Patent Publication Number: US-6659449-B2

Title: Pickup device for use in an image forming apparatus

Description:
CLAIM OF PRIORITY 
     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from my application PAPER PICK-UP DEVICE FOR IMAGE FORMING APPARATUS filed with the Korean Industrial Property Office on Dec. 29, 2000 and there duly assigned Serial No. 86388/2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a pickup device for use in an image forming apparatus, such as a printer, a copier, or the like, for picking up paper from a cassette and feeding the picked up paper to an image forming engine portion. More particularly, the invention relates to a pickup device for use in an image forming apparatus having a pickup unit for driving a pickup roller upward and downward in association with loading/unloading of the cassette. 
     2. Related Art 
     Generally, an image forming apparatus, such as a laser printer, a copier or the like, has a pickup device for sequentially picking up paper which is stacked or piled on a cassette detachably mounted in a main body of the image forming apparatus. The picked up paper is fed to an image forming engine portion. 
     A conventional pickup device of an image forming apparatus includes a hopper plate formed on the bottom of the cassette which is removable from the body of the image forming apparatus. The hopper plate is biased upward by a spring. Plural sheets of paper are loaded on the hopper plate in such a manner that an uppermost sheet of paper is in close contact elastically with a pickup roller. As a result of a rotational driving force of the pickup roller, the uppermost sheet of paper is fed to the image forming engine portion. 
     Accordingly, in the conventional image forming apparatus as described above, the cassette is usually loaded in or unloaded from the image forming apparatus in a direction corresponding to the direction in which the paper is fed and discharged. Therefore, front and rear ends of the image forming apparatus have to be large enough to permit loading or unloading of a cassette for accommodating large-sized paper. 
     To solve the above-described problem, the cassette can be loaded or unloaded through a side of the body of the image forming apparatus. However, in this case, jamming of the uppermost sheet of paper often occurs while mounting the cassette in the body of the image forming apparatus. 
     SUMMARY OF THE INVENTION 
     The present invention has been developed in order to overcome the above-mentioned problems of the related art. Accordingly, it is an object of the present invention to provide a pickup device for use in an image forming apparatus capable of picking up and feeding paper through upward and downward driving of a pickup roller in association with loading/unloading of a paper cassette. 
     Another object of the present invention is to provide a pickup device for reducing the volumetric appearance of the image forming apparatus by feeding the paper in a direction perpendicular to a paper cassette loading or unloading direction. 
     Yet another object of the present invention is to provide a pickup device capable of detecting and displaying information about the amount of remaining paper or lack of paper while picking up and feeding the paper from the paper cassette. 
     In order to accomplish the above objects, the invention provides a pickup unit for use in an image forming apparatus for picking up a sheet of paper from a stack or pile of paper loaded in a cassette which is detachably mounted in a body of the image forming apparatus. The paper is provided to an image forming engine portion. The pickup unit includes: a pickup roller for feeding an uppermost sheet of paper from the pile of paper on the cassette in a predetermined direction by contacting it, and thus transmitting a rotational driving force thereto; loading/unloading means for moving the pickup roller upward and downward in association with the loading/unloading of the cassette; and driving means for transmitting the rotational driving force to the pickup roller, thereby feeding paper from the cassette sequentially. 
     According to one aspect of the present invention, the loading/unloading means includes: a cam projection protruding from a leading end of the cassette; a supporting frame disposed on a cassette mounting portion of the body; a cam lever formed on the supporting frame and elastically biased in a predetermined direction so as to be interfered with, and thus pivoted by, the cam projection during the loading/unloading of the cassette; a pickup bracket disposed on the supporting frame, the pickup bracket having a free end which is moved upward and downward while rotatably supporting the pickup roller; an elastic body for elastically biasing the free end of the pickup bracket toward the cassette; and a locking arm connected with the cam lever so as to be operated in association with the cam lever for selectively locking/unlocking the pickup bracket. 
     According to another aspect of the present invention, the loading/unloading means includes locking/unlocking means for selectively restricting, and thus setting, the pickup bracket to be able to move upward and downward by manipulation of a main controller which is formed on the body irrespective of the loading/unloading of the cassette. The locking/unlocking means includes: a solenoid unit disposed on the supporting frame and controlled by the main controller; a rotary shaft disposed on the supporting frame and pivoted according to operation of the solenoid unit; and a hook member disposed on one end of the rotary shaft for selectively restricting, and thus locking/unlocking, the pickup bracket according to a pivoting movement of the rotary shaft. 
     According to yet another aspect of the present invention, the pickup unit includes paper remainder detecting means for detecting the remainder of the stack of paper, and for displaying detected information. The paper remainder detecting means includes: a paper contact lever moved upward and downward by the loading/unloading means to contact with the stack of paper on the cassette; a link arm pivoted in association with the paper contact lever, the link arm having a long hole formed in a body thereof; a guide portion disposed on the supporting frame and in parallel relation with respect to a side of the link arm, the guide portion having a guide slit overlapping a travel path of the long hole during a pivoting of the link arm; a slide pin restrictively connected in such a manner that it is passed through the long hole and the guide slit, said slide pin being linearly slid according to the pivoting of the paper contact lever and the link arm; and sensing means for detecting and outputting information about a displacement location of the slide pin in the form of a signal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which like reference numerals indicate the same or similar components, and wherein: 
     FIG. 1 is a schematic sectional view showing a pickup device employed in an image forming apparatus; 
     FIG. 2 is a schematic perspective view showing the main portion (i.e., the pickup device) according to the present invention; 
     FIG. 3 is a perspective view showing in detail the structure of the pickup device of an image forming apparatus according to the present invention; 
     FIG. 4 is a plan view schematically showing the pickup unit of FIGS. 2 and 3; 
     FIG. 5 is a partially cutaway perspective view schematically showing a pickup roller driving portion formed in the pickup device of the image forming apparatus according to a preferred embodiment of the present invention; 
     FIG. 6 is a perspective view schematically showing the main portion (i.e., a paper termination/remainder detecting portion) formed in the pickup device of the image forming apparatus according to the present invention; 
     FIG. 7 is a schematic sectional view showing the paper termination/remainder detecting portion of FIG. 6, and is used to explain the operation thereof; and 
     FIG. 8 is a partially cutaway perspective view schematically showing the main portion (i.e., the pickup device) of the image forming apparatus according to the present invention, and is used to explain the operation thereof. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     This invention will be described in further detail by way of example with reference to the attached drawings. 
     FIG. 1 schematically shows a pickup device of an image forming apparatus, including a hopper plate  21  formed on the bottom of the cassette  20 , while is removable from a body  10  of the image forming apparatus. As shown, the hopper plate  21  is biased upward by a spring  22 . Plural sheets of paper  1  are loaded on the hopper plate  21  in such a manner that an uppermost sheet of the paper  1  is in close contact elastically with a pickup roller  11 . As a result of a rotational driving force of the pickup roller  11 , the uppermost sheet of paper  1  is fed to the image forming engine portion (not shown). 
     Accordingly, in the image forming apparatus as described above, the cassette  20  is usually loaded in or unloaded from the image forming apparatus in a direction corresponding to the direction in which the paper is fed and discharged. Therefore, front and rear ends of the image forming apparatus have to be large enough to permit loading or unloading of a cassette for accommodating large-sized paper. 
     To solve the above-described problem, the cassette  20  can be loaded or unloaded through a side of the body of the image forming apparatus. However, jamming of the uppermost sheet of paper often occurs while mounting the cassette  20  in the body of the image forming apparatus. 
     FIG. 2 is a schematic perspective view showing the main portion (i.e., the pickup device) according to the present invention. Referring to FIG. 2, the pickup device of the image forming apparatus according to the present invention includes a pickup unit  200  mounted in a cassette mounting portion  101  of an image forming apparatus body  100  for sequentially picking up and feeding the paper from the cassette  120  to an image forming engine portion  110 . 
     According to the present invention, the pickup unit  200  includes a pickup roller  201  for feeding the paper in a direction perpendicular to a loading/unloading direction of cassette  120 , a loading/unloading portion  200 A for driving the pickup roller  201  upward and downward with respect to an upper portion of the paper in association with the loading/unloading of the cassette  120 , and a driving portion  200 B for transmitting a rotational driving force to the pickup roller  201  for sequentially feeding the paper from the cassette  120 . 
     According to the pickup device of the image forming apparatus of the present invention, the pickup roller  201  is mounted in a direction perpendicular to the cassette loading/unloading direction. As shown in FIG. 2, the cassette  120  is loaded or unloaded in a direction perpendicular to the direction in which the paper is picked up and fed with respect to the image forming apparatus body  100 . 
     FIG. 3 is a perspective view showing in detail the structure of the pickup device of an image forming apparatus according to the present invention, while FIG. 4 is a plan view schematically showing the pickup unit of FIGS. 2 and 3. Referring to FIGS. 3 and 4, the loading/unloading portion  200 A includes: a cam projection  121  formed on a leading end of the cassette  120 , and having a cam curve formed thereon; a supporting frame  210  mounted on the cassette mounting portion  101  of the body  100 ; a cam lever  220  mounted on the supporting frame  210  for being interfered with, and pivoted by, the cam projection  121  during loading/unloading of the cassette; a locking arm  230  for pivoting in association with the cam lever  220  in a direction opposite to that of the cam lever  220 ; and a pickup bracket  240  pivotally mounted on a supporting shaft  241 , which is mounted on the supporting frame  210 , for being restricted and moved upward and downward by the locking arm  230 . 
     The cam lever  220  is elastically biased downward toward the cassette  120  by a spring  221  disposed on the body  100 , and cam lever  220  is connected to the locking arm  230  via a rotational shaft  222  that is used for the rotation in unison of the cam lever  220  and the locking arm  230 . 
     The locking arm  230  restricts the movement of the pickup bracket  240  to the upward and downward direction as a locking pin  231 , formed on a free end of the locking arm  230 , directly and indirectly interferes with the pickup bracket  240  during a pivoting of the locking arm  230 . 
     The locking arm  230  indirectly restricts the movement of the pickup bracket  240  to the upward and downward direction by being operated in association with a hook member  262  of a locking/unlocking means  200 C and/or a paper contact lever  270  of a paper remainder detecting means  200 D. The locking/unlocking means  200 C and the paper remainder detecting means  200 D will be described later. 
     Although it is not shown in the drawings, the locking pin  231  of the locking arm  230  may directly restrict movement of the pickup bracket  240  to the upward and downward direction. 
     While rotatably supporting the pickup roller  201 , the free end of the pickup bracket  240  is elastically biased downward to the cassette  120  by the spring  242 , which is disposed on a supporting portion  242   a  of the supporting frame  210 . 
     Since the pickup roller  201  feeds the uppermost paper on the cassette  120  under proper pressure, slip occurrence is prevented. 
     FIG. 5 is a partially cutaway perspective view schematically showing a pickup roller driving portion formed in the pickup device of the image forming apparatus according to a preferred embodiment of the present invention. According to the present invention, as shown in FIG. 5, the driving portion or means  200 B of the pickup roller  201  includes a driving motor  250  supported on the supporting frame  210 , and a power transmitting means disposed on the pickup bracket  240  for transmitting the rotational driving force of the driving motor  250  to the pickup roller  201 . 
     According to one aspect of the present invention, the power transmitting means includes a belt pulley  251  connected to an output side of the driving motor  250 , a driven gear  202  disposed on a rotary axle of the pickup roller  201 , and a plurality of connecting gears  252  disposed in the pickup bracket  240  for connection to the belt pulley  251 . 
     Meanwhile, in the pickup device of the image forming apparatus according to the present invention, pickup unit  200  (referring back to FIG. 3) includes the locking/unlocking means  200 C for selectively restricting and movably setting the pickup bracket  240  upward and downward by the manipulation of a main controller (not shown), formed in the body  100 , irrespective of the loading/unloading of the cassette  120 . 
     According to one aspect of the present invention, the locking/unlocking means  200 C includes a solenoid driving unit  260  disposed on the supporting frame  210  so as to be controlled by the key input manipulation of the main controller (not shown), a rotary shaft  261  disposed on the supporting frame  210  so as to be rotated by the operation of the solenoid driving unit  260 , and a hook member  262  disposed on one end of the rotary shaft  261  for directly or indirectly restricting and thus locking/unlocking, the pickup bracket  240  according to the rotation of the rotary shaft  261 . 
     In association with the paper contact lever  270  of the paper remainder detecting means  200 D, the hook member  262  indirectly interferes with, and thus restricts the movement of, the pickup bracket  240  to the upward and downward directions. 
     In the pickup device of the image forming apparatus according to the present invention, a pickup unit  200  includes the paper remainder detecting means  200 D for detecting and indicating information about lack of paper and/or remainder of paper stacked on the cassette  120 . 
     FIG. 6 is a perspective view schematically showing the main portion (i.e., a paper termination/remainder detecting portion) formed in the pickup device of the image forming apparatus according to the present invention, FIG. 7 is a schematic sectional view showing the paper termination/remainder detecting portion of FIG. 6, used to explain the operation thereof, and FIG. 8 is a partially cutaway perspective view schematically showing the main portion (i.e., the pickup device) of the image forming apparatus according to the present invention used to explain the operation thereof. 
     Referring to FIG. 6, the paper remainder detecting means  200 D includes paper contact lever  270  rotatably disposed on the rotary shaft  272  on the supporting frame  210  in a parallel relation with respect to one side of the pickup bracket  240 , a link arm  273  rotated in association with the paper contact lever  270 , a guide portion  275  disposed on the supporting frame  210  in a parallel relation with respect to the link arm  273 , and a slide pin  276  movably passed through the link arm  273  and the guide portion  275 . 
     The paper contact lever  270  includes a locking elevation  271   a  and a locking segment  271   b  respectively protruding from the body thereof. Accordingly, as the locking elevation  271   a  and the locking segment  271   b  are respectively restricted by the hook member  262  of the locking/unlocking means  200 C, movement of the paper contact lever  270  is restricted to the upward and downward directions. 
     The link arm  273  has a long hole  273   a  formed lengthwise on the free end thereof, while the guide portion  275  has a guide slit  275   a  formed lengthwise on the body thereof and overlapping a traveling path of the long hole  273   a  during a pivoting of the link arm  273 . 
     Accordingly, in the process of being inserted through the long hole  273   a  and the guide slit  275   a , the slide pin  276  is connected to the connecting portion  276   a  so as to be displaced by being linearly moved along the guide slit  275   a  during the pivoting of the link arm  273 . 
     In this case, information as to the displacement location of the slide pin  276  is detected by a sensing means S in the form of a signal which is output to the main controller (not shown). Accordingly, the information about paper remaining in the cassette  120  is displayed. 
     The sensing means S may have a structure in which an outline of the guide slit  275   a  of the guide potion  275  is formed as an electric conductor electrically connected to a power input/output lead line. The sensing means S may also have a structure in which a conductor contacts the end of the slide pin  276 , thereby detecting electrical resistance or an electric current value variably output according to the displacement location of the slide pin  276 , and converting the detected value into a corresponding electrical signal. Furthermore, the sensing means S may have a structure in which one of various types of sensors, such as a photo-sensor, is employed to detect the displacement location of the slide pin  276 , and to output the detected result in the form of a corresponding electric signal. 
     Referring to FIGS. 3 thru  6 , while the paper contact lever  270  is moved downwardly by the sequential restriction and release of the locking pin  231  and the hook member  262 , the paper contact lever  270  is upwardly moved only by the restriction of the locking pin  231  during the pivoting of the locking arm  230 . 
     The pickup bracket  240  has a projecting portion  240   a  protruding from the body thereof so as to be mounted on the body of the paper contact lever  270 . Accordingly, the pickup bracket  240  is moved upward and downward in association with the paper contact lever  270 . 
     The pickup device of the image forming apparatus according to the present invention includes a paper termination detecting means for detecting presence of the paper on the cassette  120 . In other words, the paper termination detecting means detects whether or not there is a ‘no paper’ state. 
     The paper termination detecting means includes a slit  122  (see FIGS. 2,  3 , and  7 ) formed in the bottom of cassette  120  for permitting the leading end of the paper contact lever  270  to pass therethrough. 
     Accordingly, as shown in FIG. 7, when the leading end of the paper contact lever  270  passes downward through the slit  122 , the slide pin  276  detects the ‘no paper’ state according to the signal output as the slide pin  276  is moved to a corresponding location. 
     In another embodiment, information about the ‘no paper’ state can also be displayed by forming a separate sensor, such as a photo-sensor (not shown), around the slit  122  for detecting whether or not the leading end of the slide pin  276  has passed through the slit  122 . 
     The operation for picking up paper from the cassette  120  with the pickup device of the image forming apparatus, constructed as described above according to the present invention, will now be described in greater detail below with reference to the accompanying drawings. 
     As shown in FIGS. 2,  3  and  8 , when the cassette  120  holding paper is mounted on the cassette mount portion  110 , the cam lever  220  interferes with the cam projection  121  formed on the leading end of the cassette  120 , and is thus pivoted upward while the locking arm  230  is simultaneously pivoted downward. 
     Accordingly, the locking elevation  271   a  of the paper contact lever  270  is released by the locking pin  231  of the locking arm  240 , while the locking segment  271   b  of the paper contact lever  270  is continuously restricted by the hook member  262  of the locking/unlocking means  200 C. As a result, the paper contact lever  270  is maintained in an initial setting state. 
     In such a situation, as the user manipulates the control panel and thus inputs a print command to the main controller of the image forming apparatus, the main controller (not shown) operates the solenoid unit  260  of the locking/unlocking means  200 C, and thus pivots the rotary shaft  261  to a predetermined angle. 
     Accordingly, the hook member  262  is rotated in association with the rotary shaft  261 , and the paper contact lever  270  is released from the locking segment  271   b . As the paper contact lever  270  is released from the locking segment  271   b , the free end of the paper contact lever  270  falls free, and accordingly, the paper contact lever  270  is displaced downward into contact with an uppermost paper of the stack of paper on the cassette  120 . 
     Meanwhile, due to the downward displacement of the paper contact lever  270 , the paper remainder detecting means  200 D is operated. That is, during the downward displacement of the paper contact lever  270 , the link arm  273  is accordingly pivoted, and the slide pin  276  located in the long hole  273   a  is slid linearly along the guide slit  275   a  of the guide portion  275 . 
     The downward displacement distance of the paper contact lever  270  is determined according to the height of the stack of paper on the cassette  120 , while the displacement location of the slide pin  276  is also determined according to such determined downward displacement distance of the paper contact lever  270 . 
     Since the information about the displacement location or displacement distance of the slide pin  276  can be detected by the sensing means S connected thereto, and can be output to the main controller, the information about the paper remaining in the cassette  120  can be displayed. 
     To implement a signal detecting and outputting method of the sensing means S, the outline of the guide slit  275   a  of the guide portion  275  can be formed of a conductor connected to the lead line of the power input/output. In another embodiment, the end of the slide pin  276  may be brought into contact with the conductor for detecting electrical resistance or an electric current value variably output according to the displacement location of the slide pin  276 , and for converting such detected value into an electrical signal. 
     Further, since the paper contact lever  270  is gradually de-elevated by a minute distance according to the gradual decrease in the stack of paper in the cassette  120 , the change in the displacement distance can be reflected through the slide pin  276 , while the information about the amount of paper remaining in the cassette  120  is provided in real time. 
     Here, in the event of complete exhaustion of the paper in the cassette  120 , the leading end of the paper contact lever  270  passes through the slit  122  formed in the bottom of the cassette  120 . Based on such a state of the paper contact lever  270 , the ‘no paper’ state can be detected and displayed. The information can be detected by using the above-described sensing means S, or by using another sensor, such as a photo-sensor, that can detect whether or not the leading end of the paper contact lever  270  has passed through the slit  122 . 
     As described above, as the paper contact lever  270  is displaced downward, the pickup bracket  240  is released from the locking segment  271   b , and is thus downwardly displaced. 
     The pickup bracket  240  is elastically biased downward by the tension of the spring  242  disposed on the leading end thereof, and accordingly, the pickup roller  201  contacts the uppermost paper in the pile of paper on the cassette  120  under a predetermined tension. 
     When the paper contact lever  270  and the pickup bracket  240  are downwardly displaced, by the sequential controlling of the main controller (not shown), the pickup roller driving means  200 B is operated. Accordingly, the rotational driving force of the driving motor  250  is transmitted to the pickup roller  201  through the power transmitting means, such as the belt pulley  251  and the plurality of connecting gears  252 , and the pickup roller  201  sequentially feeds the paper stacked in the cassette  120  to the image forming engine portion  110 . 
     Meanwhile, according to the pickup device of the image forming apparatus according to the present invention, in the event of complete paper exhaustion, the cassette  120  is removed from the image forming apparatus body so as to be loaded with a new stack of paper. In such a case, the cam lever  220  is released by the cam projection  121  of the cassette  120 , and pivoted downward by the tension of the spring  221 , while the locking arm  230  is simultaneously pivoted upward accordingly. 
     Accordingly, the locking pin  231  of the locking arm  230  restricts, and thus lifts, the locking elevation  271   a  of the paper contact lever  270 , while the projecting portion  240   a  formed at one end of the pickup bracket  240 , and mounted on the locking segment  271   b  of the paper contact lever  270 , is restricted and simultaneously lifted. 
     Accordingly, in the pickup device of the image forming apparatus according to the present invention, since the pickup roller  201  is elevated or de-elevated in association with the loading/unloading of the cassette  120 , possible collision of the cassette  120  with the pickup roller  201 , or interference of the pickup roller  201  with the paper, can be prevented. 
     According to the pickup device of the image forming apparatus according to the present invention, the following effects can be achieved. 
     First, the overall size of the image forming apparatus can be reduced. In other words, since the pickup roller  201  is moved upward and downward in association with the loading/unloading of the cassette  120  to prevent interference between the pickup roller  201  and the uppermost paper during the loading of the cassette  120 , the cassette  120  can be loaded and unloaded with respect to the body of the image forming apparatus in a perpendicular direction relative to the direction in which the paper is fed and discharged. As a result, the image forming apparatus according to the present invention can be kept relatively compact compared to a method in which the cassette is loaded and unloaded in the same direction as the direction in which paper feeding and discharge take place. 
     Second, since the pickup roller  201  is downwardly displaced according to the loading/unloading of the cassette and the input of the print command, the possible collision between the cassette  120  and the pickup roller  201 , and interference between the pickup roller  201  and the paper, can be prevented. Accordingly, the occurrence of mechanical problems can be minimized, and improved performance and life span can be expected. 
     Finally, since information about the exhaustion of paper and/or the amount of paper remaining in the cassette  120  can be detected and provided in real time upon loading the cassette  120  or performing the printing process, the user is provided with convenience in use. 
     Although the preferred embodiments of the present invention have been described, it will be understood by those skilled in the art that the present invention should not be limited to the described preferred embodiments, but various changes and modifications can be made within the spirit and scope of the present invention as defined by the appended claims.