Injection Unit Hollow Cylindrical Casing Rotary Drive
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Solution Overview
Problem
Existing injection molding technologies face challenges in efficiently translating and rotating injection screws due to high frictional loads and energy consumption, particularly in maintaining fluid-tight seals and managing axial thrust loads during the injection and plasticizing phases.
Innovation Solution
The proposed solution involves a hollow cylindrical casing with a piston that is rotationally locked to the casing, allowing for axial translation and rotation, and a dual pressure chamber system with a fluid conduit for fluid communication, which reduces frictional loads by ensuring the seal interfaces move only axially, and a rotary drive using a hollow electric motor for efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional injection screw drive mechanism is used, then the injection screw can be translated and rotated, but high frictional loads and energy consumption occur due to seal interfaces moving in both axial and rotational directions
Solution Approach 1:
The invention separates the translation and rotation functions into two distinct mechanisms: a fluid cylinder for axial translation and a rotary drive for rotation. This segmentation allows each mechanism to optimize its sealing approach, with the fluid cylinder seal moving only axially and the rotary drive seal moving only rotationally, reducing frictional loads and energy consumption while extending seal service life.
Solution Approach 2:
The invention transitions from a single mechanism handling both translation and rotation to a two-dimensional approach where translation is handled by linear fluid pressure actuation and rotation is handled by a separate rotary drive mechanism. This dimensional separation eliminates the compound motion problem that causes high friction in conventional single-mechanism designs.
2Device complexity
If a single mechanism is used to both translate and rotate the injection screw, then device complexity is reduced, but frictional loads and energy consumption increase
Solution Approach 1:
The invention divides the screw drive system into two independent subsystems: a fluid cylinder subsystem for translation and a rotary drive subsystem for rotation. Each subsystem has its own sealing requirements and optimization criteria, allowing both to be simpler and more efficient than a single complex mechanism attempting to handle both motions simultaneously.
Solution Approach 2:
The injection screw itself serves dual functions: it acts as both the translation element (moved by fluid pressure) and the rotation element (driven by the rotary drive). This multi-functionality of the screw reduces overall device complexity despite having separate translation and rotation mechanisms.
3Ease of operation
If seal interfaces move in both axial and rotational directions, then a single mechanism can control both motions, but frictional loads increase and service life decreases
Solution Approach 1:
The sealing system is segmented into two distinct sealing interfaces: one in the fluid cylinder for axial translation and another in the rotary drive for rotation. Each seal operates in a single direction of motion, eliminating the high friction associated with compound motion and significantly extending service life while maintaining ease of motion control through independent actuation of each mechanism.
4Device complexity
If axial thrust loads are not properly managed, then the structure can be simpler, but the injection molding process efficiency and reliability decrease
Solution Approach 1:
The invention extracts the axial thrust load management function from the rotary drive mechanism and assigns it exclusively to the fluid cylinder mechanism. The fluid cylinder is designed to handle the full axial thrust loads during injection and plasticizing, allowing the rotary drive to focus solely on rotation without bearing excessive axial loads, thereby improving overall system efficiency and reliability.
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 enhances the service life of seals, reduces energy consumption, and effectively manages axial thrust loads, improving the efficiency and reliability of the injection molding process by maintaining a fluid-tight seal and optimizing the operational efficiency of the injection unit.
Implementation Method 1
a first pressure chamber provided between a first face of the piston and the cylinder cap... against which fluid in the chamber bears when pressurized
Implementation Method 2
a rotary drive in the form of a hollow motor... The housing serves as the stator and can include motor windings mounted adjacent an inner surface of the housing facing the cylindrical casing. The cylindrical casing is the rotor, and can include magnets mounted adjacent its outer surface
Data Source
AI summary
An injection drive unit includes a hollow cylindrical casing rotatably supported by a housing, the cylindrical casing having an axis and a front end and a back end spaced apart along the axis; a piston in the cylindrical casing, the piston axially slidable relative to the cylindrical casing along the axis between advanced and retracted positions, and the piston rotationally locked with the cylindrical casing to rotate therewith; and a cylinder cap generally closing off the back end of the cylindrical casing and providing a first pressure chamber between the piston and the cylinder cap, the cylinder cap including a stationary part affixed to the housing and a rotary part affixed to the cylindrical casing, at least the stationary part providing a stationary end face opposed to the piston and against which fluid in the first pressure chamber bears when pressurized.