FR3074785A1 - PROCESS FOR MANUFACTURING A CONTAINER CAP, BLANK OF PLUG AND PLUG OBTAINED BY CARRYING OUT THE PROCESS - Google Patents

Abstract

A method of manufacturing a container stopper (1), comprising a step of producing, by molding a plastic material, a plug blank (1), which step of producing the blank is followed by a finishing step of the plug by folding a retaining band (22), characterized in that a line (20) of weakening is formed between the axial end (22A) of the retaining band (22) and a end (12B) of the skirt (12), that is to say at the junction between the retaining strip (22) and the skirt (12) at the level where the folding for finishing the cap is to be performed later, so that the line (20) of weakening is also a fold line and that after a first opening of the plug (1), only the retaining band remains on the container. Blank of plug (1) and plug (1) obtained by the implementation of the method.

Description

Method for manufacturing a container cap, blank cap and cap obtained by implementing the method.

The present invention relates to a method for manufacturing a container cap, the cap blank and the cap obtained by implementing the method.

The invention relates, in general, to the caps of molded plastic containers which include, when considered placed on a container with its neck facing upwards, an upper part, consisting of a skirt surmounted a wall which covers the neck of the container, and a lower part which is intended to remain around the neck after the first opening of the stopper, while the rest of the skirt is provided removable relative to the neck. The separation between the upper part and the lower part is authorized by the presence of frangible bridges, which are distributed along the periphery of the skirt and are broken when the cap is opened for the first time. The bridges constitute a line of weakness and their rupture serves as a witness to a first opening, for the attention of users. In the context of the present invention, the nature of the removable connection between the upper skirt part and the container neck is indifferent, even if the invention relates more particularly to caps capable of being screwed onto the container necks.

The invention is more particularly concerned with plugs in which the weakening line is cut. These are plugs in which the weakening line comprises, for example, a succession of notches made through and along the periphery of the wall of the skirt, so as to define, between two successive notches, one of the aforementioned frangible bridges, d on the one hand, and the retention of the non-removable lower part of the skirt around the neck of the container is produced by a protruding strip of the skirt, made integrally with the latter, on the other hand. Obtaining the weakening line by cutting presents economic and practical interests, in particular compared to the molding of the weakening line, the molding requiring the use of complex molds, for example provided with drawers. Likewise, the use of the aforementioned band (also called tamper-evident band), which is molded together with the skirt, in order to retain the non-removable lower part of the skirt, proves to be effective. In general, at the outlet of the mold, the retaining strip is directed downward, which facilitates demolding, then, under the action of an ad hoc pusher which is introduced inside the skirt, the retaining strip retainer is folded up by folding up to a service configuration allowing it to retain a non-removable lower skirt portion by abutment against an associated bulge of the container neck. It can be considered that the manufacture of such plugs is carried out in two main stages, each of which may include one or more intermediate phases.

The first stage is a stage of making a blank of the stopper: it is that which comprises all the phases preceding the folding of the retaining strip; the second stage is a stage of finishing the stopper: it is that which mainly includes, among other things, the phase of folding the retaining strip.

This being said, the current trend is to manufacture plugs whose walls, in particular the skirt, are less and less thick, in order to limit the amount of plastic material used, both for economic and ecological reasons. The constraints of the molding and demolding operations of the plugs of the type described above then lead to the fact that, at the outlet of the mold, the retaining strip extends more and more vertically, in the downward extension of the skirt. The operation of folding the retaining strip, from its molding configuration to its service configuration, becomes more and more delicate, in the sense that the dimension, radially to the central axis of the skirt, for interference between the retaining strip and the aforementioned pusher, used to act on the retaining strip for the purpose of folding, is becoming smaller. This results in either an incomplete folding of the retaining strip, in the direction a peripheral portion of this retaining strip remains in its molding configuration, or an axial crushing of the skirt by the pusher, or even both, which poses certain problems on the stopper lines.

To circumvent this problem, it is known to use, in replacement of the aforementioned conventional pusher, more sophisticated machines, including two rods movable telescopically. A first movable rod, surrounding the second movable rod, encircles the skirt from the outside and is used to pre-fold the retaining band so as to tilt it further relative to the vertical and thus increase the radial dimension of its overflow inside the skirt; then, the second movable rod is introduced inside the skirt and comes to interfere with the pre-folded retaining band to finish bending it by folding it down to its service configuration. It is understood that, compared to a conventional pusher, the second movable rod necessarily has a smaller outside diameter, due to the presence of the first movable rod used for pre-folding. The result is that, even if the second rod acts effectively on the retaining band to fold it down to its service configuration, the connection zone between the retaining band and the skirt is necessarily less pinched than with a conventional pusher larger diameter: at the end of the manufacturing process, it sometimes happens that due to its elasticity, the retaining strip leaves its service configuration and returns to its pre-folded configuration.

Consequently, the measures taken so far are not entirely satisfactory.

The objects of the invention are to propose a method of manufacturing a plug of the type mentioned above, a blank of plug and a plug obtained by the implementation of the method which make it possible to firmly fold the retaining strip so efficient and economical.

A first object is achieved by a method of manufacturing a container stopper, intended to close the neck of a container, comprising a first step, of producing, by molding a plastic material, a blank of the stopper, which step of producing the blank, which is followed by a step of finishing the plug by folding a retaining strip, comprises at least the following phases:

a phase of molding the blank consisting of molding a skirt and a retaining strip secured to the skirt, during which:

-the skirt is molded so as to have a generally tubular shape, which extends along a central axis between a first end, closed by means for closing the neck of the container, such as a bottom wall molded with the skirt, and a second end, opposite the first, which skirt is provided with means for removable attachment to the neck of the container arranged between the two ends; and

the retaining strip, integral with the skirt, is molded in the form of a ring intended to remain permanently around the neck of the container by cooperating with retaining means provided on the neck; this strip comprising an axial end which runs over the entire lower periphery of the strip and provides a junction with the second end of the skirt; this retaining strip being molded in the extension of the skirt, beyond its second end, so that it extends, from the second end of the skirt, in the direction opposite to the first end of the skirt;

a cutting phase subsequent to the molding phase, which consists in producing in the blank a peripheral weakening line comprising frangible elements adapted to be broken during the first opening of the stopper, which weakening line connects, according to the central axis, a first part of the blank including said first end of the skirt, as well as the means for closing the neck and said fixing means, and a second part of the blank including the retaining strip;

characterized in that, during the cutting phase, the cutting to obtain the weakening line is carried out between the axial end of the strip and the second end of the skirt, that is to say at the junction between the retaining strip and the skirt, at the level where the folding for the finishing of the plug must be carried out subsequently, so that the weakening line also constitutes a folding line and that, after a first opening of the plug and breaking of the elements frangible, only the retaining strip remains permanently on the container.

According to other characteristics:

the step of finishing the plug, which follows the step of making the blank, comprises a phase of folding the retaining strip consisting in folding the latter towards the first end of the skirt by folding the retaining strip over itself at its junction with the skirt, until passing it in a so-called service configuration in which the plug can be placed on a container;

the folding phase is preceded by a pre-folding phase of the retaining strip, which consists in placing the latter, in a pre-folded configuration which is intermediate between said molding configuration and said service configuration;

the pre-folding phase is carried out after the cutting phase, before the folding phase;

the pre-folding phase is carried out simultaneously with the cutting phase, before the finishing step;

the retaining strip is molded so that, when the cap is opened for the first time after folding and placing the cap on a container, it abuts axially against the retaining means provided on the neck;

the retaining means provided on the neck consist of an associated bulge of the neck of the container;

the removable fixing means to the neck of the container arranged between the two ends are constituted by at least one screwing / unscrewing thread internal to the skirt and intended to cooperate with at least one complementary thread formed around a neck of the container. The invention also relates to a blank container cap, obtained by implementing the method which comprises:

on the one hand, a skirt of generally tubular shape, which extends along a central axis between a first end, which end is closed by means for closing the neck of a container, such as a bottom wall coming molding with the skirt, and a second end opposite the first, which skirt is provided internally with removable fixing means to the neck of a container disposed between the two ends;

on the other hand, a retaining strip in the form of a ring intended to remain permanently around the neck of a container, this retaining strip being molded in the extension of the skirt, beyond its second end , and having an axial end contiguous with the second end of the skirt so that the retaining strip extends, from the second end of the skirt, in the direction opposite to the first end of the skirt;

a peripheral weakening line comprising frangible elements adapted to be broken during the first opening of the stopper, which weakening line connects, along the central axis, a first part including said first end of the skirt and said means of fixing, and a second part provided with said retaining strip;

characterized in that, the weakening line consists of a cutout made at the junction between the retaining strip and the skirt.

The invention finally relates to a container cap, obtained by the implementation of the process which comprises:

on the one hand, a skirt of generally tubular shape, which extends along a central axis between a first end, provided with means for closing the neck of the container, such as a bottom wall molded with the skirt, and a second end opposite the first, which skirt is provided internally with removable fixing means to the neck of the container arranged between the two ends;

-on the other hand, a retaining band in the form of a ring intended to remain permanently around the neck of the container, this retaining band having an axial end contiguous with the second end of the skirt and being folded towards the first end of the skirt following the folding of the retaining strip on itself at its junction with the skirt;

characterized in that it further comprises a peripheral weakening line comprising frangible elements adapted to be broken during the first opening of the stopper, which a cut made in a weakening line is formed by at the junction between the strip retainer and the skirt, so that, after a first opening of the cap and rupture of the frangible elements, only the retaining band remains permanently on the container.

The idea behind the invention is to facilitate folding so that the risks of seeing the retaining strip be incompletely folded or of having a tendency to unfold and return to its original position, that is to say the position in which it is made, disappear. This facilitation of folding is made possible by the fact that the weakening line also constitutes a folding line.

Furthermore, the fact that the folding is carried out at the level of the weakening line has the effect that the process requires a lighter tool. In fact, the force required for folding the retaining strip is less than that required with the prior art where the folding takes place in an area completely provided with material.

However, although the folding takes place in a deliberately weakened area, there is no risk of breakage of the frangible bridges during the folding. These retain their integrity until the first use of the container.

After first use, no part of the skirt remains on the container, only the retaining band remains there, unlike the caps of the prior art where, in addition to the retaining band, an annular portion of the skirt (with a height of about 1 to 5 mm) remains attached to the container after first use.

An additional advantage of the invention results from the arrangement of the cutout in the lower part of the stopper when it is completed and placed on a container. This arrangement makes it possible to ensure good cleaning of the container and of the stopper, in particular in the case of filling and capping followed by an external rinsing of the clogged container, insofar as the slots obtained by cutting between the bridges constitute in themselves orifices for evacuating the liquid rinsing the plug, thereby avoiding constituting dedicated orifices such as those described in French patent FR 2 987 607.

The invention will be better understood on reading the description which follows, given solely by way of example and made with reference to the drawings in which:

- Figure 1 is a longitudinal half-section of a stopper manufactured in accordance with the prior art, this figure 1 illustrating the stopper, not yet open, in place on a neck of the container;

- Figure 2 is a longitudinal half-section of a stopper made in accordance with the invention, this figure 2 illustrating the stopper, not yet open, in place on a neck of the container;

- Figure 3 is a longitudinal section of a blank of the plug of Figure 2 obtained during the first step of manufacturing the plug of the invention;

- Figure 4 is an enlarged view of the detail circled IV in Figure 3;

- Figure 5 is a view similar to Figure 3, Figure 5 illustrating the cutting phase of a weakening strip to that of Figure 3;

- Figure 6 is an enlarged view of the detail circled VI in Figure 5;

- Figure 7 is a view illustrating the second manufacturing step, subsequent to that shown in Figure 6; and

FIG. 8 is a view on a larger scale of the detail circled VIII in FIG. 7.

For convenience, in the following description both with regard to the plug of the prior art (FIG. 1) or the plug according to the invention (FIGS. 2 to 8), the upper or upper terms as well as the lower terms and bottom are used considering that the stopper is in place or placed on a container which itself is standing on its base (also called bottom). Thus the top of the container is therefore its neck or neck, while the bottom is its bottom. The top of the stopper is therefore its part provided with a flat wall, the bottom is the part of the stopper by which it covers the neck of the container.

In Figure 1 is shown a plastic cap 11 made in accordance with the prior art.

This cap 11 is designed to be removably attached to a neck 2 of the container in order to close the latter.

The plug 11 and the neck 2 have respective generally tubular shapes, the central longitudinal axes of which coincide, when the plug 11 is attached to the neck 2. These axes are identified by the common reference X-X.

The container neck 2 comprises a generally cylindrical body 3 with a circular base, centered on its axis X-X. At its upper end, the body 3 defines an opening or sip 4 through which the container is filled or emptied. On the outer face of the body 3, the neck 2 is successively provided, from top to bottom, with a thread 5 in a helix and with a bulge 6 or snap ring, both radially projecting outwards.

The plug 11 is open at its lower end, while at its upper end it is closed by a substantially flat bottom wall 10 at the outer periphery of which extends downward an outer tubular skirt 12 which is centered on the axis XX and a first end 12A, said high, came integrally with the bottom wall 10. The underside of the bottom wall 10 is provided with both a protruding tubular lip 13, centered on the axis XX and arranged inside the outer skirt 12, and a protruding heel 14, running on the outer periphery of the bottom wall. When the plug 11 is attached to the neck 2, as illustrated in FIG. 1, the bottom wall 10 extends above and across the neck, while, on the one hand, the skirt 12 externally surrounds the body 3 and, on the other hand, the lip 13 and the heel 14 are respectively pressed in a sealed manner against the inner face of this body and on the outer periphery of the lip 4, to allow the plug 11 to tightly close the neck 2 of the container.

The upper part of the inner face of the skirt 12 is provided with a thread 16 radially projecting inwards and complementary with a thread 5 outside the neck 2 of the container, thus allowing the cap 11 to be screwed and unscrewed on the neck. Thus, the net 16 constitutes the removable attachment means to the neck 2 (so that the reference 16 can be used indifferently to designate these means or the net). Optionally, as illustrated, in order to facilitate the handling and the screwing or unscrewing of this plug, the upper part of the external face of the skirt 12 can be provided with reliefs, such as projecting ribs 18 which are arranged on the outer periphery of the skirt.

When the plug 11 is first opened, the skirt 12 is provided to separate into two separate parts, namely an upper part 12.1, including the first end 12A of the skirt 12, and a lower part 12.2, including a second end 12B, called lower or lower, of the skirt, the upper 12.1 and lower 12.2 parts being initially connected to each other by a line 19 of weakening. This weakening line 19 runs over the entire periphery of the skirt 12, being generally inscribed in a plane perpendicular to the axis XX, located axially in the current part of the skirt 12. The weakening line 19 is indicated by schematically by dotted lines.

Following the rupture of the weakening line 19, the upper part 12.1 of the skirt 12, which is provided internally with the aforementioned thread 16 and, if necessary, externally with the aforementioned ribs 18, can be released from the neck 2 of the container. The lower part 12.2 of the skirt 12 is, for its part, designed to remain around the neck 2 of the container, thus being qualified as a non-removable skirt part: for this purpose, this lower part 12.2 is provided internally with a band 22 retainer which is designed to cooperate by contact with the bulge 6 of the neck 2 of the container when the cap 11 is first unscrewed.

The retaining band 22 has a generally annular shape, centered on the axis X-X. An axial end 22A of the strip 22 runs over the entire inner periphery of the non-removable skirt part, having come integrally with this lower part 12.2. In the embodiment considered here, the retaining strip 22 extends from its axial end 22A to its opposite end 22B, from the second end 12B of the skirt 12, the axial end 22A of the strip 22 and the second end 12B of the skirt 12 thus being contiguous.

The opposite end 22B of the retaining strip 22 is, for its part, free: when the stopper 11 is in place on the neck 2 of a container, as visible in FIG. 1, the retaining strip 22 occupies a configuration service, in which it extends from the skirt 12 to the first end 1 2A of the skirt 12, with its opposite end 22B facing the bottom wall 10. The opposite end 22B defines a surface 24 which, when the retaining strip 22 is in the service configuration, is located axially just below the bulge 6 of the neck 2 of the container when the cap 11 is in place on this neck and thus closes the latter, as shown in Figure 1: during the first unscrewing of the cap 11, the surface 24 abuts axially upward against the bulge 6, which retains the lower part 12.2 around the neck of the container. In practice, as clearly visible in FIG. 1, as long as the plug 11 is not manipulated with a view to its first unscrewing, a clearance remains axially between the surface 24 and the underside of the bulge 6, the presence of this axial clearance resulting, among other things, from the dimensional tolerances between the cap 11 and the container neck 2. Advantageously, the opposite end 22B of the retaining strip 22 is also provided with a strip 26, which extends in a protruding manner relative to the surface 24, being here integrally formed with the rest of the strip 22 of detention.

When the stopper 11 is in place on a container and thus closes the latter, as shown in FIG. 1, the strip 26 is found radially interposed between the bulge 6 of the neck 2 of the container and the skirt 12 when the stopper 11. From this way, the strip 26 makes the operation of the abutment surface 24 more reliable. In fact, despite the existence of the aforementioned axial play between the surface 24 and the underside of the bulge 6, the strip 26 guarantees good positioning of the abutment surface 24 before the first opening of the plug 11, in particular when the place the stopper around the neck 2 of a container. It also guarantees an effective take-up of the aforementioned axial play when the cap is opened for the first time, in particular avoiding incorrect axial abutment of all or part of the surface 24 against the bulge 6, which could be due, for example, to too large radial tolerances or too pronounced misalignment between the respective axes of the cap 11 and the neck 2 of the container.

Still according to the prior art (Fig. 1), at the end of the molding of the stopper, under the action of an ad hoc pusher inserted inside the skirt 12, the retaining band 22 is folded towards the top by folding up to a service configuration enabling it to retain the lower part 12.2 of the skirt which abuts against the bulge 6 of the container neck. The folding takes place at the junction between the axial end 22A of the strip 22 and the second end 12B of the skirt 12, that is to say in an area in which relatively thick material is present. It requires significant effort and a tool dimensioned accordingly; moreover due to the elasticity of the plastic material constituting the stopper, it sometimes happens that the strip returns, at least in part, to its end of molding position, so that it can happen that such a stopper cannot properly (or not at all) seal a container.

In Figures 2 to 8 is shown a plastic plug 1, according to the invention, designed to be removably attached to a container neck 2 to close the latter and which solves the problems of the plugs of the prior art, such as the plug 11 of FIG. 1.

In fact, FIGS. 2 to 8 represent a stopper (FIG. 2), its blank (figs. 3 and 4) and certain phases and / or stages which follow the molding (cutting and finishing) (figs. 5 to 8). In Figures 3 to 6, it is not the plug which is illustrated, but a blank, insofar as, as will be understood, the retaining strip is not yet in its final position, where the plug can be placed on a container, which position is obtained at the end of the step illustrated in FIGS. 7 and 8. However, for the sake of simplicity, the term plug will be used interchangeably to designate the blank or the plug itself. -Even as long as this job is not confusing.

In practice, the plug 1 according to the invention has great similarities with the plug 11 of the prior art, so that the corresponding or comparable elements from one to the other bear the same references. In fact, as indicated below, the difference between the plug 11 of the prior art (fig. 1) and the plug according to the invention (fig. 2) or its blank (figs. 3 to 8) lies in the location of the weakening line, which location determines where the cap 1 will separate into two separate parts when the container is first opened.

In a manner known per se, the plug 1 and the neck 2 have respective generally tubular shapes, the central longitudinal axes of which coincide, under the common reference X-X, when the plug 1 is attached to the neck 2, as in FIG. 2.

The container neck 2 comprises a generally cylindrical body 3 with a circular base, centered on the axis X-X. At its upper end, this body 3 delimits a rim through which the container is filled or emptied. On the outer face of the body 3, the neck 2 is successively provided, from top to bottom, with a helical thread 5 and a bulge 6, both radially projecting outwards.

It should be noted that instead of a simple thread, the plug can be joined together by several threads or several portions of thread, without this changing the scope of the invention. Also, in the following description, the term a net will be used to designate either a single net or several fillets or portions of fillets (whether these are fillets present on the neck of the container or those, complementary, present in the cap).

As shown in FIG. 2, the plug 1 is open at its lower end, while, at its upper end, the plug is closed by a substantially flat bottom wall 10, at the outer periphery of which extends downwards an outer skirt 12, tubular, which is centered on the axis XX and whose first end 1 2A came integrally with the bottom wall 10. In the embodiment considered in the figures, the underside of the bottom wall 10 is provided with both a projecting tubular lip 13, centered on the axis XX and arranged inside the outer skirt, and a protruding heel 14, running on the outer periphery of the bottom wall. Thus, when the plug 1 is attached to the neck 2, as in FIG. 1, the bottom wall 10 extends above and across the neck, while, on the one hand, the skirt 12 externally surrounds the body 3 and, on the other hand, the lip and the heel 14 are respectively pressed in a sealed manner against the inner face of this body and on the outer periphery of the rim 4, to allow the plug 1 to seal the neck 2 container.

The upper part of the inner face of the skirt 12 is provided with a thread 16 radially projecting inward and complementary to the thread 5 outside the neck 2 of the container, thus allowing the cap 1 to be screwed and unscrewed on the neck . To facilitate handling and screwing or unscrewing of the plug, the upper part of the outer face of the skirt 12 can be provided with reliefs in the form of protruding ribs 18, which are distributed along the outer periphery of the skirt.

Similarly to the stopper of the prior art of FIG. 1, a retaining strip 22 is provided which is designed to cooperate by contact with the bulge 6 of the neck 2 of the container during the first unscrewing of the stopper 1 and separate the stopper 1 in two separate parts at a line of weakness upon first opening of the container on which it is fixed.

The retaining band 22 has a generally annular shape, centered on the axis X-X. An axial end 22A of the strip 22 runs over the entire lower periphery of the strip 22 and is joined with a second end 12B of the skirt 12. In the embodiment considered here, the retaining strip 22 extends from its axial end 22A at an opposite end 22B, from the second end 12B of the skirt 12. According to the invention, the weakening line 20 is produced by partial cutting, so as to form frangible bridges, of the entire periphery of the junction between the axial end 22A of the strip 22 and the second end 12B of the skirt 12.

Thanks to this arrangement, the weakening line 20 constitutes a fold line for the retaining strip since, when it is produced, by partial cutting, material is removed during the formation of frangible bridges. The junction is therefore more flexible, compared to the plugs of the prior art (cf. fig. 1) where the cutout to form the weakening line is formed in the wall of the skirt, at a distance from the fold line (between the ends 12 A and 12B of the skirt.

At this stage, it should be noted that, in the following description, for the sake of simplification, the formulation the junction between the skirt 12 and the retaining band 22 will be substituted for the detailed formulation the junction between the axial end 22A of the strip 22 and the second end 12B of the skirt 12, unless the context requires the use of the detailed formulation.

In FIG. 2, as well as in FIGS. 7 and 8, the line of weakness is indicated only schematically, by dotted lines, it being noted that the production, during the manufacture of the plug 1, and the constitution of this weakening line 20 will be detailed below.

By breaking the line of peripheral weakening 20, the skirt 12 can be completely disengaged from the container neck 2. Only the retaining band 22 remains around the neck 2 of the container after unscrewing the cap 1.

When the stopper 1 is in place on the container neck 2, as in FIG. 2, the retaining strip 22 occupies a service configuration, in which it extends, from the skirt 12, towards the first end 1 2A of the skirt 12, with its opposite end 22B facing the bottom wall 10. Still as shown in FIG. 2, when the retaining strip 22 is in the service configuration, this opposite end 22B delimits a surface 24 which is found situated axially just below the bulge 6 of the neck 2 of the container when the cap 1 is in place on this collar and thus closes the latter. During the first unscrewing of the plug 1, the surface 24 abuts axially upwards against the bulge 6, so that the strip 22 is found blocked around the neck of the container, which causes the bridges to break at the cutting of line 20 of weakening. In practice, as clearly visible in FIG. 1, as long as the plug 1 is not manipulated with a view to its first unscrewing, a clearance remains axially between the surface 24 and the underside of the bulge 6, the presence of this axial clearance resulting, among other things, from dimensional tolerances between the stopper 1 and the container neck 2. Advantageously, the opposite end 22B of the retaining strip 22 is provided with a strip 26, which extends in a protruding manner relative to the surface 24, being here integrally formed with the rest of the retaining strip 22 . The strip 26 is found radially interposed between the bulge 6 of the container neck 2 and the skirt 12 when the cap 1 is in place on the container neck and thus closes the latter, as shown in FIG. 2. Thus, the strip 26 makes the operation of the abutment surface 24 more reliable, since, despite the existence of the aforementioned axial clearance between the surface 24 and the lower face of the bulge 6, the strip 26 guarantees good positioning of the surface 24 before the first opening of the plug 1 , especially when placing this plug around the neck 2 of the container. Furthermore, it allows effective compensation of the aforementioned axial play when the cap is opened for the first time, in particular by avoiding poor axial abutment of all or part of the surface 24 against the bulge 6, due for example to relative radial tolerances too large or too pronounced misalignment between the respective axes of the cap 1 and the neck 2 of the container.

Hereinafter, a possible example of manufacturing the plug 1 will be described in detail, comprising two main stages, distinct and successive, respectively associated with FIGS. 3 and 4, with FIGS. 5 and 6, and with FIGS. 7 and 8.

During the first step of manufacturing the plug 1, a rough draft of it is produced.

The realization of the blank comprises a first phase, consisting of an injection molding, in a mold, of a plastic material, such as polyethylene or polypropylene.

Molding provides a blank consisting of a skirt 12, with its bottom wall 10, the thread 16 for screwing onto the neck 2 of a container, its ribs 18, if necessary, and the strip 22 of restraint. In practice, a molding core and a mold block are used for this purpose delimiting an internal molding cavity in which the aforementioned core is placed during the injection of the plastic material.

To facilitate the demoulding of the blank of the plug 1, the retaining strip 22 is molded with its opposite end 22B directed downwards: the blank of a plug 1 as obtained at the mold outlet is shown in the figures 3 and 4, on which the retaining strip 22 occupies a molding configuration, in which the retaining strip extends, from the skirt 12, in the direction opposite to the first end 1 2A of the skirt 12. However, it is advisable note that the end 22B of the retaining strip 22 is closer to the axis XX than its axial end 22A. In other words, at the end of the molding, the internal wall of the retaining strip 22 is slightly frustoconical, the truncated cone having a larger diameter near the axial end 22A than near the end 22B, as visible in FIGS. 3 to 5.

The molding phase of the blank of the plug 1 is followed by a second phase, called cutting, during which the cutting, at the junction between the skirt 12 and the retaining strip 22, is carried out of the line 20 of weakening. This cutting takes place at the limit between the axial end 22A of the retaining strip 22 and the second end 12B of the skirt 12.

This cutting phase can precede a partial folding phase, otherwise called pre-folding thereafter, of the retaining strip 22.

Alternatively, pre-folding can be done simultaneously with cutting.

Thus, in an exemplary embodiment illustrated in FIGS. 5 and 6, the pre-folding phase is implemented using a machine adapted to simultaneously perform the pre-folding and the cutting of the weakening line in accordance with the present invention.

This machine includes:

-a mandrel 100, rotatable on itself around its central longitudinal axis 102 and able to be partially introduced inside the skirt 1 2;

a support plate 104 forming a plane support for the bottom wall 10;

- A cutting blade 106 provided with a cutting edge 108;

- A device for pre-folding the retaining strip 22, called pre-folding 110, which is advantageously arranged in line with the cutting edge 108 of the blade 106 in the direction of the axis 102 of the mandrel 1 00;

a fixed frame 114, or comb, relative to which the mandrel 100 is rotated on itself and on which are fixedly secured the blade 106 and the pre-folder 110.

Preferably, the aforementioned cutting and pre-folding are carried out simultaneously. To this end, the mandrel 100 is inserted inside the skirt 12 of the plug 1, by arranging the axes XX and 102 in parallel, until the mandrel 100 axially presses the bottom wall 10 against the support plate. 104. By radially shifting the axis 102 with respect to the axis XX, the mandrel 100 presses, in a direction radial to the axis XX, a portion of the skirt 12 against, at the same time, the cutting edge 108 of the blade 106 and the pre-folder 110. By further driving the mandrel 100 in rotation about itself around its axis 102, the skirt 12 and the retaining band 22 move relative to the fixed frame 114, turning around the axis XX, while the junction between the skirt 12 and the retaining strip 22 is pressed radially against the cutting edge 108 of the blade 106 and against the pre-folder 110, so that simultaneously:

- the cutting edge 108 makes the line 20 of weakness by cutting the junction between the skirt 12 and the retaining strip 22, crossing the thickness of the said junction radially right through, while retaining fine bonds of material on this weakening line 20, not visible in the figures, which form the frangible bridges to hold the second end 12B of the skirt 12 and the axial end 22A of the retaining band 22 as long as the line 20 ' weakening is not broken when the cap 1 is first opened, and

- Simultaneously the pre-folder 110 presses, in a direction transverse to the axis XX, on the retaining strip 22 so as to pass it from its molding configuration, shown in FIGS. 3 and 4, to a pre-folded configuration , shown in FIGS. 5 and 6, which is intermediate between the molding configuration and the service configuration shown in FIG. 2.

Instead of performing a simultaneous cutting and pre-folding, it would be conceivable to carry out the pre-folding after the cutting allowing the line of weakening to be produced. To this end, it would suffice to slightly modify the arrangement of the mandrel 100, of the blade 108 and of the pre-folder 110, so that the action of the pre-folder is delayed relative to that of the blade 108; alternatively, two separate tools could be used.

As regards the cutting of the line of weakness by the blade 106, several implementation variants are possible. By way of example, in a non-illustrated manner, the cutting edge of the blade 106 is provided so as to be visible on recessed notches, distributed along its length, of the drive in rotation about the axis XX of the skirt 12 and the strip 22, the cutting edge cuts the junction between the axial end 22A of the second end radially junction of each aforementioned notch, the junction n thus the aforementioned frangible bridges. As in the example shown on peripheral groove 116 designed to receive the end of the cutting edge 1 08 when between the skirt 12 and consists of notching

108 only at the junction between the blade 106

12B of the skirt 1 2 and passing through this the retaining strip 22, in part, while, 'is not notched, further forming, the mandrel 100 is, the figures, provided with a passage of the retainer to both of the latter passes right through the junction of the retaining strip 22. Another possibility junction between the skirt 12 and the strip 22 continuously over its entire periphery and over its entire radial thickness, while leaving intact plastic ribs, molded projecting from the inner face of the skirt during molding of the latter, these ribs constituting the aforementioned frangible bridges.

As for the pre-folding of the retaining strip 22 by the pre-folder 110, it can itself be implemented in various ways. In the embodiment considered in the figures, the pre-folder 110 is formed by a rigid plate, typically metallic, arranged parallel to the blade 106. Other embodiments are possible, such as a finger or a part functionally similar, which, optionally, is provided movable relative to the fixed frame 114, in particular radially to the axis 102. Whatever the embodiment of the pre-folder 110, the action of the latter is preferably provided to pass the retaining strip 22 from its molding configuration to its pre-folded configuration, by tilting at least 20 °, or even at least 30 °, far from the skirt 12, by pushing the retaining strip 22 for the pre-fold around the weakening line 20 formed in the junction zone between the retaining strip 22 and the skirt 12, generally in the manner of a hinge connection. This tilting is indicated by the angle noted a in FIG. 6, in which the retaining strip 22 in its molding configuration is shown in solid lines and is represented in its pre-folded configuration in dotted lines, identified by the reference 220 The pre-folder 110 acts like a pusher by pushing against the retaining strip 22 in the direction of the arrow 112 shown in FIG. 6. For this purpose, the pre-folder 110 has a part or a position illustrated in dotted lines 111 in FIG. 6 which interferes with the retaining strip 22 to push it back when the skirt rotates around the mandrel 1 00.

In practice, the drive of the skirt 12 in rotation about the axis X-X can be improved by providing cooperation by complementarity of shapes between the projecting ribs 18, external, of the skirt and a corresponding external sector of the fixed frame 114.

Of course, the relative rotation between the skirt 12 and the retaining strip 22, on the one hand, and the blade 106 and the pre-folder 110, on the other hand, is carried out on a complete revolution of the skirt 12, so that the weakening line 20 is progressively cut over the entire periphery of the skirt 12 and the retaining strip 22 is pre-fired from its molding configuration to its gradually pre-folded configuration over the entire periphery of the retaining strip. In practice, it is understood that the position and the angular extent of the portion of the junction between the skirt 12 and the retaining strip 22 which interferes with the blade 106 to cut the junction do not have to be strictly identical to, respectively , the position and the angular extent of the portion of the junction between the skirt 12 and the retaining strip 22 which interferes with the pre-folder 110, 111 to pass the retaining strip 22 from its molding configuration to its pre configuration -folded: in fact, the main thing is that, once the skirt 12 has made a revolution on itself around its axis XX by driving the mandrel 100, the entire line of weakness 20 is cut, in however, leaving the frangible bridges, and the entire retaining strip 22 is tilted in the pre-folded configuration. That said, preferably, the aforementioned positions are close, or even almost identical, and the aforementioned angular expanses are close, or even almost identical: such an arrangement facilitates the arrangement of the tools necessary for the implementation of the pre-folding phase. , that is to say tools including the mandrel 100, the support plate 104, the blade 106, the pre-folder 110, 111 and the fixed frame 114.

It should be noted that the pre-folding phase may not exist, since the stopper according to the invention is much easier to fold because the weakening line is coincident with the folding line. It would therefore be conceivable to proceed with the folding immediately after cutting, starting from the position occupied by the retaining band 22 after the molding of the blank, position illustrated in FIGS. 2 to 5, where the band 22 retainer is re-entrant and therefore naturally slightly pre-folded and is softened after cutting. In such a case, the tool would not include the pre-folder 110.

At the end of the manufacturing of the blank (molding, cutting and pre-folding, if necessary), the plug 1, during manufacturing, is subjected to a second manufacturing step, shown in FIGS. 7 and 8, consisting in its finishing: in this finishing step, the blank of the plug 1 is immobilized in a fixed well 200 with respect to which is driven in rectilinear translation, along the axis XX, a pusher 202, up to the interior of the skirt 12, via its lower end 12B. The outside diameter of the pusher 202 is substantially equal to the inside diameter of the skirt 12, subtracted from the thickness of the retaining strip 22: in other words, as clearly visible in FIG. 8, the outside diameter of the pusher 202 is substantially equal to the internal diameter of the retaining strip 22 when this strip is in its service configuration. It is therefore understood that, at the start of the finishing step, that is to say when the retaining strip 22 occupies its pre-folded configuration of FIGS. 5 and 6 or its demolding position (naturally pre-folded) of the figures 3 and 4, the retaining strip 22 has an internal diameter strictly smaller than the external diameter of the pusher 202, so that the latter interferes with the retaining strip 22 as it penetrates axially inside of the skirt 12, via the second end 12B thereof. This interference causes the flap of the retaining strip 22 to change from its pre-folded configuration or initial to its service configuration, by progressive folding until the junction zone between the retaining strip and the skirt is firmly pinched. In practice, as in the embodiment considered in the figures, this folding is carried out by tilting, relative to the skirt, the retaining band 22 around the aforementioned junction zone and is facilitated by the arrangement of the line 20 attenuation according to the invention.

It is at the end of this finishing step that the plug 1 has reached its final configuration.

Claims (8)

1.- Method of manufacturing a container stopper (1), intended to close the neck (2) of a container, comprising a first step, of producing, by molding a plastic material, a blank of the plug (1), which step of producing the blank, which is followed by a step of finishing the plug by folding a retaining strip (22), comprises at least the following phases: a phase of molding the blank consisting in molding a skirt (12) and a retaining strip (22) integral with the skirt, during which: - the skirt (12) is molded so as to have a generally tubular shape, which extends along a central axis (XX) between a first end (12A), closed by means for closing the neck (2) of the container (1), such as a bottom wall (10) molded with the skirt (12), and a second end (12B), opposite the first end (12A), which skirt (12) is provided, with means (16) for removable attachment to the neck of the container arranged between the two ends (12A; 12B); and - The retaining strip (22), integral with the skirt, is molded in the form of a ring intended to remain permanently around the neck (2) of the container by cooperating with retaining means (6) provided on the neck (2); this strip (22) comprising an axial end (22A) which runs over the entire lower periphery of the strip (22) and provides a junction with the second end (12B) of the skirt (12); this retaining strip (22) being molded in the extension of the skirt (12), beyond its second end (12B), so that it extends, from the second end (12B) of the skirt ( 12), in the direction opposite to the first end (12A) of the skirt (12); a cutting phase subsequent to the molding phase, which consists in producing in the blank a line (20) of peripheral weakening comprising frangible elements adapted to be broken during the first opening of the plug (1), which line (20) weakening connects, along the central axis (XX), a first part of the blank, including said first end (12A) of the skirt (12), as well as the means for closing the neck ( 2) and said fixing means (16), and a second part of the blank, including the retaining strip (22); characterized in that, during the cutting phase, the cutting to obtain the weakening line (20) is carried out between the axial end (22A) of the retaining strip (22) and the second end (12B) of the skirt (12), that is to say at the junction between the retaining strip (22) and the skirt (12) at the level where the folding for the finishing of the plug must be carried out subsequently, so that the line ( 20) of weakening also constitutes a fold line and that, after a first opening of the stopper (1) and rupture of the frangible elements, only the retaining strip remains permanently on the container. 2, - Method according to claim 1, characterized in that the step of finishing the plug (1), which follows the step of making the blank, comprises a phase of folding the retaining strip (22) consisting to fold the latter towards the first end (12A) of the skirt (12) by folding the retaining strip (22) on itself at its junction with the skirt, until passing it in a configuration called service in which the cap can be placed on a container. 3. - Method according to claim 2, characterized in that the folding phase is preceded by a pre-folding phase of the retaining strip (22), which consists in placing the latter, in a pre-folded configuration which is intermediate between said molding configuration and said service configuration. 4. - Method according to claim 3, characterized in that the pre-folding phase is carried out after the cutting phase, before the folding phase. 5. - Method according to claim 3, characterized in that the pre-folding phase is carried out simultaneously with the cutting phase, before the finishing step. 6. - Method according to one of claims 1 to 5, characterized in that the means (16) for removable fixing to the neck of the container arranged between the two ends are constituted by at least one screwing / unscrewing thread internal to the skirt and intended to cooperate with at least one complementary net (5) formed around a container neck (2). 7. - blank for a cap (1) of a container, obtained by implementing the method according to claim 1, comprising: on the one hand, a skirt (12) of generally tubular shape, which extends along a central axis (XX) between a first end (12A), which end (12A) is closed by means for closing the neck a container, such as a bottom wall (10) molded with the skirt (12), and a second end (12B) opposite the first, which skirt (12) is provided internally with means (16) removable attachment to the neck (2) of a container disposed between the two ends (12A; 12B); - on the other hand, a retaining strip (22) in the form of a ring intended to remain permanently around the neck of a container, this retaining strip (22) being molded in the extension of the skirt (12 ), beyond its second end (12B), and having an axial end (22A) contiguous with the second end (12B) of the skirt (12) so that the retaining strip (22) extends, from the second end (12B) of the skirt (12), in the opposite direction to the first end (12A) of the skirt (12); a peripheral weakening line (20) comprising frangible elements adapted to be broken when the cap is first opened (1), which weakening line connects, along the central axis (X-X) a first part of the blank _r including the first end (12A) of the skirt (12), the means for closing the neck (2) and the said fixing means (16), and - a second part of the blank, including the retaining strip (22); characterized in that, the weakening line (20) is constituted by a cut made at the junction between the retaining strip and the skirt, that is to say between the second end (12B) of the skirt (. 12) and the axial end (22A) of the retaining strip (22). 8.- container stopper, obtained by implementing the method according to one of claims 1 to 6, comprising: on the one hand, a skirt of generally tubular shape, which extends along a central axis between a first end (12A), which end (12A) is closed by means for closing the neck of a container, such that a bottom wall (10) molded with the skirt (12), and a second end (12B) opposite the first, which skirt (12) is provided internally with means (16) for removable attachment to the neck ( 2) a container disposed between the two ends (12A; 12B); on the other hand, a retaining strip (22) in the form of a ring intended to remain permanently around the neck (2) of the container, this retaining strip (22) comprising an axial end (22A) contiguous with the second end (12B) of the skirt and being folded back towards the first end (12A) of the skirt following the folding of the retaining strip on itself at its junction with the skirt; characterized in that it further comprises a line (20) of peripheral weakening comprising frangible elements adapted to be broken when the cap is opened for the first time, which weakening line (20) being constituted by a cutout produced at the junction between the retaining strip (22) and the skirt (12), that is to say between the second end (12B) of the skirt (12) and the axial end (22A) of the strip (22) retaining, so that, after a first opening of the cap and rupture of the frangible elements, only the retaining strip remains permanently on the container.