1. Technical Field of the Invention
This disclosure generally relates to image forming apparatuses, and more specifically, to an image forming apparatus capable of preventing waste liquid from accumulating at a certain place in a drain reservoir.
2. Description of the Background
An image forming apparatus used as a printer, facsimile machine, copier, multi-functional device thereof, or plotter may have a recording head configured as, for example, a liquid discharge head for discharging liquid droplets of a recording liquid such as ink. Such image forming apparatuses discharge liquid droplets of a recording liquid from nozzles of the liquid discharge head to form a desired image on a recording medium, for example, a paper sheet.
However, in such image forming apparatuses, standby operation, high-temperature and/or low-humidity environment, and low printing frequency may increase the viscosity of the recording liquid, thereby resulting in clogging of the nozzles. Accordingly, such image forming apparatuses generally have a function to maintain and recover the discharge performance of the recording head.
As one example of such a maintenance and recovery function, a conventional image forming apparatus performs an idle discharge operation to discharge liquid droplets not contributing to image recording from nozzles at certain intervals or as needed, thus removing such viscosity-increase liquid from the recording head.
Such a conventional image forming apparatus may also have an idle discharge receiver to receive liquid droplets discharged from the nozzles during such an idle discharge operation. In such an idle discharge receiver, color materials, for example, pigment or dye, contained in a recording liquid may accumulate and grow over time. If such growth of accumulated color materials is not removed, the accumulated color materials may come into contact with a nozzle formation face of the recording head, thereby resulting in an operation failure of the recording head.
Hence, several measures have been proposed to deal with such accumulated materials.
In one example, a conventional inkjet image forming apparatus has a cleaning unit to prevent overflow or contamination of waste liquid. The cleaning unit includes a suction device to suction ink from discharge orifices, an ink passage tube through which to pass the suctioned ink, a drain reservoir to store the ink drained through the ink passage tube, and a shifting unit to shift a position of an end opening of the ink passage tube. When performing a cleaning operation using the cleaning unit, the conventional inkjet image forming apparatus shifts the position of the end opening of the ink passage tube so that such waste ink is relatively uniformly distributed over substantially an entire floor area of the drain reservoir.
In one example, a waste-liquid removal structure is proposed for a conventional inkjet image forming apparatus. The conventional image forming apparatus has a tube to guide waste liquid into a waste liquid tank, and an end opening of the tube is disposed at a certain height relative to the waste liquid tank. In order to remove the waste liquid accumulated below the end opening of the tube, the waste-liquid removal structure has a belt conveyor horizontally disposed in the waste liquid tank and a scraper uprightly disposed on a bottom portion of the waste liquid tank.
However, the above-described conventional inkjet image forming apparatuses have certain disadvantages, for example, relatively large size or highly complex configuration.
In one example, a conventional inkjet recording apparatus has a configuration in which an end opening for pigment waste liquid and an end opening for dye waste liquid are positioned adjacent each other. Such a configuration allows the two types of waste liquids to mix, thereby dissolving a solid deposit of the pigment waste liquid or suppressing solidification and accumulation of such pigment waste liquid. However, in such a conventional inkjet recording apparatus, pigment component may not be fully dissolved and therefore may result in the fixation and accumulation of such pigment waste liquid.
In one example, a conventional liquid discharge apparatus has a controller to change the rotation speed of a tube pump. In the conventional liquid discharge apparatus, the controller controls the tube pump to rotate at a relatively high speed for a given time period and then rotate at a relatively low speed for a given time period. However, such a configuration may need a relatively complex control operation to change the rotation speed of the tube pump. Moreover, repeating such a relatively complex speed change may adversely affect the durability of the tube pump.
In one example, for a conventional image forming apparatus, an idle discharge receiver is proposed that removes deposits of waste liquid accumulated at a slope portion that is provided to receive a recording liquid. The idle discharge receiver has a swing member including a plurality of swing plates coupled with coupling ribs. The swing plates are reciprocated parallel to a surface of the slope portion while keeping away from the slope portion. However, such a configuration has a disadvantage that, as the amount of ink attached to the swing member increases over time, such ink may intrude into gaps among components, so that the movement of the swing member may be prevented.
Thus, there is still a need for an image forming apparatus having a simple configuration and capable of relatively uniformly draining of waste liquid into a drain reservoir while maintaining stable operation without an increase in overall size.