A sheet conveying device includes a sheet stacker, an air blower, and a guide. The sheet stacker stacks a plurality of sheets. The air blower blows air onto the plurality of sheets. The guide faces an uppermost sheet of the plurality of sheets on the sheet stacker and contacts the uppermost sheet at a plurality of positions of the guide spaced apart from each other in a sheet conveyance direction.

A sheet feeding device includes an air blower and circuitry. The air blower includes a first suction fan, and a second suction fan serially coupled to the first suction fan. The circuitry is to stop the first suction fan at a first timing, and stop the second suction fan at a second timing different from the first timing. An image forming apparatus includes the sheet feeding device.

A sheet feeding device comprises sheet storage for storing a sheet, a merging conveying unit for feeding the sheet from the sheet storage to an image forming apparatus, a transmitting element for transmitting an ultrasonic signal to the sheet conveyed on the merging conveying unit, and a receiving element for receiving the ultrasonic signal having passed through the sheet and outputting an output signal according to strength of the received ultrasonic signal. When the sheet is a Japanese paper, the sheet feeding device detects double feeding of the sheet according to an average value of a plurality of the output signals and variation in a plurality of the output signals obtained for the one sheet. If the sheet is not double fed, the sheet is fed to the image forming apparatus. If the sheet is double fed, the sheet is discharged to the escape tray.

A sheet feeding device comprises sheet storage for storing a sheet, a merging conveying unit for feeding the sheet from the sheet storage to an image forming apparatus, a transmitting element for transmitting an ultrasonic signal to the sheet conveyed on the merging conveying unit, and a receiving element for receiving the ultrasonic signal having passed through the sheet and outputting an output signal according to strength of the received ultrasonic signal. When the sheet is a Japanese paper, the sheet feeding device detects double feeding of the sheet according to an average value of a plurality of the output signals and variation in a plurality of the output signals obtained for the one sheet. If the sheet is not double fed, the sheet is fed to the image forming apparatus. If the sheet is double fed, the sheet is discharged to the escape tray.

A sheet feeding device includes a sheet stacker configured to stack a sheet bundle; a blower configured to float a sheet on an upper portion of the sheet bundle; a conveyor configured to convey the sheet floated by the blower; a lift configured to lift up and down the sheet stacker; a first reflective optical sensor configured to detect the sheet floated by the blower; a second reflective optical sensor configured to detect the sheet bundle and a side face of the sheet stacker, the side face including a detection region to be detected by the second reflective optical sensor and a non-detection region not to be detected by the second reflective optical sensor; and circuitry configured to control the lift based on a detection result of the first reflective optical sensor and a detection result of the second reflective optical sensor. The circuitry is configured to cause the lift to lift up the sheet stacker in response to a change from a detection state to a non-detection state of the second reflective optical sensor.

A sheet feeding device, which is included in an image forming apparatus and an image forming system, includes a sheet loader, an air drawing body, an attracting and conveying device, an air duct and a blocking device. The sheet loader is a device on which a bundle of sheets is loaded. The air drawing body is configured to generate suction air. The attracting and conveying device is configured to attract a sheet on top of the bundle of sheets by the suction air and convey the sheet. The air duct is configured to intake the suction air drawn by the air drawing body, to the attracting and conveying device. The blocking device is configured to block the suction air in the air duct.

A guide member (14) has an upper surface assisting conveyance of workpieces (44) mounted on a table (12) and is arranged downstream of the table (12) in a workpiece conveyance direction. A belt drive mechanism (16) has pulleys (26a to 26d, 28a to 28b), and endless belts (32a to 32d) wound around these pulleys, and is arranged above the table (12) and the guide member (14) so as to stride over the table (12) and the guide member (14). A first opening portion is formed on a bottom portion of the belt drive mechanism (16) to generate an upward suction force. A second opening portion is formed on the upper surface of the guide member (14) to generate a downward suction force. A magnitude of the suction force generated in the first opening portion exceeds a magnitude of the suction force generated in the second opening portion.

A guide member (14) has an upper surface assisting conveyance of workpieces (44) mounted on a table (12) and is arranged downstream of the table (12) in a workpiece conveyance direction. A belt drive mechanism (16) has pulleys (26a to 26d, 28a to 28b), and endless belts (32a to 32d) wound around these pulleys, and is arranged above the table (12) and the guide member (14) so as to stride over the table (12) and the guide member (14). A first opening portion is formed on a bottom portion of the belt drive mechanism (16) to generate an upward suction force. A second opening portion is formed on the upper surface of the guide member (14) to generate a downward suction force. A magnitude of the suction force generated in the first opening portion exceeds a magnitude of the suction force generated in the second opening portion.

A sheet feed device includes: a conveyor configured to convey a top sheet of sheets floated from a sheet stack; a blower configured to blow air in an obliquely upward direction from a position lower than the conveyor toward the sheet stack; and a direction converter configured to convert a direction of the air blown by the blower to a direction which is downward more than a direction of the air at a position where the air is blown from the blower and let the air flow in between the top sheet and a second sheet subsequent to the top sheet of the sheets floated from the sheet stack.

An endless conveyer belt is stretched between drive and idle rollers. A carriage is arranged so as to reciprocate along the endless conveyer belt. A suction box is arranged between upper and lower belt portions of the endless conveyer belt and fixed to the carriage. A stopper plate is fixed to the carriage and extends across a conveyer surface and upward from the conveyer surface. A conveyance roller pair is arranged at the upstream end of the conveyer surface. A region of the conveyer surface from a stopper plate to the upstream end u forms a sheet accumulation area. A cover sheet covers a region upstream of the suction box in the sheet accumulation area. The cover sheet is subjected to tension in the longitudinal direction by a winding-type constant force plate spring and continually tensed spaced apart from the endless conveyer belt.