Patent Description:
The present invention relates to a seaming machine for fixing a lid to a container containing, for example, a food product.

In particular, the present invention relates to a seaming machine, for applying a metallic lid to a cylindrical container, it too metallic, so as to form a can for food beverages, to which the following discussion will explicitly refer without thereby losing generality.

In the field of can forming , it is known to use seaming machines different from each other and among these carousel seaming machines, i.e. of the type comprising a structure rotating about a fixed axis and a crown of forming sections coupled to the rotating structure and moved by the rotating structure along a circular seaming path.

Documents <CIT> on which the preamble of claim <NUM> is based, <CIT> and <CIT> describe respective cam machines for seaming.

Each forming section, during the rotation of the structure, receives the container with the relative lid resting on it in a loading station, firmly fixes the lid to the relative container and transfers a formed can into an unloading station.

For this purpose, each forming section comprises a support plate of the container and a seaming head arranged above the relative plate for bending and pressing the perimeter edges of the lid and of the container together.

The plate is vertically movable between a lowered loading/unloading position, in which it supports the container in a position spaced from the seaming head, and a raised seaming position.

The seaming head comprises a motorised reference spindle coaxial to the axis of the plate, and a pair of rollers arranged laterally to the spindle and of which one for bending or curling the edges of the container and of the lid and one for pressing the bent or curled edges.

The seaming cycle comprises a first operation, during which the outer edges of the lid and of the container are turned downwards on the outside of the container and substantially curled by the bending roller, and a second step, during which the curled edges are radially pressed and forced against each other by the pressing roller, so as to create a hermetic seal.

The seaming must comply with very strict specifications (some sizes must fall within a tolerance of ± <NUM>), therefore it is necessary to carry out very frequent sample checks.

A first check, carried out more frequently, is carried out on the completely seamed can, i.e. on the cans leaving the unloading station.

Although less frequently, a second check must also be carried out at the end of the bending operation, so as to check the state of the bending made by the bending roller before the subsequent pressing step is carried out.

In order to carry out the second check, it is necessary that the pressing roller does not come into contact with the container-lid assembly so as not to make any modifications to the bending carried out by the bending roller.

In known seamers, the bending and pressing rollers are moved by a mechanical cam, the profile of which defines the desired movement profile of the rollers away from and towards the respective spindle.

In some known seamers, it is possible to exclude all the pressing rollers present on the machine. Once the check on the bent edges is carried out, the exclusion of the pressing rollers is removed so as to again obtain completely seamed cans.

In known seamers, the exclusion is obtained by using mechanical cams consisting of two sectors, of which one is fixed for controlling the bending roller and one is movable for controlling the pressing roller. During the normal seaming cycle, the two sectors are kept in fixed operating positions and each one controls the relative roller, whereas during the exclusion, the movable sector is moved in a radial direction to an exclusion or rest position, in which it is not capable of controlling the pressing roller, hence the pressing operation is not carried out.

Known machines of the type described above, although used, are not much satisfactory from a functional point of view and simultaneously have high manufacturing and maintenance costs. The foregoing is essentially attributable to the fact that the cam, also when the movable sector is arranged in its operating position, is still anyway a cam having a discontinuous profile, i.e. a cam which, however very accurate from a constructive point of view, still has an inevitable discontinuity in the passage zone from one sector to the other. Such discontinuity is responsible for the formation of impacts on the cam follower members, which prejudice the structural and shape stability thereof and the duration of the cam follower members, making indispensable periodic check operations, which obviously entail machine stops and production loss.

In order to minimize the interruptions and the consequent impacts, to the advantage of the duration of the rollers, an extremely precise mechanical construction is necessary, but as such extremely expensive.

In addition to this, when the movable sector is arranged in its exclusion position, a macro interruption of the control profile is inevitably generated. In order to prevent mechanical damage to the cam followers and to the various components connected thereto, the rotating structure is rotated at a reduced speed relative to the speed with which it is rotated in the condition of complete seaming.

Consequently, the check carried out as soon as the bending operation is completed will be carried out on cans machined at a speed different from the normal production speed, introducing potential errors on the verification, since the rotation speed affects the quality of the seaming.

The object of the present invention is to manufacture a seaming machine for connecting a lid to a container, which allows solving the problems described above in a simple and cost-effective manner.

A particular object of the present invention is to manufacture a seaming machine, which allows quickly passing from a condition of complete seaming to a condition of partial seaming and vice versa without the initial setting or the efficiency of the machine being compromised or the bending operation being modified.

According to the present invention a seaming machine for connecting a lid to a container is manufactured, as claimed in claim <NUM>.

The present invention further relates to a seaming method for connecting a lid to a container.

According to the present invention, a seaming method is provided, as claimed in claim <NUM>.

The invention will now be described with reference to the accompanying figures, which illustrate a non-limiting example embodiment thereof, wherein:.

In <FIG> and <FIG>, reference numeral <NUM> indicates, as a whole, a seaming machine for connecting a metallic closing lid <NUM> to a container <NUM>, it too metallic, and containing, preferably but not necessarily a food product, and for forming a hermetically closed container <NUM>, for example a can.

For this purpose, the machine <NUM> comprises a loading or receiving station <NUM>, in which a succession of lids <NUM> advanced by a conveyor <NUM> and a succession of containers <NUM> advanced by a conveyor <NUM> converge and in which each lid <NUM> is superimposed on a relative container <NUM> in a manner known per se.

The machine <NUM> further comprises an unloading station <NUM> of the hermetically closed containers <NUM>, from which the containers <NUM> are moved away by means of an evacuation conveyor <NUM>.

Still with reference to <FIG>, between the conveyors <NUM>, <NUM> and <NUM>, the machine <NUM> comprises a seaming assembly <NUM> for connecting a relative lid <NUM> to each container <NUM>.

With reference to <FIG>, the assembly <NUM> comprises, in turn, a fixed structure <NUM>, a rotating support structure <NUM> relative to the fixed structure <NUM> about a fixed axis <NUM> and a crown of seaming sections <NUM> carried by the structure <NUM> and advanced by the structure <NUM> in succession through the stations <NUM> and <NUM> along a circular seaming path P1 (<FIG>).

With reference to <FIG>, each seaming section <NUM> comprises a relative support plate <NUM> for a container <NUM>; the plate <NUM> rotates about a seaming axis <NUM> parallel to the axis <NUM> and defines a support plane P for the container <NUM> arranged coaxial to the axis <NUM>. The plate <NUM> is actuated by a known actuator <NUM> controlled for moving the plate <NUM> along the axis <NUM> between a lowered position, illustrated with a dashed line in <FIG>, for loading a container <NUM> in the station <NUM> and for unloading the hermetically closed container <NUM> in the station <NUM>, and a raised position for seaming or connecting the lid <NUM> to the relative container <NUM>.

Each seaming section <NUM> then comprises a relative seaming head <NUM> arranged above the relative plate <NUM> (<FIG>).

Each seaming head <NUM> comprises, in a manner known per se, a reference spindle arranged coaxially and above the plate <NUM> and, placed side by side with the spindle, a bending roller <NUM> and a pressing roller <NUM> having different external profiles from each other and known per se. The rollers <NUM> and <NUM> are coupled, in a known manner, to opposite end portions 24A of a horizontal crosspiece <NUM>, an intermediate portion 24B of which is firmly connected to a lower end section 25A of a driving shaft <NUM>. The driving shaft <NUM> is coupled to the rotating structure <NUM> in a rotating manner and in an axially fixed position relative to the rotating structure <NUM> about a vertical axis <NUM> by means of a pair of bearings K.

Each shaft <NUM> is rotated in an alternating cyclic motion by a motorized cam device <NUM> common to all the heads <NUM> and configured to horizontally translate the rollers <NUM> and <NUM>, in succession and in a known manner, from and towards the relative spindles and fix each lid <NUM> to the relative container <NUM>.

The device <NUM> comprises a crank <NUM>, an end portion 29A of which is firmly connected to an end portion 25B of the shaft <NUM> and an opposite end portion 29B of which is coupled to a cam follower member <NUM> of the device <NUM>.

The device <NUM> further comprises a control cam <NUM> having a groove <NUM> slidably engaged by the cam follower member <NUM>.

With reference to <FIG> and <FIG>, the cam <NUM> is made in one piece and is coupled to the fixed structure <NUM> in a manner rotating about the axis <NUM> and in an axially fixed position by means of pairs of bearings 31A.

The cam <NUM> is rotated by a linear actuator <NUM>, between two extreme angular end-of-stroke positions, of which a retracted one illustrated in <FIG> and <FIG> and an advanced one illustrated in <FIG>, wherein the cam <NUM> is rotated counter-clockwise and towards the unloading station <NUM> by a predefined angle X. Preferably, the angle X ranges from <NUM>° to <NUM>° and is conveniently equal to <NUM>°.

Conveniently, but not necessarily, the linear actuator <NUM> is a pneumatic piston, which is arranged above a horizontal plate 11A of the fixed structure <NUM> and, in turn, arranged above the cam <NUM>. The actuator <NUM> has a jacket <NUM> hinged to the fixed structure <NUM> and an output rod <NUM> coupled to the cam <NUM> by means of a vertical pin <NUM> integral with the cam <NUM> and sliding in a curved slot <NUM> obtained through the plate 11A. The curved slot <NUM> defines a guide for an intermediate section of the pin <NUM> and is configured in such a way as to define two angular shoulders angularly spaced from each other so as to stop the intermediate section in two extreme angular end-of-stroke positions angularly spaced from each other by the angle X (<FIG> and <FIG>).

Still with reference to <FIG>, the cam <NUM> is held in the two angular end-of-stroke positions in a releasable manner by respective vertical blocking pins <NUM>, each of which slides through a relative through opening <NUM> obtained through the plate 11A and is vertically movable under the thrust of a relative pneumatic actuator <NUM> fixed to the plate 11A (<FIG>,<FIG>, and <FIG>) between a lowered blocking position, in which it makes the cam <NUM> integral with the fixed structure <NUM> (<FIG>) and a raised position, in which it allows the cam <NUM> to freely rotate relative to the fixed structure <NUM>.

In use, by keeping the cam <NUM> in its retracted position (<FIG> and <FIG>), the machine <NUM> behaves like a traditional seaming machine, in which each of the forming sections <NUM> during their movement along the path P between the loading station <NUM> and the unloading station <NUM> produces a complete seaming, i.e. its own hermetically closed container <NUM> according to the sequence of operations illustrated in <FIG>. Specifically, after the loading station <NUM>, and once a period is passed in which the plate <NUM> is raised and the roller <NUM> approaches the container <NUM>, represented by sector A1, the bending operation of the perimeter edges <NUM> of the container <NUM> and of the lid <NUM> (<FIG>) by the roller <NUM> starts. The bending operation is represented by sector A of <FIG>.

During the bending operation, the plate <NUM> remains in its raised position, as indicated by sector B, the roller <NUM> carries out the bending of the perimeter edges <NUM>, whereas the pressing roller <NUM> is kept inactive, as shown by sector C still in <FIG>.

Once the bending operation is ended, after a period indicated by sectors D, in which the roller <NUM> moves away from the bent edges <NUM> and the roller <NUM> approaches the bent edges <NUM>, the pressing operation of the bent edges <NUM> by the roller <NUM> and represented by sector E starts. During the entire pressing operation, the plate <NUM> remains raised (sector B).

Once the pressing operation is completed and before reaching the unloading station <NUM>, the plate <NUM> returns to its lowered position (sector B1), the roller <NUM> moves away from the container <NUM> (sector E1) and in the station <NUM> the hermetically closed container <NUM> is transferred to the evacuation conveyor <NUM> and evacuated. Following the evacuation and when provided for, all the planned checks are carried out at the end of the seaming so as to ascertain the optimality of the seaming of the edges <NUM> and the correct sealing of the containers <NUM>.

Whereas, when the check on the bent edges <NUM> is required, the blocking pins <NUM> are carried into their retracted position, releasing the cam <NUM> from the constraint with the fixed structure <NUM>, after which the actuator <NUM> is activated and rotates the cam <NUM> counter-clockwise in <FIG> moving it into its advanced position, illustrated in <FIG>. In this manner, sectors A, A1,C,D,E and E1 are rotated counter-clockwise, as is visible in <FIG>, by the angle X, excluding or making in actual fact non-executable the pressing operation of the bent edges <NUM> represented, as mentioned in the foregoing, by sector E. In particular, in <FIG> it is immediately evident that the rotation of the cam <NUM> in a counter-clockwise direction and towards the unloading station <NUM> and the keeping of the cam <NUM> in the rotated end-of-stroke position, in actual fact delays the start and the end of the bending operation (sector A), keeping unchanged the bending cycle followed in the complete seaming, producing, in actual fact, an intermediate semi-finished product 4A.

Still in <FIG>, it is possible to see that the value of the angle X of rotation of the cam <NUM> is such that before the start E2 of what should be the pressing operation (sector E), the bent edges <NUM> of the intermediate semi-finished product 4A are spaced vertically from the seaming head <NUM> since the plate <NUM> at such instant E2 is already in a lowered position and spaced from the relative seaming head <NUM>.

In general, the value of the angle X is such that when the start of the pressing operation is planned, the pressing roller <NUM> does not find or does not come into contact with the bent edges <NUM> so that the pressing roller <NUM> will carry out a "blank" pressing operation.

In an optimization example of the seaming cycle, the blank pressing operation starts when the plate <NUM> is approximately halfway its descent stroke towards its lowered position. Obviously, and still for a matter of optimizing the seaming cycle or on the basis of the geometric features of the bent edges <NUM>, the instant of absence of contact of the roller <NUM> with the bent edges <NUM> can be modified with reference to the position assumed by the plate <NUM> between the raised and lowered positions. For example, still from the graph of <FIG> it is apparent that following the rotation of the cam <NUM>, the moving away operation of the bending roller <NUM> from the container <NUM> is kept unchanged, hence the angle X of rotation can be such that the moving away operation ends after the plate <NUM> begins its descent towards its lowered position.

Still in <FIG>, it is apparent that the angle X of rotation of the cam <NUM> is such that the instant E2 of the start of what should be the pressing operation is arranged before the intermediate semi-finished product 4A, i.e. with only the edges bent, reaches the unloading station <NUM>.

From the foregoing it is evident that the simple rotation of the entire control cam <NUM> about the axis <NUM> towards the unloading station <NUM> by a predetermined angle allows arranging all the forming sections <NUM> in the condition to release in the unloading station <NUM> an intermediate semi-finished product 4A in which the edges <NUM> have only been subjected to the bending operation. Such intermediate semi-finished products 4A can therefore be subjected to the planned check operations.

In this regard it is important to note that with respect to the known solutions, in the described machine <NUM>, due to the rotation of the entire cam <NUM>, the bending operation of the edges is carried out exactly in the same manner and especially at a rotation speed of the rotating structure <NUM> which is exactly the same at which the rotating structure <NUM> is rotated during the complete seaming. It follows that the bending state of the edges examined following the exclusion of the pressing operation corresponds exactly to that obtained at the end of the bending operation in the complete seaming cycle.

In addition to this, still with respect to the known solutions, in the described machine <NUM>, the cam <NUM> is never modified from a geometrical or dimensional point of view for excluding the pressing operation, but simply rotated. Consequently, in the machine <NUM> there are no discontinuities and the latter cannot occur in the profile for controlling the rollers <NUM> and <NUM> preventing, in such manner, any bouncing of the cam follower and the consequent onset of stresses and vibrational states present, instead, in the known solutions.

From a constructive point of view, the described machine <NUM> is, still with respect to the known solutions, constructively simple, easily controllable and has reasonable costs. The exclusion of the pressing operation is obtained, in fact, by means of the mere actuation of a single linear actuator which rotates the cam <NUM> between two end-of-stroke angle positions defined by mechanical stops.

From the foregoing it is then evident that under no condition are the settings of the machine <NUM> lost and periodic check operations are not necessary.

From the foregoing it is evident that modifications and variations can be made to the described machine <NUM> without thereby departing from the scope of protection defined by the claims.

In particular, the actuator <NUM> could be different from the one indicated by way of example and be replaced for example by a linear electric motor or by a rotary electric motor connected to the cam <NUM> directly or through a mechanical transmission.

Furthermore, the machine <NUM> could comprise a number of forming sections different from that represented in the accompanying figures.

Claim 1:
Seaming machine for connecting a lid to a container, the machine (<NUM>) comprising a fixed structure (<NUM>), a rotating structure (<NUM>) relative to the fixed structure (<NUM>) about a fixed vertical axis (<NUM>) and a plurality of seaming sections (<NUM>) carried by said rotating structure (<NUM>); each forming section comprising a support plate (<NUM>) for a container (<NUM>) and a seaming head (<NUM>); the plate (<NUM>) being movable along a moving vertical axis (<NUM>) in opposite directions and relative to the head (<NUM>) between a lowered position and a raised position; each seaming head (<NUM>) comprising a rotating reference spindle arranged coaxially and above said support plate (<NUM>) and a bending roller (<NUM>) and a pressing roller (<NUM>) having different external profiles from each other placed side by side with the spindle; the machine (<NUM>) further comprising a mechanical operating cam (<NUM>) made in one piece, carried by said fixed structure (<NUM>) and configured to move said bending and pressing rollers (<NUM>, <NUM>) crosswise to said moving vertical axis (<NUM>) away from and towards said spindle, characterised in that said cam (<NUM>) is coupled to said fixed structure (<NUM>) in a manner rotating about said fixed vertical axis (<NUM>) and in that of comprising motorised actuator means to rotate said mechanical cam (<NUM>) between an operating position of complete seaming of the lid (<NUM>) to the container (<NUM>) and a position of partial seaming of the lid (<NUM>) to the container (<NUM>).