Sheet storage device

Abstract

A sheet storage device includes a sheet storage movable in an up-and-down direction, to stack and store sheets conveyed in a conveyance direction. The sheet storage moves down according to weight of the sheets stacked in the sheet storage.

1 . A sheet storage device comprising:
 a sheet storage movable in an up-and-down direction, to stack and store sheets conveyed in a conveyance direction,   wherein the sheet storage moves down according to weight of the sheets stacked in the sheet storage.   
     
     
         2 . The sheet storage device according to  claim 1 ,
 wherein the sheet storage is movable in the up-and-down direction tilted relative to a gravity direction.   
     
     
         3 . The sheet storage device according to  claim 2 ,
 wherein the sheet storage has:   a stacking surface:
 disposed at a bottom of the sheet storage; 
 tilted downward toward downstream in the conveyance direction; and 
 orthogonal to the up-and-down direction; and 
   a contact surface:
 disposed at a downstream end of the sheet storage in the conveyance direction; and 
 arranged in a width direction tilted relative to a direction orthogonal to the conveyance direction, and 
 the contact surface contactable a leading edge of each of the sheets. 
   
     
     
         4 . The sheet storage device according to  claim 3 ,
 wherein the sheet storage has a shape of a hollow box having:   an opening at a side opposite the contact surface; and   a side surface:   on each side of the contact surface in the width direction; and   orthogonal to the width direction and tilted relative to the conveyance direction.   
     
     
         5 . The sheet storage device according to  claim 2 ,
 wherein the sheet storage has a stacking surface tilted relative to a horizontal plane with a tilt angle,   the sheet storage stores the sheets each having:   a first portion having a first thickness; and   a second portion having a second thickness thinner than the first thickness,   in a state in which formula below is satisfied:
   θ≥tan −1 ( tN/y )
 
   where   θ indicates the tilt angle of the stacking surface,   t (mm) indicates a difference in thickness between the first portion and the second portion of each of the sheets,   y (mm) indicates a length of each of the sheets in the conveyance direction, and   N indicates maximum number of sheets stackable in the sheet storage.   
     
     
         6 . The sheet storage device according to  claim 1 , further comprising a bias to bias the sheet storage upward in the up-and-down direction,
 wherein an amount of descent due to stacking of a single sheet is set to a thickness of the single sheet.   
     
     
         7 . The sheet storage device according to  claim 1 , further comprising a holder holding the sheet storage,
 wherein the sheet storage is detachably attachable to the holder.   
     
     
         8 . The sheet storage device according to  claim 1 , further comprising:
 a shock absorber on a downstream end of the sheet storage in the conveyance direction; and   a sheet contact section on the shock absorber, the sheet contact section having a contact surface contactable a leading edge of each of the sheets in the conveyance direction,   wherein the shock absorber contacts a back face opposite to the contact surface of the sheet contact section.   
     
     
         9 . The sheet storage device according to  claim 1 , further comprising a sheet stacking tray at a bottom end of the sheet storage in a gravity direction,
 wherein the sheet stacking tray has:   different thicknesses between one end and another end in the conveyance direction; and   a stacking surface on which the sheets are stacked.   
     
     
         10 . The sheet storage device according to  claim 1 ,
 wherein the sheet storage includes a restrictor to restrict a widthwise position of each of the sheets in the sheet storage in a width direction tilted relative to a direction orthogonal to the conveyance direction.   
     
     
         11 . The sheet storage device according to  claim 10 ,
 wherein the restrictor has a tilted surface to gradually reduce a width of the sheet storage in the width direction toward downstream in the conveyance direction.