EP1272326A1

EP1272326A1 - Multicolour and multiple material injection moulding of a capsule provided with a cap pivoting about a hinge

Info

Publication number: EP1272326A1
Application number: EP01923772A
Authority: EP
Inventors: Bernard Schneider
Original assignee: Cebal SAS
Current assignee: Albea Tubes France SAS
Priority date: 2000-04-14
Filing date: 2001-04-10
Publication date: 2003-01-08
Also published as: WO2001078958A1; BR0110026A; RU2222427C1; MXPA02010024A; RU2002130501A; AU2001250463A1; PL357867A1; FR2807698A1; FR2807698B1; AR027784A1; US20030178744A1

Abstract

The invention concerns a method for sequential moulding with multiple materials for making a piece comprising at least two parts with matching shapes produced in a different plastic material, mobile relative to each other by pivoting about a hinge, which consists in: using a moulding equipment comprising a second mould (30) and a first mould (31) whereof the assembled impressions define the cavity of the open part, the mobile portions forming between them an angle of about 180°, one of the moulds (31) comprising a housing wherein slides a gate (35), capable of blocking the flow of the first plastic material; injecting the first portion (32, 34) with a first plastic material, the gate (35) providing with its side wall an obstacle to the flow of said first plastic material at the fasteners of the elements of the hinge on the second piece; causing the gate (35) to open and injecting the second plastic material into the second portion (33) of the piece.

Description

MULTI-COLOR MULTI-MATERIAL INJECTION MOLDING OF A CAPSULE PROVIDED WITH A SWIVEL HATCH AROUND A HINGE

TECHNICAL AREA

The invention relates to a method for molding capsules intended to be fixed to containers such as flexible tubes, vials or tube vials. Said capsules are provided with a pivoting cap closing a dispensing orifice. Such containers are intended for storing and distributing fluid, creamy or pasty materials, generally belonging to the cosmetic, food, household, pharmaceutical or parapharmaceutical fields. Subsequently we will group this type of container under the general term "tubes".

STATE OF THE ART

The capsules fitted with a swivel cap offer the consumer the possibility of handling the tube with one hand and the assurance of not losing the stopper which, once detached to release the dispensing orifice, can be removed and unintentionally abandoned anywhere. Such capsules have found considerable development when it has been possible to mold them in one piece, which had the consequence of significantly reducing their manufacturing cost.

The capsules thus produced include a base and a pivoting cap attached to this base. The base includes an upper plate provided with a dispensing orifice, an external skirt which is generally in the extension of the flexible skirt of the tube when the capsule is fixed on the tube and fixing elements intended to cooperate with means correspondents arranged on the head of the flexible tube. The cap is attached to the base, generally on the upper plate of said base, and often at the periphery, by means of a hinge. This generally comprises at least one film hinge, stressed in bending, and at least one, tensioning element, stressed in tension. The tensioning element, put in tension during the pivoting of the cap, facilitates the pivoting of the latter, the user only having to give a first impulse to trigger the opening or closing.

These mechanical elements (hinge and tensioner), molded in the same material w as the base and the cover are subjected to frequent mechanical stresses. This requires the choice of a particular plastic material, having suitable mechanical characteristics, - in particular good fatigue behavior due to the numerous openings provided during the use of the tube. In general, the choice is made on a material such as polypropylene which has not only better resistance to fatigue but also a more rigid elastic behavior than the material of the head of the tube, generally polyethylene.

However, the cap, molded simultaneously with the rest is necessarily 0 made of the same material, which limits on the one hand the decorative possibilities of the capsule, giving it a monotonous, banal, even appearance. unsightly and on the other hand limits the comfort of use of the tube due to the rigid nature of the cap, which provides a cold contact to the touch, unpleasant, likely to injure the thumb of the user if the projection of gripping of the 5th cap has too pronounced relief.

The Applicant has therefore sought to improve the appearance and the comfort of use of the capsule by giving the cap a color and / or a material different from that of the base. She turned to the technique of 0 bi-injection recently developed in the mold makers of capsules. The Patent applications FR 2 662 144 and EP 0826 606 are representative of the service capsules which it is now possible to obtain by means of such a process.

For FR 2 662 144, the cover, the external part of the base and the hinge elements (film hinge and tensioning elements) are made of the same rigid material, of the polypropylene type. Only the central part of the base of the capsule, which has a sealing skirt, is made of another material, of elastomeric type. The junction between the two materials is made at the periphery of the upper plate of the base, in an area remote from the hinge, which is not very mechanically stressed.

For EP 0826 606, it is a question of improving the identification and the handling of the grip zone, located partly on the cap and partly on the base of the capsule. The surface of the part of the base and of the part of the cap - corresponding in particular to said gripping zone - is covered with a layer of elastomeric material. In such a configuration, the tensioning element which connects these two parts is also entirely made of this material • elastomeric material while the other part of the cap, the other part of the base and the film hinge which connects them are in one rigid material, polypropylene type.

In these two cases, it is not exactly a service capsule made of two different materials, one occupying the entire base, the other occupying the entire cap. If we want to meet this last objective, we must place the border between the two materials at the level of the hinge (s) -film (s) and P (of) tensioning element (s) , that is to say at the areas of the capsule most mechanically stressed. There is therefore a problem of mechanical strength, in particular in fatigue, of the elements of the hinge which are at the weld between the materials. PROBLEM

The applicant sought to obtain a service capsule having a base made of a first plastic material and a cap made of a second plastic material, the border between the plastics materials having to pass at the level of the hinge separating the base of the cap, without this having consequences on the mechanical strength of said hinge during use of the tube.

OBJECT OF THE INVENTION

The subject of the invention is a sequential multi-material injection molding process for manufacturing a part comprising at least two parts of complementary shapes made of a different plastic material, movable relative to one another by pivoting around a hinge forming the border between these two parts, said hinge being able to be composed of several elements working in bending or in traction, characterized in that:!

- a molding tool is used comprising a first mold and a second mold, the imprints of which are such that, once the first and second molds are assembled and locked, they define the cavity of the open part, the movable parts forming between them a large opening angle, typically close to 180 °, the first mold comprising a housing in which slides a movable element called a lock, having two lateral faces and a frontal face, capable of blocking when it is in the closed position, the flow of the first plastic material, said lock sliding in the cavity intended to receive the second plastic material;

- the first part is injected with a first plastic material, the lock being in the low position and offering, by one of its lateral faces, a obstacle to the flow of said first plastic material at the attachments of the hinge elements on the second part

- The lock is moved so that the second plastic can reach the first plastic - the first plastic being still hot, the second plastic is injected into the second part of the room.

This method makes it possible in particular to mold, by sequential multi-material injection, a service capsule comprising a base made of a first plastic material and a cap made of a second plastic material, the cap and the base being separated from each other by a hinge comprising at

- at least one film hinge and at least one tensioning element.

In sequential bi-material injection, two different materials (by their chemical nature and / or by additives, colors, fillers, etc.) are injected one after the other so that they are combined into one single piece, without secondary operation. The device chosen for the production of these service capsules comprises two injection units, and a molding tool comprising two main parts: a first and a second mold. A movable element, which has a front wall and two side walls, slides inside the first mold so that its wall

. frontal moves in the mold cavity. This mobile element, called

"lock", thus delimits the ^" zones of successive fillings. In a first position, this mobile element forms, by one of its side walls, an obstacle to the flow of the first plastic material and in a second position, it leaves pass the second plastic material which can thus come into contact with the first plastic material. The molding tool comprises a first mold and a second mold, the combined impressions of which - when the two molds are locked against each other - form a cavity occupying the volume of the service capsule, cap wide open, typically at an angle of 180 ° with the base.

The manufacturing cycle includes: - the injection of the first plastic material into the area of the first part of the capsule, the mobile part in the closed position (lock closed)

- moving the moving part until the lock is open

- Preferably after a short stabilization of the first plastic material (of the order of a second), injection of the second plastic material in the area of the second part of the capsule.

The establishment of. the lock must meet a certain number of criteria: firstly, this position determines the border between the two materials and the geometric configuration in which the two materials will come into contact. Even by choosing two materials compatible in adhesion and / or in melting temperature, it is preferable to aim for a certain interpenetration of the materials to promote adhesion. In addition, as has been done in FR 2662 144 and EP 0826606, it is advisable to place this border in an area with little mechanical stress, in particular in fatigue.

Finally, the moving part of the tool, the lock, must be able to withstand the pressure

- exerted by the first plastic material when it comes into contact.

This pressure can indeed reach several hundred bars and the lock must be guided and supported in order to be able to resist the force which tends to move it. So that the lock does not lose its role as an obstacle to the flow of the first plastic material, it is generally sought so that, at the level of the front, the side walls of said lock are surrounded over a certain height by the tool walls. When we slide the lock in a long cavity, and we want to prevent the flow of plastic in a cavity leading to this long cavity, we do slide the lock in said cavity so that its front wall arrives upstream of the crossroads with the other vein, at a distance at least equal to the thickness of the cavity at this location.

The fatigue strength of the hinge means that the boundary between materials must not be placed exactly in the preferential flexion zone of the hinge. In the method according to the invention, the applicant has moved, without this being too visible, the border between the materials, on the side of the fasteners on the cap of the hinge (s) and of the element (s) (s) tensioner (s). Thus, camber (s) and tensioning element (s) are made, in their preferential bending and traction zones, of the plastic material of the base - the capsule, which is preferably a material having good characteristics. mechanical, particularly resistant to fatigue in bending and alternating traction, typically polypropylene.

To facilitate the injection conditions and simplify the shape of the molding tool to be produced, the combined cavities of the first mold and the second mold define, when these are locked against each other, - the volume of the service capsule, cap open at 180 °. The lock is placed in such a way that it can slide in the cavity intended for molding the substantially vertical wall of the cap located near the base. The movable part slides vertically in the first mold, pressing against the walls of said first mold, and opens into the part of the cavity corresponding to the substantially vertical wall of the cap.

Since the plastic of the base generally has a higher melting temperature than the plastic of the cap, it is natural to inject the cap first and then the base. FIG. 1 illustrates a first test outside the invention where the lock, in the closed position, descends deep (more than five times the thickness) into the cavity of the cap. The filling pressure is indeed of the order of 300 bars when the cavity is filled, and, under the effect of the force exerted on the front of the lock, the latter could, if it were not sufficiently supported, move, move back and let the plastic of the cover fill the cavity of the hinge elements.

5

Unfortunately this natural choice, consisting in placing a lock deep in the part of the vertical wall of the cap, does not produce the desired effect, because the border between the plastics is not in the desired place: it lets the plastic of the base go up widely in an area of the cap and this destroys the desired impression of clear separation between base and cap. Figure 2 illustrates the visual aspect thus obtained.

To solve the problem, the plaintiff reversed the order of injections,

75 increased the surface of the attachments of the elements of the hinge on the cap and modified the shape of the lock, it is no longer a simple prism matching the thickness of the wall of the cap but a three-dimensional piece, having a height, and possibly a thickness, different at the level of the tensioning element of the hinge and at the level of the film hinge. The slope of the oblique wall 0 of the second mold corresponding to the cavity of the attachment of the film hinge and of the tensioning element on the cap is increased substantially.

^' so that this fastener has a height at least twice the thickness of the tensioning element.

5 The lock descends until its front reaches the level of the hinge attachment, flush with the base of said oblique wall of the second tool. It is therefore not engaged in depth in the mold cavity corresponding to the vertical wall of the cap. The order of the injections is reversed: the base is first injected with the plastic material usually having a higher melting temperature. This material arrives in contact with a side wall of the lock, which, under the effect of the thrust can rest with its other side wall against the substantially vertical wall of the male part of the first tool intended to make the interior of the cap. Here, although the lock is little pressed into the cavity, its support is effective because the support is direct, without overhang and the air gap, which cannot be greater than the lateral clearance between the sliding part and the first tool is too weak for the first plastic material to be able to be introduced there easily.

Immediately after the injection of the first plastic material, the lock is raised and the plastic material of the cap is injected. This second plastic material comes into contact with the first plastic material which is still hot at the level of the fasteners of the elements of the hinge, the height of which has been considerably increased according to the invention. Thus, the height at the attachment of the tensioning element is equal to approximately twice the average thickness of the latter. The attachment of the film hinge has a height identical to that of the attachment of the tensioning element, which makes it possible to standardize the conditions of interpenetration of plastic materials at any point of the hinge. If the increase in the height of the fastener has little influence on the mechanical behavior of the film hinge, the latter already having, that is to say before the modification according to the invention, a non-uniform thickness with an area preferential bending,

^• it is not the same with the tensioning element which is clearly stiffened at the location of the fastener. However, this tensioning element, despite greater rigidity at the level of its attachment to the cap, continues to play its driving role during the rotation of the cap. The greater height of the fasteners of the hinge elements on the cap provides a wider spatial configuration of the cavity and more favorable for mixing the two plastics, by reducing the level of shear necessary to obtain a good weld of said plastics. To promote the interpenetration of plastic materials between them, the front of the lock has a non-uniform height: when the lock is mounted in the open position, the front does not go back up inside the upper tooling but remains still slightly protruding, which allows a less abrupt transition between the relatively large thickness of the substantially vertical wall of the cap and the thickness of the fastener. Leaving the lock slightly protruding at the hinge makes it possible to spare the hinge: the part of the lock remaining protruding occupies the place of a thick cap portion, which, if it had been formed with the injected plastic, would have imposed during its removal a significant deformation of the hinge and the base of the capsule, resulting in an excess thickness of said capsule base ^; having the consequence of preventing the correct closure of the cap on the base.

Finally, at the tensioning element, the lock at a height such that it can, in the closed position, close the cavity of the fastener. It suffices that the front of the lock descends slightly below the fastener since the thrust of the first plastic material is lateral and that the support can be provided by the other transverse wall, in direct support against the core of the first mold used to make the inside of the cap.

. The second plastic material can be a polyolefin - typically polyethylene or polypropylene mixed with a different charge than that of the base polypropylene - or a thermoplastic material of elastomer type or having an elastomeric behavior or a thermoplastic alloy with elastomeric behavior. The fact that the second plastic material may have a lower melting temperature than that of the first plastic material does not prevent a good weld between materials, no doubt because these are two successive injections brought together over time. The method according to the invention describes a sequential two-component injection. It goes without saying that it can be transposed to a sequential multi-material injection where the number of different materials to be injected is greater than 2 and where at least one lock is actuated between two injections. On the other hand, the object obtainable by the invention can be used for other purposes than a service capsule: it is a part comprising two parts made of a different plastic material and movable one relative to the other, pivoting around a hinge forming the border between these two parts.

Figure 1 illustrates a section of the detail of the molding tool used in the prior art to make a service capsule, the cut being made at the film hinge which connects the base (right) and the cap (to the left). The classic technique used in multi-material multi-injection uses a prismatic mobile element obstructing the flow of the first plastic which fills the cap.

FIG. 2 illustrates the appearance of the two-color service capsule obtained with the molding tools of the prior art illustrated in FIG. 1.

FIG. 3 illustrates the appearance of the two-color service capsule obtained with the method according to the invention.

FIG. 4 illustrates a cross-section of the detail of the molding tools according to the invention used to make a service capsule, the cut being made at the level of the film hinge which connects the base (on the right) and the cap (at left).

FIG. 5 illustrates a section of the detail of the molding tools according to the invention used to produce a service capsule, the section being carried out at the level of the tensioning element which connects the base (on the right) and the cap (on the left).

EXAMPLES

Example 1 (Figures 1 and 2)

The two-color service capsule 1 comprises a cap 3 made of a first plastic material and a base 2 made of a second plastic material, both of which are connected together by the following hinge elements: two film hinges 4 and a tensioning element 5.

In the conventional method used to produce this two-colored capsule, the molding tool comprises two molds, the first mold 21 and the second mold 20. Within the first mold 21, in the extension of the substantially vertical part of the cavity 23 used for molding the cap, slides a movable part, the lock 25, the front 27 of which must descend deep into the cavity 23, several millimeters below the cavity 24 corresponding to the hinge, leaving a zone 26 not filled with the plastic of the cap.

The process of sequential bi-injection using such a molding tool and in which the plastic material (transparent polypropylene) of the cap is injected before the opaque polypropylene of the base, gives a hinge zone where the border between the two plastics " goes back "clearly above the hinges, leaving a zone 6 which destroys the desired impression of frank separation between base and cap. Example 2 (Figures 3, 4 and 5)

The two-color service capsule 11 comprises a base 12 made of a first plastic material and a cap 13 made of a second plastic material, both of which are connected together by the following hinge elements: two film hinges 14 and a tensioning element 15.

In the method according to the invention used to produce this two-colored capsule 11, the molding tool comprises two molds, the first mold 31 and the second mold 30. The base is first injected, then the cap.

- Within the first mold 31, in the extension of the substantially vertical part of the cavity 33 used for molding the cap, slides a movable part, the lock 35, whose front wall 37 does not descend deep into the cavity 33 The sections of FIGS. 4 and 5 made respectively according to CC and TT, show that the lock 35 is thicker at the level of the film hinge than at the level of the tensioning element. The heights of the fasteners of the hinge elements have been increased and defined to be equal so as to standardize the welding conditions of plastics.

The slope of the oblique wall 40 of the second mold 30 corresponding to the

. cavity of the fastening of the film hinge and of the tensioning element 39 on the cover is increased substantially so that this fastening has a height at least twice the thickness of the tensioning element. The front wall 37 of the lock 35 is flush with the base of the oblique wall 40 of the second mold 30 when the lock is closed. The first plastic material abuts against the side wall 41 and despite the strong thrust, the lock cannot move more than the play required for sliding. In the open position, the lock does not fully rise, a part 36 remaining projecting inside the cavity. It takes the place of a cap portion which, if it had been formed with the injected plastic, would have been very thick and would have imposed during its removal a significant deformation of the hinge and the base of the capsule, resulting in an excess thickness of said capsule base having the consequence of preventing the correct closure of the cap on the base.

The capsule obtained gives an impression of frank separation between the cap and the base.

LIST OF ILLUSTRATIONS FIGURES 1. 2, 3, 4 AND 5

1: service capsule;

2: base; 3: cap; : hinge; : tensioner; : unsightly area 0.30: second mold; 1.31: first mold; 2.32: cavity corresponding to the base; 3.33: cavity corresponding to the cap; 4, 34: cavity corresponding to the film hinge; 5, 35: lock; 6: cavity corresponding to the unsightly zone; 6: part of the lock remaining projecting when the lock is in the open position; 7: front wall of the lock; 8: cavity corresponding to the tensioning element; 9: cavity corresponding to the attachment of the tensioning element 0: oblique wall of the second mold corresponding to the cavity of the attachment of the elements of the hinge (film hinge and tensioning element) on the cover. 1: side wall of the lock providing an obstacle to the flow of the first plastic material

Claims

1. Method of sequential multi-material injection molding for manufacturing a part comprising at least two parts of complementary shapes made of a different plastic material, movable relative to each other by pivoting around a hinge making the border between these two parts, said hinge being able to be composed of several elements working in bending or in traction, characterized in that:

- Using a molding tool comprising a first mold (31) and a second mold (30), the imprints of which are such that, once the molds are assembled and locked, they define the cavity (32, 34 and 33) of the open part, the movable parts forming between them a large opening angle, typically close to 180 °, the first mold (31) comprising a housing in which slides a mobile element called a lock (35), capable of blocking when is in the closed position, the flow of the first plastic material, said lock having two side walls (41, 42) and one. front wall (37) which moves in the cavity (33) intended to receive the second plastic material;

- the first part (32 and 34) is injected with a first plastic material, the lock being in the low position and offering, by its side wall

(41), an obstacle to the flow of said first plastic material at the attachments of the hinge elements on the second part

- The lock (35) is moved so that the second plastic can reach the first plastic - the first plastic being still hot, the second plastic is injected into the second part of the room.

2. Method according to claim 1 in which the part is a service capsule intended to be fixed on the head of a flexible tube, of a bottle or of a tube-bottle, the first part of the part being its base, the second part being the cover, the hinge connecting said base to said cover comprising at least one film hinge and at least one tensioning element. ^{l (} ₍

3. Method according to claim 2 wherein the attachment on the cap of the tensioning element has a height corresponding to at least twice the average thickness of said tensioning element.

4. Method according to claim 2 or 3, wherein, in line with the film hinge, the lock, in the open position, remains protruding into the cavity of the second part.

5. Method according to any one of claims 1 to 4 wherein the first plastic material belongs to the group of polypropylenes.

6. Method according to any one of claims 1 to 5 wherein the second plastic material belongs to the group comprising polyolefins and thermoplastic alloys with elastomeric behavior.