METHOD FOR PRODUCE A BOWL WITH A DECORATIVE FILM

Description

Technical field

[0001] The present invention relates to the technical field of overmolding parts, preferably by injection. State of the art

[0002] The production of plastic shells is known from the state of the art, implementing molding and overmolding steps. More precisely, a first element of the shell is molded by hot injection of plastic material in a dedicated mold. This first element then serves as a support for overmolding one or more layers of plastic, in order to form a thick shell. Complex and robust plastic shells, comprising several inseparable elements, are thus formed.

[0003] According to another advantage, this method also allows the manufacture of plastic shells comprising materials of different nature to functionalize the shell. For example, a plastic shell may comprise a decorative film, configured to modify its light transmission or reflection properties. Preferably, the decorative film is encapsulated between two layers of plastic in order to protect it from the external environment.

[0004] However, this manufacturing method has the disadvantage of having to mold the decorative film, or overmold the decorative film against another element. However, the hot molding or overmolding process involves an injection step, in viscous or liquid form, of the plastic material forming the decorative film. This injection step involves the formation of a decorative film whose optical properties are more or less homogeneous along the shell. According to another disadvantage, overmolding the decorative film against an element of the shell and vice versa also implies that the dimensions of the decorative film are substantially equal to one or more elements adjacent to the decorative film. This manufacturing method therefore does not allow a wide variety of possible patterns and shapes for the decorative film. Another overmolding method is described in document US 2013 / 069274 A1.

[0005] According to another disadvantage, during the overmolding stages, the faces of the decorative film are exposed to high temperatures and pressures, likely to degrade and / or deform the decorative film and therefore its pattern.

[0006] This led to the need for a new process for manufacturing thick plastic shells, including a decorative film with varied patterns and preserving its characteristics as best as possible during the manufacture of the shell. Description of the invention

[0007] In order to achieve this objective, the invention proposes a method of manufacturing a shell, comprising a decorative film, implementing a first step of molding a plastic material so as to form a first element.

[0008] The invention is characterized in that the manufacturing method implements a second step consisting of applying a decorative film against a front face of the first element, then a third step of overmolding a plastic material on at least part of the decorative film and the first element, so as to maintain the decorative film between the first element and a second element of the shell.

[0009] In other words, the decorative film and the first element of the shell are produced independently. Thus, unlike the prior art method described above, the decorative film and the first element are not exposed to high temperatures and pressures during their joining, which could modify their characteristics. Indeed, this joining step is carried out at a temperature and pressure lower than those required to inject a plastic material into a mold. As a result, the properties of the interface between the decorative film and the first element are controlled more precisely.

[0010] It should be noted that the third step implemented by the invention makes it possible to form a second element of the shell, so that at least a portion of the decorative film is protected from the external environment by the first and second elements. Preferably, at least a portion of the second element is opposite the first element to ensure better retention of the decorative film between said elements.

[0011] According to another feature of the invention, the decorative film covers only part of the front face of the first element of the hull. In other words, the surface area of ​​the decorative film may be less than the surface area of ​​the front face of the first element. The invention thus provides a manufacturing method allowing a greater variety of shapes of the decorative film.

[0012] According to another feature of the invention, the first element and / or the second element is transparent and / or translucent. One of the elements is transparent or translucent, in order to allow an observer to observe the contours of the decorative film through said element. Preferably, the first and second elements are transparent in order to allow a light source to project the contours of the decorative film onto an observation plane.

[0013] According to another characteristic of the invention, the decorative film is perforated. Thus, the light transmission properties through the decorative film are heterogeneous along said film, to allow the creation of more complex and varied patterns.

[0014] According to another advantage, the presence of one or more holes makes it possible to form passages, through the decorative film, into which the second element can penetrate during the third overmolding step, so that the second element can adhere directly to the first element and thus ensure better maintenance of the decorative film between the first and second elements.

[0015] According to another advantage, the passages can form at least one housing in which a protrusion of the first element fits, located at its front face, in order to allow better maintenance of the decorative film along said face during the third overmolding step. This embodiment advantageously makes it possible to avoid an offset of the decorative film relative to the first element during the formation of the second element of the shell.

[0016] According to another embodiment of the invention, the first element and / or the second element comprises optical diopters aligned with at least one hole perforating the decorative film. The optical diopters make it possible to locally modify the intensity of a light beam passing through an element, to offer a greater variety of illumination of the hull.

[0017] According to another feature of the invention, the decorative film comprises at least two zones transmitting light differently. For example, the decorative film may comprise at least two zones of different colors. According to another example, the surface of the decorative film may be partially grained. According to another example, the decorative film may be composed of several distinct materials.

[0018] According to another characteristic of the invention, the decorative film is covered, at least partially, by a deposit of material. Preferably, the deposit of material covers the face of the decorative film applied against the first element. Thus, the decorative film forms a heat shield, making it possible to significantly limit the rise in temperature of the deposit of material during the third step of overmolding the second element onto the decorative film. The physical properties of the deposit of material are thus preserved, which makes it possible to avoid, during the third overmolding step, degradation of the pattern delimited by said deposit. The deposit of material consists of one or more layers. The transparency of the decorative film can then be modified depending on the nature and number of superimposed layers of material, from transparent to translucent to completely opaque.

[0019] According to a preferred embodiment, the material deposit is formed from an ink, preferably comprising metallic elements based on silver, aluminum or chromium. Thus, the material deposit can be deposited on the decorative film using a screen printing technique. In order to modify the appearance of the material deposit, its surface can be lightly abraded or brushed before the third overmolding step.

[0020] According to an alternative embodiment, the manufacturing method implements an intermediate step of applying an adhesion means to the decorative film, in order to ensure better retention of the decorative film against the first element during overmolding of the second element. This intermediate step is carried out before carrying out the second step, consisting of applying the decorative film against a front face of the first element. Preferably, the adhesion means is applied at the periphery of the face of the decorative film applied against the first element. For example, the adhesion means may comprise a dedicated double-sided glue and / or adhesive.

[0021] According to another characteristic of the invention, the front face of the first element is of complex shape and the decorative film is of a shape complementary to the front face of the first element. The term "complex shape" means a raised surface. This embodiment advantageously ensures better support of the decorative film against the first element, by avoiding slippage between these elements, in particular during the third overmolding step.

[0022] According to an alternative embodiment, the front face of the first element is concave and / or convex in shape. This characteristic takes advantage of the possibilities offered by the method according to the invention to produce shells of complex shapes which do not have any defects in appearance or shape insofar as the method according to the invention makes it possible to properly control shrinkage phenomena.

[0023] According to a preferred embodiment of the invention, the decorative film is a thermoformed plastic film. The thermoforming technique makes it possible to give the decorative film a certain rigidity and support, facilitating its positioning and its support against the first element of the shell in order to prevent it from wrinkling when it is overmolded by the second element of the shell.

[0024] According to another characteristic of the invention, the thickness of the decorative film is between 0.4mm and 0.6mm, preferably of the order of 0.5mm.

[0025] According to another characteristic of the invention, the local thickness of any part of a shell portion is less than or equal to 6 mm, preferably less than 4 mm. According to a characteristic of the invention, the local thickness of the shell is between 1 mm and 5 mm and preferably equal to or greater than 3 mm in order to give it a certain mechanical resistance to be used as an outer shell. The local thickness is measured at a distance greater than 1 mm from the edges of the shell portion. By local thickness, it is meant the smallest of the distances between two opposite faces of the first and second element, of a part of a shell portion.

[0026] According to another characteristic of the invention, the manufacturing method may comprise other intermediate overmolding steps, in order to form one or more additional thicknesses between the first and second elements of the shell.

[0027] According to another characteristic of the invention, the second element of the shell comprises at least one fixing means configured to hold the shell to a support. According to one embodiment, the fixing means may comprise a complementary shaped appendage with a housing present in the support.

[0028] According to a preferred embodiment of the invention, at least one element of the shell is formed from one of the following materials: Polymethyl methacrylate (PMMA), Polycarbonate (PC), Acrylonitrile butadiene styrene (ABS) or mixtures thereof. Of course, this list is neither limiting nor exhaustive.

[0029] The various features, variations and embodiments mentioned above may be combined with each other in various combinations, provided that they are not incompatible or mutually exclusive.

[0030] The invention also relates to a lantern for a motor vehicle comprising a shell obtained from one of the manufacturing methods described above. Description of figures

[0031] The invention will be better understood from the following description, which relates to preferred embodiments, given as non-limiting examples, and explained with reference to the appended schematic drawings, in which: there figure 1 is a side view of a first element of a hull according to the invention; the figure 2 is a top view of the first element illustrated in the figure 1 ; there figure 3 is a profile view of a decorative film positioned on a first element illustrated in the figure 1 ; there figure 4 is a top view of the assembly illustrated in the figure 3 ; there Figure 5 is a side view of a hull according to the invention; the figure 6 is a top view of the hull shown in Figure 5; there figure 7 is a bottom view of a decorative screen-printed film; the figure 8 is a bottom view of a decorative film according to the figure 7 , comprising a layer of glue; the figure 9 is a view of an alternative embodiment of a hull illustrated in Figure 5 ; THE Figures 10 and 11 are schematic views of alternative embodiments of a hull illustrated in Figure 5 ; there figure 12 is a schematic view of a longitudinal section of a lantern for a motor vehicle, comprising a shell illustrated in figure 11 . Description of detailed embodiments of the invention

[0032] As a reminder, the invention proposes a new method for manufacturing a thick plastic shell, comprising a decorative film with varied patterns and preserving its characteristics as best as possible during the manufacture of the shell.

[0033] For the purposes of the invention, a shell is a part whose thickness is small compared to its developed length or measured along one of its large faces when the shell is non-developable.

[0034] According to the invention, the manufacture of the shell 2 is carried out in the following way. In a first step, a first element 4 of the shell is molded by a hot plastic injection technique in a mold designed for this purpose. The plastic material used is, for example, Polymethyl methacrylate (PMMA). As illustrated in Figures 1 and 2, the first element 4 is delimited at its largest faces, by a front face 6 opposite a rear face 8. According to the present example, the surface delimited by the front face 6 is between a few cm 2< and a few m 2< . The thickness of the first element 4, defined as the distance separating the front face 6 from the rear face 8, is between 1.5mm and 3mm, preferably between 1.7mm and 2mm. According to the present example, the first element 4 is flat.

[0035] Then, during a second stage illustrated in Figures 3 and 4, a decorative film 10 is applied against the front face 6 of the first element 4. This second step is carried out after allowing the first element 4 to cool sufficiently, so that the temperature of its front face 6 is less than 80°C, preferably less than 60°C. This limits the risks of deformation or degradation of the rear face 12 of the decorative film 10, in contact with the front face 6 of the first element 4. The decorative film 10 may be of the same or different nature as the first element 4. The decorative film is preferably thermoformed in order to give it a certain rigidity and thus facilitate its handling. The thickness of the decorative film 10, separating its rear face 12 from an opposite front face 14, is between 0.4 mm and 0.6 mm, preferably of the order of 0.5 mm. The contour 16 of the decorative film is adapted according to the pattern that it is desired to produce in the shell 2.The invention thus allows a greater variety of pattern shapes by eliminating the need to overmold the decorative film 10 directly onto the first element 4 or to overmold the first element 4 directly onto the decorative film 10. According to the present example, the decorative film 10 is perforated in several places by holes 18, forming passages through said film. According to another characteristic, the dimensions of the decorative film 10 are smaller than those of the front face 6 of the first element 2. More precisely, the decorative film 10 is centered on the front face 6 of the first element 2. Of course, within the scope of the present invention, other dimensions of the decorative film 10 and other arrangements on the first element 2 are conceivable.

[0036] During a third and final stage illustrated in Figures 5 and 6, the decorative film 10 is overmolded by injection of a plastic material, compatible with that used to form the first element 4, in order to form the shell 2 according to the invention. More precisely, the plastic material is spread against the front face 14 of the decorative film 10 and the front face 6 of the first element 4, so as to encapsulate the decorative film 10 between the first element 4 and a second element 20. The material used to form the second element 20 may be of the same or different nature as that constituting the first element 4. The thickness of the second element 20, defined as being the distance separating a rear face 22 in contact with the decorative film 10 and the first element 4, and a front face 24 opposite the rear face 22, is between 1.5 mm and 3 mm, preferably between 1.7 mm and 2 mm.

[0037] Now, several alternative embodiments of the invention are described below. The elements common to these different variants are indexed by the same numerical references.

[0038] According to a first variant embodiment illustrated in the figure 7, the decorative film 10 comprises on its rear face 12 a pattern 30 delimited by a suitable ink 32. This embodiment is particularly advantageous when a decorative film with complex and precise patterns is desired. For example, the pattern 30 may be a screen print made on the rear face 12 of the decorative film 10. According to another advantage, the decorative film 10 forms a thermal protection shield making it possible to limit the rise in the temperature of the ink during the third step of overmolding the second element 20, in order to preserve the contours and the color of the ink 34. Of course, depending on the temperature to which the decorative film 10 is exposed during this third step, the thickness and / or the nature of the decorative film may be adapted so that the temperature of the ink 32 does not exceed a critical temperature, beyond which the color of the ink and the shape of the pattern delimited by said ink may be degraded.

[0039] According to another alternative embodiment of the manufacturing method described above and not shown, prior to the second step, an adhesive 34 is applied to the periphery of the rear face 12 of the decorative film 10 during an intermediate step. The adhesive 30 is configured to allow better retention of the decorative film 10 against the first element 4, during the third step of overmolding the second element 20. The adhesive used is preferably an adhesive that does not chemically attack the elements of the shell, nor the ink covering the decorative film. Preferably, the adhesive is configured to allow an operator to reposition the decorative film at will against the first element. According to an alternative, illustrated in figure 8, the glue is applied to the ink 32 so that the glue is not visible to an observer observing the pattern 30 through the decorative film 10. This embodiment advantageously makes it possible to conceal the bonding marks behind the pattern 30.

[0040] According to another variant illustrated in the figure 9 , the first element 4 may comprise optical diopters 36 at its rear face 8, arranged so as to be aligned with the holes 18 perforating the decorative film 10. By the term “optical diopters” is meant elements modifying the trajectory of a light beam passing through the first element 4.

[0041] According to another variant illustrated in the figure 10, the first element 4 is of complex shape. The decorative film 10 covers only a portion of the front face 6 of the first element 4 and the second element 20 also covers a portion of the front face 6 of the first element 4 and a portion of the front face 14 of the decorative film 10.

[0042] According to a variant illustrated in the figure 11 , the second element 10 comprises at its front face 24 a protrusion 28 configured to cooperate with a support 38, in order to keep the shell 2 at a distance from the support.

[0043] As illustrated in the figure 12 , the invention also relates to a lantern 40 for a motor vehicle, comprising a light source 42 present in a box 44 open on one of its sides. The opening of the box is closed by a shell 2 as illustrated in the figure 11, so as to form an external wall of the lantern. As mentioned above, the decorative film 10 is perforated in several places by holes 18, so as to allow the light rays 46 emitted by the light source 42 to pass through. According to the present example, the other light rays are partially or totally absorbed by the decorative film 10 so as to more clearly demarcate the contours of the holes 18. According to an alternative not shown, the decorative film can be partially transparent and colored in order to form a background of homogeneous color on which the patterns formed by the holes 18 stand out.

[0044] Furthermore, various other modifications may be made to the invention within the scope of the appended claims. holes 18, so as to allow the light rays 46 emitted by the light source 42 to pass through. According to the present example, the other light rays are absorbed partially or totally by the decorative film 10 so as to more clearly demarcate the contours of the holes 18. According to an alternative not shown, the decorative film may be partially transparent and colored in order to form a background of homogeneous color on which the patterns formed by the holes 18 stand out.

[0045] Furthermore, various other modifications may be made to the invention within the scope of the appended claims.

Claims

1. A method for manufacturing a shell (2), comprising a decorative film (10), implementing a first step of moulding a plastic material so as to form a first element (4), characterized in that the manufacturing method implements a second step consisting in applying a decorative film (10) against a front face (6) of the first element (4), then a third step of overmoulding a plastic material on at least one part of the decorative film (10) and of the first element (4), so as to maintain the decorative film (10) between the first element (4) and a second element (20) of the shell (2), wherein the first element (4) and / or the second element (20) include optical dioptres (36) aligned with at least one hole (18) perforating the decorative film (10).

2. The method for manufacturing a shell (2) according to the previous claim, characterized in that the decorative film (10) covers only a part of the front face (6) of the first element (4) of the shell (2).

3. The method for manufacturing a shell (2) according to one of the previous claims, characterized in that the first element (4) and / or the second element (20) is transparent and / or translucent.

4. The method for manufacturing a shell (2) according to one of the previous claims, characterized in that the decorative film (10) includes at least two areas transmitting differently the light.

5. The method for manufacturing a shell (2) according to one of the previous claims, characterized in that the decorative film (10) is covered, at least partially, by a deposit of material (32).

6. The method for manufacturing a shell (2) according to the previous claim, characterized in that the deposit of material covers the face of the decorative film (10) applied against the first element (4).

7. The method for manufacturing a shell (2) according to claim 5 or 6, characterized in that the deposit of material (32) is formed from an ink, comprising preferably metallic elements.

8. The method for manufacturing a shell (2) according to one of the previous claims, characterized in that it implements an intermediate step of applying bond mean (34) on the decorative film (10), in order to ensure a better holding of the decorative film (10) against the first element (4) during the overmoulding of the second element (20).

9. The method for manufacturing a shell (2) according to one of the previous claims, characterized in that the front face (6) of the first element (4) has a complex shape and in that the decorative film (10) has a shape complementary to that of the front face (6) of the first element (4).

10. The method for manufacturing a shell (2) according to one of the previous claims, characterized in that the decorative film (10) is a thermoformed plastic film.

11. The method for manufacturing a shell (2) according to one of the previous claims, characterized in that the second element (20) of the shell (2) comprises at least one fixation means (28) configured to maintain the shell (2) to a support (38).