Dose Setting Mechanism Dual Clutch Coupling Reliability
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Solution Overview
Problem
Existing dose setting mechanisms in drug delivery devices face issues where the drive sleeve can decouple from the number sleeve and housing, leading to potential underdosing or drug loss due to rotational misalignment, especially at extremes of tolerance, without providing adequate tactile or audible feedback.
Innovation Solution
A dose setting mechanism with a clicker system that includes a first and second clicker component, where the first clicker is fixed to the housing and the second to the drive member, allowing axial movement to ensure rotational coupling or decoupling, providing tactile and audible feedback, and featuring a second clutch for secure engagement, preventing simultaneous decoupling of both clutches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single clutch mechanism is used to couple the drive sleeve to the number sleeve, then the device structure is simple, but the drive sleeve may decouple from both the number sleeve and housing simultaneously, leading to rotational misalignment and dosing errors
Solution Approach 1:
The single clutch mechanism is divided into two separate clutch mechanisms: a first clutch mechanism for coupling the drive sleeve to the number sleeve, and a second clutch mechanism for coupling the drive sleeve to the housing. This segmentation ensures that the drive sleeve cannot decouple from both components simultaneously, preventing rotational misalignment and dosing errors while maintaining reasonable structural complexity
Solution Approach 2:
A clutch member is introduced as an intermediary component that mediates between the drive sleeve, number sleeve, and housing. The clutch member engages with both the first clutch (to the number sleeve) and the second clutch (to the housing), ensuring that at least one coupling is maintained at all times, thus preventing the drive sleeve from becoming disconnected from both components
2Reliability
If the clicker teeth height is increased to provide adequate engagement, then the drive sleeve coupling reliability improves, but the dialing torque increases and dialing becomes difficult
Solution Approach 1:
The single clicker mechanism is divided into two separate clicker mechanisms: a first clicker for engaging with the clutch to provide tactile feedback during dialing, and a second clicker for engaging with the housing to prevent over-rotation. This segmentation allows each clicker to have optimized tooth heights suitable for its specific function, maintaining reliable engagement while keeping dialing torque acceptable
Solution Approach 2:
The clicker teeth are designed to engage only partially during normal operation, providing sufficient tactile feedback and engagement reliability without requiring full-depth engagement. This partial action approach ensures reliable coupling while minimizing the dialing torque required, making the device easier to operate
Data Source
AI summary
A dose setting mechanism for a drug delivery device is provided comprising a dose setting member, a drive member, a clutch, a first clicker and second clicker. The first clutch and a second clutch are designed and adapted to each other such that at any time during operation either the first clutch rotationally couples the dose setting member and the drive member and/or the second clutch rotationally couples the drive member and the first clicker component. Further, the invention refers to an injection device with such a dose setting mechanism.