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INK DELIVERY SYSTEM FOR AN INKJET
PRINTHEAD
CROSS-REFERENCE TO RELATED
APPLICATIONS
This is a continuation of application Ser. No. 08/179,866 filed on Jan. 11, 1994, now U.S. Pat. No. 5,625,396 which is a continuation of application Ser. No. 07/862,086, filed Apr. 2, 1992, now U.S. Pat. No. 5,278,584.
This application relates to the subject matter disclosed in the following U.S. Patents:
U.S. Pat. No. 4,926,197 to Childers, entitled "Plastic Substrate for Thermal Ink Jet Printer;"
U.S. application Ser. No. 07/568,000, filed Aug. 16,1990, entitled "Photo-Ablated Components for Inkjet Printheads;" abandoned
U.S. Pat. No. 5,442,384, entitled "Integrated Nozzle Member and TAB Circuit for Inkjet Printhead;"
U.S. Pat. No. 5,291,226, entitled "Nozzle Member Including Ink Flow Channels;"
U.S. Pat. No. 5,305,015, entitled "Laser Ablated Nozzle Member for Inkjet Printhead;"
U.S. Pat. No. 5,420,627, entitled "Improved Inkjet Printhead;"
U.S. Pat. No. 5,297,7331, entitled "Structure and Method for Aligning a Substrate With Respect to Orifices in an Inkjet Printhead;"
U.S. Pat. No. 5,450,113, entitled "Inkjet with improved seal arrangement;"
U.S. Pat. No. 5,300,959, entitled "Efficient Conductor Routing for an Inkjet Printhead;"
U.S. Pat. No. 5,469,199, entitled "Wide Inkjet Printhead."
The above patents are assigned to the present assignee and are incorporated herein by reference.
1 . Field of the Invention
The present invention generally relates to inkjet and other types of printers and, more particularly, to the printhead portion of an ink cartridge used in such printers.
2. Background of the Invention
Thermal inkjet print cartridges operate by rapidly heating a small volume of ink to cause the ink to vaporize and be ejected through one of a plurality of orifices so as to print a dot of ink on a recording medium, such as a sheet of paper. Typically, the orifices are arranged in one or more linear arrays in a nozzle member. The properly sequenced ejection of ink from each orifice causes characters or other images to be printed upon the paper as the printhead is moved relative to the paper. The paper is typically shifted each time the printhead has moved across the paper. The thermal inkjet printer is fast and quiet, as only the ink strikes the paper. These printers produce high quality printing and can be made both compact and affordable.
In one prior art design, the inkjet printhead generally includes: (1) ink channels to supply ink from an ink reservoir to each vaporization chamber proximate to an orifice; (2) a metal orifice plate or nozzle member in which the orifices are formed in the required pattern; and (3) a silicon substrate containing a series of thin film resistors, one resistor per vaporization chamber.
To print a single dot of ink, an electrical current from an external power supply is passed through a selected thin film resistor. The resistor is then heated, in turn superheating a thin layer of the adjacent ink within a vaporization chamber,
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causing explosive vaporization, and, consequently, causing a droplet of ink to be ejected through an associated orifice onto the paper.
One prior art print cartridge is disclosed in U.S. Pat. No.
5 4,500,895 to Buck et al., entitled "Disposable Inkjet Head," issued Feb. 19, 1985 and assigned to the present assignee.
In one type of prior art inkjet printhead, described in U.S. Pat. No. 4,683,481 to Johnson, entitled "Thermal Ink Jet Common-Slotted Ink Feed Printhead," ink is fed from an ink
10 reservoir to the various vaporization chambers through an elongated hole formed in the substrate. The ink then flows to a manifold area, formed in a barrier layer between the substrate and a nozzle member, then into a plurality of ink channels, and finally into the various vaporization chambers.
15 This prior art design may be classified as a center feed design, whereby ink is fed to the vaporization chambers from a central location then distributed outward into the vaporization chambers. Some disadvantages of this type of prior art ink feed design are that manufacturing time is
20 required to make the hole in the substrate, and the required substrate area is increased by at least the area of the hole. Further, once the hole is formed, the substrate is relatively fragile, making handling more difficult. Further, the manifold inherently provides some restriction on ink flow to the
25 vaporization chambers such that the energization of heater elements within the vaporization chambers may affect the flow of ink into nearby vaporization chambers, thus producing crosstalk. Such crosstalk affects the amount of ink emitted by an orifice upon energization of an associated
30 heater element.
SUMMARY OF THE INVENTION
This invention provides an improved ink flow path between an ink reservoir and vaporization cavities in an
35 inkjet printhead. In the preferred embodiment, a barrier layer containing ink channels and vaporization chambers is located between a rectangular substrate and a nozzle member containing an array of orifices. The substrate contains two linear arrays of heater elements, and each orifice in the
40 nozzle member is associated with a vaporization chamber and heater element. The ink channels in the barrier layer have ink entrances generally running along two opposite edges of the substrate so that ink flowing around the edges of the substrate gain access to the ink channels and to the
45 vaporization chambers.
Using the above-described ink flow path (i.e., edge feed), there is no need for a hole or slot in the substrate to supply ink to a centrally located ink manifold in the barrier layer. Hence, the manufacturing time to form the substrate is
50 reduced. Further, the substrate area can be made smaller for a given number of heater elements. The substrate is also less fragile than a similar substrate with a slot, thus simplifying the handling of the substrate. Further, in this edge-feed design, the entire back surface of the silicon substrate can be
55 cooled by the ink flow across it. Thus, steady state power dissipation is improved.
Additionally, since the central manifold providing a common ink flow channel to a number of ink channels is not required, the ink is able to flow more rapidly into the ink
60 channels and vaporization chambers. This allows for higher printing rates. Still further, by eliminating the manifolds, a more consistent ink flow into each vaporization chamber is maintained as the ink ejection sequences are occurring. Thus, crosstalk between nearby vaporization chambers is
65 minimized.
Other advantages will become apparent after reading the disclosure.
