Patent Publication Number: US-6669191-B2

Title: Sheet delivery and position controlling apparatus for a printer

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 an application for APPARATUS FOR PAPER FEEDING AND CONTROL OF FEEDING POSITION FOR INK-JET PRINTER earlier filed in the Korean Industrial Property Office on Jul. 5, 2001, and there duly assigned Serial No. 39919/2001 by that Office. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a printer, and more particularly, to a sheet delivery and position controlling apparatus for a printer which controls delivery and position of a printed sheet of paper discharged from the printer. 
     2. Description of the Related Art 
     In general, an ink jet printer is often required to successively print numerous sheets of paper. In this case, a first printed sheet is discharged into a sheet stacker through a discharging unit having a feeding roller and a discharging roller. Then, next printed sheet following the first printed sheet is successively discharged and dropped down on the top surface of the first printed sheet which has been already disposed on the sheet stacker. 
     Meanwhile, when the next printed sheet is discharged and placed on the top surface of the first printed sheet before a portion of ink material formed on the top surface of the first printed sheet is dried out, the next discharged printed sheet is stained or blurred with the ink material of the first printed sheet. In this case, a printing image formed by the ink material on the first printed sheet is damaged as well as the next printed sheet is stained with the ink material. Accordingly, printed images of both of the first and next printed sheets may be defective as a drawback. Therefore, it is disadvantageous that the printer is required an extended period of time for discharging the next printed sheet until the ink material of first printed sheet is dried out. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a sheet delivery and position controlling apparatus for an ink jet printer discharging a first printed sheet and a second printed sheet following the first printed sheet and extending a period of time for the second printed sheet to contact the first printed sheet once the second printed sheet is discharged. 
     It is another object to provide a sheet delivery and position controlling apparatus able to prevent the second printed sheet from being stained by wet ink material formed on the first printed sheet. 
     It is still another object to provide a delivery and position controlling apparatus able to prevent the first printed sheet from being damaged when the second printed sheet is discharged onto the first printed sheet. 
     It is yet another object to provide a delivery and position controlling apparatus able to maintain image quality formed on each printed sheet. 
     These and other objects may be achieved by providing a sheet delivery and position controlling apparatus for an inkjet printer including a sheet stacker, a dischargingunit having a sheet delivery roller for discharging in sequence printed sheets to the sheet stacker, and a delay unit having a swivel unit pivotally provided between the sheet delivery roller and the sheet stacker to move between a first position which does not interfere with the printed sheet discharged from the sheet delivery roller and a second position which interferes with the printed sheet discharged from the sheet delivery roller to delay the printed sheet placed on the sheet stacker by a predetermined period of time, a driving motor, a power transmission unit for transmitting power from the driving motor to the swivel unit to selectively swivel the swivel unit to the first position and the second position, and a control unit for controlling the operation of the driving motor. 
     The power transmission unit includes a driven gear coupled to the swivel center of the swivel unit to be swiveled together therewith, a worm gear provided to a shaft of the driving motor for being rotated perpendicular to a direction of rotation of the driven gear, and a clutch installed between the worm gear and the driven gear for transmitting power from the worm gear to the driven gear and controlling power transmitted to the driven gear to control the position of the swivel unit. 
     The clutch includes a worm wheel gear geared to the worm gear, a clutch shaft coupled to the center of rotation of the worm wheel gear for being rotated therewith, and being provided at one end with an inclined portion extended in diameter, a clutch gear provided to the clutch shaft for being cooperative to the driven gear and having a shaft hole inclined corresponding to the inclined portion, and a spring for elastically forcing the clutch gear toward the inclined portion to create a friction force between the inclined portion and the shaft hole. 
     The swivel unit includes a pair of swivel arms, a connecting members for connecting the pair of swivel arms, and guide members provided in the connecting member at an interval for guiding the sheet as contacting the underside thereof discharged by the sheet delivery roller at the second position. 
     The sheet delivery and position controlling apparatus of the present invention includes a stopper for limiting the moving range of the swivel arm displaced to the second position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the present 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 symbols indicate the same or similar components, wherein: 
     FIG. 1 is a perspective view for showing a sheet delivery and position controlling apparatus for an ink jet printer constructed according to the present invention; 
     FIG. 2 is a side elevation view for showing a sheet delivery and position controlling apparatus for an ink jet printer; 
     FIG. 3 is a plan view for schematically showing a delay unit of in FIG. 2; and 
     FIG. 4 is a side elevation view for showing the operation of the sheet delivery and position controlling apparatus for an ink jet printer shown in FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now to the drawings, FIGS. 1 and 2 show a sheet delivery and position controlling apparatus for an ink jet printer including a sheet stacker  10 , a discharging unit having a delivery roller  20  for discharging printed sheets in sequence to sheet stacker  10 , and a delay unit having a swivel unit  30  arranged between sheet delivery roller  20  and sheet stacker  10 , a driving motor  40 , a power transmission unit  50  for transmitting power from driving motor  40  to swivel unit  30  and a control unit  60  for controlling operation of the driving motor  40 . 
     Sheet delivery roller  20  is disposed on a side of a sheet discharging port of a printer body (not shown) of the ink jet printer. Sheet delivery roller  20  is rotationally supported to a supporting bracket  1  and rotates by a driving source (not shown). Further, sheet delivery roller  20  rotates to contact an idle roller  2  so that the printed sheets are discharged from the discharging port to sheet stacker  10 . Since idle roller  2  is pushed against delivery roller  20  with a certain pressure, the printed sheets passing through sheet delivery roller  20  and idle roller  2  are discharged in a substantially horizontal direction and then in a sheet discharging direction. 
     Sheet stacker  10  sequentially receives the printed sheets discharged by sheet delivery roller  20 . Sheet stacker  10  is placed downstream the sheet discharging direction of the printed sheets. 
     Swivel unit  30  is pivotally installed between sheet delivery roller  20  and sheet stacker  10 . Swivel unit  30  moves between the first position which does not interfere with the sheet discharged from the discharging port and the second position which interferes with the same. When swivel unit  30  disposed in the first position as shown in FIG. 2, is swiveled to the direction of an arrow A, swivel unit  30  is displaced to the second position. 
     Swivel unit  30  includes a pair of swivel arms  31 , a connecting member  33  for connecting between the pair of swivel arms  31 , and guide members  35  provided on connecting members  33  at a certain interval. Swivel arms  31  are coupled at one ends to the printer body via hinges  32  while swivel arms  31  are connected at the other ends with connecting member  33 . 
     Guide members  35  contacts a bottomside of the printed sheet discharged by sheet delivery roller  20  when swivel unit  30  is positioned at the second position. Therefore, the printed sheet stays between the discharging port and sheet stacker  10  for a longer period of time before the printed sheet is placed on sheet stacker  10  since the printed sheet is guided by guide members  35 . Such guide members  35  are provided in plural, and each of the guide members has a round shape. Therefore, the discharged printed sheet contacts guiding members  35  in a normal direction. 
     Power transmission unit  50  includes a driven gear  51  coupled to one end of swivel arm  31  or the swiveling center, a worm gear  53  installed in a shaft  41  of driving motor  40 , and a clutch  55  for controlling and transmitting power transmitted to worm gear  53  to driven gear  51 . Driven gear  51  is fixed to hinge  32  of swivel arm  31  and rotated together therewith. Therefore, driving motor  40  is preferably arranged perpendicular to a direction of rotation of driven gear  51 . 
     Clutch  55  is installed between worm gear  53  and driven gear  51 . Further, clutch  55  transmits power from worm gear  53  to driven gear  51  while controlling the magnitude of transmitted power so as to control the swiveling range of swivel unit  30 . Clutch  55 , as shown in FIG. 3, includes a worm wheel gear  56  gear-connected to worm gear  53 , a clutch shaft  57  coupled to the center of rotation of worm wheel gear  56 , a clutch gear  58  installed in clutch shaft  57 , and a spring  59 . 
     Worm wheel gear  56  is installed perpendicular to an axis of worm gear  53  so as to change power from worm gear  53  in an angle of about 90 degree. Worm wheel gear  56  is rotated together with clutch shaft  57  fixed to a center thereof. Clutch shaft  57  is provided at one end with an inclined portion gradually extended in diameter. Clutch gear  58  is installed in clutch shaft  57  to be positioned between worm wheel gear  56  and inclined portion  57   a.  Clutch gear  58  has a shaft hole  58   a  inclined to have a shape corresponding to inclined portion  57   a.  Clutch gear  58  is engaged with driven gear  51 . 
     Spring  59  is installed between clutch gear  58  and worm wheel gear  56  to bias clutch gear  58  toward inclined portion  57   a.  Therefore, a spring force of spring  59  generates friction force between inclined portion  57   a  and shaft hole  58   a.  Under the friction force, clutch gear  58  can be transmitted with power from clutch shaft  57  and thus rotated. Also, when swivel unit  30  is applied with a load larger than the friction force, clutch gear  58  fails to receive power from clutch shaft  57 , but performs a sliding movement. 
     Control unit  60  controls the operation of driving motor  40  based upon information about the sequence and the discharging speed of the printed sheets discharged by sheet delivery roller  20 . Control unit  60  is coupled to a main controller (not shown) in the printer to receive a signal representing of the number of sheets to be printed. Control unit  60  controls driving motor  40  to move swivel unit  30  in the first or second positions in accordance with the signal. If the signal represents that only one sheet is printed, driving motor  40  moves swivel unit  30  in the first position. If the signal represents that more than two sheets are printed, swivel unit  30  is moved to the second position after a first printed sheet is discharged. 
     Meanwhile, preferably, a stopper  70  is further provided to limit the moving range of swivel unit  30  when swivel unit  30  moves to the second position. Therefore, when swivel unit  30  is stopped by stopper  70 , a load is applied to swivel unit  30 . Due to the load applied to swivel unit  30 , clutch gear  58  coupled to swivel unit  30  slides about clutch shaft  57  and thus does not transmit power to driven gear  51  as shown above. As a result, it can be prevented that the load is applied to driving motor  40 . 
     The operation of the sheet delivery and position controlling apparatus for an ink jet printer configured as above according to the embodiment of the invention will be described as follows. 
     When a number of sheets are printed in succession, swivel unit  30  is placed at the first position as shown in FIG.  2 . Then, the first printed sheet discharged by sheet delivery roller  20  is directly stacked on sheet stacker  10  without being interfered by swivel unit  30 . Right after the first printed sheet is discharged, control unit  60  controls and starts driving motor  40 . When driving motor  40  is started, power is transmitted to worm wheel gear  56  and clutch shaft  57  via worm gear  53 . In this case, clutch gear  58  is rotated together by the friction force created between clutch shaft  57  and clutch gear  58  by the biased force caused by spring  59 . Power transmitted to clutch gear  58  is transmitted to driven gear  51 , and swivel unit  30  is swiveled in the direction of the arrow A. 
     When swiveled in a certain degree, swivel unit  30  is stopped by stopper  70  at the second position, as shown in FIG. 4, and is not swiveled further. In this second position, the load applied to swivel unit  30  by stopper  70  is larger than the friction force generated between inclined portion  57   a  and shaft hole  58   a.  Therefore, even if driving motor  40  is successively operated, power from clutch shaft  57  is not transmitted to clutch gear  58 . In other words, clutch gear  58  is stopped, whereas only clutch shaft  57  is rotated freely. Therefore, even if control unit  60  may not precisely control the operation of driving motor  40 , it is prevent that driving motor  40  is overheated due to the load. 
     Meanwhile, swivel unit  30  is placed at the second position, guide members  35  provided on swivel unit  30  is positioned to interfere with the discharged printed sheet. Therefore, the successively discharged printed sheets including the second sheet are guided by guide member  35  at a position substantially higher than a horizontal position until the printed sheets drop down to be stacked on sheet stacker  10 . Referring to FIG. 4, a first path of the discharged printed sheet without being guided by guide member  35  is designated as C, and a second path of the discharged printed sheet guided by guide member  35  is designated as B. In other words, comparing the second path B to the first path C, the second path B shows the extended period of time required for the printed sheet to be discharged and stacked on sheet stacker  10 . Therefore, in the case of successive printing, when the ink material on the first printed sheet is not dried out yet, the time period for the next discharged printed sheet to be placed on the first discharged printed sheet is extended until the wet ink of the first discharged printed sheet is dried. Further, it is unnecessary to ensure an additional drying time period for drying the wet ink material so that high speed printing operation can be achieved. 
     Further, even if driving motor  40  is stopped where swivel unit  30  is positioned at the second position, it can be restricted that swivel motor  30  returns to the first position under self-weight. In other words, the friction force generated by the biased force of spring  59  restricts rotation of clutch gear  58 , and secondly worm wheel gear  56  is geared substantially perpendicular to worm gear  53  to prevent free rotation of worm wheel gear  56 , so that swivel unit  30  can be maintained at the second position. Therefore, in the case of successive printing, after being operated for a while to move swivel unit  30  to the second position, driving motor  40  can be maintained as stopped. Therefore, power required for swiveling swivel unit  30  and maintaining the position thereof can be reduced. 
     In FIG. 5, when swivel unit  30  is disposed in the first position in step  510 , a signal representing the number of sheets to be printed or one of high speed operations for printing a number of sheets is fed from the main controller of the printer to control unit  60  in step  520 . If a reference is 1 and the signal represents more than 2 in step  530 , swivel unit  30  moves in the second position in step  550  after a first printed sheet is discharged in step  540 . 
     Meanwhile, the printing operation is over, driving motor  40  rotate in a reverse direction to place swivel unit  30  to the first position. 
     According to the sheet delivery and position controlling apparatus for an ink jet printer of the invention as described hereinbefore, the time period required for the next printing sheet to reach the preceding printing sheet can be extended. Therefore, the additional delay time period is omitted after the preceding sheet is printed so that high speed printing and stable image quality can be obtained. Further, the position of the swivel unit is controlled by using the clutch so that the swivel unit can be return-prevented and position-controlled using a simple system.