FR2620376A2 - Method for obtaining grips (belts) for cases made of reinforced cellular plastic - Google Patents

Abstract

Method for manufacturing grips (belts) for cases made of cellular plastic reinforced by metal or plastic profiled elements, of the type in which is introduced, directly into a mould equipped with high-frequency electrodes and having the dimensions corresponding to the finished product to be obtained, the quantity of the resin/foaming-agent mixture which is necessary and sufficient to obtain this finished product, the reinforcing element is introduced onto or into the mass of this mixture, the mould is closed and subjected to the high-frequency field for the time necessary to melt the PVC and to release the gases arising from the decomposition of the foaming agent, and the resulting finished product is extracted from the mould, which method is characterised in that the resin is used in the form of a liquid or "plastisol", and the metered quantity of the said "plastisol" is injected into a closed mould in which a vacuum is maintained.

Description

The present invention relates to methods for obtaining seat belts of reinforced cellular plastic material # in the automobile industry, of the type involving heating by a high frequency electric field, and more precisely a method of this type, in which is introduced directly into a mold fitted with high frequency electrodes and having the dimensions corresponding to the finished product, the necessary and sufficient quantity of the mixture of PVC powder or granules and of foaming agent for obtaining this finished product, the reinforcing element is introduced onto, or into the powder or granular mass, the mold is closed, it is subjected to the field at high frequency for the time necessary for the melting of the
PVC and gaseous release from the decomposition of the foaming agent, and the resulting finished product is extracted from the mold.

It has indeed appeared that this technique still presents certain application difficulties, in particular in the following cases
1. Production of parts with large variations in thickness. This is the case illustrated in FIG. 1 of the appended drawing, to the present Application which shows a part whose main portion l is connected to thin tabs 2.

 2. Precise centering of a metal reinforcement. This is illustrated in Figure 2, which shows, in cross section, a part 3, of relatively small thickness, but in which the flat metal insert 4 must be perfectly centered. Such centering is very difficult to achieve.

 3. The filling of the mold can only be done in an open mold. The distribution of the powder or granules is delicate. The joint surfaces must be free of powder or granules before closing the mold. This operation must be carried out very carefully, otherwise the joint surfaces of the molds will be damaged during closing.

 The present invention eliminates all of these difficulties. It consists in using, in place of a resin in pulverulent or granular form, a liquid form of the same resin, usually designated by the term "plastisol", and in injecting the metered amount of said plastisol into a closed mold in which the vacuum is maintained.

 Depending on whether the mold is partially or completely filled, the dosage of "plastisol" can be done by means of a metering pump or by jar under air pressure.

This technique makes it possible to produce very diverse parts, as illustrated in FIGS. 3 to 9 of the appended drawing:
- Figure 3 shows an evolutionary part 5 of complex shape.

 FIG. 4 represents a flat part 6 reinforced by a metal grid 7.

 - Figure 5 shows a U-shaped part, 8 reinforced by an expanded metal profile.

 In the case of FIGS. 4 and 5, it will be noted that the liquid plastisol easily passes through the meshes and the perforations, just as it is easily distributed in the thin areas of the parts.

 These different parts can receive very diverse surface conditions, for example the reproduction of a graining, an imitation of leather, wood, fabric, and the like.

 - Figures 6 and 7 illustrate in section, parts 10 and 11 reinforced by plastic or metallic surface profiles 12 and 13.

 FIGS. 8 and 9 illustrate the fixing, to parts 14 and 15, of fixing pins 16 or of stapling rails 17.

 In addition to these technical advantages, this new variant of the known method has various economic advantages. Thus the raw material is less expensive, since the manufacture of powders or granules is an expensive operation. In addition, the manufacturing times are shorter, because the liquid injection is much faster than the dosage of powder or granule.

Claims (3)

1. 4 Process for the production of crates belts in cellular plastic material reinforced by profiled elements in plastic or metallic material, of the type in which one introduces directly into a mold equipped with high frequency electrodes and having the dimensions corresponding to the product finished obtaining the necessary and sufficient quantity of the mixture of resin and foaming agent for obtaining this finished product, we introduce on, or in the mass of this mixture, the reinforcing element, we close the mold, we subjected to the field at high frequency for the time necessary for the melting of the PVC and the gaseous evolution resulting from the decomposition of the foaming agent, and the resulting finished product is extracted from the mold, a process characterized in that the resin is used in liquid or "plastisol" form. and the metered amount of said "plastisol" is injected into a closed mold in which the vacuum is maintained. 2. Method according to claim 1, characterized in that according to whether the mold is partially or completely filled, the metering of the plastisol can be done by means of a metering pump or by pot under air pressure. 3. Method according to claims 1 and 2, characterized in that the parts obtained can -receive surface conditions such as the reproduction of a graining, an imitation of leather, wood, fabric, and the like.