EP0251966B1 - Method and plant for the manufacture of a building element imitating an accumulation of dry stones - Google Patents

Abstract

A method of manufacturing a building block which imitates a pile of dry stones. According to the method, the stones (10) are placed side-by-side on the bottom of a mold whose inside shape corresponds to the desired block shape, said bottom being constituted by a grating. Cement is then cast inside the mold. The cement (11) is compressed in order to force it to spread out uniformly inside the mold and to creep between the stones (10). While the cement is kept under pressure, water is projected through the bottom grating against the outside face of the block (1), so as to remove any cement which may be found thereon. Pressure is then removed from the cement and it is allowed to set. Finally the block (1) is extracted from the mold.

Description

The present invention relates to a method of manufacturing a building element imitating a stack of dry stones, as well as an installation making it possible to implement this method.

In his previous patent FR 2 545 129, the applicant described a prefabricated element of the type mentioned, which is constituted by a plate of cement (or any other similar curable binder), one of the faces of which is covered with visible juxtaposed stones which are retained in this cement; two opposite edges of the plate have the form of broken lines, for example in a zigzag, nestable one inside the other; this arrangement makes it possible to hide the joints between two neighboring elements when these are assembled, in particular for erecting a wall or for laying a paving, the assembly thus obtained imitating a continuous stacking of dry stones.

Currently, to manufacture an element of this kind, the applicant begins by placing the stones - for example granite-cut waste - side by side on the bottom of a mold whose top is open and whose sides have an identical shape. to that of the element to be manufactured. It possibly places on the layer of stones a metal reinforcement intended to improve the mechanical resistance of the finished element, then pours fluid cement into the mold. After setting the cement by drying, it removes the finished element from the mold.

Experience has shown that this traditional process of the applicant was not entirely satisfactory since the cement does not always fill the mold completely and correctly, which creates voids unacceptable for the aesthetic appearance or the mechanical resistance of the element. , and sometimes leads to poor retention of the stones by the cement; moreover, poured cement frequently reaches the exposed parts of the stones, and hardens on these parts during drying, which alters the appearance of the finished product.

DE-A-2 358 505 describes a process and a machine for the production of washed concrete blocks. The method includes the steps of placing coarse pieces of concrete side by side on the bottom of a mold whose shape corresponds to that of the element to be produced, filling the mold with fluid cement, compressing the cement to force it to spread evenly inside the mold and infiltrate between the pieces of concrete, stop compressing the cement and let it set and finally, extract the element from the mold.

In addition, this method comprises a step of washing the lower face called the "external face" of the block while the bottom of the mold is removed. In order to prevent the pieces of concrete and the cement from flowing down, it is essential that the cement be hard at heart but tender on the side to be washed. To do this, a chemical retarder must be used.

This additional step complicates the implementation of the method since it is necessary to have at its disposal:

- a cement mixed with a retarder for the area of the block which is located in the vicinity of the concrete aggregates;

- ordinary cement for the rest of the block.

The invention aims to solve these problems by proposing a manufacturing process of the kind mentioned above which is easy and economical to implement and which makes it possible to obtain very good quality finished elements, with a low percentage of scrap, while being suitable for medium or large series production.

These results are achieved by the fact that the bottom of the mold is constituted by a grid and by the fact that, while the cement is kept compressed, water is sprayed through the grid-shaped bottom on the external face of the element so as to remove the cement therein.

The meshes of the grid constituting the mold base are naturally determined according to the average dimensions of the stones used, so that they do not allow the smallest of these stones to pass, while being large enough not to obstruct the passage water jets to remove excess cement.

It may be advantageous, if it is desired to obtain reinforced elements, resistant in particular to tensile stresses, to place in the mold, before pouring the cement, a metal frame (for example a trellis or a mesh).

On the other hand, to improve the appearance of the finished element and the quality of retaining the stones by the cement, it is preferable to wash the stones placed in the mold, then to spray on them an admixture favoring the attachment of the cement, before pouring it.

Very simply, the compression of the cement in the mold can be carried out by means of a movable pressure plate, parallel to the bottom of the mold in the form of a grid, this pressure plate constituting in a way the cover of the mold.

The projection of water onto the stones through the grid is preferably done in two phases, a washing proper by pressurized water jets, followed by rinsing by sprinkling in rain (by production of droplets).

CH-A-287 804 describes an installation for manufacturing a construction element which comprises a series of movable molds placed one after the other on a rolling track, the latter passing through a series of successive stations in which various steps of manufacturing the element are carried out. Conveying means are provided, which allow the molds to be transferred from station to station.

The installation which is also the subject of the invention and which makes it possible to implement the method previously mentioned, is of the type described in CH-A-287 804. It is remarkable by the fact that the bottom of the molds is constituted of a grid and in that the successive stations include means which make it possible to carry out the following operations:

- place the stones side by side on the bottom of a mold whose internal shape corresponds to that of the element;

- fill the mold with fluid cement;

- compress the cement to force it to spread evenly inside the mold and to infiltrate between the stones;

- the cement being kept compressed, spray water through the grid-shaped bottom on the external face of the element so as to remove the cement therein;

- stop compressing the cement and let it set;

- extract the element from the mold.

In a preferred embodiment of the invention, each mold is composed of two separate parts capable of being joined to one another;

- an upper part in the form of a frame whose internal shape corresponds to the contour of the element;

- a lower part carrying the bottom in the form of a grid and provided with wheels ensuring its rolling on the track.

When it is desired to manufacture elements in accordance with the patent FR 2 545 129 already cited, two opposite edges of the upper part are given the form of broken lines, with complementary contours which fit together.

The cement compression device, which equips the installation, advantageously comprises a carriage guided in translation parallel to the track and arranged to accompany the mold during the cement compression and water spraying stages, as well as a press plate movable relative to the carriage, means being provided for moving this press plate against the mold in order to compress the cement therein.

Other characteristics and advantages of the invention will appear from the description and the appended drawings which show a preferred embodiment thereof.

In these drawings:

- Figure 1 is a perspective view of a building element which has been manufactured by the method according to the invention;

- Figures 2 and 3 are respectively schematic perspective views of the upper and lower parts of the mold;

- Figure 4 is a schematic view of the installation, intended to illustrate the different stages of the method according to the invention.

The building element 1 shown in Figure 1 is a generally rectangular plate, dimensions 50 x 25 x 8 cm; the opposite small sides 12-13 of this plate are zigzag shaped. This element is essentially made of cement 11 but is provided on one of its faces with a layer of exposed stones 10 just seated and practically contiguous, retained by the cement.

By the term "cement" is meant not only the actual cement (mixture of calcium carbonate and aluminum silicate), but in general any curable binder which can be used in construction, for example concrete. In this cement is embedded a metal reinforcing frame 14 such as a lattice of crisscrossed iron bars welded for example.

The stones 10 are for example waste from the size of granite, pebbles, shales, white stones from Touraine, etc. Their dimensions are chosen according to local availability and / or the desired construction style.

The assembly of the elements 1, for the realization of a construction, is done in a similar way to the assembly of concrete blocks or traditional slabs, using mortar, cement or mortar. The interlocking of the zigzag edges of two contiguous plates, during their assembly, makes it possible to hide the joints between the plates, giving the construction the appearance of a stack of particularly aesthetic dry stones.

This type of prefabricated element can be used for the construction of buildings and various pavements, in particular of walls or low walls, chimneys, barbecues, wells, steps and pavements for gardens and pedestrian ways.

The mold shown in FIGS. 2 and 3 consists of an upper part 2 and a lower part 3.

Part 2 has the form of a frame having two opposite sides 20 rectilinear and two other sides 21, 22 in broken lines, the shape and the dimensions of the interior space delimited by these sides corresponding to the outline of element 1 that we want to manufacture.

The lower part 3 also has the shape of a frame, of dimensions equal to or slightly greater than those of the frame 2; this frame 3 supports a horizontal grid 30 which consists of two crossed series of parallel bars. The mold part 3 is mounted on two pairs of idler wheels, which are guided in translation on a pair of horizontal rails 4, this part 3 therefore constituting a mobile carriage.

Appropriate means, the design and production of which are within the reach of those skilled in the art and which have not been shown for the sole purpose of simplification, allow the two parts 2 and 3 to be joined together after the frame 2 has been placed on the frame 3. These fixing means may consist of clamping members of known type, for example with lever and / or eccentric, which achieve rapid blocking and unblocking of part 2 on part 3 .

Figure 4 illustrates the procedure for manufacturing a building element of the kind shown in Figure 1, using the mold which has just been described; this figure schematically shows the various stations of the installation making it possible to implement this process.

In this figure 4, the lower part of the drawing should be understood as being an extension of the upper part, the connection of the two parts corresponding to the marks B-Bʹ.

The track 4 of the carriage 3 travels all the stations where the different stages of manufacturing the element 1 will be carried out. A plurality of identical molds 2-3 are provided, which can circulate one after the other on track 4, this to avoid time dead at each work station.

A suitable conveyor such as a movable chain 40 fitted with pusher cleats 41 (partially shown) makes it possible to drive the molds into the installation, from station to station; the molds move from left to right in Figure 4; the speed of their movement is for example of the order of 0.1 to 0.2 m / s.

The installation comprises a station (II) equipped with a washing device 6 and an adjuvant spraying device 7, both arranged above the trajectory of the molds; these devices are fitted with downwardly directed liquid spray nozzles.

The installation includes a station (IV) equipped with a cement compression device 5, placed above the trajectory of the molds. This includes a carriage 51 fitted with wheels 55 and guided in translation on a horizontal track 56, parallel to track 4. Track 56 consists of upper and lower rails 560 respectively 561, which positively hold the wheels 55 to both up and down.

This device 5 also includes a pressure plate 50 carried by the carriage 51 and movable in translation relative to the latter in the vertical direction. Vertical columns 54 guide the plate 50 relative to the carriage 51, while a double-acting hydraulic cylinder 52 ensures the movement of the plate 50, by means of a cylinder rod 53.

The pressure plate 50 is a rectangular plate of dimensions slightly larger than those of frame 2.

On the top of the carriage 51 is fixed a square piece 57 to which is attached the free end of a horizontal control rod 58. The latter constitutes the rod of a hydraulic or pneumatic cylinder, single acting, arranged to move positively the carriage 51 in the opposite direction to that of the mold 2-3 (arrow H), and so as not to hinder the movement of said carriage - by putting its piston chamber at atmospheric pressure - when the latter moves in the same sense as the mold (arrow I).

Immediately downstream of the station (IV) is a station (V) equipped with a washing device 8 and a rinsing device 9, these two devices being located below the trajectory of the molds, and being provided with water spray nozzles which are directed upwards.

The stroke of the jack 59 is sufficient to allow the carriage 51 to pass vertically over the two devices 8 and 9.

Appropriate control members, manual or automatic, make it possible to start the projection devices 6, 7, 8 and 9 and the jacks 52, 59 in synchronism with the passage of the molds in the installation.

The manufacture of a building element of the kind mentioned by means of this installation is done as follows:

An operator located at the first station (designated (I)) places the upper part 2 on the lower part 3 of a mold, and fixes it there by means of the clamping members provided for this purpose.

Then another operator places inside the mold 2-3 thus formed, on the grid 30, a layer of stones 10 while trying to make them contiguous, as much as possible; it then possibly deposits on this layer a metal frame 14, either directly or at a certain distance by means of appropriate spacers.

Driven by the cleat chain 40, the mold 2-3 then passes to the station (II) under the devices 6 and 7 which respectively, by spraying water, wash the stones 10 (as well as, if necessary, the frame 14) and, by spraying, coat them with an appropriate adjuvant of known type intended to promote the bonding of the cement.

On leaving the station (II), the upper part 2 of the mold is filled with fluid cement which covers the stones 10 and the frame 14 (station (III)). This filling can be carried out either manually by one or more operators, or automatically by means of a discharge hopper placed above the trajectory of the molds, or even semi-automatically.

The mold filled with cement then arrives at the compression station (IV), the pressure plate 50 is lowered by extension of the jack 52, so as to come to bear against the mass of cement 11 (arrow J). It follows a pressurization of the cement which is forced to occupy completely and homogeneously the entire interior space of the mold, the cement seeping in particular from top to bottom between the stones 10 to the grid. 30 ; during this compression, the plate 50 plays the role of the mold cover and shapes the internal face of the element 1.

As an indication, experience has shown that a pressure of the order of 5,000 Pa is satisfactory to obtain a good distribution of the cement in the mold, when dealing with a cement of normal fluidity.

The compression force developed on the cement by the plate 50, and transmitted to the carriage 51, is absorbed by the upper rails 561 of the track 56, so as to prevent the carriage from being raised.

During the pressurization, the device 5 accompanies the mold in its translational movement on track 4, while the piston chamber of the jack 59 is brought to atmospheric pressure (arrow I). This assembly thus crosses the station (V) (arrow K) where the visible part of the stones 10, bearing against the grid 30, is washed and then rinsed by successive jets of water at high and low pressures produced by the devices 8, respectively 9.

The washing jets remove the cement which has infiltrated not only on the visible parts of the stones, but also which has lodged in the interstices separating the stones up to the grid 30, cement which could remain visible on the product. finished and remove from it its appearance of dry stones. This washing is preferably done at an adjustable pressure, so that the power of the jets can be adapted to the fluidity of the cement and to the sizes of the stones used; As an indication, the pressure of the water jets is for example between 0.5 and 5 × 10⁵ Pa.

The subsequent rinsing by droplets of water with the aid of the device 9 is intended to remove stains and splashes of cement which may remain after washing, or which may be produced by this washing itself.

The cement is then decompressed as a result of the retraction of the jack 52, this retraction causing the plate 50 to rise (arrow L, post (VI).

Simultaneously, the jack 59 which had retracted as a result of the advance of the carriage 51 (itself driven by the mold 2-3) is put in extension, causing the return of the device 5 to the station (IV) (arrow M). This device is then ready to act on the next mold.

The mold 2-3 is then sent (arrow N) to a storage and drying area not shown, for example on a drying carousel where the setting of the cement takes place. After hardening, an operator demoulds the finished element 1; the extraction of the element from the mold is facilitated by the fact that this mold is in two parts, the latter being able to be advantageously separated for the purpose of demolding.

The raceway 4 is preferably a closed circuit, which allows the empty mold 3-4 to be brought back to station 1 after demolding, this empty mold then being ready to receive a new load.

It goes without saying that the present invention is not limited to the preferred embodiment which has just been described by way of example; on the contrary, it encompasses all variants.

This is how one could, for example, to increase the production rate, mount several molds on the same cart circulating in the installation, for example a group of four molds per cart.

Furthermore, the molds are not necessarily fixed on the carriages but can be simply placed on them.

The grid constituting the bottom of the mold is not necessarily formed of crossed bars. The term "grid" means any perforated plate capable of properly retaining the stones and the cement in the mold while allowing the passage of the jets of washing water.

Claims (10)

1. Process of manufacturing a building block imitating a pile of dry stones, said block including an outside face which is lined with visible justaposed stones held in place by cement, said process including the stages which consist in :
   - placing the stones (10) side by side on the bottom of a mold (2-3) whose inside shape corresponds to the shape of the block ;
   - filling the mold with fluid cement (11) ;
   - compressing the cement (11) in order to force it to be uniformly distributed within the mold (2-3) and to creep between the stones ;
   - removing pressure from the cement (11) and allowing it to set ;
   - extracting the block (1) from the mold
   characterized in that the bottom of the mold (2-3) is composed of a grating (30) and by the fact that, while the cement is kept under pressure, water is projected through the bottom grating (30) against the outside surface of the block (1) so as to remove any cement to be found thereon.
2. Process according to claim 1, characterized in that prior to casting the cement, a metal reinforcement member (14) is placed in the mold.
3. Process according to one of claims 1 and 2, characterized in that prior to casting the cement (11), the stones (10) placed in the mold (2, 3) are washed.
4. Process according to claim 3, characterized in that after washing the stones (10) placed in the mold, and prior to casting the cement (11), an additive is projected onto the stones for facilitating cement adherence.
5. Process according to one of claims 1 to 4, characterized in that the cement (11) is compressed by means of a moving pressure plate (50) which moves parallel to the bottom of the mold in the form of a grating (30), said pressure plate constituting a cover for the mold (2-3).
6. Process according to one of claims 1 to 5, characterized in that the water is projected through the bottom grating (30) in two stages :
   - a washing stage using jets under pressure ; and
   - a rinsing stage using a spray of droplets.
7. Installation for implementing the process according to one of claims 1 to 6, which comprises a series of moving molds (2-3) placed one after another on a running track (4), said molds passing through a series of successive stations, conveyor means being provided for moving the molds from station to station, characterized in that the bottom of the mold (2-3) is composed of a grating (30) and that the successive stations comprise means to perform the following stages :
   - placing the stones (10) side by side on the bottom of a mold (2-3) whose inside shape corresponds to the shape of the block ;
   - filing the mold with fluid cement (11) ;
   - compressing the cement (11) in order to force it to be uniformly distributed within the mold (2-3) and to creep between the stones ;
   - while the cement is kept under pressure, projecting water through the bottom grating against the outside surface of the block so as to remove any cement to be found thereon ;
   - removing pressure from the cement (11) and allowing it to set ;
   - extracting the block (1) from the mold.
8. Installation according to claim 7, characterized in that the Molds (2-3) are made of two distinct portions, capable of being fixed to one another :
   - a top portion (2) in the form of a frame whose inside shape corresponds to the outline of the block (1) ;
   - a bottom portion (3) having the grating bottom (30) and provided with wheels (31) for running along the track (4).
9. Installation according to claims 8, characterized in that the top portion (2) of the mold in the form of a frame has two opposite edges (21, 22) in the form of irregular lines having complementary outlines which are interfittable in each other.
10. Installation according to one of claims 7 to 9, characterized in that it is equipped with a cement compression device (5) comprising a carriage (51) which is guided in translation parallel to the running track and which is arranged to accompany the mold (2-3) during said stages in which the cement is compressed and during which water is projected, together with a pressure plate (50) which is movable relative to the carriage (51), with means (52-53) being provided to urge said pressure that against the mold (2-3) in order to compress the cement found therein.

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