According to one embodiment, a post-processing apparatus includes a first sensor, a second sensor, and a control unit. The first sensor detects an object in a predetermined area in which a predetermined post-process is performed on a sheet conveyed from an image forming apparatus. The second sensor detects an object at a position closer to an opening in the area than the position of the first sensor with respect to the opening through which the sheet passes when the post-processed sheet is discharged from the area. When the second sensor detects an object before the first sensor detects the object, the control unit performs a predetermined process for preventing the occurrence of a failure.

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.

A fastening member detection device includes a contact structure that moves with respect to a medium while contacting the medium, a vibration detector that detects vibration that occur in the contact structure, and a controller that determines whether there is a fastening member that fastens the medium, based on the vibration.

A medium conveying apparatus includes a first optical sensor located on an upper part of the housing and in a central part of the housing in a direction perpendicular to a medium conveying direction, a second optical sensor located on an upper part of the housing and on a side of the first optical sensor in the direction perpendicular to the medium conveying direction, and a processor to detect a folding of a medium based on the first signal or the second signal, and stop feeding of the medium by the feed roller in accordance with a detection result of the folding of the medium. The first light emitter emits first light toward a downstream side of the medium in the medium conveying direction, and the second light emitter emits second light toward an upstream side of the medium in the medium conveying direction.

An image forming device including an optical sensor, an ultrasound sensor, and a conveyance guide. The optical sensor and the ultrasound sensor are disposed alongside a conveyance path of a sheet and are used to determine sheet type. The conveyance guide guides the sheet along the conveyance path. The conveyance guide is structured such that, on the conveyance path between the optical sensor and the ultrasound sensor, the sheet is in contact with the conveyance guide while a portion of the sheet is in a light irradiation range of the optical sensor and a different portion of the sheet is in an ultrasound irradiation range of the ultrasound sensor.

A recoding medium conveying device includes a conveyance belt, a first sensor, a second sensor, and circuitry. The conveyance belt has an endless loop shape and a length capable of conveying a plurality of recording media in one rotation. The first sensor is disposed upstream from the conveyance belt in a conveyance direction of a recording medium and is configured to detect the recording medium. The second sensor is configured to detect a home position of the conveyance belt. The circuitry is configured to adjust a rotation speed of the conveyance belt, while the conveyance belt makes one rotation, to eliminate an amount of deviation between a first detection timing of the recording medium detected by the first sensor and a second detection timing of the home position of the conveyance belt detected by the second sensor.

An image forming apparatus includes a load detection sensor located on a feeder to detect whether a print medium is loaded on the feeder, an overload detection sensor to detect an overload state of a discharger, and a controller to detect a width of the print medium according to a combination of a feeder load state of a feeder load detection signal of the load detection sensor and an overload state of a discharger overload detection signal of the overload detection sensor and control an image former to perform printing by applying different print modes according to the detected width of the print medium.

A relay conveyance device includes a relay conveyance path arranged between an image forming apparatus and a post processing device to convey a sheet from the image forming apparatus to the post processing device, two reversing units reversing a surface side and a back-face side of the sheet, and a control device controlling conveyance of the sheet on the relay conveyance path. The relay conveyance path includes two reverse paths respectively passing through the two reversing units, a branch section branching into the two reverse paths at an upstream side, and a confluence section joining the two reverse paths. The control device controls the branch and confluence sections to convey the sheet while alternately switching the two reverse paths, measures an interval time between the sheets passing through the confluence section, and controls conveyance of the sheet in the two reverse paths so as to uniformize the interval time.

Provided are a sheet position detection apparatus, a sheet conveyance apparatus, and an image formation apparatus. The sheet position detection apparatus has a first and a second conveyance roller which are arranged to oppose across a sheet to be conveyed and to nip the sheet, and a detector configured to detect an end position of the sheet, the detector has a light emitter and a light receptor arranged on the first conveyance roller side, the light emitter and the light receptor are arranged such that a light emitted from the light emitter is reflected on a reflective face of the second conveyance roller and enters the light receptor, and the detector detects passage of an end of the sheet based on a change in the amount of light entering the light receptor when the sheet shields a light emitted from the light emitter.

A sheet conveying device includes a detector configured to detect an attitude of a conveyance target medium, a corrector configured to perform a correcting operation based on a detection result of the detector, and circuitry configured to calculate an angular displacement correction amount and a lateral displacement correction amount of the conveyance target medium, cause the corrector to perform the correcting operation in a direction perpendicular to a sheet conveying direction, based on the lateral displacement correction amount, after the corrector grips the conveyance target medium, and cause the corrector to rotate by the angular displacement correction amount of the conveyance target medium before the corrector grips the conveyance target medium and to perform the correcting operation in a direction of rotation of the conveyance target medium, based on the angular displacement correction amount, after the corrector grips the conveyance target medium.