Abstract:
An image forming apparatus having a housing that includes a front face, a rear wall, a pair of side walls, a bottom surface, and a top surface with a discharge surface formed therein. A cover, having a planar upper surface, is mounted on protrusions extending along each side of the top surface. The discharge surface is formed between the protrusions and has a depth proximate the rear wall that is greater than a depth proximate the front face. A cutout is formed between the cover and the front face, the cutout being in either the cover or the front face which allows discharge of the printed material. The printed material when discharged onto the discharge surface extends beyond the front face.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an image forming apparatus mountable in a limited amount of space and, more particularly, to a laser beam printer mountable in a limited amount of space.  
         [0003]     2. Description of the Related Art  
         [0004]     Japanese Examined Patent Publications Nos. 6-97354 and 7-40168 disclose laser beam printers to which a process unit, accommodating a photosensitive drum, and a consumable article, such as toner, is detachably attached.  
         [0005]     In a printer disclosed in the Japanese Patent Publication 6-97354, space must be provided above the printer to facilitate replacement of the process unit. Thus, the space above the printer cannot be freed for effective use.  
         [0006]     In a printer disclosed in the Japanese Patent Publication 7-40168, an attaching/detaching direction of a paper feed cassette is perpendicular to a mounting direction of a process unit. Specifically, the paper feed cassette is pulled out to the front from the printer, while the process unit is pulled out to the right therefrom. Accordingly, space for attaching/detaching the paper feed cassette, as well as space for replacing the process unit, are required at the front and on the right side of the printer, respectively. As a result, a footprint of the printer, i.e., the required size of the surface on which the printer is disposed, is increased.  
       SUMMARY OF THE INVENTION  
       [0007]     It is therefore an object of the invention to provide an image forming apparatus that has a small footprint, and thereby enables space around the printer to be freed for effective use.  
         [0008]     To attain this object, in an image forming apparatus according to the invention, a paper feed cassette accommodating unit, an image forming unit, and a paper discharge unit are arranged vertically within a housing. Accordingly, the footprint of the image forming apparatus can be reduced.  
         [0009]     Further, an opening for attaching/detaching a process unit and another opening for attaching/detaching a paper feed cassette are formed on the front face of the housing. Thus, it is unnecessary to open the upper surface of the housing. Since both the opening for attaching/detaching the process unit and the opening for attaching/detaching the paper feed cassette are provided on the front face of the housing, the same space that is used for attaching/detaching the paper feed cassette can be used for attaching/detaching the process unit. Accordingly, it is unnecessary to take the trouble to open the periphery of the image forming apparatus prior to attaching/detaching the process unit. As a result, the operations of attaching/detaching are facilitated, and the footprint of the image forming apparatus can be reduced.  
         [0010]     It is preferable that the process unit is designed to be detachably attached to the housing in a direction perpendicular to an axial direction of a photosensitive drum that is accommodated in the process unit.  
         [0011]     In this case, the attaching/detaching direction of the process unit and a paper discharge direction can be easily made to be the same. Further, the attaching/detaching direction of the paper feed cassette can be easily made to be the same (directed to the front). Accordingly, it is unnecessary to open sides of the apparatus other than the front side. As a result, the footprint can be reduced and space around the image forming apparatus can be freed for effective use.  
         [0012]     A laser scanner may be disposed above the process unit within the housing.  
         [0013]     In this case, the laser scanner will not interfere with the process unit when the process unit is attached/detached from the front side of the housing. Thus, it is unnecessary to move the laser scanner prior to attaching/detaching the process unit. Since the laser scanner can be moved upward without opening the upper portion of the housing, space above the housing can be freed for effective use.  
         [0014]     Further, it is preferable that the upper surface of the housing is made to be planar. In this case, another device can be placed on the upper surface of the housing, and space for paper discharged by a paper discharge unit can be provided below the device. Thus, space above the housing can be effectively used.  
         [0015]     The paper discharge unit may be accommodated within the housing, and an opening for removing paper discharged by the paper discharge unit may be provided in the housing. In this case, paper discharged by the paper discharge unit can be removed through the opening, while space above the housing is available for effective use.  
         [0016]     Further, when a leading edge of paper discharged by the paper discharge unit is arranged to project outwardly from the front of the housing, discharged paper can be readily removed.  
         [0017]     Further, the upper surface of the housing is made to be detachable. The upper portion of the paper discharge unit can then be opened when needed.  
         [0018]     Still further, an operation panel accepting a user&#39;s operations and an insertion slot for allowing manual paper insertion may be provided on the front face of the housing. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     Preferred embodiments of the invention will be described in detail with reference to the following figures wherein:  
         [0020]      FIG. 1  is a perspective view showing a first embodiment of the invention;  
         [0021]      FIG. 2  is a vertical sectional view of the first embodiment;  
         [0022]      FIG. 3  is a sectional view showing a process cartridge;  
         [0023]      FIG. 4  is a block diagram showing a control system of the first embodiment;  
         [0024]      FIGS. 5A and 5B  illustrate a cover,  FIG. 5A  being a perspective view of a printer, and  FIG. 5B  being a sectional view of the cover sectioned perpendicular to a front to rear direction of the printer;  
         [0025]      FIG. 6  is a perspective view showing a second embodiment of the invention;  
         [0026]      FIGS. 7A and 7B  illustrate a cover,  FIG. 7A  being a perspective view of a printer, and  FIG. 7B  being a sectional view of the cover sectioned perpendicular to a front to rear direction of the printer;  
         [0027]      FIG. 8  is a perspective view showing a third embodiment of the invention;  
         [0028]      FIG. 9  is a block diagram showing a control system of the third embodiment;  
         [0029]      FIGS. 10A and 10B  show a fourth embodiment of the invention,  FIG. 10A  being a perspective view showing the fourth embodiment, and  FIG. 10B  being a perspective view showing a printer having an additional telephone function; and  
         [0030]      FIG. 11  is a block diagram showing a control system of the fourth embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     First Embodiment  
       [0031]     An image forming apparatus according to a first embodiment of the invention as applied to a laser beam printer will be described with reference to FIGS.  1  to  5 B.  FIG. 1  is a perspective view showing the laser beam printer, and  FIG. 2  is a vertical sectional view of the laser beam printer.  
         [0032]     As shown in  FIGS. 1 and 2 , the laser beam printer  1  is provided with a print unit PU having a housing  2 . Mounted below the print unit PU, which is a substantially rectangular parallelepiped, is a paper feed cassette  10  with a handle  13 . The paper feed cassette  10  accommodates a stack of paper and is detachably attached to a cassette mount  80  provided for the housing. The cassette mount  80  has an opening  82  provided on the front face of the housing  2  to allow attaching/detaching of the paper feed cassette  10 . A user can remove the paper feed cassette  10  from the printer  1  by holding the handle  13  and pulling the paper feed cassette  10  toward the front (in the direction of arrow P of  FIG. 2 ).  
         [0033]     In the paper feed cassette  10 , a paper lifter plate (not shown) upwardly urged by a pressure spring (not shown) is provided. The uppermost sheet of paper stacked on the paper lifter plate makes contact with a paper feed roller  14  that rotates in the direction of arrow F shown in  FIG. 2 . The uppermost sheet is separately fed with aid of a separation pad  15 .  
         [0034]     Provided on the front face of the printer  1  are an operation panel  91  having an operation button  91 A and an LED (light-emitted diode)  91 B, and an insertion slit  92  into which paper other than that accommodated in the paper feed cassette  10  (for example, OHP films) is inserted.  
         [0035]     The opening  82 , the operation panel  91 , and the insertion slit  92  are all provided on the front face of the housing  2 , which allows the user to operate all of them readily from the same side.  
         [0036]     As shown in  FIG. 2 , a process cartridge  20  is disposed above the paper feed cassette  10 . The process cartridge  20  includes a photosensitive member cartridge  20 A and a developer cartridge  20 B. The photosensitive member cartridge  20 A accommodates a photosensitive drum  21  that makes contact with the paper to transfer toner thereon, a transfer roller  22  opposed to the photosensitive drum  21 , and a scorotron type charger  28  that generates corona discharge to positively charge the surface of the photosensitive drum  21 .  
         [0037]     The developer cartridge  20 B accommodates a toner-containing developing chamber  24 , a developing roller  25  that supplies toner to the photosensitive drum  21 , and a supply roller that supplies toner to the developing roller  25 . The developing chamber  24  is provided with an agitator  24 A for agitating toner.  
         [0038]     The photosensitive member cartridge  20 A and the developer cartridge  20 B can be separated from each other. The detailed structure of the photosensitive member cartridge  20 A and the developer cartridge  20 B is described in U.S. patent applications Ser. Nos. 09/281,947 and 09/281,948, which are herein incorporated by reference.  
         [0039]     The process cartridge  20  is detachably attached to the housing  2  with the photosensitive member cartridge  20 A and the developer cartridge  20 B assembled. When the process cartridge  20  is detached from the printer  1 , the photosensitive member cartridge  20 A and the developer cartridge  20 B are pulled out in their assembled condition.  
         [0040]     A cover  33  is provided on the front face of the printer  1 . The cover  33  is pivotally attached at its lower end to a pivot shaft  33 A. The above-described insertion slit  92  is formed integrally with the cover  33 . An opening  34  for attaching/detaching the process cartridge  20  is revealed by pivoting the cover  33  clockwise in  FIG. 2  (in the direction of arrow R in  FIG. 1 ). The user can pull out the process cartridge  20  in the direction of arrow Q through the opening  34  and attach a new process cartridge  20  therethrough.  
         [0041]     As shown in  FIG. 2 , paper supplied from the paper feed cassette  10  and paper inserted from the insertion slit  92  are guided to a common paper feed path S. A pair of resist rollers  31 ,  32  is rotatably mounted between the process cartridge  20  and the paper feed cassette  10 .  
         [0042]     The photosensitive drum  21  is accommodated in the photosensitive member cartridge  20 A such that the axial direction of the photosensitive drum  21  is perpendicular to the mounting direction of the process cartridge  20  to the housing  2 . This makes the paper feed direction to be the same as the mounting direction of the process cartridge  20 . In other words, the paper feed cassette  10  and the process cartridge  20  can be mounted from the same side, that is, the front side. Accordingly, operability of the printer  1  is improved and valuable space around the printer  1  is available for effective use.  
         [0043]     Mounted above the process cartridge  20  is a laser scanner unit  40  that is provided with a laser generator (not shown) that emits a laser beam, a polygon mirror  41  that is driven to rotate, a lens  42 , a reflection mirror  43 , a reflection mirror  44 , a lens  45 , and a reflection mirror  46 . As shown in  FIG. 2 , a laser beam L reflected by the polygon mirror  41  irradiates to the photosensitive drum  21 , through the lens  42 , the reflection mirrors  43 ,  44 , and the lens  45 , to form an electrostatic image on the surface of the photosensitive drum  21 .  
         [0044]     The laser scanner unit  40  provided above the process cartridge  20  will not interfere with the process cartridge  20  when it is replaced. Accordingly, the laser scanner unit  40  does not need to be moved prior to replacement of the process cartridge  20 , and thus displacement of an optical axis can be prevented.  
         [0045]     A fixing unit  50  for fixing toner onto the paper is provided on the left side of the process cartridge  20 . The fixing unit  50  is provided with a heat roller  51  that heats and melts the toner transferred onto the paper, a pressure roller  52  that presses the supplied paper against the heat roller  51 , and a pair of transport rollers  53 ,  54 .  
         [0046]     A curved chute  61  is pivotally attached on the left of the feed rollers  53 ,  54 , as shown in  FIG. 2 , to reverse the paper feed direction. In an extending direction of the chute  61 , a pair of discharge rollers  64 ,  65  is attached to support the paper transported along the chute  6 . 1  and discharge it to a paper discharge tray  70  formed on the upper surface of the print unit PU.  
         [0047]     On either side of the paper discharge tray  70  (on the right and left sides and at the back in  FIG. 1 , and at the front and back in  FIG. 2 ), a protrusion  71  with a planar upper surface is provided and, as shown in  FIG. 2 , the paper discharge tray  70  is stepped down from the upper surface of the protrusion  71 .  
         [0048]      FIG. 4  is a block diagram showing a control system of the laser beam printer. As shown in  FIG. 4 , the operation panel  91 , the laser scanner unit  40 , the fixing unit  50 , and a motor  102  for driving the photosensitive drum  21  and the various rollers are all connected to a printer controller  101 . The printer controller  101  controls operations of each part of the laser beam printer  1 .  
         [0049]     The paper feed operation will now be described.  
         [0050]     When the paper feed roller  14  is rotated in a predetermined timed sequence, paper is fed from the paper feed cassette  10  sheet by sheet. The paper is reversed in its feeding direction and guided to the paper feed path S with aid of a guide  35 . Upon the arrival of the leading edge of the paper at the resist rollers  31 ,  32 , the position of the leading edge is adjusted, and then the paper is transported between the photosensitive drum  21  and the transfer roller  22 .  
         [0051]     On the other hand, the surface of the photosensitive drum  21  charged by the charger  28  is irradiated with a laser beam emitted from the laser scanner unit  40  and an electrostatic latent image is formed thereon. When the electrostatic latent image on the photosensitive drum  21  is opposed to the developing roller  25 , toner carried by the supply roller  27  and the developing roller  25  turns the electrostatic latent image into a toner image. The toner image on the photosensitive drum  21  is transferred onto the paper passing between the photosensitive drum  21  and the transfer roller  22 .  
         [0052]     Then, the paper with the transferred toner image thereon passes between the heat roller  51  and the pressure roller  52 . At this time, heat and pressure are applied to the toner image on the paper and the toner image is fixed onto the paper.  
         [0053]     Further, the paper having passed between the transport rollers  53 ,  54  is transported along the chute  61  and discharged while sandwiched by the discharge rollers  64 ,  65  to the paper discharge tray  70  with its printed surface facing down.  
         [0054]     As shown in  FIG. 5A , a cover  81  can be placed on the upper surface of the protrusion  71 . At this time, the paper discharge tray  70  is covered by the cover  81 .  
         [0055]     As shown in  FIGS. 5A and 5B , the cover  81  is provided with legs  81 A projecting downward. The lower end surfaces of the legs  81 A are made flat. The cover  81  is placed on the upper portion of the housing  2  such that the lower end surfaces of the cover  81  are brought into contact with the upper surface of the protrusion  71 . A cutaway  81 B is formed in the cover  81 , as shown in  FIG. 5B . The cover  81  is placed on the upper surface of the protrusion  71  such that the cutaway  81 B is positioned on the front face of the housing  2 . Thus, the user can access the paper discharge tray  70  to remove the paper stacked thereon through the cutaway  81 B.  
         [0056]     As shown in  FIGS. 5A and 5B , the upper surface  81 C of the cover that encloses the paper discharge tray  70  is made flat, allowing other peripheral devices to be mounted on the cover  81 . Accordingly, space above the printer  1  can be effectively used.  
         [0057]     Since the paper stacked on the paper discharge tray  70  can be removed through the cutaway  81 B, a peripheral device, if mounted on the cover  81 , will not interfere with the paper removal. A peripheral device mounted on the cover  81  may be electrically connected to the printer  1  so that image data can be exchanged therebetween. Peripheral devices to be mounted on the cover  81  include a communication device for facsimile transmission and an image scanner for reading images.  
         [0058]     To facilitate the removal of paper from the paper discharge tray, it is possible to project one edge of the discharged paper from the cover  81 . Specifically, a distance from the stopper  72  ( FIG. 2 ), against which the other edge of the discharged paper abuts, to the cutaway  81 B should be adjusted to be shorter than the length of the paper (for example, A4- or B5-size paper) by a predetermined length. The distance may be adjusted according to the size of paper most frequently used in the printer  1  or according to the minimum size of paper usable in the printer  1 . With this arrangement, one edge of the paper projects from the cutaway  81 B, allowing the user to remove the paper easily by holding its one edge.  
         [0059]     When the cover  81  is mounted on the printer  1 , a vertical distance between the paper discharge tray  70  and the cover  81 , that is, a vertical distance of an opening formed by the cutaway  81 B, restricts the number of sheets stackable on the paper discharge tray  70 . Thus, the cover  81  should be designed by considering the number of sheets discharged at a time. For example, it is preferable that the paper discharge tray  70  can stack the maximum number of sheets accommodated in the paper feed cassette  10 .  
         [0060]     In the above-described laser beam printer  1  according to the first embodiment of the invention, attaching/detaching the paper feed cassette  10 , attaching/detaching the process cartridge  20 , manual paper feeding, removal of discharged paper, and operation of the operation panel  91  can be all performed on the front side of the printer  1 . Accordingly, all these operations and jobs can be performed by leaving space available only on the front side of the printer  1 . Since it is unnecessary to open the lateral and upper sides of the printer  1  and unnecessarily to move the printer  1 , the printer  1  is easily operable by the user. Further, the footprint of the printer  1  can be minimized and a limited amount of space can be made available for effective use.  
       Second Embodiment  
       [0061]     A second embodiment of the invention will be described with reference to  FIGS. 6 and 7 .  
         [0062]     The second embodiment is almost the same as the first embodiment except for a certain difference. As shown in  FIG. 6 , a protrusion  71 - 2  in the second embodiment projects to a higher position than the protrusion  71  in the first embodiment. A cutaway  71 B is formed in the protrusion  71 - 2  that allows the paper discharge tray  70  to extend to the front face of the printer  1 .  
         [0063]     In the second embodiment, as shown in  FIGS. 7A and 7B , a planar cover  81 - 2  can be mounted on the protrusion  71 - 2 . The protrusion  71 - 2  is provided instead of the legs  81 A of the cover  81  in the first embodiment. As shown in  FIG. 7A , because the user can remove the discharged paper from the paper discharge tray  70  through the cutaway  71 B, space on the upper side of the cover  81 - 2 , that is, space above the printer  1 , can be used freely. For example, various peripheral devices can be mounted on the upper surface of the cover  81 - 2 .  
         [0064]     At the same time, as the protrusion  71 - 2  provides space for stocking the discharged paper, any one of various peripheral devices can be mounted directly on the protrusion  71 - 2  without the cover  81 - 2  interposed therebetween. In such an arrangement, paper discharged on the tray  70  can be removed from the front side of the printer  1  through a clearance (cutaway  71 B) between the tray  70  and a peripheral device mounted thereon. Even directly mounting a peripheral device having a flat bottom surface on the protrusion  71 - 2  provides space for stacking discharged paper and for allowing access to the discharged paper, without causing any inconveniences.  
         [0065]     Accordingly, space above the printer  1  can be effectively used when the cover  81 - 2  is not interposed.  
         [0066]     Also, in the second embodiment, it is possible to project one edge of the paper from the cover  81 - 2  by adjusting the distance from the stopper, against which the other edge of the paper abuts, to the cutaway  71 B to be shorter than the length of the paper (for example, A4- or B5-size paper) by a predetermined length. Thus, the user can remove the paper easily by grasping the projecting one edge of the paper.  
         [0067]     When the cover  81 - 2  or a peripheral device is mounted on the protrusion  71 - 2 , the number of stackable sheets is restricted by the vertical space provided above the paper discharge tray  70 . Accordingly, the height of the protrusion  71 - 2  should be designed by considering the number of stackable sheets. Specifically, it is preferable that the number of sheets accommodated in the paper feed cassette  10  can be stacked on the paper discharge tray  70 .  
         [0068]     Alternatively, if the paper discharge tray  70  is spaced 1 cm or more from the upper end surface of the protrusion  71 - 2 , at least 50 or more sheets can be stacked. With this arrangement, the paper discharge tray  70  becomes more practical and unlikely to be filled with paper discharged by a single print output.  
       Third Embodiment  
       [0069]     A third embodiment of the invention will now be described with reference to  FIGS. 8 and 9 . The third embodiment shows an exemplary case where a scanner unit for reading images is mounted above the printer  1  of  FIG. 1 .  
         [0070]     As shown in  FIG. 8 , the printer  1  is provided with a print unit PU, that is common to the first embodiment, and a scanner unit  110  mounted above the printer unit PU for reading images. The print unit PU and the scanner unit  110  are accommodated in the single housing  
         [0071]     The scanner unit  110  is mounted above the print unit PU. The scanner unit  110  is provided with a document tray  111  that holds documents to be fed into the scanner unit  110 , an image reader  112  ( FIG. 9 ) that scans and reads images on the fed documents and converts the read images into electrical signals, and an operation panel  115  that receives operations as reading commands. Documents having passed the image reader  112  are discharged to a document discharge tray  117 .  
         [0072]     The document tray  111 , the operation panel  115 , and the document discharge tray  117  are provided so that the user can operate all of them from the front side of the printer  1 . Paper on which printing has been performed by the print unit PU is discharged to the paper discharge tray  70  disposed below the document discharge tray  117 .  
         [0073]      FIG. 9  is a block diagram showing a control system of the third embodiment. As shown in  FIG. 9 , in the scanner unit  110 , a driving motor  113  that drives a predetermined paper feed mechanism to feed paper, the image reader  112 , and the operation panel  115  are connected to a reading controller  114 . The reading controller  114  is also connected to a printer controller  101  of the print unit PU, which is the same as the printer controller  101  shown in  FIG. 4 .  
         [0074]     The reading controller  114  and the printer controller  101  are arranged so as to communicate with each other, and thereby images read by the scanner unit  110  can be printed by the print unit PU. A predetermined interface or a connecting terminal may be provided so that a personal computer can process images read by the scanner unit  110 .  
         [0075]     In this way, since any operation of both the print unit PU and the scanner unit  110  can be performed from the front side of the printer  1 , the printer  1  provides excellent operability to the user.  
       Fourth Embodiment  
       [0076]     A fourth embodiment of the invention will now be described with reference to  FIGS. 10A, 10B  and  11 . The fourth embodiment shows an exemplary case where a reading/communication unit  130  is mounted above the print unit PU of  FIG. 1 .  
         [0077]     As shown in  FIG. 10A , the printer  1  is provided with a print unit PU that is common to the first embodiment and a reading/communication unit  130  mounted above the print unit PU. The print unit PU and the reading/communication unit  130  are accommodated in the single housing  2 .  
         [0078]     The reading/communication unit  130  has an image reading function and an image transmission/reception (facsimile) function. The reading/communication unit  130  is provided with an operation panel  135  having a touch panel on the screen of a liquid crystal display. Image reading, transmission and the like can be commanded through operation of the operation panel  135 . Further, an image reader  112 A is built in the reading/communication unit  130  to read images on documents sent from a document tray  131 . The documents read by the image reader  112 A are discharged to a document discharge tray  139 . The document tray  131 , the operation panel  135 , and the document discharge tray  139  are all provided so as to be operable from the front side of the printer  1 . Paper on which printing is performed by the print unit PU is discharged to a paper discharge tray  70  disposed below the document discharge tray  139 .  
         [0079]      FIG. 11  is a block diagram showing a control system of the fourth embodiment. The reading/communication unit  130  has a driving motor  113 A that drives a predetermined paper feed mechanism to feed documents, an image reader  112 A that reads images on the documents fed by the paper feed mechanism, and a reading controller  114 A to which the operation panel  135 , the driving motor  113 A, and the image reader  112 A are connected. The reading/communication unit  130  is further provided with a receiver  132  that receives data sent via public communication lines, a transmitter  133  that transmits data via public communications lines, a communication controller  134  to which the operation panel  135 , the receiver  132 , and the transmitter  133  are connected.  
         [0080]     Since the reading controller  114 A, the printer controller  101 , and the communication controller  134  can communicate with each other, the print unit PU can print images read by the image reader  112 A, or read images can be faxed via the transmitter  133 . Further, a predetermined interface and a connecting terminal may be provided so that a personal computer can process images read by the image reader  112 A or images received via the receiver  132 .  
         [0081]     In this way, since any operation of both the print unit PU and the reading/communication unit  130  can be performed from the front side of the printer  1 , the printer  1  provides excellent operability to the user.  
         [0082]     A printer  1  shown in  FIG. 10B  is provided with an additional telephone function as compared to the printer  1  of  FIG. 10A .  
         [0083]     In this printer  1 , a reading/communication unit  140  is provided above the printer unit PU. The reading/communication unit  140  has an image reading function, an operation panel  141  accepting operational commands for facsimile/telephone functions, and a handset allowing telephone conversation via telephone lines. A document tray  143  and a document discharge tray  144  are also provided so at to be operable from the front side of the printer  1 . Since any operation can be performed from the front side of the printer  1 , the printer  1  provides excellent operability to the user.