Chamfered Bump Mechanism for Injection Needle Safety
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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 lead to inadvertent triggering or difficulty in activation.
Innovation Solution
A safety device with a tubular body and needle cover that includes a chamfered bump to reduce the stress on the needle cover, allowing for a lower and more consistent activation force, achieved through a retainer that transmits the user's force to the needle cover, with features such as chamfered abutment surfaces and a locking ring to facilitate easy passage over the bump.
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 needle cover can be reliably activated, but the activation becomes difficult and may cause inadvertent triggering
Solution Approach 1:
The patent changes the geometric parameters of the bump structure by introducing a chamfer at the first end of the bump. This modifies the contact mechanics between the needle cover and the bump, reducing the activation force required while maintaining reliable activation. The chamfer creates a more gradual contact surface that distributes stress more evenly.
Solution Approach 2:
The chamfered surface acts as a cushioning feature that reduces stress concentration at the contact point. By designing the bump with a chamfered first end, the patent pre-establishes a stress-distributing geometry that prevents sudden, high-force impacts during activation, making the activation process smoother and more controlled.
2Device complexity
If a sharp first end is used on the bump, then the structure is simpler, but the stress on the needle cover increases causing variable and higher activation force
Solution Approach 1:
The patent applies local quality modification by adding a chamfer only at the first end of the bump where contact with the needle cover occurs. This localized geometric modification targets the specific area that generates stress concentration, while the rest of the bump structure remains simple. The chamfer is strategically positioned to affect only the critical contact zone.
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 of the body has a first end provided with a chamfer extending in a circumferential direction.