FR2602909A1 - METHOD FOR MANUFACTURING TOUCH CONTACTING ARRANGEMENT AND PROVISIONING TOUCH CONTACTORS - Google Patents

Abstract

THE PRESENT INVENTION RELATES TO A PROCESS FOR MANUFACTURING AN ARRANGEMENT OF TOUCH SWITCHES AND AN ARRANGEMENT OF TOUCH SWITCHES. DEVICE CHARACTERIZED BY THE FACT THAT THE KEY BODIES 5 ARE SHAPED FROM A SYNTHETIC MATERIAL HARDER THAN THE CARPET 1 AND ARE SHAPED IN ONE PIECE ON DOMES 2 OF THE CARPET 1.

Description

Method for manufacturing a touch contactor arrangement

  and provision of touch switches.

  The invention relates to a method for the manufacture of a touch contactor arrangement in which a resilient flexible mat is provided on the one hand with hard key bodies which are made of synthetic material, in particular moldings of PBTB (polyterephthalate). butylene) or PETP (polyethylene terephthalate) molding materials and other parts of contact beads which can be contacted with contact surfaces and are made of a carpet-like material but conductor of electricity .

  In addition, the invention relates to a touch contactor arrangement. In Markt & Technik No. 4 of 28 January 1983, page 20,

  carpets formed of silicone rubber. These are hot-vulcanized to contact beads which are formed of a rubber which has been rendered electrically conductive by the incorporation of amorphous hydrocarbons. It is possible to form the mats so that the touch bodies are formed of the silicone rubber itself. However, such touch bodies are hardly suitable for typewriter keyboards or data entry devices.

  In these cases, separately prefabricated key bodies made of PBTP (polybutylene terephthalate) molding materials or PETP (polyethylene terephthalate) molding materials are placed on the carpet.

  changed. Such molding bodies of PBTP (polybutylene terephthalate) or modified PETP (polyethylene terephthalate) molding materials have the advantage of being sufficiently hard, of resisting wear, of being able to be manufactured with stable dimensions and can easily be printed or rendered multicolored.

  DE-OS 30 45 962 describes a keyboard in which the carpet

  is formed of polymethyl methacrylate, polystyrene, polyvinyl chloride or elastomers, preferably silicone rubber.

  Usual touch bodies of PBTP molding materials or modified PETP molding materials are not provided here.

  If a contactor arrangement is made from the beginning

  of a carpet and touch body separated, it is necessary then to take particular measures to connect the bodies of key to the carpet and to align them with respect to this one. As a result, the constitution becomes expensive and the assembly complicated.

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  The problem of the invention is to simplify a process of the species indicated at the beginning without restrictions to the form that can be given

to the touch body.

  According to the invention, the above problem is solved, in a process of the kind indicated at the beginning, by the fact that the carpet is made of a thermoplastic elastomer, in particular a polyether-ester, which the the contact beads are also made from a thermoplastic elastomer, in particular a polyether ester which has been rendered electrically conductive by additives and the moldings forming the touch bodies, the carpet and contact beads, in a multi-step manufacturing process,

  inside a plastic injection mold.

  Polyester thermoplastic elastomers (polyethylene esters)

  are, for example, known under the trade name Hytrel. The base of such a thermoplastic elastomer is polyoxytetramethylene glycol (PTMEG), 1,4-butanediol and terephthalic acid. By adjusting the relative proportions of these substances, different hardnesses and elasticities can be established. Since in spite of variations in relative proportions, the bodies are part of a single group of polymers, they assemble durably without difficulty.

  Another thermoplastic elastomer is known on the market under the trade name Pebax. Chemically, by the directed selection of flexible polyether blocks and rigid polyamide blocks, the positive properties and the ease of use of the materials

  thermoplastics are here combined with the flexibility of elastomers.

  Different hardness or flexibility can be obtained.

  Polybutylene terephthalate molding materials or modified polyethylene terephthalate molding materials are set from which to form the touch bodies in a manner

  such that the touch bodies become hard in the usual way.

  The thermoplastic elastomer is adjusted or implemented from which it is necessary to manufacture the carpet in such a way that the carpet becomes flexible and elastic. The thermo-plastic elastomer is made conductive from which it is a question of manufacturing the contact beads with electrically conductive additives, for example carbon black or carbon black replacement materials. A particularly advantageous point here is that the formed moldings

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  chemically similar elastomers forming the touch bodies,

  the carpet and the contact beads come together in one piece.

  Advantageous arrangements of the invention and an arrangement of touch switches manufactured according to the method are indicated in

  the description below. In the drawings: FIG. 1 is a partial elevation in section of a layout

  contactors and FIG. 2 shows a plane of the arrangement of contactors

according to Figure 1.

  On a flexible mat 1 are formed multiple contactor domes 2. The mat is not electrically conductive. On each dome 2 is provided internally a contact bead 3 which, when a keyboard is fully mounted, is above two conductors of a base plate 'not shown more precisely. When the dome 2 is depressed, the two conductors can be electrically connected

  between them by the contact bead 3, electrically conductive.

  At the top of the dome 2 is formed a cylindrical neck 4. This is continued by a key body 5, mainly rectangular in the plane (see Figure 2). The key body 5 has a perimetric edge 6 which is applied over the neck 4. The key body 5 has a shape which has been satisfactory in the typewriter keys. By pressing the key body 5, the flexible dome

  and elastic 2 is deformed so that its contact bead 3 connects the mentioned conductors. After the key body is released, the dome 2 returns the key body 5 to its position.

  The key body 5 is hard in comparison with the carpet 1 and more specifically, not only because the wall thicknesses in the region of the key body 5 are larger than the wall thickness of the carpet 1, but because the material in the region of the body of tu30 che 5, is harder than that of the carpet 1. The body of key 5 carries appropriate printed symbols or is manufactured by molding

by injection in two colors.

  The manufacture of the contactor contact arrangement described is carried out approximately in the following manner: A multi-part injection mold present in a part,

  hollows corresponding to the shape of the contact beads 3 and domes 2 and in the other part, depressions corresponding to the touch bodies 5.

  The surfaces facing each other of the mold parts are

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  of shape corresponding to that of carpet 1 or its domes 2.

  In the recesses of one of the mold parts, a thermoplastic elastomer, for example a polyether ester, which has been rendered electrically conductive by carbon black, is injected. In the corresponding valleys for the domes, a non-conductive thermoplastic elastomer, for example a polyether ester, is injected. In the recesses of the other mold part, an alkylene polyterephthalate molding material, in particular PBTP or PETP, is injected, optionally in two colors, which is adjusted in such a way that the pressing bodies 5 become hard. This results in high wear resistance and good dimensional fidelity of the key bodies 5. The lines of separation between the material of the key body 5 and that of the carpet 1 on the one hand, and between the material of the beads of 3 and that of the belt 1, on the other hand, are shown in phantom in FIG. 1. In this multi-step manufacturing process, the materials of the belt 1 and the contact beads 3 and, on the one hand, 5M touch bodies, on the other hand, bind closely together since they are based on the same group of materials. Melting points of materials

are close to each other.

  Overall, we obtain a contactors arrangement

  one-piece key which, as to the mechanical and electrical properties of its different regions, is adapted to the requirements.

  Another advantage of the described process is that the hardening of the thermoplastics is faster than vulcanization in the case of carpets known in the art.

silicone rubber.

2602909

Claims (7)

  1) A method for producing a touch contactor arrangement in which a resilient flexible mat carries / on the one hand, hard key bodies which are made of synthetic material, in particular PBTB molding materials (polyterephthalate). butylene) or modified polyethylene terephthalate (PETP) molding materials and, on the other hand, contact beads which can be brought into contact with contact surfaces and are made of a carpet-like material but conductive of electricity, characterized in that the carpet is made of a thermoplastic elastomer, in particular a polyether ester, which is also manufactured from thermoplastic elastomer contact beads, in particular a polyether ester. which has been made conductive of electricity by additives and that the molded parts forming the touch bodies, the carpet and the contact beads are securely assembled into a multi-stage manufacturing process, inside a mold injection molding synthetic material.   2) Method according to claim 1, characterized in that   Polyalkylene terephthalate butts, particularly polybutylene terephthalate butts and / or modified polyethylene terephthalate molding materials, are manufactured.   3) Process according to any one of claims 1 and 2, characterized in that in a multi-stage injection molding process, the key bodies, possibly in several colors, the carpet and the contact beads are manufactured. as a single molded piece of synthetic material.   4) Method according to any one of claims 1 to 3, characterized in that one injects first in a mold half the body and in another mold half the contact beads and that before hardening of the touch bodies and contact beads, the carpet is injected between them and then the bodies   the carpet and the contact beads harden together.   ) Contactor arrangement made by the process   according to any one of claims 1 to 4, characterized in that the key bodies (5) are formed of a synthetic material 35 harder than the carpet (1) and are integrally formed on domes (2) of the carpet (1). 6 2602909   6) Arrangement according to claim 5, characterized in that the key body (5) is mounted on a neck (4) of the dome (2).   7) Arrangement according to claim 6, characterized in that the neck (4) is cylindrical and the key body (5) is rectangular in section.   8) Arrangement according to any one of claims 5 to 7, characterized in that the body of touch (5) has a flange   (6) applying over the neck (4).