WO2001060601A1

WO2001060601A1 - Sandwich-type composite material and cases for instruments, in particular musical, made from same

Info

Publication number: WO2001060601A1
Application number: PCT/FR2001/000383
Authority: WO
Inventors: Philippe Marie Guy De Trogoff; Laurence Marie Fernande O'neill
Original assignee: Philippe Marie Guy De Trogoff; Neill Laurence Marie Fernande
Priority date: 2000-02-15
Filing date: 2001-02-09
Publication date: 2001-08-23
Also published as: FR2804899B1; AU3564101A; FR2804899A1

Abstract

The invention concerns a sandwich-type material, for use in making cases for instruments, in particular musical instrument and cello case made from same. The composite material (10) consists of a first skin (11), made of metallized acrylonitrile-butadiene-styrene (ABS), a core (12) made of polyvinyl chloride (PVC) foam, and a second skin (13) made of polyester terephthalate (PTEG). The three elements are assembled by bonding, using a single-component heat-activated polyurethane adhesive. The invention is particularly useful for making cases for musical instruments.

Description

COMPOSITE MATERIAL OF SANDWICH TYPE AND CASE OF INSTRUMENTS, ESPECIALLY MUSIC,

MADE FROM THIS MATERIAL

The invention relates to a composite material of the sandwich type, which can be used for the manufacture of instrument cases, in particular musical instruments, and cello case produced from this material.

Composite materials are often used for the production of parts where the weight / mechanical characteristics couple is essential. For parts that require very high rigidity, use is made of the so-called "composite sandwich" technique.

A composite sandwich has three different elements, which are integral: a first skin, an inner core, a second skin.

The first skin is made of thermosetting resin (epoxy-polyester-phenolic, etc.), reinforced with fabrics (glass-carbon etc.). The fabrics (twill-taffeta ...) are chosen and arranged in a preferential direction according to the efforts and constraints to which the piece will be subjected. The first skin can be obtained by manual stratification, under vacuum, or by the use of prepreg fabrics. The polymerization takes place at room temperature, in an oven or in an autoclave depending on the systems. The thickness of this first skin can vary from a few tenths to a few tens of mm, depending on the parts.

The core of the sandwich is generally made of a cellular material, the characteristics of which are: lightness and good resistance to compression. The most used materials are honeycombs (steel- aluminum- plastic) and polyurethane, polyvinyl chloride (PVC) foams.

The second skin takes up the constituent elements of the first skin, but its thickness is much smaller, since it only has the role of closing the "sandwich". The three elements of the composite sandwich are assembled by gluing, sometimes under vacuum, using thermosetting resin (epoxy or other), sometimes with high temperature adhesive films.

All these successive and complicated operations, very demanding in terms of skilled labor, using very sophisticated and expensive materials, have confined the use of composite sandwiches to excessively specialized applications in aeronautics, formula 1, ocean racing , high speed train (TGV), etc. For example, a cello case, made using this technique and with these materials, would weigh only 3.5 or 4 kg, but its price could exceed 15,000 F; therefore, cello cases are usually made of fiberglass or wood covered with fabric.

Currently known cello cases made by thermoforming of acrylonitrile butadiene styrene (ABS) plates. In the vast majority of cases, except for the very inexpensive standard cases, devoid of internal coating, the filling fabric is formed and glued automatically during the transformation operation. The ABS-formed case has a hot-formed PVC male-female profile, which provides sealing and has nine locks. Its weight is 5.5 to 7 kg, depending on the models and finishes.

The cello requires a very protective case. The best existing cases are heavy, because of the thickness of their walls, but are, despite this, not very rigid, which requires numerous closing points, thus making their handling inconvenient. The high-end cases play on the finish and the nobility of the materials, but however do not solve the problems of weight and rigidity.

The object of the present invention is to remedy these drawbacks. This invention, as characterized, solves the problem of creating a composite sandwich material, with which it is possible to make instrument cases, and in particular cello cases, offering great lightness, good rigidity, and excellent impact resistance, and this, for an acceptable price.

The sandwich-type composite material according to the invention is characterized in that it consists essentially of:

- a first skin in metallized acrylonitrile butadiene styrene (ABS),

- a core of polyvinyl chloride foam (PVC),

- a second skin in polyester terephthalate (PTEG).

The assembly of the three elements is obtained by vacuum bonding.

The process for manufacturing instrument cases, from the composite material according to the invention, comprises the following steps:

a) thermoforming, on a positive mold, of the first ABS skin - demolding and trimming,

b) application of polyurethane adhesive with a spray gun to the internal face of the first ABS skin, obtained in the previous step (a) - drying at room temperature,

c) press cutting of the elements of the core,

d) hot and vacuum forming, on a positive mold, of the elements of the core,

e) application of polyurethane glue with a spray gun to the core elements obtained in the previous step (d) - ambient drying, f) positioning of the pre-glued core elements on the internal face of the first thermoformed ABS skin, also pre-glued., g) placing the first skin-core complex under vacuum in a shaping device, then heating under a radiant panel, so as to reactivate the adhesive while maintaining the vacuum. Cooling - demolding,

h) application of polyurethane glue with a spray gun to the second skin - ambient drying,

i) application of polyurethane adhesive with a spray gun to the internal face of the first skin-core complex,

j) thermoforming, in a negative mold, of the second skin on the first skin-core complex, to close the sandwich, with reactivation of the adhesive under the radiant panel. Cooling - demolding.

According to a preferred embodiment, concerning, more particularly, the manufacture of cello cases, the thickness of the first skin is 1 mm for the cover and 1.50 mm for the bottom; the core is made of 8 mm thick foam with a density of 50 kg / m3; the second skin to a thickness of 0.5 mm.

The sandwich thus obtained is assembled by vacuum bonding, in a former, using a single-component polyurethane adhesive, applied with a gun and reactivated under a radiant panel.

The cutouts of the bottom and edges of the body of the case are made so that the different parts come to overlap each other, like a puzzle, while leaving, here and there, small reserves made up of parts of missing puzzle, allowing the second skin to stick directly to the first skin, thus trapping the soul. There are three to four locks for connecting the cover to the body of the case.

The advantages obtained, thanks to this invention, consist essentially in that the weight of a cello case is thus reduced from 4 to 4.5 kg, compared with 5 to 7 kg for the cases currently existing, and that the rigidity and the tightness obtained are such that the number of locks required can be reduced to 3 or 4, against 8 to 10 with the current technique, in that the impact resistance of the walls of the case is such that the instrument it contains is effectively protected against shocks, small or large, which can occur in all situations, and this, while maintaining this kind of case in a very reasonable price range compared to similar cases. The price incidence of 30 to 40% is perfectly acceptable for the protection of high-end, particularly expensive and delicate instruments.

Other characteristics and advantages will appear in the following description of a cello case, produced according to the invention, given by way of nonlimiting example, with regard to the appended drawings, in which:

FIG. 1 represents a side view, in perspective, of a sample of the composite material,

FIG. 2 represents an exterior view from below, in perspective, of the body of the case,

FIG. 3 represents an external view from above, in perspective, of the cover of the case,

FIG. 4 represents a side view of the case, furnished with a cello shown in dotted lines,

FIG. 5 represents a front view of the case according to FIG. 4, FIG. 6 represents a left view of the case according to FIG. 4.

The figures represent a composite material 10 of the "sandwich" type, comprising a first skin 11, a core 12 and a second skin 13, used for the production of a cello case 20, consisting of a body 21 and a cover 22; small reserves 212, left in the bottom 210 where the edges 211 allow the second inner skin 13 to come and stick directly to the first outer skin 11, trapping the core 12 of the material 10.

By examining FIG. 1 in more detail, it can be seen that the composite material 10 consists of the following three elements:

- A first skin 11 in metallized ABS, with a thickness of 1 mm for producing the cover 22 of the case 20, and 1.5 mm for the bottom 210 of said case 20; ABS having been selected for its mechanical characteristics of impact resistance, its good thermoformability and an excellent presentation. Other materials, such as polycarbonate and its derivatives, could however also be used,

- a core 12 of PVC foam, very light, the density of which can vary from 50 to 80 kg / m3, depending on the qualities; this PVC foam, very resistant to compression, almost indestructible, is used for its physical and mechanical characteristics,

- a second skin 13 made of PETG, 0.5 mm thick, chosen for its excellent thermoformability and its relatively low forming temperature range (60 to 70 °), which makes it possible to keep polyvinyl chloride foam (PVC) on which this skin is thermoformed all its thickness and all of its mechanical characteristics. The three elements are assembled by vacuum bonding with polyurethane glue.

Referring to Figures 2 and 3, we note that, for the production of cello cases 20, the first skin 11 of the sandwich 10 is obtained by thermoforming on a positive mold of a metallized ABS plate, of thickness 1.5 mm for the bottom 210 of the case, and 1 mm for the cover 22 of the latter.

Thermoforming on a positive mold notably allows, thanks to bubbling, to obtain regular thicknesses on the bottom and on the walls of the case.

The core 12 of the sandwich 10 is cut in the press using appropriate cutting tools, then formed under vacuum on a positive mold, after having been softened under a radiant panel. The cutouts of the bottom 210 and of the edges 211 of the body 21 of the case 20 are made in such a way that the different parts come to overlap one another, like a puzzle, while leaving, here and there, small reserves 212 (missing puzzle parts), which allow the second skin (inside) 13 to stick directly to the first skin (outside) 11, thus trapping the core 12 and preventing any delamination defect. The various bondings are carried out under vacuum in a conformator using a one-component polyurethane adhesive, applied with a gun and reactivated under a radiant panel.

Now examining FIGS. 4, 5 and 6, it can be seen that the case 20, produced as indicated above, completely and effectively envelops and protects a cello 30, which is perfectly wedged in all directions. The rigidity of the case 20 also makes it possible to limit the number of locks for closing the cover 22 to three or four.

The production of a cello case from the composite material of the "sandwich" type, according to the invention, is only one example of application of this one, because other kinds of cases can also be produced with this material and according to this process, subject to minor adaptations not going beyond the scope of the invention.

Claims

1. Composite material of the “sandwich” type, characterized in that it consists essentially of a first skin (11) made of metallized acrylonitrile butadiene styrene (ABS), of a foam core (12) polyvinyl chloride (PVC) and a second skin (13) polyester (PTEG).

2. Composite material according to claim 1, characterized in that its first skin (11), its core (12) and its second skin (13) are assembled by gluing.

3. Composite material according to claim 2, characterized in that the adhesive used is a one-component polyurethane adhesive.

4. Application of the “sandwich” type composite material according to claim 1, for the manufacture of instrument cases, characterized in that this manufacture is carried out according to the following steps:

a) thermoforming, on a positive mold, of the first skin (11) - demolding and trimming,

b) applying the adhesive with a spray gun to the internal face of the first skin (11) obtained in the previous step (a) and drying at room temperature,

c) press cutting of the elements of the core (12),

d) hot and vacuum forming, on a positive mold, of the elements of the core (12),

e) application of the glue with a spray gun to the elements of the core (12), obtained in the previous step (d), followed by drying at room temperature, f) positioning of the elements of the core (12) on the internal face of the first skin (11) pre-glued in step (b),

g) placing the first skin (11) and core (12) complex under vacuum in a former, then heating under a radiant panel to reactivate the adhesive while maintaining the vacuum, followed by cooling and demolding,

h) application of glue with a spray gun to the second skin (13) and drying at room temperature,

i) application of glue with a spray gun to the internal face of the first skin (11) and core (12) complex,

j) thermoforming, in negative mold, of the second skin (13), on the first skin (11) and core (12) complex to close the sandwich (10), with reactivation of the adhesive under the radiant panel, followed by cooling and demolding.

5. Application of the composite material of the "sandwich" type according to claim 4, in the manufacture of cello cases, characterized in that the thickness of the first skin (11) is 1 mm for the cover and 1, 5 mm for the bottom (210), in that the core (12) consists of a foam with a density of 50 kg / m3 and 8 mm thick and in that the second skin (13) has a thickness of 0.5 mm.

6. Application of the composite material of the "sandwich" type according to claim 5, in the manufacture of cello cases, characterized in that the cutouts in the bottom (210) and edges (211) of the body (21) of the case (20) are made so that the different parts come to overlap each other, like a puzzle, while leaving, here and there, small reserves (212) made up of puzzle parts missing, allowing the second skin (13) to stick directly to the first skin, thus trapping the core (12).

7. Application of the composite material of the "sandwich" type according to claim 5, in the manufacture of cello cases, characterized in that the locks for connecting the cover (22) to the body (21) of the case (20) are three to four in number.