US3851618A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electrostatic coating apparatus
Assignee: Ransburg Corp
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Filing: 1974-01-14
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Granted: 1974-12-03
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Expires: 1994-01-14
Abstract
Abstract A method and apparatus employs the currents of a high voltage electrostatic system to determine incipient grounded conditions. The electric current in the ground return to its high voltage electrostatic system is sensed to provide a signal. All alternating current components of the signal above substantially pure direct current are attenuated to provide a resulting DC signal that increases as a grounded article approaches a charged electrode. In one embodiment the resultant DC signal is sampled at a rate fast enough to acticipate the fastest expected approach of a grounded article to the charged electrode. Every other sample is retained so that it may be compared with the sample immediately following it. The samples are compared in a summing circuit which provides a signal corresponding to the change in conditions in the ground return circuit. A level is selected corresponding to incipient grounding of the charged high voltage electrode. If a difference of the successive samples exceeds this level, an alarm is actuated providing a useful output.
Inventors
- 👤 S Bentley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 04:46
CPC Classifications
H; H02; H02H; H02H7/00; H02H7/003; B; B05; B05B; B05B5/00; B05B5/08; B05B5/10; H02H3/00; H02H3/44; H02H3/445
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
242 words
In an electrostatic coating system including a high voltage supply having two terminals; a conveyor for transporting articles to be coated; an electrostatic coating device connected with the one terminal of the high voltage supply to create electrostatic deposition of atomized coating material; and means connected between the other terminal of the high voltage supply and ground to sense the electric current between the high voltage supply and ground, and to disconnect the high voltage supply from its energizing source, the improvement in which the means connected between the above terminal and ground includes a low pass type operational network to provide a signal with attenuation of all electrical current components significantly above direct current, while amplifying direct currents; a clock to generate a sampling gate for the signal; two gated sampling circuits to detect the direct current level of the signal when gated by the clock, one of the gated sampling circuits being connected to a holding circuit for the detected signal for one cycle of the gating signal, and the other gated sampling circuit being connected to an inverting circuit to invert the signal from the other gated sampling circuit; a summer to determine the difference of the signal from the holding circuit and the inverted signal from the other gated sampling circuit; and a level detector to generate an operative signal in the event the level exceeds a predetermined level which represents incipient grounding of the high voltage electrode.
Claim 2
Dependent Claim
242 words
In an electrostatic coating system including a high voltage supply having two terminals; a conveyor for transporting articles to be coated; an electrostatic coating device connected with the one terminal of the high voltage supply to create electrostatic deposition of atomized coating material; and means connected between the other terminal of the high voltage supply and ground to sense the electric current between the high voltage supply and ground, and to disconnect the high voltage supply from its energizing source, the improvement in which the means connected between the above terminal and ground includes a low pass type operational network to provide a signal with attenuation of all electrical current components significantly above direct current, while amplifying direct currents; a clock to generate a sampling gate for the signal; two gated sampling circuits to detect the direct current level of the signal when gated by the clock, one of the gated sampling circuits being connected to a holding circuit for the detected signal for one cycle of the gating signal, and the other gated sampling circuit being connected to an inverting circuit to invert the signal from the other gated sampling circuit; a summer to determine the difference of the signal from the holding circuit and the inverted signal from the other gated sampling circuit; and a level detector to generate an operative signal in the event the level exceeds a predetermined level which represents incipient grounding of the high voltage electrode.
Claim 3
Dependent Claim
57 words
A system of claim 1, wherein the low pass operational network includes an active filter designed to transform the voltaGe input into an output by the transfer function -HWo2/S2+ Alpha WoS+Wo2 in which H equals 10, Wo equals 10 cycles per second, and Alpha equals Square Root 2 for maximally flat Butterworth Response with 40 db/decade roll-off.
Claim 4
Dependent Claim
28 words
A system of claim 2 wherein the clock circuit provides gating pulses with a time interval of 120th of a second to apply to the gated sampling circuits.
Claim 5
Dependent Claim
35 words
A system of claim 1 wherein the first holding circuit includes means to subtract a signal from its output proportional to the magnitude of the output signal during the time interval generated by the clock.
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) | 1977-12-02 | 1978-06-03 | 1978-12-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-02 | 1982-06-03 | 1982-12-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-02 | 1986-06-03 | 1986-12-03 | $7700.00 | Window Closed / Lapsed |