POSITION-INDICATING SYSTEM

• US 3,657,475 A
• Filed: 03/17/1970
• Issued: 04/18/1972
• Est. Priority Date: 03/19/1969
• Status: Expired due to Term

• Current Assignee: Georges Peronneau, Henr Poizat
• Original Assignee: Georges Peronneau, Henr Poizat
• Inventors: Peronneau, Georges, Poizat, Henr
• Primary Examiner(s): Claffy, Kathleen H.
• Assistant Examiner(s): Brauner, Horst F.
• Application Number:
  US05/020,369
• Time in Patent Office: 763 Days
• Field of Search: 73/141 178/18,19,20,21 324/71NE
• US Class Current: 178/18.05
• CPC Class Codes: G06F 3/0414 using force sensing means to determine a position
• CPC Class Codes: G06F 3/04142 the force sensing means being located peripherally, e.g. disposed at the corners or at the side of a touch sensing plate

Abstract

A position-indicating system, determining the coordinates of a point of a surface to which static force is applied, comprises a rigid plate which is fixed to the surface by means of at least three spaced-apart sensors. These sensors delivering each an output signal which is proportional to its distance from the point of application of the force. These signals are then processed in an electronic unit generating two voltages which represent the coordinates of the point of application of the force to the surface, as measured with reference to two axes determined by the three sensors.

Claims

1. A system for locating the point of application of static pressure to a receiving surface, comprising:

a rigid body with an exposed surface subject to the application of localized, perpendicular pressure;

a plurality of sensors fixedly mounted at spaced-apart points including a first sensor at a first point, a second sensor at a second point and a third sensor at a third point, said first and second points defining a first coordinate axis, said second and third points defining a second coordinate axis, said body being supported exclusively by said sensors, each of said sensors generating a reading signal varying with a respective component of the applied pressure acting upon said exposed surface; and

calculating means with a first set of input connections to said first and second sensors and with a second set of input connections to said second and third sensors for deriving from the reading signals thereof two output signals proportional to the coordinates of the point of application of said pressure with reference to said axes.

2. A system as defined in claim 1 wherein said calculating means includes first summing means provided with said first set of input connections, second summing means provided with said second set of input connections, third summing means provided with a third set of input connections to all said sensors, first divider means connected to said first and third summing means for deriving therefrom a first output signal proportional to the sum of the magnitudes of the reading signals of said first and second sensors divided by the sum of the magnitudes of all said reading signals, and second divider means connected to said second and third summing means for deriving therefrom a second output signal proportional to the sum of the magnitudes of the reading signals of said second and third sensors divided by the sum of the magnitudes of all said reading signals.

3. A system as defined in claim 2 wherein said sensors include a fourth sensor at a fourth point complementing said first, second and third points to a rectangle.

4. A system as defined in claim 1 wherein said sensors comprise piezoelectric elements.

5. A system as defined in claim 4, further comprising a source of alternating voltage, with an operating frequency corresponding to the natural frequency of said piezoelectric elements, connected to said elements for exciting same into generation of said reading signals with an amplitude varying inversely with the respective pressure components.

6. A system as defined in claim 5, further comprising rectifier means inserted in respective output circuits of said sensors ahead of said calculating means.

7. A system as defined in claim 1 wherein said body is a horizontal plate, each of said sensors comprising a pair of pressure-responsive elements serially connected to said calculating means, said elements bearing upon said plate from opposite sides.

8. A system as defined in claim 1 wherein said calculating means further includes threshold means connected to all said sensors for detecting the magnitudes of said reading signals, and gating means controlled by said threshold means for suppressing said output signals in the absence of a significant reading signal from at least one of said sensors.