Patent Application
20060197810
This invention relates generally to the field of digitally controlled continuous ink jet printing devices, and in particular to continuous ink jet printers in which selected droplets are deflected by a transverse flow of air or gas.
U.S. Pat. No. 6,079,821 issued to Chwalek et al. discloses a continuous ink jet printhead in which deflection of selected droplets is accomplished by asymmetric heating of the jet exiting the orifice.
U.S. Pat. No. 6,554,410 by Jeanmaire et al. teaches an improved method of deflecting the selected droplets. This method involves breaking up each jet into small and large drops and creating an air or gas cross flow relative to the direction of the flight of the drops that causes the small drops to deflect into a gutter or ink catcher while the large ones bypass it and land on the medium to write the desired image or the reverse, that is, the large drops are caught by the gutter and the small ones reach the medium.
U.S. Pat. No. 6,450,619 to Anagnostopoulos et al. discloses a method of fabricating nozzle plates, using CMOS and MEMS technologies which can be used in the above printhead. Further, in U.S. Pat. No. 6,663,221, issued to Anagnostopoulos et al., methods are disclosed of fabricating page wide nozzle plates, whereby page wide means nozzle plates that are about 4″ long and longer. A nozzle plate, as defined here, consists of an array of nozzles and each nozzle has an exit orifice around which, and in close proximity, is a heater. Logic circuits addressing each heater and drivers to provide current to the heater may be located on the same substrate as the heater or may be external to it.
For a complete continuous ink jet printhead, besides the nozzle plate and its associated electronics, a means to deflect the selected droplets is required, an ink gutter or catcher to collect the unselected droplets, an ink recirculation or disposal system, various air and ink filters, ink and air supply means and other mounting and aligning hardware are needed.
In these continuous ink jet printheads the nozzles in the nozzle plates are arranged in a straight line, they are between about 150 to 2400 per inch and, depending on the exit orifice diameter, can produce droplets as large as about 100 Pico liters and as small as 1 Pico liter.
As already mentioned, all continuous ink jet printheads, including those that depend on electrostatic deflection of the selected droplets (see for example U.S. Pat. No. 5,475,409 issued to Simon et al), an ink gutter or catcher 10 is needed to collect the unselected droplets. Such a gutter has to be carefully aligned relative to the nozzle array since the angular separation between the selected and unselected droplets is, typically, only a few degrees. The alignment process is typically a very laborious procedure and increases substantially the cost of the printhead. The printhead cost is also increased because each gutter must be aligned to its corresponding nozzle plate individually and one at a time.
The gutter or catcher may contain a knife-edge or some other type of edge to collect the unselected droplets, and that edge has to be straight to within a few tens of microns from one end to the other. Gutters are typically made of materials that are different from the nozzle plate and as such they have different thermal coefficients of expansion so that if the ambient temperature changes the gutter and nozzle array can be in enough misalignment to cause the printhead to fail. Since the gutter is typically attached to some frame using alignment screws, the alignment can be lost if the printhead assembly is subjected to shock as can happen during shipment. If the gutter is attached to the frame using an adhesive, misalignment can occur during the curing of the glue as it hardens, resulting in yield loss of printheads during their assembly.
These problems of alignment and assembly are exacerbated as the printhead lengths are increased from an inch or less to page wide which could be tens of inches long.
A need therefore exists for an assembly free and self-aligned ink gutter or catcher for page wide nozzle arrays that is free of misalignment due to changes in the ambient or operating temperature. Furthermore, a need exists for an ink gutter or catcher that is assembly free and self aligned to smaller nozzle arrays, which may then be arranged in a staggered or tiled configuration to form page wide continuous ink jet printheads. Finally, a need exists to reduce the cost of the printheads by eliminating the labor-intensive alignment procedure and the one at a time alignment process of each nozzle plate to its corresponding gutter.
The invention is directed to an ink jet printing apparatus and method of fabrication that solves or at least ameliorates some or all of the aforementioned problems associated with the prior art.
In accordance with one aspect of the present invention there is provided an ink jet printing apparatus comprising an ink droplet forming mechanism for ejecting a stream of ink droplets having a selected one of at least two different volumes toward a print medium and an integral deflector gutter structure which is integrally formed to the printhead for providing a flow of gas that interacts with the ink droplet stream to separate ink droplets having the different volumes from one another and captures excess ink from one of the at least two different volumes of the ink droplets.
In accordance with another aspect of the present invention there is provided a method of making an ink-jet printhead having an integral gutter, comprising the steps of:
a. providing a support substrate on which an ink jet printhead is integrally formed, the printhead ejecting a stream of ink droplets having a selected one of at least two different volumes toward a print medium;
b. forming a deflector gutter structure integrally on the support substrate, the deflector gutter structure having at least one passage for directing a stream of gas against the stream of ink droplets for deflecting the stream of ink droplets and at least one passageway for capturing one of the at least two different volumes of the ink droplets.
In accordance with another aspect of the invention there is provided an ink-jet printing apparatus comprising a plurality of ink-jet print assemblies positioned with respect to each other so as to form a single line of print on a media, each of said ink-jet print assemblies having an ink droplet forming mechanism for ejecting a stream of ink droplets having a selected one of at least two different volumes toward a print medium and an integral deflector gutter structure which is integrally formed to each of the printheads for providing a flow of gas that interacts with said ink droplet stream to separate ink droplets having said different volumes from one another and captures excess ink from said at least two different volumes of said ink droplets.
These and other aspects, objects, features and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiments and appended claims and by reference to the accompanying drawings.
In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawings in which:
FIGS. 2A-D illustrates the relationship between the switching frequency of the heaters of the nozzle array and the volume of ink droplets produced by the nozzles adjacent to the heaters;
The present description will be directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those of ordinary skill in the art.
With reference to
Referring in particular to
Conductors 28 and electrical contact pads 21 may be at least partially formed or positioned on the nozzle array substrate 12 and provide an electrical connection between a controller 23 and the heaters 13. Alternatively, the electrical connection between the controller 23 and heater 13 may be accomplished in any well-known manner. Controller 23 may be a relatively simple device (a switchable power supply for heater 13, etc.) or a relatively complex device (a logic controller or programmable microprocessor in combination with a power supply) operable to control many other components of the printer in a desired manner.
In FIGS. 2A-F, examples of the electrical activation waveforms provided by controller 23 to the heaters 13 are shown and their associated ink droplet size produced by the waveforms. Generally, a high frequency of activation of heater 13 results in small volume droplets 33 as shown in
With reference now to
An amount of separation D between the large, non-printing droplets 31 and the small, printing droplets 33 will not only depend on their relative size but also the velocity, density, and viscosity of the gas flow producing force 46, the velocity and density of the large printing droplets 31 and small, non-printing droplets 33, and the interaction distance (shown as L in
Referring to
An ink recovery conduit/passageway 70 is connected to outlet plenum 40 of integral deflector gutter structure 60 for receiving droplets recovered by deflector 62. Ink recovery conduit 70 communicates with ink recovery reservoir 90 to facilitate recovery of non-printed ink droplets by an ink return line 100 for subsequent reuse. Ink recovery reservoir contains open-cell sponge or foam 135, which prevents ink sloshing in applications where the nozzle array 12 is rapidly scanned. A vacuum conduit 110, coupled to a negative pressure source, can communicate with ink recovery reservoir 90 to create a negative pressure in ink recovery conduit 70 improving ink droplet separation and ink droplet removal. The gas flow rate in ink recovery conduit 70, however, is chosen so as to not significantly perturb large droplet path K. Lower plenum 40 is fitted with filter 140 and drain 130 to capture any ink fluid resulting from ink misting, or misdirected jets which has been captured by the air flow in plenum 40. Captured ink is then returned to recovery reservoir 90.
Additionally, a portion of plenum 50 diverts a small fraction of the gas flow from pump 220 and conditioning chamber 190 to provide a source for the gas which is drawn into ink recovery conduit 70. The gas pressure at gutter deflector 62 and in ink recovery conduit 70 are adjusted in combination with the design of ink recovery conduit 70 and plenum 50 so that the gas pressure in the printhead assembly near integral deflector gutter structure 60 is positive with respect to the ambient air pressure near print drum 80. Environmental dust and paper fibers are thusly discouraged from approaching and adhering to integral deflector gutter structure 60 and are additionally excluded from entering ink recovery conduit 70.
In operation, a recording medium M is transported in a direction transverse to axis X by print drum 80 in a known manner. Transport of recording medium M is coordinated with movement of printhead/nozzle array mechanism, not shown, for movement of nozzle array 12. This can be accomplished using controller 13 in a known manner. Recording media M may be selected from a wide variety of materials including paper, vinyl, cloth, other fibrous materials, etc.
The recovery air plenums 40, 50 of integral deflector gutter structure 60 is integrally formed on nozzle array 12. In the preferred embodiment, an orifice cleaning system 240 may also be incorporated into integral deflector gutter structure 60. Cleaning would be accomplished by flooding the nozzle array 12 with solvent injected through the input port 241. Used solvent is removed by drawing vacuum on the cleaning solvent through output port 242.
In the present invention the guttering structure is integrally formed with nozzle array 12. This is done in order to maintain accuracy between the ink jet nozzles 17 and the deflector 62. In a preferred embodiment of the present invention, nozzle array 12 is formed from a semiconductor material (silicon, etc.) using known semiconductor fabrication techniques (CMOS circuit fabrication techniques, micro-electro mechanical structure (MEMS) fabrication techniques, etc.). Such techniques are illustrated in U.S. Pat. Nos. 6,663,221 and 6,450,619 which are hereby incorporated by reference in their entirety. However, it is specifically contemplated and therefore within the scope of this disclosure that nozzle array 12 may be integrally formed with the gutter structure from any materials using any fabrication techniques conventionally known in the art.
Referring to
Referring to
It is specifically contemplated that integral deflector gutter structure 160 or 150 may be formed from any materials using any fabrication techniques conventionally known in the art, including high aspect photo resist, such as SU-8 so long as the integral deflector gutter structure in integrally. The structure may be attached prior to or following printhead singulation.
While the foregoing description includes many details and specificities, it is to be understood that these have been included for purposes of explanation only, and are not to be interpreted as limitations of the present invention. Many modifications to the embodiments described above can be made without departing from the scope of the invention, as is intended to be encompassed by the following claims and their legal equivalents.
