Helical Coupling Arrangement for Medicament Delivery Devices
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Solution Overview
Problem
Existing attachment methods for housing parts in medicament delivery devices require excessive force, leading to potential permanent deformation and risk of disconnection due to friction and tolerance issues, while also being complex and costly to manufacture.
Innovation Solution
A coupling arrangement with helically extending attachment and locking means that distribute force longitudinally, providing a firm, irreversible connection in both longitudinal and rotational directions using complementary shapes and undercuts, reducing the risk of deformation and simplifying manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protrusions press radially on the inner surface of the housing part with grooves to lock the parts together, then the connection becomes secure and irreversible, but excessive force is required causing friction, radial deformation risk, and potential permanent deformation of components
Solution Approach 1:
The attachment means is divided into multiple radial attachment surfaces distributed around the circumference, with each surface engaging a corresponding groove. This segmentation distributes the locking force across multiple points rather than concentrating it in a single radial direction, reducing the peak force required and minimizing deformation risk while maintaining secure connection.
Solution Approach 2:
The attachment means transitions from a single radial locking point to multiple attachment surfaces distributed in both radial and circumferential dimensions. The helical extension adds a longitudinal dimension, creating a three-dimensional distribution of attachment points that distributes force more effectively and reduces stress concentration on any single component.
2Object-affected harmful factors
If radial force between protrusions and housing part is reduced to minimize deformation risk, then component deformation is reduced, but the final connection may not be tight enough and play may occur in the connection
Solution Approach 1:
Multiple attachment surfaces distributed around the circumference engage with corresponding grooves simultaneously, distributing the connection force across multiple contact points. This segmentation allows the connection to achieve sufficient tightness through cumulative engagement while keeping the force at each individual contact point low enough to avoid deformation.
Solution Approach 2:
The helical extension of the attachment means creates a curved, three-dimensional engagement path that distributes force along the longitudinal axis. This curved geometry allows the connection to be tight and secure while reducing peak radial forces that would cause deformation, as the force is distributed along the helical path rather than concentrated at a single point.
3Reliability
If the attachment geometry is made complex to achieve secure locking, then connection reliability improves, but the moulding forms and use and complexity of mould cores are adversely affected
Solution Approach 1:
The attachment means serves multiple functions simultaneously: it provides longitudinal attachment through its helical extension, circumferential locking through radially distributed attachment surfaces, and rotational locking through the complementary groove engagement. This multi-functionality achieves secure locking reliability while maintaining a relatively simple geometric form that is compatible with standard injection moulding techniques.
Data Source
AI summary
A coupling arrangement in a medicament delivery device, the coupling arrangement being adapted to permanently attach a first and a second longitudinally elongated tubular component to each other. The coupling arrangement includes a first positive connection mechanism configured to lock the first and the second components to each other such that the components are locked from being moved in a longitudinal direction in relation to each other, and a second positive connection mechanism configured to lock the first and the second components to each other such that the components are locked from being rotated in relation to each other about a longitudinal axis of the components.