Method for obtaining mechanical lock between surfaces

Description: TECHNICAL FIELD [Detailed description of the invention]

Technical field The present invention relates to a method of obtaining a mechanical lock between two surfaces to prevent mutual movement between the two surfaces. In particular, the present invention relates to a method of obtaining a mechanical lock between two surfaces by embedding fine granules on the two surfaces. Background technology In many industrial techniques and methods, it is often necessary to prevent mutual movement of adjacent surfaces. One of these industrial technologies is found in the manufacture of closures such as doors or hoods for automobiles and other transport vehicles. These closures typically require a double layer of steel formed by joining two flat surfaces or panels of steel. The inner panel is arranged inside the outer panel, and the edge of the outer panel extends beyond the edge of the inner panel. The edges of the outer panel are bent or edge-bent over the edges of the inner panel in a process known as bending, and the resulting structure is the so-called heme flange. Permanent hem flange assembly by applying adhesive between overlapping metal surfaces to cure or weld the two panels together to permanently secure the inner panel with respect to the outer panel of the hem flange To form. After the formation of the heme flange and just before the curing or welding of the adhesive, the heme flange is transported and handled, often causing panel reciprocity, which causes a number of problems in the manufacturing process. Therefore, some immediate handling strength is utilized by utilizing an adhesive composition or other means having some initial (untreated) strength or handling strength to prevent permanent curing or movement of the panel just before welding. Need to get. Various adhesive compositions have been developed in an attempt to provide the desired initial handling strength for the formation of heme flanges. Examples of these adhesive compositions can be found, for example, in US Pat. No. 4,703,809; 4,855,001; 4,857,131; and 5,096,962. It has proven difficult to formulate one-component adhesive compositions with both high handling strength and sufficient stability or shelf life properties. Most of the adhesive compositions with adequate handling strength and shelf life are utilized only in two-component formulations, which require expensive coating techniques and equipment and after mixing and coating two parts of the adhesive. , It is necessary to fit the panel within a short time. Another method of imparting initial handling strength to the hem flange is the use of an inductive curing device with the adhesive composition. The inductive curing device is used to heat the metal panel of the hem flange to pre-gel the adhesive composition for handling strength. However, inductive curing equipment is expensive and cumbersome. When using an adhesive composition to form a hem flange, it has been proposed to use spherical glass beads to maintain a constant thickness of the adhesive composition applied between the metal panels. .. The glass beads act as spacers to prevent the metal panel from extruding (which results in the destruction of the adhesive layer). Disclosure of invention It has been discovered that the proper use of fine granules, such as glass beads, can actually provide handling strength on two surfaces regardless of the strength of the adhesive composition applied to them. Accordingly, the present invention eliminates the need for high handling strength adhesive compositions and corresponding expensive coating and induction expensive devices. More specifically, the present invention provides fine granules between two surfaces that have a compressive strength higher than the yield strength of each of the surfaces, sufficient to embed a significant number of fine granules on both of the surfaces. It relates to a mechanical locking method between two surfaces, which consists of a step of pressing two surfaces with pressure in each other direction. Surprisingly, it was found that embedding a significant number of fine granules on both surfaces provided considerable mechanical locking or handling strength regardless of the strength of the adhesive. It is desirable that the method of the present invention be used for forming a hem flange. Therefore, the present invention also (a) The step of arranging the first panel adjacent to the second panel so that the edge of the second panel extends beyond the edge of the first panel; (b) The step of providing fine granules having a compressive strength higher than the yield strength of each of the two surfaces to the overlapping portion of the two panels; (c) The step of folding the non-overlapping part of the second panel over the edge of the first panel; and (d) The present invention relates to a method for forming a hem flange, which comprises a step of applying pressure to the overlapping portion of both panels so that a considerable number of fine granules are embedded in both panels. A brief description of the drawing FIG. 1 is a schematic representation of a hem flange with fine granules between two metal panels just before pressure is applied by a hemming die. FIG. 2 is a schematic diagram of a heme flange after pressure is applied by a heme processing die showing that fine granules are embedded in both metal panels. The best mode for carrying out the invention The present invention provides two surfaces with microgranule with a compressive strength higher than the yield strength of each of the two surfaces, and the two surfaces with sufficient pressure to embed a significant number of fine granules on both of the surfaces. It relates to a method of mechanically fixing two surfaces, which consists of the steps of pressing in the direction of each other. Suitable surfaces for use in the methods of the invention can be essentially thick enough to embed fine granules, and a flat surface such as a panel is desirable. The surface is preferably a malleable surface such as a metal surface, and can be made of various metals including steel, iron, aluminum, brass, copper, and the like. Its surface can also consist of various non-metallic materials such as thermosetting and thermoplastic resins. Examples of thermosetting resins include glass-filled epoxy resins and glass-filled polyesters, and examples of thermoplastics include polyureas and polycarbonates. This method is used to mechanically fix two identical, two similar or two different surfaces. At present, it is desirable to utilize flat steel sheets such as cold-rolled steel and galvanized steel used in the manufacture of hem flanges for transport vehicles in the present invention. Steel sheets used for forming hem flanges typically have a thickness in the range of about 0.051 to 0.152 cm, preferably about 0.071 to 0.081. As mentioned above, the yield strength of the surface must be lower than the compressive strength of the fine granules. The yield strength of the surface is typically available from the supplier of the particular surface. As is technically known, it is generally obtained from the stress-strain curve of the materials that make up the surface. The microgranule useful for the method of the present invention can be composed of a material having a compressive strength higher than the yield strength of the surface to be embedded. Examples of materials capable of inducing granules include glass, ceramics and hard metals such as stainless steel or titanium. The microgranule has a shape or size that is partially or completely embedded in two opposing surfaces, preferably substantially spherical. At present, it is desirable to use spherical glass beads as the fine granules of the present invention. When spherical, the fine granules have the required diameter depending on the space required between the two surfaces after implantation. In the case of heme flanges utilizing substantially spherical granules, the spherical granules typically have a diameter in the range of about 0.013 to 0.13 cm, preferably about 0.025 to 0.050 cm. Granules used for a given application should have as uniform a diameter distribution as possible, but slight variations in diameter between the granules are acceptable. If there is a variation in diameter, the larger diameter granules are embedded before the smaller diameter granules during the molding of the hem flange. As mentioned above, the compressive strength of the granules must be greater than the yield strength of each of the two surfaces. When mechanically immobilizing two different surfaces with different yield strengths, the compressive strength of the fine granules must be higher than each of the respective yield strengths of the two surfaces. In this case, the degree of embedding in each surface varies in relation to the yield strength of a particular surface. The compressive strength of the fine granules is typically determined by applying a load until the granules between the hardened surfaces break, as is typically available from the supplier of the particular granule and is technically known. Fine granules can be provided in various ways between the two surfaces. For example, the granules can be provided between the surfaces in pure form or in combination with the carrier material. The carrier material can be essentially a liquid or viscous medium type. Examples of carrier materials useful in the present invention include various polymer materials such as polyurethane, epoxy resins and acrylic polymers. The carrier material in the manufacture of hem flanges can be an adhesive composition conventionally used to bond hem flanges. However, since the embedded fine granules independently provide handling strength, the adhesive itself does not need to have considerable initial handling strength. Adhesive compositions used as carrier materials for heme flanges are conventional adhesive compositions used to operate heme flanges, such as the acrylic resin compositions described in US Pat. No. 4,703,809; 4,855,001; 4,857,131; and 5,096,962. Can be a thing. The adhesive composition is used as a one-component or two-component adhesive composition as is technically well known. And the fine granules can be contained in one or both of the two liquids in the case of the two liquid type. The adhesive composition containing the fine granules is applied to the panel to be fixed before forming the hem flange, or is injected into the preformed hem flange before applying pressure with a heming die that embeds the fine granules. The amount of fine granules provided between the two surfaces will vary depending on the application and the desired effect. For heme flanges that utilize spherical microgranules, the spherical microgranule is typically used with the carrier material at a concentration in the range of about 2-25, preferably 3-10% by volume of the carrier material. The two mechanically fixed surfaces are pressed against each other by utilizing a die, press or other effective means. As mentioned above, the two surfaces must be pressed against each other with sufficient pressure to embed a significant number of fine granules on each surface. As used herein, "substantial number" means the number of fine granules that must be implanted to obtain sufficient mechanical lock in a given application, and typically at least the majority of fine granules. The force required to embed a significant number of fine granules depends on the degree of embedding required and the yield stress of the particular surface to be immobilized. For hem flanges that use steel plates, the inner and outer panels are mechanically pressed when the pressure required to move the inner panel with respect to the outer panel (hereinafter referred to as "moving force") is approximately 22.7 kg or more. It is considered to be fixed. Therefore, for hem flanges, the term "equivalent number" is about 3.5 kg / cm.²It means the number of fine granules that must be embedded in order to obtain a mobility of (50 psi) or more. For hemes and flanges containing steel plates, typically approximately 245 to 770 kg / cm when using spherical fine granules.²Desirably about 420-560 kg / cm²Pressure within the range of is required. The pressure is evenly applied over the overlapping parts of the panel to ensure that a significant number of fine granules are embedded, while a small number of granules crush without adversely affecting fixation strength but do not completely crush the fine granules. Need to be added. In addition, the pressure should be applied so that the fine granules do not exit the opposite side of the panel and cause an awkward ridge on the outer surface of the heme flange. Typically, high concentrations or large diameters of glass beads require high pressure to obtain a given degree of embedding. The above embedding pressure should be distinguished from the pressure used to make the hem flange assembly with glass beads that act only as mechanical spacers to keep the adhesive thickness constant. (The latter pressure is 35 ~ 210kg / cm²Is in the range of). It should be noted that a small number of large glass beads are irregularly partially embedded during the heme-flange process, which utilizes the glass beads as mechanical spacers for a given application. However, this irregular and small number of implants never causes mechanical locking according to the present invention. The procedure for embedding substantially spherical fine granules in the hem flange is shown in FIGS. 1 and 2. As shown in FIG. 1, the inner panel 10 is arranged adjacent to the outer panel 12. The edge of the outer panel 12 extending beyond the edge of the inner panel 10 is then bent or crimped over the edge of the inner panel 10 to form the outer panel upper 14 and the outer panel lower 16. The glass beads 18 were provided between the overlapping portion of the inner panel 10 and the outer panel 12. The hemming die applies force to the upper 14 of the outer panel to push the inner panel 10 toward the lower 16 of the outer panel. FIG. 2 shows that spherical granules 18 were embedded in both the inner panel 10 and the lower outer panel 16. The spherical granules form a mechanical lock between the two panels to resist the shear force F. When implementing the method of the invention, especially for non-heme flanges, only a small amount to determine the optimum size and amount of granules needed to provide the required mechanical lock to the two opposing surfaces with a given force. Experiment is required. The following examples are shown for the purpose of explaining the present invention, and do not limit the scope of the invention specified in the claims. Example 1 Figures 1 and 2 are used for reference in describing the procedures of this example. Thickness is 0.076 cm and yield strength is 1890 kg / cm²Two 1in x 4in (2.54cm x 10.16cm) steel coupons were stacked vertically and molded into the shape of a hem flange as shown in Fig. 1. 3850kg / cm just before forming the hem flange²An acrylic adhesive composition (Road's trade name VERSILOK252) containing approximately 10% by volume of spherical glass beads having a compressive strength of 0.025 cm and an average diameter of 0.025 cm is applied between the overlapping portion of the inner panel 10 and the outer panel 12. .. The adhesive is used in the absence of curability and acts only as a carrier material. Approximately 0.0327 cm between 1.27 cm x 2.54 cm rectangular overlaps between panels³Apply the adhesive. Next, about 252 kg / cm²Pressure P is evenly applied to the upper 14 of the outer panel to embed the glass beads. Comparative example 2 The hem flange assembly is manufactured according to Example 1, except that the carrier material does not contain glass beads. Tensile test Heme flange assemblies manufactured according to Example 1 and Comparative Examples are tested for tensile strength by connecting a third metal coupon to the bottom of the outer panel. Next, pressure is applied as a shear force F as shown in FIG. 2 by using an Instron tensile tester. Next, for eight samples from both Example 1 and Comparative Example 2, record the force required to pull the inner panel from the outer panel. The average force required to separate the panel of the hem flange assembly of Example 1 is 22.5 kg, whereas it is required to separate the panel of the hem flange assembly of Comparative Example 2. The average force is 2.9 kg. The above examples show the substantial handling strength provided alone by the fine granules embedded in the molding of the hem flange by the method of the present invention.