Injection Needle Safety Device Bump Geometry
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Solution Overview
Problem
Active safety devices for injection devices require a high and variable activation force to move the needle cover from the retracted to the extended position, which can be inconvenient and risky for users.
Innovation Solution
A safety device with a tubular body and a needle cover that moves between retracted and extended positions, featuring a retainer and bumps with a specific central angle and chamfer design to reduce the activation force and its variability, allowing easier and more consistent activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high activation force is used to move the needle cover from retracted to extended position, then the safety mechanism is reliably activated, but the ease of operation deteriorates and user convenience is reduced
Solution Approach 1:
The invention employs a dynamic mechanical system where the needle cover is held in a locked retracted position by a locking element engaging with a locking surface on the body. Upon distal movement, the system transitions dynamically: the locking element disengages from the locking surface, allowing the needle cover to move to the extended position. This dynamic locking/unlocking mechanism ensures reliable activation while reducing the force required compared to static high-friction systems.
Solution Approach 2:
The activation mechanism is segmented into distinct functional elements: a locking element, a locking surface, a bump, and a release element. The locking element separates the needle cover from the body through engagement and disengagement. The bump and release element provide controlled mechanical interaction to facilitate transition. This segmentation allows each component to be optimized for its specific function, reducing overall activation force while maintaining reliability.
2Ease of operation
If a high and variable activation force is used, then the needle cover can be moved to extended position, but the consistency and predictability of activation deteriorates
Solution Approach 1:
The invention changes the mechanical parameters of the system by introducing a bump with a specific geometry (central angle between 22.5°-45°) that interacts with the locking element. This geometric parameter modification creates a controlled mechanical interaction that standardizes the activation force. The release element's geometry is also optimized to provide consistent distal movement. These parameter changes transform variable, high-force activation into consistent, lower-force activation.
3Ease of operation
If the bump central angle is increased to reduce activation force, then ease of operation improves, but the structural stability and resistance to inadvertent activation may deteriorate
Solution Approach 1:
The invention optimizes the bump's central angle parameter to fall within the specific range of 22.5°-45°. This parameter optimization balances two competing requirements: a larger angle reduces activation force and improves ease of operation, while a smaller angle provides greater mechanical stability and resistance to inadvertent activation. The release element's geometry is concurrently optimized to work with this angle range, ensuring that the locking mechanism remains stable during normal use but can be reliably activated when needed.
Data Source
AI summary
The safety device includes a tubular body extending along a longitudinal axis. The tubular body is configured to receive the medical container, a needle cover movable relative to said body between a retracted position, and an extended position in which the needle cover distally extends from the retracted position in order to shield the injection needle after activation of the safety device, a release element configured to move the needle cover from the retracted to the extended position after activation of the safety device, and a retainer for maintaining the release element in a compressed condition when the needle cover is in the retracted position. The retainer is configured to transmit a user's activation force to the needle cover once the injection operation is completed. The needle cover includes a distal abutment surface, said distal abutment surface abutting against a proximal abutment surface of a bump protruding from the body in the retracted position of the needle cover. The bump extends in a circumferential direction according to a central angle comprised between 22.5°-45°.