Needle-equipped syringe eccentric core pin molding
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Solution Overview
Problem
The existing needle-equipped syringe manufacturing process using insert molding often results in an excessively inclined injection needle due to uneven pressure and speed of resin injection, leading to manufacturing inefficiencies, cap attachment issues, and potential medical practice complications.
Innovation Solution
The syringe design incorporates a barrel with a thick and thin part at the proximal end, where the injection needle is integrally molded with the nozzle part, and an injection molding die with a core pin eccentric to the resin injection gate, ensuring the needle's axis is parallel to the syringe body, reducing inclination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If insert molding is performed with the core pin positioned at the center of the recessed part, then the manufacturing process is simple, but the resin pressure and speed become ununiform around the core pin, causing the core pin to incline and the injection needle axis to be excessively inclined
Solution Approach 1:
The core pin is intentionally positioned eccentrically (asymmetrically) relative to the recessed part, specifically shifted toward the resin injection gate side. This asymmetric positioning compensates for the uneven resin pressure distribution during injection molding, ensuring that the core pin remains stable and the injection needle axis aligns properly with the barrel axis, thereby improving manufacturing precision without requiring complex additional components
2Reliability
If the injection needle is excessively inclined, then manufacturing is simpler, but it becomes difficult to attach the cap securely, leading to cap separation during sterilization and transport
Solution Approach 1:
By changing the positional parameter of the core pin (eccentric positioning toward the injection gate), the injection needle inclination is controlled to be within an acceptable range. This ensures that the needle axis remains substantially parallel to the barrel axis, allowing the cap to be attached securely without risk of separation during subsequent sterilization and transport processes
3Productivity
If the injection needle is excessively inclined, then manufacturing is simpler, but medical practice efficiency decreases due to the need to adjust syringe direction during puncture
Solution Approach 1:
The core pin is positioned asymmetrically (eccentrically) toward the resin injection gate side, which compensates for the natural inclination that would otherwise occur during injection molding. This asymmetric positioning ensures that the injection needle axis remains substantially parallel to the barrel axis, eliminating the need for direction adjustment during medical puncture procedures and thereby improving medical practice efficiency
Data Source
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AI summary
To provide a needle-equipped syringe which reduces an inclination of a needle as much as possible by reducing an inclination of a core pin when insert molding is performed. A needle-equipped syringe (10) includes an barrel (12) which has a cylindrical body (14), a nozzle part (13) provided at a distal end of the body (14), and an opening part (16) provided at a proximal end of the body (14) and is molded with resin and an injection needle (11) which is held by the nozzle part (13). The injection needle (11) and the barrel (12) are integrally molded in the needle-equipped syringe (10) so that an axis of the injection needle (11) is substantially parallel to an axis of the body (14). The body (14) has a thick part (14b) and a thin part (14a) at positions opposed to each other across the axis of the body (14) in the proximal end part of the body (14). An axis of an inner peripheral surface of the body is eccentric with respect to an axis of an outer peripheral surface of the body (14) in the proximal end part of the body (14).