Patent Publication Number: US-7715771-B2

Title: Structure for discharging papers in a tandem type color image forming machine

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a division of Ser. No. 11/184,807, filed Jul. 20, 2005 now U.S. Pat. No. 7,343,124 and which is being incorporated in its entirety herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to a tandem type color image forming machine such as an electrostatic copying machine, a laser printer or a facsimile. 
   DESCRIPTION OF THE PRIOR ART 
   In general, a tandem type color image forming machine comprises a plurality of image forming units for forming images with different color toners, a conveyor belt mechanism having a conveyor belt including a linear moving area for carrying paper, and a paper feed cassette for storing paper in its image forming machine body. The image forming units are arranged along the linear moving area of the conveyor belt with a space therebetween, and the conveyor belt mechanism comprises transfer units for transferring toner images formed by the image forming units to paper, corresponding to the image forming units (refer to JP-A 2003-107838) (the term “JP-A” as used herein means an “unexamined published Japanese patent application”). 
   However, in this tandem type color image forming machine, as the conveyor belt mechanism is arranged sideways so that the linear moving area of the conveyor belt extends almost in the lateral direction and the paper feed cassette is arranged sideways below the conveyor belt mechanism, the width (size in the right-and-left direction when the image forming machine is seen from the front) of the image forming machine body becomes large, whereby the entire image forming machine body becomes bulky in the width direction. 
   Meanwhile, there is also known a tandem type color image forming machine in which a conveyor belt mechanism is arranged longitudinally so that the linear moving area of a conveyor belt extends almost in the vertical direction and image forming units are arranged along the linear moving area of the conveyor belt with a space therebetween (refer to JP-A2003-345101). However, as a paper feed cassette is arranged sideways in the lower end portion of the inside of the image forming machine body in this tandem type color image forming machine, the width of the image forming machine body becomes large. Particularly when large-sized paper is stored in the paper feed cassette, the paper feed cassette becomes large in size, whereby the entire image forming machine body becomes bulky in the width direction. The above problem is also existent in a tandem type color image forming machine in which image forming units are arranged along the linear moving area of a primary transfer belt (intermediate transfer belt) with a space therebetween. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a novel tandem type color image forming machine which enables the width of its image forming machine body to be made smaller than that of the prior art, thereby making it possible to make the entire image forming machine body more compact in the width direction than that of the prior art. 
   According to the present invention, the above object can be attained by a tandem type color image forming machine comprising a plurality of image forming units for forming images with different color toners, a belt mechanism comprising an endless belt including a linear moving area, and a paper feed cassette for storing paper in its image information machine body, the image forming units being arranged along the linear moving area of the belt with a space therebetween, wherein 
   the belt mechanism is arranged longitudinally so that the linear moving area of the belt extends almost in the vertical direction, and the paper feed cassette is arranged longitudinally in the lateral direction of the belt mechanism or below the belt mechanism. 
   Preferably, a pair of discharge rollers are arranged in the upper end portion of the inside of the image forming machine body, and a pocket for receiving and storing paper discharged from the pair of discharge rollers and going downward by its own weight is formed on one side face of the image forming machine body in such a manner that it extends along the one side face in the vertical direction. 
   Preferably, the belt is a conveyor belt including the linear moving area for carrying paper, the belt mechanism is a conveyor belt mechanism comprising the conveyor belt, and the paper feed cassette is arranged in the lateral direction of the conveyor belt mechanism. 
   Preferably, the conveyor belt of the conveyor belt mechanism is arranged around a plurality of rollers, a charging conveyor roller is pressed against one of the rollers arranged in the lower end area of the conveyor belt on the upstream side of the linear moving area of the conveyor belt through the conveyor belt, and the position of the paper feed cassette relative to the conveyor belt mechanism is determined such that paper stored in the paper feed cassette is delivered downward toward a nip portion between the charging conveyor roller and the conveyor belt. 
   Preferably, a paper inversion conveyor passage for inverting paper fed downward from the paper feed cassette and carrying it upward toward the linear moving area of the conveyor belt is formed between the paper feed cassette and the conveyor belt mechanism. 
   Preferably, a fixing unit is arranged above the conveyor belt mechanism in the upper end portion of the inside of the image forming machine body, a paper conveyor passage for guiding paper which is carried by the conveyor belt mechanism and to which toner images have been transferred to the fixing unit is formed between the conveyor belt mechanism and the fixing unit, and the paper conveyor passage and the linear moving area of the conveyor belt are aligned with each other almost in the vertical direction. 
   Preferably, a pair of discharge rollers are arranged in the upper end portion of the inside of the image forming machine body, a paper discharge passage is formed between the fixing unit and the pair of discharge rollers in such a manner that it extends upward from the fixing unit, curves and goes toward the pair of discharge rollers almost in the lateral direction, and a pocket for receiving and storing paper discharged from the pair of discharge rollers and going downward by its own weight is formed on one side face of the image forming machine body in the downstream direction of the pair of discharge rollers in such a manner that it extends along the one side face in the vertical direction. 
   Preferably, the belt is a conveyor belt including the linear moving area for carrying paper, the belt mechanism is a conveyor belt mechanism comprising the conveyor belt, and the paper feed cassette is arranged below the conveyor belt mechanism. 
   Preferably, a paper feed conveyor passage for carrying paper fed upward from the paper feed cassette upward toward the linear moving area of the conveyor belt is formed between the paper feed cassette and the conveyor belt mechanism, a fixing unit is arranged above the conveyor belt mechanism in the upper end portion of the inside of the image forming machine body, a paper conveyor passage for guiding paper which is carried by the conveyor belt mechanism and to which toner images have been transferred to the fixing unit is formed between the conveyor belt mechanism and the fixing unit, and the paper conveyor passage, the linear moving area of the conveyor belt and the paper feed conveyor passage are aligned with one another almost in the vertical direction. 
   Preferably, a pair of discharge rollers are arranged in the upper end portion of the inside of the image forming machine body, a paper discharge passage is formed between the fixing unit and the pair of discharge rollers in such a manner that it extends upward from the fixing unit, curves and goes toward the pair of discharge rollers almost in the lateral direction, and a pocket for receiving and storing paper discharged from the pair of discharge rollers and going downward by its own weight is formed on one side face of the image forming machine body in the downstream direction of the pair of discharge rollers in such a manner that it extends along the one side face in the vertical direction. 
   Preferably, the belt is a primary transfer belt including the linear moving area to which toner images formed by the image forming units are transferred in such a manner that they are superimposed one upon another, the belt mechanism is a primary transfer belt mechanism comprising the primary transfer belt, and the paper feed cassette is arranged in the lateral direction of the primary transfer belt mechanism. 
   Preferably, a secondary transfer unit for transferring toner images transferred to the primary transfer belt to paper fed from the paper feed cassette is provided in the image forming machine body and opposed to the top portion of the primary transfer belt, a paper feed conveyor passage for guiding paper fed upward from the paper feed cassette between the primary transfer belt and the secondary transfer unit almost in the lateral direction is formed between the paper feed cassette and the primary transfer belt mechanism, and a fixing unit is arranged on the extension line in the downstream direction of the paper conveyor passage almost in the lateral direction of the top portion of the primary transfer belt mechanism in the upper end portion of the inside of the image forming machine body. 
   Preferably, a pair of discharge rollers are installed in the upper end portion of the inside of the image forming machine body, a paper discharge passage is formed between the fixing unit and the pair of discharge rollers in such a manner that it extends upward from the fixing unit, curves and goes toward the pair of discharge rollers almost in the lateral direction, and a pocket for receiving and storing paper discharged from the pair of discharge rollers and going downward by its own weight is formed on one side face of the image forming machine body in the downstream direction of the pair of discharge rollers in such a manner that it extends along the one side face in the vertical direction. 
   Preferably, a paper discharge tray for receiving paper discharged by the pair of discharge rollers is provided on the top surface of the image forming machine body. 
   Preferably, a secondary transfer unit for transferring toner images transferred to the primary transfer belt to paper fed from the paper feed cassette is provided in the image forming machine body and opposed to the bottom portion of the primary transfer belt, a paper feed conveyor passage for guiding paper fed downward from the paper feed cassette between the primary transfer belt and the secondary transfer unit almost in the lateral direction is formed between the paper feed cassette and the primary transfer belt mechanism, and a fixing unit is arranged on the extension line in the downstream direction of the paper feed conveyor passage almost in the lateral direction of the bottom portion of the primary transfer belt mechanism in the lower end portion of the inside of the image forming machine body. 
   Preferably, a pair of discharge rollers are installed in the upper end portion of the inside of the image forming machine body, a paper discharge passage is formed between the fixing unit and the pair of discharge rollers in such a manner that it extends upward from the fixing unit, curves and goes toward the pair of discharge rollers almost in the lateral direction, and a pocket for receiving and storing paper discharged from the pair of discharge rollers and going downward by its own weight is formed on one side face of the image forming machine body in the downstream direction of the pair of discharge rollers in such a manner that it extends along the one side face in the vertical direction. 
   Preferably, a paper discharge tray for receiving paper discharged by the pair of discharge rollers is provided on the top surface of the image forming machine body. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram showing an embodiment of a tandem type color image forming machine constituted according to the present invention; 
       FIG. 2  is a perspective view schematically illustrating a state where a paper feed cassette is drawn forward from the image forming machine body of the image forming machine shown in  FIG. 1 ; 
       FIG. 3  is a perspective view schematically illustrating a state where a cassette is partially turned to the outside of the cassette body in the paper feed cassette shown in  FIG. 1  and  FIG. 2 ; 
       FIG. 4  is a sectional view of the paper feed cassette shown in  FIG. 3 ; 
       FIG. 5  is a perspective view schematically illustrating a state where the cassette is completely turned to the outside of the cassette body in the paper feed cassette shown in  FIG. 1  and  FIG. 2 ; 
       FIG. 6  is a schematic diagram showing another embodiment of a tandem type color image forming machine constituted according to the present invention; 
       FIG. 7  is a schematic diagram showing still another embodiment of a tandem type color image forming machine constituted according to the present invention; 
       FIG. 8  is a schematic diagram showing a further embodiment of a tandem type color image forming machine constituted according to the present invention; 
       FIG. 9  is a schematic diagram showing a still further embodiment of a tandem type color image forming machine constituted according to the present invention; 
       FIG. 10  is a schematic diagram showing a still further embodiment of a tandem type color image forming machine constituted according to the present invention; 
       FIG. 11  is a perspective view schematically illustrating the image forming machine shown in  FIG. 10  together with a bundle of paper sheets inserted into the paper feed cassette arranged in the image forming machine body from a paper feed opening formed in the image forming machine body; 
       FIG. 12  is a schematic diagram showing a still further embodiment of a tandem type color image forming machine constituted according to the present invention; and 
       FIG. 13  is a perspective view schematically illustrating the image forming machine shown in  FIG. 12 . 
       FIG. 14  is a schematic diagram showing an alternate embodiment of  FIG. 7  wherein the paper feed cassette is located below the belt mechanism. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Preferred embodiments of a tandem type color image forming machine constituted in accordance with the present invention will be described in more detail with reference with the accompanying drawings. The illustrated tandem type color image forming machine is a tandem type color LED printer. In  FIGS. 1 to 13 , substantially the same constituent elements are given the same reference symbols. 
   With reference to  FIG. 1 , a tandem type color image forming machine (to be simply referred to as “image forming machine” hereinafter)  100  has an image-forming machine body  2  of nearly a rectangular parallel piped shape. In this image forming machine body  2 , a plurality of image forming units for forming images with different color toners, i.e., a black toner image forming unit  4 , a cyan toner image forming unit  6 , a magenta toner image forming unit  8  and a yellow toner image forming unit  10  in this embodiment are installed in this order from the top toward the bottom in  FIG. 1 . These image forming units  4 ,  6 ,  8  and  10  are each provided with image forming elements such as a photosensitive material drum  12 , a charging unit  14 , an LED head  16  which is part of exposure means, a developing unit  18  and a cleaning unit  20 . The developing units  18  of the image forming units  4 ,  6 ,  8  and  10  are each equipped with a toner container  22  for supplying a respective color toner. For simplifying illustration in  FIG. 1 , reference numerals for the image forming elements are given only to the black toner image forming unit  4 . 
   In the image forming machine body  2 , there are further installed a belt mechanism comprising an endless belt including a linear moving area, i.e., a conveyor belt mechanism  26  comprising a conveyor belt  24  including a linear moving area  24   a  for carrying paper P in this embodiment, and a paper feed cassette  28  for storing the paper P. The image forming units  4 ,  6 ,  8  and  10  are arranged along the linear moving area  24   a  of the conveyor belt  24  with a space therebetween. The conveyor belt mechanism  26  comprises transfer units for transferring toner images formed by the image forming units  4 ,  6 ,  8  and  10  to the paper P, i.e., transfer rollers  30  in this embodiment, corresponding to the photosensitive material drums  12  of the image forming units  4 ,  6 ,  8  and  10 . The linear moving area  24   a  of the conveyor belt  24  exists between the photosensitive material drums  12  and the respective transfer rollers  30 . For simplifying illustration, the reference numeral  30  for these transfer rollers is given only to the transfer roller for the photosensitive material drum  12  of the black toner image forming unit  4 . 
   The conveyor belt mechanism  26  is arranged longitudinally so that the linear moving area  24   a  of the conveyor belt  24  extends almost in the vertical direction. The conveyor belt  24  which is an endless belt is looped over a plurality of rollers, i.e., a drive roller  32  and follower rollers  34 ,  36  and  38  in this embodiment. The drive roller  32  driven in the clockwise direction in  FIG. 1  by an unshown electric motor is disposed at the top of the conveyor belt mechanism  26 , and the follower roller  34  is existent at the bottom of the conveyor belt mechanism  26  almost right below the drive roller  32  in the vertical direction. The follower roller  36  is off to the lower right of the drive roller  32  in  FIG. 1  in the upper end area of the conveyor belt  24 . The follower roller  38  is off to the upper right of the follower roller  34  in  FIG. 1  in the lower end area of the conveyor belt  24 . The follower roller  34  is in pressure contact with another follower roller  40  from the left direction in  FIG. 1 . The linear moving area  24   a  of the conveyor belt  24  is formed between the drive roller  32  and the follower roller  34 . The other linear moving area  24   b  is formed between the follower roller  36  and the follower roller  38 . The other linear moving area  24   b  extends substantially in parallel to the linear moving area  24   a  with a space therebetween in the lateral direction in  FIG. 1 . The image forming units  4 ,  6 ,  8  and  10  are arranged on the left side of the linear moving area  24   a  in  FIG. 1 . When the drive roller  32  is turned in the clockwise direction in  FIG. 1 , the conveyor belt  24  is turned in the same direction. The follower rollers  34 ,  36  and  38  are also turned in the same direction by the conveyor belt  24 . The linear moving area  24   a  of the conveyor belt  24  is moved upward in  FIG. 1 . 
   A charging conveyor roller  41  is pressed against the follower roller  38  which is one of the rollers arranged in the lower end area of the conveyor belt  24  on the upstream side of the linear moving area  24   a  of the conveyor belt  24  through the conveyor belt  24 . The charging conveyor roller  41  has the function of partially charging the conveyor belt  24  as negative or positive bias is applied to the charging conveyor roller  41  by unshown bias application means so that paper P fed from the paper feed cassette  28  is electrostatically adsorbed to and carried on the conveyor belt  24 . The charging conveyor roller  41  follows the movement of the conveyor belt  24 . Below the conveyor belt  24  wrapped around the lower end area of the outer wall of the follower roller  34  having a relatively large diameter, an arcuate guide plate G is installed with a space therebetween. The guide plate G is provided to guide the end of the paper P electrostatically adsorbed to and carried on the conveyor belt  24  to a nip portion between the follower roller  34  and the follower roller  40 . A paper detection sensor S 1  for detecting the end of the paper P adsorbed to and carried on the conveyor belt  24  is arranged at a position on the downstream side of the charging conveyor roller  41 . The timing when the end of the paper P fed from the paper feed cassette  28  passes is detected by the paper detection sensor S 1  to calculate the timing of outputting an image to the respective photosensitive material drum  12 . The paper detection sensor S 1  has a timing setting function in place of a pair of resist rollers. 
   The image forming units  4 ,  6 ,  8  and  10  are arranged on the left side of the image moving area  24   a  of the conveyor belt  24  with a space therebetween in the vertical direction in  FIG. 1 . The paper feed cassette  28  is arranged longitudinally so that the paper P is delivered downward and spaced apart from the conveyor belt mechanism  26  in the lateral direction (right side in the lateral direction of the conveyor belt mechanism  26  in  FIG. 1 ). 
   With reference to  FIGS. 1 to 5 , the paper feed cassette  28  comprises a box-like cassette body  42  and a box-like cassette  44  movably stored in the cassette body  42 . The cassette body  42  is rectangular with the shorter side at the top when seen from the front of the image forming machine body  2  (when the sheet is seen from the front in  FIG. 1  and  FIG. 4 ; when seen in the direction of an arrow A in  FIG. 2 ,  FIG. 3  and  FIG. 5 ) and is supported such that it can be drawn from the front face  2 A ( FIG. 2 ) of the image forming machine body  2  over unshown slide rails. The slide rails may be, for example, the Accuride (registered trademark) ball bearing type slide rails. A rectangular opening  3  with the shorter side at the top is formed in the front face  2 A of the image forming machine body  2  in conformity with the cassette body  42 . The cassette body  42  has, when seen from the front, a front wall  42 A and a rear wall  42 B which are opposed to and parallel to each other with a space therebetween in the front-and-rear direction, a top wall  42 C and a bottom wall  42 D which are opposed to and parallel to each other with a space therebetween in the vertical direction, and one side wall  42 E for covering one sides (left sides in  FIG. 1 ) of the front wall  42 A, rear wall  42 B, top wall  42 C and bottom wall  42 D. The other side face (right side face in  FIG. 1 ) of the cassette body  42  is open rectangular. In the corner portion where the bottom wall  42 D and the one side wall  42 E cross each other, an opening  43  ( FIG. 4 ) for delivering paper is formed. In  FIG. 1 , the top wall  42 C, bottom wall  42 D and one side wall  42 E are not shown for simplifying illustration (they are also not shown in  FIGS. 6 to 9 ). 
   A paper feed roller  46  is disposed on the left side when seen from the front in the lower end portion of the inside of the cassette body  42 . The paper feed roller  46  is fitted onto the center portion of a shaft  46 A by an unshown one-way clutch, and the front end and the rear end of the shaft  46 A are rotatably supported to the front wall  42 A and the rear wall  42 B, respectively. Not shown, the rear end of the shaft  46 A projects backward from the rear wall  42 B, and a driven coupling is fitted onto the projecting portion of the shaft  46 A. When the paper feed cassette  28  is pushed into the inside of the image forming machine body  2  from the front face  2 A toward the unshown rear face, the driven coupling is detachably connected to an unshown drive coupling provided in the image forming machine body  2  and driven by an unshown electric motor installed in the image forming machine body  2 . 
   The cassette  44  has when seen from the front a front wall  44 A and a rear wall  44 B which are opposed to and parallel to each other with a space therebetween in the front-and-rear direction, one side wall  44 C and the other side wall  44 D which are opposed to and parallel to each other with a space therebetween in the direction perpendicular to the direction shown by the arrow A in  FIG. 5 , and a bottom wall  44 E for covering the bottoms of the front wall  44 A, the rear wall  434 B, the one side wall  44 C and the other sidewall  44 D. A rectangular opening is formed in the top face (in  FIG. 5 ) of the cassette  44 . A separation claw  53  (only one is shown in  FIG. 1 ,  FIG. 4  and  FIG. 5 ) for the paper P is provided in the corner where the one side wall  44 C and the front wall  44 A cross each other and in the corner where the one side wall  44 C and the rear wall  44 B cross each other at the upper end in  FIG. 5  of the cassette  44 . The cassette  44  is supported such that it can turn round the shaft  48  between an acting position (position shown in  FIG. 1 ) where it is stored in the cassette body  42  and anon-acting position (position shown in  FIG. 5 ,  FIG. 4  shows a halfway position) where it is opened to the outside of the cassette body  42 . The shaft  48  projects forward and backward from corner areas where the front wall  44 A and the rear wall  44 B of the cassette  44  intersect with the one side wall  44 C and the bottom wall  44 E and is rotatably supported to unshown bearings formed in the front wall  42 A and the rear wall  42 B of the cassette body  42 . 
   The cassette  44  is provided with a paper supporting plate  50  on which paper sheets P are stacked while it is open to the non-acting position and a paper fall preventing plate  52  for pressing the paper sheets P stacked on the paper supporting plate  50  against the paper supporting plate  50 . The paper supporting plate  50  has a shaft  54  which projects from the upper end of the paper supporting plate  50  in the front-and-rear direction in  FIG. 1  and  FIG. 4  and is rotatably supported to unshown bearings formed in the front wall  44 A and the rear wall  44 B of the cassette  44  in the upper end corner portions (on the inner sides of corners where the other side wall  44 D and the bottom wall  44 E cross each other) of the inside of the cassette  44 . Thus, the paper supporting plate  50  is supported such that it turns round the shaft  54  in the cassette  44 . A compression coil spring  56  for urging the lower end portion of the paper supporting plate  50  against the paper feed roller  46  is interposed between the lower end portion ( FIG. 1  and  FIG. 4 ) of the paper supporting plate  50  and the corresponding lower end portion (lower end portion of the bottom wall  44 E) of the cassette  44 . One end (upper end in  FIG. 1  and  FIG. 4 ) of the paper fall preventing plate  52  is supported to bearings  45  ( FIG. 5 ) provided at the upper end in  FIG. 5  of corner areas where the front wall  44 A and the rear wall  44 B of the cassette  44  intersect with the other side wall  44 D in such a manner that it can turn round a shaft  58 . An unshown twisted coil spring for urging the paper fall preventing plate  52  in the counterclockwise direction in  FIG. 1  and  FIG. 4  round the shaft  58  is fitted onto the shaft  58 . A cut-out  52 A for preventing interference with the paper feed roller  46  is formed in the center portion at the other end (center portion at the lower end in  FIG. 1  and  FIG. 4 ) of the paper fall preventing plate  52 . 
   While the cassette  44  is opened to the non-acting position ( FIG. 5 ) and the paper fall preventing plate  52  is opened (unshown), the paper sheets P are stacked on the paper supporting plate  50 . The paper sheets P stacked on the paper supporting plate  50  are pressed against the paper supporting plate  50  by closing the paper fall preventing plate  52 . In this state, the cassette  44  is turned round the shaft  48  from the non-acting position ( FIG. 5 ) to the acting position ( FIG. 1 ) and stored in the cassette body  42 . A lock mechanism which can be freely unlocked and may have known constitution is provided between the cassette  44  and the cassette body  42 . The lower end portion of the stacked paper P positioned at the left end in  FIG. 1  is pressed against the paper feed roller  46 . The paper feed cassette  28  is pushed into the image forming machine body  2  over the above-described slide rails and locked at a predetermined mounting position in such a manner that it can be freely unlocked. A lock mechanism which can be freely unlocked and may have known constitution is provided between the cassette body  42  and the image forming machine body  2 . The paper feed cassette  28  is pushed into the mounting position in the image forming machine body  2  from the opening  3  ( FIG. 2 ) and drawn forward from the front face  2 A of the image forming machine body  2  from the mounting position. The position of the paper feed cassette  28  relative to the conveyor belt mechanism  26  is determined so that the paper P stored in the paper feed cassette  28  can be delivered downward toward the nip portion between the charging conveyor roller  41  and the conveyor belt  24  while the paper feed cassette  28  is set in the image forming machine body  2 . As shown in  FIG. 1 , the opening  43  for paper feeding of the paper feed cassette  28  is positioned right on the upstream side of the nip portion. 
   Returning to  FIG. 1 , a fixing unit  60  is disposed above the conveyor belt mechanism  26  in the upper end portion of the inside of the image forming machine body  2 . A paper conveyor passage  62  for guiding the paper P to which toner images have been transferred and which is carried by the conveyor belt mechanism  26  to the fixing unit  60  is formed between the conveyor belt mechanism  26  and the fixing unit  60 . The paper conveyor passage  62  and the linear moving area  24   a  of the conveyor belt  24  are aligned with each other almost in the vertical direction. 
   A pair of discharge rollers  64  for discharging the paper P on which toner images have been fixed and which is carried from the fixing unit  60  from the image forming machine body  2  is arranged above the fixing unit  60  in the upper end portion of the inside of the image forming machine body  2 . A paper discharge passage  66  for guiding the paper P on which toner images have been fixed by the fixing unit  60  and which is carried from the fixing unit  60  to the pair of discharge rollers  64  is formed between the fixing unit  60  and the pair of discharge rollers  64 . The paper discharge passage  66  extends upward from the fixing apparatus  60 , curves and then goes toward the pair of discharge rollers  64  almost in the lateral direction (right direction in  FIG. 1 ). 
   With reference to  FIG. 1  and  FIG. 2 , a paper discharge port  68  is formed at a downstream position of the pair of discharge rollers  64  in the upper end portion of the image forming machine body  2 . A pocket  70  for receiving and storing the paper P discharged from the pair of discharge rollers  64  almost in the lateral direction and going downward by its own weight is formed on one side face  2   a  of the image forming machine body  2  in the downstream direction (right direction in  FIG. 1 ) beyond the pair of discharge rollers of the paper discharge passage  66  in such a manner that it extends along the one side face  2   a  in the vertical direction. The one side face  2   a  is formed almost vertically. The pocket  70  has a front wall  70 A, a rear wall  70 B and a bottom wall  70 C all of which project outward from the one side face  2   a  of the image forming machine body  2  a predetermined length, and an end wall  70 D for covering the ends of the front wall  70 A, the rear wall  70 B and the bottom wall  70 C. The front wall  70 A and the rear wall  70 B extend vertically in parallel to each other with a space therebetween in the front-and-rear direction and are rectangular with the shorter side at the top when seen from the front. The bottom wall  70 C for covering the lower ends of the front wall  70 A and the rear wall  70 B has a flat rectangular shape. A cut-out  71  extending downward from the upper end with a predetermined width in the front-and-rear direction is formed in the center portion in the front-and-rear direction of the end wall  70 D. A box-like paper receiving portion whose upper end is open rectangular is formed between the pocket  70  and the one side face  2   a  of the image forming machine body  2 . It is preferred that the paper receiving position of the pocket  70  should be selected according to the size of paper P. 
   In the thus constituted image forming machine  100 , when the paper feed roller  46  of the paper feed cassette  28  is driven, only one sheet of the paper P stored in the paper feed cassette  28  is fed by the separation function of the separation claws  53 . When the end of the paper P reaches the nip portion between the charging conveyor roller  41  and the conveyor belt  24  to be nipped, the rotation of the paper feed roller  46  is stopped. The paper P is carried toward the linear moving area  24   a  while it is adsorbed to the conveyor belt  24  by cooperation between the charging conveyor roller  41  and the conveyor belt  24 . The paper feed roller  46  follows the movement of the paper P fed by the function of the above-described one-way clutch (idled round the shaft  46 A ( FIG. 5 )). Thus, the paper P carried by the conveyor belt mechanism  26  is conveyed between the photosensitive material drums  12  and the transfer rollers  30  of the image forming units  10 ,  8 ,  6  and  4  by the linear moving area  24   a  of the conveyor belt  24 . In the image forming units  10 ,  8 ,  6  and  4 , the surfaces of the photosensitive material drums  12  charged uniformly by the charging units  14  are exposed by the LED heads  16  to form electrostatic latent images which are then developed by the developing units  18  to become toner images. The toner images are transferred to the paper P carried over the linear moving area  24   a  of the conveyor belt  24  by the transfer rollers  30  sequentially from the toner image formed by the image forming unit  10  on the upstream side in such a manner that they are superimposed one upon another. The color toner images transferred to the paper P are fixed on the paper P while they pass through the fixing unit  60 . The paper P on which the toner images have been fixed is discharged into the pocket  70  by the pair of discharge rollers  64  and stored. The toner not transferred and remaining on the surfaces of the photosensitive material drums  12  is removed by the cleaning units  20 . 
   In the image forming machine  100  of the present invention, the belt mechanism, i.e., the conveyor belt mechanism  26  in this embodiment is arranged longitudinally so that the linear moving area  24   a  of the conveyor belt  24  extends almost in the vertical direction, and the paper feed cassette  28  is arranged longitudinally and spaced apart from the conveyor belt mechanism  26  in the lateral direction. Therefore, the width (right-and-left direction in  FIG. 1 ) of the image forming machine body  2  can be made smaller than that of the prior art, thereby making it possible to make the entire image forming machine body  2  more compact in the width direction than in the prior art. Accordingly, the image forming machine  100  of the present invention is particularly advantageous for use at an office in which the installation space in the lateral direction is limited. 
   In the image forming machine  100  of the present invention, as the position of the paper feed cassette  28  relative to the conveyor belt mechanism  26  is determined so that the paper P stored in the paper feed cassette  28  can be delivered downward toward the nip portion between the charging conveyor roller  41  and the conveyor belt  24 , a paper feed conveyor passage from the paper feed cassette  28  to the conveyor belt mechanism  26  can be omitted. As a result, the entire image forming machine body  2  can be made more compact in the width direction and the longitudinal direction (vertical direction) than in the prior art. 
   In the image forming machine  100  of the present invention, the paper conveyor passage  62  and the linear moving area  24   a  of the conveyor belt  24  are aligned with each other almost in the vertical direction. This constitution contributes to the reduction of the size in the width direction of the image forming machine body  2  and can suppress the occurrence of a jam because there is no curve in the conveyor passage of the paper P between the linear moving area  24   a  of the conveyor belt  24  and the fixing unit  60 . 
   In the image forming machine  100  of the present invention, the pair of discharge rollers  64  are provided in the upper end portion of the inside of the image forming machine body  2 . The paper discharge passage  66  is formed between the fixing unit  60  and the pair of discharge rollers  64 . The paper discharge passage  66  extends upward from the fixing unit  60 , curves and then goes toward the pair of discharge rollers  64  almost in the lateral direction. The pocket  70  for receiving and storing the paper P discharged almost in the lateral direction by the pair of discharge rollers  64  and going downward by its own weight is formed on one side face  2   a  of the image forming machine body  2  in the downstream direction of the pair of discharge rollers  64 , that is, at a downstream position beyond the pair of discharge rollers  64  in the paper discharge passage  66  in such a manner that it extends along the one side face  2   a  in the vertical direction. This constitution contributes to the reduction of the size in the width direction of the image forming machine body  2 , and the ends of the paper sheets P discharged from the paper discharge port  68  ( FIG. 2 ) of the image forming machine body  2  are aligned in the pocket  70 . In the illustrated embodiment, as the paper P is discharged into the pocket  70  in such a manner that its image formed surface faces up, the result of image forming operation can be checked while a plurality of paper sheets P are stored in the pocket  70 . 
     FIG. 6  shows another embodiment of the image forming machine of the present invention. In the conveyor belt mechanism  26  of the image forming machine  200  shown in  FIG. 6 , the linear moving area  24   a  of the conveyor belt  24  is arranged longitudinally to extend almost vertically, and the image forming units  4 ,  6 ,  8  and  10  are arranged along the linear moving area  24   a  of the conveyor belt  24  with a space therebetween in the vertical direction in this order from the top toward the bottom. This basic constitution is substantially the same as that of the image forming machine  100  shown in  FIG. 1 . However, it differs from the image forming machine  100  shown in  FIG. 1  in that the paper P is fed from the paper feed cassette  28  by a pick-up roller  80  and carried to the conveyor belt mechanism  26  along a paper inversion conveyor passage  202 . 
   Stated more specifically, the paper P stored in the paper feed cassette  28  is delivered to the paper inversion conveyor passage  202  by the pick-up roller  80  provided in the paper feed cassette  28 . The pick-up roller  80  which may have known constitution is installed substantially at the same position as the paper feed roller  46  in the above embodiment in the cassette body  42 . As a matter of course, the one-way clutch in the above embodiment is not provided between the pick-up roller  80  and the unshown shaft. In the image forming machine body  2  of the image forming machine  200 , the paper inversion conveyor passage  202  for inverting the paper P fed downward from the paper feed cassette  28  by the pick-up roller  80  and guiding it upward toward the conveyor belt mechanism  26  is formed between the paper feed cassette  28  and the conveyor belt mechanism  26 . The paper inversion conveyor passage  202  is provided with a pair of paper separation rollers  204 , a pair of conveyor rollers  206  and a pair of resist rollers  208  in this order from the upstream to the downstream. The cassette  44  of the paper feed cassette  28  is not provided with the separation claws  53  ( FIG. 5 ). Other constitution is substantially the same as that of the image forming machine  100  shown in  FIG. 1  and its description is omitted. 
   The size in the vertical direction of the entire image forming machine body  2  of the image forming machine  200  shown in  FIG. 6  becomes larger than that of the image forming machine  100  by the installation space of the paper inversion conveyor passage  202 . However, as this image forming machine  200  has substantially the same feature as the image forming machine  100  excluding this, substantially the same effect as that of the image forming machine  100  can be obtained. In the image forming machine  200  shown in  FIG. 6 , the paper feed cassette  28  is spaced apart from the conveyor belt mechanism  26  in the lateral direction in  FIG. 6 . It may be spaced apart from the conveyor belt mechanism  26  in the lateral direction in  FIG. 6  with the image forming units  4 ,  6 ,  8  and  10  interposed between it and the conveyor belt mechanism  26 . 
     FIG. 7  shows still another embodiment of the image forming machine of the present invention. In the image forming machine body  2  of the image forming machine  300  shown in  FIG. 7 , the image forming units  4 ,  6 ,  8  and  10  are arranged in this order from the top toward the bottom in  FIG. 7  like the image forming machines  100  and  200 . In the image forming machine body  2 , there are further installed a primary transfer belt mechanism  304  comprising a primary transfer belt  302  including a linear moving area  302   a  to which toner images formed by the image forming units  10 ,  8 ,  6  and  4  are transferred sequentially in such a manner that they are superimposed one upon another, the paper feed cassette  28  for storing the paper P and a secondary transfer roller  306  which is a secondary transfer unit for transferring toner images transferred to the primary transfer belt  302  to the paper P fed from the paper feed cassette  28 . The image forming units  4 ,  6 ,  8  and  10  are arranged along the linear moving area  302   a  of the primary transfer belt  302  of the primary transfer belt mechanism  304  in this order from the top toward the bottom with a space therebetween in the vertical direction. 
   The primary transfer belt mechanism  304  is arranged longitudinally so that the linear moving area  302   a  of the primary transfer belt  302  extends almost in the vertical direction. The other linear moving area  302   b  of the primary transfer belt  302  extends parallel to the linear moving area  302   a  with a space therebetween on the left side in  FIG. 7 . The drive roller  32  positioned at the top of the primary transfer belt  302  is turned in the counterclockwise direction in  FIG. 7 . When the drive roller  32  is turned, the linear moving area  302   a  of the primary transfer belt  302  is moved upward. The image forming units  4 ,  6 ,  8  and  10  are arranged on the right side in  FIG. 7  of the linear moving area  302   a . The paper feed cassette  28  is arranged longitudinally and spaced apart from the primary transfer belt mechanism  304  in the lateral direction (on the right side in  FIG. 7  with the image forming units  6 ,  8  and  10  interposed between it and the primary transfer belt mechanism  304 ). In the paper feed cassette  28 , the pick-up roller  80  which is disposed in the upper end portion of the inside of the cassette body  42 , the paper supporting plate  50 , the paper fall preventing plate  52  and the compression coil spring  56  have been inverted from their positions in the paper feed cassette  28  of the image forming machine  200  with respect to the cassette  44  (the support mechanism for the cassette  44  is basically the same). The secondary transfer roller  306  is opposed to the top portion of the primary transfer belt  302  (top portion wrapped around the drive roller  32 ). 
   A paper feed conveyor passage  308  for guiding the paper P fed upward from the paper feed cassette  28  to the top portion of the primary transfer belt mechanism  304  almost in the lateral direction is formed between the paper feed cassette  28  and the primary transfer belt mechanism  304 . In the paper feed conveyor passage  308 , a pair of separated paper feed rollers  310  and a pair of resist rollers  312  are installed in this order from the upstream to the downstream. The fixing unit  60  is arranged on the extension line in the downstream direction of the paper feed conveyor passage  308  almost in the lateral direction of the top portion of the primary transfer belt mechanism  304  in the upper end portion of the inside of the image forming machine body  2 . The pair of discharge rollers  64  are disposed above the fixing unit  60 , and a paper inversion discharge passage  314  for inverting the paper P which is carried from the fixing unit  60  and on which toner images have been fixed by the fixing unit  60  and guiding it to the pair of discharge rollers  64  is formed between the fixing unit  60  and the pair of discharge rollers  64 . A paper discharge tray  316  for receiving the paper P discharged from the pair of discharge rollers  64  almost in the lateral direction is provided on the top face of the image forming machine body  2 . The pocket  70  is formed on one side face  2   a  of the image forming machine body  2  in the downstream direction (right direction in  FIG. 7 ) of the paper discharge tray  316  in such a manner that it extends along the one side face  2   a  in the vertical direction. 
   In the thus constituted image forming machine  300 , the surfaces of the photosensitive material drums  12  charged uniformly by the charging units  14  of the image forming units  10 ,  8 ,  6  and  4  are exposed by the LED heads  16  to form electrostatic latent images which are then developed by the developing units  18  to become toner images. The toner images are transferred to the surface of the linear moving area  302   a  of the primary transfer belt  302  of the primary transfer belt mechanism  304  sequentially from the toner image formed by the image forming unit  10  on the upstream side in such a manner that they are superimposed one upon another. The toner images transferred to the surface of the linear moving area  302   a  of the primary transfer belt  302  are transferred to the surface of the paper P fed from the paper feed cassette  28  along the paper feed conveyor passage  308  by the secondary transfer roller  306  at the top of the primary transfer belt  302 . The color toner images transferred to the paper P are fixed on the paper P while they pass through the fixing unit  60 . The paper P on which the color toner images have been fixed is discharged onto the paper discharge tray  316  or into the pocket  70  by the pair of discharge rollers  64 . The paper P having a relatively small size is discharged onto the paper exhaust tray  316  and the paper P having a relatively large size is discharged into the pocket  70 . The toner not transferred and remaining on the surfaces of the photosensitive material drums  12  is removed by the cleaning units  20 . The toner not transferred and remaining on the surface of the primary transfer belt  302  is removed by an unshown other cleaning unit. 
   In the image forming machine  300  shown in  FIG. 7 , the primary transfer belt mechanism  304  which is a belt mechanism is arranged longitudinally so that the linear moving area  302   a  of the primary transfer belt  302  which is a belt extends almost in the vertical direction, and the paper feed cassette  28  is arranged longitudinally and spaced apart from the primary transfer belt mechanism  304  in the lateral direction. Therefore, the width of the image forming machine body  2  (size in the right-and-left direction in  FIG. 7 ) can be made smaller than that of the prior art, thereby making it possible to make the entire image forming machine body  2  more compact in the width direction than in the prior art. Accordingly, the image forming machine  300  of the present invention is particularly advantageous for use at an office in which the installation space in the lateral direction is limited. 
   In the image forming machine  300  shown in  FIG. 7 , the secondary transfer unit for transferring toner images transferred to the primary transfer belt  302  to the paper P fed from the paper feed cassette  28 , i.e., the secondary transfer roller  306  in this embodiment is provided in the image forming machine body  2 . The secondary transfer roller  306  is opposed to the top portion of the primary transfer belt  302 , and the paper feed conveyor passage  308  for guiding the paper P fed upward from the paper feed cassette  28  between the primary transfer belt  302  and the secondary transfer roller  306  almost in the lateral direction is formed between the paper feed cassette  28  and the primary transfer belt mechanism  304 . The fixing unit  60  is arranged on the extension line in the downstream direction of the paper feed conveyor passage  308  almost in the lateral direction of the top portion of the primary transfer belt mechanism  304  in the upper end portion of the inside of the image forming machine body  2 . As a result, the entire image forming machine body  2  can be made more compact in the width direction and the longitudinal direction (vertical direction) than in the prior art. 
   In the image forming machine  300  shown in  FIG. 7 , the paper feed cassette  28  is arranged on the right side of the image forming units  6 ,  8  and  10  in  FIG. 7  but may be arranged on the left side in the image forming machine body  2 . In this case, the paper feed cassette  28 , the image forming units  4 ,  6 ,  8  and  10  and the primary transfer belt mechanism  304  are inverted round a virtual vertical axis from their positions shown in  FIG. 7 . The pair of discharge rollers  64  are disposed in the right direction of the fixing unit  60 , and the paper discharge tray  316  is omitted. The paper P discharged from the pair of discharge rollers  64  is discharged into the pocket  70  directly. 
   The image forming machine  300  as shown in  FIG. 14  is similar to the image forming machine illustrated in  FIG. 7 . Thus, reference is made to the description of the elements for  FIG. 7 , herein. By contrast with  FIG. 7 , the present embodiment of  FIG. 14  illustrates a paper feed cassette  28  arranged longitudinally below the conveyor belt mechanism  26 . This configuration reduces the size in the width direction of the image forming machine body  2 . 
     FIG. 8  shows a further embodiment of the image forming machine of the present invention. The image forming machine  400  shown in  FIG. 8  is a modification of the image forming machine  300  shown in  FIG. 7 . In the image forming machine  400  shown in  FIG. 8 , the primary transfer belt mechanism  304  and the image forming units  4  to  10  have been inverted from the positions of the primary transfer belt mechanism  304  and the image forming units  4  to  10  in the image forming machine  300  shown in  FIG. 7  in the vertical direction. That is, the drive roller  32  of the primary transfer belt mechanism  304  is positioned at the bottom of the primary transfer belt  302 , and the follower roller  34  is positioned at the top of the primary transfer belt  302 . The image forming units  4 ,  6 ,  8  and  10  are arranged along the linear moving area  302   a  of the primary transfer belt  302  in this order from the bottom toward the top with a space therebetween in the vertical direction. 
   The primary transfer belt mechanism  304  is arranged longitudinally so that the linear moving area  302   a  of the primary transfer belt  302  extends almost in the vertical direction. The other linear moving area  302   b  of the primary transfer belt  302  is arranged parallel to the linear moving area  302   a  with a space therebetween on the left side in  FIG. 8 . The drive roller  32  is turned in the clockwise direction in  FIG. 8 . When the drive roller  32  is turned, the linear moving area  302   a  of the primary transfer belt  302  is moved downward. The image forming units  4 ,  6 ,  8  and  10  are arranged on the right side in  FIG. 8  of the linear moving area  302   a . The paper feed cassette  28  is arranged longitudinally and spaced apart from the primary transfer belt mechanism  304  in the lateral direction (arranged on the right side of the primary transfer belt mechanism  304  with the image forming units  4 ,  6 ,  8  and  10  interposed therebetween in  FIG. 8 ). The constitution and arrangement of the paper feed cassette  28  are substantially the same as those of the image forming machine  200  shown in  FIG. 6 . 
   The secondary transfer roller  306  is opposed to the bottom portion (bottom portion wrapped around the drive roller  32 ) of the primary transfer belt  302 . The paper feed conveyor passage  308  for guiding the paper P fed downward from the paper feed cassette  28  toward the bottom portion of the primary transfer belt mechanism  304  almost in the lateral direction is formed between the paper feed cassette  28  and the primary transfer belt mechanism  304 . In the paper feed conveyor passage  308 , the pair of separated paper feed rollers  310  and the pair of resist rollers  312  are installed in this order from the upstream to the downstream. The fixing unit  60  is arranged on the extension line in the downstream direction of the paper feed conveyor passage  308  almost in the lateral direction of the top portion of the primary transfer belt mechanism  304  in the lower end portion of the inside of the image forming machine body  2 . The pair of discharge rollers  64  are disposed above the fixing unit  60  in the upper end portion of the inside of the image forming machine body  2 , and the paper inversion discharge passage  314  for inverting the paper P which is carried from the fixing unit  60  and on which toner images have been fixed by the fixing unit  60  and guiding it to the pair of discharge rollers  64  is formed between the fixing unit  60  and the pair of discharge rollers  64 . An intermediate portion of the paper inversion discharge passage  314  extends almost vertically along the inner wall of the other side face  2   b  of the image forming machine body  2  (the other side face  2   b  opposite to the one side face  2   a  in the lateral direction in  FIG. 8 ). The intermediate portion of the paper inversion discharge channel  314  is provided with pairs of paper conveyor rollers  313 ,  315 ,  318  and  320  with a space therebetween. The other constitution of the image forming machine  400  is substantially the same as that of the image forming machine  300  shown in  FIG. 7  and its description is omitted. 
   In the thus constituted image forming machine  400 , the surfaces of the photosensitive material drums  12  charged uniformly by the charging units  14  of the image forming units  10 ,  8 ,  6  and  4  are exposed by the LED heads  16  to form electrostatic latent images which are then developed by the developing units  18  to become toner images. The toner images are transferred to the surface of the linear moving area  302   a  of the primary transfer belt  302  of the primary transfer belt mechanism  304  sequentially from the toner image formed by the image forming unit  10  on the upstream side in such a manner that they are superimposed one upon another. The toner images transferred to the surface of the linear moving area  302   a  of the primary transfer belt  302  are transferred to the surface of the paper P fed from the paper feed cassette  28  along the paper feed conveyor passage  308  by the secondary transfer roller  306  at the bottom of the primary transfer belt  302 . The color toner images transferred to the paper P are fixed on the paper P while they pass through the fixing unit  60 . The paper P on which the color toner images have been fixed is carried to the pair of discharge rollers  64  along the paper inversion discharge passage  314  and discharged onto the paper discharge tray  316  or into the pocket  70  by the pair of discharge rollers  64 . In the image forming machine  400  shown in  FIG. 8 , the primary transfer belt mechanism  304  which is a belt mechanism is arranged longitudinally so that the linear moving area  302   a  of the primary transfer belt  302  which is a belt extends almost in the vertical direction, and the paper feed cassette  28  is arranged longitudinally and spaced apart from the primary transfer belt mechanism  303  in the lateral direction. Therefore, the width of the image forming machine body  2  (size in the right-and-left direction in  FIG. 8 ) can be made smaller than that of the prior art, thereby making it possible to make the entire image forming machine body  2  more compact in the width direction than in the prior art. Accordingly, the image forming machine  400  of the present invention is particularly advantageous for use at an office in which the installation space in the lateral direction is limited. 
   Not shown, a copying machine having a small width can be realized by placing a scanner unit at the top of the image forming machine  300  or  400  shown in  FIG. 7  or  8  in such a manner that it extends in the front-and-rear direction (direction perpendicular to the face of the sheet in  FIG. 7  or  FIG. 8 ). Since this scanner unit is positioned above the paper discharge tray  316  with a space therebetween, the paper discharge tray  316  can be used in the state shown in  FIG. 7  or  FIG. 8 . Therefore, this copying machine is an in-barrel paper discharge type copying machine. 
     FIG. 9  shows a still further embodiment of the image forming machine of the present invention. In the image forming machine  500  shown in  FIG. 9 , the linear moving area  24   a  of the conveyor belt  24  of the conveyor belt mechanism  26  extends almost vertically, and the image forming units  4 ,  6 ,  8  and  10  are arranged along the linear moving area  24   a  of the conveyor belt  24  in this order from the top toward the bottom with a space therebetween in the vertical direction. Although this basic constitution is substantially the same as that of the image forming machine  200  shown in  FIG. 6 , the image forming machine  500  greatly differs from the image forming machine  200  shown in  FIG. 6  in that the paper feed cassette  28  is arranged longitudinally below the conveyor belt mechanism  26 . The constitution of the paper feed cassette  28  is substantially the same as that of the paper feed cassette  28  of the image forming machine  300  shown in  FIG. 7 . The linear moving area  24   a  of the conveyor belt  24  is arranged on the right side in  FIG. 9 , the other linear moving area  24   b  is arranged on the left side, and the image forming units  4 ,  6 ,  8  and  10  are arranged on the right side of the linear moving area  24   a  of the conveyor belt  24 . The drive roller  32  positioned at the top of the conveyor belt  24  is turned in the counterclockwise direction. 
   A paper feed conveyor passage  79  for carrying the paper P delivered upward from the paper feed cassette  28  upward toward the linear moving area  24   a  of the conveyor belt  24  is formed between the paper feed cassette  28  and the conveyor belt mechanism  26 . The paper feed conveyor passage  79  is provided with the paper detection sensor S 1 . This paper detection sensor S 1  has the same function as the paper detection sensor S 1  of the image forming machine  100  shown in  FIG. 1 . The fixing unit  60  is arranged above the conveyor belt mechanism  26  in the upper end portion of the inside of the image forming machine body  2  like the image forming machines  100  and  200  shown in  FIG. 1  and FIG.  6 . The paper conveyor passage  62  for guiding the paper P which is carried by the conveyor belt mechanism  26  and to which the toner images have been transferred to the fixing unit  60  is formed between the conveyor belt mechanism  26  and the fixing unit  60  like the image forming machines  100  and  200  shown in  FIG. 1  and  FIG. 6 . The paper conveyor passage  62 , the linear moving area  24   a  of the conveyor belt  24  and the paper feed conveyor passage  79  are aligned with one another almost in the vertical direction. This constitution greatly contributes to the reduction of the size in the width direction of the image forming machine body  2  and can suppress the occurrence of a jam as there is almost no curve in the conveyor passages of the paper P. Since other constitution is substantially the same as that of the image forming machine  200  shown in  FIG. 6 , its description is omitted. 
   Since the conveyor belt mechanism  26  of the image forming machine  500  shown in  FIG. 9  is arranged longitudinally so that the linear moving area  24   a  of the conveyor belt  24  extends almost in the vertical direction and the paper feed cassette  28  is arranged longitudinally below the conveyor belt mechanism  26 , the size in the width direction of the image forming machine body  2  can be made smaller than those of the image forming machines  100 ,  200 ,  300  and  400  shown in  FIG. 1 ,  FIG. 6 ,  FIG. 7  and  FIG. 8 , thereby making it possible to make the entire image forming machine body  2  more compact than those of the image forming machines  100 ,  200 ,  300  and  400 . Accordingly, the image forming machine  500  of the present invention is particularly advantageous for use at an office in which the installation space in the lateral direction is limited. 
     FIG. 10  and  FIG. 11  show a still further embodiment of the image forming machine of the present invention. In the image forming machine  600  shown in  FIG. 10  and  FIG. 11 , a paper feed cassette  628  is arranged longitudinally in the image forming machine body  2  almost like the paper feed cassette  28  of the image forming machine  100  shown in  FIG. 1 . The paper feed cassette  628  comprises a box-like cassette  644  and a paper fall preventing plate  652  but does not have the cassette body  42  of the paper feed cassette  28 . Although the cassette  644  is fixed in the image forming machine body  2  and has the same box-like shape as the cassette  44  of the paper feed cassette  28 , the front wall  44 A does not exist. This is because the paper P is supplied into the cassette  44  from an opening  602  in the front face  2 A of the image forming machine body  2  as will be described hereinafter. In the cassette  644 , the paper supporting plate  50  and the compression coil spring  56  are installed substantially in the same manner as in the paper feed cassette  28 . The paper fall preventing plate  652  is fixed in the image forming machine body  2  to cover the cassette  644 . Although a paper feed roller  646  has substantially the same constitution as the paper feed roller  46  of the paper feed cassette  28 , its shaft  46 A (see  FIG. 5 ) is rotatably supported to the image forming machine body  2 . The opening  602  for supplying paper into the paper feed cassette  628  from the front side of the image forming machine body  2  is formed in the front face  2 A of the image forming machine body  2 . The opening  602  is rectangular with the shorter side at the top. An opening  604  which extends horizontally in the width direction of the image forming machine body  2  is formed below the opening  602  in the front face  2 A of the image forming machine body  2 . The opening  604  is rectangular with the longer side at the top. 
   An operation arm  606  is fixed to the lower end portion of the paper supporting plate  50 . The operation arm  606  has a horizontal portion  606   a  which extends horizontally in the front-and-rear direction of the image forming machine body  2 , an upright portion  606   b  which extends upward from the rear end of the horizontal portion  606   a  at a right angle, and a knob  606   c  provided at the front end of the horizontal portion  606   a . The horizontal portion  606   a  and the upright portion  606   b  of the operation arm  606  are formed from a metal plate integratedly. The upright portion  606   b  of the operation arm  606  is fixed to the right face in  FIG. 10  of the lower end portion of the paper supporting plate  50 , and the horizontal portion  606   a  extends to the front side of the image forming machine body  2  through the opening  604  of the image forming machine body  2 . The knob  606   c  of the operation arm  606  is positioned on the front side of the image forming machine body  2 . An opening  608  through which the upright portion  606   b  of the operation arm  606  extends is formed in the one side wall  44 C of the cassette  644 . The opening  608  is rectangular and prolonged sideways to allow the movement in the right-and-left direction in  FIG. 10  of the upright portion  606   b . An opening  643  for paper feeding is formed between the left end in  FIG. 10  of the one side wall  44 C of the cassette  644  and the lower end portion in  FIG. 10  of the paper fall preventing plate  652 . 
   Since the other constitution of the image forming machine  600  shown in  FIG. 10  is substantially the same as the image forming machine  100  shown in  FIG. 1 , its description is omitted. As obvious from the above description, the paper feed cassette  628  of the image forming machine  600  cannot be drawn from the image forming machine body  2 . To supply the paper P into the paper feed cassette  628 , the knob  606   c  of the operation arm  605  is used to move the operation arm  606  to the right in  FIG. 10  along the opening  604  manually. The paper supporting plate  50  connected to the operation arm  606  is turned round the shaft  54  in the counterclockwise direction in  FIG. 10  in defiance of the spring force of the compression coil spring  56 . As a result, a space (not shown) is formed between the paper fall preventing plate  652  and the paper supporting plate  50  in the cassette  644 , whereby a bundle of paper sheets P can be inserted into the space in the cassette  644  from the opening  602  formed in the front face  2 A of the image forming machine body  2 . It is preferred that a side wall which is not shown in the figure should be formed on the front side in  FIG. 10  of the paper fall preventing plate  652  to prevent the bundle of paper sheets P stored in the cassette  644  from shifting to the front side. 
   When a finger is released from the knob  606   c  of the operation arm  606  after the bundle of paper sheets P is stored in the cassette  644 , the paper supporting plate  50  is turned round the shaft  54  in the clockwise direction in  FIG. 10  by the spring force of the compression coil spring  56 . Since the bundle of paper sheets P stored in the cassette  644  is urged toward the paper fall preventing plate  652 , the lower end of the paper sheet P positioned at the left end in  FIG. 10  is brought into pressure contact with the paper feed roller  646  to enable paper feeding. 
   Since the image forming machine  600  shown in  FIG. 10  and  FIG. 11  has substantially the same constitution as the image forming machine  100  shown in  FIG. 1  except that the paper feed cassette  628  is fixed in the image forming machine body  2 , substantially the same effect as that of the image forming machine  100  can be obtained. 
     FIG. 12  and  FIG. 13  show a still further embodiment of the image forming machine of the present invention. In the image forming machine  700  shown in  FIG. 12  and  FIG. 13 , a paper feed cassette  728  is arranged longitudinally in the image forming machine body  2  substantially in the same manner as the paper feed cassette  28  of the image forming machine  100  shown in  FIG. 1 . The paper feed cassette  728  comprises a box-like cassette  744  and the paper fall preventing plate  652  but not the cassette body  42  of the paper feed cassette  28 . The cassette  744  has substantially the same box-like shape as the cassette  44  of the paper feed cassette  28  and is rotatably supported in the image forming machine body  2  by a pair of shafts  748 . The pair of shafts  748  are arranged likewise in the cassette  744  substantially at the same position as in the cassette  44  of the paper feed cassette  28 . The cassette  744  can turn between an acting position where it is substantially stored in the image forming machine body  2  (position shown by a solid line in  FIG. 12  and position shown in  FIG. 13 ) and a non-acting position where it is turned round the pair of shafts  748  in the clockwise direction in  FIG. 12  from the acting position (position shown in a two-dotted chain line in  FIG. 12 ). The right end face in  FIG. 12  of the bottom wall  44 E of the cassette  744  becomes substantially flush with the one side face  2   a  of the image forming machine body  2  when the cassette  744  is located at the acting position. An opening  702  is formed in the one side face  2   a  of the image forming machine body  2  to allow the above turning of the cassette  744 . A lock mechanism which can be unlocked freely and may have known constitution is interposed between the cassette  744  and the image forming machine body  2 . 
   In the cassette  744 , there are installed the paper supporting plate  50  and the compression coil spring  56  substantially in the same manner as in the paper feed cassette  28 . The paper fall preventing plate  652  and the paper feed roller  646  have substantially the same constitution as those of the image forming machine  600  and are disposed in the image forming machine body  2  substantially in the same manner. The pocket  70  is integrated with the right end face in  FIG. 12  of the bottom wall  44 E of the cassette  744 . 
   Since the other constitution of the image forming machine  700  shown in  FIG. 12  and  FIG. 13  is substantially the same as that of the image forming machine  100  shown in  FIG. 1 , its description is omitted. As obvious from the above description, the paper feed cassette  728  of the image forming machine  700  cannot be drawn from the image forming machine body  2  but can be turned. To supply the paper P into the paper feed cassette  728 , the cassette  744  is turned round the pair of shafts  748  from the acting position to the non-acting position. Since the top side of the paper supporting plate  50  is made open outside the one side face  2   a  of the image forming machine body  2  when the cassette  744  is located at the non-acting position, a bundle of paper sheets P can be supplied onto the paper supporting plate  50  from above. The turning angle of the cassette  744  is preferably set to the minimum angle at which the paper P can be supplied onto the paper supporting plate  50 . 
   After the bundle of paper sheets P is supplied onto the paper supporting plate  50  from above, the cassette  744  is turned from the non-acting position to the acting position. As a result, the paper P stored in the cassette  744  can be fed. When the cassette  744  is located at the acting position, the pocket  70  extends along the one side face  2   a  of the image forming machine body  2  in the vertical direction and can store the paper P discharged from the pair of discharge rollers  64 . 
   The image forming machine  700  shown in  FIG. 12  and  FIG. 13  has substantially the same constitution as the image forming machine  100  shown in  FIG. 1  except that the paper feed cassette  728  is rotatably arranged in the image forming machine body  2  and that the pocket  70  is integrated with the cassette  744 . In the image forming machine  700 , when the cassette  744  is turned to the non-acting position, it projects outward from the one side face  2   a  of the image forming machine body  2 , thereby requiring a space in the width direction. However, by minimizing the turning angle of the cassette  744 , the size in the width direction of the image forming machine  700  can be made smaller than that of the prior art. When the cassette  744  is located at the acting position, the size in the width direction of the image forming machine body  2  can be made smaller than that of the prior art substantially like the image forming machines  100 ,  200 ,  300 ,  500  and  600 . 
   In the above image forming machines  100 ,  200 ,  300 ,  500 ,  600  and  700 , as the fixing unit  60  is arranged in the upper end portion of the inside of the image forming machine body  2 , its heat is easily removed to the outside of the image forming machine body  2  and a rise in the inside temperature of the image forming machine body  2  can be suppressed. In the above image forming machines  100 ,  200 ,  300 ,  400  and  500 , as the paper feed cassette  28  can be drawn forward from the image forming machine body  2 , the supply of the paper P can be performed on the front side of the image forming machine body  2 . In the image forming machine  600 , the paper feed cassette  628  is fixed in the image forming machine body  2  but the paper  2  can be supplied from the front side of the image forming machine body  2 , thereby making it possible to reduce the spaces on both sides in the width direction of the image forming machine body  2 . In the above image forming machines  100 ,  200 ,  300 ,  400  and  500 , the paper feed cassettes  28  for storing small-sized to large-sized paper sheets can be drawn from the image forming machine body  2  while the size in the width direction of the image forming machine body  2  can be minimized. Therefore, they are of great practical value. 
   In general, the term “paper feed cassette” in the image forming machine means a paper feed cassette comprising a box-like cassette which can be drawn from the image forming machine body. However, in this text, the term “paper feed cassette” means not only this known paper feed cassette but also the paper feed cassette  628  of the image forming machine  600  comprising the cassette  644  which is fixed in the image forming machine body  2  or the paper feed cassette  728  of the image forming machine  700  comprising the cassette  744  which is rotatably arranged in the image forming machine body  2 .