Safety Syringe Segmented Hook Retraction Mechanism
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Solution Overview
Problem
Existing safety syringes face issues with accidental retraction, insufficient resistance to hold the needle in place, incomplete locking of the plunger, and excessive residual medicine retention, which affect their usability and compliance with medical standards.
Innovation Solution
The safety syringe design incorporates a retraction syringe assembly with hooks and fingers that are easily manufactured and quality-controlled, providing enhanced resistance and ergonomic operation, and a stepped connection between the plug and plunger to minimize the force required for needle retraction and reduce medicine loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an annular fixing sleeve is used to hold the needle in place, then the needle can be retained during normal use, but the device can be accidentally retracted when force is applied to pierce rubber stoppers
Solution Approach 1:
The fixing mechanism is segmented into multiple hooks distributed around the needle hub rather than a single continuous fixing sleeve. This segmentation allows the hooks to collectively provide strong retention during normal use while individually yielding when sufficient force is applied, enabling accidental retraction to occur only when deliberately activated by piercing rubber stoppers with adequate force
Solution Approach 2:
The hooks are designed with specific geometric parameters including angle, length, and thickness that allow them to maintain elastic deformation within a safe range during normal operation, but exceed their elastic limit when force is applied to pierce rubber stoppers. This parameter optimization enables the transition from a stable retained state to an accidental retraction state under specific conditions
2Ease of operation
If the plunger is allowed to move freely to activate retraction, then the retraction mechanism can be activated, but the plunger can be accidentally removed from the casing
Solution Approach 1:
The locking mechanism is designed to automatically engage when the plunger reaches the distal end of the casing, preventing accidental removal before retraction activation is complete. This preliminary locking action ensures the plunger remains securely retained in the casing during normal operation and after retraction, while still allowing intentional movement for activation
Solution Approach 2:
The plunger-casing interaction transitions from a static friction-based retention to a dynamic lock-based retention. The lock engages automatically when the plunger reaches the distal end, providing reliable retention while allowing the plunger to move freely during the activation stroke. This dynamic system balances ease of operation for retraction activation with reliability for preventing accidental removal
3Reliability
If a friction-based fixing sleeve is used to hold the needle, then the needle can be retained, but excessive force is required to activate retraction and medicine is lost
Solution Approach 1:
The continuous friction-based mechanical retention of the fixing sleeve is replaced with a discrete hook-based retention system. The hooks engage with the needle hub at specific points rather than providing continuous friction, reducing the force required to activate retraction and minimizing medicine loss while maintaining reliable needle retention during normal use
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
The design improves the safety and usability of the syringe by preventing accidental retraction, ensuring proper locking, and minimizing medicine loss, while being easier to manufacture and quality-control, thus meeting medical standards.
Implementation Method 1
a spring forces the syringe into a cavity located within the plunger
Implementation Method 2
The fixing sleeve 112 is configured to generate a frictional force that prevents the spring 110 from expanding and thus holds the needle 106 and needle seat 108 at a fixed position
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A safety syringe (500) having a casing (502) with the distal end (510) of the casing (502) divided by one or more slots (542) into a plurality of fingers (540) that are external to and extend distally from the casing (502). Each finger (542) has a hook (544). The hooks (544) engage a needle seat (534) to hold a retraction assembly with the needle (532) protruding from the casing (502). Movement of a slider (536) within the casing (502) causes the hooks (544) to release the needle seat (534).