WO2017178972A1

WO2017178972A1 - Line for the production of sanitary articles

Info

Publication number: WO2017178972A1
Application number: PCT/IB2017/052090
Authority: WO
Inventors: Elio Cristoforo MARRA
Original assignee: Siti - B&T Group S.P.A.
Priority date: 2016-04-12
Filing date: 2017-04-11
Publication date: 2017-10-19
Also published as: EP3442760A1; BR112018071044A2; ITUA20162529A1; CN109311181A; CN109311181B

Abstract

A line for the production of sanitary articles comprises a support frame (2), at least one molding group (4) slidably associated with the support frame (2) along a first direction (3), wherein the molding group (4) comprises at least two lateral molds (6, 7) and a lower central mold (8) adapted to selectively delimit one molding cavity (5) of at least one sanitary article (S), members (9) for moving the two lateral molds (6, 7) and the lower central mold (8) in a mutual abutment or moving away along the first direction (3) and further members (11) for moving the lower central mold (8) outside the molding cavity (5) in order to facilitate the access, from the side and/or from above, to a sanitary article (S) formed and supported on the lower central mold (8).

Description

"LINE FOR THE PRODUCTION OF SANITARY ARTICLES

TECHNICAL FIELD OF THE INVENTION

The present invention regards a line for the production of sanitary articles, by means of the pressurized casting of slip within molds or groups of molds.

PRIOR ART

Today, the molding of sanitary articles occurs by means of the pressurized casting of slip within molds or groups of molds of modular type comprising two or more parts connectable together to define a molding cavity.

The number of parts that constitute the mold can vary as a function of the geometry of the article to be produced, for example with reference to the presence of undercut portions, of openings, etcetera or lack thereof.

The single parts of the mold can be connected to a line support structure, in hung configuration, and slidable movable along the same.

Therefore, the single parts which constitute a mold can be mutually moved closer or away, in order to be placed in mutual abutment, to delimit a molding cavity, or moved away in order to allow the extraction of the sanitary article from the mold following its molding.

The molds are abutted together along the line structure, to form a set of molds that is clamped at the ends in order to prevent, during the molding step, the undesired leakage of slip through the junction portions along which the single parts of the molds are mutually abutted.

Once the molding step has been completed, there is then a step of extracting the formed article.

Such step is extremely delicate since the formed article is found in a so-called "green" state, i.e. not yet provided with the mechanical strength that it will have following a subsequent step of firing in a furnace.

Therefore, during the extraction step the green sanitary article could be irreparably damaged and hence determine a discard, with consequent negative repercussions on the production costs. In making sanitary articles such as toilet bowls or bidets, it is known to use molds comprising for example three mutually movable parts, of which two laterally delimit the molding cavity, while the remaining central parts delimit such cavity, respectively, from above and from below.

During the extraction step, following the casting step, the lateral, upper and lower parts of the mold are separated from each other, by mutually moving them away along the support structure. Then, one proceeds by partially lowering the lower central part and introducing, in the cavity thus delimited, a gripping member adapted to clamp the formed article without damaging it.

With the sanitary article firmly clamped, one proceeds by further lowering the lower part of the mold, separating the base portion of the article therefrom.

In the case of the production of toilet bowls and bidets, the complexity of the shapes obliges the use of multiple-part molds, 3 to 5 parts for each single body, and such complexity also affects the spaces available for the extraction of the products from the molds.

Indeed, in order to be able to extract the article from the molding cavity delimited between the open parts of the mold, it is necessary to execute a relative vertical movement between the lateral, upper and lower parts of the mold, so as to release the article from towards the interior of the molding cavity and, then, extract the article from the molding cavity by moving the grip members back.

During the extraction of the article from the mold group, it is necessary to pay particular attention to the portions of the lower part and of the upper part of the mold projecting inside the molding cavity, for the purpose of preventing the article from impacting against such portions and being damaged.

It is also observed that, in order to facilitate the insertion of the grip members between the molds, it is necessary to considerably space the lateral walls and the upper and lower central portions from each other along the support structure, in order to provide the necessary maneuvering space for the grip members themselves.

One such production line of toilet bowls and/or bidets thus requires particular attention during the extraction step. As stated, in order to be able to extract the product from the molds, it is necessary to mutually move away the lateral, upper and lower parts of the molds and, therefore, the architecture of the casting machines set for the molding must provide for suitable spaces for ensuring the necessary travel of the molds and of their single parts for the purpose of providing a suitable maneuvering space and facilitating the extraction step. In the presence of a casting machine with a pre-established architecture, such travel is determined by the overall proportions of the machine itself and, usually, it is predefined and non-modifiable; therefore, the shape and the geometric proportions of the objects that can be produced with one such machine are strongly limited by the geometry of the machine itself. In detail, the travel with which the single parts of the mold can be mutually moved away determines the access space that can be provided to the grip members for the movement thereof within the molding cavity during the extraction of the model, thus affecting the geometry and maximum dimensions of the model that can be achieved.

In addition, the need to considerably space the molds from each other along the support structure in order to arrange the aforesaid maneuvering space for the grip members, along with the high number of maneuvers required for extracting the molded article from the molding cavity, prolongs the extraction times, negatively affecting the production rate of the entire production line.

US 2016/0009001 Al describes an apparatus for making sanitary articles by means of the pressurized casting of slip inside a modular mold.

There is the need in the field to improve the performances of a line for the production of sanitary articles by means of the pressurized casting of slip within molds or mold groups, in the scope of a solution that is easy to actuate and with high production rate, capable of overcoming the above-lamented drawbacks of the production lines of known type.

OBJECTS OF THE INVENTION

Therefore, the main object of the present invention is to improve the state of the art relative to a line for the production of sanitary articles by means of pressurized casting of slip in modular molds.

In the scope of such task, one object of the present invention is to provide a line for the production of sanitary articles able of overcoming the drawbacks of the production lines of known type, with particular reference to the possibility of facilitating the extraction of the formed articles from the respective mold groups, preventing the articles from being damaged during their extraction.

Another object of the present invention is to provide a production line for sanitary articles in which the step of extraction requires lower actuation times than those of the known solution, which increases the production rate of the entire line.

A further object of the present invention is to provide a production line for sanitary articles that is easy to use.

Another object of the present invention is to provide a production line that allows making sanitary articles of different shape even if in the scope of a solution with high production efficiency.

According to one aspect of the present invention, a line is provided for the production of sanitary articles according to claim 1.

According to a further aspect of the present invention, a framework with variable geometry is provided for a line for the production of sanitary articles according to claim 12.

The dependent claims refer to preferred and advantageous embodiments of the invention.

A production line for sanitary articles according to the present invention can also be easily used in production plants for the integration or substitution of a preexisting production line.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will be more evident from the detailed description of a preferred but not exclusive embodiment of a production line for sanitary articles illustrated by way of a non-limiting example in the enclosed drawing tables in which:

figure 1 is a side view of a detail of a production line according to the present invention;

figure 2 is a detailed view of several components of a production line pursuant to figure 1 ;

figures 3, 5 and 7 are side views of several operating steps of a production line for sanitary articles according to the present invention; and

figures 4 and 6 are front views of several steps for opening the molds of a production line for sanitary articles according to the present invention.

EMBODIMENTS OF THE INVENTION

With reference to the enclosed figures, a line for the production of sanitary articles is indicated overall with the reference number 1.

The production line 1 according to the present invention allows molding sanitary articles by means of the pressurized injection of slip inside single molding cavities, according to modes known in the field and hence not described hereinbelow.

In the enclosed figures and in the following description, with the term "sanitary article" reference is made to a toilet bowl, even if it is intended that the production line 1 according to the present invention can be used in the production of different sanitary items, such as bidets, without any limitation.

As illustrated in the enclosed figures, the production line 1 comprises a support frame 2 that is extended along a first direction 3, for the slidable support of at least one molding group 4 for the molding of respective sanitary articles S.

Preferably, the production line 1 comprises a plurality of molding groups 4 arranged in succession, one after the other, along the support frame 2.

The presence of a plurality of molding groups 4 along the support frame 2 allows the simultaneous molding of a plurality of sanitary articles S in the scope of a solution with high production rate.

According to one version of the present invention, illustrated in the enclosed figures, the single molding groups 4 are connected in hung configuration with respect to the support frame 2.

By way of example, with reference to figure 1 , a first molding group 4 is illustrated with a continuous section line while a second molding group 4' is illustrated with a discontinuous section line, in a position abutted on the first molding group 4.

During the molding step, the single molding groups 4 are placed along the support frame 2 abutted against each other, forming a set of molds that is clamped at the opposite ends by means of clamping means not illustrated in the enclosed figures. Nevertheless, further embodiments of the production line according to the present invention are possible with respect to that described above, in which the support frame 2 comprises an upper portion for the hung connection of several molding groups 4 and a lower portion 2' for the slidable support of other molding groups 4, without any limitation.

The single molding groups 4 can comprise multiple molds, mutually movable, adapted to delimit at their interior - once placed in mutual abutment - at least one molding cavity 5. Subsequently, by means of the mutual moving away of the molds, the extraction of the green-molded sanitary article S from the molding cavity 5 is allowed.

According to one version of the present invention, the molding group 4 can comprise at least two lateral molds 6, 7 and one lower central mold 8, interposed between the two lateral molds 6, 7.

The lateral molds 6, 7 and the lower central mold 8, one placed in mutual abutment, delimit the molding cavity 5.

The lateral molds 6, 7, as well as the lower central mold 8, reproduce a reverse image of a respective portion of the sanitary article S to be molded.

In the enclosed figures, the lateral molds 6, 7 and the lower central mold 8 are schematically illustrated as blocks, even if it is intended that the same have respective shaped cavities adapted to reproduce the shape of respective portions of the sanitary article S to be made.

More in detail, it is observed that the two lateral molds 6, 7 and the lower central mold 8 are mutually movable with respect to the support frame 2, along the first direction 3. The production line 1 comprises means 9 for moving the two lateral molds 6, 7 and the lower central mold 8 mutually closer, until they abut against each other, or away from each other along the first direction 3.

For such purpose, the moving means 9 can comprise trolleys 10, each associated with a respective lateral mold 6, 7 or with the lower central mold 8 as well as driving means, not illustrated in the enclosed figures, operatively connected to the molds 6, 7 and/or 8 and adapted to selectively control the movement of the latter along the support frame 2.

According to one version of the present invention, the lateral molds 6, 7 and the lower central mold 8 can be mutually connected by means of cross means or the like, not illustrated in the enclosed figures, such that the movement of one of the two lateral molds 6, 7 along the first direction 3, moving away from the other of the central molds 6, 7, causes the driving of the lower central mold 8 and its movement relative to both the two lateral molds 6, 7. On the other hand, the movement of one of the lateral molds 6, 7 closer to the other also causes the driving of the lower central mold 8 closer to such other lateral mold 6, 7.

The lateral molds 6, 7 and the lower central mold 8 each have respective abutment portions which when placed in mutual abutment cause the sealing of the molding cavity 5, for the purpose of preventing the leakage of slip introduced under pressure within the same.

The production line 1 comprises further means for moving the lower central mold 8 away from the molding cavity 5, indicated overall with 1 1 (see figures 3, 5 and 7)·

As better described hereinbelow, the further moving means 1 1 are configured in order to allow the relative movement of the lower central mold 8 with respect to the lateral molds 6, 7 along a second direction 13 orthogonal or substantially orthogonal to the first direction 3.

More precisely, the further moving means 1 1 cause the movement of the lower central mold 8 with respect to the lateral molds 6, 7 in a manner such to facilitate the access, from the side and/or from above, to the sanitary article S formed and supported on the lower central mold 8, facilitating the extraction thereof from the molding group 4 itself, as better described hereinbelow.

The further moving means 1 1 can comprise first driving means 12 for driving the lower central mold 8 with respect to the two lateral molds 6, 7 along a second direction 13 substantially orthogonal to the first direction 3.

More in detail, the first driving means 12 determine the driving of the lower central mold 8 closer to or away from the two lateral molds 6, 7, below thereto. The further moving means 1 1 can comprise second driving means 14 for moving the lower central mold 8 with respect to the lateral molds 6, 7 along a third direction 15, substantially orthogonal to the first direction 3 and to the second direction 13, as better described hereinbelow.

In particular, the second driving means 14 are configured in order to allow the movement of the lower central mold 8 and, consequently, of the sanitary article S which after its molding is supported on the lower central mold 8, completely outside the molding cavity 5 in order to render it easily accessible both from the side and from above, in order to facilitate the extraction thereof from the molding group 4.

Each molding group 4 comprises a structure with variable geometry 16, for the support at least of the lower central mold 8.

The further moving means 1 1 are operatively connected to the structure with variable geometry 16 in order to determine the movement of the lower central mold 8 relative to the other molds 6, 7 of the molding group 4, along the second direction 13 and/or the third direction 15.

More particularly, the structure with variable geometry 16 can comprise an upper portion 17, a lower portion 18 and a central portion 19 of connection between the upper portion 17 and the lower portion 18, wherein the lower portion 18 is movable with respect to the upper portion 17 along the second direction 13 and/or the third direction 15.

According to a preferred version of the present invention, the structure with variable geometry 16 is substantially configured as a "C". The lower central mold 8 is operatively connected to the lower portion 18 of the structure with variable geometry 16.

As stated, the lower portion 18 is movable with respect to the upper portion 17 and to the central portion 19 in order to allow the moving away of the lower central mold 8 from the molding cavity 5.

For such purpose, according to one version of the present invention, the structure with variable geometry 16 can comprise a first guide 20, of extensible or articulated type, associated with the central connection portion 19 in order to allow the mutual moving closer or away movement between the lower portion 18 and the upper portion 17 along the second direction 13.

More in detail, the first guide 20 can be of extensible type and comprise a first element 21 and a second element 22 connected mutually movable along the second direction 13, e.g. by means of a trolley 23 or a slidable guide or friction guide or similar means suitable for such purpose.

In particular, the first element 21 can be constrained to the upper portion 17 while the second element 22 can be constrained to the lower portion 18.

Alternatively, the first guide 20 can be of telescopic type, in which the first element 21 and the second element 22 are slidably and mutually associated, one inside the other.

The first driving means 12 are operatively connected to the central portion 19 and, more precisely, to the movable portions of the first guide 20, in order to move the upper portion 17 and the lower portion 18 closer or away from each other along the second direction 13.

According to one version of the present invention, the first driving means 12 can comprise an actuator of linear type, of piston-cylinder type, pinion-rack type or similar type, adapted to drive the lower central mold 18 along the second direction 13.

Analogous to that described above, the structure with variable geometry 16 can comprise a second guide 24 associated with the lower portion 18 in order to allow the lower portion 18 and the lateral molds 6, 7 to move closer or away from each other along the third direction 15.

More precisely, the second guide 24 can be of extensible or articulated type and comprise at least one fixed portion 25 and at least one movable portion 26, mutually movable.

By way of example, the fixed portion 25 can be constrained to the central portion 19 while the movable portion 26 can be associated below the lower central mold 8.

The second driving means 14 are operatively associated with the lower portion 18 of the structure with variable geometry 16 in order to control the mutual movement between the fixed portion 25 and the at least one movable portion 26 along the third direction 15.

The second driving means 14 can comprise an actuator of linear type, of piston- cylinder type, pinion-rack type or similar type, operatively associated with the second guide 24, adapted to drive the lower central mold 18 along the third direction 15.

According a further aspect of the present invention, the molding group 4 can comprise an upper central mold 27, interposed between the two lateral molds 6, 7, above the lower central mold 8.

According to a preferred version, the upper central mold 27 can have at least one element projecting inside the molding cavity 5, not illustrated in the enclosed figures, adapted to make at least one respective opening in the sanitary article S. The upper central mold 27 is operatively and slidably connected to the support frame 2.

More in detail, the upper central mold 27 can be connected to the upper portion 17 of the structure with variable geometry 16. Therefore, following the movement of the structure with variable geometry 16 along the support frame 2, in the first direction 3, the movement is caused both of the upper central mold 27 and of the lower central mold 8.

Possibly, the production line 1 according to the present invention can comprise a further central mold 28, commonly defined "fifth part", for obtaining at least one undercut portion inside the molding cavity 5.

According to one version of the present invention, the further central mold 28 can be operatively associated with the structure with variable geometry 16, in a manner so as to be movable along the second direction 13, for the purpose of supporting respective portions of the sanitary article S. If desired, the further central mold 28 can be moved simultaneously with the lower central mold 8 along the second direction 13.

Hereinbelow, a brief description is reported of the operation of a production line 1 according to the present invention.

During the step of molding at least one sanitary article S, a molding group 4 is placed in a first work configuration, in which the single lateral molds 6, 7, the lower central mold 8 and possibly, if provided, the upper central mold 27 are placed in mutual abutment to delimit a sealed molding cavity 5.

Inside the molding cavity 5, slip is injected under pressure, up to the filling of the cavity itself.

At the end of the step of filling and subsequent solidification, the step starts for extracting the molded sanitary article S from the molding group 4.

The extraction step initially provides for the mutual moving away of the lateral molds 6, 7 and of the lower central mold 8, and possibly of the upper central mold 27, if provided, along the first direction 3, up to the complete extraction of the sanitary article S from the lateral molds 6, 7.

Following the moving away of the molds 6, 7, 8 and, if provided, of the upper central mold 27, along the first direction 3, the sanitary article S is then supported at least on the lower part by the lower central mold 8.

If an upper central mold 27 is present, the sanitary article S is retained between the latter and the lower central mold 8.

In addition, if a further central mold 28 is present, the sanitary article S is at least partly in abutment against the latter.

Hence, by means of the first driving means 12, the lower central mold 8 is moved, and if present the further central mold 28 connected thereto is moved, vertically away from the lateral molds 6, 7 and, if present, from the upper central mold 27, along the second direction 13, actually lowering the sanitary article S with respect to the height at which the lateral molds 6, 7 themselves are positioned.

Subsequently, by means of the second driving means 14, the lower central mold 8 is moved away from the lateral molds 6, 7 and, if present, from the further central mold 28, and hence from the molding cavity 5, along the third direction 15, until the sanitary article S is completely extracted outside the molding cavity 5 itself. Finally, for the removal of the sanitary article S, supported by the lower central mold 8, grip members can be used, not illustrated in the enclosed figures, that are adapted to fasten around the sanitary article S without damaging it and to lift it with respect to the lower central mold 8, until the separation thereof from the support is caused.

From that described above, it is evident that the production line 1 according to the present invention allows attaining the preset objects.

At the end of the extraction step, in fact, the sanitary article S is positioned completely outside the molding cavity 5 and thus is easily accessible, both from the side and from above, in order to facilitate the removal thereof from the lower central mold 8 on which it is supported.

In the immediate vicinity to the lower central mold 8, placed in extracted configuration, in fact, there are no obstacles that can limit or interfere with the movement of the grip members adapted to pick up the sanitary article S.

Furthermore, in the production line 1 according to the present invention, the lateral molds 6, 7 and the lower central mold 8, and possibly the upper central mold 27 if provided, can be mutually moved along the first direction 3 with a smaller travel with respect to that provided in the known solutions.

In the production line 1 , in order to extract the molded sanitary article S from the molding cavity 5, it is not necessary to introduce the grip members inside the latter, since the sanitary article S itself is moved away and completely extracted from the molding cavity 5 by means of the lower central mold 8.

Through the movement of the lower central mold 8 along the second direction 13 and the third direction 15, away from the molding cavity 5, it is in fact possible to arrange the sanitary article S completely outside the molding cavity 5 delimited between the lateral molds 6, 7, the lower central mold 8 and, if present, the upper central mold 27.

The step of removing the sanitary article S from the molding group 4 is thus easy to carry out, independent of the configuration and dimensions of the sanitary article S. In fact, the removal of the sanitary article S from the molding group 4 provides for the relative movement of the molds 6, 7, 8 and, if present, of the upper central mold 27, which is actuated in an automated manner and is such to prevent damaging the sanitary article S. Hence, the subsequent separation of the sanitary article S from the lower central mold 8 occurs by means of the grip members that are movable relative to the lower central mold 8 outside the molding cavity 5. The removal step, therefore, can be carried out efficiently and quickly since the absence of obstacles in the immediate proximity to the lower central mold 8, placed in a position completely extracted from the molding cavity 5, avoids possible impacts thereof against obstacles, such as the portions of the lateral molds 6, 7 or of the upper central mold 27, if provided, projecting inside the molding cavity 5.

In fact, the times necessary for the extraction of the sanitary article S from the molding group are reduced with respect to the solutions of known type, which increases the production rate of the production line 1.

For such purpose, it is underlined that in order to be able to extract the sanitary article S from the molding group, it is possible to mutually space the lateral molds with a smaller travel than that which is necessary in the solutions of conventional type, in the scope therefore of a solution that allows an overall reduction of the time necessary to carry out such activity.

The entire production line 1 is more compact, since it is not necessary to provide a wide lateral access opening to the sanitary article S for the introduction of the grip elements inside the molding cavity 5; in addition, there is also more freedom in the design of the models, with particular reference to the size of the height or to the overall geometry thereof, allowing the production of pieces that are complex or having advanced design.

The invention thus conceived is susceptible of numerous modifications and variations, all falling within the scope of the inventive concept.

In addition, all details can be substituted by other technically equivalent elements. In practice, the materials used as well as the contingent sizes and shapes can be of any type in accordance with requirements, without departing from the protective scope of the following claims.

Claims

claims

Production line for sanitary articles, said production line comprising a support frame (2), at least one moulding group (4) associated to said support frame (2) in a sliding manner along one first direction (3), wherein said moulding group (4) comprises at least two lateral moulds (6, 7) and a lower central mould (8) provided between said two lateral moulds (6, 7) along said first direction (3), designed to selectively delimit one moulding cavity (5) of at least one sanitary article (S), means (9) for moving saidat least two lateral moulds (6, 7) and said lower central mould (8) in a reciprocal abutment or moving away along said first direction (3), said production line being characterized in that it comprises further means (1 1) for moving said lower central mould (8) externally with respect to said moulding cavity (5) delimited between said lateral moulds (6, 7), in order to facilitate the access, from the side and from the above, to a sanitary article (S) provided in an extracted position from said mould cavity (5) and supported on said lower central mould (8).

Production line for sanitary articles according to claim 1 , wherein said further moving means (1 1) comprise first means (12) for driving said lower central mould (8) below said two lateral moulds (6, 7), approaching to or moving away from each other, along a second direction ( 13) substantially orthogonal to said first direction (3).

Production line for sanitary articles according to claim 1 or 2, wherein said further moving means (1 1) comprise second means (14) for driving said lower central mould (8) away from said lateral moulds (6, 7) along a third direction (15) substantially orthogonal to said first direction (3) and said second direction (13).

Production line for sanitary articles according to claim 2 or 3, wherein said moulding group (4) comprises one structure having a variable geometry (16) to which said lower central mould (8) and said further moving means (1 1) are operatively connected, for the selective movement of said lower central mould (8) along said second direction (13) and/or said third direction (15).

5. Production line for sanitary articles according to the previous claim, wherein said structure having a variable geometry (16) comprises an upper portion (17), a lower portion (18) to which said lower central mould (8) is connected, and a vertical central portion (19), for the connection between said upper portion (17) and said lower portion (18), wherein said lower portion (18) is movable with respect to said upper portion (17) along at least said second direction (13) and/or said third direction (15).

6. Production line for sanitary articles according to claim 5, wherein said structure having a variable geometry (16) comprises, at said central portion (19), at least a first guide (20), of the extensible or articulated type, for the translation of said lower portion (18) along said second direction (13).

7. Production line for sanitary articles according to claim 5, wherein said structure having a variable geometry (16) comprises, at said lower portion (18), at least a second guide (24), of the extensible or articulated type, for the translation of said lower portion ( 18) along said third direction (15).

8. Production line for sanitary articles according to claim 4, wherein said moulding group (4) comprises an upper central mould (27), provided between said at least two lateral moulds (6, 7), upperly aligned with respect to said lower central mould (8), wherein said upper central mould (27) is suitable for delimiting the above of said moulding cavity (5).

9. Production line for sanitary articles according to the previous claim, wherein said upper central mould (27) is connected to said upper portion (17) of said structure having a variable geometry (16).

10. Production line for sanitary articles according to claim 4, comprising a further central mould (28), for obtaining undercut portions in said moulding cavity (5), wherein said further central mould (28) is operatively associated to said structure having a variable geometry (16).

1 1. Production line for sanitary articles according to the previous claim, wherein said further central mould (28) is movable with respect to said lateral moulds (6, 7) along at least said first direction (3) and/or said second direction (13).

12. Structure having a variable geometry (16) for a production line for sanitary articles, wherein said structure having a variable geometry (16) is configured substantially as a "C" and comprises an upper portion (17), a lower portion (18) and a central vertical portion (19) for the connection between said upper portion (17) and said lower portion (18), and means (1 1) for moving said lower portion (18) away from or towards said upper portion (17) and said central portion (19) along at least two directions (13, 15) perpendicular with each other.