The present invention refers to a process to provide the upper closure of a container formed in metal sheet, such as a closed pail or other container comprising a peripheral lateral wall, with a cylindrical form or an inverted and slightly frusto-conical form and presenting an upper end portion and a lower end portion, to which respective end walls are attached. Prior Art

The containers of the type considered herein have their upper and lower end walls respectively and peripherally double-seamed in the upper end portion and lower end portion of the peripheral lateral wall, the upper end wall being provided with an a generally eccentric opening having a contour substantially smaller than that of the peripheral lateral wall, and with a gripping handle contained in the interior of the axial projection of the contour of the container, in order to allow the latter to be lifted by the gripping handle attached only to the upper end wall. The opening provided on the upper end wall is configured to define a seat to which is applied a lid generally formed in a plastic material . Due to the complexity of the double-seaming processes, which require the use of specific and generally expensive equipment, these double-seaming phases in the manufacture of the container considered herein are rarely carried out in the product filling facilities. Thus, the containers are closed in the manufacturer's facilities, by double-seaming the end walls to the peripheral lateral wall of the container, being then shipped to the facilities for filling the product to be commercialized. Since the containers are shipped with the end walls already double-seamed to the peripheral lateral wall, they cannot be fitted one inside the other, requiring to be arranged side-by-side and stacked in the transport vehicles and also in the storage places, both at the container manufacturer and at the filling facilities, requiring a physical space presenting an undesirable large volume in relation to the mass of the material, considerably increasing the shipping and storage costs and requiring special cares to transport these containers.

Another drawback of these containers supplied to the responsible for the filling operation with the end walls already attached, generally by double-seaming, results from the fact that the filling can be only carried out through the opening of reduced dimension provided in the upper end wall. Thus, the time for filling the product is longer than that corresponding to the filling carried out without the upper end wall, as it occurs upon filling containers which are superiorly closed by a removable lid and provided with a suspension handle applied to the peripheral lateral wall and not to the lid. Aiming to overcome the inconveniences cited above, it was proposed a constructive solution object of the Brazilian patent application PI 0804305-1, "CONTAINER IN METAL SHEET", filed on 10/09/2008 by the present applicant. In this prior solution, the upper end wall can be easily, quickly, reliably and hermetically affixed to the peripheral lateral wall of the container by the filler of the product, without requiring double- seaming operations. According to said prior constructive solution of the same applicant, the upper peripheral edge of the peripheral lateral wall and the outer peripheral edge of the upper wall are conformed to allow them, through a simple and simultaneous deformation operation to be carried out by the filler, to be reliably and hermetically affixed to each other, generally with the aid of an elastic sealing element, in the form of a gasket compressed between the deformed edges of the peripheral lateral wall and the upper wall. In the applications in which a high degree of axial retention is required between the upper wall, provided with a suspension handle, and the peripheral lateral wall of the container, the upper end portion of the latter and the peripheral upper skirt of the upper end wall are provided with one or more circumferential ribs and grooves which cooperate with each other, upon fitting the upper end wall in the interior of the upper end portion of the peripheral lateral wall.

Although the provision of the circumferential ribs and gropves leads to a substantial increase in the degree of axial retention of the upper end wall, as well as in the degree of hermeticity in said upper closure of the container, these ribs and grooves are provided separately in the skirt of the upper end wall and in the peripheral lateral wall of the container, by the manufacturer of the latter, requiring an undesirable dimensional precision in the manufacture of the two parts, in order to allow fitting them at the final closure of the container and obtaining the desired degrees of axial retention and additional sealing. This prior solution, although providing the advantages mentioned in said prior patent application of the same applicant, has the inconvenience of requiring costly manufacturing procedures . Summary of the Invention

Due to the inconvenience commented above in relation to the prior solution, it is an object of the present invention to provide a process for closing a container in metal sheet, having a peripheral lateral wall, a lower end wall and an upper end wall which is provided with a small discharge opening and with a suspension handle and which can be easily, quickly, reliably and hermetically affixed to the peripheral lateral wall by the filler of the product to be packaged, without requiring double- seaming operations or costly operations for conforming the peripheral lateral wall and the upper end wall with reduced dimensional tolerances .

The present process is applied for closing a container in metal sheet, of the type which comprises a tubular body formed by a peripheral lateral wall having an upper end portion and a lower end portion, to which respective upper and lower end walls are attached. According to the invention, the closing process comprises the steps of forming the tubular body in metal sheet, conforming its upper and lower end portions, so as to provide them, respectively, with an upper retention hook and with a lower retention hook, the lower retention hook being conventionally double- seamed to the lower end wall .

The upper end wall is conformed in metal sheet, so as to present a peripheral upper skirt with its end edge being bent to configure an upper closure hook when the container is superiorly closed, still empty or already filled with the product.

The upper closure hook and the upper retention hook and also the peripheral upper skirt of the upper end wall and the upper end portion of the peripheral lateral wall are then deformed together, in order to provide a seaming of said hooks, upon compressing an intermediary elastic sealing element, and also the formation of at least one outer circumferential retention rib in the peripheral upper skirt and a respective inner circumferential retention groove in the upper end portion of the peripheral lateral wall, tightly fitting the retention rib.

The closing process proposed by the invention allows the upper end wall to be hermetically and reliably seamed to the tubular body of the container, without requiring the costly and complex operations of double- seaming or previously forming the retention ribs and grooves with expensive dimensional tolerances which hamper the manufacture and raise the costs of these containers .

With the proposed process, the containers can be manufactured without the retention ribs and grooves and conveyed to be filled, with the upper end wall still as a separate piece, but with the lower end wall already duly double-seamed to the tubular body.

In the proposed solution, the whole cross section of the still open upper end portion can be used during the filling, reducing the operation time before the operation of fitting and retaining the respective end wall in the interior of the peripheral lateral wall, by means of simple and concomitant axial and radial compression operations, to provide the deformation of both the closure hook and the upper retention hook and the concomitant formation of the circumferential rib and groove .

In case the peripheral lateral wall is constructed so as to taper from one end portion to the other, generally from the upper end portion to the lower end portion, in a continuous or stepped manner, the containers can be stored and shipped without the upper end wall and in a condition in which they remain partially fitted one inside the other in stacks, allowing a substantial economy in storage and transportation volume until they are closed at the filling facility and, preferably, after the filling operation . Brief Description of the Drawings The invention will be described below, with reference to the enclosed drawings, given by way of example of one of the possible embodiments of the invention and in which : Figure 1 represents a top plan view of the present container, with its peripheral lateral wall presenting a circular contour; Figure 2 represents a partial diametrical sectional view of the container, illustrating the upper end wall and lower end wall affixed to the peripheral lateral wall, said section taken according to line II-II in figure 1; Figure 3 represents an enlarged exploded detail of the region of figure 2 which illustrates the fitting of the upper end wall in the upper end portion of the peripheral lateral wall, illustrating the form of the component parts before seating the upper end wall onto the peripheral lateral wall;

Figure 4 represents the same detail of figure 3, but illustrating the upper end wall already seated and only provisionally retained to the peripheral lateral wall; Figure 5 represents a reduced lateral view of the container represented in figure 4 when a seaming device is applied thereto for compressing the closure hook and the upper retention hook, for forming the axial retention rib and groove. Figure 5A represents a view similar to that of figure 4, but illustrating the application of the seaming device to provide the simultaneous deformation of the closure hook and upper retention hook and of the peripheral upper skirt together with the upper end portion of the peripheral lateral wall, so as to form the circumferential rib and groove to be tightly fitted together;

Figure 6 represents a view similar to that of figure 5, but illustrating only the container; and Figure 7 represents a partial diametrical sectional view of two containers constructed according to the present process, deprived of the upper end wall and partially fitted one into the other. Description of the Invention

The present closing process is applied to a container formed in metal sheet, usually tinplate, and comprising a tubular body C formed by a peripheral lateral wall

10, with any polygonal cross section, usually circular and having an upper end portion 10a and a lower end portion 10b, in which respective upper end wall 20 and lower end wall 30 are affixed.

According to the invention, after conforming a metal sheet portion to form the tubular body C, the latter is submitted to an operation for conforming the upper end portion 10a and lower end portion 10b of the peripheral lateral wall 10. The conformation of the upper end portion 10a is made so as to provide, therein, an upper peripheral edge 10c which is outwardly and downwardly bent, defining an upper retention hook 11 with a profile in the approximate form of an inverted U. In the preferred form of the invention, the upper retention hook 11 is conformed to present an inner lateral leg 11a defined by part of the upper end portion 10a of the peripheral lateral wall 10, an arched base leg lib and an outer lateral leg lie which is convergent in relation to the inner lateral leg 11a. The conformation of the lower end portion 10b of the peripheral lateral wall 10 is made to provide a lower peripheral edge 1Od which is outwardly bent to define a lower retention hook 12 which may present any known prior art configuration to allow the fixation, for example by double-seaming, of the likewise conformed peripheral edge of the lower end wall 30, also in metal sheet and with any conventional construction. The solution used to reliably and hermetically affix the lower end wall 30 to the tubular body C is not a particular aspect of the present process, which fixation may be carried out at the manufacturer's facilities by any adequate method.

After conforming the tubular body C and the upper retention hook 11 and the lower retention hook 12, a peripheral edge of the lower end wall 30 is affixed to the tubular body C, generally by double - seaming . Concomitantly to the formation of the tubular body C and to the closing of its lower end wall 30, a metal sheet portion is conformed to define the upper end wall 20 comprising a median panel 21, which is optionally provided with well known prior art stiffening circumferential ridges, and with a peripheral upper skirt 22, projecting axially outwardly and which is configured to be tightly fitted, under interference, in the interior of the upper end portion 10a of the peripheral lateral wall 10. The peripheral upper skirt 22 has an end edge 22c which is outwardly, downwardly and inwardly bent, so as to define a closure hook 23 with a profile in the approximate form of an inverted U. In the preferred and illustrated form, the closure hook 23 is conformed to present an inner lateral portion 23a, defined by an upper part of the peripheral upper skirt 22 of the upper end wall 20, an arched base portion 23b and an outer lateral portion 23c which is convergent in relation to the inner lateral portion 23a and which internally incorporates an end flange 23d which projects upwardly.

According to the process of the invention, the peripheral upper skirt 22 of the upper end wall 20 can be then fitted and seated in the interior of the upper end portion 10a of the peripheral lateral wall 10, with the container being empty or already filled with the product, said fitting being carried out to seat the closure hook 23 onto the upper retention hook 11, sandwiching an elastic sealing element 40 previously provided between said hooks 23, 11. (See figures 4, 5A and 6) .

In the solution illustrated in the drawings, the fitting of the closure hook 23 onto the upper retention hook 11 is made so that the arched base portion 23b of the former is seated on the arched base leg lib of the latter, with the elastic sealing element 40, for example a plastisol film, being disposed between said arched base portion 23b and arched base leg lib. As illustrated, the elastic sealing element 40 is preferably applied under the arched base portion 23b of the closure hook 23, so as to be seated against the arched base leg lib of the upper retention hook 11 upon fitting and seating the upper end wall 20 in the interior of the upper end portion 10a of the peripheral lateral wall 10. The exploded view of figure 3 illustrates the form imparted to the parts before closing the container. In this stage, the diameter of the free end edge of the outer lateral leg lie of the upper retention hook 11 is slightly smaller than the diameter of the free upper edge of the end flange 23d which projects upwardly outwardly inclined. Thus, upon seating the upper end wall 20 in the condition illustrated in figure 4, both said parts suffer an elastic deformation to allow the end flange 23d to be fitted under the free end edge of the outer lateral leg lie of the upper retention hook 11.

Being the container ready to be closed, generally after having already been filled with the product to be packaged, with the upper end wall 20 being , already fitted and seated in the interior of the upper end portion 10a of the peripheral lateral wall 10, the closure hook 23 and the upper retention hook 11 and also a portion of the peripheral upper skirt 22 and a confronting region of the upper end portion 10a may be submitted to a joint deformation operation, so as to provide the seaming of the closure hook 23 onto the upper retention hook 11, compressing the elastic sealing element 40 therebetween and further forming at least one outer circumferential retention rib 24 in the peripheral upper skirt 22 and one inner circumferential retention groove 14 in the upper end portion 10a of the peripheral lateral wall 10, said retention rib 24 being tightly fitted in the interior of the retention groove 14, guaranteeing a tight and reliable coupling between the parts of tubular body C and upper end wall 20, without requiring especial manufacturing cares for allowing the retention rib 24 to perfectly follow the inner contour of the retention groove 14.

The deformation of both the closure hook 23 and the upper retention hook 11 is obtained by applying an inward and upward radial force, in opposition to the application of an outward radial force, against the peripheral upper skirt 22 and the upper end portion 10a of the peripheral lateral wall 10, in order to simultaneously form the retention rib 24 and the retention groove 14. In the preferred and illustrated construction, the fitting of the closure hook 23 onto the upper retention hook 11 is made so that the arched base portion 23b of the closure hook 23 is seated onto the arched base leg lib of the upper retention hook 11, the seaming of the closure hook 23 onto the upper retention hook 11 also being made so as to seat the inner lateral portion 23a, arched base portion 23b and outer lateral portion 23c of the closure hook 23 respectively against the inner lateral leg 11a, arched base leg lib and outer lateral leg lie of the upper retention hook 11, compressing the elastic sealing element 40 and having the end flange 23d projecting upwardly to the interior of the upper retention hook 11, between the outer lateral leg lib and the inner lateral leg 11a of the latter. As illustrated in figures 5 and 5A, the deformations for seaming the hooks and for forming the retention rib 24 and the retention groove 14 can be easily carried out after the filling of the product, by means of a seaming device 50 which comprises a plurality of outer peripheral fingers 51 and a plurality of inner peripheral fingers 52, said outer peripheral fingers 51 and inner peripheral fingers 52 being configured to jointly define circular alignments, with a variable diameter as a function of the operation of the seaming device 50, and to act simultaneously against the hooks from the outer side of the container and against the peripheral upper skirt 22, so as to simultaneously produce the seaming deformation of both the upper closure hook 23 and the upper retention hook 11 and the formation of both the retention rib 24 and the retention groove 14. As can be noted in figure 5A, the outer peripheral fingers 51 and inner peripheral fingers 52 are configured to impart, to the respective parts against which they are seated, the desired con-formation to obtain both the seaming of the hooks and the fitting between the peripheral upper skirt 22 and the upper end portion 10a of the peripheral lateral wall 10, guaranteeing a strong axial retention between the upper end wall 20 and the tubular body C of the container, besides establishing a sealing region additionally to that defined by the seaming of the closure hook 23 and upper retention hook 11, with the provision of the elastic sealing element 40 therebetween .

Further as illustrated, after finishing the deformation of the closure hook 23 and upper retention hook 11, the outer lateral leg lie of the upper retention hook 11 and the outer lateral portion 23c of the closure hook 23 assume a substantially rectilinear and downwardly and radially inwardly inclined profile, guaranteeing a strong, reliable and tight fixation of the upper end wall 20 to the peripheral lateral wall 10. With the purpose of facilitating the accommodation of the two parts to be fixed to each other, as well as the operations of plastic deformation of the metal sheet upon the initial and final formation of the two hooks, the inner lateral leg 11a of the upper retention hook 11 and the inner lateral portion 23a of the closure hook 23 are initially conformed to present a profile that is substantially rectilinear and slightly inclined upwardly and radially outwardly.

According to the illustrated embodiment, the retention rib 24 and the retention groove 14 are constructed so as to present a cross section with the approximate form of a rounded V, in a convex and in a concave arc, respectively.

Depending on the characteristics of the application of the elastic sealing element 40, it may have a portion of its extension penetrating and being compressed between the inner lateral leg 11a and the inner lateral portion 23a of the upper retention hook 11 and of , _^ the closure hook 23, respectively, as illustrated in figure 5. Considering that the construction of the present container aims at obtaining a closure which is easily executed, but which can comply with the safety requirements applied to the containers for dangerous products, the peripheral lateral wall can be provided with energy absorbing means by controlled plastic deformation. Thus, the peripheral lateral wall 10 can present two regions respectively adjacent to the upper end portion 10a and lower end portion 10b, each occupying about 10% to 15% of the height of the peripheral lateral wall 10 and conformed in a plurality of circumferential grooves 1Oe presenting a profile in the form of a laid V with a rounded apex. These regions present a pleated structure which tends to deform before an undue deformation of the container occurs in the regions in which the end walls 20, 30 are affixed to the peripheral lateral wall 10.

As can be observed in figures 1 and 2, considering that the two upper end wall 20 and lower end wall 30 are affixed, in a non-removable manner, to the peripheral lateral wall 10, the median panel 21 of the upper end wall 20 is provided with a generally eccentric opening 21a of smaller diameter, and with a gripping handle 60 generally positioned in the central region of said upper end wall 20, the gripping handle 60 being integrally affixed in said upper end wall 20, so as to allow the container, even if filled, to be lifted by- said gripping handle 60. In this type of construction, the smaller diameter opening 21a is usually closed by a removable lid; preferably constructed in a plastic material and which is not illustrated herein, as it forms no part of the present invention. As already previously mentioned and further illustrated in figure 7 of the enclosed drawings, the peripheral lateral wall 10 of the container can be constructed to allow the partial telescopic fitting between two stacked containers. In the illustrated embodiment, the peripheral lateral wall 10 has an inverted and slightly frusto-cOnical form, the smaller base coinciding with the lower end wall 30 and the larger base being preferably situated in a plane axially spaced back in relation to the mounting plane of the upper end wall 20 and in which the peripheral lateral wall 10 is deformed to define an outer circumferential projection 19.

With this construction, a container can be telescopically fitted inside another inferiorly disposed container deprived of the upper end wall, this fitting, as illustrated in figure 7, being carried out until the outer circumferential projection 19 is seated onto the free edge of the upper end portion 10a of the peripheral lateral wall 10 of the inferiorly disposed container, allowing the thus stacked containers to occupy a total volume substantially inferior to the volume that would be occupied with the same number of inferiorly and superiorly closed containers stacked one on top of the other. With this partial fitting arrangement, the containers can be stored and shipped with a great economy in volume and, accordingly, in cost.

While only one embodiment of the invention has been illustrated herein, it should be understood that the present closing process can suffer alterations in the deformation characteristics of the involved parts, without departing from the constructive concept defined in the claims that accompany the present specification.