IT202100014210A1 - ISOSTATIC BUFFER FOR PRESSING CERAMIC POWDERS - Google Patents

Description

DESCRIPTION

of the Italian Patent for Industrial Invention entitled: ?ISOSTATIC BUFFER FOR PRESSING CERAMIC POWDERS?

TECHNICAL FIELD

The present invention relates to an isostatic punch for pressing ceramic powders, preferably for forming ceramic tiles.

PRE-EXISTING TECHNIQUE

As ? known, in the ceramic tile manufacturing sector ? The use of isostatic plugs is known, which are used to form ceramic tiles starting from powders of ceramic raw materials, for example in atomized form, by compacting or pressing.

Pi? in detail, for this operation of forming a tile (green) ? is the use of presses known which comprise two opposite molds equipped with one or more? cavities inside which respective plugs are housed which are intended to act on the ceramic powder in order to compact it and shape corresponding tiles (green) which are then intended to be fired.

The two opposite pads have respective free deformable surfaces (structured or smooth), one of which defines the living surface of the tiles and one defines the laying surface (or mark) of the tile.

To reduce the non-uniformity? of density? of the ceramic powders compacted by the pair of punches in each molding chamber, which, as known, causes differentiated shrinkage during firing with consequent undesired deformations of the finished tile, ? The use of isostatic punches has been known for some time, which provide for the use of an incompressible fluid, such as oil, which, circulating in each punch, balances the pressures exerted by the punch on the ceramic powders during pressing.

In practice, the oil moves inside the punch in such a way that the areas of the molding chamber where the ceramic powder is present in lower density? are crushed more than the areas of the molding chamber where the ceramic powder? present in greater density? so that, overall, you get a uniform distribution of the density? of the powders contained inside the molding chamber, or in the tile (green) formed. However, the use of isostatic plugs of the known type is not completely free from drawbacks, among which is the fact that swellings are created, formed by the movement of oil from one part to the other of the pad, in certain areas (corresponding to areas with a lower density of dust) of the free surface of the pad. These swellings of the free surface, therefore, generate corresponding surface deformations (or bumps) in the tile, in correspondence with which the tile will be? with less thickness.

These thinner areas of the tiles are extremely unsightly and, especially in large tiles (which are generally subjected to cutting and/or size reduction operations), they are particularly problematic, since in the cut tile they are particularly evident (for example lateral observation of the tile) or, in any case, involve the formation of a greater number/volume of processing waste.

EXHIBITION OF THE INVENTION

An object of the present invention ? that of overcoming the aforementioned drawbacks of the prior art, in the context of a simple, rational and low-cost solution, for example by means of an isostatic plug, which while maintaining its ?isostatic function? of homogenization of the density? of powders, makes it possible to obtain uniform pressing of the ceramic powders over the entire extension of the tile and makes it possible to reduce, if not even eliminate, the aforementioned non-uniformity? surface (or embossing) of the tile surfaces. In detail, an aim of the present invention ? to increase the flatness? surface of the tiles (even on the laying surface, or in the internal areas of the same, where the desired laying relief is not present).

These purposes are achieved by the characteristics of the invention set forth in the independent claim. The dependent claims outline preferred and/or particularly advantageous aspects of the invention.

The invention, in particular, makes available an isostatic punch for pressing ceramic powders, which comprises:

- a support body defining a concave seat provided with a bottom wall;

- a plate arranged in the concave seat at a non-zero distance from the back wall;

- a membrane of elastically yielding material which covers the entire plate and closes the concave seat at the top, in which the membrane has a free surface configured to come into contact with the ceramic powders for forming them;

characterized by the fact that the plate ? a solid plate without holes or through slots and ? floatingly supported with respect to the back wall. Thanks to this solution, the plug object of the present invention allows to optimize the formation of tiles, avoiding the formation of unevenness. superficial (or embossed) in the tile surfaces.

Advantageously, between the plate and the back wall there can be be defined as a space for the circulation of an incompressible fluid, in which the space? placed in fluid communication with a fluid supply conduit protruding on an outer surface of the support body.

Thanks to this, the interspace defines a circulation chamber for the fluid that can circulate freely over the entire width of the same keeping the plate (and with it the free surface of the membrane) free to float and adapt to the pressure conditions at which it? subjected during use.

Still, the interspace pu? be delimited above by an entire lower face of the plate facing the bottom wall and detached from a lower portion of the membrane interposed between the bottom wall and the plate.

Advantageously, an entire upper face of the plate facing away from the back wall can adhere to an upper portion of the membrane interposed between the plate and the free surface of the membrane.

According to an advantageous aspect of the invention, the tampon can comprising spacers interposed between the bottom wall and the plate, wherein the spacers are compliant, preferably elastically.

Thanks to this solution, the spacers act as a mechanical support for the plate (in the pad formation phase) and, at the same time, define a yielding support for the plate during use, improving the possibilities? movement of the plate within the membrane.

For example, the spacers can have a first surface in contact with the bottom wall and a second surface in contact with a bottom face of the plate facing the bottom wall.

Again, each spacer can? present a toroidal shape and, preferably ? consisting of a ring like an ?o-ring?.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will become apparent from reading the following description provided by way of non-limiting example, with the aid of the figures illustrated in the attached tables.

Figure 1 is a schematic front view, in partial section, of a press for forming tiles according to the invention.

Figure 2 ? a sectional view of an isostatic plug, according to the invention. Figure 3 ? the view of figure 2 in an operative configuration.

BEST WAY TO CARRY OUT THE INVENTION

With particular reference to these figures, yes? generally indicated by 10 a press for forming ceramic tiles.

The press 10 globally comprises a pair of molds 15, of which a lower mold and an upper mold (or countermould).

Each mold 15 comprises a base supporting a matrix within which ? practiced at least one opening (passing), or a plurality? of openings, what ? called alveolus.

Each cavity of the lower mold ? vertically aligned with a corresponding cavity of the upper mould.

Inside each alveolus ? entered, for example with the possibility? to slide axially, a respective pad, generally indicated with the reference number 20.

The plugs 20, respectively, define the bottom and the top of a forming chamber (with variable volume) within which the ceramic powders for forming tiles (green) are compacted.

The molds 15 are mutually movable between a loading position, in which (the punches 20 which define a molding chamber) are spaced apart from each other to allow the loading of ceramic powder onto the punch 20 which defines the bottom of the respective molding chamber, and a forming position, in which (the punches 20 which define a forming chamber) are brought together to allow compacting of the previously loaded ceramic powders. At least one of the plugs 20 delimiting a molding chamber or each of them? of the ?isostatic? type and ? described in detail below.

The example illustrates in particular the pad 20 intended to reproduce the brand of the tile, ie the laying surface of the tile itself.

The plug 20 comprises a support body 21 (also called base or ?punch?), which ? for example rigid (ie non-deformable under the usual stresses to which it is subjected in operation), preferably made of a metallic material, preferably steel.

The Support Corps 21 ? preferably a plate-shaped monolithic body.

For example, the support body 21 overall has a prismatic shape, for example with a quadrangular or polygonal base in general (or of any shape). The support body 21 has a base wall, which ? intended to be turned, in operation, towards the base of the mold 15, for example planar. Furthermore, the support body 21 comprises a lateral jacket projecting from the base part, for example at right angles thereto.

The support body 21 comprises a top (frame or) wall, opposed to the base wall, which defines/delimits at the top a concave seat 210 (with the concavity facing the outside of the support body 20 or in any case lowered) , for example of homologous shape to the shape of the summit wall? itself (with rounded edges), which ? open at the top? and closed by a bottom wall 211, for example planar.

The concave seat 210 ? circumscribed perimetrically (for the entire perimeter) by an inclined connecting surface which surrounds the bottom wall 211 and connects it with the top wall? and/or the side shirt.

The pad 20 also comprises a supply duct 212 obtained in the support body 21, for example so as to pass through it from side to side.

The supply line 212 ? configured to enter the concave seat 210, how better will it be? described below, a fluid, for example an incompressible fluid such as oil.

The supply conduit 212 has a first end? defining an inflow mouth, emerging in at least one between the base wall and the side jacket of the support body 21 and at least one second end, defining an outflow mouth, emerging inside the concave seat 210, for example at of the bottom wall 211 thereof.

The first end? ? configured to be connected, in a known way, to a pressurized fluid supply circuit, not shown since it is of a known type.

The pad 20 also comprises a plate 30, which is arranged inside the concave seat 210.

Plate 30 ? for example a plate having two opposite main faces, of which a lower face 31 (flat) facing the bottom wall 211 and an opposite upper face 32 (also flat and parallel to the lower face 31).

The distance between the lower face 31 and the upper face 32 of the plate 30 defines the (reduced) thickness of the plate 30, which ? less than the depth of the concave seat 210, for example ? between 1 mm and 8 mm, preferably between 2 mm and 7 mm, for example equal to 2 mm or 3 mm.

The plate 30 overall has a shape (in plan view) substantially similar to the shape of the bottom wall 211 of the concave seat 210 in which ? accepted. Furthermore, the plate 30 overall has dimensions (in plan view) substantially the same as the dimensions of the back wall 211 (or slightly greater). Plate 30 ? for example made of metallic material, for example steel. For example, plate 30 ? substantially rigid (ie non-deformable under the usual stresses to which it is subjected in operation).

For purposes of the present invention, plate 30 is a solid plate, i.e. it does not have any holes or slots passing through it in the direction of the thickness.

For example, the entire lower face 31 and/or the entire upper face 32 ? a continuous (seamless) planar surface.

Preferably, on the (entire) lower face 31 of the plate 30 (in the manufacturing phase of the plug 20)? applied a coating of a substance or release agent (disposable), whose function will be? better clarified below.

Plate 30 ? contained within the concave seat 210 with radial play, in particular between the connection surface of the concave seat 210 and the outer periphery of the plate 30? defined as a perimeter (empty) gap that surrounds the (entire) plate 30.

Plate 30 ? supported in support by the bottom wall 211 of the plug 20, preferably at a non-zero distance from it.

In practice, the lower face 31 of the plate 30 is maintained at a non-zero distance from the bottom wall 211 of the concave seat 210 of the plug 20.

This distance between the lower face 31 of the plate 30 and the bottom wall 211 of the concave seat 210 of the pad 20 is preferably smaller than the distance between the upper face 32 and the top wall? of buffer 20.

In other words, plate 30 ? proximal to the bottom wall 211 of the concave seat 210 of the plug 20.

How better will it come? described below, plate 30 ? floatingly supported inside the concave seat 210 and/or the distance between the lower face 31 of the plate 30 and the bottom wall 211 of the concave seat 210 of the pad 20 ? variable.

For this purpose, the plug 20 comprises one or more spacers 40 configured to be interposed between the plate 30 and the bottom wall 211 of the concave seat 210, so as to keep the bottom face 31 of the plate 30 and the bottom wall 211 of the concave seat 210 of the pad 20 spaced apart.

Preferably, each spacer 40 ? directly interposed between the lower face 31 of the plate 30 and the bottom wall 211 of the concave seat 210 of the pad 20.

In other words, each spacer 40 has a first (lower) contact surface in (direct) contact with the bottom wall 211 of the concave seat 210 and a second (upper) contact surface in contact (direct or by interposition of the release coating ) with the lower face 31 of the plate 30.

The thickness of each spacer 40 defines the distance (punctual) of the plate 30 from the bottom wall 211 of the concave seat 210.

For example, each spacer 40 (or a plurality of them) is yielding (in the sense of its thickness), for example in an elastic way.

For example, each spacer 40 ? made of an elastically compliant material, such as rubber.

Preferably, each spacer 40 ? shaped like a ring having a central hole with a through axis orthogonal to the lower face 31 of the plate 30 and to the bottom wall 211 of the concave seat 210 of the plug 20.

even more preferably, each spacer 40 has a toroidal shape (that is, has a circular radial section), or ? like an ?o-ring?. Advantageously, the first contact surface and the second contact surface have variable dimensions, depending on the flattening of the spacer 40, i.e. they vary between a minimum size corresponding to a configuration of minimum flattening of the spacer 40 (corresponding in turn to the maximum distance between the lower face 31 of the plate 30 and the bottom wall 211 of the concave seat 210 of the pad 20, which in any case is always not zero), and a maximum dimension corresponding to a configuration of maximum crushing of the spacer 40 (corresponding in turn to the minimum distance between the lower face 31 of the plate 30 and the bottom wall 211 of the concave seat 210 of the plug 20).

In practice, the spacers 40 keep the plate 30 in suspension inside the concave seat 210, in a substantially floating manner, ie floating on the spacers 40 which yield in an elastic manner.

For example, a 40 ? coaxially arranged above the outflow mouth of the feed duct 212, so as to extend the same axially from the bottom wall 211 of the concave seat 210 to the lower face 31 of the plate 30.

The plug 20 also comprises an elastically yielding membrane 50.

The membrane 50 ? placed inside the concave seat 210, so as to cover the entire plate 30, or to cover the upper face 32 of the same, and close the concave seat 210 at the top.

The membrane 50 ? provided with a free surface 51, for example structured or variously shaped according to the shape to be given to the surface (for laying or visible) of the tile, which? intended to come into contact with ceramic powders for forming tiles.

The free surface 51 ? contained within the concave seat 210 (and has a respective concave or planar shape).

The membrane 50 adheres, for example by chemical adhesion, to the internal walls of the concave seat 210 (substantially permanently).

In particular, the membrane 50 has an adhesion surface (convex), which follows the internal walls of the concave seat 210, which adheres to the bottom wall 211 and to the connection surface of the concave seat 210.

In detail, the membrane 50 (completely) fills every empty space between its free surface 51 and the internal walls of the concave seat 210, i.e. the bottom wall 211 and the connection surface of the concave seat 210, with the exception of the inlet of the feed duct 212 and its axial extension up to the lower face 31 of the plate 30.

Preferably, the membrane 50 ? made of polymeric resin, for example of the type commonly used in isostatic punches for forming ceramic tiles, or in particular of the polyurethane type (for example a polyurethane elastomer).

Advantageously, the membrane 50 ? made by injection of the polymeric resin, in fluid or liquid form inside the concave seat 210 (within which the spacers 40 and/or the plate 30 are housed, so as to completely drown the plate 30 (and the spacers 40) covering the face upper 32 of the same.

Subsequently, the plug 20 with the resin still in fluid form is closed at the top by a matrix (bearing the "negative" of the free surface 51 of the desired membrane 50) and the resin is subsequently hardened/cross-linked, for example by means of a pressing and /or a heat treatment. The spacers 40 act as a mechanical support during a phase of injection of the resin into the concave seat 210 to keep the plate 50 in the correct position (non-zero distance from the bottom wall 211 of the concave seat 210).

In practice, the membrane 50, once formed and hardened, has a lower portion, which is interposed between the bottom wall 211 of the concave seat 210 and the lower face 31 of the plate 30 and an upper portion interposed between the free surface 51 and the upper face 32 of the plate 30, which are joined and connected by a lateral frame which ? bounded perimetrically by a portion of the connecting surface of the concave seat 210 and the outer periphery of the plate 30.

The membrane 50 also has a release surface, which ? formed at the interface between the (entire) lower face 31 of the plate 30 and the (lower portion of) the membrane 50 itself.

Such a detachment surface, in practice, ? as wide as the overall width of the lower face 31 of the plate 30.

This release surface? separated (non-adherent) from the lower face 31 of the plate 30, thanks to the release action exerted by the substance or release agent applied to the lower face 31 of the plate 30.

In practice, between the (detachment surface of the lower portion of) the membrane 50 and the lower face 31 of the plate 30 ? defined a cavity 60 (empty), which ? in fluid communication with the supply duct 212 (by means of the spacer 40 which defines the axial extension thereof). This gap 60 ? variable volume and/or shape.

When the interspace 60 ? empty (or devoid of fluid), the detachment surface of the membrane 50 ? in contact with the lower face 31 of the plate 30; when the interspace 60 has a predetermined quantity? of fluid inside it, the detachment surface of the membrane 50 ? detached from the lower face 31 of the plate 30.

The fluid introduced into the pad 20 by means of the supply duct 212 is then injected into the (only) interspace 60 so as to form a pressure balancing cushion and ? free to move in the interspace 60 by lifting the plate 30 from the detachment surface thereof and/or making the plate 30 float/float (and with it the entire upper portion of the membrane 50 with its free surface 51).

The lower portion of the membrane 50 assists/amplifies or replaces the yielding support action performed by the spacers 40.

For example, the membrane 50 has a hardness (expressed in Shore A) lower than/equal to the hardness (expressed in Shore A) of each spacer 40.

The plate 30 has a (flexural) stiffness greater than the (compressive) stiffness of each spacer 40 and/or of the membrane 50.

The plate 30, in practice, dampens and distributes the oscillations of the fluid over its entire amplitude, allowing, at the same time, to have a compensation of the pressing pressures as a function of the punctual variations in density. of ceramic powder in the molding chamber and an attenuation of punctual deformations, with consequent greater planarity? of the surface of the tiles obtained.

The invention so? conceived ? susceptible to numerous modifications and variations, all of which are within the scope of the inventive concept.

Furthermore, all the details can be replaced by other technically equivalent elements. In practice, the materials used, as well as? the contingent shapes and dimensions may be any according to requirements without thereby departing from the scope of protection of the following claims.

Claims (7)

1. An isostatic pad (20) for pressing ceramic powders, comprising: - a support body (21) defining a concave seat (210) provided with a bottom wall (211); - a plate (30) arranged in the concave seat (210) at a non-zero distance from the bottom wall (211); - a membrane (50) of elastically yielding material which covers the entire plate (30) and closes the concave seat (210) at the top, in which the membrane (50) has a free surface (51) configured to come into contact with the ceramic powders for forming them; characterized in that the plate (30) ? a solid plate without holes or through slots and ? floatingly supported with respect to the back wall (211). The plug (20) according to claim 1, wherein between the plate (30) and the bottom wall (210) is defined as a cavity (60) for the circulation of an incompressible fluid, in which the cavity ? placed in fluid communication with a fluid supply conduit (212) protruding on an outer surface of the support body (210). 3. The plug (20) according to the preceding claim, wherein the gap (60) is delimited above by an entire lower face (31) of the plate (30) facing the bottom wall (211) and detached from a lower portion of the membrane (50) interposed between the bottom wall (211) and the plate (30) . 4. The pad (20) according to claim 1, wherein an entire upper face (32) of the plate (30) facing away from the bottom wall (211) adheres to an upper portion of the membrane (50) interposed between the plate (30) and the free surface (51) of the membrane (50). The pad (20) according to claim 1, which comprises spacers (40) interposed between the bottom wall (211) and the plate (30), wherein the spacers (40) are compliant, preferably elastically. 6. The pad (20) according to the preceding claim, wherein the spacers (40) have a first surface in contact with the bottom wall (211) and a second surface in contact with a lower face (31) of the plate (30 ) facing the back wall (211). 7. The pad (20) according to claim 5 or 6, wherein each spacer (40) has a toroidal shape, preferably ? consisting of a ring like an ?o-ring?.