US5508788A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Image forming apparatus having contact charger wtih superposed AC/DC bias
Assignee: Toshiba Corp
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Filing: 1994-08-16
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Granted: 1996-04-16
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Expires: 2014-08-16
Abstract
Abstract An image forming apparatus including a contact charger for charging the surface of an image carrying body, a latent image forming unit for forming an electrostatic latent image on the charged image carrying body, a developing device for developing the latent image to form a visible image, a power source for applying a DC/AC superposed bias to the contact charger, a detector for detecting the current value of the superposed bias applied to the contact charger, and a device for controlling the AC:DC voltage ratio of the superposed bias applied to the contact charger, in accordance with a detected value from the detector. The AC bias is between 150 to 400 V while the DC bias is set between 500 to 800V.
Inventors
- 👤 Takeshi Watanabe
- 👤 Minoru Yoshida
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 16:32
CPC Classifications
G; G03; G03G; G03G15/00; G03G15/02; G03G15/0266; G03G15/0208; G03G15/0216
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
113 words
An image forming apparatus, comprising: contact charging means for charging the surface of an image carrying body; image forming means for forming an image on the charged image carrying body; means for applying a DC/AC superposed bias to the contact charging means; detecting means for detecting a current value of the superposed bias applied to the contact charging means; and means for controlling the AC:DC ratio of the superposed bias applied to the contact charging means, in accordance with a detected value from the detecting means, wherein said superposed bias is a bias obtained by superposing an AC bias of 150 to 400 V on a DC bias of 500 to 800 V.
Claim 2
Dependent Claim
113 words
An image forming apparatus, comprising: contact charging means for charging the surface of an image carrying body; image forming means for forming an image on the charged image carrying body; means for applying a DC/AC superposed bias to the contact charging means; detecting means for detecting a current value of the superposed bias applied to the contact charging means; and means for controlling the AC:DC ratio of the superposed bias applied to the contact charging means, in accordance with a detected value from the detecting means, wherein said superposed bias is a bias obtained by superposing an AC bias of 150 to 400 V on a DC bias of 500 to 800 V.
Claim 3
Dependent Claim
35 words
An image forming apparatus according to claim 1, wherein said superposed bias is a bias obtained by superposing an AC bias of 300 to 400 V on a DC bias of 500 to 650 V.
Claim 4
Dependent Claim
47 words
An image forming apparatus according to claim 1, wherein said controlling means comprises means for lowering the voltage ratio for the AC and DC components of the superposed bias in accordance with a reduction of the current value of the superposed bias, detected by the detecting means.
Claim 5
Dependent Claim
49 words
An image forming apparatus according to claim 1, wherein said controlling means comprises means for lowering the voltage ratio for the AC and DC components of the superposed bias in stages in accordance with a reduction of the current value of the superposed bias, detected by the detecting means.
Claim 6
Dependent Claim
48 words
An image forming apparatus according to claim 1, wherein said controlling means comprises means for continuously lowering the voltage ratio for the AC and DC components of the superposed bias in accordance with a reduction of the current value of the superposed bias, detected by the detecting means.
Claim 7
Dependent Claim
17 words
An image forming apparatus according to claim 1, wherein said contact charging means comprises a brush charger.
Claim 8
Dependent Claim
17 words
An image forming apparatus according to claim 1, wherein said contact charging means comprises a rotating-brush charger.
Claim 9
Dependent Claim
17 words
An image forming apparatus according to claim 1, wherein said contact charging means comprises a stationary-brush charger.
Claim 10
Dependent Claim
97 words
An image forming apparatus, comprising: contact charging means for charging the surface of an image carrying body; image forming means for forming an image on the charged image carrying body; means for applying a DC/AC superposed bias to the contact charging means; and means for controlling the AC:DC ratio of the superposed bias applied to the contact charging means, in accordance with a surface potential of the image carrying body, wherein said superposed bias is a bias obtained by superposing an AC bias of 150 to 400 V on a DC bias of 500 to 800 V.
Claim 11
Dependent Claim
97 words
An image forming apparatus, comprising: contact charging means for charging the surface of an image carrying body; image forming means for forming an image on the charged image carrying body; means for applying a DC/AC superposed bias to the contact charging means; and means for controlling the AC:DC ratio of the superposed bias applied to the contact charging means, in accordance with a surface potential of the image carrying body, wherein said superposed bias is a bias obtained by superposing an AC bias of 150 to 400 V on a DC bias of 500 to 800 V.
Claim 12
Dependent Claim
36 words
An image forming apparatus according to claim 9, wherein said controlling means comprises means for changing voltage ratios for the DC and AC components of the superposed bias in accordance with the frequency of image formation.
Claim 13
Dependent Claim
35 words
An image forming apparatus according to claim 9, wherein said superposed bias is a bias obtained by superposing an AC bias of 300 to 400 V on a DC bias of 500 to 650 V.
References Cited (Backward Citations)
US4672505A
Cited
US5420671A
Cited
JPH0212276A
Cited
JPH0269781A
Cited
US5144368A
Cited
US5229818A
Cited
US5305177A
Cited
JPH04181962A
Cited
JPH05181350A
Cited
US5365316A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-04-16 | 1999-10-16 | 2000-04-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-04-16 | 2003-10-16 | 2004-04-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-04-16 | 2007-10-16 | 2008-04-16 | $7700.00 | Window Closed / Lapsed |