Metal can having a snap-engaging lid

Abstract: The container body is formed from thin sheet metal suitably shaped to define a side wall (3) closed lowerly by a base (4); the lid is arranged to hermetically seal the container body (1), and has a peripheral edge comprising a downwardly bent portion (21), an inwardly projecting element (22) and an annular gasket means (40) for the hermetic sealing; the upper mouth of the container body (1) is formed only from the actual metal sheet forming the side wall (3) by being bent in such a manner as to define, in cross-section, an internal first portion (11) positioned as a continuation of the side wall (3) and orientated substantially perpendicularly, a substantially outwardly and downwardly extending second portion (12) positioned as a continuation of and external to the first portion (11) and radius-joined to the first portion (11), and an inwardly and downwardly extending third portion (13) positioned as a continuation of the second portion (12), the radius-joining zone (14) between the first portion (11) and second portion (12) being arranged to engage the gasket (40) in an hermetically sealing manner, and the third portion (13) being arranged to snap-engage the inwardly projecting element (22) of the lid.

Description: The invention relates to the hermetically sealed packaging of products in relatively small containers, in particular for food products in retail sale. The container volume is usually between 100 cc and 1000 cc; however in special cases the volume can be different. For this purpose, containers have been known for a considerable time having a glass (or plastic) body hermetically sealed by mainly metal lids of the so-called "pry-off" type, ie a lid which is opened by forcing it upwards to deform it. Metal containers or cans have also been known for a considerable time, which are sealed by a lid in the form of a flat metal sheet which is clinched to the upper edge of the container body. To open the container, the lid possesses a line of reduced cross-section defining a portion which is torn off. Packaging in cans has various advantages over glass containers, and in particular cans are cheaper, are less fragile to handle and are lighter. However the known sealing system for cans has drawbacks compared with the sealing of glass containers. In particular, with these latter when the lid has been removed the container body has an upper mouth which is completely free and completely smooth, making it very comfortable to extract the product from the container body as this latter behaves substantially as a bowl or cup. In contrast, after a can has been opened it comprises along its upper annular mouth, as a residual part of the lid, a flat annular rim projecting towards the centre and having a cutting edge, this disturbing both the extraction of the product by free fall and the use of the container as a bowl, for example an animal eating directly from the can risks being injured. In US-A-4111330 a can is shown having a container body formed from thin sheet metal suitably shaped, whose annular upper mouth is formed from only the actual thin metal sheet forming the side wall; the can has also a lid arranged to hermetically seal the container body and having a peripheral edge comprising a downwardly bent portion and an inwardly projecting element. However the upper rim of the metal sheet forming the container body has an end projecting outwardly and upwardly, placed at a distance from the upper mouth of the container which defines a dangerous cutting edge and also defines a concave portion acting as a unhygienic receptacle of dirt and deteriorating substances. The container according to the present invention comprises a container body formed from thin sheet metal suitably shaped to define a containing chamber; the container body is combined with a lid which is arranged to hermetically seal the container body and has its peripheral annular edge comprising a downwardly bent portion with an inwardly projecting element, and an annular gasket means for the hermetic sealing. The upper annular mouth of the container body is formed only from the actual thin metal sheet forming the side wall (i.e. it is not formed from the metal sheet which in the known art forms the lid), which is bent to define, in cross-section, a first portion extending from the side wall, a substantially outwardly and downwardly extending second portion external to the first portion and radius-joined to the upper edge of the inner portion, and an inwardly and downwardly projecting final third portion. The lid has a corner concave zone delimited by a peripheral annular portion downwardly bent together with a flat peripheral portion , wherein an annular gasket means is placed to provide hermetic seal; and the annular radius-joining zone between said first and second portions is arranged to engage the gasket means of the lid in an hermetically sealing manner, the third portion being arranged to snap-engage the inwardly projecting element of the lid. The container of the invention combines the merits of glass containers with the merits of cans, and eliminate the aforesaid drawbacks. In particular, it provides a container body having substantially the same aforedescribed advantages typical of glass containers (advantages consequent on the fact that the mouth is completely open and smooth), and also having the following advantages: the manufacturing and raw material cost of the container body is considerably reduced (by a percentage variable from 30% to 80%); the container body is considerably less fragile than glass and hence offers higher mechanical strength, this being useful in particular in heat treatment and during the various handling stages; the container body is lighter than glass; the container body is opaque to light, this being an advantage for light-sensitive products; the container body can be easily decorated externally. The invention is described in detail hereinafter with the aid of the accompanying figures, which illustrate one embodiment thereof by way of non-limiting example. Figure 1 is a partly sectional view of the container body according to the invention. Figure 2 is an enlarged section through a detail of the container according to the invention. Figure 3 is a section on the plane III-III of Figure 2. The container comprises a container body 1 which is combined with a lid 2. The lid 2 is able to form an hermetic seal and is of the type already known and used in combination with a glass or plastic container body. The lid shown in the figures is a type of lid known by the name "PRESON" and manufactured by CBM CLOSURE. Essentially, it comprises a plastic ring 20 defining the peripheral annular edge of the lid and associated with a circular metal covering element 30 positioned inwards of the ring 20. The ring 20 comprises a peripheral cylindrical portion 21 which is bent downwards and has at its end an annular element 22 projecting radially inwards. The peripheral portion 21 is joined to a flat annular portion 23 lying above it. The peripheral portion 21, the flat portion 23 and the projecting element 22 together form a downwardly and inwardly facing annular channel. The metal element 30 possesses a peripheral annular portion 31 which is bent downwards. The portion 31 and the flat peripheral portion 32 joined to it are positioned adjacent to the inner surface of said channel of the ring 20. The inner surface of the metal element 30 is conveniently coated with a layer of enamel 33 for food use. In the corner zone between the two portions 31 and 32 there is provided an annular gasket means 40 to provide the hermetic seal. In a different embodiment of the lid, not shown in the figures (but known), the plastic ring 20 is not provided, there being provided only the metal component, the peripheral edge of which performs the function of the plastic ring 20, and in particular comprises a downwardly bent portion (replacing the peripheral portion 21) and an inwardly projecting annular element (replacing the projecting element 22). The container body 1 (with the exception of its upper annular mouth) is formed from thin sheet metal by the usual known methods for forming tin cans. In particular, according to the illustrated embodiment, the container body 1 can be formed from two pieces clinched together, namely a more or less cylindrical side wall 3 formed from a rectangular metal sheet curved and welded along a generator of the cylindrical surface, and a substantially flat base 4 clinched to the lower circumference of the wall 3. In a different embodiment, not shown in the figures (but known), the container body 1 is formed by deep-drawing a single sheet (for example of aluminium alloy), to obtain a cylindrical side wall (substantially as the wall 3) closed lowerly by a more or less flat base. According to the invention, the upper annular mouth of the container body 1 is formed from the actual sheet metal forming the side wall 3. In this respect, the upper portion of the wall 3 is bent in such a manner as to define, in cross-section: an internal first portion 11 positioned as a continuation of the side wall 3 and orientated substantially vertically; a substantially outwardly and downwardly extending second portion 12 positioned as a continuation of and external to the first portion 11 and radius-joined to the upper edge of the first portion 11; an inwardly and downwardly extending third portion 13 positioned as a continuation of the second portion 12. The upper annular mouth of the container body 1 is in geometrical relationship with the peripheral annular part of the lid 2 such that the annular radius-joining zone 14 between the first portion 11 and the second portion 12 is arranged to engage hermetically with the gasket means 40. Specifically, the annular radius-joining zone 14 lies, in plan view, within the annular zone occupied in plan view by the gasket 40. In addition, the third portion 13 is arranged to engage the projecting element 22. The minimum diameter of the inner surface of the projecting element 22 is less than the maximum diameter of the joining zone between the second portion 12 and the third portion 13. This interference keeps the lid 2 retained on the body 1. Figure 2 shows the lid 2 associated with the container body. The projecting element 22 embraces the third portion 13 and creates a constraint which prevents the lid separating from the container body 1 (unless it is forced by external factors). The radius-joining region 14 presses against the lower surface of the gasket means 40 to considerably deform it and create an hermetic seal. The seal shown in Figure 2 is obtained by creating within the container, by known methods, a zone of less than atmospheric pressure, for example by firstly heating the product contained in the container body 1, applying the lid 2 to the mouth of the container body 1 (with the projecting element 22 engaged by the third portion 13) and finally allowing the whole assembly to cool. The seal obtained in this manner is as hermetic and reliable as the seal obtained with the same lids applied to glass containers. Numerous modifications of a practical and applicational nature can be made to the invention, but without leaving the scope of the inventive idea as claimed hereinafter.

Claims: A container for hermetically sealed packaging, comprising: a container body (1) formed from thin sheet metal suitably shaped to define a side wall (3) closed lowerly by a base (4); a lid arranged to hermetically seal the container body (1) and having a peripheral edge comprising a downwardly bent portion (21) and an inwardly projecting element (22); the annular upper mouth of the container body (1) being formed from only the actual thin metal sheet forming the side wall (3) and being bent in such a manner as to define, in cross-section: an internal first portion (11) positioned as a continuation of the side wall (3) and orientated substantially vertically; a substantially outwardly and downwardly extending second portion (12) positioned as a continuation of and external to the first portion (11) and radius-joined to the first portion (11); characterised by that the upper mouth is bent in such a manner as to define, in cross-section, an inwardly and downwardly extending third portion (13) positioned as a continuation of the second portion (12); the lid having a corner concave zone delimited by a peripheral annular portion (31) downwardly bent together with a flat peripheral portion (32), wherein an annular gasket means (40) is placed to provide hermetic seal; and the annular radius-joining zone (14) between the first portion (11) and second portion (12) being arranged to engage the gasket (40) in an hermetically sealing manner, and the third portion (13) being arranged to snap-engage the inwardly projecting element (22) of the lid.

Inventors: AVANZINI ERNESTO, AVANZINI, ERNESTO, Avanzini, Ernesto, FA.BA - Fab. Barattoli - S.p.A.
Applicants: BA SIRMA S P A FA, FA.BA SIRMA - S.P.A.
Application year: 1996
Main classification: B65D51
IPC codes: B65D51