Claims
1. Method for manufacturing blocks from two or more starting mixes, in which a final mix, obtained from the composition of the starting mixes, is poured into a formwork where it undergoes a vacuum vibrocompression step followed by a step involving hardening of the binder used for preparation of the starting mixes, characterized in that a primary mix is prepared under a vacuum and at least one secondary mix is prepared separately under a vacuum, said mixes being different from each in terms of at least one characteristic, and the two mixes are combined under a vacuum with a volume ratio such that the primary mix is preponderant, resulting in a final mix having inclusions of the secondary mix in the mass of the primary mix, following which this final mix is poured under a vacuum into the formwork and then undergoes the aforementioned operations.
2. Method according to Claim 1, characterized in that said vacuum is equal to 20-25 mbar.
3. Method according to Claim 1, characterized in that said different characteristic of said two mixes consists in their colour or shade of colour.
4. Method according to Claim 1, characterized in that said different characteristic of said two mixes consists in their particle size.
5. Method according to Claim 4, characterized in that said granulated material used for said primary mix is a stone material and has a particle size of about 20-30 mm.
6. Method according to Claim 5, characterized in that said granulated material used for said secondary mix is a stone material and has a particle size of up to 1-2 mm.
7. Method according to Claim 1, characterized in that the volume ratio between said primary mix and said secondary mix is about 5-15% of the secondary mix relative to the primary mix.
8. Method according to Claim 1, characterized in that said at least one secondary mix, once prepared under a vacuum inside said secondary mixer, is discharged under a vacuum into said main mixer when said first mix is already formed inside it, discharging of the secondary mix being performed with the main mixer operating at a slow speed to prevent complete mixing of the two mixes.
9. Plant for manufacturing articles in the form of blocks, comprising a main mixer, in which a primary mix is prepared under a vacuum, and at least one secondary mixer inside which said at least one secondary mix is prepared under a vacuum, said secondary mixer being able to feed under a vacuum said at least one second mix to said main mixer so as to form a final mix, said final mix being discharged under a vacuum into a formwork, the plant also comprising a vacuum vibrocompression section, characterized in that said main mixer and said at least one secondary mixer are kept under a desired vacuum and the discharge outlet of said at least one secondary mixer communicates with the mixing chamber of said main mixer, said main mixer having an internal volume at least equal to the sum of the volume of the primary mix and the volume of the secondary mix.
10. Plant for manufacturing articles in the form of blocks according to Claim 8, characterized in that said mixers are kept under a vacuum of about 25-50 mbar.
11. Plant according to Claim 9, characterized in that said secondary mixer is mounted above said main mixer so that said at least one secondary mix, once prepared inside said secondary mixer, is discharged under a vacuum into said main mixer when said primary mix is already formed inside it.
12. Plant according to Claim 9, characterized in that at least one secondary device for metering an additive is associated with said main mixer. |
"Method and plant for manufacturing blocks of conglomerate stone material"
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The present invention relates to the manufacture of articles of conglomerate material in the form of blocks and, more specifically, to a method and a plant for manufacturing articles in the form of blocks which can be sawn so as to produce slabs.
For many years a technology for manufacturing blocks obtained from an initial mix formed by a granulated stone (in particular marble, granite) or stone-like material and an organic binder (a hardening resin) or an inorganic (cementitious) binder has been known; according to this technology the mix is charged into a formwork of suitable dimensions and undergoes a vacuum vibrocompression operation and then passes to a hardening step using a procedure which depends specifically on the nature of the binder.
Italian patent No. 1,181,570 describes a method and a plant of this kind and envisages that the step of mixing the initial mix is also performed under a vacuum.
Still in connection with the preparation of articles in the form of blocks it is worth mentioning the mixer forming the subject of Utility Model Application No. TV98U000023. This mixer, which operates under a vacuum and supplies a formwork, has a plurality of metering devices which are connected to the internal chamber of the mixer so as to pour a desired additive (for example a pigment) into the mix, preventing the internal chamber of the mixer, at any time during its operating cycle, from coming into contact with the external atmosphere, which would negatively affect the vacuum which must be constantly present inside it.
All this technology is intended for the manufacture of articles in the form of slabs which are similar as far as possible to natural stone material, this material, especially in the case of marble, having varying colours and in particular a veined effect. In fact, observing a slab of marble or granite, especially a finished and therefore smoothed and polished slab, it can be noted how this slab very often has two or more components with a different colour and size.
Hitherto, however, in the case of the manufacture of blocks, with the technology available industrially it has been possible only to manufacture entirely under a vacuum articles composed of mixes which are substantially monochromatic.
The main object of the present invention is to provide a method and a plant for manufacturing blocks in which the aesthetic and chromatic characteristics of natural stone materials are reproduced, both in terms of mixture of inclusions of varying sizes and in terms of varying colours and/ or shades of colour.
This object is achieved with a method for manufacturing blocks from two or more starting mixes, in which a final mix, obtained from the composition of said starting mixes, is poured into a formwork where it undergoes a vacuum vibrocompression step followed by a step involving hardening of the binder used for preparation of the starting mixes, said method being characterized in that a first mix or primary mix is prepared under a vacuum and at least one second mix or secondary mix is
prepared separately under a vacuum, said mixes being different from each in terms of at least one physical characteristic and/or in terms of particle size, and the two mixes are combined under a vacuum with a volume ratio such that the first mix is preponderant, resulting in a final mix having inclusions of the secondary mix in the mass of the primary mix, following which this final mix is poured under a vacuum into the formwork and then undergoes the aforementioned operations.
In the above definition it is stated that the two mixes differ in terms of at least one physical characteristic, which characteristic may consist of the colour (or the shade of colour when the basic colour is the same) and/or the particle size.
In this latter case, the particle size of the primary mix is preferably coarse and even more preferably in the region of 20-30 mm, while the particle size of the granulated material used for the second mix is very fine, in the region of up to 1-2 mm.
As regards the volume ratio of the two mixes which are mixed together to form the final mix, it is chosen, as already mentioned, so that the primary mix is preponderant. Preferably the secondary mix is present in an amount equal to 5-15% by volume of the primary mix.
In the case where more than one secondary mix is used, the sum of their volume amounts is equal to the value indicated above.
In turn the plant for implementing the method of the present invention envisages essentially a main mixer operating under a vacuum, inside which said primary mix is prepared, and at least one secondary mixer which operates under a vacuum and inside which said at least one secondary mix is prepared, said secondary mixer being able to feed under a vacuum said at least one secondary mix to said main mixer which in turn discharges under a vacuum said mix into a formwork so as to perform subsequently the operations indicated above for forming of the block, namely its vacuum vibrocompression and the hardening step, said main mixer and said at least one secondary mixer being kept under a desired vacuum, preferably of about 25-50 mbar.
In the preferred embodiment of this plant, said secondary mixer is mounted above said main mixer so that said at least one secondary mix, once prepared inside said secondary mixer, is discharged into said main mixer when said first mix is already formed inside it, so that the two mixes, Le. first mix and second mix, are mixed together, while maintaining, however, their essential identity, namely without the formation of a single mix which would therefore be monochromatic and have unique characteristics such as distribution of the granulated material.
In connection with this embodiment, it is possible to envisage, together with the secondary mixer, metering devices able to dispense, in selected amounts, any additives to said first mix, said metering devices being preferably of the type described in the already mentioned Utility Model Application TV98U000023.
In all cases said main mixer and said at least one secondary mixer are kept under a desired vacuum of about 25-50 mbar, which remains for the whole operating cycle of the mixers, discharging of said secondary mix inside the primary mixer being performed in such a way as to prevent the internal
chamber of the mixers coming into contact with the external atmosphere, which would negatively affect the desired vacuum condition.
In connection with the plant defined above it is evident that a characteristic of the primary mixer is that of having an internal volume suitable for containing not only said primary mix, but also the at least one secondary mix which must be poured under a vacuum into the primary mixer when both the mixes have been prepared.
The aspects and advantages of the present invention will emerge more clearly from the detailed description which follows, provided in relation to the accompanying drawings, which show schematically a side view of the plant according to the present invention.
In the drawings Fig. 1 shows the plant during discharging of the final mix into the formwork for forming the block, while Fig. 2 shows the same plant during charging of the primary materials into the two mixers, with the feed openings open.
With reference to the drawing, the plant comprises generally two sections A, B and C, respectively intended for:
(i) preparation of the mix or mixes and filling of a formwork;
(it) vacuum vibrocompression and
(iii) extraction
As regards the sections B and C these consist of machines and operations which are well known in this technology and for a description thereof reference may be made to Italian patent No. 1,181,570. If we now consider section A, this comprises a tunnel-like frame, which is delimited by a base 100, a vault with a flat ceiling 102 and openings which can be sealingly closed at the two ends, indicated by 104 and 106 respectively, by means of gates.
Rails for the displacement of carriages 108, which contain the formworks generally indicated by the reference number 110, are preferably provided on the base 100.
The base with rails 100 continues into the sections B and C so as to allow the subsequent displacement of the carriages 108. The section B is also formed as a tunnel, in the same way as section A, and has at its downstream end (in the direction of displacement of the carriages indicated by the arrow F) an opening 112 which can be sealingly closed by a gate.
As already mentioned, in section B the step involving vibrocompression of the material contained in the formwork 110 is performed under a vacuum, so that it is necessary to avoid any contact with the exterior during the active vibrocompression step.
The ceiling 102, which obviously must be able to withstand the weight of the machines which it supports as well as the stresses induced by operation of this machinery, supports the main mixer 114 which is preferably of the type described in Utility Model Application No. TV98U000023, to which reference may be made for further explanations.
From the schematic drawing it can be readily understood that it consists of a mixer with two horizontal-axis shafts, having a bottom discharge outlet 116 for the finished mix communicating with the formwork 110.
Preferably the discharge outlet 116 extends over the entire width of the formwork 110 which is made to perform a reciprocating movement between the two positions shown in the figures along the abovementioned rails so as to ensure uniform and balanced filling of the formwork.
Obviously, during the other operating phases of the mixer 114, the discharge outlet 116 is closed so as to contain the mix inside the mixer.
At the top the mixer 114 is provided with an opening for introduction of the materials to be mixed together, said opening being able to be sealingly closed by means of a structure which forms part of the support carriage 120 of the secondary mixer 122. From Figures 1 and 2 it can be clearly seen that the carriage 120 is movable on rails or rollers between the two positions constituting a closed condition and open condition, respectively, in relation to the opening 118.
From the same figures it can also be understood how the secondary mixer 122 is preferably of the same type as the main mixer 116, so that further clarification is not required.
Fig. 2 shows, moreover, the solution in which, in addition to the secondary mixer, the carriage 120 is provided with secondary metering devices 124 for introducing other additives (for example pigments) into the main mixer 116.
It is evident that the operation under a vacuum of the two mixers as well as introduction of the second mix prepared inside the mixer 122 and any other additives takes place when the carriage is in the position shown in Fig. 1.
It is also worth noting that the vacuum condition is desirable and therefore also envisaged inside the secondary mixer 122 because in this way the incorporation of air also into the secondary mix is avoided, benefiting the properties of the final article understood as being both blocks and slabs resulting from sawing of the block.
In the above description reference has been made to at least one secondary mix and therefore to at least one secondary mixer, since the final mix could also comprise a main mix prepared in the main mixer 116 and more than one secondary mix or second mix, each prepared in a dedicated secondary mixer.
In this case the carriage 120 could transport all the secondary mixers, conveying each of them in succession opposite the charging opening of the main mixer 11 and maintaining always the vacuum condition.
During implementation of the method according to the present invention, with reference to the example of a primary mixer and a single secondary mix:
(a) during a first step, in the position shown in Fig. 2, the various ingredients of each of the two mixes are respectively charged at atmospheric pressure into the mixers 114 and 122; then the secondary
mixer 122 is brought into the position shown in Fig.l, its feed opening is closed and then the two mixers are made to operate until each mix is ready for filling the formwork;
(b) when mixing has been completed, in the position shown in Fig. 1, the secondary mix is discharged into the mixer 114, the stirring blades of which are operated slowly so that the secondary mix is eventually partially mixed with the first mix;
(c) the discharge outlet of the mixer 122 is closed and the discharge outlet 116 of the mixer 114 is opened, the formwork being filled by slowly rotating the blades of the mixer 114;
(d) at the end of filling of the formwork, the carriage 108 is transferred into the section B, while a new carriage with associated formwork is positioned in section A.
As already mentioned, the essential characteristic feature of the present invention lies in the fact that at least two mixes are used, all prepared under a vacuum, the first mix of which, being preponderant in terms of volume and hence weight, is formed preferably with granulated material with a coarse particle size (20-25 mm), while the second mix (or the second mixes if there are more than one) is formed preferably with a fine granulated material (up to 1 mm) and is present in a decidedly smaller amount in terms of both volume and weight.
The tests carried out with the plant according to the present invention have resulted in the production of slabs (obtained from sawing blocks) in which it is possible to discern a first component consisting of the first mix and therefore with large-size stone inclusions, surrounded by zones of the component consisting of the secondary mix (with a different colour).
As already mentioned above, the difference between the two primary and secondary mixes may also consist in a difference in colour (for example black marble and white marble) which may be an alternative to or present together with the different particle size.
A difference in terms of type of stone-like materials forming the two mixes is also possible.
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