Provided is a sheet conveyance apparatus armored with a housing, the sheet conveyance apparatus includes: a sheet conveyor that feeds a sheet to a downstream side in a direction of conveyance; a conveyance guide that guides the sheet to be conveyed; an ultrasonic sensor that detects the sheet guided by the conveyance guide; and a shield member that is conductive, wherein the ultrasonic sensor includes: a transmitter that transmits an ultrasonic wave having a predetermined frequency; and a receiver that receives the ultrasonic wave, the transmitter and the receiver are arranged along the conveyance guide, and the shield member is disposed between the housing and the receiver in a sheet-face perpendicular direction at an ultrasonic-irradiation position of the sheet being conveyed, the shield member covering an entirety of the receiver in plan view in the sheet-face perpendicular direction.

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 medium conveying apparatus includes a conveyance roller to convey a medium, an imaging device to image the medium, a DC motor to drive the conveyance roller, a processor to detect that a front end of the medium reaches between the conveyance roller and the imaging device, set a current limit value of the DC motor to a first limit value until the front end of the medium reaches between the conveyance roller and the imaging device, and change the current limit value to a second limit value larger than the first limit value after the front end of the medium has reached between the conveyance roller and the imaging device, and drive the conveyance roller by rotating the DC motor based on the second limit value when the imaging device performs imaging.

An ultrasonic sensor includes a first base facing a conveying surface, a transmission section on a first axis tilted relative to the conveying surface and at a far side of the first base for transmitting an ultrasonic wave toward the first axis, and a reception section on the first axis and at a far side of the conveying surface for receiving the ultrasonic wave. The transmission section has a plurality of transmission elements for transmitting the ultrasonic wave arranged to cross the first axis. The first base has a first aperture through which the ultrasonic wave transmitted from the transmission section along the first axis passes. An area of the first aperture is smaller than an area of an ultrasonic wave transmission surface of the transmission section. The transmission section delays driving the transmission elements to converge the ultrasonic wave transmitted from the transmission section toward the first aperture.

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.

The detection unit includes a first contact member, which comes into contact with a first surface of a recording material and a second contact member, which comes into contact with a second surface of the recording material, the first contact member and the second contact member being disposed so as to oppose each other thus being capable of nipping the recording material, and the first contact member and the second contact member are movable in a direction in which the first contact member and the second contact member nip the recording material, and is rotatable about an axis line extending in a predetermined direction, the predetermined direction being orthogonal to the direction in which the first contact member and the second contact member are movable and being orthogonal to a conveyance direction of the recording material.

A sheet feed roller portion (12) feeds a plurality of bound sheets (51) to a conveying path (18). The ultrasonic sensor (19) detects a voltage value that changes according to a thickness of the sheet (51) at a measurement position (P2) on the conveying path (18). A determination processing portion (53) determines whether or not a voltage difference between voltage values of the sheet (51) detected by the ultrasonic sensor (19) is equal to or greater than a preset threshold value. A light amount adjustment processing portion (54) adjusts a light amount of light emitted from a CIS sensor (23) and irradiated onto the sheet (51) when the determination processing portion (53) determines that the voltage difference is equal to or greater than the threshold value.

A sheet conveying apparatus includes a tray having a plurality of sheets, a feeder to successively convey sheets stacked on the tray, a controller, and a double-feed sensor to detect double feed when the feeder conveys a plurality of sheets in an overlapping manner. When a double-feed length, which corresponds to a length, in a conveyance direction of the sheet, of a region in which the double feed has been detected by the double-feed sensor, is larger than a predetermined distance, the controller determines that the double feed has occurred. When the double-feed length is smaller than the predetermined distance and a sheet size is smaller than a predetermined size, the controller determines that the double feed has occurred. When the double-feed length is smaller than the predetermined distance and the sheet size is larger than the predetermined size, the controller determines that the double feed has not occurred.

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.

An ultrasonic apparatus includes a first ultrasonic sensor that transmits an ultrasonic wave to an object and receives the ultrasonic wave reflected by the object, a second ultrasonic sensor that transmits an ultrasonic wave to the object and receives the ultrasonic wave reflected by the object, an determination circuit that outputs an error signal when the difference between a first distance between the first ultrasonic sensor and the object calculated based on ultrasonic wave transmission and reception processing using the first ultrasonic sensor and a second distance between the second ultrasonic sensor and the object calculated based on ultrasonic wave transmission and reception processing using the second ultrasonic sensor is equal to or greater than a threshold value.