Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
  • H01Q15/14—Reflecting surfaces; Equivalent structures
  • H01Q15/141—Apparatus or processes specially adapted for manufacturing reflecting surfaces
  • H01Q15/142—Apparatus or processes specially adapted for manufacturing reflecting surfaces using insulating material for supporting the reflecting surface
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04B—KNITTING
  • D04B1/00—Weft knitting processes for the production of fabrics or articles not dependent on the use of particular machines; Fabrics or articles defined by such processes
  • D04B1/14—Other fabrics or articles characterised primarily by the use of particular thread materials

Definitions

• the present invention relates to an improved process allowing the incorporation of a metallic structure inside a plastic material in order to produce molded articles; it also relates to a new type of metal structure particularly suitable for the implementation of such a method as well as the molded articles comprising such a structure, and which have the characteristic of reflecting or blocking electromagnetic waves and / or being good conductor of static electricity.
• plastic will be used broadly to designate any type of material such as for example: - thermoplastic materials such as polyolefins
• thermosetting materials such as unsaturated polyesters, epoxies, polyurethanes, phenolics, etc.
• elastomers such as natural rubber, synthetic rubbers (SBR, nitrile rubber), thermoplastic elastomers (styrenics, polyolefins, polyurethanes, etc.), etc. which can be shaped by any type of process such as for example injection molding, thermoforming, extrusion / blowing, rotational molding ....
• One solution to solve this problem consists in covering the molded part with a reflective surface layer, a solution which is used in particular for producing reflective assemblies (antennas for example).
• a surface coating has the drawback of being subjected to external aggressions, and can therefore deteriorate over time.
• such techniques require complex and expensive materials and processes for their implementation.
• thermoplastic fibers which have a higher heat shrinkage than that of said conductive fibers.
• a wire has the characteristic that during a heat treatment, a shrinkage of the thermoplastic fibers occurs in the axial direction, which means that the conductive fibers are spiraled around said thermoplastic fibers.
• thermoplastic wire network which leads to an irregularity in the thermoplastic wire network, - a "spiral" deformation which causes poor reflection of the waves and less conductivity due to lack of contact.
• metal assemblies in particular stainless steel, are still used, which have the disadvantages of being complicated to use, long to install, and are of a high cost.
• the method according to the invention consists, after having produced a fine knitted article, preferably with picked stitches, flexible in order to ensure deformability, in associating said knitted fabric with a plate or sheet of plastic material, and it is characterized in that the association of the metallic knitting is carried out immediately at the outlet of the assembly allowing the formation of a sheet or plate of plastic material, the association being produced by calendering while the plastic plate formed is not yet cooled, thus allowing the incrustation of said knitted structure at least on the surface inside said plate or sheet of plastic material.
• Such a procedure makes it possible to produce a complex which can be used as it is to produce a thermoformed part which can be used such as or possibly serve as an insert during a subsequent injection molding operation.
• wires of any type for example metallic wires of circular section
• this composite material can be used directly to obtain finished parts by thermoforming, or possibly be used as an insert during an overmolding operation or any other operation for producing plastic parts.
• the new type of knitted metal structure according to the invention is a knitting produced according to the so-called “mesh” technique. picked “, and is characterized in that the wire which composes it is a continuous metal wire in the form of a line or blade, that is to say a material which, unlike conventional wires which have a circular section or can be inscribed in a circle, have a substantially rectangular section, that is to say of a very small thickness compared to their width.
• the wire which composes it is a continuous metal wire in the form of a line or blade, that is to say a material which, unlike conventional wires which have a circular section or can be inscribed in a circle, have a substantially rectangular section, that is to say of a very small thickness compared to their width.
• a copper line or blade having a width of between 0.3 mm and 1.5 mm and a thickness of 0.001 mm to 0.003 mm is preferably used as the metallic wire, this wire preferably being silver to obtain better conductivity and wave reflection;
• the line or metal strip is combined with a synthetic wire which easily binds with the thermoplastic material on which it will be complexed and this at a rate of approximately 5 to 10% relative to the weight of the metal wire; in such a case, if it is possible to use textile blades or lines previously sheathed with plastic materials, it is advantageous to make such an association on the knitting craft itself, by knitting the two filamentary elements (metal and synthetic yarn ), in a vanized weave, that is to say allowing to have a superposition of two elementary threads in the knitted fabric, and this so that one of the faces of said knitted fabric consists predominantly of son d 'a nature (metal), while the other side is, in turn, made up predominantly of synthetic son; the synthetic yarn can be of the same nature as the plastic, ensuring a good bond with the component of the thermoplastic plate; it is also possible to use an extensible yarn such as for example a textured yarn or a highly elastic yarn such as those sold under the brand LYCRA or similar products which makes it
• FIG. 2 illustrates the manner in which a thermoformed finished part is produced directly from a structure produced according to the method according to the invention
• FIG. 3 illustrates the way in which an insert produced in accordance with the process according to the invention is used for an injection molding operation.
• the invention therefore relates to a process which allows the incorporation of metallic structures inside a plastic material, with a view to producing molded articles.
• Such a plate can be used to produce parts completely terminated directly by thermoforming as illustrated in FIG. 2, or possibly serve as a previously thermoformed insert used during an overmolding / injection operation as shown in FIG. 3.
• the plate or sheet made up of the plastic / knit complex is brought between two respective upper and lower heating assemblies (10,11).
• the part can be used as an insert during an overmolding operation as illustrated in FIG. 3, said insert being placed inside a mold (20) of suitable shape and the plastic material being injected via a conventional assembly (21) inside the mold.
• a new type of knitted structure will preferably be used, which is also part of the invention, and which is made from continuous metal wires in the form of a line or blade, for example a copper line or blade having a width between 0.3 mm and 1.5 mm and a thickness from 0.001 to 0.003 mm.
• this wire is also silver.
• the line or metal blade is associated with a plastic thread (synthetic thread), the association of the two elements being carried out on the knitting loom itself by knitting using a vanized weave, weave which can be either of the jersey type, or possibly include weft floats obtained by means of loaded meshes.
• a knitted structure produced in the following manner is particularly suitable for implementing the method.
• a mesh structure is produced in accordance with the invention by knitting, according to a vanized crepe weave (a weave / jersey row, a weave / loaded mesh row), two wires brought simultaneously inside each row, one consisting of a copper wire in the form of line NM32 (31, 25 tex), the other by a polyamide yarn of 45 dtex.
• Knitting in the form of vanization makes it possible to obtain a knitted fabric, one of the faces of which consists for the most part of the threads of metallic lines which mask the polyamide threads which are located on the other side of the said knit , such an article weighs 75 gr./m2 and can be used, either to be incorporated directly inside plastics during a molding operation or, preferably, in accordance with the method according to the invention, to produce a intermediate product which itself can either be used directly to make a finished part, or to serve as an insert during an overmolding operation.
• Molded articles having such a metallic structure on one side or embedded inside the plastic material can be used for all the applications in which it is desired to obtain EME-ESD protection.
• such a solution has numerous advantages in that the mesh network can be easily arranged, conforms to the deformation of the plastic during molding, deformation of the mesh up to 300% in both directions.
• such a product makes it possible to produce nested, staircase joint plans, hence an effective barrier to waves and a secure grounding.
• the laminated surface of the wire leads to sharp angles allowing better penetration into plastic surfaces.
• the articles produced can be easily recycled, the plastic reinforced by such a structure is not polluting unlike plastics loaded with metal powders or fibrils, or simply coated with a surface coating layer.
• thermoformable flat product with the addition of a sheet of metallic knitted fabric.
• stainless steel, pure copper and silver in the plate state which can be incorporated into an assembly according to various resin transformation processes.

Landscapes

• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Injection Moulding Of Plastics Or The Like (AREA)
• Laminated Bodies (AREA)
• Knitting Of Fabric (AREA)
• Reinforced Plastic Materials (AREA)
• Casting Or Compression Moulding Of Plastics Or The Like (AREA)
• Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=9429264

Family Applications (1)

Country Status (8)

Families Citing this family (12)

Family Cites Families (7)

• 1992
  • 1992-04-21 FR FR9205130A patent/FR2690172B1/fr not_active Expired - Fee Related
• 1993
  • 1993-04-20 KR KR1019930703779A patent/KR940701476A/ko not_active Application Discontinuation
  • 1993-04-20 US US08/167,885 patent/US5487804A/en not_active Expired - Fee Related
  • 1993-04-20 CA CA002103043A patent/CA2103043A1/fr not_active Abandoned
  • 1993-04-20 WO PCT/FR1993/000385 patent/WO1993021367A1/fr not_active Application Discontinuation
  • 1993-04-20 JP JP5518066A patent/JPH06508803A/ja active Pending
  • 1993-04-20 AU AU39580/93A patent/AU3958093A/en not_active Abandoned
  • 1993-04-20 EP EP93909030A patent/EP0591502A1/de not_active Withdrawn

Non-Patent Citations (1)

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