FR2598648A1 - Mould for the manufacture of composite components and process for obtaining it - Google Patents

Abstract

Mould 1, 10 for the manufacture of composite components 2, characterised in that it consists a shape produced from a synthetic foam and in that its useful walls are covered with a different material other than foam.

Description

MOLD FOR THE MANUFACTURE OF COMPOSITE PARTS, AND METHOD FOR
VIEW OF ITS OBTAINING.

 The present invention relates to a mold intended for the manufacture of parts, and in particular of composite parts. It also relates to the process with a view to obtaining it.

 Plastic or composite parts have, as everyone can see, invaded our daily life. These types of parts are found in just about every field, and to name a few, note the automobile, boating, and home appliances. However, the technique for producing said pieces has remained laborious and very expensive to this day. In fact, according to the prior art, the molds intended for manufacturing are produced in different difficult successive stages which we will briefly describe below.

 We first make a model in wood or plaster, which must be the exact replica of the final piece to be made.

This operation is relatively simple for the realization of models of small dimensions, but it represents by itself a considerable work which is delicate and expensive, when one must make final parts of large dimensions. This is the case, for example, for the manufacture of a boat hull which can often reach several meters in length or even several tens of meters, and the model must also have these dimensions. So we can imagine all the difficulties that such an operation represents. But that's not all, because the said model must be not only perfect from the point of view of its dimensions, but also from the point of view of its forms, but also in its surface state. This is why it must then be checked, and sanded thoroughly, to be then coated with a release agent.This is again a long and delicate operation, therefore expensive. But that's not all, because the model is then used to obtain the final mold.

This is generally obtained by application on the model of successive layers of resin and glass fabric or the like.

After polymerization, the mold is separated from the model, and it is thanks to it that we can manufacture the desired part (s)
It is therefore easy to understand why the sanding of the model must be done with particular care. It is indeed its surface condition, which will condition the final external appearance of the manufactured part. But despite all the care given to the sanding of the model, we realize once the manufactured part is finished, that it always lets appear appearance defects, which will then have to be thoroughly reworked. In some cases, it is even necessary to remastify and repaint.

 As we have just demonstrated, the previous processes are complicated, delicate and expensive. But there are also other disadvantages. We can cite for example the fact, that large models made of wood or plaster are by their untransportable weight, at least without specialized equipment such as traveling crane. In addition the dimensional stability of these is more than doubtful, because they are sensitive to heat and humidity.

 The present invention therefore seeks to remedy these drawbacks and proposes a method, as well as a mold intended for its implementation, which is particularly simple and has a low cost price.

 The mold according to the invention consists of a shape produced with synthetic foam, the mechanical strength of which is provided by a composite material.

 Advantageously, the final appearance of the useful surface of the mold is obtained by applying thin sheets of aluminum or gel-coat after passing a primer.

 The developable or adjusted forms can be obtained directly in foam bars by cutting or machining, and optionally by assembling such elements.

 The other shapes can be obtained by one or more thin foam plates, which are deformed and kept in the desired position.

 The foam used can be poyurethane, epoxy or phenolic foam, or acrylic, polyethylene, polyvinylchloride or extruded or expanded polystyrene foam.

 The process for producing the mold according to the invention is particularly simple and inexpensive. It allows a very appreciable time saving which can reach 50 to 200% according to the size of this one. It also makes it possible to obtain a precise mold, of perfect symmetry, and having dimensional stability without competition. In fact, the mold according to the invention is insensitive to heat and humidity. It makes it possible to produce multiple shapes, namely, the said mold can combine convex, concave, right angles, acute, obtuse, reentrant or salient surfaces. On the other hand, the mold obtained is light and can be moved without any particular problem.

 The invention can be used in all types of industries and for example the automobile, nautical industry, aviation, household appliances, leisure, etc., and the fields concerned are those of contact laminates, laminates sandwiches, composites and low pressure injection.

 Other characteristics and advantages of the invention which will follow with regard to the appended drawings, which are given only by way of nonlimiting examples.

 Figure 1 is a perspective showing a mold according to the invention, and a part made therewith.

Figures 2, 3 and 3a show an element of the mold
Figure 2 is a perspective.

 FIG. 3 is a section along the transverse plane P of FIG. 2.

 Figure 3a shows a detail of Figure 3.

 Figures 4 to 12 show the different stages of production of the mold according to the invention. Figures 4 to 10 are perspective views while Figures 10 to 12 are cross sections.

 Figure 1 shows a mold (1) according to the invention, as well as a composite part (2) produced with it. The mold (i) may for example be intended to obtain the half hull of a catamaran float, a mast, a hull of a boat, or any other composite part. The mold can be either constructed in one piece, or made up of several individual elements (10) assembled with one another. Figures 2 and following show one of these elements.

 I, es Figures 3 to 12 show a first embodiment and its production method.

 According to this first embodiment, the mold (1,10) is such that its shape is made with one or more thin plates (16) of synthetic foam, and the useful wall (30) consists of one or more plates of thin aluminum (18). The struture of the mold t1, 10) is advantageously produced by an assembly of different couples (4) arranged vertically on a torque support (5). The said pairs (4) and support v5) are cut from synthetic foam sheets having a thickness of about 10 to 15 millimeters, The pairs (4) are braced by beams i6), constituted for example by polyethylene tubes with a diameter of 22 millimeters. The shape of the mold is produced by foam plates (16) with a thickness of 4 to 6 millimeters. The resistance of the mold is produced by reinforcing fabric (8 ′ and (8 ′) which can be, for example, glass fabric or the like, associated with resin of the epoxy or phenolic type.

Advantageously, the mold can include lateral (9) and upper (11) edges also produced with foam plates with a thickness of approximately 10 to 15 millimeters. The foam used in the production of the mold can be either polyurethane, epoxy or phenolic foam, or acrylic, polychlorovynil or extruded or expanded polystyrene foam. Advantageously, foam of the extruded polystyrene or acrylic type will be used. According to one of the characteristics of the invention, the useful part of the mold is covered with one, or several aluminum plates (18) of small thickness.

 Thus this or these plates can have for example a thickness of 0.05 to 0.4 millimeter to be sufficiently deformable and resistant.

 The different phases of the process for obtaining the mold according to the invention are shown in Figures 4 to 12.

 FIG. 4 represents the preparation of the pairs (4) of the lateral (9) and upper (11) edges as well as of the supports which are cut from sheets of synthetic foam.

The thickness of these plates can be from 5 to 20 millimeters.

The different elements (4,5,, 11) are then positioned relative to each other and then glued, as according to the figure (5). The couples (4) are then braced by beams (6). Figure 6 shows schematically, the establishment of these healds. To do this we trace on the song of couples
marks (12), and cut passages (13) intended to receive the said -woven fabrics. It then suffices to put glue (14) in the passages (13) and to position the so-called smooth (6) there.

 Figure 7 shows the setting of the side edges (9).

 FIG. 8 represents another phase of the process, which consists in gluing foam sheets (16) inside the mold. These sheets are first cut from foam sheets with a thickness of about 4 to 6 millimeters and then glued in the mold to the pairs (4) and the beams (6). Any excess material (160) is then removed. It may be advantageous to reinforce the mold with composite material (8,8 ') as shown in FIG. 9.

 FIG. 10 represents one of the important phases of the process, which consists in gluing, after cutting, thin aluminum plates (18). These ensure the good finish of the useful part of the mold, and are for example bonded to the resin by a vacuum process. To do this, simply pass the resin on the one hand on the foam plates (16) and on the other hand under the aluminum plates (18), and put them in contact (Figure 10). Bonding can be carried out under vacuum, as shown in FIGS. 11 and 12. For this purpose, the assembly to be bonded is isolated under a polyethylene sheet (20) glued all around the mold, and comprising a hole (21) connected to a vacuum pump (22) by a pipe (23). Starting the pump will cause the vacuum in the enclosure (24), and the polyethylene sheet (20) will be pressed against the aluminum plates ( figure 12). The vacuum will be maintained throughout the polymerization of the resin, or the drying of the adhesive.

The polyethylene sheet will then be removed, and if necessary the joints between the plates will be puttyed, to give a correct appearance to the useful surface of the mold.

 It would not go beyond the scope of the invention If the shape of the mold was not obtained with an assembly of thin plates, but was produced with a block of synthetic foam. One could for example (see Figure 2), obtain a shape (300) in a block of length L, width 1, and height h. Said shape being produced by any suitable means such as molding, machining, slicing or cutting.

 In the previously described embodiment, the useful wall of the mold is covered with aluminum foil, but it could be otherwise. Indeed, we could just as easily replace the aluminum sheets with a layer of resin and a polyester or epoxy primer. The primer can also be replaced by gel-coat itself polyester or epoxy.

 Of course, the invention is not limited to the embodiments described and shown by way of examples, but it also includes all the technical equivalents and their combinations.

Claims (12)

 1) Mold (1.10) for the manufacture of composite parts (2), characterized in that it consists of a shape (4,5,11,16,30) made of synthetic foam, and that its useful walls are covered with a different material (8,18) other than foam.  2) Mold according to claim 1, characterized in that its useful walls are covered with one or more aluminum plates (18) of small thickness.  3) Mold according to claim 1, characterized in that its useful walls are covered with a resin and a primer or a polyester or epoxy gel-coat.  4) Mold according to any one of the preceding claims, characterized in that its shape is produced in a block of synthetic foam (30).  5) A mold according to any one of claims l to 3, characterized in that its shape is produced by one or more thin plates of synthetic foam (16).  6) Mold according to claim 5, characterized in that the thin foam plate (s) (16) are glued or welded to pairs (4) themselves constituted by synthetic foam plates.  7) Its re-endicolon mold (, characterized in that the couples (4) are interconnected by cylindrical rails (6).  8) Method for manufacturing the mold according to any one of the preceding claims, characterized in that it consists of the following different stages:  a- make the shape of the mold using synthetic foam.  b- cut aluminum plates (18) of small thickness.  c- stick the aluminum plates (18) on the useful walls of the mold.  9) Method according to claim 8, characterized in that step "c" is replaced by the following step:  d- put resin on the useful wall of the mold then put a primer or gel-coat, polyester or epoxy.  10) Method according to any one of claims 8 and 9, characterized in that step "a" consists of the following successive steps:  e- cut the couples (4) and the couples supports () in synthetic foam plates, for example in extruded polystyrene or similar.  f- position the torques (4) on the supports (5) by gluing them.  g- install healds (6) to brace the couples (4).  h- cut the foam plates (16d to make the shape of the mold.  i- stick the plates (16) on the pairs - (4), to make the useful walls of the mold.  11) Method according to any one of claims 8 and 10, characterized in that the bonding of the aluminum plates (18) is done under vacuum.  12) Method according to any one of the preceding claims, characterized in that after step "i", it ~ reinforces the structure by laying a reinforcing fabric (8.8 '), fiberglass or the like coated with resin.