FR2688162A1 - PROCESS FOR PRODUCING PRESSURE MOLDED CONCRETE ELEMENTS AND APPARATUS FOR CARRYING OUT SAID METHOD. - Google Patents

Abstract

A method wherein (a) a predetermined amount of concrete is fed into a mould (3) on a moulding plate (29) which is removably mounted on a vibrating table (4); (b) the concrete in the mould (3) is compressed to give an element (2) having a predetermined shape, while applying compressive force with a compression means (23), as well as vibratory forces with said vibrating table (4); (c) a vibrating table (4) between at least two stationary holders (50, 51) for the moulding plate (29) is used with the top of the vibrating table (4) substantially contacting the bottom of the plate (29) when it is not in use; and (d) a screen (27) is inserted between the moulding plate (29) and the mould (3) before placing said mould (3) on said moulding plate (29).

Description

The present invention relates to a method for manufacturing die-cast concrete elements.
The present invention also relates to an apparatus for manufacturing elements in pressure molded concrete by implementing the method of the invention.

 Various processes are known for manufacturing elements in die-cast concrete, for example pavers, concrete blocks, slabs, which are elements of simple and regular shapes, but also elements of more complicated shapes such as curbs.

These known methods include the steps of
- bring a predetermined volume of concrete into a mold placed on a molding table
- compress the concrete inside the mold to manufacture at least one element of predetermined shape
- unmold this element and evacuate it on a support.

 We know that these methods have several drawbacks; there is a dispersion of the density, and therefore of the resistance, of the concrete between various points of the same concrete element, or between points located in the same place on various elements produced in the same molding operation. This dispersion, which is all the more marked and annoying the larger the element and the larger the molding surface, is likely to cause points of weakness, defects, cracks, likely to cause the scrap of the elements concerned, and may require cement overdoses to ensure, if possible, that all the elements produced meet the conditions of the corresponding specifications.

 The various attempts made so far to try to improve the regularity and the homogeneity of the concrete without limiting the production have not brought a satisfactory solution.

 On the contrary, the current tendency is to seek at the same time-an increase in the productivity of the presses and an improvement in the quality of the products in die-cast concrete, while increasing the molding surface and / or the dimensions of these products, and therefore the risk of homogeneity defects.

 The aim of the present invention is to remedy the drawbacks of known methods and to propose a method which makes it possible both to increase the productivity of the installations and to improve the quality of the products obtained while increasing the molding surface and / or the dimensions of said products.

 Another object of the present invention is to provide an apparatus for implementing the method of the invention.

According to the invention, the method of the aforementioned type is characterized in that it further comprises the following steps
- the concrete is first brought into a preliminary mold in which it is packed to form a preform of a predetermined shape
- The preliminary mold is transferred above the main mold, and the packed concrete is passed from the preliminary mold into said main mold.

 The present invention, by separating and carrying out independently of one another and parallel to each other, the operations of preparing the concrete, on the one hand, and compressing the concrete in the main mold, d on the other hand, thus proposes a process which makes it possible both to increase the throughput of the press and to take care of the preparation of the concrete in order to reduce the amplitude of the aforementioned dispersion and improve the quality and the homogeneity of the products. This improvement in the quality and homogeneity of the products makes it possible to increase the dimensions thereof.

 According to an advantageous version of the invention, a thickness of concrete substantially equal to the thickness at this point of the preform that one wishes to manufacture in said mold is brought into line with any point of the base of the preliminary mold. preliminary.

 One can thus obtain, at any point of the element, a rate of compaction at the level of the blank, and a compression rate at the level of the finished element, which are substantially constant; it also removes practically any backflow of concrete from the overfilled areas towards the underfilled areas, under the effect of the compression of said concrete: it is known in fact that the areas initially too full are overcompressed while the areas initially insufficiently filled are too little compressed, too sparse and therefore fragile.

 According to an advantageous version of the invention, the concrete is brought into the preliminary mold so that the concrete has a substantially zero horizontal speed.

 This ensures uniform filling of the mold, practically eliminating the noted insufficiency of the filling carried out on refusal by a moving drawer for the parts of the mold located at the end of the drawer travel.

 According to a preferred version of the invention, a movable strip is interposed between the mold and the molding table during the concrete molding and compression operation, and, after this operation, the mold is lifted, which contains the element concrete, and the compression means, and the strip is moved.

 The fact of interposing such a strip between the molding table and the mold facilitates the operation of vibrating the concrete, which is generally carried out at the same time as that of compression. This makes it possible to carry out compression directly on the upper part of the molding table, which is practically impossible in the absence of a strip; in fact, the presence of the strip eliminates the risk of metal-on-metal hammering due to decompression harmonics which create independent displacements of the mold, the supports of the products and the table. This avoids having to perform in a conventional manner the compression on wooden supports traditionally used for handling concrete elements once completed. The lifespan of these wooden supports is thus considerably increased.

 Likewise, a person skilled in the art will understand that it is easy to clean such a strip during its movement, which makes it possible to easily remove all of the concrete debris and waste: this clearly improves the surface condition of the concrete elements. , and eliminates the operating irregularities previously due to the presence of such waste and debris on the molding table or on the supports.

According to another aspect of the invention, the apparatus covered by it comprises, in a known manner
- Means for bringing a predetermined volume of concrete into a mold placed on a molding table
- Means for compressing the concrete inside the mold in order to manufacture at least one element of predetermined shape
- means for demolding this element and placing it on a support
- Means for evacuating said support.

According to the invention, this device is characterized in that it further comprises
- a preliminary mold adapted to receive said predetermined volume of concrete
- Means for compacting the concrete in the preliminary mold and forming a blank of predetermined shape
- Means for transferring the preliminary mold above the main mold, and means for passing the concrete blank from the preliminary mold into said main mold.

 Other features and advantages of the invention will appear in the detailed description below.

In the accompanying drawings, given only by way of nonlimiting examples
- Figure 1 is a schematic view partially in section, along II in Figure 3, of an apparatus according to a preferred embodiment of the invention;
- Figure 2 is a view similar to Figure 1, the apparatus being shown at another time in the manufacturing cycle
- Figure 3 is a schematic view partially in section along III-III in Figure 1
- Figure 4 is a schematic view partially in section along IV-IV in Figure 3, of a first embodiment of the apparatus of Figure 1
- Figure 5 is a view similar to Figure 4, the apparatus being shown at another time in the manufacturing cycle
- Figure 6 is a view similar to Figure 4 of another embodiment of the apparatus of Figure 1
- Figure 7 is a very enlarged view of a detail of Figure 3
- Figure 8 is a partial sectional view along VIII-VIII in Figure 7
- Figure 9A is a half view similar to Figure 8 of another embodiment of the invention;
- Figure 9B is a half view similar to Figure 8 of another embodiment of the invention.

In the embodiment shown in Figures 1 to 3, the apparatus 1 for manufacturing elements 2 of die-cast concrete comprises, in known manner, as shown in Figure 3
- Means for bringing a predetermined volume of concrete into a main mold 3 placed on a molding table 4
- Means for compressing the concrete inside the main mold 3 in order to manufacture at least one element 2 of predetermined shape
- Means for demolding this element 2 and placing it on a support 5
- means for removing said support 5.

According to the invention, the apparatus 1 further comprises
- A preliminary mold 6 adapted to receive said predetermined volume of concrete
- Means 7 for compacting the concrete in the preliminary mold 6 and forming a blank 8 of predetermined shape;
means for transferring the preliminary mold 6 above the main mold 3, and means 23 for passing the concrete blank 8 from the preliminary mold 6 into said main mold 3.

 As shown in Figures 1 and 2, the apparatus 1 comprises two concrete hoppers 9, 10. The hoppers 9, 10 generally receive two different qualities of concrete the first hopper 9 contains a relatively large concrete adapted to constitute the body 2a, 8a, of the element 2 and of the blank 8. The second hopper 10 contains a concrete relatively thin adapted to constitute the upper part 2b, 8b, the only visible part, of the concrete element 2 and the blank 8.

 Each hopper 9, 10 is equipped with a device for extracting and dosing concrete of a known type, for example a helmet, not shown, and with a drawer, respectively 11, 12.

 The apparatus 1 comprises, for each drawer 11, 12, means, shown diagrammatically by the rod 13, 14, of a jack not shown, for bringing the corresponding drawer 11, 12 filled with concrete above the preliminary mold 6, and to remove the drawer 11, 12 with the excess volume of concrete overflowing from said preliminary mold 6.

 The apparatus 1 also comprises (see FIG. 3) closing means 15 intended to isolate the drawer 11, 12 from the preliminary mold 6, and means not shown, for example a jack, for opening said closing means 15 in order to put in communication the drawer 11, 12 and the preliminary mold 6 when said drawer 11, 12 is in position above said preliminary mold 6, and to close said closing means 15 in order to isolate the drawer 11, 12 from the preliminary mold 6 and causing the excess volume of concrete overflowing from said preliminary mold 6 to flow back into the drawer 11, 12.

 Thus, in the embodiment of FIG. 3, this operation has already taken place once with the first drawer 11 to constitute, inside the preliminary mold 6, the body 8a of rough concrete of the blank 8.

In this FIG. 3, the drawer 12 is above the preliminary mold 6, and the closure 15 closes (arrow 16) by causing the excess fine concrete 17 which overflows from the mold 6 to flow back into the drawer.

 The closure 15 is shown in the figures in the form of a movable cover 15 of the preliminary mold 6.

 As can be seen in Figure 1 and as will be described in detail below, the preliminary mold 6 has a bottom 18 of predetermined shape 18a substantially symmetrical with respect to a horizontal plane of that of the upper part 8b of the blank 8 that we want to manufacture.

 In the example shown, this background 18, the function of which will be seen below, has a variable shape. It is given the first form 18a above before and during the arrival of the concrete.

 After the arrival of the concrete, said bottom 18 of the preliminary mold 6 is given a horizontal planar shape 19 for packing the concrete with a packing tool 7, the lower surface 21 of which has the shape that we want to give to the upper part of draft 8.

 The compacting tool 7 is known per se and need not be described in detail here. It is movable in the vertical direction between a high position 7a, shown in solid lines in FIG. 3 and in dashes in FIG. 2, in which it allows the two drawers 11 and 12 to come successively above the preliminary mold 6 (as shown schematically in dashed lines in FIG. 1), and a low position 7b represented in solid lines in FIG. 2, in which it cups the blank 8 inside the preliminary mold 6.

 The preliminary mold 6 is transferred in the position shown diagrammatically in dashes at 6a above the main mold 3 by any known means not shown, for example a jack. This movement is shown diagrammatically by the arrow 22 in FIG. 3.

 In this position, the pestle 23 intended to compress the concrete inside the main mold 3, leaves its high position shown in solid lines in Figure 3 and descends inside the preliminary mold placed in position 6a to pass the blank 8 in packed concrete of said preliminary mold in position 6A in the main mold 3: the pestle 23 is then in its low position shown in dashes at 23a in FIG. 3.

The pestle 23 is a conventional pestle.

 As shown in particular in Figures 3, 4 and 6, the main mold 3 is supported on a conventional molding table 4 which is also a vibrating table vibrated by vibrators 25, 26 with eccentric.

 The apparatus 1 also includes a movable strip 27 adapted to be interposed during the molding and compression operation between the main mold 3 and the molding table 4, and means for moving said strip 27.

 The strip 27 is a known conventional strip, relatively flexible, capable of withstanding the compression and vibration forces to which it is subjected.

 In the embodiment shown in FIGS. 4 and 5, the strip 27a is a discontinuous strip wound on a drum 28.

 In the compression situation shown in FIG. 4, a metal plate 29 is placed on the molding table 4, and the strip 27a is interposed between the plate 29 and the main mold 3. The pestle is in its low position 23a and compresses the concrete element 2. A wooden support 5 is ready to receive the concrete element 2.

 In the situation represented in FIG. 5, which corresponds to another later instant of the manufacturing cycle, the main mold 3 and the pestle 23 are lifted above the molding table 4, the strip 27a has been partially wound on the drum 28 by releasing the molding table 4. The plate 29 has also been moved away from the molding table on which a wooden support has been placed 5. All that remains is to lower the main mold 3 and the pestle 23 on the support 5 and to reassemble the mold 3 without moving the pestle 23 to unmold the concrete element and place it on the support 5. These various movements are shown diagrammatically by the arrow 24.

 We can then remove the support 5 carrying a concrete element 2, as shown in dashed lines on the right-hand side of FIG. 5 and as indicated by the arrow 30. We then return to the initial situation shown diagrammatically in FIG. 3.

 A rotary brush 31 makes it possible to clean the strip 27a during its movement.

 In the embodiment shown diagrammatically in FIG. 6, the strip is an endless strip 27b wound around a motor drum 32 and a deflection drum 33. Its upper strand is movable from left to right in the figure in the direction of arrow 34. The metal plate 29a is fixed to the molding table 4. When the molding and compression operation is complete, it suffices to lift the mold 3 and the pestle 23 as before and to advance the strip 27b to place the support prepared in position 5a on the strip 27b on the molding table 4, then to evacuate this support downstream in position 5b with the concrete element 2 that has just been demolded.

 The device also includes a rotary brush 31.

 In the embodiment of FIGS. 7 and 8, the bottom 20, having the shape 18a, of the preliminary mold 3 comprises a series of elongated elements forming contiguous vertical knives 35, and means forming cams 36, 37 for lifting at least some of these knives 35.

 As shown in Figure 8, the cams 36, 37 have steps 40a, 40b, 40c, and a bearing 40d adapted to lift the corresponding knives 35a, 35b, 35c, and 35d to 35j to constitute the projecting part of the shape 18a from the bottom 20.

 The apparatus 1 comprises conventional means, not shown, such as jacks, for lifting the cams 36, 37 and the knives 35 before the concrete is brought into the preliminary mold 6, then for lowering these cams 36 and 37 and depositing the knives 35 on the transverse supports 38 and 39 so that these knives constitute the horizontal flat surface 19 shown diagrammatically in dashes in FIG. 7 and indicated in solid lines in FIG. 2.

In the embodiment of FIG. 8, a flexible or elastic membrane 44 is interposed between the knives 35 and the concrete
In the embodiment of FIG. 9A, the shape 18a is obtained by means of an inflatable bladder 41 which is inflated in a conventional manner, for example by means of a hydraulic liquid 42 in any manner known per se .

 In the embodiment of FIG. 9B, a sliding insert 43, for example made of metal, the upper part of which has the shape 18a, is adapted to be introduced inside the preliminary mold 6 before the arrival of the concrete, and to be removed from the mold 6 once it is filled with concrete, by means of conventional control means not shown, for example a jack.

We will now describe the different stages of the process of the invention, with reference to the figures
- First, the predetermined volume of concrete is brought into the preliminary mold 6, in which it is packed to form a blank 8 of predetermined shape
- Transfer the preliminary mold 6 above the main mold 3, and pass the blank 8 packed concrete from the preliminary mold 6 in said main mold 3
- The concrete is compressed inside the main mold 3 to manufacture at least one element 2 of predetermined shape
- this element 2 is removed from the mold and removed on a support 5
- using the closure 15, the concrete is brought into the preliminary mold 6 so that the concrete has a substantially zero horizontal speed
- It is brought into line with any point of the base of the preliminary mold 6 a thickness of concrete substantially equal to the thickness at this point of the blank 8 that we want to manufacture in said preliminary mold 6;
- The shape of the bottom 18 of the preliminary mold 6 is modified during the blank manufacturing operation;
- This bottom is given before and during the arrival of the concrete, a first shape 18a which is substantially symmetrical with respect to a horizontal plane of that of the upper part of the blank 8 which one wishes to manufacture
- After the arrival of the concrete, the bottom 18 of the preliminary mold 6 is given a second shape 19 which is substantially identical to the shape of the bottom of the element 2 of concrete that is to be made, and the concrete is packed with the compaction tool 7 whose lower surface 21 has the shape that we want to give to the upper part of the blank 8
- a moving strip 27, 27a, 27b is interposed between the main mold 3 and the molding table 4 during the molding and compression operation, and, after this operation, the mold 3 is lifted, which contains the element 2 concrete, and the compression means 23, and the strip 27, 27a, 27b is moved
- During the movement of the strip 27, 27a, 27b, a support 5 is interposed between the molding table 4 and the main mold 3 on which it is removed from the mold and then discharged the concrete element 2 which has just been manufactured.

 Of course, the invention is not limited to the embodiments which have just been described, and many changes and modifications can be made to them without departing from the scope of the invention.

 What has been described above with two hoppers, two drawers and two qualities of concrete, is obviously applicable in the case of a single hopper, a single drawer and a single quality of concrete.

 The cover 15 of the intermediate mold 6 can be replaced by a movable bottom of the drawers, or by a flexible strip which is removed when each drawer is in place above the preliminary mold 3.

 It is possible to use a preliminary mold 6 with a fixed bottom having the shape 18a symmetrical with the surface of the element 2 to be manufactured, and a compacting tool with a flat bottom: the shape change of the concrete would then be done during the transfer into the mold main 3 of the blank 8 contained in the preliminary mold 6.

 One can, in general, use for each step of the process of the invention, means equivalent to those described above and fulfilling the same function.

 We can thus bring the concrete by a conveyor belt, equipped if necessary with an integrating scale. The preliminary mold can be placed on a scale to weigh the concrete. You can also lower the bottom of the preliminary mold after the arrival of large concrete and before that of fine concrete.

 All of the above has been shown schematically in the case of a single concrete element covering the entire surface of the mold, but is obviously applicable in the case of large molds comprising several cells, separated by ribs, making it possible to manufacture at each operation several concrete elements in this case, the compacting tool 7 and the pestle 23 have several projections corresponding respectively to said cells.

 The lower surface of the concrete element (elements) 2 may obviously not be planar, and include for example several bearings.

 The strip 27, 27a, 27b can be replaced by a short section of strip or the like which is removed from the molding table, for example to clean it, while it is slid over the molding table and under the mold a support 5 for depositing the molded elements there, and then slide on the molding table and out of it the support 5 carrying the elements 2 that have just been removed from the mold.

 The present invention has been described implemented on an apparatus comprising a vibration table and a pestle, in which the assembly formed by the vibration table, the mold with the concrete elements, and the pestle is energetically vibrated. while exerting a certain compressive force with the pestle.

 It is understood that the invention also applies to devices not having a vibration table and in which the concrete elements are subjected in the mold to a very high pressure without vibration.

Claims (16)

 1. A method for manufacturing elements (2) of die-cast concrete, this method comprising the steps of t  - bring a predetermined volume of concrete into a mold (3) placed on a molding table (4)  - compressing the concrete inside the mold (3) to manufacture at least one element (2) of predetermined shape  - unmold this element (2) and evacuate it on a support (5)  characterized in that it further comprises the following steps  - the concrete is first brought into a preliminary mold (6) in which it is packed to form a preform (8) of predetermined shape  - The preliminary mold (6) is transferred above the main mold (3), and the packed concrete is passed from the preliminary mold (6) into said main mold (3).  2. Method according to claim 1, characterized in that one brings the plumb of any point of the base of the preliminary mold (6) a thickness of concrete substantially equal to the thickness at this point of the blank (8) that we want to manufacture in said preliminary mold (6).  3. Method according to claim 2, characterized in that one modifies the shape of the bottom (18) of the preliminary mold (6) during the manufacturing operation, in that one gives to this bottom, before and during the arrival of the concrete, a first shape (18a) which is substantially symmetrical with respect to a horizontal plane from that of the upper part of the blank (8) which it is desired to manufacture, in that, after the arrival of the concrete, the bottom (18) of the preliminary mold (6) is given a second shape (19) substantially identical to the shape of the bottom of the concrete element (2) that one wants to manufacture, and in that 'the concrete is packed with a compacting tool (7) whose lower surface (21) has the shape that we want to give to the upper part of the blank (8).  4. Method according to one of claims 1 to 3, characterized in that the concrete is brought into the preliminary mold (6) so that the concrete has a substantially zero horizontal speed.  5. Method according to any one of claims 1 to 4, characterized in that one interposes a movable strip (17, 17a, 17b) between the main mold (3) and the molding table (4) during l molding and compression operation, and in that, after this operation, the mold (3), which contains the concrete element (2), and the compression means (23) is lifted and the strip ( 27, 27a, 27b).  6. Method according to any one of claims 1 to 5, characterized in that, after the molding and compression operation, the mold (3), which contains the concrete element (2), is raised, and the compression means (23) and there is interposed between the molding table (4) and the mold (3) a support (5) on which it is demolded and then discharged the element (2) of concrete which has just been make  7. Apparatus for manufacturing elements (2) in pressure molded concrete by implementing the method according to any one of claims 1 to 6, this apparatus comprising  - Means for bringing a predetermined volume of concrete into a mold (3) placed on a molding table (4)  - Means (23) for compressing the concrete inside the mold (3) to manufacture at least one element (2) of predetermined shape  - Means for demolding this element (2) and placing it on a support (5)  - means for evacuating said support (5)  characterized in that it further comprises  - A preliminary mold (6) adapted to receive said predetermined volume of concrete  - Means (7) for compacting the concrete in the preliminary mold (6) and forming a blank (8) of predetermined shape;  - Means for transferring the preliminary mold (6) above the main mold (3), and means for passing the concrete blank (8) from the preliminary mold (6) into said main mold (3).  8. Apparatus according to claim 7, comprising at least one drawer (11, 12), and means for bringing the drawer (11, 12) filled with concrete above the preliminary mold (6), and for removing the drawer (11, 12) with the excess volume of concrete overflowing from said preliminary mold (6), characterized in that it comprises closing means (15) intended to isolate the drawer (11, 12) from the preliminary mold (6), and means for opening said closing means (15) in order to put the drawer (11, 12) and the preliminary mold (6) into communication when the drawer (11, 12) is in position above said preliminary mold (6 ), and to close said closing means (15) in order to isolate the drawer (11, 12) from the preliminary mold (6) and to cause the excess volume of concrete overflowing from said preliminary mold to flow back into the drawer (11, 12) (6).  9. Apparatus according to one of claims 7 or 8, characterized in that the preliminary mold (6) has a bottom (18) of predetermined shape (18a) substantially symmetrical with respect to a horizontal plane from that of the upper part of the blank (8) that we want to manufacture.  10. Apparatus according to one of claims 7 to 9, characterized in that the preliminary mold (6) comprises means forming a bottom of variable shape.  11. Apparatus according to claim 10, characterized in that the bottom of the preliminary mold (6) comprises inflatable means (41) and means for inflating said inflatable means (41) giving them a predetermined shape.  12. Apparatus according to claim 10, characterized in that the bottom of the preliminary mold comprises a series of elongated elements forming knives (35) substantially vertical and contiguous, and means forming cams (36, 37) for lifting at least some of these knives (35).  13. Apparatus according to claim 10, characterized in that the preliminary mold (6) comprises sliding means (43) forming a bottom of predetermined shape, and means for introducing said sliding means (43) inside the preliminary mold (6).  14. Apparatus according to any one of claims 7 to 13, characterized in that it comprises a movable strip (27, 27a, 27b) adapted to be interposed during the molding operation between the main mold (3) and the molding table (4), and means for moving said strip (27, 27a, 27b).  15. Apparatus according to claim 14, characterized in that the strip is an endless strip (27b) which carries the supports (5).  16. Apparatus according to one of claims 14 or 15, characterized in that it comprises means (31) for cleaning the strip (27, 27a, 27b) after a molding operation.