Auto-Injector Trigger Mechanism for High Viscosity Medicament Delivery
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Solution Overview
Problem
Current auto-injector devices face challenges in administering high viscosity medicaments, as they require strong drive springs that result in high impact and force during needle insertion and injection, potentially causing discomfort and increasing the risk of incomplete doses due to user tremors and manual dexterity issues.
Innovation Solution
The auto-injector features a mechanism with a trigger button and detent mechanism that allows for controlled needle insertion and medicament delivery, utilizing a combination of springs and ramped engagements to manage force and motion, ensuring consistent injection depth and complete dose delivery without excessive user effort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If strong drive springs are used to expel high viscosity medicaments, then the medicament can be delivered through the needle, but high impact and force are felt by the user during needle insertion and injection
Solution Approach 1:
The drive mechanism is segmented into multiple springs (first drive spring and second drive spring) that operate at different stages of the injection process. The first spring provides initial force for needle insertion while the second spring continues the expulsion process, distributing the force application over time and reducing peak impact forces on the user.
Solution Approach 2:
The first drive spring is pre-compressed and ready to provide immediate force upon trigger activation. This preliminary preparation ensures that the high viscosity medicament can be expelled efficiently without requiring the user to apply excessive force during the actual injection, as the system has already stored the necessary energy.
2Ease of operation
If manual devices are used for injection, then the user can control the injection process, but the user must continuously press the button/plunger which requires sustained physical effort and can cause trembling
Solution Approach 1:
The auto-injector device performs the injection function automatically once triggered. The drive springs self-generate the force needed to insert the needle and expel the medicament without requiring the user to continuously apply pressure. The user simply needs to activate the device once, and the system completes the injection autonomously.
Solution Approach 2:
The injection process is divided into distinct periodic stages: needle insertion phase (driven by first spring), medicament expulsion phase (driven by second spring), and retraction phase. Each stage is automatically executed in sequence, eliminating the need for sustained manual pressure while maintaining precise control over the injection process.
3Quantity of substance
If the button/plunger extension is made long to ensure complete dose delivery, then the full dose can be administered, but it becomes inconvenient for the user to reach and operate
Solution Approach 1:
The mechanical button-plunger system is replaced with a trigger-activated spring mechanism. The trigger button requires minimal travel distance and can be operated with a simple pressing motion, eliminating the need for users to reach or extend their fingers over long distances. The drive springs provide the extended mechanical action needed for complete dose delivery without requiring corresponding user reach.
4Quantity of substance
If high forces are applied to expel high viscosity medicaments, then the medicament flows through the needle, but the likelihood of delivering an incomplete dose increases due to user tremors
Solution Approach 1:
The manual button-pressing mechanism is replaced with a spring-driven system that provides consistent, controlled force for medicament expulsion. The springs generate the necessary high forces to push high viscosity medicaments through the needle without requiring user hand strength or stability, eliminating the impact of user tremors on dose completeness.
Solution Approach 2:
The force application parameters are optimized through the spring mechanism design. The springs provide sustained, controlled force over the entire expulsion duration, maintaining optimal pressure to ensure complete dose delivery. This controlled parameter application prevents the intermittent, tremor-affected force application that occurs with manual devices.
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
This design reduces user discomfort and ensures consistent, complete medicament delivery by distributing the injection force effectively, minimizing the impact of user tremors and improving the ease of use for administering high viscosity medicaments.
Implementation Method 1
The first drive spring is arranged to bear against the needle and the second drive spring is arranged to bear against the plunger. The first drive spring and the second drive spring are pre-compressed.
Implementation Method 2
A resilient beam is provided on the chassis and extends in the distal direction. The resilient beam is deflectable in the outward direction by the inward movement of the carrier.
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
Described is an injection device for administering a dose of a medicament comprising a case having a proximal end and a distal end, a carrier adapted to accommodate a syringe, and a trigger button. In a first state, the trigger button is coupled to the case and/or the carrier and abuts the distal end of the case. In an intermediate state, the case moves proximally relative to the carrier and the trigger button, and the trigger button engages the carrier. In a second state, the trigger button and the carrier move proximally relative to the case, and the trigger button disengages the carrier and engages the case.