|Title of Invention||
A METHOD FOR SHAPING AN ASSEMBLY
|Abstract||This invention relates to a method for shaping an assembly comprising two plastic parts able to move with respect to one another and which are found in at least one configuration where their contact surfaces conform in shape, comprising following stages: (a) joining a fIrst external tooling whose imprint is globally convex and an internal tooling including a core and shaping of a fIrst plastic part; (b) separating the said fIrst external tooling and leaving the fIrst part on the internal tooling; (c) placing a second external tooling whose imprint will define, together, with the globally convex surface of the first part, a space of small thickness over at least part of said globally convex surface; (d) molding of the second part with a plastic material at a temperature exceeding the melting temperature of the plastic material of said first part; ( e) separating the tools and removing the assembly of the two parts.|
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.
Stafcer 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 molded 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 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 overmold 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 molding 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 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 flavors and scents.
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 overmolded 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 assembly 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, comprising the following stages:
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 of said globally convex surface;
d) -bringing said second external tooling and said shaped
first part close together and then molding 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.
Stage a) corresponds to a traditional shaping process, such as injection molding or compression molding or even thermoforming. The first part has a surface which will be in 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 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 even holes, these holes being occupied by the core or the internal tooling. Thus, in the case 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. 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 stabilized when one starts stage c), 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 d), 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 mold. 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 mold in some respect. We shall call this separation the "last phase of mold separation" or "final mold 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 mold.
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 molded (overmolded) onto the neck with
polypropylene carried at a greater temperature near 80°C than the melting temperature of the neck. The result, which is surprising'"and remarkable, is undoubtedly due to holding the internal tooling during the molding 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 molding 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 favorable 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 stabilization of the two
plastic materials before the last phase of mold 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 stabilization of the two plastic materials before displacing one part relative to the other. This displacement is in a certain way the last phase of mold separation of the second part. Dimensional stabilization of the first part is accelerated by the annealing due to the molding of the second part, but complete stabilization 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 stabilization of the plastic materials. It is the final user who will himself carry out the last phase of mold separation of the cap by using the unscrewing mechanism intended for the first opening of the tube.
The applicant has determined that this stabilization, probably caused by complete withdrawal of the second plastic material, will improve the quality of the close contact between the parts. The practically zero clearance which is established between the two contact surfaces makes this bond
perfectly airtight. Such coherence between 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.
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 mold 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 stabilization, 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 stabilization 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 mold 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 fulfill 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 molded polypropylene on necks made of polyethylene, these caps which have an average diameter between 15 and 45 millimeters and a skirt thickness between 0.5 and 2
millimeters, the small axis to large axis ratio must remain greater than 0.9.
The same principle can be generalized 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 fulfill 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 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 oh the first part, it would be necessary at the time that the fijst 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 mich simpler
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Indeed, we have seen that there is evjery 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 molding attachment of the second. Due to the effect of the heat,
the flow and the second plastic material ahd 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 favorable to slight trapping and sufficient to ensure snapping on or anchorLng of the second part on the first. Subsequently, we will discuss an exarcple of snapping on and another of anchoring.
Other characteristics and advantages will appear in the description of the particular devices of tie invention which are given subsequently by way of non-limiting examples.
Figure l represents, in axial section, a head of a tube provided with an attached (overmolded) stopper , without any threading means.
Figure 2a represents, in axial^ fcectioi, a head of a tube provided with an attached (overmolded)', stopper that can be screwed on, the threading occupying only tie base of the neck.
Figure 2b represents, in axjial sectioi, a head of a tube in the shape of a cannula provided with a scrawable attached
(overmolded) stopper, whereby the threading occupies only a small section of the common contact surface between the stopper and the head.
Figure 3a represents, in axial view, a head of a tube with attached (overmolded) hinge box.
Figure 3b shows, in a top view, the head of a tube with an attached (overmolded) hinge box of figure 3a,
Figure 3c represents, in axial view, enlargement of the anchorage zones of the base of the hinge on the head of the tube of figure 3a,
Figure 4a is a view in axial section illustrat:.ng 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 ]illustrat:.ng stage d) of the fabrication process in accordance with the invention used for implementation of the head of figure 2a.
Figure 5a represents another head of jthe tube with stopper attached, the neck in its upper part and t^he stopper being represented in axial section. The stopper is attached (overmolded) and provided with a tear-off security strip.
Figure 5b represents, enlarged and in axial section, another means which will guarantee tear-off security placed directly on the skirt of an attached (overmolded) stopper Buch as that shown
in figure 2a.,
Figure 6a represents, in axial eecticjn, a head of the tube with double-body stopper, one section with! double skirt being attached (overmolded) to the head then connected to an obturator disk of the upper hollow space.
Figure 6b represents, in axial section, a deta:.l 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 (overmolded) stopper, which after the upper skirt is pushed in and then immobilized according to the process described in the French patent application No. 96-05342, becomes the double-skirt stopper of figure 7b.
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 head must then be used repeatedly throughout use of the product.
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 summarized 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 molds 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 molding 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 2° and
3°, 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 5 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 include at its end 8 an internal release which, associated with the said wall in undercut position of 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 molding 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 ll1 with cone-shaped threading 20, which is short, multiple, steep, and having a specially shaped section characterized by low height and relief: 0.3 mm. The slope of the spiral is quite steep,
between 15 and 25°. The angular length of the thread is only
30°: this makes the larger part of the neck surface smooth, thereby imparting to it a clean appearance, which satisfies the user aesthetically as well as hygienically because there is less risk of retaining the product distributed by the tube.
Tooling sets 50 and 51 are then removed, but the head is held in supported fashion on core 40, 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 40, describe a space 56 of small thickness which will be occupied by the future cap 51. 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, 3', and 52), one injects some polypropylene at a temperature
of 210°C. Although the neck is made of polyethylene, whose melting temperature is less than the injection temperature, the cap 51 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 (0.3 mm) with a steep slope, and multiple: this facilitates centering 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 stabilization 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 mold 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 5: Head of the tube with attached hinge box.
The process for implementation of this tube 1,,!, 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 molding 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 considerable tightening which traps the plastic material that fills the space of groove 32 and serves as the base for the film hinge 36, which is used to pivot the assembly unit of the box 33 to release the distribution opening 4 ! ' ' .
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-of f-^security.
The head of figure 5a is another example of a cap which can be made by this process, characterized 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 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, molded 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 molded in relief with the neck 3'. During attachment of cap 5', 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 51. During the initial opening the spot is sheared and falls off; therefore, it plays the role of "^visualization indicator of infringement of the packaging.
Example 7: Head of a tube with double-body cap.
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 20 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 cap 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 cap is characterized by the close contact of the cap 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 cap that has an upper skirt that can be pressed down following the process described in French patent application No. 96-05342.
Figure 7a presents another head of the tube 70 provided with the-Tough shape of a cap 75 attached directly to neck 3'.
The neck 3' is provided at its base with threading 2 0 with short, steep, multiple, and shallow threads. The rough shape 75 has an initial section 71 directly attached to neck 31, which includes a first skirt 80 attached to a plate 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 molding 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 immobilization 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 appearance is frequently preferred in the cosmetic industry, but it presents^wrth respect to the latter two advantages: the contact surface is thinner, which improves the conditions of separation of the cap; and there is no need to introduce a separately manufactured part, which allows one to have very high manufacturing rates.
As indicated in the French patent application No. 96-05342 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 molded or can be manufactured separately.
The product obtained by the process in accordance with French patent application No. 96-05342 is characterized 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.
economy of material, especially by considerable decrease of the thickness at the level of the contact surfaces; 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.
1. A process for the formation of an assembly (10 and 5; 10! and 5 *; 10 *! and 5' ! ; 10 ' f f and 5 ! ' ') which comprises 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, comprising the following stages:
a) shaping a first part (10; 101 ; 10' *; 10 ' ' ' ) made of
plastic by bringing an internal tooling (40 and 41)
and a first external tooling (50 and 51) 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 (11, 11!) being meant to be in contact with the second plastic part (5; 5'; 5'f; 5' 'f), and said internal tooling comprising at least a core (40) which enters the internal space of said globally convex surface;
b) separating said first external tooling (50 and 51) and leaving the first part on the internal tooling (40 and 41) ;
c) placing a second external tooling (55) the internal surface of which defines, together with the globally convex surface (11; ll1) of the first part, a space (56) of small thickness over at least part of said
globally convex surface;
d) bringing said second external tooling (55) and said
shaped first part (10; 10'; 10'; 10 ' ' ' ) close
together and then molding the second part (5; 5'; 5,!;
5'1) by filling said space (56) with a plastic
material at a temperature exceeding the melting
temperature of the plastic material of said first part ;
e) separating the toolings (55 and 52; 40 and 41) and
removing the assembly of the two parts thus obtained (10
and 5; 10' and 5', 10 *' and 5'; 10 ' ' ' and 5' ") .
2. Process according to claim 1, characterized in that the plastic material of said first part (10; 10'; 10! '; 10'f ') is not completely stabilized at the beginning of stage c).
3. Process according to claim 1, characterized in that it further comprises the following final stage:
f) Cooling and complete stabilization of both plastic
materials before the last phase of mold separation from the second part (5; 5'; 511; 5,TI) which consists in a relative displacement of one part (5; 5'; 51') or of one section of one part (5111) with respect to the other one
(10, 10' ; 10"; 10" ' ') .
4. Process according to claim 1, characterized in that the core (40) of the internal tooling (40 and 41) has an external shape which is close at all points to the overall convex shape (11') of the first part (101).
5. Process according to claim 1, wherein the plastic of the second component comprises a sliding agent.
6. Process according to claim 1, wherein the first part (5; 5r ; 5' ! ; 5' ' ') is made of polyethylene and in that the second part (10; 10'; 10'; 10'') is made of polypropylene.
7. Process according to claim l, wherein the overall convex surface of the first part and the overall concave surface of the second part are provided with means for temporary connection of the two parts which effectively participate in final mold separation of the second part.
8. A process for the formation of a container head provided with a stopper cap (10 and 5; 10' and 5f; 10 ' ' and 5'*; 1011' and 5'') comprising the following stages:
a) shaping of the head (10; 10?; 10'; 10T ' ') made of
plastic by bringing an internal tooling (40 and 41) and a-first external tooling (50 and 51) closer together, the imprint of said first external tooling forming the external surfaces of the shoulder and of the neck (3; 3■; 3' ' ; 3 * ' !) and said internal tooling (4 0 and 41) comprising a core (40) determining at least the internal surface of the neck (3; 3'; 3!!; 3' ' ') ;
b) separating said first external tooling (50 and 51) and
leaving the head on the internal tooling (40 and 41) ,*
c) placing a second external tooling (55) the internal
surface of which defines, together with the external surface (11; 11'; 11'; 11,,!) of the neck (3; 3'; 3!,; 3! ' ') , a space (56) of small thickness over said external surface;
d) bringing said second external tooling (55) and said head
(10; 10!; 10'■; 10'') close together and then molding the cap (5; 5'; 5'; 5,!!) by filling said space (56) with a plastic material at a temperature exceeding the
melting temperature of the plastic material of said head;
e) separatiing the toolings (55 and 52; 40 and 41) and
removing the head provided with its cap (10 and 5; 10! and 5 ' , 10 ' ' and 5' '; 10' ! ' and 5 ' ') .
f) Cooling and complete stabilization of both plastic
materials before the last phase of mold separation from the cap (5; 5'; 5'r; 5 r ' ') which consists in a relative displacement of the cap (5; 5!; 5,!) or of a part of the cap (5,!I) with respect to the neck (10; 10!; 10'1; 10' ' ' ) .
9. Process according to claim 8, wherein said cap (5; 5'; 5" ; 5' * ') is made of polypropylene and said neck (10; 10'; 10!'; 10'*) is made of polyethylene.
10. Container head (10) provided with a cap (5) and comprising a shoulder (2) and a truncated-cone-shaped neck (3), characterized in that the outer surface (11) of the neck (3) does not have any projection and is in close contact, without play, with the inner surface of the cap (5), so that a perfectly airtight support of the cap (5) on the neck (3) is ensured.
11. Container head (10) provided with a cap (5) and comprising
a shoulder (2) and a neck (3) with elliptical orthogonal
sections, characterized in that the outer surface (11) of the
neck (3) does not have any projection and is in close contact,
without play, with the inner surface of the cap (5), so that a
perfectly airtight support of the cap (5) on the neck (3) is
12. Container head (10) provided with a cap (5) and comprising a shoulder (2) and a neck (3), characterized in that the outer surface of the neck and inner surface of the cap have completely complementary screwing means corresponding to a threading made up of a single thread with trapezoidal section, and wherein the plastic of the cap contains a sliding agent.
13. Container head (10') provided with a cap (5r) and comprising--a shoulder (2') and a neck (3r), characterized in that the outer surface (11!) of the neck (3') and the inner surface of the cap have completely complementary screwing means (20) corresponding to steep, multiple, short, shallow threads.
14. Container head provided with a cap according to claim 12 or 13, characterized in that the cap is provided with means for tear-off security (59).
15. Container head provided with a cap (51) according to claim 12 or 13, characterized in that the outer surface of the neck is provided with a spot (49) and in that the outer surface of the cap (51) is provided with respect to said spot with an opening (48) running on from the orifice completely complementary of said spot (49), playing the role of a visualization indicator of infringement of said container.
16. Container head (60; 70) provided with a cap (65; 75)
according to claim 12 or 13, characterized in that the cap
(65; 75) comprises two components ( 61 and 63; 71 and 76!)
interlocked with one another and wherein, when the cap (65;
75) is closed, at least a portion of an inner surface of one
of the components (61; 71) is in close contact, without play,
with the outer surface of the neck and the shoulder.
17. Container head (70) provided with a cap (75) according to
claim 16, characterized in that said cap (75) comprises two
components (71 and 76') are interlocked with one another by a
ratcheting mechanism, a portion of one component (71) having
the fomrof a plate (72) provided with stops (74) on its periphery (73), the other component having the form of a skirt (76') surrounding the neck and provided on its inner surface with longitudinal grooves (77) adjacent to cavities (78) which trap the stops (74) on the plate (72).
|Indian Patent Application Number||1207/MAS/1997|
|PG Journal Number||26/2007|
|Date of Filing||05-Jun-1997|
|Name of Patentee||CEBAL S A|
|Applicant Address||98 BOULEVARD VICTOR HUGO 92115 CLICHY.|
|PCT International Classification Number||B29C45/00|
|PCT International Application Number||N/A|
|PCT International Filing date|