Ratchet System with Switchable Coupling for Dose Stability
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Solution Overview
Problem
Drug delivery devices face challenges in ensuring stability and effective design, particularly in rotational couplings, which can lead to improper dosing and safety risks due to mechanical instability and vulnerability to external forces.
Innovation Solution
A ratchet system comprising a first, second, and third member with a switchable coupling mechanism and mechanical interface, allowing rotational locking in one direction while enabling easy rotation in the other, with a dead-angle follower coupling and energy storage mechanism to manage torque and dose setting, ensuring stability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a rotational coupling mechanism is used to allow dose setting rotation, then ease of operation is improved, but stability under external forces deteriorates
Solution Approach 1:
The coupling mechanism dynamically switches between two states: a first state during dose setting where the follower coupling allows relative rotation between the dose setting member and drive member, and a second state during dose delivery where the coupling is locked to prevent unintended rotation. This dynamic state change resolves the contradiction by providing ease of operation when needed and stability when required.
Solution Approach 2:
The system changes the torque transfer capability parameter of the coupling mechanism between two discrete values: a first torque limit in the unlocked state that permits rotation, and a second higher torque limit in the locked state that prevents rotation under external forces. This parameter change enables the mechanism to satisfy both ease of operation and stability requirements under different operating conditions.
2Reliability
If a locked coupling mechanism is used to prevent unintended dispensing, then reliability is improved, but ease of operation deteriorates
Solution Approach 1:
The coupling mechanism is designed to be dynamically controllable, transitioning from a locked state that prevents unintended dispensing to an unlocked state that enables easy dose setting. The follower coupling specifically facilitates this by allowing controlled relative rotation during dose setting while maintaining stability during delivery, thus resolving the contradiction between reliability and ease of operation.
Solution Approach 2:
The system incorporates an energy storage member that automatically locks the coupling mechanism after dose setting by overcoming the retaining force, and automatically unlocks during dose delivery when the energy storage member releases. This self-service mechanism eliminates the need for separate user actions to switch between locked and unlocked states, making the system both reliable and easy to operate.
3Reliability
If a switchable coupling mechanism is introduced to manage torque, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into the follower coupling mechanism: it simultaneously acts as a torque limiting element, a switchable coupling, and a dose setting facilitator. By combining these functions into a single integrated mechanism rather than separate components, the system achieves improved reliability through better torque management while minimizing the increase in device complexity.
Data Source
AI summary
A system comprises a first member, a second member, and a third member, wherein the first and second members are rotatable relative to the third member, wherein the first and second members are coupled to one another by a dead-angle follower coupling, wherein the dead-angle follower coupling is configured such that the first and second members are rotatable relative to one another, wherein the second and third members are rotationally coupled to one another by a switchable coupling mechanism, wherein the switchable coupling mechanism is switchable between two different states, a locked state and a non-locked state, wherein the maximum torque transferable between the second and third members via the switchable coupling mechanism in the locked state is greater than in the non-locked state, wherein the switchable coupling mechanism is in the locked state when the first member is in a locking position relative to the second member.