EP0360703A2 - Method of making a non-cutting score line, and products so obtained - Google Patents

Abstract

According to the invention, a metal product of thickness <= 1 mm is compressed between a narrow elongated relief (2,3) and a succession of alternating reliefs (10) and recesses (11) arranged opposite this narrow relief ( 2,3), the differences in level between said alternating reliefs (10) and recesses (11) being transverse with respect to said narrow relief (2,3) and the compression force being such that the minimum thicknesses of said metal product after compression are included between 0.01 and 0.15 mm. This process makes it possible to obtain tear lines without injurious asperities. The invention also relates to the products obtained, it is particularly advantageous in the field of packaging.

Description

The present invention relates to a method for producing an easy tearing device for a thin metallic product.
This product is typically a sheet of thickness less than or equal to 1 mm, or else a shaped thin product, such as a can, or a capping or overcapping means, made inviolable by this easy tearing device. The invention also relates to the products obtained.

Are known on cans and on caps or overcaps, aluminum or tin, lines of tearing or weakness obtained by non-through incision or through through incision interrupted by breakable connecting bridges. For the user, these means of easy opening can often cause accidental injuries, broken edges or bridges having small sharp edges or rough edges.

The Applicant has sought to obtain tear lines that do not have such drawbacks, that is to say non-injurious after opening.

STATEMENT OF THE INVENTION

The first object of the invention is a method of producing a tear line for a metal product with a thickness of less than or equal to 1 mm, characterized in that this metal product is compressed between a narrow elongated relief and a succession alternating reliefs and hollows arranged opposite this narrow relief, the differences in level between said alternating reliefs and hollows being transverse with respect to said narrow relief, and the compression force being such that the minimum thicknesses of said metal product after compression are between 0.01 and 0.15 mm.
This process has been tested on aluminum with a purity of 99.5% and on aluminum alloy in the annealed state as in the hardened state, and it gives an entirely surprising result: the tearing of the products thus formed. gives edges and tear slices with no rough edges that are offensive to the fingers. The transformation caused by the compression of the product between the particular reliefs of the invention and its effect eliminating the sharp asperities are only imperfectly understood by the tests and examinations described, but its essential conditions have been identified so that the application of the process any metal product encountering wounding or cutting tear problems must be offered.
In summary, the effect of the compression of the treated metallic product is as follows: the narrow elongated relief firmly presses the metallic product against each relief on which this product abuts and it then cuts it deeply, depending on the nature and the geometry of this narrow relief and the compression force. Continuously in space and possibly time, the narrow elongated relief tends to push the adjacent portion of the metal product into the recess following the relief, which causes the product to bend in this recess depending on the length of this recess, which is also the spacing of the two successive reliefs, with a lower notch and possibly interrupted of this adjacent portion.

It is noted that these portions of the metal product which are slightly or not notched ensure its solidity for transport and the complementary shaping or shapings, for example the crimping of a capsule on the neck of a bottle. These portions must at the same time be easy to break, essentially by shearing force, in the tearing process. The objective of the measures which will follow is to obtain an easy tearing without aggressive roughness, and at the same time still sufficient tensile strength.

In general, the alternating reliefs and hollows used in the process of the invention follow one another in a pitch typically between 0.5 and 10 mm, the spacing of the reliefs, which is the length of the hollows with reference to the elongated relief narrow and conditions the length of the portions ensuring the residual tensile strength of the product, being between 0.2 and 4 mm. Opposite the narrow elongated relief has, for its solidity and for the good control of the depths of notch, a V-profile of total angle 50 to 110 ° with an end radius of 0.03 to 0 , 15 mm.

In the case where the metal product is made of tinplate or aluminum or alloy, metals in alloys which have a similar behavior with regard to the tearing problems and deformations described, and has a thickness of between 0.06 and 0.4 mm, the preceding measurements remain valid, and preferential conditions are detailed below.
An interesting case is then that where the product is a container, for example a can, or a capsule.
It is in this case practical to place the narrow elongated relief on a mandrel or punch fitted with a typical radial clearance of 1 to 3 mm on the diameter in the body of said container or the skirt of said capsule, the alternating reliefs and hollows being worn. by an external body, for example a wheel, which, during compression, is in relative rotation relative to this mandrel or punch coated with the product. Instantaneous compression then first concerns the area of the product clamped between the narrow relief of the punch and the relief or reliefs facing it on the wheel.

Preferably, particularly in this case but also generally, the alternating reliefs and hollows have the shape of teeth having two parallel edges making an angle of at least 20 ° with the direction of the narrow elongated relief in the compression position, these teeth being alternated with hollows of length 0.3 to 1.5 mm, the pitch (tooth + hollow) being 0.5 to 3 mm. Teeth edges roughly perpendicular to the direction of the elongated relief are preferred when making a single tear line.

An advantageous arrangement comprises: a rotary mandrel (or punch), the narrow elongated relief being disposed perpendicular to the axis of rotation of this mandrel, and the alternating reliefs and hollows forming a knurled ring carried by a crazy wheel whose rotation is parallel to the axis of rotation of the mandrel during compression, which locally clamps the body of the container or the skirt of the capsule between said narrow elongated relief and the knurled ring.

Usually, the tinplate or aluminum or alloy product being between 0.08 and 0.3 mm thick, the compression force is adjusted so as to obtain minimum thicknesses after compression between 0.01 and 0.08 mm.

According to a particular case of the method using a rotary mandrel and a crazy wheel, the mandrel carries 2 narrow peripheral reliefs and the wheel carries 2 knurled rings coming in front of said narrow peripheral reliefs so as to simultaneously produce the 2 tearing edges of a tongue tearable from container or capsule. The transverse edges of the teeth of the two knurled rings are then preferably inclined symmetrically with respect to the direction of the peripheral reliefs of the mandrel, so as to better hold the metal and to produce tearing edges that are well parallel, these inclinations typically being from 20 to 40 ° with the perpendicular to this direction of the peripheral reliefs.

Another subject of the invention is the metal products produced, of thickness less than or equal to 1 mm, comprising at least one tear line having on one face a notch line comprising deep portions of thickness at the bottom of the notch between 0.01 and 0.15 mm alternated with solid portions or more slightly notched with lengths along this notch line between 0.2 and 4 mm, with a pitch between 0.5 and 10 mm.

These products are also recognizable by their other face which has, at the right of this notch line, transverse marks at least 20 ° with this notch line, and longitudinal undulations accompanying these marks, both being the same. not just the deep portions of the notch line.

In the case of a tinplate or aluminum or alloy product and of thickness typically between 0.08 and 0.3 mm in the tearing portion, the preceding values are preferably:
- thickness at the bottom of the notch of the deep portions of the notch line of the tear line: 0.01 to 0.08 mm;
- unit length of the solid or slightly notched portions located between these deep portions: 0.3 to 1.5 mm;
- these deep portions of the notch line and these portions solid or slightly notched being arranged in a repeating step of 0.5 to 3 mm.

When this product is a can or capsule, the tear line of the invention being located on the body of the box or on the skirt of the capsule, the notch line of this tear line is typically located on the inner face of this body or this skirt and the corresponding transverse marks and longitudinal undulations are particularly visible on its outer face. In this case as well as in the general case, the surface on the side of the notch also has small undulations, the identification of the undulations on the other face being however easier since they accompany the marking of this face by the transverse edges. teeth that compressed it.

In the case of such a can body or such a capsule skirt, there may be 2 tear lines forming the edges of a tearable tongue, this has already been indicated and will be illustrated below by an example. .

The advantages of the invention are summarized as follows:
- surprising obtaining of tear lines giving tears without injurious asperities;
- These tear lines are tight, unlike lines of weakness with bridges;
- a particularly simple embodiment, using only standard tools, for a very short time: either a single compression, particularly in the case of a flat product, or work in rotation on one to a few turns;
- mechanical resistance across the tear line still sufficient.

The invention applies to all metals or alloys whose nature and state leads to asperities which are injurious to tearing. It is particularly important in the case of mass-market packaging, typically made of tinplate or aluminum or alloy containing at least 97% Al.

EXAMPLES AND EXAMINATIONS

• Figure 1 shows the punch and the thumbwheel used in the tests, in partial exterior view.
• FIG. 2 represents a capsule with its tear-off tab, seen externally on the 1/2 right view and internally seen on the 1/2 left view.
• Figure 3 shows a section along the axis of a tear edge of the previous tongue.
• Figures 4 and 5 show two sections of the tear zone or line perpendicular to the previous section and passing respectively through the lines AA and BB.
• FIG. 6 represents the contour according to the thickness of a torn tab, in the profile projector.
• FIG. 7 represents the broken edge of such a tab, and FIG. 8 is a section perpendicular to the previous view passing through the medium CC of its portion broken by shearing.

EXAMPLE 1

This example relates to low-alloy Al capsules (grade 1050 of the Aluminum Association with a skirt of 0.14 mm and an internal diameter of 29.5 mm near their head, at the level of the tear-off tongue which will be shaped.

We previously tried to run on similar capsules tear tabs on two internally notched edges with a thickness at the bottom of the notch of 0.02 mm: the tearing is easy, but the torn edges are sharp and make this solution unacceptable .

A complementary shaping of the capsules was carried out here, using according to the invention (FIG. 1):
- a punch 1 or rotary mandrel carrying 2 parallel peripheral reliefs 2 and 3, with a center distance e = 7 mm, protruding from the cylindrical surface 4 of the punch 1 by 0.4 mm and end profiles 5 in V at 90 ° with a point rounding of 0.05 mm;
- and a crazy knurled wheel 6 around its axis of rotation 7, carrying 2 parallel knurled rings 8 and 9 with a center distance of 7 mm and a width of 2 mm projecting from the rest of the knurled wheel 6 and of oblique toothing of pitch 1 mm with teeth 10 of length 0.4 mm depending on the direction of the knurled rings.

The height of the teeth 10 was 0.5 mm, and the recesses 11 between teeth of 0.6 mm length had inclined edges. The transverse edges 12 of the teeth 10 were + 30 ° and - 30 ° relative to the main direction of the knurled rings 8 and 9, as shown in FIG. 1.

For the shaping of the tear lines, the punch 1 was capped with a capsule 13 (FIG. 2), this punch 1 was rotated at 1485 rpm and the wheel 6, the axis of rotation 7 of this wheel 6 being parallel to the axis of rotation 14 knurled 8 or 9 being at the level of the V-shaped end profile 5 of a peripheral relief 2 or 3 of the punch 1. The force of application of the punch was 4 daN.
The compression was stopped for each capsule after a variable number of turns, at least 1 turn. This number of turns had no influence on the tearing behavior. After shaping the tear lines 15 and 16, the opening 17 and the primer or end 18 of the tear-off tongue 19 have been punched in addition, the preparation of which is thus completed.
The tearing edges of this tab 19 are not visible externally (1/2 right view of Figure 2).

TEAR-OUT RESULTS AND EXAMS

In FIG. 3, which represents a longitudinal section of a tear zone or line such as 16 passing through the line of the notches produced by the end 5 of the V-profile at 90 ° from the peripheral relief 3 of the punch 1 (FIG. 1 and 2), we see an alternation of portions in Al 20 comprising in the cutting plane a notch 21 of small depth 0.02 mm and a notched thickness 22 of 0.14 mm and of highly notched portions 23 of residual thickness at the bottom of notch 0.02 mm with a thickness of 0.16 mm at the edge of the notch. FIG. 4 shows the profile of the corresponding notch or groove 24 with this notch bottom 25 of thickness 0.02 mm. In FIG. 3, it can be seen that the deformations caused by the compression of the skirt 26 of the capsule 13 between the relief 3 and the knurled ring 9 are: longitudinal undulations 27 of the right and reverse surfaces affecting the compressed zone and its surroundings, sudden changes in slope 28, which correspond to the impact of the transverse edges 12 of the teeth 10, resulting in or constituting marks particularly visible on the external face of the capsule 13. The edges at an angle angle = 30 ° of the portions little notches 20 correspond to the inclined edges of the hollows of the knurled ring 9. The pitch of the portions 20 and 23 is 1 mm like the pitch of the reliefs of this ring 9.

The tear tests of the tabs 19 of ten capsules 13 prepared according to the method described all led to slightly rough but not cutting tears.

Figure 6 shows the outline of a tab 19 torn according to its thickness to the profile projector: the apparent thickness varies from 0.07 to 0.22 mm, which is mainly due to the deformations already reported and those caused by the tear.

In FIG. 7, representing a part of the torn edge 29 of the tongue 19, the two zones 30 and 31 having longitudinal grooves 32 correspond to a 45 ° face of two neighboring deep cuts 24, while the intermediate zone 33 corresponds to broken non-incised metal. The streaks 32 are due to the depression of the relief 3 of the punch. With the perpendicular section in FIG. 8, it can be seen that this broken metal 33 has the shape of a folded lip, which is in continuity with the broken notch bottom 25 of the heavily notched portion (FIGS. 8 and 7). The offset d between the tip of the lip 33 and the tear in the notch bottom 25 is 0.10 mm.

Thus for the tear lines of the invention, this mode of rupture and the unevenness of the surface in the tear zone seem to play an important role in the non-aggressiveness of the torn edges.

EXAMPLE 2

We took 5 capsules of the same geometry as the previous capsules, made of aluminum alloy of grade 8011 from A.A. (at approximately Si 0.7% and Fe 0.8%), in the H24 state, that is to say 1/2 hard, these capsules being crude from drawing and drawing.

These capsules were shaped in the same way as above, with the same compression force.
The minimum thickness of the bottom of the grooves is slightly greater, from 0.04 to 0.05 mm. The tear-off tabs tear without giving off any harshness, with edges that are soft to the touch as before. But the tearing effort is a little more important.

To return to a lower force in the case of this 1/2 hard state, it is possible in particular: to increase the compression force to return to minimum thicknesses of lower groove bottoms; or lengthen the teeth or shorten the hollows between teeth. This example shows that the method of the invention makes it possible to adapt to various cases.

Claims (14)

1. Method for producing a tear line (15,16) of a metal product (13,26) of thickness less than or equal to 1 mm, characterized in that this metal product (13,26) is compressed between a narrow elongated relief (2,3) and a succession of alternating reliefs (10) and recesses (11) arranged opposite this narrow relief (2,3), the differences in level between said reliefs (10) and recesses (11 ) alternating being transverse with respect to said narrow relief (2,3), and the compression force being such that the minimum thicknesses of said metal product (13,26) after compression are between 0.01 and 0.15 mm. 2. Method according to claim 1, wherein the reliefs (10) and the recesses (11) alternate follow one another in a pitch of between 0.5 and 10 mm, the spacing of the reliefs (10) or length of the recesses (11 ) being between 0.2 and 4 mm. 3. Method according to any one of claims 1 or 2, wherein the narrow elongated relief (2,3) has a V-profile of total angle 50 to 110 ° with an end radius of 0.03 to 0 , 15 mm. 4. Method according to any one of claims 1 to 3, wherein the metal product (13,26) is made of tinplate or aluminum or alloy and has a thickness between 0.06 and 0.4 mm. 5. Method according to claim 4 wherein the product (13,26) is a container or a capsule (13), the narrow elongated relief (2,3) being carried by a mandrel or punch (1) fitted with play in the body of said container or the skirt (26) of said capsule (13) and said alternating reliefs (10) and hollow (11) being carried by a body (6) which is in relative rotation relative to this mandrel or this punch (1 ). 6. The method of claim 5, wherein the reliefs (10) and the recesses (11) alternate have the shape of teeth (10) having two parallel edges (12) making an angle of at least 20 ° with the direction of narrow elongated relief (2,3) in the compression position, these teeth (10) being alternated with recesses (11) of length 0.3 to 1.5 mm in a pitch of 0.5 to 3 mm. 7. The method of claim 6, wherein the punch (1) is rotatable, the narrow elongated relief (2,3) being arranged perpendicular to the axis of rotation of this punch (1) and the reliefs (10) and hollow (11) alternating form a knurled ring (8, 9) carried by an idler wheel (16) whose axis of rotation (7) is parallel to the axis of rotation (14) of the punch (1) during compression, the container body or the skirt (26) of the capsule (13) then being clamped between said elongated relief and said knurled ring (8, 9) 8. Method according to any one of claims 4 to 7, in which the product (13,26) of tinplate or aluminum or alloy has a thickness of between 0.08 and 0.3 mm, the compression force being adjusted so as to obtain minimum thicknesses after compression of between 0.01 and 0.08 mm. 9. The method of claim 7, wherein the rotary punch (1) carries 2 narrow peripheral reliefs (2 and 3) and the wheel carries 2 knurled rings (8 and 9) coming opposite said narrow peripheral reliefs (2 and 3) so as to simultaneously produce the 2 tearing edges (15 and 16) of a tear-off tab (19) of said container or of said capsule (13). 10. Metallic product (13,26) of thickness less than or equal to 1 mm, comprising at least one tear line (15,16) giving torn edges without injurious asperities, line (15,16) having on one side a notch line (16) comprising deep portions (23) of thickness at the bottom of notch (25) between 0.01 and 0.15 mm alternated with solid or more slightly notched portions (20) of lengths according to this notch line (16) between 0.2 and 4 mm, with a pitch between 0.5 and 10 mm. 11. Product (13,26) according to claim 10, the other side of which has, in line with said notch line (16), transverse marks (28) making at least 20 ° with this notch line (16) and longitudinal undulations (27), these marks (28) and these undulations (27) being the same as the deep portions (23) of said line notch (16). 12. Product (13,26) according to any one of claims 10 or 11, in tinplate or aluminum or alloy with a thickness between 0.08 and 0.3 mm, the deep portions (23) of the line notch (16) having a thickness at the bottom of the notch (25) of between 0.01 and 0.08 mm and being alternated with solid or slightly notched portions (20) of lengths between 0.3 and 1, 5 mm, with a pitch between 0.5 and 3 mm. 13. Can or capsule (13) according to claim 12, the body of this box or the skirt (26) of this capsule (13) carrying a tear line (15,16) including the notch line (16 ) is located on its inner face. 14. Box or capsule (13) according to claim 13, carrying 2 tear lines (15 and 16) forming the edges of a tear-off tab (19).

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