Sheet feeding apparatus

An sheet feeding apparatus comprising:

• a sheet feed portion for feeding a plurality of sheets of different sizes in a direction of thickness thereof in an upright state;
• a suction belt having a belt hole for drawing each sheet fed from said sheet feed portion by suction, so as to feed out each sheet drawn by suction with the belt hole;
• drive means for driving said suction belt;
• negative pressure generating means for generating a pressure for drawing the sheet by suction in the belt hole;
• a valve for selectively applying the negative pressure from said negative pressure venerating means to the belt hole;
• a pressure sensor for measuring a pressure in the belt hole;
• a first detection sensor for detecting the sheet fed out by said suction belt;
• a second detection sensor for detecting the belt hole after the sheet is fed out;
• and
• control means for controlling operations of said valve and said drive means on the basis of detection outputs from said pressure sensor and said first and second detection sensors,
• wherein, after a predeternmined period T—between times at which said suction belt is started to drive—elapses, when the negative pressure in the belt hole detected by said pressure sensor is not less than a predetermined valve, said control means again starts to drive said suction belt.

A sheet feeding apparatus comprising:

• a sheet feed portion which feeds a plurality of sheets of different sizes in a direction of thickness thereof in an upright state;
• a suction belt having a belt hole for drawing each sheet fed from said sheet feed portion by suction, so as to feed out each sheet drawn by suction with the belt hole;
• drive motor for driving said suction belt;
• a blower, in communication with said suction belt, which creates a pressure tending to draw the sheet by suction to the belt hole;
• a valve which selectively applies the negative pressure from said blower to the belt hole;
• a pressure sensor which measures a pressure in the belt hole;
• a first detection sensor which detects a leading end of the sheet fed out by said suction belt;
• a second detection sensor which detects the belt hole after the sheet is fed out;
• and
• control circuit which controls operations of said valve and said drive motor on the basis of detection outputs from said pressure sensor and said first and second detection sensors, so that after a predetermined period T—between times at which said suction belt is started to drive—elapses, when the negative pressure in the belt hole detected by said pressure sensor is not less than a predetermined value, said control circuit again starts to drive said suction belt.

A sheet feeding apparatus comprising:

• a sheet feed portion for feeding a plurality of sheets of different sizes in a direction of thickness thereof in an upright state;
• a suction belt having a first hole and a second hole for drawing each sheet fed from said sheet feed portion by suction, so as to feed out each sheet drawn by suction with one of said first and second holes;
• a drive motor that drives said suction belt;
• a blower that generates a pressure for drawing the sheet by suction in one of said first and second holes;
• a valve for selectively applying the negative pressure from said blower to one of said first and second holes that is temporarily in communication with said blower;
• a pressure sensor for measuring a pressure in said first or second hole that is temporarily in communication with said blower;
• a first detection sensor for detecting the sheet fed out by said suction belt;
• a second detection sensor for detecting, after the sheet is fed out, said first or second hole that was temporarily in communication with said blower;
• and
• a control circuit that controls operations of said valve and said drive motor on the basis of detection outputs from said pressure sensor and said first and second detection sensors;
• and
• wherein said first and second holes are spaced apart from each other at a predetermined interval on said belt so that only one of said first and second holes communicates with said blower at any one time.