Sheet stacking apparatus

Abstract

A sheet stacking apparatus includes a stacking unit, a regulating member, and a detection device. The stacking unit has a stacking surface on which sheets to be fed in a sheet-feeding direction are stacked. The regulating member is movable in the sheet-feeding direction and configured to regulate the sheet by coming into contact with an upstream edge of the sheet in the sheet-feeding direction on the stacking surface. The detection device is configured to detect a size of the sheet on the stacking surface. The detection device includes a rotatable member configured to rotate about an axis in response to movement of the regulating member, the axis extending parallel to the sheet-feeding direction as viewed from above and being positioned below the stacking surface. The detection device also includes a sensor configured to detect a position of the rotatable member.

What is claimed is: 
     
         1 . A sheet stacking apparatus, comprising:
 a stacking unit having a stacking surface on which sheets to be fed in a sheet-feeding direction are stacked;   a regulating member being movable in the sheet-feeding direction and configured to regulate the sheet by coming into contact with an upstream edge of the sheet in the sheet-feeding direction on the stacking surface; and   a detection device configured to detect a size of the sheet on the stacking surface,   wherein the detection device includes
 a rotatable member configured to rotate about an axis in response to movement of the regulating member, the axis extending parallel to the sheet-feeding direction as viewed from above and being positioned below the stacking surface, and 
 a sensor configured to detect a position of the rotatable member. 
   
     
     
         2 . The sheet stacking apparatus according to  claim 1 ,
 wherein the sensor is configured to output different signals between when the rotatable member is at a first position at which the regulating member is in contact with the rotatable member and when the rotatable member is at a second position at which the regulating member is separated from the rotatable member.   
     
     
         3 . The sheet stacking apparatus according to  claim 2 ,
 wherein the rotatable member rotates by gravity from the first position to the second position in response to the regulating member being separated from the rotatable member.   
     
     
         4 . The sheet stacking apparatus according to  claim 1 , further comprising:
 a feeder unit configured to feed the sheet on the stacking surface in the sheet-feeding direction.   
     
     
         5 . The sheet stacking apparatus according to  claim 4 ,
 wherein among multiple pairs of a long sheet and a short sheet with respect to the sheet-feeding direction, the long sheet and the short sheet being equal-width standard-sized sheets that the sheet stacking apparatus can handle, a first pair is defined as a pair including a shortest one among the long sheets of the multiple pairs, and a second pair is defined as a pair including a longest one among the short sheets of the multiple pairs, and   wherein the sensor of the detection device changes output when the regulating member moves between a position at which the regulating member regulates the long sheet of the first pair and a position at which the regulating member regulates the short sheet of the second pair.   
     
     
         6 . The sheet stacking apparatus according to  claim 1 , further comprising:
 an abutting portion with which a leading edge of the sheet in the sheet-feeding direction comes into contact when the sheet is on the stacking surface,   wherein the regulating member regulates a position of a trailing edge of the sheet in the sheet-feeding direction, and   wherein a difference between maximum and minimum sizes, in the sheet-feeding direction, that the sheet stacking apparatus can handle is greater than a distance between the abutting portion and a position of the regulating member at which the output of the sensor changes in response to movement of the regulating member.   
     
     
         7 . The sheet stacking apparatus according to  claim 1 , further comprising:
 an abutting portion with which a leading edge of the sheet in the sheet-feeding direction comes into contact when the sheet is on the stacking unit,   wherein the regulating member regulates a position of a trailing edge of the sheet in the sheet-feeding direction, and   wherein a distance between the abutting portion and a position of the regulating member at which the output of the sensor changes in response to movement of the regulating member is 279.4 mm or more and 355.6 mm or less.   
     
     
         8 . The sheet stacking apparatus according to  claim 1 ,
 wherein the regulating member is configured to press the rotatable member to cause the rotatable member to rotate, and   wherein the regulating member comes into contact with the rotatable member at a position below the stacking surface.   
     
     
         9 . The sheet stacking apparatus according to  claim 1 , further comprising:
 an apparatus body; and   a container movably supported by the apparatus body,   wherein the stacking unit, the regulating member, and the detection device are disposed in the container.   
     
     
         10 . An image forming apparatus, comprising:
 the sheet stacking apparatus according to  claim 1 ; and   an image forming unit configured to form an image on the sheet fed from the sheet stacking apparatus.