PUSH BUTTON KEYBOARD WITH OSCILLATOR KEYING

• US 3,772,684 A
• Filed: 01/26/1972
• Issued: 11/13/1973
• Est. Priority Date: 01/26/1972
• Status: Expired due to Term

• Current Assignee: John R. Scantlin
• Original Assignee: John R. Scantlin
• Inventors: Scantlin, John R.
• Primary Examiner(s): Habecker, Thomas B.
• Application Number:
  US05/220,936
• Time in Patent Office: 657 Days
• Field of Search: 340/365C,365L
• US Class Current: 341/32
• CPC Class Codes: H03K 17/972 having a plurality of control members, e.g. keyboard
• CPC Class Codes: H04L 25/40 Transmitting circuits; Receiving circuits repeater circuits, relay circuits H04L25/20

Abstract

A push button keyboard with no moving contacts. A keyboard with an oscillator for each push button, with pushing of the button changing the oscillator frequency. Circuitry for sequentially sampling the push button oscillators for comparison with a master oscillator to determine push button position. Circuitry providing a hysteresis band to eliminate push button bounce and indefinite button motion problems.

Claims

1. In a keyboard with a plurality of push buttons, the combination of:

a housing;

a coil mounted in said housing;

a push button mounted in said housing within said coil for movement between not pushed and pushed positions;

means carried by said push button for movement toward and away from said coil for changing the inductance of said coil as said push button is moved to the pushed positions, said inductance changing means including a magnetic core member and a closed loop conductor member, with one of said members moving toward said coil and the other of said members moving away from said coil as said push button is moved to the pushed position;

an oscillator having said coil in the resonant circuit thereof, with change in inductance of said coil changing the frequency of said oscillator; and

circuit means coupled to said oscillator for detecting a change in oscillator frequency and producing a button pushed signal.

2. A keyboard as defined in claim 1 including a multilayer printed circuit board with an opening for said push button, and with said coil comprising interconnected conducting loops about said opening on layers of said board.

3. A keyboard as defined in claim 2 wherein said oscillator includes said coil and a capacitor, with said capacitor comprising conducting plates on layers of said board adjacent said push button opening.

4. A keyboard as defined in claim 2 including a plurality of adjacent openings in said board with a push button positioned in each opening, and with an oscillator for each opening, with each oscillator comprising interconnected conducting loops about the opening on layers of the board.

5. In a keyboard with a plurality of push buttons, the combination of:

a housing;

a coil mounted in said housing;

a push button mounted in said housing for movement between not pushed and pushed positions;

means driven by said push button for changing the inductance of said coil as said push button is moved to the pushed position;

an oscillator having said coil in the resonant circuit thereof, with change in inductance of said coil changing the frequency of said oscillator;

circuit means coupled to said oscillator for detecting a change in oscillator frequency and producing a button pushed signal; and

a multilayer printed circuit board with an opening for said push button, and with said coil comprising interconnected conducting loops about said opening on layers of said board;

said housing including a bore with a shoulder, and said push button including a plunger with a shoulder, with said push button positioned in said bore with a coil spring about said plunger between said shoulders urging said push button to a not pushed position, and including means for mounting said printed circuit board on said housing with the board opening aligned with the housing bore, said plunger having a radially compressible end with a retainer tip, with said inductance changing means including a conducting ring carried on said plunger at said tip and a magnetic sleeve carried on said plunger between said ring and plunger shoulder so that said spring is compressed and said ring is moved out of said coil and said sleeve is moved into said coil as said push button is moved from the not pushed position to the pushed position.

6. In a keyboard with a plurality of push buttons, the combination of:

a housing;

a coil mounted in said housing;

a push button mounted in said housing for movement between not pushed and pushed positions;

means driven by said push button for changing the inductance of said coil as said push button is moved to the pushd position;

an oscillator having said coil in the resonant circuit thereof, with change in inductance of said coil changing the frequency of said oscillator; and

circuit meAns coupled to said oscillator for detecting a change in oscillator frequency and producing a button pushed signal;

said circuit means for detecting including;

a second master oscillator operating at a substantially constant frequency in the frequency range of said one oscillator;

means for comparing the frequencies of said oscillators; and

means for determining when the frequencies differ by at least a predetermined amount.

7. In a keyboard with a plurality of push buttons, the combination of:

a housing;

a coil mounted in said housing;

a push button mounted in said housing for movement between not pushed and pushed positions;

means driven by said push button for changing the inductance of said coil as said push button is moved to the pushed position;

an oscillator having said coil in the resonant circuit thereof, with change in inductance of said coil changing the frequency of said oscillator;

circuit means coupled to said oscillator for detecting a change in oscillator frequency and producing a button pushed signal; and

a multilayer printed circuit board with an opening for said push button, and with said coil comprising interconnected conducting loops about said opening on layers of said board;

said circuit means for detecting including;

a second master oscillator operating at a substantially constant frequency in the frequency range of said one oscillator and including a coil comprising interconnected conducting loops on layers of said board and corresponding to said one oscillator coil;

means for comparing the frequencies of said oscillators; and

means for determining when the frequencies differ by at least a predetermined amount.

8. A keyboard as defined in claim 7 wherein said master oscillator includes the coil and a capacitor, with said master oscillator capacitor comprising conducting plates on layers of said board corresponding to the capacitor of said one oscillator.

9. In a keyboard with a plurality of push buttons, the combination of:

a housing;

a plurality of coils mounted in said housing;

a plurality of push buttons mounted in said housing for movement between not pushed and pushed positions;

means driven by each of said push buttons for changing the inductance of a corresponding coil as the push button is moved to the pushed position;

a plurality of oscillators each having a coil in the resonant circuit thereof, with change in inductance of the coil changing the frequency of the oscillator; and

circuit means coupled to said oscillators for detecting a change in oscillator frequency and producing a button pushed signal;

said circuit means including;

a master oscillator operating at a substantially constant frequency in the frequency range of said push button oscillators;

means for comparing the frequency of said master oscillator and another oscillator; and

a multiplexer for sequentially connecting said push button oscillators to said means for comparing, with said means for comparing operating with the connected push button oscillator to produce the button pushed signal regardless of the current position of the push button of the previously connected oscillator.

10. In a keyboard with a plurality of push buttons, the combination of:

a housing;

a coil mounted in said housing;

a push button mounted in said housing for movement between not pushed and pushed positions;

means driven by said push button for changing the inductance of said coil as said push button is moved to the pushed position;

an oscillator having said coil in the resonant circuit thereof, with change in inductance of said coil changing the frequency of said oscillator; and

circuit means coupled to said oscillator for detecting a change in oscillator frequency and producing a button pushed signal;

with said one oscillator operating at a first frequency when said push button is not pushed and at a second frequency when said pusH button is pushed, and with said circuit means for detecting including;

a second master oscillator operating at a third frequency intermediate said first and second frequencies;

means for comparing the frequencies of said oscillators; and

means for determing when the frequency of said one oscillator changes from said first frequency toward said second frequency past said third frequency by a predetermined amount and then producing the button pushed signal, and for determining when the frequency of said one oscillator changes back toward said first frequency and producing the button pushed signal until said one oscillator reaches said third frequency.

11. A keyboard as defined in claim 10 wherein said first and second frequencies differ from said third frequency in the order of 10 percent of said third frequency, and said predetermined amount is in the order of a few percent of said third frequency.

12. In a keyboard with a plurality of push buttons, the combination of:

a housing;

a coil mounted in said housing;

a push button mounted in said housing for movement between not pushed and pushed positions;

means driven by said push button for changing the inductance of said coil as said push button is moved to the pushed position;

an oscillator having said coil in the resonant circuit thereof, with change in inductance of said coil changing the frequency of said oscillator; and

circuit means coupled to said oscillator for detecting a change in oscillator frequency and producing a button pushed signal;

said circuit means for detecting including;

a second master oscillator operating at a frequency in the range of said one oscillator;

a first counter for counting the output of said one oscillator;

a second counter for counting the output of said master oscillator;

means for periodically starting counting of said first and second counters at the same time and stopping counting by said first counter when said second counter reaches a predetermined count state; and

means for producing the pushed signal when the count state of said first counter is more than a predetermined amount different on one side of the count state of said second counter at the end of the count cycle.

13. A keyboard as defined in claim 12 including:

means for storing the pushed signal of said one oscillator; and

means for blocking production of the pushed signal at the end of the next counting cycle if a pushed signal was produced at the end of the previous counting cycle, including means for connecting the stored pushed signal to said means for blocking as an input.

14. A keyboard as defined in claim 13 wherein said means for producing includes means for producing the opposite of the pushed signal when the count state of said first counter differs on the other side of the count state of said second counter.

15. A keyboard as defined in claim 14 wherein said means for producing includes means for blocking production of opposite of the pushed signal when the count state of said first counter is equal to or different on said one side of the count state of said second counter at the end of the next counting cycle when a pushed signal was stored at the end of the previous counting cycle.

16. A keyboard as defined in claim 12 including:

a plurality of said push button oscillators, with a coil, push button and means for changing inductance for each of said oscillators;

a multiplexer for sequentially connecting said push button oscillators to said first counter with each of said push button oscillators having an address;

means for generating a code corresponding to the address of the particular push button oscillator connected to said first counter during a counting cycle; and

means for transmitting said code to a line when a pushed signal is produced.