US 4,227,044 AGranted

Pen status system for digitizer pen

AssigneeTalos Systems, Inc.

InventorGeorge A. Fencl

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Abstract

A pen status indicating system for a digitizer pen utilized in conjunction with a digitizer having a grid of spaced conductors positioned beneath a writing surface. The digitizer includes an electronic system which scans the spaced conductors and senses signals produced in the spaced conductors by a transmitting coil located near the writing tip of a pen used to write on the writing surface. The pen status indicating system senses whether the writing tip of the pen is pressed against the writing surface. The pen status indicating system includes a split inductor having a movable core coupled in direct communication with a pen cartridge having the writing tip connected thereto. When the pen is raised, the movable core occupies a first position relative to the secondary winding of the split inductor windings and when the pen is lowered, the movable core is caused to occupy a second position relative to the split inductor windings, causing a phase reversal in a signal produced on a center tap conductor of the split inductor. A sensing circuit including a phase sensitive detector, a filter, and a comparator produces a pen status output signal in response to the signal on the center tap conductor.

Claims10

Dependent claims

In a digitizer, a pen status indicating system for indicating whether a writing tip of a pen is pressed against a writing surface, said pen status indicating system comprising in combination:

a. a housing for said pen;
b. a pen cartridge including a writing tip and a reservoir containing writing fluid;
c. resilient means for resiliently resisting movement of said writing tip toward said housing and urging said writing tip toward said writing surface;
d. inductive means having first and second series connected windings and a center tap for producing an AC pen status signal on said center tap, said inductive means including a movable core connected in substantially fixed relationship to said writing tip;
e. signal applying means for applying a first AC signal to said inductive means, said signal applying means also applying said AC signal to a pen coil to effect transmission of an electromagnetic signal for reception by grid conductors of said digitizer;
f. connecting means for connecting the end of said reservoir to said movable core, causing said movable core to occupy a first position when said writing tip is pressed against said writing surface and a second position when said writing tip is moved away from said writing surface;
and
g. sensing circuit means coupled to said intermediate tap of said secondary winding for producing a pen status logic signal indicating whether said movable core is in said first position or said second position, wherein said sensing circuit means includes a phase sensitive detector circuit for detecting and producing an output signal which is a positive signal when said movable core is in one of said positions and a negative signal when said movable core is in the other of said positions.

5 more elements

Dependencies are inferred from the claim text.