Discriminating contact sensor

• US 3,911,215 A
• Filed: 03/18/1974
• Issued: 10/07/1975
• Est. Priority Date: 03/18/1974
• Status: Expired due to Term

• Current Assignee: George S. Hurst, William C. Colwell Jr
• Original Assignee: George S. Hurst, William C. Colwell Jr
• Inventors: Hurst, George S., Colwell, William C. Jr.
• Primary Examiner(s): Robinson, Thomas A.
• Application Number:
  US05/452,784
• Time in Patent Office: 568 Days
• Field of Search: 200/86R,153M,46,159 178/18,19,20 33/1M 340/272
• US Class Current: 178/18.05
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

A sensor construction is described for normally maintaining two juxtaposed electrical potential carrying sheets, at least one being flexible, separated from each other but permitting contact therebetween when an object of specified radius of curvature is pressed against the flexible sheet. The separation of the sheets is accomplished by producing discrete small buttons of insulation, preferably on the flexible sheet, with the spacing and the height of the buttons determining the largest radius of curvature to which the sensor will respond. This construction is specifically applied to a telescriber sensor or the like whereby contact is made only by depression of the flexible sheet with a writing instrument and not by any portion of a writer'"'"''"'"'s hand.

Claims

1. A discriminating contact sensor which will respond only to a contacting object having a radius of curvature less than a specific value, which comprises:

a first sheet of a flexible material capable of being energized to establish an electrical potential thereon, a second sheet capable of being energized to establish an electrical potential thereon in juxtaposition with the first sheet, and a plurality of substantially uniform discrete insulating buttons electrically separating the first and second sheets throughout the sensor, the buttons having a height and an average spacing whereby the maximum radius of curvature of the object to which the sensor will respond is approximately equal to the square of the average spacing between the buttons divided by eight times the height of the buttons.

2. The sensor of claim 1 wherein the insulating buttons are substantially circular in a section parallel to the first and second sheets and have a diameter from about 0.001 to about 0.015 in., an average spacing between adjacent buttons of from about 0.025 to about 0.075 in. and a height in a direction perpendicular to the first and second sheets of from about 0.0005 to about 0.015 in.

3. An improved electrographic sensor for writing thereon of the type wherein a uniform resistive sheet having electrodes attached thereto for the application of orthogonal electrical potentials is overlaid with a flexible conductive sheet and spaced therefrom so as to normally prevent contact therebetween but permit contact when the flexible sheet is deformed by an object having a radius of curvature less than a specific value, wherein the improvement comprises:

discrete insulator buttons of substantially uniform size electrically separating the sheets throughout the sensor, the buttons having a height and an average spacing whereby the maximum radius of curvature of the object to which the sensor will respond is approximately equal to the square of the average spacing between the buttons divided by eight times the height of the buttons.

4. The sensor of claim 3 wherein the insulating buttons are attached to the surface of the conductive sheet.

5. The sensor of claim 3 wherein the buttons have a diameter from about 0.001 to about 0.015 in., the height thereof is from about 0.0005 to about 0.015 in., and the average spacing between the buttons is from about 0.025 to about 0.075 in.

6. The sensor of claim 3 wherein the electrodes attached to the resistive sheet are a plurality of spot electrodes equally spaced along each edge of the resistive sheet;

and further comprising a plurality of discrete resistors each of which are connected between adjacent of the spot electrodes whereby a series resistor network is formed along each edge of the resistive sheet.