Patent ID: 8302959

Claim:
A remaining sheet volume detecting apparatus, comprising: a first loading unit that loads sheets; a first moving unit that moves the first loading unit to a feeding position of one of the loaded sheets; a first feeding unit that feeds the one of the loaded sheets from a top position of the first loading unit which has reached the feed position; a lift-up motor to elevate and lower the first loading unit; a sheet thickness detecting unit that detects a thickness of the one of the sheets fed by the first feeding unit; a load thickness detecting unit that detects if thickness of the loaded sheets within the first loading unit reaches a certain load thickness, the loaded sheets gradually decreasing according to the sheet feeding performed by the first feeding unit; and a remaining sheet volume calculating unit that, before the load thickness detecting unit detects that the thickness of the loaded sheets within the first loading unit has reached the certain load thickness, calculates remaining sheet volume based on the lift-up time by the lift-up motor and, after the load thickness detecting unit detects that the thickness of the loaded sheets within the first loading unit has reached the certain load thickness, calculates remaining sheet volume by sequentially subtracting the sheet thickness detected by the sheet thickness detecting unit from the certain load thickness detected by the loading thickness detecting unit, each time the sheet is fed by the first feeding unit.