VARIABLE CAPACITIVE APPARATUS

• US 3,671,822 A
• Filed: 12/17/1970
• Issued: 06/20/1972
• Est. Priority Date: 12/17/1970
• Status: Expired due to Term

• Current Assignee: AT&T Teletype Corporation (AT&T, Inc.)
• Original Assignee: Theodore M. Leno
• Inventors: Theodore, M. Leno
• Primary Examiner(s): E. A. Goldberg
• Application Number:
  US05/099,186
• Time in Patent Office: 551 Days
• Field of Search: 317/249R,246,245,250 200/DIG.1
• US Class Current: 361/288
• CPC Class Codes: B41J 5/14 Construction of key levers

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.

Claims

1. A variable capacitance device comprising:

a first conductor with at least one planar surface;

a second conductor with at least one planar surface;

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;

means for mounting the edge of the fourth conductor substantially in the plane of the surface of the second conductor;

a push button;

means responsive to at least some movement of the push button for pivoting the third conductor substantially along the edge thereof for altering the average distance between the surface of the first conductor and the surface of the third conductor, whereby the capacitive coupling between the first and third conductors is altered; and

means responsive to further movement of the push button for pivoting the fourth conductor along the edge thereof for altering the average distance between the surface of the second conductor and the surface of the fourth conductor, whereby the capacitive coupling between the second and fourth conductors is altered after the alteration of the capacitive coupling between the first and third conductors.

2. A device according to claim 1, wherein the two pivoting means comprise:

first means for normally biasing the third conductor to a position adjacent to the first conductor;

second means for normally biasing the fourth conductor to a position adjacent to the second conductor;

means responsive to at least some movement of the push button for overcoming the first biasing means and for moving the third conductor to a position remote from the first conductor; and

means responsive to further movement of the push button for overcoming the second biasing means and for moving the fourth conductor to a position remote from the second conductor.

3. A variable capacitance device comprising:

a first conductor with at least one planar surface;

a second conductor constructed of magnetically permeable material and having at least one planar surface and at least one edge;

means for mounting the edge of the second conductor substantially in the plane of the surface of the first conductor;

a permanent magnet for normally biasing the second conductor to a position adjacent to the first conductor; and

means for overcoming the bias of the permanent magnet and for pivoting the second conductor substantially along the edge thereof for increasing the average distance between the surface of the first conductor and the surface of the second conductor, whereby the capacitive coupling between the first and second conductors is altered.

4. A variable capacitance device comprising:

a first conductor with at least one planar surface;

a second conductor constructed of a magnetically permeable material and having at least one planar surface and at least one edge;

means for mounting the edge of the second conductor substantially in the plane of the surface of the first conductor;

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; and

means for applying force to the leverage means.

5. A device according to claim 4, 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.

6. A device according to claim 5, wherein a manually depressible key is attached to the other end of the spring.

7. 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;

a dielectric surface on at least one of the first and third conductors;

a dielectric surface on at least one of the second and fourth conductors;

a manually movable push button;

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; and

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.

8. A device according to claim 7, further comprising:

first means for biasing the first and third conductors in close proximity to each other;

second means for biasing the second and fourth conductors in close proximity to each other;

wherein the first altering means comprises means responsive to some movement of the push button for overcoming the first biasing means; and

wherein 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.

9. 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;

a sheet of solid dielectric material adhered to the surface of at least one of the first and second conductors;

means for biasing the first and second conductors in close proximity to each other;

means responsive to a mechanical input for overcoming the biasing means and for altering the distance between the first and second conductors in a direction between substantially perpendicular to the planar surface of at least one of the first and second conductors, whereby the capacitive coupling between the first conductor and the second conductor is altered.

10. A device according to claim 9, wherein the biasing means comprises a magnet.

11. A device according to claim 10, wherein the magnet is a permanent magnet.

12. A device according to claim 11, 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.

13. A device according to claim 9, 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.

14. A variable capacitance device comprising:

a conductor with at least one planar surface;

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;

a corner substantially in the plane of the surface of the first conductor;

the second conductor positioned with the bend thereof pivotally mounted substantially in the corner; and

means for applying a force to the end of the elongated projection of the second conductor for pivoting the second conductor substantially along the edge thereof at its bend for altering the average distance between the surface of the first conductor and the surface of the second conductor, whereby the capacitive coupling between the first and second conductors is altered.

15. A device according to claim 14, wherein the pivoting means comprises:

means for normally biasing the second conductor to a position adjacent to the first conductor; and

means for overcoming the biasing means and for moving the second conductor to a position remote from the first conductor.

16. A device according to claim 15 wherein the overcoming means comprises:

a push button; and

means interconnecting the push button with the end of the projection on the second conductor.

17. A device according to claim 16 wherein the coupling comprises a spring.

18. 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:

a magnet for normally biasing the movable plate to the first position, the movable plate being made of ferromagnetic material; and

a mechanical linkage for shifting the movable plate to the second position against the biasing action of the magnet, for changing the state of the switch.