WO2011104732A1 - A unit for applying a label on a relative article - Google Patents

Abstract

A labelling unit (15) comprising supporting means (20) movable along a given path (P) past a label input station (11); the supporting means (20) comprising a main body (25) displaceable along the path (P), a top. platform (26) and releasable fastening means (27) to secure the top platform (26) onto the main body (25); the releasable fastening means (27) comprise first and second engaging means (33, 32) respectively carried by the main body (25) and the top platform (26) and which can be coupled and uncoupled by a sliding movement along a direction (X) transversal to the path (P), and a retaining element (36) movable transversally to the mentioned direction (X) between a fastening position and a release position, in which it respectively prevents or allows uncoupling of the first and second engaging means (33, 32).

Description

A UNIT FOR APPLYING A LABEL ON A RELATIVE ARTICLE

TECHNICAL FIELD

The present invention relates to a unit for applying a label, in particular made of heat-shrinking film, on a relative article, such as a bottle or a generic container, which the following description will refer to, although this is in no way intended to limit the scope of protection as defined by the accompanying claims.

BACKGROUND ART

As it is generally known, labelling machines are used to apply labels to containers or articles of all sort. Typically used with beverage bottles or vessels are tubular labels (commonly called "sleeve labels"), which are obtained by:

- cutting the web unwound from a supply roll into a plurality of rectangular or square labels;

- bending each label in a cylindrical configuration such that the opposite vertical edges overlap one another; and

- welding the overlapped edges of each cylindrical label.

A particular type of labelling machine is known which serves to bend and weld labels in a tubular configuration and to produce insertion of containers into 2 IT2010/000079

the so formed tubular labels . This kind of machine basically comprises a carousel rotating about a vertical axis to define a circular path, along which it receives a succession of unlabelled containers and, then, a succession of rectangular or square labels from respective input wheels, produces application of the labels in' a tubular configuration onto the respective containers and releases the labelled containers to an output wheel .

More specifically, the carousel comprises a plurality of labelling units which are equally spaced about the rotation axis , are mounted along a peripheral edge of the carousel and are moved by the latter along the above-mentioned circular path.

Each labelling unit comprises a bottom supporting assembly adapted to support the bottom wall of a relative container and an upper retainer adapted to cooperate with the top portion of such container to hold it in a vertical position during the rotation of the carousel about the vertical axis.

Each supporting assembly comprises a vertical hollow supporting mount, secured to a horizontal plane of a rotary frame of the carousel, and a cylindrical receiving member, engaging the supporting mount in sliding and rotating manner with respect to its axis, and adapted to carry a relative container on its top surface and a relative label on its lateral surface .

In particular, each supporting mount comprises a vertical tubular body and a top platform secured to the tubular body by a plurality of screws and provided with a central hole, through which the relative receiving member may be axially displaced.

Each receiving member can be displaced between a raised position and a fully retracted position within the tubular body of the relative supporting mount .

In the raised position, each receiving member protrudes from the top platform of the relative supporting mount and is adapted to receive a relative label on its lateral surface from the label input wheel; in particular the label is wrapped around the receiving member such that the opposite vertical edges of the label overlap one another.

In order to produce this complete wrapping, the receiving member is rotated about its axis during the transfer of the label from the label input wheel.

In the fully retracted position, which is reached at the container input and output wheels, the top surface of each receiving member is flush with the upper surface of the top platform of the supporting mount so that containers are transferred onto and from the carousel along the same transfer plane.

After the welding of the overlapped edges of a tubular label, the displacement of the relative receiving member from the raised position to the fully retracted position produces the insertion of the relative container inside the label, making the so obtained container ready to be transferred to the output wheel.

Each label is retained on the lateral surface of the relative receiving member by suction; in particular, at least a region of the lateral surface of each receiving member is provided with a plurality of holes in turn connected to a pneumatic suction device.

It is evident from the above that any change of the container bottom surface or diameter entails a replacement of all the receiving members and all the top platforms of the supporting mounts of the labelling machine, with consequent long dismantlement and reassemble times as well as high costs .

As a matter of fact, the operator has to act on a really large number of screws (normally four per each supporting mount) , which have to be first unscrewed to allow disassembly of the top platforms and the relative receiving members from the tubular bodies of the supporting' mounts and then retightened on the new platforms. DISCLOSURE OF INVENTION

It is an object of the present invention to provide a labelling unit, which allows to overcome the above drawback in a straightforward and low-cost manner.

This object is achieved by a labelling unit as claimed in claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:

Figure 1 shows a schematic plan view, with parts removed for clarity, of a labelling machine provided with a plurality of labelling units in accordance with the teachings of the present invention;

Figures 2 and 3 show larger-scale views in perspective of some labelling units of the Figure 1 labelling machine in proximity of a label transfer station;

Figure 4 shows a larger-scale view in perspective, with parts removed for clarity, of a supporting mount of the labelling unit according to the present invention;

Figure 5 shows an exploded larger-scale view in perspective of the Figure 4 supporting mount;

Figure 6 shows another view in perspective of a top platform of the Figure 5 supporting mount; and Figures 7 to 9 are larger-scale sections taken along line VII-VII in Figure 5 and showing the supporting mount in different assembling steps.

BEST MODE FOR CARRYING OUT THE INVENTION

Number 1 in Figure 1 indicates as a whole a labelling machine for applying labels 2 (Figures 2 and 3) to respective articles or more specifically containers, particularly bottles 3, each of which (Figures 1 to 3) has a given longitudinal axis A, is bonded at the bottom by a bottom wall 4 substantially perpendicular to axis A, and has a top neck 5 substantially coaxial with axis A.

Machine 1 comprises a conveying device that serves to bend and weld labels 2 in a tubular configuration (Figure 3). and to produce insertion of bottles 3 into the so formed tubular labels 2.

In the preferred embodiment as illustrated on the Figures 1 to 3 , the conveying device comprises a carousel 7, which is mounted to rotate continuously (anticlockwise in Figure 1) about a respective vertical axis B perpendicular to the Figure 1 plane .

The carousel 7 receives a succession of unlabelled bottles 3 from an input wheel 8, which cooperates with carousel 7- at a first transfer station 9 and is mounted to rotate continuously about a respective longitudinal axis C parallel to axis B. The carousel 7 also receives a succession of rectangular or square labels 2 from an input drum 10, which cooperates with carousel 7 at a second transfer station .11 and is mounted to^' rotate continuously about a respective longitudinal axis D parallel to axes B and C.

The carousel 7 releases a succession of labelled bottles 3 to an output wheel 12, which cooperates with carousel 7 at a third transfer station 13 and is mounted to rotate' continuously about a respective longitudinal axis E parallel to axes B, C and D.

As shown in Figure 1, transfer station 11 is arranged, along path P, downstream from transfer station 9 and upstream from transfer station 13.

The carousel 7 comprises a number of operating or labelling units 15, which are equally spaced about axis B, are mounted along a periphex-al edge of carousel 7, and are moved by carousel 7 along a circular path P extending about axis' B and through transfer station 9, 11 and 13.

With reference to Figures 2 and 3, the units 15 are secured to a horizontal rotary table 14 of carousel 7 , have respective axes F parallel to axes B, C, D, E and extend coaxially through respective holes (not shown) of the rotary table 14 and on both sides of such table.

Each unit 15 is adapted to receive a relative bottle 3 from input wheel 8 in a vertical position, i.e. coaxially with the relative axis F, and to hold said bottle 3 in such position along path P from transfer station 9 to transfer station 13.

Units- 15 being identical to each other, only one is described below for the sake of simplicity and clarity; it is clear that the features described hereafter are common to all the labelling units 15.

In particular, unit 15 comprises, above the rotary table 14 of carousel 7, a supporting assembly 17 adapted to support the bottom wall 4 of a relative bottle 3 and an upper retainer 18 adapted to cooperate with the top neck 5 of the bottle 3.

In particular, supporting assembly 17 comprises:

- a hollow supporting mount 20 of axis F, which is secured to a top surface of rotary table 14 around the relative hole thereof; and

- a hollow cylindrical receiving member 22, engaging the supporting mount 20 in sliding and rotating manner with respect to axis F, and adapted to carry coaxially a relative bottle 3 on its top end and a relative label 2 on the outer surface of its lateral wall 24.

More 'specifically, the bottle 3 rests on a support plate 21 (only dimly visible in Figures 2 and 3) , which is carried by the top end of receiving member 22 through the interposition of a relative bearing (not visible) , so as to be angularly free from receiving member 22; in this way, rotational movements of receiving member 22 around axis F are not transmitted to the bottle 3.

With particular reference to Figures 4 to 9, supporting mount 20 comprises a vertical tubular body 25 and a top platform 26 secured to the body 25 by releasable fastening means 27 and provided with a central hole 28, through which receiving member 22 may be axially displaced.

More specifically, top platform 26 comprises a plate 29, along which bottles 3 are transferred onto and from unit 15, and a tubular coupling portion 30, axially protruding from plate 29 and adapted to be engaged into a top portion 31 of body 25. As clearly shown in Figures 5 and 6 to 9, plate 29 also protrudes from coupling portion 30 in a plane orthogonal to axis F.

Moreover, in the example shown, coupling portion 30 of top platform 26 is delimited by an outer cylindrical surface 30a, whilst top portion 31 of body 25 is delimited by an inner cylindrical surface 31a complementary to surface 30a so as to be engaged by the latter .

Advantageously, releasable fastening means 27 comprise first and second engaging means 32, 33 respectively carried by coupling portion 30 of top 10 00079

platform 26 and by top portion 31 of body 25 and which can be coupled and uncoupled by a sliding movement along a direction X parallel to axis F; releasable fastening means 27 also comprise locking means 35 in turn provided with a retaining element 36 movable transversally to direction X between a fastening position and a release position, in which it respectively prevents or allows uncoupling engaging means 32, 33.

In particular, engaging means 32 comprise a number of (in the example shown four) male elements or projections 37, extending radially outwards from surface 30a of coupling portion 30 of top platform 26, equally spaced around axis F and having rectangular profiles.

Engaging means 33 comprise a number of receiving seats 38 provided on surface 31a of top portion 31 of body 25 and equally spaced around axis F so as to receive respective projections 37.

More specifically, each seat 38 is defined by a slot having a profile complementary to the one of the relative projection 37 and delimited, in direction X, by a top entry opening 39 and by a bottom abutment surface 40 facing entry opening 39. In use, each entry opening 39 allows insertion of the relative projection 37 into the relative seat 38 along direction X, whilst the relative bottom abutment surface 40 cooperates with said projection 37 when the latter is fully housed within said seat 38.

With reference to Figures 5, 7, 8 and 9, retaining element 36 comprises a movable ring 41 coaxially arranged on a top edge of top portion 31 of body 25 and which can be rotated around axis F between the fastening position and the release position.

In particular, movable ring 41 is provided, on its inner surface, with a plurality of (in the example shown four) notches 42 equally spaced around axis F and each having, in the circumferential direction, the same width as seats 38.

In the release position, each notch 42 of movable ring 41 is aligned with a relative one of seats 38 in direction X so as to allow axial insertion of the relative p'rojection 37 into the notch 42 and the seat 38.

In the fastening position, notches 42 are angularly offset around axis F with respect to seats 38 and do not communicate with the latter, so that each portion 43 of movable ring 41 between two adjacent notches 42 closes entry opening 39 of a relative seat 38 and prevents extraction of the relative projection 37 from said seat 38 along direction X.

A fixed ring 45, superimposed on movable ring 41 and secured to top portion 31 of body 25 by a plurality of screws 46, maintains the movable ring 41 in an axially fixed position with respect to axis F. In particular, fixed ring 45 has, on its radially outer surface, a plurality of (in the example shown four) equally spaced projections 47, which are secured in pairs to respective external appendices 48, 49 of top portion 31 of body 25 by means of screws 45.

The angular displacements of movable ring 41 around axis F are limited by the interaction of a radially outer protruding portion 50 of movable ring 41 with the adjacent appendices 48, 49 of top portion 31.

More specifically, protruding portion 50 has a triangular profile in a plane orthogonal to axis F and is provided with a through hole 51.

Locking means 35 also comprise a locking pin 52 carried by top portion 31 of body 25 in a sliding manner along direction X and having one end portion 53 adapted to releasably engage hole 51 of protruding portion 50 to lock movable ring 41 in the fastening position.

In particular-, locking pin 52 is slidably housed within a through hole 54 of one (48) of appendices 48, 49 and has a protruding head 55 at an end portion opposite end portion 53. Locking pin 52 is movable between a raised or' locking position, in which end portion 53 protrudes from appendix 48 along direction X on the side of movable and fixed rings 41, 45 and can engage hole 51 of protruding portion 50 of movable ring 41, and a lowered or unlocking position, in which end portion 53 is fully housed within hole 54 of appendix 48.

As shown in Figure 5, locking pin 52 is elastically loaded by a helical spring 56 towards the locking position; helical spring 56 is wound round locking pin 52 and has a bottom end cooperating with an abutment surface 57 of appendix 48 and a top end cooperating with a portion of locking pin 52.

With reference to Figures 2 and 3, receiving member 22 can be moved along axis F between a fully retracted position within the relative supporting mount 20 (not shown) and a raised position (Figures 2 and 3) .

In the fully retracted position, receiving member 22 is completely housed within body 25 of the relative supporting mount 20 so that support plate 21 is flush with plate 29 of top platform 26.

In the raised position, receiving member 22 protrudes from plate 29 and is adapted to receive, on the outer surface of its lateral wall 24, a relative label 2 from input drum 10.

More specifically, labels 2 are cut in a know manner from a web 58 (Figure 1) by a cutting device 59 (only schematically shown in Figure 1) and fed to input drum 10 to be then transferred to the relative receiving members 22 in the raised position.

As shown in Figures 2 and 3, the cut labels 2 are retained on a lateral surface 60 of input drum 10 by suction; in fact, the lateral surface 60 of input drum 10 is divided into a given number, three in the embodiment shown, of suction regions 61, which are equally spaced about axis D, are each provided with a plurality of through holes 62 connected to a pneumatic suction device (known per se and not shown) and are adapted to cooperate with respective labels 2.

In a completely analogous manner (Figures 2-6 and 10) , lateral wall 24 of the receiving member 22 is ^• provided with a plurality of through holes 63, in turn connected to a pneumatic suction device (known per se and not shown) so as to retain the relative label 2 on its outer surface by suction.

At the transfer station 11, receiving member 22 can be rotated about the relative axis F in order to produce the complete wrapping of the relative label 2, coming from input drum 10, on the outer surface of its lateral wall 24. In particular, each label 2, fed by input drum 10, is wrapped around the relative receiving member 22 in the raised position so as to form a cylinder with the opposite vertical edges 64 overlapped one another. In the light of the above, receiving member 22, during its travel along path P with the other components of unit 15, is subjected to distinct movements in different operative steps of the labelling machine 1:

- a displacement along axis F from the fully retracted position to the raised position, after a bottle 3 has been transferred to unit 15;

- a rotational movement about axis F to receive a relative label 2 from input drum 10 and to allow bending of such label in the cylindrical configuration; and

- a displacement from the raised position to the fully retracted position to allow insertion of the bottle 3 within the label 2 welded in the tubular configuration.

These movements are basically obtained by means of an actuator assembly 65 (only schematically shown in Figures 2 and 3) carried by rotary table 14 and provided with an output shaft (not shown) coaxially coupled to the receiving member 22; in particular, actuator assembly 65 is arranged underneath rotary table 14 and is secured to a bottom surface of the rotary table 1 .

As visible in Figures 2 and 3, bottles 3 are hold on the relative units 15 by the interaction of bottom supporting assemblies 17 with the respective upper retainers 18; more specifically, the retainer 18, corresponding to the described supporting assembly 17, comprises, in a known manner, a cylindrical movable member 66, which protrudes vertically from an upper rotary portion 67 of carousel 7, can be displaced along the relative axis F and has a bell-shaped free end portion 68 adapted to cooperate with the top neck 5 of the bottle 3 carried by such supporting assembly 17.

More specifically, the displacements of each movable member 66 are controlled in a known manner so as to maintain the same distance between its end portion 68 and the corresponding plate 21, during the movement of the relative unit 15 along the portion of path P from transfer station 9 to transfer station 13, and to increase such distance at transfer stations 9, 13 and during the portion of path P from station 13 to station 9. In this way, bottles 3 are securely hold in their vertical positions during the travel from station 9 to station 13 and are free to be transferred at such stations 9 and 13 from input wheel 8 and to output wheel 12, respectively.

With reference to Figure 1, machine 1 further comprises a plurality of welding devices 70, each of which arranged in front of, and in a radially inner position than, the relative unit 15 and adapted to cooperate, in a known manner, with the label 2 wrapped around the corresponding movable member 22 for welding the overlapped edges 64 and to produce a tubular configuration of such label.

After completion of the welding of a tubular label 2, the downward movement of the relative movable member 22 towards the fully retracted position within the relative supporting mount 20 produces the insertion of the relative bottle 3 inside said tubular label. The so formed labeled bottle 3 is then fed to a shrinking tunnel (known per se and not shown) , where shrinking and adhesion of the label 2 to the external surface of the bottle 3 occurs.

The duration of the most significant operating steps of the machine 1 is schematically shown in Figure 1 by indicating the corresponding angles of rotation of the carousel 7 about axis B, along which said steps are performed; in particular, angle a refers to the lifting movement of the receiving members 22 from the fully retracted position to the raised position, angle β refers to the label transfer from the input drum 10 to the relative receiving member 22, angle γ refers to the welding operation on the overlapped edges 64 of the tubular labels 2, and angle d refers to the downward movement of the receiving members 22 to produce insertion of the bottles 3 within the corresponding tubular labels Operation of machine 1 will now be described with reference to the labelling of one bottle 3 , and therefore to one labelling unit 15 , and as of the instant in which the receiving member 22 of such unit 15 is in the fully retracted position within the relative supporting mount 20 and has just received the unlabelled bottle 3 from input wheel 8.

In this condition, the bottle 3, which rests on plate 21 carried by the receiving member 22, is hold in the vertical position by the combined action of the receiving member 22 and the relative upper retainer 18.

During the subsequent movement of unit 15 along path P (angle a in Figure 1) , the actuator assembly 65 is actuated to produce a translational movement of the receiving member 22 towards the desired raised position.

It should be noted that this translational movement may be also obtained by means of a cam system, known per se and not shown.

At the transfer station 11, the input drum 10 reaches an angular position around axis D adapted to put the label 2 into contact with the receiving member 22 passing through such station; in this condition (angle β) , a pure rotational movement of receiving member 22 around axis F is required to produce complete wrapping of the label · 2 in a known manner around such receiving member 22 (Figure 3). More specifically, the label 2 reaches a cylindrical configuration with the opposite vertical edges 64 overlapped one another.

At this point, the label 2 is ready to be welded along the edges 64 by activation of the welding device 70 (angle y) .

During the last part of the path P (angle d) , the receiving member 22 must be returned to the fully retracted position within the relative supporting mount 20, so as to produce the insertion of the bottle 3 inside the so formed tubular label 2.

A heat-shrinking step (not shown) can be then performed on the bottles 3 exiting from the carousel 7 to obtain shrinking and adhesion of the label 2 to the bottle external surface.

In the case in which it is necessary to change format of the containers or bottles 3 to be processed by machine 1, for instance to pass to a new bottle having a bottom diameter different from the previously processed one, top platforms 26 and receiving members 22 have to be replaced by new ones having suitable sizes; in particular, the new receiving member 22 should have a diameter related to the bottle diameter to be carried on its plate 21 and the new top platform 26 should have a diameter of hole 28 suitable to be engaged by the new receiving member 22 in a sliding and rotating manner.

Thanks to the new configuration of fastening means 27, the dismantling operation of each top platform 26, together with the relative receiving member 22, from the relative body 25 requires the following quick steps:

displacing locking pin 52 into the unlocking position so as to obtain disengagement of its end portion 53 from hole 51 of protruding portion 50 of movable ring 41;

- rotating movable ring 41 about axis F from the fastening position to the release position so as to align notches 42 with the corresponding seats 38 and to allow extraction of projections 37 from the seats 38 along direction X; and

- raising top platform 26 along direction X up to obtain disengagement of projections 37 from the relative seats 38 and coupling portion 30 from top portion 31 of body 25.

The connection of each new platform 26 to the respective^' bodies 25 can be obtained by repeating the above steps in the reverse mode. In particular, coupling portion 30 of the new top platform 26 is inserted into top portion 31 of body 25 along direction X so that each projection 37 engages the relative seat 38. Once coupling portion 30 is fully housed within top portion 31, movable ring 41 can be displaced into the fastening position by- gripping protruding portion 50 and by maintaining locking pin 52 in the unlocking position against the thrust of spring 56. At this point, locking pin 52 can be let to return to the locking position, under the action of spring 56, wherein end portion 53 engages hole 51 of protruding portion 50 so locking movable ring 41 in the fastening position.

The advantages of the labelling units 15 according to the present invention will be clear from the above description .

In particular, as previously explained, the new solution of fastening means 27 permits a very quick and easy change of the top platforms 26 and the respective receiving members 22, without requiring to use specially provided tools, such as screwdrivers. This also means to reduce the machine stop time for performing the necessary replacements, so permitting a considerable saving.

Clearly, changes may be made to labelling machine 1 and labelling units 15 as described and illustrated herein without, however, departing from the scope of protection as defined in the accompanying claims.

Claims

1) A labelling unit (15) comprising supporting means (20) fed, at an article input station (9) , with an article (3) to be labelled, and movable along a given

5 path (P) through a label input station (11) , in which a relative label (2) is fed to the labelling unit (15) to be applied on said article (3) , and an article output station (13) , in which the labelled article (3) is released; said supporting means (20) comprising a main

10 body (25)' displaceable along said path (P) , a top platform (26) , along which said article (3) is transferred onto and from the labelling unit (15) , and releasable fastening means (27) to secure said top platform (26) onto said main body (25) , characterized in

15 that said releasable fastening means (27) comprise:

first and second engaging means (33, 32) respectively carried by said main body (25) and said top platform (26) and which can be coupled and uncoupled by a sliding movement along a direction (X) transversal to

20. said path (P) ; and

- a retaining element (36) movable transversally to said direction (X) between a fastening position and a release position, in which it respectively prevents or allows uncoupling of said first and second engaging means

25 (33 , 32) . 2) A unit as claimed in claim 1, wherein said first and second engaging means (33, 32) comprise at least a receiving seat (38) and a male portion (37) which can be coupled and uncoupled along said direction (X) .

5 3) A' unit as claimed in claim 2, wherein said receiving seat (38) has an entry opening (39) for permitting insertion of said male element (37) along said direction (X) , and an abutment surface (40) facing said entry opening (39) and cooperating with said male element

10 (37) when fully housed in the receiving seat (38) , and wherein said retaining element (36) comprises at least a stop portion (43) closing said entry opening (39) in said fastening position to prevent extraction of said male element (37) from said receiving seat (38) along said

15. direction (X) .

4) A unit as claimed in anyone of the foregoing claims, wherein said main body (25) comprises at least a tubular coupling portion (31) having an axis (F) parallel to said direction (X) and adapted to receive a

20 complementary portion (30) of said top platform (26) , and wherein said receiving seat (38) is obtained on an inner surface (31a) of said coupling portion (31) and said male element (37) comprises a projection (37) of said complementary portion (30) .

25 5) - A unit as claimed in claim 4, wherein said retaining element (36) comprises a movable ring (41) fastened to a free edge of said coupling portion (31) in an axially fixed position and in a rotating manner about said axis (F) , said movable ring (41) comprising said stop portion (43) and at least one notch (42) which, in the release position, can be selectively aligned with said entry opening (39) of said receiving seat (38) along said direction (X) to allow insertion or extraction of said male · element (37) into or from said receiving seat (38) .

6) A unit as claimed in anyone of the foregoing claims, wherein it further comprises a locking element (52) to lock said retaining element (36) in a releasable manner in said fastening position.

' 7) A unit as claimed in claim 6, wherein said locking element (52) is carried by said main body (25) in a movable manner along said direction (X) between a locking position, in which it cooperates with said retaining element (36) to prevent any displacement thereof towards said release position, and an unlocking position, in which it is detached from said retaining element (36) to allow the latter to reach said release position.

8) A unit as claimed in claim 7, wherein said locking element (52) is elastically loaded towards said locking position.

9) A unit as claimed in anyone of claims 4 to 8 , wherein said main body (25) and said top platform (26) have tubular configurations around said axis (F) , said_· unit (15) further comprising a receiving member (22) engaging said top platform (26) and said main body (25) in sliding manner along said axis (F) , and adapted to carry coaxially a relative article (3) on its top end and a relative label (2) on the outer surface of its lateral wall (24) .

10) A unit as claimed in claim 9, wherein said first engaging means (33) comprise a plurality of receiving seats (38) equally spaced around said axis (F) and obtained on said inner surface (31a) of said coupling portion (31) of said main body (25) , and wherein said second engaging means (32) comprise a plurality of male elements (37) equally spaced around said axis (F) and provided on said complementary portion (30) of said top platform (26) .