Sheet stacking apparatus

In a sorting apparatus in which copy sheets are sorted into tray members moved past a sheet path, wherein each tray member is arranged with a first tray portion inclined to the horizontal plane on which sides of copy sheets are received and a second tray portion against which edges of the copy sheets are received, the improvement comprising:

• a frame,
• at least two light weight plate members positioned on said frame in spaced relation with at least one plate member on each side of the center line of the sheet path and terminating the sheet path at an acute angle to said first tray portion,
• said plate members being pivotable on an axis parallel to and adjacent said second tray portion to move relative to the tray member whereby a copy sheet entering the tray member strikes said plate members transferring kinetic energy to rotational kinetic energy which is absorbed by the topmost sheets in said tray member upon return of said plate members to a rest position,
• wherein each of said plate members is in the shape of a polygon which is relatively thin, said polygon having a leading edge in the sheet path forming said acute angle with said first tray portion,
• wherein said acute angle decreases as the tray member fills with copy sheets whereby curling of sheets along said second tray portion is minimized.