Sheet folding mechanism, sheet post-processing apparatus and method thereof

A sheet folding mechanism comprising:

• a folding unit configured to form a folding line by folding a center of a sheet bundle having a plurality of sheets;
• a shaft positioned on an output side of the folding unit and having a horizontal shaft axis orthogonal to the carrying direction in which the sheet bundle is carried;
• a pair of discharge rollers provided on the shaft in the longitudinal direction thereof;
• a pair of pinch rollers configured to nip the sheet bundle in cooperation with the pair of discharge rollers;
• a pair of corrugation rollers each having a cam surface on an outer peripheral surface thereof, and an eccentric bearing provided inside the outer peripheral surface and axially supported by the shaft so as to be movable in the direction of the shaft axis;
• a roller position variable member configured to vary a distance between the pair of corrugation rollers;
• a drive unit configured to rotate the shaft in a normal direction and a reverse direction opposite from the normal direction;
• and
• a controller configured to control driving of the drive unit and cause the roller position variable member to vary the distance according to the number of sheets in the sheet bundle.

A sheet post-processing apparatus comprising:

• a folding unit configured to form a folding line by folding a center of a sheet bundle having a plurality of sheets printed by and output respectively from an image forming apparatus;
• a receiving unit configured to receive information on the number of sheets from the image forming apparatus;
• a shaft positioned on an output side of the folding unit and having a horizontal shaft axis orthogonal to the carrying direction of the sheet bundle;
• a pair of discharge rollers provided on the shaft in the longitudinal direction thereof;
• a pair of pinch rollers configured to nip the sheet bundle in cooperation with the pair of discharge rollers;
• a pair of clutches configured to transmit a rotational force about the shaft axis only in the direction opposite from the normal direction which causes the sheet bundle to be discharged;
• a pair of corrugation rollers, each of the corrugation rollers having a cam surface including a first diameter portion having a diameter larger than a diameter of the discharge roller and a second diameter portion having a diameter smaller than the diameter of the first diameter portion on an outer peripheral surface thereof, and an eccentric bearing to be fixed to each of the pair of clutches inside the outer peripheral surface;
• a lock member configured to prevent the pair of corrugation rollers from idling about the shaft axis in the direction to cause the sheet bundle to be discharged;
• a drive unit configured to rotate the shaft in the normal direction and the reverse direction, and a controller configured to control driving the drive unit and cause the corrugation rollers to apply corrugation on the sheet bundle using any one of the first diameter portions and the second diameter portions according to the information on the number of sheets that the receiving unit receives, and a threshold value stored in advance.

A sheet post-processing apparatus comprising:

• a folding unit configured to form a folding line by folding a center of a sheet bundle having a plurality of sheets printed by and output respectively from an image forming apparatus;
• a receiving unit configured to receive information on the number of sheets from the image forming apparatus;
• a shaft positioned on an output side of the folding unit and having a horizontal shaft axis orthogonal to the carrying direction of the sheet bundle;
• a pair of discharge rollers provided on the shaft in the longitudinal direction thereof;
• a pair of pinch rollers configured to nip the sheet bundle in cooperation with the pair of discharge rollers;
• a pair of corrugation rollers each having a cam surface on an outer peripheral surface thereof, and an eccentric bearing provided inside the outer peripheral surface and axially supported by the shaft so as to be movable in the direction of the shaft axis;
• a roller position variable member configured to vary a distance between the pair of corrugation rollers;
• a drive unit configured to rotate the shaft in a normal direction and a reverse direction opposite from the normal direction;
• and
• a controller configured to control driving of the drive unit and cause the roller position variable member to vary the distance on the basis of the information on the number of sheets received by the receiving unit and a threshold value held in advance.

A method of applying corrugation on the sheet, comprising:

• forming a folding line by folding a center of a sheet bundle having a plurality of sheets and sending the sheet bundle to a pair of discharge rollers;
• rotating the discharge rollers in the normal direction to discharge the sheet bundle together with a pair of pinch rollers, and sending the sheet bundle to a pair of corrugation rollers via a pair of one-way clutches fixed to the shaft;
• bringing any one of first diameter portions having a diameter larger than a diameter of the discharge rollers and second diameter portions having a diameter smaller than the diameter of the first diameter portions of cam surfaces on outer peripheral surfaces of the respective corrugation rollers into contact with the folding line according to the number of sheets;
• and
• applying corrugation of different amounts to the sheet bundle using either the first diameter portions or the second diameter portions.