Disposable Syringe with Needle-Housing Piston Rod
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Solution Overview
Problem
Reusable disposable syringes, particularly in developing countries, pose a significant risk for the spread of infectious diseases due to inadequate sterilization and reuse, as existing auto-disable syringes are expensive and challenging to manufacture with minimal components while preventing pressure refilling.
Innovation Solution
A disposable injector with a solid piston and deformable sealing elements having a convex surface, which creates high static friction to prevent manual refilling, utilizing a piston rod with a tubular section for housing the hypodermic needle and an actuating surface to directly contact the piston, ensuring the piston cannot be moved back towards the actuating end, thus preventing reuse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a traditional syringe with a piston connected to the plunger is used, then the syringe can be refilled by pulling the plunger, but this enables reuse and poses infection risks
Solution Approach 1:
The invention extracts the connection between the piston and plunger that enables refilling. The piston is designed without any connecting features to the plunger, and the plunger has no features to connect to the piston. This separation eliminates the refilling capability while maintaining single-use functionality, directly addressing the infection prevention requirement.
Solution Approach 2:
The invention applies preliminary anti-action by designing the piston and plunger from the outset with no connecting features, preventing any possibility of refilling before it can occur. The deformable sealing element is positioned to create high static friction that resists any attempt to move the piston backward, proactively blocking reuse attempts.
2Reliability
If auto-disable syringes with multiple components are used to prevent reuse, then infection prevention is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The invention merges the needle housing function and plunger actuation function into a single integrated piston rod component. The tubular section houses the needle while the actuating surface directly contacts the piston, eliminating the need for separate connection mechanisms and reducing overall device complexity while maintaining auto-disable functionality.
Solution Approach 2:
The piston rod serves multiple functions simultaneously: it houses the needle in its tubular section, provides the actuating surface to push the piston, and acts as the plunger. This multi-functionality reduces the number of separate components needed while achieving the same infection prevention goals.
3Ease of operation
If a piston with large vertical abutting surface is used, then friction is reduced for smooth operation, but the ability to resist pressure filling is compromised
Solution Approach 1:
The invention changes the physical parameters of the sealing element by making it deformable with a convex surface. This allows the sealing element to dynamically adjust its contact characteristics: it deforms to create high static friction for resisting pressure filling, then deforms further during actuation to reduce dynamic friction for smooth piston movement, optimizing both resistance and smoothness.
Solution Approach 2:
The sealing element transitions from a static sealing surface to a dynamic one that changes its friction characteristics during operation. The deformable material allows the sealing element to adapt its friction properties based on the operational phase: high static friction when at rest to prevent pressure filling, and reduced dynamic friction during movement for smooth operation.
4Reliability
If a solid piston without connecting features is used, then refilling is prevented, but the piston rod must be longer to ensure proper actuation
Solution Approach 1:
The invention uses nesting by placing the needle inside the tubular section of the piston rod. This allows the piston rod to serve dual purposes: housing the needle and providing the actuating mechanism. The nested arrangement maximizes the utilization of the piston rod's length, reducing the need for excessive extension while maintaining proper actuation capability.
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
The design effectively prevents syringe refilling by requiring a high initial pressure to move the piston, ensuring the syringe is used only once, thereby reducing the risk of disease transmission and simplifying manufacturing and usage.
Implementation Method 1
creates high static friction to prevent manual refilling
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
The present invention relates to an injector comprising a cylinder with a longitudinal axis and an inner wall; a solid piston inserted into the cylinder without a preset orientation; a hypodermic needle attached to an outlet at an outlet end of the cylinder opposite an actuating end of the cylinder; and a piston rod having a tubular section for housing the hypodermic needle, the tubular section having a needle insertion end comprising an engagement device for engaging a complementary engagement device of the outlet or the hypodermic needle, and a needle protection end opposite the needle insertion end, which tubular section comprises an actuating surface to push the piston, wherein the piston rod has a length, which is equal to or larger than an operating length of the cylinder defined by the distance from the actuating end of the cylinder to the outlet end of the cylinder minus the dimension of the piston parallel with the longitudinal axis. The injector of is suited for delivery of a pharmaceutical composition, such as a vaccine.