Paper feeder and medium processing apparatus including the same

A paper feeder includes a load tray where cut-sheet-type media are loaded; a pickup member configured to withdraw the cut-sheet-type media from the load tray; and a blowing unit configured to supply pulse air from a downstream side of the load tray in a loading direction of the cut-sheet-type media to a front end portion of the cut-sheet-type media loaded on the load tray.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Korean Patent Application No. 10-2016-0057808, filed on May 11, 2016, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

The present disclosure relates to paper feeders that separate sheets of a cut-sheet-type medium piece by piece and pulls them out from a load tray and medium processing apparatuses including the paper feeders.

2. Description of the Related Art

Apparatuses such as printers, scanners, and ticketing machines that use a cut-sheet-type medium, for example, cut paper (hereinafter referred to as ‘paper’), employ feeders that pull out cut-sheet-type media from a load tray where a plurality of cut-sheet-type media are loaded by separating the cut-sheet-type media piece by piece.

Various pieces of paper may be supplied by feeders. For example, paper may have various basis weight, surface roughness, etc. Paper that has a surface coating layer, tracing paper, perforated paper, etc. have strong adhesion between pieces of paper, and thus, it is difficult to separate the pieces of paper one by one.

Accordingly, a method of weakening the adhesion between pieces of paper loaded on the load tray is needed in order to decrease the possibility of multi-feeding.

SUMMARY

Provided are paper feeders capable of stably feeding a cut-sheet-type medium, and medium processing apparatuses including the paper feeders.

According to an aspect of an embodiment, a paper feeder includes: a load tray where cut-sheet-type media are loaded; a pickup member configured to pick up the cut-sheet-type media from the load tray; and a blowing unit configured to supply pulse air from a downstream side of the load tray in a loading direction of the cut-sheet-type media to a front end portion of the cut-sheet-type media loaded on the load tray.

The paper feeder may further include a separation unit configured to separate, piece by piece, the cut-sheet-type media picked up from the load tray by the pickup member, wherein the blowing unit may be connected to the separation unit to allow the pulse air to be supplied.

The blowing unit may include: a blower; and a pulsation member connected to the separation unit to allow air supplied from the blower to pulsate.

The pulsation member may include: a windmill including one or more wings and connected to the separation unit to rotate; and a guide member configured to guide the air supplied from the blower to the windmill.

The guide member may be configured to form an air chamber and may include an air inlet connected to the blower and an air outlet opened toward the load tray, and the windmill may be located in the air chamber. The one or more wings may be configured to divide the air chamber into two or more sub chambers.

A side wall of the guide member may be open and the guide member may include an air inlet connected to the blower and an air outlet opened toward the load tray, the windmill may include a blocking plate that corresponds to the open side wall of the guide member and is configured to form an air chamber along with the guide member, and the one or more wings may be configured to divide the air chamber into two or more sub chambers.

The separation unit may include: a feed roller configured to rotate in a first direction for transporting the cut-sheet-type media picked up by the pickup member in the loading direction; a retard roller engaged with the feed roller; a driving gear configured to provide a driving force in a second direction for transporting the cut-sheet-type media in an opposite direction to the loading direction to the retard roller; and a torque limiter configured to limit the driving force in the second direction transferred to the retard roller, wherein the windmill may be configured to rotate together with the retard roller.

The retard roller may include a rotation axis, and a roller portion installed at the rotation axis to contact the feed roller, and the windmill may be coupled to one of the rotation axis and the roller portion.

The torque limiter may be configured to connect the driving gear and the rotation axis to each other.

The torque limiter may be configured to connect the rotation axis and the roller portion to each other.

The windmill may be connected to the rotation axis by one or more gears.

The paper feeder may further include: a sensor configured to detect excessive lifting of the front end portion of the sheet-type media.

According to an aspect of another embodiment, a medium processing apparatus includes: the paper feeder; and a medium processor configured to process the cut-sheet-type media supplied from the paper feeder.

DETAILED DESCRIPTION

Embodiments of a paper feeder and a medium processing apparatus employing the same will be described hereinafter with reference to the accompanying drawings, wherein like reference numerals refer to like elements throughout, and size or thickness of each element may be exaggerated for clarity of description. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

FIG. 1is a schematic structural diagram of a paper feeder1according to an embodiment. Referring toFIG. 1, the paper feeder1includes a load tray10where a cut-sheet-type medium (hereinafter referred to as ‘paper P’), for example, cut paper, is loaded, and a pickup roller (a pickup member)20that withdraws the paper P loaded on the load tray10from the load tray10. The pickup roller20, for example, contacts paper P1placed at the top from among pieces of paper P loaded on the load tray10. The pickup member is not limited to a roller and may be in other various forms such as a belt.

When the pickup roller20rotates, the paper P1is picked up from the load tray10. In some cases, the paper P1and one or more pieces of paper P2under the paper P1may be picked up together. This case is referred to as multi-feeding.

Multi-feeding occurs when adhesion between the pieces of paper P loaded on the load tray10is large. When adhesion between the pieces of paper P loaded on the load tray10is large, misfeeding may occur. In this case, the paper P is not picked up even though the pickup roller20rotates. In other words, when the papers P stick together, the paper P may not be picked up from the load tray10.

The paper feeder1may further include a separation unit30that separates and carries one piece of paper, for example, the paper P1only, when multi-feeding occurs. The separation unit30may have various structures such as a friction separation structure, a reverse separation structure, or the like.

FIG. 2shows the separation unit30with a reverse separation structure, according to an embodiment. Referring toFIG. 2, the separation unit30may include a feed roller31, a retard roller32, and a torque limiter33. The feed roller31and the retard roller32rotate while being engaged with each other. The feed roller31rotates in a first direction B1for transporting the paper P in a loading direction A1. The retard roller32rotates in a second direction B2for transporting the paper P in an inverse direction A2of the loading direction A1. A driving gear34provides a driving force in the second direction B2to the retard roller32. The torque limiter33limits the driving force in the second direction B2transferred to the retard roller32. The torque limiter33limits the driving force in the second direction B2transferred to the retard roller32according to a magnitude of load torque applied to the retard roller32. When a load torque applied to the retard roller32is greater than a threshold torque provided by the torque limiter33, the torque limiter33blocks the driving force of the second direction B2transferred to the retard roller32. In this case, the retard roller32rotates in a third direction B3due to the feed roller31.

The torque limiter33may have various known structures. For example, the torque limiter33may be realized by a spring clutch structure.

The retard roller32may include a rotation axis321, and a roller portion322installed at the rotation axis321and engaged with the feed roller31. When the rotation axis321and the roller portion322are integrally formed with each other or the roller portion322is fixed to the rotation axis321, the rotation axis321and the driving gear34are connected to each other by the torque limiter33. For example, a clutch spring (not shown) may be inserted in the rotation axis321or a hub fixed to the rotation axis321, and a predetermined threshold torque may be provided according to a tightening force of the clutch spring. The driving gear34provides a driving force in the second direction B2to the clutch spring. When a load torque applied to the rotation axis321is less than a threshold torque, the rotation axis321rotates in the second direction B2. When the load torque applied to the rotation axis321becomes greater than the threshold torque, the clutch spring extends, thereby blocking a driving force of the driving gear34.

When the roller portion322is rotatably installed at the rotation axis321, the rotation axis321and the roller portion322are connected to each other by the torque limiter33. For example, a clutch spring (not shown) may be inserted in the rotation axis321or a hub fixed to the rotation axis321, and a predetermined threshold torque may be provided according to a tightening force of the clutch spring. An end of the clutch spring may be connected to the roller portion322. The driving gear34is fixed to the rotation axis321and rotates the rotation axis321in the second direction B2. When a load torque applied to the roller portion322is less than a threshold torque, the roller portion322rotates in the second direction B2, and when the load torque applied to the roller portion322becomes greater than the threshold torque, the clutch spring extends, thereby blocking a driving connection between the rotation axis321and the roller portion322.

A separation operation via the configurations described above will be briefly described below.

When there is no paper P between the feed roller31and the retard roller32, or only one piece of paper P comes between the feed roller31and the retard roller32, a load torque applied to the retard roller32is greater than a threshold torque of the torque limiter33, and thus, a driving force applied to the retard roller32is blocked by the torque limiter33. Accordingly, the retard roller32rotates in a third direction B3for transporting the paper P in the loading direction A1along with the feed roller31.

When two or more pieces of paper P, for example, the paper P1and the paper P2, come between the feed roller31and the retard roller32, the paper P1and the paper P2respectively contact the feed roller31and the retard roller32. In this case, a frictional force between the paper P1and the paper P2is less than that between the paper P2and the retard roller32. Accordingly, slipping occurs between the paper P1and the paper P2, and a load torque applied to the retard roller32is less than a threshold torque provided by the torque limiter33. The retard roller32rotates in the second direction B2, and the paper P2is transported in the inverse direction A2of the loading direction A1by the retard roller32. Accordingly, only the paper P1passes between the feed roller31and the retard roller32and is transported in the loading direction A1.

When the number of pieces of paper P picked up from the load tray10by the pickup roller20is excessively large, separation performance by the separation unit30may be degraded. Therefore, the number of pieces of paper P picked up from the load tray10by the pickup roller20needs to be reduced as much as possible. In order to improve paper picked up reliability of the paper feeder1by decreasing chances of multi-feeding or misfeeding, adhesion may be weakened by separating pieces of paper P loaded on the load tray10from each other. The paper feeder1according to the present embodiment may include a blowing unit40that separates pieces of paper P from each other by supplying air to the pieces of paper P.

A transversal blow structure for supplying air in a transverse direction, that is, a width direction of the paper P perpendicular to the loading direction A1, may also be used. In the transversal blow structure, a blowing unit40is installed at one side along the width direction of the paper P. In this case, a blowing unit40having a large blowing capacity is used to sufficiently supply air from one side along the width direction of the paper P to the other side. In this case, at the side having a blowing unit40installed, the paper P may be lifted excessively, and thus, misfeeding may occur. When a blowing unit40is installed at each of one side and the other side along the width direction of the paper P, costs may increase. In addition, although the transversal blow structure may be, for example, used when the paper feeder1is mounted in a housing in the form of a box, the transversal blow structure is externally exposed in a paper feeder, such as a multi-purpose tray (MPT) or a document feeder of a scanner, having a structure in which one side portion or both side portions of the load tray10in a transverse direction are open. Thus, use of the transversal blow structure is inconvenient.

The blowing unit40according to the present embodiment supplies air from a downstream side of a front end portion PF to the front end portion PF with respect to the loading direction A1of the paper P. A direction of air supplied to the front end portion PF by the blowing unit40may be an opposite direction of the loading direction A1. In this regard, the term ‘opposite direction’ does not specifically refer to the direction A2only, and refers to a direction from the downstream side of the front end portion PF toward the front end portion PF.

The blowing unit40having such a structure may be easily applied to the paper feeder, such as an MPT or a document feeder of a scanner, having a structure in which one side portion or both side portions of the load tray10in a transverse direction are open.

When air is supplied to the front end portion PF of the paper P by the blowing unit40, pieces of paper P loaded on the load tray10are lifted and separated from each other, and thus, adhesion between the pieces of paper P may be weakened. The blowing unit40according to the present embodiment supplies pulse air. When air pulsates, shock in the form of a pulse is applied to the paper P, and accordingly, the pieces of paper P may be further easily separated from each other.

The blowing unit40supplies the pulse air to the front end portion PF of the paper P loaded on the load tray10.

Although a blower41may be intermittently driven in order to supply pulse air, in this case, a driving circuit of the blower41may be complicated, and thus, the costs may increase. Although a shutter may be installed in an air path extending from the blower41to a front end of the paper P, a means for driving, such as a solenoid, for driving the shutter is required, and thus, the structure may be complicated, and the costs may increase.

The blowing unit40is linked with the separation unit30to supply pulse air. The blowing unit40may include the blower41and a pulsation member42, and the pulsation member42may allow air supplied from the blower41to pulsate, thereby guiding the air to the front end portion PF of the paper P loaded on the load tray10. According to the present embodiment, the pulsation member41is used to supply pulse air in connection with rotation of the retard roller32. Thus, pulse air is supplied without intermittently driving the blower41or using a shutter and a means for driving the shutter.

FIG. 3is a plan view of the paper feeder1according to an embodiment, andFIG. 4is a schematic cross-sectional view taken along line X1-X1′ ofFIG. 3.FIGS. 5A and 5Bare cross-sectional views showing an example of a combination method used by a windmill420and the rotation axis321. InFIG. 3, the feed roller31is omitted.

Referring toFIGS. 3, 4, 5A, and 5B, the pulsation member42may include the windmill420. As illustrated by solid lines inFIG. 3, the torque limiter33may connect the driving gear34and the rotation axis321to each other. Also, as illustrated by dashed lines inFIG. 3, the torque limiter33may connect the rotation axis321and the roller portion322to each other.

The windmill420may be coupled to the rotation axis321of the retard roller32and rotate along with the rotation axis321. The windmill420includes one or more wings421. The windmill420according to the present embodiment includes three wings421. A diameter of the windmill420may be less than that of the retard roller32, and more particularly, may be less than that of the roller portion322so as not to interfere with a pick up of the paper P.

The windmill420may be fixed to the rotation axis321. The windmill420may be fixed to the rotation axis321by a tight fit method. Also, as shown inFIG. 5A, the windmill420may be fixed to the rotation axis321by a snap-fit method. For example, the rotation axis321may include a D-cut portion321-1, and the windmill420may include a through hole423complementary thereto. An elastic arm425that includes a hook424protruding inwards may be provided on a wall of the through hole423. The rotation axis321may include a groove321-2. When the windmill420is pushed in an axial direction of the rotation axis321to insert the D-cut portion321-1into the through hole423, the hook424contacts the rotation axis321, thereby elastically pushing the elastic arm425outwards. When the hook424reaches the groove321-2, the elastic arm425returns inwards, thereby inserting the hook424into the groove321-2.

As shown inFIG. 5B, the windmill420may be fixed to the roller portion322. Referring toFIG. 5B, the roller portion322may include a hub322-1inserted into the rotation axis321, and a rubber portion322-2inserted into an outer circumference of the hub322-1. The windmill420may include the elastic arm425extending to an inner side of the hub322-1, and an end portion of the elastic arm425may include the hook424protruding outwards. The hub322-1includes a groove322-3which the hook424is coupled to. Accordingly, the windmill420may rotate along with the roller portion322.

Although not shown, the windmill420may be integrally formed with the roller portion322. For example, the windmill420may be integrally formed with the hub322-1.

A guide member430guides air supplied from the blower41to the windmill420. The guide member430may form an air chamber440, and the windmill420may be installed in the air chamber440.

The guide member430may form the air chamber440by surrounding the windmill420. The guide member430includes an air inlet431and an air outlet432. In the present embodiment, the blower41axially supplies air to the windmill420. Accordingly, the air inlet431is provided on one side wall433of the guide member430in a direction of the rotation axis321. The air outlet432is provided on a side wall434near the load tray10.

For assembly convenience of the retard roller32which the windmill420is coupled to, an opposite side wall435of the air inlet431of the guide member430may be open. A blocking plate422extending in a diameter direction may be provided on one side of the windmill420in a direction of the rotation axis321. The blocking plate422may form the air chamber440along with the guide member430. The wing421may divide the air chamber440formed by the guide member430and the blocking plate422into two or more. According to the present embodiment, the air chamber440is divided into three sub chambers44by the three wings421.

FIG. 6is a plan view of the paper feeder1according to an embodiment, andFIG. 7is a schematic cross-sectional view taken along line X2-X2′ ofFIG. 6. InFIG. 6, the feed roller31is omitted. The paper feeder1according to the present embodiment differs from the paper feeder1shown inFIGS. 3 and 4in that the blower41transversely supplies air to the guide member430.

Referring toFIGS. 6 and 7, since the blower41transversely supplies air to the windmill420, the air inlet431is provided on one side wall436of the guide member430in a transverse direction. The air outlet432is provided on the side wall434near the load tray10. For assembly convenience of the retard roller32coupled to the windmill420, one side wall435of the guide member430in a direction of the rotation axis321may be open. The blocking plate422extending in a diameter direction and forming the air chamber440along with the guide member430may be provided on one side of the windmill420in a direction of the rotation axis321.

In the embodiments shown inFIGS. 3 to 7, the windmill420includes the three wings421. However, the windmill420may include only one wing421. In this case, the wing421may extend in a diameter direction of the windmill420, and thus, two sub chambers44may be formed. In some embodiments, two, four, or more wings421may be used.

Due to the configurations described above, the windmill420may rotate along with the retard roller32. Air supplied by the blower41flows into the air chamber440via the air inlet431. The air is compressed in sub chambers44that do not face the air outlet432from among the sub chambers44. As the windmill420rotates, the sub chambers44sequentially face the air outlet432, and the compressed air is supplied to the front end portion PF of the paper P loaded on the load tray10via the air outlet432. Since air compressed in the sub chambers44is sequentially discharged via the air outlet432, pulse air may be supplied to the front end portion PF of the paper P loaded on the load tray10. As described above, the paper feeder1may supply pulse air due to use of the pulsation member42.

In the previous embodiment, the windmill420rotates along with the retard roller32as the windmill420is installed at the rotation axis321of the retard roller32. However, a structure for rotating the windmill420is not limited thereto.FIG. 8is a plan view of the paper feeder1according to an embodiment. InFIG. 8, the feed roller31and the blower41are omitted. Referring toFIG. 8, the windmill420is rotatably installed at a rotation axis420-1. A first gear323is installed at the rotation axis321of the retard roller32, and a second gear420-2engaged with the first gear323is installed at the rotation axis420-1. Accordingly, the windmill420may rotate along with the retard roller32. In some embodiments, one or more gears (not shown) may be disposed between the first and second gears323and420-2to set a rotation speed and a rotation direction.

Referring toFIG. 1again, the paper feeder1may further include a sensor45for detecting paper being lifted. The sensor45detects how much the paper P loaded on the load tray10is lifted by the blowing unit40. When the paper P is excessively lifted, the paper P picked up from the load tray10by the pickup roller20crashes into the feed roller31and thus may not come between the feed roller31and the retard roller32, and a paper jam may occur. The sensor45detects the paper P being excessively lifted. For example, the sensor45may be located in a location spaced apart by a predetermined distance in a loading direction of the paper P from the paper P1placed at the top from among pieces of paper P loaded on the load tray10and may emit light toward the load tray10, and may receive light reflected from one or more pieces of paper P lifted by air supplied from the blowing unit40, thereby detecting whether the paper P is excessively lifted. A separation distance SD of the sensor45from the paper P1may be determined by taking into account a distance between the pickup roller20and the separation unit30, a diameter of the feed roller31, and the like.

A controller50determines, based on a detection signal of the sensor45, whether the paper P is excessively lifted. The controller50checks whether paper is excessively lifted before starting to withdraw paper and after starting to withdraw paper.

For example, after driving the blower41to rotate at a reference rotation speed, the controller50checks whether the paper P is excessively lifted before starting to drive the pickup roller20. For example, the controller50may check whether the paper P is excessively lifted from the sensor45after T msec lapses since starting to drive the blower41. When the paper P is excessively lifted, adhesion between pieces of paper P loaded on the load tray10is rather alleviated by initial rotation of the blower41, and accordingly, the controller50starts to drive the pickup roller20after decreasing a rotation speed of the blower41. The rotation speed of the blower41may be about half the reference rotation speed. In addition, the controller50may start to drive the pickup roller20after turning off the blower41. After the pickup roller20starts to be driven, the controller50checks again whether one or more pieces of paper P picked up from the load tray10by the pickup roller20are excessively lifted. When the paper P is excessively lifted, the controller50decreases a rotation speed of the blower41. The rotation speed of the blower41may be about half a reference rotation speed. The controller50may change the rotation speed of the ventilator41to the reference rotation speed before starting to withdraw next paper P. Also, the controller50may turn off the blower41, and may turn on the blower41before starting to withdraw next paper.

FIG. 9is a plan view of the paper feeder1according to an embodiment. InFIG. 9, the feed roller31is omitted. Referring toFIG. 9, the paper feeder1according to the present embodiment is the same as the paper feeder1shown inFIG. 3except that a compression chamber450is disposed between the blower41and the guide member430. Air supplied from the blower41passes through the compression chamber450and is supplied to the inside of the guide member430via the air inlet431.

FIG. 10is a plan view of the paper feeder1according to an embodiment. InFIG. 10, the feed roller31is omitted. Referring toFIG. 10, the paper feeder1according to the present embodiment is the same as the paper feeder1shown inFIG. 6except that the compression chamber450is disposed between the blower41and the guide member430. Air supplied from the blower41passes through the compression chamber450and is supplied to the inside of the guide member430via the air inlet431.

By the configurations described above, when the blower41starts to be driven earlier than the separation unit30, air is compressed in the compression chamber450and the air chamber440, and when the windmill420starts to rotate as the separation unit30starts to be driven, the compressed air may be supplied with strong pressure to the front end portion PF of the paper P, and thus, adhesion between pieces of paper P may be effectively weakened.

FIG. 11is a diagram of the paper feeder1after starting to drive the separation unit30and the blower41and before starting to drive the pickup roller20.FIG. 12is a diagram of the paper feeder1having the paper P1placed at the top picked up from the load tray10.FIG. 13is a diagram of the paper feeder1having the two pieces of paper P1and P2picked up from the load tray10. InFIGS. 11 to 13, the guide member430is briefly shown, and the blower41is omitted. A paper pick up operation of the paper feeder1according to the previous embodiments will now be described with reference toFIGS. 11 to 13.

First, a paper pick up operation in a structure where the torque limiter33connects the rotation axis321and the roller portion322to each other and the windmill420is fixed to the rotation axis321will be described.

In this case, the rotation axis321rotates in the second direction B2all the time due to the driving gear34, and the windmill420also rotates in the second direction B2all the time. The roller portion322rotates in the second direction B2or the third direction B3, depending on whether there is paper P between the feed roller31and the roller portion322and how many pieces of paper P there are therebetween.

The separation unit30and the blower41start to be driven. The separation unit30and the blower41may start to be driven simultaneously, or either one of the separation unit30and the blower41may start to be driven earlier. In the present embodiment, the separation unit30starts to be driven after the blower41starts to be driven. The blower41is driven at a reference rotation speed.

When the compression chamber450is provided, the blower41is driven and air is compressed in the compression chamber450and the air chamber440while the separation unit30is not driven. After T msec lapses since the blower41starts to be driven, whether the paper P is excessively lifted is determined based on a detection signal of the sensor45. When excessive lifting of the paper P is detected, a rotation speed of the blower41may be decreased so as to be lower than the reference rotation speed, and the blower41may be turned off.

Referring toFIG. 11, when the separation unit30and the blower41start to be driven, the rotation axis321rotates in the second direction B2. Since the roller portion322contacts the feed roller31, a load torque applied to the roller portion322is greater than a threshold torque of the torque limiter33. Accordingly, the roller portion322rotates in the third direction B3along the feed roller31. The windmill420rotates in the second direction B2along with the rotation axis321.

The blower41supplies air to sub chambers44a,44b, and44c. The sub chamber44ais connected to the air outlet432, and accordingly, air supplied to the sub chamber44ais supplied to the front end portion PF of the paper P via the air outlet432. Air is supplied to flow between pieces of paper P, and the pieces of paper P are lifted with respect to each other. Thus, adhesion between the pieces of paper P weakens.

As the windmill420rotates in the second direction B2, the sub chamber44band the sub chamber44csequentially face the air outlet432, and air is supplied toward the front end portion PF. Air supplied to the sub chambers44band44cmay be compressed in the sub chambers44band44cwhile the sub chambers44band44cdo not face the air outlet432. As described above, as the sub chambers44a,44b, and44csequentially face the air outlet432, pulse air is supplied to the front end portion PF of pieces of paper P loaded on the load tray10, and thus, the pieces of paper P vibrate, thereby further weakening the adhesion between the pieces of paper P. In a structure where the air chamber440is not formed, that is, in a structure where the guide member430merely guides air supplied from the blower41to the windmill420, air supplied to the sub chambers44band44cmay not be compressed.

Referring toFIG. 12, the pickup roller20starts to be driven. Only the paper P1contacting the pickup roller20may be picked up from the load tray10by the pickup roller20. In this regard, when excessive lifting of the paper P is detected by the sensor45, a rotation speed of the ventilator41may be decreased.

Since a load torque applied to the roller portion322is greater than a threshold torque of the torque limiter33even in a state where the paper P1is between the feed roller31and the roller portion322, the roller portion322rotates in the third direction B3along the feed roller31. Accordingly, the paper P1is transported in the loading direction A1.

The windmill420rotates in the second direction B2with the rotation axis321. Accordingly, air is compressed in the sub chambers44a,44b, and44cand is sequentially supplied in the form of pulsation to the front end portion PF via the air outlet432. In this regard, since the air is blocked by the paper P1fed by the feed roller31and the retard roller32, the air is not dispersed and further strongly acts upon the front end portion PF. Accordingly, a possibility that the paper P2under the paper P1is picked up following the paper P1during a pick up of the paper P1may be decreased.

Several pieces of paper P may be picked up from the load tray10by the pickup roller20. That is, multi-feeding may occur. Referring toFIG. 13, several pieces of paper P, for example, the paper P1and the paper P2, may be picked up from the load tray10and come between the feed roller31and the roller portion322. Thus, slipping may occur between the paper P1and the paper P2in an area where the feed roller31and the roller portion322contact each other, and a load torque applied to the roller portion322becomes less than a threshold torque of the torque limiter33. Thus, the roller portion322rotates in the second direction B2along with the rotation axis321, and the paper P2is transported in the inverse direction A2of the loading direction A1by the roller portion322. Accordingly, only the upper paper P1is separated from the pieces of paper P and transported in the loading direction A1. Even in this case, air is blocked by the paper P2fed by the retard roller32in the inverse direction A2, and accordingly, the air is not dispersed and further strongly acts upon the front end portion PF, and a possibility that the paper P under the paper P2is picked up after the paper P2may be decreased.

Next, a paper pick up operation in a structure where the torque limiter33connects the driving gear34and the rotation axis321to each other and the windmill420is fixed to the rotation axis321will be described.

In this case, the rotation axis321and the roller portion322rotate together in the same direction, and the windmill420also rotates in the same direction as the rotation axis321. When there is no paper P between the feed roller31and the roller portion322or there is only one piece of paper P therebetween as shown inFIGS. 11 and 12, a load torque applied to the retard roller32is greater than a threshold torque of the torque limiter33, and accordingly, a power connection between the driving gear34and the rotation axis321is blocked. Thus, the retard roller32rotates in the third direction B3due to the feed roller31, and the windmill420also rotates in the third direction B3. When there are two or more pieces of paper P between the feed roller31and the roller portion322as shown inFIG. 13, a load torque applied to the retard roller32is less than a threshold torque of the torque limiter33, and accordingly, the power connection between the driving gear34and the rotation axis321is maintained. Thus, the retard roller32rotates in the second direction B2due to the driving gear34, and the windmill420also rotates in the second direction B2.

A paper pick up operation in the case where the torque limiter33connects the rotation axis321and the roller portion322to each other and the windmill420is fixed to the roller portion322or is integrally formed with the roller portion322and in the case where the torque limiter33connects the driving gear34and the rotation axis321to each other and the windmill420is fixed to the roller portion322or is integrally formed with the roller portion322is the same as the paper pick up operation in the structure where the torque limiter33connects the driving gear34and the rotation axis321to each other and the windmill420is fixed to the rotation axis321.

As shown inFIG. 8, when the windmill420is connected to the rotation axis321by a gear structure, the windmill420rotates in an opposite direction to the rotation axis321, and a resulting paper pick up operation is the same as described above except a rotation direction of the windmill420.

The paper feeder1described above may be applied to various apparatuses.FIG. 14is a block diagram of a medium processing apparatus including the paper feeder1, according to an embodiment. Referring toFIG. 14, the medium processing apparatus includes the paper feeder1, and a medium processor2that receives the paper P from the paper feeder1and processes the paper P. The processed paper P may be discharged to an output tray3.

FIG. 15is a schematic structural diagram of a scanner600including the paper feeder1, according to an embodiment. Referring toFIG. 15, the scanner600includes the paper feeder1and a medium processor that reads an image while transporting a document D supplied from the paper feeder1. The medium processor may include a document feeding unit600aand a reading unit600bthat reads an image from a document. The paper feeder1has been described with reference toFIGS. 1 to 13. Since the scanner600is an apparatus that reads an image recorded on the document D, the paper feeder1transports the document D.

The reading unit600bincludes a reading member650for reading an image from the document D. The reading member650emits light toward the document D, receives light reflected from the document D, and reads an image of the document D. As the reading member650, a contact type image sensor (CIS), a charge coupled device (CCD), or the like may be used.

The scanner600uses a flatbed method in which the document D is located at a fixed location and a reading member such as a CIS or a CCD reads an image while moving, a document feeding method in which a reading member is located at a fixed location and the document D is transported, or a combination thereof. The scanner600according to the present embodiment is a scanner that uses a combination of the flatbed method and the document feeding method.

The reading unit600bincludes a platen glass660on which the document D is placed to read an image from the document D by using the flatbed method. Also, the reading unit600bincludes a reading window670for reading an image from the document D by using the document feeding method. The reading window670may be, for example, a transparent member. In an embodiment, an upper surface of the reading window670may have the same height as an upper surface of the platen glass660.

When the document feeding method is used, the reading member650is located below the reading window670. When the flatbed method is used, the reading member650may be moved in a sub-scanning direction S, that is, in a length direction of the document D, below the platen glass660by a means of transport that is not shown. Also, when the flatbed method is used, the platen glass660may be externally exposed in order to place the document D on the platen glass660. For this, the document feeding unit600amay rotate with respect to the reading unit600bto expose the platen glass660.

The document feeding unit600atransports the document D so that the reading member650may read an image recorded on the document D, and discharges the read document D. For this, the document feeding unit600aincludes a document feeding path610, and the reading member650reads an image from the document D transported along the document feeding path610. The document feeding path610may include, for example, a supply path611, a reading path612, and a discharge path613. The reading member650is disposed in the reading path612, and an image recorded on the document D is read by the reading member650while passing through the reading path612. The supply path611is a path for supplying the document D to the reading path612, and the document D loaded on the load tray10is supplied to the reading path612via the supply path611. The discharge path613is a path for discharging the document D having passed through the reading path612. Accordingly, the document D loaded on the load tray10is transported along the supply path611, the reading path612, and the discharge path613and is discharged to the discharge tray630.

Transport rollers621and622for transporting the document D picked up from the load tray10by the paper feeder1may be disposed in the document feeding path610. Each of the transport rollers621and622may have a structure in which a driving roller and a driven roller rotate while being engaged with each other.

Transport rollers623and626for transporting the document D may be disposed in the reading path612. For example, the transport rollers623and626for transporting the document D may be disposed at both sides of the reading member650. Each of the transport rollers623and626may have a structure in which a driving roller and a driven roller rotate while being engaged with each other. A reading guide member624facing the reading member650is disposed in the reading path612. The reading guide member624is pressed against the reading window670by self-weight or an elastic member625, and the document D is transported to come between the reading window670and the reading guide member624. Although not shown, a reading roller that is elastically pressed against the reading window670and rotates to transport the document D supplied therebetween may be used instead of the reading guide member624.

A discharge roller627that discharges the document D that has been read is disposed in the discharge path613. The discharge roller627may have a structure in which a driving roller and a driven roller rotate while being engaged with each other.

By the configurations described above, the document D supplied from the paper feeder1is transported along the supply path611, the reading path612, and the discharge path613, and the reading member650may read an image from the document D.

FIG. 16is a schematic structural diagram of an image forming apparatus700including the paper feeder1, according to an embodiment. Referring toFIG. 16, the image forming apparatus700includes the paper feeder1, and a printing unit (medium processor)700athat prints an image on the paper P supplied from the paper feeder1. As shown by solid lines inFIG. 16, the paper feeder1may be in the form of a cassette feeder and be located under the printing unit700a. Also, as shown by dashed lines inFIG. 16, the paper feeder1may be realized in the form of an MPT located at one side portion of the printing unit700a.

The printing unit700aaccording to the present embodiment may print an image on the paper P by using various methods such as an electro photography method, an inkjet method, a thermal transfer method, or a thermal sublimation method. The image forming apparatus according to the present embodiment prints a color image on the paper P by using the electro photography method. Referring toFIG. 16, the printing unit700amay include a plurality of developing devices710, an exposure device720, a transfer device, and a fusing device740.

For color printing, the plurality of developing devices710may include, for example, four developing devices710for developing images of cyan C, magenta M, yellow Y, and black K. The four developing devices710may accommodate toner of cyan C, magenta M, yellow Y, and black K, respectively. The printing unit700amay further include a developing device710for accommodating toner of various color, such as light magenta, white, etc., in addition to the color described above, and developing an image of such color.

The developing device710includes a photosensitive drum7a. The photosensitive drum7ais an example of a photoreceptor having an electrostatic latent image formed on a surface thereof, and may include a conductive metal pipe and a photosensitive layer formed on the outer circumference thereof. A charging roller7cis an example of a charger that charges the photosensitive drum7ato have a uniform surface potential. A cleaning blade7dis an example of a cleaning means that removes toner and a foreign material remaining on a surface of the photosensitive drum7aafter a transfer process that will be described later.

The developing device710supplies toner accommodated therein to an electrostatic latent image formed on the photosensitive drum7aand thus develops the electrostatic latent image into a visible toner image. Examples of developing methods include a one-component developing method using toner and a two-component developing method using toner and carrier. The developing device710according to the present embodiment uses the one-component developing method. A developing roller7bis used to supply toner to the photosensitive drum7a. A developing bias voltage for supplying toner to the photosensitive drum7amay be applied to the developing roller7b.

The one-component developing method may be classified into a contact developing method in which the developing roller7band the photosensitive drum7arotate in contact with each other and a non-contact developing method in which the developing roller7band the photosensitive drum7arotate spaced apart from each other by about tens to hundreds of microns. A supply roller7esupplies toner in the developing device710to a surface of the developing roller7b. A supply bias voltage for supplying toner in the developing device710to a surface of the developing roller7bmay be applied to the supply roller7e.

The exposure device720forms an electrostatic latent image on the photosensitive drum7aby irradiating light modulated according to image information on the photosensitive drum7a. As the exposure device720, a laser scanning unit (LSU) using laser diode as a light source, a light-emitting diode (LED) exposure device using an LED as a light source, or the like may be used.

The transfer device may include an intermediate transfer belt731, a first transfer roller732, and a second transfer roller733. A toner image developed on photosensitive drums7aof the four developing devices710is temporarily transferred to the intermediate transfer belt731. The intermediate transfer belt731is circulated while being supported by supporting rollers734,735, and736. Four first transfer rollers732are disposed at locations facing the photosensitive drums7aof the four developing devices710with the intermediate transfer belt731therebetween. A first transfer bias voltage for first transferring a toner image developed on the photosensitive drum7ato the intermediate transfer belt731is applied to the four first transfer rollers732. The second transfer roller733faces the intermediate transfer belt731. A second transfer bias voltage for transferring the toner image first transferred to the intermediate transfer belt731to the paper P is applied to the second transfer roller733.

Upon receiving a printing command from a host (not shown), a controller (not shown) charges a surface of the photosensitive drum7ato a uniform potential via the charging roller7c. The exposure device720forms an electrostatic latent image on the photosensitive drum7aby scanning four light beams modulated according to image information of each color to the photosensitive drums7aof the four developing devices710. The developing roller7bdevelops the electrostatic latent image into a visible toner image by supplying C, M, Y, K toner to corresponding photosensitive drums7a, respectively. Developed toner images are firstly transferred to the intermediate transfer belt731. The paper P is transported from the paper feeder1to a transfer nip formed by the second transfer roller733and the intermediate transfer belt731. The toner images firstly transferred on the intermediate transfer belt731are secondly transferred to the paper P by the second transfer bias voltage applied to the second transfer roller733. When the paper P passes through the fusing device740, the toner images are fused to the paper P by heat and pressure. The paper P on which fusing has been performed is externally discharged by the discharge roller750.

The scanner600and the image forming apparatus700may each be used separately or may be combined with each other to be used in the form of a multifunctional apparatus.FIG. 17is a schematic diagram of an all-in-one device according to an embodiment.

Referring toFIG. 17, the scanner600is disposed on the printing unit700a. Structures of the scanner600and the printing unit700aare the same as those shown inFIGS. 15 and 16. The paper feeder1that supplies the paper P to the printing unit700amay be realized in various forms. For example, the paper feeder1shown inFIGS. 1 to 11may be used in the form of a MPT located at a side portion of the printing unit700aas shown inFIG. 16, a main cassette feeder810installed under the printing unit700a, a secondary cassette feeder820installed under the main cassette feeder810, a high capacity feeder830installed below the main cassette feeder810or under the secondary cassette feeder820, a high capacity feeder840installed at a side portion of the printing unit700a, or the like.