Sheet stacking apparatus, sheet feeding apparatus, image forming apparatus, and image forming system

Abstract

A sheet stacking apparatus includes a tray capable of stacking plural sheets, and four wires with one end of each of them being connected to a corresponding one of portions at four corners of the tray. On the downstream side of the tray concerning a sheet feeding direction, the other end of each of two wires is connected via pulleys provided above the tray. A winding unit in the apparatus vertically moves the tray hung by the four wires by winding up or rolling down the two wires. On a side opposite to the side of the tray where the connecting portion to which one end of each of the two wires connected to the winding unit is connected, the other end of each of the remaining two wires are connected via pulleys provided above and below the tray, respectively.

1 .- 15 . (canceled) 
     
     
         16 . A sheet feeding apparatus comprising:
 a stacking unit capable of stacking a sheet;   a feeding unit configured to contact and feed an uppermost sheet stacked by the stacking unit;   a first lifting unit configured to lift the stacking unit;   a second lifting unit different from the first lifting unit and configured to lift the stacking unit;   a third lifting unit different from the first lifting unit and the second lifting unit and configured to lift the stacking unit; and   a roll-up unit configured to raise the stacking unit by rolling up the first lifting unit and the second lifting unit, and lowering the stacking unit by releasing the first lifting unit and the second lifting unit,   wherein the stacking unit includes, in a conveyance direction, a first connecting portion, a second connecting portion, and a third connecting portion, to which the first lifting unit, the second lifting unit, and the third lifting unit are, respectively, connected at a plurality of positions,   with respect to the conveyance direction, the second connecting portion is provided on a downstream side of the third connecting portion, and the first connecting portion is provided on a downstream side of the second connecting portion,   the first lifting unit is provided to be connected to the first connecting portion and to lift the first connecting portion by acting on the first connecting portion when rolled up by the roll-up unit,   the second lifting unit is provided to be connected to the second connecting portion and to lift the second connecting portion by acting on the second connecting portion when rolled up by the roll-up unit, and   the third lifting unit is provided to be connected to the second connecting portion at one end, to be connected to the third connecting portion at the other end, and, when the roll-up unit rolls up the first lifting unit and the second lifting unit, to be drawn to the second connecting portion lifted by an action of the second lifting unit and to lift the third connecting portion by acting on the third connecting portion on the stacking unit.   
     
     
         17 . The apparatus according to  claim 16 , wherein in the second connecting portion, a connecting point with the second lifting unit and a connecting point with the third lifting unit are the same. 
     
     
         18 . The apparatus according to  claim 16 , wherein in the second connecting portion, a connecting point with the second lifting unit and a connecting point with the third lifting unit are different in a predetermined range, and a distance between the connecting point with the second lifting unit and the connecting point with the third lifting unit is shorter than a distance between the first connecting portion and the second connecting portion, and shorter than a distance between the second connecting portion and the third connecting portion. 
     
     
         19 . The apparatus according to  claim 16 , further comprising:
 a first support unit provided below the stacking unit and configured to support the third lifting unit; and   a second support unit provided above the stacking unit and configured to support the third lifting unit,   wherein the third lifting unit drawn to the second connecting portion lifts the stacking unit via the first support unit and the second support unit.   
     
     
         20 . The apparatus according to  claim 19 , wherein the stacking unit can be vertically moved between the first support unit and the second support unit. 
     
     
         21 . The apparatus according to  claim 20 , wherein a position of the second support unit is changeable in a direction of vertically moving the stacking unit, and a lifting action of the second lifting unit is adjusted by changing the position of the second support unit. 
     
     
         22 . The apparatus according to  claim 19 , wherein the first support unit and the second support unit are pulleys. 
     
     
         23 . The apparatus according to  claim 16 , further comprising a driving unit configured to generate a driving force of rotating the roll-up unit in a first direction and a second direction. 
     
     
         24 . The apparatus according to  claim 16 , wherein the first lifting unit, the second lifting unit, and the third lifting unit are, respectively, connected to corresponding connecting portions at positions outside a stacking region where the stacking unit can stack the sheet. 
     
     
         25 . The apparatus according to  claim 16 , wherein the stacking unit includes concave portions between the first connecting portion and the second connecting portion, and between the second connecting portion and the third connecting portion, and the first connecting portion, the second connecting portion, and the third connecting portion are provided in beam-like convex portions formed by providing the concave portions. 
     
     
         26 . The apparatus according to  claim 16 , wherein in the conveyance direction, a tail end of a sheet of a stackable maximum size is positioned on an upstream side of the second connecting portion. 
     
     
         27 . An image forming apparatus comprising:
 a stacking unit capable of stacking a sheet;   a feeding unit configured to contact and feed an uppermost sheet stacked by the stacking unit;   an image forming unit configured to form an image on the sheet fed by the feeding unit;   a first lifting unit configured to lift the stacking unit;   a second lifting unit different from the first lifting unit and configured to lift the stacking unit;   a third lifting unit different from the first lifting unit and the second lifting unit and configured to lift the stacking unit; and   a roll-up unit configured to raise the stacking unit by rolling up the first lifting unit and the second lifting unit, and lowering the stacking unit by releasing the first lifting unit and the second lifting unit,   wherein the stacking unit includes, in a conveyance direction, a first connecting portion, a second connecting portion, and a third connecting portion to which the first lifting unit, the second lifting unit, and the third lifting unit are, respectively, connected at a plurality of positions,   with respect to the conveyance direction, the second connecting portion is provided on a downstream side of the third connecting portion, and the first connecting portion is provided on a downstream side of the second connecting portion,   the first lifting unit is provided to be connected to the first connecting portion and to lift the stacking unit by acting on the first connecting portion when rolled up by the roll-up unit,   the second lifting unit is provided to be connected to the second connecting portion and to lift the stacking unit by acting on the second connecting portion when rolled up by the roll-up unit, and   the third lifting unit is provided to be connected to the second connecting portion at one end, to be connected to the third connecting portion at the other end, and, when the roll-up unit rolls up the first lifting unit and the second lifting unit, to be drawn to the second connecting portion lifted by an action of the second lifting unit and to lift the stacking unit by acting on the third connecting portion on the stacking unit.