Envelope processing apparatus and image forming system

1. An envelope processing apparatus for enclosing an enclosure into an envelope conveyed to an enclosing position, the envelope processing apparatus comprising:

a conveyance roller configured to convey the envelope to the enclosing position;

a first envelope length calculator configured to,

calculate a first envelope length of the envelope in an envelope conveyance direction in which the envelope is conveyed in a close state in which a flap of the envelope closes;

a flap opener configured to open the flap while the conveyance roller conveys the envelope;

a second envelope length calculator configured to calculate a second envelope length of the envelope in the envelope conveyance direction in an open state in which the flap opens;

a first envelope detector configured to detect a leading end of the envelope in the envelope conveyance direction at a first detection time and detect a trailing end of the envelope in the envelope conveyance direction in the close state at the second detection time;

a second envelope detector configured to detect the leading end of the envelope in the envelope conveyance direction at a third detection time and detect the trailing end of the envelope in the envelope conveyance direction in the open state at a fourth detection time;

the first envelope length calculator is further configured to calculate the first envelope length based on a time difference between the first detection time and the second detection time and a conveyance speed of the envelope at which the envelope is conveyed;

the second envelope length calculator is further configured to calculate the second envelope length based on a time difference between the third detection time and the fourth detection time and the conveyance speed of the envelope; and

a controller configured to,

calculate a flap length of the flap in the envelope conveyance direction based on the first envelope length and the second envelope length,

control enclosing of the enclosure into the envelope based on the flap length, and

control the conveyance roller to interrupt conveyance of the envelope at the enclosing position.

2. The envelope processing apparatus according to claim 1 , further comprising:

an envelope conveyance path through which the envelope is conveyed to the enclosing position,

wherein the flap opener is in the envelope conveyance path.

3. The envelope processing apparatus according to claim 1 , wherein each of the first envelope detector and the second envelope detector includes a sensor.

4. The envelope processing apparatus according to claim 1 , further comprising:

a flap holder configured to detect and hold the flap of the envelope.

5. The envelope processing apparatus according to claim 4 , wherein the controller is further configured to

determine the enclosing position based on a detection result sent from the flap holder and the flap length; and

control the conveyance roller to convey the envelope to the enclosing position.

6. The envelope processing apparatus according to claim 4 , wherein the flap holder includes:

a flap detecting sensor configured to detect the flap; and

a flap holding roller configured to hold the flap.

7. The envelope processing apparatus according to claim 1 , further comprising

a sealer configured to close the flap of the envelope enclosed with the enclosure so as to seal the envelope.

8. The envelope processing apparatus according to claim 7 , wherein the controller is further configured to:

change a sealing position where the sealer seals the envelope based on the flap length.

9. An image forming system comprising:

an image forming apparatus configured to form an image on a medium; and

an envelope processing apparatus configured to enclose the medium sent from the image forming apparatus into an envelope conveyed to an enclosing position,

the envelope processing apparatus comprising,

a conveyance roller configured to convey the envelope to the enclosing position,

a first envelope length calculator configured to calculate a first envelope length of the envelope in an envelope conveyance direction in which the envelope is conveyed in a close state in which a flap of the envelope closes,

a flap opener configured to open the flap while the conveyance roller conveys the envelope,

a second envelope length calculator configured to calculate a second envelope length of the envelope in the envelope conveyance direction in an open state in which the flap opens,

a first envelope detector configured to detect a leading end of the envelope in the envelope conveyance direction at a first detection time and detect a trailing end of the envelope in the envelope conveyance direction in the close state at a second detection time,

a second envelope detector configured to detect the leading end of the envelope in the envelope conveyance direction at a third detection time and detect the trailing end of the envelope in the envelope conveyance direction in the open state at a fourth detection time,

the first envelope length calculator is further configured to calculate the first envelope length based on a time difference between the first detection time and the second detection time and a conveyance speed of the envelope at which the envelope is conveyed,

the second envelope length calculator is further configured to calculate the second envelope length based on a time difference between the third detection time and the fourth detection time and the conveyance speed of the envelope, and

a controller configured to,

calculate a flap length of the flap in the envelope conveyance direction based on the first envelope length and the second envelope length, and

control enclosing of the medium into the envelope based on the flap length.

10. The image forming system according to claim 9 , wherein the medium includes a sheet.

11. The image forming system according to claim 9 , further comprising:

a folding apparatus configured to fold the medium bearing the image and send the folded medium to the envelope processing apparatus.

12. The image forming system according to claim 11 , wherein the folding apparatus is further configured to:

change a folding position on the medium based on at least one of the first envelope length and the second envelope length and the flap length.

13. The image forming system according to claim 11 , wherein the folding apparatus is further configured to:

change a type of folding based on at least one of the first envelope length and the second envelope length.

14. The image forming system according to claim 9 , further comprising:

a post-processing apparatus configured to,

perform post-processing on the envelope enclosed with the medium, and

change a post-processing position on the flap based on the flap length.

15. The image forming system according to claim 14 , wherein the post-processing includes punching the flap.

16. The image forming system according to claim 14 , wherein the post-processing includes binding the flap.

17. The image forming system according to claim 9 , further comprising:

an envelope conveyance path through which the envelope is conveyed to the enclosing position,

wherein the flap opener is in the envelope conveyance path.

18. The image forming system according to claim 9 , wherein each of the first envelope detector and the second envelope detector includes a sensor.

19. The image forming system according to claim 9 , further comprising:

a flap holder configured to detect and hold the flap of the envelope.

20. The image forming system according to claim 19 , wherein the controller is further configured to:

determine the enclosing position based on a detection result sent from the flap holder and the flap length; and

control the conveyance roller to convey the envelope to the enclosing position.