Paper feeding apparatus for image forming apparatus

Abstract

A paper feeding apparatus for an image forming apparatus efficiently aligns the leading edge of a paper as being fed into the image forming apparatus regardless of the thickness of the paper. The paper feeding apparatus includes: first and second feeding roller assemblies rotatably installed on a paper feeding path and at least one tension idle wheel installed in anyone of the first and second feeding roller assemblies. The tension idle wheel is resiliently and elastically deformable in the radial direction thereof when the first and second feeding roller assemblies come into close contact with each other. A leading-edge alignment member is installed downstream of the first and second feeding roller assemblies to align the leading edge of a paper as being fed with respect to the apparatus.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 2005-91441, filed Sep. 29, 2005, in the Korean Intellectual Property Office, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image forming apparatus. In particular, the invention is directed to a paper feeding apparatus for an image forming apparatus.

2. Description of the Related Art

As shown in FIG. 1, a conventional image forming apparatus comprises a paper supply unit 1, a pickup unit 2 and a feeding unit 10, in which a paper P in the paper supply unit 1 is picked up by the pickup unit 2 and introduced in the feeding unit 10. The paper P introduced in the feeding unit 10 and an image is formed on one surface thereof while it is transmitted through a developing unit 3 and a transfer unit 4. The image formed on the paper is fixed as the paper passes a fixing unit 5, and then the paper is outwardly discharged through a paper discharge unit 6.

Meanwhile, the feeding unit 10 has an alignment device for aligning the leading edge of the paper from the supply 1 in a straight line. FIG. 2 shows a feeding unit 10 provided with an example of a leading-edge alignment device for the paper.

As shown in FIG. 2, the feeding unit 10 comprises a plurality of first feeding rollers 13 fitted on a driving shaft 12 and spaced from each other. A motor 11 is connected to the driving shaft 12. A plurality of second feeding rollers 15 are installed on an idle rotary shaft 14, which is spaced from the driving shaft 12, to confront with the first feeding rollers 13, and a leading-edge alignment shutter 16 for aligning the leading edge of the paper.

The leading-edge alignment shutter 16 for the paper is installed in such a way that when the leading edge of the paper P is aligned in a straight line, the leading-edge alignment shutter 16 rotates in the direction indicated by the arrow by the force from feeding the paper so as to open a paper feeding path under the influence of an elastic device.

In the above-mentioned paper feeding apparatus of a conventional image forming apparatus, if the paper being fed is thick or the inertia of a picked-up paper is higher than the elastic force of the elastic member for elastically supporting the leading-edge alignment shutter 16 for the paper, the leading-edge alignment shutter 16 may rotate and open the paper feeding path before the leading edge of the paper is correctly aligned. In such a case, the paper is misaligned when it is introduced into the developing unit 3. Print errors and misaligned printing of an image on the paper can occur.

SUMMARY OF THE INVENTION

Accordingly, the present invention solves the above-mentioned problems. One object of the present invention is to provide a paper feeding apparatus for an image forming apparatus having an improved construction so that the leading edge of a paper being fed into the image forming apparatus is always properly aligned regardless of the thickness of the paper.

In order to achieve the above-mentioned objects, a paper feeding apparatus for an image forming apparatus, comprises: first and second feeding roller assemblies rotatably installed on a paper feeding path; at least one tension idle wheel positioned on one of the first and second feeding roller assemblies, the tension idle wheel being elastically deformed in the radial direction thereof when the first and second feeding roller assemblies come into close contact with each other; and a leading-edge alignment member installed downstream of the first and second feeding roller assemblies for aligning a leading edge of a paper being fed to the invention.

According to a preferred embodiment of the present invention, the tension idle wheel slip-feeds the paper while the first and second feeding roller assemblies are spaced from each other. In addition, the paper feeding apparatus may further comprise: a sensing unit having a plurality of sensors for sensing the leading edge of the paper; and a driving unit for rotationally driving the leading-edge alignment member so as to open the paper feeding path and concurrently enabling the first and second feeding roller assemblies to come into close contact with each other when the sensing unit signals that the leading edge of the paper is aligned.

The second feeding roller assembly may comprise a plurality of rollers, and a flexible rotary shaft for rotatably supporting the rollers and elastically deformed by an external force.

The tension idle wheel may be installed in the second feeding roller assembly to be capable of idling.

In one embodiment, the tension idle wheel comprises: an outer rim which comes into contact with the first feeding roller assembly; an inner rim fitted on the rotary shaft of the second feeding roller assembly; and a plurality of spokes for connecting the outer rim to the inner rim, the spokes being convoluted in a predetermined angle in the radial direction. The number of the spokes can be in the range of 2 to 5. Typically, the spokes are convoluted in a same direction.

In addition, it is preferable that the tension idle wheel be integrally formed from resin, and that the outer rim has a smooth machined outer surface so that the paper slips over the outer rim.

The flexible rotary shaft may be formed from an optical fiber so that it can also serve as a signal transmission path for the sensors.

In another embodiment, the leading-edge alignment member for the paper may comprise a blocking part positioned in the paper feeding path and an operating part vertically depending from the blocking part. The paper feeding apparatus may further comprise: a hinge for pivotally supporting the leading-edge alignment member for the paper so that the blocking part selectively opens the paper feeding path; and an elastic member for elastically supporting the paper's leading-edge alignment member, so that the blocking part blocks the paper feeding path.

The elastic member may comprise a plurality of holders supported by the rotary shaft of the second feeding roller assembly, and a plurality of holders interposed between the respective holders and the operating part of the paper's leading-edge alignment member.

In addition, the driving unit may comprise: a cam member for selectively compressing an end of the operating part, so that the paper's leading-edge alignment member is rotated in the direction for opening the paper feeding path; and a motor for rotating the cam member, the motor being driven according to a signal from the sensing unit.

The elastic force of the flexible rotary shaft may be set to be lower than the force exerted by the compression coil springs, so that when the paper's leading-edge alignment member rotates, the rotary shaft is elastically deformed, whereby the first and second feeding roller assemblies come into close contact with each other.

Another aspect of the invention is to provide a method of aligning a paper in an image forming apparatus including the steps of: feeding a paper through a paper feed path of the apparatus into contact with a movable gate of a leading edge alignment member to align a leading edge of the paper with the gate, sensing alignment of the leading edge of the paper with the gate, and opening the gate in response to the sensed alignment and feeding the paper past the gate and through the paper feed path.

These and other aspects of the invention will become apparent from the following detailed description of the invention, which taken in conjunction with the annexed drawings, disclose various embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above aspects and features of the present invention will be more apparent from the description for certain embodiments of the present invention taken with reference to the accompanying drawings, in which:

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

FIG. 2 is a perspective view showing a main part of a paper feeding apparatus employed in the image forming apparatus of FIG. 1;

FIG. 3 is a side elevational view of an image forming apparatus according to an embodiment of the present invention;

FIG. 4 is a front elevational view of FIG. 3;

FIG. 5 is a perspective view of a feeding roller assembly of a paper feeding apparatus according to an embodiment of the present invention;

FIG. 6 is a perspective view of a tension idle wheel provided in the feeding roller assembly of FIG. 5;

FIGS. 7A and 7B are top views for showing the alignment of a leading edge of a paper for a paper feeding apparatus according to an embodiment of the present invention;

FIG. 8 is a side elevational view showing the feeding rollers in the feeding roller assembly, which are engaged and rotated with each other as shown in FIG. 3; and

FIG. 9 is a front elevational view of the apparatus of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinbelow, the preferred embodiments of the present invention are described in detail with reference to accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein are omitted when it may make the subject matter of the present invention rather unclear.

As shown in FIGS. 3 to 6, a paper feeding apparatus of an image forming apparatus according to an embodiment of the present invention includes a first feeding roller assembly 110, a second feeding roller assembly 120, a plurality of tension idle wheels 200, a paper's leading-edge alignment member 300, a sensing unit 400, and a driving unit 500.

The first feeding roller assembly is rotatably installed on a paper feeding path C. The first feeding roller assembly 110 includes a first rotary shaft 111 and a plurality of first feeding rollers 112 mounted on the rotary shaft 111 and spaced from each other. The first rotary shaft 111 is connected with a drive source not shown in the drawings.

The second feeding roller assembly 120 is spaced from the first feeding roller assembly 110. The second feeding roller assembly 120 selectively comes into contact and rotates with the first feeding roller assembly 110 to feed a paper P shown in FIG. 3. The second feeding roller assembly 120 includes a second rotary shaft 121 and a plurality of feeding rollers 122 mounted on the second rotary shaft 121 and spaced from each other.

The second rotary shaft 121 is formed from a flexible material that is elastically deformable by an external force so that the first and second feeding roller assemblies 110 and 120 can selectively come into close contact and rotate with each other as described later.

A plurality of the tension idle wheels 200 are installed on the second feeding rollers 120 and being capable of idling as shown in FIGS. 3 and 5. When the first and second feeding roller assemblies 110 and 120 are spaced apart from each other, the tension idle wheels 200 come into contact with the roller 112 as shown in FIG. 4 and rotate with the first feeding roller assembly 110, thereby slip-feeding a paper P. When the first and second roller assemblies 110 and 120 come into contact with each other, the tension idle wheels 200 are elastically deformed in the radial direction thereof, whereby the close contact of the feeding roller assemblies 110 and 120 are not disturbed by the tension idle wheels 200. Although the drawing shows the tension idle wheels 200 installed on the second feeding roller assembly 120 by way of an example, the tension idle wheels 200 may be installed on the first feeding roller assembly 110.

Each of the above-mentioned tension idle wheels 200 comprises an outer rim 210, an inner hub or rim 220 and spokes 230, which are integrally formed from a material such as resin. The outer rim 210 comes into contact with a respective feeding roller 112 in the first feeding roller assembly 110. The surface of the outer rim 210 is machined to be smooth so that it has a low frictional coefficient. In this manner, slippage occurs when the outer rim 210 comes into contact with a paper P, thereby enabling the slip-feeding of the paper.

The inner rim 220 is fitted on and supported by the rotary shaft 121 of the second feeding roller assembly 120. The spokes 230 connect the outer rim 210 and the inner rim 220. As shown in FIG. 6, four spokes 230 are convoluted in a same direction. The spokes 230 are shaped in this manner so that the tension idle wheel 200 easily deforms when an external force is applied to the tension idle wheel 200. However, the number of the spokes 230 is not limited to four, and it is sufficient if two or more spokes are provided.

The leading-edge alignment member 300 for the paper is installed to selectively open the paper feeding path downstream of the first and second feeding roller assemblies 110 and 120 as shown in FIG. 3. The leading-edge alignment member 300 blocks the paper feeding path C, when the paper is fed slowly by the tension idle wheels 200 and the first feeding roller assembly 110 as slippage occurs between the paper P, the first feeding roller assembly 110 and the tension idle wheels 200, so that the leading end of a paper comes into contact with the paper's leading-edge alignment member, thereby evenly aligning the paper.

The leading-edge alignment member 300 for the paper comprises a gate or blocking part 310 and an operating part 320 in the form of an arm vertically depending from the blocking part 310 shown in FIGS. 3 and 7A. A pivot hinge 330 pivotally supports the leading-edge alignment member 300 so that the blocking part 310 selectively opens and closes the paper feeding path C. In addition, spring assembly or elastic part 340 resiliently engages the leading-edge alignment member 300 in such a way that the blocking part 310 selectively blocks the paper feeding path C. As shown in FIGS. 7A, 7B and 8, the alignment member has a plurality of arms that engage the springs of the elastic part 340 to bias the alignment member in a closed position. The operating arm shown in FIG. 7A has a length greater than the arms engaging the springs.

The elastic part 340 is a spring assembly comprising a plurality of holders 341 shown in FIGS. 3 and 8 supported by the rotary pivot shaft 121 of the second feeding roller assembly 120, and a plurality of compression coils or springs 342 interposed between the holders 341 and a respective operating arm 320 of the leading edge alignment member 300.

A sensing unit 400 shown in FIG. 3 comprises a plurality of sensors installed in parallel just before the blocking part 310 of the leading-edge alignment member 300 in order to sense whether the leading-edge of the paper P is properly aligned. In the present embodiment, if the second flexible rotary shaft 121 is made from an optical fiber, it is possible for the rotary shaft 121 also to serve as a signal transmission line without an additional signal transmission path for the sensors. The sensors 400 can be optical sensors, infrared sensors, or ultrasonic sensors. The sensor 400 detects the leading edge of the paper P to determine the orientation of the paper on the alignment with respect to the apparatus to ensure that the printed image is properly aligned on the paper.

If the sensing unit 400 signals that the leading edge of a paper is properly aligned, a driving unit 500 rotationally drives the paper's leading-edge alignment member 300 to open the paper feeding path C and concurrently moves the first and second feeding roller assemblies 110 and 120 into close contact with each other, so that the paper P with the properly aligned leading edge is fed to the apparatus.

As shown in FIG. 3, the driving unit 500 includes a cam member 510 for selectively compressing an end of the operating arm 320 of the leading-edge alignment member 300, so that the leading-edge alignment member 300 is rotated in the direction for opening the paper feeding path C. A motor 520 is connected to the cam member for rotating the cam member 510. The motor 520 is driven according to a signal from the sensing unit 400 which senses the aligned paper.

In addition, the elastic force of the second flexible rotary shaft 121 is selected to be lower than that of the compression force of the coil springs 342, so that when the leading edge alignment member 300 rotates about the pivot hinge 330, the rotary shaft 121 is elastically deformed as shown in FIG. 9, whereby the first and second feeding roller assemblies 110 and 120 come into close contact with each other.

The alignment of a leading edge of the paper and the feeding of the paper of the paper feeding apparatus configured as described above according to an embodiment of the present invention are now described with reference FIGS. 3, 4, 7A, 7B, 8 and 9.

FIGS. 3 and 4 are side and front elevational views showing the state in which the leading end of a paper P picked up by the apparatus and introduced between the first and second feeding roller assemblies 110 and 120, respectively. The first feeding roller assembly 110 and the second feeding roller assembly 120 are spaced from each other and the tension idle wheels 200 mounted on the second feeding roller assembly 110 are in contact with the first feeding roller assembly 110.

The paper P introduced between the tension idle wheels 200 and the first feeding roller assembly 110 is fed by the feeding force exerted by the first feeding roller assembly 110. At this time, if the paper 110 is fed in the misaligned position as shown in FIG. 7A, one side P of the leading edge of the paper P first comes into contact with the blocking part 310 of the paper's leading-edge alignment member 300. In this position, slippage occurs between the first feeding roller assembly 112, the paper P, and the tension idle wheels 200, whereby the other side P2 of the leading edge of the paper P turns and comes into contact with the blocking part 310 since the one side P1 of the leading edge of the paper is stopped. As a result, the leading edge of the paper is evenly aligned with the apparatus and the blocking part 310. The proper alignment of the leading edge of the paper is shown in FIG. 7B.

The completion of alignment of the leading edge of the paper as shown in FIG. 7B is sensed, for example, at the time all the sensors of the sensing unit 400 arranged in the widthwise direction of the paper are turned from “ON” to “OFF.” Then, after a predetermined length of time has passed, the driving unit 500 is driven by a controller (not shown in the drawing), so that the paper feeding path C is opened and concurrently the first and second feeding roller assemblies 110 and 120 are rotated while being in close contact with each other, to feed the paper P with the leading edge.

Referring to FIGS. 8 and 9, as the motor 520 is driven, the cam member 510 fitted on the shaft of the motor 520 rotates. As a result, the paper's leading-edge alignment member 300 rotates clockwise about the hinge 330 shown in FIG. 8. Therefore, the end of the blocking part 310 moves away from the paper feeding path C, whereby opening the paper feeding path C. At the same time, as the operating part 320 compresses the compression coil springs 342 of the elastic part 340, the second rotary shaft 121 is elastically deformed so that the second feeding roller assembly 120 comes into close contact with the first feeding roller assembly 110. At this time, the tension idle wheels 200 mounted on the second feeding roller assembly 120 are radially deformed, so that they do not prevent the first and second feeding rollers 112 and 122 from coming into close contact with each other.

The paper P is then fed along the opened paper feeding path C, and when the tail end of the paper being fed passes the plurality of sensors, the motor 520 is driven in a reverse direction, thereby returning the leading-edge alignment member 300 and the second feeding roller assembly 120 to their original positions.

As described above, according to the present invention, the alignment of the leading edge of a paper being fed is performed not by using the force for feeding the paper but by opening a paper feeding path after aligning the leading edge of the paper while slippage occurs in the paper when the paper feeding path is blocked. Therefore, the leading edge of the paper can be efficiently aligned regardless of the thickness of the paper. In addition, according to the present invention, because the alignment of the leading-edge of a paper can be smoothly performed even if the paper is thick, it is possible to reduce the occurrence of print error caused by the serpentine feeding of a paper.

Although representative embodiments of the present invention have been shown and described in order to exemplify the principle of the present invention, the present invention is not limited to the specific embodiments. It will be understood that various modifications and changes can be made by one skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, it shall be considered that such modifications, changes and equivalents thereof are all included within the scope of the present invention.

Claims

1. A paper feeding apparatus for an image forming apparatus, comprising: first and second feeding roller assemblies rotatably mounted in a paper feeding path; at least one tension idle wheel mounted on either the first and second feeding roller assemblies, the tension idle wheel being resiliently deformable in a radial direction thereof when the first and second feeding roller assemblies come into close contact with each other; and a leading-edge alignment member positioned downstream of the first and second feeding roller assemblies to align the leading edge of a paper as being fed through the feeding path.

2. A paper feeding apparatus as claimed in claim 1, wherein the tension idle wheel slip-feeds the paper when the first and second feeding roller assemblies are spaced apart from each other.

3. A paper feeding apparatus as claimed in claim 1, further comprising: a sensing unit having a plurality of sensors for sensing alignment of a leading edge of the paper with respect to the apparatus; and a driving unit for rotationally driving the leading-edge alignment member to open the paper feeding path and concurrently causing the first and second feeding roller assemblies to come into close contact with each other when the sensing unit senses that the leading edge of the paper is in a predetermined alignment with respect to the apparatus.

4. A paper feeding apparatus as claimed in claim 3, wherein the second feeding roller assembly comprises: a plurality of rollers; and a flexible rotary shaft for rotatably supporting the rollers, wherein the rotary shaft can be elastically deformed by an external force.

5. A paper feeding apparatus as claimed in claim 3, wherein the tension idle wheel is installed in the second feeding roller assembly to be capable of idling.

6. A paper feeding apparatus as claimed in claim 5, wherein the tension idle wheel comprises: an outer rim which comes into close contact with the first feeding roller assembly; an inner hub mounted on the rotary shaft of the second feeding roller assembly; and a plurality of spokes connecting the outer rim and the inner rim, the spokes being convoluted in a predetermined angle in the radial direction.

7. A paper feeding apparatus as claimed in claim 6, wherein the tension idle wheel includes 2 to 5 spokes convoluted in a same direction.

8. A paper feeding apparatus as claimed in claim 7, wherein the tension idle wheel is integrally formed from a resin.

9. A paper feeding apparatus as claimed in claim 8, wherein the outer rim has a smooth machined outer surface so that slippage occurs between a paper and the outer surface of the rim.

10. A paper feeding apparatus as claimed in claim 4, wherein the flexible rotary shaft is formed from an optical fiber and is coupled to the sensors to function as a signal transmission path for the sensors.

11. A paper feeding apparatus as claimed in claim 4, wherein the leading-edge alignment member comprises a blocking part positioned in the paper feeding path and an operating arm vertically depending from the blocking part, and wherein the paper feeding apparatus further comprises: a hinge for pivotally supporting the leading-edge alignment member so that the blocking part selectively opens and closes the paper feeding path; and a spring member for biasing the leading-edge alignment member to the closed position to block the paper feeding path.

12. A paper feeding apparatus as claimed in claim 11, wherein the spring member comprises: a plurality of spring holders supported by the rotary shaft of the second feeding roller assembly; and a plurality of springs positioned between the respective holders and respective operating arms of the leading-edge alignment member.

13. A paper feeding apparatus as claimed in claim 12, wherein the leading edge alignment member includes an operating arm, and where the driving unit comprises: a cam member for selectively compressing an end of the operating arm, so that the leading-edge alignment member rotates in the direction to open the paper feeding path; and a motor for rotating the cam member, the motor being driven according to a signal from the sensing unit.

14. A paper feeding apparatus as claimed in claim 13, wherein the resilience and flexibility of the flexible rotary shaft is weaker than a force exerted by the compression coil springs, so that when the leading-edge alignment member rotates, the rotary shaft is resiliently deformed, whereby the first and second feeding roller assemblies come into close contact with each other.

15. An image forming apparatus comprising: first and second feeding roller assemblies rotatably mounted in a paper feeding path of the apparatus; at least one tension idle wheel mounted on one of the first and second feeding roller assemblies, the tension idle wheel coming into close contact and rotating with the corresponding feeding roller assembly to slip-feed a paper through the paper feeding path when the first and second feeding roller assemblies are spaced apart from each other, and where the tension idle wheel is resiliently deformable in the radial direction thereof when the first and second feeding roller assemblies come into close contact with each other; a leading edge alignment member for the paper positioned to selectively open and close the paper feeding path downstream of the first and second feeding roller assemblies, the leading-edge alignment member aligning a leading edge of the paper being slip-fed by the tension idle wheel when the leading-edge alignment member is in a closed position blocking the paper feeding path; a sensing unit having a plurality of sensors for sensing alignment of the leading edge of the paper with respect to the apparatus; and a driving unit for rotationally driving the leading-edge alignment member to open the paper feeding path when the sensing unit senses a predetermined alignment of the paper and concurrently causing the first and second feeding roller assemblies to come into close contact with each other to feed the paper through the paper feeding path of the apparatus.

16. The image forming apparatus of claim 15, wherein the first feeding roller assembly includes a first roller, the second feeding roller assembly includes a second roller, and the first roller assembly is movable from a first position where the tension idle wheel contacts the second roller and the first roller is spaced from the second roller, and a second position where the first roller contacts the second roller to feed the paper through the paper feeding path.

17. The image forming apparatus of claim 16, wherein the at least one tension wheel and the first roller are rotatably mounted on a flexible shaft.

18. The image forming apparatus of claim 17, wherein the at least one tension wheel has a diameter greater than a diameter of the first roller.

19. The image forming apparatus of claim 16, wherein the leading-edge alignment member includes a movable gate member to close and block the paper feeding member, and wherein the first and second feed roller assemblies feed the paper to contact the gate member to align the paper with an edge of the gate member.

20. A method of aligning a paper in an image forming apparatus, the method comprising: feeding a paper through a paper feed path of the apparatus into contact with a movable gate of a leading edge alignment member to align a leading edge of the paper with the gate, sensing alignment of the leading edge of the paper with the gate, and opening the gate in response to the sensed alignment and feeding the paper past the gate and through the paper feed path.

21. The method of claim 20, wherein the apparatus includes a first feed roller having a first roller and a tension idle wheel, and a second feed roller having a second roller, the tension idle wheel having a diameter greater than a diameter of the first roller and being resiliently deformable, the method comprising: contacting the idle wheel with the second roller in a first position to feed the paper through the paper feed path into contact with the movable gate, and simultaneously opening the gate and moving the first feed roller to a second position in response to the first feed roller to a second position in response to the sensed alignment of the paper, wherein the first feed roller contacts the second roller an the idle wheel is deformed when the first feed roller is in the second position.