Electrical writing pen and sensor

• US 3,886,311 A
• Filed: 04/22/1974
• Issued: 05/27/1975
• Est. Priority Date: 05/16/1972
• Status: Expired due to Term

• Current Assignee: CalComp, Inc. (Martin Marietta Corporation)
• Original Assignee: James L. Rodgers, Joseph L. Tyrrell
• Inventors: Rodgers, James L., Tyrrell, Joseph L.
• Primary Examiner(s): Robinson, Thomas A.
• Application Number:
  US05/463,154
• Time in Patent Office: 400 Days
• Field of Search: 178/18,19,20 340/347AD,146.3SY 73/432R,432A 346/139C 33/1M
• US Class Current: 178/20.04
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0441 using active external devices, e.g. active pens, for receiving changes in electrical potential transmitted by the digitiser, e.g. tablet driving signals

Abstract

A writing pen for detecting time varying electrostatic field components and used in conjunction with a writing table which generates a unique electrostatic field is disclosed.

Claims

1. An information transmission system including a writing instrument for detecting the information to be transmitted and a writing table with associated electronic circuitry having positions represented by time varying electrostatic field components, said writing instrument comprising, in combination:

a. a pen cartridge containing ink and including a pen point at one end thereof for transferring said ink to a writing surface for effecting a visual record of the path of said pen point;

b. a pen cartridge housing having a longitudinally extending cavity for receiving and supporting said pen cartridge in said housing with said pen point extending from said housing;

c. an electrostatic field pick up element forming a part of said pen point for detecting and re-radiating said electrostatic field components in proximity to the point of contact between said pen point and said writing table;

d. an electrostatic field sensing element secured in said housing adjacent said pen point of said pen cartridge for detecting said electrostatic field components radiated by said pick up element and issuing an output signal in response thereto;

e. signal amplifying means secured to said pen cartridge housing at an end remote from said pen point;

f. electrical conducting means extending uninterrupted substantially the length of said housing and connected to said field sensing element and to said signal amplifying means; and

g. means defining an opening in said cartridge housing extending longitudinally thereof and communicating with said cavity to permit said pen cartridge to be removed and replaced without disconnecting said electrical conducting means.

2. The system as set forth in claim 1, wherein said electrostatic field sensing element comprises a coil, said coil being axially aligned with said pen cartridge.

3. The system as set forth in claim 2, wherein said coil circumscribes said pen point.

4. The system as set forth in claim 1, wherein said pen cartridge comprises a ballpoint pen.

5. The system as set forth in claim 1, including a switch means mounted in said pen cartridge housing adjacent said signal amplifying means actuated by said pen cartridge for providing an electrical indication that said pen cartridge is in operative contact with said writing table.

6. The system as set forth in claim 1, wherein said electrostatic field pick up element comprises said pen point.

7. The system as set forth in claim 1 wherein said pen point and said electrostatic field sensing element are capacitively coupled.

8. The system as Set forth in claim 7, including an electrical shield disposed within said housing intermediate the extremity of said pen point and said electrostatic field sensing element for reducing stray capacitance about said electrostatic field sensing element.

9. The system as set forth in claim 8 wherein said electrostatic field sensing element is positioned within said housing to permit axial movement of said pen point without affecting the capacitive coupling between said pen point and said electrostatic field sensing element.

10. The system as set forth in claim 8 wherein said shield is an inverted hollow truncated cone and circumscribes said pen point.