Reusable Autoinjector Hinge Loading Mechanism
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Solution Overview
Problem
Current auto-injectors for administering liquid medicaments require multiple user actions for resetting and loading, which can lead to user discomfort and increased risk of incomplete doses or needle stick injuries, especially for reusable devices.
Innovation Solution
A reusable auto-injector design featuring a hinge mechanism that allows the device to be split into two portions for easy loading and unloading of syringes, with a drive spring that is compressed by rotating the portions, reducing user effort and incorporating safety features like interlock mechanisms and a spring and damper unit for reliable needle retraction and dose delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a reusable auto-injector is designed to allow loading and unloading of syringes, then the device can be used for multiple injections, but the complexity of the device increases and the risk of user error increases
Solution Approach 1:
The housing is divided into two rotatable portions (first portion and second portion) that can be separated relative to each other. This segmentation allows the user to access and load/unload syringes by simply rotating the portions, without needing to disassemble the entire device. The segmented design maintains reusability while minimizing complexity.
Solution Approach 2:
The syringe is nested within the housing, specifically positioned in the first portion. The needle is contained within the syringe, and the plunger is nested within the syringe barrel. This nested arrangement allows compact storage while enabling easy access to the syringe for loading and unloading operations.
2Reliability
If the drive spring is made strong enough to deliver the full dose, then complete dose delivery is ensured, but the force required to compress the spring increases user effort
Solution Approach 1:
The loading mechanism transitions from a linear compression motion to a rotational motion. By rotating the first and second portions of the housing relative to each other, the user winds the drive spring through a rotational path. This dimensional change allows the user to apply smaller forces over a longer path, making it feasible to compress a strong drive spring without requiring excessive user effort.
Solution Approach 2:
The drive spring is compressed in a periodic winding motion through rotation, rather than a single continuous linear compression. This periodic action allows the user to build up the required spring force gradually through multiple rotational turns, reducing the peak force requirement at any single moment.
3Ease of operation
If the needle is exposed for injection, then dose delivery is enabled, but the risk of needle stick injuries increases
Solution Approach 1:
The needle is pre-covered by a needle cover before injection. The user performs preliminary actions of removing the needle cover and positioning the device before the needle becomes exposed. After injection, the needle is automatically retracted or covered again. This preliminary and follow-up protective action reduces needle stick injuries while maintaining injection capability.
Solution Approach 2:
The needle exposure is minimized in time - the needle is exposed only for the brief moment when injection is actually occurring. The rapid transition from covered to exposed and back to covered state reduces the window of opportunity for accidental needle stick injuries, while still allowing complete dose delivery during the brief exposure period.
4Reliability
If the device includes safety interlock mechanisms, then accidental activation is prevented, but the number of user actions increases
Solution Approach 1:
The safety interlock mechanism is merged with the loading mechanism. The same rotational motion of the first and second housing portions that enables syringe loading also operates the safety interlock to enable or disable injection. This combining of functions reduces the total number of separate user actions required, while still providing reliable accidental activation prevention.
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 simplifies the process of resetting and loading the auto-injector, reduces user effort, enhances safety by preventing accidental activation and needle stick injuries, and ensures complete dose delivery with reliable syringe emptying.
Implementation Method 1
a drive spring capable of, upon activation: pushing the needle from a covered position inside the housing into an advanced position through the orifice and past the proximal end, and operating the syringe to supply the dose of medicament
Implementation Method 2
The elongate housing comprises a distal portion and a proximal portion connected by a hinge, the hinge having a rotational axis offset from a longitudinal axis of the auto-injector and oriented transversally with respect to the longitudinal axis. The portions are rotatable about the hinge relative to each other
Implementation Method 3
a spring and damper unit for reliable needle retraction and dose delivery
Data Source
Figure 1~2
Figure 3~5B
Figure 5C~7
AI summary
The invention relates to an auto-injector (1 ) for administering a dose of a liquid medicament (M), comprising: an elongate housing (2) arranged to contain a syringe, the housing (2) having a distal end (D) and a proximal end (P) with an orifice, wherein the syringe (3) is slidably arranged with respect to the housing (2), a drive spring (8) capable of, upon activation: pushing the needle (4) from a covered position inside the housing (2) into an advanced position through the orifice and past the proximal end (P), and operating the syringe (3) to supply the dose of medicament (M), and activating means (16) arranged to lock the drive spring (8) in a compressed state and capable of releasing the drive spring (8) for injection, wherein the elongate housing (2) comprises a distal portion (2.1 ) and a proximal portion (2.2) connected by a hinge (10), the portions (2.1, 2.2) rotatable about the hinge (10) between an aligned position and a maximum opening angle, wherein the drive spring (8) may be compressed by rotating the portions (2.1, 2.2) towards the maximum opening angle, wherein the activating means (16) are arranged to lock the drive spring (8) in the compressed state when the portions (2.1, 2.2) are rotated at least almost to the maximum opening angle and wherein a loading bay (7) for holding the syringe (3) is arranged in the proximal portion (2.2).