JP2840734B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly, to an image recording apparatus such as a copying machine or a printer that records images on both sides of a sheet.

[Related Art] In recent years, there has been an increasing demand for an image recording apparatus that records images on both sides of a sheet. As this type of apparatus, there has been a laser beam printer as shown in FIG.

Referring to FIG. 2, 1 is a cassette for stacking sheets, 2 is a paper feed roller for separating and feeding sheets stored in the cassette one by one, and 3 is paper picked up by the paper feed roller A pair of registration rollers for aligning the tips of the photoconductors and assuring the printing accuracy of an image, 4 is a process unit including a photosensitive drum 5 inside, 6 is a laser scanning unit for irradiating a laser beam onto the photosensitive drum 5, A fixing device for fixing an image recorded on a sheet. The sheet passes through the paper discharge path 8 during one-sided printing, is turned over, and is discharged onto the tray 9.

On the other hand, when printing on both sides, the flapper 10 is switched, guided into the switchback unit 11, and guided to the forward / reverse rotation roller 12. When the sensor 14 detects that the rear end of the sheet has passed the sheet guide 13, the forward / reverse roller 12 reverses the rotation direction and guides the sheet to the sheet transport paths 15 a, 15 b, and 15 c for feeding the second surface.

The paper transport path on the second side must be able to be controlled independently of the paper transport path on one side, and is therefore driven differently from the paper transport path on one side. A sensor 16 is provided on the paper path for feeding the second side, and when the leading edge of the sheet passes through the sensor, the sheet is temporarily stopped to control the timing of the paper feed when printing the second side. ing.

When the sheet is switched back in the switchback unit 11, the paper transport path 15a for the second-side sheet feeding,
In 15b and 15c, the printing surface becomes the surface of the paper drum 5 side, and when printing an image again, the printing surface comes to the surface opposite to the drum 5.

[Problems to be Solved by the Invention] However, in the above conventional example, the switchback unit protrudes to the operation surface side, and the sheet is discharged to the operator side at the time of switchback. (2) Use space becomes large, (3) When clearing jams, and when replacing cartridges,
The front cover must be opened and closed, but the switchback unit protrudes, so that the front cover cannot be opened widely, and there have been problems such as jam clearance and cartridge replacement being very difficult.

[Means for Solving the Problem (and Action)] The present invention aims to solve such a problem.

A configuration of the present invention for achieving the above object includes a cassette for storing sheets, a sheet conveyance path on which sheets fed from the cassette are conveyed, and a sheet conveyed in the sheet conveyance path. An image forming unit for forming an image, a switchback mechanism for switching back the sheet on which the image is formed by the image forming unit, and a sheet switched back by the switchback mechanism to the image forming unit again. A re-feeding conveyance path for feeding, a discharge port for discharging a sheet on which an image has been formed by the image forming unit, and a sheet stacking unit on which sheets discharged from the discharge port are stacked. In the image forming apparatus, the sheet stacking unit is disposed above the cassette and on an upper surface of the device, and the image forming unit is provided on the cassette. The switchback mechanism is located in the vicinity of the discharge port, and is disposed above the sheet stacking unit, and a switchback operation by the switchback mechanism substantially projects the sheet stacked on the sheet stacking unit. An image forming apparatus, wherein the switchback mechanism and the re-feeding conveyance path are detachable from the apparatus main body as a unit.

Embodiment 1 FIG. 1 is a view best showing the present invention. In the figure, reference numeral 20a denotes an upper cassette, and 20b denotes a lower cassette, which are mounted on the apparatus main body from the right as viewed in FIG. Separation pads 21a and 21b are built in the upper and lower cassettes 20a and 20b,
The sheet fed by the feed roller 22 is separated,
Double feed is prevented. The sheet fed from the upper cassette 20a reaches the registration roller 25 in the main body, and the leading edge is aligned.
Perform skew correction and the like. On the other hand, the sheet fed from the lower cassette 20b is controlled by the lower registration rollers 23 to form a loop by suppressing the sheet front end and perform skew correction once, and then the sheet transport path 24 provided in the upper cassette 20a.
To the registration roller 25 in the main body, and performs front end alignment, skew correction, and the like as in the case of the upper cassette. The sheet fed from the registration roller 25 forms an image in the image forming unit 26, and after the image is fixed in the fixing unit 27,
Normally, the paper is discharged to the paper discharge unit 28 with the printing surface facing down.

A switchback unit 29 is optionally attached to the upper part of the apparatus.

The first transport roller 3 is provided in the switchback unit 29.
0, forward / reverse roller pair 31 capable of forward / reverse rotation and contact / separation, second
Registration roller pair 32, a horizontal registration correcting mechanism (for example, a configuration in which the roller 32 can move in the thrust direction) for aligning the horizontal registration when printing the second side, a guide 37,
A PL and a sensor 36 are provided, and the switchback unit 29 is attached so that double-sided printing can be performed. In the switchback unit, the sheet on which the image has been printed is transferred to the first conveying roller pair.
After passing through 30, it is conveyed to the forward / reverse roller pair 31. The sheet is temporarily discharged in the direction of the paper discharge unit 28 by the forward / reverse rotation roller 31, and after the sensor 36 detects that the rear end has passed the guide 34, the forward / reverse rotation roller reversely rotates, and the paper is conveyed for printing on the second side. It is fed to runways 37 and 38. Paper runway 37, 38 for the second side
The sheet conveyed is temporarily stopped by the double-sided registration roller pair 39 also serving as a manual feed roller of the main body, the leading end registration and skew correction are performed, and then the sheet is fed a little, and then the second side printing is performed. Wait for the print signal to come. In this state, the trailing edge of the sheet is slightly out of the forward / reverse rotation roller 31 to the side of the paper traveling path 37 for printing the second side.

When printing on both sides continuously, the first sheet to be printed on the second side is the switchback unit.
The forward / reverse rotation roller 31 is separated in anticipation of the time to reliably reach the second roller 32 in 29. The upper roller is raised counterclockwise by the plunger PL. Thereafter, the next sheet printed on the first side is conveyed by the first carrying roller 30 and passes between the separated forward and reverse rotation rollers 31 (the preceding sheet and the succeeding sheet pass each other). In this state, the first sheet already on the paper transport paths 37 and 38 for the second side printing is waiting for a signal at the double-sided registration roller 39, but if the signal does not come immediately, the next sheet is Rear roller is the first roller
It is held while being sandwiched between 30.

With the above configuration, the sheet on which the first surface is printed can be stopped independently of the driving of the paper transport of the apparatus main body. So-called alternate sheet feeding, in which printing on the second side of the sheet is continuously and alternately performed, is possible.

In this configuration, since the sheet is inverted almost within the installation area of the apparatus, the double-sided function can be added without increasing the installation area or the area required for the operation at all. Further, since the switchback unit does not protrude to the operator side, for example, the jam processing cartridge can be easily replaced. Further, since the sheet is not discharged to the operator side at the time of switchback, the operator does not feel discomfort. Also, all operations can be performed from one side (eg, right side) as viewed in FIG.

If double-sided printing is not performed, the discharge rollers 40
Is stopped, and the transport roller 30, the guide 34, the forward / reverse rotation roller 31
The flapper F is moved so as to feed the sheet toward the sheet feeding section, and the sheet is discharged from the forward / reverse rotation roller 31.
Can increase the loading capacity.

[Effects of the Invention] As described above, in the present invention, the switchback mechanism is disposed near and at a different position from at least one of the main body discharge ports, and the switchback mechanism is switched within the substantially projected area of the stacked recorded sheets. By performing the above operation, the installation area and operation space of the main body can be reduced, and the operability of the apparatus is improved.

Further, the switchback mechanism and the re-feeding conveyance path can be detached and attached as a unit, and this unit can be easily mounted on the upper part of the apparatus main body.

[Brief description of the drawings]

 FIG. 1 shows an image forming apparatus according to the present invention. FIG. 2 shows a conventional image forming apparatus. 29 is a switchback unit 31, 49 is a forward / reverse roller 37, 38, 50a, 50b is a sheet transport path for second-side printing 28, 47 is a paper discharge unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-64932 (JP, A) JP-A-58-182655 (JP, A) JP-A-60-227272 (JP, A) JP-A-58-182 85450 (JP, A) JP-A-53-123141 (JP, A) JP-A-62-56230 (JP, A) JP-A-60-12557 (JP, U) JP-A-58-31543 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) B65H 83/00-85/00 G03G 15/00

Claims (2)

(57) [Claims] A cassette for storing sheets, a sheet transport path for transporting the sheets fed from the cassette, and an image forming apparatus for forming an image on the sheets transported in the sheet transport path. , A switchback mechanism for switching back a sheet on which an image is formed by the image forming unit, and a refeeding conveyance for feeding the sheet switched back by the switchback mechanism to the image forming unit again An image forming apparatus comprising: a path; a discharge port for discharging a sheet on which an image is formed by the image forming unit; and a sheet stacking unit on which sheets discharged from the discharge port are stacked. The image forming unit is located above the cassette and above the cassette; and the sheet stacking unit is located above the cassette. The switchback mechanism is located near the outlet,
The switchback operation by the switchback mechanism is performed within a substantially projected area of the sheets stacked on the sheet stacking unit, and the switchback mechanism and the re-feeding conveyance path are detachable from the apparatus body as a unit. Characteristic image forming apparatus. 2. An image forming apparatus according to claim 1, wherein said unit is mounted on an upper part of the apparatus main body.