EP1958745A2

EP1958745A2 - Isostatic buffer for pressing tiles and corresponding manufacturing method

Info

Publication number: EP1958745A2
Application number: EP08002726A
Authority: EP
Inventors: Luciano Silvestrini
Original assignee: MARTINELLI ETTORE Srl
Current assignee: MARTINELLI ETTORE Srl
Priority date: 2007-02-16
Filing date: 2008-02-14
Publication date: 2008-08-20
Also published as: EP1958745A3; ITMI20070298A1

Abstract

An isostatic buffer for pressing tiles comprising a base (12), a plate (13) applied to an upper face of the base and a cladding of a yieldable material (26) applied to said upper face (14) of the base to incorporate at least partially said plate and make a pressing surface of the buffer, the base comprising at least a conduit (16, 18) that leads by means of an opening (16c) onto the upper face of the base to feed incompressible fluid to an isostatic circuit formed between the plate (13) and the yieldable cladding (26). The isostatic circuit is confined between the cladding of a yieldable material (26) and an upper face of the plate (13) opposite the base, said plate being provided with a through hole (20) superimposed with said opening (16c) of the conduit to convey the incompressible fluid in the isostatic circuit.

Description

The present invention relates to an innovative isostatic buffer of the type used for producing ceramic tiles, and also to a method for manufacturing such a buffer.
In the tile-manufacturing field it has been known for some time how to make isostatic buffers the pressing surface of which is made of a cladding of a yieldable material (for example rubber or resin) below which there is formed an isostatic circuit filled in use with an incompressible fluid, typically oil.
The isostatic circuit comprises various chambers that communicate with one another (or possibly also a single chamber) and the fluid is distributed in the inside thereof so as to compensate for possible lacks of homogeneity in the density and compactness of the earth that is being pressed.
In the past various types of isostatic buffers and various methods for the manufacturing thereof have been proposed.
According to a known technique, the chambers of the isostatic circuit are obtained directly in a face of a metal base of the buffer (typically made of steel), which is then covered with a membrane made of rubber or of other yieldable materials so as to close the chambers above and form the pressing surface.
The lack of homogeneity in the materials that form the isostatic circuit, however, caused the so-called "transparency effect", i.e. the presence on the finished tile (fired and possibly glazed) of the image of the isostatic circuit. This effect is very undesirable and, if present, makes the product of a low qualitative level. Such buffers, furthermore, were affected by seal problems at the contact with the various materials that form the isostatic circuit.
According to another known technique, there is applied a drilled blade (made of metal or plastics) to an upper face of the base of the buffer, which is then coated with a cast of yieldable material (rubber or resin) so as to incorporate the blade. After the casting, the cladding is vulcanised; then oil is introduced into a cavity between the blade and the cladding to form the isostatic circuit of the buffer. The oil flows below the blade from the side facing the base.
Using this prior art, it may happen that the blade is not maintained in the correct position in the casting stage, with the possibility of giving rise to drawbacks in the isostatic circuit. Further, the fluid is not always able to be distributed in an even manner in the cavity below the blade, on the side facing the base. This may entail negative consequences both for the final quality of the tile and for the reliability of the buffer over time.
The general object of the present invention is to overcome the aforesaid drawbacks by providing a method for manufacturing isostatic buffers which is rapid and cheap, and which enables a functional and reliable buffer to be obtained.
A further object is to provide a buffer with a simple, cheap structure, so as to have a satisfactory seal and which is able to limit considerably the transparency effect in the tiles produced.
In view of these objects, it has been decided to make, according to the invention, an isostatic buffer for pressing tiles comprising a base, a plate applied to an upper face of the base and a cladding made of a yieldable material that at least partially incorporates said plate and makes a pressing surface of the buffer, the base comprising at least a conduit that leads by means of an opening onto the upper face of the base to feed incompressible fluid to an isostatic circuit formed between the plate and the yieldable cladding, characterised in that the isostatic circuit is confined between the cladding made of a yieldable material and an upper face of the plate opposite the base, said plate being provided with a through hole superimposed with said opening of the conduit to convey the incompressible fluid in the isostatic circuit.
Still according to the invention it was decided to devise a method for manufacturing isostatic buffers for pressing tiles, comprising the steps of:

providing a base of the buffer provided with at least a conduit that leads onto an upper face of the base,
inserting a plugging element into said conduit with an end protruding with respect to said face of the base,
applying to said face of the base a plate provided with a hole that is fitted on said end of the plugging element,
applying material intended for making a yieldable cladding of the buffer on said face of the base so as to incorporate at least partially the plate,
removing said plugging element from the conduit in the base,
introducing incompressible fluid through the conduit in the base and the hole in the plate to fill a cavity between the cladding made of a yieldable material and an upper face of the plate opposite the base.

In order to make the explanation of the innovative principles of the present invention and the advantages thereof over the prior art clearer, with the help of the attached drawings a possible embodiment applying such principles will be disclosed below. In the drawings:

figure 1 is a plan view of an isostatic buffer according to the invention, with the yieldable cladding removed and the plate visible,
figure 2 is a raised view of the buffer in figure 1,
figure 3 is a section view according to the plane A-A indicated in figure 1 in a first step of the buffer manufacturing process with the plate applied to the base of the buffer before the cladding is applied,
figure 4 is a section view that is similar to the preceding view, in which the cladding of a yieldable material was applied,
figure 5 is a section view that is similar to the preceding view in which the plugging element has been removed and the buffer is ready to be loaded with the oil,
figure 6 is a section view of the buffer in an operating condition with the fluid inserted under pressure into the isostatic circuit,
figure 7 is a section view according to the plane B-B indicated in figure 1 after the pressurised fluid has been introduced into the isostatic circuit,
figure 8 is an embodiment of the buffer according to the invention.

With reference to figures 1, 2, 6 and 7, there is shown an isostatic buffer 11 for pressing tiles comprising a base 12, a plate 13 applied to an upper face 14 of the base 12, and a cladding made of a yieldable material 26 applied to the face 14 to incorporate at least partially the plate 13 and make a pressing surface 40 of the buffer. The base 12 is made of a metal, for example of steel. In figure 1 yieldable material 26 is removed to enable the plate 13 to be viewed, which is preferably made of an elastically deformable material. The plate 13 forms a drilled grille with a plurality of through slots 22. In the preferred embodiment of the invention, the slots 22 are generally cross-shaped. Between four adjacent slots 22 an almost square plate 21 is defined that is connected to the adjacent plates 21 by means of connections 24. Each plate 21 has a resting protrusion 32 at the bottom that rests against the upper face 14 of the base. On the edge of the plate 13 incisions 23 are formed. It should be noted that the plates 21 could also have a different shape, for example rectangular, hexagonal, triangular or also circular. The slots could be rectilinear and not cross-shaped, as shown in the figure.
Advantageously, the cladding 26 incorporates the plate 12 so as to occupy zones 25 between the plate 13 and the upper face 14 of the base 12. The connections 24 are distanced from the face 14 and below the latter areas 25 are formed that are occupied by the cladding 26. The resting protrusions 32 are tapered and also form zones in which the cladding 26 is arranged between the base 12 and the plate 13. Advantageously, the spaces between the protrusions have a preferably trapezoidal section that widens towards the base. The presence of the areas 25 enables solid anchoring of the cladding 26 to the plate to be obtained and enables the buffer seal to be improved.
The upper face 14 of the base 12 is provided with a dip 50 that receives the plate 13 and the cladding 26. Along a raised edge 17 of the dip 50 there is formed at least a groove that forms an undercut to promote hooking of the cladding 26 to the base 12. Preferably, two perimeter grooves 61 can be made along the edge 17, as indicated in figures 3-4 showing buffer manufacturing steps that will be disclosed below. The edge 17 is dimensioned and shaped so as to withstand the stress to which the buffer is subjected during use.
The base 12 comprises at least a conduit 16 that leads by means of an opening 16c onto the upper face 14 of the base 12 to feed incompressible fluid 31 to an isostatic circuit formed between the plate 13 and the yieldable cladding 26. As an incompressible fluid any oil can be used that is normally used for isostatic buffers in the prior art. The isostatic circuit is formed by a cavity 30 above the plate 13, between the cladding 26 and an upper face 41 of the plate 13 opposite the base 12.
The plate 13 is provided with a through hole 20 (clearly visible in figure 5, where the buffer is shown before the oil is introduced) which is superimposed with the opening 16c of the conduit 16, so as to enable the oil 31 to enter the cavity 30. The oil does not flow below the plate 13, and the plate 13 remains adhering below to the base 12 also during buffer operation. The cavity 30 is formed by deforming the yieldable cladding 26, which rises through the pressure of the oil. This enables a satisfactory isostatic effect to be obtained in pressing the earth loaded on the buffer 11.
On the upper face 41 of the plate 13 opposite the base 12, preferably, there is applied a detaching element, in order to facilitate the forming of the cavity 30 when the buffer 11 is loaded with oil. On the other hand, a glue is applied to the lower face 42 of the plate 13 facing the base 12 to prevent oil being able to flow below the plate 13.
Advantageously, also the face 14 of the base, and in particular the bottom 43 of the dip 50, can be covered with glue, to improve the adhesion of the cladding 26 and of the plate 13 to the base.
As will be resumed below with reference to the buffer manufacturing method, the conduit 16 is suitable for being plugged by a plugging element 15 (shown in figures 3, 4) that occupies the hole 20 in the plate 13 during the step of applying the yieldable cladding. The conduit 16 comprises an opening 16b aligned on the opening 16c for extracting/inserting the plugging element 15, and a side opening 16a on a side of the base 12 for introducing the incompressible fluid. It should be noted that the opening 16a could also be absent, and the oil could be introduced directly from the opening 16b.
Preferably, the base 12 comprises two conduits 16, 18 for feeding the incompressible fluid arranged spaced apart near opposite sides of the buffer (fig. 1). The conduit 18 is similar to the hole 16 and comprises an opening that leads onto the face 14 of the base. The plate 13 is provided with another hole 19 that is suitable for aligning on the opening of the conduit 18 on the face 14, to enable the oil to be supplied. This teaching enables optimum positioning of the plate 13 to be obtained during the step of casting the yieldable cladding, in addition to enabling the isostatic fluid to be supplied correctly. The conduit 18 could also be shaped in a different manner from the hole 16.
A buffer 11 manufacturing cycle according to the invention will now disclosed with reference to figures 3 to 6. In these figures there is shown only the conduit 16, but it must be understood that similar operations are performed at the conduit 18 on the opposite side of the buffer 11.
Initially, the base 12 is provided, which is provided with the conduit 16 and the dip 50 on the upper face 14 thereof, as disclosed previously.
In the conduit 16 the plugging element 15 is inserted with the end 15a protruding from the bottom 43 of the dip 50 on the face 14 of the base.
The plugging element 15 is inserted in a stable manner into the conduit to ensure correct positioning and anchoring of the plate 13 during the step of applying the cladding. For this purpose, the plug 15 can be provided with a thread to be screwed into a corresponding threaded portion of the conduit 16.
To the face 14 of the base the plate 13 is then applied with a hole 20 fitted on said end 15a of the plugging element 15, as shown in figure 3. The head 15a of the plug is flush with the upper surface 41 of the plate 13, to enable the hole 20 to be maintained completely free during the casting step.
The plate 13 is still firmly anchored to the base exploiting the plugs 15 (a plug is also provided on the opposite side of the buffer in the conduit 18), and rests with the resting protrusions 32 on the bottom 43 of the dip 50 in the base.
Advantageously, before applying the plate 13 to the base glue is spread both on the bottom 43 of the base and on the lower face 42 of the plate 13. On the other hand, detaching element is applied to the upper face 41 of the plate 13.
Then the material intended to make the yieldable cladding 26 can be applied to the face 14 of the base so as to incorporate the plate 13 (fig. 4).
The material (a rubber or a resin of the type used for the cladding of the isostatic buffers) is applied by casting into the dip 50, after which vulcanisation is performed to form the cladding 26. The cladding is well anchored to the plate, occupying the slots 22 and also the zones below the plate 13, in particular the zones 25 below the connections 24 between adjacent platelets 21 of the plate 13.
After vulcanisation has been performed, the plugging element 15 is removed from the conduit 16 through the opening 16b arranged aligned on the opening 16c on the face 14 of the base. The opening 16b arranged on a lower face of the base is then closed with a seal cap 28, as shown in figure 5.
The presence of the plug 15 during the step of applying the cladding 26 enables the hole 20 to be kept free in the plate, beyond the conduit 16 for the subsequent supplying of the oil.
A joint 29 can then be applied at the opening 16a on the conduit 16 obtained on a side of the base 12. To the joint 29 a known hydraulic unit is attached to supply the oil 31 in the conduit 16.
Through the conduit 16 and the hole 20 the oil 31 reaches the cavity 30 between the upper face 41 of the plate 13 and the cladding 26, as shown in figures 6 and 7. A plurality of isostatic chambers are thus created above the plates 21. The chambers are connected together hydraulically and are able to develop the so-called "isostatic effect" to compensate for possible defects in loading the earth. The oil can be loaded at a pressure between 0.5 and 5 bar.
The yieldable cladding 26 is applied to the buffer so as to fill almost all the dip 50 on the face 14 thereof of the base, engaging also the undercuts defined by the grooves 61 on the edge 17 of the face 14, to have better anchoring on the base 12.
In figure 8 there is shown a view, similar to figure 6, of an embodiment of the buffer in figure 6. For the sake of simplicity, elements similar to those in figure 6 are indicated with the same numbering, not requiring a further description. According to the version, the plate 13 has a collar 120 that surrounds the hole 20 below. The base 12 has a corresponding step widening 116 at the mouth 16c of the conduit. In this manner, when the plate 13 is positioned on the base, the collar 120 and widening 116 coupling performs a function of perfect centring of the plate and maintains the holes 20 well aligned on the conduits 16.
As a further modification the plate has a peripheral edge zone raised from the base and which is provided with a plurality of holes or slots 122 aligned along the edge and more external resting feet 170 on the bottom of the seat in the base. The feet may advantageously have a cylindrical shape.
Further, the thin circumferential grooves 61 are refitted by a groove or rounded circumferential depletion 161 to connect the side edge and the upper face of the base that receives the plate 13. It has been found that all this ensures optimum gripping of the yieldable cladding even in the event of diagonal square masonry. Further, machining of the edge is facilitated.
At this point it is clear how the objects of the present invention have been achieved.
In particular, a rapid and cheap method for manufacturing buffers for pressing tiles has been provided.
The isostatic circuit is arranged entirely above the plate, which in use is positioned solidly in relation to the base. This enables an excellent isostatic effect to be achieved and equal pressing in all parts of the tile to be obtained.
It is further possible to apply the yieldable cladding, maintaining the plate in the correct position, owing to the presence of the heads of the plugging elements to which the plate is anchored. This enables an isostatic circuit to be obtained that is positioned in the desired manner below the pressing surface.
The buffer obtained according to the invention is provided with an isostatic circuit that is not in contact with steel parts, which enables the transparency effect to be reduced. Further, the buffer has a satisfactory seal.
The buffer is further characterised by great constructional simplicity and low production costs. In order to anchor the plate to the base, it is in fact sufficient to provide holes on the plate 13 that are suitable for receiving the heads of the plugging elements, without the need for particular or costly machinings on the buffer pieces.
Further, the buffer can be rubber-coated with various masonry patterns as the machinings are not linked to the pattern.
Naturally, the above description of an embodiment applying the innovative principles of the present invention is provided by way of example of such innovative principles and must not therefore be taken to limit the legal scope of what is claimed herein.
For example, the slots 22 could also be absent, and the isostatic circuit could consist of a single large chamber above the plate.

Claims

Isostatic buffer for pressing tiles comprising a base (12), a plate (13) applied to an upper face of the base and a cladding made of a yieldable material (26) that at least partially incorporates said plate and makes a pressing surface of the buffer, the base comprising at least a conduit (16, 18) that leads by means of an opening (16c) onto the upper face of the base to feed incompressible fluid to an isostatic circuit formed between the plate (13) and the yieldable cladding (26), characterised in that the isostatic circuit is confined between the cladding of a yieldable material (26) and an upper face of the plate (13) opposite the base, said plate (13) being provided with a through hole (20) superimposed with said opening (16c) of the conduit to convey the incompressible fluid into the isostatic circuit.
Isostatic buffer according to claim 1, characterised in that the upper face (14) of the base is provided with a dip (50) that houses the plate (13) and the cladding (26).
Isostatic buffer according to claim 2, characterised in that along an edge (17) of the dip (50) there is at least a groove (61, 161) that forms an undercut to promote hooking of the cladding (26) to the base (12).
Isostatic buffer according to claim 1, characterised in that the coat made of a yieldable material (26) partially incorporates the plate (13) so as to occupy zones (25) between the plate (13) and the upper face (14) of the base (12).
Isostatic buffer according to claim 1, characterised in that the plate (13) comprises resting portions (32) that contact the upper face (14) of the base (12).
Isostatic buffer according to claim 1, characterised in that the plate (13) has a plurality of through slots (22) and is shaped as a grille.
Isostatic buffer according to claim 6, characterised in that said slots (22) are generally cross-shaped and define a plurality of plates (21), each of which has a resting protrusion (32) that rests on the upper face (14) of the base (12).
Isostatic buffer according to claim 1, characterised in that there is applied a detaching element to the upper face (41) of the plate (13) opposite the base (12).
Isostatic buffer according to claim 1, characterised in that there is applied a glue to the lower face (42) of the plate (13) facing the base (12).
Isostatic buffer according to claim 1, characterised in that the conduit (16) inside the base (12) is suitable for being plugged by a plugging element (15) that occupies the hole (20) in the plate (13) during the step of applying the yieldable cladding (26).
Isostatic buffer according to claim 10, characterised in that the conduit (16) in the base comprises an opening (16b) aligned on the opening (16c) on the upper face (14) intended for extracting/inserting the plugging element (15), and a side opening (16a) on a side of the base (12) for introducing the incompressible fluid.
Isostatic buffer according to claim 1, characterised in that it comprises two conduits (16, 18) for feeding the incompressible fluid, corresponding to two holes (19, 20) in the plate (13).
Isostatic buffer according to claim 12, characterised in that said conduits (16, 18) are arranged spaced apart near opposite sides of the buffer (11).
Isostatic buffer according to claim 1, characterised in that the plate (13) is made of an elastically deformable material.
Isostatic buffer according to claim 1, characterised in that the base (12) is made of metal.
Isostatic buffer according to claim 1, characterised in that the through hole (20) comprises a collar (120) that is inserted into a complementary widening (116) of said opening (16c) of the conduit.
Isostatic buffer according to claim 1, characterised in that the plate comprises along the peripheral edge thereof resting feet (170) on the upper face of the base.
Isostatic buffer according to claim 17, characterised in that in a zone along the peripheral edge of the plate that is raised from the upper face of the base and is near the feet there are holes or through slots (122) for grasping the yieldable cladding.
Isostatic buffer according to claim 3, characterised in that the groove (161) has a rounded shape for connecting the side edge and the upper face of the base that receives the plate (13).
Isostatic buffer according to claim 7, characterised in that the resting protrusions (22) are tapered towards the base.
Isostatic buffer according to claim 20, characterised in that between the protrusions there are defined spaces with a section that widens towards the base and which are filled by the yieldable cladding.
Isostatic buffer according to claim 21, characterised in that the spaces have a generally trapezoidal section.
Method for manufacturing isostatic buffers for pressing tiles comprising the steps of:
- providing a base (12) of the buffer provided with at least a conduit (16, 18) that leads onto an upper face (14) of the base,

- inserting a plugging element (15) into said conduit (16) with an end (15c) protruding with respect to said face (14) of the base,

- applying to said face (14) of the base a plate (13) provided with a hole (20) that is fitted on the said end (15c) of the plugging element (15),

- applying material intended for making a yieldable cladding (26) of the buffer on said face (14) of the base so as to incorporate at least partially the plate (13),

- removing said plugging element (15) from the conduit (16) in the base,

- introducing incompressible fluid (31) through the conduit (16) into the base and the hole (20) in the plate to fill a cavity (30) between the cladding of made of a yieldable material (26) and an upper face (41) of the plate (13) opposite the base (12).
Method according to claim 23, in which the material intended for making the yieldable cladding is applied to the base (12) through casting and is then vulcanised to obtain the yieldable cladding (26) intended for making a pressing surface (40) of the buffer.
Method according to claim 23, in which the material intended for making the yieldable cladding occupies areas between the plate (13) and the upper face (14) of the base (12).
Method according to claim 23, in which the yieldable cladding (26) is applied to the base (12) at a dip (50) on said face (14) thereof, the plate (13) being received in the dip.
Method according to claim 23, in which there is applied a detaching element to the face of the plate (13) opposite the base (12), there being applied glue to the face facing the base (12).
Method according to claim 23, in which before applying the plate (12) to the base, glue is applied to the face (14) of the base (12).
Method according to claim 23, in which the plugging element (15) is extracted from the conduit (16) through an opening (16b) aligned on the opening (16c) of the conduit that opens on the upper face (14) of the base, the conduit being provided with a further opening (16a) on a side of the base (12) for supplying incompressible fluid.