CONTACTLESS ELECTRONIC KEYBOARD ARRAY

• US 3,594,487 A
• Filed: 08/25/1969
• Issued: 07/20/1971
• Est. Priority Date: 08/25/1969
• Status: Expired due to Term

• Current Assignee: Jones John Paul Jr
• Original Assignee: Jones John Paul Jr
• Inventors: JONES JOHN PAUL JR
• Application Number:
  US04/852,590
• Time in Patent Office: 694 Days
• US Class Current: 84/688
• CPC Class Codes: H03K 17/97 using a magnetic movable element
• CPC Class Codes: H03K 17/972 having a plurality of control members, e.g. keyboard

Abstract

An electronic keyboard system includes a key structure comprising primary and secondary coils coupled together by a magnetic shaft when moved to produce primary signals from a pulse train in the secondary. A magnetic shield between the coils produces a sharp transistor between no-signal and signal condition in the secondary winding as the shaft is moved past a critical position. Electronic circuitry provides for converting the pulse train into a single output pulse for each key depression, by use of a single Schmidt trigger circuit coupled into an encoding matrix to produce a coded signal for each separate key.

Claims

1. Structure operable in an electronic keyboard comprising in combination, an electronic key device manually actuable from a key button having a longitudinally oriented shank coupled to the key button and movable axially over a confined span of longitudinal movement, magnetic material of low reluctance in at least a portion of said shank extending a predetermined distance along the axis of movement and movable with the shank, biasing means holding the shank in a nominal return position, a first coil wound about said shank to permit its axial movement through the coil and extending in the region of said magnetic material to substantially the terminal end of the magnetic material at the end of the shank remote from the key button, a second coil wound about the axis of said shank to permit its axial movement through the coil and placed substantially adjacent said first coil beyond the terminal end of the magnetic material in said shank, and a magnetic plate of low reluctance material placed between the coils and closely enough surrounding said shank to establish a low reluctance flux path return from said remote end of the magnetic material when the magnetic material is confined within the first coil as the key button is in said return position, whereby said two coils are mutually magnetically coupled with a low reluctance path through the magnetic material of said shank only when the shank is moved enough to pass the end of the magnetic material in the shank through said magnetic plate to enter the second coil.

2. Structure as defined in claim 1 wherein a hood of low reluctance magnetic material surrounds said coils, said plate and said shank to provide a low reluctance return path for magnetic flux extending from said remote end of said magnetic material in the shank.

3. Structure as defined iN claim 1 including a source of continuous pulses coupled to said first coil, means coupled to said second coil for receiving a plurality of pulses from said source whenever the shank is moved from said return position, and means converting said plurality of pulses to a single output pulse comprising a hysteresis circuit responsive to two selected threshold valves encountered intermediate in a range of amplitudes of pulses from said source encountered as the magnetic material of said shank enters the second coil during shank movement to produce only one output response pulse for each shank reciprocation, said single output pulse being derived from said output response pulse.

4. Structure as defined in claim 3 wherein said hysteresis circuit comprises a flip-flop circuit, and structure integrating pulses from said source of pulses to set the flip-flop at one threshold level and to reset the flip-flop at a different threshold level from the integrated pulses.

5. Structure as defined in claim 1 having a source of pulses connected for transfer between said two coils when the magnetic material of said key shank is axially moved into a position encompassing both said coils, including hysteresis circuit means responsive to pulses transfered from said source at the coils to provide a single indication of a reciprocation cycle of said shank including means integrating said pulses and means detecting two different threshold levels of the integrated pulses to define therebetween a hysteresis band where variations of pulse amplitude due to variations of coupling between said coils are made ineffective.