Capacitor array sensors for determining conformity to surface shape

• US 4,908,574 A
• Filed: 07/29/1988
• Issued: 03/13/1990
• Est. Priority Date: 09/03/1986
• Status: Expired due to Term

• Current Assignee: The ExOne Company (Desktop Metal, Inc.)
• Original Assignee: Extrude Hone Corporation
• Inventors: Risko, Donald, Rhoades, Lawrence J., Resnick, Ralph L.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): WILLIAMS, HOWARD L
• Application Number:
  US07/225,820
• Time in Patent Office: 592 Days
• Field of Search: 324/61 R, 324/61 P, 324/61 QS, 324/61 QL, 361/278, 361/280, 361/283, 361/287, 361/290, 901/9, 901/10, 901/33, 901/34, 901/35, 901/44, 901/45, 901/46
• US Class Current: 324/675
• CPC Class Codes: B25J 13/083 fitted with slippage detectors
• CPC Class Codes: B25J 13/084 Tactile sensors in general G01L5/16, G01L5/22
• CPC Class Codes: B25J 13/086 Proximity sensors
• CPC Class Codes: B25J 19/02 Sensing devices
• CPC Class Codes: G01B 5/205 of turbine blades or propellers
• CPC Class Codes: G01B 7/023 for measuring distance between sensor and object G01B7/082 and G01B7/102 take precedence
• CPC Class Codes: G01D 5/2417 by varying separation
• CPC Class Codes: G01L 1/146 for measuring force distributions, e.g. using force arrays G01L1/148 takes precedence
• CPC Class Codes: G01L 5/228 using tactile array force sensors

Abstract

A sensor for sensing and quantifying the conformity of a workpiece surface contour to a predetermined design contour. The sensor consists of an array of capacitor elements on a surface having the negative image of the predetermined design contour, against which the workpiece is mated. In operation, each of the capacitor elements and the workpiece are connected to a corresponding oscillator circuit so that the frequency of each circuit is a function of the capacitance between the individual plate element and the workpiece, while the capacitance is a function of the distance between the individual plate element and the workpiece. Hence the overall output of the circuits is a function of the conformity of the workpiece surface contour to the contour or topology of the sensor surface.

Claims

1. A capacitance sensor array for sensing and quantifying conformity of a workpiece surface contour to design requirements comprising a plurality of capacitor elements formed in a three-dimensional array of contour topology conforming to the topology of the design requirements of said workpiece, means for actively connecting each of said capacitor elements and said workpiece to one of a plurality of corresponding oscillator circuits while said capacitor elements are closely spaced from said workpiece so that the oscillation frequency of each of said circuits is a function of the capacitance between each said capacitor element and said workpiece, and means for generating an output from said sensor which is a function of the conformity of the contour topology of said workpiece to the contour topology of said array of capacitor elements determined by response of the said plurality of oscillator circuits.

2. The sensor of claim 1 wherein said capacitance between each of said capacitor elements and said workpiece is a function of the distance between the element and said workpiece.

3. The sensor of claim 1 wherein each of said capacitor elements has a frontal area of from 0.01 to 100 square millimeters.

4. The sensor of claim 1 wherein each of said capacitor elements has an area of from 0.1 to 10 square millimeters.

5. The sensor of claim 1 wherein said output is a plurality of signals corresponding to the oscillation frequency of each of said oscillators.

6. The sensor of claim 1 further having a signal processing means to process the signals from said plurality of oscillator circuits.

7. The sensor of claim 6 wherein said signal processing means evaluates the capacitance signals to detect and record conformity of the workpiece contour to the design contour.

8. The sensor of claim 6 wherein said signal processing means is employed to generate control signals for a tool which is operatively associated with said workpiece to work the surface of said workpiece to bring it into conformity with the design contour.

9. The sensor of claim 1 wherein said capacitor elements are plate elements.

10. The sensor of claim 1 wherein said capacitor elements are pin elements.

11. The sensor of claim 1 wherein said array is a hexagonal array of hexagonal capacitor plate elements.

12. A capacitance sensor array for sensing and quantifying conformity of a workpiece surface contour to design requirements comprising a plurality of capacitor elements formed in a three-dimensional array of contour topology conforming to the topology of the design requirements of said workpiece, a plurality of oscillator circuits in an amount such that there are more capacitors than oscillator circuits, means for actively connecting in multiplexed fashion a number of said capacitor elements and said workpiece to each of said oscillator circuits while said capacitor elements are closely spaced from said workpiece so that the oscillation frequency of each of said circuits is a function of the capacitance between each said capacitor element and said workpiece, and means for generating an output from said sensor which is a function of the conformity of the contour topology of said workpiece to the contour topology of said array of capacitor elements determined by response of the said plurality of oscillator circuits.