Image forming apparatus

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119(a) of Korean Patent Application No. 2005-88421, filed Sep. 22, 2005 in the Korean Intellectual Property Office, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to an image forming apparatus. More particularly, the present invention relates to an image forming apparatus which can evenly align papers discharged from the image forming apparatus.

2. Description of the Related Art

In general, an image forming apparatus comprises a paper-feeding unit 1, a conveying unit 2, a developing unit 3, a transfer unit 4, a fixing unit 5, and a paper-discharge unit 10, as shown in FIG. 1. The paper-discharge unit 10 is provided with a full-of-paper detection lever 20 for detecting the level of papers discharged by the paper-discharge unit 10 stacked in a discharged paper stacking unit 13. The full-of-paper detection lever 20 is capable of stopping the printing operation of the image forming apparatus when it is determined that the amount of printed papers discharged and stacked in the discharged paper stacking unit 13 exceeds a predetermined level.

FIG. 2 is a cross-sectional view schematically showing the discharged paper stacking unit of the conventional image forming apparatus. As shown in the drawing, the paper-discharge unit 10 comprises a paper discharge roller 11 and a backup roller 12, by means of which an image formed paper is discharged to the discharged paper stacking unit 13. The discharged paper stacking unit 13 is designed to be capable of receiving only a predetermined amount of paper, and the full-of-paper detection lever 20 is installed adjacent to the paper discharge unit 10 to determine whether the amount of paper stacked in the discharged paper stacking unit 13 exceeds the designed amount.

The full-of-paper detection lever 20 shown in FIG. 2 is typically formed as a plastic molded article and guides the top surface of a paper P discharged to the discharged paper stacking unit 13. The full-of-paper detection lever 20 contacts the top surface of the paper P and rotates in the direction indicated by the arrow in FIG. 2 while the paper P is discharged and stacked in the discharged paper stacking unit 13.

Meanwhile, the full-of-paper detection lever 20 is connected to a detection sensor. When the full-of-paper detection lever 20 is rotated by coming into contact with the top surface of the discharged paper P exceeds a predetermined level, the detection sensor is turned on. On the other hand, when the papers stacked in the discharged paper stacking unit 13 are less than a designed stacking amount, the detection sensor is turned off. Thus, the detection sensor outputs a detection signal to a controller to indicate whether the discharged paper stacking unit 13 is full of paper. If the discharged paper stacking unit 13 is full of paper P, the image forming apparatus stops the printing operation for a short time to allow a user to remove the printed papers stacked in the discharged paper stacking unit 13.

In recent, high-speed image forming apparatuses, however, paper is rapidly discharged from the image forming apparatus, which causes the paper to be unevenly stacked in the discharged paper stacking unit as shown in FIG. 3. If the papers are unevenly stacked in this manner, the amount of paper stacked in the discharged paper stacking unit is small in comparison with the amount of papers intended to be stacked when designing the discharged paper stacking unit because the papers curl and form gaps between them.

Accordingly, there is a need for an improved image forming apparatus that evenly aligns papers discharged from the image forming apparatus.

SUMMARY OF THE INVENTION

An aspect of the present invention is to address at least the above problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide an image forming apparatus with a paper alignment means which can evenly align the papers discharged from the image forming apparatus, thereby increasing the amount of papers to be stacked in a discharged paper stacking unit.

In accordance with an aspect of the present invention, an image forming apparatus comprises a body having a discharged paper stacking unit, a detection unit for detecting whether a paper is discharged or not, a paper alignment unit, and a controller. The paper alignment unit compresses the top surface of a paper discharged to the discharged paper stacking unit so as to make the discharged paper closely contact the discharged paper stacking unit or a paper previously stacked in the discharged paper stacking unit, thereby aligning the discharged paper. The controller controls the paper alignment unit according to a signal output from the detection unit.

According to an exemplary embodiment of the present invention, the paper alignment unit comprises a driving source operated according to a signal output from the detection unit, a rotary shaft connected with the driving source, and a lever member secured to the rotary shaft and rotating 360 degrees as the rotary shaft rotates.

The lever member may be formed from rubber and curved at the portion that confronts with the paper.

At least one lever member may be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic view of the construction of a conventional image forming apparatus;

FIG. 2 shows papers normally stacked in a discharged paper stacking unit;

FIG. 3 shows papers unevenly stacked in a discharged paper stacking unit when the papers are rapidly discharged;

FIG. 4 is a schematic view of a discharged paper stacking unit of an image forming apparatus according to an exemplary embodiment of the present invention;

FIG. 5 is a top plan view of FIG. 4; and

FIGS. 6 to 10 are views illustrating the operation of the paper alignment unit of the discharged paper stacking unit shown in FIG. 4.

Throughout the drawings, the same reference numerals will be understood to refer to the same elements, features, and structures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The matters defined in the description such as a detailed construction and elements are provided to assist in a comprehensive understanding of the embodiments of the invention. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

As shown in FIG. 4, an image forming apparatus according to an exemplary embodiment of the present invention comprises a detection unit 100, a paper alignment unit 200 and a controller 300.

The detection unit 100 is installed adjacent to a paper-discharge unit 10 for discharging printed paper out of the image forming apparatus. The detection unit 100 senses a paper with an image fixed by a fixing unit (not shown) being introduced into the paper-discharge unit 10 so as to be discharged out of the image forming apparatus. In an exemplary embodiment, the detection unit 100 comprises a photo-sensor with a light-emitting part and a light-receiving part.

The paper alignment unit 200 is installed adjacent to the paper-discharge unit 10 and cooperates with the paper-discharge unit 10 so as to evenly align the papers as they are being discharged in a discharged paper stacking unit 13.

The paper alignment unit 200 includes a driving source 210, a rotary shaft 220 and a lever member 230.

The driving unit 210 may be provided with a motor operated according to a control signal from the controller 300. Although not shown in the drawings, according to another exemplary embodiment of the present invention, it is possible to configure the driving source 210 using a gear train which is connected to the paper-discharge unit 10.

The rotary shaft 220 is connected with the driving source 210 and is arranged substantially parallel with the paper-discharge unit 10, as shown in FIG. 5.

The lever member 230 is formed from elastic rubber with a certain level of friction. The lever member 230 is secured to the rotary shaft 220 and rotated 360 degrees in response to the rotating movement of the rotary shaft 220. Two or more such lever members may be provided. The lever member 230 compresses the top surface of a paper P discharged through the paper-discharge unit 10, thereby making the paper P closely contact the discharged paper stacking unit 13 or a previously discharged paper, so that the paper P can be evenly aligned. This procedure will be described in further detail later.

The controller 300 receives ON/OFF signals output from the detection unit 100 so as to control the movement of the paper alignment unit 200. Specifically, the detection unit 100 may detect the entrance of a paper into the paper-discharge unit 10 and the discharge of the paper out of the paper-discharging unit 10, and the controller 300 may set the time point for initiating movement of the paper alignment unit 200 based on the output of the detection unit 100 so that the discharged paper P can be aligned in the discharged paper stacking unit 13.

The operation of an image forming apparatus having the paper alignment unit according to an exemplary embodiment of the present invention will now be described with reference to FIGS. 6 to 10.

When a printed paper P is introduced into the paper-discharge unit 10 as shown in FIG. 6, the detection unit 100 outputs a detection signal and the paper-discharge unit 10 rotates and discharges the printed paper to the paper-discharge unit 13.

If the paper is discharged to the paper-discharge unit 10 as shown in FIG. 7, the detection unit 100 outputs a signal for informing the controller 300 that the paper P departs from the paper-discharge unit 10. The controller 300 sets this instant as the time point for initiating the movement of the paper alignment unit 200 and outputs an operating signal to the driving source 210. If the driving source outputs rotational power, the rotary shaft 220 connected with the driving source 210 and the lever member 230 secured to the rotary shaft 220 rotate in the direction indicated by the arrow. Although the instant the paper P departs from the paper discharging unit 200 may be set as the time point for initiating the movement of the paper alignment unit 200 as described above, it is also possible to set a time point after the paper has departed from the paper-discharge unit 10 and stacked in the discharged paper stacking unit 13 as the time point for initiating movement of the paper alignment unit 200.

If the lever member 230 rotates after the trailing edge of the paper P has departed from the paper-discharge unit 10 as described above, the lever member 230 compresses the rear end of the top surface of the paper P in the direction indicated by arrow A, so that the paper P closely contacts the papers PS already stacked in the discharged paper stacking unit 13, as shown in FIG. 8.

As shown in FIG. 9, if the discharged paper P closely contacts the previously stacked papers PS, the lever member 230 draws the discharged paper P in the direction indicated by arrow B, so that the discharged paper P comes into contact with the wall 14 of the discharged paper stacking unit 13, thereby aligning the leading edge of the discharged paper P.

The lever member 230 is formed of a resilient material, such as rubber. After having aligned the leading edge of the discharged paper, the lever member is continuously rotated over 360 degrees. The lever member elastically deforms, and then returns to its original position. If a new paper P is detected by the detection unit 100 in the paper-discharge unit 10, the above-mentioned movement of the lever member 230 is repeated.

It is desirable to coordinate the period for a 360 degree rotation of the lever member 230 with the period for discharging one sheet of printed paper, so that each time one sheet of paper is discharged, the lever member 230 rotates one time. The lever member 230 may be formed in a straight or curved shape in longitudinal cross-section depending on the amount of paper to be stacked on the discharged paper stacking unit 13. For example, if the bottom of the discharged paper stacking unit 13 and the lever member 230 are far away from each other, the lever member 230 may have a straight shape in longitudinal cross-section. On the other hand, if the bottom of the paper-discharging section 13 and the lever member 230 are not far away from each other, the lever member 230 may have a curved shape, so that the lever member 230 has a circular arc in longitudinal cross-section.

Although not shown in the drawings, the image forming apparatus according to an exemplary embodiment of the present invention may incorporate a conventional full-of-paper detection sensor in order to detect whether the discharged paper stacking unit 13 is full of discharged paper or not. Alternatively, it is also possible to separately provide a sensor such as a torque meter on the paper alignment unit 200 and to set a torque required for rotating the lever member 230 at the designed stacking amount of papers as a reference value, so that it can be determined that the discharged paper stacking unit 13 is full of paper when a torque required for rotating the lever member 230 exceeds a reference value.

According to the exemplary embodiments of the present invention, it is possible to increase the amount of papers to be stacked in a discharged paper stacking unit of an image forming apparatus, and the papers stacked in the discharged paper stacking unit can be evenly aligned.

While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.