US3634740A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electrostatic holddown
Assignee: AB Dick Co
•
Filing: 1970-04-20
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Granted: 1972-01-11
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Expires: 1990-04-20
Abstract
Abstract An interdigitated grid, powered by a high-voltage generator, and covered by a bed of material having a bulk resistivity which will allow an electrostatic charge to be built up quickly, but decay in holding power in a very short time.
Inventors
- 👤 Phillip J Stevko
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 19:52
CPC Classifications
G; G03; G03G; G03G15/00; G03G15/60; G03G15/605; G03B; G03B27/00; G03B27/32; G03B27/52; G03B27/62; G03B27/6207; G03B27/6214
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
132 words
In an electrostatic sheet holding apparatus having a base supporting a plurality of electrodes, the electrodes being respectively commonly connected in two individual sets, and means for applying an electrical potential to said electrodes of the two sets so as to develop an electrostatic field adjacent to the surface of the base and electrostatically attract a sheet to said surface; the improvement comprising a cover plate over said electrodes, said cover plate being a thin sheet of a semiconductor material stable under light in its conductive characteristics, having a bulk resistivity of not more than 1015 ohm-centimeters, and characterized in that a charge induced by said electrodes will not persist and will dissipate substantially immediately upon removal of any applied potential to said electrodes and thereby release a sheet from said surface.
Claim 2
Dependent Claim
132 words
In an electrostatic sheet holding apparatus having a base supporting a plurality of electrodes, the electrodes being respectively commonly connected in two individual sets, and means for applying an electrical potential to said electrodes of the two sets so as to develop an electrostatic field adjacent to the surface of the base and electrostatically attract a sheet to said surface; the improvement comprising a cover plate over said electrodes, said cover plate being a thin sheet of a semiconductor material stable under light in its conductive characteristics, having a bulk resistivity of not more than 1015 ohm-centimeters, and characterized in that a charge induced by said electrodes will not persist and will dissipate substantially immediately upon removal of any applied potential to said electrodes and thereby release a sheet from said surface.
Claim 3
Dependent Claim
66 words
In a sheet-holding apparatus as defined in claim 1, said means for applying an electrical potential being a direct current source of high voltage and low amperage, and said cover plate having a thickness related to the applied voltage such that a field generated by said electrodes will penetrate said cover plate and induce a charge in any electrostatically chargeable object in contact with said plate.
Claim 4
Dependent Claim
13 words
In a sheet-holding apparatus as defined in claim 1, said electrodes being interdigital.
Claim 5
Dependent Claim
81 words
In a sheet-holding apparatus as defined in claim 1, means for transporting said sheet-holding apparatus between a horizontal attitude loading position and a vertical position; control means for applying the potential when said holddown device is moved in a direction away from said loading position toward said vertical position, said control means disconnecting said potential source when said device is returned to said loading position to turn off the power to said electrodes whereby the electrostatic influence is substantially instantaneously terminated.
Claim 6
Dependent Claim
15 words
The exposure device as claimed in claim 4 wherein the third electrode is a polyvinylchloride.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-01-10 | 1975-07-12 | 1976-01-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-01-10 | 1979-07-12 | 1980-01-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-01-10 | 1983-07-12 | 1984-01-11 | $7700.00 | Window Closed / Lapsed |