Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-03-09
2001-11-20
Nguyen, Judy (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S023000, C347S033000
Reexamination Certificate
active
06318835
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to an ink-jet printer, and more particularly, to an ink-jet printer having a maintenance mechanism for preventing a malfunction of a recording head of the ink-jet printer.
2. Description of the Related Art
Conventionally, many types of ink-jet printers having cleaning mechanisms have been known. In such ink-jet printers, ink drops are ejected from nozzles of a recording head toward a recording medium, which is being transported by a transporting device (e.g., platen roller). When the recording head is not in use (that is, when the printing operation is not performed), the nozzle surface of the recording head is covered with a suction cap, and the ink remaining in the recording head is sucked out by a suction pump via the suction cap. The nozzle surface is subsequently wiped by a wiper to keep the recording head clean.
U.S. Pat. No. 5,138,343 discloses an ink-jet printer as discussed above. In general, the suction cap is moved toward, and drawn back from, a cleaning position by a carriage-driving motor and an associated cam. The suction pump is activated by a paper-feed motor and another cam. Thus, the actions of the suction cap and the suction pump are controlled separately using different driving power sources. The wiper is always positioned at the cleaning position on the sliding path of the carriage.
Because the suction cap and the suction pump are activated by separate cams and motors in the conventional ink-jet printers, the structure and control of the cleaning mechanism are complicated.
SUMMARY OF THE INVENTION
This invention was conceived to overcome the problems of the conventional art. Specifically, it is an object of the invention to provide an ink-jet printer with a maintenance mechanism, which has a simple structure and requires a simple control operation. In order to achieve this object, a paper-feed motor is used to activate not only the platen roller but also the suction cap, the suction pump, and the wiper to clean the recording head.
The ink-jet printer with a maintenance mechanism according to the invention comprises a recording-medium transporter for transporting a recording medium, a driving unit for driving the recording-medium transporter, and a recording head having a nozzle surface in which a plurality of nozzles are provided to eject ink drops. The ink-jet printer also has a suction cap for covering the nozzle surface, a suction pump for sucking ink out of the recording head via the suction cap, and a wiper for wiping the nozzle surface of the recording head. A carriage holds the recording head. A lock secures the carriage at a predetermined position. The suction cap, the suction pump, and the wiper are driven by a cam which receives a driving force from the driving unit. A power connection/disconnection mechanism is provided to transfer the driving force of the driving unit to the cam and cut off the power transfer at a desired timing.
The ink-jet printer further comprises a shifting mechanism for moving the recording-head between a recording area, where the recording operation is performed on the recording medium, and a maintenance area, where the recording head is cleaned using the suction cap, the suction pump, and the wiper. The power connection/disconnection mechanism has a coupler. When the recording head enters the maintenance area, the coupler allows the driving force to be transferred from the driving unit to the cam to activate the suction cap, the suction pump, and the wiper.
The driving unit is a single driving motor. The recording-medium transporter is, for example, a platen roller. The cam is driven by the single driving motor in the forward direction.
The cam comprises a first cam surface for moving the suction cap and the wiper held on the associated holders forward toward, and backward from, the nozzle surface of the recording head, and a second cam surface for activating the suction pump.
The power connection/disconnection mechanism has a stepped gear that is movable along its gear shaft. The coupler has a first lever, a second lever, and a link coupling the first and second levers. The first lever contacts the carriage on which the recording head is mounted when the carriage moves to the maintenance area. The second lever causes the stepped gear to move along its gear shaft.
The suction pump comprises a first piston, a second piston, and a pump housing. The first and second pistons and the housing define a pump chamber. The volume of the pump chamber varies depending on the positions of the first and second pistons. The second cam surface of the cam has a groove for driving the first piston, and a groove for driving the second piston.
The cam also has a third cam surface that extends between the first and second cam surfaces. This third cam surface causes the lock to move between a locked position and an unlocked position.
Grooves are formed in the second cam surface so that the suction pump performs a first suction with a small vacuum and a second suction with a large vacuum in one revolution of the cam.
The cam is provided with grooves on the opposite surface. These groove are designed so that the suction cap is brought onto the nozzle surface to allow the ink to be sucked out of the recording head by the suction pump during the first suction, and the suction cap is gradually separated from the nozzle surface to discharge the ink from the suction cap by the suction pump during the second suction.
A cap holder for holding the suction cap also has a preservation cap for covering the nozzle surface of the recording head when the recording operation is not performed. A pivoting guide is provided to guide the preservation cap directly over the nozzles and seal the nozzle apertures.
In accordance with the ink-jet printer of the invention, the driving unit for driving the recording-medium transporter is also used to drive the cam for activating the suction cap, suction pump, and the wiper. This structure reduces the number of elements used in the ink-jet printer and, consequently, the entire cost can be reduced. In addition, by simply rotating the cam by one revolution, a maintenance cycle is completed by the suction cap, the suction pump, and the wiper. Because the cam is rotated in only one direction (i.e., in the forward direction), it is not necessary to consider backlash.
When the recording head is slid from the recording area to the maintenance area, the driving unit is connected to the cam via a gear train which meshes via the coupler. Thus, simple lateral movement of the recording head allows the cam to rotate in the forward direction, which activates the suction cap, the suction pump, and the wiper to clean the recording head.
The suction pump is activated by the second cam surface. The suction cap and the wiper are driven by the first cam surface. Thus, the suction pump is operated independently from the suction cap and wiper with a single cam. This structure greatly simplifies the control operation.
The recording head can be secured at a predetermined position in the maintenance area by the lock which is activated by the third cam surface.
A maintenance cycle is completed by moving the suction cap and the wiper toward the recording head, sucking the ink out of the recording head using the suction pump, and drawing the suction cap and the wiper back.
In this cycle, when the suction cap covers the nozzle surface, the ink is sucked out of the recording head into the suction cap by the suction pump. Then, at least a portion of the suction cap is removed from the nozzle surface, and the ink is discharged from the suction cap by the suction pump. With this two-step suction, the ink remaining in the recording head can be efficiently removed.
In particular, two kinds of suctions are performed in a cycle under a small suction and a large suction. This can prevent air from mixing into the ink which is flowing through multiple ink paths and generating air bubbles in the recording head.
REFERENCES:
patent: 5115250 (1992-05-01), Harmon et al.
patent:
Brother Kogyo Kabushiki Kaisha
Hsieh Shih-Wen
Nguyen Judy
Oliff & Berridg,e PLC
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