Abstract:
A paper ejection unit included in a print apparatus for stacking printed paper to provide a print apparatus for making it possible to provide compatibility between large-capacity stacking of short-size paper frequently used and easiness of handling printed paper of large size. Attention is focused on the fact that the weight of paper that can be handled safely is determined by the paper stack height for each paper size, and it is made possible to change the paper stackable amount for each paper size by a paper stack table moved down gradually with an increase in the stack amount of printed paper and a paper stack table height detector for detecting the position of the paper stack table.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to a paper ejection unit in a print apparatus which includes the paper ejection unit and a image formation unit.  
           [0003]    2. Background Art  
           [0004]    Hitherto, when a predetermined table height detector provided in a paper ejection unit in a print apparatus detects a paper stack table moved down with an increase in the stack amount of printed paper, the paper ejection unit has been determined full of paper, the paper stack operation of the paper ejection unit has been stopped, and a message indicating that the paper ejection unit is full of paper has been displayed on an operation section of the image formation apparatus.  
           [0005]    For example, in an image formation apparatus using electrophotography, such as a copier or a laser beam printer, a paper ejection unit for stacking paper ejected from the image formation apparatus needs to be compatible with various paper sizes and stack a large amount of paper with the widespread use of a high-speed image formation apparatus compatible with various paper sizes. The sizes of paper most frequently used with the image formation apparatus are short sizes of A4, B5, letter, etc. If 2,000 or more sheets of paper of large sizes of B4, A3, leisure, etc., are stacked in an image formation apparatus having a paper ejection unit capable of stacking 2,000 or more sheets of paper of the short sizes (75 g/m 2 ), the total weight containing a printed paper taking-out cage exceeds 20 kg and thus a problem occurs in handling of the operator.  
           [0006]    In JP-B-7-115794, the paper-full stack amount is changed based on paper size information.  
           [0007]    In related art, the paper top face is detected for detecting the paper stack amount. However, if print is stopped midway or the apparatus is powered down at the time, a problem remains in paper stack amount detection at the restart time if the paper top face is detected for detecting the paper stack amount.  
         SUMMARY OF THE INVENTION  
         [0008]    It is an object of the invention to solve the above-described problems. Attention is focused on the fact that the weight of paper that can be handled safely is determined by the paper stack height for each paper size, and it is made possible to change the paper stackable amount for each paper size by a paper stack table moved down gradually with an increase in the stack amount of printed paper and a paper stack table height detector for detecting the position of the paper stack table.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a schematic drawing as a front view of a paper ejection unit of the invention.  
         [0010]    [0010]FIG. 2 is a schematic drawing as a sectional side view of the paper ejection unit of the invention.  
         [0011]    [0011]FIG. 3A is a schematic drawing to show paper stack table height detection of the paper ejection unit of the invention.  
         [0012]    [0012]FIG. 3B is a schematic drawing to show paper stack table height detection of the paper ejection unit of the invention.  
         [0013]    [0013]FIG. 3C is a schematic drawing to show paper stack-table height detection of the paper ejection unit of the invention.  
         [0014]    [0014]FIG. 3D is a schematic drawing to show paper stack table height detection of the paper ejection unit of the invention.  
         [0015]    [0015]FIG. 3E is a schematic drawing to show paper stack table height detection of the paper ejection unit of the invention.  
         [0016]    [0016]FIG. 4 is a block diagram of the print apparatus of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    Referring now to the accompanying drawings, there is shown a preferred embodiment of the invention.  
         [0018]    [0018]FIG. 1 is a schematic drawing of a print apparatus. A paper ejection unit  1  is placed at the rear of an image formation apparatus  2  such as a copier or a laser beam printer and comprises transport means  4  for downward transporting paper (cut sheet of paper) sent from an eject roller  3  placed in the image formation apparatus  2 , a first paper transport passage  7  for transporting paper to an upper-stage paper stack section  5 , a second paper transport passage  8  for transporting paper to a lower-stage paper stack section  6 , paper transport passage switch means  9  for switching paper into the first paper transport passage  7  and the second paper transport passage  8 , a paper eject roller pair  11  for ejecting paper transported on the paper transport passages  7  and  8  onto paper stack tables  10  placed in the upper-stage paper stack section  5  and the lower-stage paper stack section  6 , the upper-stage paper stack section  5 , and the lower-stage paper stack section  6 . The transport means  4  consists of five pairs of rollers and is placed in the first paper transport passage  7  and the second paper transport passage  8  for transporting paper output from the image formation apparatus  2  to the upper-stage paper stack section  5  and the lower-stage paper stack section  6 . A paper stack face detection sensor (not shown) is disposed above each of the paper stack tables  10  in the upper-stage paper stack section  5  and the lower-stage paper stack section  6 .  
         [0019]    In the upper-stage and lower-stage paper stack sections  5  and  6 , as shown in FIG. 2, a fork  12  on which the paper stack table  10  is mounted is supported movably up and down and is provided with a winding wire  16  connected directly to a paper stack table height detection member  15  for moving up and down by a wire winding gear  14  joined to a motor  13 . Further, paper stack table height detection sensors  17   a ,  17   b ,  17   c , and  17   d  (simply, table sensors) are disposed on the moving up and down line of the paper stack table height detection member  15 , and further a lower limit sensor  18  for sensing the lowest down position of the fork  12  is disposed below the paper stack table height detection sensor  17   d.    
         [0020]    Further, as shown in FIG. 2, the paper ejection unit  1  is provided with a printed paper taking-out cage  20  for taking out the printed paper stacked on the paper stack table  10 . The size of the printed paper taking-out cage  20  is determined according to the size of paper to be stacked on the paper stack table  10 .  
         [0021]    [0021]FIG. 4 shows the block diagram of the print apparatus in this embodiment. As shown in FIG. 4, the paper ejection unit  1  has a controller  100  and a size detector  101 . The controller  100  is connected to the table sensors  17   a ,  17   b ,  17   c  and  17   d  and the lower limit sensor  18 . The detection signals of the table sensors are transmitted to the controller  100  to transfer to the image formation apparatus  2 . The size detector  101  detects the size of the printed paper taking-out cage  20  and outputs a result of the detection to the controller  100 . Then the controller  100  determines the size of the printed paper based on the output from the size detector  101 .  
         [0022]    The image formation apparatus  2  has a controller  102 , and an operation panel  103  for entering information therein. The operation panel  103  is connected to the controller  102  to transmit information thereto. The controller  102  and the controller  100  of the paper ejection unit  1  is mutually connected to receive and transmit data therebetween. Therefore, the information entered at the operation pane  1103  can be transmitted to the controller  100  of the paper ejection unit  1 .  
         [0023]    Further, the image formation apparatus  2  has a paper size detector  104  for detecting the size of the paper to be printed therein. The paper size detector  104  outputs the result of the detection to the controller  102 .  
         [0024]    In the embodiment of the described configuration, as indicated by the position of the paper stack table height detection member  15  in FIGS.  3 A- 3 E, in the state of FIG. 3A, namely, if the paper stack table height detection member  15  is sensed by none of the table sensors, the controller informs the image formation apparatus  2  that the paper stack amount is about 0 to 500 sheets (the number of stacked sheets of paper in terms of 75 g/m 2  paper). Likewise, in the state of FIG. 3B, if the paper stack table height detection member  15  is sensed by the table sensor  17   a , the controller  100  informs the image formation apparatus  2  that the paper stack amount is about  500  sheets; in the state of FIG. 3C, if the paper stack table height detection member  15  is sensed by the table sensor  17   b , the controller  100  informs the image formation apparatus  2  that the paper stack amount is about  1 , 000  sheets; in the state of FIG. 3D, if the paper stack table height detection member  15  is sensed by the table sensor  17   b , the controller informs the image formation apparatus  2  that the paper stack amount is about 1,500 sheets; and in the state of FIG. 3E, if the paper stack table height detection member  15  is sensed by the table sensor  17   d , the controller  100  informs that the image formation apparatus is informed that the paper stack amount is about 2,000 sheets. If the operator interrupts print or when a fault occurs, if print is restarted without removing all printed paper  19  on the paper stack table  10 , the paper table height position is sensed as described above, whereby it is made possible to always inform the image formation apparatus  2  how much paper is stacked in the paper ejection unit.  
         [0025]    To print short-size paper, such as A5, B5, A4, or letter paper, in the described configuration, if 2,000 sheets of paper are stacked, the paper weight is 10 kg or less and handling is easy and thus when the paper stack table height detection member  15  is sensed by the table sensor  17   d , the paper stack amount is set down as the maximum. That is, when the paper stack amount is about 2,000 sheets, and then the image formation apparatus  2  is informed of a paper-full state. To print large-size paper, such as B4, A3, or leisure paper, if a paper-full state is applied when the paper stack amount is 2,000 sheets of paper, the paper weight containing the printed paper taking-out cage  20  exceeds 20 kg and it becomes difficult for the operator to handle. Thus, when the paper stack table height detection member  15  is sensed by the table sensor  17   c , the paper stack amount is set down as the maximum. That is, when the paper stack amount is about 1,500 sheets, the image formation apparatus  2  is informed of a paper-full state. In the image formation apparatus  2 , an algorithm may be adopted wherein if the operator interrupts print and once draws out the paper stack table  10  from the paper ejection unit  1  and then again sets the paper stack table  10 , the presence or absence of paper on the paper stack table  10  is detected by a paper presence/absence detector (not shown) and reprint-is enabled only if no paper exists. In this case, the maximum paper stack amount may be applied when the count of number-of-ejected-paper-sheets count means (not shown) for counting the number of ejected paper matches a predetermined value after the paper stack table height detection member  15  is detected by the table sensor  17   c  in place of  17   d . By this, it is also made possible to change the paper stackable amount, and a similar advantage can be provided. The paper stackable amount is changed by a controller  100  or  102  using as a trigger, paper size information provided by a detection signal of a paper size detector  104  placed in a paper feed section of the image formation apparatus  2 . In addition to the paper size information provided by the paper size detector  104 , paper size information or paper stack amount specification information may be inputted from the operation panel  103  of the image formation apparatus  2  or a host such as a personal computer (not shown), whereby a similar advantage can also be provided. The output of the size detector  101  may be used as the paper size information, whereby a similar advantage can be provided.  
         [0026]    As described above, according to the invention, the paper stackable amount of the paper ejection section can be specified based on the paper size information or any desired paper stack amount specification information entered by the operator, so that handling of printed paper can be optimized.