FR3085614A1 - HYBRID MOLD FOR PLASTIC INJECTION - Google Patents

Abstract

The present invention relates to a mold (1) for the injection molding of a part on a press, comprising at least a first fixed half-shell (2) and a second movable half-shell (3), said mold (1) being remarkable in that at least one of the first and second half-shells (2,3) comprises at least one carcass (4,5) and a skin (6,7) capable of being fixed on the internal face of the carcass (4,5) associated, in that each carcass (4,5) has on its internal face a pre-impression corresponding to a blank of the shape of one of the two faces of the molded part, and in that each skin (6,7) has at least on its external face a pre-imprint whose shape is complementary to the pre-imprint of the associated carcass (4,5), and on its internal face an imprint corresponding to the finished form of one of the two faces of the molded part.

Description

Technical area

The present invention relates to the general field of injection molding, in particular plastic. It relates more specifically to a mold for plastic injection but also to the method of manufacturing said mold.

Prior art

Injection molding is a technique intended for the manufacture in large or very large series of parts often very precise requiring no subsequent machining, and which one finds in very many manufactured products: automobile, household appliances, computer hardware, furniture, etc.

In the field of injection molding, it is known to use metal molds installed on a press and usually consisting of two shells, one movable and the other fixed, which are strongly pressed one against the other at the time of molding and then discarded to allow ejection of the molded part.

The design of the molds is very delicate, because in addition to the fact that the parts must be removed from the mold easily, it must be ensured that the mold is completely filled before the material solidifies. Furthermore, the external appearance of the molded part directly depends on the quality and precision of the molds. The latter are therefore first machined in the mass in a particularly careful manner by long milling or electroerosion operations, then they undergo various equally long finishing operations such as polishing and hard chromium plating. The cost of the molds is therefore very high and can only be amortized by mass production.

In addition, it is common for parts to retract

PROTO1-FR-1_TEXTE DEPOSE_RG / AG during cooling and sometimes enclose very strongly portions of the molds around which they were poured, they must then be extracted by means of sliding rods called ejectors, which further increase the cost of the molds.

Statement of the invention

The purpose of the present invention is to provide a mold for injection molding, in particular plastic, reliable, quick to manufacture and to implement, and particularly suitable for the manufacture of parts in small series.

According to the invention, a mold is therefore proposed for injection molding of a part on a press, comprising at least a first fixed half-shell and a second movable half-shell to be strongly pressed against the first half. shell at the time of molding and then discarded to allow ejection of the molded part, said mold being remarkable in that at least one of the first and second half-shells comprises at least one carcass arranged to be secured by its external face on said press, and a skin capable of being fixed on the internal face of the associated carcass, in that each carcass has on its internal face a pre-impression corresponding to a blank of the shape of one of the two faces of the molded part , and in that each skin has at least on its external face a pre-imprint whose shape is complementary to the pre-imprint of the associated carcass, and on its internal face an imprint co corresponding to the finished shape of one of the two faces of the molded part.

Each skin is preferably obtained by an additive manufacturing method.

According to an advantageous embodiment, the carcass of the first half-shell has a plurality of transverse orifices extending between its external and internal faces, and opening into the pre-impression and at least one of

PROTO1-FR-1_TEXTE DEPOSE_RG / AG their ends outside of said carcass, the associated skin has a plurality of transverse orifices extending between its external and internal faces and opening out of said skin, these transverse orifices being opposite said transverse orifices of said carcass, when the skin is placed in the latter, and the skin is fixed to the carcass of the first half-shell by inserting studs simultaneously into said respective transverse orifices of skin and carcass.

The transverse orifices of the skin of the first half-shell are preferably at least partially arranged in flanges projecting from the external face of said skin, said flanges being inserted in grooves of complementary shape hollowed out in the internal face. of the associated carcass, when fixing said skin.

According to an advantageous embodiment, the carcass of the second half-shell comprises a plurality of threads extending substantially perpendicularly to its external face from its pre-impression, the associated skin comprises a plurality of orifices passing right through it and opening out on one side in its pre-impression and on the other in its impression, said orifices being coaxial with the threads of said carcass, when the skin is placed in the latter, and the skin is fixed on said carcass by inserting a fixing screw in each of the orifices of said skin and by screwing it into the threads of the carcass.

The orifices and internal channel of the skin of the second half-shell are preferably at least partially arranged in flanges projecting from the external face of said skin, said flanges being inserted in grooves of complementary shape hollowed out in the internal face of the associated carcass, during the fixing of said skin.

PROTO1-FR-1_TEXTE DEPOSE_RG / AG

According to an advantageous embodiment, each fixing screw is at least partially hollow and closed, in a removable manner, by a plug at its free end, and comprises a transverse orifice allowing the interior of said screw to be brought into relation. fixing and the exterior, each fixing screw - plug assembly being configured so that the free end of said plug is flush with the internal face of the skin when the latter is fixed to the carcass of the second half-shell, said carcass 10 has an internal channel opening out at the right of its pre-impression and capable of being connected to a network of compressed air, and the skin comprises an internal channel aerally connecting said transverse orifices of the fixing screws between them and with said internal channel of the carcass, when the skin 15 is placed in the latter.

Brief description of the figures

Other advantages and characteristics will emerge more clearly from the description which of a mold according to the appended invention in which:

- Figure 1 is a mold according to the invention;

- Figure 2 is an internal of the carcass of the of Figure 1;

- Figure 3 is an internal of the carcass of Figure 1;

- Figure 4 is an internal skin associated

- Figure 5 is an external skin of the liver

- Figure 6 is a will follow of an ion embodiment with reference to the exploded perspective view of a perspective view of the second half-shell face of the mold perspective view of the first half-shell face of the mold perspective view of the face of the carcass of Figure 2;

perspective view of the face ure 4;

perspective view of the face

PROTO1-FR-1_TEXTE DEPOSE_RG / AG internal skin associated with the carcass of Figure 3;

- Figure 7 is a perspective view of the outer face of the skin of Figure 6;

- Figure 8 is a section of the assembly of the skin of Figure 4 on the carcass of Figure 2 associated;

- Figure 9 is a detail view of the assembly of Figure 8;

- Figure 10 is an exploded perspective view of a fastener of the assembly of the skin of Figure 4 on the carcass of the second half-shell of Figure 2 associated.

Best way to realize the technical invention

Referring to Figures 1 to 3, the invention relates to a mold 1 for an injection molding press, not shown, conventionally comprising two half-shells 2,3, the first half-shell 2 being fixed and the second half-shell 3 being movable in translation so as to be strongly pressed against the first half-shell 2 at the time of molding and then moved apart to allow the molded part to be ejected.

Each of the first and second half-shells 2,3 comprises at least one carcass 4,5 and a skin 6,7.

However, it is well understood that, if one of the two half-shells does not require complex and costly machining, only the other half-shell of the mold 1 according to the invention may comprise a carcass and a skin, without coming out of the scope of the present invention.

Each carcass 4,5 is advantageously metallic and arranged to be secured by its external face 41,51 on the injection molding press, said external face 41,51 being generally planar. To do this, each carcass 4.5 conventionally comprises, on the one hand, longitudinal grooves 42.52 arranged on the side of said external face 41.51

PROTO1-FR-1_TEXTE DEPOSE_RG / AG able to cooperate with the press to secure each carcass 4,5 according to a sliding connection and, on the other hand, holes 43,53 able to receive each of the centering columns, not shown, cooperating with rings to center the first and second half-shells 2,3 of the mold 1.

The term “internal face” denotes the face of a carcass or skin located on the side of the interior of the mold 1, that is to say on the side of the molded part, and the external face of the face of a carcass or skin located on the opposite side.

Furthermore, each carcass 4.5 has on its internal face 44.54 a pre-impression 45.55 corresponding to a blank in the shape of one of the two faces of the molded part, said pre-impression 45.55 being at least partially recessed and / or projecting. The two faces of the molded part are separated by the joint plane separating the first and second half-shells 2,3 of the mold 1.

In addition, the carcass 4 of the first half-shell 2 comprises a plurality of transverse orifices 46 extending between its external 41 and internal 44 faces, and opening into the pre-cavity 45 and at at least one of their ends outside said carcass 4.

Similarly, the carcass 5 of the second half-shell 3 also comprises:

- An internal channel 56 (see FIG. 8) opening in line with its pre-impression 55 and capable of being connected to a network of compressed air to bring compressed air to the level of the skin 7 of the second half shell 3, and

- A plurality of threads 57 extending substantially perpendicular to the external face 51 of the carcass 5 of the second half-shell 3 from said pre-cavity 55, and being able to cooperate with fixing screws 8 of the skin 7 on said carcass 5.

The mold 1 also includes skins 6,7 capable of being

PROTO1-FR-1_TEXTE DEPOSE_RG / AG fixed respectively on the carcasses 4,5 of the first and second half-shells 2,3.

With reference to FIGS. 4 to 7, each skin 6,7 has at least on its external face 61,71 a pre-impression 62, 72 whose shape is complementary to the pre-impression 45,55 of the associated carcass 4,5, and on its internal face 63,73 an imprint 64,74 corresponding to the finished shape of one of the two faces of the molded part.

In addition, with reference to FIGS. 6 and 7, the skin 6 has a plurality of transverse orifices 65 extending between its external 61 and internal 63 faces and passing right through it opening out of said skin 6 , these transverse orifices 65 being arranged to be opposite the transverse orifices 46 of the carcass 4 of the first half-shell 2, when the skin 6 is placed in said carcass 4, that is to say to say when the pre-imprint 62 of said skin 6 is in contact with the pre-imprint 45 of the carcass 4.

Thus, with this configuration, to fix the skin 6 on the carcass 4 of the first half-shell 2, studs, not shown, are advantageously inserted simultaneously into the respective transverse orifices 65, 46 of the skin 6 and of the carcass 4 , when the skin 6 is placed in said carcass 4.

In addition, with reference to FIGS. 4 and 5, the skin 7 has a plurality of orifices 75 passing through it right through, and emerging on one side in its pre-imprint 72 and on the other in its imprint 74, said orifices 75 being coaxial with the threads 57 of the carcass 5 of the second half-shell 3, when the skin 7 is placed in said carcass 5, that is to say when the pre-imprint 72 of said skin 7 is in contact with the pre-impression 55 of the carcass 5.

Furthermore, with reference to FIG. 8, the skin 7

PROTO1-FR-1_TEXTE DEPOSE_RG / AG has an internal channel 76 aeraulically connecting its orifices 75 to each other and opening out at the level of its pre-impression 72 opposite the internal channel 56 of the carcass 5 when the skin 7 is in place in the latter, so as to bring compressed air at the orifices 75 of the skin 7.

Thus, with this configuration, to fix the skin 7 on the carcass 5 of the second half-shell 3, the fixing screws 8 are inserted into the orifices 75 of the skin 7 and they are screwed into the threads 57 of the carcass 5 , when the skin 7 is placed in the latter.

However, the skins 6.7 may be fixed respectively to the carcasses 4.5 of the first and second half-shells 2.3 for any other suitable means without departing from the scope of the present invention.

The skins 6,7 of the mold 1 according to the invention are advantageously produced by an additive manufacturing method.

By additive manufacturing is meant here any manufacturing method which is opposed to subtractive manufacturing where material is removed to achieve the desired shape. Thus, conventionally, in additive manufacturing, the three-dimensional parts are constructed by adding successive layers of material under the control of a computer.

It is well understood that with the specific configuration of the mold 1 according to the invention, it is possible to quickly manufacture said mold 1 at a lower cost in order to produce injection molded parts in small series. Indeed, the carcasses 4,5 do not require precise and careful machining because they only have a pre-impression corresponding to the roughing of the faces of the molded part, and the skins 6,7 can be obtained quickly by additive manufacturing because they are of reduced thickness.

Furthermore, to further reduce the thickness of the

PROTO1-FR-1_TEXTE DEPOSE_RG / AG skins 6,7, the transverse orifices 65 of the skin 6 and the orifices 75 and internal channel 76 of the skin 7 are preferably at least partly arranged respectively in flanges 66,77 arranged in projection on the respective external faces 61,71 of the skins 6,7.

When fixing the skins 6,7 on the carcasses 4,5, said flanges 66,77 are then inserted respectively into grooves 47,58 of complementary shape hollowed respectively in the internal faces 44,54 of said carcasses 4,5.

It is understood that the implementation of the respective flanges 66,77 of the skins 6,7 makes it possible to further reduce the overall thickness of said skins 6,7 and therefore a saving on the time and the cost of their manufacture, because the material used in additive manufacturing is particularly expensive.

Furthermore, there is shown in the figures 6,7 skins made in two parts 6A, 6B and 7A, 7B (Cf. Figure 1) then assemble to be placed in the associated carcasses 4,5. However, it goes without saying that the skins 6, 7 can also be produced in one, three, four, etc. parts without departing from the scope of the present invention.

Finally, with reference to FIGS. 8 to 10, each of the fixing screws 8 intended to fix the skin 7 on the carcass 5 of the second half-shell 3 is advantageously at least partially hollow to allow the passage of compressed air, and closed, removably by a plug 9, at its free end, that is to say on the side of the skin 7. Each fixing screw 8 further comprises a transverse orifice 81 making it possible to put the interior in relation of said fixing screw 8 and the outside to allow the passage of compressed air from the internal channel 76 of the skin 7.

Finally, with reference to FIG. 9, each set of fixing screws 9 - plug 9 is configured so that the face

PROTO1-FR-1_TEXTE DEPOSE_RG / AG internal 91 of the free end of said plug 9 is flush with the internal face 73 of the skin 7 when the latter is fixed to the carcass 5 of the second half-shell 3 of the mold 1.

Thus, with this configuration of each fixing screw 9 - plug 9 assembly, once the molded part and the first and second half-shells 2,3 have been spaced apart, compressed air is injected which propagates successively in the internal channel 56 of the carcass 5, in the internal channel 76 of the skin 7, in the orifice 81 then inside each fixing screw 8 so as to push the plug 9 to separate it from the associated fixing screw 8 in order to eject the molded part from the second half-shell 3 and therefore from the mold 1.

Therefore, we understand that before molding a new part it is necessary to replace a plug 9 to close each fixing screw 8.

Possibility of industrial application

The mold 1 according to the invention applies to any type of injection molding and not only to plastic injection molding.

Finally, it goes without saying that the examples of mold 1 in accordance with the invention which have just been described are only specific illustrations, in no way limiting the invention.

Claims (6)

1 - Mold (1) for injection molding of a part on a press, comprising at least a first fixed half-shell (2) and a second movable half-shell (3) to be strongly pressed against the first half-shell (2) at the time of molding and then discarded to allow the molded part to be ejected, said mold (1) being characterized in that at least one of the first and second half-shells (2,3) comprises at least one carcass (4, 5) arranged to be secured by its external face (41,51) on said press, and a skin (6,7) capable of being fixed on the internal face (44,54) of the associated carcass (4,5), in that each carcass (4,5) has on its internal face (44,54) a pre-impression (45,55) corresponding to a blank of the shape of one of the two faces of the molded part, and in that each skin (6,7) has at least on its external face (61,71) a pre-impression (62,72) whose shape is complementary to the pre-impression (45,55) of the associated carcass (4,5), and on its internal face (63,73) an imprint (64,74) corresponding to the finished shape of one of the two faces of the molded part. 2 - Mold (1) according to claim 1 characterized in that each skin (6,7) is obtained by an additive manufacturing method. 3 - Mold (1) according to any one of claims 1 or 2 characterized in that the carcass (4) of the first half-shell (2) has a plurality of transverse orifices (46) extending between its faces external (41) and internal (44), and opening into the pre-impression (45) and at at least one of their ends outside said carcass (4), in that the associated skin (6) has a plurality of transverse holes (65) PROTO1-FR-1_TEXTE DEPOSE_RG / AG extending between its external (61) and internal (63) faces and emerging outside of said skin (6), these transverse orifices (65) being opposite said transverse holes (46) of the carcass (4), when the skin (6) is placed in the latter, and in that the skin (6) is fixed on the carcass (4) of the first half-shell (2) by inserting studs simultaneously into said respective transverse orifices (65,46) of the skin (6) and of the carcass (4). 4 - Mold (1) according to claim 3, characterized in that the transverse orifices (65) of the skin (6) of the first half-shell (2) are at least partially arranged in flanges (66) arranged in protrusion on the external face (61) of said skin (6), said flanges (66) fitting into grooves (47) of complementary shape hollowed out in the internal face (44) of the associated carcass (4), during fixing said skin (6). 5 - Mold (1) according to any one of claims 1 to 4, characterized in that the carcass (5) of the second half-shell (3) comprises a plurality of threads (57) extending substantially perpendicularly to its external face (51) from its pre-imprint (55), in that the associated skin (7) has a plurality of orifices (75) passing right through and opening on one side into its pre-imprint ( 72) and the other in its imprint (74), said orifices (75) being coaxial with the threads (57) of said carcass (5), when the skin (7) is placed in the latter, and that the skin (7) is fixed to said carcass (5) by inserting a fixing screw (8) in each of the orifices (75) of said skin (7) and by screwing it into the threads (57) of the carcass (5). PROTO1-FR-1_TEXTE DEPOSE_RG / AG 6 - Mold (1) according to claim 5, characterized in that the orifices (75) and internal channel (76) of the skin (7) of the second half-shell (3) are at least partly arranged in flanges (77) projecting from the external face (71) of said skin (7), said flanges (77) being inserted in grooves (58) of complementary shape hollowed out in the internal face (54) of the carcass (5 ) associated, when fixing said skin (7). 7 - Mold (1) according to one any of claims 5 or 6, characterized by what each screw of fixing (8) is at less in part hollow and closed, of removably, by a plug (9) at its free end, and comprises a transverse orifice (81) making it possible to relate the inside of said fixing screw (8) to the outside, each set of fixing screws (8 ) - plug (9) being configured so that the free end of said plug (9) is flush with the internal face (73) of the skin (7) when the latter is fixed to the carcass (5) of the second half shell (3), in that said carcass (5) has an internal channel (56) opening out at the level of its pre-impression (55) and capable of being connected to a network of compressed air, and in that the skin (7) has an internal channel (76) aerally connecting said transverse orifices (81) of the fixing screws (8) between them and with said internal channel (56) of the carcass (5), when the skin (7) is put in place in the latter.