Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
1999-03-15
2001-04-24
Tran, Huan (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
76
Reexamination Certificate
active
06220700
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an ink jet recorder that comprises a print head capable of moving vertically up and down relative to the recording paper, and particularly to an ink jet recorder exhibiting good printing performance irrespective of the vertical position of the print head relative to the recording paper.
2. Description of the Related Art
There are two common types of ink jet recorder, namely the integrated head-ink tank type of recorder wherein a small capacity ink tank is contained integrally in the print head, and the separate head and ink tank type of recorder which comprises a large capacity ink tank positioned independently of the print head and wherein ink is supplied to the print head via a tube from the ink tank. Among the latter type of recorder are those which, in view of design or space considerations, or because of the existence of a plurality of printing areas, comprise a print head that can be moved vertically inside the main recorder unit and thus have its up and down position changed.
In the separate head and ink tank type of recorders having print heads that can be moved up and down, the ink tank is fixed in a stationary position, wherefore, when the vertical position of the print head is changed, the positional relationship in the vertical dimension between the print head and the ink tank changes accordingly. As a result of changes in this positional relationship, the back pressure (water head) acting on the print head varies, which can have an adverse effect on printing performance.
SUMMARY OF THE INVENTION
The present invention has been devised in view of the such defects in recorders based on the prior art. An object of the present invention is to provide an ink jet recorder wherein the printing position is varied in the up and down direction, and wherewith the ink back pressure acting on the print head can be maintained more or less constant, irrespective of the position of the print head, so that good printing performance can be secured.
According to a first aspect of the present invention, an ink jet recorder is provided which comprises: an ink jet head for ejecting ink onto a recording medium; an ink tank for supplying ink to the ink jet head; an ink jet head moving device for moving the ink jet head up and down relative to the ink tank; a head position detector for detecting the up and down position of the ink jet head; and a pressure adjuster for adjusting the pressure of the ink supplied to the ink jet head from the ink tank based on detection signals from the head position detector.
By implementing the ink jet recorder of the present invention, the up and down position of the ink jet head is detected by the head position detector, and the ink pressure acting on the ink jet head is maintained more or less constant by the pressure adjuster based on the detection results, irrespective of the vertical position of the head. Thus constant printing performance can be secured.
In the recorder of the present invention, the pressure adjuster may comprise a fluid level regulator attached to the ink tank for varying the height of the ink level in the ink tank, and a controller that drives the fluid level regulator based on detection signals from the head position detector, thereby controlling the ink level height in the ink tank. The ink pressure acting on the print head can easily be adjusted by using such a fluid level regulator to vary the ink level in the ink tank. The fluid level regulator may be an ink tank moving device for moving the ink tank up and down. The ink fluid level can easily be varied with the ink tank moving device.
The ink tank moving device may be configured, for example, with a rack attached to the ink tank, extending vertically up and down, a pinion gear that meshes with the rack, and a drive device for turning the pinion gear. The ink jet head moving device may comprise a carriage for holding the ink jet head, a support member that supports the carriage so that it can be moved up and down, and a carriage drive device for moving the carriage on the support member and along the support member. The support member may include a horizontal beam for supporting part of the carriage so that it can slide and a pair of vertical beams that support both ends of the horizontal beam so that it can slide. By the ink head moving device, the ink jet head is made freely movable up, down, left, and right in a plane parallel to the recording medium. The carriage drive device may contain, for example, a pair of pulleys, a belt wound about the pulleys and joined to the carriage, and a motor for turning one of the pulleys.
The ink jet recorder of the present invention may also comprise a purging device having a suction cap that caps the ink jet head and sucks ink therefrom. The pressure adjuster may cause a negative pressure to act on the ink jet head, according to the up and down position of the head, when the ink jet head is recording, and may cause a positive pressure to act on the ink jet head nozzle or nozzles when the ink jet head is being purged by the purging device through the suction cap. When the ink jet head is in a printing area, the ink pressure acting on the ink jet head is maintained more or less constant, irrespective of the up and down position of the head, as already described. When the print head is in a restoration area (maintenance area) for which the purge device is provided, on the other hand, a positive pressure is made to act on the nozzle or nozzles of the ink jet head, whereby air bubbles once sucked from the ink jet head by the suction purge are prevented from flowing back inside the print head after the suction operation is finished.
According to a second aspect of the present invention, an ink jet recorder is provided which comprises: an ink jet head for ejecting ink onto a recording medium; an ink tank for supplying ink to the ink jet head through a tube; a head moving device for moving the ink jet head up and down relative to the ink tank; and a pressure adjuster for adjusting the pressure on the ink supplied from the ink tank to the ink jet head, in response to the movement of the ink jet head by the head moving device.
With the ink jet recorder according to the second aspect, the pressure adjuster adjusts the pressure on the ink supplied to the ink jet head from the ink tank in response to the movement of the ink jet head by the head moving device. Thus the ink pressure acting on the ink jet head is maintained more or less constant, irrespective of the up and down position of the head, and constant printing performance is assured. The pressure adjuster may comprise a fluid level regulator attached to the ink tank for varying the height of the ink level in the ink tank, and a controller for controlling the ink level in the ink tank by driving the fluid level regulator in response to the movements of the ink jet head by the head moving device. The fluid level regulator may be an ink tank moving device for moving the ink tank up and down, and a control circuit may be configured so that the drive signals input to the head moving device are also input to the ink tank moving device. When this is done, the ink tank can be moved up and down synchronously with the ink jet head.
REFERENCES:
patent: 5969735 (1999-10-01), Haigo
patent: 10-129003 (1998-05-01), None
Brother Kogyo Kabushiki Kaisha
Oliff & Berridg,e PLC
Tran Huan
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