Ball Screw Valve Pin Actuation for Injection Molding
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Solution Overview
Problem
The accurate and reliable actuation of valve pins in injection molding apparatuses, particularly in hot runners, is critical but often not effectively managed by existing technologies, leading to inefficiencies and potential operational issues.
Innovation Solution
The implementation of a system comprising a back plate, driven pulley, ball screw, ball nut, motor, and belt configuration that allows precise control of valve pins through rotational motion, enhancing efficiency and load management by using ball screws and ball nuts for precise translation and minimizing motor size requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plate actuates valve pins in unison, then the valve pins can be controlled simultaneously, but the plate movement accuracy and reliability are difficult to ensure
Solution Approach 1:
The patent divides the plate actuation system into individual valve pin actuators, each with its own drive mechanism. This segmentation allows each valve pin to be actuated independently with precise control, eliminating the reliability and accuracy issues associated with moving a large plate in unison while still achieving coordinated operation through synchronized control of individual actuators.
2Device complexity
If traditional screw mechanisms are used for valve pin actuation, then the structure is simple, but high forces cause seizing or galling
Solution Approach 1:
The patent replaces traditional friction-based screw mechanisms with a ball screw mechanism. The ball screw uses circulating balls between the screw and nut to convert rotational motion to linear motion with significantly reduced friction. This substitution maintains the simplicity of the screw mechanism while eliminating the seizing and galling problems that occur with high forces in traditional screw systems.
3Force
If high forces are handled by traditional actuation systems, then the force capacity is sufficient, but the motor size becomes large
Solution Approach 1:
The patent employs a ball screw mechanism that provides mechanical advantage through its lead angle and friction reduction. This allows a smaller motor to generate the same linear force at the valve pin compared to traditional direct-drive or friction-based screw systems. The ball screw's efficiency in converting rotational torque to linear force enables compact motor sizing while maintaining high force capacity.
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 configuration ensures reliable and efficient actuation of valve pins, capable of handling high forces with reduced motor size and minimizing seizing or galling, thereby improving the operational consistency and efficiency of injection molding processes.
Implementation Method 1
a screw connected to the driven pulley to rotate with the driven pulley... a nut connected to the valve pin plate and mated with the screw
Implementation Method 2
the screw is a ball screw and the nut is a ball nut
Implementation Method 3
a belt coupling the driven pulley and the drive pulley
Data Source
AI summary
An injection molding apparatus includes a back plate, a driven pulley connected to the back plate and rotatable with respect to the back plate, a screw connected to the driven pulley to rotate with the driven pulley, a motor having an attached drive pulley, a belt or chain coupling the driven pulley and the drive pulley, a valve pin plate, a nut connected to the valve pin plate and mated with the screw, at least one valve pin connected to the valve pin plate, a manifold fixed with respect to the back plate, and at least one nozzle connected to the manifold. The valve pin extends through the nozzle to control flow of molding material. The screw can be a ball screw and nut can be a ball nut. The screw can have one portion connected to the driven pulley and another portion connected to a mold plate in a rotatable manner. The valve pin plate may be an assembly with an upper plate, a lower plate, and at least one valve pin holder fixed between the upper plate and the lower plate, the valve pin being fastened to the valve pin plate assembly with the valve pin holder. The positions of the screw and nut can be reversed.