EP0439399B1 - Modular unit for making prestressed concrete products - Google Patents

Description

The present invention relates to an independent module for manufacturing prestressed concrete products, its preparation device and the products obtained with such modules.

Among the industrial building products, there are known products made of prestressed concrete by adhesive wires such as beams, slabs, lintels, etc.

The manufacturing technique for these products is based on the provision in the molds, before concreting, of special steels for prestressing; these are held by one of their ends beyond one end of the mold, and receive at their other end, beyond the other end of the mold, a force causing them to have elastic elongation. After pouring, setting and drying the concrete, the steels are relaxed and released, thus putting the molded product in prestress.

This technique requires being able to maintain the steels on adequate supports while they are under tension. It is known, in order to maintain these steels, to have anchors provided with special keys at each of their ends or to button them.

Steels are generally wires which can be used over long lengths, the tension being the same in all respects. The consumption of long products (beams and beams) being important, we developed the mass production technique on large benches. These consist of a long (50 to 100 meters and more) and flat slab on which there is a plurality of modules, each comprising several molds arranged in parallel. Steel wires run the entire length of the bench between two massifs where they are anchored. The molds of the adjacent modules are aligned so that a cable passes successively through all of the modules.

Many problems related to this technique of large benches have appeared, in particular for the positioning of steels, the relaxation of steels before cutting, demolding, etc., to which the applicant has proposed numerous solutions described, for example in FR- A-2 403 431, FR-A-2 486 660, FR-A-2 385 510, FR-A-2 375 409.

• les poutres ou les prédalles ont toutes obligatoirement le même nombre de fils de précontrainte et cela sous-entend des produits du même type;
• il est impossible de fabriquer des produits de formes différentes dans un module, ni d'un module à l'autre;
• le banc de précontrainte est une installation volumineuse, fixe, comportant un génie civil important.

This technique of manufacturing prestressed products on large benches, if it is well developed, however presents constraints:

• the beams or the slabs must all have the same number of prestressing threads and this implies products of the same type;
• it is impossible to manufacture products of different shapes in a module, nor from one module to another;
• the prestressing bench is a voluminous, fixed installation, with significant civil engineering.

With regard to the slabs, when they are not prestressed, one of the production techniques is manufacturing on a carousel. It is a closed circuit composed of successive stations, each station corresponding to a particular operation.

This technique adapts well to the production of medium-sized elements of the order of a few meters (up to about 20 meters), transportable from station to station and inside an oven, and capable of be handled easily. It also adapts to variable production rates according to demand.

This carousel technology is flexible, because products produced in small groups (two or three slabs per table) when they are small, can be produced individually when they are large, which allows great adaptation to Requirement. However, these carousels are generally underused because demand in pre-slabs is irregular and the installation is oversized to absorb the high demands.

Carousel installations are known for elongated products preloaded in particular by patents US-A-3,577,610, GB-A-2,113,600 or US-A-3,281,911, however the products are produced in independent molds, one from the other. other and not grouped and arranged in a module, and the molds themselves have a framework supporting the prestressing forces.

EP-A-0 057 635 describes a device for producing elongated prestressed products in a carousel. The head screens on which the ends of the wires are anchored relate directly to the concrete product. It is therefore not possible to relax the wires in the screens before cutting them, which is a serious drawback from the point of view of operator safety and for the quality of the product. On the other hand, the shape of the molds cannot be arbitrary because the demoulding must take place by lifting the product simultaneously with the release of the tensioning hooks. Finally, the device does not allow the production of prestressed pre-slabs because it is impossible in practice to produce head screens supporting the stress imposed by the large number of steel wires without deformation.

In the Belgian patent n ° 492.711 of December 13, 1949, a device for the production of elements of prestressed vibrated concrete has been described, constituted by a rigid rectangular frame constituted by two parallel beams on which two sleepers are supported or headers, the wires being placed between these two crosspieces and stretched by an appropriate machine then keyed one by one.

One objective of the invention is the production of an independent module for manufacturing prestressed concrete products of small dimension of the beam, beam or pre-slab or other type in molds usable in large benches such as those described in the patents of the applicant. cited above, for example.

The subject of the invention is a module for manufacturing flat or elongated products of prestressed concrete of the type comprising, on the one hand, a rigid frame made up of two longitudinal members held parallel by at least two spacers and intended to receive at least one mold placed on the spacers, on the other hand, a means of attachment by trimmers and of tensioning a bundle of steel wires intended to pass through said mold, characterized in that one of the trimmers is fixed, mounted at one end of the side members , the other is mobile, connected to the other end of the side members by at least one tensioning jack, the trimmers being and remaining mechanically independent of the mold.

The module is also remarkable in that the headers each carry a comb for prepositioning the wires.

• la figure 1 est une vue schématique en perspective d'un module spécialisé pour des produits allongés selon l'invention.
• la figure 2 est une vue en perspective éclatée du module de la figure 1.

The invention is illustrated by the appended drawings in which:

• Figure 1 is a schematic perspective view of a specialized module for elongated products according to the invention.
• FIG. 2 is an exploded perspective view of the module of FIG. 1.

As can be seen in FIGS. 1 and 2, the module 1 is a rectangle frame inside which the formworks are arranged. According to the invention, the formwork can be either: a pre-slab plate 3a, beams molds 3b of the type described in the aforementioned patents, or lintel molds 3c. The frame is formed on the one hand by two parallel longitudinal longitudinal members 2, or equivalent elements, dimensioned to take up the prestressing forces, maintained by spacers 4 preferably profiles, on the other hand by two trimmers 5, 6 perpendicular to the longitudinal members , intended to receive a comb where the prestressed steel wires 20 are positioned and anchored and to tension the bundle of wires.

One 5 of the two headers is fixed, rigidly mounted at one of the ends 7 of the side members, the other 6 is mobile and is connected to the opposite ends 8 of said side members by a jack 9 for tensioning.

Preferably the two headers 5 and 6 each carry a support 49 for the prepositioning of the wires.

The upper surface of the spacers 4 defines a plane on which the molds 3 rest (Figure 2).

With the exception of the movable header 6, the components 2, 3, 4, 5, 9 are mechanically rigidly assembled so that the various manipulations do not cause harmful deformations.

These modules 1 can be incorporated into the various systems for manufacturing concrete elements by carousels, therefore their dimensions are variable. However, it is possible to set as a medium base a width of 2.70 m x 12.50 m long and a height requirement of the order of 60 cm; this last dimension is dependent on the products to be manufactured while the other two are more related to the geometry of the manufacturing carousel which will receive the modules.

Two profiles 10 are also arranged along the side members 2, on the outer sides. These are profiles bearing and guide provided for moving the module in the carousel.

The originality of the module is that it can be prepared in a station separate from the path of the carousel, and above all that the steel wires 20 can be put in place on a comb which will then be installed in the forms 3 themselves installed. in the module, this installation being carried out in a station provided for this purpose.

As can also be seen, the shape of the molds does not depend on the demolding process, because one can use molds that open laterally, like those used in production on large benches.

Finally, the great advantage of this module is that it can be used in a carousel without substantially modifying the operation of said carousel. The carousel, hitherto reserved for the production of slabs becomes a multi-product installation. In addition, the modules being prepared outside the carousel circuit, the operation is not interrupted by the change of form, and the production can be continuous.

Claims (2)

1. A module for the manufacturing of flat or elongated prestressed concrete products of the type comprising :
   on the one hand :

   - a rigid frame constituted by two longitudinal beams (2) kept parallel by at least two spacers (4) and intended for receiving at least one mould (3) disposed on the spacers;

   on the other hand :

   - a means for fastening by means of head frames and for tensioning a bundle (38) of steel wires intended for running through said mould,

   characterized in that one (5) of the head frames is fixed, mounted at one end (7) of the longitudinal beams while the other head frame (6) is movable, connected to the other end (8) of the longitudinal beams by at least one tensioning jack (9), the head frames being and remaining mechanically independent from the mould (3).
2. A module according to Claim 1, characterized in that the head frames (5, 6) are each carrying a support (49) for an element for prepositioning the wires.

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