Auto-injection Device Locking Mechanism for Syringe Retention
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Solution Overview
Problem
Existing injection devices struggle to maintain sterility of sealed hypodermic syringes during use, as the weak return spring is insufficient to overcome the drive spring's force, leading to syringe misalignment and potential damage when the boot is removed, especially in disposable syringes.
Innovation Solution
An injection device with a releasable locking mechanism and a housing closure member that engages the boot, preventing the syringe from being driven forward until the boot is removed, along with a multi-component drive system and damping fluid to ensure controlled extension and retraction of the syringe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a weak return spring is used to allow the drive spring to do work on components during injection, then the drive spring can effectively advance the syringe, but the syringe cannot be reliably retained when the boot is removed requiring manual repositioning
Solution Approach 1:
A locking mechanism acts as an intermediary between the drive spring and syringe, preventing the syringe from moving forward until the boot is removed. The locking mechanism includes a locking member that engages with a locking surface on the syringe, ensuring the syringe remains in the correct position during boot removal without requiring the return spring to provide sufficient holding force.
2Ease of operation
If the boot is simply pulled away from the syringe, then the boot can be removed, but the syringe is pulled out of the injection device and may snap back causing damage or misalignment
Solution Approach 1:
The locking mechanism applies a preliminary counteracting force to prevent the syringe from moving forward when the boot is pulled off. The locking member engages with the locking surface on the syringe body, creating a mechanical constraint that counteracts the force generated when the boot is removed, thereby preventing the syringe from being pulled out of the housing or snapping back to its initial position.
3Reliability
If the locking mechanism is made robust to retain the syringe, then the syringe can be securely held, but the device complexity increases
Solution Approach 1:
The locking mechanism is segmented into distinct functional components: a locking member with a locking surface, a release mechanism, and associated springs. This segmentation allows each component to perform its specific function independently, simplifying the overall design while maintaining reliability. The locking member and release mechanism can be operated independently, and the mechanism can be integrated with the existing drive and return spring systems without requiring a completely new complex system.
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 device ensures the syringe is securely locked in the retracted position until the boot is removed, preventing accidental extension and ensuring proper alignment and sterility during injection, while the multi-component drive and damping fluid maintain efficient and controlled operation.
Implementation Method 1
a return spring, the restoring force of which must be overcome by the drive spring
Implementation Method 2
a drive spring and some form of release mechanism that releases the syringe from the influence of the drive spring
Data Source
AI summary
An injection device is described having a housing that receives a syringe having a boot that covers its needle. The syringe is biased by a return spring from an extended position to a retracted position. A drive spring advances the syringe from its retracted position to its extended position. A return spring restores the syringe to its refracted position. A releasable locking mechanism retains the syringe in its refracted position. A sleeve can be depressed to release the locking mechanism. A cap covers the sleeve, thus preventing the locking mechanism from being released. When the cap is removed, it takes the boot with it and no longer prevents the locking mechanism from being released. Then, the locking mechanism can be released and the injection cycle begun.