Needle Assembly Elastic Member Deformation Control
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Solution Overview
Problem
In drug injection devices where a syringe and needle assembly are connected via taper fitting, the elastic member can deform, leading to liquid passing failures due to blockage of the needle tube, especially when the deformation is extensive, causing issues with fitting depth and connection force variations.
Innovation Solution
A needle assembly with a specific design featuring a needle tube, a retaining portion with a female tapered fitting, and an elastic member that deforms within a controlled range to prevent blockage, ensuring the needle tube protrudes appropriately to maintain liquid flow, with the deformation portion extending between 35% to 50% of the elastic member's length and the needle tube protruding between 45% to 245% of the deformation portion's length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If the elastic member deforms extensively to reduce dead volume, then the dead volume is reduced, but the needle tube may be blocked causing liquid passing failure
Solution Approach 1:
The needle tube is pre-positioned to protrude from the elastic member by a predetermined amount (0.5-2.0mm) before connection. This preliminary positioning ensures that even when the elastic member deforms during connection, the needle tube remains exposed and unblocked, preventing liquid passing failure while still allowing dead volume reduction through elastic deformation.
Solution Approach 2:
The invention controls the deformation characteristics of the elastic member by selecting appropriate material properties and geometric parameters. The elastic member is designed with specific elasticity modulus and dimensions to achieve controlled deformation that reduces dead volume while maintaining sufficient needle tube exposure. This parameter optimization balances the contradiction between dead volume reduction and liquid passing reliability.
2Reliability
If the needle tube protrudes longer to prevent blockage, then liquid passing reliability is improved, but the dead volume increases
Solution Approach 1:
The needle tube is pre-positioned to protrude from the elastic member by a predetermined amount (0.5-2.0mm) before connection. This preliminary positioning ensures that even when the elastic member deforms during connection, the needle tube remains exposed and unblocked, preventing liquid passing failure while still allowing dead volume reduction through elastic deformation.
Solution Approach 2:
The elastic member is designed to dynamically adjust its deformation based on connection conditions. During connection, the elastic member deforms to reduce dead volume, but the needle tube maintains sufficient protrusion (0.5-2.0mm) to prevent blockage. This dynamic behavior allows the system to optimize both liquid passing reliability and dead volume reduction under different operational states.
3Adaptability or versatility
If the elastic member is made more compliant to accommodate fitting variations, then adaptability is improved, but the risk of needle tube blockage increases
Solution Approach 1:
The needle tube is pre-positioned to protrude from the elastic member by a predetermined amount (0.5-2.0mm) before connection. This preliminary positioning ensures that even when the elastic member deforms during connection, the needle tube remains exposed and unblocked, preventing liquid passing failure while still allowing dead volume reduction through elastic deformation.
Solution Approach 2:
The invention combines the elastic member with the needle tube in an integrated assembly where the needle tube passes through the elastic member. This merging allows the elastic member to accommodate fitting depth variations and connection force differences (improving adaptability) while the protruding needle tube remains exposed to prevent blockage (maintaining reliability). The two functions are combined in a single integrated structure.
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 configuration effectively prevents liquid passing failures by ensuring the needle tube remains unobstructed, reducing dead volume, and maintaining a secure connection despite variations in fitting depth and connection force, enhancing the reliability of the drug injection process.
Implementation Method 1
the elastic member deforms when the drug ejection portion comes into contact with the elastic member
Data Source
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AI summary
The present invention provides a needle assembly which prevents a liquid passing failure, and a drug injection device which includes this needle assembly. A needle assembly according to the present invention includes: a retaining portion which holds a needle tube in a state wheproximalear end of the needle tube protrudes; and an elastic member which includes a close contact portion which closely contacts and retains the needle tube which protrudes toward a fitting opening, and a deformation portion which extends from the close contact portion toward the fitting opening and deforms when the drug ejection portion comes into contact with the elastic member, and which is provided in a fitting portion. Further, the length of the deformation portion is in a range of 35% or more and 50% or less with respect to the length of the elastic member, and the length of the needle tube which protrudes from the close contact portion toward the fitting portion is in a range of 45% or more and 245% or less with respect to the deformation portion.