Abstract:
An apparatus to feed paper in an image forming device, which picks up papers with various thickness received in the feeding stand without a feeding error, and transfers the same to the developing unit. The apparatus includes, a feeding stand to receive a plurality of papers, and having a separating guide inclined at a predetermined angle with which the front end of the paper makes contact with; a main pickup roller that makes contact with the paper on the uppermost layer in the upper part of the feeding stand to pick up the paper towards the separating guide using frictional force generated via rotational contact with the paper; and an auxiliary pickup roller positioned between the main pickup roller and the separating guide to apply a predetermined pressure to the paper upon picking up of the paper by the main pickup roller.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of Korean Patent Application No. 2003-53976 filed Aug. 5, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an image forming device, more particularly, to an apparatus to feed paper in an image forming device, which picks up papers of various thicknesses in a feeding stand of the image forming device, and transfers the same to a developing unit without a feeding error. 
   2. Description of the Related Art 
     FIG. 1  is a perspective view of a conventional apparatus to feed paper in a printing apparatus that comprises: a feeding cassette  10  in which paper is received, and a pickup unit  20  to pick up the received paper. 
   The feeding cassette  10  receives a plurality of papers to allow the printing apparatus to sequentially perform print operations. The feeding cassette  10  has a dam-type separating guide  11  with which a front end of the paper makes contact, and the separating guide  11  is provided with at least one friction plate  12 . 
   The pickup unit  20  is installed to the main machine of the printing apparatus (not shown) corresponding to the feeding cassette  10  provided. The pickup unit  20  includes: a pickup roller  21  to pick up the paper in the feeding cassette  10 ; a pickup arm  22  having a gear train to operate the pickup roller; and an operating motor  23  to deliver power to the pickup arm  22 . 
   According to the conventional feeding apparatus, when the operating motor  23  operates according to a print signal from a controlling unit (not shown), the pickup roller  21  rotates via the gear train, and the paper is picked up by rotation of the pickup roller  21 . The picked up paper P is separated and transferred by the separating guide  11  installed to a front end of the feeding cassette  10 . 
   According to the conventional apparatus, a predetermined distance between the pickup roller  21  and the separating guide  11  is maintained regardless of the thickness of the paper, thus, overlapped transfer of papers could occur when paper with low stiffness (e.g. a thin paper) is picked up, and a printing error is generated due to a pick up error when paper with high stiffness (e.g. a thick paper) is picked up. 
   In addition, because the distance between the pickup roller  21  and the separating guide  11  is maintained constant, and a slope of the separating guide  11  is fixed, a high torque is required to pick up a thick paper, resulting in high power consumption and damage to the front end of the paper due to a resisting force against the separating guide  11 . 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention is provided to solve the above and/or other problems of the conventional art, thus, an apparatus to feed paper in an image forming device, which picks up papers of various thicknesses in a feeding stand and transfers the same to a developing unit without a feeding error is provided. 
   According to another aspect of the present invention, an apparatus to feed paper in an image forming device that uniformly controls operating torque and reduces power consumption, and noise is provided. 
   In order to accomplish the above and/or other aspects of the present invention, an apparatus to feed paper in an image forming device includes: a feeding stand to receive a plurality of papers and having a separating guide with which a front end of the plurality of papers makes contact with; a main pickup roller installed so as to make contact with an uppermost layer of the plurality of papers in an upper part of the feeding stand to separately transfer the plurality of papers towards the separating guide; and an auxiliary pickup roller to apply a predetermined pressure to the plurality of papers upon transfer of the plurality of papers via the main pickup roller. 
   Additional aspects and 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. 
   In accordance with another aspect of the present invention, an apparatus to feed paper in an image forming device includes: a feeding stand to receive a plurality of papers, having a separating guide inclined at a predetermined angle with which a front end of the plurality of papers makes contact; a main pickup roller installed to make contact with an uppermost layer of the plurality of papers in an upper part of the feeding stand to transfer the paper towards the separating guide using frictional force generated by rotational contact with the plurality of papers; an auxiliary pickup roller positioned between the main pickup roller and the separating guide to apply a predetermined pressure on the plurality of papers upon transfer of the plurality of papers via the main pickup roller; and an exciting unit to prevent overlapped transfer of the plurality of papers by providing vibration to the plurality of papers. 
   According to an aspect of the present invention, a vertical pressure application force including the weight of the auxiliary pickup roller is set larger than buckling force of a paper having general thickness. Thus, buckling is induced between the auxiliary pickup roller and the separating guide by a front end resistance force of the separating guide so that the paper is picked up. And in a case where thick paper is received via the feeding stand, pickup by slipping against the separating guide is generated at the front end of the thick paper so that the auxiliary pickup roller is raised up. 
   Additionally, according to an aspect of the invention, the main pickup roller is installed to an end of a pickup bracket having a gear train to transfer external power to the main pickup roller, and the auxiliary pickup roller is rotatably installed to an axis of the main pickup roller via at least one supporting plate. 
   According to another aspect of the invention, the distance between the auxiliary pickup roller and the separating guide is within a range of 10˜35 mm, and the vertical pressure application force may be in a range of 30˜70 gf. 
   According to an aspect of the present invention, a surface of the auxiliary pickup roller comprises a friction member having more than a predetermined frictional force. 
   According to an aspect of the present invention, the auxiliary pickup roller is installed to run idle and rotates only when paper is transferred or operates with the same linear velocity as the main pickup roller. 
   Further, according to another aspect of the invention, at least two auxiliary pickup rollers are provided. And, the auxiliary pickup roller may also be provided as combination of a plurality of divided roller members. 
   According to another aspect of the invention, a pressure applying unit or method to generate and maintain vertical pressure application force of the auxiliary pickup roller may be provided where the pressure applying unit or method is supported via the pickup bracket at one end and is supported via the supporting plate at another end, and has an elastic member to apply pressure on the supporting plate. A torsion spring, a coil spring, or a plate spring may be used as the elastic member. 
   According to another aspect of the present invention, an exciting unit to prevent overlapped transfer of paper may be additionally provided. The exciting unit includes at least one cam member eccentrically connected to an axis projected from an arbitrary gear of the gear train to transfer power to the main pickup roller, and to generate vibration using disproportion of mass due to rotation of the cam member. 
   According to an aspect of the present invention, the exciting unit may use a vibration member. 
   According to yet another aspect of the present invention, the apparatus to feed paper in an image forming device includes: a feeding stand to receive a plurality of papers and having a separating guide inclined at a predetermined angle with which the front end of the plurality of papers makes contact; a main pickup roller installed to make contact with the plurality of papers on the uppermost layer in the upper part of the feeding stand to pick up the plurality of papers towards the separating guide using frictional force generated by rotational contact with the plurality of papers; and an auxiliary pickup roller positioned between the main pickup roller and the separating guide to apply a predetermined pressure on the paper when the paper is pick up by the main pickup roller, where the main pickup roller is of a cam structure having an eccentric axis, and picks up a paper in an impact manner by generating vibration upon rotation. 
   According to an aspect of the present invention, a vertical pressure application force including the weight of the auxiliary pickup roller is set larger than buckling force of paper having general thickness. Accordingly, in a case where the paper having general thickness is fed into the feeding stand, buckling is induced between the auxiliary pickup roller and the separating guide by front end resisting force of the separating guide so that the paper is picked up, alternatively, when thicker paper is fed into the feeding stand, pickup by slipping against the separating guide is generated at the front end of the thick paper so that the auxiliary pickup roller is raised up. 
   In addition, a pair of idle rollers that are rotatable are provided to the eccentric axis in order to prevent vibration occurring upon impact-picking of a paper by the cam type main pickup roller, and the idle roller may have a friction member with a surface having a predetermined frictional force. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and/or other aspects 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: 
       FIG. 1  is a perspective view to show an apparatus to feed a paper in a printing apparatus according to a conventional art; 
       FIG. 2  is a perspective view to show an apparatus to feed paper in an image forming device according to an aspect of the present invention; 
       FIG. 3A  is a view schematically showing feeding operation of a thin paper in an image forming device according to an aspect of the present invention; 
       FIG. 3B  is a view schematically showing feeding operation of a thick paper in an image forming device according to an aspect of the present invention; 
       FIG. 4  is a perspective view showing an apparatus to feed a paper in an image forming device according to another aspect of the present invention; and 
       FIG. 5  is a perspective view to show an apparatus to feed a paper in an image forming device according to still another aspect of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. 
   In the following description of the present invention, detailed descriptions of well-known functions or constructions are omitted. 
   As shown in  FIG. 2  through  FIG. 3B , an apparatus to feed paper in an image forming device according to an aspect of the present invention, includes: a feeding stand  10 , a main pickup roller  100 , and an auxiliary pickup roller  200 . The feeding stand  10  is integrally formed in a frame of the image forming device (not shown), and has a separating guide  11  that makes contact with a front end of a paper P in an inner surface of the separating guide  11 . The separating guide  11  has a predetermined dam-type slope, and a plurality of friction members  12  attached to the surface of the separating guide  11 . 
   The main pickup roller  100  is provided with power via a power transferring unit  110  of a main machine of the image forming device, and rotates to pick up the paper P in the feeding stand  10 . 
   The power transferring unit  110  includes: an operating axis  111  to transfer power from an operating source (not shown) in the main machine of the printing apparatus, and a pickup bracket  112 . 
   A power transferring gear  111   a  is connected to the operating axis  111  to transfer power from the operating source to the operating axis  111 . 
   The inside of the pickup bracket  112  is provided with the gear train that includes a power input part  112   a  connected to the operating axis  111 , and a power output part  112   b  connected to the main pickup roller  100 . 
   Further, one end of a pickup arm  113  is connected, in a hinge manner, to the main machine of the image forming device to support the main pickup roller  100 , and the other end is connected to the power output part  112   b . The auxiliary pickup roller  200  is installed between the main pickup roller  100  and the separating guide  11  through the pickup arm  113 . The auxiliary pickup roller  200  is installed between the main pickup roller  100  and the separating guide  11  via at least one supporting plate  210  that includes a first connecting part  211  rotatably connected to the rotational axis  101  of the main pickup roller  100 , and a second connecting part  212  to which the auxiliary pickup roller  200  is rotatably installed. According to an aspect of the invention the distance L between the auxiliary pickup roller  200  and the separating guide  11  is within a range of 10˜35 mm. 
   Although pressure can be applied to the paper P in the feeding stand  10  using the weight of the auxiliary pickup roller  200 , according to an aspect of the invention, the paper P in the feeding stand  10  is pressed via an elastic member having a torsion spring with one end connected to the rotational axis of the main pickup roller  100 , and with another end connected to the supporting plate  210 . Although a torsion spring  220  has been used for exemplary purposes, a coil spring or a plate spring could be used as the elastic member as far as elastic force is provided on the auxiliary pickup roller  200 . 
   In addition, according to an aspect of the present invention, the apparatus to feed paper in the image forming device includes an exciting unit  300  to prevent overlapped transfer of paper by applying vibration on the paper P when the paper P is picked up by the main pickup roller  100 . 
   The exciting unit  300 , as shown in  FIG. 2 , has a cam member including an eccentric rotational axis to transfer vibration, due to a disproportion of mass occurring upon rotation, to the power transferring unit. The cam member is rotated via one of the gears constituting the power transferring unit  110 . According to an aspect of the present invention, a pair of exciting units  300  are provided to both sides of the power transferring unit  110 , and a vibration element using a piezo-electric body may be used as the exciting unit  300 . 
     FIG. 3A  and  FIG. 3B  show a pickup operation, which is based on thickness of a paper, performed by the apparatus to feed the paper in the image forming device according to an aspect of the present invention shown in  FIG. 2 . As shown in  FIG. 3A , a thin paper P 1  picked up via the main pickup roller  100  proceeds to the separating guide  11  while rotating the auxiliary pickup roller  200 . The auxiliary pickup roller  200  is connected to the rotational axis  101  of the main pickup roller  100  through the supporting plate  210  so that the auxiliary pickup roller  200  runs idle. Because the pickup bracket  112  having the gear train does not transfer power delivered to the main pickup roller  100  to the auxiliary pickup roller  200 , the auxiliary pickup roller  200  is merely rotated by frictional force created when the paper P 1  picked up by rotation of the main pickup roller  100  passes through the auxiliary pickup roller  200 . 
   The auxiliary pickup roller  200  is installed so as to maintain a predetermined interval L from the separating guide  11 . As shown in  FIG. 3A , when thin paper P 1  is provided to the feeding stand, a front end of the paper P 1  is bent between the auxiliary pickup roller  200  and the separating guide  11  to generate buckling, thereby, allowing each paper to be picked up separately. Although the main pickup roller  100  actually picks up the paper P 1 , pressure application force of the auxiliary pickup roller  200  that exerts pressure application force in a vertical direction to the paper P 1  is relatively high compared to stiffness of the paper P 1  which is thin, thus, the buckling that the front end of the paper P 1  is bent while picked up, is not generated between the main pickup roller  100  and the separating guide  11 , but between the auxiliary pickup roller  200  and the separating guide  11 . Therefore, the auxiliary pickup roller  200  provides the same effect of picking up the thin paper P 1  similar to a pickup roller that is power-operated. 
   As shown in  FIG. 3B , when a thick paper P 2  is picked up by the main pickup roller  100 , the thick paper P 2  proceeds to the separating guide  11  while rotating the auxiliary pickup roller  200 . In this case, because the thick paper P 2  has a relatively high stiffness compared to the thin paper P 1 , the thick paper P 2  is not easily bent. Therefore, the pressure application force of the auxiliary pickup roller exerted in the direction perpendicular to the paper P 2  is controlled to be lower than the stiffness of the thick paper P 2  so that the auxiliary pickup roller  200  could be raised upward by the stiffness of the thick paper P 2  when the thick paper P 2  passes through the auxiliary pickup roller  200  while rotating the auxiliary pickup roller  200 . In that case, the thick paper P 2  is picked up, forming a smooth curve as shown in  FIG. 3B  with the front end of the paper P 2  slipped against the separating guide  11  by torque applied on the application point T of the main pickup roller  100 . Further, relative position of the application point T of the main pickup roller  100  to pick up the thick paper P 2  is situated a rear portion of the feeding stand  10  compared to the application point t of the auxiliary pickup roller  200 , thus, the main pickup roller  100  picks up the thick paper P 2  by only using torque required to pick up the thin paper P 1  described above. Therefore, operation noise due to load increase in the operating motor that transfers operating force to the main pickup roller  100  could be reduced and power consumption could be reduced. 
   Further, according to an aspect of the apparatus to feed paper in the image forming device of the present invention, because additional load due to variations in the thickness of the paper in the feeding stand  10  does not occur, an operating force applied to the main pickup roller  100  can be made constant. In addition, due to the disproportion of rotational force generated by rotation of the exciting unit  300  having the eccentric rotational axis, additional pressure application force is irregularly applied to the main pickup roller  100 , whereby, vibration is generated. Accordingly, the paper P is more easily separated so that overlapped transfer of the paper is prevented. 
   As shown in  FIG. 4 , a plurality of auxiliary pickup rollers  200  are provided to the apparatus to feed paper according to another aspect of the present invention. In this case, as a contact area between the auxiliary pickup roller  200  and the paper P is reduced, pressure application force per unit area increases, but load of the operating motor could be maintained constant regardless of the thickness of the paper P, and overlapped transfer of the paper is prevented in the same manner. However, because the same pickup operation described above is used, a description thereof will be omitted. 
     FIG. 5  is a drawing to show the apparatus to feed a paper in the printing apparatus having an eccentric rotational axis of the pickup roller to pick up the paper P, according to another aspect of the present invention. 
   The eccentric pickup roller  400  is connected to the rotational axis  101  in an eccentric manner, and picks up the paper P in the feeding stand  10 , directly hitting the paper P. In this case, as the paper P makes contact with the eccentric pickup roller  400  intermittently, the whole power transferring unit  110  including the pickup bracket  112  may be shaken. Therefore, in order to prevent such shaking, an idle roller  410  is provided coaxially with respect to the rotational axis  101  of the eccentric pickup roller  400  that runs idle. In addition, the outer periphery of the eccentric pickup roller  400  is equipped with friction members similar to the above-mentioned friction members  12 , which are provided to the separating guide  11 , to exert resisting force over a predetermined level. 
   Therefore, as the paper P is hit upon during pick up by the eccentric pickup roller  400 , simultaneous pick up of a plurality of papers or a printing error generated due to pickup failure is prevented. Also, unlike the aspect of the invention previously described, because the eccentric pickup roller  400  functions as the exciting unit, the exciting unit  300  is not required. 
   According to the apparatus to feed paper in the image forming device of the present invention, pick up failure of thick paper can be prevented, thus, torque of the operating motor is maintained constant regardless of the thickness of the paper. Therefore, noise of the operating motor generated due to load increase upon picking up of the thick paper is reduced, and power consumption of the image forming device is also reduced. 
   In addition, during pickup operation, the pressure application force is irregularly applied to the main pickup roller repeatedly via the exciting unit so that vibration is generated, thus, overlapped transfer of the paper that may occur when the paper is picked up, is additionally prevented. 
   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.