GB1600801A - Drawn cans of metal (or alloy) particularly preserve cans - Google Patents

Description

(54) IMPROVEMENTS RELATING TO DRAWN CANS OF METAL (OR ALLOY), PARTICULARLY PRESERVE CANS (71) We, FEREMBAL, A French Corporation, of 6 Boulevard du General Leclerc, 92115 Clichy, France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be described in and by the following statement: This invention relates to a drawn can of a metal (or alloy) having a drawn end portion integral with the body of the can.

The invention relates more particularly to metal cans normally used for packing food preserves. These cans may be closed at the opposite end by an end piece which is distinct from the can body but is attached thereto, usually by crimping.

The present cans, which are of a metal or alloy, must be able to withstand the sterilising heat treatment to which food preserve cans are subjected during their sterilisation.

In the course of this treatment, the cans' integral end portions must be able to be deformed in order to accommodate the variations of internal pressure due to changes of temperature inside the can.

During the rising of the temperature the internal pressure increases and causes the can end portions to undergo deformation of such a nature that the inside volume of the can is increased.

During cooling the fall of internal pressure which occurs inside the can gives rise to a reduction of the volume of the latter. This reduction of volume must be such that the volume of the can after cooling will be as small as possible.

This volume is generally equal to the original volume, so that the profile of the can end portions after sterilisation generally coincides with the original profile.

The profile of the can end portions after sterilisation must be such that the can is not suspect that is to say that this profile is not modified by any variation of internal conditions in the can which is brought about by normal handling of the can closed at both ends.

In order to achieve this result it is desirable that on the one hand the profile of the can end portion after sterilisation should be in a stable mechanical state, that is to say its deformation should have little sensitivity to slight variations of internal conditions resulting from normal handling of the can and of its two end members, and on the other hand that the passage from the profile of the can end portion corresponding to the maximum inside volume of the can to the profile obtained after sterilisation takes place in such a manner that the metal (or alloy) employed works as long as possible in the elastic range before entering the plastic range.

This result can be verified by the finding that, after a high internal can pressure has fallen to the initial pressure, the can end portion resumes a position close to its original position through the simple decrease of the internal pressure in the can.

Insofar as, in connection with the stability of the can end portions in the course of the handling of the cans, a definition has been given of a stable mechanical state of the profile after sterilisation, the deformation of the profile takes place discontinuously, that is to say the deformation energies are not liberated continuously in the course of the deformation of the profile.

The original deformation energies of the profile, which generally relate to the central portion of the profile and which lie within the elastic range of the material, are liberated by an "energy jump"; the can end portion then "bangs" and the subsequent energies deforming the profile are distributed regularly, thus leading to a continuous deformation of the profile in dependence on the increase of pressure inside the can.

When the pressure inside the can falls it is then possible to pass from the deformed state to the final state while remaining within the elastic range of the material.

Certain sterilisation processes lead to the creation of high pressure inside the can. The profile defined in respect of the present invention aims to provide the can end portion with an ability to withstand a high internal pressure without however leading to its deterioration in respect of the elastic properties of the material.

Drawn can end portions of a bellows type comprising, from the periphery towards the centre, an elastically deformable annular portion, a succession of steps, and a flat or slightly spherical central zone known as the rosette or button have long been known.

In French Patent No. 2,353,445 there is already described a metal end piece for a metal packing structure, particularly for a preserve can, of the type comprising, from the periphery towards the centre, a generally horizontal crimping edge which is curled over to a greater or lesser extent so as to permit lap-jointing, a substantially vertical wall, an outwardly projecting flexibility ring, a succession of steps, and a flat or slightly spherical central zone known as the rosette or button, this metal end piece being characterized by a radius of the lap-joint zone of the bottom of the dish defined by the substantially vertical wall close to 1 mm with a minimum angle of closure of 30 , by a radius of the lap-joint zone of the flexibility ring greater than twice the said radius of the dish bottom, by a breadth of the said lap-joint zone of the flexibility ring which is less than or equal to six times the thickness of the metal of the end piece, by a succession of undulations inscribed in two parallel conical envelopes spaced apart by a maximum distance of six times the said thickness of the metal whose slope is suited to the diameters of the structure's ends, these undulations having straight connecting portions less than or equal to six times the thickness of the metal, and by a connecting undulation situated between the flexibility ring and the said succession of undulations and having a radius greater than twice the said radius of the dish bottom.

It is an object of the present invention to provide a drawn can having an integral end portion which, from a peripheral wall towards the centre, comprises a flexibility ring, a succession of undulations, and a flat or domed central zone, which can end portion is amenable to deformation within the elastic range of the material of which the can body together with its integral end portion is made, without this deformation being regular, an energy jump lying within the elastic zone ensuring a stable state of the can end portion after sterilisation.

According to the present invention, we provide a drawn can of a metal (or alloy) having a drawn end portion integral with the body of the can, this end portion comprising, from a peripheral wall towards the centre, an axially outwardly projecting flexibility ring, as herein defined, having a radius of curvature (in axial section) of the order of a millimetre; a succession of undulations inscribed in two approximately parallel concave envelopes which are recessed with respect to the relevant end of the can body and which are spaced apart by a maximum distance of five times the thickness of the metal (or alloy) of the end portion, these undulations consisting of portions curvilinear in axial section connected by portions running therebetween, and these connecting portions being straight in axial section, and therefore frustoconical in three dimensions, and having an axial section a length less than or equal to six times the thickness of the metal (or alloy) of the end portions; and a flat or domed central region constituting a can end rosette or button.

The invention also includes a can as just specified. when filled and closed by a can end piece crimped or otherwise attached thereto.

The "flexibility ring" mentioned in the present description and claims is an elastically deformable annular section integral with the sections of the can end portion adjacent to it on its inner and outer sides, and is disposed substantially immediately within the peripheral wall (or substantially immediately within an envelope representing a continuation of the peripheral wall).

The metal end piece for a metal packing structure described in French Patent No.

2,353,445 is designed to be crimped on (e.g.) a preserve can body and therefore comprises, from the periphery towards the centre, before the flexibility ring, the steps, and the central zone, a generally horizontal crimping edge which is curled over to a greater or lesser extent so as to permit lap-jointing, a substantially vertical wall defining a dish, and a dish bottom, whereas a can end portion integrakl with the body of a drawn can according to the present invention, being drawn, does not have the same configuration as that mentioned above, because it must not only be amenable to a method of fabrication based on drawing, but must also comply with the same characteristics required in the finished state.

The can end portion integral with the body of a can according to the invention has optimum characteristics which are substantially better than those of drawn can ends known at the present time, and it is the result of numerous tests and studies relating to its profile, i.e. its axial section. The latter plays an important part in respect of the course of the progressive deformation affording the present can end portion.

It is also found that very slight modifications of appearance entail substantial modifications in the progressive deformation affording this can end portion. Thus, the present can end portion is the result of various compromises developed after numerous tests and material strength calculations relating to modifications of the various characteristics of the axial section of the can ends concerned.

The can end portion integral with the body of the can of the invention is defined by a certain number of elements the combination of which leads to the obtaining of the characteristics set forth above.

In order to define these elements more easily, it will be assumed that a peripheral section of the can end portion in question is composed of a hoop-like ring, which may or may not be preceded by a moulding (i.e. an outward enlargement); this hoop-like ring is disposed substantially immediately within the peripheral wall (or substantially immediately within an envelope representing a continuation of the peripheral wall) of the can body. This ring is followed by a series of undulations, and a flat or domed central button.

According to the invention, as indicated above, a can end portion of this kind has an annular bead of arcuate cross-section, lmm being the approximate radius of the latter; this annular bead is followed by a succession of undulations inscribed in the above-mentioned approximately parallel concave envelopes which are spaced a maximum distance apart of five times the thickness of the metal (or alloy) of the end portion, these undulations being connected by straight portions running therebetween, these connecting portions being, in axial section, shorter than or equal to six times the thickness of the metal (or alloy).

One form of construction of a can according to the invention will now be described with reference to the accompanying drawing, the single figure of which is a half-view in axial section of a can according to the invention The can shown in the single figure in the drawing comprises, from a peripheral wall 12 (the can body wall) towards the centre, a flexibility ring 14 which is outwardly convex and thus projects outwards, a succession of undulations 17, which are four in number, and a central button 16. The flexibility ring 14 has a diameter slightly less than that of the wall 12, the latter being approximately equal to the nominal diameter D of the can body, and has a radius of curvature close to 1 mm.In addition, on the peripheral wall 12, in a position adjacent to the ring 14, the latter may or may not be preceded by a moulding 11 (i.e. an outward enlargement) shown in dashed lines in the drawing.

The undulations 17, which intervene between the ring 14 and button 16, are inscribed in two envelopes 18 which are separated by a distance d shorter than or equal to five times the thickness e of the metal (or alloy). It will be seen that the envelopes 18 are approximately parallel concave envelopes which are recessed with respect to the relevant end of the can body. The slope of these envelopes 18 in relation to the reference plane P, which is substantially perpendicular to the wall 12 of the can body, is suited to the nominal diameter D of the can; the slope at the outermost undulation 17, which may be called the peripheral slope, may for example be substantially 7%. Between the undulations 17 there are connecting portions, which are straight in axial section and which are shorter than or equal to six times the thickness of the metal (or alloy).Two of these straight portions are shown in the drawing, at 19 and 20. The number of undulations 17 depends on the diameter of the can end. Furthermore, the undulations 17, as seen in axial section, are not identical in respect of their radius of curvature.

Finally, it is desirable that the central button 16 should have the smallest possible diameter compatible with regulations in force, and should have a spherical shape.

In order to illustrate the invention more completely, there will be given below a numerical example of application intended for ordinary 0.206 litre cans.

Overall diameter close to 83 mm Radius of curvature (in axial section) ring 14 1.2 mm Distance d (breadth of undulations 17: see Figure) 4 e Radius of undulations 17 2 mm Number of undulations 17 4 Straight portions 19 and 20 2 e e being the thickness of the metal (or alloy) Return vacuum in cm Hg Pressure (kg/cm2) Present can end Usual can end 1 0 10 1.5 5 18 1.8 8 25 The can end portion integral with the body of the present can therefore has great flexibility.

WHAT WE CLAIM IS: 1. A drawn can of a metal (or alloy) having a drawn end portion integral with the body of the can, this end portion comprising, from a peripheral wall towards the centre, an axially outwardly projecting flexibility ring, as herein defined, having a radius of curvature (in axial section) of the order of a millimetre; a succession of undulations inscribed in two approximately parallel concave envelopes which are recessed with respect to the relevant end of the can body and which are spaced apart by a maximum distance of five times the thickness of the metal (or alloy) of the end portion, these undulations consisting of portions curvilinear in axial section connected by portions running therebetween, and these connecting portions being straight in axial section, and therefore frustoconical in three dimensions, and having in axial section a length less than or equal to six times the thickness of the metal (or alloy) of the end portion; and a flat or domed central region constituting a can end rosette or button.

2. A can according to Claim 1, characterized in that the flexibility ring is preceded by a moulding forming an outward enlargement in a position adjacent to the said ring.

3. A can according to Claim 1 or 2, characterized in that the number of the said undulations is four, the peripheral slope of the envelopes in which they are inscribed being substantially 7%.

4. A drawn can of a metal (or alloy) having a drawn end portion integral with the body of the can, substantially as hereinbefore described with reference to the accompanying drawing.

5. A can according to any of claims 1 to 4, when filled and closed by a can end piece crimped or otherwise attached thereto.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. In order to illustrate the invention more completely, there will be given below a numerical example of application intended for ordinary 0.206 litre cans. Overall diameter close to 83 mm Radius of curvature (in axial section) ring 14 1.2 mm Distance d (breadth of undulations 17: see Figure) 4 e Radius of undulations 17 2 mm Number of undulations 17 4 Straight portions 19 and 20 2 e e being the thickness of the metal (or alloy) Return vacuum in cm Hg Pressure (kg/cm2) Present can end Usual can end

1 0 10 1.5 5 18 1.8 8 25 The can end portion integral with the body of the present can therefore has great flexibility.

WHAT WE CLAIM IS: 1. A drawn can of a metal (or alloy) having a drawn end portion integral with the body of the can, this end portion comprising, from a peripheral wall towards the centre, an axially outwardly projecting flexibility ring, as herein defined, having a radius of curvature (in axial section) of the order of a millimetre; a succession of undulations inscribed in two approximately parallel concave envelopes which are recessed with respect to the relevant end of the can body and which are spaced apart by a maximum distance of five times the thickness of the metal (or alloy) of the end portion, these undulations consisting of portions curvilinear in axial section connected by portions running therebetween, and these connecting portions being straight in axial section, and therefore frustoconical in three dimensions, and having in axial section a length less than or equal to six times the thickness of the metal (or alloy) of the end portion; and a flat or domed central region constituting a can end rosette or button.

2. A can according to Claim 1, characterized in that the flexibility ring is preceded by a moulding forming an outward enlargement in a position adjacent to the said ring.

3. A can according to Claim 1 or 2, characterized in that the number of the said undulations is four, the peripheral slope of the envelopes in which they are inscribed being substantially 7%.

4. A drawn can of a metal (or alloy) having a drawn end portion integral with the body of the can, substantially as hereinbefore described with reference to the accompanying drawing.

5. A can according to any of claims 1 to 4, when filled and closed by a can end piece crimped or otherwise attached thereto.