Sheet feeder device and image forming apparatus

A sheet feeder device comprising:

• a pick-up roller capable of abutting against and separating away from a sheet carried on a predetermined sheet carrying section, the pick-up roller being operative to feed the sheet when abutting against the sheet;
• a pick-up roller driving section operative to position the pick-up roller into each of at least three stepwise positions including a retracted position spaced a predetermined distance apart from the sheet, a sheet feed position in which the pick-up roller abuts against the sheet, and a standby position intermediate the retracted position and the sheet feed position:
• and
• a control section for controlling positioning of the pick-up roller by the pick-up roller driving section, wherein
• the predetermined distance is a distance defining a sufficient space in which the pick-up roller is upwardly spaced a predetermined height h of allowance apart from a height H of a stack of a maximum number of sheets loaded on the predetermined sheet carrying section, and
• during an operation for feeding a series of sheets, the control section controls the pick-up roller to first be in the sheet feed position in which the pick-up roller abuts against the stack of sheets loaded on the predetermined sheet carrying section, then, after feeding a sheet from the stack of sheets, to be in the standby position during a period from a point in time just after feeding of said sheet to a point in time just before feeding of a succeeding sheet of the series of sheets, after which time the pick-up roller is sequentially controlled to be in the sheet feed position to feed the next sheet in the series of sheets and then to be in the standby position during the period from the point in time just after feeding of the next sheet in the series of sheets to a point in time just before feeding of the next succeeding sheet of the series of sheets, until all sheets in the series of sheets have been fed.