FR2831229A1 - Joining procedure for two components consists of inserting self-hardening plastic into adjoining shaped holes and leaving to set - Google Patents

Abstract

The procedure for joining two components (1, 2), e.g. for attaching a component to a vehicle trim strip, uses a plastic or other soft self-hardening material (3) inserted into adjoining cavities in the two components, one of which is undercut to ensure a reliable fixing. The plastic or soft material is poured or molded in the cavities and allowed to set to form a reliable fixing. The undercut cavity can be made in a variety of shapes, including dovetail or hooked section, and it can be used to hold one end of a fastener that receives the second component. The plastic material, preferably a plastomer or elastomer, can be applied manually or with a pneumatic tool and can, where necessary, be heated to harden it.

Description

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Method for joining two parts to each other, by complementarity of forms, and device for implementing said method
The present invention relates to a method of producing an obstacle connection between two parts, using a connection means comprising a curable plastic or plasticizable material. The invention also relates to a device for implementing said method according to the invention.

 When two parts are connected together, for example when attaching a fastener to a decorative strip of a motor vehicle, it is very often necessary to ensure that a decorative surface of the strip, visible after mounting finished, is not damaged, or that its visual appearance is not altered in any way. For example, no hole opening for a screw connection should be made in the room. In the same way, too much heating when the connection is made can have very negative consequences on the visual appearance of the decorative surface and ultimately render the part unusable.

It is known to connect parts in such a way that a decorative surface of a part is not degraded. Usually, a bonded bond is used between the two parts
In a bonded assembly, the surfaces of the parts to be bonded must be mechanically prepared beforehand, which can be achieved by sandblasting or by the action of various suitable chemical substances. Mechanical preparation, on the one hand, is used to clean surfaces for bonding, that is, to remove dirt, grease and other impurities; on the other hand, sanding makes the bonding surfaces rough, which has the effect of increasing their surface.

 Very often, the materials of the parts do not allow a direct application of the adhesive to mechanically prepared surfaces, because the anchoring of the adhesive is insufficient. The problem is solved by applying a bonding product on the surfaces of the parts. An additional hardening varnish is then applied to the bonding product.

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 In general, it is only after these preparation operations that the adhesive can be applied to the bonding surfaces and that the parts can be assembled. Once the parts are assembled and tightened, the adhesive is left to harden.

 A bonded bond undoubtedly has many advantages., It makes it possible in particular to connect them pieces in practically any material. Above all, a bonded connection makes it possible to connect non-weldable parts together or even very fine parts. It is frequently used to join metals with other materials, such as wood, plastics, rubber, glass or porcelain.

 However, a bonded bond has a number of drawbacks. An important drawback is that a bonded bond often does not withstand high loads, even with rough surfaces. This is all the more true in the case of tensile forces which are not exerted parallel to the bonding surfaces: in this case no bonding by obstacle (microscopic) reinforces the bonded bond and only the adhesion forces of the bonded bond act.

 On the other hand, a bonded bond does not offer sufficient resistance to bad weather and often its stability depends to a large extent on external influences.

 In addition, as seen above, a relatively large number of operations are necessary to make a bonded bond, which involves a commitment in important material and involves costs in energy and in high materials. It should also be noted that the significant polluting emissions which accompany bonding are not without posing certain ecological problems.

 Parts can also be connected other than by gluing, for example by welding. An important drawback of the welding connection is that it can only be applied with weldable materials and that even weldable materials, for example certain aluminum alloys, are sometimes difficult to weld. Furthermore, welding leads to a high thermal stress on the material, which can alter the visual appearance of a decorative surface of a part to the point that the part no longer meets the requirements and is no longer usable.

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 From there, the object of the present invention is to provide a method for connecting two pieces together, among which at least one has a decorative face whose visual appearance must not be altered by the connection, which allows d 'Avoid the disadvantages of the methods known from the prior art.

 The published application of German patent DE 199 29 480 A1 describes a bonding process, in which recesses, holes or undercuts are arranged in planar objects to be assembled, which recesses, holes or undercuts are then filled with adhesive. when pasting.

 US Patent No. 2, 255.184 presents a method of assembling parts, in which the parts, for bonding purposes, are each provided with an undercut cavity open on one side.

 US Patent No. 3, 309123 presents a method of assembling parts, in which the connecting means for assembling the parts comprises hooks.

 The German utility model DE 1 956 803 U presents a method of assembling parts, in which the parts have cavities inclined relative to the surface of the parts.

 The published application of the German patent DE 1 752343 presents a method of assembling parts, in which, in a bonded connection, an additional connection means is added, in the form of a hollow rod.

 However, none of the documents mentioned proposes a process such as that of the invention.

 The invention provides a method for connecting a first part and a second part together using a curable plastic or plasticizable material, in which the first part is provided with at least two cavities inclined with respect to the surface of the part, in particular obtained by rotation of 1800 around an axis normal to the surface of the part, which communicate with each other and open into the same face of the part, in which the second part is provided with at least two holes through holes, which are aligned with the cavities in the first part, and in which the first part is connected to the second part by casting or molding the plastic or plasticizable material in the through holes and in the cavities.

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 To connect the two parts, the plastic or plasticizable material is poured or molded into the cavities of the first and second parts. Additional openings which open into the cavities can be provided for this purpose. Due to the inclination of the cavities, the curable material present in them is firmly anchored in the part concerned. The curable material, at the end of the through holes remote from the assembly face of the part, forms a collar which retains the second part.

 A configuration of this type allows a very simple filling using the curable material, filling which is carried out either via the through hole in the second part, or via the inclined cavity which opens into the surface of the first part.

 The invention also provides a method for connecting a first part and a second part to each other using a curable plastic or plasticizable material, in which the first part is provided with at least one open undercut cavity. on one side, in which the plastic or plasticizable material is cast or molded, in which the plasticizable material has hooks for connection to the second part, the hooks of the plastic or plasticizable material being connected to the second part.

 Advantageously, the non-through hole has a circular or rectangular cross section. The circular through hole, preferably, has a cross-sectional diameter in the range of 0.1 to 5 mm, preferably in the range of 0.1 to 2 mm.

 According to an advantageous embodiment of the invention, the undercut cavity open on one side is a groove.

 According to the present invention, the plastic or plasticizable material can be poured or injected into the cavities or through holes concerned by application of an overpressure or a vacuum.

 As regards the curable material, it is preferably a thermoplastic material (plastomer), a thermosetting material (duromer) or an elastomer.

 As thermoplastic materials, it is possible in particular to use all plastics, for example polyolefins, vinyl polymers, polyamides, polyesters, polyacetates, polycarbonates, polyurethanes and ionomers.

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 Suitable thermosetting materials are, in particular, all plastics made from curable resins, for example diallyphthalate resins, epoxy resins, urea formaldehyde resins, melamine formaldehyde resins, phenolformaldehyde resins and unsaturated polyester resins.

 As elastomeric materials, all the polymers obtained by vulcanization of natural or synthetic rubbers can be used.

 The curable material can be a multi-component, for example it can be a two-component material. To increase the resistance of the bond, one can still use. fiber-reinforced materials.

 The plastic or plasticizable material can likewise be an adhesive. In addition to the obstacle bond according to the invention, the adhesive forces of the bonded bond make it possible to obtain a bond by adhesion and thus further increase the strength of the assembly. . Unlike a traditional bonded bond, in which there is essentially an adhesion bond, it is possible to obtain with the method according to the invention a combined bond by adhesion and by complementarity of forms. The resistance of the connection between the parts can be increased, when the joining surfaces of the two parts are provided at least partially with adhesive.

 As an alternative solution, the curable material can be metallic. The metal, for its casting or its molding in the cavities or through holes according to the invention, open on one side, in the first and if necessary in the second part, must only be heated to a temperature higher than the temperature of solidus.

 In the present invention, the first part and possibly the second part may include a decorative surface which does not undergo any optically penalizing alteration due to the connection between the first and the second part. The second part, however, is preferably a fastening element, in particular in the form of a clip, a clip or the like, for the indirect fixing of the first part to a device or to a mounting element. Particularly advantageously, the connection between the first and the second part can be dismantled by plasticizing the hardened material. In particular, a fastening element (i.e. the second

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 part) for indirect fixing of the first part can be removed. Thus for example it is possible to place on the first part, for further machining thereof, a fixing element which, advantageously, will be easily eliminated at the end of the machining of the first part.

 The invention is described in detail in the following with reference to the drawings. These show: FIG. 1a to Id, four different embodiments of assembled parts; Figure 2a to 2d, four different embodiments of undercut cavities, open on one side; Figures 3a, 3b an embodiment of the connecting means; Figure 4, an application of two assembled parts, and Figure 5, a device for molding the plasticizable material.

 Let us first examine Figures 1a to Id. Figures 1a to Id show by way of example four different embodiments of assembled parts; in FIGS. 1 a and 1 b, a first part 1 has a non-through hole and a second part 2 has a through hole, while in FIGS. 1 c and Id, a first part and a second part each have a non-through hole . The non-through hole and the through hole in the parts can be made by laser drilling or by milling.

Generally, below a diameter of about 2 mm, the machining of the holes can only be done by laser. An advantage of laser machining is the low power required which allows economical processing.

 To connect the two parts 1,2, a plastic or plasticized material was introduced into the non-through holes and the through holes, which then hardened.

 In embodiments 1a and 1b, the hardened material 3, at the end of the through holes 3 remote from the assembly surface of the two parts 1, 2, forms a collar which retains the second part 2. With the attachment of the collar combined with the undercut of the non-through hole, a connection is obtained by complementarity of shapes between the two parts 1, 2. In the embodiment of FIG. 1 b, unlike the embodiment of FIG. 1a, a layer 4 of hardened material is additionally disposed between the two parts 1,2. This layer can be used as an adhesive layer

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 additional, in cases where the curable plastic or plasticizable material is an adhesive. Likewise, this makes it possible to maintain a certain space between the two assembled parts, for example in order to prevent an electrically conductive contact. The filling of the through hole and the non-through hole of the parts 1, 2 assembled with the curable plastic or plasticizable material 3 preferably takes place by injection or by molding of the material through the through hole in the second part.

 In the embodiments according to FIGS. 1c and Id, both the first part 1 and the second part 2 only have through holes. A connection by complementarity of shapes is carried out by the hardened material 3 introduced into the non-through holes in the undercut.

In the embodiment of Figure Id, as in that of Figure 1b, a layer 4 of hardened material is placed between the two parts 1,2. The filling of non-through holes using plastic or plasticizable material can be achieved by molding said material during assembly of the parts. An injection of the material with the parts already assembled requires the presence of at least one additional opening opening into the non-opening holes.

 Figures 2a to 2d show by way of example four different embodiments of undercut cavities open on one side. In embodiments 2a and 2b, the cavity is shaped as a single non-opening hole with a conical or rectangular cross-section 5 or 6. In the embodiments of FIGS. 2c and 2d, the two cavities 7 are inclined relative to the surface of the part and are arranged symmetrically, turned 180, with respect to a normal 11 on the surface of the part. Due to the inclination of the cavities 7 relative to the surface of the part, a hardenable material placed therein is firmly anchored in the part. In the embodiment of Figure 2d, the two cavities 8 are arranged on the same face of the part 1 and open into the surface. A second part 2 assembled with the first part 1 has two complementary through holes 10. To connect the two parts 1, 2, a hardenable material is poured or molded in the through holes and in the cavities. The hardened material has at the ends of through holes 10 remote from the assembly surface of the collars 12 which hold the part 2.

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 Similar collars 9 which hang on the part 1 are formed at the level of the openings of the cavities 8. These reinforce the connection by complementarity of shapes between the two parts 1 and 2.

 Figures 3a and 3b show an embodiment of the connecting means used according to the invention. In the embodiment of Figure 3a, the connecting means is formed of curable material 3 which is molded in a conical non-through hole of the part 1. The material 3 is provided with hooks 13 for connection with the second part. This means that the material 3, at least in the places where the hooks are provided, is non-deformable and that the plasticization takes place only at the end intended to be molded in the non-through hole. In the embodiment of FIG. 3b, a connecting element in the form of a rod 14 has been put in place in the conical non-opening hole of the first part 1 before the casting of the hardenable material 3. This rod 14, at its end inserted in the non-through hole, has a widening 15 which is anchored in the part 1. By casting or by molding the hardening material 3, the rod 14 is fixed in the non-through hole and, in particular , is blocked in rotation around the axis of the rod and therefore cannot be detached from the connection by complementarity of shapes. The rod 14 can serve as a fixing means for the indirect fixing of the part 1, in particular for a complementary machining of the part 1.

 FIG. 4 shows by way of example, the use of two parts 1, 16 linked in accordance with the invention, the first part 1 being an aluminum or aluminum alloy part to be anodized and the second part being a support 16 of the anodizing bath with contact means 17 for the part 1. A connection between the part 1 and the support 16 is made using a plasticizable material 3 partially molded in a hole not emerging from the first part , which is further provided with hooks 13 for attachment to the support 16. As regards the face of the part 1 opposite the electrically connected face, it may be a decorative surface to be anodized, the l 'aspect should not be altered by the connection between the part 1 and the support 16. This is achieved by the method according to the invention.

 FIG. 5 shows by way of example a device for molding a plasticizable material 3 curable in a non-through hole 18 of the first part 1. The device comprises a guide tube 18, disposed at

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 the proximal end in the present case, to guide the plasticizable material 3, a heating tube 19, arranged at the distal end in the present case, to thermally plasticize the plasticizable material 3, as well as a piston 20 for pushing the plasticized end of the plasticizable material 3 into the non-through hole 18. The plasticizable material 3 is heated using the heating tube 19, at least up to its plasticization temperature, after which it is pushed back in the non-through hole 18 by an axial pressure exerted on the piston 20, that is to say in the direction indicated by the arrow. The axial pressure required depends on the degree of plasticization of the material and can be applied manually or by mechanical means, in particular in the form of a pneumatic cylinder. The heating of the heating tube 19 can be obtained by resistance heating or by induction heating.

 In summary, it will be noted that the method according to the invention for connecting two parts together, among which at least one may have a decorative surface which must not be altered, has essential advantages compared to traditional methods. In particular compared to a bonded connection, the method according to the invention can be implemented with a lower number of steps and a much reduced commitment in devices, which allows economical manufacturing. In addition, the emissions of polluting substances are lower, which constitutes an ecological advantage. The method according to the invention makes it possible to connect by complementarity of shapes and, where appropriate, also by adhesion to practically all materials. Depending on the material used as the hardenable material, such a bond is weather-resistant and withstands high loads. When using an adhesive, the fatigue strength can be calculated in a simple manner based on the configuration and parameters of the material, the adhesion strength can be calculated from the characteristics of the usual adhesives and the pairs of materials. Finally, a connection by complementarity of shapes between two parts can, if necessary, be dismantled in a simple manner by plasticization of a curable non-adhesive material.

Claims (3)

1. Method for connecting a first part (1) to a second part (2) using a curable plastic or plasticizable material (3), characterized in that the first part (1) has at least two inclined cavities with respect to the surface of the part, in particular obtained by rotation about an axis normal to the surface of the part, which communicate with each other and open into the same face of the part, in that the second part is provided with '' at least two through holes, which are aligned with the cavities in the first part, and in that the first part is connected to the second part by casting or molding the plastic or plasticizable material (3) in the through holes and in the cavities.  2. Method for connecting a first part (1) to a second part (2) using a curable plastic or plasticizable material (3), characterized in that the first part (1) comprises at least one cavity in undercut open on one side, in which the plastic or plasticizable material is cast or molded, in that the plastic or plasticizable material has hooks for the connection with the second part (2), and in that the hooks of the plastic or plasticizable material are connected to the second part.  3. Method according to claim 1 or 2, characterized in that it is applied to connect a first part (1) of aluminum or aluminum alloy to a part (16) serving as support and ensuring the electrical connection for a anodizing the first part.