Sheet-thickness detector device and sheet-processing apparatus, image-forming apparatus having the same

A sheet-processing apparatus comprising:

• a sheet-guide member for guiding a sheet;
• a magnetic field sensor directly contactable with a sheet guided by said sheet-guide member;
• a magnetic guide element that is urged toward said magnetic field sensor, wherein said magnetic field sensor comprises an approach-guide plane disposed on an upstream side in a sheet-conveying direction for guiding a sheet to a position between the magnetic guide element and the magnetic field sensor;
• a control unit adapted to receive output from said magnetic sensor and determine sheet thickness based thereon;
• and
• sheet-processing means for performing processing on a sheet after the thickness of the sheet has been detected by sheet passage between said magnetic field sensor and said magnetic guide clement.

An image-forming apparatus comprising:

• a sheet-guide member for guiding a sheet;
• a magnetic field sensor directly contactable with a sheet guided by the sheet-guide member;
• a magnetic guide element that is urged toward said magnetic field sensor, wherein said magnetic field sensor, comprises an approach-guide plane disposed on an upstream side in a sheet-conveying direction for guiding a sheet to a position between said magnetic guide element and said magnetic field sensor;
• a control unit adapted to receive output from said magnetic field sensor and determine sheet thickness based thereon;
• and
• image forming means for forming images on a sheet after the sheet thickness has been detected by sheet passage between the magnetic field sensor and the magnetic guide element.

A sheet-thickness detector device comprising:

• a magnetic field sensor directly contactable with a sheet;
• a magnetic guide element;
• and
• a pressurizing spring for urging one of said magnetic field sensor and said magnetic guide element toward the other,
• wherein a thickness of the sheet is detected when the sheet passes between said magnetic field sensor and said magnetic guide element, and
• wherein one of said magnetic field sensor and said magnetic guide element has an approach-guide plane disposed on an upstream side in a sheet-conveying direction for guiding the sheet to a position where the sheet is between said magnetic guide element and said magnetic field sensor.