Universal Plunger Rod With Movable Part For Stopper Compatibility
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Solution Overview
Problem
Existing plunger rods are often incompatible with different plunger stoppers, leading to bending, breakage, and unsafe connections, and contribute to plastic waste due to single-use design.
Innovation Solution
A plunger rod with a movable part that harpoons the inner wall of the plunger stopper via interference fit, allowing secure connection and disconnection without screwing, and is reusable across different stoppers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional screwing connecting means are used between plunger rod and plunger stopper, then connection strength is improved, but compatibility with different plunger stopper designs deteriorates and device complexity increases
Solution Approach 1:
The plunger rod is designed with a universal connecting means comprising a sleeve with an open proximal end and a distal end, allowing it to connect with various plunger stopper designs (different materials, thread designs, cavity dimensions) through a single standardized interface. The sleeve can receive different types of plunger stoppers and secure them through interference fit or friction fit, eliminating the need for multiple specialized connecting mechanisms.
Solution Approach 2:
The invention extracts the thread engagement function from the plunger rod itself and relocates it to the sleeve component. The sleeve contains the threading and engagement features, while the plunger rod maintains a simplified cylindrical distal end. This separation allows the plunger rod to be universally compatible while the sleeve adapts to different plunger stopper types.
2Loss of substance
If plunger rod is made reusable for multiple injections, then plastic waste is reduced, but risk of contamination and connection reliability deteriorates
Solution Approach 1:
The injection device is segmented into reusable components (plunger rod, sleeve, needle hub) and single-use components (plunger stopper, container). The plunger rod with its standardized sleeve interface can be safely disconnected and reused with new plunger stoppers, while the single-use plunger stopper ensures contamination prevention. This segmentation allows reusability where safe and single-use where critical for sterility.
Solution Approach 2:
The sleeve acts as an intermediary component between the plunger rod and plunger stopper. It provides a standardized interface that ensures reliable connection while allowing the plunger rod to be disconnected and reused. The sleeve's design with interference fit or friction fit mechanisms maintains connection reliability across multiple uses.
3Reliability
If plunger rod is designed for secure connection to plunger stopper, then connection reliability is improved, but ease of disconnection and reconstitution deteriorates
Solution Approach 1:
The connecting means incorporates dynamic elements including a movable seal and flexible sealing member that allow the connection to be securely formed during injection while enabling easy disconnection. The seal can move axially to accommodate connection and disconnection, and the flexible sealing member deforms to maintain reliability during use but allows straightforward separation when needed for reconstitution.
Data Source
AI summary
A plunger rod to be connected to a plunger stopper, including a rod, a sleeve having a movable part capable of moving from a first radial position to a second radial position under the effect of a centrifugal force applied thereon. Said rod being capable of sliding in translation within said sleeve from a first axial position to a second axial position under the effect of a distal pressure exerted on its proximal end. Releasable locking means configured for temporary locking said rod in its second axial position. The invention also relates to a method for connecting/disconnecting the plunger rod and a plunger stopper.