Patent Publication Number: US-7593683-B2

Title: Paper arranging device, and electrophotographic image forming apparatus with the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the priority under 35 U.S.C. § 119 from Korean Patent Application No. 10-2004-81356, filed on Oct. 12, 2004, and Korean Patent Application No. 10-2004-106546, filed on Dec. 15, 2004, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present general inventive concept relates to a paper arranging device, and more particularly, to an electrophotographic image forming apparatus with the same. 
   2. Description of the Related Art 
   In general, an electrophotographic image forming apparatus prints a desired image by developing a latent image formed on a circumference of a photosensitive medium through optical scanning into a visible image by supplying toner onto the latent image, transferring the visible image onto paper, and fusing the visible image with the paper. The visible image is transferred onto and fused with the paper as the paper is transferred along a predetermined path. A paper arranging device arranges the paper to be moved toward the photosensitive medium so as to transfer the visible image onto a desired part of the paper. The paper arranging device is installed before the photosensitive medium in the predetermined path along which the paper is transferred. 
     FIGS. 1 and 2  are diagrams illustrating the operation of a conventional paper arranging device  10  to be installed in a conventional electrophotographic image forming apparatus. Referring to  FIGS. 1 and 2 , the paper arranging device  10  includes a driving roller  12 , an idle roller  14 , a photosensor  16 , and a lever  18 . The driving roller  12  and the idle roller  14  face each other, thus forming a nip N. The lever  18  is pressed and rotated by a tip Pa of moving paper P. The driving roller  12  is rotated by power generated by a motor (not shown), and the driving roller  12  is selectively connected to or disconnected from the motor through an electronic clutch (not shown). 
   Until the tip Pa of the paper P moving upward (see the arrows of  FIGS. 1 and 2 ) arrives at the lever  18 , the electronic clutch does not connect the driving roller  12  to the motor, thereby preventing the driving roller  12  and the idle roller  14  from being rotated. When the tip Pa of the paper P presses a first end  18   a  of the lever  18  upward, the lever  18  is rotated to turn a second end  18   b  of the lever  18  downward. Then, referring to  FIG. 2 , the second end  18   b  is separated from the photosensor  16 , and the photosensor  16  senses the paper P. Next, the tip Pa of the paper P is curled by the nip N to arrange the paper P. The electronic clutch connects the driving roller  12  to the motor a predetermined time after the photosensor  16  senses the paper P, and the driving roller  12  and the idle roller  14  are rotated to transfer the paper P. A light scanning device (not shown) and a photosensitive medium (not shown) operate sequentially after a predetermined time after the electronic clutch operates so as to transfer an image onto a desired part of the paper P. 
   The conventional paper arranging device  10  sets times, i.e., an exposure time, when the light scanning device and the photosensitive medium begin to operate according to a time when the electronic clutch begins to operate. Thus, a delay in the operation of the electronic clutch increases an error between a substantial position and desired position of an image on the paper P. 
     FIGS. 3 through 5  are diagrams illustrating the operation of another conventional paper arranging device  50  to be installed in a conventional electrophotographic image forming apparatus. Referring to  FIGS. 3 through 5 , the paper arranging device  50  includes a driving roller  52 , an idle roller  54 , lower and upper levers  58  and  64 , and lower and upper photosensors  56  and  62 . The driving roller  52  and the idle roller  54  face each other, thus forming a nip N, and are installed between the lower and upper levers  58  and  64  and also between the lower and upper photosensors  56  and  62 . The driving roller  52  is rotated by power generated by a motor (not shown), and selectively connected to or disconnected from the motor through an electronic clutch (not shown). 
   Until a tip Pa of paper P moving upward (see the arrows of  FIGS. 3-5 ) arrives at the lower lever  58 , the electronic clutch does not connect the driving roller  52  to the motor, thereby preventing the driving roller  52  and the idle roller  54  from being rotated. When the tip Pa of the paper P presses a first end  58   a  of the lower lever  58  upward, the lower lever  58  is rotated to turn a second end  58   b  of the lower lever  58  downward. Then, referring to  FIG. 4 , the second end  58   b  of the lower lever  58  is separated from the lower photosensor  56 , and the lower photosensor  56  senses the paper P. Next, the tip Pa of the paper P is stopped and curled by the nip N, and thus, the paper P is arranged. The electronic clutch connects the driving roller  52  and the motor a predetermined time after the lower photosensor  56  senses the paper P, and the driving roller  52  and the idle roller  54  are rotated to transfer the paper P. 
   When the tip Pa of the paper P passes through the nip N and presses a first end  64   a  of the upper lever  64  upward, the upper lever  64  is rotated to turn a second end  64   b  of the upper lever  64  downward. Then, referring to  FIG. 5 , the second end  64   b  of the upper lever  64  is separated from the upper photosensor  62 , and the upper photosensor  62  senses that the tip Pa of the conventional paper P has passed through the paper arranging device  50 . A light scanning device (not shown) and photosensitive medium (not shown) begin to operate a predetermined time after the upper photosensor  62  senses the paper P, and transfer an image onto a desired part of the paper P. 
   The conventional paper arranging device  50  of  FIGS. 3-5  sets times, i.e., an exposure time, when the light scanning device (not shown) and a photosensitive medium (not shown) begin to operate according to a time when the upper photosensor  62  senses the paper P. Therefore, unlike the paper arranging device  10  of  FIGS. 1-2 , an irregular delay in the operation of the electronic clutch does not remarkably increase an error between a substantial position and a desired position of the image on the paper P. However, as compared to the conventional paper arranging device  10  of  FIGS. 1-2 , the conventional paper arranging device  50  of  FIGS. 3-5  requires an additional photosensor and an additional lever, thereby increasing manufacturing costs. 
   SUMMARY OF THE INVENTION 
   The present general inventive concept provides a paper arranging device with a sensor and a lever, which is capable of minimizing an error between a substantial position and a desired position of an image on paper, and an electrophotographic image forming apparatus with the same. 
   Additional aspects and advantages of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept. 
   The foregoing and/or other aspects and advantages of the present general inventive concept may be achieved by providing a paper arranging device usable with an electrophotgraphic image forming apparatus, the paper arranging device comprising a driving roller and an idle roller disposed adjacent to each other to form a nip, a first sensor to sense a location of moving paper, and a lever having a first end which extends to a perimeter of the nip to block a tip of the paper moving toward the nip and a second end which extends to a perimeter of the sensor, the lever being rotatable with respect to a predetermined pivot axis between the first end and the second end of the lever. When the first end of the lever is pressed by the tip of the moving paper and reaches a first position, the first sensor determines that the tip of the paper is entering the nip and generates a first sensing signal. When the first end of the lever is pressed by the tip of the moving paper and reaches a second position at which the paper has proceeded farther than at the first position, the first sensor determines that the tip of the paper has passed through the nip and generates a second sensing signal. 
   A time when the driving roller is rotated may be determined based on the first sensing signal output from the first sensor. 
   A time when a photosensitive medium of the electrophotographic image forming apparatus on which a latent image is formed is exposed to light, may be determined based on the second sensing signal output from the first sensor. 
   The paper arranging device may further include a stopper to regulate a rotation angle of the lever. 
   The lever may be elastically biased, such that the first end of the lever can return to an initial position thereof where the first end of the lever blocks the tip of the paper moving toward the nip. 
   The first sensor may be a photosensor. 
   The paper arranging device may further include a second sensor which is spaced apart from the first sensor and senses the location of the moving paper. When the first end of the lever is pressed by the tip of the paper and reaches a third position deviating from a path of the paper, the second sensor may determine that the paper is passing through the nip and may generate a third sensing signal. When the first end of the lever returns to the initial position from the third position, the second sensor may determine that an end of the paper has passed through the nip and may generate a fourth sensing signal. 
   The second sensor may be a photosensor. 
   The foregoing and/or other aspects and advantages of the present general inventive concept may be achieved by providing an electrophotographic image forming apparatus comprising a light scanning device to scan light corresponding to an image signal, a photosensitive medium on which a latent image is formed when the photosensitive medium is exposed to the light, a paper arranging device, and a controller to control times when a driving roller of the paper arranging device is rotated and when the photosensitive medium is exposed to the light based on a first sensing signal and a second sensing signal output from a first sensor of the paper arranging device. The paper arranging device includes the driving roller and an idle roller which are positioned before the photosensitive medium along a path of paper, the driving roller and the idle roller disposed adjacent to each other, to form a nip, the first sensor to sense a location of the moving paper, and a lever having a first end which extends to a perimeter of the nip to block a tip of the paper moving toward the nip and a second end which extends to a perimeter of the first sensor, the lever being installed to be rotatable with respect to a predetermined pivot axis between the first end and the second end of the lever. When the first end of the lever is pressed by the tip of the paper and reaches a first position, the first sensor determines that the tip of the paper is entering the nip and generates the first sensing signal. When the first end of the lever is pressed by the tip of the paper and reaches a second position at which the paper has proceeded farther than at the first position, the first sensor determines that the tip of the paper has passed through the nip and generates the second sensing signal. 
   The paper arranging device may further include a clutch to selectively transfer power generated by a driving source to the driving roller, and the controller may control time when the driving roller is rotated by operating the clutch based on the first sensing signal output from the first sensor. 
   The controller may control when the photosensitive medium is exposed to the light by operating the light scanning device and the photosensitive medium based on the second sensing signal output from the first sensor. 
   The paper arranging device may further include a stopper to regulate a rotation angle of the lever. 
   The lever may be elastically biased, such that the first end of the lever returns to an initial position thereof where the first end of the lever blocks the tip of the paper moving toward the nip. 
   The first sensor may be a photosensor. 
   The paper arranging device may further include a second sensor which is spaced apart from the first sensor and senses a location of the moving paper. When the first end of the lever is pressed by the tip of the paper and reaches a third position deviating from the path of the paper, the second sensor may determine that the paper is passing through the nip and may generate a third sensing signal. When the first end of the lever returns to the initial position from the third position, the second sensor may determine that an end of the paper passes through the nip and may generate a fourth sensing signal. 
   The second sensor may be a photosensor. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
       FIGS. 1 and 2  are diagrams illustrating the operation of a conventional paper arranging device to be installed in a conventional electrophotographic image forming apparatus; 
       FIGS. 3 through 5  are diagrams illustrating the operation of another conventional paper arranging device to be installed in a conventional electrophotographic image forming apparatus; 
       FIG. 6  is a schematic cross-sectional view illustrating an electrophotographic image forming apparatus according to an embodiment of the present general inventive concept; 
       FIG. 7  is a perspective view illustrating a paper arranging device according to an embodiment of the present general inventive concept; 
       FIGS. 8 through 11  are diagrams illustrating operations of the paper arranging device of  FIG. 7 ; 
       FIG. 12  is a perspective view illustrating a paper arranging device according to another embodiment of the present general inventive concept; and 
       FIGS. 13 through 17  are diagrams illustrating operations of the paper arranging device of  FIG. 12 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present general inventive concept while referring to the figures. 
     FIG. 6  illustrates an electrophotographic image forming apparatus  100  according to an embodiment of the present general inventive concept. Referring to  FIG. 6 , the electrophotographic image forming apparatus  100  includes a case  101 , a developing unit  110  installed to be easily mounted into and removed from the case  101 , a fusing unit  130 , a transfer roller  125 , and a light scanning unit (LSU)  127 . In the electrophotographic image forming apparatus  100 , as illustrated in  FIG. 6 , paper P is delivered along a reverse C-shaped transfer path. 
   The developing unit  110  includes a housing  111  to store a developing solution, i.e., toner, a photosensitive medium  115  to form a latent image thereon through optical scanning, a charging roller  113  that charges the photosensitive medium  115 , a waste developing solution cleaner  114  that removes waste developing solution from the photosensitive medium  115 , a developing roller  117  that develops the latent image formed on a circumference of the photosensitive medium  115  into a visual image by supplying the developing solution to the latent image on a circumference of the photosensitive medium  115 , a doctor blade  118  that controls a thickness of the developing solution adhering to a surface of the developing roller  117 , and a supply roller  119  that supplies the developing solution to the developing roller  117 . An agitator  121  is installed in the housing  111  to stir the developing solution so that the developing solution does not harden. The developing unit  110 , as illustrated in  FIG. 6 , is a cartridge type. Thus, when the developing solution stored in the developing unit  110  is consumed, the developing unit  110  can be replaced with a new developing unit. 
   The transfer roller  125  is installed to face the photosensitive medium  115 . The visual image developed on the circumference of the photosensitive medium  115  is transferred onto the paper P passing between the transfer roller  125  and the photosensitive medium  115 , using a transfer bias or contact pressure between the transfer roller  125  and the photosensitive medium  115 . 
   The fusing unit  130  includes a heat roller  131  and a pressure roller  133  installed to face the heat roller  131 . When the paper P onto which the visual image is transferred passes between the heat roller  131  and the pressure roller  133 , the visual image is fused with the paper P through thermocompression that uses heat and pressure. 
   The electrophotographic image forming apparatus  100  further includes a pickup roller  145 , a paper arranging device  150 , and an exit roller  135 . The pickup roller  145  picks up a sheet of the paper P stacked in a paper feeding cassette  140  installed at a bottom of the case  101 . The paper arranging device  150  provides a transfer power to the picked up paper P, and arranges the picked up paper P to be delivered toward the photosensitive medium  115  such that the visual image can be transferred onto a predetermined portion of the paper P. The paper arranging device  150  includes a driving roller  152  and an idle roller  154 . The exit roller  135  helps to drive the paper P printed with the image to an output tray  102  at an outer portion of the case  101 . 
   Operations of the electrophotographic image forming apparatus  100  will now be described. The photosensitive medium  115  is charged with a predetermined electric potential through the charging roller  113 , and exposed to light L scanned by the light scanning device  127  to form a latent image on the circumference of the photosensitive medium  115 , the latent image corresponding to an image to be printed. The toner contained in the housing  111  of the developing unit  110  is supplied to the photosensitive medium  115  on which the latent image is formed, through the supply roller  119  and the developing roller  117 . Then, the latent image is developed into the visual image. The paper P stacked in the paper feeding cassette  140  is picked up by the pickup roller  145 , fed and arranged by the paper arranging device  150 , and passes between the photosensitive medium  115  and the transfer roller  125 . Then, the visual image developed on the circumference of the photosensitive medium  115  is transferred onto a side of the paper P facing the photosensitive medium  115 . When the transferred visual image passes through the fusing unit  130 , the fusing unit  130  applies heat and pressure onto the paper P to fuse the visual image with the paper P. Thereafter, the paper P is transferred to the output tray  102  by the exit roller  135 . 
     FIGS. 7 through 11  illustrate a paper arranging, device  150 A according to an embodiment of the present general inventive concept. The paper arranging device  150 A includes a driving roller  152  and an idle roller  154  that are installed closely together to face each other, thus forming a nip N therebetween, a photosensor  160  that senses the location of the paper P that is being delivered, and a lever  165  pressed and rotated by a tip Pa of the moving paper P. The driving roller  152  is rotated by power generated by a motor (not shown) installed in the case  101  (see  FIG. 6 ), and connected to the motor via an electronic clutch  192 . The power generated by the motor is selectively transferred to the driving roller  152  through the electronic clutch  192 . The electronic clutch  192  is electrically connected to a controller  190 , and operates in response to a control signal generated by the controller  190 . The motor, the electronic clutch  192 , and the controller  190  are obvious to those ordinarily skilled in the art, and detailed descriptions thereof will be omitted. The driving roller  152  may have a cutout portion, and the lever  165  may be disposed in the cutout portion. 
   A first end  166  of the lever  165  extends to the nip N at an initial position such that the first end  165  contacts the tip Pa of the paper P as the tip Pa of the paper P approaches the nip N by the pickup roller  145  (see  FIG. 6 ) in a forward movement direction, and a second end  167  of the lever  165  extends to the photosensor  160  such that the second end  167  is positioned above a slit  161  of the photosensor  160  at the initial position. The lever  165  is installed to be rotatable with respect to a predetermined pivot  168  between the first and second ends  166  and  167 . The lever  165  is elastically biased by a spring  177  in a counterclockwise direction to return the lever  165  to the initial position even when the tip Pa of the moving paper P presses the lever  165  to rotate the lever  165  in a clockwise direction with respect to the pivot  168 . An end of the spring  177  is connected to a predetermined frame (not shown) in the case  101  (see  FIG. 6 ), and another end thereof is connected to the lever  165 . A stopper  175  is further installed in the case  101  to control a rotation angle of the lever  165  rotated in the counterclockwise direction by the spring  177  after the paper P passes through the nip N. When the lever  165  is rotated in the counterclockwise direction by the spring  177 , the stopper  175  stops the rotation of the lever  165  at the initial position. As illustrated in  FIGS. 8-11 , the lever  165  is rotated in the clockwise direction by the paper P and in the counterclockwise direction by the spring  177 , but the present general inventive concept is not limited thereto. The lever  165  may alternatively be rotated in the counterclockwise direction by the paper P and the clockwise direction by the spring  177 . 
   The slit  161  is formed in the photosensor  160  lengthwise such that the second end  167  of the lever  165  can pass through the photosensor  160 . A light emitting unit (not shown) that emits a laser light, and a light receiving unit (not shown) that receives the laser light are mounted on opposite inner walls of the slit  161 . The construction of the slit  161  is obvious to those ordinarily skilled in the art, and thus, a detailed description thereof will not be described. The photosensor  160  is electrically connected to the controller  190 , senses a position of the paper P, generates first and second sensing signals indicating the position of the paper P, and transmits the first and second sensing signals to the controller  190 . 
   Operations of the paper arranging device  150 A of  FIGS. 7-11  will now be described. Referring to  FIG. 8 , when the lever  165  is at the initial position, the first and second ends  166  and  167  of the lever  165  are positioned directly under the nip N and above the photosensor  160 , respectively. Until the paper P picked up by the pickup roller  145  (see  FIG. 6 ) moves upward and the tip Pa of the paper P reaches the first end  166  of the lever  165 , the electronic clutch  192  disconnects the driving roller  152  from the motor in response to a control signal generated by the controller  190 . In this case, the driving roller  152  and the idle roller  154  installed adjacent to the driving roller  152  do not rotate. 
   Referring to  FIG. 9 , when the tip Pa of the paper P presses the first end  166  of the lever  165  upward to a first position, the lever  165  is rotated in the clockwise direction to turn the second end  167  of the lever  165  downward. Thus, the second end  167  of the lever  165  enters the slit  161  of the photosensor  160 , and the laser light emitted by the light emitting unit of the photosensor  160  is blocked by the second end  167  of the lever  165 , thereby preventing light from being input to the light receiving unit. In this case, the photosensor  160  determines that the tip Pa of the paper P is approaching the nip N, and generates the first sensing signal. 
   Then, the tip Pa of the paper P is stopped and curled by the nip N to arrange the paper P. The first sensing signal output from the photosensor  160  is transmitted to the controller  190 . The controller  190  generates a control signal a first interval after the controller  190  receives the first sensing signal, and transmits the control signal to the electronic clutch  192  to operate the electronic clutch  192 . When the electronic clutch  192  operates, the driving roller  152  is connected to the motor, and as a result, the driving roller  152  and the idle roller  154  installed adjacent to the driving roller  152  rotate to move the paper P. 
   Referring to  FIG. 10 , the first end  166  of the lever  165  is continuously rotated in the clockwise direction while being pressed by the tip Pa of the paper P passing through the nip N. Referring to  FIG. 11 , when the first end  166  reaches a second position at which the paper P has proceeded farther than at the first position, the second end  167  of the lever  165  does not intercept the light emitted by the light emitting unit of the photosensor  160 . Thus, the laser light is received by the light receiving unit, and the photosensor  160  determines that the tip Pa of the paper P has passed through the nip N, and generates the second sensing signal. 
   The second sensing signal output from the photosensor  160  is transmitted to the controller  190 . The controller  190  generates and transmits a control signal a second interval after receiving the second sensing signal, so that the light scanning device  127  and the photosensitive medium  115  (see  FIG. 6 ) operate to expose the photosensitive medium  115  to light L. The second interval is computed from the moving speed of the tip Pa of the paper P passing through the nip N and the distance between the nip N and the photosensitive medium  115 . The operations of the light scanning device  127  and the photosensitive medium  115  are not substantially affected by an irregular delay in the operation of the electronic clutch  192 , thereby minimizing an error between a substantial position and desired position of the image printed on the paper P. 
   If the paper arranging device  150 A is installed in an electrophotographic image forming apparatus, an error between a desired position and a substantial position of an image to be formed on paper is minimized, thereby improving the quality of printing. Further, the paper arranging device  150 A requires one sensor and one lever, thereby reducing manufacturing costs. 
     FIGS. 12 through 17  illustrate a paper arranging device  150 B according to another embodiment of the present general inventive concept. Compared to the paper arranging device  150 A of  FIGS. 7 through 11 , the paper arranging device  150 B of  FIGS. 12 through 17  further includes a second photosensor  200  installed to be spaced apart from a first photosensor  160 . The first and second photosensors  160  and  200  are upper and lower photosensors positioned along a circumference of a circle with a center at the pivot axis  168  of the lever  165 . Similar to the first photosensor  160 , the second photosensor  200  is electrically connected to the controller  190 , and generates third and fourth sensing signals and transmits the third and fourth sensing signals to the controller  190  when the second photosensor  200  senses the location of the paper P. 
   The operation of the paper arranging device  150 B of  FIGS. 12-17  will now be described in detail. Referring to  FIG. 13 , when the lever  165  is present at the initial position, the first end  166  of the lever  165  is positioned directly under the nip N and the second end  167  of the lever  165  is positioned above the first photosensor  160 . Until the paper P is delivered upward and a tip Pa of the paper P contacts the first end  166  of the lever  165 , the electronic clutch  192  disconnects the driving roller  152  from a motor (not shown) according to a control signal output from the controller  190 , thereby preventing the driving roller  152  and the idle roller  154  from rotating. 
   Referring to  FIG. 14 , when the tip Pa of the paper P presses the first end  166  of the lever  65  upward to the first position, the lever  165  is rotated in the clockwise direction to turn the second end  167  of the lever  165  downward. Thus, the second end  167  enters a first slit  161  (see  FIG. 12 ) of the first photo sensor  160 , and the laser light emitted by the light emitting unit (not shown) of the first photosensor  160  is blocked by the second end  167 . In this case, the first photosensor  160  determines that the tip Pa of the paper P is approaching the nip N, and generates the first sensing signal. 
   Then, the tip Pa of the paper P is stopped and curled by the nip N to arrange the paper P. The first sensing signal output from the first photosensor  160  is transmitted to the controller  190 . The controller  190  generates a control signal and transmits the generated control signal to the electronic clutch  192  at the first time interval after the controller  190  receives the first sensing signal, thereby operating the electronic clutch  192 . When the electronic clutch  192  operates, the driving roller  152  is connected to the motor, and the driving roller  152  and the idle roller  154  installed adjacent to the driving roller  152  rotate, thus moving the paper P. 
   Referring to  FIG. 15 , the lever  165  is continuously rotated while the first end  166  of the lever  165  is pressed by the tip Pa of the paper P, which passes through the nip N. As illustrated in  FIG. 16 , when the first end  166  reaches the second position at which the paper P has proceeded farther than at the first position, the second end  167  does not intercept the laser light emitted by the light emitting unit of the first photo sensor  160 . Thus, the light is received by the light receiving unit of the first photosensor  160 , and the first photosensor  160  determines that the tip Pa of the paper P has passed through the nip N, and generates the second sensing signal. 
   The second sensing signal output from the first sensor  160  is transmitted to the controller  190 . The controller  190  generates and transmits a control signal at the second interval after it receives the second sensing signal, such that the light scanning unit  127  and the photosensitive medium  115  (see  FIG. 6 ) operate to expose the photosensitive medium  115  to the light L. The second interval is computed from the moving speed of the nip N of the paper P passing through the nip N and the distance between the tip Pa and the photosensitive medium  115 . Therefore, the operations of the light scanning unit  127  and the photosensitive medium  115  are not substantially affected by an irregular delay in the operation of the electronic clutch  192 , thereby minimizing an error between a substantial position and desired position of an image to be formed on the paper P. 
   When the paper P is moving upward, the first end  166  of the lever  165  reaches a third position which deviates from a path of the paper P. Referring to  FIG. 17 , the second end  167  of the lever  165  enters a second slit  201  (see  FIG. 12 ) of the second photosensor  200  at the third position. In this case, laser light emitted by a light emitting unit (not shown) of the second photosensor  200  is blocked by the second end  167  and is not received by a light receiving unit (not shown) of the second photosensor  200 . Therefore, the second photosensor  200  determines that the paper P is passing through the nip N, and generates the third sensing signal. 
   When an end Pb of the paper P passes through the nip N, the lever  165  is rotated in the counterclockwise direction by the spring  177  until the lever  165  bumps against a stopper  175  and is stopped. When the lever  165  is stopped, the lever  165  returns to the initial position, as illustrated in  FIG. 13 . In this case, the second end  167  of the lever  165  does not intercept the light emitted by the light emitting unit of the second photosensor  200 , and the light is input to the light receiving unit of the second photosensor  200 . Then, the second photosensor  200  determines that the end Pb of the paper P has passed through the nip N and generates the fourth sensing signal. 
   The third and fourth sensing signals are sequentially generated by the second photosensor  200  and transmitted to the controller  190 . The controller  190  may compute the length of the paper P from the moving speed of the paper P and an interval between the third and fourth sensing signals. When the controller  190  does not receive the fourth sensing signal within a predetermined length of time after it receives the third sensing signal, the controller  190  may determine that a paper jam has occurred during the movement of the paper P, and transmit a message to a display panel (not shown) of the electrophotographic image forming apparatus  100  (see  FIG. 6 ) to inform a user of the paper jam. 
   If the paper arranging device  150 B is installed in an image forming apparatus, an error between a substantial position and desired position of an image to be formed on paper is minimized, thereby improving the quality of printing. 
   The paper arranging device  150 B as described above may measure the length of supplied paper and senses the paper jam, and thus, an image forming apparatus does not require additional elements to perform these operations, thereby reducing manufacture costs. 
   Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.