Toggle Clamping Mechanism Ball Spline Crosshead Guidance
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Solution Overview
Problem
Existing toggle clamping mechanisms in injection molding machines face issues with the inclination of movable platens due to clearance between bushings and guide rods, leading to misalignment of mold surfaces and defective product shapes.
Innovation Solution
The mechanism employs two ball spline shafts parallel to the ball screw to guide the crosshead, with adjustable support members to maintain the crosshead's position on a center axis, eliminating play between the ball spline shafts and nuts to prevent inclination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If bushings are inserted into the crosshead and guide rods are used for guidance, then the crosshead can slide along the guide rods, but clearance between the bushings and guide rods causes the crosshead position to deviate from the center axis and leads to inclination of the movable platen
Solution Approach 1:
The patent replaces the traditional bushing-guide rod mechanical sliding system with a ball spline shaft-ball spline nut mechanism. This substitution eliminates clearance issues by using precision ball bearings within the ball spline shaft, providing both smooth movement and accurate positioning. The ball spline shaft is guided by the movable platen through the ball spline nut, ensuring the crosshead remains centered without inclination.
2Manufacturing precision
If four ball spline shafts are used as tie rods to guide the movable platen, then the inclination of the movable platen is prevented, but the device complexity and cost increase
Solution Approach 1:
The patent merges the guidance function into the existing toggle link structure by integrating a single ball spline shaft within the crosshead. This consolidation eliminates the need for separate guidance mechanisms (such as four ball spline shafts as tie rods) while maintaining the ability to prevent platen inclination. The ball spline shaft works in conjunction with the toggle links to achieve both clamping and guidance functions.
3Manufacturing precision
If the front sides of guide rods are raised to correct crosshead displacement, then some position compensation is achieved, but clearance between bushings and guide rods still allows the crosshead to incline
Solution Approach 1:
The patent replaces the adjusted guide rod system with a ball spline shaft mechanism that inherently maintains precise positioning. The ball spline shaft, equipped with internal ball bearings, provides consistent angular relationships between upper and lower toggle links throughout the clamping cycle. This substitution ensures reliable angle consistency while maintaining corrected crosshead position, eliminating the residual inclination problem of the guide rod approach.
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 effectively maintains the crosshead's position on a center axis, reducing the inclination of the movable platen and ensuring parallel mold surfaces, thereby preventing misalignment and defective product shapes.
Implementation Method 1
a ball spline shaft (8) provided approximately parallel to a ball screw (11) for driving the crosshead (7), and a ball spline nut (9) provided in the crosshead (7). The crosshead (7) is guided by the ball spline shaft (8).
Data Source
AI summary
A toggle clamping mechanism for an injection molding machine includes a toggle link, a crosshead connected to the toggle link, and a driving device for driving the crosshead. A ball spline shaft is provided parallel to a ball screw for driving the crosshead. Further, a ball spline nut provided in the crosshead is engaged with the ball spline shaft so that the crosshead may be guided by the ball spline shaft.