EP2797817A1

EP2797817A1 - A can with a polygonal cross section

Info

Publication number: EP2797817A1
Application number: EP12816226.0A
Authority: EP
Inventors: Antonio Carlos Teixeira ÁLVARES; Silvério Cândido DA CUNHA
Original assignee: Brasilata SA Embalagens Metalicas
Current assignee: Brasilata SA Embalagens Metalicas
Priority date: 2011-12-27
Filing date: 2012-12-18
Publication date: 2014-11-05
Also published as: MX2014008035A; CN104159828A; US20140353319A1; TW201339058A; BRPI1105354A2; WO2013097009A1; KR20140107402A; JP2015507581A

Abstract

The present can comprises a tubular body (C) formed by lateral walls (10) of rectangular contour and which are connected, two by two, by longitudinal edges (13), said tubular body (C) being closed by an upper wall (11) and a lower wall (12). Each lateral wall (10) incorporates a structural reinforcing means defined by a plurality of depressions (50, 60) having a polygonal or circular contour and located side by side, without overlapping and occupying at least one portion of the area of each lateral wall (10).

Description

A CAN WITH A POLYGONAL CROSS SECTION

Field of the Invention

The present invention refers to a can with a tubular body having a horizontal cross section of polygonal shape, usually square or rectangular, and end edges to which are respectively affixed, for example by means of a double seam, a bottom wall and an upper wall, which may be annular, having a large discharge opening closed by a pressure lid, or of the integral type provided with a small discharge opening closed by a respective lid. The invention allows the subject can to be used to contain several types of bulk products in the liquid, paste or particulate state.

Background of the invention

Metallic sheet containers are well known in the art, taking the form of cans with a lateral wall of square, rectangular or cylindrical contour, and having an integral upper wall provided with a small discharge opening, or an annular upper wall provided with a large discharge opening, in which is defined a closing seat for the seating of a pressure lid.

The tubular body of this type of can is usually obtained from conventional operations of cutting the metallic sheet, calendering the metallic sheet into a tubular cylindrical shape, and longitudinally welding or seaming the metallic sheet, for laterally closing the tubular body of the can.

Aiming at increasing the structural strength of the lateral wall of the tubular body, the latter is often submitted to an operation, usually in a milling machine, to form, in the lateral wall of the cylindrical tubular body, a plurality of structural circumferential ribs, adjacent or axially spaced from each other and projecting slightly inwardly or outwardly of the tubular body of the can. Said ribs are obtained by deformation of the lateral cylindrical wall of the tubular body, allowing for the increase of the structural resistance of the lateral wall in the radial direction and, consequently, the production of a can with a thinner metallic sheet, thereby significantly reducing the cost of the final product.

The above mentioned constructive solution is more suitably applied to cans having a cylindrical tubular body, in which the continuous cylindrical ribs do not cause relevant structural weakening of the can in the axial direction. In said cans, the thickness of the metallic sheet may be reduced, since said reduction is compensated by the increased structural resistance to radial loads, and the resistance to the compression loads is not reduced to levels at which the structure of the can is compromised when filled and submitted to stacking .

However, in the case of cans presenting a polygonal cross section, more specifically the cans with a square cross section having rounded longitudinal edges, the provision of such structural ribs with a continuous circumferential development, for increasing the resistance of the walls to radial loads and for allowing reducing the thickness of the metallic sheet, has not shown to be acceptable. Said ribs weaken, beyond acceptable levels, the longitudinal edges of the can, which undergo a great reduction in^~-their resistance to axial compression loads, impairing the operation of the can.

The attempts to compensate the thickness reduction of the metallic sheet, in cans having a square cross section, by providing continuous circumferential ribs, have not reached a satisfactory result due to the degree of weakening generated on the longitudinal edges of the can.

Due to the aforementioned drawback, it has been proposed the provision of structural ribs only in the lateral wall portions of the can, that is, at the panels which define the lateral walls of a can presenting a square or rectangular cross section.

Patent application BR PI 9801887-6 and in its Certificates of Addition CI and C2 with the same number (US 6.712575 Bl) of the same assignee, propose a technical solution which provides the structural ribs only in the portions of lateral wall (the lateral panels) of the tubular body of the can, which solution comprises the provision of the aforementioned continuous circumferential ribs on the still cylindrical tubular wall, followed by the expansion of the tubular body into the desired polygonal cross section, whereby the circumferential ribs are eliminated at the region of the rounded edges of the expanded polygonal tubular body.

Although allowing for the production of a can having a polygonal contour with a structure significantly more resistant than those without ribs, said prior solution still presents one aspect to be improved, resulting from the fact that the regions in which are formed the longitudinal edges of the can, which regions, initially provided with ribs in the cylindrical tubular body, are afterwards deformed for eliminating said ribs from said regions, upon the expansion of the cylindrical tubular body into the desired polygonal shape. Said deformation of the metallic sheet in opposite directions, in the regions of the longitudinal edges of the can, causes some material fatigue which, in addition to the fact that the deformation of the metallic sheet back to the original condition is not complete, prevents the structural resistance of the can, particularly to compression radial loads, from reaching even higher values.

Aiming at minimizing the undesirable effects of the double deformation of the metallic sheet in the region of the longitudinal edges of the can, the same assignee proposed, in the Certificates of Addition C2 BR C2 9801887-6, to provide longitudinal rib extensions at said edges of the can. Although providing new axial structural strengthening elements, said longitudinal rib extensions at the longitudinal edges of the can did not eliminate the effects of the double deformation of the metallic sheet, as mentioned above, thereby maintaining the limitation regarding the achievement of a substantial increase of the structural resistance of the can.

Due to the aforementioned limitations, it has been proposed the solution object of the patent document BR PI 0003728-1 (WO 0197998 Al) of the same assignee, according to which only the lateral walls of the can (of polygonal cross section, usually square) are provided with circumferential and longitudinal ribs, having a substantially increased structural resistance, without causing weakening of the longitudinal edges of the can and allowing reducing the thickness of the sheet metallic used to build the lateral walls of the can.

In this prior art solution, as commented above, the cylindrical tubular body of the can is expanded without forming any extension of structural rib, either on the flattened lateral walls, or on the rounded longitudinal edges matching with the adjacent flattened lateral walls. Each of the flattened lateral walls are then provided with a plurality of transversal rib extensions and with at least one longitudinal rib extension, said rib extensions being defined by means of a radial plastic deformation of the respective region of the flattened lateral walls of the tubular body. Usually, each lateral wall is provided with transversal rib extensions, which may be adjacent to each other or spaced apart, and with two longitudinal rib extensions, located next to the longitudinal edges of the can.

Although leading to an increase in the structural resistance of the can and to the possibility of reducing the metallic sheet thickness, the prior art constructive solution still causes the structural resistance of the can, to the compression loads and to the expansion loads resulting from internal pressure, to largely depend on the thickness of the metallic sheet, that is, on the resistance of the latter to the radial expansion loads and to the compression axial loads acting on the lateral walls of the can.

From the above, it is thus desirable to search for a technical solution which is able to provide structural resistance to a can of the type considered herein, by using a thinner metallic sheet.

Summary of the Invention

The present invention has the object of providing a can having a polygonal cross section, usually square or rectangular, having lateral walls presenting a desired structural resistance against radial and axial loads, by using a metallic sheet thinner than that usually required to achieve the same structural resistance .

The present invention has also the object of providing a can with a polygonal cross section as mentioned above, which may have the flattened lateral walls of the tubular body thereof easily reinforced by radial and localized plastic deformations, as a function of the different load levels to which said walls are submitted .

The present can comprises a tubular body formed by lateral walls of rectangular contour and which are connected, to by two, by longitudinal edges, said tubular body being closed by an upper wall and a lower wall .

According to the invention, each lateral wall incorporates a structural reinforcing means defined by a plurality of depressions of polygonal or circular contour, located side by side, without overlapping and occupying at least one portion of the area of each respective lateral wall, thus allowing to provide, to each area of a lateral wall of the can, the required resistance to withstand the axial compression loads and radial expansion loads.

Brief Description of the Drawings

The invention will be described below, with reference to the attached drawings, given by way of example of a possible embodiment of the invention, and in which: Figure 1 illustrates a partially cut perspective view of the tubular body of a can built according to the prior art and having each of the lateral walls thereof provided with a first type of known structural reinforcing means, in the form of transversal and longitudinal rib extensions projecting to the interior of the tubular body;

Figure 2 is a perspective view of the tubular body of a can similar to that of figure 1, but having each of the lateral walls thereof provided, according to a first constructive variant of the present invention, with a first type of structural reinforcing means, defined by truncated pyramid depressions of rectangular bases, with no overlapping and occupying the area of each lateral wall of the tubular body of the can; Figure 2A illustrates a lateral view of the tubular body of the can of figure 2;

Figure 2B illustrates a partially cut view of the lateral wall of the can, taken according to line II-II in figure 2A;

Figure 3 illustrates a perspective view of the tubular body of a can similar to that of figure 2, having the lateral walls thereof each provided with a second type of structural reinforcing means, according to a second constructive embodiment of the present invention, defined by frusto-conical depressions of rectangular bases, with no overlapping and occupying the area of each lateral wall of the tubular body of the can;

Figure 3Ά illustrates a lateral view of the tubular body of the can of figure 3; and

Figure 3B illustrates a partially cut view of the lateral wall of the can, taken according to line III- III in figure 3A.

Detailed Description of the Invention

In the construction illustrated in the attached drawings, the present can is of the type which comprises a tubular body C having a horizontal cross section with a square contour, having four lateral walls 10 of rectangular contour (only two being illustrated in figure 1) , an upper wall 11 and a lower wall 12, both of integral metallic sheet and having the peripheral portions thereof respectively affixed, usually by double seaming, to an upper end edge 10a and a lower end edge 10b of the lateral walls 10.

The four lateral walls 10 are connected to each other by longitudinal edges 13, which are rounded and match with the adjacent lateral walls 10 which are flat.

In the construction illustrated in figure 1, the upper wall 11 is further provided with a small discharge opening 14, closed by a suitable lid, and also with a small suspension handle 15.

In the embodiment illustrated in figures 2 and 3, the upper wall 11 may be in the form of a structural ring, peripherally seamed to the lateral walls 10 and having an inner opening which defines a seat, onto which is seated and axially retained a known pressure lid 16. The formation of the can may be obtained by the known steps of cutting a metallic sheet of predetermined thickness and having dimensions designed to form, after its bending and longitudinally seaming or welding, a cylindrical tubular body C with a perimeter substantially equal to the perimeter of the polygonal section of the can to be produced.

The tubular body C, still in the form of a calendered cylinder, is then expanded so that the cylindrical lateral wall is radially deformed, as illustrated in figure 1, into the desired format of polygonal cross section, with flattened lateral walls 10 connected by longitudinal edges 13, rounded and matching with the adjacent lateral walls 10.

After the tubular body C is expanded into a polygonal shape, the deformation of the flattened lateral walls 10 is carried out, in order to provide them with structural reinforcing means, as described below.

Figure 1 illustrates a prior art embodiment, object of BR PI 003728-1 (WO 0197998A1), according to which each lateral wall 10 of the tubular body C is provided with a first type of structural reinforcing means, defined by a plurality of transversal ribs 20 located in planes orthogonal to the axis of the tubular body C, and by a pair of longitudinal ribs 30, each being located next to one of the longitudinal edges 13 and which, in the illustrated embodiment, are connected to the ends of the transversal ribs 20.

In the embodiment illustrated in FIG. 1, said ribs 20, 30 project inward to the tubular body C.

Figures 2, 2A and 2B illustrate a tubular body C built in a manner similar to that described for the can of FIG. 1, but having the four lateral walls 10 thereof provided with a first variant of the structural reinforcing means of the invention, which is defined by a plurality of truncated pyramid depressions 50, of rectangular bases and rounded corners, located side by side, without overlapping and occupying at least one portion of the area of each respective lateral wall of the tubular body C of the can.

In the illustrated embodiment, the truncated pyramid depressions 50 are spaced apart from each other by a distance which corresponds to 1/40 to 1/20 of the width of the lateral wall 10.

It should be understood that the depth, the dimensions of the contour and the inclination of the lateral walls of each of the truncated pyramid depressions 50 are defined as a function of the degree and type, radial and axial, of structural resistance to be provided to the lateral walls 10 of the tubular body C.

For square 18 liter cans, the truncated pyramid depressions 50 were produced with a depth sufficient to provide, to the respective portion of area of the lateral wall, the required resistance to the compression axial loads and expansion radial loads resulting from the weight of the liquid, paste or granular product contained in the can.

The inclination of the lateral walls of each truncated pyramid depressions 50 is defined so as to impart the necessary strength to the wall in the radial direction, without impairing the structural resistance to the compression axial loads.

The contour of said truncated pyramid depressions 50 is dimensioned to define an area corresponding from about 1/16 to 1/8 of the area of the respective lateral wall 10 in which said truncated pyramid depressions 50 are provided.

Generally, the depth of the truncated pyramid depressions 50 is about 0.1 to 20 times the thickness of the metallic sheet.

Each truncated pyramid depressions 50 has a bottom wall 51 projecting inward of the tubular body C. However, it should be understood that said depressions may have to be produced, from the inside to the outside, in each lateral wall 10, in order that the bottom walls 51 are kept projecting outwardly from the plane of the respective lateral wall 10.

As it will be seen below, this first variant of the reinforcing means of the invention, illustrated in figures 2, 2A and 2B, provided a substantial increase of the structural resistance of the lateral walls 10 of the can, when submitted to compression loads resulting from stacking the cans.

Figures 3, 3A and 3B illustrate a tubular body C built in a manner similar to that described for the can of figures 1 and 2, but having the four lateral walls 10 thereof provided with a second variant of the structural reinforcing means of the invention, which is defined by a plurality of frusto-conical depressions 60, located side by side, without overlapping and occupying at least one portion of the area of each respective lateral wall 10 of the tubular body C of the can.

In the configuration illustrated in figures 3, 3A and 3B, the frusto-conical depressions 60 occupy the entire area of each lateral wall 10, being located approximately tangent to each other.

Similarly to the above description related to the embodiment of figures 2, 2A and 2B, the depth and dimensions of the contour and the inclination of the lateral walls of each of the frusto-conical depressions 60 are defined as a function of the degree and type, radial and axial, of the structural resistance to be provided to the lateral walls 10 of the tubular body C.

For square 18 liter cans, the frusto-conical depressions 60 were produced with a depth sufficient to provide, to the respective area portion of the lateral wall, the required structural resistance to the compression axial loads and to the expansion radial loads.

The inclination of the lateral walls of each frusto- conical depression 60 is defined so as to impart the necessary structure to the wall in the radial direction, without compromising the structural resistance to the axial compression loads. In the case of the frusto-conical depressions 60, the inclination of the lateral walls has less influence in the resistance of the lateral walls to the axial compression loads, due to the circular contour of said depressions 60.

The contour of said frusto-conical depressions 60 is dimensioned to define an area corresponding from about 1/16 to 1/8 of the area of the respective lateral wall 10 into which said depressions are provided.

Generally, the depth of the frusto-conical depressions 60 is about 0.1 to 20 times the thickness of the metallic sheet. Each frusto-conical depression 60 has a bottom wall 61 projecting to the interior of the tubular body C. However, it should be understood that said depressions may have to be produced from the inside to the outside, in each lateral wall 10, in order that the bottom walls 61 are kept projecting outwardly from the plane of the respective lateral wall 10.

As commented below, this second variant of the reinforcing means of the invention, illustrated in figures 3, 3A and 3B presented, in relation to the first variant of figures 2, 2A and 2B, an even larger increase of the structural resistance of the lateral walls 10 of the can, when submitted to compression loads resulting from stacking the cans.

Table I below illustrates the result of the tests conducted with the three structural reinforcing means illustrated in figures 1 to 3B, in order to simulate the conditions of the axial compression to which a filled can is subject, and onto which are stacked 10 cans also filled with a material having a specific weight substantially equal to water.

Forces equivalent to the stacking were applied onto the can and there were used cans having different metallic sheet thickness: 0.27mm which is the commonly used; 0.22mm and 0.19 mm.

TABLE I

As can be noted, the structural reinforcing means of figures 2 and 3 were those that resulted in the smaller deformations of the lateral wall 10, particularly in relation to the deformations of the prior art construction represented in figure 1, under the same compression conditions, especially in the tests which used metallic sheets having the thickness reduced to the values of 0.22 and 0.19 mm.

The structural reinforcing means defined by the frusto conical depressions 60 (illustrated in figures 3, 3A and 3B) presented the best results, and it should be also noted that these frusto-conical depressions 60 have the further advantage of not leading to the concentration of residual stresses in specific points of the depressions, allowing these stresses to be distributed along the entire extension of said frusto conical depressions 60.

The frusto-conical shape, which may be derived to the format of a truncated spherical cap, when applied to depressions having the bottom wall 61 projecting inwardly of the tubular body C of the can, provides the lateral wall 10 with an increased resistance to deformation, caused not only by the internal pressures of the product stored in a filled can, but mainly by the compression loads caused by stacking cans in a filled condition.

As can be better observed in figures 2B and 3B of the drawings, the truncated pyramid depressions 50 and frusto conical depressions 60 may have their depth progressively reduced in the vertical direction, from the lowermost depressions 50, 60 toward the uppermost depressions 50, 60 in each lateral wall 10 of the tubular body C.

The depth variation of the depressions 50, 60 of both constructive forms is possible due to the fact that the lower regions and median regions of each lateral wall 10 undergo a greater lateral pressure produced by the filled product, and also by the vertical loads in the case of stacking the cans.

With the new construction of the structural reinforcing means for the lateral walls 10 of the tubular body C of the can, it becomes possible to obtain a can with a polygonal cross section having both a reduced metallic sheet thickness and the desired structural resistance.

Although not illustrated herein, it should be understood that the depth of the depressions 50, 60 in each lateral wall 10 of the tubular body C may be optionally and progressively reduced in the horizontal direction, from the median depressions toward the lateral depressions adjacent to the longitudinal edges 13 of the tubular body C. The progressive depth reductions of the depressions 50, 60 may occur in the vertical and horizontal directions, either alternatively or simultaneously.

In both constructive forms illustrated for the depressions 50, 60, the depth of each lateral wall 10 of the tubular body C is progressively reduced, according to a plane P inclined in relation to said lateral wall 10 and comprising the bottom walls 51 and 61 of the depressions 50, 60.

It should be further understood that the depth variation of the depressions 50, 60 of each lateral wall 10 may be carried out in each depression, according, at least, to one of the aforementioned vertical and horizontal directions. In this case, the bottom walls 51, 61 of the depressions 50, 60 remain located in planes parallel in relation to the plane of the respective lateral wall 10, but spaced therefrom by different values defined as a function of the depth to be imparted to each of the depressions 50, 60.

It should be understood that modifications in the dimension, shape and number of the structural reinforcing depressions may be carried out, without departing from the inventive scope defined by the accompanying claims.

Claims

1. A can with a polygonal cross section, comprising a tubular body (C) formed by lateral walls (10) of rectangular contour and which are connected, two by two, by longitudinal edges (13), said tubular body (C) being closed by an upper wall (11) and a lower wall (12), the can being characterized in that each lateral wall (10) incorporates a structural reinforcing means defined by a plurality of depressions (50, 60), having a contour selected between the polygonal and circular shapes and located side by side, without overlapping and occupying at least one portion of the area of each lateral wall (10) .

2. The can, according to claim 1, characterized in that the contour area of each depression (50, 60) corresponds from 1/16 to 1/8 of the area of the lateral wall (10), and in that the depth of each depression (50, 60) is defined between 0.1 to 20 times the thickness of the metallic sheet.

3. The can, according to any of claims 1 or 2, characterized in that the depth of the depressions (50, 60), in each lateral wall (10) of the tubular body (C) , is progressively reduced in the vertical direction, from the lower depressions toward the upper depressions.

4. The can, according to claim 3, characterized in that each depression (50, 60) has a bottom wall (51, 61) projecting toward the interior of the tubular body (C) , the depth of the depressions (50, 60) in each lateral wall (10) of the tubular body (C) being progressively reduced according to a plane (P) inclined in relation to said lateral wall (10) and containing the bottom walls (51, 61) of the depressions (50, 60).

5. The can, according to claim 4, characterized in that the depressions (60) are frusto-conical .

6. The can, according to claim 5, characterized in that the frusto-conical depressions (60) are approximately tangent to each other.

7. The can, according to claim 4, characterized in that the depressions (50) are truncated pyramids having rectangular bases and rounded corners.

8. The can, according to claim 7, characterized in that the depressions (60) are spaced from each other by a distance corresponding from 1/40 to 1/20 of the width of the lateral wall (10) .