JP2699400B2 - Paper cooling device for electrophotographic printer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet cooling device of an electrophotographic printer for cooling a printing sheet after fixing in a heat fixing type printer.

[Background of the Invention]

2. Description of the Related Art In an electrophotographic printer, as a method of fixing toner for forming characters and figures on printing paper, thermal fixing for heating paper and melting and fixing the toner on the paper is widely used. The fixed sheet is folded by a stacker (sheet folding apparatus) and stored. At this time, the heat-fixed paper is folded without being cooled sufficiently, and if the folded paper temperature is equal to or higher than the glass transition point of the toner, toner When the printing surface is opened after a lapse of a predetermined time, the toner on the printing surface may peel off and part of characters and figures may be missing. This phenomenon is called a toner stick, and is a serious obstacle to the print quality of the printer.

In order to prevent the toner stick from being generated, the sheet heated by the fixing may be cooled, and the sheet temperature may be lowered to the glass transition point of the toner or lower. Until now, natural cooling and forced cooling with a small fan or blower have been used to cool the paper.However, the printing speed of ultra-high-speed printers with a printing speed of about 15,000 lines / minute is high. The time for cooling becomes short, and sufficient cooling cannot be performed. For this reason, the paper path system between the fixing and the stacker must be lengthened, and a large fan or blower must be installed to enhance the cooling of the paper. I have.

FIG. 4 shows an example of the above-mentioned conventional sheet cooling apparatus. The printing paper 1 heated and fixed by the preheater 10 and the heat roll 8 is forcibly cooled by the cooling air blown from the cooling blower 11, then folded by the paddle 4 and accumulated on the table 6. In the conventional cooling device, in the case of a high-speed printer in which the speed of the paper 1 passing between the cooling blowers 11 is high, the time during which the cooling air can be received becomes short, and a sufficient cooling effect cannot be obtained. Therefore, in order to prevent the occurrence of toner stick, it is necessary to provide a large fan or blower corresponding to the paper traveling speed to cool the paper.
For this reason, problems such as an increase in the size of the apparatus, an increase in the weight of the apparatus, power consumption, and an increase in manufacturing cost have been problems.

[Object of the invention]

The object of the present invention is to eliminate the above-mentioned disadvantages of the prior art,
An object of the present invention is to provide a paper cooling device that is small, lightweight, inexpensive, consumes little power, and has high cooling efficiency.

[Summary of the Invention]

The present invention provides a stacker with a small cooling fan to which a duct having a horizontally long and short opening is attached, and sends a cooling air horizontally to the upper part of the folded sheet from the sheet width direction, so that a gap between the sheets is obtained. Focusing on the fact that the cooling air passes through the gap and allows the cooling air to be applied to the paper for a long time, improving the cooling efficiency, and the cooling fan is set so that the cooling air always hits the top of the folded paper. The duct shape, the mounting device, and the structure of the paper guide in the paper width direction are devised.

(Example of the invention)

FIGS. 1 and 2 show the overall configuration of a sheet cooling apparatus as a specific embodiment of the present invention, and FIG. 3 shows its operation.

A paper guide 2 slidable in accordance with the width of the printing paper 1 has a duct 3 having a horizontally long and short opening 3a.
It is mounted slightly below the center of rotation. The cooling fan 5 is attached to the opening 3b opposite to the duct opening 3a, and the duct opening 3a is narrowed narrower than the opening 3b on the opposite side. Cooling air from the cooling fan 5 blows out from the duct opening 3a. On the other hand, the printing paper after fixing is folded by the action of the paddle 4 and is deposited on the stacker table 6. The stacker table 6 is lowered when a certain amount of paper 1 is accumulated, and the height position of the folding surface 1a of the printing paper is always maintained at a position slightly lower than the rotation center of the paddle 4.

The sheet cooling effect at the time of printing in such a configuration will be described below. As shown in FIG. 3, the paper folding surface 1a during printing is kept at the same height as the upper surface 3c of the duct opening 3a. Therefore, due to the wind pressure of the cooling air blown out from the duct opening 3a, the sheet 1b facing the duct opening 3a rises and a gap is formed between the pages of the sheet 1b. The sheet 1 is cooled by the cooling air flowing through the gap. This cooling method has the following advantages. First, the sheet 1 is folded and receives cooling air while passing from the duct opening upper surface 3c to the duct opening lower surface 3d (time during which the sheets are stacked by the duct opening height h). Therefore, the cooling time is much longer than that of the conventional cooling device in which the sheet can receive the cooling air only momentarily as shown in FIG. Due to the function of receiving the cooling air for a long time, even when the cooling fan is used with a small size and a small output, the cooling can be performed with a high cooling effect.

Further, since the cooling fan 5 and the duct 3 are attached to the paper guide 2 which can be slid according to the width of the printing paper, the distance d between the duct opening and the paper is uniquely determined, so that cooling can be performed efficiently regardless of the type of paper. .

Next, since the cooling air is applied only to the folded part of the paper, the paper under folding is not affected by the wind pressure,
Stable folding can be performed, and the occurrence of paper jams in the stacker is small.

In the above embodiment, the position of the duct 3 in the height direction is fixed, but as shown in FIG. 5, a sensor 12 for detecting the position of the sheet folding surface 1a is attached to the duct 3.
The same effect can be obtained even if the duct 3 and the cooling fan 5 are moved up and down along the paper guide 2 by the motor 13 linked to 12.

In the above embodiment, the duct 3 and the cooling fan 5 are installed on the back side of the printing paper 1 as viewed from the operator side, but may be installed on the near side of the operator.

Instead of using the cooling fan 5, a cooling air may be taken in from outside the stacker using a duct.

〔The invention's effect〕

According to the present invention, a sufficient cooling effect that does not generate a toner stick can be obtained even with a small and lightweight cooling device, so that the printer can be reduced in size, weight, cost, and power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a front view of a sheet cooling apparatus showing an embodiment according to the present invention, and FIG. 2 is a side view of the same. FIG. 3 is an enlarged side view for explaining the operation of the present invention. FIG. 4 is a front view showing a conventional technique of a sheet cooling device to which the present invention is applied. FIG. 5 is a side view showing an application example of the present invention. In the figure, 1a is a folding surface of the printing paper, 2 is a paper guide, 3a is a duct opening, and 5 is a cooling fan.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-56-36667 (JP, A) JP-A-60-236973 (JP, A) Fully open 1987-190256 (JP, U) Really open 1987 46461 (JP, U)

Claims (3)

(57) [Claims] A fixing device for applying at least a heating effect to the printing paper holding the toner image to fix the toner image onto the printing paper; and a printing paper fed from the fixing device is folded and stacked and held on a table. A sheet folding device for supplying a cooling air to the printing sheet sent from the fixing device, and a sheet cooling device for an electrophotographic printer, wherein a duct opening of the sheet cooling device is disposed on the table. Paper cooling of the electrophotographic printer, wherein cooling air from the duct opening is supplied along the paper width direction of the stacking paper so as to correspond to the side surface corresponding to the paper length of the stacking paper stacked on the paper. apparatus. 2. A sheet cooling device for an electrophotographic printer according to claim 1, wherein said duct opening is provided so as to be movable in said sheet width direction. 3. The sheet cooling device for an electrophotographic printer according to claim 1, wherein the duct opening on the printing sheet facing surface has a horizontally long rectangular shape.