Abstract:
A first body houses a photoconductor is provided with a second body openably and closably attached to the first body. Additionally, a unit is provided to be swingable with respect to the second body such that an exposure surface of the unit is disposed at an exposure position opposing the photoconductor when the second body is closed. The exposure surface of the unit is disposed at a retreated position facing toward the rotary shaft of the second body when the first body is opened. Since the exposure surface of the unit faces toward the rotary shaft of the second body when the second body is opened, the exposure surface is not exposed to outside of the second body.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2008-098289, filed on Apr. 4, 2008, the entire subject matter of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     Aspects of the present invention relate to an image forming apparatus, such as an electrophotographic printer. 
     BACKGROUND 
     An image forming apparatus such as color printer employs an LED exposure method. For example, a color printer employing the LED exposure method, includes four drum units, which are provided corresponding to colors of yellow, magenta, cyan, and black and are disposed in parallel in an apparatus body, and an LED head, which is provided corresponding to each of the drum units and includes a plurality of LEDs arrayed linearly. 
     A stacker cover is provided on an upper surface of the apparatus body. The stacker cover is supported on a rotary shaft extending along the upper edge of the apparatus body and rotates about the rotary shaft so that the upper surface of the apparatus body can be opened and closed. The four LED heads are attached to the stacker cover. When the stacker cover is closed, each LED head opposes a photoconductor, which is provided in the corresponding drum unit, from above. In addition, when the stacker cover is opened, the LED heads are disposed outside the apparatus body. In this state, each drum unit can be exchanged (for example, refer to JP-A-2003-112446). 
     SUMMARY 
     However, when the stacker cover is opened, an exposure surface (surface opposing a photoconductor) of the LED head is exposed outside opposite to the rotary shaft side of the stacker cover. Therefore, there occurs a problem that the exposure surface of the LED head is damaged, or dust adheres to the exposure surface of the LED head. 
     In order to address the problem, the inventor of the present application proposed a configuration in which a first body that houses a photoconductor therein and a second body openably and closably attached to the first body are provided. Additionally, an LED unit is provided to be swingable with respect to the second body such that an exposure surface of the LED unit is disposed at an exposure position opposing the photoconductor when the second body is closed, and the exposure surface of the LED unit is disposed at a retreated position facing toward the rotary shaft of the second body when the first body is opened. According to this proposed configuration, since the exposure surface of the LED unit faces toward the rotary shaft of the second body when the second body is opened, the exposure surface is not exposed to outside of the second body. Accordingly, it can be suppressed that the exposure surface is damaged or dust adheres to the exposure surface. 
     However, if the second body is closed roundly, the LED unit rotates fast such that the exposure surface of the LED moves fast from the retreated position to the exposure position. Then, the exposure surface of the LED unit does not stop appropriately at the exposure position, and the LED unit largely swings close to the exposure position. As a result, there is a possibility that the LED unit would interfere with other components disposed in the apparatus body. 
     Accordingly, it is an aspect of the present invention to provide an image forming apparatus capable of preventing undesired swing of a swingable member when the second body is displaced from an open posture to a closed posture, and the swingable member swings from an adjacent posture to a distant posture with the displacement. 
     According to an exemplary embodiment of the present invention, there is provided an image forming apparatus comprising: a first body formed with an opening; a second body which is supported on the first body, and which is rotatable about an axis between an open posture in which the opening is opened and a closed posture in which the opening is closed; a swingable member which comprises one end swingably supported on the second body, and another end opposite to the one end, wherein the swingable member takes a distant posture in which the other end is distant from the second body when the second body is in the closed posture, wherein as the second body is rotated from a first angle position at which the second body is rotated by a first angle from the closed posture, toward the open posture, the swingable member swings from the distant posture toward an adjacent posture in which the other end is closer to the second body than the distant posture, and wherein as the second body is rotated from the open posture toward the first angle position, the swingable member swings toward the distant posture; and a regulating mechanism which regulates a swingable range of the swingable member when the second body is rotated from a third angle position at which the second body is rotated by a third angle from the closed posture, toward the closed posture. 
     According to another exemplary embodiment of the present invention, there is provided an image forming apparatus comprising: a first body comprising an opening and a shaft provided at one end of the opening; a second body rotatably supported by the shaft between an open posture in which the opening is opened and a closed posture in which the opening is closed; an operation member which is slidably supported on the second body; an arm comprising one end which is connected to the first body and another end opposite to the one end, the other end connected to the operation member to be slidable with respect to the second body; a movable member which is movably supported on the second body, and includes an engagement part, wherein the movable member is moved by the operation member; a swingable member comprising a first portion rotatably supported on the second body and a second portion rotatably supported on the movable member; and a regulating mechanism which is moved by contacting the operation member, and includes an engagement part engageable with the engagement part of the movable member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects of the present invention will become more apparent and more readily appreciated from the following description of exemplary embodiments of the present invention taken in conjunction with the attached drawings, in which: 
         FIG. 1  is a side sectional view showing a printer according to an exemplary embodiment of the present invention; 
         FIG. 2  is a side sectional view showing a state where a top cover is opened in the printer shown in  FIG. 1 ; 
         FIG. 3  is a perspective view showing a state where the top cover is opened in the printer shown in  FIG. 1 ; 
         FIG. 4  is a perspective view showing a right cover side plate; 
         FIG. 5  is a perspective view showing the positional relationship of an arm regulating member, an operation member, and an arm; 
         FIG. 6  is a perspective view showing a state where the top cover is in the closed posture; 
         FIG. 7  is a perspective view showing a state where the top cover is disposed at a second angle position rotated by a second angle from the closed posture; 
         FIG. 8  is a perspective view showing a state where the top cover is disposed at a first angle position rotated by a first angle from the closed posture; 
         FIG. 9  is a perspective view showing a state where the top cover is in the open posture; 
         FIG. 10  is a perspective view showing an LED unit; 
         FIG. 11  is a perspective view showing a cover side plate and a movable member when the top cover is in the closed posture; 
         FIG. 12  is a perspective view showing the cover side plate and the movable member when the top cover is in the open posture; 
         FIG. 13  is a side view showing the movable member and the LED unit when the top cover is in the closed posture; 
         FIG. 14  is a side view showing the movable member and the LED unit when the top cover is disposed at a second angle position rotated by a second angle from the closed posture; 
         FIG. 15  is a side view showing the movable member and the LED unit when the top cover is disposed at the first angle position rotated by the first angle from the closed posture; 
         FIG. 16  is a side view showing the movable member and the LED unit when the top cover is in the open posture; 
         FIG. 17  is a side view showing the movable member and the LED unit when the top cover is disposed at a third angle position rotated by a third angle from the closed posture, from the state of  FIG. 16 ; 
         FIG. 18  is a back view showing the positional relationship between a locking member and an operation member; and 
         FIG. 19  is a perspective view showing the locking member. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
     1. Entire Configuration of a Color Laser Printer 
       FIG. 1  is a side sectional view showing a printer  1  according to an exemplary embodiment of the present invention.  FIG. 2  is a side sectional view showing a state where a top cover  4  is opened in the printer  1  shown in  FIG. 1 . 
     A printer  1  is a tandem color laser printer. The printer  1  includes a main body casing  2  as an example of a first body and a top cover  4  as an example of a second body. The main body casing  2  is formed in the shape of a box formed with an opening  16  on an upper surface. The top cover  4  is rotatably supported on a rotatable shaft  15  provided on the upper end of the main body casing  2 . The top cover  4  is rotatably supported to be displaceable between a closed posture in which the opening  16  is closed and an open posture in which the opening  16  is opened, according to the rotating operation thereof. 
     In the main body casing  2 , four drum units  3  are disposed in parallel. The drum units  3  are provided corresponding to colors of black, yellow, magenta, and cyan and are arrayed in order of black, yellow, magenta, and cyan in the conveyance direction of a sheet P using a conveyance belt  9 , which will be described later. Each drum unit  3  can be mounted in the main body casing  2  or removed from the main body casing  2  through the opening  16 , which is formed on the upper surface of the main body casing  2 , when the top cover  4  is in the open posture. 
     It is noted that, for the drum units  3 , K (black), Y (yellow), M (magenta), and C (cyan) indicating respective colors are added to ends of reference numerals in  FIGS. 1 and 2 . 
     Each drum unit  3  includes a photosensitive drum  6  as an example of a photoconductor and a developing roller  7 . A surface of the photosensitive drum  6  is uniformly charged by a scorotron-type charger (not shown) as the photosensitive drum  6  rotates. 
     On the other hand, LED units  5  are rotatably supported on the top cover  4 . Four LED units  5  are disposed in parallel corresponding to the drum units  3 . The tip of each LED unit  5  is disposed at a position facing a circumferential surface of the photosensitive drum  6  when the top cover  4  is in the closed posture. In addition, the LED units  5  are retracted from the inside of the main body casing  2  when the top cover  4  is in the open posture. In this case, the tip of the LED unit  5  faces toward the rotatable shaft  15  of the main body casing  2  as shown in  FIG. 2 . 
     The photosensitive drum  6  uniformly charged by the scorotron-type charger is selectively exposed by the LED units  5 . By this exposure, electric charges are selectively removed from the surface of the photosensitive drum  6 . As a result, an electrostatic latent image is formed on the surface of the photosensitive drum  6 . A developing bias is applied to the developing roller  7 . When the electrostatic latent image faces the developing roller  7 , toner is supplied from the developing roller  7  to the electrostatic latent image due to the potential difference between the electrostatic latent image and the developing roller  7 . As a result, a toner image is formed on the surface of the photosensitive drum  6 . 
     In addition, a sheet feed cassette  8  in which the sheet P is set is disposed on a bottom portion of the main body casing  2 . The sheet P set in the sheet feed cassette  8  is conveyed on the conveyance belt  9  by various rollers. The conveyance belt  9  is wound around a pair of driving roller  10  and driven roller  11  and is disposed to face the four photosensitive drums  6  from the lower side. A transfer roller  12  is disposed at a position facing each photosensitive drum  6  with an upper part of the conveyance belt  9  interposed therebetween. The sheet P conveyed on the conveyance belt  9  passes between the conveyance belt  9  and the photosensitive drums  6  sequentially as the conveyance belt  9  travels. Then, a toner image on the surface of the photosensitive drum  6  is transferred onto the sheet P by a transfer bias applied to the transfer roller  12  when the toner image faces the sheet P. 
     A fixing unit  13  is provided at a downstream side of conveyance belt  9  in the conveyance direction of the sheet P. The sheet P on which the toner image is transferred is conveyed to the fixing unit  13 . In the fixing unit  13 , the toner image is fixed on the sheet P by heat and pressure. The sheet P on which the toner image is fixed is discharged to a sheet discharge tray  14  on the upper surface of the main body casing  2  by various rollers. 
     It is noted that, in a state where the top cover  4  is closed, an upstream side in the conveyance direction of the sheet P using the conveyance belt  9  is taken as a front side of the printer  1 . Left and right sides in the printer  1  is determined when the printer  1  is viewed from the front side. In each drawing, arrows indicating front and rear, upper and lower, and left and right directions are shown. 
     2. Top Cover 
       FIG. 3  is a perspective view showing a state where the top cover  4  is opened in the printer shown in  FIG. 1 .  FIG. 4  is a perspective view showing a right cover side plate. 
     The top cover  4  is formed in an approximately rectangular plate shape in plan view. A pair of cover side plates  24  that support the four LED units  5  rotatably and collectively is attached to the top cover  4 . 
     On a bottom surface of the top cover  4 , the pair of cover side plates  24  are disposed spaced apart therebetween in the left and right direction (hereinafter, also referred to as a width direction). As shown in  FIG. 4 , each cover side plate  24  includes a mounting plate  27 , which extends in the front and rear direction and has an approximately rectangular plate shape in plan view, and a support plate  77 , which extends downward from an inner edge portion of the mounting plate  27  in the width direction and has a rectangular plate shape in side view. 
     The mounting plate  27  is attached to the bottom surface of the top cover  4  by an attaching screw (not shown) in a state where an upper surface of the mounting plate  27  is in contact with the bottom surface of the top cover  4 . 
     A connecting portion  20  is formed at the rear end of the mounting plate  27 . The connecting portion  20  is formed in a triangular plate shape in side view protruding from the mounting plate  27  downward from the rear side. An annular rotatable shaft housing portion  26  is formed at a rear-side lower end of the connecting portion  20 . The rotatable shaft housing portion  26  has a C shape in side view while a rear-side portion of the rotatable shaft housing portion  26  is cut. The rotatable shaft  15  (refer to  FIG. 1 ) provided in the main body casing  2  is rotatably fitted in the rotatable shaft housing portion  26 . As a result, the cover side plate  24  (top cover  4 ) is rotatably supported around the rotatable shaft  15 . 
     At the lower end of the support plate  77 , four LED support portions  28  are formed with equal distances therebetween in the front and rear direction. Each LED support portions  28  is formed in a semicircular shape in side view protruding downward from the lower end of the support plate  77 . An LED support hole  29  is formed to pass through the LED support portion  28  in the width direction. 
     A movable boss hole  72  formed in the arc from the upper end of the cover side plate  24  downward to the front side is formed between the rearmost LED support hole  29  of the support plate  77  of the right cover side plate  24  and the LED support hole  29  in front of the rearmost LED support hole  29 . A movable boss  71 , which will be described later, is inserted in the movable boss hole  72 . 
     A slide rail  22  is formed in a middle portion of the mounting plate  27  of the right cover side plate  24  in the front and rear direction. The slide rail  22  is formed in a long and narrow hole shape that extends frontward from the approximately middle of the mounting plate  27  and passes through the mounting plate  27  in the up and down direction. 
     As shown in  FIG. 3 , an operation member  23  that is slidable along the slide rail  22  and an arm regulating member  30  for regulating the slide range of an arm  21 , which will be described later, are attached to the right cover side plate  24 . 
     (1) Operation Member 
       FIG. 5  is a perspective view showing the positional relationship of the arm regulating member  30 , an operation member  23 , and the arm  21 . 
     As shown in  FIGS. 4 and 5 , the operation member  23  includes a main body  31 , which extends in the front and rear direction and has an approximately rectangular plate shape in side view, and an inclined portion  32 , which extends from the rear end of the main body  31  downward to the rear side and has an approximately parallelogram shape in side view. A contact portion  33  which protrudes rearward and whose rear end surface is inclined is formed at the lower end of the inclined portion  32 . 
     A slider  34  that extends in the front and rear direction and has a T shape in front view is formed on an upper surface of the main body  31 . Since an upper portion of the slider  34  is disposed on the slide rail  22  of the cover side plate  24  and a lower portion (portion connected with the main body  31 ) of the slider  34  is exposed downward from the slide rail  22 , the operation member  23  becomes slidable along the slide rail  22 . 
     As shown in  FIG. 4 , an L rib  35  having an L shape is formed in front of the inclined portion  32  on a bottom surface of the main body  31 . The L rib  35  extends downward from the bottom surface of the main body  31  and is bent from the lower end inward in the width direction. The tip of the L rib  35  faces a locking lever  65  of a locking member  59 , which will be described later, in the front and rear direction. 
     Further, as shown in  FIG. 4 , a groove  36  in which an arm boss  43 , which will be described later, is inserted is formed on a right side surface of the front end of the main body  31 . The lower end of the groove  36  is open downward. 
     (2) Arm 
     The main body casing  2  includes a pair of main body side plates  39  facing each other and spaced apart in the left and right direction. A support portion  40  having a triangular shape in side view is formed at the upper end of each of the main body side plates  39  (shown by an imaginary line in  FIG. 3 ). A support shaft hole (not shown) is formed to pass through the support portion  40  in the width direction. 
     The arm  21  is formed in a long and narrow quadrangular prism shape and includes a pair of arm side plates  37  facing each other in the left and right direction and an arm connecting plate  38  that connects the arm side plates  37  to each other. An arm shaft  41  is provided between one ends of the arm side plates  37 . The arm shaft  41  is rotatably inserted in a support shaft hole of the support portion  40 . Accordingly, the arm  21  is rotatably supported around the arm shaft  41  with respect to the main body casing  2 . 
     As shown in  FIG. 5 , at the other end of the right arm  21 , an arm boss  43  protruding inward in the width direction is formed on the arm side plate  37  at the inner side in the width direction. The arm boss  43  of the right arm  21  is fitted in the groove  36  of the operation member  23 . Thus, the other end of the right arm  21  is connected to the cover side plate  24  (top cover  4 ) to be slidable integrally with the operation member  23 . 
     As shown in  FIG. 3 , a hook-like spring locking portion  44  that protrudes rearward and is bent upward in a state where the arm  21  is erected with respect to the main body casing  2  is formed in a middle portion of the arm connecting plate  38 . One end of an arm spring  45  is locked to the spring locking portion  44 . The other end of the arm spring  45  is locked to a locking portion (not shown) provided at the rear end of the main body side plate  39 . Accordingly, the arm  21  is urged rearward by the arm spring  45 . 
     (3) Arm Regulating Member 
     The arm regulating member  30  is attached to a bottom surface of the mounting plate  27  of the cover side plate  24 . The arm regulating member  30  is formed in an approximately rectangular long and narrow plate shape in plan view, as shown in  FIG. 5 . An arm regulating groove  46  which extends in the front and rear direction and has front and rear ends blocked is formed on a bottom surface of the arm regulating member  30 . The other end of the arm  21  is inserted in the arm regulating groove  46  in a state where the arm boss  43  provided at the other end of the arm  21  is fitted in the groove  36  of the operation member  23 . Accordingly, since the arm  21  is movable within a range corresponding to the length of the arm regulating groove  46  in the front and rear direction, the movement beyond the range is regulated. 
     3. Opening and Closing Operations of a Top Cover 
       FIG. 6  is a perspective view showing a state where the top cover  4  is in the closed posture.  FIG. 7  is a perspective view showing a state where the top cover  4  is disposed at a second angle position rotated by a second angle from the closed posture.  FIG. 8  is a perspective view showing a state where the top cover  4  is disposed at a first angle position rotated by a first angle from the closed posture.  FIG. 9  is a perspective view showing a state where the top cover  4  is in the open posture. 
     Hereinafter, an operation of the top cover  4  will be described mainly referring to  FIGS. 6 to 9 . In each drawing, the right arm  21  is shown by an imaginary line for the simplicity purpose. 
     As shown in  FIG. 6 , when the top cover  4  is in the closed posture, each arm  21  has approximately horizontal posture and the other end of the right arm  21  is disposed at the front end of the arm regulating groove  46 . The operation member  23  is disposed at the front end within a slidable range. 
     In this state, the tip of each LED unit  5  is separated from the top cover  4  to be disposed at a distant position at which the LED unit  5  can expose a surface of the photoconductor drum  6  (refer to  FIG. 1 ). 
     When the top cover  4  rotates from this state, the other end of each arm  21  slides rearward to cause each arm  21  to rotate in a direction erecting with respect to the main body casing  2 , as shown in  FIG. 7 . The operation member  23  moves rearward with the movement of the other end of the right arm  21 . 
     When the top cover  4  is disposed at the first angle position rotated by the first angle (for example, 40°) from the closed posture, the inclined portion  32  comes in contact with a link boss  75 , which will be described later, from the front side as shown in  FIG. 8 . 
     When the top cover  4  further rotates in this state, the other end of each arm  21  further slides rearward to cause each arm  21  to rotate in the direction erecting with respect to the main body casing  2 , as shown in  FIG. 9 . The operation member  23  further moves rearward with the movement of the other end of the arm  21 , and the link boss  75  is guided to the inclined surface of the contact portion  33  to ride on the contact portion  33 . 
     In the state where the top cover  4  is in the open posture, the tip of each LED unit  5  is adjacent to the top cover  4  and is disposed at the adjacent position facing toward a side of the rotatable shaft  15  (refer to  FIG. 1 ). 
     4. LED Unit 
       FIG. 10  is a perspective view showing the LED unit  5 . The LED unit  5  includes an LED head  49 , two holders  48  for holding the LED head  49 , and a connecting member  47  for connecting the holders  48 . 
     The LED head  49  is formed in an approximately inverted triangle shape in side view extending in the width direction. In addition, the LED head  49  is formed by unitizing an LED array (not shown) arrayed linearly along the main-scanning direction (width direction) and a SELFOC lens array (not shown). A bottom surface of the LED head  49  is configured as an exposure surface from which light is emitted. 
     Each holder  48  is formed in an approximately rectangular shape in side view extending in a direction perpendicular to the longitudinal direction of the LED unit  49 . In addition, the LED head  49  is held between one ends of the holders  48 . 
     The connecting member  47  is formed in a rod shape extending in the width direction and is disposed between the other ends of the holders  48 . Swinging bosses  50  protruding outward in the width direction are formed at both ends of the connecting member  47  in the width direction. As shown in  FIG. 3 , since the swinging boss  50  is inserted in the LED support hole  29  of each cover side plate  24 , the LED unit  5  is supported to be swingable with respect to the cover side plate  24 (top cover  4 ). 
     As shown in  FIG. 10 , an arm portion  51  protruding upward to the rear side is formed on a right end surface of the connecting member  47 . A displacement boss  52  protruding outward in the width direction is formed on a protruding end of the arm portion  51 . The displacement boss  52  is swingably supported on a movable member  53 , which will be described later. 
     5. Movable Member 
       FIG. 11  is a perspective view showing the cover side plate  24  and the movable member  53  when the top cover  4  is in the closed posture.  FIG. 12  is a perspective view showing the cover side plate  24  and the movable member  53  when the top cover  4  is in the open posture.  FIG. 13  is a side view showing the movable member  53  and the LED unit  5  when the top cover  4  is in the closed posture.  FIG. 14  is a side view showing the movable member  53  and the LED unit  5  when the top cover  4  is disposed at the second angle position rotated by the second angle from the closed posture. 
       FIG. 15  is a side view showing the movable member  53  and the LED unit  5  when the top cover  4  is disposed at the first angle position rotated by the first angle from the closed posture.  FIG. 16  is a side view showing the movable member  53  and the LED unit  5  when the top cover  4  is in the open posture.  FIG. 17  is a side view showing the movable member  53  and the LED unit  5  when the top cover  4  is disposed at a third angle position rotated by a third angle from the closed posture, from the state of  FIG. 16 .  FIG. 18  is a back view showing the positional relationship between the locking member  59  and the operation member  23 .  FIG. 19  is a perspective view showing the locking member  59 . 
     The movable member  53  is formed in an approximately rectangular plate shape in side view extending in the front and rear direction and is disposed on the left side of the right cover side plate  24  as shown in  FIG. 11 . In the movable member  53 , displacement boss holes  54  in which the displacement bosses  52  of the LED unit  5  are inserted are formed at equal distances therebetween in the front and rear direction. A portion of the movable member  53  where each displacement boss hole  54  is formed is formed to have a larger width in the up and down direction than the other portions. In addition, the displacement boss hole  54  located at the rearmost side is formed in an elliptical shape extending in the up and down direction compared with the other three displacement boss holes  54 . 
     A receiving portion  55  having a shape cut from the upper end is formed in a middle portion of the movable member  53  in the front and rear direction. A locking boss  69  (refer to  FIG. 19 ) of the locking member  59 , which will be described later, is inserted in the receiving portion  55 , such that the movement of the movable member  53  is regulated. 
     A hook-like spring locking portion  56  that protrudes leftward and is bent frontward is formed at the rear end of the movable member  53 . One end of a spring  57  for urging the movable member  53  rearward is locked to the spring locking portion  56 , as shown in  FIG. 13 . In addition, a hook-like spring locking portion  58  that protrudes leftward and is bent rearward is formed in the cover side plate  24  as shown in  FIG. 11 . The other end of the spring  57  is locked to the spring locking portion  58 . 
     The movable boss  71  protruding rightward is formed between the rearmost displacement boss hole  54  of the movable member  53  and the displacement boss hole  54  positioned therebefore. The movable boss  71  passes through the movable boss hole  72  (refer to  FIG. 4 ) formed in the cover side plate  24  to protrude rightward. 
     6. Locking Member 
     The locking member  59  is swingably supported on the right side surface of the right cover side plate  24 . 
     As shown in  FIG. 19 , the locking member  59  includes a main body portion  60  having an annular plate shape in side view, an urged portion  61  which extends frontward from the peripheral edge of the main body portion  60  and has a triangular shape in side view, and a locking boss support portion  62  which extends rearward from the peripheral edge of the main body portion  60  and has a rectangular shape in side view. 
     In the main body portion  60 , a support shaft hole  63  is formed to pass therethrough in the width direction. A support shaft (not shown) for rotatably supporting the locking member  59  on the cover side plate  24  is inserted in the support shaft hole  63 . An annular edge portion  64  extending leftward is formed in the peripheral edge of the main body portion  60 . The edge portion  64  is formed in a C shape in side view including an open portion  81  by being cut frontward from the lower end. The main body portion  60  includes a locking lever  65  rotatable around the support shaft hole  63  and a spring  66  for urging the locking lever  65 . 
     The locking lever  65  includes: a rotary portion  78  which has an inner diameter equal to the diameter of the support shaft hole  63 , and is provided to be rotatable around the support shaft hole  63 , and has an annular plate shape in side view; a spring locking portion  79  extending from the peripheral surface of the rotary portion  78  in a direction perpendicular to the axial line of the support shaft hole  63 ; and a lever portion  80  extending from the peripheral surface of the rotary portion  78  in a direction opposite the spring locking portion  79 . 
     The end of the spring  66  is locked to the spring locking portion  79 . The other end of the spring  66  is locked to the main body portion  60  in a state where a compressive force is applied. Accordingly, an urging force in a clockwise direction as viewed from the left side is always applied to the locking lever  65 . 
     The spring licking portion  79  is formed to protrude outward from the open portion  81  and to be bent to the right side. 
     The urged portion  61  has an urged surface  67  formed to extend frontward from the outer peripheral surface of the edge portion  64 . One end of a coil spring  68 , which will be described later, is in contact with the urged surface  67 . The locking boss  69  which extends leftward and has a cylindrical shape in side view is formed at the rear end of the locking boss support portion  62 . As shown in  FIG. 11 , the locking boss  69  is inserted in an arc shaped locking boss insertion hole  70  formed in the cover side plate  24  and is fitted in the receiving portion  55  of the movable member  53  in a state where the top cover  4  is closed. 
     The coil spring  68  is provided between the locking member  59  and the cover side plate  24 . As shown in  FIG. 13 , one end of the coil spring is in contact with the urged portion  61  of the locking member  59  from below. The other end of the coil spring  68  is fixed to the cover side plate  24 . Accordingly, an urging force in a direction of rotating the locking member  59  counterclockwise as viewed from the left side is applied to the locking member  59 . 
     7. Link Member 
     As shown in  FIG. 6 , a link member  73  is swingably supported on a link shaft  74  provided in the cover side plate  24 . The link member  73  is formed to extend in a direction perpendicular to the axial direction of the link shaft  74 , and a link boss  75  protruding rightward is formed at one end of the link member  73 . In addition, a movable boss hole  76  in which the movable boss  71  is fitted is formed at the other end of the link member  73 . 
     8. Operation of a Movable Member 
     Hereinafter, an operation of the movable member  53  will be described with reference to  FIGS. 13 to 17 . In each drawing, the cover side plate  24  and the operation member  23  are shown by imaginary lines for the simplicity purpose. 
     As shown in  FIG. 13 , when the top cover  4  is in the closed posture, the operation member  23  is disposed at the front end within a slidable range. 
     In this state, the movable member  53  is urged rearward by the spring  57 . The locking member  59  is urged by the coil spring  68 , and the locking boss  69  is fitted in the receiving portion  55  of the movable member  53 . The tip of each LED unit  5  is separated from the top cover  4  to be disposed at a distant position at which the LED unit  5  can expose the surface of the photoconductor drum  6  (refer to  FIG. 1 ). 
     When the top cover  4  rotates toward the second angle position rotated by the second angle (for example, 35°) from the above state, the operation member  23  moves rearward and the L rib  35  comes in contact with the locking lever  65  of the locking member  59  from the front side as shown in  FIG. 14 . When the top cover  4  further rotates from this state, the locking boss  69  is separated from the receiving portion  55 . That is, the lower end of the locking lever  65  is pressed rearward against the L rib  35 , the lever portion  80  (refer to  FIG. 19 ) comes in contact with the edge portion  64  (refer to  FIG. 19 ), and the locking member  59  rotates counterclockwise as viewed from the right side. Then, the locking boss  69  (refer to  FIG. 19 ) moves in a direction of being lifted upward. As a result, regulation of movement of the movable member  53  is released. In addition, the urged portion  61  (refer to  FIG. 19 ) moves in a direction of being pressed downward. Accordingly, a compressive force is applied to the coil spring  68 . In addition, when the top cover  4  is disposed at the first angle position rotated by the first angle (for example, 40°) from the closed posture, the contact portion  33  of the operation member  23  comes in contact with the link boss  75  of the link member  73  from the front side thereof, as shown in  FIG. 15 . From this state, when the top cover  4  further rotates, the contact portion  33  of the operation member  23  presses the link boss  75  of the link member  73  pressed rearward. Then, each LED unit  5  starts to rotate around the LED support hole  29 . That is, the link boss  75  rides on the contact portion  33  of the operation member  23  by further rearward movement of the operation member  23 . Then, the link member  73  rotates around the link shaft  74  to move the movable member  53  downward to the front side through the movable boss  71 . As a result, each LED unit  5  rotates around the LED support hole  29  and the other end faces toward the rotatable shaft  15  (refer to  FIG. 1 ). 
     After the lower end of the locking lever  65  moves ahead of the L rib  35  in a state (state of  FIG. 15 ) of being pressed rearward by the L rib  35 , the lower end of the locking lever  65  is separated from the L rib  35  as shown in  FIG. 16 . Then, the coil spring  68  to which the compressive force has been applied is restored, and accordingly, the locking member  59  rotates clockwise as viewed from the right side. 
     When the top cover  4  is rotated to a third angle position rotated by the third angle (for example, 40°) from the open posture, the operation member  23  moves frontward and the link boss  75  is separated from the contact portion  33  as shown to FIG.  17 . Then, the movable member  53  moves upward to the rear side by the urging force of the spring  57 . As a result, each LED unit  5  rotates around the LED support hole  29  and the other end is disposed at a distant position separated from the top cover  4 . 
     The locking boss  69  of the locking member  59  is fitted into the receiving portion  55  of the movable member  53  simultaneously when the link boss  75  is separated from the contact portion  33 . As a result, movement of the movable member  53  is regulated. 
     9. Operations and Effects 
     As described above, the opening  16  is formed in the main body casing  2 . The top cover  4  is attached to the main body casing  2 . The top cover  4  is rotatably supported around the rotatable shaft  15 . The opening  16  of the main body casing  2  is opened when the top cover  4  is in the open posture and is closed when the top cover  4  is in the closed posture. One end of each LED unit  5  is swingably supported on the top cover  4 . When the top cover  4  is in the closed posture, the LED unit  5  takes the distant posture in which the other end opposite the one end is distant from the top cover  4 . As the top cover  4  is rotated from the first angle position at which the top cover  4  is rotated by the first angle from the closed posture, toward the open posture, the LED unit  5  swings from the distant posture toward an adjacent posture, in which the other end is more close to the top cover  4  than the distant posture. As the top cover  4  is rotated toward the first angle position from the open posture, the LED unit  5  is rotated toward the distant posture with the rotation. As the top cover  4  is rotated toward the closed posture from the second angle position at which the top cover  4  is rotated by the second angle from the closed posture, the swingable range of the LED unit  5  is regulated by the locking member  59 . Thus, it is possible to prevent undesired swinging of the LED unit  5 , which is large sufficient to cause interference with other components disposed in the main body casing  2  when the top cover  4  rotates from the open posture to the closed posture. Accordingly, interference between the LED unit  5  and components disposed in the main body casing  2  can be prevented. 
     Furthermore, the photoconductor drum  6  is housed in the main body casing  2 . The LED unit  5  includes an exposure device for exposing a surface of the photoconductor drum  6 . Since the LED unit  5  faces the surface of the photoconductor drum  6  when the top cover  4  is in the closed posture, the surface of the photoconductor drum  6  can be exposed by the LED unit  5 . 
     In addition, when the top cover  4  rotates from the closed posture toward the open posture, the swingable range of the LED unit  5  is regulated by the locking member  59  until passing the second angle position at which the top cover  4  is rotated by the second angle from the closed posture. In addition, when the top cover  4  is rotated to pass the third angle position toward the open posture side, the regulation performed by the locking member  59  is released so that the LED unit  5  freely swings. Accordingly, when the top cover  4  is rotated from the closed posture toward the open posture, undesired swinging of the LED unit  5  can be prevented until passing the second angle position and rotation of the LED unit  5  from the distant posture to the adjacent posture can be allowed after passing the second angle position. As a result, satisfactory rotation of the LED unit  5  from the distant posture to the adjacent posture can be secured while preventing the interference between the LED unit  5  and components disposed in the main body casing  2  when the top cover  4  rotates from the closed posture toward the open posture. 
     In addition, the LED unit  5  is supported by the movable member  53 . When the movable member  53  moves in a direction perpendicular to the rotatable shaft  15 , the LED unit  5  swings. The locking member  59  regulates the amount of movement of the movable member  53 . Accordingly, the swingable range of the LED unit  5  can be regulated. 
     Moreover, if the top cover  4  is rotated from the open posture to the third angle position and is disposed at the third angle position, the LED unit  5  takes the distant posture and the amount of movement of the movable member  53  is regulated by the locking member  59 . Thus, the swingable range of the LED unit  5  can be regulated simultaneously when the LED unit  5  takes distant posture. 
     The arm  21  is provided between the main body casing  2  and the top cover  4 . One end of the arm  21  is rotatably supported on the main body casing  2 . On the other hand, the other end of the arm  21  opposite the one end is slidably connected to the top cover  4  in a direction perpendicular to the rotatable shaft  15 . Accordingly, since the top cover  4  is provided to be rotatable with respect to the main body casing  2 , the other end of the arm  21  slides in conjunction with the displacement between the open posture and the closed posture of the top cover  4 . The locking member  59  regulates the amount of movement of the movable member  53  and releases the regulation in conjunction with sliding of the other end of the arm  21 . Accordingly, regulation of the amount of movement of the movable member  53  and release of the regulation can be reliably switched in conjunction with the displacement between the open posture and the closed posture of the top cover  4 . 
     Further, the locking member  59  has a projection. And, a receiving portion in which a projection is received is formed in the movable member  53 . The amount of movement of the movable member  53  is regulated by receiving of the locking boss  69  into the receiving portion  55 , and regulation of the amount of movement of the movable member  53  is released by separation of the locking boss  69  from the receiving portion  55 . Accordingly, regulation of the amount of movement of the movable member  53  and release of the regulation can be realized with a simple configuration of the locking boss  69  and the receiving portion  55 . 
     Further, the receiving portion  55  is formed at a position facing the locking boss  69  simultaneously with disposition of the top cover  4  at the third angle position when the top cover  4  is rotated toward the third angle position from the open posture. Accordingly, it is possible to regulate the amount of movement of the movable member  53  simultaneously when the top cover  4  is disposed at the third angle position. 
     In addition, the locking member  59  has the locking lever  65  and the locking boss  69  that are integrally formed. The printer  1  includes the operation member  23 . The operation member  23  operates the locking lever  65  to separate the locking boss  69  from the receiving portion  55  in conjunction with the displacement of the top cover  4  between the closed posture and the open posture. Accordingly, regulation of the amount of movement of the movable member  53  can be released in conjunction with the displacement of the top cover  4 . 
     In addition, the movable member  53  is urged in a direction of becoming adjacent to the rotatable shaft  15  by the spring  57 . Since such an urging force is applied to the movable member  53 , the amount of movement of the movable member  53  is regulated. Accordingly, it can be prevented that the movable member  53  largely vibrates in a direction of becoming adjacent to the rotatable shaft  15  and a direction becoming distant from the rotatable shaft  15 . Therefore, undesired swinging of the LED unit  5  can be suppressed. 
     In addition, the four LED units  5  are provided. The movable member  53  holds the four LED units  5  collectively. Accordingly, the four LED units  5  can be displaced to the distant posture and the adjacent posture collectively by moving the movable member  53 . 
     In the above-described exemplary embodiment, the third angle is larger than the second angle. However, the present invention is not limited thereto. The third angle may be same as the second angle. 
     While the present invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.