US3569983A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Writing circuit for electrostatic recorders
Assignee: Varian Medical Systems Inc
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Filing: 1968-05-22
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Granted: 1971-03-09
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Expires: 1988-05-22
Abstract
Abstract There is disclosed electrostatic recording apparatus in which the potential swing of the stylii electrode is reduced to a level that a single readily available conventional low voltage rated transistor may be used as the driver for each of the recording stylii. The reduction in stylii voltage swing is made possible by the use of a pulsed bias, called enhancement pulses, on the stylii backup electrode. The pulse width of the enhancement pulses is maintained sufficiently short, as of less than 2 microseconds, to permit the amplitude of the pulse to exceed the minimum potential required for electrostatic recording (charging of the recording medium). For a stylii potential swing of 300 volts, typical parameters for the frequency, amplitude and pulse width of the enhancement pulses are 110 kHz., 600 volts and 1 microsecond, respectively. In addition to the reduction in the number of transistors and power supplies required, significant improvement in the quality of the low frequency and DC signal recordings without a comparable degration of high frequency performance is also obtained.
Inventors
- 👤 Edward W Marshall
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 03:02
CPC Classifications
G; G03; G03G; G03G15/00; G03G15/22; G03G15/32; G03G15/321; G03G15/325
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
226 words
In an electrostatic recorder responsive to an input signal means for providing avalanche discharge in a normally nonconductive fluid to form a charge image on a suitable dielectric type recording medium, the combination comprising: a first and second electrode means proximate one another defining a charging path therebetween formed by the normally nonconductive fluid and at least a portion of the recording medium; a switching circuit means responsive to the input signal means for generating relatively wide and low amplitude writing pulses which establish a writing electric field through the charging path between the first and second electrode means, the writing electric field being of insufficient strength to cause avalanche discharge in the fluid; and an oscillator means for providing relatively narrow and high amplitude enhancement pulses which establish an enhancement electric field through the charging path in additive relation to the writing electric field, the enhancement field having a strength greater than the DC avalanche stress of the fluid but having a duration insufficient to cause noticeable charging of the recording medium, the additive effect of the write electric field and the enhancement electric field being sufficient to cause avalanche discharge in the fluid causing current to flow between the electrode means and form a charge image on the recording medium, the interval between enhancement pulses being less than the width of the writing pulses.
Claim 2
Dependent Claim
226 words
In an electrostatic recorder responsive to an input signal means for providing avalanche discharge in a normally nonconductive fluid to form a charge image on a suitable dielectric type recording medium, the combination comprising: a first and second electrode means proximate one another defining a charging path therebetween formed by the normally nonconductive fluid and at least a portion of the recording medium; a switching circuit means responsive to the input signal means for generating relatively wide and low amplitude writing pulses which establish a writing electric field through the charging path between the first and second electrode means, the writing electric field being of insufficient strength to cause avalanche discharge in the fluid; and an oscillator means for providing relatively narrow and high amplitude enhancement pulses which establish an enhancement electric field through the charging path in additive relation to the writing electric field, the enhancement field having a strength greater than the DC avalanche stress of the fluid but having a duration insufficient to cause noticeable charging of the recording medium, the additive effect of the write electric field and the enhancement electric field being sufficient to cause avalanche discharge in the fluid causing current to flow between the electrode means and form a charge image on the recording medium, the interval between enhancement pulses being less than the width of the writing pulses.
Claim 3
Dependent Claim
36 words
The electrostatic recorder of claim 1 wherein the first electrode means is on one side of the recording medium and the second electrode means is a backup electrode on the opposite side of the recording medium.
Claim 4
Dependent Claim
39 words
The electrostatic recorder of claim 2 wherein the writing pulses are of one polarity and are applied to the first electrode means, and the enhancement pulses are of the opposite polarity and are applied to the backup electrode means.
Claim 5
Dependent Claim
15 words
The electrostatic recorder of claim 3 wherein the first electrode is a format printing roll.
Claim 6
Dependent Claim
44 words
The electrostatic recorder of claim 4 wherein a power supply is provided for establishing a DC bias electric field through the charging path, the sum of the DC bias and the enhancement electric field being greater than the DC avalanche stress of the fluid.
Claim 7
Dependent Claim
27 words
The electrostatic recorder of claim 3 wherein the first electrode means is a plurality of writing stylii to which the switching circuit meanS selectively applies writing pulses.
Claim 8
Dependent Claim
23 words
The electrostatic recorder of claim 6 wherein the writing pulses are at least 25 microseconds in width and about 300 v. in amplitude.
Claim 9
Dependent Claim
18 words
The electrostatic recorder of claim 3 wherein the enhancement pulses have a duration of less than 2 microseconds.
Claim 10
Dependent Claim
23 words
The electrostatic recorder of claim 8 wherein the repetition rate of the enhancement pulses is from about 30 kilohertz to about 110 kilohertz.
Claim 11
Dependent Claim
201 words
In an electrostatic recorder responsive to writing pulses for charging a dielectric recording medium, the combination comprising: a backup electrode; a plurality of writing stylii mounted proximate to the backup electrode with the recording medium therebetween, the writing stylii responsive to the writing pulses for charging the dielectric recording medium; a pulse source having a repetition rate of from about 30 kilohertz to about 110 kilohertz coupled to the backup electrode for providing a series of narrow large amplitude pulses for biasing the recording medium, each of the pulses having an amplitude above the minimum DC potential required for recording DC signals on the recording medium; a chart roll for electrostatically printing on the recording medium; a chart roll backup electrode spaced apart from the chart roll with the recording medium therebetween; a DC power supply for providing a bias between the chart roll and the chart roll backup electrode; and circuit means for coupling the DC supply to the chart roll backup electrode, the circuit means comprising means for rectifying and filtering the pulses from the pulse source for providing a DC potential on the chart roll backup electrode higher than the DC potential supplied by the DC power supply.
Claim 12
Dependent Claim
201 words
In an electrostatic recorder responsive to writing pulses for charging a dielectric recording medium, the combination comprising: a backup electrode; a plurality of writing stylii mounted proximate to the backup electrode with the recording medium therebetween, the writing stylii responsive to the writing pulses for charging the dielectric recording medium; a pulse source having a repetition rate of from about 30 kilohertz to about 110 kilohertz coupled to the backup electrode for providing a series of narrow large amplitude pulses for biasing the recording medium, each of the pulses having an amplitude above the minimum DC potential required for recording DC signals on the recording medium; a chart roll for electrostatically printing on the recording medium; a chart roll backup electrode spaced apart from the chart roll with the recording medium therebetween; a DC power supply for providing a bias between the chart roll and the chart roll backup electrode; and circuit means for coupling the DC supply to the chart roll backup electrode, the circuit means comprising means for rectifying and filtering the pulses from the pulse source for providing a DC potential on the chart roll backup electrode higher than the DC potential supplied by the DC power supply.
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) | 1974-03-08 | 1974-09-07 | 1975-03-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-03-08 | 1978-09-07 | 1979-03-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-03-08 | 1982-09-07 | 1983-03-09 | $7700.00 | Window Closed / Lapsed |