AU720189B2

AU720189B2 - Process for high speed manufacture of assemblies made of plastic parts

Info

Publication number: AU720189B2
Application number: AU30983/97A
Authority: AU
Inventors: Marc Joyeux; Michel Rebeyrolle; Bernard Schneider
Original assignee: Cebal SAS
Current assignee: Albea Tubes France SAS
Priority date: 1996-06-06
Filing date: 1997-06-03
Publication date: 2000-05-25
Anticipated expiration: 2017-06-03
Also published as: PL330292A1; CA2257925A1; EP0907480A1; HUP9902324A3; TNSN97097A1; PL183966B1; EP0907480B1; BR9709541A; CN1082424C; TW393393B; JP2000511481A; ES2166999T3; ATE207405T1; WO1997046362A1; ZA974964B; KR20000016332A; AU3098397A; TR199802512T2; AR008226A1; DE69707673T2

Description

Process for High Speed Manufacture of Assemblies Made of Plastic Parts Field of the Invention The invention pertains to an economical process for the high-speed manufacture of assemblies comprised of at least two parts made of plastic that can move with respect to one another and are to be found in at least one configuration where their surfaces contact to complement each other and conform in shape very tightly.

State of the Art Such assemblies can be found in a large number of items, items which include two parts which are temporarily connected so that they form one piece by means of screwing or riveting for example, such as flexible tubes provided with stoppers or, more frequently, container heads provided with their sealing caps, or items which have components in rotation relative to one another, such as articulation balls and socket joints, hinges, perforated rotating screw-tops or lids, or even sliding components, such as drawers for make-up cases or zippers.

The joint parts are manufactured separately and then put together. The operations of separate manufacturing and assembly are time-consuming and expensive because they require specific machines. For a long time, there have been attempts to lower the return cost of the production rate for such assemblies by attempting to construct the parts in a single manufacturing cycle without having the need to assemble them. When placed from the outset in one of their use configurations, they must nevertheless be able to be moved easily with respect to one another.

The patent application FR 2 451 867 therefore proposes a process which allows one to manufacture a flexible tube provided with a cap, which is moulded directly around the neck. In order to be able to easily unscrew the cap of the neck, the neck is made of a material with a melting point greater than that of the resin of the cap, or made entirely of metal, or of a metal and plastic multiple layer, the synthetic resin forming the interior wall of the tube and the neck. When manufactured this way, the neck does not melt when c04257 (2 in contact with the molten resin. Additionally, the current problem of recycling metal-plastic items and the use of metal or metal-plastic tubes causes many large-scale manufacturing difficulties, because their great deformability imposes handling precautions which are not compatible with the desired industrial manufacturing rates, which is several hundreds of units per minute.

In the application FR 2,320,870, there was an attempt to overmould a cap directly onto the neck of a flexible tube made of material which should not become soft or melt under the temperature and pressure conditions during moulding attachment of the cap. In addition to the metal and metal-plastic solutions proposed previously, the author has developed a solution based on heat-setting resin of the urea formaldehyde type. But this solution calls for using a separately manufactured insertion piece lo which is removed from the desired goal. On the other hand, the attachment of such an insertion piece to the rest of the tube cannot be accomplished by welding because of the incompatibility of such a resin with materials that are currently used for the skirts of tubes and, in this case, the purely mechanical attachment of the insertion piece to the skirt can only cause problems of airtightness and a barrier to flavours and scents.

Processes for obtaining such assemblies composed of parts made entirely of polymers have also been proposed in patent applications DE 19 41 479, EP 0 073 356, US 3 281 295, W091/01213 and JP 61 047 223. A first part is made, and then a second part is moulded on the first cooled part which acts, at least partly, as a mould. In DE 19 41 479, EP 0 073 356, US 3 281 295, W091/01213 and JP 61 047 223, the material of the second part has compulsorily a melting (or softening) temperature lower than the melting (or softening) temperature of the first part. Apparently the same materials used in EP 0 073 356, since the material is not mentioned.

The Problem Posed Having attempted to come up with a solution pertaining to the same area as that of the previously mentioned documents, the applicant reports that she was responding to a problem greater than that of caps overmoulded onto a neck, a problem which also pertains to any fabrication process at a high speed of items which include the assembly of pieces which have complementary contact surfaces able to move with respect to one another, for which the avoidance of separate fabrication and the automated assembly of these parts represents an important economic benefit.

Summary of the Invention The process in accordance with the invention pertains to the manufacturing of items or parts of items comprised of a joint which includes at least two parts made of plastic able to move with respect to one another and which are found in at least one configuration where their contact surfaces conform in shape, characterised in that it includes the following stages: O C 0c 1

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c04257 3 a) shaping a plastic first part by bringing an internal tooling and a first external tooling closer together, at least part of the overall surface of the imprint of said first external tooling on said part being globally convex, said globally convex surface being meant to be in contact with the second plastic part, and said internal tooling comprising at least a core which enters the internal space of said globally convex surface; b) separating said first external tooling and leaving the first part on the internal tooling; c) placing a second external tooling the internal surface of which defines, together with the globally convex surface of the first part, a space of small thickness over at least part to of said globally convex surface; d) bringing said second external tooling and said shaped first part close together and then moulding the second part by filling said space with a plastic material at a temperature exceeding the melting temperature of the plastic material of said first part; e) separating the toolings and removing the assembly of the two parts thus obtained.

:00: Accordingly, a first aspect of the present invention provides a forming process for an assembly comprising at least two plastic parts, mobile with respect to each other and located in at least one configuration in which their contact surfaces match complementary shapes, comprising the following steps: a) forming of a first plastic part made by bringing up a first external tooling, the *000 cavity of which defines at least the globally convex shape of a surface designed to come into contact with the second part and an internal tooling comprising at least one core entering into the internal volume of the said globally convex surface; b) spacing of the said first external tooling and holding the first part on the internal 25 tooling; c) placement of a second external tooling, the cavity of which cooperates with the said globally convex surface to delimit a thin volume with the globally convex surface of the first part; d) bringing up the said second external tooling and the first part then moulding of the second part; e) spacing of toolings and extraction of the set of the two parts thus formed; characterised in that the second part is moulded by filling the said thin volume adjacent to the said globally convex surface with a plastic material which is heated at a temperature exceeding the melting temperature of the plastic from which the first part is 3i made.

5 [R:\LI BA03065.doc:tlt 0a 06 0.

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44 a a 3a A second aspect of the present invention provides a forming process for a container head comprising a neck and equipped with a stopper cap comprising the following steps: a) moulding of the plastic head by bringing up a first external tooling the cavity of which defines the outside surface of the shoulder and the outside surface of the neck and an internal tooling comprising a core designed to form at least the inside surface of the neck; b) spacing of the said first external tooling and holding the head on the internal tooling; c) placement of a second external tooling, the cavity of which cooperates with the outside surface of the neck to delimit a thin volume; Sd) bringing up the said second external tooling and the head and then moulding of the cap; e) spacing of toolings and extraction of the container head equipped with its cap formed in this way; characterised in that the capsule is moulded by filling the said thin volume 1s adjacent to the said outside surface of the neck with a plastic material heated to a temperature exceeding the melting temperature of the plastic material from which the first a..

S part is made.

a..

Stage a) corresponds to a traditional shaping process, such as injection moulding or compression moulding or even thermoforming. The first part has a surface which will be in 2 contact with the second part and which is of convex shape.

This process requires the use of the said external tooling, because it forms at least in part this globally convex surface, and that of the said internal tooling because it includes at S least one core which enters into the interior space of the convex surface. The surface is called globally convex because it can include parts of small size which project outward or S2 even holes, these holes being occupied by the core or the internal tooling. Thus, in the case o• of a neck and stopper assembly unit, the neck is part of the first part and the outer cylindrical wall of the neck, provided or not provided with threading, comprises a globally convex surface with a hole at the place of the neck distribution opening. This hole is occupied up to stage d) of the process by one part in the shape of a core appendage, the latter forming the internal surface of the neck.

The core is close to every point of the surface so that the first part, which is thereby formed, has quite a small thickness with respect to the said contact surface. Following the shape of the first part, the external tooling can be a monoblock, or on the contrary, it can include several parts with sliding rails, being joined in front before shaping.

[R:\LIBA]03065.doc:tIt Stage b) follows stage a) and precedes stage c) in a very short time: the plastic material of the first part is not yet completely stabilised when one starts stage in which the external tooling of stage a) is replaced by another external tooling, called the second external tooling which, once placed directly in contact with the first part will define with the latter, by its impression and the globally convex surface of the first part, a space of small thickness, which is to be occupied by the plastic material of the second part.

When the globally convex surface of the first part has a hole made in it, the core being held in place, its part in the form of an appendage which has been used to make the holes during stage a) is used to completely define the space to be filled. Thus, in the case of shaping a neck-stopper assembly unit, the core, which allows one to make the internal surface of the neck, is held in place and then is used for phase d) to make the part of the internal side of the stopper lining which is found opposite the opening.

The second part is shaped during stage occupying at least the space defined by bringing the second external tooling close to the first part held on the internal tooling and which, possibly by the help of core parts, serves as a mould. A globally concave surface is formed directly opposite the globally convex surface of the first part. The space left by close positioning of toolings of the first part confers on the second part the appearance of a more or less thick shell in the vicinity of this globally concave surface. At the end of the process, the second part is detached from the first by separation of the said globally convex surface and of the said globally concave surface which has served as a mould in some respect. We shall call this separation the "last phase of mould separation" or "final mould separation" of the second part.

Once it is detached the said second part is again to be assembled with the first part, while remaining movable with respect to it but while having the possibility of being held in a position in which its said globally concave surface, which has thereby been formed, is joined in tight complementary contact with the said globally convex surface of the first part, which has served as its mould.

C04257 The surface is globally concave because, being complementary to the globally convex surface, it is capable of bearing small size details or even because the core or the second external tooling are provided with extension pieces which allow one to form holes in the second part.

The plastic material used for shaping of the second part is different from that of the first part, in the sense that these two materials are not miscible. Contrary to the aforementioned documents, it is not necessary that the material of the first part have a melting point greater than that of the material of the second part. In an example which will be explained in detail subsequently, the applicant has developed a surprising solution in which the cap is made of polypropylene and the neck of polyethylene, that is to say one in which the cap is moulded (overmoulded) onto the neck with polypropylene carried at a greater temperature near 80OC than the melting temperature of the neck.

The result, which is surprising and remarkable, is undoubtedly due to holding the internal tooling during the moulding process and in proximity of the core at all points of the globally convex surface of the first part.

In this preferred implementation of the invention, it is additionally possible to impose deformations on some geometric parts of the first part during moulding of the second. Thus, by the shape of the second external tooling, or by that of the complementary tooling, or even by the very shape of the first part, one can control the flow of the second plastic material in such a way as to cause a part of it to flow out from the first part. In this way, a shoulder of the first part might see one of its walls in undercut position, in a geometric configuration favourable to light snapping on, that is to say, thereby allowing capturing of the second part by the first.

The process in accordance with the invention is advantageously concluded by stage f) which follows: f) cooling and complete stabilisation of the two plastic materials before the last phase of mould separation from the second part which consists in a relative displacement of one part or of one section of one part with respect to the other.

One then allows the assembly shaped in this manner to cool, and one waits for complete stabilisation of the two plastic materials before displacing one part relative to the other. This displacement is in a certain way the last phase of mould separation of the second part. Dimensional stabilisation of the first part is accelerated by the annealing due to the moulding of the second part, but complete stabilisation of the second plastic material can require several days. This does not prevent one from carrying out complementary fabrication operations with the assembly of these two parts, which are held together during this period of time. Thus, in the case of flexible tubes before being filled by the product that they are to contain, the head of the tube provided with its cap by means of this process is welded to a flexible skirt then the entire unit is turned over to receive the said product without there being any need to wait for complete stabilisation of the plastic materials. It is the final user who will himself carry out the last phase of mould separation of the cap by using the unscrewing mechanism intended for the first opening of the tube. The applicant has determined that -this stabilisation, probably caused by complete withdrawal of the second plastic material, will improve t/h ,quality of the close contact between the parts. The practically zero clearance which is established bptween the two contact surfaces makes this bond perfectly airtight. Such coherence between C04257 surfaces could not be obtained under production conditions on a large scale before the present invention. Thus, with this process, one can obtain neck and cap assemblies that are perfectly airtight, with means of screwing which are much less deep than those used on caps that are manufactured separately, which allows one to make them twice as thin.

s The pairs of materials that are recommended in accordance with the invention are thermoplastic materials that are immiscible with one another. Preferably, one would choose polypropylene-polyethylene, polyester-polyethylene, ethylene vinyl alcohol-polyethylene, and polyamide-polypropylene pairs.

The last phase of mould separation of the second part consists in relative displacement of one part or of one section of one part with respect to the other: it is sufficient to displace each section of the part which is located in the vicinity of the common contact surface. This displacement is effective preferably following complete dimensional and thermal stabilisation, the ideal being to include it in an operation which is traditionally executed by the final user. Again, it is not necessary to provide any supplemental force.

Indeed, if the stabilisation makes the contact between complementary surfaces close and without any clearance, it also results in an increase in untightening torque. In order to alleviate this difficulty, combined solutions have been successfully adopted: one adjusts the constituent materials, or the geometry of the surface, especially small details of which they are provided. Frequently the complementary contact surfaces are provided with means of solid temporary connection of the two parts, such as threadings, and one can adjust their shape: if they are properly designed these threadings can effectively participate in final mould separation of the second part by breaking the solid connection of the two surfaces.

These are quick-acting, multiple, tapered, and shallow threads. They can have a short length and not extend over the total length of the common contact surface. Their geometry will be specified in the examples that follow. The majority of them differ from traditional geometries but will be readily accepted to the extent that they fulfil a clearly improved function of airtightness.

In the case when these surfaces cannot support threading, or even when these threadings must correspond to specific standards, it is still possible to adjust one or the other of the plastic materials by incorporating lubricating agents within them such as zinc stearate.

With respect to neck-cap assembly units, the latter choice is not always possible because the use of a lubricating agent such as zinc stearate is not recommended in the pharmaceutical, parapharmaceutical, or cosmetic industries. In this case, one can design a neck-cap system without threading imparting to the contact surfaces of the neck and the cap cylindrical shapes but with elliptical orthogonal sections, the ratio of the small axis to the large axis remaining greater than a certain critical value. Indeed, below this value, one will not be able to avoid irreversible plastic deformation of the surfaces. In the case of caps made of moulded polypropylene on necks made of polyethylene, these caps which have an average diameter between 15 and 45 millimetres and a skirt thickness between 0.5 and 2 millimetres, the small axis to large axis ratio must remain greater than "c04257 The same principle can be generalised for geometries other than those of the neck-cap pairs: when the relative displacement of one part with respect to the other allows an axis of rotation and this axis coincides with an axis of symmetry of the common contact surface, one can arrange matters so that when this rotation does not fulfil a specific functional and permanent role of the assembly unit (case of hinges or rack and pinion connections), in order to prevent this axis being an axis of symmetry: thus, the rotation inevitably results in an overall elastic deformation of these parts, the second part being not very thick at the level of their common contact surface; and this combined deformation contributes to disconnection of the two surfaces.

The possibilities of implementation are many. The choice of materials of the two parts and/or of S 10 the geometry of their common contact surface allows one in most cases to separate the second part from the first. This process allows one to obtain a remarkable level of airtightness, until now not encountered on parts manufactured at a high production rate. But, in certain configurations, it is also necessary to ensure that the parts are kept in contact with one another. This maintenance of contact can be temporary (for example it could be a question of caps which must ensure plugging of an opening) or permanent (when, for example, it is a matter of anchoring of one part of the second part in the first).

In order to ensure the tightness of a cap, one can add to the contact surfaces a snap on mechanism comprised of complementary groove and rib, but this supplemental system does not promote final separation of the second part. In order to ensure anchoring of one section of the second part on the first, comprised, for example, of a dovetail arrangement on the first part, it would be necessary at the time that the first part is shaped, to use undercutting tools with complex, not to say impossible, kinematics. The process in accordance with the invention allows one to solve these problems in a much simpler way.

Indeed, we have seen that there is every possibility of adjusting the flow control of the plastic material during shaping of the second part. By this means, it is possible to impose deformations to geometric sections of the first part during moulding attachment of the second. Due to the effect of the heat, the flow and the second plastic material and the forces that are put into play in order to ensure this flowing, a shoulder of the first part might see one of its walls being undercut, in a geometric configuration creating a protrusion which, even if it is of small height, is favourable to slight trapping and sufficient to ensure snapping on or anchoring of the second part on the first. Subsequently, we will discuss an example of snapping on and another of anchoring.

Other characteristics and advantages will appear in the description of the particular devices of the invention which are given subsequently by way of non-limiting examples.

Figure 1 represents, in axial section, a head of a tube provided with an attached (overmoulded) stopper, without any threading means.

Figure 2a represents, in axial section, a head of a tube provided with an attached (overmoulded) stopper that can be screwed on, the threading occupying only the base of the neck.

Figure 2b represents, in axial section, a head of a tube in the shape of a cannula provided with a screwable attached (overmoulded) stopper, whereby the threading occupies only a small section of S 40 the common contact surface between the stopper and the head.

c04257 'p rr 8 Figure 3a represents, in axial view, a head of a tube with 5 attached (overmoulded) hinge box.

Figure 3b shows, in a top view, the head of a tube with an attached (overmoulded) hinge box of figure 3a.

Figure 3c represents, in axial view, enlargement of the anchorage zones of the base of the hingeon the head of the tube of figure 3a.

Figure 4a is a view in axial section illustrating stage a) of the production process in accordance with the invention used for implementation of the head of figure 2a.

Figure 4b is a view in axial section illustrating stage d) 15 of the fabrication process in accordance with the invention used for implementation of the head of figure 2a.

Figure 5a represents another head of the tube with stopper attached, the neck in its upper part and the stopper being represented in axial section. The stopper is attached (overmoulded) and provided with a tear-off security strip.

Figure 5b represents, enlarged and in axial section, another means which will guarantee tearoff security placed directly on the skirt of an attached (overmoulded) stopper such as that shown in figure 2a.

Figure 6a represents, in axial section, a head of the tube with double-body stopper, one section with double skirt being attached (overmoulded) to the head then connected to an obturator disk of the upper hollow space.

Figure 6b represents, in axial section, a detail of the neck base of the head of figure 6a at the level of the snap on rib for anti-unscrewing safety.

Figure 7a represents, in axial section, a head of the tube provided with opening of the attached (overmoulded) stopper, which after the upper skirt is pushed in and then immobilised according to the process described in the French patent application No. 96-05342, becomes the double-skirt stopper of figure 7b.

Examples The examples illustrate many variants pertaining to the implementation of flexible tubes provided with a stopper.

They can pertain in a more general way to the implementation of any head made of plastic which can be adapted to a container of any shape and made of any material, provided with a distribution opening surrounded by a neck and stopped by a cap. In the entire present text the terms "stopper," usually reserved for flexible tubes, "cap," usually reserved for containers, and "plug" are synonymous.

Traditionally, the cap and head are manufactured separately. Sooner or later it is necessary to assemble the cap and the head, at least in order to protect the product contained in the container and to prevent it leaving the container. This assembly is carried out the first time under industrial manufacturing conditions of the container or filling of the product. The sealing which thereby results must be maintained airtight before the first use. The same means for assembling the cap and the Shead must then be used repeatedly throughout use of the product.

c04257 9 In the case of flexible tubes that are manufactured on a large scale and at a high rate, such as those which are used to hold and distribute toothpaste, the stopper is screwed onto the head at the end of the manufacturing cycle by the intermediary of complex automatic machines. These machines bring, at a rate of several hundred per minute, a stopper in front of each head, the latter being provided with threading that is perfectly adjusted to the head which is facing it. Then it is placed in rotation and in translation relative to the head with respect to the plug. This operation of automatic screwing of the cap requires an investment in complex automated machines and requires specific preparation of the parts, their conventional monitoring, and their selection, in order to limit the rejection rate.

In order to make the initial assembly arrangement of the cap and head less expensive, there have been attempts to directly attach the cap to the neck which surrounds the distribution opening.

The overall geometry of the external surface of the neck and of the internal surface of the cap is cylindrical or, preferably, slightly like that of a truncated cone. As a function of the conditions of use and assurance of closing and airtightness imposed on the tube, the neck may or may not be provided with means of temporary connection with the cap. Several variants have been turned down with respect to this invention, which are summarised in the eight examples, the details of the process phases being presented in example 3. For all examples given subsequently and for which the stopper or the cap is made into one piece with the neck by screwing, it is easy to carry out as in the example of figure 5, that is to say to adjust the moulds which are subject to direct attachment of the cap to the neck in order to make at the base of the latter a tear-off security strip.

Example 1 Tube with cap attached directly to the neck, not provided with means of being screwed on.

In the first example shown in figure 1, the tube 1 is provided with a head 10 consisting of a shoulder 2 and a neck 3 pierced at its top with a distribution opening 4. The neck 3 does not have any projection and the cap 5 is attached by injection moulding directly on the external surface 11 of the neck 3. The close contact of the surfaces obtained by this process ensures perfectly airtight support of the cap 5 on neck 3.

The neck and the cap are in this example in the shape of a truncated cone with a half angle at the top between 20 and 30, but in order to facilitate final separation of the cap, it is also possible to give them a cylindrical shape with elliptical orthogonal sections, the small axis/large axis ratio being greater than 0.9.

The simple contact of the external surface 11 of the neck 3 and internal surface of the cap ensures support of the assembly unit, therefore the closing of the opening under satisfactory conditions, but if one wishes to ensure better tightness, it is enough to add to the base of neck 3 a shoulder 6. During this attachment process, if the injection point corresponds to that described in the following example and figure 4b, the greater angle of this shoulder 6 will creep, so that its vertical wall 7 is placed in slight undercut position. In a complementary manner, the internal side of the cap will Sinclude at its end 8 an internal release which, associated with the said wall in undercut position of c04257 shoulder 7, will allow barely perceptible snap on of the cap arrangement after being pushed in and will present an obstacle to untimely opening of the cap, even after several uses.

Such a tube which is quite simple and of pleasing appearance is perfectly adjusted to economical packaging of samples, for which a limited number of openings and closings is anticipated.

Example 2 Head of a tube with cap attached made of a plastic material enriched with zinc stearate.

In this second example the neck has threading on it, similar to threading that is traditionally used, comprised of a single thread of trapezoidal section and in shape of a spiral of more than 2 turns, in general 3 to 4 turns.

The cap in this case is attached with a plastic material that includes a large amount of lubricating agent, such as zinc stearate. The unscrewing force during separation is large but acceptable for caps which enable the user to hold the unit in his hand: their external wall is provided with gripping means without sliding, such as grooves, and have a large diameter, which yields a multiplying effect of the force of unscrewing. If the trapezoidal section of this installed threading can be modified, one would prefer a half-round section.

Such a solution is limited aesthetically because the cap is grooved, unlike the cap of example 1 where the external wall 9 can be perfectly smooth. On the other hand, it is limited in its applications because the lubricating agent is not always recommended in pharmaceutical, parapharmaceutical, or cosmetic industries.

On the other hand, it can offer the advantage of assuming the overall shape of the product to which the user is accustomed.

Example 3 Head of a tube with attached cap provided with short and shallow screwing threads.

The third example allows one to describe with the aid of figures 4a and 4b the process in accordance with the invention as applied to the head of a tube illustrated in figure 2a.

Figure 4a represents the shaping by injection moulding of a head of tube 10' made of polyethylene by close positioning of initial external tooling 50 whose impression defines the external wall of the neck 3' An upper tooling 51 defines the upper wall of the neck and lower external tooling 52 defines the external surface of the shoulder 2. The core 40 defines the internal wall of the neck 3' and is surmounted by an attachment 42 which presses against the upper tooling 51 in order to make the opening 4. Here, there is an initial attachment, because the end of the shoulder 2 is welded tight to the end of skirt 100 during this operation. Neck 3' which is thereby formed is, in this example, provided at the base of its truncated external wall 11' with cone-shaped threading 20, which is short, multiple, steep, and having a specially shaped section characterised by low height and relief: 0.3 mm.

The slope of the spiral is quite steep, between 15 and 250. The angular length of the thread is only 300: this makes the larger part of the neck surface smooth, thereby imparting to it a clean appearances which satisfies the user aesthetically as well as hygienically because there is less risk of rtaiing the product distributed by the tube.

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c04257 11 Tooling sets 50 and 51 are then removed, but the head is held in supported fashion on core as well as between tooling sets 41 and 52.

Without waiting for complete cooling of the head, a new external tooling 55 is put in position on tooling 52. Its impression, the external surface 11' of neck 3' and the attachment 42 of core describe a space 56 of small thickness which will be occupied by the future cap By means of this process, one can save a great deal of material, since the cap can be half as thin as when it is made separately. In this case, one can make a cap which has an average thickness of 0.7 mm.

After the tooling sets are brought close together (55, and 52), one injects some polypropylene at a temperature of 210 0 C. Although the neck is made of polyethylene, whose melting temperature is less than the injection temperature, the cap 5' is perfectly formed having at the end of its skirt a threading that is complementary to that of neck 3' threading 20. The latter is then hollow, but of shallow depth (0.3mm) with a steep slope, and multiple: this facilitates centring during insertion of the cap during reclosing.

Next, one removes the tooling sets and one removes the assembly unit. One allows the assembly unit to cool so that there will be complete dimensional stabilisation of the neck and the cap.

This does not prevent one from handling the assembly unit which has been shaped, for example by filling the tube with the product it is to contain and distribute. It is the final user who accomplishes the last phase of mould separation of the cap by making the first opening, in the traditional manner and without any particular difficulty because the unscrewing force is small.

Example 4 Head of a tube in tubular shape with cap attached In this example, shown in figure 2b, the head of tube 10" has an elongated neck 3" in the shape of a long tube and has a short base that is steep with multiple threading. As in the preceding example, the wall of the attached cap 5" closely conforms in shape to the external wall of the neck 11", ensuring perfect airtightness. The common contact surface is truncated in shape, which facilitates detachment of the cap. An optional, cylindrical external skirt allows eases gripping the cap.

Example Head of the tube with attached hinge box The process for implementation of this tube shown in axial section by figure 3a and in a top view by figure 3b, differs from the preceding views by implementation, during shaping of the head, of a deep rectilinear groove 32 at the base of the neck 30. Figure 3c shows in detail a section of this groove: during moulding of the head made of polyethylene, an edge 31 of this groove 32 is made in vertical projection.

During attachment of cap 33 this edge 31 is turned down above groove 32 by simple proximity of the second external tooling set, which is overall similar to tooling set 55 of figure 4b has an impression adjusted to this particular geometry. The injected plastic material, polypropylene, causes the shoulder 34 to creep by filling the groove 32, thereby placing the vertical wall 35. in undercut position. This wall and the edge 31, turned down and softened during attachment, together comprise 1-A conrsiterable tightening which traps the plastic material that fills the space of groove 32 and serves as C, 04257 12 the base for the film hinge 36, which is used to pivot the assembly unit of the box 33 to release the distribution opening The anchoring of this distribution head with the hinge allows one to make tubes with easy opening allowing it to be opened with a single finger of the same hand holding the tube.

Example 6 Heads of a tube with cap provided with means for tear-off security.

The head of figure 5a is another example of a cap which can be made by this process, characterised by an upper skirt 58 which facilitates gripping of the cap, a small thickness, which saves on material, a central part which reenters the interior of the opening and, at the bottom of the lower lo skirt, at the base of the neck, a tear-off security strip 59. With respect to this guarantee strip 59, the base of the neck is provided with teeth, for example snap on wheel teeth as those illustrated in figure 2 of FR 2,665,142 under reference number 9. The guarantee strip 59, moulded continuously from the skirt of the cap through the intermediary of small size supply links, occupies the hollow spaces left by the teeth and can only remain immovable during initial rotation intended for unscrewing of the cap.

Due to the effect of this rotation, imposed at the level of the cap skirt, the links break and release the cap in its unscrewing movement.

The means of unscrewing shown in figure 5a can be advantageously replaced by conical, short, multiple, steep, and shallow threading such as that described in example 3.

Figure 5b represents, enlarged and in axial section, another means which is simple and which also guarantees tear-off security. This means is provided on the skirt of cap 5' of figure 2a. Here, we are speaking of a spot 49 moulded in relief with the neck 3' During attachment of cap the second external tooling set is provided with respect to this spot 49 having truncated cone appendage, which provides an opening 48 on the skirt of cap During the initial opening the spot is sheared and falls off; therefore, it plays the role of a visualisation indicator of infringement of the packaging.

Example 7 Head of a tube with double-body cap S c04257 The cap 65 encasing head 60 of figure 6a is comprised itself of two parts: the first 61 is attached directly to shoulder 62 and the neck, identical to neck 3' provided with threading with short, multiple, steep, and shallow threads of figure 2a. It includes an external skirt 66, which is placed in the extended section of body 100 of the tube. An obturator 63 is attached above the first part 61 to cover the annular hollow section 64 of the first part 61 and thus comprises a plug which improves the aesthetic appearance of the tube assembly.

The contact between the first part 61 and the .head of the tube corresponds to a large surface since it covers the external wall of the neck and the shoulder. Final separation of this part 61 is even possible by means of the lever arm effect which multiplies the forces applied to the external wall of the external square 66 located in the extended area of the body of tube 100.

Such a tube provided with such a plug is characterised by the close contact of the plug not only against the wall of the neck but also against that of the shoulder, thus allowing one to achieve exceptionally effective airtightness.

Example 8 Head of the tube with rough shape of an attached plug that has an upper skirt that can be pressed down following the process described in patent application W097 39953 Figure 7a presents another head of the tube 70 provided with the rough shape of a plug attached directly to neck The neck 3' is provided at its base with threading 20 with short, steep, multiple, and shallow threads. The rough shape 75 has an initial section 71 directly attached to neck which includes a first skirt 80 attached to a platform 72 whose periphery 73, of diameter greater than that of the first skirt 80, is provided with three stops 74, with an upper skirt 76 which imparts to the assembly unit the shape of an overturned hat. The internal surface of the upper skirt 76 is provided, with respect to each of the three stops 74, with longitudinal groove 77 that is not very deep which begins from the lower extremity of the upper skirt 76 and rises at least to a cavity 78 which is slightly deeper, which is capable of trapping a stop 74.

Immediately following injection moulding of this rough shape 75, one removes the external tooling set, but one keeps the internal tooling sets of the same type as the internal tooling sets 40 and 41 of figure 4a. A plate can then rest on the upper end of the skirt while imposing a compression movement: the three links 79 give way and the upper skirt 76 is compressed by being wrapped around plate 72, the stop 74 are guided into grooves 77. When the cavities 78 arrive at the level of the stop 74, the latter are trapped and there is immobilisation of the skirt 76, which becomes a skirt 76' surrounding the neck and one piece with plate 72 because of the ratcheting mechanism. The final result is shown in figure 7b.

Like the previous solution, this solution allows one to obtain stoppers of a large diameter whose aesthetic is frequently preferred in the cosmetic industry, but it presents with respect to the latter two advantages: the contact surface is thinner, which improves the conditions of separation of the plug; and there is no need to introduce a separately manufactured part, which allows one to have very high irianufacturing rates.

A c4257 cO4257 As indicated in the patent application W097/39953 it is also possible to adapt such a rough plan of a cap to any head made of plastic for a container, with any shape and made of any material whatsoever, provided with a neck, the upper skirt to be pressed down then made one piece with the plate which can simultaneously be moulded or can be manufactured separately.

The product obtained by the process in accordance with French patent application No. 96- 05342 is characterised by the presence of a two-part cap made into one piece with one another, for example by a ratchet mechanism: one having the shape of a plate and the other that of a skirt surrounding the neck. In a preferred implementation, the skirt is provided on its internal surface with longitudinal grooves adjacent to some cavities, which open out or not, which trap the stops of the plate. By means of the process in accordance with the invention, the said plate has been attached to the neck to become one section with another skirt, provided with means of temporary solid connection which are perfectly complementary with those of the neck, for example the short and shallow screwing threads of example 3.

Advantages economy of material, especially by considerable decrease of the thickness at the level of the contact surfaces; irr 0J,

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c04257 economy in the large scale manufacturing cycle, by avoiding stages of separate manufacture and automated assembly; perfect airtightness of a completely tight contact; great flexibility which allows a large number of variants, with a large number of geometries, made possible because of this process.

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c04257

Claims

1. Forming process for an assembly comprising at least two plastic parts, mobile with respect to each other and located in at least one configuration in which their contact surfaces match complementary shapes, comprising the following steps: a) forming of a first plastic part made by bringing up a first external tooling, the cavity of which defines at least the globally convex shape of a surface designed to come into contact with the second part and an internal tooling comprising at least one core entering into the internal volume of the said globally convex surface; b) spacing of the said first external tooling and holding the first part on the internal tooling; io c) placement of a second external tooling, the cavity of which cooperates with the said globally convex surface to delimit a thin volume with the globally convex surface of the first part; d) bringing up the said second external tooling and the first part then moulding of the second part; e) spacing of toolings and extraction of the set of the two parts thus formed; characterised in that the second part is moulded by filling the said thin volume adjacent to the said globally convex surface with a plastic material which is heated at a temperature exceeding the melting temperature of the plastic from which the first part is made.

2. Process according to claim 1, characterised in that the plastic in the first part is not completely stabilised when step c) is started.

3. Process according to claim 1, characterised in that it is completed by the following final step: f) cooling and complete stabilisation of the two plastic materials before the last mould removal phase of the second part that consists of relative displacement of one part or some of a part with respect to the other part.

4. Process according to claim 1, characterised in that the core of the internal tooling is close S 25 to the globally convex surface of the first part at all points. S: Process according to claim 1, characterised in that the plastic material of the second part .0.0 includes a sliding agent.

6. Process according to claim 1, characterised in that the first part is made of polyethylene and the second part is made of polypropylene.

7. Process according to claim 1, characterised in that the globally convex surface of the first part and the globally concave surface of the second part are equipped with temporary fixing means 0 that cooperate with the last mould removal phase of the second part.

8. Forming process for a container head comprising a neck and equipped with a stopper cap comprising the following steps: 35 a) moulding of the plastic head by bringing up a first external tooling the cavity of which defines the outside surface of the shoulder and the outside surface of the neck and an internal tooling comprising a core designed to form at least the inside surface of the neck, b) spacing of the said first external tooling and holding the head on the internal tooling; c1c) 1 placement of a second external tooling, the cavity of which cooperates with the outside surface 40 of thneck to delimit a thin volume; c042 57 17 d) bringing up the said second external tooling and the head and then moulding of the cap; e) spacing of toolings and extraction of the container head equipped with its cap formed in this way; characterised in that the capsule is moulded by filling the said thin volume adjacent to the said outside surface of the neck with a plastic material heated to a temperature exceeding the melting temperature of the plastic material from which the first part is made.

9. Process according to claim 8, characterised in that it is completed by the o0 following final step: I) cooling and complete stabilisation of the two plastic materials before the last mould removal phase of the cap that consists of a relative displacement of the cap or part of the cap with respect to the neck. Forming process for a container head according to claim 8, characterised in that 15 the cap is made of polypropylene and that the neck is made of polyethylene. 1:1. A container head formed according to the process of any one of claims 1 to said container head equipped with its cap comprising a cylindrical neck, the outside surface of the said neck not having any sharp edges and, when the receptacle is closed, coming into intimate contact without play with the inside surface of the said cap, characterised in that the 2o said cap is made of a material which has a melting temperature greater than that of the material making up the neck and that the said neck has an elliptical orthogonal cross section, the ratio of the small axis/large axis remaining greater than 0.9. i i 12. A container head formed according to the process of any one of claims 1 to said container head equipped with its cap comprising a neck, the outside surface of the neck 25 and the inside surface of the cap being in intimate contact without play when the receptacle is closed, and comprising perfectly complementary screwing means corresponding to a thread composed of a single thread with a trapezoidal cross section characterised in that the said cap is made of a plastic that has a melting temperature exceeding that of the material making up the neck, in that the said threaded neck is made of a single piece and in that the plastic material of the cap contains a sliding agent.

13. A container head formed according to the process of any one of claims I to said container head equipped with its cap comprising a neck, and when the container is plugged, the outside surface of the neck and the inside surface of the cap are in intimate contact without play, characterised in that the said capsule is made of a plastic material for 'lvhich the melting temperature is greater than the material making up the neck and in that [R:\LI BA]03065 .doc:tlt a a a a a. 18 the said outside surface of the neck and the inside surfade of the cap comprise perfectly complementary screwing means corresponding to shallow threads.

14. Container head equipped with its cap comprising a neck according to claim 13, characterised in that the said shallow threads are steep, multiple and short threads. Container head equipped with its closing cap according to any one of claims 11 to 14, characterised in that the cap is equipped with a tear-off security in its lower part.

16. Container head equipped with its closing cap according to any one of claims 11 to 15, characterised in that the outside surface of the neck is equipped with a spot and in that the inside surface of the cap is equipped with an opening facing the said disk extending the I orifice which is perfectly complementary to the said spot, playing the role of a visualisation indicator of infringement or said container.

17. Container head equipped with its cap according to any one of claims 11 to characterised in that the cap has two parts fixed together, at least part of the inside surface of one of them, when the cap is in the closed position, being in intimate contact without play I 5 with the outside surface of the neck and the shoulder.

18. Container head equipped with a cap according to claim 17, characterised in that the said cap comprises two parts fixed together by a ratcheting mechanism, part of one of them being in the form of a plate fitted with stops around its periphery, the other being in the shape of a skirt surrounding the neck and equipped with longitudinal grooves on its 2o inside surface adjacent to cavities that trap the stops on the plate.

19. Forming process for an assembly comprising at least two plastic parts, mobile with respect to each other and located in at least one configuration in which their contact surfaces match complementary shapes, substantially as hereinbefore described with reference to the accompanying drawings.

20. Forming process for a container head comprising a neck and equipped with a stopper cap, substantially as hereinbefore described with reference to the accompanying drawings.

21. Container head equipped with its cap comprising a cylindrical neck, the outside surface of the said neck not having any sharp edges and, when the receptacle is closed, coming into intimate contact without play with the inside surface of the said cap, substantially as hereinbefore described with reference to the accompanying drawings.

22. Container head equipped with its cap comprising a neck, the outside surface of the neck and the inside surface of the cap being in intimate contact without play when the receptacle is closed, and comprising perfectly complementary screwing means [R/LIBA0306 oclt IR:\L1BA03065.doc:tlt it-- 19 corresponding to a thread composed of a single thread with a trapezoidal cross section, substantially as hereinbefore described with reference to the accompanying drawings.

23. Container head equipped with its cap comprising a neck, and when the container is plugged, the outside surface of the neck and the inside surface of the cap are in intimate Scontact without play, substantially as hereinbefore described with reference to the accompanying drawings. Dated 16 March, 2000 Cebal SA Patent Attorneys for the Applicant/Nominated Person i0 SPRUSON FERGUSON C [R:\LIBA]03065.doc:tlt