Abstract:
An image forming apparatus, comprising a case that accommodates an image forming unit; a sheet cassette that is capable of moving relative to the case; and a cover disposed above the sheet cassette, wherein the cover covers a side of the case in which the sheet cassette is removably set in the case, the cover is capable of opening and closing, and a slot, through which a sheet is capable of being inserted, is formed between the cover and the sheet cassette with a lower end of the cover defining an upper end of the slot.

Description:
INCORPORATED BY REFERENCE  
       [0001]     This application claims priority from Japanese Patent Application No. 2003-435822, filed Dec. 26, 2003, the subject matter of which is incorporated herein in its entirety by reference thereto.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of Invention  
         [0003]     The invention relates to an image forming apparatus.  
         [0004]     2. Description of Related Art  
         [0005]     There exists a printer, for example, in U.S. Pat. No. 6,612,763, in which a front cover of the printer includes a manual slot through which a sheet is manually inserted and fed into the printer. With such a structure, printing is favorably performed on thick paper such as postcards.  
       SUMMARY OF THE INVENTION  
       [0006]     When a paper jam occurs in the printer, the front cover is opened in order to clear the paper jam. However, as disclosed in U.S. Pat. No. 6,612,763, for example, when a paper jam occurs before the sheet completely passes through the manual slot that passes through the front cover, the front cover is difficult to open. If the front cover is forcibly opened, the paper may possibly tear.  
         [0007]     Accordingly, one exemplary aspect of this invention is to provide an image forming apparatus that favorably feeds a sheet that is manually inserted therein and that readily clears a paper jam.  
         [0008]     An exemplary image forming apparatus may include a case that accommodates an image forming unit; a sheet cassette that is capable of moving relative to the case; and a cover disposed above the sheet cassette, wherein the cover covers a side of the case in which the sheet cassette is removably set in the case, the cover is capable of opening and closing, and a slot, through which a sheet is capable of being inserted, is formed between the cover and the sheet cassette with a lower end of the cover defining an upper end of the slot.  
         [0009]     Another exemplary image forming apparatus may include a case that accommodates an image forming unit; a sheet cassette that is capable of moving relative to the case; and a cover disposed above the sheet cassette, wherein the cover covers a side of the case in which the sheet cassette is removably set in the case, the cover is capable of opening and closing, and a slot, through which a sheet is capable of being inserted, is formed between the cover and the sheet cassette with an upper end of the sheet cassette defining a lower end of the slot.  
         [0010]     Another exemplary image forming apparatus may include a case that accommodates an image forming unit; a sheet cassette that is capable of moving relative to the case; and a cover disposed above the sheet cassette, wherein the cover covers a side of the case in which the sheet cassette is removably set in the case, the cover is capable of opening and closing, and a slot, through which a sheet is capable of being inserted, is formed between the cover and the sheet cassette with an upper end of the sheet cassette defining a lower end of the slot.  
         [0011]     Another exemplary method of forming a slot through which a sheet is inserted in order to supply the sheet to an image forming portion, may include the step of forming a gap between a lower surface of a cover that covers a side of a case and a sheet cassette disposed below the cover, wherein the sheet is fed to the image forming portion through the gap. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     Embodiments will be described in detail with reference to the following figures in which like elements are labeled with like numbers and in which:  
         [0013]      FIG. 1  is a perspective view of a laser beam printer according to an embodiment of the invention;  
         [0014]      FIG. 2  is a side sectional view of the laser beam printer;  
         [0015]      FIG. 3  is a side sectional view of a process unit of the laser beam printer;  
         [0016]      FIG. 4  is a block diagram for controlling the laser beam printer;  
         [0017]      FIG. 5  is a perspective view of the laser beam printer showing a sheet inserted into the laser beam printer;  
         [0018]      FIG. 6  is a perspective view of the laser beam printer showing an open front cover;  
         [0019]      FIG. 7  is a perspective view of the laser beam printer showing a sheet manually inserted, with the front cover open;  
         [0020]      FIGS. 8A and 8B  are side views of a manual slot;  
         [0021]      FIG. 9  is a perspective view of a laser beam printer according to a second embodiment;  
         [0022]      FIG. 10  is a perspective view of a laser beam printer according to a third embodiment;  
         [0023]      FIG. 11  is a perspective view of a laser beam printer according to a fourth embodiment; and  
         [0024]      FIGS. 12A-12C  are front views of various manual slots. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0025]     Embodiments of the invention will be described in detail with reference to the figures. With reference to  FIGS. 1 through 5 , a laser beam printer  1  as an example of an image forming apparatus according to a first embodiment of the invention will be described.  
         [0026]     As shown in  FIGS. 1 and 2 , the laser beam printer  1  has a case  2  with side walls  2   a ,  2   b . Disposed in a lower part of the case  2  is a sheet cassette  10  that mounts thereon a stack of sheets and is provided with a grip  13 . The sheet cassette  10  is removably set in the case  2 . The sheet cassette  10  is drawn toward the front side of the printer  1  in the direction P, as shown in  FIG. 2 , to remove the cassette  10  from the case  2 . The sheet cassette  10  is provided with a sheet mount plate (not shown) that is urged upwardly by a spring (not shown).  
         [0027]     Disposed above the sheet cassette  10  is a pick-up roller  14  rotatably supported in the case  2  of the printer  1  in the direction of the arrow (counterclockwise), and a separation pad  15  disposed in confrontation with the pick-up roller  14 . An uppermost sheet on the sheet mount plate contacts the pick-up roller  14  and is separated with the aid of the separation pad  15 .  
         [0028]     As shown in  FIG. 1 , disposed on a front face of the printer  1  is a control panel  91  including an operation button  91   a  and a LED (light-emitting diode)  91   b , as well as a manual slot  100  through which a sheet is manually inserted into the printer  1 .  
         [0029]     As shown in  FIG. 2 , a process cartridge  20  is disposed above the sheet cassette  10 . The process cartridge  20  is also removably set in the case  2 . When a paper jam occurs or the process cartridge  20  is replaced, the process cartridge  20  is drawn in the direction of arrow Q, to remove the process cartridge  20  from the case  2 .  
         [0030]     As shown in  FIG. 3 , the process cartridge  20  includes a photosensitive member cartridge  20 A and a developing cartridge  20 B detachably mounted on the photosensitive member cartridge  20 A. The photosensitive member cartridge  20 A includes a photosensitive drum  21  that carries toner image thereon, a transfer roller  22  that transfers the toner image carried on the photosensitive drum  21  onto the sheet, and a scorotron charger  28  that uniformly charges a surface of the photosensitive drum  21  by generating corona discharge. The developing cartridge  20 B includes a developing agent chamber  24  (in  FIG. 2 ) that contains toner, a developing roller  25  that supplies toner to the photosensitive drum  21 , and a supply roller  27  that supplies toner to the developing roller  25 . Disposed in the developing agent chamber  24  is an agitator  24   a  that agitates toner in the chamber  24 .  
         [0031]     The photosensitive member cartridge  20 A and the developing cartridge  20 B are separable from each other. When the process cartridge  20  is removed from the case  2  of the printer  1 , the photosensitive member cartridge  20 A and the developing cartridge  20 B are together removed from the case  2 , without being separated from each other.  
         [0032]     A front cover  33  is disposed on a front side of the printer  1  where the sheet cassette  10  is removably set in the case  2 . A shaft  33   d  is disposed on a lower end of the front cover  33 . The front cover  33  is rotatable about the shaft  33   d . In  FIG. 1 , the direction R indicates the rotating direction of the front cover  33  when it is opened. In  FIG. 6 , an axis of the shaft  33   d  is indicated by the broken lines.  
         [0033]     As shown in  FIG. 6 , formed in the case  2  of the printer  1  is an opening  34  through which the process cartridge  20  is removably set in the case  2 . When the front cover  33  is closed, the opening  34  is covered by the front cover  33 , as shown in  FIG. 1 . As the front cover  33  is rotated clockwise in  FIG. 2 , the opening  34  is uncovered, so that the process cartridge  20  can be removably set in the case  2  from the front side of the printer  1 .  
         [0034]     As shown in  FIG. 2 , a pinch roller  31  and a register roller  32  are rotatably disposed between the process cartridge  20  and the sheet cassette  10 .  
         [0035]     Disposed above the process cartridge  20  are a laser scanner unit  40  that includes a laser emitting section (not shown) that emits a laser beam, a polygon mirror  41 , lenses  42 ,  45 , and reflecting mirrors  43 ,  44 ,  46 . The surface of the photosensitive drum  21  is irradiated with laser beam that is deflected by the polygon mirror  41  and passes through the lens  42 , the reflecting mirrors  43 ,  44 , the lens  45 , and the reflecting mirrors  46 . Thus, an electrostatic latent image is formed on the surface of the photosensitive drum  21 .  
         [0036]     A fixing unit  50  that fixes toner onto the sheet is disposed behind the process cartridge  20 . The fixing unit  50  includes a heat roller  51  provided with a heat source, a pressure roller  52  in pressure contact with the heat roller  51 , and a pair of feed rollers  53 ,  54 . As the sheet is fed between the heat roller  51  and the pressure roller  52 , toner melts due to the application of heat and is fixed onto the sheet by the application of pressure. The feed rollers  53 ,  54  feed the sheet having toner fixed. As shown in  FIG. 2 , a chute  61  that is formed into a curve and reverses a sheet feeding direction, is pivotally disposed behind the feed rollers  53 ,  54 .  
         [0037]     Formed on an upper face of the case  2  is a discharge tray  70  that stacks thereon sheets that have passed through the chute  61 . Disposed on an extension of the chute  61  is a pair of discharge rollers  64 ,  65  that support the sheet fed along the chute  61  and discharge the sheet onto the discharge tray  70 .  
         [0038]     As the chute  61  is rotated rearward, the sheet is not discharged onto the discharge tray  70  but discharged onto the chute  61 . When the sheet, which is manually inserted through the slot  100 , is a thicker sheet of paper, the chute  61  is rotated rearward so that the sheet is substantially straightly discharged from the case  2  onto the chute  61 . Thus, the thick sheet can be fed reliably.  
         [0039]     A projection  71  is formed on a periphery of the discharge tray  70  (on the right, left and rear sides of the printer  1  in  FIG. 1 ), with an upper surface of the projection  71  flat. As shown in  FIGS. 1 and 2 , a stepped portion is formed between the discharge tray  70  and the projection  71 .  
         [0040]     As shown in  FIG. 4 , the control panel  91 , the laser scanner unit  40 , the fixing unit  50 , and a motor  102  are connected to a printer controller  101 . Units of the printer  1  are controlled by the printer controller  101 . Various rollers, such as the photosensitive drum  21 , the developing roller  25 , and the supply roller  27 , are driven by the motor  102 . The case  2  is arranged to accommodate the process cartridge  20 , the laser scanner unit  40 , and the fixing unit  50 .  
         [0041]     Sheet feeding will be described below. As the pick-up roller  14  is rotated at a predetermined timing, the sheets are supplied one by one from the sheet cassette  10 . The sheet is fed between the pinch roller  31  and the register roller  32  through a sheet path  35 . Skew of the sheet is corrected by the register roller  32  and fed between the photosensitive drum  21  and the transfer roller  22 .  
         [0042]     An electrostatic latent image is formed by a laser beam emitted from the laser scanner unit  40  on the surface of the photosensitive drum  21  that is charged by the charger  28 . As a portion of the photosensitive drum  21  where the electrostatic latent image is formed, is brought into confrontation with the developing roller  25 , toner supplied to the photosensitive drum  21  through the supply roller  27  and the developing roller  25 , makes the electrostatic latent image visible and thus, a visible toner image is formed on the photosensitive drum  21 . The toner image is transferred onto the sheet when the sheet passes between the photosensitive drum  21  and the transfer roller  22 .  
         [0043]     When the sheet having the toner image transferred thereon passes between the heat roller  51  and the pressure roller  52 , heat and pressure are applied to toner to fuse the toner image onto the sheet.  
         [0044]     The sheet is then fed between the feed rollers  53 ,  54  and discharged, through the chute  61 , onto the discharge tray  70  by the discharge rollers  64 ,  65  with the printed side facing down and an end of the sheet contacting an end wall  72 .  
         [0045]     The manual slot  100  will be described below. The sheet cassette  10  is slidable relative to the case  2 , as described above. The front cover  33  is pivotally provided above the sheet cassette  10 , so as to open and close. The manual slot  100  is defined by a space between the upper end of the sheet cassette  10  and the lower end of the front cover  33 .  
         [0046]     With reference to  FIGS. 12A  to  12 C, the shape of the manual slot  100  will be described.  
         [0047]     As shown in  FIG. 12A , for example, a cut portion  33   b  having a substantially rectangular shape, is formed on a lower end  33   a  of the front cover  33 . An upper end  1   a  of a front wall  11  of the sheet cassette  10  is formed flat. An area defined by the cut portion  33   b  and the upper end  11   a  functions as the manual slot  100 . The sheet, inserted from the manual slot  100 , is fed to the register roller  32  along a path that joins the sheet path  35  through a guide opening  110 .  
         [0048]     The length (i.e., left to right as show in  FIG. 12A ) of the cut portion  33   b  is slightly longer than the width of the sheet P typically used in the printer  1 . For example, when a letter size sheet P having the width of 8.5 inches is typically used, an appropriate length of the cut portion  33   b  is about 9 to 9.5 inches.  
         [0049]     The height of the cut portion  33   b  is set so that one sheet can pass through the cut portion  33   b . However, it is desirable that the height of the cut portion  33   b  be set to about 5 to 10 mm, because it is difficult to insert the sheet P through the slot  100  if the height is too low, and dust or foreign matter enters into the case  2  if the height is too high.  
         [0050]     As shown in  FIG. 12B , as another example, the lower end  33   a  of the front cover  33  is formed flat, and a cut portion  11   b  is formed on the upper end  11   a  of the front wall  10  of the sheet cassette  10 . An area defined by the cut portion  11   b  and the lower end  33   a  of the front cover  33  functions as the manual slot  100 . The sheet inserted from the manual slot  100  is fed to the register roller  32  along the path that joins the sheet path  35 , through the guide opening  110 .  
         [0051]     The length and height of the cut portion  11   b  may be set to substantially the same length and height described above in conjunction with the first example.  
         [0052]     As shown in  FIG. 12C , in yet another example, the cut portion  33   b  is formed on the lower end  33   a  of the front cover  33 , and the cut portion  11   b  is formed on the upper end  11   a  of the front wall  10  of the sheet cassette  10 . An area defined by the cut portions  11   b ,  33   b  functions as the manual slot  100 . The sheet inserted from the manual slot  100  is fed to the register roller  32  along the path that joins the sheet path  35  through a guide opening  110 .  
         [0053]     In this example, the manual slot  100  is formed by the cut portions  11   b ,  33   b . The length of the cut portions  11   b ,  33   b  may be set to substantially the same as that of the first example. The height of each of the cut portions  11   b ,  33   b  may be set to half the height of the cut portion  33   b  of the first example, so that the height of the manual slot  100  is about the same as the height of the cut portion  33  of the first example.  
         [0054]     As shown in  FIGS. 5 and 6 , the front cover  33  has a free end on an upper side thereof and the shaft  33   d  on a lower side thereof that extends parallel to the longitudinal direction of the front cover  33 . The front cover  33  is pivotally supported by the case  2  at about the shaft  33   d . When the opening  34  is closed by closing the front cover  33 , as shown in  FIG. 5 , the sheet can be inserted from the manual slot  100 .  
         [0055]     With the opening  34  uncovered by opening the front cover  33  at a predetermined angle, as shown in  FIG. 6 , a rear portion of the manual slot  100  is exposed and the upper end  11   a  of the sheet cassette  10  disposed below the manual slot  100  can be seen.  
         [0056]     By simply forming the cut portions  11   b  or  33   b , the manual slot  100  with an appropriate size can be formed. The size of the sheets that the printer  1  can guide is determined by the length of the cut portions  11   b ,  33   b.    
         [0057]     The guide opening  110  that leads to the sheet path  35  is provided behind the manual slot  100  in a sheet insertion direction from the manual slot  100 . At the opening  34  of the case  2  above the sheet cassette  10 , a space of a predetermined size that is connected to the guide opening  110  is provided. With the front cover  33  rotated at a predetermined angle, as shown in  FIG. 6 , the guide opening  110  can be seen through the space.  
         [0058]     A pair of indicators  104  that indicate positions where at least one side of the sheet P should pass, are provided on the upper end  11   a  of the sheet cassette  10  at positions recognizable with the front cover  33  rotated at the predetermined angle.  
         [0059]     The sheet P is inserted through the manual slot  100 , with the front cover  33  closed as shown in  FIG. 5 . To check the position of the manually inserted sheet P, the front cover  33  is pivotally moved at the predetermined angle, so that a relation between the sheet P, the indicators  104 , and the guide opening  110  can be checked, as shown in  FIG. 7 . After the check, the front cover  33  is closed to feed the sheet P into the case  2 . Thus, positional deviation or misalignment of the sheets P that are manually inserted from the slot  100  can be prevented.  
         [0060]     In  FIGS. 6 and 7 , a pair of indicators  104  is provided for the printer  1  for indicating the positions where sides of the sheet P, which is manually inserted from the slot  100 , are to pass. However, only one indicator  104  may be provided for the printer  1 .  
         [0061]     With reference to  FIGS. 8A and 8B , a modified example of the manual slot  100  will be described below.  FIG. 8A  shows a state of the front cover  33  that is closed. The manual slot  100  is formed by the cut portion  33   b  on the lower end  33   a  of the front cover  33 . An upper end  33   c  of the cut portion  33   b  is angled. The height of the manual slot  100  is gradually reduced inwardly. With such a structure, the sheet P can be readily inserted from the slot  100  because the height of the slot  100  on a side from which the sheet P is inserted is wider.  
         [0062]      FIG. 8B  shows the states A and B of the front cover  33  in which the front cover  33  is half open and completely open, respectively. In the state A, the front cover  33  is pivotally moved at a predetermined angle and the upper end  33   c  of the cut portion  33   b  is substantially parallel to the horizontal plane. Therefore, the sheet P can be readily inserted from the slot  100  substantially horizontally, with the front cover  33  open.  
         [0063]     In the state B, the position of the manual slot  100  cannot be seen from the front side, so that the sheet P cannot be inserted from the slot  100 . Therefore, it is preferable that a stopper be disposed in order to stop the front cover  33  at a predetermined position or at a position before the front cover  33  is completely open.  
         [0064]     In the first embodiment, the manual slot  100  is provided between the front cover  33  and the sheet cassette  10 . Therefore, opening/closing operations of the front cover  33  can be readily performed, without being influenced by the sheet P that is inserted from the slot  100 . In other words, the sheet P partially inserted does not contact the front cover  33  when the front cover  33  is opened. When a paper jam occurs with the sheet P partially inserted into the case  2  through the manual slot  100 , the front cover  33  can be opened or closed without being influenced by the jammed sheet, when the paper jam is cleared. Thus, the front cover  33  can be readily open and the sheet P cannot be torn when the paper jam is cleared.  
         [0065]     While the printer  1  allows a compact accommodation of the sheet cassette  10  in the case  2 , the manual slot  100  is formed by effectively employing the space between the sheet cassette  10  and the front cover  33 . Thus, an increase in the height of the printer  1  can be minimized and savings in the space of the printer  1  can be achieved.  
         [0066]     The lower end  33   a  of the front cover  33  constitutes a part of the manual slot  100 . As the front cover  33  is open, the space rearward of the manual slot  100  above the sheet cassette  10  is exposed. Thus, by opening the front cover  33 , the condition of the sheet P, which is manually supplied, can be readily checked.  
         [0067]     For users who are not accustomed to manual sheet insertion or are not accustomed to expensive or valuable sheets, the sheet P, when the sheet P is manually inserted from the slot  100 , can be easily checked.  
         [0068]     With the front cover  33  open, the guide opening  110  leading to the sheet path  35  can be seen, so that the sheet P can be manually set or inserted precisely. Such a structure is very useful for users who are not accustomed to manual sheet insertion and do not know how far the sheet has to be inserted inward, or who use expensive or valuable sheets.  
         [0069]     As the indicators  104  are provided on the upper end  11   a  of the sheet cassette  10 , the indicators  104  can be seen when the front cover  33  is open. Therefore, when the sheet P is manually inserted from the slot  100 , the guide mark for manually setting or inserting the sheet P can be readily identified. Thus, setting or insertion of the sheet P can be precisely made. The indicators  104  can only be seen when the front cover  33  is open. Therefore, the indicators  104  do not affect the appearance of the printer  1 , and the indicators  104  and appearances of the printer  1  can be designed independently.  
         [0070]     A second embodiment of the invention will be described with reference to  FIG. 9 . A gap of the predetermined distance is provided between the upper end  11   a  of the sheet cassette  10  and the lower end  33   a  of the front cover  33 . The gap functions as the manual slot  100 . A pair of guide members  106  that guide the sides of the sheet inserted from the manual slot  100 , is provided on the lower end  33   a  of the front cover  33 . The guide members  106  are slidable in the longitudinal direction of the front cover  33 . The guide members  106  move closer to and away from each other. As one guide member  106  is moved, the other guide member  106  is moved in association with the one guide member  106 . As a pair of the guide members  106  is provided on the lower end  33   a  of the front cover  33 , the distance that the guide members  106  can slide can be increased.  
         [0071]     In the second embodiment, the cut portion  33   b  as provided in the first embodiment, is not provided, but the gap that functions as the manual slot  100  is formed between the upper end  11   a  of the sheet cassette  10  and the lower end  33   a  of the front cover  33 . However, the cut portions  33   b ,  11   b  may be provided, as shown in  FIGS. 12A  to  12 C, and a pair of the guide members  106  may be disposed on a lower end of the cut portion  33   b  or an upper end of the cut portion  11   b.    
         [0072]     As described above, with the guide members  106 , skew of the sheet P that is manually inserted from the slot  100  can be effectively prevented.  
         [0073]     A third embodiment of the invention will be described below with reference to  FIG. 10 . In the third embodiment, the sheet P inserted form the manual slot  100  is supported by the sheet cassette  10  drawn out from the case  2  by a predetermined length. A pair of guide members  108  is provided on the upper end  11   a  of the front wall  11  of the sheet cassette  10 . A pair of the guide members  108  is slidable on the upper end  11   a  of the sheet cassette  10  in the right-left direction. Formed on the upper end  11   a  is a pair of grooves  11   c  in which the guide members  108  fit. The guide members  108  are slidably moved along the grooves  108 , so that the guide members  108  are positioned in association with the size of the sheet P, which is inserted from the manual slot  100 .  
         [0074]     As described above, with the guide members  108 , skew of the sheet P that is manually inserted from the slot  100  can be effectively prevented. The sheet P manually inserted from the slot  100  is supported by the upper end  11   a  having a relatively large area, so that the sheet P can be stably supplied into the case  2 , through the slot  100 . Skew of the sheet P that is manually inserted from the slot  100  can be effectively prevented since sides of the sheet P can be guided by the guide members  108 , as well as the slot  100 .  
         [0075]     As a pair of the guide members  108  is provided on the upper end  11   a  of the front wall  11  of the sheet cassette  10 , the distance that the guide members  108  can slide can be increased.  
         [0076]     The front wall  11  that defines a front face of the sheet cassette  10  serves as a supporter that supports the sheet P, as well as a guide that guides the sheet P with respect to the width direction thereof. Therefore, the sheet P can be inserted properly and fed stably without increasing the number of components to be used for the printer  1 .  
         [0077]     While the invention has been described with reference to the exemplary embodiments, the description of the exemplary embodiments is illustrative only and is not be construed as limiting the scope of the invention. Various other modifications and changes may occur to those skilled in the art without departing from the sprit and the scope of the invention.  
         [0078]     In the above-described embodiments, the front cover  33  has a free end on its upper side and is supported by the case  2  so as to pivot about the shaft  33   d  provided on its lower side. However, the front cover  33  may have a free end on its lower side and be supported by the case  2 , so as to pivot about the shaft  33   d  provided on an upper side thereof, as shown in  FIG. 11 .