Image forming apparatus

• US 5,835,836 A
• Filed: 09/09/1997
• Issued: 11/10/1998
• Est. Priority Date: 03/19/1997
• Status: Expired due to Term

• Current Assignee: Fuji Xerox Company Limited (Xerox Holdings Corp.)
• Original Assignee: Fujitsu Limited
• Inventors: Hirao, Naoto
• Primary Examiner(s): Smith, Matthew S.
• Application Number:
  US08/925,737
• Time in Patent Office: 427 Days
• Field of Search: 399/335-337, 399/341, 399/320, 219/216, 430/126
• US Class Current: 399/336
• CPC Class Codes: G03G 15/201 of high intensity and short duration, i.e. flash fusing
• CPC Class Codes: G03G 2215/00459 Fan fold, e.g. CFF, normally perforated
• CPC Class Codes: G03G 2215/2083 duplex

Abstract

An image forming apparatus is constructed to include a first fixing unit fixing a toner image transferred on a first side of a recording medium by a flash, a second fixing unit fixing a toner image transferred on a second side of the recording medium by a flash, and a leak preventing mechanism for preventing the flash of the first fixing unit to the second side and the flash of the second fixing unit to the first side via a region which is within a fixing region of the first and second fixing units and where no recording medium exists due to a size of the recording medium used.

Claims

1. An image forming apparatus comprising:

a first fixing unit fixing a toner image transferred on a first side of a recording medium by a flash;

a second fixing unit fixing a toner image transferred on a second side of the recording medium by a flash; and

leak preventing means for preventing the flash of the first fixing unit to the second side and the flash of the second fixing unit to the first side with respect to a region which is within a fixing region of the first and second fixing units and where no recording medium exists due to a size of the recording medium used.

2. The image forming apparatus as claimed in claim 1, wherein said leak preventing means includes a light blocking member which blocks a region which is within the fixing region and corresponds to a difference between at least a maximum size of the recording medium and the size of the recording medium used.

3. The image forming apparatus as claimed in claim 2, wherein said light blocking member is provided in a transport path of the recording medium.

4. The image forming apparatus as claimed in claim 2, wherein said light blocking member is provided independently with respect to the first and second fixing units.

5. The image forming apparatus as claimed in claim 2, wherein said light blocking member is made up of a first light blocking member provided on the first fixing unit, and a second light blocking member provided on the second fixing unit.

6. The image forming apparatus as claimed in claim 2, wherein said first and second fixing units are provided at symmetrical positions which confront each other via the recording medium.

7. The image forming apparatus as claimed in claim 2, wherein said first and second fixing units are provided at non-symmetrical positions which do not confront each other via the recording medium.

8. The image forming apparatus as claimed in claim 2, wherein said first fixing unit is arranged at a position which fixes the first side prior to the fixing of the second side by said second fixing unit along a transport direction of the recording medium, and a direction in which gravitational force acts on a toner forming the toner image formed on the first side does not penetrate the recording medium.

9. The image forming apparatus as claimed in claim 2, which further comprises:

control means for controlling voltages applied to the first and second fixing units based on print rates with respect to the first and second sides of the recording medium.

10. The image forming apparatus as claimed in claim 2, which further comprises:

a preheating unit, arranged on an upstream side of the first and second fixing units along a transport direction of the recording medium, preheating the first and second sides of the recording medium.

11. The image forming apparatus as claimed in claim 1, wherein said first and second fixing units are provided at symmetrical positions which confront each other with respect to the recording medium.

12. The image forming apparatus as claimed in claim 1, wherein said first and second fixing units are provided at non-symmetrical positions which do not confront each other with respect to the recording medium.

13. The image forming apparatus as claimed in claim 12, which further comprises:

a process part transferring the toner images on the first and second sides of the recording medium, and

a voltage applied to one of the first and second fixing units closer to said process part along a transport direction of the recording medium is set greater than or equal to a voltage applied to the other of the first and second fixing units.

14. The image forming apparatus as claimed in claim 12, which further comprises:

control means for controlling voltages applied to the first and second fixing units based on print rates with respect to the first and second sides of the recording medium.

15. The image forming apparatus as claimed in claim 12, which further comprises:

a preheating unit, arranged on an upstream side of the first and second fixing units along a transport direction of the recording medium, preheating the first and second sides of the recording medium.

16. The image forming apparatus as claimed in claim 1, wherein said first fixing unit is arranged at a position which fixes the first side prior to the fixing of the second side by said second fixing unit along a transport direction of the recording medium, and a direction in which gravitational force acts on a toner forming the toner image formed on the first side does not penetrate the recording medium.

17. The image forming apparatus as claimed in claim 1, which further comprises:

control means for controlling voltages applied to the first and second fixing units based on print rates with respect to the first and second sides of the recording medium.

18. The image forming apparatus as claimed in claim 1, which further comprises:

a preheating unit, arranged on an upstream side of the first and second fixing units along a transport direction of the recording medium, preheating the first and second sides of the recording medium.

19. The image forming apparatus as claimed in claim 18, wherein said preheating unit is selected from a group consisting of a flash fixing unit, an oven mechanism and a heat roller.

20. The image forming apparatus as claimed in claim 1, wherein said recording medium is a continuous recording paper.