Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
1998-01-09
2001-06-12
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
Reexamination Certificate
active
06244698
ABSTRACT:
BACKGROUND OF INVENTION
The present invention relates to an ink jet printer having an ink cartridge and more particularly to a printhead unit and ink cartridge used in an ink jet printer.
A small impact applied to an ink jet printer, for example when the printer drops from a height of about 1 to 2 cm, will destroy the meniscuses in the nozzle plane of the printhead. When the ink jet printer receives an impact, the impact propagates to the printhead unit contained in the printer which causes the ink in the ink passage to begin to pulsate. Because the ink passage is substantially closed by an ink absorbing member (or filter) of the ink cartridge, the pulsation of ink is reflected from the ink cartridge and travels to the nozzles in the printhead thereby destroying the meniscuses in the nozzles. In the ink jet printers currently marketed, the meniscuses may even be destroyed when the printer is merely moved. When the meniscuses are destroyed, a variety of problems may arise including: “nozzle missing” resulting in the improper discharge of ink and the “bending” of the shooting ink drop thus causing the printhead to become soiled from leaking ink thereby affecting performance. As a result, ink jet printer manufacturers generally include in the printer manual instructions on how to manually clean the printhead after the printer has been moved. This problem is more acute for portable ink jet printers that are frequently moved. This forces the user to frequently clean the printhead to maintain acceptable printer performance.
The continuous loss of ink and the need to clean the printhead as a result of the meniscus destruction problem will adversely affect the marketability of these printers. One partial solution may be to increase the size of the ink cartridge thus providing the user with additional ink. However, increasing the size of the ink cartridge makes it difficult to meet the market demand for reduced printer size and portability.
Accordingly, it is desirable to have a printhead unit for use in an ink jet printer in which the meniscuses of the nozzle plane are not destroyed on impact.
SUMMARY OF THE INVENTION
The present invention is directed to a printhead unit which detachably couples to an ink cartridge. An ink passage extends through the ink cartridge and printhead. A damper member for absorbing a pulsation of ink in an ink passage is disposed in facing relationship with the ink passage.
The damper member for absorbing a pulsation of the ink is disposed in the printhead facing the ink passage. With this unique feature, the ink pulsation caused by the impact to the printer is absorbed before it reaches the nozzle plane preserving the meniscus at the nozzle plane.
A preferred embodiment of the invention includes a printhead unit of the surface contact type in which the printhead unit is coupled with the ink cartridge in a surface contact fashion. A connection member of the printhead unit is coupled with an ink supplying port of the ink cartridge. A head needle is disposed on the connection member. The head needle is mounted on a printhead and the ink passage of the printhead unit includes a first ink passage in fluid communication with the ink supplying port of the ink cartridge, a second ink passage in fluid communication with the first ink passage, and a third ink passage in fluid communication with the second ink passage of the printhead.
In one embodiment, the damper member is provided in the connection member in a position that faces the first ink passage. The damper member is easily formed in the connection member which is separate from the printhead and the head needle because in a connection structure of the surface contact type, the ink passage opening is large. Forming the damper member in the connection member does not have any adverse effect on the supplying of ink, as it would if it was formed in the printhead.
In an exemplary embodiment, the printhead unit is constructed such that the damper member is provided in the circumferential wall of the connection member. The damper member is formed as a stagnate air recess in fluid communication with the first ink passage allowing air to stagnate therein. The stagnate air recess may easily be formed by boring a long and narrow indentation into the circumferential wall of the connection member extending in a direction perpendicular to the first ink passage. The indentation faces the first ink passage. The stagnate air recess may also include a through-hole passing through the circumferential wall of the connection member and extending in the direction perpendicular to the first ink passage. A sealing member seals both ends of the through-holes. The stagnate air recess may easily be formed by drilling a through-hole in the circumferential wall, the sealing member being a rubber ring.
In a preferred embodiment, the stagnate air recess includes a choke passage in fluid communication with the first ink passage so that the surface tension of the ink at the choke passage blocks the inflow of ink into the stagnate air recess, and a buffering space that is contiguous with the choke passage. The damper member constructed in such a manner communicates with the first ink passage through the choke passage and prevents the inflow and outflow of the ink to and from the buffering space.
In a preferred embodiment, the damper member includes a flexible sealing film member located in a position facing the first ink passage, and a stagnate air recess located in a position facing the first ink passage with the flexible sealing film member disposed between the first ink passage and the air stagnate recess. In this way, the flexible sealing film member reliably prevents the inflow and outflow of ink to and from the stagnate air recess.
In another exemplary embodiment, the damper member is provided in the circumferential wall of the connection member, and includes a passage extending from the first ink passage to the outside of the circumferential wall. A flexible sealing film member is disposed on the outer surface of the circumferential wall for sealing the passage opening in the outside of the circumferential wall. In this way, the first ink passage is opened to outside air through the flexible sealing film member. Accordingly, an unlimited amount of force resulting from the pulsation of ink can be absorbed in a reliable manner.
The sealing film member may be replaced by a combination of a sealing cap provided at the opening of the outer end of the passage, and an urging means for urging the sealing cap in the sealing direction.
The damper member may be a flexible film member being filled with a gas, for example air, and located in the first ink passage. To form the damper member for absorbing the ink pulsation, the film member is put in the first ink passage without requiring any modifications to the connection member. The film member is bonded onto the inner wall of the first ink passage so that it remains stationary.
The film member may be replaced by a flexible foam member. In this case, the plurality of pores included in the foam member absorb the pulsation of ink.
The damper member may be placed in the head needle in a location facing the second ink passage. In this case, the damper member may easily be formed in the major part (tubular part) or the expanded part (ink reservoir) of the head needle. Placing the damper member in the head needle does not have any adverse effect on the ink passage as in the case of placing the damper member in the connection member.
In another embodiment, the printhead unit of the needle connection type is coupled with the ink cartridge in a needle contact type. A head needle is coupled with an ink supplying port of the ink cartridge. The head needle is mounted on the printhead. A passage includes a fourth ink passage formed in the head needle and coupled with the ink supplying port. A fifth ink passage is formed in the printhead and communicates with the fourth ink passage. In this case, the damper member is preferably provided in the head needle so as to not adversely affect the supplying of ink.
Und
Chino Masahiko
Matsuhashi Kunihiko
Umemura Shunji
Le N.
Nghiem Michael
Seiko Epson Corporation
Stroock & Stroock & Lavan LLP
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