The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 09, 1991
Filed:
Aug. 30, 1990
Hatsuo Tajima, Matsudo, JP;
Yoshiaki Kobayashi, Tokyo, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
An image forming apparatus includes an image bearing member movable through first and second developing positions in the order named and a bias voltage applying device applies a first developing bias voltage to a first developer carrying member and a second developing bias voltage to a second developer carrying member. The first bias voltage has a phase of a first electric field for applying to the toner a force from the developer carrying member to the image bearing member for a period t11 in the first developing position and a phase of a second electric field in the opposite direction to the first for a period t21 in the first developing position. The second bias voltage has a phase of a third electric field for applying to the toner a force from the developer carrying member to the image bearing member for a period t12 in the second developing position and a phase of a fourth electric field in the opposite direction to the third for a period t22 in the second developing zone. A ratio of period t22 to period t12 is larger than a ratio of period t21 to period t11. A; and peak level of the second bias voltage in period t12 is larger than a peak level of the first bias voltage in period t11 and a peak level of the second bias voltage in period t22 is smaller than a peak level of the first voltage in period t21.