Image forming apparatus

1. An image forming apparatus comprising:

a circulation unit comprising a plurality of reversing units each configured to reverse a sheet of recording media having one surface printed at an image processor, the circulation unit being configured to re-feed the reversed sheet of recording media to the image processor; and

a controller configured to, during duplex printing of a plurality of sheets of recording media through circulation in the circulation unit, (i) control one reversing unit among the plurality of reversing units to hold at least one sheet among the plurality of sheets, (ii) while the one reversing unit is holding the at least one sheet, circulate at least one other sheet among the plurality of sheets between the circulation unit and another reversing unit among the plurality of reversing units that is not holding the at least one sheet, and (iii) after the at least one other sheet has passed the another reversing unit, control the one reversing unit holding the at least one sheet to release the at least one sheet, so as to increase an actual circulated sheet number of the circulated plurality of sheets by a number corresponding to the at least one sheet held at the one reversing unit so that the increased actual circulated sheet number is larger than a predetermined circulated sheet number by the number corresponding to the at least one sheet held at the one reversing unit;

wherein the predetermined circulated sheet number is based on a conveyance direction length of the recording media, and

wherein the controller is configured to transpose images to be printed in accordance with a discharge order of the plurality of sheets, the discharge order being determined as a result of holding the at least one sheet at the one reversing unit.

2. The image forming apparatus according to claim 1 , wherein the plurality of reversing units comprises two reversing units, and at least one of the two reversing units comprises a discharging unit configured to discharge a printed sheet of recording media.

3. The image forming apparatus according to claim 2 , wherein when a printing command includes a received sheet number that is smaller than a number obtained by adding one to the predetermined circulated sheet number, the controller is configured not to control the one reversing unit to hold the at least one sheet and to set the actual circulated sheet number at the predetermined circulated sheet number.

4. The image forming apparatus according to claim 2 , wherein when (i) the conveyance direction length of the recording media is a predetermined length, and (ii) a scheduled printed sheet number is a multiple of a number obtained by adding one to the predetermined circulated sheet number, the controller is configured to control the one reversing unit to hold the at least one sheet, and to set the actual circulated sheet number at the number obtained by adding one to the predetermined circulated sheet number.

5. The image forming apparatus according to claim 2 , wherein the controller is configured to prohibit the one reversing unit from holding the at least one sheet when, during a printing operation, a change is made to a printing condition comprising at least one of the conveyance direction length of the recording media, a paper type, a printing mode, and a process speed.

6. The image forming apparatus according to claim 1 , wherein when the at least one sheet held at the one reversing unit is exposed to outside the image forming apparatus, the controller is configured to control a notifier coupled to the controller to make a notification to prohibit removal of the at least one sheet.

7. The image forming apparatus according to claim 1 , wherein the at least one other sheet comprises a number of sheets circulable in the circulation unit, and the controller is configured to control the one reversing unit holding the at least one sheet to release the at least one sheet after all the number of sheets have passed the another reversing unit.

8. An image forming apparatus comprising:

a circulation unit comprising a plurality of reversing units each configured to reverse a sheet of recording media having one surface printed at an image processor, the circulation unit being configured to re-feed the reversed sheet of recording media to the image processor; and

a controller configured to, during duplex printing of a plurality of sheets of recording media through circulation in the circulation unit, (i) control one reversing unit among the plurality of reversing units to hold at least one sheet among the plurality of sheets, (ii) while the one reversing unit is holding the at least one sheet, circulate at least one other sheet among the plurality of sheets between the circulation unit and another reversing unit among the plurality of reversing units that is not holding the at least one sheet, and (iii) after the at least one other sheet has passed the another reversing unit, control the one reversing unit holding the at least one sheet to release the at least one sheet, so as to increase an actual circulated sheet number of the circulated plurality of sheets by a number corresponding to the at least one sheet held at the one reversing unit so that the increased actual circulated sheet number is larger than a predetermined circulated sheet number by the number corresponding to the at least one sheet held at the one reversing unit;

wherein the predetermined circulated sheet number is based on a conveyance direction length of the recording media, and

wherein the at least one other sheet comprises a number of sheets circulable in the circulation unit, and the controller is configured to control the one reversing unit holding the at least one sheet to release the at least one sheet after all the number of sheets have passed the another reversing unit.

9. The image forming apparatus according to claim 8 , wherein the plurality of reversing units comprises two reversing units, and at least one of the two reversing units comprises a discharging unit configured to discharge a printed sheet of recording media.

10. The image forming apparatus according to claim 9 , wherein when a printing command includes a received sheet number that is smaller than a number obtained by adding one to the predetermined circulated sheet number, the controller is configured not to control the one reversing unit to hold the at least one sheet and to set the actual circulated sheet number at the predetermined circulated sheet number.

11. The image forming apparatus according to claim 9 , wherein when (i) the conveyance direction length of the recording media is a predetermined length, and (ii) a scheduled printed sheet number is a multiple of a number obtained by adding one to the predetermined circulated sheet number, the controller is configured to control the one reversing unit to hold the at least one sheet, and to set the actual circulated sheet number at the number obtained by adding one to the predetermined circulated sheet number.

12. The image forming apparatus according to claim 9 , wherein the controller is configured to prohibit the one reversing unit from holding the at least one sheet when, during a printing operation, a change is made to a printing condition comprising at least one of the conveyance direction length of the recording media, a paper type, a printing mode, and a process speed.

13. The image forming apparatus according to claim 8 , wherein when the at least one sheet held at the one reversing unit is exposed to outside the image forming apparatus, the controller is configured to control a notifier coupled to the controller to make a notification to prohibit removal of the at least one sheet.

14. An image forming apparatus comprising:

a circulation unit comprising a plurality of reversing units each configured to reverse a sheet of recording media having one surface printed at an image processor, the circulation unit being configured to re-feed the reversed sheet of recording media to the image processor; and

a controller configured to, during duplex printing of a plurality of sheets of recording media through circulation in the circulation unit, (i) control one reversing unit among the plurality of reversing units to hold at least one sheet among the plurality of sheets, (ii) while the one reversing unit is holding the at least one sheet, circulate at least one other sheet among the plurality of sheets between the circulation unit and another reversing unit among the plurality of reversing units that is not holding the at least one sheet, and (iii) after the at least one other sheet has passed the another reversing unit, control the one reversing unit holding the at least one sheet to release the at least one sheet, so as to increase an actual circulated sheet number of the circulated plurality of sheets by a number corresponding to the at least one sheet held at the one reversing unit so that the increased actual circulated sheet number is larger than a predetermined circulated sheet number by the number corresponding to the at least one sheet held at the one reversing unit;

wherein the predetermined circulated sheet number is based on a conveyance direction length of the recording media,

wherein the plurality of reversing units comprises two reversing units, and at least one of the two reversing units comprises a discharging unit configured to discharge a printed sheet of recording media, and

wherein the controller is configured to prohibit the one reversing unit from holding the at least one sheet when, during a printing operation, a change is made to a printing condition comprising at least one of the conveyance direction length of the recording media, a paper type, a printing mode, and a process speed.

15. The image forming apparatus according to claim 14 , wherein when a printing command includes a received sheet number that is smaller than a number obtained by adding one to the predetermined circulated sheet number, the controller is configured not to control the one reversing unit to hold the at least one sheet and to set the actual circulated sheet number at the predetermined circulated sheet number.

16. The image forming apparatus according to claim 14 , wherein when (i) the conveyance direction length of the recording media is a predetermined length, and (ii) a scheduled printed sheet number is a multiple of a number obtained by adding one to the predetermined circulated sheet number, the controller is configured to control the one reversing unit to hold the at least one sheet, and to set the actual circulated sheet number at the number obtained by adding one to the predetermined circulated sheet number.

17. The image forming apparatus according to claim 14 , wherein when the at least one sheet held at the one reversing unit is exposed to outside the image forming apparatus, the controller is configured to control a notifier coupled to the controller to make a notification to prohibit removal of the at least one sheet.

18. The image forming apparatus according to claim 14 , wherein the at least one other sheet comprises a number of sheets circulable in the circulation unit, and the controller is configured to control the one reversing unit holding the at least one sheet to release the at least one sheet after all the number of sheets have passed the another reversing unit.