Image forming apparatus and image forming system incorporating the image forming apparatus

1. An image forming apparatus comprising:

a sheet separation device configured to separate a non-bonding portion of a two-ply sheet in which two sheets are overlapped and bonded together at one end as a bonding portion of the two-ply sheet;

a first sheet feeder configured to feed the two-ply sheet;

a second sheet feeder configured to feed an inner sheet to be inserted between the two sheets of the two-ply sheet in a state in which the non-bonding portion of the two-ply sheet is separated by the sheet separation device;

an image forming device configured to form an image on a surface of the inner sheet fed from the second sheet feeder in a sheet conveyance direction,

the sheet separation device being disposed downstream from the image forming device in the sheet conveyance direction;

a heat source disposed upstream from the sheet separation device in the sheet conveyance direction; and

circuitry configured to cause the two-ply sheet fed from the first sheet feeder, to detour the heat source to the sheet separation device.

2. The image forming apparatus according to claim 1 ,

wherein the image forming device is configured to form the image with toner on the surface of the inner sheet,

wherein the heat source is a fixing device disposed downstream from the image forming device in the sheet conveyance direction, and

wherein the fixing device is configured to fix the image with toner on the surface of the inner sheet, to the inner sheet.

3. The image forming apparatus according to claim 1 ,

wherein the image forming device is configured to form the image with ink on the surface of the inner sheet,

wherein the heat source is a drying device disposed downstream from the image forming device in the sheet conveyance direction, and

wherein the drying device is configured to dry the image with ink on the surface of the inner sheet.

4. The image forming apparatus according to claim 1 ,

wherein the circuitry is configured to cause the two-ply sheet fed from the first sheet feeder to detour the image forming device and the heat source to the sheet separation device.

5. The image forming apparatus according to claim 1 , further comprising:

a housing including the image forming device, the heat source, and the second sheet feeder; and

a sheet separator including the sheet separation device and the first sheet feeder,

the sheet separator being disposed outside the housing.

6. The image forming apparatus according to claim 1 , further comprising a bypass sheet conveyance passage,

wherein the first sheet feeder is disposed upstream from the image forming device in the sheet conveyance direction, and

wherein the two-ply sheet fed from the first sheet feeder is conveyed through the bypass sheet conveyance passage to detour the heat source.

7. The image forming apparatus according to claim 6 ,

wherein the two-ply sheet fed from the first sheet feeder is conveyed through the bypass sheet conveyance passage to detour the image forming device and the heat source.

8. The image forming apparatus according to claim 1 , further comprising a sheet lamination device configured to perform a sheet laminating operation on the two-ply sheet in which the inner sheet is inserted between the two sheets separated by the sheet separation device.

9. The image forming apparatus according to claim 1 ,

wherein the circuitry is configured to switch between a print mode in which an image is formed on the inner sheet conveyed from the second sheet feeder to the image forming device and a non-print mode in which an image is not formed on the inner sheet conveyed from the second sheet feeder to the image forming device.

10. The image forming apparatus according to claim 9 ,

wherein the circuitry is configured to cause a conveying speed of the inner sheet in the non-print mode to be faster than a conveying speed of the inner sheet in the print mode.

11. The image forming apparatus according to claim 1 , further comprising a housing including the image forming device,

wherein the circuitry is configured to select a regular print mode to:

feed the inner sheet that functions as a sheet, from the second sheet feeder while the two-ply sheet is not fed from the first sheet feeder;

cause the image forming device to print an image on a surface of the sheet;

convey the sheet with the image via the heat source; and

eject the sheet to an outside of the housing.

12. The image forming apparatus according to claim 1 ,

wherein the two-ply sheet is a laminated sheet including two sheets to be bonded together by application of heat.

13. An image forming system comprising:

the image forming apparatus according to claim 1 including a housing,

the housing including:

the image forming device;

the heat source; and

the second sheet feeder, and

a sheet separator including the sheet separation device and the first sheet feeder,

the sheet separator being detachably attached to the image forming apparatus.

14. The image forming system according to claim 13 ,

wherein the sheet separator includes a sheet lamination device configured to perform a sheet laminating operation on the two-ply sheet in which the inner sheet is inserted between the two sheets separated by the sheet separation device.