Sheet transport device and image forming apparatus

1. A sheet transport device comprising:

a main body;

a first transport path through which a transported sheet passes;

a second transport path through which the sheet that passes through the first transport path and is reversed in a transport direction thereof passes until the sheet again enters the first transport path, having a curved portion on a downstream side thereof;

a first guiding member that forms a first guiding surface of the second transport path; and

a second guiding member that forms a second guiding surface opposite to the first guiding surface formed by the first guiding member in the curved portion of the second transport path,

wherein the first guiding member is supported to be rotatable between a guiding posture where the sheet is guided and an open posture that rotates from the guiding posture to open the guiding surfaces, and is configured to move so that an interval between the first guiding member and the second guiding member in the open posture is greater than that in the guiding posture.

2. The sheet transport device according to claim 1 ,

wherein the second guiding member is supported to be rotatable between the guiding posture where the second guiding member forms the second transport path in cooperation with the first guiding member and the open posture that rotates from the guiding posture,

wherein a rotation center of the first guiding member is disposed at a position that is distant from the curved portion compared with a rotation center of the second guiding member, and

wherein the interval between the first guiding member and the second guiding member is increased as the positions of rotation shafts thereof vary when the first guiding member and the second guiding member respectively rotate to the open posture.

3. The sheet transport device according to claim 2 , further comprising:

an opening and closing door that forms a part of an appearance of the sheet transport device,

wherein the first guiding member is provided to be integrated with the opening and closing door and rotates to a position corresponding to the open posture from a position corresponding to the guiding posture according to an opening operation of the opening and closing door, and

wherein the second guiding member rotates to a position corresponding to the open posture from a position corresponding to the guiding posture due to an own weight thereof according to the opening operation of the opening and closing door.

4. The sheet transport device according to claim 3 , further comprising:

a third guiding member that forms a third guiding surface of an upstream transport path of the first transport path that is disposed on an upstream side with reference to a point where the first transport path merges into the second transport path,

wherein the third guiding member rotates according to the rotation of the first guiding member from the guiding posture to the open posture to open the third guiding surface of the upstream transport path.

5. The sheet transport device according to claim 4 ,

wherein the third guiding member forms a guiding member integrated with the second guiding member, and

wherein the integrated guiding member opens both of the second guiding surface of the second transport path and the third guiding surface of the upstream transport path according to the opening operation of the opening and closing door.

6. An image forming apparatus comprising:

a main body;

an image forming unit that forms an image on a sheet being transported on a first transport path; and

a sheet transport unit that reverses a transport direction of the sheet in which an image is formed on a first side thereof by the image forming unit while being transported on the first transport path, transports the sheet on a second transport path, through which the sheet passes until the sheet again enters the first transport path, having a curved portion on a downstream side thereof, causes the sheet to enter the first transport path on an upstream side with reference to the image forming unit, and transports the sheet on the first transport path again so that the image forming unit forms an image on a second side of the sheet,

wherein the sheet transport unit includes:

a first guiding member that forms a first guiding surface of the second transport path, and

a second guiding member that forms a second guiding surface opposite to the guiding surface formed by the first guiding member in the curved portion of the second transport path, and

wherein the first guiding member is supported to be rotatable between a guiding posture where the sheet is guided and an open posture that rotates from the guiding posture to open the guiding surfaces, and is configured to move so that an interval between the first guiding member and the second guiding member in the open posture is greater than that in the guiding posture.

7. A sheet transport device comprising:

a main body;

a first transport path through which a transported sheet passes;

a second transport path through which the sheet that passes through the first transport path and is reversed in a transport direction thereof passes until the sheet again enters the first transport path, having a curved portion on a downstream side thereof;

a first guiding member that forms a first guiding surface of the second transport path; and

a second guiding member that forms a second guiding surface opposite to the first guiding surface formed by the first guiding member in the curved portion of the second transport path and that forms a third guiding surface of an upstream transport path of the first transport path,

wherein the first guiding member is supported to be rotatable between a guiding posture where the sheet is guided and an open posture that rotates from the guiding posture to open the guiding surfaces, and is configured so that an interval between the first guiding member and the second guiding member in the open posture is greater than that in the guiding posture,

wherein the second guiding member is supported to be rotatable between the guiding posture and the open posture.

8. The sheet transport device according to claim 7 , wherein the third guiding surface is disposed on an upstream side with reference to a point where the first transport path merges into the second transport path.

9. The sheet transport device according to claim 7 , wherein the third guiding surface meets the second guiding surface at a point where the first transport path merges into the second transport path.