Abstract:
An image forming apparatus having a common sheet processing station with a sheet supply unit, at least one image forming unit which is detachably arranged with the common sheet processing station. The image forming unit forms images on a sheet carried from the common sheet processing station via a sheet carrying path. Many different image forming units may be utilized with the common sheet processing station.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This document claims priority from and contains subject matter related to Japanese patent application numbers  11-177,692, 11-229,713,  and  2000-173,374 , the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an image forming apparatus, and particularly to the image forming apparatus with a sheet carrier unit and a sheet supply tray. 
     2. Description of the Related Art 
     In conventional image forming apparatus, an image forming device in a main body forms images on a recording sheet and the sheet is conveyed from an image transferring point to a tray or a sorter by a sheet carrying mechanism. 
     Now referring to FIG.  1 ( a ), a conventional image forming apparatus is described. 
     An image forming device  10  generally includes a sheet supply tray  6  on a main body of the image forming apparatus  1 . A sorter  2  is individually placed adjacent to the image forming apparatus  1 . 
     In this type of the image forming apparatus, a paper chute of the sorter  2  is installed such that a route of the sheet conveying in the sorter  2  becomes the same route as that of the image forming device  10 . Therefore, the paper chute of the sorter  2  is located on the same position as a paper chute of the image forming apparatus  1 . 
     Recently, the demand for a small-footprint of the whole image forming apparatus is increasing. One of the conventional techniques to meet this demand is described in FIG.  1 ( b ) wherein a sorter  2  is arranged on an upper part of the image forming apparatus  1 . 
     In Japanese Laid Open patent application 10-115,959, another copying device is described. The copying device is constituted of the image forming device main body, an image reader, the carrying device for feeding the paper and a relay carrying unit, where the image forming device main body is attachable to one side surface of the carrying device for feeding the paper by a fixing means such as a screw. The image forming device main body is mainly provided with a developing device, a photoreceptor, a transfer belt, a cleaning device, an electrifying roller, and optical device and a fixing device  27 ′ and an ejecting tray  5 ′ is provided projectingly outside the side surface on a side where the optical device  26 ′ is provided as shown in Figure. 
     Further, the relay carrying unit  6 ′ is provided with a carrying path  61 ′ in a connected state to an ejecting part, in the carrying device for feeding the paper  4 ′ and further, a manual paper feeding part  62 ′ below the carrying path  61 ′. The carrying path  61 ′ of the relay carrying unit  6 ′ is provided to connect to the carrying path  28 ′ of a paper entrance part in the image forming device main body  2 ′, in a nearly vertical direction. 
     On the other hand, there is a cartridge type image forming apparatus wherein detachable devices are put on and off the main body of the image forming apparatus. 
     And then, in Japanese Laid Open patent  03-275,376,  unity image forming devices are laminated and are covered by the outer frame body. 
     However, the sheet processing station of each of the above conventional image forming apparatus is not common for different types of image forming apparatuses. That is, the sheet processing station can not be exchanged with different types of the image forming apparatus. 
     The image forming apparatus described in Japanese Laid Open patent  10-115,959  is capable of being a common paper supply tray and a paper feeding tray. But, this apparatus has not a sorter. If the sorter is connected to the apparatus, a footprint of the whole image forming apparatus becomes large. 
     SUMMARY OF THE INVENTION 
     The present invention has aspects to overcome the above problems encountered in the aforementioned art. 
     According to a first aspect of the present invention, an image forming apparatus, has a common sheet processing station with a sheet supply unit; and at least one image forming unit which is detachably arranged with the common sheet processing station, for forming images on a sheet carried from the common sheet processing station via the sheet carrying path. 
     According to a second aspect of the present invention, the common sheet processing station has a sheet supply unit which stocks recording sheets, a sheet ejecting tray and a sheet carrying path which carries the sheet from the sheet supply unit to the sheet ejecting tray. 
     According to a third aspect of the present invention, the common sheet processing station further has at least a sheet supply unit, a sheet sorter and a sheet ejecting tray. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other aspects and further features of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings, wherein: 
     FIGS.  1 ( a ) and ( b ) are conceptional views of structure of the conventional image forming apparatus; 
     FIG. 2 is a cross-sectional view of the prior art; 
     FIGS.  3 ( a ) and ( b ) are views of a first embodiment according to the present invention; 
     FIG. 4 is a cross-sectional view of a second embodiment according to the present invention; 
     FIG. 5 is a cross-sectional view of a third embodiment according to the present invention; 
     FIG. 6 is a cross-sectional view of a fourth embodiment according to the present invention; 
     FIG. 7 is a detailed structure of a transfer roller portion of the fourth embodiment; 
     FIG. 8 is a cross-sectional view of a fifth embodiment according to the present invention; 
     FIG. 9 is a cross-sectional view of a sixth embodiment according to the present invention; 
     FIG. 10 is a cross-sectional view of a seventh embodiment according to the present invention; 
     FIG. 11 is a perspective view of the image forming apparatus of an eighth embodiment according to the present invention; 
     FIG. 12 is a cross-sectional view of the eighth embodiment according to the present invention; 
     FIGS.  13 ( a ) and ( b ) are views of a ninth embodiment according to the present invention; 
     FIG. 14 is a perspective view of the image forming apparatus of the ninth embodiment according to the present invention; 
     FIG. 15 is a cross-sectional view of the ninth embodiment according to the present invention; 
     FIG. 16 is a cross-sectional view of a tenth embodiment according to the present invention; 
     FIG. 17 is a cross-sectional view of a tenth embodiment according to the present invention; 
     FIG. 18 is a cross-sectional view of a sheet processing station of the tenth embodiment according to the present invention; 
     FIG. 19 is a perspective view of a connection between an image forming device and a sheet processing station of the tenth embodiment; 
     FIG. 20 is a perspective view of the image forming device of the tenth embodiment; 
     FIG. 21 is a perspective view of a connection between an image forming device and a sheet processing station of the eleventh embodiment; 
     FIG. 22 is a perspective view of a connection between an image forming device and a sheet processing station of the twelfth embodiment; 
     FIG. 23 is a perspective view of a detailed connection between an image forming device and a sheet processing station of the twelfth embodiment; 
     FIG. 24 is a cross-sectional view of a connection between an image forming device and a sheet processing station of the twelfth embodiment; 
     FIG. 25 is a cross-sectional view of a connection between an image forming device and a sheet processing station of the twelfth embodiment; 
     FIG. 26 is a perspective view of a connecting hook of the twelfth embodiment; 
     FIG. 27 is a cross-sectional view of a connection between an image forming device and a sheet processing station of the thirteenth embodiment; 
     FIG. 28 is a cross-sectional view of a connection between an image forming device and a sheet processing station of the thirteenth embodiment; and 
     FIG. 29 is a cross-sectional view of a connection between an image forming device and a sheet processing station of the fourteenth embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present inventors identified that the sheet processing station does not need to be unique for types of image forming processes e.g. electrostatic image forming process, inkjet printing, thermal printing etc. It is preferable that the image forming devices should be exchangeable for the common sheet processing station according to user needs. 
     A description will now be given of preferred embodiments according to the present invention. 
     Explanation is omitted of the same devices, units or elements having the same function in each embodiment. 
     Now referring to FIG. 3, an image forming apparatus is made up of an image forming device  1 , a sheet convey unit  7 , and a sheet processing station  100 . The sheet processing station  100  is further made up of sheet supply trays within a sheet supply unit  6  and a sorter  8 , and the image forming device  1  is further made up of an optical system, a photoconductive drum  10 , an electrostatic charger  303 , a developing roller  304 , a fixing roller  11  and a controller  301 . Under control of the controller  301 , a laser diode  300  irradiates laser beams to the polygon mirror  302  and the polygon mirror  302  scans the photoconductive drum  10  via the reflector mirror  305 . 
     Electrostatic latent images are made on the photosensitive drum  10  which is driven to rotate and serves as an electrostatic carrier. The electrostatic charger  303  and the developing roller  304  are arranged around the photosensitive drum  10 . The electrostatic charger  303  charges electrostatically a surface of the photosensitive drum  10  in a uniform condition. The developing unit supplies a toner and develops an electrostatic latent image formed on the surface of the photosensitive drum  10  into a visible image with a toner on the basis of a laser beam irradiated from the laser diode  300 . 
     The transfer charger  19  in the sheet convey unit  7  transfers the visible image produced by the developing roller  304  to a paper that is supplied from the sheet supply unit  6  with a sheet convey belt  9   c  through the feeding paper path. The image-fixing roller  11  then fixes the visible toner image with roller  9   a    
     The optical system is arranged in the image forming device  1  at a side opposite the photoconductive drum  10 . The optical system is made up of a laser diode  300 , a rotatable polygon mirror  302  having multiple reflecting surfaces and a reflector mirror  305  which guides laser beams in a predetermined direction on the photoconductive drum  10  to form an image thereon. The optical system irradiates the photoconductive drum  10  with laser beams corresponding to image data which is transmitted from the controller  301 . 
     Under control of the controller  301 , the image forming process is started and the laser beam is irradiated from the laser diode  300  based upon image data. An electrostatic latent image is formed on the surface of the photosensitive drum  10  by scanning of the laser beam via the polygon mirror  302  and the reflector mirror  305 . 
     On the other hand, a sheet of paper is fed from one of the trays of the sheet supply unit  6 . The paper is conveyed by a guide in the sheet convey unit  7 . The toner image is transferred to the paper at the point between the photosensitive drum  10  and a transfer changer  19 . The paper to which the toner image is transferred, is further conveyed and the toner image on the paper is fixed at a point between the fixing roller  11  and a roller  9   a . The paper is guided by an upper guide  91  in the sheet convey unit  7  and finally fed to the tray  8 A or one of the other trays of sorter  8 . The sheet convey unit  7  further has a cooling device  13  which cools the conveying belt  9   c.    
     Now referring to FIG.  3 ( b ), area D shows a footprint of the conventional image forming apparatus which has a sorter. The total area of A, B and C shows the image forming apparatus according to the present invention. It is seen that the footprint of the image forming apparatus becomes smaller than one of the conventional image forming apparatus. Furthermore, the sorter is not located on the top of the image forming apparatus. Therefore, the height of the image forming apparatus is also shorter than one of the image forming apparatus as shown FIG.  1 ( b ). 
     Now referring to FIG. 4, a second embodiment is described. The sheet processing station according to the second embodiment has a sheet inserting tray  15 . When the user want to use a special paper or OHP films, the user is capable of inserting the sheet at the sheet inserting tray  15 . The image forming process is the same as the first embodiment. Moreover, the other devices have a same structure as the above first embodiment, so explanation is omitted. 
     Referring to FIG. 5, a third embodiment is described. The sheet processing station  100  has a sheet inserting tray  15  and a sheet reverse tray  16  for producing two sided copies. The sheet inserting tray  15  is the same of the second embodiment. Therefore, explanation is omitted. 
     A sheet of paper is fed from one of the trays of the sheet supply unit  6  and the image is formed at a first surface of the paper. The paper is conveyed to a chute of the reverse tray  16  by a guide in the sheet convey unit  7 . When the paper is stored into the reverse tray  16 , the image formed surface of the paper faces upwardly. In a next step, the paper is fed to the image forming device from the reverse tray  16  by a guide in the sheet convey unit  7 . A toner image is transferred to an underside of the image formed side of the paper thereby producing a two-sided copy. 
     Now referring to FIGS. 6 and 7, a fourth embodiment is described. An image forming device and a sheet processing station are the same as the above embodiments, so explanation is omitted. 
     Rollers  22   a ,  22   b ,  22   c  and  22   d  make a recessed area in the convey belt  9   c . A transfer roller  21  is located on the above recessed area. When the paper feeds from the sheet supply unit  6 , the paper separates from the belt  9   c  at the roller  22   d.  The paper is inserted into the image transfer point between the photoconductive drum  10  and the transfer roller  21  where a toner image is formed on the paper. The paper on which the toner images are formed merges with the belt  9   c  at the roller  22   a.    
     Referring to FIG. 8, a fifth embodiment is described. The sheet convey unit and the sheet processing station are the same as the fourth embodiment, so explanation is omitted. 
     In this embodiment, a full color revolver type image forming device  1 A is attached on the sheet convey unit. Under control of a controller, a revolver type developer rotates, each color toner image is formed on a photoconductive drum  10   a . Each color toner image is transferred to an intermediate transfer drum  47 . The full color toner image is then transferred to the paper at the point between the intermediate transfer drum  47  and the transfer roller  21 . 
     Now referring to FIG. 9, a sixth embodiment is described. In the sixth embodiment, an inkjet type image forming device  1 B is attached on the sheet convey unit. The other devices are capable of operating the same as described in the fifth embodiment. Under control of the controller, each head  41  ejects ink drops to the intermediate transfer drum  47 . When a full color image is formed on the intermediate transfer drum  47 , the full color image is transferred to the paper at the point between the intermediate transfer drum  47  and the transfer drum  21 . 
     Referring to FIG. 10, another embodiment of an inkjet type image forming device  1 C is described. In this embodiment, under control of the controller, each head  41  directly ejects ink drops to the paper on the belt  9   c.    
     Now referring to FIG. 11, a perspective view of another embodiment is described. The function of each device is the same as the embodiment as shown FIG.  4 . However, in this embodiment, an image forming device which has a skewed shape is located on the top of the sheet processing station in order to reduce area of the footprint of the whole image forming apparatus. The detail structure of this embodiment is described in FIG.  12 . 
     Now referring to FIGS. 13,  14  and  15 , the eighth embodiment is described. A sheet supply unit  6  and a sheet insert tray  15  are located on the upper part of a sorter  2 . A paper that is fed from one of the trays of the sheet supply unit  6  is carried into an image forming device. Images on an intermediate transfer drum  47  are transferred to the paper at a point between the intermediate transfer drum  47  and a transfer charger  18 A, and then the paper is fed to the sorter  2 , as shown by the direction arrow in FIG. 13, the embodiment shown therein may also have a sheet reversing tray  160  having a movable portion  16  that allows the image forming unit to produce an image on both sides of paper  14 . 
     Now referring to FIGS. 16,  17  and  18 , a ninth embodiment is described. A common sheet processing station is made up of a sheet supply unit  106  which has plural sheet tray  103 ,  104  and  105 , a sheet reverse unit  130  and a fixing device  112 . In FIG. 16, the single color type image forming device is employed. The image forming device is an exchangeable image forming device. When a paper is fed from one of the sheet supply tray  103 ,  104  and  105  in the sheet supply unit  106 , the paper is guided into the image forming device  150 . The toner images which is formed on a photoconductive drum  101  is transferred to the paper at a point between the photoconductive drum  101  and a transfer drum  121 . The paper is then fed into the sheet processing station again, the toner images on the paper is fixed by the fixing device  112 . 
     When the user selects double-sided printing mode, a left side of the sheet tray  123  moves down, a roller  132  feeds the paper having an image formed on one side thereof to the image forming device again by a rotation of the roller  132 . The image forming device then forms an image on the blank side of the paper to form a double sided copy. 
     Referring to FIG. 17, in this embodiment, a full color image forming device is selected instead of the above single color image forming device described in FIG.  16 . At this time, the sheet processing station  130  is capable of being common. 
     The full color image forming device  200  has a set of four photoconductive drums  201 - 204 , a developer, a charger, a cleaner, and a transfer charger for Yellow, Magenta, Cyan, and Black each. 
     Each color image on the photoconductive drums is transferred to an intermediate transfer belt  209 . The full color image is then simultaneously transferred to the paper at a point between a roller  213  and a roller  221 . The paper then is fed into the sheet processing station again, the full color toner images is fixed by the fixing roller  112 . 
     When the user selects double-sided printing mode, a left side of the sheet tray  123  moves down, a roller  132  feeds the paper to the image forming device again by a rotation of the roller  132 . The image forming device then forms an image on the blank side of the paper to form a double sided copy. 
     The above described sheet processing station  130  feeds the paper from the sheet supply unit to the image forming device, receives the paper which the toner images are formed, and fixes the toner images on the paper. When the user needs the double-sides printing, the sheet processing station feeds the paper to the image forming device again. Moreover, as seen in FIG. 18, the sheet processing station  130  may be used with either the single color image forming device  150  of FIG. 16 or the full color image forming device  200  of FIG.  17 . 
     Referring to FIGS. 19 and 20, a type of sheet processing station  130  that accepts image forming devices  150  having plural image forming process is shown. The positions of the paper ejecting chute  108  and the chute  134  of the sheet processing station correspond with the chute  151  and the chute  152  of the image forming device respectively. Therefore, the sheet processing station  130  according to the present invention is capable of employing every type of image forming process. 
     A connecting position between the image forming device and the sheet processing station is flexible. Thus, referring to FIG. 21, it is seen that the image forming device connects with an inside of the sheet processing station. Furthermore, the image forming device is capable of connecting with the outside of the sheet processing station as seen in FIG.  22 . 
     Now referring to FIG. 23, the detail connection of the image forming device and the sheet processing station is described. 
     The image forming device  150 A has a pair of protrusions  155  and a pair of holes  154 . The sheet processing station  130 A has also a pair of hooks  144 , a pair of sidebars  192  and a pair of adjustment protrusions  143 . When the image forming device  150 A is joined with the sheet processing station  130 A, the image forming device  150 A is placed put on the sidebars  192 , and slid into the sheet processing station  130 A. The pair of adjustment protrusions  143  are thereby inserted into the pair of holes  154  as shown FIG.  24 . In this situation, the hooks  144  is located on upper position. The position of the image forming device is adjusted so as to flush against the sheet processing station  130 A. 
     When the position of the image forming device is so adjusted, the pair of hooks  144  rotate around respective centers  146  in a downward direction and notches  145  contact and cover protrusions  155  as shown in FIG.  25 . The hooks  144  are also capable of arranging inside of the sheet processing station as shown FIG.  26 . 
     Now referring to FIGS. 27 and 28, another embodiment is described. In this embodiment, the image forming device  150  is set by rotating around center  180  which is arranged on the top of the sheet processing station  130 . When the image forming device is set, the corner of the image forming device is locked and the image forming device rotates downward around the center  180 . 
     As shown FIG. 28, the sheet processing station is also capable of employing a structure in which the sheet convey unit rotates around a lower comer  171  into an opening between the sheet convey unit and the sheet supply unit. 
     Now referring to FIG. 29, there is shown another mechanism of connecting the image forming device and the sheet convey unit. The image forming device is locked at a lower corner with the sheet convey unit and is rotatable around the corner. In the case that the image forming device and the sheet convey unit separate from the sheet processing station, the image forming device and the sheet convey unit simultaneously slide by a sidebar  172  away from the sheet processing station while the image forming device opens up by rotating around pivot point  161 . 
     When the image forming device and the sheet convey units are connected, the reverse process of the above is carried out. 
     Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.