EP0001882A1 - Kontaktfreier Drücktaster zur Verwendung in einer elektronischen Tastatur - Google Patents

Kontaktfreier Drücktaster zur Verwendung in einer elektronischen Tastatur Download PDF

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Publication number
EP0001882A1
EP0001882A1 EP78300393A EP78300393A EP0001882A1 EP 0001882 A1 EP0001882 A1 EP 0001882A1 EP 78300393 A EP78300393 A EP 78300393A EP 78300393 A EP78300393 A EP 78300393A EP 0001882 A1 EP0001882 A1 EP 0001882A1
Authority
EP
European Patent Office
Prior art keywords
piezoconductive
key
force
magnetic field
elastomer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP78300393A
Other languages
English (en)
French (fr)
Other versions
EP0001882B1 (de
Inventor
Franco Dr. Varesio
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telecom Italia SpA
Olivetti SpA
Original Assignee
Olivetti SpA
Ing C Olivetti and C SpA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Olivetti SpA, Ing C Olivetti and C SpA filed Critical Olivetti SpA
Publication of EP0001882A1 publication Critical patent/EP0001882A1/de
Application granted granted Critical
Publication of EP0001882B1 publication Critical patent/EP0001882B1/de
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H13/00—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch
    • H01H13/70—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard
    • H01H13/78—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard characterised by the contacts or the contact sites
    • H01H13/785—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard characterised by the contacts or the contact sites characterised by the material of the contacts, e.g. conductive polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C10/00—Adjustable resistors
    • H01C10/10—Adjustable resistors adjustable by mechanical pressure or force
    • H01C10/106—Adjustable resistors adjustable by mechanical pressure or force on resistive material dispersed in an elastic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H13/00—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch
    • H01H13/70—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard
    • H01H13/702—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard with contacts carried by or formed from layers in a multilayer structure, e.g. membrane switches
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2201/00—Contacts
    • H01H2201/022—Material
    • H01H2201/032—Conductive polymer; Rubber
    • H01H2201/036—Variable resistance
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2207/00—Connections
    • H01H2207/008—Adhesive means; Conductive adhesive
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2227/00—Dimensions; Characteristics
    • H01H2227/002—Layer thickness
    • H01H2227/012—Conductive rubber
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2227/00—Dimensions; Characteristics
    • H01H2227/002—Layer thickness
    • H01H2227/012—Conductive rubber
    • H01H2227/014—Conductive particles

Definitions

  • This invention relates to an elastomeric material which is conductive under pressure and suitable for use in keyboards of data processing equipment.
  • Elastomeric materials which are rendered conductive by adding materials such as carbon black or metal powders is the mix or composition.
  • Some compositions and processes for poducing conductive rubbers are given in the book: Conductive Rubbers as Plastics, by R. H. Norman - Elsevier, Amsterdam, London, New York, 100.
  • Elements of conductive rubber are used as contact materials in known types of keyboard.
  • piezoconductive rubbers are more interesting, that is those rubbers which become conductive under the effect of applied pressure, because they allow keyboards without contacts exposed to oxidation to be obtained, inasmuch as contact takes place within the piezoconductive material.
  • piezoconductive elastomers are used for producing fixed contact.
  • the piezoconductive effect disappears after a few thousand actuations of the elastomeric element, for which reason these materials are not suitable for use in keyboards.
  • the ject of the invention is to provide an elastomer which becomes conductive under the effect of pressure and preserves this characteric for a number of operations of the order of at least some hundreds of nousands.
  • Fig. 2 shows a key 10 which uses a path 11 of piezoconductive elastomer according to the invention and can be employed to replace a normal contact-type key as an input device for a data processing apparatus, with an interface towards semiconductor electronic circuits of high input impedance.
  • the patch preserves these characteristics for at least 100,000 operations of the same key, with a contact resistance always below 10,000 ohms.
  • the preferred metal material is a nickel powder consisting of spnerical grains and having the maximum hardness compatible with preservation of the magnetic characteristics. More particularly, good results have been obtained with a nickel powder known by the trade name of Alloy 79 GS, supplied by the Baudier Company, of Liancourt (France).
  • the powder consists of 93.94% of nickel, 3.5% of silicon, 1% of tron, 1.6% of boron and 0.05% of carbon and has a Rockwell C hardness of 18-22; the spherical granules have a diameter between 100 and 150 ⁇ .
  • a preferred composition of the piezoconductive elastomer is constituted by:
  • Preparation of the piezoconductive elastomer requires careful mixing of the powder and silicone rubber, addition of the hardener, a first degassing of the mix under vacuum and casting in the mould followed by a second degassing under vacuum and introduction into the magnetizer, which applies a magnetic field with a direction perpendicular to the faces of the sheet during the polymerization of the binder.
  • the thickness of the sheet or film of piezoconductive elastomer may vary from 0.4 to 0.8 mm, the preferred thickness being 0.6 mm.
  • the intensity of the magnetic field during the polymerization is not critical, provided that the field reaches an intensity of at least 500 oersteds. Above this value no appreciable variations are found in the results.
  • the magnetic flux is maintained throughout the time of polymerization of the elastomer by the current flowing in two windings 34 and 35.
  • the elastomer is kept at room temperature. Under these conditions, complete polymerization requires about 18 hours.
  • the time required for preparing the piezoconductive elastomeric material can be reduced to 10 minutes, still in a magnetic field, if the temperature of the mould 31 is brought to 100° C .
  • Fig. 5 shows a simple circuit used for detecting the characteristics of the key of Fig. 2, comprising a DC voltage generator 41 producing 5 V and a 50 K ⁇ limiting resistor 42 in series with the key 10.
  • Fig. 4 is a graph of the voltage drop detected across the terminals 43 and 44 of the resistor 42 as a function of the force F applied to the key. The phenomenon of hysteresis between actuation and release of the key is obvious from the graph.
  • FIG. 3 An alternative embodiment of a keyboard employing the piezoconductive rubber according to the invention is shown in Fig. 3.
  • a single sheet 24 of piezoconductive material produced in a magnetic field in accordance with the invention is used, instead of individual patches of piezoconductive elastomer as in the key of Fig. 2.
  • the sheet 24 is stuck by means of a conductive adhesive to islands 26 of a printed circuit board 25 which constitute one of the contact terminals of the keys 27.
  • a second, flexible, printed circuit board 28 is stuck by means of conductive adhesive on top of the sheet 24 of piezoconductive material at islands 29 in line with the islands 26.
  • the islands 26 and 29 constitute contact terminals of the keys 27..
  • Fig. 3 which is functionally equivalent to the modular solution of Fig. 2, is more convenient for producing keyboards with a large number of keys inasmuch as it drastically reduces the number of parts.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Push-Button Switches (AREA)
EP19780300393 1977-11-07 1978-09-18 Kontaktfreier Drücktaster zur Verwendung in einer elektronischen Tastatur Expired EP0001882B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT6948677A IT1091947B (it) 1977-11-07 1977-11-07 Materiale elastomerico conduttore sotto pressione
IT6948677 1977-11-07

Publications (2)

Publication Number Publication Date
EP0001882A1 true EP0001882A1 (de) 1979-05-16
EP0001882B1 EP0001882B1 (de) 1981-12-09

Family

ID=11312229

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19780300393 Expired EP0001882B1 (de) 1977-11-07 1978-09-18 Kontaktfreier Drücktaster zur Verwendung in einer elektronischen Tastatur

Country Status (3)

Country Link
EP (1) EP0001882B1 (de)
DE (1) DE2861435D1 (de)
IT (1) IT1091947B (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3034523A1 (de) * 1979-09-14 1981-03-19 Nissan Motor Schalter- und anzeigevorrichtung
EP0088132A1 (de) * 1981-09-16 1983-09-14 Toray Industries, Inc. Durchsichtiger flacher schalterbau und schalteinheit
DE3543890A1 (de) * 1985-12-12 1987-06-19 Thomson Brandt Gmbh Eingabeelement
WO1993004491A1 (en) * 1991-08-20 1993-03-04 Key Tronic Corporation. Inc. Single station cursor device suitable for keyboards
US5216316A (en) * 1989-12-18 1993-06-01 Ralph Ipcinski Piezo electric transducer

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2006176B2 (de) * 1969-02-24 1973-04-19 Sudduth, William B., Gloucester, Mass. (V.StA.) Elektrische schalteranordnung
FR2182099A1 (de) * 1972-04-26 1973-12-07 Battelle Memorial Institute
CH547007A (de) * 1972-04-06 1974-03-15 Wifo Forschungsinst Ag Druckempfindlicher elektrischer schalter, insbesondere fuer schwach- oder signalstrom.
DE1939642B2 (de) * 1969-08-04 1975-01-09 Standard Elektrik Lorenz Ag, 7000 Stuttgart Auf linearem Druck basierender Schalter für prellfreies Schalten
DE2729959A1 (de) * 1976-06-30 1978-01-05 Japan Synthetic Rubber Co Ltd Druckempfindlicher leiter

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2006176B2 (de) * 1969-02-24 1973-04-19 Sudduth, William B., Gloucester, Mass. (V.StA.) Elektrische schalteranordnung
DE1939642B2 (de) * 1969-08-04 1975-01-09 Standard Elektrik Lorenz Ag, 7000 Stuttgart Auf linearem Druck basierender Schalter für prellfreies Schalten
CH547007A (de) * 1972-04-06 1974-03-15 Wifo Forschungsinst Ag Druckempfindlicher elektrischer schalter, insbesondere fuer schwach- oder signalstrom.
FR2182099A1 (de) * 1972-04-26 1973-12-07 Battelle Memorial Institute
DE2729959A1 (de) * 1976-06-30 1978-01-05 Japan Synthetic Rubber Co Ltd Druckempfindlicher leiter

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
JOURNAL OF APPLIED PHYSICS, vol. 44, no. 6, June 1973, B.E. SPRINGETT: "Conductivity of a system of metallic particles dispersed in an insulating medium", pages 2925 to 2926 *
SEVENTH ANNUAL CONNECTOR SYMPOSIUM PROCEEDINGS, October 1974, Camden, New Jersey, (USA) CH. KUIST: "Anisotropic Conduction in Elastomeric Composites, pages 203 to 209 *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3034523A1 (de) * 1979-09-14 1981-03-19 Nissan Motor Schalter- und anzeigevorrichtung
EP0088132A1 (de) * 1981-09-16 1983-09-14 Toray Industries, Inc. Durchsichtiger flacher schalterbau und schalteinheit
EP0088132A4 (de) * 1981-09-16 1985-11-07 Toray Industries Durchsichtiger flacher schalterbau und schalteinheit.
DE3543890A1 (de) * 1985-12-12 1987-06-19 Thomson Brandt Gmbh Eingabeelement
US5216316A (en) * 1989-12-18 1993-06-01 Ralph Ipcinski Piezo electric transducer
WO1993004491A1 (en) * 1991-08-20 1993-03-04 Key Tronic Corporation. Inc. Single station cursor device suitable for keyboards

Also Published As

Publication number Publication date
IT1091947B (it) 1985-07-06
DE2861435D1 (en) 1982-02-04
EP0001882B1 (de) 1981-12-09

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