1. Field of the Invention
The present invention relates to a powder conveying apparatus that conveys powder contained in a powder container to a discharging unit, an image forming apparatus that includes the powder conveying apparatus, and the powder container.
2. Description of the Related Art
Electrophotographic image forming apparatuses, such as copiers, printers, facsimile machines, or multifunction peripherals having functions of copiers, printers and facsimile machines, generally form images by causing developing devices to form toner images with developer called toner or carrier. In such image forming apparatuses, toner is consumed through image formation; therefore, in general, toner cartridges containing toner are attached to the image forming apparatuses and when the toner cartridges become empty of the toner, the toner cartridges are replaced with new ones in order to replenish new toner.
In a toner supply system using the cartridges as described above, there is a user's demand to use up all toner in the cartridges in order to reduce running costs. Therefore, various methods have been employed, such as a method in which what is called a screw bottle that is a cylindrical container provided with an inner-mounted spiral protrusion is used as a toner cartridge and toner is gradually conveyed to a discharging unit by rotating the container, or a method in which a screw typically called an auger is provided inside the container and toner is conveyed to a discharging unit by rotating the screw.
In the conveying system using the auger, it is needed to arrange and rotate the screw inside the container, so that the configuration becomes complicated. Furthermore, in this conveying system, because a stack of toner is forcibly conveyed by the auger, load is applied to the toner and the toner may be aggregated or deteriorated. Moreover, arranging the screw inside the container that is a replaceable part leads to increase in costs of consumables, so that environmental loads increase because of resource consumption.
On the other hand, in the conveying system using the screw bottle, it is not needed to arrange a screw inside the container. Therefore, the configuration becomes simple. However, in this conveying system, because the container itself is rotated when it is used, the container usually has a shape of a cylinder with an outlet arranged on one side surface of the body thereof (a shape like a bottle being laid down). Therefore, the container is disadvantageous in that the capacity for housing toner becomes smaller than a container in a rectangular-solid shape or the container may be too slippery for a person to hold when the container is replaced.
Besides, the container provided with the inner-mounted auger or the screw bottle is constructed of a container called a “hard bottle” that is made of polyethylene terephthalate (PET) or the like. Therefore, there is a problem in recycling used containers. Specifically, while used containers are generally collected from users by manufacturers and then recycled, reused, or incinerated, because it is difficult to squeeze the containers of the hard bottle type to reduce the volume of the containers, the containers become bulky and costs for collection and transportation increase. Furthermore, when the collected containers are refilled with toner for reuse, there is a difficulty in cleaning the collected containers and toner filling efficiency is not good. Therefore, costs for reusing the collected containers also increase.
Alternatively, as a toner conveying system that does not use the screw bottle and the auger, there is a method in which a container is caused to oscillate (reciprocating movement) by applying shock to the container from outside or by bringing the container into contact with a stopper so that toner can be moved and discharged with the aid of the inertia force thereof (see Japanese Patent Application Laid-open No. 2002-46843, Japanese Patent Application Laid-open No. 2002-268346). In this system, when a large amount of toner is contained, the toner stacked in the container collectively moves by the oscillation, so that a satisfactory toner conveying speed can be assured per reciprocating oscillation. However, as the amount of toner in the container decreases, a stack of the toner collapses and the toner is thinly spread, so that the toner conveying speed per reciprocating oscillation decreases with a decrease in the height of the stack of the toner. Therefore, the conveying speed cannot be maintained. Furthermore, a writing system may be influenced by the oscillation of the container and image distortion may occur. Moreover, it takes a long time to fluidize the toner or the toner may be aggregated (blocked) due to an action similar to tapping that occurs by the oscillation.
There is a known developer supply device, in which a nozzle is inserted into a flexible container that houses toner and the toner is sucked out by a pump through the nozzle so as to be supplied to a developing device (see Japanese Patent Application Laid-open No. 2005-91879). In the toner supply system of this type, the volume of the flexible container is automatically reduced as the toner is sucked out by the pump. Accordingly, when the container becomes almost empty of the toner, the container is in a squeezed state. Therefore, costs needed to collect, transport, and reuse the used container can be reduced. Furthermore, because the volume of the container is reduced in accordance with the amount of toner remaining in the container, it is advantageous in that the amount of remaining toner can be recognized by the appearance of the container.
However, in the system in which the toner is sucked out by the pump, a discharge port of the container needs to be arranged with face down so that the toner can be easily sucked out through the discharge port (suction port). If the discharge port is arranged sideways and the container is placed in the horizontal direction, it is impossible to collect the toner to the vicinity of the discharge port by gravity, and the toner may be cross-linked and remain in the container without being discharged. Therefore, the container of this type, in which the toner is sucked out by the pump, cannot be placed in the horizontal direction, and the ways to place the container are largely limited. Specifically, to smoothly discharge the toner from the container, the container needs to be inclined by 50° or more with respect to the horizontal plane when the container is placed. Therefore, in the configuration using the container of this type, it is needed to ensure an installation space for a container that is practically long in a vertical direction. As a result, it is difficult to reduce the size of the entire image forming apparatus in the vertical direction.
As a method for discharging toner from a flexible container without using the pump as described above, a method has been proposed in which a convex member is pressed against and moved along a container from the outside of the container such that contained toner is pushed out through a discharge port (see Japanese Patent Application Laid-open No. H11-143195). With this method, it is possible to discharge toner even when the container is placed so as to extend in the horizontal direction.
However, in the configuration in which the toner is discharged by pushing the container by the convex member as described above, if the toner is packed due to the pressing action of the convex member, toner discharging may be inhibited. In the worse case, blocking may occur due to aggregation of the toner and the toner cannot be discharged from the container.
Japanese Patent Application Laid-open No. 2006-258926 discloses an image forming apparatus that includes a toner discharge port formed on a bottom plate of a toner cartridge; a shutter that closes the discharge port; and a shutter open-close mechanism that opens and closes the shutter. The shutter open-close mechanism opens the discharge port in accordance with an operation of attaching the toner cartridge to an apparatus main body and closes the discharge port in accordance with an operation of pulling the toner cartridge out of the apparatus main body. The shutter open-close mechanism includes engagement concave portions formed on left and right side surfaces of the shutter in the attachment direction; and engagement pins as engaging members that are arranged on the apparatus main body side and that are engaged with and disengaged from the engagement concave portions. The engagement pins engaged with the engagement concave portions are supported by an engagement maintaining means to maintain the engaged state.
When the toner cartridge is inserted and reaches near a predetermined position, the engagement pins arranged on an oscillation tray enter guide grooves arranged on a bottom plate member. At this time, the engagement pins are biased in a direction along the inner wall surfaces of the guide grooves by a spring and move relative to the movement of the toner cartridge. Inclined surfaces that shift the engagement pins outward are formed on the guide grooves, and when the inclined surfaces come into contact with the engagement pins, the engagement pins move outward. Engagement aid protrusions are formed at end positions of the inclined surfaces on the outer wall surfaces of the guide grooves. When the engagement pins pass over the inclined surfaces, the engagement pins receive a moving force from the spring and move inward. At the same time, the engagement pins come into contact with the engagement aid protrusions, so that the engagement pins are reliably engaged with the engagement concave portions of the shutter. With this engagement, the movement of the shutter is stopped while the movement of the toner cartridge is continued, so that the shutter is gradually opened to thereby open the toner discharge port.
On the other hand, when the toner cartridge is pulled out, the shutter is gradually closed. When the engagement pins engaged with the engagement concave portions are returned to the positions of the engagement aid protrusions, the shutter completely closes the toner discharge port. After the shutter closes the toner discharge port, the engagement pins come off from the engagement concave portions. Therefore, the discharge port is completely closed when the toner cartridge is pulled out, so that it is possible to prevent toner dispersion or toner leakage at the time of replacement.
However, if the toner cartridge is repeatedly replaced while the image forming apparatus is used over time, the spring is repeatedly expanded and contracted by the engagement and disengagement of the engagement pins with the engagement concave portions along with the shutter open-close operation. Accordingly, elastic fatigue occurs on the spring and the spring may be deteriorated. If the spring is deteriorated, it becomes difficult to bias the engagement pins by the spring with a desired biasing force, so that the engagement pins may not be engaged with and disengaged from the engagement concave portions. As a result, it becomes difficult to successfully open or close the shutter over time.
As a conveying system different from the above conveying systems, there is proposed a system in which a deformable container is used and a delivery member is pressed against and moved along the container from outside to discharge contained toner (see Japanese Patent Application Laid-open No. H11-143195 (Japanese Patent No. 3548402)). With this conveying system, it is possible to convey the toner with small stress, prevent aggregation or deterioration of the toner, and prevent occurrence of abnormal images due to large oscillation or shock. Furthermore, because it is possible to reduce the size of the container, when used containers to be recycled are collected and transported from user sites to manufacturers because of replacement of cartridges or bottles, the collection and the transportation can be performed easily at lower costs.
There is also a known developer supply device in which a nozzle is inserted into a discharge hole arranged on a flexible container, developer sucked out by a pump through the nozzle is supplied to a developing device, and the volume of the flexible container is automatically reduced in accordance with the supply of the developer (see Japanese Patent Application Laid-open No. 2006-085067).
Such a flexible powder container that does not have a conveying member inside thereof is advantageous in that the volume of the container can be reduced at the time of collection. However, to ensure the powder conveyance, it is difficult to place the powder container such that a longitudinal side extends in the horizontal direction. Therefore, it is difficult to place the powder container parallel to the developing device to reduce the size of the entire image forming apparatus. Specifically, if a spiral groove is formed on the flexible powder container and the container is rotated to supply developer, the container is twisted by the rotation and the developer cannot be conveyed. Furthermore, if developer is to be conveyed without arranging a delivery member inside the container, it is difficult to obtain an angle at which the gravity is utilized to move the developer. As a result, the developer may be cross-linked and remains in the powder container without being discharged. As described above, because it is difficult to place the conventional flexible developer container (powder container) in the horizontal direction, the container needs to be inclined toward the discharging unit by an angle (normally, 50° or greater) slightly greater than the repose angle of the powder. Therefore, the container that is practically long in the vertical direction needs to be arranged, so that the shape of the image forming apparatus, the capacity of the container, and the arrangement of the container are largely limited.
In the above-mentioned system in which the delivery member is pressed against and moved along the deformable container from outside in order to discharge the contained toner, air in the container is also pushed out by the stack of the toner in the container in some cases, and a greater amount of toner than needed may be discharged by the airflow. To prevent the excessive amount of toner from being discharged by air, an air filter that releases air to the outside may be arranged on a toner discharge path. However, the air filter may be gradually clogged and needs to be replaced periodically.