Patent ID: 6731890
Filing Date: 2004-05-04
Classification: G03G

Abstract:
An electrostatographic machine including at least two imaging modules having at least two respective transfer stations, said electrostatographic machine comprising:a transfer member, for said at least two transfer stations, for electrostatically transferring a toner image from a toner image carrier to a toner-image area on a receiver sheet moved through said at least two transfer stations, an insulative material transport web for transporting a receiver sheet through said at least two transfer stations, said transport web moving at a speed equal to a process speed, said transport web having a front face and a back face, said receiver sheet being adhered to said front face, said back face in contact with said transfer member, said electrostatic transfer taking place in a nip between said toner image carrier and said transfer member, said receiver sheet having a leading edge and a trailing edge during passage of said receiver sheet adhering to said transport web through said nip, said nip having an entrance and an exit, said exit separated from said entrance by a nip width, said at least two transfer stations for applying an electric field across said nip so as to urge toner particles included in said toner image to transfer from said toner image carrier to said receiver sheet, said receiver sheet including margin areas wherein said toner image is not transferred, said margin areas including a leading edge margin area and a trailing edge margin area, said electrostatographic machine further including a programmable power supply for supplying current to said at least two transfer stations and a logic and control unit for controlling said current supplied by said programmable current supply, said programmable power supply and logic and control unit including a control for transfer station current, having a predetermined time variation, wherein during a time period between a time before said leading edge enters said nip and a time after said trailing edge leaves said nip, said transfer station current is switchably altered by said programmable power supply between at least two predetermined magnitudes of transfer station current included in a plurality of predetermined magnitudes of transfer station current, a predetermined magnitude of transfer station current included in said plurality of predetermined magnitudes of transfer station current is caused to flow in response to a respective control voltage, and said respective control voltage is included in a corresponding plurality of control voltages successively produced by said logic and control unit during passage of said received sheet through said nip, and at least one of said plurality of predetermined magnitudes of transfer station current being low to provide effective wrap suppression of said receiver sheet on said transfer member, and at least one of said plurality of predetermined magnitudes of transfer station current causes said electrostatic transferring of said toner image from said toner image carrier to said toner-image area on said receiver sheet, passage of said receiver sheet through each of said nips is preceded by a leading edge interframe time interval and followed by a trailing edge interframe time interval, and when said transport web moves said receiver sheet successively through said at least two transfer stations, said receiver sheet is electrostatically adhered to said transport web prior to said receiver sheet passing through said at least two transfer stations, and wherein a respective interframe time interval corresponds to a respective interframe distance, said respective interframe distance equal to the product of said respective interframe time interval and said process speed.