EP0192011A1 - Plastic container with a neck provided with a flat tamper-proof closure and a cap, and method for opening it - Google Patents

Abstract

1. A container (1) with a neck (5) composed of plastics material and provided with a cap (12) composed of plastics material, the neck (5) being topped by an inviolability cover (9) and the cap (12) comprising a key (14 + 16) with internal raised areas, said key (14 + 16) fitting said cover (9) when the cap (12) covers the neck (5), and rotation of said cap (12) allowing rupture of the cover (9), characterised by all the following four means : a) the inviolability cover (9) comprises a smooth lateral surface (11) ; b) the plastics material of the cap key (14 + 16) is harder than the plastics material of the cover (9) ; c) the internal raised areas of the cap key (14 + 16) terminate with tapered edges (16) having, in a section perpendicular to the common axis (L) of the cover (9) and of the cap key (14 + 16) an end angle of between 7 and 20 C ; d) at least over a certain height, the successive circles perpendicular to the common axis (L) and passing through the ends (17) of said tapered edges (16) have diameters (DIAM d ) which are from 0.4 to 0.9 mm smaller than the corresponding diameters (DIAM D ) of the lateral surface (11) of the cover (9) when said cover (9) is fitted by said cap key (14 + 16).

Description

The invention relates to the field of neck containers and their caps, provided with a tamper-evident closure element.

KNOWN STATE OF THE ART

Patent application EP-A-0 119 145 of the applicant describes a container with a plastic neck, the neck being surmounted by a tamper-evident seal whose base is tearable and whose head comprising reliefs fits into a key with internal reliefs of the cap, a key whose cooperation with said reliefs of the head of the cap allows the rupture of this cap by the rotation of the cap. The casing can be done by force, the cover then remaining trapped in the key of the cap after its rupture. The centering of the cap and therefore of the key when the cap is pressed onto the neck is made easier by the presence in the cap of a crown fitting the neck with little play. This centering crown can be the crown of the key of the cap itself when the cover is roughly the same diameter as the orifice of the neck, or else a separate crown when the cover has a smaller diameter because it is connected to the edges of the orifice of the neck by a flared skirt injected obliquely.

Among the various arrangements described by the above document, it should also be noted that the base of the ruptured seal may include means for sealing the orifice of the neck, and that the cap and the neck may carry screwing means. complementary cooperating for recapping after rupture of the cover.

EXPOSURE OF THE PROBLEM

• - la surface latérale de l'opercule doit présenter des reliefs s'emboîtant dans les reliefs de la clef du capuchon.
• - les nombres des reliefs de l'opercule et de la clef du capuchon doivent être suffisants, et leurs profils étudiés, pour qu'il n'y ait pas de problème sensible d'indexage lors de l'emboîtement de l'opercule par la clef du capuchon qui doit se produire lorsqu'on met en place le capuchon sur le goulot.

The solution described in document EP-A-0 119 145 as well as its various alternative embodiments respond to the problems of the ease of opening of necked containers topped with a tamper-evident seal and of their subsequent recapping, but has the following constraints:

• - The lateral surface of the cover must have reliefs fitting into the reliefs of the key of the cap.
• - the numbers of the reliefs of the cover and of the key of the cap must be sufficient, and their profiles studied, so that there is no significant problem of indexing during the nesting of the cover by the key of the cap which must occur when the cap is placed on the neck.

These features both lead to complications in the manufacturing tool, and the reliefs of the lateral surface of the cover may have other drawbacks, for example concerning handling and / or aesthetics.

The Applicant has sought a different solution, making it possible to avoid the preceding complications and disadvantages.

STATEMENT OF THE INVENTION

As is known, the container of the invention is a plastic container provided with a cap also made of plastic, the neck being surmounted by a tear-off sealing cap at its base, and the cap comprising a key interior reliefs. This key fits the lid when the cap covers the neck, and the rotation of the cap then allows the rupture of the lid.

• b) la matière plastique de la clef du capuchon est plus dure que la matière piastique de l'opercule;
• c) les reliefs intérieurs de la clef du capuchon se terminent par des arêtes effilées:
• d) au moins sur une certaine hauteur, les cercles successifs, perpendiculaires à l'axe commun du récipient et du capuchon et passant par les extrémités des arêtes effilées des reliefs de la clef du capuchon, ont des diamètres plus faibles que les diamètres de la surface latérale de l'opercule qui leur correspondent, lors de l'emboîtement de l'opercule par la clef du capuchon.

In a new way, the sealing lid has a smooth lateral surface (means a)) and, surprisingly, the rupture of the lid is obtained by rotation of the cap pressed onto the neck by the following three additional means:

• b) the plastic material of the cap key is harder than the plastic material of the cover;
• c) the interior reliefs of the cap key end with tapered edges:
• d) at least over a certain height, the successive circles, perpendicular to the common axis of the container and of the cap and passing through the ends of the tapered edges of the reliefs of the key of the cap, have diameters smaller than the diameters of the lateral surface of the lid which correspond to them, during the fitting of the lid by the key of the cap.

There is then an interlocking with tightening of the cover by the reliefs with tapered edges of the key of the cap, and it is found that these tapered edges strip the cover in less hard plastic. After rupture of the cover, it remains trapped in the key of the cap.

The problem of indexing to obtain nesting disappears completely in the case of lids with circular section (s). The manufacturing is simplified for the cover, the lateral surface of which is smooth.

The invention can be applied to any form of cover accompanied by a shape of all of the tapered edges of the internal reliefs of the key of the cap ensuring a certain tightening during the fitting of the cover by this key. In order to have the facility of an isotropic nesting, the cover preferably has a lateral surface of revolution around its axis of symmetry which is usually that of the neck it covers. The cover has for example a frustoconical or parabolic surface. Usually, and this is the case for the examples which follow, the cover comprises a circular cylindrical lateral surface.

• A)- Opercule (tête) : PE BD (polyéthylène basse densité) réticulaire ou linéaire
  • - Clef du capuchon (capuchon) : l'une des matières plastiques suivantes :
    • - PE HD (polyéthylène haute densité)
    • - PP (polypropylène)
      
• B)- Opercule : PE HD (radicalaire ou linéaire);
  • - Clef du capuchon : PP ou une des matières du sous-groupe (X)
• C)- Opercule PP;
  • - Clef du capuchon : une des matières du sous-groupe (X)

Usually, the cap is in one piece, and the neck and the cover are in one piece with the shoulder by which the molded head is connected to the skirt of the tube. The couples of material usable for the cover on the one hand, that is to say usually also for the neck or the head of the tube, and for the key of the cap on the other hand, that is to say usually for the entire cap, are:

• A) - Lid (head): PE BD (low density polyethylene) reticular or linear
  • - Cap key (cap): one of the following plastics:
    • - PE HD (high density polyethylene)
    • - PP (polypropylene)
      
• B) - Lid: PE HD (radical or linear);
  • - Cap key: PP or one of the materials in subgroup (X)
• C) - PP cover;
  • - Cap key: one of the materials in subgroup (X)

During the fitting of the lid by the key of the cap, fitting done by covering the neck of the cap and pressing a little to push it in, the "tightening" obtained is preferably between 0.4 and 0.9 mm in diameter, and preferably still between 0.5 and 0.7 mm in diameter, this at least over a certain height, typically over at least 2 mm. For a cover having a smooth lateral surface of revolution around its axis of symmetry, the successive circles perpendicular to the common axis of the cover and of the cap key and passing through the ends of the tapered edges of the interior reliefs of the key of the cap have for this purpose diameters less than 0.4 to 0.9 mm, and preferably 0.5 to 0.7 mm, than the diameters of the lateral surface of the cover which correspond to them.

In addition, the tapered edges of the reliefs of the key of the cap are cutting, under the nesting conditions with tightening indicated above, for the lateral surface of the cover which is made of less hard plastic. Their cutting power intervenes for the ease of fitting together as well as for the quality of the streak or notch obtained which conditions the efficiency of the drive of the cover by rotation of the cap. In the training of a relief cover by a relief key fitting into the reliefs of the cover, the relief surfaces involved in the rotation drive are generally limited to narrow areas where there is contact. In contrast, in the drive of the cover of the invention, the small portions of tapered edges inserted into the plastic material of the cover intervene through all of their surfaces for the drive in rotation of the cover by the rotation of the cap. This particular efficiency of the streaking or notching with partially elastic deformation of the plastic material of the seal, streaking which occurs from the top to the bottom of the seal when the cap and therefore its key are pushed in. as well as the rigidity of the insertions of the tapered edges linked to the peripheral tightening of the endpiece by the key, explain the surprising ease of the rotary drive of the cover by the rotation of the cap with the device and according to the method of invention.

To obtain penetration of the nozzle, by stripping or notching by the tapered edges of the reliefs of the key of the cap, easy and of optimal quality for the rotation drive of the seal, the end angle of these edges tapered, in section perpendicular to the axis of symmetry of the key as well as of the cover in position for fitting the container by the cap, is preferably between 7 and 20 ° and more preferably between 10 and 16 °. These conditions can be associated with one or the other of the preferential conditions of nesting with tightening, but it is recommended to have at least at the same time a "tightening" of 0.4 to 0.9 mm in diameter and angles of ends of tapered edges between 7 and 20 °.

Finally, in a particular structure, the internal reliefs of the key of the cap are carried by a crown, the end of which easily fits on the cover, and these internal reliefs gradually widen from their lower end, so that the beginning of the insertion of the cap ensures good centering of the key on the cover and that the beginning of the striation of the lateral surface of this cover by the tapered edges of the interior reliefs of the key consists of a gradual notching of the upper part of this lateral surface. The progressive widening of the interior reliefs of the key of the cap, is preferably carried out over a height at least equal to 2 times the maximum width of said reliefs. In addition, for the good rigidity of the interior reliefs with tapered edges, it is generally preferable to maintain their width in the radial direction quite small and typically between 0.3 and 1 mm.

• A) on approvisionne un capuchon en matière plastique comportant une clef à reliefs intérieurs, le capuchon pouvant coiffer le goulot et sa clef emboîtant alors ledit opercule, la clef du capuchon ayant les caractéristiques suivantes :
  • - cette clef au moins est en matière plastique plus dure que la matière plastique du goulot et de l'opercule (comme la condition (b) concernant le dispositif);
  • - ses reliefs intérieurs se terminent par des arêtes effilées dont les extrémités se situent, au moins sur une certaine hauteur, sur des cercles successifs perpendiculaires à l'axe du capuchon de diamètres plus faibles que les diamètres correspondants de l'opercule (comme les conditions (c) et (d) concernant le disposiif).
• B) on serre l'opercule et on strie sa surface latérale, en enfonçant le capuchon sur le goulot et donc sa clef sur ledit opercule.
• C) on fait tourner le capuchon par rapport au tube, dans un sens de rotation ou dans l'autre sens, jusqu'à rupture de l'opercule, et on écarte le capuchon.

The invention also relates to a method of opening a container with a neck surmounted by a tamper-evident seal with a smooth lateral surface, in which

• A) we supply a plastic cap comprising a key with internal reliefs, the cap being able to cover the neck and its key then fitting said cover, the key of the cap having the following characteristics:
  • - this key at least is made of harder plastic than the plastic of the neck and the cover (as condition (b) concerning the device);
  • - its interior reliefs end with tapered edges whose ends are located, at least over a certain height, on successive circles perpendicular to the axis of the cap with diameters smaller than the corresponding diameters of the cover (like the conditions (c) and (d) concerning the device).
• B) the cover is tightened and its lateral surface is streaked, by pushing the cap on the neck and therefore its key on said cover.
• C) the cap is rotated relative to the tube, in one direction of rotation or in the other direction, until the cap breaks, and the cap is moved aside.

Preferably, the ends of the tapered edges of the internal reliefs of the cap key are located, at least over a certain height - in practice at least 1.5 to 2 mm - on successive circles perpendicular to the axis of the cap. diameters 0.4 to 0.9 mm lower than the corresponding diameters of the cover, and said tapered edges have. in section perpendicular to the same axis. an end angle between 7 and 20 °.

Particularly good results are obtained with the various preferential conditions already indicated in the case of the device and concerning in particular: the differences between the internal diameters on the ends of the internal tapered edges of the key of the cap and the corresponding diameters of the cover, the end angle of these tapered edges; the choice respective plastics for the key to the cap, that is to say in general for the one-piece cap, and for the cover, that is to say typically for the overmolded head of the tube.

EXAMPLES

The examples and the drawings which illustrate them relate to the common case where, in the fitting position, the neck and its sealing cap on the one hand and the cap and its key on the other hand have a common longitudinal axis. The neck and the cover, as well as the cap, then have a symmetry of revolution around the previous axis.

• . Figure 1 shows a practical example of container and cap according to the invention, in longitudinal axial section.
• . FIG. 2 represents the key to the cap of this first example, in quarter section through a plane perpendicular to the horizontal axis, plane marked I in FIG. 1.
• . FIG. 3 represents the lid of the container and the key of the cap of the first example, at the time of engagement of this key, in local axial longitudinal section passing through the ends of 2 tapered edges.
• . FIG. 4 represents the container and the cap of the first example, the cap being pushed in, in longitudinal axial section.
• . Figure 5 shows the same container and cap after rupture of the cover, in longitudinal axial section.
• . FIG. 6 represents a second example of container and cap according to the invention, the cap being pushed in, in longitudinal axial section.

The container (1) shown in FIG. 1 comprises a skirt (2) with an external diameter of 33 mm in polyethylene surmounted by an overmolded head (3) 0.8 to 1.2 mm thick in low density polyethylene, head (3) comprising itself above its shoulder (4) a neck (5) with an outside diameter of 17 mm and a height of 12 mm carrying a fancy orifice (6) with 6 recesses (7) separated by 6 raised parts (8 ), this orifice (6) having a hollow diameter of 14 mm. The neck (5) and the orifice (6) are surmounted by a tamper-evident seal (9), which comprises at its base a flared skirt (10), then above a circular cylindrical lateral surface (11) of diameter (P _D ) equal to 7.5 mm and 6 mm high, then finally an end forming a cover (111) 2 mm high.

The cap (12) of the container being inserted is made of polypropylene, it has an outside diameter of 32 mm and a height of 26 mm. Inside it carries an intermediate crown (13) with an internal diameter of 17.5 mm and a height of 20 mm intended to fit the neck (5), and a circular central crown of height 9 mm (14) bearing on its inner cylindrical surface (15) of diameter 8.0 mm 12 raised ribs (16) in the form of tapered fins.

These tapered fins (16) visible in section perpendicular to the longitudinal axis (L) in Figure 2 have, according to this section, an end angle (") of 15 °. Their width in the radial direction, constant for all the fins, is 0.55 mm. The diameter (b _d ) of the circle perpendicular to the axis (L) passing through the ends (17) of the tapered fins (16) of the key (14 + 16) of the cap (12) is 6.9 mm at level of this cut, and this diameter remains constant over 6 to 7 mm in height. During the fitting of the cover (9) by the key of the cap (14 + 16). the circles of diameter (φ _d ) of this key are therefore 7.5-6.9 - 0.6 mm less than the diameter (φ _D ) of the cylindrical lateral surface of the cover (9).

Figure 3 shows more clearly the beginning of the engagement of the cap key (14 + 16) on the cover (9). The end portion (18) of the crown (14) of the key of the cap is about 1 mm free of reliefs in the form of tapered fins (16). The reliefs of the fins (16) then begin by gradually widening from 0 to 0.55 mm by 1.5 mm. Thanks to the end portion (18) of the crown (14) free of reliefs and thanks to the progressive widening (19) of the reliefs of the fins (16), the engagement of the key of the cap (14 + 16) is in all cases easy and progressive and will ensure good centering for the start of the stripping of the cover (9) for the fins (16). FIG. 3 shows the extensions (20) of the ends (17) of the fins (16) in broken lines, which cut the cover symmetrically with respect to the axis (L), thanks to these means of centering. It is not necessary for this centering effect that the interior of the cap key (14 + 16) begins with a portion of surface (18) free of reliefs, but this free portion (18) ensures the separation of the progressive widening (19) of the fins (16) relative to the extreme edge of the crown (14) and thus gives this widening (19) and the fins (16) protection against handling shocks.

When the cap (12) and therefore its key (14 + 16) is pushed further in, the notching or the stripping of the cover (9) begins at the upper end (21) of its surface cylindrical side (11). Figure 4 shows the cap (12) in the depressed position on the neck (5) and the cover (9).

From this depressed position, it suffices to drive the cap (12) in rotation while holding the tubular container (1) with the other hand, in one direction or the other as shown by the double arrow (22). of Figure 4. The rupture of the cover (9) is easily obtained with a relative angle of rotation of 30 to 40 °, and the broken cover (9) remains trapped in the key (14 + 16) of the cap ( 12) when the latter is raised (FIG. 5), thus freeing the orifice (6) from the tube (1).

With other similar samples, it has been observed that the cap (12) can be pushed onto the cover (9) then removed and repeated this maneuver more than ten times without observing any difficulties, and that the rupture of the cover (9) was then easily obtained by rotation of the cap (12), as described above. After removing the caps (12), it was observed by eye that the lateral surfaces (11) of the lids (9) had fine, more or less apparent streaks, starting at the high end (21) of these surfaces lateral (11) and descending on 2 to 4 mm, the spacing of these streaks or stripes corresponding to the spacing of the fins (16).

It can therefore be seen that the opening method of the invention is effective, despite apparent differences in length between the fine streaks caused by the various tapered fins. We also see that these streaks appear finer than the portions of fins which have cut the lateral wall of the lids, which undoubtedly means that these portions of fins were inserted with elastic tightening on the part of the plastic material of the lid walls thus striated.

• - le goulot (50) et la couronne intermédiaire (130) du capuchon (120) comportent respectivement des filetages (51) et (131) destinés au rebouchage du récipient (100) après rupture de l'opercule (90). par vissage du capuchon sur le goulot;
• - l'opercule (90) raccordé au bord de l'orifice circulaire (60) du goulot (50) par une zone de faiblesse amincie (91) comporte successivement une jupe inférieure (9) surmontée d'une coupelle (93) et une tête (94) comportant une surface latérale cylindrique (95);
• - le capuchon (120) comporte en son centre une clef constituée par une couronne (140) portant des reliefs en forme d'ailettes effilées (160) selon l'invention, avec entrée progressive. Le diamètre intérieur sur ailettes (e _d) de la clef (140+160) est inférieur de 0,4 à 0,9 mm au diamètre extérieur (φ_D) de la surface latérale (95) de l'opercule (90). Le capuchon (120) et sa clef (140+160) sont monobloc et en matière plastique plus dure que celle de la tête du tube (100). En tournant le capuchon (120) enfoncé en rotation dans un sens ou dans l'autre selon la flèche (220), on obtient la rupture de l'opercule (90) grâce au procédé et au dispositif de "clef striante" de la présente invention. Ensuite, la jupe (92) rompue à pourtour extérieur légèrement conique ainsi que la coupelle (93) de l'opercule (90), opercule qui est alors prisonnier du capuchon (120), permettent le rebouchage étanche de l'orifice (60) du goulot (50), comme cela est connu en soi par notre demande de brevet EP-A- 0 119 145 et repris par les revendications 4 et 13 de ce document. De façon plus générale, tous les aménagements qui correspondent aux parties caractéristiques des revendications 3 à 11 et 13-14 de cette demande de brevet peuvent être utilisés avec l'opercule et la clef striante de la présente invention.

The second example of a container (100) and of a cap (120) according to the invention (FIG. 6) shows the following particularities:

• - The neck (50) and the intermediate crown (130) of the cap (120) respectively comprise threads (51) and (131) intended for recapping the container (100) after rupture of the cover (90). by screwing the cap onto the neck;
• - The cover (90) connected to the edge of the circular orifice (60) of the neck (50) by a zone of thinned weakness (91) successively comprises a lower skirt (9) surmounted by a cup (93) and a head (94) having a cylindrical side surface (95);
• - The cap (120) has in its center a key constituted by a crown (140) carrying reliefs in the form of tapered fins (160) according to the invention, with progressive entry. The inside diameter on fins (e _d ) of the key (140 + 160) is 0.4 to 0.9 mm less than the outside diameter (φ _D ) of the lateral surface (95) of the cover (90). The cap (120) and its key (140 + 160) are in one piece and made of plastic harder than that of the head of the tube (100). By turning the cap (120) pressed in rotation in one direction or the other according to the arrow (220), one obtains the rupture of the cover (90) thanks to the process and to the "striating key" device of the present invention. Then, the skirt (92) broken with a slightly conical outer periphery as well as the cup (93) of the cover (90), a cover which is then trapped in the cap (120), allow the sealing of the orifice (60) neck (50), as is known per se from our patent application EP-A-0 119 145 and taken up by claims 4 and 13 of this document. More generally, all the arrangements which correspond to the characteristic parts of claims 3 to 11 and 13-14 of this patent application can be used with the cover and the striating key of the present invention.

APPLICATIONS

The device and the opening method of the invention most often applies to tubular containers having a circular orifice with a diameter between 5 and 15 mm, or even a fancy orifice having an injection circle with a diameter included between 5 and 15 mm. The thicknesses of the welded areas of weakness are generally between 0.1 and 0.4 mm.

These tubular containers are typically provided with a cap with a diameter between 25 and 40 mm and, as described by EP-A-0 119 145, the opening torque by breaking the tamper-evident seal is then typically between 10 and 90 Nm, and between 10 and 30 Nm in the case of fancy orifices surmounted by welded seals discontinuously.

The device and method of the invention are used essentially in the field of food products for liquids, syrups, creams, products in a pasty state or in the form of gums, and for products in a divided state; in the field of pharmaceutical, hygienic or cosmetic products; in all previous presentations or consistencies, and in the area of chemicals or maintenance.

Claims (8)

1. Plastic container (1) with neck (5) provided with a plastic cap (12), the neck (5) being surmounted by a tamper-evident seal (9) and the cap (12) comprising a key (14 + 16) with internal reliefs, said key (14 + 16) fitting said cover (9) when the cap (12) covers the neck (5) and the rotation of said cap (12) then allowing the rupture of the '' seal (9), characterized by all of the following four means: a) The tamper-evident seal (9) has a smooth lateral surface (11); b) the plastic material of the cap key (14 + 16) is harder than the plastic material of the cover (9); c) the internal reliefs of the key of the cap (14 + 16) end in tapered edges (16), having a section perpendicular to the common axis (L) of the cover (9) and of the key of the cap (14 + 16) an end angle between 7 and 20 °; d) at least over a certain height, the successive circles perpendicular to the common axis (L) and passing through the ends (17) of said tapered edges (16) have diameters (0 _d ) less than 0.4 to 0, 9 mm to the diameters (φ _D ) of the lateral surface (11) of the cover (9) which correspond to them, during the fitting of said cover (9) by said key of the cap (14 + 16). 2. Container according to claim 1, characterized in that the tapered edges (16) of the internal reliefs of the key of the cap (14 + 16) have, in section perpendicular to the common axis (L) of the cover (9 ) and the key of the cap (14 + 16), an end angle (α) between 10 and 16 °. 3. Container according to any one of claims 1 or 2, characterized in that, at least over a certain height, the successive circles perpendicular to the common axis (L) of the cover (9) and of the key of cap (14 + 16) and passing through the ends (17) of the tapered edges (16) of the internal reliefs of the cap key (14 + 16) have diameters (P _d ) less than 0.5 to 0.7 mm to the diameters (φ _D ) of the lateral surface (11) of the cover (9) which correspond when said cap (9) fits together with said cap key (14 + 16). 4. Container (1) according to any one of claims 1 to 3, characterized in that the internal reliefs (16) of the key of the cap are carried by a crown (14) whose lower end (18) s' easily fits on the cover (9), and in that said interior reliefs (16) comprise a progressive widening (19) over a height at least equal to twice their maximum width. 5. Container (1) according to any one of claims 1 to 4, characterized in that the cover (9) is made of low density polyethylene, and in that the key of the cap (14 + 16) is made of a material plastic from the group consisting of: high density polyethylene, polypropylene, thermosetting resins, polycarbonates, styrenics, acetal resins, polyesters. 6. Container (1) according to any one of claims 1 to 4, characterized in that the cover (9) is made of high density polyethylene, and in that the key of the cap (14 + 16) is made of a material plastic from the group consisting of: polypropylene, thermosetting resins, polycarbonates, styrenics, acetal resins, polyesters. 7. Container (1) according to any one of claims 1 to 4, characterized in that the cover (9) is made of polypropylene, and in that the key of the cap (14 + 16) is made of a plastic of the group consisting of: thermosetting resins, polycarbonates, styrenics, acetal resins, polyesters. 8. Method for opening a container (1) with a neck (5) of plastic material surmounted by a tamper-evident seal (9) comprising a smooth lateral surface (11), characterized in that it comprises the steps following: A) we supply a plastic cap (12) comprising a key with internal reliefs (14 + 16), the cap (12) being able to cover the neck (5) and its key (14 + 16) then fitting said cover (9 ), said key of the cap (14 + 16) ₁ having the following characteristics: - This key (14 + 16) at least is made of harder plastic than the plastic of the neck (5) and the cover (9); - its interior reliefs end in tapered edges (16), having an end angle of between 7 and 20 °, the ends (17) of which lie, at least over 1.5 mm, on successive circles perpendicular to the axis of the cap with diameters (φ _d ) 0.4 to 0.9 mm smaller than the corresponding diameters (φ _D ) of the cover (9); B) the cover (9) is tightened and its lateral surface (11) is streaked, by pushing the cap on the neck (5) and therefore its key (14 + 16) on said cover (9). C) the cap (12) is rotated relative to the tube (1) in a direction of rotation (22) or in the other direction, until the cover (9) breaks, and the cap ( 12).

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