Method for manufacturing by injection, a part made of a plastic material including a technical face incorporation a reinforcing element

Abstract

This process for manufacturing a plastic part (1) having a first technical face and a second face, in a mold comprising a first shell intended to form the first face endowed with impressions intended to form technical members of the technical face and a second shell intended to form the second face, the first shell and the second shell delimiting a cavity that forms the part (1), comprises the following steps:providing a porous reinforcing element (3);draping the reinforcing element (3) over the first shell by covering the surface of the first shell and the impressions intended to form the technical members;retaining the reinforcing element (3) on the first shell by retaining means;bringing the first shell and the second shell together;injecting a plastic in order to fill the cavity, the plastic passing through the porous reinforcing element (3) in order to fill impressions intended to form the technical members;moving the first and second shells apart;ejecting the plastic part (1).

Claims

1. A method for manufacturing a part made of a plastic material having a first technical face and a second face, in a tooling comprising a first shell for forming the first face, the first shell provided with imprints for forming technical members of the first technical face and a second shell intended for forming the second face, the first shell and the second shell delimiting a cavity forming the part, wherein the method comprises the following steps of: providing a porous reinforcing element that comprises a woven textile having an opening coefficient of 50%, wherein the woven textile is a polyamide-based textile having a basis weight of about 60 g/m.sup.2; drape-molding the porous reinforcing element on the first shell, the reinforcing element covering a surface of the first shell as well as the imprints that are used to form the technical members; retaining the porous reinforcing element on the first shell in a non-mechanical fashion; bringing the first shell and the second shell close to each other; injecting a plastic material to fill the cavity, the plastic material passing through the porous reinforcing element as it fills the imprints in order to form the technical members; separating the first and second shells and; and ejecting the plastic part.

2. The method for manufacturing a part made of a plastic material according to claim 1, wherein the retaining of the porous reinforcing element is achieved by an adhesive interposed between the porous reinforcing element and the first shell.

3. The method for manufacturing a part made of a plastic material according to claim 2, wherein the adhesive is deposited over the porous reinforcing element, the porous reinforcing element being then positioned on the first shell prior to the injecting step.

4. The method for manufacturing a part made of a plastic material according to claim 2, wherein the adhesive is deposited over the first shell, the porous reinforcing element being then positioned on the first shell.

5. The method for manufacturing a part made of a plastic material according to claim 2, wherein the adhesive is pre-glued to the porous reinforcing element, then the porous reinforcing element with the adhesive is being directly positioned on the first shell.

6. The method for manufacturing a part made of a plastic material according to claim 2, wherein the adhesive is formed based on an aqueous adhesive.

7. The method for manufacturing a part made of a plastic material according to claim 1, wherein the retaining of the porous reinforcing element on the first shell is achieved by electrostatic retention of the porous reinforcing element on the first shell.

8. The method for manufacturing a part made of a plastic material, according to claim 1, wherein the retaining of the porous reinforcing element on the first shell is achieved by electromagnetic retention of the porous reinforcing element on the first shell.

9. The method for manufacturing a part made of a plastic material according to claim 1, wherein the second face of the part constitutes its apparent face.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a proper understanding, the invention is described with reference to the appended drawings representing as a non-limiting example one embodiment of the invention:

(2) FIG. 1 shows in perspective a part made of a plastic material intended to equip a motor vehicle;

(3) FIG. 2 shows in section a part made of a plastic material according to the invention;

(4) FIGS. 3 to 8 show the steps of manufacturing the part shown in FIGS. 1 and 2 of the method according to the invention.

DETAILED DESCRIPTION

(5) FIG. 1 shows a interior trim part 1 intended to ensure the interior lining of the passenger compartment of a vehicle. While the invention is described with reference to a interior trim part, the invention concerns all parts made of a plastic material intended to be embedded on a motor vehicle.

(6) The interior trim part 1 has a first face and a second face opposite to the first face.

(7) The first face is called technical face A, which carries a number of technical members such as, for example, fastening clips, staple holders 2 or networks of ribs and the second face called apparent face B, that faces the passenger compartment.

(8) As shown in FIG. 1, the interior trim part 1 has a relatively complex clumsy general shape which is preferably made of a thermoformable material and in particular thermoplastic material such as, for example, polypropylene or ABS-PC.

(9) FIG. 1 and FIG. 2 show an important feature of the interior trim part 1 according to the invention, which is the presence of a reinforcing element 3 which is drape-molded over the entire technical surface A, with the exception in the example represented in FIG. 1 of a strip limited to a few millimeters of the piece border edges.

(10) The reinforcing element 3 is constituted by a porous material which, as will be seen later on, enables the plastic material that forms the interior trim part 1 to flow throughout this same reinforcing element 3 during the injection.

(11) The reinforcing element may be, for example, formed by a polyamide-based woven textile having a basis weight of 60 g/m.sup.2 and a thickness of 180 micrometers.

(12) The method which allows making the interior trim part 1 is implemented in a conventional injection-molding tooling which is shown in FIG. 3 and which comprises a fixed shell 4 and a movable shell 5 between which is defined a cavity which forms the part to be molded. The tooling is equipped with an injection unit 6 upstreams and a conveyor 11 for the finished parts downstreams.

(13) The method comprises the following steps.

(14) The reinforcing element 3 may be initially packaged into a roll or into a stack of individual portions.

(15) Initially as shown in FIG. 4, the reinforcing element 3 which, in the example represented in this figure, originates from a roll 7 is deposited over a table 8.

(16) From its position on the table 8, the reinforcing element 3 may be displaced by a gripper arm 9 as shown in FIG. 5.

(17) The reinforcing element 3 is coated with an adhesive 10. Preferably, the adhesive 10 consists of an aqueous glue which can be deposited over the reinforcing element 3 by spraying by a spraying system 12 as illustrated in FIG. 6. The adhesive 10 may also be deposited by roll coating.

(18) In one embodiment, the reinforcing element 3 may be pre-glued.

(19) A partial drying phase of the adhesive film follows. This drying phase may take place in ambient air or may be accelerated by heat input.

(20) Afterwards, the reinforcing element 3 is placed in the molding tooling as represented in FIGS. 7 and 8.

(21) In other embodiments of the invention, it may be considered that the retention of the reinforcing element 3 is achieved by means other than a pre-glued adhesive, sprayed on the reinforcing element 3 or sprayed on the shell 4.

(22) Indeed, it may be considered to achieve the retention of the reinforcing element 3 by electrostatic means. For this purpose, the reinforcing element 3 may be ionized prior to its set-up against the shell 4.

(23) The reinforcing element 3 may also be retained by electromagnetic means. For this purpose, the reinforcing element 3 may be provided with a primer charged with metal particles and the tooling can be provided with electromagnetic elements which ensure the retention of the reinforcing element 3 against the shell 4.

(24) The reinforcing element 3 achieves a drape-molding which may extend over the entire shell that will form the technical face A. A point that is important to be noted is that the shell 4 that will form the technical face A is provided with imprints which will themselves form the ribs and other staple holders of this technical face A. The reinforcing element 3 is deposited overhang of these impressions. In other words, the reinforcing element 3 is affixed and is held by the adhesive on the shell forming the technical face A while covering the imprints that form the technical members: ribs and fastening members.

(25) The reinforcing element 3 is accurately and repeatedly positioned, for example, by a robot arm 9 and remains in position in the tooling by the adhesive 10 with which it is coated. Moreover, it may be noted that the reinforcing element 3 can be positioned on complex shapes because it is directly affixed to the shapes in question and thus avoids the need for mechanical retaining means.

(26) Alternatively, the adhesive is sprayed directly on the surface of the shell and the reinforcing element 3 is then positioned on the shell and is held in position by the adhesive.

(27) Afterwards, the tooling is closed by bringing the two shells 4 and 5 close to each other and the plastic material is injected into the molding cavity, bearing in mind that the reinforcing element 3 is held against the surface of one of the shells by the adhesive 10. It may be noted that the tooling is devoid of any specific equipment such as needles or other to ensure holding of the reinforcing element in place. During the injection, the reinforcing element 3 which is held in place by the adhesive 10 does not fold nor does it migrate beyond the technical face by the effect of the injection of the plastic material.

(28) In this respect, the method according to the invention differs from the techniques of the prior art in which a reinforcing layer is held by mechanical means which create tensions in the reinforcing layer which prove to be deleterious for the final quality of the part.

(29) During injection, the plastic material passes through the reinforcing element 3. This is made possible by the fact that the reinforcing element 3 is porous and does not prevent the plastic material from passing through the meshing thereof. This is particularly important because the plastic material in the molten state can thus pass through the reinforcing element to fill the cavities that form the ribs and other staples holders that are drape-molded by the same reinforcing element.

(30) After injection of the plastic material, the shells are separated and the interior trim part 1 is ejected. The interior trim part 1 thus obtained does not require any type of cutting or shaving recovery operation.

(31) During the injection of the plastic material, the adhesive disintegrates and does not create fouling or pollution of the tooling.

(32) It should be noted that the same tooling can indifferently make parts with a reinforcing element or parts without any reinforcing element because the tooling is not impacted by the presence or absence of a reinforcing element in the part.

(33) The invention thus provides a method for making a complex part made of a plastic material which incorporates a reinforcing element.

(34) The part thus formed has an impact resistance which, with equal mass, is very substantially improved.

(35) Hence, this method is particularly but not exclusively intended for the manufacture of automotive parts that are likely to experience significant stresses such as interior trim parts masking airbags but also parts such as degassing boxes, air distributor, oil sump . . . .

(36) Of course, the invention is not limited to the embodiment described hereinabove as a non-limiting example but encompasses all variants thereof.