A medium conveying apparatus includes a conveying roller to convey a medium, an overlap detection sensor, a processor to detect an overlap portion in which it is determined that an overlap has occurred on the medium based on a detection output by the overlap detection sensor for the medium conveyed by the conveying roller, calculate an overlap length where the overlap portion is continuous based on a detection result of the overlap portion, determine whether a multi-feed has occurred based on the overlap length, and execute an abnormal processing for the multi-feed based on a determination result of the multi-feed. The processor determines that a first overlap portion and a second overlap portion are continuous when a distance between the first overlap portion and the second overlap portion is within a predetermined distance in calculating the overlap length.

Unwinder of a thin ply product wound on a roll, of the type with automatic switching of the unwinding roll with a spare roll, said unwinder comprising—a first roll-holder assembly equipped with a first unwinding rod for a respective roll, on which the roll is adapted to be supported, and which has an axis of rotation transversal to the direction of movement of the ply unwound from the roll, —a second roll-holder assembly equipped with a second unwinding rod for a respective roll, on which the roll is adapted to be supported, said second rod being parallel to said first unwinding rod of the first roll-holder assembly, said second roll-holder assembly facing said first roll-holder assembly in an unwinding zone, wherein of said two roll-holder assemblies, one assembly holds the unwinding roll and the other assembly holds the spare roll to be switched, —a ply splicing assembly placed above said first and second facing roll-holder assemblies, —a ply accumulation unit to allow automatic switching between a roll being unwound in one said roll-holder assembly and a spare roll provided in the other roll-holder assembly, —a transversal position correction system for the side edges of the plies on the rolls present in said roll-holder assemblies.

An image reading apparatus includes a control unit configured to detect occurrence or non-occurrence of multi-sheet feed of a medium based on a reception level signal output by a reception unit in accordance with the received ultrasonic wave. The control unit, after a tip of the medium reaches the positions of the reception unit in a transport path, when the reception level signal is below a predetermined threshold, causes the driving voltage to rise, when an amount of change in the reception level signal in accordance with the rise in the driving voltage is smaller than a reference amount of change, determines that multi-sheet feed is ongoing, and when the amount of change in the reception level signal in accordance with the rise in the driving voltage is greater than the reference amount of change, determines that multi-sheet feed is not ongoing.

In some examples, a non-transitory machine readable medium can include instructions executable by a processing resource to assert a low print media level notification responsive to determination that a first amount of print media in a media receptacle of an imaging device is less than a set value, detect a second amount of print media in the media receptacle of the imaging device, compare the detected second amount of print media to a print media threshold that is based on the set value and a selectable print media value, and maintain the low print media level notification responsive to a determination that the detected second amount of print media is less than the print media threshold.

A sheet stacker includes a housing, a fence, a first distance measurement sensor, and a second distance measurement sensor. The fence is movable in a fence moving direction on the housing and is configured to regulate a position of an end of a sheet. The first distance measurement sensor is configured to measure a distance between the fence and a first portion of the housing, the first portion being on one side of the housing with respect to the fence in the fence moving direction. The second distance measurement sensor is configured to measure a distance between the fence and a second portion of the housing, the second portion being on another side of the housing with respect to the fence in the fence moving direction.

A medium conveying apparatus includes a conveying roller to convey a medium, an overlap detection sensor, a processor to detect an overlap portion in which it is determined that an overlap has occurred on the medium based on a detection output by the overlap detection sensor for the medium conveyed by the conveying roller, calculate an overlap length where the overlap portion is continuous based on a detection result of the overlap portion, determine whether a multi-feed has occurred based on the overlap length, and execute an abnormal processing for the multi-feed based on a determination result of the multi-feed. The processor determines that a first overlap portion and a second overlap portion are continuous when a distance between the first overlap portion and the second overlap portion is within a predetermined distance in calculating the overlap length.

A medium conveying apparatus includes a conveying roller to convey a medium, a width detection sensor for detecting a width of the medium conveyed by the conveying roller in a direction perpendicular to a conveying direction, an overlap detection sensor for detecting an overlap of the medium conveyed by the conveying roller, and a processor to determine whether to execute an abnormality processing for a multi-feed, based on the width of the medium acquired based on a detection result by the width detection sensor and a detection result by the overlap detection sensor. The processor acquires an overlap detection width being a width in which the medium is estimated to overlap in the direction perpendicular to the conveying direction, based on the detection result by the overlap detection sensor. The processor executes the abnormality processing when the width of the medium and the overlap detection width are equal.

A medium conveying apparatus includes a conveying roller to convey a medium, an end detection sensor for detecting a position of an end of the medium conveyed by the conveying roller, an overlap detection sensor for detecting an overlap of the medium conveyed by the conveying roller in a detection area, and a processor to determine whether an overlap detection is valid or invalid based on a positional relationship between the position of the end of the medium detected by the end detection sensor and the detection area, and execute an abnormality processing for multi-feed based on a detection result by the overlap detection sensor when it is determined that the overlap detection is valid.

A medium conveying apparatus includes a conveying roller to convey a medium, and a processor to detect transmission information of an ultrasonic wave transmitted through the medium or thickness information of the medium at a plurality of positions in the conveyed medium, calculate a size of an area in which the transmission information or the thickness information is within a predetermined range in the conveyed medium, determine whether a multi-feed of the medium has occurred, by comparing a value based on the transmission information or the thickness information with a threshold, and execute an abnormality processing when it is determined that the multi-feed of the medium has occurred. The processor changes the threshold according to the size.

A medium conveying apparatus includes a conveying roller to convey a rectangular medium, and a processor to generate an input image acquired by imaging the conveyed medium, detect an overlap of the conveyed medium, detect an object area from the input image, determine whether an outer shape of the object area is rectangular, determine whether a multi-feed of the medium has occurred based on whether the overlap of the medium has been detected and whether the outer shape of the object area is rectangular, and execute an abnormality processing when it is determined that the multi-feed of the medium has occurred.