Abstract:
An image forming apparatus which does not require securing a separate space for feeding a print medium, and a paper-feeding method thereof are disclosed. The image forming apparatus comprises: an image forming apparatus body; an image forming unit provided within the image forming apparatus body; and a paper-feeding unit movably installed in relation to the image forming apparatus body, the paper-feeding unit feeding a print medium to the image forming unit after turning the print medium in a reverse direction at least one time.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Korean Patent Application No. 2006-69329, filed Jul. 24, 2006 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Aspects of the present invention relate to an image forming apparatus and a paper-feeding method thereof. 
         [0004]    2. Description of the Related Art 
         [0005]    Recently, mobile image forming apparatuses have been widespread, wherein a user can freely connect a mobile camera, such as a digital camera or a portable phone provided with a camera, to such a mobile image forming apparatus so as to develop one or more photographs on the spot. U.S. Pat. No. 6,918,645 discloses an image forming apparatus which is configured to be operated by battery so that it can be conveniently and easily carried.  FIG. 1  shows such an image forming apparatus. 
         [0006]    In  FIG. 1 , reference numeral  1  denotes an image forming apparatus body and reference numeral  3  denotes a paper-feeding cassette. 
         [0007]    As shown in the drawing, the image forming apparatus body  1  incorporates an image forming unit for forming a given image on a print medium, and the paper-feeding cassette  3 , in which print media are loaded, is removably fitted in a mounting opening  1   a  formed through a side wall  1   a  of the image forming apparatus  1 . A pick-up roller  3   a  is provided in the mounting opening  1   a  so as to pick up a print medium from the paper-feeding cassette  3 . 
         [0008]    With this arrangement, if a user positions the image forming apparatus body  1  in a desired place and then fits the paper-feeding cassette  3  into the mounting opening  1   a , the pick-up roller  3   a  feeds a print medium loaded in the paper-feeding cassette  3  into the image forming apparatus body  1 , whereby a desired image can be printed on the print medium on the spot. 
         [0009]    However, such a conventional image forming apparatus is disadvantageous and inconvenient in that because the paper-feeding cassette  3  is separately mounted to the image forming apparatus body  1 , it is necessary to secure a space for mounting the paper-feeding cassette  3  and to carry the paper-feeding cassette  3  separately. 
       SUMMARY OF THE INVENTION 
       [0010]    Aspects of the present invention provide an image forming apparatus improved in construction in such a manner that it is not necessary to secure a space for feeding a print medium. 
         [0011]    According to an aspect of the present invention, there is provided an image forming apparatus comprising an image forming apparatus body; an image forming unit provided within the image forming apparatus body; and a paper-feeding unit movably installed in relation to the image forming apparatus body, the paper-feeding unit feeding a print medium to the image forming unit after turning the print medium in a reverse direction at least one time. 
         [0012]    According to another aspect of the present invention, paper-feeding unit comprises a pick-up roller mounted within the image forming apparatus body in such a manner as to be bi-directionally rotatable, so that when the pick-up roller rotates in a first direction, the pick-up roller moves the print medium to a pick-up position and when the pick-up roller rotates in a second direction, the paper-feeding unit picks up the print medium at the pick-up position and feeds the print medium to the image forming unit. 
         [0013]    Here, the image forming apparatus may further comprise: a pick-up sensor for sensing whether the print medium has moved to the pick-up position; and a controller for selectively controlling the driving direction of the pick-up roller in the forward/reverse direction on the basis of a sensing signal from the pick-up sensor. 
         [0014]    In addition, the image forming apparatus may further comprise a paper sensor for sensing whether the print medium fed by the pick-up roller is admitted into a print position in the image forming unit, wherein the controller stops the driving of the pick-up roller on the basis of a sensing signal for the print medium, which is applied from the print sensor. 
         [0015]    The pick-up roller may be arranged to be spaced from the print medium received in the paper-feeding unit, so that the pick-up roller can move the print medium to the pick-up position when it reversely rotates at least one time. 
         [0016]    The image forming apparatus or the paper-feeding unit may be provided with a retreating path for the tail edge of the print medium moved in the first direction by the pick-up roller. 
         [0017]    Here, the retreating path may comprise a guide slit provided in the image forming apparatus body or the paper-feeding unit so as to guide the tail edge of the print medium to the outside. 
         [0018]    The retreating path may further comprise an inclined part for guiding the tail edge of the print medium moving in the first direction to the guide slit; the inclined part provides a frictional force so as to prevent double-feeding. 
         [0019]    The image forming apparatus may further comprise a paper-feeding guider provided between the image forming apparatus body and the paper-feeding unit for guiding the leading edge of the print medium to the image forming unit when the print medium moved to the pick-up position is transferred in the second direction. 
         [0020]    The paper-feeding unit may comprise a paper-feeding cassette having a length corresponding to that of the image forming apparatus body and a width smaller than that of the image forming apparatus body. 
         [0021]    According to another aspect of the present invention, there is provided a method of feeding a print medium comprising positioning a print medium at a pick-up position by moving the print medium in a first direction and moving the print medium positioned at the pick-up position in a second direction. 
         [0022]    Here, the positioning the print medium at the pick-up position may comprise rotating a pick-up roller in the first direction. 
         [0023]    In addition, the positioning the print medium at the pick-up position may comprise: sensing whether the print medium is moved to the pick-up position; and stopping the driving of the pick-up roller in the first direction when the print medium moved to the pick-up position is sensed. 
         [0024]    The picking up the print medium may comprise reversely rotating the pick-up roller in the second direction. 
         [0025]    In addition, the paper-feeding method may further comprise: sensing whether the picked-up printing medium is admitted into the image forming unit; and stopping the rotational driving of the pick-up roller in the second direction when the print medium is admitted into the image forming unit. 
         [0026]    Additional aspects and/or advantages of the invention 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 invention. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
           [0028]      FIG. 1  is a perspective view to show schematically a conventional portable image forming apparatus; 
           [0029]      FIG. 2  is a perspective view to show schematically an image forming apparatus according to an embodiment of the present invention; 
           [0030]      FIG. 3  is a block diagram to show schematically a control system according to an embodiment of the present invention; 
           [0031]      FIGS. 4 to 8  are cross-sectional views to show a paper-feeding process in sequence; and 
           [0032]      FIG. 9  is a view to show schematically a print medium provided with a mark. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0033]    Reference will now be made in detail to the present embodiments of the present invention, 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 invention by referring to the figures. 
         [0034]    As shown in  FIGS. 2 to 4 , the image forming apparatus according to an embodiment of the present invention comprises an image forming apparatus body  10 , an image forming unit  20 , a paper-feeding unit  30 , and a controller  60 . It is understood that while embodiments of the present invention may use paper as a print medium, and the description below refers to various components in terms of the manipulation of paper (e.g. the paper-feeding unit), other aspects of the present invention may utilize any print medium. According to other aspects of the present invention, paper-feeding unit  30 , as well as other components described as manipulating paper, may also manipulate other print media. For example, paper-feeding unit  30  may manipulate other print media as well, such as transparent film. Further, it is understood that in some aspects of the present invention the image forming apparatus is a portable image forming apparatus. 
         [0035]    The image forming apparatus body  10  incorporates a series of components for forming an image on a print medium P, such as the image forming unit  20 , a battery  11 , and a control substrate  12 . Here, the battery  11  is provided for supplying a power for image forming operation, and the control substrate  12  is provided for controlling the image forming operation. However, it is understood that the image forming apparatus body may have other components, such as input ports for receiving image data from an external storage device or a wired/wireless connection. 
         [0036]    In addition, the image forming apparatus body  10  is formed with first and second paper-discharging ports  10   a  and  10   b  for discharging an image-formed print medium to the outside. Other aspects of the present invention may have more or fewer paper-discharging ports. 
         [0037]    The image forming unit  20  forms an image corresponding to an image signal inputted from the outside on a print medium P, wherein the image forming unit  20  comprises a print head  21 , a platen roller  22 , and a feed roller  23 . 
         [0038]    The print head  21  forms an image on the print medium P. The print head  21  is exemplified as a thermal transfer type head having a plurality of heaters (not shown) for heating the print medium P so as to implement a color image. However, other aspects of the present invention may utilize other types of print heads or printing techniques. 
         [0039]    The platen roller  22  compresses the print medium P against the print head  21 , thereby supporting the print medium P while printing is performed on the print medium P. As shown in  FIG. 7 , the platen roller  22  is movably mounted in such a manner as to support the print medium P against the print head  21  only while an image is being formed on the print medium P. This is to prevent the platen roller  22  from interfering with the feeding force of the print medium P given by the feed roller  23 . 
         [0040]    The feed roller  23  serves to feed and discharge an image-formed print medium P to the outside, wherein the feed roller  23  may consist of a pair of rollers. The feed roller  23  may rotate in an “R2” direction as shown in  FIG. 6 , so that the print medium P is discharged through the first paper-discharge port  10   a.    
         [0041]    However, the present invention is not limited to this. It is natural that it is possible to configure the feed roller  23  to be bi-directionally rotatable according to the paper-discharge direction of the image-formed print medium P. 
         [0042]    That is, as shown in  FIG. 8 , the feed roller  23  may rotate in an “R1” direction, thereby moving the image-formed print medium P in an “A” direction, so that the print medium P is discharged through the second paper-discharge port  10   b.    
         [0043]    Meanwhile, a paper sensor  50  is provided between the print head  21  and the feed roller  23  so as to detect whether the print medium P fed by the paper-feeding unit  30  is admitted to a print position or not. The paper sensor  50  senses the leading edge of the print medium P before the print medium P is admitted into the feed roller  23  so as to determine the timing for positioning the platen roller  22 . 
         [0044]    That is, if the paper sensor  50  senses the admission of the print medium P. the platen roller  22  moves toward the print head  21  and supports the print medium P. 
         [0045]    It is understood that the image forming unit  20  according to other aspects of the present invention may include other or different components, such as components for receiving image data. In addition to other operations, the image forming unit  20  should be able to accept a print medium from the paper-feeding unit  30 , to form an image on the print medium P, and to discharge the print medium P to the outside. 
         [0046]    The paper-feeding unit  30  is movably mounted in relation to the image forming apparatus body  10 , wherein the paper-feeding unit  30  turns the print medium P in a reverse direction at least one time, thereby accomplishing the single-sheet feeding of the print medium P to the image forming unit  20 . Such a paper-feeding unit  30  comprises a paper-feeding cassette  31 , a pick-up roller  32 , a knock-up plate  33 , a compression member  34 , a retreating path  35 , a paper-feeding guider  36 , and an idle roller  37 . 
         [0047]    The paper-feeding cassette  31  is loaded with a predetermined number of print media P in a paper loading position, and at least one end of the paper-feeding cassette  31  is removably installed to the image forming apparatus body  10 . More particularly, as shown in  FIG. 4 , one end of the paper-feeding cassette  31  is rotatably connected to the image forming apparatus body  10  by a hinge H, and the other end is removably connected to the image forming apparatus body  10 . 
         [0048]    In other words, the paper-feeding cassette  31  is mounted in such a manner as to be capable of being opened/closed in relation to the underside of the image forming apparatus body  10 . Here, the paper-feeding cassette  31  preferably has a length corresponding to that of the image forming apparatus body  10  and a width smaller than that of the image forming apparatus body  10 . However, it is understood that the paper-feeding cassette may be connected to the image forming apparatus body in any fashion. 
         [0049]    The pick-up roller  32  receives a driving force transmitted from the driving motor  32   b  through the driving motor  32   a , wherein the pick-up roller  32  is installed in the image forming apparatus body  10  in such a manner as to be capable of bi-directionally rotating. In addition, the pick-up roller  32  moves the print medium P to a pick-up position when it rotates in a first direction R 1  as shown in  FIGS. 4 and 5 , and, when it rotates in a second direction R 2  as shown in  FIGS. 6 and 7 , the pick-up roller  32  picks up the print medium P and feeds the print medium P to the image forming unit  20 . 
         [0050]    The pick-up roller  32  is positioned to be spaced from the leading edge of the print medium P contained in the paper-feeding cassette  31 , so that it can move the print medium P to the pick-up position when the pick-up roller  32  reversely rotates at least one time. 
         [0051]    The knock-up plate  33  is installed in the paper-feeding cassette  31  in such a manner as to be capable of being lifted or lowered and of elastically supporting the print medium P against the pick-up roller  32 . For this reason, the pick-up roller  32  and the print medium P are maintained in contact with each other. 
         [0052]    The compression member  34  provides an elastic force for elastically supporting the knock-up plate  33  against the pick-up roller  32 . 
         [0053]    The retreating path  35  is provided in the image forming apparatus body  10  or the paper-feeding cassette  31  and guides the tail edge of the print medium P moved in the first direction R 1  by the pick-up roller  32 . 
         [0054]    The retreating path  35  comprises a guide slit  35   a  for guiding the tail edge of the print medium P to the outside, and an inclined part  35   b  for guiding the tail edge of the print medium P to the guide slit  35   a . Here, the inclined part  35   b  provides a frictional force for single-sheet feeding of a plurality of print media P loaded in the paper-feeding cassette  31 , thereby preventing double-sheet feeding. 
         [0055]    As shown in  FIG. 4 , the guide slit  35   a  has a gap G allowing a sheet of a print medium to pass the guide slit  35   a  so as to prevent double-sheet feeding. 
         [0056]    As shown in  FIG. 6 , the paper-feeding guider  36  guides the leading edge of the print medium P, which (as shown in  FIG. 5 ) has moved to the pick-up position by the rotation of the pick-up roller  32  in the second direction R 1 , to the image forming unit  20 . 
         [0057]    The paper-feeding guider  36  is provided between the image forming apparatus body  10  and the paper-feeding cassette  31  to be opposite to the pick-up roller  32 , and more preferably to be lowered by a predetermined depth and project into the paper-feeding cassette  31 . This is to assure that the paper-feeding guider  36  guides the leading edge of the print medium P to be smoothly admitted into the image forming unit  20  while the print medium P is being fed. 
         [0058]    Meanwhile, an idle roller  37  is rotatably mounted on the paper-feeding guider  36  between the paper-feeding cassette  31  and the image forming apparatus body  32 , wherein the idle roller  37  comes into contact with the print surface of a print medium P moved in the “A” direction by the rotation of the pick-up roller  32  in the first direction R 1  and guides the print medium P. 
         [0059]    The idle roller  37  is provided so as to prevent the print surface of the print medium P from being damaged by friction, for example, by friction such as scratch caused by the paper-feeding guider  36  occurring while the print medium P is transferred. 
         [0060]    As shown in  FIG. 3 , the controller  60  receives input from the pick-up sensor  40  and the paper sensor  50  and controls the driving of the pick-up roller  32  and the image forming unit  20 . In particular, the controller  60  controls the rotating force of the feed roller  23 , the positional displacement of the platen roller  22 , the image forming operation of the print head  21 , etc., in response to the information sensed by the paper sensor  50  as described above. However, it is understood that according to other aspects, the controller  60  may receive input from any source, such as from the outside, and may control operation of any component of the image formation apparatus. 
         [0061]    In addition, the controller  60  controls the rotation of the pick-up roller  32  in the first and second directions R 1  and R 2  on the basis of information sensed by a pick-up sensor  40 , wherein the pick-up sensor  40  is positioned between the pick-up roller  32  and the paper-feeding guider  36  and senses a print medium P at the pick-up position. At this time, the controller  60  controls the driving motor  32   a  connected to the pick-up roller  32  so as to control the rotating direction of the pick-up roller  32 . 
         [0062]    The controller  60  stops the driving of the pick-up roller  32  on the basis of a sensing signal for the print medium P, which is applied from the paper sensor  50 . This is to prevent tearing and poor image formation of the print medium P caused by the difference in driving force between the pick-up roller  32  and the feed roller  23 . If the pick-up roller  32  and the feed roller  23  have different driving forces, the print medium P may become stretched or compressed, negatively impacting formation of an image on the print medium P and potentially damaging the print medium P as well. 
         [0063]    Meanwhile, as shown in  FIG. 9 , the leading edge of the print medium P has a mark M which is sensed by the pick-up sensor  40 . The mark M is located in a non-image forming area of the print medium M, so that the mark does not interfere with an image to be formed. In addition, the mark M of the print medium P can also be sensed by the paper sensor  50 . 
         [0064]    Now, the paper-feeding and image forming operations of the inventive image forming apparatus are described with reference to the accompanying drawings. 
         [0065]    As shown in  FIG. 4 , the top print medium P among the print media P loaded in the paper-feeding cassette  31  is in contact with the pick-up roller  32  by being elastically supported by the knock-up plate  33 , which is compressed by the compression member  34 . At this time, if an image forming operation signal is inputted from the outside, the pick-up roller  32  rotates in the “R1” direction, thereby moving the print medium P in the “A” direction. 
         [0066]    The tail edge of the print medium P moving in the “A” direction is guided along the inclined part  35   b , separated as a single sheet through the guide slit  35   a , and then transferred to the outside of the paper-feeding cassette  31  as shown in  FIG. 5 . At this time, the print surface of the print medium P is being transferred by the idle roller  37  without friction at the leading edge of the print medium P. 
         [0067]    Thereafter, if the mark M at the leading edge of the print medium P as shown in  FIG. 9  is sensed by the pick-up sensor  40 , the driving of the pick-up roller  32  in the first direction R 1  is stopped and the pick-up roller  32  reversely rotates in the second direction R 2 . 
         [0068]    At this time, as shown in  FIG. 6 , the leading edge of the print medium P is smoothly admitted into the image forming unit  20  by the paper-feeding guider  37  and the elasticity of the knock-up plate  33 . The print medium P fed to the image forming unit  20  in this manner is continuously moved by the rotation of the pick-up roller in the second direction R 2 , thereby being admitted into the feed roller  23 . 
         [0069]    Here, if the leading edge of the print medium P is sensed by the paper sensor  50 , which is interposed between the feed roller  23  and the print head  21 , the platen roller  22  moves toward the print head  21  as shown in  FIG. 7 . 
         [0070]    The print medium P supported by the platen roller  22  in this manner is continuously transferred by the feed roller  23  after a predetermined image is formed on the print medium P by the print head  21 , thereby being discharged to the outside. When the paper sensor  50  senses the leading edge of the print medium P, the pick-up roller  32  stops the rotational driving in the second direction R 2 . 
         [0071]    Meanwhile, the image-formed print medium P is discharged through the first paper discharge port  10   a  of the image forming apparatus body  10  as shown in  FIG. 7  or through the second paper discharge port  10   b  as shown in  FIG. 8 , depending on the rotating direction of the feed roller  23 . 
         [0072]    As described above, according to aspects of the present invention, it is not required to secure a space for mounting a paper-feeding unit because such a paper-feeding unit is provided within the image forming apparatus body. As a result, it is possible to provide a compact image forming apparatus. In addition, because the paper-feeding unit can be easily moved even if it is provided within the image forming apparatus body, the image forming apparatus can be easily and conveniently carried. These features are useful for portable image forming apparatuses, where size and ease of portability are important considerations. 
         [0073]    Although representative embodiments of the present invention have been shown and described in order to exemplify the principle of the present invention, the present invention is not limited to the specific embodiments. It will be understood that various modifications and changes can be made by one skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, it shall be considered that such modifications, changes and equivalents thereof are all included within the scope of the present invention. 
         [0074]    Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.