Inkjet Printhead Flow Restrictor for Uniform Droplet Deposition
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Solution Overview
Problem
Droplet deposition apparatuses, such as inkjet printheads, face challenges in achieving uniformity of droplet distribution over the array of fluid chambers, leading to non-uniformity in deposited patterns, which is particularly evident in large arrays where media is indexed past the chambers, and can be exacerbated by complex constructions and high pressure differentials required for fluid flow.
Innovation Solution
The introduction of a first flow restrictor passage that connects the common inlet and outlet manifolds to the array of fluid chambers, providing sufficient impedance to direct fluid flow perpendicular to the array direction, thereby reducing local variations in flow rates and simplifying the construction by minimizing the number of components and avoiding complex porous elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common inlet manifold and common outlet manifold are used to supply fluid to the array of chambers, then the construction is simplified and fluid flow is enabled through all chambers, but non-uniform fluid flow distribution occurs across the array leading to non-uniform droplet deposition
Solution Approach 1:
The patent introduces flow restrictor passages at specific locations within the manifold system to create localized flow resistance. This ensures that fluid is distributed more uniformly across different sections of the chamber array, addressing the non-uniform deposition issue without requiring complete redesign of the entire manifold structure.
Solution Approach 2:
The patent modifies the flow characteristics by introducing flow restrictors that change the local flow resistance parameters. This alters the fluid distribution pattern across the chambers, ensuring more uniform flow rates and consequently more uniform droplet deposition while maintaining the overall simplified manifold architecture.
2Manufacturing precision
If flow restrictor passages are introduced to improve fluid flow distribution, then droplet deposition uniformity is enhanced, but the device complexity increases
Solution Approach 1:
The flow restrictor passages are integrated directly into the existing manifold structure rather than being separate components. This merging approach allows the flow restriction function to be achieved without increasing the number of discrete parts, thus improving droplet uniformity while minimizing the increase in device complexity.
Solution Approach 2:
The manifold structure serves multiple functions: it supplies fluid to all chambers, provides structural support, and incorporates flow restriction capabilities through integrated passages. This multi-functionality reduces the need for additional dedicated components, balancing the improvement in deposition uniformity against minimal complexity increase.
3Productivity
If high pressure differentials are used to drive fluid flow through the array, then fluid flow rate is increased, but the apparatus requires complex pressure control systems and excessive size
Solution Approach 1:
The patent optimizes the pressure differential parameter to achieve adequate fluid flow rates without requiring excessively high pressures. By carefully selecting and positioning flow restrictors, the system achieves balanced flow distribution at moderate pressure differentials, avoiding the need for complex high-pressure control systems and reducing overall apparatus size.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the uniformity of droplet deposition by ensuring consistent fluid flow distribution across the array, reducing the complexity and cost of the apparatus while maintaining effective prevention of dust and foreign body accumulation, and allowing for gravity-based fluid supply systems without excessive size or pressure differential issues.
Implementation Method 1
at least one piezoelectric actuator element operable to cause the release, on demand, of a droplet of fluid from the chamber through the nozzle
Implementation Method 2
a first flow restrictor passage connecting said array of chambers to one of said common inlet manifold and said common outlet manifold... said first flow restrictor passage presents sufficient impedance to fluid flow such that, in use, fluid within said first flow restrictor passage adjacent said array of chambers is directed generally perpendicular to said array direction
Data Source
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AI summary
A droplet deposition apparatus, such as an inkjet printhead, is disclosed. The apparatus includes an array of fluid chambers, where each chamber has a nozzle and a piezoelectric actuator element that causes droplets to be released on-demand from the nozzle in an ejection direction. The array of chambers extends in an array direction, which is perpendicular to the ejection direction. The apparatus also includes a common inlet manifold, which supplies fluid to the array of chambers, and may also include a common outlet manifold, which receives fluid from the array of chambers; both the inlet manifold and, where present, the outlet manifold are elongate in the array direction and extend the length of the array of chambers. The apparatus also includes a flow restrictor passage, which extends the length of the array of chambers in the array direction. This may either: connect the inlet manifold to the array of chambers so that during use fluid can flow along the length of the common inlet manifold, through the flow restrictor passage, then through said array of fluid chambers, and then into and along the length of said common outlet manifold;or, in situations where a common outlet manifold is provided, it may connect the array of chambers to the outlet manifold so that during use fluid can flow along the length of the common inlet manifold, through the array of fluid chambers, then through the first flow restrictor passage, and then into and along the length of the common outlet manifold. When a cross-section taken perpendicular to the array direction is viewed, the flow restrictor, and the manifold to which it is connected, are shaped such that the flow restrictor appears as a narrow, elongate passage linking that manifold to the chambers. The flow restrictor passage presents sufficient impedance to fluid flow such that, in use, fluid within it that is adjacent to the array of chambers is directed generally perpendicular to the array direction for substantially all of the chambers in the array.