Device for electrostatically suspending a body or sample

• US 4,688,141 A
• Filed: 06/25/1985
• Issued: 08/18/1987
• Est. Priority Date: 06/25/1984
• Status: Expired due to Fees

• Current Assignee: Office National D'Etudes et de Recherches Aerospatiales
• Original Assignee: Office National D'Etudes et de Recherches Aerospatiales
• Inventors: Bernard, Alain M., Touboul, Pierre L., Canny, Jean-Paul L.
• Primary Examiner(s): Hix, L. T.
• Assistant Examiner(s): RUTLEDGE, DELLA J
• Application Number:
  US06/748,721
• Time in Patent Office: 784 Days
• Field of Search: 361/233, 324/60 C, 324/60 R, 517/13, 73/517 R, 73/516 R
• US Class Current: 361/233
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/131 with electrostatic counterbalancing means
• CPC Class Codes: H02N 13/00 Clutches or holding devices using electrostatic attraction, e.g. using Johnson-Rahbek effect

Abstract

A device for electrostatically suspending an electrically charged body coises at least two spherical electrodes serving simultaneously for capacitive position detection and electrostatic positioning control for the body.

Claims

1. A device for electrostatically suspending a sample of material comprising

a sample carrying an electrostatic charge;

at least two conductive spherical electrodes respectively fed by high voltages of opposite polarity;

a conductive screen surrounding said sample and electrodes and brought to ground potential whereby the sample is submitted to a first force proportional to the square of the sample charge, a second force proportional to the product of the electrode voltages, a third force proportional to the product of the sample charge by the electrode voltage; and

means for varying a voltage feed to the electrodes.

2. A device for electrostatically suspending a sample according to claim 1 wherein the sample electrostatic charge is positive.

3. A device for electrostatically suspending a sample according to claim 1 wherein the device further comprises a toroidal conductive electrode having its center at the mid-point of a line joining the centers of two of said spherical electrodes, said toroidal electrode being brought to a voltage having the same polarity as the charge of said sample.

4. A device for electrostatically suspending a sample as claimed in claim 1 comprising a differential transformer with a primary winding fed with alternating current and two secondary windings connected to the spherical electrodes via a circuit for superimposing sample position detection signals and sample positioning control signals to form a capacitive measuring bridge and to measure the differences in the capacitance coefficients between the sample and the electrodes, wherein electric lines connecting the electrodes to the transformer are triaxal cables with an inner sheathing connected to the mid-point of the secondary windings and an outer sheathing connected to the ground potential.

5. A device for electrostatically suspending a sample as claimed in claim 2 comprising a differential transformer with a primary winding fed with alternating current and two secondary windings connected to the spherical electrodes via a circuit for superimposing sample position detection signals and sample positioning control signals to form a capacitive measuring bridge and to measure the differences in the capacitance coefficients between the sample and the electrodes, wherein electric lines connecting the electrodes to the transformer are triaxal cables with an inner sheathing connected to the mid-point of the secondary windings and an outer sheathing connected to the ground potential.