Patent Application
20080006366
The present invention relates to the production of articles having a shape which is not flat, more specifically slightly curved, from a mix consisting of granulated inorganic materials and hardening resins as binders.
Articles obtained from a mix consisting of granulated natural stone and/or stone-like and/or ceramic materials and hardening resins are well known in the technical literature - see in particular the patents U.S. Pat. Nos. 4,698,010 and 5,264,168. Variants of these articles also exist, these being characterized by the additional use of reinforcing elements, for example metal and/or glass fibre elements—see, among other publications, the patents U.S. Pat. Nos. 5,670,007 and 6,205,727 as well as the patent application WO-A-03,035,994.
These articles always have a flat shape, both in the case of sheets and panels, where the thickness is much smaller than the other two dimensions, and in the case of parallelepiped blocks, i.e. when all three dimensions of the articles are of the same order of magnitude. Thus, although widely found on the world markets, these articles are not universally used, as instead would be desirable because of their excellent mechanical properties and other characteristics.
The main object of the invention is to provide an industrial method which allows the production of articles, in particular sheets and panels, having a shape which is slightly curved (i.e. with a radius of curvature greater than about 15 cm).
This object and other objects are achieved by a method having the characteristic features of a first set of the following claims.
Another object of the invention is to provide, among the many articles which may be produced with this method, panels with a curved shape which are used to line the metallic inner surfaces of mixing machines inside which mixes comprising abrasive ingredients are processed.
This object, together with others, are achieved by articles having the characteristic features of a second set of the following claims.
The following description will be useful for illustrating more clearly characteristic features and advantages of the invention, said description being provided solely by way of a non-exclusive example with reference to the accompanying drawings in which:
In the following description reference will be made to the production of curved panels for lining the inner surfaces of the walls of mixing machines used for processing mixes containing ingredients with abrasive properties. This description nevertheless is provided by way of an example and is not exclusive since the articles produced with the method according to the invention may, for example, also be used in the building sector (for lining internal or external walls or for covering roofs) as well as in durable consumer goods.
As shown in
According to the invention, the method for producing the article 100 comprises the following steps:
I) preparing a mix comprising granulated inorganic materials (for example stone and/or stone-like and/or ceramic materials) and an epoxy resin, which can be hardened by means of crosslinking. This type of resin is preferable to polyester resins (commonly used to produce conventional flat articles) since they harden with a very small degree of shrinkage and the dangers of distortion of the article are avoided;
II) preparing a flat forming support, protected by an anti-adhesive sheet, for example as explained in the patent U.S. Pat. No. 5,928,585. The term “anti-adhesive sheet”, used here, comprises both a sheet made with a single non-adhesive material and a sheet made with the same type of materials used for manufacturing the forming support (for example rubber) and protected with a non-adhesive and/or separating film;
III) spreading the mix over said forming support;
IV) extending over the free surface of the mix a second sheet of anti-adhesive material, of the same type as that used to protect the forming support;
V) compacting the mix by means of vacuum vibrocompression so as to obtain a panel having the consistency of plasticine, namely soft but sufficiently compact such that it does not fold during the following step of this method;
VI) transferring the mix thus compacted (together with the two sheets of anti-adhesive material) onto a rigid support with a curved shape;
VII) keeping at room temperature the panel 100A of shaped mix on the support 300 until hardened;
VIII) in order to complete (if necessary) cross-linking of the epoxy resin, heating the hardened panel to about 40° C. (i.e. to a temperature slightly higher than room temperature);
IX) removing the two sheets 200 and 250 of anti-adhesive material from the hardened panel and, if necessary;
X) trimming the edges of the hardened panel, for example using a diamond-coated disk, so as to obtain the finished article 100.
In the case where the use of the article thus produced requires a high impact strength, the step III) may envisage spreading, onto the flat forming support, two superimposed layers of mix with a reinforcing layer in between, for example a glass fibre or metal mesh or mat, for example a steel mesh.
As already mentioned,
The container 10 comprises a bottom wall 12 having feet 14 for resting on the ground P and a side wall 16. In a manner known per se, the bottom wall 12 is divided into a fixed part and a movable part or shutter (not shown) in the form of a circle segment which, in the open position, uncovers an aperture (also not shown) for discharging the mix at the end of processing.
As shown in
It has been shown in tests that the use of the panels 164, in this case made of granulated quartz (light-coloured/transparent material with a hardness factor of about 7 Mohs) or, even better, alumina or corundum of the white type light-coloured/transparent material with a very high hardness factor of about 9 Mohs) which have a very long working life (i.e. about 6-8 months of two working shifts), produces the following advantages:
it prevents the release of metal particles detached, as a result of the abrasion exerted by the hard aggregates, from the inner shell 162 of the side wall 16 of the container 10;
since the colour of the mix being processed is not contaminated, the frequency of the maintenance carried out on the said container 10 is reduced; and
cleaning of the side wall 16 whenever the mix is changed is much easier since the hardness of the panels 164 limits the appearance of scratches to which the mix could adhere.
In short, owing to the use of the sheets 164 inside the container 10, the productive efficiency of the mixing machine is increased.
In addition to the hard stone materials considered above, other inorganic materials may be used in the method according to the present invention. For example, if the articles to be produced must be extremely hard and the colour is not of importance for their specific use, carborundum may be used. Vice versa, if the applicational requirements of the articles are less demanding, granulated ceramic materials may be used.
It is understood however that, within the scope of the following claims, other variants of the method claimed hereinbelow and other applications of the articles produced in accordance with this method may be envisaged.
| Number | Date | Country | Kind |
|---|---|---|---|
| TV2005A000019 | Feb 2005 | IT | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP06/50470 | Jan 2006 | US |
| Child | 11829266 | Jul 2007 | US |
