pockets in the matrix during the injection.

In one embodiment, reinforcing elements are placed in the mold prior to injection.

• un moule étanche pourvu d'au moins un orifice d'injection formé dans la partie inférieure du moule ;
• des moyens de mise en dépression dudit moule ;
• des moyens d'injection d'une matrice dans le moule via ledit orifice d'injection ; et
• un moyen pour comprimer la matrice à prise hydraulique disposée à l'intérieur du moule et simultanément obturer l'orifice d'injection du moule.

According to a second aspect, the invention also relates to a manufacturing system by molding an element, for the implementation of the manufacturing method according to the first aspect, comprising at least:

• a sealed mold provided with at least one injection port formed in the lower portion of the mold;
• means for depressurizing said mold;
• means for injecting a matrix into the mold via said injection orifice; and
• means for compressing the hydraulically setting die disposed within the mold and simultaneously closing the injection port of the mold.

Thus, the manufacturing system according to the invention makes it possible to produce elements having a low porosity, good mechanical characteristics and a good surface state.

In one embodiment, the means for compressing the die and closing the injection port is formed by a connector having a cylinder whose upper end cooperates with the edges of the injection orifice, a feed tube opening into the cylinder and a piston movable in said cylinder between a rest position and a post-compression position in which it compresses the matrix and closes the injection port. This means is a particularly simple way to apply pressure inside the mold and simultaneously move the core.

Advantageously, the movable piston is capped with an elastomeric sleeve for sealing the connector during the post-compression step.

Advantageously, the piston comprises a punch at its end intended to come into contact with the hydraulic setting die. This particular embodiment allows in particular to affix logos or indication on the element during molding.

Preferably, the system comprises a degassing device for degassing the matrix prior to its injection into the mold so as to further reduce the porosity of the molded element.

BRIEF DESCRIPTION OF THE FIGURES

• la figure 1 est une vue schématique d'un système de fabrication selon l'invention ;
• la figure 2 est une vue détaillée de la zone d'injection du moule, notée Z1 sur la figure 1, lors de l'injection de la matrice dans la moule ; et
• la figure 3 est également une vue détaillée de la zone d'injection du moule, lors de l'étape de post compression ;
• la figure 4 est une vue détaillée d'un connecteur selon un mode de réalisation particulier de l'invention ;
• la figure 5 est une vue en coupe longitudinale de l'injecteur de la figure 4.

Other objects and advantages of the invention will become apparent from the following description, made with reference to the appended drawings, in which:

• the figure 1 is a schematic view of a manufacturing system according to the invention;
• the figure 2 is a detailed view of the injection zone of the mold, noted Z1 on the figure 1 during the injection of the matrix into the mold; and
• the figure 3 is also a detailed view of the injection zone of the mold, during the post-compression step;
• the figure 4 is a detailed view of a connector according to one embodiment particular of the invention;
• the figure 5 is a longitudinal sectional view of the injector of the figure 4 .

EXAMPLE OF REALIZATION

The system and method of manufacturing by molding an element is described in connection with the figure 1 .

In a first step, the various elements constituting the hydraulic setting die are introduced into a sealed degassing tank 1. The sealed tank 1 is provided with stirring means 7, eg blades, to evacuate the air occluded in the matrix. In a particular embodiment, the sealed tank 1 may in particular form a kneader for homogenization of the matrix.

The sealed tank 1 is kept under vacuum by means of a venturi 2 so as to allow the degassing of the matrix during its mixing. Degassing greatly improves the porosity of the matrix before injection into the mold. In order to optimize the degassing, the matrix is kneaded slowly for approximately 5 to 10 minutes, in the tank 1 kept in depression.

Subsequently, the hydraulic setting matrix present in the tank 1 is injected into a mold 4 via a supply duct 8 connecting the tank 1 to the mold 4.

During the injection, a vacuum is applied in the mold 4 so as to limit the gas bubbles that could be created in the matrix. The vacuum is here created by a vacuum pump 5 connected to one or more suction ports formed at the upper end of the mold 4. The vacuum applied in the mold is preferably maintained between 0.1 and 0.3 bar absolute during the injection step.

Moreover, in order to drive the matrix of the tank 1 to the mold 4, the tank 1 is pressurized via the compressor 3. Preferably, the injection pressure which prevails in the tank 1 is a low pressure, it is called low pressure injection. The relative injection pressure is for example between 0.4 and 0.9 bar.

Subsequently, when the matrix has been injected in sufficient quantity to fill the mold, the pressure applied in the degassing tank 1 is stopped.

In known manner, the mold 4 defines at least one fingerprint intended to receive the matrix and having the shape of the element to be molded. The mold 4 is obviously adapted to withstand the pressures used in the described method. The mold will for example be made of polyester. In known manner, the mold may in particular consist of two elements respectively forming mold and against-mold.

The mold 4 comprises at least one orifice 9 for injecting the matrix, connected to the supply duct 8 and formed in the bottom wall of the mold 4 so as to inject the matrix from the bottom to the top of the mold. Note that in some cases, and especially when the mold 4 has a large volume, it may include several ports 9s.

The mold 4 also comprises one or more orifices 10, connected to the vacuum pump, and formed in the upper wall of the mold 4.

In one embodiment of the invention, provision may be made for the mold 4 to delimit several different indentations so as to simultaneously produce several elements with the same mold.

Preferably, during injection and molding, the mold 4 is arranged so that its longitudinal dimension is substantially vertical. This arrangement makes it possible to increase the compaction of the hydraulic matrix and to limit the surface of the matrix in contact with the air during the injection.

When the injection is completed and the hydraulic setting die filled mold 4, the method then provides a post-compression step when from which is compressed the hydraulic setting matrix disposed inside the mold 4.

Means to achieve this function are detailed on figures 2 , 3 , 4 and 5 . These means comprise a connector or injector which is arranged between the supply duct 8 and the injection port 9. This connector comprises a cylinder 11 whose upper end is fixed to the edges of the orifice 9, a piston 12 movable in said cylinder and a feed tube 13. The feed tube 13 is firstly connected to the supply duct 8 and secondly connected to the cylinder 11 near its end adjacent to the orifice 9 and forms an acute angle with said cylinder 11 so that the matrix injected through the feed tube 13 flows through the cylinder and into the mold, as shown by the arrow f of the figure 2 .

The piston 12 is movably mounted in the cylinder 11 between a rest position, illustrated on the figure 2 , and a post-compression position, illustrated on the figure 3 . When the piston 12 is in its low position, the matrix flows through the connector and the mold is filled (arrow F).

Subsequently, during the post-compression step, the piston rises in the cylinder and comes to drive the material that has come to fill the cylinder 11 during injection. This remainder of matter is commonly referred to as "carrot". The stroke of the piston 12 is such that its upper end is substantially at the same level as the walls of the mold 4. Thus, the piston drives the core beyond the injection orifice, which has the effect of compressing the die inside the mold 4. In addition, the injection orifice 9 is closed.

The connector, shown on the Figures 4 and 5 , comprises a sleeve 14 of elastomer capping the piston 12 so as to seal the device. The elastomer sleeve 14 is attached to the piston via a flange 15 mounted on the piston 4. Note that the connector shown on the Figures 4 and 5 has many applications and may also be used outside the scope of the method according to the invention.

The post-compression stage lasts for the duration of setting of the hydraulic matrix, ie from approximately 2 to 12 hours depending on the matrix used.

The movement of the piston 12 can be controlled by any appropriate means. The piston may in particular be pneumatically controlled via a compressor 3, as shown in FIG. figure 1 , or mechanically.

Subsequently, the element is demolded.

In a particular embodiment, it is expected to place reinforcing elements in the mold 4 before injection, these reinforcing elements may in particular be rods.

The process is particularly suitable for the manufacture of thin elements, elongated and possibly openwork.

The invention is particularly applicable to processes in which the hydraulic setting matrix is a cementitious matrix. Preferably, the matrix will be fiber reinforced cement. The fibers may in particular be chosen from glass fibers, polypropylene fibers, polyvinyl alcohol fibers, polyacrylonitrile fibers, polyamide or polyimide fibers, aramid fibers or even carbon fibers. Mixtures of these fibers can also be used.

The hydraulic setting matrix may also be an ultra high performance concrete comprising cement, fine pozzolanic reaction elements, at least one dispersing agent, organic fibers.

Note however that the invention is not limited to this type of matrix and one can also use any other type of hydraulic setting matrix without departing from the scope of the invention.

In general, the fiber reinforced cement compositions comprise, in weight percentage, between 25 and 75% of hydraulic cement, between 25 and 75% of sand, between 0.5 and 7% of fibers such as glass fibers. or polypropylene, between 0 and 5% of polymers, between 0 and 10% of metakaolin, between 5 and 40% of water and optionally other additives.

By way of example, the manufacturing method described above has been implemented using a fiberglass-reinforced cement whose composition by weight is as follows: components Mass in kg CPA cement CEMI 42.5 50 Silky sand 50 Glass fibers 3.8 Polymer (dry extract) 2 metakaolin 7 Water 19,30

It should be noted that for this example the silica sand / cement mass ratio, also denoted S / C, is of the order of 1.

It is also noted that the water / cement mass ratio, denoted E / C, is of the order of 0.38. The mass ratio E / C is particularly important in the implementation of the process since this ratio acts on the porosity of the cement that can be obtained. Thus, according to the invention, a cement matrix is preferably chosen, the E / C ratio of which is between 0.25 and 0.45 and advantageously between 0.35 and 0.40.

In addition, the dry density of the mixture is 1.88 kg / dm ³ .

As a comparison, two elements molded from the cement matrix defined above were manufactured. The element 1 was produced according to the method according to the invention and the element 2 was produced by following a method of the prior art providing for casting the matrix in the mold and then vibrating the cement matrix disposed in the mold .

The two comparative tables below illustrate the characteristics of resistance to bending, elongation at break, shrinkage, dimensional variation and porosity of the elements 1 and 2 and thus demonstrate the advantageous properties of the elements manufactured according to the method according to the invention: Element 1 Element 2 - - Made according to the method according to the invention Made by casting the matrix and then vibrating Flexural strength MPa at 28 days LDP 7.7 5.3 dying of laughter 8.2 6.3 Long-term LDP 10 8.1 dying of laughter 10 8.1 Elongation at break (‰) 28 days 2 1.6 Long-term 0.5 0.3 Elasticity module MPa 28 days 17500 - Long-term 19000 - Element 1 Element 2 Withdrawal (mm / m) 0.48 1.1 Dimensional variation 0.48 1.4 Thermal Dilatation (m / m) ° C 10 to 15 x 10 -6 - Porosity Water absorption after 24 h (%) 5.9 12.5 Water absorption after 7 days (%) 6.6 13 Permissible bending stress 4 3

The invention is described in the foregoing by way of example. It is understood that the skilled person is able to achieve different embodiments of the invention without departing from the scope of the invention.

Claims (14)

A method of manufacturing by molding a member made of a hydraulically setting die comprising at least: a) a step of depression of a sealed mold (4); b) a step of injection into said mold (4) maintained under vacuum, of the hydraulic setting die, via at least one injection orifice (9) formed in a lower portion of said mold (4); c) a post-compression step in which the hydraulic setting die disposed inside the mold (4) is compressed and the injection orifice (9) of the mold is closed; and d) a demolding step of the element thus produced. Manufacturing method according to claim 1, characterized in that during the post-compression step a matrix core is moved towards the mold (4) beyond the injection orifice (9) so as to compress the matrix to the inside of the mold (4). Manufacturing method according to claim 1 or 2, characterized in that a pressure of 0.5 to 5 bar relative is applied during the post-compression step. Manufacturing method according to one of claims 1 to 3, characterized in that the hydraulic setting die is degassed before being injected into the mold (4). Manufacturing method according to one of claims 1 to 4, characterized in that the hydraulic setting matrix is a cement reinforced with fibers. Manufacturing method according to one of claims 1 to 5, characterized in that the injection port (9) is located at the lower end of the mold (4). Manufacturing method according to one of claims 1 to 6, characterized in that the injection pressure is between 0.4 and 0.7 bar relative. Manufacturing method according to any one of claims 1 to 7, characterized in that the vacuum applied in the mold (4) is between 0.1 and 0.3 bar absolute. Manufacturing process according to one of Claims 1 to 8, in which reinforcement elements are placed in the mold (4) before the injection. Mold manufacturing system of an element, for carrying out the manufacturing method according to one of claims 1 to 9, comprising at least: a sealed mold (4) provided with at least one injection orifice (9) formed in the lower part of the mold (4); means (5) for depressurizing said mold (4); means for injecting a matrix into the mold (4) via said injection orifice (9); said system being characterized in that it comprises means (11, 12, 13) for compressing the matrix disposed inside the mold (4) and simultaneously closing off the injection orifice (9). Manufacturing system according to claim 10, characterized in that the means for compressing the matrix and closing the injection orifice is formed by a connector comprising a cylinder (11) whose upper end cooperates with the edges of the orifice injection nozzle (9), a feed tube (13) opening into the cylinder (11) and a piston (12) movable in said cylinder (11) between a rest position and a post-compression position in which it moves a core core to the mold (4) beyond the injection port (9) to compress the die and closes the injection port (9). Manufacturing system according to claim 11, characterized in that the movable piston (12) is capped with an elastomer sleeve (14). Manufacturing system according to claim 11 or 12, characterized in that the piston (11) has a punch at its end intended to come into contact with the matrix. Production system according to one of Claims 10 to 13, characterized in that it comprises a degassing device (1, 2, 7).

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