Isobaric punch for pressing ceramic tiles and method for making said punch

Description

[0001] The invention concerns an isobaric punch for pressing ceramic tiles and a method for making said punch.

[0002] From IT-U-214739, dies for ceramic tiles are known, comprising a punch body provided with a plurality of intercommunicating cavities containing oil, said cavities being closed at an active end by an elastic membrane; inside each cavities a respective piston, peripherally provided with a sealing ring, is interposed between the oil and the membrane.

[0003] However, for a correct working of such dies, it is necessary, before using them, to introduce pressurized oil to detach the piston from the bottom of the respective cavities in such a way as to enable the pistons to move towards the inside of the cavities or towards the outside of the cavities as a result of the action, on the one hand, of the oil, and, on the other hand, of the powders to be pressed. The pressure of the oil which is necessary to obtain the detachment of the pistons is very high.

[0004] From EP-A-0759346 isobaric dies are also known, in which membrane control elements are provided, instead of pistons, which are kept at an intermediate position in the respective cavities by means of positioning elements which are squashed, or broken, or somehow neutralized, after the vulcanization of the membrane, thus releasing the control elements which are so free to move towards the powders to be pressed, or in opposite direction, due to the action, respectively, of the oil, or of the powders. In addition, positioning elements made of elastic material are described, which are interposed between the bottom of each cavity and the central portion of each control element. As a consequence, the control elements may be relatively unstable and, sometimes, may tend to block in the respective cavities when they are non uniformly stressed by the powders. Moreover, when the vulcanization of the membrane is to be made, the particular allocation of the elastic positioning elements makes necessary to carry out the vulcanization with the cavities turned downwards, to avoid the fluid material, from which the membrane will be made, filling said cavities completely.

[0005] A further drawback of such known isobaric dies is found when they have to be regenerated, because the elastic membrane, which first is heated, then torn from the body of the die, comes off from the pistons, leaving them inside the respective cavities. So the cavities have to be emptied of the pistons by extracting them one by one, and this implies a considerable waste of time.

[0006] Aim of the present invention is to improve the dies for pressing ceramic powders eliminating the drawbacks indicated above.

[0007] According to the invention, there is provided an isobaric punch for pressing ceramic tiles according to claim 1.

[0008] In this way, a greater stability of the rigid elements inserted into the cavities is ensured.

[0009] In an advantageous embodiment, said elastic means are received in a corresponding annular seat provided in said bottom portion.

[0010] This facilitates the insertion of the positioning elements into the respective cavities.

[0011] According to an advantageous embodiment, each rigid insert has a central zone and a peripheral zone, the peripheral zone having a thickness which is less than the thickness of the central zone.

[0012] In this way, risks of the rigid insert being blocked in the respective cavity, for a given radial play between the cavity and the rigid insert inserted thereinto, are considerably reduced.

[0013] According to another preferred embodiment, a peripheral sealing element is interposed between each rigid insert and the membrane, to avoid the leakages of liquid plastic material during vulcanization.

[0014] According to a further aspect of the invention there is provided a method for making an isobaric die for pressing ceramic tiles according to claim 14.

[0015] Preferably, before said vulcanization, sealing means are located on the rigid inserts, said sealing means being suitable to prevent portions of said material from penetrating into said cavities, during vulcanization.

[0016] The invention will be better understood and carried into practice referring to the enclosed drawings, showing some exemplary but not restrictive embodiments of it, wherein:

Figure 1 is a plan view of a punch of isobaric die;

Figure 2 is an enlarged section taken along line II-II of Figure 1, with a tile to be pressed introduced into the die;

Figures 3 and 4 are sections as in Figure 1, but referred to embodiments of a gasket or sealing element having an annular shape with a circular and rectangular section, respectively;

Figure 5 is a section as in Figure 2, but with a rigid insert centrally provided with cavities to improve the anchorage of the membrane;

Figures 6, 7 and 8 are sections as in Figure 2, but referred to embodiments of the elastic means with peripheral outer edge wrapping up the insert in the respective cavity;

Figure 9 is a section as in Figure 2, but referred to an embodiment without sealing elements on the side of the insert facing the membrane.

[0017] An isobaric punch 1 for pressing ceramic tiles 2 inside a matrix 3, comprises an elastic membrane 4 vulcanized on the outer face of the punch and reproducing, in negative, the back side of the tile 2. The punch 1 is provided with a plurality of cavities 5, obtained in the punch body in the areas amongst supporting appendixes 6 of the tile. The membrane 4 is provided with corresponding grooves 7 corresponding to the appendixes 6.

[0018] As shown in Figure 2, the cavities 5 are intercommunicating through a series of holes 8 obtained in the punch body in such a way as to form a circuit, closed by a screw cap 13, wherein some oil is injected.

[0019] Inside each cavity 5 there is accommodated a respective insert 9 which is free to move, during pressing, towards the tile 2, or away from it, depending on the local density of the powders forming the said tile. Each insert 9 has, preferably, an edge portion 10 having a reduced thickness, to avoid blockings even when the combined action of the powders and of the oil forces the insert to tilt with respect to the relevant cavity 5.

[0020] Between the part of edge portion 10 facing the oil and the bottom of the respective cavity 5, there is accommodated an annular shaped elastic means 11, for example consisting of a ring having circular section and preferably inserted into an annular seat 12 of each cavity.

[0021] The annular shaped elastic means 10 acts itself as a gasket element when, in making the punch, a liquid resin is poured onto the inserts and onto the free surface of the punch body to form the membrane 4. In fact, as shown in Figure 9, each insert may be directly in contact with the membrane 4 without interposition of any gasket element.

[0022] However, for a greater guarantee of sealing, it is possible to provide each insert 4 with a disk-shaped gasket element 14, which is located on each insert before the resin being poured, or before the rubber being applied.

[0023] As shown in Figure 3, the gasket element may consist of a ring 15 like the annular shaped elastic means 11, so as to obtain a reduction of the variety of pieces forming the punch 1.

[0024] In addition, Figure 5 shows that the disk-shaped gasket element 14 may have a central hole 16 to facilitate anchoring of the membrane 4 to the respective insert, so that, when it is necessary to remove the membrane for regenerating the die, the inserts stay attached to the membrane and follow it, so emptying automatically the respective cavities.

[0025] For the same reason explained above, each insert 9 may have, upon its face facing the membrane 4, a depression 17, which is advantageously truncated-cone shaped, for further improving anchoring of the membrane to the inserts 9.

[0026] As shown in Figure 6, the depression 17 may extend up to the periphery of the insert 9, so defining a raised edge 18 which may be wrapped up by a lip 19 of the elastic medium underneath, which includes, for example, a ring 20 with rectangular section. The presence of the lip 19 constitutes a further guarantee against blocking of the insert 9 in the respective cavity 5, because it makes even impossible any contact between the insert and the lateral walls of the cavity, avoiding, in this way, blockings or seizures.

[0027] As shown in Figure 7, the annular shaped elastic means 20 may even not require the presence of the raised edge 18 of the insert 9, i.e. the lip 19 may simply wrap up the outer peripheral surface of the insert 9. It is to be noted that the cavities may be made communicating with each other by means of through-openings 21 obtained on the walls 22 which define the cavities 6, or by means of holes 24 converging in a V-shaped formation.

[0028] In a preferred embodiment, the elastic means may have a semicircular section 23, in such a way as to have greater yieldingness during pressing. The various forms of cross section of the elastic means make the insert 9 more or less freely movable. For example, an insert with circular section may enter the respective cavity owing to forces which are less than forces that should be required if the insert would be provided with a rectangular or square section having corresponding dimensions.

[0029] As already said, the elastic means, in its various versions, should substantially not alter its form and dimensions during the vulcanization of the membrane 4, so that the inserts 9 are allowed to stay in an intermediate position in the respective cavity up to solidification of the membrane 4.

[0030] Subsequently, oil is introduced into the cavities, at a pressure much less than the pressure usually used, and subsequently, after the circuit 8 has been closed, pressing may start. Since the pressures exerted on the punch during pressing are much greater than the the pressures used during the vulcanization, the inserts 9 will move into the cavities 5 to compensate possible non-uniform densities of powders.

[0031] The form of the inserts 9 and of their respective edge 10 having less thickness, is such that the central portion protrudes towards the bottom of the cavity 5. Thus, the central portion may constitute a stop means of the motion of the insert towards the bottom of the cavity to prevent the elastic means from being damaged.

Claims

1. Isobaric punch (1) for pressing ceramic tiles (2), comprising a punch body provided with intercommunicating cavities (5) containing an incompressible fluid and having an end closed by an elastic membrane (4), the other end being provided with a bottom portion, a respective rigid insert (9), co-operating with respective elastic positioning means (11; 20; 23) being accommodated inside each cavity (5), said rigid insert having a central zone and a peripheral zone with an edge portion, said insert (9) facing, on the one side, said membrane (4) and, on the opposite side, being in contact with the respective elastic positioning means (11; 20; 23), characterized in that, said elastic positioning means (11; 20; 23) has an annular shape and is accommodated between said edge portion and the bottom of the respective cavity, said elastic positioning means being so configured as to actively cooperate with said rigid insert during pressing of the ceramic tiles.

2. Punch according to claim 1, characterized in that said elastic positioning means (11; 20; 23) is received in a correspondingly annular seat (12) of said cavity (5).

3. Punch according to claim 1, or 2, characterized in that said elastic positioning means has a circular cross section(11).

4. Punch according to claim 1, or 2, characterized in that said elastic positioning means has a rectangular cross section (20).

5. Punch according to claim 1, or 2, characterized in that said elastic positioning means has a cross section including at least one semicircular portion (23).

6. Punch according to any preceding claims, characterized in that said elastic positioning means (11; 20; 23) has a lip (19) peripherally wrapping up the respective insert (9).

7. Punch according to claim 1, characterized in that said insert (9) has a depression (17) to receive the membrane (4) and to anchor itself thereto.

8. Punch according to claim 1, characterized in that said insert has a peripheral zone (10) having a less thickness than the thickness of the central zone.

9. Punch according to claim 1, characterized in that said insert (9) has a central zone which protrudes towards said bottom portion to constitute a stop surface when the insert is pushed into of the cavity (5).

10. Punch according to any preceding claims, characterized in that a peripheral sealing element (14; 15) is interposed on the side of said insert (9), between the insert and the membrane (4).

11. Punch according to claim 10, characterized in that said peripheral sealing element (14; 15) is formed by a ring having dimensions and shape equal to those of said elastic means (11; 20; 23).

12. Punch according to claim 10, characterized in that said peripheral sealing element comprises an element (14) having, in plan view, the same shape of the respective cavity (5) and being forcibly insertable thereinto.

13. Punch according to claim 12, characterized in that said sealing element (14) is provided with a central opening (16).

14. Method for making an isobaric die (1) for ceramic tiles (2), comprising, in sequence, preparing a die body with intercommunicating cavities (5) having respective openings facing upwards, inserting an elastic positioning means (11; 20; 23) and a respective rigid insert (9) into each cavity (5), said rigid insert having a central zone and a peripheral zone with an edge portion and vulcanizing a membrane (4) of elastic material onto the rigid inserts (9) and onto said die body, characterized in that, the elastic positioning means (11; 20; 23) has annular shape and is accommodated between said edge portion and the bottom of the respective cavity, said elastic positioning means being so configured as to actively cooperate with said rigid insert during pressing of the ceramic tiles.

15. Method according to claim 14 characterized in that, sealing means (14; 15) is located on the rigid inserts (9) before said vulcanizing, to avoid that, during said vulcanizing, portions of said material may penetrate into said cavities (5).

16. Method according to claim 14, or 15, characterized in that, a pressure is exerted on the rigid elements (9) during vulcanizing, said pressure being such as not to deform the elastic positioning elements (11; 20; 23).

Ansprüche

1. Isobarer Stempel (1) zum Pressen von keramischen Fliesen (2), mit einem Stempelkörper, der mit eine inkompressible Flüssigkeit enthaltenden, kommunizierenden Hohlräumen (5) versehen ist, und mit einem durch eine elastische Membran (4) verschlossenen Ende, wobei das andere Ende mit einem Bodenabschnitt versehen ist, und mit einem jeweiligen festen Einsatz (9), der mit einem jeweiligen elastischen Positionierungsmittel (11; 20; 23) zusammenwirkt, das in jedem Hohlraum (5) aufgenommen ist, wobei der feste Einsatz eine zentrale Zone und eine periphere Zone mit einem Randabschnitt besitzt, wobei der Einsatz (9) auf der einen Seite zu der Membran (4) zeigt und auf der entgegengesetzten Seite im Kontakt mit dem jeweiligen elastischen Positionierungsmittel (11; 20; 23) ist, dadurch gekennzeichnet, dass das elastische Positionierungsmittel (11; 20; 23) eine ringförmige Form besitzt und zwischen dem Randabschnitt und dem Boden des jeweiligen Hohlraums aufgenommen ist, wobei das elastische Positionierungsmittel so ausgebildet ist, dass es beim Pressen der keramischen Fliesen aktiv mit dem festen Einsatz zusammenwirkt.

2. Stempel nach Anspruch 1, dadurch gekennzeichnet, dass das elastische Positionierungsmittel (11; 20; 23) in einem entsprechend ringförmigen Sitz (12) des Hohlraums (5) aufgenommen ist.

3. Stempel nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass das elastische Positionierungsmittel einen kreisförmigen Querschnitt (11) besitzt.

4. Stempel nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass das elastische Positionierungsmittel einen rechteckigen Querschnitt (20) besitzt.

5. Stempel nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass das elastische Positionierungsmittel einen Querschnitt besitzt, der zumindest einen halbkreisförmigen Abschnitt (23) beinhaltet.

6. Stempel nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass das elastische Positionierungsmittel (11; 20; 23) eine Lippe (19) besitzt, die den jeweiligen Einsatz (9) peripher umhüllt.

7. Stempel nach Anspruch 1, dadurch gekennzeichnet, dass der Einsatz (9) eine Vertiefung (17) besitzt, um die Membran (4) aufzunehmen und sich selbst an dieser zu verankern.

8. Stempel nach Anspruch 1, dadurch gekennzeichnet, dass der Einsatz eine periphere Zone (10) mit einer geringeren Dicke als die Dicke der zentralen Zone besitzt.

9. Stempel nach Anspruch 1, dadurch gekennzeichnet, dass der Einsatz (9) eine zentrale Zone besitzt, die in Richtung des Bodenabschnitts hervorsteht, um eine Stopfläche zu bilden, wenn der Einsatz in den Hohlraum (5) gedrückt wird.

10. Stempel nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass an der Seite des Einsatzes (9) zwischen dem Einsatz und der Membran (4) ein peripheres Dichtungselement (14; 15) angeordnet ist.

11. Stempel nach Anspruch 10, dadurch gekennzeichnet, dass das periphere Dichtungselement (14; 15) von einem Ring gebildet ist, dessen Abmessungen und Form gleich derjenigen des elastischen Mittels (11; 20; 23) sind.

12. Stempel nach Anspruch 10, dadurch gekennzeichnet, dass das periphere Dichtungselement ein Element (14) aufweist, das, in Draufsicht, dieselbe Form wie der jeweilige Hohlraum (5) besitzt und das darin unter Krafteinwirkung einsetzbar ist.

13. Stempel nach Anspruch 12, dadurch gekennzeichnet, dass das Dichtungselement (14) mit einer zentralen Öffnung (16) versehen ist.

14. Verfahren zum Herstellen einer isobaren Form (1) für keramische Fliesen (2), mit den aufeinanderfolgenden Schritten: Bereitstellen eines Formkörpers mit kommunizierenden Hohlräumen (5), die jeweils nach oben zeigende Öffnungen besitzen, Einsetzen eines elastischen Positionierungsmittels (11; 20; 23) und eines jeweiligen festen Einsatzes (9) in jeden Hohlraum (5), wobei der feste Einsatz eine zentrale Zone und eine periphere Zone mit einem Randabschnitt besitzt, und Vulkanisieren einer Membran (4) aus elastischem Material auf die festen Einsätze (9) und auf den Formkörper, dadurch gekennzeichnet, dass das elastische Positionierungsmittel (11; 20; 23) eine Ringform besitzt und zwischen dem Randabschnitt und dem Boden des jeweiligen Hohlraums aufgenommen ist, wobei das elastische Positionierungsmittel so ausgebildet ist, dass es beim Pressen der keramischen Fliesen aktiv mit dem festen Einsatz zusammenwirkt.

15. Verfahren nach Anspruch 14, dadurch gekennzeichnet, dass vor dem Vulkanisieren ein Dichtungsmittel (14; 15) auf den festen Einsätzen (9) angeordnet wird, um zu verhindern, dass beim Vulkanisieren Anteile des Materials in die Hohlräume (5) eindringen können.

16. Verfahren nach Anspruch 14 oder 15, dadurch gekennzeichnet, dass beim Vulkanisieren ein Druck auf die festen Elemente (9) ausgeübt wird, wobei der Druck so bemessen ist, dass er die elastischen Positionierungselemente (11; 20; 23) nicht verformt.

Revendications

1. Poinçon isobare (1) pour le pressage de carreaux de céramique (2), comprenant un corps de poinçon muni de cavités (5) en intercommunication contenant un fluide incompressible et ayant une extrémité fermée par une membrane élastique (4), l'autre extrémité étant munie d'une portion de fond, un insert rigide respectif (9), coopérant avec un moyen de positionnement élastique respectif (11 ; 20 ; 23), étant reçu à l'intérieur de chaque cavité (5), ledit insert rigide ayant une zone centrale et une zone périphérique avec une portion de bordure, ledit insert (9) faisant face, sur un premier côté, à ladite membrane (4), et, sur le côté opposé, étant en contact avec le moyen de positionnement élastique respectif (11 ; 20 ; 23), caractérisé en ce que ledit moyen de positionnement élastique (11 ; 20 ; 23) possède une forme annulaire et est reçu entre ladite portion de bordure et le fond de la cavité respective, ledit moyen de positionnement élastique étant configuré de manière à coopérer activement avec ledit insert rigide pendant le pressage des carreaux de céramique.

2. Poinçon selon la revendication 1, caractérisé en ce que ledit moyen de positionnement élastique (11 ; 20 ; 23) est reçu dans un siège annulaire correspondant (12) de ladite cavité (5).

3. Poinçon selon la revendication 1 ou 2, caractérisé en ce que ledit moyen de positionnement élastique a une section transversale circulaire (11).

4. Poinçon selon la revendication 1 ou 2, caractérisé en ce que ledit moyen de positionnement élastique a une section transversale rectangulaire (20).

5. Poinçon selon la revendication 1 ou 2, caractérisé en ce que ledit moyen de positionnement élastique a une section transversale comportant au moins une portion semi-circulaire (23).

6. Poinçon selon l'une quelconque des revendications précédentes, caractérisé en ce que ledit moyen de positionnement élastique (11 ; 20 ; 23) a une lèvre (19) enveloppant périphériquement l'insert respectif (9).

7. Poinçon selon la revendication 1, caractérisé en ce que ledit insert (9) possède un creux (17) pour recevoir la membrane (4) et pour s'y ancrer lui-même.

8. Poinçon selon la revendication 1, caractérisé en ce que ledit insert possède une zone périphérique (10) ayant une épaisseur moindre que l'épaisseur de la zone centrale.

9. Poinçon selon la revendication 1, caractérisé en ce que ledit insert possède une zone centrale qui saille en direction de ladite portion de fond afin de constituer une surface de butée lorsque l'insert est poussé dans la cavité (5).

10. Poinçon selon l'une quelconque des revendications précédentes, caractérisé en ce qu'un élément d'étanchéité périphérique (14 ; 15) est interposé sur le côté dudit insert (9), entre l'insert et la membrane (4).

11. Poinçon selon la revendication 10, caractérisé en ce que ledit élément d'étanchéité périphérique (14 ; 15) est formé par une bague ayant des dimensions et une forme identiques à celles dudit moyen élastique (11 ; 20 ; 23).

12. Poinçon selon la revendication 10, caractérisé en ce que ledit élément d'étanchéité périphérique comprend un élément (14) ayant, dans une vue en plan, la même forme que la cavité respective (5) et étant insérable en force dans celle-ci.

13. Poinçon selon la revendication 12, caractérisé en ce que ledit élément d'étanchéité est muni d'une ouverture centrale (16).

14. Procédé de fabrication d'un moule isobare (1) pour des carreaux de céramique (2) comprenant, en séquence, la préparation d'un corps de moule avec des cavités (5) en intercommunication ayant des ouvertures respectives orientées vers le haut, l'insertion d'un moyen de positionnement élastique (11 ; 20 ; 23) et d'un insert rigide respectif (9) dans chaque cavité (5), ledit insert rigide ayant une zone centrale et une zone périphérique avec une portion de bordure, et la vulcanisation d'une membrane (4) de matériau élastique sur les inserts rigides (9) et sur ledit corps de moule, caractérisé en ce que le moyen de positionnement élastique (11 ; 20 ; 23) possède une forme annulaire et est reçu entre ladite portion de bordure et le fond de la cavité respective, ledit moyen de positionnement élastique étant configuré de manière à coopérer activement avec ledit insert rigide pendant le pressage des carreaux de céramique.

15. Procédé selon la revendication 14, caractérisé en ce qu'un élément d'étanchéité (14 ; 15) est situé sur les inserts rigides (9) avant ladite vulcanisation, pour éviter que, pendant ladite vulcanisation, des portions dudit matériau ne puissent pénétrer dans lesdites cavités (5).

16. Procédé selon la revendication 14 ou 15, caractérisé en ce qu'une pression est exercée sur les éléments rigides (9) pendant la vulcanisation, ladite pression étant propre à ne pas déformer les éléments élastiques de positionnement (11 ; 20 ; 23).

Drawing