Medicament Delivery Sub-Assembly Snap-Fit for Transport Locking
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Solution Overview
Problem
Existing medicament delivery devices face issues with the actuation mechanism being unintentionally activated during transportation due to the disengagement of components, leading to potential breakage and wear of protrusions, which can cause operation failures.
Innovation Solution
A sub-assembly design with a snap-fit coupling mechanism between the coupling member and the main body, using engagement elements with protrusions and a rim to maintain a predetermined relative axial position, preventing unintentional rotation and movement during transport, thereby reducing the risk of component breakage and ensuring secure assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the coupling member is designed to be rotatable relative to the main body using flexible tabs and recesses, then the device can be actuated during transportation, but the protrusions may break or wear due to continuous interference, causing operation failure
Solution Approach 1:
The coupling mechanism is divided into two distinct functional segments: a snap-fit coupling for axial positioning and rotation prevention, and a rotational coupling mechanism for actuation. This segmentation allows each part to perform its specific function without interfering with the other, eliminating the wear problem while preserving actuation capability.
Solution Approach 2:
Instead of using protrusions that continuously interfere with the coupling member to prevent rotation (which causes wear), the invention inverts the approach by using a snap-fit coupling that positively locks the axial position and prevents rotation through engagement of the first engagement element with the second engagement element, eliminating continuous interference and wear.
2Stability of the object's composition
If protrusions are used to maintain relative axial position between coupling member and main body, then assembly is secured, but the protrusions are at risk of breakage or wear from continuous interference
Solution Approach 1:
The invention inverts the wear-prone protrusion interference mechanism by implementing a snap-fit coupling where the first engagement element with protrusion positively engages with the second engagement element (rim with recess). This inversion transforms continuous interference into periodic engagement only during assembly, eliminating wear while maintaining stable axial positioning.
Solution Approach 2:
The snap-fit coupling performs the axial positioning action preliminarily during assembly, establishing the correct relative position before the rotational actuation mechanism is engaged. This preliminary action ensures stable positioning without requiring continuous interference during operation or transport.
3Ease of manufacture
If the sub-assembly is designed for easy assembly into housing, then manufacturing efficiency is improved, but plastic particles may be generated from protrusion breakage
Solution Approach 1:
By inverting the coupling mechanism from continuous protrusion interference to snap-fit engagement, the invention eliminates the source of plastic particle generation (protrusion breakage and wear) while maintaining easy assembly. The snap-fit coupling provides clear assembly feedback and requires minimal force, ensuring efficient assembly without harmful particle generation.
Data Source
AI summary
A sub-assembly for medicament delivery device is presented having a plunger rod, a biasing member, a main body arranged to receive the plunger rod and the biasing member and comprising a holding member and a coupling member arranged to be rotatable relative to the main body. One of the main body and the coupling member includes a first engagement element having a protrusion extending substantially radially and the other one of the main body and the coupling member has a second engagement element which can be engaged with the protrusion such that the protrusion of the first engagement element is engaged with the second engagement element to form a snap-fit coupling to restrict the movement of the coupling member relative to the main body in a proximal direction when the holding member is in the holding position.