Print wheel control
AssigneeComputer Entry Systems Corporation
InventorJohn Gilkeson Guthrie
Life of this patent
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Abstract
A control system for operating a single high-speed print wheel is disclosed. The control system includes a print wheel drive motor having a coded disc with transparent portions forming a four-level Gray code for indicating the position of the print wheel. An optical and electronic system is used for positioning the print wheel and also for the purpose of providing an electronic detent which uses the motive power of the print wheel drive for holding the print wheel in selected printing positions. A similar optical and electronic system is used for controlling a paper advance mechanism. The disclosed system also includes a print hammer with a voice coil type drive to permit positive, bidirectional hammer control.
Claims14
A system for controlling a print wheel comprising:
- motive power means coupled to said print wheel for driving said print wheel,
- position encoding means coupled to said print wheel for providing an indication of the position of said print wheel, said position encoding means including a code wheel having a ring of alternately spaced opaque and transparent regions of equal length for providing a coded indication of the angular position of said print wheel,
- first electronic detenting means coupled to said print wheel for selectively locking said print wheel in printing position, said first electronic detenting means including a pair of spaced light emitting devices and a pair of similarly spaced photo sensitive switching means, said light emitting devices and said photo sensitive switching means being positioned on opposite sides of said code wheel so that said opaque and transparent regions pass therebetween, said light emitting devices being spaced from one another by a distance less than said length of said opaque regions.
- paper advancing means coupled to said system for controlling the positioning of documents relative to said print wheel, and
- second electronic detenting means coupled to said paper advancing means for causing incremental movement thereof.
An electronic detenting circuit for holding a rotary element such as a print wheel in a selected position, comprising:
- indicator wheel means coupled to said rotary element, said indicator wheel means including alternating regions of fixed length characterized by first and second detectable properties,
- detector circuit means including a pair of sensing elements positioned adjacent said indicator wheel means for detecting said regions by sensing said first and second properties, said sensing elements spaced from one another by a distance such that both sensing elements can be placed adjacent regions characterized by one of said first and second detectable properties and such that slight motion of said indicator wheel means will cause one of said sensing elements to move adjacent to a region characterized by the other of said first and second detectable properties;
- and,
- control circuit means coupled to said detector circuit means for generating a motive force resisting movement of said rotary element away from said selected position.
A print wheel and document advance apparatus control system comprising:
- print wheel motor means coupled to said print wheel for rotating said print wheel,
- document advancing motor means coupled to said document advance apparatus,
- feedback control circuits coupled to said print wheel and document advancing motor means for controlling the speed of said motor means,
- opto-electronic detent means coupled to both said motor means for locking said print wheel and said document advance apparaus in selected positions, said detent means including a first coded indicator wheel coupled to said print wheel motor means and a second coded indicator wheel coupled to said document advancing motor means, first and second hybrid optical and electronic circuits for indicating movements of said indicator wheels and detent feedback circuitry for resisting movement of said motor means away from said selected positions;
- and, position indicating and selecting means coupled to said print wheel motor means for providing a continuous indication of the position of said print wheel and for driving said print wheel to desired printing positions, said position indicating and selecting means including a plurality of light emitting diodes positioned on one side of said first coded indicator wheel, decoder means coupled to said light emitting diodes for sequentially energizing said diodes in a predetermined sequence, and a plurality of photo transistors corresponding in number to said light emitting diodes for sensing the respective optical outputs thereof and positioned on the other side of said first coded indicator wheel, said photo transistors coupled to one another so as to provide a single output.
Dependencies are inferred from the claim text.