Molding Unit Carriage Control via Cam Actuation
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Solution Overview
Problem
Conventional molding units for thermoplastic containers by blow molding face challenges in achieving fast and precise control of mold bottom movements for boxing operations, particularly due to the heavy weight of pneumatic jacks, which limits production speed and shortens the service life of components like cam follower rollers.
Innovation Solution
A method utilizing a carriage with three actuating means, including a piston in a stationary cylinder for precise positioning and a cam follower for extraction, where the piston is pushed towards its rest position during extraction, and the working fluid pressure is balanced between chambers to reduce the actuating force required for carriage movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a pneumatic jack is used to move the mold bottom, then sufficient force for boxing operation is achieved, but the heavy weight limits production speed and shortens component service life
Solution Approach 1:
The patent replaces the traditional pneumatic jack system with a cam actuating device that uses mechanical cam-follower action to move the mold bottom. The cam profile is designed to provide the necessary force for boxing operations while enabling faster cycle times and reducing component wear compared to pneumatic systems.
Solution Approach 2:
The cam actuating device provides dynamic control of the mold bottom movement, allowing optimization of the motion profile to achieve both sufficient force during boxing operations and high speed during extraction phases. The cam mechanism enables variable velocity and force characteristics throughout the motion cycle.
2Productivity
If a cam actuating device is used for fast and precise control of mold bottom movements, then production speed is improved, but insufficient force is available for boxing operations
Solution Approach 1:
The cam profile is specifically designed to provide high force output during the boxing phase of the cycle while maintaining fast motion during extraction. The varying cam geometry allows the mechanism to deliver peak force when needed for boxing operations while achieving high speeds during other phases of the cycle.
3Productivity
If the carriage is moved quickly for extraction, then production efficiency is improved, but the service life of cam follower rollers is shortened due to increased wear
Solution Approach 1:
The cam profile parameters are optimized to balance extraction speed with follower roller loading characteristics. By carefully designing the cam geometry, the system achieves high extraction speeds while controlling the contact forces and wear rates on the follower rollers, thereby extending component service life.
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 method reduces the actuating force needed for container extraction, extending the life of components and saving energy, while maintaining high production efficiency and precision in molding operations.
Implementation Method 1
with the piston being able to slide between a lower rest position and an upper boxing position in which it pushes the carriage to its upper molding position by pressurizing a working fluid in the lower working chamber relative to the pressure prevailing in the upper chamber
Implementation Method 2
the third actuating means comprises a cam follower roller that is mounted to rotate on the carriage
Data Source
AI summary
A method for controlling a molding unit (10) for the forming of a container made of thermoplastic material by blow molding of a preform, with the unit (10) including:a carriage (24) that carries, in a stationary manner, a mold bottom (16);at least one stationary cylinder (32) housing a piston (98) that slides between a lower rest position and an upper boxing position in which it pushes the carriage (24) from an intermediate position to an upper molding position;actuating elements for moving the carriage (24) from its upper molding position to a lower extraction position;with the method including an extraction step (E4) wherein the movement of the carriage (24) toward its lower extraction position is initiated while the piston (98) has not yet returned into its lower rest position.