Retractable Syringe Plunger Spring Compression Mechanism
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Solution Overview
Problem
Prior art retractable syringes with spring-driven retraction mechanisms face challenges with larger volumes, as the size of the spring required for retraction is too large to fit, and users dislike the feel of gradual spring compression during plunger depression, discouraging use.
Innovation Solution
A spring-driven mechanism that retains the spring in a compressed state until decompression is needed for retraction, using a plunger with two members that maintain the spring in an initial compressed state and disengage to facilitate decompression, ensuring smooth operation and preventing subsequent plunger movement after fluid delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring-driven retraction mechanism is used in prior art retractable syringes, then the needle can be automatically retracted into the barrel, but the spring size becomes too large to fit into higher volume syringes (3, 5, 10 mL)
Solution Approach 1:
The spring is pre-compressed during plunger insertion and held in this compressed state by the plunger mechanism. This preliminary compression stores the retraction force needed for needle retraction without requiring a large spring, as the spring is already in the energy-loaded state before use.
Solution Approach 2:
The spring operates in a changed state - compressed rather than relaxed - during normal syringe use. The plunger maintains the spring in a compressed parameter state, and upon plunger removal, the spring decompresses to drive retraction. This parameter change allows a smaller spring to provide the necessary retraction force.
2Reliability
If a spring-driven retraction mechanism is used, then needle retraction is achieved, but users dislike the feel of gradual spring compression during plunger depression
Solution Approach 1:
The spring is pre-compressed during plunger insertion before the user needs to depress the plunger. This preliminary action completes the spring compression phase before use, so the user does not experience gradual compression during plunger depression. The spring is already in the compressed state ready to drive retraction.
Solution Approach 2:
The plunger itself performs the spring compression function during its insertion stroke. As the plunger moves into the barrel, it automatically compresses the spring and maintains it in this state. The system uses the plunger's own motion to service the spring compression need, eliminating the need for separate user action.
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
Enables effective retraction in higher volume syringes like 3, 5, and 10 mL, providing a smoother user experience and preventing syringe reuse by maintaining the spring in a compressed state until fluid delivery, thus disabling the syringe post-use.
Implementation Method 1
a spring-driven mechanism to automatically disable the retractable syringe and thereby prevent re-use of the retractable syringe, wherein the spring is retained in an initial compressed state by the plunger until decompression of the spring is required to drive retraction of the plunger and syringe needle engaged therewith
Data Source
AI summary
A retractable syringe includes a barrel, a collar mounted to the barrel, a retraction spring and a needle mount. The plunger includes a first plunger member and a second plunger member that are releasably coupled to initially compress the spring. The second plunger member further includes a seal to prevent fluid leakage between plunger and barrel. After depression of the plunger to deliver the syringe fluid contents, the first plunger member engages the needle mount with needle attached thereto and is rotatably uncoupled from the second plunger member to allow decompression of the retraction spring, which forces retraction of the first plunger member, needle mount and needle engaged therewith. The first plunger member and the collar include elements that co-operatively disable subsequent depression or withdrawal of the plunger. Following retraction of the first plunger member, the second plunger member and seal prevent refilling and re-use of the syringe.