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:
Jun. 17, 1997
Filed:
May. 24, 1995
Ricoh Company, Ltd., Tokyo, JP;
Abstract
An image transferring device incorporated in an image forming apparatus and capable of surely preventing a sheet from wrapping around a photoconductive element and from being incompletely separated from a transfer belt. A transfer bias and discharge are effected to prevent changes in the resistances of the transfer belt and sheet ascribable to changes in environment from translating into changes in a current to flow to the photoconductive element, and to efficiently dissipate a charge deposited on the belt. Various members constituting the device are positioned relative to one another such that the discharging effect is achievable most effectively while preventing the transfer bias from causing dielectric breakdown in any constituent part. For example, if a discharge member is spaced from a transfer electrode by L.sub.3 and if the transfer electrode is spaced from a nip portion between the transfer belt and image bearing member by a distance L.sub.2, than L.sub.3 .gtoreq.L.sub.2. Additionally, if the vokage applied to the transfer electrode is V.sub.O, than L.sub.2 .gtoreq.a.vertline.V.sub.O .vertline., where a is 1.0 (mm/kv); if a distance between the nip and an upstream roller entraining the belt is L.sub.1, than L.sub.1 .gtoreq.a.vertline.V.sub.O .vertline.; and if the distance between to discharge members is L.sub.4, the transfer belt has a time constant of .tau., and a process speed is .nu., than .tau..ltoreq.L.sub.4 /.nu.. Finally, the transfer belt has a double layer structure made up of an outer layer having a surface resistivity of 1.times.10.sup.9 to 1.times.10.sup.12 .OMEGA. and an inner layer having a surface resisitivity of 8.times.10.sup.6 to 8.times.10.sup.8 .OMEGA. and a volume resisitivty of 5.times.10.sup.8 to 5.times.10.sup.10 .OMEGA.cm.