Disposable Needle Tip Design for Precision Liquid Droplet Control
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Solution Overview
Problem
Disposable plastic needles used for transferring liquids into dosage containers face challenges in controlling droplet size and behavior at the needle tip, leading to inaccuracies in filling due to their weaker strength characteristics compared to metal needles.
Innovation Solution
A needle design with a reduced wall thickness at the tip portion, featuring a chamfer or sharp rim, which reduces the formation of larger droplets and minimizes their separation from the needle tip, enhancing filling accuracy and matching droplet sizes with metal needles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If disposable plastic needles are used instead of metal needles, then cost and ease of disposal are improved, but droplet control and filling accuracy deteriorate
Solution Approach 1:
The needle incorporates a tip portion with reduced wall thickness compared to the main body, creating a localized region with different mechanical properties. This local quality change allows the tip to control droplet formation while the thicker body maintains overall structural integrity, resolving the contradiction between disposable plastic material limitations and filling accuracy requirements.
2Device complexity
If uniform wall thickness is used throughout the needle body, then manufacturing simplicity is improved, but droplet size control and separation behavior worsen
Solution Approach 1:
The needle features a tip portion with reduced wall thickness specifically at the outlet end, creating a localized region that influences droplet formation and separation. This local variation in wall thickness allows better droplet control without significantly complicating the overall manufacturing process, as it can be achieved through standard molding techniques with varying wall thickness specifications.
3Ease of manufacture
If plastic needle material is used, then disposability and cost are improved, but strength characteristics compared to metal needles deteriorate
Solution Approach 1:
The needle design features a tip portion with reduced wall thickness that concentrates structural reinforcement where needed in the thicker body sections, while the thinner tip reduces overall material usage. This local quality differentiation allows plastic material to achieve sufficient strength characteristics for disposable use while maintaining the functional requirements for droplet control.
Solution Approach 2:
The needle is made from polymeric material that combines properties of disposability with sufficient mechanical strength through proper material selection and structural design. The reduced wall thickness at the tip portion optimizes the strength-to-weight ratio, allowing the plastic needle to function equivalently to metal needles in terms of strength and flexibility while maintaining disposability advantages.
Data Source
AI summary
A needle (1, 100, 110) for precision filling of dosage containers, such as vials, ampoules etc. is provided. The needle ideally comprises an elongate plastics body (2) having a through channel (5) extending between inlet (3) and outlet (4) openings. A tip portion (7b) at the outlet opening (4) has a chamfer (8) tapering towards the outlet opening (4) and an end surface (9) around the opening so that the tip portion (7b) is frusto-conical. The surface area of the end surface (9) is sufficiently smaller than the area of the cross-section of the needle body (2) so that in use the needle (1) is capable of providing for formation of smaller droplets of liquid at the outlet (4) compared to needles without such body thickness reduction at the time when the liquid flow through the needle is shut off. The end surface (9) may be so narrow as to take the form of a sharp rim.