Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting – Measuring a weight or volume
Reexamination Certificate
1997-09-08
2002-03-12
Silbaugh, Jan H. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
Measuring a weight or volume
C264S040100, C264S071000, C264S072000, C264S102000, C264S297900, C264S333000, C425S086000, C425S162000, C425S405100, C425S432000, C425S434000, C106S723000, C106S738000
Reexamination Certificate
active
06355191
ABSTRACT:
The present invention relates to artificial stone products in form of slabs or blocks consisting of a granulated stone material bound by means of a cementitious binding, useful for pavings and wall coverings.
The invention also relates to a method and apparatus for their production.
It is known that, for many centuries, natural stone materials such as marble, granite, etc. have been used in the form of slabs and panels both for paving and for wall claddings.
Natural stone materials are extracted from quarries in the form of blocks and the blocks are subjected to an operative cycle which provides for many operations and processes such as, for example, sawing, facing, polishing, etc.
Alongside their unquestionable aesthetic properties and their equally undeniable mechanical properties, however, natural stone materials have some problems and disadvantages.
In the first place every block extracted from a quarry differs, sometimes slightly, but also sometimes considerably from blocks extracted from the same quarry, so that it is not possible to produce floors or claddings with large surface areas which do not have considerable aesthetic and/or colour differences. In the second place, even at the stage of the extraction of blocks from quarries, a considerable portion of the material excavated or extracted, for example, by blasting, remains unused or becomes unusable in the course of processing.
By way of example, it may be mentioned that the percentage of the stone material excavated from quarries which is used, that is, which is sent in the form of blocks for subsequent processing does not exceed 20-30%, with obvious wastage which is not only disadvantageous from an industrial point of view but also constitutes a factor in environmental pollution and in the disfiguring of the landscape in the regions surrounding quarries.
Attempts have been made in the past and are still being made today to use this resulting stone material (that is, the aforementioned 70% which is not used directly) in the manufacture of artificial stone products.
In order to solve this problem several solutions have been proposed and practiced, which can be classified in two main groups or approaches. A first approach consists in the manufacture of so-called “terrazzo” cementitious products or tiles which are constituted essentially by granulated natural stone material dispersed in a cementitious matrix.
The particular method used for this product produces tiles which are very thick (particularly relative to the dimensions of the individual tiles) and consequently also heavy which, naturally, is disadvantageous with regard to their subsequent handing, particularly at the stage when the tiles are laid.
A “terrazzo” tile generally has dimensions of 40×40 cm (with thicknesses of no less than 3.5 cm) or 30×30 cm (with thickness of 2.7 cm) or other less commonly-used dimensions.
Moreover, their mechanical properties are relatively poor.
In fact, the flexural strength (9.5-10 N/sq.mm) and the abrasion resistance (560-580 cu.mm.) values are certainly not high, whilst water absorbtion reaches 9-10% by weight.
A further disadvantage of this cementitious product lies in its appearance which reveals the presence of the cementitious binding in which the granulated material is incorporated so that, from an aesthetic point of view, “terrazzo” tiles have never been held in gear esteem and their widespread use is due mainly to their cheapness.
Each tile is produced individually by a method which provides for the following steps:
(1) a layer of a starting mixture or mix, constituted by (a) the inert granulated material reduced to the desired particle size beforehand, and (b) a cementitious binding formed by cement and water in which the percentage of water is decidedly in excess of the quantity normally necessary to achieve the binding effect, is spread on the base of a mould and subjected to slight vibration for several seconds;
(2) a second layer of very lean cementitious binding barely moistened with water is placed on top of this first layer (which is intended to form the so-called visible face of the tile);
(3) a pressure is applied over this second layer so as to force the excess water present in the first layer to be transferred into the overlying layer to make up its water percentage to values suitable for bringing about the subsequent setting and hardening steps;
(4) the product is extracted from the mould and is allowed to rest for the time necessary for setting to take place on tables or shelving where it is also left for the time necessary to complete the hardening step (usually about 25 days).
With reference to the manufacturing of tiles or slabs, in more recent years, industrial investigations and developments have been carried out in relation to industrial methods in which a granular filler of stone material, usually the waste from the excavation of natural stone materials, brought to a suitable particle size beforehand, is mixed in suitable proportions with a binding either of a cementitious nature or constituted by a setting synthetic resin.
The resulting mixture is subjected to a first forming step, for example, by the filling of suitable moulds or similar forming devices so as to form a layer of the desired thickness.
The mould or forming device is then subjected to a mechanical compaction operation (preferably by the action of a plate press) with the simultaneous application of a vibratory motion, the mould being kept under vacuum.
Upon completion of this step, which lasts for a few minutes, a hardening step takes place in a manner which depends upon the nature of the binding.
More specifically, in the case of the cementitious binding, this is a conventional setting and subsequent hardening step for which the product is left to rest for the necessary time.
In the case of a binding constituted by synthetic resin, however, hardening takes place in a short time in the presence of a catalyst with the application of heat, or cold by the joint action of a catalyst and a promoter;
This method is advantageous, not only because of its compatibility with modern industrial production standards but also, and above all, because it leads to decidedly more advantageous products.
Amongst the advantages it should be pointed out, in the first place, that it is possible to manufacture slabs of truly considerable dimensions much larger than those of “terrazzo” tiles and also larger than tiles or products made of natural stone materials.
In the second place, the resulting product has a completely homogeneous appearance so that it is possible to produce very large floors or external claddings for buildings.
In the third place, the mechanical characteristics of the resulting slabs are decidedly better than those of “terrazzo” tiles.
The second approach is that of the manufacturing of blocks having size comparable with that of the blocks obtained by excavation from quarries, to be later sawed into slabs.
In the common practice the manufacturing of blocks of stone materials has been and is practiced by prevailingly using calcareous stone materials (since these materials, differently from siliceous materials like granite, can be easily sawed by means of tools bearing diamond insert segments) and Portland cement or more generally hydraulic bindings having a cementing function.
Unfortunately these blocks show the same disadvantageous features of the already mentioned cementitious products, since in their production cement slurries must be used containing water excess, owing to the need of using fluid mixtures capable of readily filling the interstices between the particles of granulated natural stone.
By the way the water excess with respect to the cement causes the mechanical properties of the products to be heavily lowered and moreover the slabs obtained from the blocks undergo diffused fissures caused by the alternated shrinkage and dilatation of the product, these phoenomena being increased by the excessive porosity of the product originated by the evaporation of the too much excess water and by the reduced mechanical re
Lackenbach Siegel
Nissen J. Harold
Poe Michael I.
Silbaugh Jan H.
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