EP2897772B1

EP2897772B1 - Mold for forming tiles and the like

Info

Publication number: EP2897772B1
Application number: EP13801720.7A
Authority: EP
Inventors: Paola Martinelli; Stefano Cassani; Emanuele COSTETTI
Original assignee: Martinelli Ettore Srl
Current assignee: Martinelli Ettore Srl
Priority date: 2012-09-19
Filing date: 2013-09-05
Publication date: 2017-08-23
Anticipated expiration: 2033-09-05
Also published as: WO2014045149A1; ES2648517T3; EP2897772A1; ITMI20121558A1

Description

The present invention relates to a mould for forming tiles and the like.
In the art moulds are known where a pair of half-moulds are combined to form one or more cavities for receiving the poured powder which, once pressed, forms the ceramic product. Since the density of the powder may, for various reasons, vary inside the cavity or between one cavity and another of the mould, for some time so-called "isostatic" moulds have proposed where, in at least one half-mould, the pressing block which supports the mould die rests on an incompressible-fluid bed present in the chamber behind the block. The volume of oil inside the chamber, suitably varied during pressing, allows the degree of compaction of the powder inside the mould to be varied. Generally, in the case of multiple-impression moulds, the various support blocks for each impression have interconnected fluid beds such that there is automatic compensation of the density between the various impressions of the mould.
EP 1403017 describes a mould of the abovementioned type according to the preamble of claim 1, which uses resilient laminas which engage inside side walls of the blocks so as to push the latter towards their more retracted position. When the laminas are in a nondeflected condition the block is in its more retracted position. By supplying fluid into the chamber behind the block, the block moves outwards, causing the resilient laminas to flex.
Resiliently pushing the blocks into the more retracted position is for example useful for keeping the pressing dies all at the same height during the powder filling operations. Moreover it is possible to use the isostatic mould in the manner of a conventional mould by simply removing completely the incompressible fluid. In the case where there is no fluid or a low pressure of the fluid, it is also possible to prevent the blocks from performing uncontrolled movements on their support plates.
The use of resilient laminas is, however, subject to various drawbacks.
For example, the travel allowed by the laminas is very limited and the laminas are subject to flexing which easily causes breakage thereof, resulting in the need for frequent maintenance of the mould.
On the other hand, the space around the impressions of the mould is restricted and it is difficult to imagine alternative systems.
Moreover, the laminas have a resilient behaviour which is inadequate for ensuring uniform filling of the mould, said behaviour being too critical, in particular after various pressing cycles.
US6093012 discloses a mould for manufacturing concrete mouldings having a pressure plate which is suspended by screws on which compression helical springs are mounted.
US4588368 discloses a moulding apparatus in which a pre-compression die is returned by bolts which are pre-tensioned by compression helical springs.
The general object of the present invention is to provide a mould with an isostatic plate provided with resilient means for performing pushing towards the rest position, said means being small-size, robust and efficient.
In view of this object the idea which has occurred, according to the invention, is to provide a mould for forming tiles according to claim 1. In order to illustrate more clearly the innovative principles of the present invention and its advantages compared to the prior art, examples of embodiment applying these principles will be described below, with the aid of the accompanying drawings. In the drawings:

Figure 1 shows a partial, schematic, longitudinally sectioned view of a first embodiment of a mould according to the invention;
Figure 2 shows an enlarged and partially cross-sectioned view of the mould according to Figure 1;
Figure 3 shows a partial, perspective, schematic view of the mould according to Figure 1;
Figure 4 shows a partial and exploded, perspective, schematic view of the mould according to Figure 1;
Figure 5 shows a partial enlarged view of a variant of the mould according to Figure 1;
Figure 6 shows a partial, schematic, longitudinally sectioned view of a second embodiment of a mould according to the invention;
Figure 7 shows a partial, perspective, schematic view of the mould according to Figure 6;
Figure 8 shows a partial and exploded, perspective, schematic view of the mould according to Figure 6;
Figure 9 shows a partial enlarged view of a variant of the mould according to Figure 6.

With reference to the figures, Figure 1 shows a mould, denoted generally by 10, for forming tiles and the like (usually by means of pressing of a suitable powder material). For the sake of simplicity, the figure shows only the right-hand part of the mould, the left-hand part being generally a mirror-image thereof (if the mould is of the single-row type).
The mould 10 comprises a bottom half-mould 11 and a top half-mould 12 which define at least one forming cavity 13 inside which the material is pressed.
The two half-moulds are generally intended to be mounted on respective pressing surfaces 14, 15 of a suitable press, not shown in that it may be easily imagined by a person skilled in the art.
At least one of the two half-moulds comprises a bearing plate 16 having at least one seat 17 which contains in a sealingly slidable manner a pressing block 18 intended to support thereon a die 19 with a half-impression of the product to be formed. Generally the half-impression coincides with one of the two sides of a tile, while the side edge is obtained by a containing frame 31 into which the dies are inserted.
The example according to Figure 1 shows a top half-mould, but the same solution may be used for the bottom mould alone, or for both of them, for example depending on the needs and the specific practical requirements.
A chamber 20 which is intended to receive incompressible fluid for pushing the block towards the outside of the seat is thus formed between block and bottom of the seat, according to the conventional operating mode of isostatic-plate moulds. Resilient means 21 for resiliently pushing the block towards the bottom of the seat are present between the and the peripheral edge of the block.
Advantageously, these resilient means are distributed around the lateral perimeter of the block so as to provide a uniform pushing action along the periphery of the block, as can be seen more clearly in Figure 3 and as will be further clarified below.
As can be clearly seen again in Figure 1 and in a partly cross-sectioned view from a direction rotated through 90° in Figure 2, the resilient means comprise a flange 22 which projects laterally from the peripheral edge of the block 18 and which is connected to the plate by means of connection pins 23 with the arrangement, in between, of a resilient spacer 24 which opposes sliding of the block towards the outside of the seat formed in the plate. The block may thus perform its sliding movement (in a vertical direction in the figure), sliding inside the seat in the plate parallel to the pins, so as to engage inside the seat against the action of the oil or (compressing the resilient element 24 when the fluid enters into the chamber 20) so as to project further from the seat.
In the first embodiment described, the pin 23 advantageously passes slidably through the flange 22 and is fixed into the plate by means of a first end 25 thereof. The said resilient spacer 24 is present between the opposite second end 26 of the pin and the flange 22 and thus reacts between said second end of the pin and the flange so as to oppose sliding of the block towards the outside of the seat formed in the plate.
Advantageously, the pin is formed in the manner of a screw which is screwed into the plate 16 (provided with suitable threaded holes) and has an enlarged head which forms the said second end 26. The resilient spacer 24 presses advantageously against the head of the screw via a metal bearing lamina 27. Again advantageously, rigid tubular spacers or bushes 28 are mounted on the screws 23 so as to limit screwing of the screws. In this way the screws may be firmly screwed into the plate without stressing the resilient spacer. Advantageously, the rigid spacers are suitably designed with lengthwise dimensions compared to the thickness of the resilient spacer so as to allow the prestress of the said resilient spacer to be controlled.
As can be clearly seen in Figure 3 and, more particularly, in the exploded view of Figure 4, the bearing lamina 27 is advantageously in the form of a frame which follows the perimeter of the block and in which the screws 23 which form the pins are screwed at intervals along its length so as to surround the block. The size of the mould may be such that, when the block is pushed completely inside the seat via the resilient means 21, the block is arranged against the bottom of the seat.
It may however be advantageous for a small distance to remain between the block and bottom of the seat, for example in order to facilitate subsequent entry of the fluid or avoid any "sticking" of the block to the bottom of the seat. This space (denoted by "d" in Figure) may also be only of the order of a few tenths of a millimetre.
In order to prevent contact between the block and the bottom of the seat advantageously an end-of-travel stop is provided, being easily obtained by means of contact of the flange 22 against the edge of the plate 16 which surrounds the block, as can be seen in Figures 1 and 2.
The flange is formed as a frame which surrounds the block as one or two parts (Figures 3 and 4 show a flange consisting of two parts) and which preferably bears against a contact edge 30 present on the block side walls which project from the block seat in the plate. The contact edge may advantageously form part of a groove present in the side walls of the block and inside which the said frame is partially inserted. The resilient spacer is formed by a layer of elastomeric material, in particular chosen from polyurethane elastomers (for example: ADIPRENE®, VULKOLLAN®, ADIPOL®, ULTRAFLEX®) or NBR (Nitrile Butadiene Rubber).
As can be clearly seen in Figure 4, it has also be found to be advantageous if the layer of elastomeric material follows the perimeter of the block so as to be passed through at intervals by the pins extending along its length. For example, the elastomeric layer may be easily cut in the form of a generally rectangular frame from a sheet of suitable thickness.
Again advantageously, the layer of elastomeric material, the flange and the bearing lamina may all be in the form of a frame with a similar impression so as to completely overlap each other, as can again be clearly seen in the exploded view of Figure 4.
Figure 4 shows how the blocks may be advantageously at least two in number (and advantageously also a set of blocks arranged in rows and columns so as to form a matrix of pressing impressions). Each block is slidable in its seat in the plate and has its own resilient means along the perimeter. The respective chambers intended to receive incompressible fluid are interconnected by means of ducts 32, according to the arrangement envisaged for this type of mould.
Figure 5 shows a variant in which a resiliently yielding element 29 is arranged between the flange 22 and plate 16, said element allowing the block to be kept resiliently spaced from the bottom of the seat by a distance 'd' also before introduction of the oil. Advantageously, the yielding factor and thickness 'D' of the element 29 (which may be a layer of yielding material arranged along the entire length of the flange 22) are chosen so that the pressing forces generated during use of the mould may compress the resilient element 29 and eliminate the distance 'd'. This allows the block to be brought into contact against the bottom of the seat, for example when there is no fluid inside the chamber (or when the pressure of the fluid is sufficiently low) or when transfer of fluid to the chambers of the other blocks occurs. This thus results in the aforementioned advantages of a small space between the block and the bottom of the seat when the mould is in the rest condition, ensuring at the same time that the block moves gently towards the bottom of its seat. The material of the element 29 may be advantageously chosen from those which can be used for the resilient spacer 24.
Figure 6 shows a second embodiment of a mould according to the invention.
This figures shows only partially the bottom half-mould, it being easy for the person skilled in the art to imagine the general overall structure of the mould on the basis of the description provided hitherto and below. With the embodiment in Figure 6 it is possible to obtain an even smaller vertical dimension and it is therefore particularly useful for the bottom half-mould. The same solution may in any case be used for the top mould alone or both moulds.
For the sake of simplicity, parts similar to those of the preceding embodiment will be indicated by the same number, increased by 100.
Figure 6 therefore shows the half-mould 111 of a mould 110 provided in accordance with the invention for forming tiles and the like.
The half-mould comprises a bearing plate 116 with at least one seat 117 which contains in a sealingly slidable manner a pressing block 118 intended to receive, mounted thereon, a die 119 with a half-impression of the product to be formed. The half-impression is combined (together with the other half-mould, not shown) so as to form the forming cavity (13 in Figure 1) of the complete mould.
A chamber 120 is formed between the block and the bottom of the seat and is intended to receive incompressible fluid for pushing the block towards the outside of the seat.
Resilient means 121 are present between plate and peripheral edge for resiliently pushing the block towards the bottom of the seat.
In the same way as for the preceding embodiment the resilient means are advantageously distributed around the lateral perimeter of the block, as can be seen for example in Figure 7.
The resilient means comprise a flange 122 which projects laterally from the side walls of the block 118 and which is connected to the plate by means of connection pins 123 with the arrangement, in between, of at least one resilient spacer 124 which opposes sliding of the block towards the outside of the seat formed in the plate. The block may thus perform its sliding movement (in a vertical direction in the figure), sliding inside the seat in the plate, so as to engage inside the seat against the action of the oil or (compressing the resilient element 124 when the fluid enters into the chamber 120) so as to project further from the seat.
As can be seen clearly again in Figure 6, the pin 123 is connected to the flange by means of a first end 125 thereof and passes slidably through the plate 116. The resilient spacer 124 is present between the opposite second end 126 of the pin and the plate 116 and thus reacts between the second end of the pin and the plate so as to oppose the sliding movement of the block towards the outside of the seat in the plate.
Advantageously, the pin is formed in the manner of a screw with an enlarged head which forms the said first end 125 and with a second end 126 which is screwed into a lamina 127 bearing against the resilient spacer 124.
Again advantageously, rigid tubular spacers or bushes 128 for limiting screwing of the screws and controlling the prestress of the resilient spacer are mounted on the screws 123. In this way the screws may be firmly screwed without stressing the resilient spacer owing to a suitable choice of length of the bushes. The heads of the screws may be conical and received inside flared seats in the flange, as can be seen in the figures.
As can be deduced from Figure 7 and clearly seen in the exploded view of Figure 8, the bearing lamina 27 is advantageously in the form of a frame which follows the perimeter of the block and in which the screws 123 which form the pins are screwed at intervals along its length so as to surround the block.
In a similar manner it can be seen how the flange 122 may advantageously also be in the form of a frame which surrounds the periphery of the block, with the screws arranged at intervals passing through it.
Advantageously the bearing lamina 127 is seated inside a channel 140 formed in the plate, together with the resilient spacer 124 (advantageously formed as a continuous frame with a progression similar to that of the lamina 127).
As with the preceding solution, the size of the mould may be such that, when the plug is pushed completely inside the seat via the resilient means 121, the block is arranged against the bottom of the seat, but it may be advantageous for a small distance to remain between the block and the bottom of the seat.
In order to prevent contact between the block and the bottom of the seat advantageously an end-of-travel stop is provided, being easily obtained by means of contact of the flange 122 against the edge of the plate 116 which surrounds the block, as can be clearly seen in Figure 6.
The flange is formed as a frame which surrounds the block and which preferably bears on a contact edge 130 present on the block side walls which project from the block seat in the plate The contact edge may advantageously form part of a groove present in the side walls of the block and inside which the said frame is partially inserted. In particular, as can be clearly seen in the figures, the block may be formed with two plates superimposed and interconnected so as to grip completely between them the innermost edge of the flange, while ensuring that the system may be assembled when the flange is formed as one piece.
In this second solution also the resilient spacer is formed by a layer of elastomeric material, in particular chosen from polyurethane elastomers or NBR (Nitrile Butadiene Rubber) which is advantageously shaped (for example cut from a sheet) so as to follow the perimeter of the block and be passed through at intervals by the pins along its length.
The possible frame-like forms of the various parts which form the resilient means are clearly visible in Figure 8.
Figure 7 shows how the blocks may be advantageously at least two in number (and advantageously also a set of blocks arranged in rows and columns so as to form a matrix of pressing impressions), with each block which is slidable in its own seat in the plate and which has its associated resilient means along the perimeter. The respective chambers intended to receive incompressible fluid are interconnected by means of ducts 132, according to the arrangement envisaged for this type of mould. In this way, there will be a fluid redistribution during pressing which optimizes pressing of the powder in the various cavities.
Figure 9 shows a variant in which a resiliently yielding element 129 is advantageously arranged between the flange 122 and plate 116, said element allowing the block to be kept resiliently spaced from the bottom of the seat by a distance 'd'.
In a similar manner to the preceding embodiment, the yielding factor and thickness 'D' of the element 129 (which may also be formed in the manner of a frame along the entire length of the flange 122) may be chosen so that the pressing forces generated during use of the mould may compress the resilient element 129 and eliminate the distance 'd' so that, upon pressing, the block is able to make contact against the bottom of the seat, if necessary.
The material of the element 129 may be advantageously chosen from those which can be used for the resilient spacer 124.
At this point it is clear how the predefined objects have been achieved.
For example, the mould according to the invention is strong, easy to maintain and assemble and has optimum resilience and repeatability characteristics.
In particular, with a mould according to the invention it is possible to ensure that the various dies of the mould are all at the same height upon loading of the powder, ensuring a more uniform product.
The quality of the products obtained with moulds according to the invention is therefore greater.
Obviously, the above description of embodiments which apply the innovative principles of the present invention is provided by way of example of these innovative principles and must therefore not be regarded as limiting the scope of the rights claimed herein.
Moreover, it is possible to introduce oil into the isostatic plate so as to increase the distance of each block from the bottom of its seat in the plate and consequently also the volume of the oil chamber of each block: it is thus possible to ensure an isostatic behaviour also in the case of a high degree of non-uniformity during filling of the powder into the various impressions of the mould.
The mould may also be supplemented with accessories in the form of known systems for loading the powder and unloading the pressed product and/or known isostatic systems (for example of the known type with "isostatic marks") for ensuring locally a uniform density of the powder inside the cavity.

Claims

Mould (10, 110) for forming tiles and the like, comprising a bottom half-mould (11, 111) and a top half-mould (12, 112) which define at least one forming cavity (13), at least one of the two half-moulds comprising a bearing plate (16, 116) with at least one seat (17, 117) inside which a pressing block (18, 118) is sealingly slidable, between block and bottom of the seat there being formed a chamber (20, 120) intended to receive incompressible fluid for pushing the block towards the outside of the seat, resilient means (21, 121) being present between the plate and the peripheral edge of the block so as to push resiliently the block towards the bottom of the seat, characterized in that the resilient means comprise a flange (22, 122) which projects laterally from the peripheral edge of the block and is connected to the plate by means of connection pins (23, 123) with arrangement, in between, of at least one resilient spacer (24, 124) which opposes sliding of the block towards the outside of the seat in the plate, the resilient spacer (24, 124) being formed by a layer of elastomeric material and the flange being formed as a frame which surrounds the block (18, 118) as one or two parts.
Mould according to Claim 1, characterized in that the connection pin (23) passes slidably through the flange (22) and is fixed in the plate (16) by means of a first end (25) thereof, between an opposite second end (26) of the pin and flange there being provided the said resilient spacer (24) reacting between said second end of the pin and flange so as to oppose sliding of the block towards the outside of the seat formed in the plate.
Mould according to Claim 2, characterized in that the pin (23) is formed as a screw screwed into the plate and with a head which forms the said second end (26) and against which the resilient spacer bears via a metal lamina (27) arranged in between.
Mould according to Claim 3, characterized in that the bearing lamina (27) is in the form of a frame which follows the perimeter of the block and in which the screws which form the pins are screwed at intervals along its length.
Mould according to Claim 1, characterized in that the pin (123) is connected to the flange (122) by means of a first end (125) thereof, passing slidably through the plate (116), and between an opposite second end (126) of the pin and the plate (116) there is present the said resilient spacer (124) reacting between said second end of the pin and plate so as to oppose sliding of the block towards the outside of the seat formed in the plate.
Mould according to Claim 5, characterized in that the pin is formed in the manner of a screw with a head (125) which forms the said first end and with a second end (126) which is screwed into a lamina (127) bearing against the resilient spacer.
Mould according to Claim 6, characterized in that the bearing lamina (127) is in the form of a frame which follows the perimeter of the block and in which the screws which form the pins are screwed at intervals along its length.
Mould according to Claim 7, characterized in that the bearing lamina is seated inside a channel (140) formed in the plate.
Mould according to Claim 1, characterized in that an end-of-travel stop which prevents contact between the block and bottom of the seat is provided between the flange (22, 122) and plate (16, 116).
Mould according to Claim 1, characterized in that a resiliently yielding element (29, 129) for keeping the block resiliently spaced from the bottom of the seat is arranged between the flange (22, 122) and plate (16, 116).
Mould according to Claim 1, characterized in that the resilient spacer (24, 124) is formed by a layer of elastomeric material, preferably chosen from among polyurethane elastomers or NBR.
Mould according to Claim 11, characterized in that the layer of elastomeric material follows the perimeter of the block so as to be passed through at intervals by the pins (23, 123) along its length.
Mould according to Claim 1, characterized in that the flange (22, 122) is a frame which surrounds the block and which rests on a contact edge (30, 130) present on the side walls of the block which project from the seat of the block in the plate.
Mould according to Claim 13, characterized in that the said contact edge (30, 30) forms part of a groove present in the side walls of the block and inside which the said frame is partially inserted.
Mould according to Claim 3 or 6, characterized in that rigid spacers (28, 128) for limiting screwing of the screws are mounted on the screws.
Mould according to Claim 1, characterized in that the blocks are at least two in number, each inside an associated seat in the plate and with the respective chambers (20, 120) for receiving incompressible fluid which are interconnected.