Needle Safety Shield Position-Biased Actuation Mechanism
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Solution Overview
Problem
Conventional needle safety devices can be inadvertently activated by shock or vibration, leading to unintended deployment of the protection sheath, which increases the risk of needlestick injuries for healthcare workers.
Innovation Solution
A needle safety shield with a position-biased actuation assembly that includes an outer tube, an inner tube, and a thrust spring, where the inner tube is retained in a retracted position by a radially inwardly-extending stop and is moved to an extended position only when the actuator head displaces the activation ring, preventing accidental activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional safety device with a protection sheath and latch mechanism is used, then the needle can be protected after injection, but shock or vibration may inadvertently cause the latches to release and the protection sheath to move to the extended position
Solution Approach 1:
The safety mechanism is designed so that the latch can only be released after the plunger rod has been fully depressed to compress the thrust spring. This preliminary action ensures that the safety shield is locked in place during transportation and assembly, and can only be deployed after the injection is complete, preventing accidental activation by shock or vibration.
Solution Approach 2:
The thrust spring is pre-compressed by the plunger rod movement, creating a counteracting force that prevents the latch from releasing unless the plunger rod is fully depressed. This preliminary anti-action counterbalances any shock or vibration forces that might otherwise cause inadvertent activation of the protection sheath.
2Ease of operation
If the protection sheath is held in a retracted position by radially outwardly biased latches, then the needle is exposed for aspiration and injection, but the latches may unexpectedly release due to shock or vibration
Solution Approach 1:
The latch mechanism transitions from a static, shock-sensitive design to a dynamic system where the latch position is controlled by the plunger rod movement. The latch is held in the retracted position by the compressed thrust spring, and only moves to the extended position when the plunger rod is fully depressed, making the system adaptive to the injection process rather than vulnerable to external shocks.
Solution Approach 2:
The mechanism incorporates feedback through the thrust spring that senses the position of the plunger rod. The spring remains compressed during injection, providing continuous feedback that keeps the latch engaged and the needle exposed. Only when the plunger rod is fully depressed does the spring expand, signaling that injection is complete and triggering the latch release and protection sheath deployment.
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 solution ensures that the safety shield remains in a retracted position during transportation and assembly, preventing unexpected activation and minimizing the risk of needlestick injuries by requiring deliberate action to deploy the protection sheath.
Implementation Method 1
A thrust spring has a proximal end bearing against the activation ring and a distal end bearing against the inner tube. A compressive force is applied to the actuation ring by the thrust spring when the inner tube is in the retracted position. The thrust spring moves the inner tube from the retracted position to the extended position when the rim of the actuator head displaces the activation ring releasing the inner-tube pin from the actuation-ring stop.
Data Source
AI summary
A needle safety shield 10 for use with a syringe 10 having a barrel 14, a needle and a plunger rod 16. The safety shield 10 has a first tube 22. A second tube 26 is arranged for sliding movement within the first tube 22. A pin 46 is connected to one of the first and second tubes 22, 26. An activation ring 32 has a stop 72. A drive spring 34 biases the activation ring 32 in a proximal direction to place the stop 72 in engagement with the pin 46 to retain the first and second tubes 22, 26 in a retracted configuration. The movement of the plunger rod 16 to engage the activation ring 32 compresses the drive spring 34, moving the activation ring 32 distally, and moving the stop 72 out of engagement with the pin 46, allowing the drive spring 34 to move the first and second tubes 22, 26 into an extended configuration.