Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-07-14
2001-08-07
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S033000, C347S036000
Reexamination Certificate
active
06270183
ABSTRACT:
This application is related to U.S. Pat. No. 5,886,714, granted Mar. 3, 1999. This application is assigned to the same assignee as said patent, said patent being incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates generally to inkjet printing and, more particularly to inkjet printers having on line service stations having spittoons, wipers for wiping inkjet orifices and orifice caps for capping an array of nozzles on a printhead.
Conventional inkjet print engines contain three primary components which are generally organized in series. These components are the platen (including a print zone) the spittoon, in which excess print drops are disposed, and the service station where cartridge wiping and capping functions occur.
In a conventional inkjet print engine, there may be two or more ink cartridges, or printheads, mounted side by side on a transversing carriage which moves substantially perpendicular to the path of media, such as paper, which pass through the machine to be printed upon. Caps are used to prevent the cartridges from drying out during periods of non-use and they are spaced at a center to center distance of the cartridges, as the cartridges are mounted in the carriage, so that each cartridge can be simultaneously capped during periods of inactivity.
Wipers for cleaning the cartridge nozzles during servicing are often mounted on the same center to center distance of the cartridges mounted in the carriage. This allows the wipers to move in synchrony while simultaneously wiping the cartridges. This feature renders the wipers capable of being actuated by a common mechanism.
The spittoon can be one common receptacle for receipt of excess ink drops from the cartridges, although in some cases incompatibilities between inks has resulted in the use of separate spittoons.
In conventional inkjet printers, the three above described components are disposed linearly with a consequent unwanted increase in the width of the finished inkjet engine. In recognition of the problem presented by a wide system, an attempt at optimization, such as staggering the wipers between the caps, has been made. Even here, however, the width of the inkjet printer is the sum of service station width (comprised of capping width, plus one wiper, since the other wiper is disposed between the two caps) plus the platen (having a width at least equal to the width of the media to be printed upon), plus the width of the two spittoons.
As a limitation generally recognized in any attempt to optimize printer design, the spittoons should be located outside the platen area, or print zone, since, during printing the cartridges spit droplets at the same time a sheet of media is being printed on. The caps, on the other hand, can be inside the print zone since the cartridges require capping only during non-use.
With regard to printhead wiping during a print job, some conventional print engines have used a technique of wiping in the middle of the print job. As the carriage is driven to the side over the service station, cartridge wiping occurs after which the carriage is returned to the platen to continue printing on the media. While this approach may result a narrower print engine, such mid-page wiping is detrimental because of “wait banding”. This is often seen as a white streak across the media caused by a difference in timing from print swath to print swath during the printing process.
Further, dimensional hygroscopic limitations may cause problems. This is seen especially in paper media, wherein time constants can cause a different amount of expansion in the print media, depending upon how long the previous swath has absorbed the ink deposited thereon. This difference of expansion can cause swath to swath advance errors between swaths with no wiping, as compared to swaths with wiping.
In view of the foregoing, it is apparent that there is a need for a narrower print engine which would consume less desk space for the user. Among advantages of such a narrower print engine would be shorter carriage travel over a shorter slider rod. This would result in a more efficient printer which would be sturdy in construction. Advantageously, such a printer would result in lower product weight and cost.
While the following detailed description relates to inkjet printers, it will be recognized that the principles set forth apply also to a number of small footprint devices, such as copiers, fax machines, scanners and combinations thereof.
DISCLOSURE OF THE INVENTION
In a presently preferred embodiment of the invention disclosed herein, there is provided a small footprint device, such as an inkjet printer, having a set of printhead cartridges for applying ink droplets to a medium sheet, the printer including a housing having a pair of side plates. A platen, mounted in the housing between the side plates, helps to define a centrally disposed print zone. Sets of centrally disposed wiper openings, and cap openings, within the platen, help to facilitate, respectively, printhead cartridge wiping services before the medium sheet has passed through the print zone and printhead capping services after the medium sheet has passed through the print zone. A set of rib members extends upwardly from the platen top surface for substantially avoiding residual ink contamination on the underside of the medium sheet as it passes through the print zone.
The present invention affords several advantages. In the case of an inkjet printer, for example there is provided a small footprint device which is narrower than conventional printers. This is accomplished by moving the service station to a location within the platen area, or print zone, thereby intercepting the media travel path. The result is an inkjet printer having a smaller desktop footprint that can be produced with less weight and at lower cost. In addition, a sturdier printer is possible. Since printhead servicing is performed in the print zone, the distance of carriage travel is reduced. As a result, the carriage slider rod has approximately the same length as the main media drive shaft and both can be mounted between a pair of side plates. This results not only in static and system dynamic advantages but also in a printer which, because of a reduction in essential parts, is easier to assemble than conventional printers.
Further, a substantially coequal slider rod and main drive shaft enable use of a large drive gear at an end of the drive shaft, thereby eliminating concern for clearance of a printhead carriage over the gear. Similarly, use of a larger encoder is enabled, thereby improving the quality of the print document.
A still further advantage of the present invention is that the printhead service station is placed in proximity to the main drive shaft so that a drive shaft driven shifting mechanism can be utilized to drive wiping and capping operations. In this manner, the conventional service station motor is eliminated.
In view of the foregoing, an inkjet printer embodying the presently preferred embodiment of the invention is smaller and sturdier in construction and is mechanically simpler than conventional printers, requiring fewer parts to assemble.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
REFERENCES:
patent: 3898671 (1975-08-01), Berry et al.
patent: 5148203 (1992-09-01), Hirano
patent: 5621441 (1997-04-01), Waschauser et al.
patent: 5644347 (1997-07-01), Schwiebert et al.
patent: 5663751 (1997-09-01), Holbrook
patent: 5680162 (1997-10-01), Taylor et al.
Hewlett--Packard Company
Hsieh Shih-Wen
Le N.
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