US3671822A - Variable capacitive apparatus - Google Patents

Variable capacitive apparatus Download PDF

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Publication number
US3671822A
US3671822A US99186A US3671822DA US3671822A US 3671822 A US3671822 A US 3671822A US 99186 A US99186 A US 99186A US 3671822D A US3671822D A US 3671822DA US 3671822 A US3671822 A US 3671822A
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United States
Prior art keywords
conductor
conductors
planar surface
biasing
edge
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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.)
Expired - Lifetime
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US99186A
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English (en)
Inventor
Theodore M Leno
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.)
AT&T Teletype Corp
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Teletype Corp
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Publication date
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Publication of US3671822A publication Critical patent/US3671822A/en
Assigned to AT&T TELETYPE CORPORATION A CORP OF DE reassignment AT&T TELETYPE CORPORATION A CORP OF DE CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). EFFECTIVE AUG., 17, 1984 Assignors: TELETYPE CORPORATION
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J5/00—Devices or arrangements for controlling character selection
    • B41J5/08—Character or syllable selected by means of keys or keyboards of the typewriter type
    • B41J5/14—Construction of key levers

Definitions

  • ABSTRACT A variable capacitance apparatus particularly adapted for use with a manually-operated keyboard and having two parallel, conductive plates with a dielectric therebetween. Depression of a key moves one conductive plate farther from the other conductive plate so as to reduce the capacitive coupling between the conductive plates, in order to determine whether the key has been depressed.
  • This invention relates to electrical switching apparatus and method and more particularly to a switching apparatus and method in which the switching action involves the change of capacitive coupling between two conductive plates.
  • a variable capacitor comprises a first planar conductive surface and a second conductive surface separated therefrom by dielectric material wherein thedistance'between the first and second conductive surfaces is varied in order to vary the capacitive coupling between the conductors.
  • FIG. 1 is a cross-sectional view showing a manually-movable, magnetically-biased, key-operated capacitor plate that is held into engagement with a dielectric-covered companion electrode plate;
  • FIG. 2 is similar to FIG. 1, but showing the key partially depressed
  • FIG. 3 is crosssectional view of an alternate embodiment in which the movable capacitor plate is pivoted on a flexure 'oint;
  • J FIG. 4 shows another alternative embodiment having a hinged pivot in which the capacitor plates are magnetically biased away from each other and shows a circuit for determining capacitive coupling; and
  • FIG. 5 shows an embodiment similar to that shown in FIG. 4, but with a push-push mechanism comparable to that used in a retractable ball-point pen.
  • a plastic housing contains a pair of steel, magnetic shielding plates 12 on the interior surfaces of opposite sides of the plastic housing 10.
  • Two permanent magnets 14 and 16 are placed in the housing next to the shielding plates 12.
  • a pair of bronze, fixed electrode plates 18 and 20 are bonded each to one face of the magnets 14 and 16, respectively, and have connector tabs projecting out of the bottom of the plastic housing 10.
  • a dielectric material 22 is used to coat those surfaces of the fixed plates 18 and 20 which face toward the center of the plastic housing 10.
  • a pair of bent, ferromagnetic, electrode swing plates 24 and 26 are placed so that they can pivot on the bottom of the plastic housing 10 and are magnetically attracted by the permanent magnets 14 and 16, respectively, to positions wherein they press against the dielectric surfaces 22.
  • a common pin 30 extends through the bottom of the plastic housing 10 between the two swing plates 24 and 26.
  • a flexible electrical connection 32 is made between the common pin 30 and each of the swing plates.
  • the capacitance between the common pin 30 and either of the fixed electrode plates 18 or 20 is at a maximum. If the capacitance were suitably sampled at this time, it would indicate that the plates 24 and 26 were in their unenergized position; because, a maximum of electrical energy would be coupled through the capacitors formed by the plates 24 and 18 and by the plates 26 and 20.
  • a keytop 40 is connected by a push rod 42 to the interior of the plastic housing 10.
  • a shoulder 44 on the push rod 42 is in engagement with a trip spring 46 which is also in engagement with the bent-over portion of the swing plate 26.
  • a shoulder 48 on the push rod 42 is connected by a spring 50 to the bent-over portion of the swing plate 24.
  • the trip springs 46 and 50 are compressed and exert increasing amounts of force upon the bent-over portions of their associated swing plates 24 and 26.
  • the trip spring 46 is so constructed that, upon depression of the keytop 40 to the position shown in FIG. 2, the spring 46 finally builds up a sufficient force to overcome the magnetic attraction of the permanent magnet 16, thereby causing the swing plate 26 to separate from its associated dielectric surface 22 as shown in FIG. 2.
  • the trip spring 50 is so constructed that only upon still further depression of the keytop 40 to the position indicated by the dotted lines 51 in FIG. 2 following the separation of the swing plates 26, is sufficient force exerted by the trip spring 50 on the bent-over por tion of the swing plate 24 to cause the swing plate 24 to separate from its associated fixed plate 18.
  • FIG. I and 2 is capable of providing one output upon a normal depression of the keytop 40 and of providing a second output to cause repetition of a character upon further depression of the same key.
  • FIG. 3 wherein the permanent magnet 16 is connected to fixed electrode 52, and the surface of the magnet 16 itself is one plate of the capacitor.
  • a ferromagnetic swing plate 54 is mounted to an electrode 56 by a tlexure joint 58.
  • a keytop 40 is constructed so as to fit around the outside of the plastic housing 10.
  • a trip spring 46 is connected between the keytop 40 and the swing plate 54. In the normal, unactuated position of the switch of FIG. 3, the magnet 16 attracts and holds the swing plate 54 firmly against the dielectric material 22 to assure maximum capacitive coupling between the electrodes 52 and 56.
  • a permanent magnet 16 is firmly mounted within a housing on a conductive framework connected to an electrode 62.
  • a ferromagnetic, conductive swing plate 64 is rotatably mounted on a pivot 66 and is normally attracted by the magnet 16.
  • a flexible electrical connection 68 assures electrical continuity between the electrode 62 and the swing plate 64.
  • the spring 46 is compressed until sufficient force is exerted by the spring 46 on an arm of the plate 64 to overcome the magnetic attraction of the permanent magnet 16. This permits the swing plate 64 to separate from the magnet 16 and rotate under the urging of the spring 46 clockwise about-the pivot 66 until the swing plate 64 is parallel to and abutting a dielectric material 22 on the surface of a fixed electrode 70.
  • the capacitive coupling between the electrodes 62 and 70 is minimum in the deenergized condition of the switch.
  • the swing plate 64 is in closer proximity to the fixed electrode 70, resulting in increased capacitive coupling between the electrodes 62 and 70.
  • FIG. is a variation which is illustrated -with respect to the structure of FIG. 4 but which might readily be applied to the embodiments shown in FIGS. 1, 2 and 3.
  • a push-to-latch, push-to-release cam 80 is mounted on the plastic housing 10.
  • the keytop 40 is connected to the cam follower 82 and is thus held in the depressed condition every second time that it is depressed.
  • Push-push mechanisms such as the cam 80 and follower 82 are well known in the prior art and will not be described further herein.
  • One typical capacitance sampling circuit 90 is shown in connection with the structure of FIG. 4.
  • the circuit 90 could be used equally well with the structures of FIGS. 1, 2 and 3.
  • Other types of capacitance sampling circuits will be readily apparent to one of ordinary skill in the art.
  • an AC generator 92 delivers a constant amplitude AC signal to the electrode 70.
  • the input of a rectifying detector 94 is connected to the electrode 62, and the detector 94 delivers an output that is a DC voltage having a magnitude that is representative of the amplitude of the AC voltage coupled from the electrode 70 to the electrode 62.
  • An amplifier 96 delivers an amplified DC signal to a Schmitt Trigger 98 or other voltage thresholdsensor which produces an output signal only when its signal input exceeds a predetermined magnitude.
  • the voltage levels can then be predetermined or adjusted at such magnitudes that the Schmitt trigger will produce an output voltage only when the voltage coupling between the electrodes 62 and 70 is equal to or greater than the coupling that exists when the swing plate 64 is pressed up against the dielectric 22 of FIG. 4.
  • a variable capacitance device comprising:
  • a third conductor with at least one planar surface and having at least one edge
  • a fourth conductor with at least one planar surface and having at least one edge; means for mounting the edge of the third conductor substantially in the plane of the surface of the first conductor;
  • a variable capacitance device comprising:
  • a second conductor constructed of magnetically permeable material and having at least one planar surface and at least one edge;
  • a permanent magnet for normally biasing the second conductor to a position adjacent to the first conductor
  • a variable capacitance device comprising:
  • a second conductor constructed of a magnetically permeable material and having at least one planar surface and at least one edge;
  • a permanent magnet for normally biasing the second conductor to a first stop position either adjacent to or away from the first conductor
  • leverage means for overcoming the attraction of the magnet in response to the application of force thereto and for moving the second conductor to a second stop position opposite to the first stop position;
  • 60 means for applying force to the leverage means.
  • a device wherein the force-applying means comprises a spring mounted at one end to the leverage means and having the other end positioned for manual energization.
  • a device according to claim 5, wherein a manually depressible key is attached to the other end of the spring.
  • a variable capacitance device comprising:
  • a first conductor having at least one planar surface
  • a second conductor having at least one planar surface
  • a third conductor having at least one planar surface arranged to be positioned substantially parallel with the planar surface of the first conductor
  • a fourth conductor having at least one planar surface arranged to be positioned substantially parallel with the planar surface of the second conductor
  • first means responsive to at least some movement of the push button for altering the distance between the first and third conductors in a direction substantially perpendicular to the planar surface of at least one of the first and third conductors, whereby the capacitive coupling between the first conductor and the third conductor is altered;
  • second means responsive to further movement of the push button for altering the distance between the second and fourth conductors in a direction substantially perpendicular to the planar surface of at least one of the second and fourth conductors, whereby the capacitive coupling between the second conductor and the fourth conductor is altered after the capacitive coupling between the first and third conductors is altered,
  • a device further comprising:
  • the first altering means comprises means responsive to some movement of the push button for overcoming the first biasing means
  • the second altering means comprises means responsive to further movement of the push button for overcoming the second biasing means after the first biasing means has been overcome.
  • a variable capacitance device comprising:
  • a first conductor having at least one planar surface
  • a second conductor having at least one planar surface arranged to be positioned substantially parallel with the planar surface of the first conductor
  • At least one of the first and second conductors being constructed of a ferromagnetic material
  • the biasing means comprises a magnet
  • a device wherein the permanent magnet is positioned adjacent the other of the first and second conductors and on the side opposite the ferromagnetic conductor, wherein the ferromagnetic conductor is attracted toward the other conductor.
  • a device wherein only one of the conductors is constructed of ferromagnetic material and the other of the conductors is disposed so that the biasing means comprises magnetic force normally attracting the ferromagnetic conductor toward the permanent magnetic conductor.
  • a variable capacitance device comprising:
  • a second conductor with at least one planar surface and having at least one edge
  • said second conductor being shaped to form a bend at the edge thereof with an elongated projection from said bend, said projection having an end remote from said bend;
  • pivoting means comprises:
  • a device according to claim 15 wherein the overcoming means comprises:
  • a device according to claim 16 wherein the coupling comprises a spring.
  • An improved capacitive switch of the type including a pair of spaced conductive plates, one of which is movable between first and second positions to vary the spacing between the plates and thus the capacitance, wherein the improvement comprises:
  • the movable plate being made of ferromagnetic material

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  • Switches That Are Operated By Magnetic Or Electric Fields (AREA)
  • Push-Button Switches (AREA)
US99186A 1970-12-17 1970-12-17 Variable capacitive apparatus Expired - Lifetime US3671822A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US9918670A 1970-12-17 1970-12-17

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US3671822A true US3671822A (en) 1972-06-20

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US99186A Expired - Lifetime US3671822A (en) 1970-12-17 1970-12-17 Variable capacitive apparatus

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US (1) US3671822A (cs)
CA (1) CA947384A (cs)
DE (1) DE2162044C3 (cs)
FR (1) FR2118697A5 (cs)
GB (1) GB1370488A (cs)
IT (1) IT957106B (cs)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3760243A (en) * 1972-09-21 1973-09-18 Gen Electric Capacitive keyswitch
DE2455434A1 (de) * 1973-11-29 1975-06-05 Teletype Corp Schaltungsanordnung zur feststellung des zustandes eines kapazitiven drucktastenschalters
US3943812A (en) * 1973-11-02 1976-03-16 Nippon Gakki Seizo Kabushiki Kaisha Touch responsive sensor in electronic keyboard musical instrument
US4034234A (en) * 1975-01-10 1977-07-05 Texas Instruments Incorporated Switching module for solid-state keyboard
US4095066A (en) * 1976-08-04 1978-06-13 International Business Machines Corporation Hinged flyplate actuator
US4209819A (en) * 1978-03-13 1980-06-24 Key Tronic Corporation Capacitive keyswitch
US20120293020A1 (en) * 2011-05-19 2012-11-22 Choon Sae Lee Device for Collecting Energy Wirelessly
US20140168875A1 (en) * 2012-12-19 2014-06-19 Lenovo (Singapore) Pte. Ltd. Thin Keyboard
US20150092330A1 (en) * 2013-09-28 2015-04-02 James M. Kershek Keyboard for an electronic device
US10936019B2 (en) * 2018-12-13 2021-03-02 Lenovo (Singapore) Pte Ltd Apparatus for preventing keytops from protruding from a top surface of an electronic apparatus

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3017944A1 (de) * 1980-05-10 1981-11-12 Rafi Gmbh & Co Elektrotechnische Spezialfabrik, 7981 Berg Kapazitives schaltelement
DE3018010C2 (de) * 1980-05-10 1985-01-17 Rafi Gmbh & Co Elektrotechnische Spezialfabrik, 7981 Berg Kapazitiver Taster als elektrischer Signalgeber
US4357646A (en) * 1981-01-21 1982-11-02 Illinois Tool Works Inc. Capacitive keyswitch with overtravel mechanism on moveable plate
US4352144A (en) * 1981-01-21 1982-09-28 Illinois Tool Works Inc. Capacitive keyswitch with overtravel plunger mechanism

Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE351686C (de) * 1922-04-12 Telephonwerke G M B H Deutsche Regelbarer Kondensator fuer Hochspannungskreise
US2179068A (en) * 1937-12-09 1939-11-07 Sprague Specialties Co Variable condenser
US2432089A (en) * 1941-11-06 1947-12-09 Sperry Gyroscope Co Inc Variable capacity pick-off for compass systems
US2438477A (en) * 1940-07-10 1948-03-23 Dodds John Mathieson Tuning circuit for radio transmitters
US2543570A (en) * 1947-03-22 1951-02-27 Gen Motors Corp Thickness gauge
US2589351A (en) * 1947-02-27 1952-03-18 Charles N Ehrlich Variable condenser
US2744222A (en) * 1952-03-24 1956-05-01 Beckman Instruments Inc Dynamic capacitor
US3183912A (en) * 1962-05-31 1965-05-18 George S Mogilner Diathermy machine
US3230431A (en) * 1962-09-20 1966-01-18 Standard Kollsman Ind Inc Combination feed-through and trimmer capacitor
US3293640A (en) * 1964-05-22 1966-12-20 Chalfin Albert Electronic systems keyboard and switch matrix
US3488565A (en) * 1968-02-07 1970-01-06 Erwin S Teltscher Ultra-flat variable capacitor assembly
US3551860A (en) * 1967-11-23 1970-12-29 Vladimir Alexeevich Smirnov Electromagnetic device for electric-circuit control and protection systems

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE351686C (de) * 1922-04-12 Telephonwerke G M B H Deutsche Regelbarer Kondensator fuer Hochspannungskreise
US2179068A (en) * 1937-12-09 1939-11-07 Sprague Specialties Co Variable condenser
US2438477A (en) * 1940-07-10 1948-03-23 Dodds John Mathieson Tuning circuit for radio transmitters
US2432089A (en) * 1941-11-06 1947-12-09 Sperry Gyroscope Co Inc Variable capacity pick-off for compass systems
US2589351A (en) * 1947-02-27 1952-03-18 Charles N Ehrlich Variable condenser
US2543570A (en) * 1947-03-22 1951-02-27 Gen Motors Corp Thickness gauge
US2744222A (en) * 1952-03-24 1956-05-01 Beckman Instruments Inc Dynamic capacitor
US3183912A (en) * 1962-05-31 1965-05-18 George S Mogilner Diathermy machine
US3230431A (en) * 1962-09-20 1966-01-18 Standard Kollsman Ind Inc Combination feed-through and trimmer capacitor
US3293640A (en) * 1964-05-22 1966-12-20 Chalfin Albert Electronic systems keyboard and switch matrix
US3551860A (en) * 1967-11-23 1970-12-29 Vladimir Alexeevich Smirnov Electromagnetic device for electric-circuit control and protection systems
US3488565A (en) * 1968-02-07 1970-01-06 Erwin S Teltscher Ultra-flat variable capacitor assembly

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3760243A (en) * 1972-09-21 1973-09-18 Gen Electric Capacitive keyswitch
US3943812A (en) * 1973-11-02 1976-03-16 Nippon Gakki Seizo Kabushiki Kaisha Touch responsive sensor in electronic keyboard musical instrument
DE2455434A1 (de) * 1973-11-29 1975-06-05 Teletype Corp Schaltungsanordnung zur feststellung des zustandes eines kapazitiven drucktastenschalters
US4034234A (en) * 1975-01-10 1977-07-05 Texas Instruments Incorporated Switching module for solid-state keyboard
US4095066A (en) * 1976-08-04 1978-06-13 International Business Machines Corporation Hinged flyplate actuator
US4209819A (en) * 1978-03-13 1980-06-24 Key Tronic Corporation Capacitive keyswitch
US20120293020A1 (en) * 2011-05-19 2012-11-22 Choon Sae Lee Device for Collecting Energy Wirelessly
US9030053B2 (en) * 2011-05-19 2015-05-12 Choon Sae Lee Device for collecting energy wirelessly
US20140168875A1 (en) * 2012-12-19 2014-06-19 Lenovo (Singapore) Pte. Ltd. Thin Keyboard
US9299513B2 (en) * 2012-12-19 2016-03-29 Lenovo (Singapore) Pte Ltd Thin keyboard
US20150092330A1 (en) * 2013-09-28 2015-04-02 James M. Kershek Keyboard for an electronic device
US9501105B2 (en) * 2013-09-28 2016-11-22 Intel Corporation Keyboard for an electronic device
US10936019B2 (en) * 2018-12-13 2021-03-02 Lenovo (Singapore) Pte Ltd Apparatus for preventing keytops from protruding from a top surface of an electronic apparatus

Also Published As

Publication number Publication date
GB1370488A (en) 1974-10-16
DE2162044A1 (de) 1972-07-06
FR2118697A5 (cs) 1972-07-28
DE2162044C3 (de) 1979-12-06
IT957106B (it) 1973-10-10
CA947384A (en) 1974-05-14
DE2162044B2 (de) 1979-04-19

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Owner name: AT&T TELETYPE CORPORATION A CORP OF DE

Free format text: CHANGE OF NAME;ASSIGNOR:TELETYPE CORPORATION;REEL/FRAME:004372/0404

Effective date: 19840817