Plural Material Dispensing System With Internal Rod Passage
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Solution Overview
Problem
Plural component metering systems, such as those used for thermal interface materials, face challenges with material curing on piston rods during the refill stroke, leading to abrasive conditions that cause significant wear on seals and other components, affecting the accuracy and longevity of the pumping process.
Innovation Solution
A dispensing system that includes a motor-driven mechanism to simultaneously dispense and reload component materials, using a slide bracket and pistons to ensure balanced pressures and prevent material curing on the rod, with features like a concave downstream end of the piston and sloped edges to prevent material separation and wear, and true first-in, first-out pumping to avoid excessive residence time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the piston rod is driven past the inlet during the dispense stroke, then material is delivered to the outlet, but the exterior of the rod becomes wetted by the material and cures during the refill stroke, creating abrasive conditions that cause significant wear on seals and other components
Solution Approach 1:
The patent extracts the harmful function of the piston rod exterior being wetted by material. By introducing an internal passage through the rod that delivers material directly from the inlet to the outlet, the system eliminates the need for material to contact the rod's exterior surface, thereby preventing curing and abrasive wear on seals and components.
Solution Approach 2:
The internal passage acting as a mediator channel allows material to travel through the piston rod without contacting the rod's exterior. This intermediary pathway separates the material flow from the rod surface, preventing the harmful curing effect while maintaining efficient material delivery.
2Ease of operation
If material is pumped through the system, then dispensing function is achieved, but excessive residence time causes material to cure on surfaces, affecting accuracy and longevity
Solution Approach 1:
The internal passage design enables material to skip along the rod interior and be rapidly delivered to the outlet, minimizing residence time. The direct through-passage allows material to quickly traverse the pump mechanism without lingering on surfaces where it could cure, thereby maintaining dispensing accuracy.
3Productivity
If the rod is withdrawn during the refill stroke to create vacuum, then material is drawn into the pumping chamber, but cured material on the rod creates abrasive conditions
Solution Approach 1:
The patent removes the source of abrasive material by extracting the curing function from the rod exterior. The internal passage ensures material does not contact the rod surface, so when the rod is withdrawn during refill, there is no cured material left behind to create abrasive conditions.
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
The system enhances the accuracy and longevity of plural component material dispensing by preventing material curing on the rod, reducing wear, and ensuring proper mixing, with the potential for over a million dispense and reload cycles without part replacement.
Implementation Method 1
On the refill stroke, a vacuum condition is created as the rod is withdrawn, and the vacuum draws material into the pumping chamber after the rod is withdrawn past the inlet.
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A plural material dispensing system (10) includes a pump (38) having a cylinder (52) mounted between a first bracket (32) and a second bracket (34), a piston (54) disposed within the cylinder (52), and a pump rod (48) extending from the piston (54) and out of the first bracket (32). Material is provided to the cylinder (52) through a flow path extending through the pump rod (48). The piston (54) drives material downstream out of the cylinder (52), and the interface between the piston (54) and the inner surface of the cylinder (52) provides a dynamic seal during pumping. The flow of material into and out of the pump (38) is controlled by actively-controlled inlet and outlet valves.