Stacking apparatus

Abstract

There is provided a stacking apparatus capable of stably conveying and stacking sheets without occurrence of damage or buckling of the sheets in the structure of discharging the curled sheets one by one. In regard to each of a plurality of clamp guides which project toward stacking trays from conveyance means to guide sheets S, the projecting position varies in accordance with a size and an amount of stacked sheets Sa on the stack trays. The stacking tray comprises an inclined surface and a curved surface. An upper guide is located to face the inclined surface by a predetermined interval, and the upper guide is located not to face the curved surface or is located to face it by an interval larger than a predetermined interval.

What is claimed is: 
     
         1 . A sheet stacking apparatus, comprising:
 a tray on which a sheet is placed in an inclined condition; and   a guide unit that guides a sheet conveyed on the tray and restrains an end of the sheet placed on the tray,   wherein the guide unit comprises a plurality of movable guides which are divided in a width direction of the sheet and are movable in accordance with the sheet placed on the tray.   
     
     
         2 . The sheet stacking apparatus according to  claim 1 , wherein
 a plurality of the divided movable guides respectively move by a driving force of a common driving unit such that a leading end of the guide abuts on the sheet placed on the tray or the tray.   
     
     
         3 . The sheet stacking apparatus according to  claim 2 , wherein
 a torque limiter or a spring member is provided to correspond to each of a plurality of the divided movable members, wherein when the leading end abuts on the sheet or the tray, the movement of the guide unit is stopped by an operation of the corresponding torque limiter or spring member.   
     
     
         4 . The sheet stacking apparatus according to  claim 1 , wherein
 a rolling element is attached on a leading end of each of a plurality of the divided movable guides, wherein the rolling element abuts on the sheet or the tray.   
     
     
         5 . The sheet stacking apparatus according to  claim 4 , wherein
 the rolling element can be driven to be rotated only in one direction.   
     
     
         6 . The sheet stacking apparatus according to  claim 1 , wherein
 the guide unit moves such that at the time when the leading end of the sheet is conveyed along the guide unit, the leading end of the guide is located in the projecting state of having moved to the tray-side, and at the time when the rear end of the sheet is conveyed along the guide unit, the leading end of the guide is located in the retract state of having retracted from the tray-side.   
     
     
         7 . The sheet stacking apparatus according to  claim 6 , wherein
 at the time when the guide unit transitions from the projecting state to the retract state, at least one of the time of the transition, a speed of the transition and a conveyance speed of a sheet differs depending upon environment or sheet type.   
     
     
         8 . The sheet stacking apparatus according to  claim 6 , further comprising a discharge roller for discharging the sheet conveyed by a conveyance unit to the tray,
 wherein the discharge roller holds the sheet together with the guide unit at the time the guide unit is in the projecting state, and holds the sheet together with the conveyance unit at the time the guide unit is in the retract state.   
     
     
         9 . The sheet stacking apparatus according to  claim 1 , wherein
 the tray includes an inclined surface and a curved surface, wherein the sheet conveyed to the tray goes up in the upward direction against gravity along the inclined surface, hangs downward via the curved surface, and is placed on the tray.   
     
     
         10 . The sheet stacking apparatus according to  claim 9 , further comprising an upper guide facing the inclined surface to have a predetermined interval therefrom,
 wherein a plurality of driven rolling elements are arranged along the sheet conveyance direction on the upper guide.   
     
     
         11 . A sheet stacking apparatus in which a sheet is supported in an inclined condition by a tray, and a part of the sheet is stacked in a hanging-downward condition from the tray,
 wherein the tray includes an inclined surface and a curved surface, wherein the sheet conveyed to the tray goes up in the upward direction against gravity along the inclined surface and hangs downward via the curved surface,   an upper guide facing the inclined surface to have a predetermined interval therefrom is provided, wherein the upper guide is not faced the curved surface or faced a part of the curved surface in having an interval larger than the predetermined interval.   
     
     
         12 . The sheet stacking apparatus according to  claim 11 , wherein
 an end of the upper guide in a direction where the sheet is conveyed is positioned upstream of a boundary between the inclined surface and the curved surface in the conveyance direction.   
     
     
         13 . The sheet stacking apparatus according to  claim 12 , wherein
 the sheet is pulled out from a roll sheet around a roll core of which the sheet is wound, and   a distance from the boundary to the end in the travel direction of the sheet is smaller than 1.2 times a diameter of an outer periphery of the roll core.   
     
     
         14 . The sheet stacking apparatus according to  claim 11 , wherein
 the sheet is pulled out from a roll sheet around a roll core of which the sheet is wound, and   the predetermined interval is a distance smaller than a radius of curvature of an outer periphery of the roll core.   
     
     
         15 . The sheet stacking apparatus according to  claim 11 , wherein
 the sheet is pulled out from a roll sheet around a roll core of which the sheet is wound, and   a radius of curvature of the curved surface is larger than a radius of curvature of an outer periphery of the roll core.   
     
     
         16 . The sheet stacking apparatus according to  claim 11 , wherein
 a plurality of driven rolling elements which retract when pushed by the sheet are provided to be arranged along the sheet conveyance direction on the upper guide.   
     
     
         17 . The sheet stacking apparatus according to  claim 11 , wherein
 a friction member is attached in the vicinity of the distal end of the curved surface.   
     
     
         18 . The sheet stacking apparatus according to  claim 11 , wherein
 the inclined surface comprises a plurality of inclined surfaces which are divided in the width direction of the sheet.   
     
     
         19 . The sheet stacking apparatus according to  claim 1 , wherein
 the sheet comprises a plurality of sheets, which are printed by an inkjet printer to be conveyed and stacked on the tray.