Uniform Shear Valve for Extrusion Melt Fracture
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Solution Overview
Problem
Extrusion machines often experience melt fracture and melt memory effects due to non-uniform shear flows through existing valves, leading to irregularities and breakage of extruded polymers, especially at higher flow rates, and the high pressure required for flow control makes operation difficult.
Innovation Solution
A uniform shear valve design featuring a body with annular walls, a flow control member with tapered ends, and a uniform flow area defined by gaps between seats, which reduces pressure and creates consistent shear, eliminating melt fracture and memory effects while simplifying the operation of the flow control member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional valve with non-uniform flow area is used to control polymer flow, then flow rate control is achieved, but melt fracture and melt memory effects occur causing polymer irregularities and breakage
Solution Approach 1:
The valve body incorporates a uniform flow area with constant cross-sectional dimensions between the inlet and outlet, ensuring uniform shear rate distribution across the entire flow cross-section. This local uniformity in flow characteristics prevents melt fracture and melt memory effects while maintaining effective flow control.
Solution Approach 2:
The invention changes the geometric parameters of the flow path by defining a uniform flow area with constant cross-sectional dimensions, as opposed to conventional tapered or varying cross-sections. This parameter change ensures uniform shear rate distribution and eliminates the harmful effects of non-uniform flow on polymer quality.
2Stress or pressure
If high pressure is applied to control polymer flow through the valve, then flow control is effective, but the force required to operate the flow control member becomes difficult
Solution Approach 1:
The valve design incorporates a uniform flow area that acts as an intermediary between the high-pressure inlet and the outlet, distributing the pressure uniformly across the flow cross-section. This reduces pressure concentration on the flow control member, making operation easier while maintaining effective flow control.
3Productivity
If the valve creates non-uniform shear flow to control polymer discharge, then flow control is achieved, but surface undulations and irregularities develop on the extruded polymer
Solution Approach 1:
The uniform flow area ensures that every point across the flow cross-section experiences the same shear rate, creating uniform local flow conditions throughout the valve. This uniformity prevents surface undulations and irregularities while maintaining effective polymer discharge control.
Solution Approach 2:
The valve design creates homogeneous flow conditions by maintaining a uniform cross-sectional area throughout the flow path, ensuring consistent shear rate distribution. This homogeneity eliminates surface defects and produces high-quality extruded polymer with smooth surfaces.
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 uniform shear valve effectively prevents melt fracture and memory effects, ensuring consistent polymer profiles and reducing the operational force required for flow control, allowing for easier maintenance and automation of the extrusion process.
Implementation Method 1
A uniform flow area is defined by a gap between the first seat and the second seat... the uniform shear valve effectively prevents melt fracture and memory effects, ensuring consistent polymer profiles
Data Source
AI summary
A uniform shear valve for an extruder machine includes a body having a generally annular wall that defines an interior area extending along a longitudinal axis thereof. The interior area extends between an inlet proximate a first end of the body and a second end of the body. The second end is opposite the first end. The body has a first bore extending through the wall along a traverse axis substantially perpendicular to the longitudinal axis at a first position and second position. A flow control member is sealingly and slidingly positioned partially in the first bore at the first position and extends out of the body. The flow control member defines a first seat on an end thereof. An outlet is located in the first bore at the second position. A second seat is positioned proximate the outlet and is concentric with the first seat along the traverse axis. A uniform flow area is defined by a gap between the first seat and the second seat.