Piston Exhaust Passage for Gas Venting in Injection Devices
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Solution Overview
Problem
Existing food injection devices face inefficiencies due to trapped gas between the piston and liquid in the needle tube, requiring excessive force to push the piston, as the absorbed pressure increases the force needed for injection.
Innovation Solution
The injection device incorporates a design with an exhaust passage and groove system that allows compressed gas between the piston and liquid to be discharged, reducing pressure and thrust required for piston movement, featuring a helical exhaust passage and a check valve to prevent external air from entering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the needle tube is sealed to prevent leakage, then liquid discharge reliability is improved, but gas accumulates between piston and liquid requiring excessive force
Solution Approach 1:
The exhaust passage is segmented into multiple sections (first exhaust passage and second exhaust passage) with different functions. The first exhaust passage handles gas discharge during normal operation, while the second exhaust passage provides an alternative path when the first is blocked, thereby maintaining reliability while managing gas accumulation through structured segmentation.
Solution Approach 2:
The exhaust passage acts as an intermediary channel between the piston cavity and the external environment. It provides a dedicated pathway for gas to escape, mediating between the sealed injection system and the need for gas venting, thus reducing the force required to push the piston while maintaining liquid discharge reliability.
2Force
If the exhaust passage is open to discharge gas, then force needed to push piston is reduced, but external air may enter and contaminate liquid
Solution Approach 1:
The exhaust passage system dynamically adapts its function based on operating conditions. During liquid injection, the passage allows gas to escape in one direction. When the system is at rest or under reverse pressure, the liquid column itself blocks the passage from the external side, preventing air entry. This dynamic behavior resolves the contradiction between gas discharge and contamination prevention.
Solution Approach 2:
The liquid column, which could be seen as an obstacle to exhaust passage functionality, is converted into a protective barrier. When external air tries to enter through the exhaust passage, the liquid column blocks the flow, transforming the potential harm (air contamination) into a beneficial protective mechanism that prevents contamination while allowing gas discharge during injection.
3Reliability
If the piston is designed to seal tightly against needle tube wall, then liquid leakage is prevented, but gas compression increases force requirement
Solution Approach 1:
The sealing system is segmented into two zones: a tight sealing zone between the piston and needle tube wall to prevent liquid leakage, and a gas venting zone through the exhaust passage to allow gas escape. This segmentation allows the piston to maintain reliable sealing while avoiding excessive gas compression forces.
Solution Approach 2:
The harmful element (trapped gas) is extracted from the sealed piston-needle tube system through the exhaust passage. By providing a dedicated extraction path for gas, the system maintains tight sealing for liquid while removing the gas that would otherwise increase force requirements.
4Productivity
If the needle tube has large internal diameter for high viscosity liquid flow, then liquid discharge efficiency is improved, but gas volume increases requiring more force
Solution Approach 1:
The exhaust passage introduces a new dimensional pathway (radial dimension through the piston wall) for gas discharge, independent of the axial liquid flow path. This allows the needle tube to maintain a large internal diameter for efficient liquid discharge while the exhaust passage handles gas removal in a different dimensional space, avoiding the trade-off between diameter and gas volume.
Solution Approach 2:
The exhaust passage acts as an intermediary system that decouples the relationship between liquid flow efficiency and gas volume management. It provides a separate channel that handles gas removal independently, allowing the needle tube internal diameter to be optimized for liquid discharge without being constrained by gas volume considerations.
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 design reduces the force needed to push the piston, ensuring efficient liquid discharge without additional thrust, even with high viscosity liquids, by effectively managing gas compression and preventing backflow of air.
Implementation Method 1
a space between the piston and liquid in the needle tube. A small amount of gas occupy the space which cannot be discharged from the needle tube. As the piston is pressed, the pressure of the space absorbs the force
Implementation Method 2
featuring a helical exhaust passage and a check valve to prevent external air from entering
Data Source
AI summary
An injection device able to evacuate air bubbles trapped with injectable liquid includes a needle tube, a push rod slidable installed in the needle tube and a piston secured on one end of the push rod. The piston includes a main body and a cover, the main body defines a through hole and an exhaust passage in air communication with the through hole. The cover is secured on the main body to shield the through hole and the exhaust passage, and the cover defines an exhaust hole in air communication with one end of the exhaust passage to allow gas but not the liquid to escape from under the piston.