FR2657031A2 - Method of producing a non-intersecting tear line, and products obtained - Google Patents

Abstract

In the case of a container or a cap made of tinplate or made of aluminium or alloy, having a thickness between 0.06 and 0.4 mm, this product is compressed between a narrow elongate raised feature (20, 30) and a succession of raised features (100) and of hollows (110) which are arranged alternately facing this narrow raised feature (20, 30) the variations in level between the said alternating raised features (100) and hollows (110) being transverse with respect to the said narrow raised feature (20, 30) and the compressive force giving minimum thicknesses after compression between 0.01 and 0.15 mm, the said alternating raised features (100) and hollows (110) being carried by a mandrel or punch (60) fitted into the body or the skirt of the said product, whereas the said narrow elongate raised feature (20, 30) is carried by a body (10) in relative rotation with respect to this mandrel or punch (60). The invention also relates to the container or the cap obtained by this method, the line of cutting (kerf) of its tear line being on the outside and including a particular structure.

Description

PROCESS FOR MAKING A SCRAP LINE
NOT CUTTING AND PRODUCTS OBTAINED.

The process and the product which are the subject of the present invention constitute improvements to the processes and products described in French patent application No. 88-12547.

The main invention described in the above application gives a solution for obtaining non-injurious tear lines after tearing, on thin metallic products, for example containers or capsules with easy opening.

The solution of the main invention consists of a process for producing a tear line for a metal product less than or equal to 1 mm, characterized in that this metal product is compressed between a narrow elongated relief and a succession of alternating reliefs and hollows arranged opposite this narrow relief, the differences in level between said alternating reliefs and hollows being transverse 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 experimented on aluminum with 99.5% purity and on aluminum alloy in the annealed as well as the hardened state, and it gives a completely surprising result: the tearing of the products thus formed gives edges and tear edges with no roughness that is 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 to any metallic product encountering wounding or cutting tear problems must be proposed.

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 smaller cut and possibly interrupted from this adjacent portion.

The portions of the metal product with little or no cuts 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 following measures is to obtain an easy tear without aggressive roughness, while 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 coming in front of the relief elongated narrow and thus 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 1100 with an end radius of 0.03 and 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 respect to the problems of tearing and deformations described, and has a thickness of between 0.06 and 0 , 4 mm, the previous measurements remain valid, and preferential conditions are specified below.

An interesting case is then that where the product is a container, for example a can, or a capsule.

According to the present invention, it is then advisable for said alternating reliefs and hollows to be carried by a nested mandrel or punch, with a diametral clearance of less than 0.5 mm, in the body of said container or the skirt of said capsule, said narrow elongated relief being carried by an external body which, during compression, is in relative rotation relative to this mandrel or this punch.

This arrangement is much preferable to the reverse arrangement recommended in the main application, reverse arrangement in which the narrow elongated relief is carried by the mandrel or punch while the alternating reliefs and hollows are carried by the outer body in relative rotation with respect to this mandrel or punch. This arrangement would require a diametral clearance of the mandrel typically greater than 2mm.

The tests on Al capsules described in the main application (its
Example 1) were in fact continued on several hundred capsules, they were made using the reverse arrangement recalled above and resulted in a number of irregular tear lines. The study of the defective samples showed that there were sometimes slippages of the capsule relative to the narrow elongated relief carried by the punch, so that in the second turn of the capsule relative to the external body, which is a crazy wheel carrying the alternating reliefs and hollows, the already shaped tear strip leaves the alignment of said reliefs of the knurl and the punch, the reliefs of this strip being damaged or destroyed. In other words, with this so-called reverse arrangement, the shaping of a tear line in more than one turn quite easily leads to degradation of said tear line.

On the contrary with the new recommended arrangement, the results remain constantly good whatever the number of rotations of relative rotation of the capsule relative to the wheel or external body carrying the narrow elongated relief. During work, the capsule is pressed against the punch or mandrel by the compression of the wheel, and it rotates with the mandrel. The observed result is to be compared to the fact that the arrangement now adapted places the succession of reliefs and hollows providing the most attachment inside on the mandrel, while the elongated relief allowing sliding is now on the external tool, this arrangement also allows a small clearance of the capsule relative to the mandrel. This after-the-fact remark does not, however, make it possible to predict the surprising result achieved: namely tear lines of good quality, regardless of the number of turns of their shaping, on large series of capsules.

Preferably, the alternating reliefs and hollows are formed by teeth each having two parallel edges making a constant angle with the direction of the narrow elongated relief in the compression position, these teeth being alternated with hollows of lengths 0.3 to 1 , 5 mm, the pitch (tooth + hollow) being from 0.5 to 3 mm. Edges of teeth roughly perpendicular to the direction of the elongated relief are preferred when making a single tear line and suitable when making several tear lines at the same time.

According to an advantageous arrangement, the alternating reliefs and hollows form a knurled ring being arranged perpendicular to the axis are carried by a rotary mandrel or punch perpendicular to its axis of rotation, and the narrow elongated relief is carried by a crazy thumbwheel whose axis of 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 an idler wheel, the mandrel carries 2 knurled rings and the wheel carries 2 narrow peripheral reliefs coming in front of said knurled rings so as to simultaneously produce the 2 tearing edges of a tearable tongue container or capsule. The transverse edges of the teeth of the two knurled rings can either be inclined symmetrically with respect to the direction of the peripheral reliefs of the knurl, so as to hold the metal even better and to produce tearing edges which are well parallel, these inclinations being typically 5 at 400 with respect to the perpendicular to this direction of the peripheral reliefs, that is to say not inclined.

The main invention also relates to the metal products produced, of thickness less than or equal to 1 mm, comprising at least one tear line having on one side a notch line comprising deep portions of thickness at the bottom of notch between 0.01 and 0.15 mm alternated with solid portions or more weakly notched with lengths along this line of notch 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 and longitudinal undulations accompanying these marks, both being the same as 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 line
tear line notch: 0.01 to 0.08 mm
- unit length of full or weak portions
notches located between these deep portions: 0.3 to 1.5
mm;
- these deep portions of the notch line and these portions
solid or slightly indented being arranged in a pitch
repeat from 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 located according to the present invention on the outer face of this body or this skirt and the corresponding transverse marks and longitudinal undulations are particularly visible on its inner face.

In this case as well as in the general case, the external 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 edges transverse teeth that have compressed.

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, as already indicated and illustrated below by a new example.

The advantages of the invention are recalled
- surprising obtaining of tear lines giving
tears without hurtful roughness
- these tear lines are waterproof, unlike
lines of weakness with bridges
- particularly simple implementation, using only
standard tools, for a very short time: either
a single compression, particularly in the case of a
flat product, i.e. a work in rotation on one to a few
towers
- 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.

EXAMPLE AND EXAMINATIONS
The present example and the associated examinations differ from those of the main application in particular by the reversal of the means for shaping the tear lines of the capsules, the wheel here carrying the narrow elongated reliefs and the rotary punch or mandrel carrying knurled rings coming face of said narrow reliefs.

Most of the reference numbers in the drawings are those of the main application with an "O" in the suffix, since this is a new example with the above reversals, even when the drawings are similar to the previous ones.

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 J seen from the right and seen internally on the X seen from the left.

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 pass respectively through lines AA and BB.

FIG. 6 represents the outline, according to the thickness, of a torn tab, in the profile projector.

Figure 7 shows the broken edge of such a tab.

Figure 8 is a section perpendicular to the previous view, passing through the medium CC of its portion broken by shearing.

EXAMPLE
A complementary shaping of the capsules was carried out using, according to the invention: (FIG. 1)
- a crazy wheel 10 around its axis of rotation 140 bearing
two parallel peripheral reliefs 20 and 30 with center distance e '=
15 mm protruding from the cylindrical surface 40 of the dial 10
0.5 and end profile 50 in V to 900 with a flat
0.02 mm,
a conical punch 50 or rotary mandrel around an axis 70,
bearing 2 parallel flush knurled rings 80 and 90
15mm center-to-center and 2mm wide pitch oblique toothing
1 mm with 100 teeth 0.2 mm wide.

The height of the teeth 100 was 0.9 and the recesses 110 between teeth of width 0.8 mm with inclined edges. The transverse edges 120 of the teeth 100 were + 100 and - 100 relative to the axis of the punch 60, respectively for each of the knurled rings 80 and 90.

For the shaping of the tear lines, the punch 60 was capped with a capsule 130 (FIG. 2), the latter conforming to the punch without play, this punch 60 was rotated at 1200 revolutions / minute and applied against the wheel 10, the axis of rotation 140 of this wheel 10 being parallel to the generator 35 of the wheels 80 and 90 to the punch 60. The application force of the wheel was 4 daN.

 The compression by this wheel 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 150 and 160, the opening 170 and the primer or end 180 of the tear-away tab 190 have been punched in addition, the preparation of which is thus completed.

The tearing edges of this tab 190 are visible externally (right view of Figure 2). The two outer bow lines 191 alternately having deep parts 192 and narrowing such as 193, 194 and 195, these narrowing correspond to the small internal reliefs 196 and 197 of the tearing lines 150 and 160 (view on the left of the figure 2).

TEAR-OUT RESULTS AND EXAMS
In FIG. 3, which represents a longitudinal section of a tear zone or line such as 160 passing through the line of the notches produced by the end 50 of the V-profile at 900 of the peripheral relief 30 of the wheel 60 (FIG. 1 and 2), one sees more precisely the alternation of portions in Al 200 comprising in the cutting plane a notch 210 of shallow depth 0.02 mm (FIG. 5) with an notched thickness 220 of 0.14 mm, and of heavily notched portions 230 of residual thickness at the bottom of the notch 0.02 mm with a thickness of 0.16 mm at the edge of the notch. Figure 4 shows the profile of the corresponding notch or groove 240 with this notch bottom 250 of thickness 0.02 mm. In Figure 3, we see that the deformations caused by the compression of the skirt 260 (Figure 2 ) of the capsule 130 between the relief 30 and the knurled ring 90 are: longitudinal undulations 270 of the right and reverse surfaces affecting the compressed area and its surroundings, sudden changes in slope 280, which correspond to the impact of the transverse edges 120 teeth 100, resulting in or constituting marks particularly visible on the external face of the capsule 130. The edges at an angle fr = 300 of the notched portions 200 correspond to the inclined edges of the hollows of the knurled ring 90. The pitch of the portions 200 and 230 is 1 mm like the pitch of the reliefs of this ring 90.

The tear tests of the tongues 190 of fifty capsules 130 prepared according to the method described all led to slightly rough but not cutting tears.

Figure 6 shows the outline of a tongue 190 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 290 of the tongue 190, the two zones 300 and 310 having longitudinal grooves 320 correspond to a face at 450 of two neighboring deep cuts 240, while the intermediate zone 330 corresponds to broken non-incised metal. The striations 320 are due to the depression of the relief 30 of the dial. With the perpendicular section in FIG. 8, it can be seen that this broken metal 330 has the shape of a folded lip, which is in continuity with the broken notch bottom 250 of the heavily notched portion (FIGS. 8 and 7). The offset between the tip of the lip 330 and the tear in the bottom of the notch 250 is 0.10 mm.

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

Claims (9)

1. Method for producing a tear line for a container or a  capsule (130) of tinplate or aluminum or alloy thickness  between 0.06 and 0.4 mm, characterized in that this is compressed  metallic product (130) between a narrow elongated relief (20.30) and a  succession of alternating reliefs (100) and recesses (110) arranged opposite  of this narrow relief (20, 30), the differences in level between said reliefs  (100) and hollow (110) alternating being transverse to said  narrow relief (20, 30) and the compression force being such that the  minimum thicknesses of said metal product (130) after compression  are between 0.01 and 0.15 mm, according to claim 4 of the  main patent application, and wherein said reliefs (100) and  alternating hollow (110) are carried by a nested mandrel or punch (60)  with diametral clearance of less than 0.5 mm in the body of said container, or  the skirt (260) of said capsule (130), said narrow elongated relief (20,  30) being carried by a body (10) which is in relative rotation by  relative to this mandrel or punch (60). 2. Method according to claim 1, in which the reliefs (100) and the  alternating hollows (110) follow one another in a pitch of between 0.5 and 10  mm, the spacing of the reliefs (100) or length of the recesses (110) being  between 0.2 and 4 mm. 3. Method according to any one of claims 1 or 2, wherein  the narrow elongated relief (20, 30) has a V-shaped profile with a total angle 50 to  1100 with an end radius of 0.03 to 0.15 mm. 4. Method according to any one of claims 1 to 3, wherein  the alternating reliefs (100) and recesses (110) are formed by teeth  (100) each having two parallel edges (120) at an angle  constant with the direction of the narrow elongated relief (20, 30) in the  compression position, these teeth (100) being alternated with hollows  (110) of lengths 0.3 to 1.5 mm in steps of 0.5 to 3 mm. 5. Method according to claim 4, in which the punch (60) is  rotary, the reliefs (100) and hollow (110) forming a knurled ring  (80, 90), being arranged perpendicular to the axis of rotation of this  punch (60) and the narrow elongated relief (20, 30) being carried by a  idler wheel (10) whose axis of rotation (140) is parallel to the axis  of rotation (70) of the punch (60) during compression, the body of the  container or the skirt (260) of the capsule (130) then being clamped between  said elongated relief (20, 30) and said knurled ring (80, 90). 6. Method according to any one of claims 1 to 5, wherein the  container or capsule has a thickness between 0.08 and 0.3 mm,  the compression force being adjusted so as to obtain thicknesses  minimum after compression between 0.01 and 0.08 mm. 7. The method of claim 5, wherein the rotary punch (60)  wears 2 knurled rings (80) and (90) and the knurl wears 2 reliefs  narrow peripherals (20 and 30) coming opposite said rings  knurled (80) and (90) so as to simultaneously realize the 2 edges of  tearing (150 and 160) of a tear-off tab (190) of said  container or capsule (130). 8. Tin can or capsule (130) in tinplate or aluminum or  alloy of thickness between 0.08 and 0.3 mm, comprising at least  a tear line (150, 160) giving torn edges without  offensive asperities, line (150, 160) having on one side a  notch line (191) having deep portions (230)  thickness at the bottom of the notch (250) between 0.01 and 0.08 mm  alternated with full or more slightly indented portions (200)  lengths along this notch line (160) of between 0.3 and  1.5 mm, with a pitch of between 0.5 and 3 mm, according to claim  12 of the main patent application, said notch line (191)  being located on the outer face of the body of said box or of the  skirt (260) of said capsule (130), and the inner face of said body  or of said skirt (260) having in line with said notch line  (191) transverse marks (280) and longitudinal undulations  (270), some (280) and others (270) as well as the portions  deep (230) of said notch line (191). 9. Box or capsule according to any one of claims 8, bearing 2  tear lines (150 and 160) forming the edges of a tongue  tearable (190).