FR2752541A1 - Injection moulded container body with hinged lid - Google Patents

Abstract

Method of producing a hinged assembly (1) having a part (2) forming a receptacle body and presenting an opening (2a) in one surface and another part (10) forming a cover that can rotate with respect to the first part and in one position contact its surface and cover the opening. Method consists of injecting the two pieces in such a way as to create the hinge means (16), around an axis of rotation (12) with a direction parallel to the open surface, which co-operates between the two parts to close the opening by relative rotation; mould each of the parts by plastic injection moulding into a cavity with the aid of a means allowing distinct injection. The two parts are connected at their hinge means during injection of the materials but the injection is controlled for each part so that they do not weld together.

Description

 The invention relates to a method for obtaining an articulated assembly comprising two parts.

 The invention relates in particular to closing an opening formed in a junction surface of a part forming a body for receiving a product by means of a second part forming a cover. The cover is movable in rotation relative to the body in order, in one position, to come into contact with the junction surface and close the opening.

It is certainly commonly known to produce assemblies of the aforementioned type. It is thus already known to produce such assemblies according to a method in which:
- The two parts are injected so as to create articulation means around an axis of rotation whose direction is substantially parallel to the junction surface, these articulation means being intended to cooperate with each other in order to allow or close access to the opening, by relative rotation of the parts,
- Each of the parts is molded by injection of plastic material (s) into a molding cavity using separate injection means (or group of means).

 For all practical purposes, it is specified that it is understood by direction of the axis of rotation parallel to the junction surface that the axis is not intersecting (in particular not perpendicular) to the junction surface.

 However, the invention aims to optimize the production of these assemblies by reducing the number of phases necessary for their production and by increasing the range of possible types of articulation between the various parts constituting the assembly. This improves the robustness and reliability of the part obtained while reducing the costs necessary for the preparation of the finished part.

To solve these problems, the invention proposes that:
the parts are linked together substantially at the level of their articulation means during the injection of material (s), and
- The injection is controlled so that the materials of each of the parts do not weld, that is to say that there is practically no cohesion so that the parts can be made to move relative to one another. to the other after the material has cooled.

 According to the teaching of the prior art, the parts were produced during separate injection phases, then assembled after cooling.

Such a method requires carrying out at least one more phase than the number of parts constituting the assembly in order to obtain the articulated assembly, requires waiting for the parts to be cooled before assembling them and requires the design of articulation means allowing assembly of the parts by assembly after separate production of each of the parts.

 According to the invention, the step of assembling the parts is eliminated. It is then no longer necessary to design assemblies such that it is possible to assemble the various parts constituting them (after separate production of each of them). These sets can then no longer be removable, they are more reliable and more robust for a lower cost.

 For all practical purposes, it is specified that the materials that can be used are in particular the following: polypropylene (PP), acrylonitrile butadiene styrene (ABS), polystyrene (PS), polyoxymethylene, polyacetal, polyformaldehyde (POM), polyethylene terephthalate (PET) or polyethylene terephthalate derivatives such as PCTG and FETG.

 The invention therefore makes it possible to produce the articulated assembly by simultaneous injection of the parts or according to offset injection stages.

 Simultaneous injection consists of injecting material into a mold having a single cavity, this simultaneously from two groups of injection means corresponding to each part, respectively. Injection parameters (grade of material injected, pressure, temperature, speed, flow rate, injection time, number and locations of injection points, ...) and characteristics of the mold (shape, thickness, width, length, ...) used to control the injection, can then be determined so that the fronts (flow) of material from each group of injection means meet at specific locations intended to form the border of the two parts .

 By "simultaneous" injection, it should be understood that the two materials are not necessarily injected strictly between the same two times, but that there is a period during which the two materials are injected at the same time.

 This operation has good repeatability since it is able to guarantee consistency of the injection parameters and characteristics of the mold. It also allows the articulated assembly to be produced in a single phase. The development can in particular be facilitated by the use of software developed for this purpose.

 The absence of (or the weak) cohesion between the two parts can be obtained by using some of the following criteria: materials having different transformation temperatures (in particular different change of state temperatures), injection at temperatures or pressures different, materials of different hardness or grades, ...

 "Sequential" (or time-shifted) injection can be subdivided into three different types. The first type of sequential injection consists of injecting two different materials into a single cavity, but by providing (unlike the simultaneous injection) a pause time between the end of the injection of a material and the start of the injection of the other. Thus, the absence of cohesion between the two materials can be obtained even more simply.

The second type of sequential injection consists, like the first type, in providing a pause time between the injection of the two materials, but also in delimiting the part of the injection cavity reserved for the first part using 'a part forming a "lock" or "barrier", removed before the injection of the second part. This amounts to:
- separate the mold cavity into two parts using such a lock,
- inject a first material into one of the parts of the molding cavity,
- remove the lock, and
inject a second material into the part of the mold cavity not yet filled.

 The delimitation of the volumes constituting the molding cavity and corresponding to each of the parts can thus be obtained even more simply.

The third type of sequential injection consists of:
inject a first material into a first cavity,
- then place the part obtained in a second molding cavity into which a second material is injected into the part not occupied by the first material.

 The second injected material somehow molds the first part, which then plays a role similar to that of a core.

The invention has also sought to provide a particularly suitable solution for the articulation of a cover on a body. To this end, the invention provides, in order to produce the articulation means having the characteristics mentioned above, that:
- one of the parts is injected so as to create:
- at least one tree (or section of tree) arranged as follows
the axis of rotation,
- a main part, and
- at least two holding zones to link the tree (or
section of tree) near each of its ends at the
main part of the room, and
- the other part is injected forming a bore surrounding the shaft (or section of shaft) over most of its length to pivot around it along the axis of rotation.

As a variant, the invention provides that:
one of the parts is injected so as to create at least one shaft (or section of shaft) arranged along the axis of rotation, and
- The other part is injected to create a main part and at least two holding zones connecting the tree (or section of tree) near each of its ends to the main part of this last part.

 These solutions, based in particular on “clevis” type joints, make it possible to obtain a robust, reliable and simple connection, therefore inexpensive.

 The invention has also attempted to provide a functional and ergonomic assembly of simple and practical use. For this, the injection is controlled to create an almost zero clearance between each of the articulation means.

 In practice, it is possible to modify the play existing between the parts to make it almost zero by modifying the shapes of the articulation means or the injection time, or even the injection temperature and / or the withdrawal of each of the materials injected. . It should be noted that the shapes of the articulation means can be all the more freely modified when the constraint of the mounting no longer exists. Indeed, it was until then compulsory to leave a fairly largely positive play between the means of articulations to be able to engage them one in the other. The almost zero clearance between the articulation means generates friction allowing the cover to be held in position for any opening angle, which is all the more appreciable since clearance can be adjusted almost at will from the control of the injection.

The invention will appear even more clearly in the description which follows, made with reference to the appended drawings in which:
FIGS. 1 and 2 show a first alternative embodiment of an articulated assembly according to the invention, respectively in side view and in top view,
FIG. 3 shows an enlarged top view of the articulation means of the first alternative embodiment,
FIGS. 4 and 5 show a second alternative embodiment of an articulated assembly according to the invention respectively in side view and in top view,
FIG. 6 shows an enlarged top view of the articulation means of the second alternative embodiment,
- Figures 7 to 14 show different variants of the process allowing the assembly of the assembly illustrated in Figures 1 to 3:
FIGS. 7 to 10 show in side view and from above different stages of a first variant of the process,
FIGS. 11 and 12 respectively show a side view and a top view of a second variant of the process,
- Figures 13 and 14 show respectively in side view and from above a third variant of the process.

 In Figures 1 to 3, there is illustrated an articulated assembly I defining a cosmetic case. This box essentially comprises a body 2 and a cover 10. The body has on one face 4, two openings 8a, 8b allowing access to two pockets 6a, 6b containing a product. In order to close the openings 8a, 8b, a cover 10 is articulated relative to the body 2.

 This cover 10 is movable in rotation relative to the body 2 about an axis 12 by means of articulation means 16, 18. In order to achieve satisfactory sealing of the openings 8a, 8b, the axis 12 is disposed outside the openings and is substantially contained in the plane of the access face 4. In fact, the axis 12 is slightly offset inside the body 2 so as to retract therein. The axis is therefore parallel to the access face 4. In other words, the axis 12 has a direction substantially perpendicular to the normal to the access face 4. The axis 12 can also be considered as substantially parallel to any plane tangent to the external contour of the body, at the level of the axis of rotation.

 In Figure 1, the cover 10 is shown in solid lines in the open position and in phantom in its closed position. The passage from one position to the other takes place by rotation of the cover 10 around the axis 12 as illustrated by the double arrow 14. In the closed position, the face 4 forms a junction surface between the body 2 and cover 10.

 The articulation means 16, 18 comprise a cylindrical shaft 16 arranged along the axis 12 and provided at each of its ends with a stud 16a, 16b guided in rotation in a bore 18a, 18b produced in the body 2.

These bores are formed in two holding zones 20a, 20b arranged at each end of the shaft 16 and are linked together by a solid part constituting the main part 3 of the body. Thus, it can be considered that the body 2 surrounds the shaft 16. The articulation means form a clevis-type articulation, the robustness and the reliability of the articulation are thus improved. In particular, the problems of robustness of the hinge type hinges where the shaft is held on one side (cantilever arrangement) are thus resolved.

 Furthermore, the outside diameter D16 of the pins 16a, 16b is substantially equal to the inside diameter dls of the bores 18a, 18b. Also, the length L20 between the two holding zones is substantially equal to the length L16 of the shaft 16. These two dimensional conditions each allow friction between the body 2 and the cover 10 to be obtained, so that the cover 10 is kept in its open position (whatever it is) relative to the body 2.

 In FIGS. 4 to 6, a variant of articulation means is illustrated. The body 22 comprises a main part 23 in which are formed two tubular recesses 24a, 24b arranged along an axis 32. These tubular recesses generate two corresponding shaft sections 28a, 28b, forming an integral part of the body 22 and linked to the body at the level holding zones 34a, 34b, 34c, 34d arranged on either side (at each end) of each of the shaft sections. The holding zones are linked together by the main part 23 of the body.

 The cover 30 is provided with bores 26a, 26b positioned around each of the shaft sections 28a, 28b in the direction of the axis 32. The bores 26a, 26b have a "closed" profile in the form of a circle ( therefore not "open" such as an arc of a circle), this in order to improve the robustness of the connection between the body 22 and the cover 30.

 FIGS. 7 and 8 illustrate, according to a first variant of the process, the production of the body 2 by injection of plastic material 42 into a mold 44 comprising two parts 44a, 44b between which a cavity 46 is formed. The injection is carried out by the intermediary of injection means 48 formed by nozzles 48a, 48b.

 The body 2 is then ejected and placed in a second mold 54, more precisely in a cavity 56 formed between two parts 54a, 54b of the mold. The cover 10 is then obtained by injection of plastic material 60 using an injection nozzle 58 disposed in the part of the cavity 56 where the body is not present. The progression of the front 57 of material 60 is illustrated by the arrow 59. The injection stops when the entire cavity 56 is filled, the material 60 coming into contact with the body 2.

 A variant for obtaining the body 2 is illustrated in FIGS. I1 and 12. This variant consists in using the mold 54 of FIGS. 9 and 10 and in placing there a lock 62 dividing the cavity 56 into two half-cavities 56a and 56b. The cavity 56a then corresponds to the cavity 46, it therefore remains to inject the material 42 by the injection nozzles 48a, 48b to obtain the body 2. After removing the lock 62 from the mold 56, it remains to operate as previously described to obtain the cover 60.

 Another variant is illustrated in FIGS. 13 and 14. The elements common to the previous illustrations have been repeated with the same numbering. Here, too, it is a question of injecting into the cavity 56 of the mold 54 material to produce the body 2 and the cover 10. However, here no lock is used to separate the two materials 42, 60.

 In fact, it is the control of the injection conditions, as explained above which determines the volume occupied by each of the materials.

 The material 42 intended to form the body 2 and injected by the nozzles 48a, 48b, and the material 60 intended to form the cover 10 and injected by the nozzles 58a, 58b are injected simultaneously. The material flow 42 splits into two fronts 72a, 72b when it meets a partition 70 of the mold 54 intended to form an operating clearance between the body and the cover on the finished assembly. The displacement of the fronts 72a, 72b is illustrated by the arrows 74a, 74b.

 The material flow 60 also splits into two fronts 76a, 76b when it meets the partition 70. The movement of these fronts 72a, 72b is illustrated by the arrows 79a, 79b.

 In the situation illustrated, the fronts 72a and 72b on the one hand, the fronts 79a, 79b on the other hand are currently forming the two holding zones 20a, 20b of the body 2 respectively (see FIG. 2) and the shaft 16.

 In order to more easily obtain the desired shape of the body 2 and of the cover 10, complementary injection means are placed near the junction between the two materials. Here, two nozzles 78a, 78b have been arranged to inject material 60 in the direction of the arrows 76a, 76b, which makes it possible to obtain the pins 18a, 18b on the cover.

 As an alternative to the illustrations in FIGS. 13 and 14, a pause time could be provided between the injection of one of the materials and the start of the injection of the other.

 It will be understood that, whatever the process of obtaining, the body and the cover are directly assembled during the molding of the part. I1 is therefore possible to make connections between the body and the cover usually qualified as "not mountable / not dismountable" (assembly and disassembly impossible without rupture of one of the parts after completion of each of them) as described above. .

 Of course, the invention is in no way limited to the embodiments described above. Thus, although an assembly is described defining a cosmetic case, the invention also applies to a service capsule, a device for dispensing liquid cream, a jar opening for cosmetic product, etc.

Claims (9)

Claims  1. Method for obtaining an articulated assembly (1) comprising a first part (2) forming a body for receiving a product and having in an junction surface (4) an opening (8a, 8b), and a second part (10 ) forming a cover movable in rotation relative to the first part so as to come into contact with the junction surface in one position and close the opening of the body, in which process:  - The two parts are injected so as to create articulation means (16, 18 26a, 28a; 26b, 28b) around an axis of rotation (12) whose direction is substantially parallel to the junction surface, these articulation means being intended to cooperate with one another in order to allow or close access to the opening, by relative rotation of the parts,  - Each of the parts is molded by injection of plastic material (s) into a molding cavity (46, 56) using separate injection means (or group of means) (48, 58), said process being characterized in that:  the parts are linked together substantially at the level of their articulation means during the injection of material (s), and  - The injection is controlled so that the materials (42, 60) of each of the parts do not weld.  2. Method according to claim 1, characterized in that:  - material is injected into a mold having a single cavity (56) from two groups of injection means (48a, 48b; 58a, 58b) injecting the material from each of the parts,  - Controlling the injection so that the fronts (72a, 74a, 76a, 76b) of material from each group of injection means meet at specific locations intended to form the border of the two parts.  3. Method according to claim 2, characterized in that at least during a period of injection, the two materials are injected simultaneously.  4. Method according to claim 2, characterized in that one spares an exposure time between the end of the injection of a first material and the start of the injection of a second material.  5. Method according to claim 4, characterized in that:  - the molding cavity is separated into two parts using a lock (62),  - a first material is injected into one of the parts of the molding cavity,  - the lock is removed, and  - A second material is injected into the part of the molding cavity which is not yet filled.  6. Method according to claim 1, characterized in that:  - a first material is injected into a first cavity,  - The part obtained is then placed in a second molding cavity into which a second material is injected into the part not occupied by the first material.  7. Method according to any one of the preceding claims, characterized in that:  - one of the parts is injected so as to create:  - at least one tree (or section of tree) (28a, 28b) arranged  along the axis of rotation (12; 32),  - a main part (3, 23), and  - at least two holding zones (30a, 30b, 30c, 30d) for  link the tree (or section of tree) near each of its  ends at the main part of the room, and  - The other part forming a bore (26a, 26b) surrounding the shaft (or section of shaft) is injected over most of its length to pivot around it along the axis of rotation (32).  8. Method according to any one of claims 1 to 6, characterized in that:  one of the parts is injected so as to create at least one shaft (or section of shaft) (16) arranged along the axis of rotation (12), and  - the other part is injected to create a main part (3) and at least two holding zones (20a, 20b) connecting the tree (or section of tree) near each of its ends to the main part of this last piece.  9. Method according to any one of the preceding claims, characterized in that the injection is controlled so that the play between said means of articulation of the parts is in certain places almost zero.