Developer holding apparatus, image forming unit, and image forming apparatus

A developer holding apparatus includes a first chamber, a second chamber, a communication port, and a shutter. The first chamber holds a developer material therein. The second chamber is adjacent the first chamber, and holds the developer material therein. The first chamber communicates with the second chamber through the communication port. The shutter opens and closes the communication port.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a developer holding apparatus that holds a developer material therein, an image forming unit that uses the developer holding apparatus, and an image forming apparatus that uses the developer holding apparatus.

2. Description of the Related Art

Developer holding apparatus that hold a developer material therein are well known. A developer holding apparatus is shipped from the factory with a developer material loaded therein, and is attached to an image forming unit or an image forming apparatus when in use. The developer holding apparatus supplies the developer material for forming an image.

Japanese Patent Laid-Open No. 2011-118040 discloses an image forming unit and an image forming apparatus that employ such a developer holding apparatus.

Even when a developer holding device is designed to have a large capacity, the device is required to have improved reliability.

SUMMARY OF THE INVENTION

An object of the invention is to provide a developer holding apparatus capable of efficiently supplying a developer material to an image forming unit or an image forming apparatus.

A developer holding apparatus includes a first chamber, a second chamber, a communication port, and a shutter. The first chamber holds a developer material therein. The second chamber is adjacent the first chamber, and holds the developer material therein. The first chamber communicates with the second chamber through the communication port. The shutter opens and closes the communication port.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention will be described with reference to the accompanying drawings. The invention is not limited to these embodiments. A developer holding apparatus according to the present invention is used with an image forming unit or an image forming apparatus which may take a variety of forms. For simplicity, the invention will be described with respect to an image forming apparatus.

First Embodiment

FIG. 1illustrates an outline of an image forming apparatus29according to a first embodiment of the present invention.

The image forming apparatus29includes a paper transporting path28that includes paper transporting rollers17-19and discharging rollers23-26. A paper cassette16is disposed upstream of the paper transport path28, and holds a stack of paper13as a recording medium. A stacker27is located downstream of the paper transporting path28, and temporarily holds printed paper. The paper transporting path28also includes a transfer roller12that transfers a developer image onto the paper13and a fixing unit22that fuses the developer image into the paper13. The transfer roller12is disposed immediately under an image forming unit21.

FIG. 2illustrates the outline of the image forming unit21. The image forming unit21includes a developer holding apparatus5, disposed at an upper portion of the image forming unit21, and a print engine10disposed under the developer holding apparatus5. The print engine10includes a photoconductive drum1, a charging roller2, a light emitting diode (LED) head3, and a developing roller6, a cleaning blade9, a transport spiral15, and a waste toner holder20. The photoconductive drum1is rotatably supported so that the photoconductive drum1is driven in rotation by a drive source (not shown). The photoconductive drum1is capable of storing charges on its surface. The LED head3illuminates the charged surface of the photoconductive drum1in accordance with print data, thereby creating an electrostatic latent image on the photoconductive drum1.

The charging roller2is in pressure contact with the surface of the photoconductive drum1, and supplies a predetermined amount of charge to the surface of the photoconductive drum1. The charging roller2rotates in the same direction as the photoconductive drum1. The LED head3is disposed over the photoconductive drum1, and illuminates the charged surface of the photoconductive drum1to dissipate the charge on the photoconductive drum1, thereby forming an electrostatic latent image on the photoconductive drum1. The developer holding apparatus5is located above the print engine10, holds a developer material (e.g., toner)4therein, and supplies the developer material4to the print engine10.

A developing roller6receives the developer material4from the developer holding apparatus5, and supplies the developer material4to the electrostatic latent image formed on the photoconductive drum1. A developer material supplying roller8supplies the developer material4to the developing roller6. The developing blade7is in pressure contact with the developing roller6, and forms a layer of the developer material4having a predetermined thickness on the developing roller6.

The print engine10includes an opening51through which the developer material4is received from the developer holding apparatus5. Once the developer holding apparatus5is attached to the print engine10, the opening51(FIG. 3) is in alignment with a rectangular opening40(FIG. 3) formed in the developer holding apparatus5.

The transfer roller12is disposed immediately under the photoconductive drum1. The cleaning blade9is located immediately downstream of the transfer roller12with respect to rotation of the photoconductive drum1. The cleaning blade9is in pressure contact with the surface of the photoconductive drum1, and scrapes the residual developer material adhering to the surface of the photoconductive drum1after transfer of the developer image onto the paper, thereby collecting the waste developer material into the waste developer holder20. The spiral15is located in the vicinity of the cleaning blade9, and transports the scraped residual developer material into a side frame (not shown).

FIG. 3is a cross-sectional view of the developer holding apparatus5according to the first embodiment. The developer holding apparatus5will be described with reference toFIG. 3. The developer holding apparatus5is attached to the print engine10, and supplies the developer material4into the print engine10. The developer holding apparatus5includes a developer material chamber43that holds the developer material4therein, a waste developer material chamber32that holds the residual developer material that failed to be transferred onto the paper13, and a handle43athat is gripped by the user when the user attaches the developer holding apparatus5onto the print engine10.

The developer material chamber43includes a sub chamber38in the shape of a small-diameter hollow cylinder that holds a small amount of the developer material4therein, a main chamber39in the shape of a large-diameter hollow cylinder that holds a large amount of the developer material4therein, and a communication port42through which the first and second chambers38and39communicate with each other. The sub chamber38has a shape such that a small-diameter hollow cylinder is cut in a plane parallel to the longitudinal axis of the small-diameter hollow cylinder. The main chamber39has a shape such that a large-diameter hollow cylinder is cut in a plane parallel to the longitudinal axis of the large-diameter hollow cylinder. The first and second chambers38and39are put together at their portions cut in the planes parallel to the corresponding longitudinal axes. The developer material4is directed from the main chamber39into the sub chamber38through the communication port42, and then into the print engine10via the opening33bformed in the shutter33(FIG. 4), the opening40formed in the sub chamber38, and the opening51formed in the print engine10.

Once the developer holding apparatus5is attached to the print engine10, the developer material chamber43is oriented such that the main and sub chambers39and38are positioned substantially horizontally side by side and their bottoms lie substantially in a horizontal plane. In this manner, the developer holding apparatus5is maintained at a minimum height in the image forming apparatus29.

The sub chamber38includes a shutter33, a sub agitator30, and the opening40.

The shutter33is rotatably received in the sub chamber38, and simultaneously opens and closes the opening40and the communication port42. In other words, the shutter33rotates in the sub chamber38to open and close the opening40. The shutter33also rotates in the sub chamber38to open and close the communication port42through which the sub and main chambers38and39communicate with each other. After the developer holding apparatus5has been attached to the print engine10, the user operates a lever (not shown) to rotate the shutter33between an opening position and a closing position. The shutter33closes both the opening40and the communication port42simultaneously, so that the developer material4is prevented from leaking from the developer holding apparatus5when the developer holding apparatus5is subjected to impact due to, for example, dropping. A sealing member41and a sealing wall33dcooperate with each other to close the opening40hermetically, thereby preventing the developer material4in the sub chamber38from leaking through the opening40. A sealing wall33ccloses the communication port42, thereby preventing the pressure by the developer material4in the main chamber39from being exerted on the developer material in the sub chamber38. This configuration prevents the sealing effect at the opening40from deteriorating. In other words, the shutter33and the sub chamber38serves as a buffer mechanism between the main chamber43and the print engine10.

FIG. 4is a perspective view of the shutter33.FIG. 5is a cross-sectional view of a pertinent portion of the shutter33shown inFIG. 4. The shutter33has a generally cylindrical shape, and has an outer diameter slightly smaller than the inner diameter of the sub chamber38, so that the shutter33is rotatable in the sub chamber38. The shutter33is formed of ABS resin.

The shutter33includes six arcuate or circumferential ribs33a, opening33b, a closing wall33c, an opening33e, a closing wall33d, and the sealing member41.

The circumferential ribs33aare in the shape of an arc, which defines a part of the outer and inner diameters of the shutter33. The circumferential ribs33aare aligned at predetermined intervals H in a direction parallel to the rotational axis X1(FIG. 5) of the shutter33, thereby defining openings33ebetween adjacent circumferential ribs33a. The openings33ehave a dimension H in the longitudinal direction of the shutter33. Each circumferential rib has a width of t. In the present embodiment, the dimension H is 30 mm and the width of t is 4 mm. The number of circumferential ribs33a, which will be described later, may be selected according to the number of the sub films of a sub agitating film35of the sub agitator30, for example, in the range of 1 to 5 or more than 7. When the shutter33opens the communication port42, the circumferential ribs33aprevent the sub agitating film35from entering the main chamber39and a main agitating film37from entering the sub chamber38. In other words, the circumferential ribs33aprevent the sub agitator30and a main agitator49(FIG. 8) from interfering with each other even when the communication port42is open.

The opening33b(FIG. 4) has substantially the same size and shape as the opening40formed in the sub chamber38, and is positioned at substantially longitudinally mid portion of the developer material holding apparatus5. When the shutter33is rotated in an opening direction, the opening33bbecomes aligned with the opening40so that the sub chamber38communicates with the print engine10through the openings33band40and the developer material4is supplied into the print engine10.

When the shutter33is rotated in a closing direction (opposite to a Q direction shown inFIG. 3), the closing wall33cbecomes aligned with the communication port42, closing the communication port42.

When the shutter33rotates in the closing direction, the closing wall33dis brought into alignment with the opening40, closing the opening40.

The sealing member41provides a sealing environment for the opening40. The sealing member41is located on the outer surface of the shutter33, and is in the shape of a rectangular ring that surrounds the substantially rectangular opening40. When the developer holding apparatus5has been attached to the print engine10, the opening40faces the print engine10substantially downward.

The relative positions among the opening40, the communication port42, the opening33e, and the closing wall33cof the shutter33are related as follows: When the shutter33is rotated so that the opening33ebecomes aligned with the communication port42(opening position), the opening33ebecomes aligned with the communication port42. When the shutter33is rotated to bring the closing wall33cinto alignment with the communication port42(closing position), the closing wall33dbecomes aligned with the opening40.

The sub agitator30rotates in the sub chamber38, while agitating the developer material4in the sub chamber38. The sub agitator30includes a bar structure34and the sub agitating film35. When the sub agitator30rotates, the sub agitating film35extending radially from the bar structure34scrapes the inner circumferential surface of the sub chamber38. The bar structure34includes rotational shafts34athat project from a body of the bar structure34. The rotational shafts34aextend oppositely substantially in the longitudinal direction of the bar structure34, and are rotatably received in bearings (not shown) mounted at the longitudinal end walls of the sub chamber38, so that the sub agitator30rotates in the sub chamber38. The rotational axis X2(FIG. 6) of the rotational shafts34ais substantially in line with the centerline of the inner cylindrical space in the sub chamber38.

FIG. 6illustrates the sub agitator30. The bar structure34includes a first mounting surface34band two inclined second mounting surfaces34c. The bar structure34is in a single piece construction. The first mounting surface34bis laterally centered between two longitudinal ends of the bar structure34. The two second mounting surfaces34care positioned with the first mounting surface34blocated between the two second mounting surfaces. The first mounting surface34bis contiguous with the second mounting surfaces34c. The mounting surface34bextends in a direction substantially parallel to the rotational axes of the rotational shafts34a. Each of the second mounting surfaces34cextends in such a direction as to become further away from the longitudinal axes of the rotational shafts34anearer the longitudinal end of the rotational shaft34a. The bar structure34also includes five ribs34dbetween the rotational shafts34a

The sub agitating film35has cuts35b1-35b4to define five resilient thin sub films35a1-35a5that can resiliently deflect independently of one another, so that the sub films35a1-35a5resiliently scrape the inner surface of the shutter33. The sub films35a1-35a5are mounted on the mounting surfaces34band34cof the bar structure34, and extend from the first mounting surface34band second mounting surface34c. When the bar structure34rotates, the free ends Y1-Y5of the sub films35a1-35a5scrape the inner surface of the circumferential ribs33abut do not interfere with the main agitating film37in the main chamber39.

The free end of the sub film35a3is further away from the longitudinal axes of the rotational shafts34athan the free ends Y4and Y2of sub film35a4and35a2. The free ends of the sub films35a4,35a5,35a2, and35a1are further away from the rotational axis of the rotational shafts34anearer the longitudinal free ends of the bar structure34.

The sub agitating film35extends from the bar structure34in a direction substantially perpendicular to the rotational axes of the shafts34a, and is in resilient contact with the inner surface of the shutter33, thereby ensuring that the developer material4in the sub chamber38is supplied into the print engine10. In other words, the sub films35a1and35a5located near the longitudinal ends of the sub agitator30contact the inner surface of the sub chamber38under higher pressure than the sub films35a2and35a4located between the sub films35a1and35a5, so that the developer material4adhering to the inner surface of the sub chamber38is collected toward a longitudinally middle portion of the sub chamber38. The free end of the sub film35a3is further away from the rotational axes of the shafts34athan the portion of the sub films35a1and35a5immediately adjacent to the thin sub film35a3, and strongly scrapes the inner surface of the shutter33, thereby guiding the developer material4toward the opening40. In this manner, the developer material4may be discharged into the print engine10through the opening40.

Specifically, the distance R1(FIG. 3) between the rotational axis of the shafts34aand the inner surface of the sub chamber38is 26 mm. The distance L1between the free ends of the sub films35a1and35a5and the rotational axis of the rotational shafts34ais 30 mm. Since the distances R1and L1are related such that R1<L1, the sub agitating film35is in resilient contact with the inner circumferential surface of the shutter33.

FIG. 7is a side view of the sub agitator30.

The sub agitating film35has a substantially L-shaped cross section with a long side35mand a short side35s. The short side35sis fixed to the mounting surfaces34band34cby, for example, thermal caulking.

The five sub films35a1-35a5have lengths D1, D2, D3, D4, and D5(FIG. 6) in the longitudinal direction of the sub agitator, respectively.

The sub films35a1,35a2, and35a3have distances L1, L2, L3, and L4from the rotational axis of the rotational shaft34a, respectively. The L1is the distance of the free end Y1of the sub film35a1from the rotational axis of the rotational shaft34a, the free end Y1being at the longitudinal end of the sub agitating film35. The L2is the distance of the free end Y1of the sub film35a1, immediately adjacent the sub film35a2, from the rotational axis of the rotational shaft34a. The L3is the distance of the free end Y2of the sub film35a2from the rotational axis of the rotational shaft34a, the free end Y2being immediately adjacent the sub film35a3. The L4is the distance of the free end Y3of the sub film35a3from the rotational axis of the rotational shaft34a. The distances L1-L4and R1are related such that R1<L3<L1<L4, and allow the sub agitating film35to be in resilient contact with the inner circumferential surface of the shutter33, thereby ensuring that the developer material4is efficiently supplied into the engine10through the opening40.

The sub films35a4and35a5and the sub films35a1and35a2are symmetrical with respect to the sub film35a3, and therefore the description of the distances of the thin sub films35a4and35a5from the rotational axes of the shafts34ais omitted. Referring toFIG. 6, the dimensions D1-D5and the distances L1-L4are related such that D1, D2, and D3are 40 mm, D4is 50 mm, D5is 36 mm, L1is 30 mm, L2is 28 mm, L3is 26 mm, and L4is 35 mm. The sub agitating film35is formed of polyethylene terephthalate (PET), and has a thickness of 0.1 mm. However, the sub agitating film35may be formed of a variety of materials and have a variety of dimensions. In addition, the sub agitating film35may have more than five sub films. The bar structure34may be formed of other material than ABS resin.

FIG. 8is a perspective view of the main agitator49andFIG. 9is a cross-sectional view taken along a line C-C inFIG. 8. The main agitator49includes a bar structure36formed in a one piece construction and a resilient thin film37mounted thereto. The bar structure36includes a mounting bar36d, rotational shafts36a, and supporting bars36e. The rotational shafts36aoppositely extend in a longitudinal direction of the bar structure36. The supporting bars36eextend in a radial direction from the mounting bar36d. The resilient thin film37is mounted securely to the mounting bar36dat a portion depicted at “A,” and extends in a direction perpendicular to the supporting bars36e. The rotational shafts36aare in line with a centerline of the cylindrical space of the main chamber39. The shafts36aare rotatably received in bearings at longitudinal ends of the main chamber39, and the main agitator49rotates in a direction shown by arrow Z (FIG. 3).

The mounting bar36dspans across the supporting bars36e, thereby defining a space36bbounded by the supporting bars36e, bar36f, and the mounting bar36d. The resilient thin film37is fixed at its one end to the mounting bar36d, and extends to the inner circumferential surface of the main chamber39. The mounting bar36dincludes a tapered end36cformed on a leading end thereof, tapered with respect to rotation of the main agitator49, the tapered end being formed along the full length of the mounting bar36d. When the main chamber39holds a large amount of the developer material4therein, the resilient thin film37may be unable to efficiently agitate the developer material4but the tapered end36cof the mounting bar36dis able to push its way through the pile of developer material while allowing the developer material4escaping through the space36b. In this manner, the tapered end36cprevents overloading of the resilient thin film37.

When the main agitator49rotates in the Z direction, the resilient thin film37rotates so that the portion of the resilient thin film37fixed to the mounting bar36dis a leading end and the free end of the resilient thin film37is a trailing end with respect to the direction of rotation of the main agitator49. In other words, the resilient thin film37trails upstream of the direction of rotation of the main agitator49. The free end resiliently drags the developer material4on the inner circumferential surface of the main chamber39, thereby collecting the developer material4. The resilient thin film includes five sub films37a1-37a5configured to resiliently deform independently of one another. Just as in the resilient thin film35of the sub agitator30, when the main agitator49rotates, the free ends Z1-Z5of the sub films37a1-37a5scrape the outer circumferential surface of the circumferential ribs33abut do not interfere with the sub films35a1-35a5in the sub chamber38.

This configuration minimizes the load exerted on the resilient thin film37during the rotation of the main agitator49. The distance L5between the rotational axis of the shafts36aand the free end of the resilient thin film37is 56 mm. Selecting the distances R2and L5such that R2<L5causes the free ends Z1-Z5of the resilient thin film37to resiliently contact the inner circumferential surface of the main chamber39.

The waste developer material chamber32may be separated from the developer material holding chamber43, and includes a developer receiving opening50and a spiral31. The developer receiving opening50receives the waste developer material, which failed to be transferred onto the paper13. The waste developer material is directed through the developer receiving opening50into the back end of the waste developer material chamber32for efficient utilization of storing space.

The main agitating film37has cuts37b1-37b4to define five resilient thin sub films37a1-37a5that can resiliently deflect independently of one another, so that the sub films35a1-35a5resiliently scrape the inner circumferential surface of the shutter33. Each of the sub films37a1-37a5have holes37cformed therein which alleviate the load on the sub films37a1-37a5exerted by the developer material4. The sub films37a1-37a5have lengths D1, D2, D3, D4, and D5extending in a direction parallel to the rotational axis of the shafts36a, respectively, and a distance L5(FIG. 9) between the free ends Z1-Z5of sub films37a1-37a5and the rotational axis of the shafts36a. The resilient thin film37has a thickness of 0.1 mm, and is formed of polyethylene terephthalate (PET). The bar structure36is formed of ABS resin. However, the resilient thin film37and the bar structure36may be formed of a variety of materials.

FIG. 10illustrates the positional relation among the circumferential ribs33a, and the cuts35b1-35b4between the adjacent sub films35a1-35a5and the cuts37b1-37b4between the adjacent sub films37a1-37a5. It is to be noted that the circumferential ribs33ado not face the cuts35b1-35b4and37b1-37b4, or the cuts35b1-35b4and37b1-37b4do not face the circumferential rib33aso that the circumferential ribs33ado not enter the cuts35b1-35b4. Therefore, the circumferential ribs33aprevent the sub films37a1-37a5from entering the sub chamber38and the sub films35a1-35a5from entering the main chamber39.

The bar structure36formed of ABS resin is more rigid than the main agitating film37formed of PET. The supporting bars36eextend from the bar36fin directions perpendicular to the direction in which the rotational shafts36aand the bar36fextend. The main agitating film37is supported on a side of the supporting bars36eopposite the bar36f, and lies in a plane that forms an angle in the range of 60-150 degrees with the supporting bars36e, preferably perpendicular to the bar36f. In other words, the main agitating film37is away from the bar36fand rotational shafts36a, and lies in a plane parallel to the rotational shaft36aand the bar36f.

{Operation of Image Forming Apparatus}

Rollers17-19cooperate to receive the paper13from the paper cassette16and feed the paper13into the transport path28. The transfer roller12transfers the developer image onto the paper13. The fixing unit22fixes the developer image on the paper13. After fixing, the paper13is discharged onto the stacker27.

The image forming unit21will be described.

The charging roller2uniformly charges the surface of the photoconductive drum1. The LED head3illuminates the charged surface of the photoconductive drum1to form an electrostatic latent image on the surface. The developer holding apparatus5is on the print engine10, and supplies the developer material4into the print engine10. The supplying roller8supplies the developer material4to the developing roller6. The developing blade7forms a thin layer of the developer material4. The thin layer is then brought into contact with the electrostatic latent image, thereby developing the electrostatic latent image into a developer image14. The developer image is then transferred by the transfer roller12onto the paper13. The residual developer, which failed to be transferred onto the paper13, is collected by the cleaning blade9, and is transported by the spiral15to the side frame (not shown) of the print engine10. The residual developer is further transported from the side frame to the developer receiving opening50through which the residual developer is stored into the waste developer material chamber32. The residual developer in the waste developer material chamber32is spread by the spiral31so that the residual developer is efficiently stored in the waste developer material chamber32.

The developer holding apparatus5will be described with reference toFIG. 11.FIG. 11illustrates the developer holding apparatus5before it is unsealed, i.e., immediately after shipment from the factory. When the developer holding apparatus5remains unsealed, the opening40remains closed by the sealing wall33dand sealing member41so that the developer material4will not leak from the developer holding apparatus5. The communication port42is closed by the closing walls33c. Therefore, even if unwanted physical forces are exerted on the developer holding apparatus5due to vibration during transportation and inadvertent dropping, the pressure of the developer material4in the main chamber39is not transmitted to the developer material in the sub chamber38. In other words, the shutter33serves as a buffer mechanism, preventing the pressure of the developer material4in the main chamber39from being transmitted to the developer material in the sub chamber38. This configuration prevents the developer material in the sub chamber38from leaking from the sub chamber38through the opening40.

It is to be noted that the sub chamber38holds a smaller amount of developer material than the main chamber39. Therefore, when the unwanted physical forces are exerted on the developer holding apparatus5due to vibration during transportation or inadvertent dropping, only the pressure of the developer material in the sub chamber38is exerted on the closing wall33dthat closes the opening40. Therefore, the pressure exerted on the closing wall33dcan be minimized.

FIGS. 12-14illustrate the position of the main agitator49as the main agitator49rotates in the Z direction. The operation of the developer holding apparatus5will be described with reference toFIGS. 12-14. Assume that when the main agitator49is inFIG. 12position, the user operates a lever (not shown) to open the shutter33. The opening40is opened and the developer material4may be supplied from the developer holding apparatus5into the print engine10. When the opening40is opened, the openings33eare also in alignment with the communication port42so that the developer material4may be supplied from the main chamber39into the sub chamber38.

Referring toFIG. 13, the main agitator49rotates so that the sub films37a1-37a5transport the developer material4from the main chamber39into the sub chamber38. The sub agitator30also rotates so that the sub films35a1-35a5transport the developer material4from the sub chamber38into the print engine10. The circumferential ribs33aprevent the sub films37a1-37a5from entering the sub chamber38and the sub films35a1-35a5from entering the main chamber39, the sub films37a1-37a5rubbing the outer arcuate surface of the circumferential ribs33aand the sub films35a1-35a5rubbing the inner arcuate surface of the circumferential ribs33a.

The sub films35a1-35a5of the sub agitator30and the sub films37a1-37a5of the main agitator49rotate simultaneously to efficiently transport the developer material4into the print engine10.

Until the developer holding apparatus5is attached to the print engine10, the closing wall33cof the shutter33prevents the pressure of the developer material4in the main chamber39from being exerted on the developer material4in the sub chamber38, thereby minimizing the chance of the developer material4leaking from the sub chamber38through the opening40. This configuration increases the reliability of the developer holding apparatus5.

The circumferential ribs33aserve to isolate the sub films37a1-7a5from the sub films35a1-35a5, and prevent the sub films37a1-7a5and the sub films35a1-35a5from interfering with each other. This prevents abnormal sounds or the increase in load on the sub films37a1-7a5and35a1-35a5which would otherwise be caused by the sub agitating film35and main agitating film45interfering with each other.

One way of preventing the sub films35a1-35a5from interfering with the sub films37a1-37a5is to cause the sub agitator30and the main agitator49to rotate in such away that the sub films35a1-35a5and37a1-37a5do not meet at the communication port42when they are rotating. However, such a configuration may lead to complicated design and assembly of the developer holding apparatus5. Employing the circumferential ribs33asimplifies the structure of the developer holding apparatus5and eliminates the complicated configuration of the sub films35a1-35a5and37a1-37a5such that they do not meet at the communication portion42when they are rotating.

If the sub and main agitators30and49are to be designed such that the sub films35a1-35a5and37a1-37a5do not meet at the communication port42when they are rotating, the sub films37a1-37a5should be highly resilient so that the sub films37a1-37a5repel the developer material4sufficiently and restore their original shape. However, when the sub films37a1-37a5repel the developer material4, they may make abnormal sounds.

Second Embodiment

FIG. 15is a perspective view of a main agitator49according to a second embodiment.

The sub agitating film35is formed of polyethylene terephthalate (PET), and has a thickness of 0.1 mm. However, the sub agitating film35may be formed of a variety of materials and have a variety of dimensions. In addition, the sub agitating film35may have more than five sub films. The bar structure34may be formed of other material than ABS resin.

FIG. 16is an expanded view of a pertinent portion of the main agitating film45. The bar structure36and main agitating film45according to the second embodiment will be described with reference toFIGS. 15 and 16. Elements similar to those of the first embodiment have been given the same reference numerals as the first embodiment, and their description is omitted.

The main agitating film45has substantially the same shape as the main agitating film37except that each of sub films45a1-45a5of the main agitating film45has a corresponding pair of cuts or slits45cas shown inFIG. 16that define a deformable strip45atherebetween. The cuts45chave a length k of 2 mm, and are spaced apart by a distance P1of 6 mm.

FIG. 17illustrates the positional relation between the circumferential ribs33aof the shutter33and the cuts45cof the main agitating film45. As is clear fromFIG. 17, each deformable strip45afaces a corresponding one of the circumferential ribs33a.

When the main agitator49rotates, the main agitating film45rotates so that the deformable strip45abetween a pair of cuts45cis brought into pressure contact with a corresponding one of the circumferential ribs33a. Thus, the free ends of the main agitating film45except for the deformable strip45aextend toward the sub chamber38but not further than the inner surfaces of the circumferential ribs33a(FIG. 19), so that the sub agitating film35and main agitating film45do not interfere with each other.

The operation of the developer holding apparatus5will be described. Just as in the first embodiment, the developer holding apparatus5shipped from the factory holds a large amount of the developer material4as shown inFIG. 11.

FIG. 18illustrates the operation of the developer holding apparatus5according to the second embodiment.

FIG. 19is an expanded view of a portion depicted at “d” inFIG. 18. The pertinent portion of the operation of the developer holding apparatus5will be described with reference toFIGS. 18 and 19. Referring toFIG. 18, when the main agitator49rotates, the developer material4is conveyed through the opening33eof the shutter33from the main chamber39into the sub chamber38. The circumferential ribs33aat the opening33ein the shutter33prevent the sub agitating film35from entering the main chamber39. Referring toFIG. 19, the deformable strip45aof the main agitating film45abuts the corresponding one of the circumferential ribs33a, so that the deformable strip45adeflects away from the circumferential rib33a, and a base portion45bof the deformable strip45abetween the cuts45cabuts the outer arcuate surface G of the circumferential ribs33a.

It is to be noted that the edge portions of the main agitating film45except the deformable strips45aextend into the openings33efurther than the outer arcuate surface of the circumferential ribs33aand serves to push the developer material4in the sub chamber38toward the opening40. This increases the ability of the main agitating film45to deliver the developer material4into the sub chamber38.

The sub and main agitators30and49rotate further from a position as shownFIG. 13, reaching a position as shown inFIG. 14where the developer material4is pushed by the sub agitating film35toward the opening40.

As described above, the second embodiment provides the following effects in addition to those of the first embodiment. When the main agitating film45rotates and abuts the outer surface of the circumferential ribs33a, the free end portions of the main agitating film45except for the deformable strips45aextend into the openings33ebut not further than the inner circumferential surface of the circumferential ribs33a. This configuration is effective in minimizing the chance of the developer material4being left unused in the main chamber39.

The free end portions except for the deformable strips45aextend into the openings33but do not interfere with the sub agitating film35, thereby eliminating abnormal sounds or the increase in load on the sub films37a1-7a5and35a1-35a5, which would otherwise be caused by the sub agitating film35and main agitating film45interfering with each other.

FIGS. 20 and 21illustrate a first modification to the second embodiment. A main agitating film46according to the first modification has substantially the same shape as the main agitating film45according to the second embodiment. The main agitating film46has L-shaped cuts46bthat define a deformable strip46a. The L-shaped cuts46binclude a short side46b1and a long side46b2. The short side46b1extends in a direction substantially perpendicular to a direction in which rotational shafts36aextend. The long side46b2extends in a direction substantially parallel to the direction in which the rotational shafts36aextend. The short side46b1has a length k, e.g., 2 mm. The long side46b2has a length P, e.g. 6 mm.

The deformable strip46aabuts the outer arcuate surface of the circumferential rib33a, and provides similar effects to the main agitating film45of those of the second embodiment.

FIGS. 22 and 23illustrate a second modification to the second embodiment. A main agitating film47according to the second modification has substantially the same shape as the main agitating film45according to the second embodiment. The main agitating film47has T-shaped cuts47b. Each T-shaped cut47bincludes a base leg47b1and an upstanding leg47b2disposed centrally normally to the base leg47b1. The base leg47b1extends in a direction substantially parallel to a direction in which the shafts36aextend, and the upstanding leg47b2extends in a direction substantially perpendicular to a direction in which the shafts36aextend, thereby defining two deformable strips47a1and47a2. The upstanding leg47b2has a length k of 2 mm, and extends from a longitudinally middle point of the long side. The base leg47b1has a length 2×P2, e.g., 2×3 mm.

When the main agitating film47rotates, the deformable strips47a1and47a2abut the outer arcuate surface of the circumferential rib33a, providing effects similar to those obtained from the main agitating film45of the second embodiment.

FIGS. 24 and 25illustrate a third modification to the second embodiment. The third modification differs from the second embodiment in that a main agitating film48has a plurality of cutouts48a. The cutout48ahas a depth k, e.g., 2 mm and a width P3, e.g., 3 mm.

When the main agitating film48rotates, the circumferential ribs33aenter the corresponding cutouts48a, providing effects similar to those of the main agitating film45of the second embodiment.

The present invention has been described in terms of a developer material holding apparatus for use in a printer. However, the invention may also be applied to conventional image forming units and image forming apparatus including a facsimile machine, a copying machine, and a multifunction peripheral that is equipped with a developer material holding device and an image forming unit.