Syringe Exostructure With Ratchet Plunger for Reproducible Dosing
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Solution Overview
Problem
Existing syringes lack precision in delivering discrete, reproducible doses of medicaments like botulinum toxin and hyaluronic acid to multiple injection sites during a single procedure, leading to inaccuracies and risks of incorrect dosing due to thumb force variations and measurement errors.
Innovation Solution
A syringe exostructure that includes a drive plunger, plunger bar, drive pawl, and locking pawl, which allows incremental advancement of the plunger bar to deliver precise, pre-selected doses by engaging and disengaging with a toothed ratchet surface, preventing reverse movement, and providing tactile feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional syringes are used without additional guidance structures, then the device remains simple and inexpensive, but injection accuracy and precision deteriorate due to hand tremors and improper positioning
Solution Approach 1:
The exostructure is divided into multiple functional segments: a positioning component with alignment features, a stabilizing component with finger rests, and a guiding component with motion constraints. Each segment addresses a specific aspect of injection accuracy while maintaining modular simplicity.
Solution Approach 2:
The exostructure acts as an intermediary device between the syringe and the user's hand. It provides a mechanical interface that guides hand motion and positions the syringe, mediating the interaction to improve precision without requiring complex active control systems.
2Measurement precision
If the syringe is held freely without external support, then the operation is flexible and easy to perform, but injection precision deteriorates due to hand tremors and fatigue
Solution Approach 1:
The exostructure provides support and constraint only at specific critical locations: finger rests are positioned at exact points on the syringe barrel, alignment features are placed at the plunger interface, and guiding surfaces are located where hand contact occurs. This localized support improves precision without restricting overall handling flexibility.
Solution Approach 2:
The exostructure allows dynamic adjustment during the injection process. The guiding features constrain motion to the desired path while permitting natural hand movements and adjustments, adapting to user technique variations without compromising precision.
3Measurement precision
If no alignment features are provided, then the device structure remains simple, but the syringe may be positioned at incorrect angles leading to injection errors
Solution Approach 1:
The alignment features utilize asymmetric geometry to enforce correct syringe orientation. The positioning component includes asymmetric guides and the stabilizing component has asymmetric finger rest arrangements that naturally guide the syringe into the proper angular position, preventing incorrect orientations through geometric constraint rather than complex active control.
Data Source
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AI summary
A syringe exostructure incudes a main body which removably receives a syringe having a syringe barrel and a syringe plunger. A drive plunger is reciprocatably mounted on the main body, and a plunger bar is slidably received on the drive plunger. The plunger bar is configured to removably couple to the syringe plunger. A drive pawl coupled to the drive plunger for transferring downward motion to the plunger bar as the drive plunger is advanced and disengages from the plunger bar when the drive plunger is retracted. A locking pawl fixed to the main body for engaging the plunger bar and allowing the plunger bar to be advanced by the drive plunger as the drive plunger is advanced but prevents the plunger bar from being retracted by the drive plunger as the drive plunger is retracted.