Capacitive transducer apparatus and method of manufacture thereof for computer display user interface

• US 6,504,703 B1
• Filed: 06/06/1997
• Issued: 01/07/2003
• Est. Priority Date: 06/06/1997
• Status: Expired due to Fees

• Current Assignee: Bokam Engineering, Inc.
• Original Assignee: Bokam Engineering, Inc.
• Inventors: Kamentser, Boris, Kamentser, Eugenia
• Primary Examiner(s): Kincaid, Kristine
• Assistant Examiner(s): Dinkins, Anthony
• Application Number:
  US08/870,635
• Time in Patent Office: 2,041 Days
• Field of Search: 361/275.3, 361/277, 361/278, 361/280, 361/281, 361/283.2, 361/283.3, 361/287, 361/288, 361/290, 361/291, 361/292, 361/296, 361/299.1, 361/298.2, 310/338, 200/600, 307/116, 307/119, 307/148
• US Class Current: 361/290
• CPC Class Codes: G01L 5/223 to joystick controls

Abstract

A capacitive transducer apparatus converts mechanical force to electrical signal parameters by change of spacing between plates of a plurality of capacitors. The apparatus has two mechanical components. The first component includes an articulating member such as a post surrounded by a first capacitive plate. Means are provided for causing the articulating member to articulate responsive to user manipulation thereof, and thereafter, to return to a quiescent position. The second component includes a second capacitive plate made up of a plurality of printed metalized members disposed about the articulating member substantially parallel to the first capacitive plate. A circuit is provided for detecting respective signals from a plurality of capacitors formed by the plates, the respective signals varying in value depending on articulation of the articulating member which alters the capacitance of the respective capacitors depending on the direction and magnitude of an applied force. The capacitors preferably include flat, electrically conductive members on a planar substrate, such as etched conductive regions on a printed circuit board, and the articulating member includes an electrically conductive member whose varying proximity to the conductive region, due to the manipulation by the user, produces a correspondingly varying capacitance value. The magnitude of the capacitance is determined by a data acquisition system, preferably including RC oscillators and a microcontroller.

Claims

1. A capacitive transducer apparatus for converting mechanical force applied to an elongated member to corresponding electrical signals having at least one parameter dependent upon the direction and magnitude of the applied force;

the apparatus comprising;

a pair of spaced, substantially parallel, conductive planar surfaces, a first one of said surfaces being fixed irrespective of the force applied to said elongated member, a second one of said surfaces being mechanically affixed to said elongated member and being responsive to movement of said elongated member for altering at least the spacing relative to the first one of said surfaces thereby changing the capacitance formed by said surfaces;

means connected to said first and second surfaces for converting said capacitance to said corresponding electrical signals.

2. The apparatus recited in claim 1 wherein each said surface comprises a plurality of distinct elements, each of said elements of said first surface cooperating with a corresponding one of said elements of said second surface to form a plurality of distinct variable capacitors;

and

wherein said means for converting comprises means associated with each of said variable capacitors for converting each of said capacitors to a distinct electrical signal.

3. The apparatus recited in claim 2 wherein each of said surfaces comprises four substantially symmetrical quadrants forming said distinct elements.

4. The apparatus recited in claim 3 wherein said means for converting comprises a separate oscillator for each of said four quadrants, the frequency of oscillation of each said oscillator being a function of the spacing between respective opposed quadrants of said first and second surfaces.

5. The apparatus recited in claim 1 wherein said at least one parameter is frequency of oscillation and wherein said means for converting comprises at least one oscillator, the oscillator frequency of which is dependent upon said spacing.

6. The apparatus recited in claim 5 wherein said at least one oscillator comprises a variable resistor.

7. The apparatus recited in claim 5 wherein said at least one oscillator comprises a laser-trimmed resistor.

8. The apparatus recited in claim 1 wherein said elongated member comprises a post extending substantially perpendicular to said surfaces in the absence of the applied force.

9. The apparatus recited in claim 8 further comprising a printed circuit board, said first surface being a metalized plate printed on said board;

said second surface being a metalized plate substantially suspended above said first surface;

said post being affixed to said second surface at substantially the center thereof, the apparatus further comprising a dielectric material positioned between said first and second surfaces.

10. The apparatus recited in claim 8 wherein each of said surfaces comprises four substantially symmetrical quadrants forming said plurality of distinct elements.

11. The apparatus recited in claim 10 further comprising a printed circuit board, said first surface being a metalized plated printed on said board;

said second surface being a metalized plate substantially suspended above said first surface;

said post being affixed to said second surface at substantially the center of said four quadrants.

12. The apparatus recited in claim 11 further comprising an aperture at said center of said four quadrants beneath said post and a terminal on said printed circuit board below said post permitting selective depression of said post for connecting said second surface to said terminal.

13. The apparatus recited in claim 1 further comprising a ceramic substrate, said first surface being a metalized layer printed on said substrate.

14. A method of fabricating a force transducer for converting applied mechanical force to a frequency of oscillation;

the method comprising the following steps;

a) providing a ceramic substrate;

b) metalizing a selected shape on one surface of said substrate;

c) suspending a metal plate in substantially parallel spaced relation to said metalized shape;

d) affixing a post perpendicularly to said plate for tilting said plate upon articulation of said post;

e) electrically connecting said selected shape and said metal plate as a capacitive input to an oscillator circuit;

f) providing said oscillator circuit on a second surface of said substrate, said oscillator circuit including a screen printed resistor and a Schmitt trigger device; and

g) laser trimming said resistor until a desired frequency of oscillation of said oscillator circuit is achieved.