Abstract: According to the various aspects of the invention, a method and apparatus for mixing electrographic developer is provided. An elongate shaft having two ends and an intermediate location between the two ends is rotated. Developer is moved away from the intermediate location toward one of the ends with an inner helical ribbon mounted concentrically to the elongate shaft for rotation therewith. Developer is moved away from the one of the ends toward the intermediate location with an outer helical ribbon mounted concentrically to the elongate shaft for rotation therewith, the inner helical ribbon is disposed within the outer helical ribbon. Developer is moved away from the intermediate location toward another of the ends with another inner helical ribbon mounted to the elongate shaft for rotation therewith.

Abstract: The developer replenishment apparatus includes a first developer container for accommodating the developer for replenishment, a first conveyance member disposed in the first developer container to discharge the developer for replenishment through a first opening of the first developer container, a second developer container for receiving the developer for replenishment discharged from the first opening, an agitating member disposed in the second developer container to agitate the developer for replenishment, a second conveyance member disposed in the second developer container to discharge the developer for replenishment through a second opening of the second developer container toward the developing apparatus, and a driving device which does not drive the second conveyance member but drives the agitating member when driving the first conveyance member. The bulk density of the developer is thereby stabilized to make possible replenishment with the developer at high accuracy.

Abstract: In a device and method for developing a charge image on a photoconductor of an electrophotographic printer or copier, a developer chamber is provided having a first and a second end in which at least a portion of the developer is contained. A mixer is provided for thoroughly mixing the developer in the developer chamber. The mixer generates a flow of the developer that is directed from a first end of the developer chamber to a second end. An inlet for developer is provided at the first end of the developer chamber and an overflow is provided at the second end. The developer exits the developer chamber via the overflow when its level in the region of the second end exceeds a prescribed height. A conveyor conveys the developer that has exited the developer chamber at the overflow toward the inlet.

Abstract: A developing unit has first and second partition walls and which divide the inside of a developer reservoir into first to third chambers parallel to the developing roller, and first to third mixers which are disposed in the first to third chambers. The first mixer supplies developer to the developing roller by stirring and carrying from one end side to the other end side. The second mixer feeds by stirring and carrying the toner replenished from a replenish device and developer fed from the first chamber to one end side of the first mixer. The third mixer feeds the toner collected from a collection mechanism to one end side of the first mixer by stirring and carrying at a speed lower than the second mixer.

Abstract: A toner/developer mixing roller is rotatably disposed in an inside of a housing to mix a developer with toner supplied into the housing to supply a mixture of the developer and the toner to a developing roller. The toner/developer mixing roller includes a roller body and a sheet of a reticular form rolled around the roller body.

Abstract: An apparatus and method for dampening annoying resonance noise in auger systems. The dampening effect is accomplished by an insert placed within an inner bore of an auger. The insert itself may be continuous or in segments and be comprised of material capable of absorbing vibrational energy. One embodiment of an insert is a tube that is purposefully cut longer than the auger itself in order to induce bending of the tube and contact with the sides of the auger bore.

Abstract: An object of the present invention is to provide a developing apparatus capable of reducing unevenness of density of an image in a longitudinal direction of a photosensitive member. For this purpose, in the present invention, a developing apparatus includes a developer bearing member, and a developer carrying screw placed adjacently to the developer bearing member in parallel with the developer bearing member, and an inclination angle of “a carrying surface facing in a developer carrying direction of a spiral blade of the developer carrying screw” to a shaft of the developer carrying screw is equal to or less than 60 degrees.

Abstract: The image forming apparatus has a communicating portion from the first chamber 24 to the second chamber 25, and a communicating portion from the first chamber 24 to the third chamber 26, which are separated from each other. With this structure, an active flow of fresh toner into the third chamber 26, where a developer having a low toner ratio and low toner concentration is stirred together with recycle toner during an image forming operation is suppressed.

Abstract: A developing apparatus includes a rotatable, developer carrying body for carrying a one-component developer and a rotatable, agitating member for agitating the one-component developer. The one-component developer is magnetic toner at least containing a bonding resin and magnetic iron oxide. When wettability of the magnetic toner relative to a mixture solution of methanol and water is measured at the transmittance of light having a wavelength of 780 nm, a methanol concentration at the transmittance of 80% is within the range of 45 to 65 volume %, and wherein 0.1?b/a?0.2 is established where a (rps) denotes the rotation speed of the developer carrying body, and b (rps) denotes the rotation speed of the agitating member.

Abstract: An image forming apparatus includes a first developing device and a second developing device for developing an electrostatic latent image formed on an image bearing member and a developing portion; a rotatable member supporting the first and second developing devices, the rotatable member being rotatable along a path through the developing portion; a first developer supply container and a second developer supply container, supported on the rotatable member, for supplying developer into the first developing device and into the second developing device; wherein the developer in the first developer supply container is fed using rotation of the rotatable member, whereas the developer in the second developer supply container is fed without using rotation of the rotatable member.

Abstract: A developing device has a rotary developer carrier, a rotary developer supply and collection member, a first and second rotary developer stirring members for stirring the developer while conveying and circulating the developer between them in the direction opposite to each other and having the same developer conveyance power, and a third rotary developer stirring member having a zero conveyance power in the rotary axis direction, which are provided in a housing in parallel with each other in this order in the direction to leave a latent image carrier. A toner replenishment inlet is provided at an upper part where the second and third stirring members face each other, and on an upstream side of the second stirring member in the developer conveyance direction, and the second and third stirring members are rotated downwardly at the position where both developer stirring members face each other.

Abstract: A developing apparatus having a developing container for containing developer including toner and carrier, and developing an electrostatic image formed on an image bearing member, includes a carrying member for carrying the developer in the developing container, and a discharge port provided in the developing container for discharging any excess developer resulting from the supply of the developer. The developer carrying capability of the carrying member is greater in an area near the discharge port than in an area downstream of the discharge port in the carrying direction of the developer.

Abstract: An image forming apparatus includes: a developing device; a container for containing developer; a developer detector for outputting an output signal corresponding to presence or absence of developer, the developer detector being attached to a wall surface of the container so that a detector plane faces toward inside of the container; an agitating device for sliding on the detector plane of the developer detector and for agitating developer in the container; a controller for controlling a movement speed of the agitating device so that a relation between rise time T0 required for rise of the output signal outputted from the developer detector and time T1 when the agitating device covers the detector plane of the developer detector meets T0>T1.

Abstract: A developing device 31 includes three shielding members 20 that divide an inner space of the developing device 31 into a developing chamber 23 and toner hopper chambers 21. The shielding members 20 in predetermined conditions prevent toner inside the developing chamber 23 from entering the toner hopper chambers 21. When toner empty condition of the developing chamber 23 is detected, the shielding member 20a is driven to rotate so as to supply toner 22a into the developing chamber 23. When the toner empty condition is detected for the second time, then the shielding members 20a, 20b are driven to rotate for supplying toner 22b to the developing chamber 23. In this manner toner can be supplied to the developing chamber 23 without allowing the toner returning to the toner hopper chambers 21.

Abstract: A developer is carried to a developing region by a developer carrier and develops a static latent image formed on a latent image carrier. The developer to be supplied to the developer carrier is circulated in a first circulating path while being stirred. The developer also is circulated in a second circulating path. Here, at least a part of the first circulating path and at least a part of the second circulating path are common, intersect or contact each other. In a portion where both of the circulating paths are common, intersect or contact each other, a part of the developers in both of these paths are interchanged. In this manner, an image whose image density is uniform and stable can be obtained. Further, it is possible to achieve a small developing device that includes a long-life developer.

Abstract: The developer agitating member has a shaft portion, a spiral rib and an inclined rib protruding from the outer peripheral surface of the shaft portion and provided in the spiral rib in the axial direction of the shaft portion. As a result, in a developing apparatus, a process cartridge and an image forming apparatus, the developer agitating member can efficiently agitate and convey a developer.

Abstract: When a sensor in an image forming device detects fog on the photosensitive belt, the CPU of the image forming device controls the shutter in each toner hopper unit to open and drives a discharging auger to rotate, causing degraded toner to be discharged from the developing chamber into a waste toner accommodating chamber. After this discharging operation is completed, the CPU closes the shutter and begins driving a supply auger to rotate in order to supply new toner from the accommodating chamber into the developing chamber, thereby replacing most of the old toner in the developing chamber with new toner.

Abstract: A replaceable toner cartridge for a printing apparatus includes a waste toner auger rotationally driven by a printer drive gear. The auger includes a drive element for engaging the printer drive gear. The auger drive element includes drive paddles extending radially from the auger shaft. Each drive paddle has a radial edge adjacent an inclined radial face surface, so that the as the auger drive element and the printer drive gear axially engage one another, the drive paddles of the auger drive element and the gear lobes of the printer drive gear slide along one another until the auger drive element and the printer drive gear solidly engage one another. Each drive paddle also has an extension perpendicular to the radial direction of the paddle to increase the spacing between the axial engagement surface of the printer drive gear and the radial edge of the drive element paddle.

Abstract: A developing device includes a developer bearing member and a developer container for containing a developer therein. The developer container has a plurality of developer containing rooms (chambers) provided with developer conveyers for conveying the developer toward the developer bearing member. The rotational speed of the developer conveyor in the room nearest to the developer bearing member is higher than that of the developer conveyers in the other rooms, or the volume of the room nearest to the developer bearing member is smaller than that of the other rooms, or the thickness of the developer conveyer in the room nearest to the developer bearing member is smaller than that of the developer conveyers in the other rooms, or the Young's modulus of the developer conveyor in the room nearest to the developer bearing member is smaller than that of the developer conveyers in the other rooms.

Abstract: An object of the present invention is to provide a developing apparatus capable of reducing unevenness of density of an image in a longitudinal direction of a photosensitive member. For this purpose, in the present invention, a developing apparatus includes a developer bearing member, and a developer carrying screw placed adjacently to the developer bearing member in parallel with the developer bearing member, and an inclination angle of “a carrying surface facing in a developer carrying direction of a spiral blade of the developer carrying screw” to a shaft of the developer carrying screw is equal to or less than 60 degrees.

Abstract: The developer agitating member has a shaft portion, a spiral rib and an inclined rib protruding from the outer peripheral surface of the shaft portion and provided in the spiral rib in the axial direction of the shaft portion. Thereby, in a developing apparatus, a process cartridge and an image forming apparatus, the developer agitating member can efficiently agitate and convey a developer.

Abstract: In a developing apparatus, the interior of a case is divided into a first space positioned on a developer supply side for the supply of a developer to an image bearing member and a second space which is supplied with a replenishing toner, first and second agitating members are included and are adapted to be rotated to agitate and convey the developer are disposed within the first and second spaces, respectively, and a screw member is provided having n threads (n≧2) is used as the first agitating member disposed in the first space, and a screw member having (n−x) threads (x≧0) is used as the second agitating member disposed in the second space.

Abstract: The invention relates generally to development apparatus for mixing and applying developer material to a latent image on an image-bearing member in an electrostatographic reproduction machine, such as a copier or printer. More particularly, this invention relates to a blender of the type for mixing electrostatographic developer comprising a plurality of blender segments mounted on a shaft. A resilient spacer is provided, according to an aspect of the invention, wherein said resilient spacer and said plurality of blender segments are compressed between said pair of stops. Residual looseness due to tolerance stack-up is eliminated.

Abstract: A two-component developing device to stir a developer with toners so as to fully and evenly stir the toners. The two-component developing device developer carrying members (1 to 3) for carrying the developer (130) containing carriers and toners, to a latent image carrier (12), a stirring and carrying screw (6) for stirring the toners with the developer. The stirring and carrying screw (6) includes a screw shaft, a spiral screw (61) with a relatively short diameter, and another spiral screw (62) with a relatively long diameter, which are alternately wound around the same screw shaft. By arranging the short-diameter spiral screw (61) as a member for stirring the surface layer of the developer, the developer can be fully stirred while being carried on the face of a blade thereof.

Abstract: A development system including a housing, a developer roll mounted in the housing, for depositing marking particles on an imaging surface having an electrostatic latent image thereon, an auger, for mixing and transporting the marking particles and carrier constituents of the developing material and; transferring mixed developer material to the developer roll, the auger comprising an elongate strip of magnetic material having a helix structure; a nonmagnetic sleeve enclosing the elongate strip of magnetic material; and means for rotating the elongate strip of magnetic material within the nonmagnetic sleeve, the elongate strip of magnetic material generates a magnetic field for transporting the developer material axially along an outer surface of the nonmagnetic sleeve when rotated by the rotating means.

Abstract: A toner transport apparatus for electrographic printing machines that uses the distance between a toner storage container holding a supply of toner material and a developer housing to admix the toner with the developer. A first flexible auger transports the toner from the toner storage container to the developer housing and a second flexible auger transports some of the toner and developer from the developer housing back to the toner hopper where it is mixed with fresh toner.

Abstract: An extended life-toner cartridge provides a set of required agitator paddle movement signals that fall within the expected parameters of the print engine controller—not-withstanding a higher toner level that would normally alter the paddle movement signals beyond acceptable timing ranges. The cartridge includes a toner tank agitator paddle assembly with a paddle movement reporting mechanism that particularly compensates for the larger volume of toner in the tank. In addition, the toner tank can include an enlarged tank extension for increasing reservoir capacity.

Abstract: A cartridge detachably mountable to a main body of an image forming apparatus, includes a developing frame, a developer carrying member provided in the developer frame and adapted to hold and carry developer, a developer containing container for containing the developer and for supplying the developer to the developer frame, a seal member for unsealably sealing an opening portion through which the developer is supplied from the developer containing container to the developing frame, a rotary member for supplying the developer toward the developer carrying member, a first drive transmitting device for effecting drive transmission between the developer carrying member and the rotary member, and a second drive transmitting device for transmitting the driving to the seal member to unseal the seal member.

Abstract: A development system including a housing, a developer roll mounted in the housing, for depositing marking particles on an imaging surface having an electrostatic latent image thereon, an auger, for mixing and transporting the marking particles and carrier constituents of the developing material and; transferring mixed developer material to the developer roll, the auger comprising an elongate strip of magnetic material having a helix structure; a nonmagnetic sleeve enclosing the elongate strip of magnetic material; and means for rotating the elongate strip of magnetic material within the nonmagnetic sleeve, the elongate strip of magnetic material generates a magnetic field for transporting the developer material axially along an outer surface of the nonmagnetic sleeve when rotated by the rotating means.

Abstract: A slide-rotating collar integrally mounted on a resin shaft is configured to have a projected portion at one end of a metallic plate and a recessed portion at the other end thereof such that both ends engageably face each other without aligning in a shaft line direction. The shaft may be used in an electrostatic developing device in an image forming apparatus.

Abstract: A toner container is detachably mountable on an image forming apparatus and includes a container body that contains toner therein. An agitating member is disposed within the container body and agitates the toner within the container body. First and second rotating portions rotate together with a rotary shaft of the agitating member at both end sides of the rotary shaft. The first and second rotating portions are exposed to the exterior of the container body, wherein the container body includes a first mark at a position corresponding to a predetermined position of the first rotating portion and a second mark at a position corresponding to a predetermined position of the second rotating portion.

Abstract: A magnetic brush development station including a housing forming, at least in part, a reservoir for developer material. A development roller is mounted within the housing for delivering developer material from the reservoir to a development zone. A plurality of rotatable augers are located in the housing for mixing developer material within the reservoir, and are arranged substantially side-by-side with respective parallel longitudinal axes, the most outboard of the plurality of augers being positioned to be raised and toward the center with respect to the housing of the development station. Accordingly the overall width of the development station is reduced while maintaining centerline distances between each of the plurality of augers so that individual augers do not interfere with one another.

Abstract: A magnetic brush development station with a housing forming a reservoir for developer material has a plurality of augers located in the housing for mixing developer material. A drive for the plurality of augers includes an assembly having a body extending through the development station housing. A plurality of bearings are positioned in the body with a spacer between the plurality of bearings. A rotatable shaft is connected between the plurality of augers and an auger drive member. A seal for the rotatable shaft has a lip formed of a material which is able to stretch sufficiently to maintain sealing contact with the shaft while the shaft is being rotated by the auger drive member.

Abstract: A developer stirring member, provided in a developer container for accommodating a developer, for stirring the developer, the developer stirring member includes a stirring blade stirring the developer; a rotatable supporting member for supporting the stirring blade, the supporting member being provided with a plurality of projections; wherein stirring blade is provided with a plurality of openings for engagement with the projections, respectively. This provides for easy assembly and recycling.

Abstract: A developing-agent receiving device, to which a developing agent is replenished from a developing-agent replenishment container, includes a developing-agent storage part which is provided with a receiving opening part for receiving the developing agent from the developing-agent replenishment container, and which stores the developing agent, and a stirring unit which is rotatable around a rotary shaft to stir the developing agent within the developing-agent storage part. The stirring unit conveys the developing agent received from the receiving opening part along the rotary shaft of the stirring unit. The stirring unit has a first stirring member of screw shape which is provided in the vicinity of the receiving opening part and a second stirring member which is provided at a position farther away from the receiving opening part than the first stirring member and which is smaller in developing-agent conveying capacity than the first stirring member.

Abstract: A developing device of an image forming apparatus using a two-component developer including toner and carrier includes a developer stirring device to stir the developer to change the toner of the developer, a developing sleeve to rotate and to carry on its surface the developer, and a conductive doctor blade or configured to regulate a thickness of the developer on the developing sleeve. The doctor blade is either grounded or receives a voltage of an electric polarity opposite to that of the toner. An electric potential of the developing sleeve is set to a same electric polarity as that of the toner, and the toner is moved toward a latent image formed on a photoconductor of the image forming apparatus so as to adhere to the latent image by an electric field formed between the developing sleeve and the latent image on the photoconductor.

Abstract: This invention relates to a device for detecting when the magnetic toner in the developing unit of an image formation device is empty, and prevents erroneous detection of empty toner even when the fluidity of the magnetic toner becomes poor. The developing device (3) has a stirring unit (30) having a cleaning member (22) for cleaning the position of a toner sensor (10), a toner accumulation section (24), and a magnetic metal member (21). The magnetic metal member (21) and toner accumulation section (24) for preventing erroneous detection of the toner-empty alarm are located at the sensor position of the stirring unit, so it is possible for the toner sensor to synthetically generate output that toner is detected, and thus making it possible to prevent erroneous detection that the toner is empty.

Abstract: A developing device and an image forming apparatus includes a developer container for containing a developer made up of magnetic particles and a toner; a developer carrier for bearing and transporting the developer; a first agitating and transporting unit provided in the developer container, the first agitating and transporting unit transporting the developer while agitating the developer; a second agitating and transporting unit provided in the developer container, the second agitating and transporting unit transporting the developer transported by the first agitating and transporting unit while agitating the developer, thereby supplying the developer to the developer carrier; and a restricting member provided in the developer container, the restricting member restricting passage of an upper portion of the developer transported by the first agitating and transporting unit, thereby achieving a desired developer surface level.

Abstract: A toner reserve container provided with a toner replenishing roller and a replenishing port which constitute a toner replenishing portion is arranged adjacent to a developing hopper and is provided with a toner conveying unit. The conveying unit includes an agitator rotated about a rotary shaft and a conveying sheet fixed to the agitator and scooping up and conveying toner to the toner replenishing roller. The conveying sheet has a plurality of slits formed close to the end portion where it is fixed to the agitator and extending in the direction from the end portion to the tip end of the conveying sheet. When the conveying sheet is rotated and deformed, the plurality of slits absorb rotational load to keep toner conveyed by the conveying sheet stable for a long period of time.

Abstract: A developer includes a toner container divided by a partition into first and second chambers. The first and the second chambers communicate with each other via first and second openings. A third opening is also formed in the partition for passing excessive toner from the second to the first chamber. The first chamber is provided with a first screw for transferring the toner from the first to the second opening, while the second chamber with a second screw for transferring the toner in the opposite direction. A toner scraping blade is arranged above the second screw. The toner scraped in the second chamber is led into the first chamber through the third opening. Adjusting means is provided for controlling the passage of the toner through the third opening, thereby achieving uniform toner distribution in the second chamber.

Abstract: A toner cartridge including a cartridge body for containing toner, an agitating paddle for agitating toner and a toner blocking/setting prevention member operative in cooperation with the agitating paddle for preventing toner in the cartridge body from blocking or setting is provided. The toner blocking/setting prevention member may include a contacting projection provided on an agitating wing of the agitating paddle which contacts with a delivering spiral to oscillate the same. Further, the toner blocking/setting member may include an oscillating plate which is repelled by the rotation of the agitating paddle to assist in agitating toner.

Abstract: A magnetic brush development station including a housing forming, at least in part, a reservoir for developer material. A development roller is mounted within the housing for delivering developer material from the reservoir to a development zone. A plurality of rotatable augers are located in said housing for mixing developer material within the reservoir, and are arranged substantially side-by-side with respective parallel longitudinal axes, the most outboard of the plurality of augers being positioned to be raised and toward the center with respect to the housing of the development station. Accordingly the overall width of the development station is reduced while maintaining centerline distances between each of the plurality of augers so that individual augers do not interfere with one another.

Abstract: A developing apparatus includes a developer containing portion containing a developer having a weight average particle diameter of not more than 7 &mgr;m, a developer bearing member for bearing a developer, and an agitating member that agitates the developer contained in the developer containing portion. The agitating member is intermittently driven with respect to rotation of a developing sleeve. The agitating member is driven to rotate for one page every time the image forming apparatus performs a predetermined number of printing operations. A rod member having a crank-like shape may be used as the agitating member and both of the end portions serve as the center of rotation. By controlling the drive of the agitating member, it is possible to effectively adjust the supply of toner to the developing sleeve and prevent the density lowering phenomena caused due to inflow of a large amount of the new toner presented at the rear of the developing container.

Abstract: The present invention provides a developing apparatus comprising a developer containing container, an agitating member for agitating developer contained in the developer containing container, a drive transmitting member for transmitting a power to the agitating member by engaging a rotary shaft of the agitating member, and a bearing adapted to rotatably hold the drive transmitting member and attached to the developer containing container, and wherein the bearing has a dislodgment preventing member with respect to the developer containing container.

Abstract: A developing apparatus is equipped with a development casing, a development roller, and developer stirring shafts that rotate together with the development roller. In this developing apparatus, the developer stirring shafts are disposed adjacent to each other and are also disposed substantially in parallel with the development roller. Each developer stirring shaft has a rotational axis that rotates together with the development roller and has a plurality of stirring vanes of an approximately elliptic shape laid out at a predetermined angle with respect to the rotational axis. The rotational axis is provided substantially in parallel with the development roller. The stirring vanes are disposed substantially in parallel with each other, with the opposing stirring vanes between the adjacent developer stirring shafts having mutually different installation positions in the axial direction.

Abstract: A slide-rotating collar integrally mounted on a resin shaft is configured to have a projected portion at one end of a metallic plate and a recessed portion at the other end thereof such that both ends engageably face each other without aligning in a shaft line direction. The shaft may be used in an electrostatic developing device in an image forming apparatus.

Abstract: A developing device for use in an image forming apparatus includes a developing agent supply unit which supplies a developing agent to a photoreceptor, a first mixing unit provided near the developing agent supply unit to convey the developing agent in a first conveyance direction while mixing the developing agent, a second mixing unit provided underneath the first mixing unit to receive the developing agent at a downstream end along the first conveyance direction so as to supply the developing agent to the developing agent supply unit while mixing and conveying the developing agent in a second conveyance direction, and a developing agent scoop-up unit provided substantially in the middle in a height direction between the first mixing unit and the second mixing unit along the second conveyance direction to receive the developing agent from the second mixing unit and draw up the received developing agent to the first mixing unit.

Abstract: Disclosed is in a two-component developing device to stir a developer with the supplied toners so as to fully stir even a large amount of supplied toners. The two-component developing device comprising developer carrying members (1 to 3) for carrying the developer (130) containing carriers and toners, to a latent image carrier (12), a stirring and carrying screw (6) for stirring the supplied toners with the developer. The stirring and carrying screw (6) comprises a screw shaft, a spiral screw (61) with a relatively short diameter, and another spiral screw (62) with a relatively long diameter, which are alternately wound around the same screw shaft. By arranging the short-diameter spiral screw (61) as a member for stirring the surface layer of the developer, the developer can be fully stirred while being carried on the face of a blade thereof.

Abstract: A developing apparatus has a developer container for containing developer, a developer bearing member for bearing the developer within the developer container and for carrying the developer to a position opposed to an image bearing member. A first agitating member agitates the developer within the developer container, and a second agitating member agitates the developer within the developer container. The second agitating member is positioned farther than the first agitating member with respect to the image bearing member and an uppermost part of the second agitating member is higher than an uppermost part of the first agitating member.

Abstract: An image forming apparatus includes a development mechanism using a two-component development agent and which includes a development roller and first and second transfer screws. The first transfer screw, arranged at a position approximately horizontal and in parallel to the development roller, includes a first number of screw spirals for transferring the development agent from a first end to a second end of the first transfer screw and conveying the development agent to the development roller. The second transfer screw, arranged approximately horizontal and in parallel to the first transfer screw, includes a second number of screw spirals for transferring the development agent from a first end to a second end of the second transfer screw and conveying the development agent from the second end of the second transfer screw to the first end of the first transfer screw. The first and second numbers of the screw spirals are different from each other.