Patent Publication Number: US-6990303-B2

Title: Image forming apparatus equipped with fixing device

Description:
The present application is a continuation of U.S. application Ser. No. 10/370,491, filed Feb. 24, 2003, now U.S. Pat. No. 6,819,895, the entire contents of which are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an image forming apparatus with a fixing device that is capable of easily removing paper jammed in a nip. 
   2. Description of the Related Art 
   A fixing device incorporated in an image forming apparatus is composed of a heating roller and a pressure roller that is in pressure contact with the heating roller. The pressure roller is provided with a pressurizing mechanism to pressure contact the pressure roller to the heating roller. This pressurizing mechanism also serves as a pressure releasing mechanism to release pressure. 
   However, when a sheet of paper is jammed in the bellows shape in the nip position between the heating roller and the pressure roller, it is difficult for a user to release the jamming of paper. Therefore, a serviceman removes a fixing device from the main body of the image forming apparatus and removes a cover fixed to the fixing device with screws for a user. Further, a serviceman released the pressure roller from the heating roller and removed jammed paper. 
   A fixing device capable of easily removing jammed paper is disclosed in Japanese Patent Publication No. 2001-318555 (Laid open to public inspection on Nov. 16, 2001). This fixing device is composed of a heating roller, a pressure roller to pressure contact this heating roller, a pressurizing means to pressing the pressure roller to the heating roller, and a pressure releasing lever to release the pressing force of the pressurizing means. Further, this fixing device is provided with a separating mechanism to separate the pressure roller from the heating roller interlocking with the pressing force releasing operation by the pressure releasing lever. That is, the fixing device has the separating mechanism to separate the pressure roller from the heating roller interlocking with the pressing force releasing operation by the pressure releasing lever, a sheet of paper jammed in the bellows shape can be easily pulled out. Accordingly, a jammed paper can be removed certainly without leaving broken pieces of the paper between the heating roller and the pressure roller. 
   However, the above-mentioned fixing device was fixed with screws or an engaging mechanism in the main body of an image forming apparatus. In this case, when the paper jamming is caused, the fixing device cannot be easily taken out of the main body and there was such a defect that the operability became bad. 
   In Japanese Patent Publication No. 10-301432 (laid open to public inspection on Nov. 13, 1998), an image forming apparatus capable of releasing pressure of the pressure roller and easily detaching a fixing device from the main body of the apparatus is disclosed. That is, this apparatus is provided with slide rails that are supported slidably in the main body, a fixing device that is held detachably to/from the slide rails, and an operating means provided between the main body and the fixing device for approving the pull-out of the fixing device and releasing the pressure contact between the hearing roller and the pressure roller. According to this structure, when troubles such as paper jamming and the like are caused, the fixing device can be easily removed or installed. In addition, the image forming apparatus is equipped with the pressure contact of the pressure roller releasing mechanism and an effect to easily remove jammed paper is provided. However, the above-mentioned fixing device can be removed easily from the main body of the apparatus but the fixing device is also completely removed from the slide rails. It will be dangerous to remove jammed sheets by putting the heated fixing device on a table. In addition, to insert the once removed fixing device to insert into the main body of the apparatus, the fixing device must be engaged with the slid rails again and a difficult work is required to return the fixing device into the main body of the apparatus. Furthermore, the fixing device is moved along the longitudinal direction of the heating roller and the pressure roller and therefore, the moving distance is long and the work is worrisome. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide an image forming apparatus capable of moving a fixing device easily from the main body to the outside and certainly removing jammed paper by separation the pressure roller from the heating roller. 
   According to the present invention, an image forming apparatus is provided. This image forming apparatus comprises: a box shaped main body and a fixing device provided in the main body. This fixing device is composed of: a heating roller having a length nearly corresponding to the maximum width of paper; a pressure roller having a substantially same length as the length of the heating roller and is brought in contact with the heating roller; and a pressure contacting/separating mechanism to press contact/separate the pressure roller to/from the heating roller. The fixing device can be taken out to the outside by moving it in the direction orthogonal to the long direction of the heating roller and the pressure roller. 
   Further, according to the present invention, an image forming apparatus is provided. This image forming apparatus comprises: a box shaped main body; guide members fixed in the inside of the main body; rail members attached to the guide members so as to slide on the guide member; supporting members fixed to the rail members so as to pull out to the outside from the main body; and a fixing device fixed to the supporting members and movable between the inside and the outside of the main body of the image forming apparatus. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front view schematically showing the structure inside a copying machine; 
       FIG. 2  is a perspective view showing a fixing device removed from the main body of a copying machine; 
       FIG. 3  is an exploded perspective view showing the structure of an oscillation lever and a structure to attach the oscillation lever to the cover of a fixing device; 
       FIG. 4  is front views showing the state to fix the oscillation lever at 3 stage positions; 
       FIG. 5  is a exploded perspective view showing the main body of a copying, supporting frames and a fixing device in a second embodiment; and 
       FIG. 6  is a perspective view showing the partially cut fixing device removed from the main body to the outside. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A first embodiment of the present invention will be described referring to the attached drawings. 
     FIG. 1  shows a copying machine  1  as an example of an image forming apparatus. The copying machine  1  has a box type main body  3  comprising a top surface, a bottom surface, a front surface  2   a , a rear surface  2   b , first and second sides  2   c  and  2   d , and a document table  4  on which documents that are objects to be copied. On the document table  4 , a cover  5  for retaining documents is provided so that it can be opened/closed. 
   Below the document table  4 , there is provided a scanner section  6  to apply a light to a document placed on the document table  4 , read the reflected light as image data and generate image signal based on the read image data. 
   Below the scanner section  6 , there is provided a paper receiving portion  7  to receive a discharged image formed and paper P. 
   Further below the paper receiving portion  7 , there is an image forming portion  8  to form an image on a paper P based on an image signal that is generated in the scanner section  6  or an image signal that is input from an external device (not shown). 
   The image forming portion  8  includes an exposing device  9 , a photosensitive drum  10 , a developing device  11 , a transfer charger  13 , and separation charger  14 . The exposing device  9  injects laser beams corresponding to image signals supplied from the scanner portion  6  or an external device. An electrostatic latent image is formed on the surface of the photosensitive drum  10  based on the exposing scanning by the laser beams injected from the exposing device  9 . The developing device  11  forms a toner image by feeding toners to an electrostatic latent image formed on the surface of the photosensitive drum  10 . The transfer charger  13  transfers a toner image formed on the surface of the photosensitive drum  10  on a paper P taken out from a paper supply cassette  12 . The separation charger  14  functions to separate the paper P with the toner image transferred from the surface of the photosensitive drum  10 . 
   In the conveying path of the paper P passed the separation charger  14 , there is provided a fixing device  15  that allows the paper P having a transferred toner image. The fixing device  15  is so provided that it can be taken out to the outside of the main body  3  by opening the cover  50  provided on the first side  2   c  of the main body  3  as described later. The fixing device  15  is composed of a heating roller  16  having a slightly longer size than the maximum width size of a paper P and a pressure roller  17  that pressure contacts the heating roller  16  and physically in the same length as the heating roller  16 . When a paper P having a toner image formed thereon passes a nip portion formed between the heating roller  16  and the pressure roller  17 , the toner image is fused by the heat and the fused toner image is fixed on the paper P. 
   The paper P conveyed in the vertical direction and passed through the fixing device  15  is bent by about 90° in the left direction shown in  FIG. 1  and discharged in the paper receiving portion  7 . 
   As shown in  FIG. 2 , first and second holes  20   a  and  20   b  are formed in parallel to each other on a front frame  18  arranged at the front surface  2   a  side of the main body  3 . On a rear frame  19  arranged at the rear surface  2   b  side of the main body  3 , a first hole  21   a  and a second hole  21   b  are formed side by side opposing to the first hole  20   a  and the second hole  20   b  on the front frame  18  side. A latch  47  provided on an oscillation lever  40  that is described later is engaged with these holes  20   a ,  20   b ,  21   a  and  21   b . Below the first and second holes  20   a  and  20   b  formed on the front frame  18 , a first pin  22   a  and a second pin  22   b  are provided with a prescribed distance between them. Similarly, below the first and second holes  21   a  and  21   b  formed on the rear frame  19 , first and second pins  23   a  and  23   b  are provided with a prescribed distance between them. When viewed from the side surface  2   c  of the main body  3 , the inner side first pin  22   a  and the first pin  23   a  are somewhat longer than the second pins  22   b  and  23   b  at this side. 
   The holes  20   a ,  20   b ,  21   a  and  21   b  and the pins  22   a ,  22   b ,  23   a  and  23   b  are used for fixing the fixing device  15  in the main body  3 . 
   The fixing device  15  is arranged in a slender box shaped cover with the top opened and composed of the heating roller  16  slightly longer than the maximum width size of paper P and the pressure roller  17  in the almost same length of the heating roller  16 . The heating roller  16  and the pressure roller  17  are mounted in the cover  24  via a pair of the frames  25  and  26 . Both ends of the pressure roller  17  are mounted rotatably to the cover  24  via bearings  27  and  28  provided to the cover  24 . The bearings  27  and  28  are mounted to oblong holes  29  and  30  formed on the cover  24  movably in the nearly horizontal direction. Both ends of the pressure roller  17  are inserted into the oblong holes (not shown) formed on a pair of the frames  25  and  26  arranged in the cover  24 . 
   Below both ends of the back surface  31   a  in the longitudinal direction of the cover  24 , a first U-shape hollow fixing guides  32  and  33  are formed. That is, the first fixing guides  32  and  33  are located in the hollow positions from the hollow positions from both side surfaces  31   b  of the cover  24 . Further, below the both side surfaces  31   b  of the cover  24 , there are formed second guides  34  and  35  projecting in the U-shape, respectively. 
   On the both side surfaces  31   b  of the cover  24 , there are shafts  36  and  37  are projecting for mounting an oscillation lever  40  ( FIG. 3 ) so as to oscillate. Further, on the both side surfaces  31   b  of the cover  24 , projecting guide pins  38  and  39  are provided to guide the oscillation of the oscillation levers  40  by engaging in the guide holes  49  ( FIG. 3 ) formed on the oscillation levers  40 . 
     FIG. 3  shows a pressure contacting/separating mechanism B for pressure contacting/separating the pressure roller  17  to/from the heating roller  16 . This pressure contacting/separating mechanism B includes the oscillation levers  40  mounted to both side surfaces  31   b  of the cover  24 . Further, two units of the oscillation levers  40  are provided as they are mounted to both side surfaces  31   b . In  FIG. 3 , one oscillation lever  40  mounted to one side surface  31   b  opposing to the front frame  18  is shown. 
   The oscillation lever  40  is formed with a slender plastic plate  41 . At this side of the lower end of the plate  41 , a supporting hole  42  is formed for fixing the plate  41  rotatably by inserting the shaft  36  provided on the cover  24  projecting therefrom. Further, at the rear side of the lower end of the plate  41 , there is formed an engaging claw  43  that is engaged with the pin  22   b  provided on the front frame  18  projecting therefrom. 
   At the middle portion in the longitudinal direction of the plate  41 , a notch shape housing  44  is formed. A spring  45  is housed in the housing  44 . That is, one end of the spring  45  is fixed to the inner side wall of the housing  44  and a pressure plate  46  is attached movably to the free end of the spring  45 . The pressure plate  46  contacts the outer surface of the bearing  27  that supports the pressure roller  17 . 
   Above the housing  44  formed on the plate  41 , a latch  47  projecting to the front frame  18  side is formed. The latch  47  is formed to be able to project/retract to/from the plate  41  so as to engage in the first and second holes  20   a  and  20   b  formed on the front frame  18 . 
   On the upper edge of the plate  41 , a handle  48  is formed for a user to grasp when oscillating the plate  41 . 
   Further, below the housing  44  formed on the plate  41 , a circular slit  49  is formed. The guide pin  38  that is projecting to the side  31   b  of the cover  24  is inserted into this slit  49 . That is, the slit  49  and the guide pin  38  inserted into the slit  49  function as the guide when oscillating the plate  41 . 
   Next, the operation when installing the fixing device in the main body  3  will be explained referring to  FIG. 2˜FIG .  4 . 
   The oscillation lever is mounted to the side  31   b  in the state able to oscillate, and the fixing device  15  is inserted between the front frame  18  and the rear frame  19  in the arrow direction A in the tilted state shown in  FIG. 4A . When the fixing device  15  is inserted, the first fixing guides  32  and  33  engage with the first pins  22   a  and  23   a , respectively, third guides  34  and  35  engage with the second pins  22   b  and  23   b , respectively, and the fixing device  15  is stopped. In this state of the fixing device  15  stopped, when a user pushes the oscillation lever  40  to the position shown in  FIG. 4C  by way of the state shown in  FIG. 4B  by grasping the handle  48 , the latch  47  goes into the first holes  20   a  and  21   a  formed on the front frame  18  and the rear frame  19  and engages with the holes. 
   By the above operations, the fixing device  15  is fixed in the main body  3 . Then, when the cover  50  provided on the side  2   c  of the main body  3  is closed, the fixing device  15  becomes usable. 
   Next, the operation to separate the pressure roller  17  in the fixing device  15  from the heating roller  16  when removing a jammed paper P in the fixing device  15  and the operation to remove the fixing device  15  from the main body  3  will be explained below referring to  FIG. 1˜FIG .  4 . 
   A user opens the cover  50  provided on the side  2   c  of the main body  3  to the position shown in the dotted line in  FIG. 1  so as to be able to access the fixing device  15 . As the oscillation lever  40  is at the position shown in  FIG. 4C , the pressure roller  17  is in contact with the heating roller  16  by the spring  45  and the pressure plate  46 . When a user depresses the latch  47 , it comes off the first hole  20   a  and the engagement of the latch  47  with the first hole  20  is released (the first hole  21  and the latch  47  at the right side is also released similarly). Thereafter, when the oscillation lever  40  is turned down by pinching the handle  48  of the oscillation lever  40 , the latch  47  goes into the second hole  20   b  and the oscillation lever is engaged with the latch  47  and the second hole  20   b  and stops to move. At this time, the press contact of the pressure roller  17  to the heating roller  16  by the pressure plate  46  is released, and the pressure roller  17  is slightly separated from the heating roller  16 . At this time, user is able to remove a jammed paper P from the fixing device  15 . 
   However, when it is difficult to remove a jammed paper in the above-mentioned state, it is also possible to take out the fixing device  15  to the outside from the main body  3 . 
   That is, in the fixing device is engaged with the latch  47  and the second hole  20   b , when user depresses the latch  47 , the latch  47  comes off the second hole  20   b  and the engagement of the latch  47  with the second hole  20   b  is released. (Similarly, the engagement of the right side second hole  21   b  with the latch  47  is released). Therefore, it is only required to further turn down the oscillation lever  40  to the position shown in  FIG. 4A . At this time, the engagement of an engaging claw  43  formed on the lower edge of the oscillation lever  40  with the second pin  22  is released. As the engaging claw  43  comes off the second pin  22   b , user is enabled to remove the fixing device  15  to the outside of the main body  3 . When the fixing device  15  is removed to the outside, a paper P jammed in the fixing device can be easily removed. 
   Further, in the above embodiment, the fixing device  15  is taken out to the outside of the main body  3  by moving in the direction orthogonal to its longitudinal direction. Accordingly, when compared with an image forming apparatus of which fixing device cannot be taken out from the main body unless the heating roller and pressure roller are moved in the longitudinal direction like the fixing device disclosed in the above-mentioned Japanese Patent Application No. 10-301432, the moving distance of the fixing device of this invention is short and the fixing device  15  can be easily taken out to the outside of the main body. 
   Next, a second embodiment of the present invention wherein the fixing device can be easily installed/removed to/from the main body will be explained referring to  FIG. 5 . Further, the same component elements as those in the first embodiment will be assigned with the same reference numerals and the detailed explanation thereof will be omitted. 
   On the front surface  2   a  and the rear surface  2   b  of the main body  3 , slide guides  51  and  52  are provided, respectively. In the slide guides  51  and  52 , slide rails  53  and  54  are inserted to slide back and forth. At both ends of the slide rails  53  and  54 , roller pairs  55   a ,  55   b  and  56   a ,  56   b  are mounted. There is a supporting frame  57  connected to connect a pair of rails  53  and  54 . At both ends of the supporting frame  57 , there are arranged the front frame  18  and the rear frame  19  for fixing the fixing device  15  similar to those shown in  FIG. 2 . On the front frame  18  and the rear frame  19 , the first holes  20   a ,  21   a , the second holes  20   b ,  21   b , the first pins  22   a ,  23   a  and the second pins  22   b ,  23   b  are formed likewise those explained in the first embodiment. 
   Further, magnets  58  and  59  are attached to the edges of the front frame  18  and the rear frame  19 . 
     FIG. 5  shows the state of the fixing device  15  that is removed from the supporting frame  57 . To install the fixing device  15  to the supporting frame  57 , insert the fixing device  15  between the front frame  18  and the rear frame  19  as explained in the first embodiment. The first fixing guides  32  and  33  engage with the first pins  22   a  and  23   a , respectively. At the same time, the third guides  34  and  35  engage with the second pins  22   b  and  23   b , respectively and the fixing device  15  is mounted to the supporting frame  57 . In this state of the fixing device  15  installed, when a user pushes the oscillation lever  40  to the position shown in  FIG. 4C  by way of the state shown in  FIG. 4B  by grasping the handle  48 , the latch  47  goes into the first holes  20   a  and  21   a  formed on the front frame  18  and the rear frame  19  and is engaged there, and the fixing device  15  is completely fixed to the supporting frame  57 . 
   When the fixing device  15  fixed on the frame  57  is pushed in the direction of the main body  3 , the guide rails  53  and  54  are slid in the slide guides  51  and  52  and the fixing device  15  is set between the front surface  2   a  and the rear surface  2   b  of the main body  3 . At this time, the magnets are electrically absorbed to the edges of the front surface  2   a  and the rear surface  2   b  and fixed definitely in the main body  3 , and the cover  50  is closed. 
   When the cover  50  is opened and he fixing device  15  is pulled out of the main body  3 , the fixing device  15  can be moved to the position shown by the dotted line in  FIG. 1 . With the fixing device  15  at this position, a jammed paper can be removed. 
     FIG. 6  shows the state of the fixing device  15  removed to the outside of the main body  3 . There are provided a first conveying guide comprising a plurality of guide claws and the second conveying guides  61  comprising a plurality of guide claws for conveying a paper P smoothly between the heating roller  16  and the pressure roller  17 . When the fixing device  15  is removed to the outside from the main body  3 , the second conveying guide  61  is taken out in one unit with the fixing device  15  but the first conveying guide  60  is so provided as to remain in the main body  3 . 
   Further, there is a connector  62  provided on the right side of the fixing device  15  shown in  FIG. 6 . The connector  62  does not supply electric power to the fixing device  15  when it was taken out to the outside but supplies power from the power source portion of the main body  3  to heat the heating roller  16  of the fixing device  15  when the fixing device  15  is returned in the main body  3 . Accordingly, during the work to move the fixing device  15  to the outside of the main body  3  and remove a jammed paper, no power is supplied and the heating roller is cooled down gradually and thus, there is an effect not to cause burn injury or other accidents. 
   As described above in detail, according to the present invention, while securing safety of user, a paper jammed in the nip position between the heating roller and the pressure roller can be easily removed by separating the pressure roller from the heating roller. According to the second embodiment wherein the fixing device is removed to the outside of the main body by way of the rails, a jammed paper can be removed in the state with the fixing device is pulled out to the position shown by the dotted line in  FIG. 1 . In addition, the fixing device is moved in the direction orthogonal to its longitudinal direction and therefore, its moving distance can be made short.