OPERATION OF IMAGE FORMING APPARATUS BACKGROUND

[01] An example of an image forming apparatus, which is an apparatus performing generation, printing, reception, transmission, or the like, of image data, may include a printer, a copy machine, a facsimile, a multi-function printer in which functions of the printer, the copy machine, the facsimile are integrated, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[02] FIG. 1 is a block diagram illustrating components of an image forming apparatus according to an example of the disclosure;

[03] FIG. 2 is a view schematically illustrating the image forming apparatus of FIG. 1 ;

[04] FIG. 3 is a view schematically illustrating an example of a feeding apparatus according to an example of the disclosure;

[05] FIG. 4 is a view for describing feeding of papers having different feeding start points in time when the feeding apparatus according to an example of the disclosure performs a reverse rotation operation for a predetermined time;

[06] FIG. 5A includes views for describing operations of the feeding apparatus depending on P1 illustrated in FIG. 4;

[07] FIG. 5B includes views for describing operations of the feeding apparatus depending on P2 illustrated in FIG. 4;

[08] FIG. 5C includes views for describing operations of the feeding apparatus depending on P4 illustrated in FIG. 4;

[09] FIG. 6 is a perspective view of the feeding apparatus according to an example of the disclosure;

[10] FIG. 7A is a view for describing an operation in which the feeding apparatus according to an example of the disclosure feeds a paper in a feeding direction;

[1 1] FIG. 7B is a view for describing an operation in which the feeding apparatus according to an example of the disclosure reversely feeds a paper in an opposite direction to the feeding direction;

[12] FIG. 8A is a view for describing operations of the feeding apparatus for P1 , P2, and P3 illustrated in FIG. 4;

[13] FIG. 8B is a view for describing operations of the feeding apparatus for P4 illustrated in FIG. 4;

[14] FIG. 9A is a view for describing an operation in which a feeding apparatus according to another example of the disclosure feeds a paper in a feeding direction;

[15] FIG. 9B is a view for describing an operation in which the feeding apparatus according to another example of the disclosure reversely feeds a paper in an opposite direction to the feeding direction;

[16] FIG. 10A is a view for describing operations of the feeding apparatus for P1 , P2, and P3 illustrated in FIG. 4;

[17] FIG. 10B is a view for describing operations of the feeding apparatus for P4 illustrated in FIG. 4;

[18] FIG. 11 is a view for describing feeding of papers having different feeding start points in time when the feeding apparatus according to an example of the disclosure performs a reverse rotation operation on a paper passing through a sensor for a predetermined time; and

[19] FIG. 12 is a flow chart illustrating a method of feeding a paper in an image forming apparatus according to the disclosure.

DETAILED DESCRIPTION

[20] An image forming apparatus according to the related art prints an image as it is without taking a separate measure in the case in which two or more printing papers overlap each other and are doubly fed on a feeding path.

[21] Therefore, a printing defect that an image corresponding to one page is printed on the two or more printing papers occurs, and since a user should find and remove pages for which a printing defect occurs one by one and reprint the corresponding page, printing papers, ink, and toner are wasted, and there is an inconvenience due to the reprint.

[22] Hereinafter, various examples will be described in detail with reference to the drawings. Examples described below may be modified into several different forms. To clearly describe features of examples, a detailed description for contents well-known to those skilled in the art to which the following examples belong will be omitted.

[23] Meanwhile, when any component is referred to as being“connected to” another component in the specification, it means that any component and another component are“directly connected to” each other or are“connected to” each other with the other component interposed therebetween. In addition, when any component is referred to as“including” another component, it means the inclusion of other components rather than the exclusion of other components, unless explicitly described to the contrary.

[24] In the specification, an“image forming job” may refer to various jobs (for example, printing, scanning, or faxing) related to an image, such as forming of the image, creating/storing/transmitting of an image file, or the like, and a“job” may refer to the image forming job, and may also include a series of processes for performing the image forming job.

[25] In addition, the“image forming apparatus” refers to an apparatus that prints a printing data created in a terminal apparatus such as a computer on a recording paper. An example of such an image forming apparatus may include a copier, a printer, a facsimile, a multi-function printer (MFP) in which functions of the copier, the printer, and the facsimile are complexly implemented through one apparatus, or the like. The image forming apparatus may refer to all apparatuses that may perform the image forming job, such as a printer, a scanner, a fax machine, an MFP, a display apparatus, or the like.

[26] In addition, a“hard copy” may refer to an operation of outputting an image on a printing medium such as a paper, or the like, and a“soft copy” may refer to an operation of outputting an image on a display apparatus such as a television, a monitor, or the like.

[27] Further,“contents” may refer to all kinds of data that become targets of the image forming job, such as a photograph, an image, a document file, or the like.

[28] Further, a“printing data” may refer to a data converted into a format printable in a printer. Meanwhile, when the printer supports direct printing, a file itself may be the printing data.

[29] Further, a“user” may refer to a person performing a manipulation related to the image forming job using the image forming apparatus or using a device connected to the image forming apparatus in a wired or wireless manner. Further, a“manager” may refer to a person having an authority to access all functions and systems of the image forming apparatus. The“manager” and the “user” may be the same person.

[30] FIG. 1 is a block diagram illustrating components of an image forming apparatus according to an example of the disclosure.

[31] Referring to FIG. 1 , an image forming apparatus 100 includes a printing engine 110, a feeding apparatus 1 , and a processor 140.

[32] The printing engine 110 performs an image forming job. In detail, the printing engine 110 may perform the image forming job by performing an operation of forming an image on an image forming medium and transferring the formed image to a printing paper. Detailed components and operations of the printing engine 110 will be described below with reference to FIG. 2.

[33] The feeding apparatus 1 moves loaded printing papers to a feeding path. In detail, the feeding apparatus 1 may pick up the printing paper loaded in a cassette 10 (see FIG. 2) and feed the picked-up printing paper to the feeding path, for the printing paper to be fed to the printing engine 110. To this end, the feeding apparatus 1 may include at least one driving source, a plurality of rollers, and the like. Detailed components and operations of the feeding apparatus 1 will be described below with reference to FIG. 3. [34] The processor 140 controls the respective components in the image forming apparatus 100. In detail, when the processor 140 receives a printing data from a printing control terminal apparatus, the processor 140 may control an operation of the printing engine 110 to print the received printing data, and control the feeding apparatus 1 to provide the printing paper to the printing engine 110.

[35] The processor 140 may control the feeding apparatus 1 to fundamentally improve separation efficiency between papers S to prevent double feed.

[36] In more detail, the processor 140 may control the feeding apparatus 1 to feed the printing paper S in a feeding direction in a process of picking up the printing paper S, control the feeding apparatus 1 to move the printing paper S in an opposite direction to the feeding direction for a predetermined time, and then control the feeding apparatus 1 to again move the printing paper S in the feeding direction.

[37] The processor 140 may control the feeding apparatus 1 to rotate both of a retard roller 40 and a feeding roller 30 in the opposite direction to the feeding direction for a predetermined time.

[38] The processor 140 may control the feeding apparatus 1 to reversely feed the printing paper passing between the retard roller 40 and the feeding roller 30 per feeding period of the printing paper in the opposite direction to the feeding direction.

[39] The image forming apparatus forming an image on the printing paper fed at a constant speed forms the image with a feeding time, that is, a feeding period, of the printing paper. The feeding period is determined depending on the feeding speed of the printing paper, and a speed of the printing paper fed at the feeding period needs to be constant.

[40] The feeding speed of the paper is controlled through an arrival time T3 (see FIG. 4) in which the printing paper S arrives at a position at which it is sensed by a sensor 50. In this way, a paper interval may be maintained without overlap with the preceding paper. The feeding speed may be adjusted by retarding a pick-up timing or increasing the feeding speed of the paper depending on a state where the paper is sensed by the sensor 50.

[41] The feeding period of the printing paper may be changed depending on a method of controlling power connection between the driving source and the rollers.

[42] In the case in which a front end of the printing paper S passes through the retard roller 40 and the feeding roller 30, the picked-up printing paper S may be reversely fed in the opposite direction to the feeding direction per feeding period. In the case in which the front end of the printing paper S does not pass through the retard roller 40 and the feeding roller 30, the picked-up printing paper S may be stopped.

[43] The retard roller 40 and the feeding roller 30 may periodically rotate reversely in the opposite direction to the feeding direction depending on the feeding period.

[44] The feeding apparatus 1 needs to rotate the retard roller 40 and the feeding roller 30 in the opposite direction to the feeding direction per predetermined period to prevent double feed of two or more papers S.

[45] The processor 140 may control the feeding apparatus 1 to again feed the printing paper S fed in the opposite direction to the feeding direction for the predetermined time in the feeding direction.

[46] When a printing job is executed, the processor 140 may control rotation levels of the retard roller 40 and the feeding roller 30 in the opposite direction to the feeding direction depending on whether or not the sensor 50 outputs a sensed signal.

[47] When the printing paper S is not sensed by the sensor 50, the processor 140 may control the feeding apparatus 1 to rotate both of the retard roller 40 and the feeding roller 30 in the opposite direction to the feeding direction for a predetermined time.

[48] When the printing paper S is sensed by the sensor 50, the processor 140 may control the feeding apparatus 1 to reversely rotate both of the retard roller 40 and the feeding roller 30 until the printing paper is not again sensed by the sensor 50, and then reversely rotate both of the retard roller 40 and the feeding roller 30 for a predetermined time.

[49] The processor 140 may control the feeding apparatus 1 to again feed the printing paper S fed in the opposite direction to the feeding direction for the predetermined time in the feeding direction until the printing paper is sensed by the sensor 50, stop the printing paper for a predefined time, and then feed the printing paper in the feeding direction.

[50] In the case in which the printing paper S is not sensed by the sensor 50, the processor 140 may control the feeding roller 30 and the retard roller 40 to rotate in the feeding direction. In addition, in the case in which the printing paper S is sensed by the sensor 50, the processor 140 may control the feeding apparatus 1 to rotate both of the retard roller 40 and the feeding roller 30 in the opposite direction to the feeding direction until the printing paper S is not sensed by the sensor 50, and then rotate both of the retard roller 40 and the feeding roller 30 in the opposite direction to the feeding direction for a predetermined time.

[51] Detailed operations related to such a feeding control will be described with reference to FIG. 2.

[52] Meanwhile, components of the image forming apparatus are illustrated and described hereinabove, but various components may be further included in the image forming apparatus at the time of implementing the image forming apparatus. For example, in the case in which the image forming apparatus 100 supports a scan function, a scan portion may be further included in the image forming apparatus 100, in the case in which the image forming apparatus 100 has a fax transmitting/receiving function, a fax transmitting/receiving portion may be further included in the image forming apparatus 100, and a component such as a touch screen for displaying a state of the image forming apparatus may be further included in the image forming apparatus 100.

[53] FIG. 2 is a view schematically illustrating the image forming apparatus of FIG. 1. Hereinafter, the image forming apparatus 100 including the feeding apparatus according to an example of the disclosure will be described.

[54] Referring to FIG. 2, the image forming apparatus 100 according to an example of the disclosure includes the feeding apparatus 1 , the printing engine 110, and an output portion 190.

[55] The feeding apparatus 1 accommodates a predetermined number of printing papers S therein, and is formed to pick up the printing papers S one by one and feed the picked-up paper to the printing engine 110.

[56] The printing engine 110 forms a predetermined image on the printing paper S fed from the feeding apparatus 1. The printing engine 110 may include a photosensitive drum 111 , a charger 112, an exposing device 113, a developing device 114, a transferring device 115, and a fusing device 118. Meanwhile, a case in which the printing engine 110 and the feeding apparatus 1 are different components is illustrated, but the feeding apparatus 1 may be one component in the printing engine 110.

[57] An electrostatic latent image is formed in the photosensitive drum 111 . In detail, an image may be formed in the photosensitive drum 111 by operations of a charger 112 and an exposing device 113 to be described below. The photosensitive drum 111 may be called an image forming medium, a photosensitive drum, a photosensitive belt, or the like, depending on its form.

[58] Hereinafter, components of the printing engine 110 corresponding to one color are described by way of example for ease of explanation, but the printing engine 110 may include a plurality of photosensitive drums 111 , a plurality of chargers 112, a plurality of exposing devices 113, a plurality of developing devices 114, and an intermediate transferring belt at the time of being implemented.

[59] The charger 112 charges a surface of the photosensitive drum 111 with a uniform potential. The charger 112 may be implemented in a form such as a Corona charger, a charging roller, a charging brush, or the like.

[60] The exposing device 113 forms the electrostatic latent image on the surface of the photosensitive drum 111 by changing surface potential of the photosensitive drum 111 depending on image information to be printed. As an example, the exposing device 113 may form the electrostatic latent image by irradiating modulated light to the photosensitive drum 111 depending on the image information to be printed. The exposing device 113 having such a form may be called a light scanner, or the like, and may use a light emitting diode (LED) as a light source.

[61] The developing device 114 accommodates a developer therein, and supplies the developer (for example, a toner) to the electrostatic latent image to develop the electrostatic latent image into a visible image. The developing device 114 may include a developing roller 117 supplying the developer to the electrostatic latent image. For example, the developer may be supplied from the developing roller 117 to the electrostatic latent image formed on the photosensitive drum 111 by a developing electric field formed between the developing roller 117 and the photosensitive drum 111 .

[62] The visible image formed on the photosensitive drum 111 is transferred to the printing paper by the transferring device 115 or the intermediate transferring belt (not illustrated). The transferring device 115 may transfer the visible image to the printing paper in, for example, an electrostatic transferring manner. The visible image is attached to the printing paper by electrostatic attractive force.

[63] The fusing device 118 fuses the visible image to the printing paper by applying heat and/or pressure to the visible image on the printing paper. A printing job is completed by a series of processes as described above.

[64] Meanwhile, the feeding apparatus 1 may perform an operation of rotating each component of the printing engine 110 described above. Meanwhile, at the time of implementation, one feeding apparatus 1 may simultaneously rotate a plurality of components of the printing engine 110 described above or a plurality of motors may be combined with one another to rotate the plurality of components described above.

[65] In addition, the feeding apparatus 1 according to the disclosure may also be applied to an inkjet printer. Therefore, although not illustrated, the printing engine 110 may be formed of an ink spraying head spraying a predetermined ink depending on a printing data.

[66] The output portion 190 outputs the printing paper having a predetermined image formed while passing through the printing engine 110 to the outside of the image forming apparatus 110. The output portion 190 may include a plurality of output rollers.

[67] The feeding apparatus 1 according to an example of the disclosure, which is to improve separation efficiency between papers, may also be applied to a large capacity feeding apparatus provided separately from an automatic paper scanning apparatus of scanning printing papers of which non-feed, a jam, double feed, or the like, is problematic and an image forming apparatus.

[68] The feeding apparatus according to an example of the disclosure as described above, in the image forming apparatus including the feeding apparatus, the separation efficiency between the papers may be improved to prevent the double feed of the papers in advance, such that damage to the driving source of the feeding apparatus or the motor due to an overload may be prevented, and a double feed phenomenon occurring in the image forming apparatus may be prevented in advance to prevent damage to the components.

[69] As described above, the disclosure may be applied to a C path-type image forming apparatus as well as an S path-type image forming apparatus. Meanwhile, a case in which one loading box is included in the image forming apparatus is illustrated and described in the illustrated example, but a plurality of loading boxes may be provided in the image forming apparatus, and the feeding apparatus 1 may provide printing papers in the respective loading boxes to the printing engine 110.

[70] Hereinafter, a detailed structure in which the feeding apparatus according to an example of the disclosure may separate papers to prevent the double feed will be described.

[71] FIG. 3 is a view schematically illustrating an example of a feeding apparatus according to an example of the disclosure.

[72] Referring to FIG. 3, the feeding apparatus 1 according to an example of the disclosure may include a cassette 10, a pick-up roller 20, a feeding roller 30, a retard roller 40, and a pressure sensor 50 sensing pressure between the feeding roller 30 and the retard roller 40.

[73] The cassette 10 loads printing papers S, and is formed to accommodate a predetermined number of printing papers S therein.

[74] The pick-up roller 20 is installed above the cassette 10, picks up the loaded paper S, and feeds the picked-up paper toward the feeding roller 30. The pick-up roller 20 is formed to move a paper S1 positioned at the uppermost portion among the papers S loaded in the cassette 10 toward the feeding roller 30.

[75] The pick-up roller 20 reciprocates between a pick-up position for picking up the paper S loaded in the cassette 10 and a spacing position for spacing the pick-up roller 20 apart from the paper S. The pick-up roller 20 may be positioned at the pick-up position when it performs a feeding operation, and may be positioned at the spacing position when it does not perform the feeding operation.

[76] The feeding roller 30 is installed at a front end of the cassette 10, and moves the paper S loaded in the cassette 10 toward transmitting rollers 60. In detail, the feeding roller 30 is formed to move the paper S picked up by the pick- up roller 20 in the cassette 10 toward the transmitting rollers 60.

[77] The transmitting rollers 60 are a pair of rollers rotating while facing each other, and move the paper S fed by the feeding roller 30 to the printing engine 110.

[78] The retard roller 40 is provided to prevent the double feed of the printing papers S fed from the cassette 10 while facing the feeding roller 30.

[79] The retard roller 40 is rotatable in a forward direction or a reverse direction with respect to a shaft 42. The retard roller 40 is rotatably coupled to a hinge portion 44 to be movable to a pressing position at which it presses the feeding roller 30 and a pressing release position at which it is spaced apart from the feeding roller. The retard roller 40 may rotate to press the feeding roller 30 or release the pressing of the feeding roller 30 depending on a movement of a link 46 of which one end is fixed to the hinge portion 44.

[80] In the case in which two or more papers are fed in a state where the retard roller 40 presses the feeding roller 30, the retard roller 40 separates the papers from each other to allow only one paper to be fed to the printing engine 110.

[81] The retard roller 40, which applies a predetermined pressure to the printing paper S passing between the feeding roller 30 and the retard roller 40, may be formed in a roller shape. The retard roller 40 is elastically deformed to form a feeding nib through which the printing paper S passes, between the retard roller 40 and the feeding roller 30.

[82] In the related art, rotation directions of the feeding roller 30 and the retard roller 40 are opposite to each other. Therefore, in the case in which two printing papers are picked up by the pick-up roller 20, one of the two printing papers is normally fed by the feeding roller 30, but the other of the two printing papers is returned to the pick-up roller 20 by the retard roller 40.

[83] The feeding apparatus according to the related art as described above may return one paper positioned at the lowermost portion among several papers entering the feeding nib between the feeding roller 30 and the retard roller 40 up to the upstream immediately before the feeding nib. However, due to one paper positioned at the lowermost portion, fed to the upstream immediately before the feeding nib, the next papers sequentially entering the feeding nip may not be reversely fed, and a plurality of papers may become in a bundle state to remain in a wedge shape in the upstream of the retard roller 40. The papers reversely fed and becoming in the bundle state may be doubly fed, and are fed in the bundle state, such that a printing defect occurs.

[84] To avoid such defects, the feeding apparatus 1 according to an example of the disclosure, which is to improve capability to separate the printing papers without decreasing productivity, feeds the printing paper S in the opposite direction to the feeding direction during a predetermined condition after the printing paper S is picked up. The image forming apparatus of which capability to separate the papers from each other is fundamentally improved by separating the papers while reversely feeding the picked-up paper may be provided.

[85] The image forming apparatus 100 according to an example of the disclosure includes the feeding apparatus 1 having a structure and an operation sequence capable of moving the printing paper S entering the feeding roller 30 and the retard roller 40 in the opposite direction to the feeding direction per fed printing paper. The double feed or the printing defect is decreased through effective paper separation of the feeding apparatus 1 .

[86] The feeding apparatus 1 according to the disclosure may include the sensor 50.

[87] The sensor 50 is positioned at an upstream portion of the feeding roller 30, that is, a front end of the feeding roller, and may sense whether or not the paper is positioned at a predetermined position in the feeding direction.

[88] The sensor 50 may decide whether or not the paper normally progresses to the transmitting rollers 60 by sensing the paper passing through the feeding roller 30 and the retard roller 40. When the sensor 50 recognizes the paper, the sensor 50 is continued in a turn-on state. The processor 140 may decide that a front end of the paper S passes through the sensor 50 in the case in which the sensor 50 is changed from a turn-off state into the turn-on state.

[89] The processor 140 may decide that the front end of the paper S is positioned at the downstream of the sensor 50 when the sensor 50 is in the turn-off state.

[90] In addition, paper sensing sensors may be additionally disposed on a paper moving path to confirm whether or not the paper is normally fed in a paper feeding process. The processor 140 may decide whether or not the printing paper is normally fed depending on signals output from a plurality of paper sensing sensors.

[91] Here, the feeding apparatus may further include a registration sensor for providing the printing paper to the printing engine 110 at an accurate point in time. [92] The feeding apparatus 1 of the image forming apparatus 100 may be controlled to reversely feed the paper in the opposite direction to the feeding direction per fed paper regardless of a position of the front end of the picked-up printing paper s, in a method of feeding the printing paper s.

[93] Meanwhile, the feeding apparatus may also be controlled to reversely feed the paper in the case in which the front end of the paper S passes through the sensor 50 depending on the position of the front end of the picked-up printing paper S. This will be described below with reference to FIG. 11.

[94] The processor 140 may control the feeding apparatus 1 to reversely feed the printing paper S passing between the retard roller 40 and the feeding roller 30 in the opposite direction to the feeding direction per predetermined period. The predetermined period may be set to a feeding period depending on a feeding speed of the printing paper.

[95] The feeding apparatus 1 may reversely feed all the printing papers S passing through the retard roller 40 and the feeding roller 30 in the opposite direction to the feeding direction regardless of the position of the front end of the picked-up paper S to improve the separation performance. The processor 140 may control the feeding apparatus 1 to reversely feed each printing paper S passing between the retard roller 40 and the feeding roller 30. That is, each of the picked-up printing papers S is reversely fed in the opposite direction to the feeding direction per paper passing through the retard roller 40 and the feeding roller 30. An operation of feeding the paper S by the feeding apparatus 1 will be described in detail with reference to FIGS. 4, and 5A to 5C.

[96] The processor 140 may control the feeding apparatus 1 to again feed the printing paper S fed in the opposite direction to the feeding direction for the predetermined time in the feeding direction.

[97] Meanwhile, since the printing papers are picked up in the cassette by the roller and are provided to the printing engine 110 as described above, when coated papers, tracing papers, papers having many perforated lines, or the like, which are printing papers having a high frictional coefficient, are used, a frictional coefficient between the papers is increased, such that it is likely that double feed of the papers will occur. When the double feed of the papers occurs, a front end margin defect occurs or a jam occurs.

[98] In the feeding apparatus 1 , the double feed that two or more printing papers S are simultaneously fed may occur due to static electricity generated between the papers S, which are printing media, a change in frictional force between the printing paper S and the pick-up roller 20, or the like. The double feed may cause a jam phenomenon that the paper is jammed in the image forming apparatus 100, resulting in reduction of feeding reliability.

[99] To prevent the double feed phenomenon occurring in the feeding apparatus 1 according to an example of the disclosure, the feeding roller 30 feeding the printing papers S to the printing engine 110 is disposed above the feeding path through which the printing papers S are fed, and a torque in an opposite direction to the feeding path may be applied to the feeding roller 30 and the retard roller 40 disposed below the feeding path for a predetermined time to effectively separate the papers from each other, thereby preventing two or more printing papers S from being simultaneously fed into the image forming apparatus 100.

[100] FIG. 4 is a view for describing feeding of papers having different feeding start points in time when the feeding apparatus according to an example of the disclosure performs a reverse rotation operation for a predetermined time, and FIGS. 5A to 5C are views for describing operations of the feeding apparatus depending on P1 to P4 illustrated in FIG. 4.

[101] Referring to FIG. 4, P1 illustrates processes of feeding the paper S in the case P1 in which the front end of the picked-up paper S is positioned at the downstream immediately before the pick-up roller 20 and the feeding nib, P2 illustrates processes of feeding the paper S in the case P2 in which the front end of the paper S is positioned between the feeding roller 30 and the retard roller 40, and P3 illustrates processes of feeding the paper S in the case P3 in which the front end of the paper S is positioned at the downstream immediately before the sensor 50. P4 illustrates processes of feeding the paper S in the case P4 in which the front end of the picked-up paper S passes through the sensor 50.

[102] First, the processes of feeding the paper S in the case P1 in which the front end of the picked-up paper S is positioned at the downstream immediately before the pick-up roller 20 and the feeding nib will be described with reference to P1 of FIG. 4 and FIG. 5A.

[103] In this case, the paper S is not detected by the sensor 50.

[104] The feeding roller 30 and the retard roller 40 may rotate in the opposite direction to the feeding direction to feed the paper S in the opposite direction to the feeding direction for a predetermined time T1 . However, in this case, the paper S is not positioned between the feeding roller 30 and the retard roller 40, and is thus positioned in place in a stop state. That is, the feeding roller 30 and the retard roller 40 rotate in the opposite direction to the feeding direction, but the paper s is maintained in the stop state.

[105] The paper S is stopped for a predefined time T2, and is then fed again in the feeding direction until it is sensed by the sensor 50.

[106] When the fed paper S is sensed by the sensor 50, the paper S is stopped for a predefined time T31 , and is then fed toward the printing engine 110 in the feeding direction at a point in time in which it is to be fed.

[107] To maintain a paper interval between the papers S, the paper S may be fed from a pick-up process and arrive at the sensor 50 for a predetermined time T3. To adjust the predetermined time T3, the paper S may be stopped for the predefined time S31 after it arrives at the sensor 50, and be then fed again.

[108] Next, processes of feeding the paper S in the cases P2 and P3 in which the front end of the picked-up paper S is positioned between the upstream immediately before the feeding nib and the downstream immediately before the sensor 50 will be described with reference to P2 and P3 of FIG. 4 and FIG. 5B.

[109] Since the front end of the paper S is positioned at the upstream immediately before the feeding nib, the paper S may be fed in the opposite direction to the feeding direction depending on the reverse rotation of the feeding roller 30 and the retard roller 40. In addition, since the front end of the paper S is positioned at the downstream immediately before the sensor 50, the paper S is not detected by the sensor 50.

[1 10] The feeding apparatus 1 feeds the paper S in the opposite direction to the feeding direction for a predetermined time T1. Thereafter, the feeding apparatus 1 again feeds the reversely fed paper S in the feeding direction until the paper S is sensed by the sensor 50, after a predefined time T2 elapses. When the fed paper S is sensed by the sensor 50, the feeding apparatus 1 stops the paper S for a predefined time T32 or T33, and then feeds again the paper toward the printing engine 110 in the feeding direction at a point in time T3 in which the paper is to be fed.

[1 1 1] A paper S that is not sensed by the sensor 50 among the printing papers S passing between the feeding roller 30 and the retard roller 40 is reversely fed for a predetermined time T1 , and the printing paper S may pass between the feeding roller 30 and the retard roller 40 for this time T1 . The predetermined time T1 may be calculated in advance in the image forming apparatus 100 using the feeding speed and a moving distance of the printing paper.

[1 12] The retard roller 40 may rotate in the opposite direction to the feeding direction for a predetermined time to reversely feed the paper S. Likewise, the feeding roller 30 may also rotate together with the retard roller 40 in the opposite direction to the feeding direction for a predetermined time. A plurality of papers may be reversely fed to be certainly returned by rotating the feeding roller 30 and the retard roller 40 together in the opposite direction to the feeding direction.

[1 13] When the papers S are reversely fed, the retard roller 40 becomes a driving side and the feeding roller 30 becomes a driven side, and largest return force thus acts on a paper S2 disposed at the lowermost portion, in direct contact with the retard roller 40 in a paper bundle. Therefore, even when the papers S are reversely fed, separation between the papers of the paper bundle occurs. That is, even when the papers S are returned in the opposite direction to the feeding direction, the papers may be separated from each other, such that the double feed of the papers may be effectively prevented. [1 14] In addition, the papers may be reversely fed so that the paper bundle passes through the feeding nib, thereby rotating the retard roller 40 in the feeding direction in a state where the paper bundle is not in contact with the retard roller 40. Therefore, in the feeding apparatus according to the related art, a situation that the remaining paper bundle other than a paper disposed at the uppermost portion, separated and then fed by the retard roller is in contact with the surface of the retard roller 40 to stop the rotation of the retard roller 40 may be prevented.

[1 15] The reversely fed papers S are again fed in the feeding direction, and when the papers are fed in the feeding direction, the feeding roller 30 becomes a driving side and the retard roller 40 becomes a driven side, and largest feeding force thus acts on a paper S1 disposed at the uppermost portion, in direct contact with the feeding roller 30 in the paper bundle. Therefore, even when the papers S are fed, separation between the papers of the paper bundle occurs once more.

[1 16] The paper S stopped for a predetermined time T1 is fed again in the feeding direction until it is sensed by the sensor 50, after a predefined time T2 elapses. When the fed paper S is sensed by the sensor 50, the paper S is stopped for a predefined time T32 or T33, and is then fed again toward the printing engine 110 in the feeding direction at a point in time in which it is to be fed.

[1 17] FIG. 5B illustrates feeding of the paper S in the case P2 in which the front end of the paper S is positioned between the feeding roller 30 and the retard roller 40. However, when the front end of the paper is positioned between a space between the feeding roller 30 and the retard roller 40 and the downstream immediately before the sensor 50, an operation of feeding the paper and driving of the feeding apparatus 1 for feeding the paper S are the same as each other, and a description for the case P3 in the case in which the front end of the paper is positioned at the downstream immediately before the sensor 50 is thus omitted.

[1 18] Finally, processes of feeding the paper S in the case P4 in which the front end of the picked-up paper passes through the sensor 50 will be described with reference to FIGS. 4 and 5C.

[1 19] Since the front end of the paper S may be positioned at the upstream immediately before the sensor 50, the paper S is detected by the sensor 50.

[120] The feeding apparatus 1 reversely feeds the paper S in the opposite direction to the feeding direction until the sensor 50 does not sense the paper S. When the paper S is not sensed by the sensor 50 due to the reverse feeding, the feeding apparatus 1 feeds the paper S in the opposite direction to the feeding direction for a predetermined time T1 as in the processes of feeding the papers of P2 and P3.

[121] The feeding apparatus 1 again feeds the reversely fed paper S in the feeding direction until the paper S is not sensed by the sensor 50, after a predefined time T2 elapses. When the fed paper S is sensed by the sensor 50, the paper S is stopped for a predefined time T34, and is then fed toward the printing engine 110 in the feeding direction at a point in time in which it is to be fed.

[122] The paper S of which a portion passes through the sensor 50 is reversely fed until the sensor 50 does not sense the paper S, and is fed as in P2 when the sensor 50 is turned off. That is, the paper S reversely fed until it is not sensed by the sensor 50 is further reversely fed for a predetermined time T 1.

[123] The retard roller 40 rotates in the opposite direction to the feeding direction for a time until the paper S is not sensed by the sensor 50 and the predetermined time T1 , to reversely feed the paper S. Likewise, the feeding roller 30 also rotates together with the retard roller 40 in the opposite direction to the feeding direction. Even when the papers S are returned in the opposite direction to the feeding direction, the papers may be separated from each other, such that the double feed of the papers may be effectively prevented.

[124] The reversely fed papers S are again fed in the feeding direction, and even when the papers S are again fed in the feeding direction, separation between the papers in the paper bundle occurs. [125] A time in which the retard roller 40 and the feeding roller 30 reversely rotate may be determined depending on a feeding start position of the paper S through a sensed signal output of the sensor 50.

[126] In detail, when the picked-up paper S is not sensed by the sensor 50, the feeding roller 30 and the retard roller 40 may rotate in the opposite direction to the feeding direction to feed the paper S in the opposite direction to the feeding direction for a predetermined time T1. When the picked-up paper S is sensed by the sensor 50, the feeding roller 30 and the retard roller 40 may rotate in the opposite direction to the feeding direction to feed the paper S in the opposite direction to the feeding direction until the paper S is not sensed by the sensor 50. Then, the feeding roller 30 and the retard roller 40 may rotate in the opposite direction to the feeding direction to feed the paper S in the opposite direction to the feeding direction as in the case in which the paper S is not sensed by the sensor 50.

[127] The feeding apparatus 1 according to an example of the disclosure may be used together with various double feed detecting apparatuses such as an ultrasonic wave type double feed detecting apparatus, a thickness change type double feed detecting apparatus, a retard roller operation change type double feed detecting apparatus, and the like, capable of sensing the double feed.

[128] When the double feed detecting apparatus is used together with the feeding apparatus according to an example of the disclosure, double feed that may occur even in the case in which a reverse feeding operation is performed on each of the fed papers may be detected, and when the double feed is detected, paper feeding may be rapidly stopped and a bundle of the doubly fed papers may be returned to the cassette 10, such that a lifespan of components configuring the feeding apparatus 1 may be increased.

[129] FIG. 6 is a perspective view of the feeding apparatus according to an example of the disclosure.

[130] Referring to FIG. 6, the feeding apparatus 1 according to an example of the disclosure may include the pick-up roller 20, the feeding roller 30, the retard roller 40, a feeding motor 120, a feeding clutch 150, a pick-up clutch 160, and the sensor 50.

[131] FIG. 6 is a view illustrating a detailed structure of the feeding apparatus 1 , and a description for the pick-up roller 20, the feeding roller 30, the retard roller 40, and the sensor 50 described above is omitted.

[132] The feeding motor 120 generates a torque capable of rotating the feeding roller 30, the pick-up roller 20, and the retard roller 40. The torque of the feeding motor 120 is transferred to the feeding roller 30 through the feeding clutch 150. For example, in the case in which the feeding clutch 150 is turned on, the torque of the feeding motor 120 is transferred to the feeding roller 30 and the pick-up roller 20, such that the feeding roller 30 and the pick-up roller 20 rotate. To the contrary, in the case in which the feeding clutch 150 is turned off, the torque of the feeding motor 120 is not transferred to the feeding roller 30, such that the feeding roller 30 and the pick-up roller 20 do not rotate. That is, the pick-up roller 20 is configured to rotate together with the feeding roller 30 when the feeding roller 30 rotates.

[133] The torque of the feeding motor 120 is transferred to a pick-up roller cam 161 through the pick-up clutch 160 to descend the pick-up roller 20. For example, when the pick-up clutch 160 is turned on, the torque of the feeding motor 120 is transferred to the pick-up roller cam 161 , such that the pick-up roller cam 161 rotates. The pick-up roller 20 descends by the rotation of the pick-up roller cam 161 to be in contact with the paper S of the cassette 10.

[134] To the contrary, in the case in which the pick-up clutch 160 is turned off, the torque of the feeding motor 120 is not transferred to the pick-up roller cam 161 , such that the pick-up roller cam 161 does not press the pick-up roller 20 downward. Therefore, the pick-up roller 20 is maintained in a state where it is spaced apart from the paper S of the cassette 10 by a pick-up roller spring 21.

[135] The feeding clutch 150 and the pick-up clutch 160 may be implemented by electronic clutches of which turn on/off may be controlled by the processor 140.

[136] The torque of the feeding motor 120 is transferred to the retard roller 40 to rotate the retard roller 40. The retard roller 40 is directly connected to the feeding motor 120, such that when the feeding motor 120 is operated, the retard roller 40 also rotates in one direction.

[137] In the case in which the paper S picked up in the cassette 10 is fed, the retard roller 40 rotates in the feeding direction of the paper by the rotation of the feeding roller 30 to feed the paper S toward the printing engine 110. The picked-up paper S is reversely fed in the opposite direction to the feeding direction for a predetermined time for separation between the papers S. To reversely feed the paper S, both of the retard roller 40 and the feeding roller 30 rotate in the opposite direction to the feeding direction of the paper to feed the paper S toward the cassette 10.

[138] The paper S reversely fed for the predetermined time is again fed in the feeding direction. Even in the case in which the paper is again fed in the feeding direction, the separation between the papers S occurs by the feeding roller 30 and the retard roller 40.

[139] The feeding roller 30 and the retard roller 40 may reversely rotate in the opposite direction to the feeding direction for a predetermined time T1 when the paper is picked up. The predetermined time T1 may be set to a time in which the front end of the paper S passes between the feeding roller 30 and the retard roller 40. The predetermined time T1 may be set so that the front end of the paper S may pass between the feeding roller 30 and the retard roller 40 in consideration of a kind of paper S, strength of the motor, and rotation levels of the rollers.

[140] FIG. 7A is a view for describing an operation in which the feeding apparatus according to an example of the disclosure feeds a paper in a feeding direction.

[141] Referring to FIG. 7A, the feeding motor 120 is turned on and the feeding clutch 150 is turned on, for the feeding apparatus 1 according to an example of the disclosure to feed the printing paper S in the feeding direction. In this case, the feeding motor 120 rotates, and a torque of the feeding motor 120 is transferred to the feeding roller 30 through the feeding clutch 150, such that the feeding roller 30 rotates.

[142] In this case, since the pick-up roller 20 is connected to the feeding roller 30, when the feeding roller 30 rotates, the pick-up roller 20 also rotates. In this case, the pick-up clutch 160 is turned on. Since the pick-up clutch 160 is in a turn-on state, the torque of the feeding motor 120 is transferred to the pick-up roller cam 161 , such that the pick-up roller cam 161 rotates. The pick-up roller 20 descends by the rotation of the pick-up roller cam 161 to be in contact with the paper S of the cassette 10.

[143] Therefore, the paper S of the cassette 10 is fed between the feeding roller 30 and the retard roller 40 by the rotation of the pick-up roller 20. In addition, since a retard roller cam 151 elevating the retard roller 40 is positioned at a position at which it does not press the retard roller 40, the retard roller 40 is pressed upward by an elastic member 41 to be in contact with the feeding roller 30 at a predetermined pressure.

[144] In this case, the torque of the feeding motor 120 is also transferred to a torque limiter installed coaxially with the retard roller 40. In this case, a torque in an opposite direction to a rotation direction of the feeding roller 30 is transferred to the torque limiter. However, since the feeding roller 30 and the retard roller 40 formed of rubber having a high frictional coefficient are in contact with each other and the torque limiter is configured to be slipped at a predetermined load or more, when the feeding roller 30 rotates, the retard roller 40 rotates depending on the feeding roller 30. For example, when the feeding roller 30 rotates in a clockwise direction, the retard roller 40 rotates in a counterclockwise direction by the feeding roller 30. That is, the feeding roller 30 and the retard roller 40 rotate in the feeding direction of the paper, respectively. Therefore, the paper S is fed in the feeding direction.

[145] FIG. 7B is a view for describing an operation in which the feeding apparatus according to an example of the disclosure reversely feeds a paper in an opposite direction to the feeding direction.

[146] Referring to FIG. 7B, the feeding clutch 150 is turned off and the feeding motor 120 is turned on, for a predetermined time T1 , for the feeding apparatus 1 according to an example of the disclosure to reversely feed the printing paper S in the opposite direction to the feeding direction. In this case, the feeding motor 120 rotates, but a torque of the feeding motor 120 is blocked by the feeding clutch 150, such that the torque of the feeding motor 120 is not transferred to the feeding roller 30. Therefore, the feeding roller 30 may freely rotate. In this case, since the pick-up roller 20 is connected to the feeding roller 30, when the feeding roller 30 does not rotate, the pick-up roller 20 does not also rotate.

[147] In addition, the pick-up clutch 160 is turned off. In this case, the pick-up roller 20 is maintained at a position to which it ascends by the pick-up roller spring 21 to be in a state where it is spaced apart from the paper S of the cassette 10. Therefore, even though the feeding motor 120 rotates, the paper S of the cassette 10 is not fed between the feeding roller 30 and the retard roller 40.

[148] In addition, since a retard roller cam 151 descending the retard roller 40 is positioned at a position at which it does not press the retard roller 40, the retard roller 40 is pressed upward by the elastic member 41 to be in contact with the feeding roller 30 at a predetermined pressure.

[149] In this case, the torque of the feeding motor 120 is transferred to the retard roller 40. In detail, when the feeding motor 120 rotates, the retard roller 40 rotates in the counterclockwise direction, which is the opposite direction to the feeding direction.

[150] Since the feeding roller 30 and the retard roller 40 are in contact with each other and the feeding roller 30 is in a state where it may freely rotate, when the retard roller 40 rotates, the feeding roller 30 rotates depending on the retard roller 40. For example, when retard roller 40 rotates in the clockwise direction, the feeding roller 30 rotates in the counterclockwise direction by the retard roller 40. That is, the retard roller 40 and the feeding roller 30 rotate in the opposite direction to the feeding direction, respectively. Therefore, the paper S is fed in the opposite direction to the feeding direction.

[151] FIG. 8A is a view for describing operations of the feeding apparatus 1 in the cases P1 , P2, and P3 in which the front end of the paper S is positioned at the downstream of the sensor 50.

[152] Referring to FIG. 8A, in the cases P1 , P2, and P3 in which the front end of the picked-up paper S is positioned at a position before it passes through the sensor 50, the feeding roller 30 and the retard roller 40 may reversely rotate in the opposite direction to the feeding direction for a predetermined time T1 for each of the fed papers S.

[153] In more detail, the feeding apparatus 1 feeds the printing paper S in the feeding direction in a process of picking up the printing paper S. Then, the feeding clutch 150 is turned off and the feeding motor 120 is turned on to reversely feed the paper S for the predetermined time T1 . In this case, the feeding motor 120 rotates, but the torque of the feeding motor 120 is blocked by the feeding clutch 150, such that the torque of the feeding motor 120 is not transferred to the feeding roller 30. Therefore, the feeding roller 30 may freely rotate. In this case, since the pick-up roller 20 is connected to the feeding roller 30, when the feeding roller 30 does not rotate, the pick-up roller 20 does not also rotate.

[154] In addition, the pick-up clutch 160 is turned off. In this case, the pick-up roller 20 is maintained at the position to which it ascends by the pick-up roller spring 21 to be in the state where it is spaced apart from the paper S of the cassette 10. Therefore, even though the feeding motor 120 rotates, the paper S of the cassette 10 is not fed between the feeding roller 30 and the retard roller 40.

[155] In addition, since a retard roller cam 151 descending the retard roller 40 is positioned at a position at which it does not press the retard roller 40, the retard roller 40 is pressed upward by the elastic member 41 to be in contact with the feeding roller 30 at a predetermined pressure.

[156] In this case, the torque of the feeding motor 120 is transferred to the retard roller 40. In detail, when the feeding motor 120 rotates, the retard roller 40 rotates in the counterclockwise direction, which is the opposite direction to the feeding direction. [157] Since the feeding roller 30 and the retard roller 40 are in contact with each other and the feeding roller 30 is in the state where it may freely rotate, when the retard roller 40 rotates, the feeding roller 30 rotates depending on the retard roller 40. For example, when retard roller 40 rotates in the clockwise direction, the feeding roller 30 rotates in the counterclockwise direction by the retard roller 40. That is, the retard roller 40 and the feeding roller 30 rotate in the opposite direction to the feeding direction, respectively. Therefore, the paper S may be stopped or reversely fed for the predetermined time T 1 .

[158] The sensor 50 is maintained in a turn-off state for the predetermined time T1.

[159] The paper S stopped or reversely fed by the reverse rotation of the feeding roller 30 and the retard roller 40 for the predetermined time T1 is stopped for a predefined time T2, and is again fed in the feeding direction until the paper S is sensed by the sensor 50. Driving of the feeding apparatus 1 feeding the stopped or reversely fed paper S in the feeding direction will be described. The feeding motor 120 is turned on, and the feeding clutch 150 is turned on. In this case, the feeding motor 120 rotates, and the torque of the feeding motor 120 is transferred to the feeding roller 30 through the feeding clutch 150, such that the feeding roller 30 rotates.

[160] In this case, since the pick-up roller 20 is connected to the feeding roller 30, when the feeding roller 30 rotates, the pick-up roller 20 also rotates. In this case, the pick-up clutch 160 is turned on. Since the pick-up clutch 160 is in the turn-on state, the torque of the feeding motor 120 is transferred to the pick-up roller cam 161 , such that the pick-up roller cam 161 rotates. The pick-up roller 20 descends by the rotation of the pick-up roller cam 161 to be in contact with the paper S of the cassette 10.

[161] Therefore, the paper S of the cassette 10 is fed between the feeding roller 30 and the retard roller 40 by the rotation of the pick-up roller 20. In addition, since the retard roller cam 151 elevating the retard roller 40 is positioned at the position at which it does not press the retard roller 40, the retard roller 40 is pressed upward by the elastic member 41 to be in contact with the feeding roller 30 at a predetermined pressure.

[162] In this case, the torque of the feeding motor 120 is also transferred to the torque limiter installed coaxially with the retard roller 40. In this case, the torque in the opposite direction to the rotation direction of the feeding roller 30 is transferred to the torque limiter. However, since the feeding roller 30 and the retard roller 40 formed of rubber having a high frictional coefficient are in contact with each other and the torque limiter is configured to be slipped at a predetermined load or more, when the feeding roller 30 rotates, the retard roller 40 rotates depending on the feeding roller 30. For example, when the feeding roller 30 rotates in the clockwise direction, the retard roller 40 rotates in the counterclockwise direction by the feeding roller 30. That is, the feeding roller 30 and the retard roller 40 rotate in the feeding direction of the paper, respectively. Therefore, the printing paper s moves in the feeding direction.

[163] To maintain a paper interval between the papers after the printing paper S is sensed by the sensor 50, the paper S is fed toward the printing engine 110 after a predetermined time T3 elapses. The paper S is stopped for times T31 , T32, and T33 from after the paper S is sensed by the sensor 50 until a time T3.

[164] In this case, the sensor 50 is maintained in a turn-off state for the times T31 , T32, and T33 until the time T3.

[165] To stop the paper S, the feeding clutch 150 is turned off and the feeding motor 120 is turned on. In this case, the feeding motor 120 rotates, but the torque of the feeding motor 120 is blocked by the feeding clutch 150, such that the torque of the feeding motor 120 is not transferred to the feeding roller 30.

[166] In addition, the pick-up clutch 160 is turned off. In this case, the pick-up roller 20 is maintained at the position to which it ascends by the pick-up roller spring 21 to be in the state where it is spaced apart from the paper S of the cassette 10. Therefore, even though the feeding motor 120 rotates, the paper S of the cassette 10 is not fed between the feeding roller 30 and the retard roller 40.

[167] When a time elapses from a feeding start point in time to arrive at the time T3 in a state where the paper S arrives at the sensor 50, the feeding apparatus 1 again moves the printing paper S in the feeding direction.

[168] FIG. 8B is a view for describing operations of the feeding apparatus 1 in the case in which feeding starts in a state where the front end of the paper S completely passes through the sensor 50.

[169] Referring to FIG. 8B, in the case in which the front end of the picked-up paper S is positioned in a state where it passes through the sensor 50, the feeding apparatus 1 may reversely feed the paper S until the front end of the paper S is positioned at the downstream of the sensor 50. The processor 140 may control the feeding roller 30 and the retard roller 40 to reversely rotate in the opposite direction to the feeding direction until the sensor 50 is turned off.

[170] An operation of the feeding apparatus 1 reversely feeding the paper S until the paper S is not sensed by the sensor 50 will be described.

[171] The feeding clutch 150 is turned off and the feeding motor 120 is turned on until the sensor 50 may not sense the paper S due to the reverse feeding of the paper S. In this case, the feeding motor 120 rotates, but the torque of the feeding motor 120 is blocked by the feeding clutch 150, such that the torque of the feeding motor 120 is not transferred to the feeding roller 30. Therefore, the feeding roller 30 may freely rotate. In this case, since the pick-up roller 20 is connected to the feeding roller 30, when the feeding roller 30 does not rotate, the pick-up roller 20 does not also rotate.

[172] In addition, the pick-up clutch 160 is turned off. In this case, the pick-up roller 20 is maintained at the position to which it ascends by the pick-up roller spring 21 to be in the state where it is spaced apart from the paper S of the cassette 10. Therefore, even though the feeding motor 120 rotates, the paper S of the cassette 10 is not fed between the feeding roller 30 and the retard roller 40.

[173] In addition, since a retard roller cam 151 descending the retard roller 40 is positioned at a position at which it does not press the retard roller 40, the retard roller 40 is pressed upward by the elastic member 41 to be in contact with the feeding roller 30 at a predetermined pressure.

[174] In this case, the torque of the feeding motor 120 is transferred to the retard roller 40. In detail, when the feeding motor 120 rotates, the retard roller 40 rotates in the counterclockwise direction, which is the opposite direction to the feeding direction.

[175] Since the feeding roller 30 and the retard roller 40 are in contact with each other and the feeding roller 30 is in the state where it may freely rotate, when the retard roller 40 rotates, the feeding roller 30 rotates depending on the retard roller 40. For example, when retard roller 40 rotates in the clockwise direction, the feeding roller 30 rotates in the counterclockwise direction by the retard roller 40. That is, the retard roller 40 and the feeding roller 30 rotate in the opposite direction to the feeding direction, respectively.

[176] After the sensor 50 is turned off due to the reverse feeding of the paper S, the paper S is reversely fed for a predetermined time T1 , is stopped for a predefined time T2, is fed in the feeding direction until the paper S is sensed by the sensor 50, is again stopped for a predefined time T34, and is then fed toward the printing engine 110 at a point in time in which the paper is to be fed, as in the case in which the front end of the paper S is positioned at the downstream of the sensor 50 as described in FIG. 8A. An operation of the feeding apparatus for feeding the paper S reversely fed until the sensor 50 is turned off is the same as that of the feeding apparatus 1 as described in FIG. 8A, and a description therefor is thus omitted.

[177] FIG. 9A is a view for describing an operation in which a feeding apparatus according to another example of the disclosure feeds a paper in a feeding direction, and FIG. 9B is a view for describing an operation in which the feeding apparatus according to another example of the disclosure reversely feeds a paper in an opposite direction to the feeding direction.

[178] A feeding apparatus 1 according to another example of the disclosure may include a pick-up roller 20, a feeding roller 30, a retard roller 40, a feeding motor 120, a retard motor 130, a pick-up clutch 160, and a sensor 50. [179] The pick-up roller 20, the feeding roller 30, the retard roller 40, and the sensor 50 are the same as those of the feeding apparatus 1 described in FIG. 6, and a description therefor is thus omitted.

[180] Referring to FIGS. 9A and 9B, the feeding motor 120 generates a torque capable of rotating the feeding roller 30 and the pick-up roller 20. The feeding motor 120 may selectively rotate in a forward direction or a reverse direction, and the feeding roller 30 and the pick-up roller 20 connected to the feeding motor 120 may also rotate in the forward direction or the reverse direction. Here, the terms “forward direction” and “reverse direction” are used to distinguish rotation directions from each other for convenience of explanation.

[181] In the case in which the feeding motor 120 rotates in the forward direction, a torque of the feeding motor 120 is transferred to the feeding roller 30 and the pick-up roller 20, such that the feeding roller 30 and the pick-up roller 20 rotate in the forward direction. That is, the feeding roller 30 and the pick-up roller 20 may rotate in the clockwise direction, which is the feeding direction of the paper, by the rotation of the feeding motor 120 in the forward direction. To the contrary, in the case in which the feeding motor 120 rotates in the reverse direction, a torque of the feeding motor 120 in the reverse direction is transferred to the feeding roller 30 and the pick-up roller 20, such that the feeding roller 30 and the pick-up roller 20 rotate in the reverse direction. That is, the feeding roller 30 and the pick-up roller 20 may rotate in the counterclockwise direction, which is the opposite direction to the feeding direction of the paper, by the rotation of the feeding motor 120 in the reverse direction. The pick-up roller 20 may be configured to rotate in the same rotation direction as that of the feeding roller 30.

[182] A torque of the retard motor 130 is transferred to the retard roller 40 to rotate the retard roller 40. The retard roller 40 is directly connected to the retard motor 130, such that when the retard motor 130 is operated, the retard roller 40 also rotates in one direction.

[183] The torque of the retard motor 130 is transferred to a pick-up roller cam 161 through the pick-up clutch 160 to descend the pick-up roller 20. For example, when the pick-up clutch 160 is turned on, the torque of the retard motor 130 is transferred to the pick-up roller cam 161 , such that the pick-up roller cam 161 rotates. The pick-up roller 20 descends by the rotation of the pick-up roller cam 161 to be in contact with the paper s of the cassette 10.

[184] To the contrary, in the case in which the pick-up clutch 160 is turned off, the torque of the retard motor 130 is not transferred to the pick-up roller cam 161 , such that the pick-up roller cam 161 does not press the pick-up roller downward. Therefore, the pick-up roller 20 is maintained in a state where it is spaced apart from the paper S of the cassette 10 by a pick-up roller spring 21.

[185] The pick-up clutch 160 may be implemented by an electronic clutch of which turn on/off may be controlled by the processor 140.

[186] The feeding roller 30 and the retard roller 40 may rotate in the opposite direction to the feeding direction for a predetermined time T1 when the paper is picked up.

[187] Driving of the feeding apparatus 1 feeding the stopped or reversely fed paper S in the feeding direction will be described with reference to FIG. 9A.

[188] Referring to FIG. 9A, the feeding motor 120 may rotate in the forward direction. In this case, a torque of the feeding motor 120 in the forward direction is transferred to the feeding roller 30 and the pick-up roller 20, such that the feeding roller 30 and the pick-up roller 20 rotate in the forward direction. That is, the feeding roller 30 and the pick-up roller 20 may rotate in the clockwise direction, which is the feeding direction of the paper, by the rotation of the feeding motor 120 in the forward direction.

[189] In this case, the retard motor 130 is turned on, and the pick-up clutch 160 is turned on. In this case, the torque of the retard motor 130 is transferred to the retard roller 40, such that the retard roller 40 rotates in the counterclockwise direction, which is the opposite direction to the feeding direction. Since the pick- up clutch 160 is in the turn-on state, the torque of the retard motor 130 is transferred to the pick-up roller cam 161 , such that the pick-up roller cam 161 rotates. The pick-up roller 20 descends by the rotation of the pick-up roller cam 161 to be in contact with the paper S of the cassette 10.

[190] Therefore, the paper S of the cassette 10 is fed between the feeding roller 30 and the retard roller 40 by the rotation of the pick-up roller 20. In addition, since a retard roller cam 151 elevating the retard roller 40 is positioned at a position at which it does not press the retard roller 40, the retard roller 40 is pressed upward by an elastic member 41 to be in contact with the feeding roller 30 at a predetermined pressure.

[191] In this case, the torque of the retard motor 130 is also transferred to a torque limiter installed coaxially with the retard roller 40. In this case, the torque in the opposite direction to the rotation direction of the feeding roller 30 is transferred to the torque limiter. However, since the feeding roller 30 and the retard roller 40 formed of rubber having a high frictional coefficient are in contact with each other and the torque limiter is configured to be slipped at a predetermined load or more, when the feeding roller 30 rotates, the retard roller 40 rotates depending on the feeding roller 30. Therefore, when the feeding roller 30 rotates in the clockwise direction, the retard roller 40 rotates in the counterclockwise direction by the feeding roller 30. That is, the feeding roller 30 and the retard roller 40 rotate in the feeding direction of the paper, respectively.

[192] Separation between the papers occurs while the papers being fed in the feeding direction by forward rotation of the feeding roller 30 and the retard roller 40.

[193] An operation of reversely rotating the feeding roller 30 and the retard roller 40 to feed the paper S in the opposite direction to the feeding direction will be described with reference to FIG. 9B.

[194] The feeding motor 120 rotates in the reverse direction. In this case, a torque of the feeding motor 120 in the reverse direction is transferred to the feeding roller 30 and the pick-up roller 20, such that the feeding roller 30 and the pick-up roller 20 rotate in the reverse direction. That is, the feeding roller 30 and the pick-up roller 20 rotate in the counterclockwise direction, which is the opposite direction to the feeding direction of the paper. [195] In this case, the retard motor 130 is turned on, and the pick-up clutch 160 is turned off. In this case, the torque of the retard motor 130 is transferred to the retard roller 40, such that the retard roller 40 rotates in the counterclockwise direction, which is the opposite direction to the feeding direction. Since the pick- up clutch 160 is in the turn-off state, the pick-up roller 20 is maintained at a position to which it ascends by a pick-up roller spring 21 to be spaced apart from the paper S of the cassette 10. Therefore, even though the feeding motor 120 reversely rotates, the paper S of the cassette 10 is maintained in a stop state.

[196] Therefore, when the front end of the paper S passes between the retard roller 40 and the feeding roller 30, the paper S is reversely fed, and when the front end of the paper S does not arrive between the retard roller 40 and the feeding roller 30, the paper s is maintained in a stop state.

[197] Therefore, sufficient separation between the papers may occur while the papers being reversely fed by reverse rotation of the feeding roller 30 and the retard roller 40.

[198] FIG. 10A is a view for describing operations of the feeding apparatus 1 in the case in which the front end of the paper S is positioned at the downstream of the sensor 50.

[199] Referring to FIG. 10A, in the case in which the front end of the picked-up paper S is positioned at a position before it passes through the sensor 50, the feeding roller 30 and the retard roller 40 may reversely rotate in the opposite direction to the feeding direction for a predetermined time T1 for each of the fed papers S.

[200] To reversely feed the paper S for the predetermined time T 1 , the feeding motor 120 rotates in the reverse direction, and the torque of the feeding motor 120 in the reverse direction is transferred to the feeding roller 30 and the pick-up roller 20, such that the feeding roller 30 and the pick-up roller 20 rotate in the reverse direction. That is, the feeding roller 30 and the pick-up roller 20 rotate in the counterclockwise direction, which is the opposite direction to the feeding direction of the paper. [201] In this case, the retard motor 130 is turned on, and the pick-up clutch 160 is turned off. In this case, the torque of the retard motor 130 is transferred to the retard roller 40, such that the retard roller 40 rotates in the counterclockwise direction, which is the opposite direction to the feeding direction. Since the pick- up clutch 160 is in the turn-off state, the pick-up roller 20 is maintained at a position to which it ascends by the pick-up roller spring 21 to be spaced apart from the paper S of the cassette 10. Therefore, even though the feeding motor 120 reversely rotates, the paper S of the cassette 10 is maintained in a stop state.

[202] Sufficient separation between the papers may occur while the papers being reversely fed by reverse rotation of the feeding roller 30 and the retard roller 40.

[203] Referring to FIG. 10A, the paper S stopped or reversely fed by the reverse rotation of the feeding roller 30 and the retard roller 40 for the predetermined time T1 is stopped for a predefined time T2, and is again fed in the feeding direction until the paper S is sensed by the sensor 50.

[204] In the case the feeding motor 120 rotates in the forward direction, and the torque of the feeding motor 120 in the forward direction is transferred to the feeding roller 30 and the pick-up roller 20, such that the feeding roller 30 and the pick-up roller 20 rotate in the forward direction. That is, the feeding roller 30 and the pick-up roller 20 may rotate in the clockwise direction, which is the feeding direction of the paper, by the rotation of the feeding motor 120 in the forward direction.

[205] In this case, the retard motor 130 is turned on, and the pick-up clutch 160 is turned on. In this case, the torque of the retard motor 130 is transferred to the retard roller 40, such that the retard roller 40 rotates in the counterclockwise direction, which is the opposite direction to the feeding direction. Since the pick- up clutch 160 is in the turn-on state, the torque of the retard motor 130 is transferred to the pick-up roller cam 161 , such that the pick-up roller cam 161 rotates. The pick-up roller 20 descends by the rotation of the pick-up roller cam 161 to be in contact with the paper S of the cassette 10. [206] Therefore, the paper S of the cassette 10 is fed between the feeding roller 30 and the retard roller 40 by the rotation of the pick-up roller 20. In addition, since the retard roller cam 151 elevating the retard roller 40 is positioned at the position at which it does not press the retard roller 40, the retard roller 40 is pressed upward by the elastic member 41 to be in contact with the feeding roller 30 at a predetermined pressure.

[207] In this case, the torque of the retard motor 130 is also transferred to the torque limiter installed coaxially with the retard roller 40. In this case, the torque in the opposite direction to the rotation direction of the feeding roller 30 is transferred to the torque limiter. However, since the feeding roller 30 and the retard roller 40 formed of rubber having a high frictional coefficient are in contact with each other and the torque limiter is configured to be slipped at a predetermined load or more, when the feeding roller 30 rotates, the retard roller 40 rotates depending on the feeding roller 30. Therefore, when the feeding roller 30 rotates in the clockwise direction, the retard roller 40 rotates in the counterclockwise direction by the feeding roller 30. That is, the feeding roller 30 and the retard roller 40 rotate in the feeding direction of the paper, respectively. Therefore, the paper S is fed in the feeding direction. Separation between the papers occurs once more while the papers being fed by forward rotation of the feeding roller 30 and the retard roller 40.

[208] FIG. 10B is a view for describing operations of the feeding apparatus 1 in the case in which feeding starts in a state where the front end of the paper S completely passes through the sensor 50.

[209] In this case, the feeding motor 120 rotates in the reverse direction until the sensor 50 may not sense the paper S due to the reverse feeding of the paper S. In this case, the torque of the feeding motor 120 in the reverse direction is transferred to the feeding roller 30 and the pick-up roller 20, such that the feeding roller 30 and the pick-up roller 20 rotate in the reverse direction. That is, the feeding roller 30 and the pick-up roller 20 rotate in the counterclockwise direction, which is the opposite direction to the feeding direction of the paper. [210] In this case, the retard motor 130 is turned on, and the pick-up clutch 160 is turned off. In this case, the torque of the retard motor 130 is transferred to the retard roller 40, such that the retard roller 40 rotates in the counterclockwise direction, which is the opposite direction to the feeding direction. Since the pick- up clutch 160 is in the turn-off state, the pick-up roller 20 is maintained at a position to which it ascends by the pick-up roller spring 21 to be spaced apart from the paper S of the cassette 10.

[21 1] The paper S reversely fed until the sensor 50 is turned off is reversely fed for a predetermined time T1 , is stopped for a predefined time T2, is fed in the feeding direction until the paper S is sensed by the sensor 50, is again stopped for a predefined time T34, and is then fed, as in the case in which the front end of the paper S is positioned at the downstream of the sensor 50 as described in FIG. 10A. An operation of the feeding apparatus for feeding the paper S reversely fed until the sensor 50 is turned off is the same as that of the feeding apparatus 1 as described in FIG. 10A, and a description therefor is thus omitted.

[212] Since the feeding apparatus according to an example of the disclosure may feed the printing paper S in the opposite direction to the feeding direction for a predetermined condition after the paper S is picked up, the double feed of the papers may be prevented by a simple configuration.

[213] In addition, since the feeding apparatus according to an example of the disclosure rotates both of the retard roller 40 and the feeding roller 30 in the opposite direction to the feeding direction for the predetermined time for separation between papers S, capability to separate the papers S from each other may be fundamentally improved, and an operating ratio of the image forming apparatus 100 according to an example of the disclosure may thus be improved.

[214] FIG. 11 is a view for describing feeding of papers having different feeding start points in time when the feeding apparatus according to an example of the disclosure performs a reverse rotation operation on a paper passing through a sensor for a predetermined time.

[215] Hereinabove, the feeding apparatus 1 performing an operation of reversely feeding the paper S per feeding period regardless of a position of the front end of the paper S at which the feeding starts to improve separation performance between the papers has been described.

[216] The processor 140 of the feeding apparatus 1 illustrated in FIG. 11 may control the feeding apparatus 1 to reversely feed the paper in the case in which the front end of the paper S of which the feeding starts passes through the sensor 50. That is, the feeding apparatus 1 does not perform the operation of reversely feeding the paper S in the opposite direction to the feeding direction in the case in which the picked-up paper S is not sensed by the sensor 50, and may reversely feed the paper S in the opposite direction to the feeding direction in the case in which the picked-up paper S is sensed by the sensor 50.

[217] According to the feeding apparatus 1 illustrated in FIG. 11 , in the case in which the front end of the paper S arrives at the sensor 50, the paper S may be reversely fed in the opposite direction to the feeding direction, and in the case in which the front end of the paper S does not arrive at the sensor 50, the paper S is fed in the feeding direction.

[218] Referring to FIG. 11 , P10 illustrates processes of feeding the paper S in the case P10 in which the front end of the picked-up paper S is positioned at the downstream immediately before the pick-up roller 20 and the feeding nib, P20 illustrates processes of feeding the paper S in the case P20 in which the front end of the paper S is positioned between the feeding roller 30 and the retard roller 40, and P30 illustrates processes of feeding the paper S in the case P30 in which the front end of the paper S is positioned at the upstream immediately before the sensor 50. P40 illustrates processes of feeding the paper S in the case P40 in which the front end of the picked-up paper S passes through the sensor 50.

[219] First, operations of the feeding apparatus 1 in the cases P10 and P20 in which the front end of the paper S is positioned at the downstream of the sensor 50 are described.

[220] In the cases P10 and P20 in which the front end of the picked-up paper S is positioned before it passes through the sensor 50, the paper S is fed in the feeding direction. Detailed operations of feeding the paper S in the feeding direction are described with reference to FIGS. 7 A and 9A, and a description therefor is thus omitted.

[221] Operations of the feeding apparatus 1 in the cases P30 and P40 in which the front end of the paper S passes through the sensor 50 are described. In the case of papers S easy to be doubly fed, having a large frictional force between the papers, when the front end of the paper passes through the sensor 50 at a feeding start point in time, a double feed occurrence ratio is increased. Therefore, in the feeding apparatus 1 according to an example of the disclosure, when the paper S is sensed by the sensor 50, the paper S is reversely fed.

[222] In the case in which the front end of the picked-up paper S is positioned in a state where it passes through the sensor 50, the feeding apparatus 1 may reversely feed the paper S until the front end of the paper S is positioned at the downstream of the sensor 50. The feeding roller 30 and the retard roller 40 may reversely rotate in the opposite direction to the feeding direction until the sensor 50 is turned off. Detailed operations of feeding the paper S in the opposite direction to the feeding direction until the sensor 50 is turned off are described with FIGS. 7B and 9B, and a description therefor is thus omitted.

[223] The paper S reversely fed until the sensor 50 is turned off is reversely fed for a predetermined time T1 , is stopped for a predefined time T2, is fed in the feeding direction until the paper S is sensed by the sensor 50, is again stopped for a predefined time T34, and is then fed again toward the printing engine 110 in the feeding direction at a point in time in which the paper is to be fed, as in the case in which the front end of the paper S is positioned at the downstream of the sensor 50. Detailed operations of feeding the paper S in the feeding direction are described with reference to FIGS. 7A and 9A, and a description therefor is thus omitted.

[224] When the paper S is reversely fed in the case in which the front end of the paper S passes through the sensor 50 at the feeding start point in time unlike the feeding apparatus illustrated in FIG. 4 that reversely feeds all the fed papers, a time for feeding the paper may be reduced, such that the feeding apparatus may be applied to a high speed machine. In addition, the number of operations of reversely feeding the paper may be reduced, such that a lifespan of components configuring the feeding apparatus 1 may be increased.

[225] FIG. 12 is a flow chart illustrating a method of feeding a paper in an image forming apparatus according to the disclosure.

[226] Referring to FIG. 12, the printing paper S picked up using the feeding roller 30 and the retard roller 40 is first provided to the printing engine 110 (S1210). In detail, after an image starts, the printing paper S loaded in the cassette 10 is picked up, and moves to the feeding path.

[227] After the printing paper S is picked up, each of the fed printing papers is fed in the opposite direction to the feeding direction for a predetermined time (S1220). In a process of reversely feeding the printing paper S, both of the retard roller 40 and the feeding roller 30 rotate in the opposite direction to the feeding direction. The paper S reversely fed for the predetermined time escapes between the feeding roller 30 and the retard roller 40 by the reverse feeding, and a plurality of papers are reversely fed while being separated from each other.

[228] Then, the reversely fed printing paper S is again fed in the feeding direction (S1230). Both of the retard roller 40 and the feeding roller 30 rotate in the feeding direction.

[229] Therefore, in the method of feeding a paper according to the disclosure, the papers may be fundamentally separated from each other in the image forming apparatus to prevent the double feed. The method of feeding a paper as illustrated in FIG. 12 may be executed on the image forming apparatus having the components of FIG. 1 or FIG. 2 or be executed on an image forming apparatus having other components.

[230] Meanwhile, the method of feeding a paper described above may be implemented by a program and be provided to a display apparatus. For example, a program including the method of feeding a paper may be stored and provided in a non-transitory computer readable medium. [231] The non-transitory computer-readable medium is not a medium that stores data therein for a while, such as a register, a cache, a memory, or the like, but refers to a medium that semi-permanently stores data therein and is readable by an apparatus. In detail, the various applications or programs described above may be stored and provided in the non-transitory computer readable medium such as a compact disk (CD), a digital versatile disk (DVD), a hard disk, a Blu-ray disk, a universal serial bus (USB), a memory card, a read only memory (ROM), or the like.

[232] Although examples of the disclosure have been illustrated and described hereinabove, the disclosure is not limited thereto, but may be variously modified without departing from the spirit and scope of the disclosure claimed in the claims. These modifications are to fall within the scope of the disclosure.