Apparatus for producing thin tiles of cement paste

Abstract: In the press, which includes one or more stations, each mold comprises a bed (53) stiffened by grids (53A, 53B), a plate (59) and a filtration layer (69) for the liquid of the paste, and also channeling for disposal of the liquid; on the bed is a peripheral seal (65) for supporting the frame (67) of the mold; the plate (59) contains a plurality of narrow channels (71) for drainage of the filtered liquid, said channels being connected to the liquid disposal channeling, with the filtration layer (69) laid over the top of these.

Description: The invention relates to an apparatus that has been devised to manufacture thin tiles from cement paste, with means for removing the excess liquid during pressing in the molds of rotary presses comprising one or more stations set up for the production of such tiles. In the case of turntable presses having multiple stations, which are conventional for the manufacture of tiles from cementicious material, a very fluid mortar is first poured into the mold prior to a relatively dry sandy layer, which under pressure absorbs the excess liquid from the mortar, which is to form the visible part of the tile after smoothing and polishing. When apparatus of this type has been used for the manufacture of thin tiles from cement paste without an underlayer, the problem has arisen of how to get rid of the excess liquid present in the cement paste, which has to be sufficiently fluid to pour into the bottom of the mold and spread over the entire surface bounded by the mold frame. The most common method has been to use the suction action of a vacuum, which is set up to draw the liquid through a filter present within the mold. This arrangement has not been found to be efficient largely because the depression to which the material is subjected to draw the liquid out can cause microfissures to develop within the material itself, despite the pressure, and these of course are not acceptable either aesthetically, or from the point of view of the possibility of forming lines that are predisposed to crack within the relatively thin tile, during installation or even after installation and during use. Furthermore an apparatus for manufacturing these thin tiles must be capable of achieving very great pressure in order to form the tiles and ensure that the tile can quickly be handled after its formation by pressure in the mold. It is to reconcile the differing demands of this work that the present apparatus has been devised. FR 2117398 A shows an apparatus with the features of the preamble of claim 1. Basically, the apparatus according to the invention - for making thin tiles from cement paste by pressing it in molds of rotary presses comprising multiple stations - has the features of claim 1. More particularly the bed of each mold may comprise: a grid with parallel ribs defining the liquid disposal channels, and bridge components that intersect said ribs; and metallic structures in the form of a perforated lamina and a mesh, both above and resting upon said grid, which structures support at least one layer of easily interchangeable filter fabric. A metallic structure in the form of a fine mesh, for supporting the layer of filter fabric, can be embedded around its edge in said peripheral seal on which the peripheral frame of the mold is supported. A final filter fabric can be hooked to the perimeter of the frame by intermediate elastic tensioning components. This final filter fabric, which is very fine, can thus easily be replaced. The apparatus comprises at least one suction means fitted to the pressure block in order to carry away the liquid that may collect between the frame and the block during pressing. Also, and optionally, the pressure block may contain an elastic liner forming a peripheral seal with the inner wall of the frame. Another object of the invention is to improve the structure of the molds, particularly as concerns filtration, in order to produce satisfactory products. This and other objects and advantages will become clear in the following text. To this end the apparatus according to the invention comprises a plate with a plurality of narrow channels for draining off the filtered liquid, said channels being connected to the liquid disposal channeling. In one possible embodiment, said narrow channels are divided into two series of channels, the channels of each series being parallel with each other and the channels of one series intersecting the channels of the other series. Said narrow channels will be sufficiently deep and/or their base will be sloping and run out at the edge to permit easy disposal of the liquid, and also to simplify cleaning. The plate can be machined with liquid disposal channeling on the underside, with a plurality of discharge holes interfering with said channeling and beginning in a seat on the upper side for a perforated lamina with holes interfering with said narrow channels and corresponding to said discharge holes; a seat being formed in said perforated lamina for a replaceable seal - of rubber or the like - designed to fit the frame of the mold. To each of said discharge holes in the plate there may correspond four holes in the lamina. A seat may be formed in the top of the plate to accommodate either the perforated lamina or, alternatively, a lamina with rubber, to prepare the mold for the production of conventional two-layer tiles. The apparatus comprises a pressure block able to enter the frame of the mold with a small amount of play. In a further development of the invention, suction holes are formed around the perimeter of said block in the vicinity of the lower pressure face and connected to channeling leading to suction means, for the disposal of liquid collected between the frame and the block during pressing. Advantageously, said suction means comprise at least one annular manifold into which said suction holes feed, and at least one pipe for creating from outside of the block a vacuum in said manifold. A plurality of pipes can be distributed around said annular manifold to ensure an even vacuum throughout the annular manifold. Said suction holes may be beveled at the outer end for complete suction of the liquid phase that collects between the frame and the block. The invention will be understood more fully on examining the description with reference to the accompanying drawing, which shows non-restrictive examples of apparatus for making thin tiles. In particular, in the drawing: Fig. 1 shows an exploded view of the components of a filtration and drainage bed; Fig. 2 is a section through the mold ready for pressing; Fig. 3 shows the section marked III-III in Fig. 2; Fig. 4 shows an alternative embodiment to Figs. 2 and 3 relating to the structure of the pressure block; Fig. 5 shows an enlarged detail of the area indicated by arrow f v in Fig. 1; Fig. 6 shows a local section through a mold in an alternative embodiment; Fig. 7 shows a partly sectional view on VII-VII as marked in Fig. 6; Fig. 8 shows a local section on VIII-VIII as marked in Figs. 7 and 9; Fig. 9 shows, in a similar way to Fig. 7, an alternative embodiment; Fig. 10 is a section showing a mold with certain associated components; Figs. 11, 12 and 13 show successive stages in the operation of a modified bed, Fig. 13 being a section through XIII-XIII as marked in Fig. 12; Fig. 14 is a view on XIV-XIV as marked in Fig. 13; Figs. 15 and 16 show a bed complete with its frame, and a local section through XVI-XVI as marked in Fig. 15; Figs. 17 and 18 show a further alternative embodiment in section on XVII-XVII as marked in Fig. 18 with other components in an exploded view, and a plan view of the bed; Fig. 19 shows how a bed can be equipped and used for the manufacture of traditional two-layer tiles; and Figs. 20, 20A and 21 show an embodiment of the invention, with a mold in vertical cross section, in an enlarged detail of Fig. 20 and as viewed from the plane marked XXI-XXI in Fig. 20. In the form illustrated in Figs. 1-5 of the appended drawing, the bed of a mold - for presses constituting the apparatus as defined above - comprises a sturdy structure 1 supporting the bed of the mold for which the general reference is 3. This bed 3 contains a grid of lengthwise components 3A stood edge-on on a flat base 3B that in turn stands on the structure 1; these ribs 3A define a series of lengthwise channels 5 in the bed 3. Running between the lengthwise components or ribs 3A and above and through the channels 5 are bridge components 3C supported between the adjacent lengthwise components 3A to form a sturdy grid that forms part of the bed 3. This grid 3A, 3C together with the inner perimeter 3E of the bed 3 forms a seat 7 (Fig. 1) for a perforated plate 9 that may take the form of a stainless steel lamina with suitably distributed holes whose dimensions and spacing are such as to give good support to a fine steel mesh 11, which is thus supported by the plate 9 almost without deformation. The edge of the steel mesh 11 is embedded in a rubber seal 13, which is vulcanized around the outer edge of the mesh 11 and corresponds in shape to the shape defined by the peripheral walls 3E of the bed 3. In particular (see Fig. 5) the rubber seal 13 includes on its upper surface a peripheral projection 13A to which corresponds the bottom edge 15A of the mold frame 15, when the latter is placed on the bed 3. Advantageously, the metal mesh 11 is shaped around its edge in such a way that while its edge is embedded in the seal 13, its upper surface internal to the seal 13 is flush with the upper surface of this seal 13. Over the metal mesh 11 is a filter component made of a large-mesh fabric marked 16 that lies over the mesh 11, continuing to be supported by the latter during pressing. Stretched over the top of the large-mesh filter fabric 16 is another, fine-mesh filter fabric 17, which may be of so-called nylons fibers or the like. This fine-mesh filter fabric 17 is fitted so as to be easily detachable for rapid replacement in view of the fact that this fabric wears quickly, being in contact with the material from which the tile is to be pressed. In particular the fabric 17 may be fitted on one side with eyes 17A that can then be engaged on pegs 3K on the outside of the bed 3, and on the other side may have spring hooks 17B for engagement on eyes 17A similar to the previous eyes, the springs being designed to hook around pegs 1K formed in the structure 1 or otherwise positioned. In this way the fine-mesh filter fabric 17 can be stretched quickly over the fabric 16 and hence over the mesh 11 and seal 13, and can quickly be replaced. The bed 3 contains passages 3P (see in particular Fig. 3) communicating with the channels 5, defined by the lengthwise components 3A, beneath the bridge components 3C. In this way the liquid that collects in the channels 5 can discharge via the passages 3P through discharge holes 19 into a collecting manifold 21 for disposal. The above-described structure of the bed of the drainage and filtration mold makes it possible to achieve great strength tending to withstand the very high stresses imposed on the material M introduced into the mold defined by the bed 3 and frame 15; in addition the filtration and drainage structure as described does not present particular obstacles to the outflow of the liquid, which it filters off during pressing and which is removed without significant impediment. Pressing is effected by means of a block 24 that matches the space defined by the frame 15 and that may optionally include a border 24A slightly smaller than the space defined by the frame 15 and with a sealing liner 24B on its underside for contact with the material M. When the block 24 is driven into the space defined by the frame 15 - after the material M of relatively high fluidity has first been poured in - the material M is pressed and the excess liquid is discharged through the filtration and drainage structure composed of components 17, 16, 11 and 9 into the channels 5 for disposal, by the pressure exerted by the block 24. Any liquid that escapes back up between the inner edge of the frame 15 and the border 24A of the block 24 can easily be reabsorbed by the pressed material without harmful effects on the consistency of the latter achieved by the pressing action. The amount of liquid that escapes back upward as stated above can be limited by providing, as shown in Fig. 4, an elastic sealing liner 24E in the block 24: under pressure this liner 24E can press against the inner edge of the frame 15 to make it leaktight and impede the backward escape of this water between the frame and block. In addition, in order to exclude or at least limit the amount of liquid that could escape back up between the frame 15 and block 24 during pressing - or above the liner 24 when present - it is possible to fit the block 24 with suction means 24X (Fig. 4) that would be able to remove at least some of this escaped liquid. By constructing a mold in the manner described above it is possible to produce quite thin tiles that are easy to handle after pressing because of the severe pressures achievable in molds of this construction, the effect of which is so to reduce the residual moisture in tiles made of the material M that not only can they be handled following pressing, but the material of the tiles is also dense enough and compressed enough to circumvent the problems indicated earlier, which were typical of the output of equipment known in the field. As illustrated in Figs. 6 ff of the drawing, the bed of a mold - for presses constituting the apparatus as defined above - comprises a sturdy structure 51 supporting the bed of the mold for which the general reference is 53. This bed 53 contains a grid of lengthwise ribs 53A stood edge-on on a flat base 53B that in turn stands on the structure 51; these ribs 53A define a series of lengthwise channels 55 in the bed 53. Running between the lengthwise components or ribs 53A and above and through the channels 55 are bridge components 53C consisting of bars supported between the adjacent lengthwise components 53A to form a sturdy grid that forms part of the bed 53. This grid 53A, 53C together with the inner perimeter of the bed 53 forms a seat 53E for a perforated lamina 59; the bed 53 may take the form of a stainless steel plate with holes 61 made by machine in rows in two mutually perpendicular directions in positions such that the grid structure 53A, 53C corresponds to linear zones running between adjacent rows of holes 61. Around its edge, the lamina 59 forms a stepped seat 63 for an easily replaceable rubber seal 65; on this seal 65 rests the bottom edge 67A of the frame 67 of the mold, when this is positioned on the bed 53. 68 is the block. Laid over the plate 59 is the filter 69 which may be paired with a second filter 69 or may be layered, and which is interposed between the plate 59 and the frame 67. The pressing block 68 passes down into the frame 67 to compress the fluid mass and expel a large percent of the liquid phase through the filter 69. To ensure steady drainage, the upper surface of the plate 59 (on which the filter 69 rests) is formed into narrow channels 71 lying in one direction (Fig. 7) or two or more directions, as marked 71 and 73 in Fig. 9; the channels are laid out so as to interfere with the holes 61, where the water (with particles of cement) that has passed through the filter 69 is discharged. The bed 53 contains passages 53P (see in particular Fig. 10) communicating with the channels 55, defined by the lengthwise components 53A, underneath the bridge components 53C. In this way the liquid collected by the channels 55 can be discharged via the passages 53P through discharge mouths 74 into a collecting manifold 75 for disposal. Figs. 11-16 show a particularly efficient embodiment of a plate designed to replace the bed 53 of the version shown in Figs. 6-10. In this version the bed 53 is formed by a plate 103 machined to form edge-on ribs 103A defining channels 105, which are excavated mechanically as far as the perimeter of the two opposite sides of the plate 103; a base 103B - equivalent to the base 53B - rests on the structure 51; formed at one of the ends of the channels 105 are the passages 103P to allow the water to flow out toward the discharge 74 leading to the manifold 75. A removable closure 103K can be provided at the opposite end from the passage 103P to allow easy cleaning of the channels 105. The top of the plate 103 is machined to form the seat 103E for accommodating the perforated lamina such as 59 with holes 61 and with channels 71 and optionally 73. Once the channels 105 have been machined, and hence after the ribs 103A have been defined, through holes 103F are drilled between the seat 103E and the channels 105 at intervals from each other and lined up to correspond to the channels 105 with which they interfere, as can be seen clearly in Figs. 12-16. When the perforated lamina 59 with its seal 65 is positioned in the seat 103E in the plate 103, the holes 61 of said lamina 59 will each correspond - at least partially - with the holes 103F, in such a way as to ensure that the filtered water is discharged directly through the holes 103F into the channels 105. In practice each hole 103F will connect with four holes 61 in the lamina 59 (see Fig. 16). The liquid filtered through the filter 69 drains along the channels 71 and, if provided, 73, and there is therefore a very steady direct outflow of the liquid passing through the filter 69 toward the discharge point, with no significant variations in the path obstructed to a greater or lesser degree along the filtering surface. The filter interposed between the plate 53 or 103 and the frame 67 may be composed of an ordinary fine-mesh fabric filter 69A and a large-mesh fabric underfilter 69B in order to bear the stresses of the pressure at the interspaces defined by the narrow channels 71 and, where provided, 73, and by the holes 61. An alternative embodiment of the plate 103 is shown in Figs. 17 and 18. A large plate 203 is machined to form a peripheral seat or channel 203E for an easily replaceable seal 215 equivalent to the seal 65. The plate 203 replaces the plate 53 or 103 and also the perforated lamina 59 because said plate 203 contains at least one and preferably two series of deep but narrow mutually perpendicular channels 205A and 205B extending to the edges of the plate, in such a way as also to form water discharge channels. In this case the collecting means will be formed by an annular manifold which collects the water from all four sides of the plate from the open ends of the channels 105A and 105B. However, it is also possible to stop up the ends of the channels on some of the sides in order to limit the area into which the water drains, since the channels 205A and 205B communicate with each other. The channels 205A and 205B can all be of the same depth but it is also possible for the channels of one series to be of a different depth to the channels of the other series. In fact the bottoms of the channels of at least one series may be sloping to promote the discharge of the water toward one side of the plate 203 or to two preferred sides. A filtration bed as described above can also be modified quickly by replacing certain of its parts, in order to produce a structure for the pressing of traditional two-layer tiles, simply by replacing the plate 59 with the holes 61 in the seat 53E, as can be seen in Fig. 19. The plate 59 with the holes 61 is replaced with a strong lamina 309A to which is applied a liner 309B of vulcanized rubber on the lamina 309A and advantageously also forming a sealing edge 309C around the inside of the wall of the seat such as 53E or 103E. The vulcanized rubber 309B supports the bottom edge of the frame 67. This gives a mold for two-layer tiles, i.e. tiles with a bottom layer of fluid mortar, optionally with marble fragments, and a semidry top layer to absorb the excess water from the first or bottom layer, done in an entirely conventional way for the formation of two-layer concrete tiles. It is thus possible to convert a press for thin single-layer concrete tiles into an apparatus for forming two-layer tiles, and vice versa, by the simple replacement of inexpensive, easily replaceable parts that are easy to handle. As can also be seen in Fig. 6, but more particularly in Figs. 20 and 21, the frame 67, which rests on and is pressed onto the seal 65 of the bed 53, is designed to receive the block 301 with a small amount of play. More specifically the block 301 can be made with an underplate 303 attached to the underside of the block 301 to form the surface that contacts and compresses the fluid mortar B designed to form the thin tile; the underplate 303 is very slightly smaller than the internal dimensions of the frame or ring 67 while the block 301 itself can be slightly smaller. On the underside of the underplate 303 is a liner 305 of rubber or other material, which may have indentations or reliefs to give particular markings on the surface of the tile formed from the fluid mortar B. Because the frame 67 is pressed onto the seal 65 and thus creates a highly watertight join, some of the liquid phase that separates from the material of the pressed tile produced from the fluid mortar B, and which does not pass through the filtering liner 69, tends to rise back upward between the frame 67 and the underplate 303, even occupying the space S between the block 301 and that part of the frame 67 that is above the underplate 303. When the block 301 is lifted after pressing, this water, accumulated between the block and the frame, tends to return onto the material of the tile, altering its composition and in particular weakening the outer edges of the pressed and not yet dried tile. A system is therefore provided to eliminate this accumulated water or other liquid phase from the region S in order to ensure that water does not run back down onto the freshly pressed tile. To this end a suction network is provided between the gap S and a vacuum source so that the liquid is sucked out during the pressing or rather during the last phase of pressing, when the compression is at its greatest, so that the water or other liquid phase cannot drain back around the edges of the newly pressed tile as the block is lifted away. Holes 307 are formed in the underplate 303 in a perpendicular arrangement to the perimeter of this underplate and with outward beveling 307A that almost reaches the active lower surface of the underplate 303, 305. The holes 307 are distributed in any suitable uniform way around the perimeter of the underplate 303 and connect at the inward end with an annular manifold which may take the form of a channel 309 also cut into the underplate 303 and which is closed by the attachment of the underplate to the underside of the block 301, thereby forming an annular manifold. Two annular seals may be fitted between the underplate 303 and the block 301, inside and outside of the manifold 309 to ensure leaktightness between the underplate 303 and the block 301, as marked at 310 and 311. One or more holes 313 are formed in the block 301 and may be distributed in some suitable way around the manifold 309: they are combined by connectors 315 to hoses 317 connected to a vacuum source. The arrangement of the holes 313 is such as to produce an approximately uniform vacuum both in the manifold 309 and in the holes 307, which are distributed around the perimeter of the liner of the underplate 303. As a means of achieving this uniformity and the regularity of the presence of the suction holes 307, branches 309A of the manifold 309 can be provided at the corners of the underplate 303 so as to ensure suction is also provided at holes 307X located in the comer regions of the underplate 303. The holes 313 can also be made to connect with these branches 309A and can therefore be positioned in the corner regions of the underplate 303. By establishing the connection between the vacuum source connected to the hoses 317 and the entire suction network represented by the holes 313, manifold 309 and holes 307, the ability to remove the liquid from the gap S by suction both during pressing and more particularly at the conclusion of pressing and before the block is lifted away, is established. The liquid can at any rate be disposed of and prevented, after collecting in the gap S, from draining back down onto the pressed tile around its perimeter. It should be understand that the drawing shows only an example purely as a practical demonstration of the invention, it being possible to alter said invention as regards shapes and arrangements without thereby departing from the scope of the concept on which the invention is based. The presence of any reference numerals in the appended claims is for the purpose of facilitating the reading of the claims with reference to the description and drawing, and does not limit the scope of protection represented by the claims.

Claims: An apparatus for making thin tiles from cement paste with presses comprising one or more stations, the presses comprising molds in which the cement paste is pressed, each mold comprising a frame, a pressure block, which is able to enter the frame of the mold, and a bed (3), stiffened by grids (3A, 3C; 9; 11; 17) of increasing fineness, which filters and drains the liquid from the paste, with channeling (5) for disposal of the liquid, on which bed (3) is a peripheral seal (13) for supporting the frame (15) of the mold, characterized in that at least one suction mean is fitted to the pressure block (24) in order to carry away the liquid that may collect in the gap between the frame and the block during pressing. The apparatus as claimed in at least claim 1, characterized in that it comprises a plate with a plurality of narrow channels for draining off the filtered liquid, said channels (71, 73) being connected to the liquid disposal channeling. The apparatus as claimed in claims 1 or 2, with the pressure block (301) able to enter the frame (67) of the mold with a small amount of play, characterized in that suction holes (307) are formed around the perimeter of said block (301) in the vicinity of the lower pressure face and connected to channeling (309, 313, 317) leading to suction means, for the disposal of liquid collected between the frame (67) and the block (301) during pressing, or at least in the last phase of pressing. The apparatus as claimed in claim 3, characterized in that said suction means comprise at least one annular manifold (309) into which said suction holes (307) feed, and at least one pipe (315, 317) for creating from outside of the block a vacuum in said manifold (309). The apparatus as claimed in claim 4, characterized in that it comprises a plurality of pipes (313; 317) distributed around said annular manifold (309) to ensure an even vacuum throughout the annular manifold. The apparatus as claimed in at least one of claims 3-5, characterized in that said holes (307) are beveled at the outer end (307A). The apparatus as claimed in at least one of the preceding claims, characterized in that the final filter fabric (17) is hooked to the frame by intermediate elastic tensioning components (17B). The apparatus as claimed at least in claim 2, characterized in that said narrow channels are divided into two series of channels (71 and 73), the channels of each series being parallel with each other and the channels of one series intersecting the channels of the other series. The apparatus as claimed in claim 2 or 8, characterized in that said narrow channels (205A, 205B) are sufficiently deep and/or their base is sloping and runs out at the edge to permit disposal of the liquid. The apparatus as claimed in claim 2 or 8, characterized in that it comprises a machined plate (103) with liquid disposal channeling (105) on the underside, with a plurality of discharge holes (103F) interfering with said channeling (105) and beginning in a seat (103E) on the upper side for a perforated lamina (59) with holes (61) interfering with said narrow channels (71 and/or 73) and corresponding to said discharge holes (103); a seat (63) being formed in said perforated lamina (59) for a replaceable seal (65) designed to fit the frame (67) of the mold. The apparatus as claimed in claim 10, characterized in that to each of said discharge holes (103F) in the plate (103) there correspond four holes (61) in the lamina (59). The apparatus as claimed in claim 10, characterized in that a seat (53E; 103E) is formed in the top of the plate (53; 103) to accommodate either the perforated lamina (59, 61) or alternatively a lamina (309A) with rubber (309B), to prepare the mold for the production of two-layer tiles.

Inventors: LONGINOTTI ALFREDO, LONGINOTTI, ALFREDO
Applicants: LONGINOTTI MECCANICA S R L, LONGINOTTI MECCANICA S.R.L.
Application year: 1998
Main classification: B28B7
IPC codes: B28B7