Metal Containers and Process and Installation for Manufacturing Metal Containers

This application relates to and claims the benefit of International Application No. PCT/ES2023/070776, filed Dec. 21, 2023, which claims the benefit and priority to European Patent Application No. EP23382011.7, filed Jan. 10, 2023, each of which is incorporated by reference herein in its entirety.

The present invention relates to a process and an installation for manufacturing metal containers and to the metal containers obtained with the process.

Metal containers for containing beverages, foods, or cosmetic and pharmaceutical products, such as beverage cans, deodorant aerosol sprays, etc., are well known. Metal containers of this type are manufactured from a metal disc, generally an aluminum disc, which is subjected to a hot extrusion and forming process referred to as impact extrusion.

The installation for manufacturing metal containers initially comprises a metal disc feeder and an extrusion press in which the metal disc is extruded to form a metal container. The container obtained in the press comprises a cylindrical body with a side wall, a bottom, and an open end opposite the bottom. In a later phase, the installation comprises a necking machine, in which the cylindrical body of the container is formed to obtain a neck with a curled portion at the open end. The process to obtain the curled portion is commonly known as “curling”. Furthermore, the installation comprises other machines for performing operations for washing, applying coatings, painting, and screen printing on the container, among others.

In a further installation, the container is completely finished by placing a valve comprising a gasket supported on the curled portion of the open end to establish an airtight closure of the container. For example, the finished container may be an aerosol which is formed by the cylindrical body and a sprayer comprising the valve that is arranged at the open end closing the cylindrical body of the container.

Ensuring good contact between the curled portion of the open end and the valve gasket is critical to guarantee a proper airtight closure of the container. The curled portion is obtained in the necking machine by curving the open end outwardly (curling), such that the curled portion has a rounded shape which does not allow a good contact to be ensured. Therefore, in order to improve contact with the valve gasket and thus improve the closure of the open end of the container, obtaining a flat surface at the curled portion of the open end is known. For example, EP915029A1 shows a process of manufacturing a metal container in which the flat surface is obtained by machining the upper part of the curled portion.

Disclosed is an installation for manufacturing metal containers, and a metal container obtained with the process.

One aspect of the invention relates to a process for manufacturing metal containers, comprising the following steps:

According to the invention, in order to obtain the flat surface, the process comprises:

Another aspect of the invention relates to an installation for manufacturing metal containers according to the above process, comprising:

Another aspect of the invention relates to the metal container obtained with the process described above.

In this way, in the first sub-step, the applied pressure changes the geometry of the curled portion from round to flat, which increases the surface available for supporting the valve gasket that is to be later arranged in order to close the open end of the metal container; however, the flat surface obtained is coated with the coating and is, therefore, slippery, which does not ensure a good contact with the valve gasket. In the second step, the machining removes the coating and leaves the metal exposed, so the flat surface is rougher and allows a better fixing of the valve gasket.

In document EP915029A1, the flat surface is obtained in a single step, by machining the rounded upper part of the curled portion, leaving the metal exposed. The side wall of the metal container is very thin (between 0.5-0.7 mm thick), and single-step machining weakens the curled portion, since it removes the coating and part of the metal, creating a central point in the curled portion that is not very thick and can cause later breaking or leaking. This means that the machining must be very precise in order to avoid weakening the curled portion. With the process of the invention, in the first sub-step, material is not removed and the geometry of the curled portion goes from round to flat but maintains the same thickness, which means that the subsequent machining in which the coating is removed is simpler and safer because a flat surface is machined directly, therefore minimizing the risk of weakening the curled portion.

These and other advantages and features will become apparent in view of the figures and detailed description.

The manufacture of metal containers, for example, containers made of aluminum such as cans or aerosols, for containing a product, such as beverages, foods, or cosmetic and pharmaceutical products, requires a process in which different machines which are arranged in an installation for manufacturing metal containers are used. Depending on the operations to be performed for manufacturing the container, different types of machines can be used, and the machines can be arranged in the installation in different ways.

The containers are processed in the installation continuously and at a high speed, for example, processing in the order of two hundred containers per minute. The machines are automatically linked by means of transfer units, such as linear conveyor belts, rotary carrousels, or similar elements, which transfer the containers from one machine to another.

shows a block diagram of a non-limiting example of an installation for manufacturing metal containers. The installation comprises a feeder, an extrusion press, a trimming machine, a washing machine, a drying machine, an internal varnishing machine, a polymerization furnace, a print set comprising a glazing machine, a lithographic printing machine, and an overprint varnishing machine, a necking machine, an inspection machine, and a packaging machine.

The discsare lubricated and supplied from the feederto the extrusion presswhere the discsare extruded to form metal containers. Preferably the discsare aluminum discs.

Each metal containerobtained in the extrusion presshas a cylindrical bodywith a main axis X. The containeris made in a single piece. The cylindrical bodycomprises a side wall, a bottom, and an open endopposite the bottom.

shows a schematic example of the transformation of a metal discinto a metal containerby means of an extruderof the extrusion presswhich forces the material of the metal discto deform and be transformed into the cylindrical body. The extrusion process is well known and not described in further detail.

The open endof the containersis trimmed in the trimming machineto remove impurities, and the containersare brushed. The containersare then washed in the washing machineto remove impurities that may remain in the metal, for example, with alkaline water, and the containersare then dried in the drying machine.

After drying, a coatingis applied on the inside of the cylindrical bodyof the containersin the internal varnishing machineto create a protective barrier between the metal of the containerand the product to be contained in the container. The coatingcan be a lacquer that complies with Regulation (EC)/and Regulation (EC)/on “Materials and articles intended to come into contact with food”. Once the coatinghas been applied, the containeris heated in the polymerization furnaceto harden the coating, for example, the containers are heated at a temperature of about 250° C. depending on the type of lacquer used.

An outer coating of the containeris applied in the glazing machineof the print set to prepare it for printing on same in the lithographic printing machine, and the containeris then externally coated in the overprint varnishing machineto protect the print.

The open endof the containeris then deformed in the necking machineto create a neckwith a curled portion. The neckis configured to receive a closure element for closing the container, such as the valve of an aerosol sprayer. Lastly, the containeris inspected in the inspection machineto detect cracks in any area of the finished container, and lastly, the containersare grouped together in the packaging machineby batches to be sent to an external factory where the containersare filled with the final product (beverages, foods, or cosmetic and pharmaceutical products), and the open endof the containersis closed with the closure element.

The necking machinecomprises a clamping tablewith clamping stationsfor clamping the containersby the bottom, and a tool tablewith tool stationsto form the upper endof the containers. The clamping tableis facing the tool table, and the clamping stationsand tool stationsare movable with respect to the others to form the containers. See.

The clamping tableis rotary and oriented vertically. The clamping tablehas a rotational movement around a horizontal axis, in an indexed manner in defined positions. The clamping tablecomprises the plurality of clamping stationsarranged on the periphery thereof. The containersreach the clamping tablein a sequential manner, with the containersbeing fed to said clamping table, and with each containerbeing arranged in one of the clamping stations.

The tool tablehas a translational movement A towards the clamping tablefrom a set back position to a forward position, and a translational movement B from the forward position to the set back position. After each indexed rotational movement of the clamping table, the tool tableadvances with the translational movement A and moves backwards with the translational movement B, before the following rotational movement of the clamping table. The tool tablecomprises the plurality of tool stationsarranged on the periphery thereof. Each tool stationis located in a position facing one of the clamping stationsduring formation of the container, said formation occurring during the translational movement of the tool table. An operation for forming the open endof the containeroccurs in each tool station. The tool stationsare configured depending on the shape of the containerto be obtained. For example, the tool tablecan have forty tool stations. The containersare formed by means of stamping strokes between the stationsandof the forming machine.

show the steps of transforming a metal discinto a metal containerwith a curled portionon the neckof the open endof the metal container.shows the metal discwhich is supplied to the extrusion press.shows the metal containerafter exiting the extrusion press.shows the open endthat has been trimmed in the trimming machine.shows the containerafter exiting the internal varnishing machinewith the coatingapplied on the inside of the cylindrical bodyof the container.shows the containerwith the neckformed at the open end.shows the containerwith the curled portionformed after curving the neckoutwardly. The neckand the curled portionare made in the necking machine.

shows an enlarged detail ofdenoted with reference IV, where the rounded shape of the curled portioncan be observed. According to the invention the process comprises obtaining a flat surfacein the curled portionof the open endof the metal container. To obtain the flat surfacethe process comprises a first sub-step wherein the curled portionis pressed to obtain the flat surfacein a plane N normal to the main axis X of the cylindrical bodyof the metal container(see), and a second sub-step wherein the curled portionthat has been previously pressed is machined to remove the coatingfrom the curled portion, leaving the metal of the metal containerexposed. (See). A flat surfacewithout the coatingis thereby obtained, which allows the metal of the containerto be seen, thereby allowing the valve gasket that is to be later arranged to be suitably supported and to establish a proper airtight closure with the open endof the container, since the metal of the containeris rougher than the coating. In addition, obtaining the surface in two sub-steps minimizes the risks of reducing the thickness of the curled portion.

As observed in, when the curled portionis pressed, the flat surfaceis obtained in the upper part of the curled portion, maintaining the thickness of the curled portion. In other words, in the first sub-step a first flat surfaceis obtained in the upper part of the curled portionand a second flat surface′ is obtained in the lower part of the curled portion, which is parallel to the first flat surface, wherein the thickness of the curled portionbefore and after pressing the curled portionis the same. For example, the side wallof the metal containerhas a thickness of between 0.5-0.7 mm, and therefore the curled portionhas a thickness of between 0.5-0.7 mm, and after pressing the curled portion, the same thickness of between 0.5-0.7 mm is maintained.

Preferably, in the second sub-step the curled portionis machined at an angle comprised between 5° and −5° with respect to the normal plane N, even more preferably at an angle of 0° with respect to the normal plane N.

Preferably, the excess material of the coatingremoved from the curled portionis aspirated. Although the first sub-step presses the coatingof the curled portionand facilitates later machining, traces of coatingmay remain at the open end, such that said material is aspirated, preferably the excess material of the coatingis aspirated while machining is being performed.

After the extrusion of the metal disc, a containerwith a thin side wallis obtained, for example, the side wallof the metal containerhas a thickness of between 0.5-0.7 mm, such that in the second sub-step, the curled portionis machined with a depth of less than 0.1 mm to minimize the risk of weakening the curled portion. That depth allows the coatingto be removed without weakening the curled portion.

Preferably, in the second sub-step the coatingof the curled portionthat has been pressed is removed and part of the metal is removed from the metal container. This allows guaranteeing a complete removal of the coatingand allows the metal of the container to be lightly machined to improve the fixing with the valve gasket that is to be later arranged.

Preferably, the flat surfaceis formed in the necking machine. Some of the tool stationsof the forming machineare thereby used to make the flat surface.

One of the tool stationshas a first toolingfor pressing the curled portionand obtaining the flat surface, and another one of the tool stationshas a second toolingfor machining the curled portionand removing the coating, leaving the metal of the metal containersexposed.

For example, the first toolingmay comprise rotating cylindrical wheels that press the curled portionof the containerand obtaining the flat surface, and the second toolingmay comprise front cutting blades for machining the previously pressed curled portionand removing the coating.

The first flat surfaceof the upper part of the curled portionis obtained by applying pressure on the upper part of the curled portionand the second flat surface′ of the lower part of the curled portionis generated at the same time by the pressure exerted on the upper part of the curled portion. When aluminum is used as the material of the container, it is not necessary to use a lower die to obtain the second flat surface′ of the lower part of the curled portion, and it is sufficient for the first toolingto apply pressure on the upper part of the curled portion.

In this sense, the neckof the containeris initially formed progressively in the first tool stationsof the necking machine, in the antepenultimate tool stationthe neckis curved outwardly to obtain the curled portion, in the penultimate tool station, with the first tooling, the curled portionis pressed to obtain the flat surface, and in the last tool station, with the second tooling, the coatingthat covers the previously pressed curled portionis machined. The second toolingmay comprise a pipe for aspirating the chips of coatingthat detach during machining.

shows an aerosolcomprising the metal containerand a sprayerarranged in the metal container, andshows the sprayerof the aerosolresting on the curled portionof the open endof the metal container.

Accordingly, the aerosolcomprises a metal containeras described above and a sprayerarranged in the metal containerfor spraying the product from the interior of the metal container.

The metal containerof the aerosolcomprises a cylindrical bodyhaving a main axis X and a coatingapplied to the interior of the cylindrical body. The cylindrical bodycomprises a side wall, a bottomand an open endopposite the bottom, and the open endhas a neckwith a curled portionhaving a flat surfacein a plane N normal to the main axis X of the cylindrical body, wherein the flat surfaceis manufactured in a first sub-step wherein the curled portionis pressed to obtain the flat surfacein the normal plane N with respect to the main axis X of the cylindrical bodyof the metal container, and a second sub-step wherein the curled portionthat has been previously pressed is machined to remove the coatingfrom the curled portion, leaving the metal of the metal containerexposed.

The metal of the side walland the metal of the curled portionhave the same thickness after obtaining the flat surface.

The sprayerhas a valvewith a gasketwhich is supported on the flat surfaceto establish an airtight closure of the open endof the metal container.

The valvehas a flanged portionwhich fits over the curled portionof the neckof the metal container, and between the flanged portionand the curled portionis disposed the gasket.

The gasketis an elastic element which is compressed in the cavity defined between the flanged portionand the curled portion. The flat surfaceof the curled portionensures the contact of the gasketand improves the sealing of the metal container.

Embodiments are disclosed in the following clauses/

Clause 1. Process for manufacturing metal containers, comprising the following steps:

Clause 2. Process according to clause 1, wherein in the second sub-step, the curled portion () is machined at an angle comprised between 5° and −5° with respect to the normal plane (N).

Clause 3. Process according to clause 2, wherein the curled portion () is machined at an angle of 0° with respect to the normal plane (N).