Abstract:
An image forming apparatus includes LED heads protected from scratching. An optical head is mounted on an inner side of a lid pivotally mounted to a body of the apparatus. A protector is mounted to the lid. A mechanism is operatively coupled to the lid such that when the lid is positioned at an open position, the protector is at a protection position where the lid covers a light-emitting surface of the optical head and when the lid is positioned at an exposure position, the protector is at an exposure position where the lid does not cover the light-emitting surface of the optical head is. When the lid is pivoted past a position at which the lid forms an angle with the body, the mechanism begins to cause the protector to move from the protection position toward the exposure position.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an image forming apparatus that employs electrophotography, and more particularly to an image forming apparatus provided with a means for protecting an optical head that serves as an exposing unit.  
         [0003]     2. Description of the Related Art  
         [0004]     Some conventional electrophotographic printers employ an exposing unit, commonly called an LED head. One such printer incorporates a lid pivotally assembled to a body of the printer and a process cartridge detachably installed into the body. The process cartridge includes primarily a photoconductive drum, charging unit, developing unit, and toner cartridge. The lid includes an LED head mounted on the inner surface of the lid. When the lid is completely closed, the light-emitting surface of the LED head is positioned relative to the photoconductive drum so that the LED head can properly illuminate the surface of the photoconductive drum.  
         [0005]     The problem with the conventional electrophotographic printers is that when a lid or cover is opened to dismount a process cartridge from the apparatus, the process cartridge can contact an LED head to scratch the light-emitting surface of the LED head. Such inadvertent contact of the process cartridge with the LED head causes adverse effects to print quality.  
       SUMMARY OF THE INVENTION  
       [0006]     An object of the present invention is to solve the aforementioned problems associated with conventional printers.  
         [0007]     Another object of the present invention is to provide an image forming apparatus in which when a lid or cover is opened to dismount a process cartridge from the apparatus, a process cartridge will not contact an LED head to scratch the light-emitting surface of the LED head.  
         [0008]     An image forming apparatus includes LED heads protected from being scratched when a lid or cover is opened to dismount a process cartridge from the apparatus. A lid is pivotally mounted to a body of an image forming apparatus. The lid is operated by the user so that the lid is positioned either at a first position where the lid closes an opening formed in the body or a second position where the lid opens the opening. An optical head is mounted on an inner side of the lid. A protection member is mounted to the lid, the protection member being positioned either at a third position where the lid covers a light-emitting surface of the optical head or at a fourth position where the lid does not cover the light-emitting surface of the optical head. A mechanism is operatively coupled to the lid such that when the lid is pivoted relative to the body, the mechanism causes the protection member to be positioned either at the third position or at the fourth position. When the lid is positioned at the first position, the protection member is at the fourth position. When the lid is pivoted to a position at which the lid forms an angle with the body, the mechanism begins to cause the protection member to move from the third position toward the fourth position. When the lid is positioned at the second position, the protection member is at the fourth position.  
         [0009]     The mechanism includes a gear, a rack, and a gear train. The gear is rotatably supported on the lid. The rack is mounted to the body. When the lid is pivoted to a position at which the lid forms the angle with the body, the gear moves into a meshing engagement with the rack. The gear train is mounted to the body, and transmits rotation of the gear to the protection member. The lid and the protection member are operatively coupled through the gear train such that when the lid is pivoted from the first position to the second position, the protection member moves from the third position to the fourth position.  
         [0010]     The protection member includes a first member and a second member. The first member is supported by the lid. The second member is coupled to the first member. When the protection member is at the third position, the second member being movable to a fifth position where the light-emitting surface is exposed.  
         [0011]     The optical head is one of a plurality of optical heads that are mounted to the lid and extend in a longitudinal direction substantially perpendicular to a shaft about which the lid is pivoted.  
         [0012]     The image forming apparatus further includes a plurality of process cartridges each of which incorporates a photoconductive drum that is illuminated by a corresponding one of the plurality of optical heads. The plurality of process cartridges are detachably attached to the body and aligned along a path in which a recording medium is transported. When the lid is at the first position, each of the plurality of optical heads is between adjacent process cartridges.  
         [0013]     The optical head is a light emitting diode (LED) head.  
         [0014]     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limiting the present invention, and wherein:  
         [0016]      FIG. 1  is a schematic view illustrating a pertinent portion of an image forming apparatus according to a first embodiment of the invention;  
         [0017]      FIG. 2  is a perspective view of a head mounting section and a supporting mechanism;  
         [0018]      FIG. 3  illustrates the head mounting section, LED heads, and process cartridges when the head mounting section is at an open position;  
         [0019]      FIG. 4  illustrates the head mounting section when it is at a closed position;  
         [0020]      FIG. 5  illustrates the LED heads with a top cover removed when the head mounting section is at the closed position;  
         [0021]      FIG. 6  is a perspective view illustrating the arrangement of a shaft relative to the head mounting section;  
         [0022]      FIG. 7  and  FIG. 8  illustrate an LED shutter and an opening/closing mechanism that causes the LED shutter to open and close;  
         [0023]      FIG. 9  is an enlarged view of the vicinity of a gear in  FIG. 8 ;  
         [0024]      FIG. 10  is a perspective view illustrating the operation of the gear and a rack;  
         [0025]      FIG. 11  is an enlarged perspective view of a pertinent portion in  FIG. 10 ;  
         [0026]      FIG. 12  is a perspective view illustrating a pertinent portion of a head mounting section employed in an image forming apparatus according to a second embodiment;  
         [0027]      FIG. 13  illustrates when a second shutter has rotated to a dotted line position in  FIG. 14 ;  
         [0028]      FIG. 14  is a perspective view illustrating an LED shutter as seen from the front; and  
         [0029]      FIG. 15  is a perspective view illustrating the LED shutter as seen from the back. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
     First Embodiment  
       [0000]     {Construction} 
         [0030]      FIG. 1  is a schematic view illustrating a pertinent portion of an image forming apparatus according to a first embodiment of the invention.  
         [0031]     Referring to  FIG. 1 , an image forming apparatus  1  includes a body  3  and a lid  2  that pivotally attached to the body  3  ( FIG. 3 ) to open and close an opening  20  formed in the body  3 . A paper cassette  4  holds a stack of recording paper therein. A feeding section  5  feeds the recording paper at regular intervals from the paper cassette  4  into a paper-transporting path  6 . Paper transporting rollers  7 - 12  are aligned along the paper-transporting path  6  and transport the recording paper along the paper-transporting path  6 . Process cartridges  13 - 16  are aligned straight along the paper-transporting path  6  and detachably attached to the body  3 . A transfer unit  17  includes a transfer belt that faces the process cartridges  13 - 16  to define a straight portion of the paper-transporting path  6 . A fixing unit  18  fuses toner images on the recording paper into a permanent image.  
         [0032]     The lid  2  is formed with a head mounting section  21  on its inner side. The head mounting section  21  is formed in the vicinity of the photoconductive drums  19  in the process cartridges  13 - 16 . The head mounting section  21  supports LED heads  22 - 25  and LED shutters  26 - 29  that cover the LED heads  22 - 25  by means of a later described mechanism.  
         [0033]     An X-axis denotes a direction in which the recording paper passes through the process cartridges  13 - 16 . A Y-axis denotes a direction in which the rotational axis of the photoconductive drums  19  extends. A Z-axis denotes a direction that is perpendicular to both the axes X and Y. The X-, Y-, and Z-axes also apply to other figures.  
         [0000]     {Operation} 
         [0034]     The operation of pertinent portions of the image forming apparatus  1  of the aforementioned configuration will be described.  
         [0035]     The recording paper held in the paper cassette  4  is fed by the feeding section  5  into the transporting path  6  and is transported by the paper transporting rollers  7 - 9  to the process cartridge  13 . The belt of the transfer unit  17  transports the recording paper through the process cartridges  13 - 16  sequentially, so that toner images of black (B), yellow (Y), magenta (M) and cyan (C) are transferred onto the recording paper in sequence. Then, the recording paper reaches the fixing unit  18 . After fixing, the recording paper is advanced by the paper transporting rollers  10 ,  11 , and  12  to a stacker  30  formed on an outside surface of the image forming apparatus  1 .  
         [0036]     A description will be given of the head mounting section  21  and a supporting mechanism that rotatably supports the head mounting section  21 .  
         [0037]      FIG. 2  is a perspective view of the head mounting section  21  and the supporting mechanism that rotatably supports the head mounting section  21  both when the head mounting section  21  is at a closed position P 1  to close the opening  20  ( FIG. 3 ) and when the head mounting section  21  is at an open position P 2  to open the opening  20 . The head mounting section  21  is either at the closed position P 1  or at the open position P 2  depending on whether the mounting section  21  is closed or opened.  FIG. 3  illustrates the head mounting section  21 , LED heads  22 - 25 , and the entire process cartridges  13 - 16  when the head mounting section  21  is at the open position P 2 . For convenience of explanation, the LED shutters  26 - 29  are not shown.  
         [0038]     Referring to  FIG. 3 , the process cartridges  13 - 16  are oriented so that the rotational axes of the photoconductive drums  19  are parallel to the Y-axis. The process cartridges  13 - 16  for toner images (B), (Y), (M), and (C) are aligned at regular intervals in a direction parallel to the X-axis. The process cartridges  13 - 16  are detachably mounted to a basket  3   a  of the body  3 . The process cartridges  13 - 16  can be detached from the body  3  by pulling them up in a direction shown by arrow A.  
         [0039]     The LED heads  22 - 25  are mounted to the head mounting section  21  by way of a head holder  31  and extend in such directions as to lie adjacent to the corresponding process cartridges  13 - 16  when the head mounting section  21  is at the closed position. When the head mounting section  21  is at the closed position P 1 , light-emitting surfaces  22   a - 25   a  of the LED heads  22 - 25  are close to the circumferential surfaces of the corresponding photoconductive drums  19 . The LED heads  22 - 24  lie between adjacent process cartridges  13 - 16 .  
         [0040]      FIG. 4  and  FIG. 5  illustrate the supporting mechanism that supports the head mounting section  21 .  FIG. 4  illustrates the head mounting section  21  when it is at the closed position P 1 .  FIG. 5  illustrates the LED heads with a top cover removed when the head mounting section  21  is at the closed position P 1 .  
         [0041]     A bracket  51  is fixed to the body  3  and rotatably supports a shaft  52 . A coupling  42  and a side wall  41   a  ( FIG. 6 ) are joined together. A free end  42   a  ( FIG. 4 ) of the coupling  42  is fixed to the shaft  52 . Thus, the head mounting section  21  is pivotal about the shaft  52  between the closed position P 1  and the open position P 2  in directions shown by arrows C and D. The LED shutters  26 - 29  rotate in such a way that when the head mounting section  21  is at the open position P 2  as shown in  FIG. 2 , The LED shutters  26 - 29  cover the light-emitting surfaces  22   a - 25   a  of the LED heads  22 - 25 . The LED shutters  26 - 29  rotate in such a way that when the head mounting section  21 ′ is at the closed position P 1  as shown in  FIG. 5 , the head mounting section  21  uncovers the light-emitting surfaces  22   a - 25   a.    
         [0000]     {Opening/Closing Mechanism for Shutters} 
         [0042]     An opening/closing mechanism for the LED shutters  26 - 29  will be described.  FIG. 6  is a perspective view illustrating the arrangement of a shaft  55  relative to the head mounting section  21 .  FIGS. 7 and 8  illustrate the operation and configuration of the opening/closing mechanism.  FIG. 9  is an enlarged view of the vicinity of a gear  56  in  FIG. 8 . The X-, Y-, and Z-axes are oriented in the same directions as those in  FIG. 1 .  
         [0043]     As shown in  FIG. 6 , the shaft  55  has four gears  57  fixedly mounted at positions corresponding to the LED shutters  26 - 29 , respectively, and the gear  56  mounted to one longitudinal end portion of the shaft  55 .  
         [0044]     Referring to  FIG. 5 , the coupling  42  supports the shaft  55  at the connection of a top cover  41  and the coupling  42  in such a way that the shaft  55  extends in the X-axis and is rotatable. The bracket  51  has a rack  61  that extends in a path in which the gear  56  moves when the coupling  42  rotate about the shaft  52  in the D direction. When the user causes the head mounting section  21  to pivot in the D direction, the coupling  42  rotates about the shaft  52  through a predetermined angle θ 1 , so that the gear moves into a meshing engagement with the rack  61 .  
         [0045]      FIG. 7  and  FIG. 8  illustrate the LED shutter  26  and an opening/closing mechanism  54  that causes the LED shutter  26  to open and close. The opening/closing mechanism  54  is provided on each of the LED shutters  26 - 29 . The opening/closing mechanisms  54  are of the same configuration and the one provided for the LED shutter  26  will be described by way of example.  
         [0046]     Referring to  FIG. 7 , the LED shutter  26  is mounted on a shaft  26   a . The shaft  26   a  is rotatably supported at its longitudinal ends  26   b  ( FIG. 9 ) and  26   c  by the supporting portions  31   b  ( FIG. 9 ) and  31   c  of the head holder  31 . A torsion spring  26   e  is mounted on one longitudinal end portion of the shaft  26   a . The torsion spring  26   e  urges the LED shutter  26  in a direction shown by arrow F, so that the LED shutter  26  is maintained at a position where the LED shutter  26  abuts limiters  31   a  and  31   d  and the entire LED head  22  is exposed.  
         [0047]     Referring to  FIG. 9 , a shutter gear  26   d  is mounted on one longitudinal end portion of the shaft  26   a . The first intermediate gear  58  includes a helical gear  58   a  and the spur gear  58   b  concentrically mounted on a shaft  58   c . The shutter gear  26   d  is in a meshing engagement with the spur gear  58   b . The shaft  58   c  extends in the Y-axis perpendicular to the X-axis, and is rotatably supported on the side wall  41   a  ( FIG. 6 ) of the top cover  41  and a bracket  59  fixed to the side wall  41   a . The helical gear  58   a  is in a meshing engagement with another helical gear  60   a  of a second intermediate gear  60 . The second intermediate gear  60  has a shaft  60   c  that extends in a direction parallel to the X-axis and is rotatably supported on the bracket  59  fixed to the side wall  41   a . The second intermediate gear  60  has a spur gear  60   b  in a meshing engagement with a gear  57  fixedly mounted to the shaft  55 .  
         [0048]     As is clear from  FIG. 9 , when the shaft  55  rotates in the D direction, the helical gear  60   a  rotates in the C direction. Thus, the rotation of the second intermediate gear  60  is transmitted to the first intermediate gear  58  through the helical gear  58   a , so that the first intermediate gear  58  rotates in the F direction. The rotation of the first intermediate gear  58  in the F direction is then transmitted to the shutter gear  26   d  through the spur gear  58   b , so that the shaft  26   a  rotates in a direction shown by arrow E. Thus, the shutter  26  begins to rotate against the urging force of the torsion spring  26   e  ( FIG. 7 ) in the E direction, from the exposure position where the shutter  26  abuts the limiters  31   a  and  31   d  to the protection position (dotted lines in  FIG. 8 ) where the shutter  26  covers the light-emitting surfaces of the LED head  22 .  
         [0000]     {Interlocked Operation of Head Mounting Section and LED Shutter} 
         [0049]     A description will now be given of the operation of the LED shutter  26  in which the LED shutter  26  rotates in the C and D directions between the closed position P 1  and the open position P 2 .  
         [0050]     When the head mounting section  21  is at the closed position P 1  ( FIG. 2 ), the head mounting section  21  is at the position where the head mounting section  21  abuts the limiters  31   a  and  31   d , i.e., the exposure position where the entire LED head  22  is exposed.  FIG. 5  illustrates the LED shutters  26 - 29  on the head mounting section  21  with the top cover  41  ( FIG. 4 ) omitted. When the head mounting section  21  is opened in the D direction from the position in  FIG. 5 , the head mounting section  21  begins to pivot about the shaft  52 . After the head mounting section  21  has rotated through an angle from the closed position P 1 , the gear  56  moves into a meshing engagement with the rack  61 .  
         [0000]     {Operation of Gear and Rack} 
         [0051]      FIG. 10  is a perspective view illustrating the operation of the gear  56  and the rack  61 .  FIG. 11  is an enlarged perspective view of a pertinent portion in  FIG. 10 .  
         [0052]     When the head mounting section  21  further rotates in the D direction after the gear  56  has moved into a meshing engagement with the rack  61 , the gear  56  begins to rotate in the D direction as shown in  FIG. 11 . The movement of the gear  56  in the D direction causes the shaft  26   a  and LED shutter  26  to gradually rotate against the urging force of the torsion spring  26   e  ( FIG. 7 ) in the E direction. Thus, When the head mounting section  21  reaches the open position P 2  ( FIG. 2 ), the LED shutter  26  will have rotated through about 180 degrees from the exposure position (dotted lines) to the protection position (solid lines) in  FIG. 10 .  
         [0053]     When the head mounting section  21  rotates in the C direction from the open position P 2  ( FIG. 2 ) where the LED shutter  26  is at the protection position toward the closed position ( FIG. 2 ), the gear  56  rotates in the C direction while remaining in a meshing engagement with the rack  61 . The rotation of the gear  56  in the C direction causes the shaft  26   a  and the LED shutter  26  to rotate in the F direction. When the head mounting section  21  has rotated through a certain angle so that the gear  56  moves out of a meshing engagement with the rack  61 , the LED shutter  26  will have rotated through about 180 degrees in the F direction from the protection position to the exposure position. Then, the urging force of the torsion spring  26  continues to maintain the LED shutter  26  at the exposure position.  
         [0054]     Because, when the lid is opened, the LED shutter covers the light-emitting surfaces of the LED, thereby preventing inadvertent contact or interference of the light-emitting surfaces of the LED head with the process cartridge during the replacement of the process cartridge. The configuration not only prevents damage to the light-emitting surfaces but also provides stable printing.  
         [0055]     The LED heads extend in the directions substantially perpendicular to the rotational axis of the lid. Therefore, when the head mounting section is pivoted, one longitudinal ends of the LED heads first approaches the rotational axis and then the other longitudinal ends gradually enter spaces between adjacent process cartridges. Thus, if the LED shutter begins to rotate before the lid has opened sufficiently, the LED shutter will interfere with the body  3 . However, because the LED shutter begins to rotate after the lid has opened sufficiently, the LED shutter will not interfere with the body  3 .  
         [0056]     A tandem type image forming apparatus includes a plurality of LED heads and process cartridges aligned. In order to design a compact image forming apparatus, it is desirable that the process cartridges are closely spaced and the LED heads are accommodated and moved in a minimum space. The LED shutter according to the embodiment begins to rotate only after the lid has been opened sufficiently. Therefore, a large space is not necessary for preventing the LED shutter from interfering with the various portions of the image forming apparatus during the pivotal movement of the LED shutter.  
       Second Embodiment  
       [0057]      FIG. 12  is a perspective view illustrating a pertinent portion of a head mounting section  71  employed in an image forming apparatus according to a second embodiment.  
         [0058]     The head mounting section  71  differs from the head mounting section  21  in the configuration of LED shutters  72  disposed corresponding to LED heads  22 - 25 . An opening/closing mechanism for the LED shutters  72  is the same as the first embodiment. The elements similar to those in the first embodiment have been given the same or similar reference numerals and the description thereof is omitted. The LED shutters  72  are of the same configuration and the one provided for the LED head  22  will be described by way of example. A description will be given of a portion different from the first embodiment.  
         [0059]     Referring to  FIG. 12 , the LED shutter  72  includes a first shutter  73  and a second shutter  74 . The second shutter  74  is rotatable relative to the first shutter  73 .  FIGS. 14 and 15  are perspective views of the LED shutter  72 .  FIG. 14  illustrates the LED shutter  72  as seen from the front and  FIG. 15  illustrates the LED shutter  72  as seen from the back.  
         [0060]     Referring to  FIG. 14  and  FIG. 15 , a shaft  73   a  is formed integral with the first shutter  73 . The first shutter  73  and the second shutter  74  are coupled to each other through hinges  75  and  76 , so that the second shutter  74  is rotatable about an axis  78  relative to the first shutter  73 . A torsion spring  77  is mounted between the first shutter  73  and the second shutter  74  to urge the second shutter  74  in a direction shown by arrow H, and a limiter  73   b  formed on the first shutter  73  restricts the rotation of the second shutter  74 .  
         [0061]     If no external force acts on the second shutter  74 , the torsion spring  77  and the limiter  73   b  cooperate to hold the second shutter  74  at a normal position (solid line position in  FIGS. 14 and 15 ) where a side wall  74   a  of second shutter  74  is in substantially the same plane as the first shutter  73  and an edge portion  74   b  extending at an angle with the side wall  74   a  covers the light-emitting surface  22   a  of the LED head  22 .  
         [0062]     When the LED shutter  72  is at the normal position, the LED shutter  72  operates in exactly the same manner as the LED shutter  26  in the first embodiment. Referring to  FIG. 12 , the LED shutter  72  is in the normal position, the head mounting section  71  is at the open position P 2  where the opening  20  of the body  3  is not closed, and the LED shutter  72  has rotated to the protection position where the LED shutter  72  covers the light-emitting surface  22   a  of the LED head  22 .  
         [0063]     Referring to  FIG. 12 , if the operator opens the second shutter  74  in a direction shown by arrow I so that the second shutter  74  rotates about the axis  78 , the second shutter  74  rotates in the I direction against the urging force of the torsion spring  77  ( FIGS. 14 and 15 ) to reach a dotted line position in  FIG. 14 .  
         [0064]      FIG. 13  illustrates when the second shutter  74  has rotated to the dotted line position in  FIG. 14 . Even when the head mounting section  71  is at the open position P 2  where the LED shutters  72  cover the light-emitting surfaces  22   a - 25   a , the operator can rotate the second shutters  74  manually when the maintenance of the apparatus is performed, so that the LED heads  22 - 25  are exposed. Because the torsion spring  77  urges the second shutter  74  at all times in the H direction, the second shutter  74  can return to the normal position in  FIG. 12  once the operator releases the second shutter  74 .  
         [0065]     As described above, the second embodiment provides the same advantages as the first embodiment. Further, even when the LED shutter  72  is at the protection position where the LED shutter  72  covers the light-emitting surfaces of the LED heads  22 - 25 , the LED head may be exposed as required so that the maintenance works such the cleaning of the light-emitting surfaces of the LED head can be performed easily.  
         [0066]     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art intended to be included within the scope of the following claims.