Adjustable Two-Piece Plunger Rod for Syringe Packaging
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Solution Overview
Problem
Syringes with breakable plunger rods that break into pieces render the assembly inoperable, and prefilled syringes require longer plunger rods, leading to increased packaging costs and space requirements due to the need for full-length plunger rods in packaging.
Innovation Solution
A two-piece plunger rod with adjustable length, comprising a distal and proximal portion that can be locked at various lengths, allowing for flexible fluid expulsion and reduced packaging needs by accommodating different fluid volumes without requiring full extension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single piece plunger rod is used in prefilled syringes to accommodate full barrel length, then the syringe can store and deliver full fluid volume, but packaging size and material usage increase
Solution Approach 1:
The plunger rod is divided into two separate pieces: a distal portion that remains in the barrel and a proximal portion that can be extended or retracted. This segmentation allows the plunger rod to be stored in a compact configuration within the barrel during packaging, reducing packaging volume, while still enabling full fluid volume delivery when the proximal portion is extended during use.
2Reliability
If a breakable plunger rod is used to prevent reuse, then syringe reuse is prevented, but the syringe assembly becomes inoperable after breaking
Solution Approach 1:
The plunger rod transitions from a static single-piece or breakable design to a dynamic two-piece design where the proximal portion can be slid relative to the distal portion. This dynamic configuration allows the syringe to remain operable after the distal portion breaks, as the proximal portion can be removed and a new distal portion can be attached, maintaining syringe functionality while ensuring single-use safety.
3Measurement precision
If a two-piece plunger rod with adjustable length is used, then packaging space is reduced and fluid dispensing precision is improved, but device complexity increases
Solution Approach 1:
The plunger rod is segmented into two pieces with specific structural features: the distal portion includes a tab with notches having ramped surfaces and stop faces, while the proximal portion includes corresponding depressions. This segmentation enables compact packaging and precise fluid dispensing through the locking mechanism, while the modular design actually simplifies manufacturing compared to a single complex piece.
Solution Approach 2:
The proximal portion of the plunger rod is designed to slide within and nest against the distal portion when retracted. This nesting configuration minimizes the overall length of the plunger rod assembly during packaging, reducing packaging volume requirements while maintaining the capability for precise fluid dispensing when extended to operational length.
Data Source
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AI summary
Medical devices comprising a syringe barrel and a two-piece plunger rod (400) are provided. According to one or more embodiments, the two-piece plunger rod includes a distal portion (410) and proximal portion (420) slidably mounted to the distal portion. The distal and proximal portions include a tab and plurality of grooves which engage to adjust the overall length of the plunger rod to a plurality of locked lengths. The locked lengths of the plunger rod permit varying amount of fluid to be expelled from the barrel.