Needle Shield Locking Mechanism for Injection Devices
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Solution Overview
Problem
Existing injection devices with needle shields often face issues such as premature locking during use, jamming, and complexity in the locking mechanism, which can lead to incomplete dose administration and user discomfort.
Innovation Solution
The use of a biasing means to transfer activation force to a deflectable lock element, allowing for a robust and compact needle shield lock design with low friction movement, enabling the needle shield to be securely locked in a shielded position after use without premature activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the needle shield locks immediately after deflection for injection, then the locking function is activated, but the patient may be surprised by activation sound and/or reaction force and remove the device from the skin prematurely
Solution Approach 1:
The lock is prepared and positioned in advance but not activated until the appropriate moment. The lock mechanism is pre-loaded and ready, but the actual locking action occurs only after the needle shield has completed its movement to the retracted position, avoiding premature activation that would startle the patient.
Solution Approach 2:
The system anticipates the potential harm of premature locking by designing a sequence where the locking action is delayed. The cushioning effect is achieved through the timing sequence - the loud clicking sound and reaction force of locking are postponed until after the patient has settled and the injection is complete, preventing the startle response.
2Reliability
If the needle shield locks when the device is prematurely removed from the skin, then the lock engages, but the patient is unable to receive the intended dose
Solution Approach 1:
The system performs preliminary positioning of the lock mechanism in advance, but the actual locking action is conditioned on the needle shield reaching its final retracted position. This ensures that locking only occurs after the injection sequence is complete or the device has been properly removed, preventing premature locking that would block dose administration.
Solution Approach 2:
The locking mechanism is designed to respond to the position feedback of the needle shield. The lock only engages when it detects that the needle shield has reached the appropriate position (fully retracted or fully extended), providing a feedback-based control system that prevents premature locking and ensures proper sequencing of operations.
3Reliability
If a robust locking mechanism is implemented, then the needle shield lock is secure, but the device becomes unnecessarily complex with further components
Solution Approach 1:
The locking mechanism is merged with the existing needle shield structure and spring system. Rather than adding separate locking components, the invention utilizes the natural movement and existing elements of the needle shield assembly to create the locking function, thereby achieving robust security without increasing device complexity.
Solution Approach 2:
Existing components in the needle shield assembly serve multiple functions - the spring provides both the driving force for needle shield movement and the energy for lock engagement, while the lock element itself serves both as a positioning feature and a security mechanism. This multi-functionality reduces the need for additional dedicated locking components.
4Strength
If the needle shield lock uses rigid lock components, then the lock function is robust, but the movement exhibits higher friction between components
Solution Approach 1:
The lock elements are designed with curved or rounded surfaces that facilitate smooth engagement and disengagement. The curvature allows rigid components to move past each other with reduced friction by distributing contact forces over a larger area and avoiding sharp edges that would create high friction points.
Solution Approach 2:
The geometry and surface properties of the lock components are optimized to balance rigidity with low friction. This may involve changing the contact angle, surface finish, or dimensional parameters of the rigid components to minimize friction while maintaining the necessary structural strength for reliable locking.
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 solution ensures reliable needle protection, prevents incomplete dose administration, and simplifies the device design, enhancing user experience and manufacturing efficiency.
Implementation Method 1
the biasing means is configured to provide a resiliency in the radial direction for resiliently transferring an activation force from the lock activator towards the deflectable lock element
Data Source
Figure 1a~1b
Figure 1c
Figure 2a~2b
AI summary
An injection device for expelling a dose of drug from a held cartridge (600) is described. A needle shield (350, 380) is axially movable relative to a base (200, 220, 230) between a proximal collapsed position and a distal extended position. A needle shield lock comprises a deflectable lock element (392) operable to prevent the needle shield (350, 380) from being moved towards the proximal collapsed position. A lock activator (402) associated with a plunger (310, 400) exerts an activation force on the deflectable lock element when the plunger assumes a final position. A biasing means (403) is arranged to act between the lock activator (402) and the deflectable lock element (392), the biasing means (403) being configured to resiliency transfer the activation force from the lock activator (402) to the deflectable lock element (392) to enable the needle shield (350, 380) to become locked in the distal extended position but only when the plunger (310, 400) assumes the final position.