Injection Device Release Latch Mechanism for Needle Retraction
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Solution Overview
Problem
Current injection devices, both manual and auto-injectors, face challenges such as user effort, incomplete dosing, and needle safety, particularly for elderly or dexterous-impaired individuals, due to the need for continuous mechanical energy and potential exposure to needle sticks during and after use.
Innovation Solution
An injection device with a syringe, stopper, and drive means, featuring a release latch member that interrupts force propagation to allow needle retraction after a predefined dose is delivered, using a viscous damper to delay the compression of a plunger spring, ensuring complete dose delivery and safe needle retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a manual device with button/plunger is used, then the user can control the injection process, but the user must provide continuous mechanical energy and may deliver incomplete dose due to dexterity problems
Solution Approach 1:
The device uses a spring mechanism that automatically provides the force needed to push the stopper and deliver the medicament without requiring continuous user effort. The user only needs to trigger the mechanism, after which the system serves itself to complete the injection reliably.
Solution Approach 2:
The spring is pre-loaded with energy before use, storing the mechanical force needed for injection. This preliminary action eliminates the need for the user to provide continuous force during the injection process, ensuring reliable dose delivery even for users with dexterity problems.
2Reliability
If auto-injector with spring energy is used, then complete dose delivery is ensured, but needle retraction after injection is not achieved
Solution Approach 1:
The device separates the injection function from the needle retention function. The spring is configured to push the stopper and needle assembly only to a specific position that delivers the complete dose, but not far enough to permanently eject the needle from the syringe, allowing the needle to remain accessible for proper disposal while ensuring complete dosing.
3Reliability
If button/plunger extension is increased, then full dose delivery is possible, but hand shaking and discomfort increase
Solution Approach 1:
The device replaces the manual mechanical system (user pressing button/plunger) with an automated spring-driven system. The spring provides the necessary mechanical force to push the stopper through the entire行程 to deliver the full dose, eliminating the need for the user to maintain continuous pressure and reducing hand shaking and discomfort.
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 reliable needle retraction and complete dose delivery, reducing user effort and enhancing safety by automatically hiding the needle within the syringe, thus preventing needle sticks and ensuring accurate dosing, especially with expensive medications.
Implementation Method 1
using a viscous damper to delay the compression of a plunger spring
Data Source
Figure 1~2
Figure 3~5B
Figure 5C~7
AI summary
The invention relates to an injection device, comprising a syringe (3) with a hollow needle (4) and a stopper (6) for sealing the syringe (3) and displacing a medicament (M) stored in the syringe (3), the injection device further comprising a drive means (8), a plunger (9) arranged for pushing against the stopper (6) and an arrangement for transferring a translation of the drive means (8) to the plunger (9), the arrangement comprising an elongate release latch member (22) pivoted at one end which is connected to either the drive means (8) or the plunger (9), the release latch member (22) having another end for engaging the respective other one of the drive means (8) or the plunger (9), wherein the release latch member (22) is arranged to have its non- pivoted other end disengaged by rotation due to contact between at least one ramp (15.2, 22.1) and another component when the stopper (6) has at least nearly displaced all of a predefined dose of the medicament (M), wherein a length of the release latch member (22) is specified so as to provide a clearance between the plunger (9) and the drive means (8) when the release latch member (22) is engaged in order to allow at least the plunger (9), the stopper (6) and the hollow needle (4) to be retracted at least far enough to hide the needle (4) inside the syringe (3) or inside a housing (2) after disengaging the release latch member (22).