ROTARY SEAMER

TECHNICAL FIELD AND BACKGROUND ART.

The present invention relates to a rotary seamer. A seamer is a machine that enables to apply a lid to a container to close it hermetically, connecting the edge of the lid to the edge of the container by folding them one onto the other.

Such containers have cylindrical geometry, e.g. they are constituted by cans. In practice, seaming is achieved by setting the container in rotation around its own axis, in a seaming station in which the container interacts with an appropriately shaped idle pivot, i.e. shaped such as to cause said folding of the edges of the container and of the corresponding lid.

The seaming station is pivotally associated to a seaming turret, also called carrousel because it rotates around its own axis.

According to the prior art in the field of seamers, during the seaming operation the container (rotating in the seaming station) interacts with a first and with a second idle pivot, in succession.

For this purpose, the seamer comprises a plurality of seaming blocks, each provided, according to the seamer model, with one or two idle pivots and connected to a shaft hinged on the seaming turret.

In this way, rotating said shaft first in one direction and then in the other, each idle pivot is made to interact (one at a time) with the container.

More specifically, once the container and the lid are integral with the seaming site (through the action of a mandrel and the vertical thrust of a

piston), the seaming operation starts. Following the profile of a cam, a lever causes said shaft to rotate on its own axis in such a way as to make first an idle pivot and then the other one approach the container; during these approaching motions, the sheet metal of container and lid are first rolled together, then crushed obtained a hermetic seal between the interior of the can and the external environment.

This stated, note that the present invention relates, in particular, to the manner of connection of the seaming block to the shaft. Therefore, the technical solution of the invention relates to some fundamental components of the seaming turret, such as the seaming block and the shaft whereon the seaming block must be mounted. The idle pivots mounted on the seaming block are the tools whereon most of the seaming result depends, so it is of fundamental importance that the mechanism that makes them work is as rigid and free of play as possible.

Moreover, it is important for the removal and mounting of the seaming blocks on the turret to be as rapid as possible, to speed machine maintenance operations. Currently, there are mainly two types of shaft ends for mounting the seaming block on the related shaft: the bevel one with disc shaped tongue and the grooved one.

During the seaming operation, the seaming block moves in an alternating rotation to make first one idle pivot work and then the other one and the work load thus produces an alternating torque Stressed in this way, the seaming block loses stiffness because both

solutions in practice allow a certain play in the direction of rotation of the seaming block relative to the axis of the shaft. In the first case, the play is due to the conicity, which is not sufficient to lock the two components together, and to the clearance required for mounting the tongue; in the second case, the play is the required one to mount the groove in its seat.

In other technical solutions, the seaming block defines a cavity with longitudinal development, complementarily shaped relative to an end of the shaft with square cross section, in order to be coupled thereto by inserting the shaft into the cavity; in these cases, means are used to anchor the seaming block to the shaft transversely, which act in a predetermined, transverse direction such as to create at least one contact surface between shaft and cavity In any case, known solutions are disadvantageous because they require relatively long mounting times and they do not allow to reach high levels of precision and strength in the assembly. DISCLOSURE OF THE INVENTION.

An object of the present invention is to eliminate the aforesaid drawbacks and to make available a seamer in which the mounting of the seaming blocks on the respective shafts is fast and particularly strong and precise.

Said object is fully achieved by the seamer of the present invention, which is characterised by the content of the appended claims and in particular in that the shaft and the cavities are so shaped that said contact surface has at least one oblique portion relative to the direction in which

said means act.

The seamer according to the present invention is also provided, originally, with means for eliminating the plays linked to the construction tolerances of the seaming block and of the shaft. Said means comprise, in particular,

- a first thrusting element associated to said seaming block and movable in said predetermined transverse direction between a position of non interference with the shaft and a position of tightening, in which it presses on a surface of the shaft that is orthogonal to said transverse direction;

- a second thrusting element associated to said seaming block and movable in said predetermined transverse direction or parallel thereto between a position of non interference with the shaft and a working position, in which it presses one of its ends having rounded shape on a surface of a countersink defined by the shaft on said surface, orthogonal to said transverse direction.

BRIEF DESCRIPTION OF DRAWINGS.

This and other characteristics shall become more readily apparent from the following description of a preferred embodiment, illustrated purely by way of non limiting example in the accompanying drawing tables, in which:

- figure 1 shows a partially sectioned front view of a seamer according to the present invention;

- figure 2 shows an exploded view of a detail of the seamer of figure 1, i.e. a shaft and a seaming block;

- figure 3 shows a sectioned view, according to a transverse plane, of the detail of figure 2;

- figure 4 shows a sectioned view, according to a longitudinal plane, of the detail of figure 2; - figure 5 shows an enlargement of the detail A of figure 4;

- figure 6 shows the detail of figure 3, in a subsequent mounting step;

- figure 7 shows the detail of figure 4, in a subsequent mounting step;

- figure 8 shows the detail of figure 3, in an additional subsequent mounting step; - figure 9 shows the detail of figure 4, in an additional subsequent mounting step.

BESTMODEFORCARRYING OUTTHEINVENTION.

In figure 1, the reference number 1 designates a seamer according to the present invention, whereof is shown, in particular, a portion of a seaming turret 2 rotating around its own axis 3. To the seaming turret 2 are pivotally associated a pan 4 and a mandrel 5, which define a seaming site, to set a container 6 and a lid 7 in rotation around their own axis 8.

The reference number 9 designates a seaming block provided with rotating idle pivots 10 (in particular a first and a second rotating pivot, but according to the seamer model there may be a single pivot per block and consequently the number of the blocks and of the pivots doubles).

The seaming block 9 is anchored to a shaft 11 hinged on the seaming turret 2, such that it can rotate around its own axis 12.

Figure 2 shows an exploded perspective view of the shaft 11 and of the seaming block 9. The shaft 11 has a first end 13, hinged in the seaming

turret 2, and a second end 14.

The seaming block 9 internally defines a cavity 15 with longitudinal development, complementarily shaped relative to said second end 14 of the shaft 11 in such a way that it can be coupled thereto by inserting the shaft 11 into the cavity 15. Note that a certain play is provided between the cavity 15 and the second end 14 of the shaft 11, to facilitate the insertion of one into the other.

Note that said second end 14 of the shaft 11 and the cavity 15 preferably have constant section along a longitudinal axis (i.e. along the axis 12 of rotation of the shaft 11).

In the figures, the reference number 16 designates means for anchoring the seaming block 9 to the shaft 11. Said means are associated to the seaming block 9 in such a way as to act in a predetermined transverse direction 17 to create at least one contact surface between the shaft 11 and the cavity 15, oblique relative to the direction in which the means act. Note that said means are associated to the seaming block 9 in such a way as to act in a said predetermined transverse direction 17 to create preferably two contact surfaces between the shaft 11 and the cavity 15, oblique relative to the direction in which the means act. Said second end 14 of the shaft 11, originally, has triangular prism shape.

However, the second end 14 (and consequently the cavity 15 of the seaming block 9) may have different conformations. For example, said second end 14 may have triangular or trapezoidal section. In any case, the conformation of the second end 14 is such that the

locking means, acting on said second end 14 in said predetermined direction 17, determine a distribution of pressure on at least one surface (but preferably two surfaces) of contact between shaft 11 and cavity 15 not orthogonal to said predetermined direction. Said means for anchoring the seaming block 9 to the shaft 11 are obtained, in the preferred embodiment illustrated herein, in the manner described hereafter.

A first threaded thrusting element 18 engages in a through hole obtained in the seaming block 9, to place said cavity 15 in communication with the exterior. Said first thrusting element 18 is movable in said predetermined transverse direction 17.

When the second end 14 of the shaft 11 is inserted into the cavity 15, operating the first thrusting element 18 on a surface 19 of said end 14 orthogonal to said predetermined direction 17, a pressure is created in a contact surface 20 between the end 14 and the cavity 15 (as shown in figure 8).

A screw 21 is coupled to the seaming block 9. Preferably, said screw 21 is threaded with the same pitch as the first thrusting element 18 and it is movable in a cavity (substantially a through hole) obtained internally to the screw 18 itself with appropriate threading.

Inside the first thrusting element 18 is also housed a ball 22, positioned between one end of the screw 21 and the cavity 15, or the end 14 of the shaft 11. The ball 22 is free to move but not to exit said cavity internal to the first thrusting element 18, prevented by a special projection 23 (shown in figure 5). The ball 22 and the screw 21 constitute a second

thrusting element.

Moreover, the end 14 of the shaft 11 (in particular its surface 19 orthogonal to said predetermined direction 17) defines a countersink 24, preferably having conical shape. Said countersink 24 is positioned such that, when the second end 14 of the shaft 11 is inserted in the cavity 15, an axis of symmetry of the countersink 24 is parallel to said predetermined direction 17, but at a predetermined distance therefrom, in order to produce a certain misalignment between said second thrusting element and the countersink 24. Operating the second thrusting element, i.e. operating the screw, a pressure is created between the ball 22 and a surface of the countersink 24; this entails a relative displacement of the seaming block 9 relative to the shaft 11, in a plane orthogonal to said predetermined direction 17 (in particular vertically, because horizontally the cavity 15 and the end 14 centre themselves), tending towards an alignment of the axis of the second thrusting element (i.e. of said predetermined direction 17) relative to the axis of the countersink 24.

It is thereby possible to obtain, originally, an elimination of the plays due to construction tolerances. Note that the second thrusting element, alternatively to the preferred embodiment illustrated (which provides the screw 21 and the ball 22), may also comprise a thrusting element movable between a position of non interference with the end 4 of the shaft 11 and a position in which it presses its own rounded end (e.g. with hemispherical shape) against the surface of the countersink 24.

However, it should be noted that the technical solutions providing for the use of the ball 22 presents some disadvantages.

To obtain the elimination of the plays, superficial pressures must be exerted, so the pressing element must be sufficiently hard not to be deformed. It is not possible to use a threaded element with spherical head made of thermally hardened steel because it would corrode, being exposed to the outside environment. The same element made of stainless steel cannot be used, because it would seize together with the pivot because of the sliding of the spherical surface on the conical surface of the countersink 24 during the screwing operation; moreover, a stainless steel screw stressed to the load necessary to eliminate play would be deformed in the pressure area, to the point that it could not longer be extracted. On the contrary, in the preferred embodiment a ball 22 made of thermally hardened stainless steel is used, which is thrust out of its seat in such a way that relative to the countersink 24 there is no relative sliding of the surface but only a thrust. In this way, the threaded element (i.e. the screw 21) can thus be made of stainless steel, with the ability to resist corrosion. The present invention also makes available a method for mounting the seaming block 9 in the shaft 11. Said mounting method is described in detail hereafter. In a first step (shown in figures 3 and 4) the seaming block 9 is applied to the shaft 11. The seaming block 9, whereon are mounted the threaded element 18 and

21 and the ball 22, is applied to the second end 14 of the shaft 11, preferably with triangular prism shape.

A second step (shown in figures 6 and 7) enables to obtain an elimination of the plays, as follows. Acting on the screw 21, the ball 22 is thrust against the second end 14 of the shaft 11 at the countersink 24. In this way, a dual effect is produced: in the first place, the seaming block 9 is made to adhere to the shaft 11, eliminating horizontal play, then the seaming block 9 is thrust to abut against the shaft 11 eliminating vertical play. The ball 22 then makes surfaces of the seaming block 9 and of the shaft 11 (at the second end 14) that are opposite and face each other (having triangular profiles) adhere to each other and it produces a resulting vertical that thrusts the seaming block 9 upwards to abut on the shaft 11. A third step (shown in figures 8 and 9) enables to obtain a locking of the seaming block, as follows.

Once plays are eliminated through the second step, stiffness is provided to the system by tightening the first thrusting element 18 (which is preferably a threaded element). Keeping still with a spanner the second thrusting element (i.e. the screw 21), one acts on the first thrusting element 18, moving it towards the seaming block 9 and pressing it against it, in particular on a surface of the seaming block 9 orthogonal to the direction of advance of the first thrusting element 18 (i.e. said predetermined transverse direction). The pitch of the inner and outer threads of both thrusting elements must be equal, in order not to alter the position of the second thrusting element

that eliminated play.

Therefore, the following invention presents the following advantages. In the first place, maintenance times are considerably reduced; the result of eliminating mounting plays makes it possible to maintain unaltered the adjustments of the idle pivots 10, hereafter called rollers.

Adjusting the rollers means their positioning relative to the mandrel 5 obtained acting on appropriate adjusting screws (not shown because they are not part of the present invention). Adjustment of the rollers 10 is achieved by attempts and it consists of a major part of the time required to set up the machine; obviously, the more rollers need to be adjusted, the longer the time required to do so, so eliminating this activity translates into an economic advantage.

Moreover, the particular conformation of the second end 14 of the shaft 11 and of the cavity 15, combined with the action of means pressing transversely in a predetermined direction, enables to obtain a particularly rapid and strong locking of the seaming block 9 relative to the shaft 11. The particular conformation of the second end 14 of the shaft 11 and of the cavity 15 also entails that the step of associating the seaming block 9 to the shaft 11 occurs in a univocal angular position of the seaming block 9 relative to the shaft 11, even though the execution of said step of associating is particularly rapid.

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