Electrostatic tablet writing stylus
First Claim
1. A device for sensing a dynamic electrostatic field through a tablet of paper on a writing table comprisinga stylus of conductive material having an extended body portion and tip for writing on said tablet,a tubular member of conductive material surrounding said stylus over at least a portion thereof near said tip and insulated therefrom,amplifying means directly connected to said tubular member, andmeans for connecting said stylus to ground reference potential for said amplifying means.
2 Assignments
0 Petitions
Accused Products
Abstract
An improved device for capacitively detecting signals generated in a writing table by a grid of conductive wires that produce a varying electrostatic field near its surface to be picked up through a stack of paper with the table functioning as one plate of a capacitor, and a conductive stylus as the other plate. The improvement consists of grounding the stylus, which has an extended body portion surrounded by a tubular member, extending the tubular member to a point very near the stylus tip where it functions as the second plate of a capacitor, and connecting the tubular member to a preamplifier mounted in the device.
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Citations
7 Claims
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1. A device for sensing a dynamic electrostatic field through a tablet of paper on a writing table comprising
a stylus of conductive material having an extended body portion and tip for writing on said tablet, a tubular member of conductive material surrounding said stylus over at least a portion thereof near said tip and insulated therefrom, amplifying means directly connected to said tubular member, and means for connecting said stylus to ground reference potential for said amplifying means.
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5. A device for sensing a dynamic electrostatic field through a tablet of paper on a writing table comprising
a stylus of conductive material having an extended body portion and tip for writing on said tablet, a tubular member of conductive material surrounding said stylus and insulated therefrom, said tubular member having a portion extending to a position very near said stylus tip, said extended portion being coaxial with said tip and insulated therefrom, a housing of conductive material enclosing a substantial portion of said stylus and surrounding tubular member, amplifying means directly connected to said tubular member, and means for connecting said stylus to circuit ground for said amplifying means, whereby said tubular member capacitively couples directly to said amplifying means an electrical signal corresponding to said dynamic electrostatic field.
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7. In a device for capacitively coupling into an amplifier signals generated in a writing table by a grid of conductive wires that produce a varying electrostatic field near its surface while said device is in use for writing on a tablet on said table, said table functioning as one plate of a capacitor, and a conductive stylus in said device functioning as the other plate of said capacitor, the improvement comprising means for grounding said stylus, thereby to remove it from the capacitive coupling circuit, and providing a tubular member of conductive material near the writing tip of said stylus, said tubular member being coaxial with said tip and insulated therefrom, and means for directly connecting said tubular member to said amplifier.
Specification