Punching device in a sheet finisher for an image forming apparatus

A sheet finisher comprising:

• conveying means for conveying a sheet;
• punching means for punching the sheet being conveyed by said conveying means;
• sheet edge sensing means for detecting a horizontal shift of the sheet by sensing an edge parallel to a direction of sheet conveyance of the sheet being conveyed by said conveying means;
• first drive means for moving said sheet edge sensing means in a direction perpendicular to the direction of sheet conveyance;
• second drive means for moving said punching means in the direction perpendicular to the direction of sheet conveyance such that a position of said punching means is adjusted in accordance with a horizontal shift of the sheet calculated based on the detected horizontal shift of the sheet detected by said sheet edge sensing means;
• and
• control means for controlling said first drive means and said second drive means;
• wherein when said sheet edge sensing means has sensed the edge of the sheet, said control means returns said sheet edge sensing means to a stand-by position.

A sheet finisher comprising:

• conveying means for conveying a sheet;
• punching means for punching the sheet being conveyed by said conveying means;
• sheet edge sensing means for detecting a horizontal shift of the sheet by sensing an edge parallel to a direction of sheet conveyance of the sheet being conveyed by said conveying means;
• first drive means for moving said sheet edge sensing means in a direction perpendicular to the direction of sheet conveyance;
• second drive means for moving said punching means in the direction perpendicular to the direction of sheet conveyance such that a position of said punching means is adjusted in accordance with a horizontal shift of the sheet calculated based on the detected horizontal shift of the sheet detected by said sheet edge sensing means;
• and
• control means for controlling said first drive means and said second drive means;
• wherein said sheet edge sensing means senses opposite edges of the sheet parallel to the direction of sheet conveyance.

A sheet finisher comprising:

• a sheet conveyer configured to convey a sheet;
• a punching unit configured to punch the sheet;
• a sheet edge sensor configured to detect a horizontal shift of the sheet by sensing an edge parallel to a direction of sheet conveyance of the sheet;
• a first motor configured to move said sheet edge sensor in a direction perpendicular to the direction of sheet conveyance;
• a second motor configured to move said punching unit in the direction perpendicular to the direction of sheet conveyance such that a position of said punching unit is adjusted in accordance with a horizontal shift of the sheet calculated based on the detected horizontal shift;
• and
• a control circuit configured to control said first and second motors by a pre-selected pulse ratio.

A sheet finisher comprising:

• a sheet conveyer configured to convey a sheet;
• a punching unit configured to punch the sheet;
• a sheet edge sensor configured to detect a horizontal shift of the sheet by sensing an edge parallel to a direction of sheet conveyance of the sheet;
• a first motor configured to move said sheet edge sensor in a direction perpendicular to the direction of sheet conveyance;
• a second motor configured to move said punching unit in the direction perpendicular to the direction of sheet conveyance such that a position of said punching unit is adjusted in accordance with a horizontal shift of the sheet calculated based on the detected horizontal shift;
• and
• a control circuit configured to control said first and second motors;
• wherein when said sheet edge sensor has sensed the edge of the sheet, said control circuit returns said sheet edge sensor to a stand-by position.

A sheet finisher comprising:

• a sheet conveyer configured to convey a sheet;
• a punching unit configured to punch the sheet;
• a sheet edge sensor configured to detect a horizontal shift of the sheet by sensing an edge parallel to a direction of sheet conveyance of the sheet;
• a first motor configured to move said sheet edge sensor in a direction perpendicular to the direction of sheet conveyance;
• a second motor configured to move said punching unit in the direction perpendicular to the direction of sheet conveyance such that a position of said punching unit is adjusted in accordance with a horizontal shift of the sheet calculated based on the detected horizontal shift;
• and
• a control circuit configured to control said first and second motors;
• wherein said sheet edge sensor senses opposite edges of the sheet parallel to the direction of sheet conveyance.