Abstract:
A developer cartridge which is rotatably mounted in the developing unit of an image forming apparatus, and supplies a developer to the developing unit while rotating includes a cylindrical cartridge main body having a developer outlet hole in the outer surface near one end, and a ring-like cartridge-side shutter which is fitted on the outer surface near one end of the cylindrical cartridge main body to be movable along the rotating shaft of the cylindrical cartridge main body between a position where the developer outlet hole is opened and a position where the developer outlet hole is closed. The developing unit has a guide for inserting the developer cartridge and a driving unit for rotating the developer cartridge, and the guide has a main body-side shutter with a hole. When the developer cartridge is mounted, the cartridge-side shutter moves from the position where the developer outlet hole is closed to the position where the developer outlet hole is opened, and the developer outlet hole aligns itself with the hole of the main body-side shutter. The cylindrical cartridge main body and the main body-side shutter integrally rotate to align the developer outlet hole and the hole of the main body-side shutter with a developer replenishment port formed below the main body-side shutter. Every time this happens, the developer in the developer cartridge is supplied from the developer replenishment port to the developing unit via the developer outlet hole and the hole of the main body-side shutter.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an image forming apparatus and, more particularly, to an improvement in the developer replenishment mechanism of the image forming apparatus. 
     An image forming apparatus for forming an electrostatic latent image on an image carrier, developing the image with toner in a developing unit, and transferring the toner image onto a sheet, comprises a container (toner cartridge or toner bottle) for replenishing the developing unit with toner. This toner cartridge has a spiral on its inner surface. When the toner cartridge itself rotates, the contained toner is squeezed out from an outlet port along the spiral and supplied to the developing unit. 
     The outlet port of the toner cartridge is open in mounting a new toner cartridge on the apparatus main body or dismounting an empty toner cartridge from the apparatus main body. For this reason, toner escapes from the outlet port and scatters in the apparatus to contaminate the apparatus. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a developer cartridge which prevents a developer from escaping from a outlet port and scattering in an apparatus in mounting/dismounting on/from the apparatus main body. 
     It is another object of the present invention to provide an image forming apparatus having the developer cartridge which prevents a developer from escaping from the outlet port and scattering in the apparatus in mounting/dismounting on/from the apparatus main body. 
     According to the present invention, there is provided a developer cartridge which is rotatably mounted in a developing unit of an image forming apparatus, and supplies a developer to the developing unit while rotating, comprising a cylindrical cartridge main body having a developer outlet hole in an outer surface near one end, and a ring-like cartridge-side shutter which is fitted on the outer surface near one end of the cylindrical cartridge main body to be movable along a rotating shaft of the cylindrical cartridge main body between a position where the developer outlet hole is opened and a position where the developer outlet hole is closed, wherein the developing unit has a guide for inserting the developer cartridge and a driving unit for rotating the developer cartridge, the guide has a main body-side shutter with a hole, and when the developer cartridge is mounted, the cartridge-side shutter of the cylindrical cartridge main body moves from the position where the developer outlet hole is closed to the position where the developer outlet hole is opened, the developer outlet hole aligns itself with the hole of the main body-side shutter, and every time the cylindrical cartridge main body and the main body-side shutter integrally rotate to align the developer outlet hole and the hole of the main body-side shutter with a developer replenishment port formed below the main body-side shutter, the developer in the developer cartridge is supplied from the developer replenishment port to the developing unit via the developer outlet hole and the hole of the main body-side shutter. 
     According to the present invention, there is provided an image forming apparatus comprising a developing unit for developing an electrostatic latent image on an image carrier with a developer, and a transfer unit for transferring the developed developer image onto a transfer medium, wherein the developing unit has a developer cartridge rotatably mounted to supply the developer to the developing unit while rotating, a guide for inserting the developer cartridge, and a driving unit for rotating the developer cartridge; the developer cartridge has a cylindrical cartridge main body having a developer outlet hole in an outer surface near one end, and a ring-like cartridge-side shutter which is fitted on the outer surface near one end of the cylindrical cartridge main body to be movable along a rotating shaft of the cylindrical cartridge main body between a position where the developer outlet hole is opened and a position where the developer outlet hole is closed; the guide has a main body-side shutter with a hole; and when the developer cartridge is mounted, the cartridge-side shutter of the cylindrical cartridge main body moves from the position where the developer outlet hole is closed to the position where the developer outlet hole is opened, the developer outlet hole aligns itself with the hole of the main body-side shutter, and every time the cylindrical cartridge main body and the main body-side shutter integrally rotate to align the developer outlet hole and the hole of the main body-side shutter with a developer replenishment port formed below the main body-side shutter, the developer in the developer cartridge is supplied from the developer replenishment port to the developing unit via the developer outlet hole and the hole of the main body-side shutter. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumetalities and combinations particularly pointed out hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. 
     FIG. 1 is a sectional view showing the schematic structure of an image forming apparatus according to an embodiment of the present invention; 
     FIG. 2 is an exploded perspective view showing a toner replenishment unit of the image forming apparatus according to the embodiment of the present invention; 
     FIGS. 3A and 3B are views showing a state in which a toner cartridge is mounted in the toner replenishment unit; 
     FIGS. 4A and 4B are perspective views showing a state in which the toner cartridge of the image forming apparatus according to the embodiment of the present invention is positioned by an inlet guide to mesh with a driving unit; 
     FIGS. 5A,  5 B, and  5 C are schematic views showing exchange of the toner cartridge; 
     FIG. 6 is a perspective view showing a toner cartridge according to the embodiment of the present invention; 
     FIG. 7 is a perspective view showing a state in which a cartridge-side shutter covers a toner outlet port in the toner cartridge according to the embodiment of the present invention; 
     FIG. 8 is a perspective view showing a toner cartridge driving mechanism on the apparatus main body side according to the embodiment of the present invention; 
     FIG. 9 is a perspective view showing a toner cartridge according to another embodiment of the present invention; 
     FIG. 10 is a sectional view showing part of a toner cartridge according to still another embodiment of the present invention; and 
     FIG. 11 is a perspective view showing part of the toner cartridge according to still another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Preferred embodiments of the present invention will be described below with reference to the several views of the accompanying drawing. 
     FIG. 1 is a sectional view showing a whole copying machine according to a preferred embodiment of the present invention. In FIG. 1, a copying machine  1  comprises at its lower portion a cassette sheet feeder  2  which stores many sheets. The copying machine  1  further comprises an LCF sheet feeder  3  for feeding many sheets of the same size, and a manual sheet feeder  4  capable of feeding various kinds of sheets. 
     The copying machine  1  comprises at its upper portion an image reading section  5  for reading a document, an automatic document feeder  6  for feeding a document to the image reading section  5 , an image storage section  7  for storing image data read by the image reading section  5 , and a laser optical device for reading out the stored image data and writing the image on an image forming section  8 . 
     The image forming section  8  is made up of a photosensitive drum  10 , developing unit  11 , cleaner  12 , charger  13 , discharge lamp  14 , and transfer/separation charger  15 . The developing unit  11  is equipped with a toner cartridge  16  for replenishing the developing unit  11  with toner, and a driving unit  17  for driving the toner cartridge  16 , as shown in FIG.  3 A. 
     As shown in FIG. 3B, the outer surface of the toner cartridge  16  near its end has a projection  24  for positioning the toner cartridge  16  in mounting it on the copying machine main body. The projection  24  stands at a predetermined position with respect to an outlet hole  21  formed in a cap (constricted portion)  20 . 
     FIG. 2 is an exploded perspective view showing the toner replenishment unit of the copying machine main body. FIGS. 3A and 3B are views showing a state in which the toner cartridge is mounted in this toner replenishment unit. 
     In FIG. 2, an inlet guide  18  is attached to the copying machine main body, and has a guide hole of a size enough to receive the toner cartridge  16 . As shown in FIG. 3B, a recess  25   a  is formed at a predetermined position of the guide hole. The recess  25   a  fits with the projection  24  formed on the toner cartridge  16 . 
     A mounting lever  25   b  is attached to the inlet guide  18 . Upon mounting the toner cartridge  16 , the mounting lever  25   b  presses the end of the toner cartridge  16  so as to prevent the toner cartridge  16  from popping out. A spring  26  for pressing the toner cartridge  16  into the copying machine main body is attached between the mounting lever  25   b  and the toner cartridge  16 . 
     As shown in FIG. 3A, the copying machine main body also comprises the driving unit  17  for rotating the toner cartridge  16 . As shown in FIG. 2, the driving unit  17  is constituted by a motor  27 , belt  28 , pulley  29 , driving gears  30  and  31 , convey auger  32 , driving gears  33  and  34 , spring  35 , driving plate  36 , holder guide  37 , holder  38 , and holder cover  39 . 
     In this driving unit  17 , the motor  27  rotates the pulley  29  via the belt  28  to rotate the driving gear  30  meshed with the pulley  29 . The driving gear  30  meshes with the driving gears  31  and  33 . The convey auger  32  is attached to the driving gear  31  and rotated by it. 
     The driving gear  33  meshes with the driving gear  34 , to which the driving plate  36  is attached. 
     The driving plate  36  has a driving hole for driving the toner cartridge  16 . The driving gear  34  has an elliptical hole. The shaft of the driving plate  36  extends through the elliptical hole to allow the driving gear  34  to slide axially with respect to the driving plate  36 . The driving hole of the driving plate  36  is formed at a predetermined position with respect to the elliptical hole of the driving gear  34 . 
     The holder guide  37  also has an elliptical hole. The shaft of the driving plate  36  extends through this elliptical hole to connect the holder guide  37  to the driving gear  34 . The holder guide  37  rotates integrally with the driving plate  36  by rotation of the driving gear  34 . 
     The holder guide  37  has a toner replenishment hole  40 , which is formed at a predetermined position with respect to the elliptical hole. A projection  41  stands at a predetermined position with respect to the elliptical hole of the driving shaft  34 . 
     As shown in FIG. 3A, the toner cartridge  16  is mounted in the copying machine  1  after the mounting lever  25 b on the front of the copying machine  1  is released. At this time, the projection  24  of the toner cartridge  16  meshes with the recess  25   a  at the guide hole of the inlet guide  18 . 
     The recess  25   a  is formed at, e.g., an upper portion of the guide hole of the inlet guide  18 , and the projection  24  of the toner cartridge  16  corresponds in position with the recess  25   a . The cap  20  of the toner cartridge  16  has the outlet hole  21  and a projection  22  at predetermined positions. 
     The toner cartridge  16  is positioned by the inlet guide  18  to mesh with the driving unit. That is, by positioning the toner cartridge  16  in this manner, the toner replenishment port  40  of the holder guide  37  of the driving unit  17  aligns itself with the outlet port  21  of the cap  20  to enable toner replenishment. At the same time, the projection  22  of the cap  20  fits in the driving hole of the driving plate  36  to enable rotating the toner cartridge  16  by the driving unit  17 . 
     FIGS. 4A and 4B show a state in which the toner cartridge  16  is positioned by the inlet guide  18  to fit with the driving unit. FIG. 4A shows a state in which the inlet guide  18  and holder  38  are mounted, and FIG. 4B shows a state in which the inlet guide  18  and holder  38  are dismounted to expose the convey auger  32 . 
     FIGS. 5A to  5 C are schematic views showing exchange of the toner cartridge  16 . 
     When toner in the toner cartridge  16  mounted in the copying machine goes empty, an empty sensor arranged in the developing unit  11  displays an empty display on the control panel of the copying machine  1 . Then, the user opens the front cover of the copying machine  1  to pull out the toner cartridge  16  axially (to the right on the page). 
     The toner cartridge  16  is pulled in a direction indicated by an arrow (to the right) from the state shown in FIG. 5A in which the toner cartridge  16  is mounted in the copying machine. FIG. 5B shows a state in which the toner cartridge  16  is pulled by 4 or 5 mm. In this state, the driving gear  34  is pressed to the right by the operation of the spring  35  to release the meshing between the driving gears  33  and  34 . Hence, no rotation driving force is transferred from the driving gear  33  to the toner cartridge  16 . 
     Further, the toner cartridge  16  is pulled to the right. FIG. 5C shows a state in which the toner cartridge  16  is pulled by  7  mm from the state of FIG.  5 A. In this state, the toner cartridge  16  is disengaged from the driving plate  36 . 
     After the toner cartridge  16  is dismounted, a new toner cartridge is mounted in the copying machine. The mounting procedures are reverse to the dismounting procedures described with reference to FIGS. 5A to  5 C. 
     More specifically, the toner cartridge  16  is set at a predetermined position in the machine main body (state shown in FIG.  5 C), and pressed axially (to the left on the page). Then, the projection  22  of the cap  20  fits in the driving hole of the driving plate  36  (state shown in FIG.  5 B). In this state, however, the driving gears  33  and  34  do not yet mesh with each other. 
     The toner cartridge  16  is further axially pressed, and the driving plate  36  and driving gear  34  move to the left against the repulsion force of the spring  35 . The driving gear  34  meshes with the driving gear  33  to allow rotation of the toner cartridge  16  by the driving unit  17 . 
     In this case, as described above, the toner replenishment port  40  (not shown in FIGS. 5A to  5 C) of the holder guide  37  aligns itself with the outlet port  21  (not shown in FIGS. 5A to  5 C) of the cap  20  to enable toner replenishment. 
     FIG. 6 is a perspective view showing a toner cartridge according to the embodiment of the present invention. In FIG. 6, a toner cartridge  100  has a toner outlet port  101  on the side surface of a constricted portion which is formed at one end of the toner cartridge  100  and inserted into the inlet guide  18 . A spiral is formed on the inner surface of the toner cartridge  100 . Rotation of the toner cartridge  100  squeezes toner in the toner cartridge  100  along the spiral, and when the toner outlet port  101  faces down, the toner is discharged from the toner outlet port  101 . 
     The constricted portion at one end of the toner cartridge  100  is equipped with a cartridge-side shutter  102 . As shown in FIG. 7, the cartridge-side shutter  102  covers the toner outlet port  101  before mounting the toner cartridge  100  in the machine main body or after dismounting it. 
     A toner scattering prevention seal  103  is attached to the toner outlet port  101  of the constricted portion at one end of the toner cartridge  100 . 
     The cartridge-side shutter can have a through hole. That is, before the toner cartridge  100  is mounted in the machine main body, the cartridge-side shutter covers the toner outlet port  101 . In mounting, the cartridge-side shutter moves axially to align the through hole with the toner outlet port  101 . 
     FIG. 8 is a perspective view showing a toner cartridge driving mechanism on the machine main body side. In FIG. 8, a main body-side toner cartridge driving mechanism  200  has a coupling structure formed integrally with a main body-side shutter  201 , which has a main body-side shutter opening  202 . The constricted portion at one end of the toner cartridge  100  fits with the main body-side shutter  201  so as to align the toner outlet port  101  with the main body-side shutter opening  202 . Accordingly, the toner cartridge  100  is mounted in the machine main body. 
     Before the toner cartridge  100  is mounted in the machine main body, the cartridge-side shutter  102  covers the toner outlet port  101 , as shown in FIG.  7 . In mounting, the cartridge-side shutter  102  is pressed by the main body-side shutter  201  to slide and retract axially, thereby exposing the toner outlet port  101 , as shown in FIG.  6 . 
     The main body-side shutter  201  is rotated by the driving mechanism  200  to transfer the rotational force to the toner cartridge  100 . The toner replenishment port (not shown) of the machine main body is formed below the main body-side shutter  201 . Every time the main body-side shutter opening  202  and toner outlet port  101  rotate and face down, toner in the toner cartridge  100  is discharged from the toner outlet port  101  and main body-side shutter opening  202 . The toner is supplied to the machine main body through the toner replenishment port of the machine main body. In other words, the toner is intermittently supplied by rotation of the toner cartridge  100 . 
     The toner cartridge driving mechanism  200  having the coupling structure formed integrally with the main body-side shutter  201  can decrease the number of components for rotating the toner cartridge  100 , compared to a structure using a dedicated driving mechanism. This can reduce the product cost. 
     In dismounting the toner cartridge  100  from the machine main body, the cartridge-side shutter  102  is caught by the main body-side shutter  201  to slide forward and covers the toner outlet port  101 . For this reason, toner does not scatter in dismounting the toner cartridge  100  from the machine main body. 
     To effectively replenish the developing unit with toner in the toner cartridge  100 , a diameter a of the toner outlet port  101  of the toner cartridge  100 , a diameter b of the main body-side shutter opening  202 , and a diameter c of the toner replenishment port of the machine main body preferably satisfy a relation of a≦b≦c. When the hole is also formed in the cartridge-side shutter  102 , as described above, a diameter d of this hole and the above holes preferably satisfy a relation of a≦d≦b≦c. 
     If the main body-side shutter  201  is made of an elastic material such as rubber, it can function as a vibration insulator, and airtightness between the main body-side shutter  201  and the toner cartridge  100  can be enhanced. A conventional main body-side shutter is made of a flexible material such as plastic, and this material cannot satisfactorily enhance airtightness. By changing such material to rubber (natural rubber or silicone rubber), thermal deformation can be greatly suppressed. 
     FIG. 9 is a perspective view showing a toner cartridge according to another embodiment of the present invention. In the toner cartridge shown in FIG. 9, a spiral  302  is formed on the inner surface of a constricted portion  301  of a toner cartridge  300  that fits with the machine main body. With this structure, the toner cartridge  300  is automatically dismounted from the machine main body by rotating the toner cartridge  300  counterclockwise. 
     In this case, claws  303  are attached near the other end of the toner cartridge  300 . In counterclockwise rotation, the claws  303  are caught by the machine main body to stop rotation of the toner cartridge  300 . However, the rotational force still acts to push the toner cartridge  300  in a direction indicated by an arrow by the operation of the spiral  302 . 
     The toner cartridge  300  shown in FIG. 9 is axially supported by a roller  304 . This roller  304  can be made of an elastic member such as rubber to obtain a high acoustic insulation effect. 
     FIGS. 10 and 11 are a sectional view and perspective view, respectively, showing the end of a toner cartridge according to still another embodiment of the present invention. 
     In a toner cartridge  400  shown in FIG. 10, a disconnection-prevention rib (projection)  404  is attached near the end of a constricted portion  401  of the toner cartridge  400  in order to prevent a cartridge-side shutter  402  from slipping off the constricted portion  401  of the toner cartridge  400 . When the cartridge-side shutter  102  slides on the surface of the constricted portion  401  to close a toner outlet port  403 , the disconnection-prevention rib  404  prevents the cartridge-side shutter  402  from slipping off the constricted portion  401  of the toner cartridge  400 . 
     A position where the stopper rib  404  is formed is a position where the cartridge-side shutter  402  completely covers the toner outlet port  403  when the cartridge-side shutter  402  slides toward the constricted portion  401  to a maximum degree. 
     The stopper rib  404  may be formed into a ring shape on the entire constricted portion  401  of the toner cartridge  400 , but may be one or a plurality of projections. 
     FIG. 11 shows still another embodiments of a toner cartridge having a disconnection-prevention structure for the cartridge-side shutter. In a toner cartridge  500  shown in FIG. 11, the surface of a constricted portion  501  and the inner surface of a cartridge-side shutter  502  are threaded. Rotation of the cartridge-side shutter  502  moves the cartridge-side shutter  502  to open/close a toner outlet port  503 . Movement of the cartridge-side shutter  502  is stopped at an unthreaded portion. 
     As has been described in detail above, the toner cartridge of the present invention has two, cartridge-side shutter and main body-side shutter. Before mounting the toner cartridge in the developing unit, the toner outlet port of the toner cartridge is kept closed by the cartridge-side shutter. The toner replenishment port of the developing unit is kept closed by the main body-side shutter. Only in mounting/dismounting the toner cartridge on/from the developing unit, the toner outlet port of the toner cartridge and the toner replenishment port of the developing unit are opened/closed. Accordingly, toner can be effectively prevented from scattering in the developing unit in mounting/dismounting the toner cartridge on/from the developing unit. 
     Since the toner cartridge driving mechanism and main body-side shutter are integrated, the number of components can be decreased to reduce the cost. 
     Further, if particularly the main body-side shutter is made of an elastic material, it can function as a vibration isolator. At the same time, airtightness between the main body-side shutter and toner cartridge can be enhanced. Thermal deformation can also be greatly suppressed. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.