A theoretical threshold corresponding to a transport path is set, and a control unit acquires a calculation value calculated based on a detection result of double feeding detection unit and a transport length of a document, determines occurrence of double feeding when the calculation value is greater than the theoretical threshold (step S120), and determines non-occurrence of double feeding when the calculation value is smaller than the theoretical threshold. In addition, if a non-detection period for double feeding occurs (step S110), the control unit sets a cumulative value in step S115. As a result, detection of double feeding is ended in a short period while a document is being transported, and in a case that double feeding is no longer detected, determination of double feeding will not be made.

A theoretical threshold corresponding to a transport path is set, and a control unit acquires a calculation value calculated based on a detection result of double feeding detection unit and a transport length of a document, determines occurrence of double feeding when the calculation value is greater than the theoretical threshold (step S120), and determines non-occurrence of double feeding when the calculation value is smaller than the theoretical threshold. In addition, if a non-detection period for double feeding occurs (step S110), the control unit sets a cumulative value in step S115. As a result, detection of double feeding is ended in a short period while a document is being transported, and in a case that double feeding is no longer detected, determination of double feeding will not be made.

A sheet feeder includes a controller configured to control an emitter to emit an ultrasonic wave toward a target sheet being fed along a sheet guide, control a measurer to measure a first reception intensity of a first component of the ultrasonic wave received by a receiver during a first period of time, control the measurer to measure a second reception intensity of a second component of the ultrasonic wave received by the receiver during a second period of time, and determine a feeding state of the target sheet in a detectable area between the emitter and the receiver within the sheet guide, based on the first reception intensity and the second reception intensity.

A sheet feeding apparatus includes: a placer that allows a plurality of sheets to be placed on the placer; an air feeder including a front-end fan that generates an airflow from a front-edge side in a sheet feeding direction of a bundle of sheets placed on the placer toward the bundle of sheets; an attracting conveyor that attracts an uppermost sheet separated by the air feeder from the bundle of sheets placed on the placer and conveys the uppermost sheet; a detector that detects, in the conveyance of the uppermost sheet by the attracting conveyor, an amount of co-feeding of a next sheet together with the uppermost sheet; and a hardware processor that executes air-volume control to the front-end fan such that an air volume of the front-end fan increases with an increase in the amount of co-feeding detected by the detector.

A sheet feeding apparatus includes: a placer that allows a plurality of sheets to be placed on the placer; an air feeder including a front-end fan that generates an airflow from a front-edge side in a sheet feeding direction of a bundle of sheets placed on the placer toward the bundle of sheets; an attracting conveyor that attracts an uppermost sheet separated by the air feeder from the bundle of sheets placed on the placer and conveys the uppermost sheet; a detector that detects, in the conveyance of the uppermost sheet by the attracting conveyor, an amount of co-feeding of a next sheet together with the uppermost sheet; and a hardware processor that executes air-volume control to the front-end fan such that an air volume of the front-end fan increases with an increase in the amount of co-feeding detected by the detector.

A feeding apparatus includes a feeding member, first and second conveying members, a separation member, and drive and control units. The feeding member feeds a recording material placed on a tray. The separation member and the first conveying member form a nip portion and separates recording materials at the nip portion. The second conveying member conveys a conveyed recording material. The drive unit drives at least the feeding member. The control unit controls to feed first and second recording materials such that a second recording material front edge passes the nip portion before a first recording material rear edge passes the nip portion, and controls to stop the second recording material after the second recording material front edge has passed the nip portion such that the first recording material rear edge reaches the second conveying member before the second recording material front edge reaches the second conveying member.

A feeding apparatus includes a feeding member, first and second conveying members, a separation member, and drive and control units. The feeding member feeds a recording material placed on a tray. The separation member and the first conveying member form a nip portion and separates recording materials at the nip portion. The second conveying member conveys a conveyed recording material. The drive unit drives at least the feeding member. The control unit controls to feed first and second recording materials such that a second recording material front edge passes the nip portion before a first recording material rear edge passes the nip portion, and controls to stop the second recording material after the second recording material front edge has passed the nip portion such that the first recording material rear edge reaches the second conveying member before the second recording material front edge reaches the second conveying member.

A sheet conveyance apparatus including a transmission unit that transmits an ultrasonic wave toward a sheet and a reception unit that receives the ultrasonic wave includes a change unit that changes a distance of a conveyance path of the sheet according to sheet information about the sheet to be conveyed.

A lateral positioning device (100) for a sheet element (20, 20′) in a sheet element processing machine; a detector lever (130) articulated relative to a horizontal axis, which performs a descending movement from a high position to a low position; a first end (132) of the detector lever (130) contacts, in a low position of the lever, with an upper face of the sheet element. A second end (133) of the detector lever (130) is fitted with a target (135) that cooperates with a position detector (140) to generate a signal dependent on the thickness of the sheet element (20, 20′) and the number of sheet elements (20, 20′) present at the level of the first end (132) of the detector lever (130).

A conveying mechanism has a pair of nipping members configured to nip a sheet from both sides thereof at a nipping position and to convey the sheet from upstream to downstream side. The pair of nipping members includes a conveying roller. A controller performs: a motor controlling process of controlling the motor to perform a conveying operation of the sheet by rotation of the conveying roller; a reaction-force calculating process of calculating a reaction-force inference value which corresponds to reaction force that acts on the motor, by removing a friction component generated due to rotation of the motor from a disturbance inference value, the disturbance inference value being calculated from both a control input to the motor and a control output relative to the control input; and a warning process of outputting warning in response to occurrence of multiple feeding of the sheet, based on the reaction-force inference value.