Resettable Drug Delivery Device Locking Element
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Solution Overview
Problem
Existing drug delivery devices with last dose mechanisms require precise timing of axial and rotational positions of the piston rod and drive sleeve for resetting, which can be cumbersome and not suitable for all devices, especially those with relative rotation of the drive member for last dose mechanisms.
Innovation Solution
A drug delivery device with a locking element that allows independent axial movement and relative rotation during dose setting, dispensing, and resetting, decoupling from the drive member during dispensing to prevent undesired movement, and featuring a resilient drive spring for reduced user force requirements, along with a gauge element for dose indication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a last dose mechanism with nut and threaded engagement is used, then the mechanism can track dose delivery, but resetting requires precise timing of axial and rotational positions which increases operational complexity
Solution Approach 1:
The device separates the resetting function into independent components: the locking element can move axially to engage/disengage the nut from the drive member's threaded portion without requiring coordinated rotational movement. This segmentation allows the nut to be reset independently of the drive member's rotational position, simplifying the resetting operation while maintaining reliable dose tracking.
Solution Approach 2:
The locking element is designed with dynamic movement capabilities, allowing it to shift axially between engaged and disengaged states. This dynamic behavior enables the locking element to automatically engage with the nut during normal operation and disengage during resetting, providing adaptability that simplifies user operation while maintaining mechanism reliability.
2Measurement precision
If the locking element is rotationally constrained to the drive member during dose setting, then dose setting accuracy is maintained, but the drive member cannot rotate independently for last dose mechanism resetting
Solution Approach 1:
The locking element provides conditional rotational constraint: during dose setting, it maintains rotational coupling with the drive member to ensure accuracy; during resetting, it can disengage axially to allow independent rotation of the drive member. This dynamic switching between constrained and independent states resolves the contradiction between precision and flexibility.
Solution Approach 2:
The system separates the rotational constraint function from the axial positioning function. The locking element's threaded engagement with the nut provides rotational constraint during dose setting, while its independent axial movement capability allows disengagement for resetting without affecting the drive member's rotational freedom.
3Device complexity
If manual driving force is used for dose dispensing, then device simplicity is maintained, but user force requirements increase
Solution Approach 1:
The resilient drive spring acts as an intermediary between the user's manual input and the dose dispensing mechanism. The spring stores energy during dose setting and releases it during dispensing, amplifying the user's input force and reducing the effort required to operate the device, while maintaining the overall simplicity of the mechanical drive system.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables easier and more reliable resetting of the last dose mechanism without axial position constraints, reduces user effort through spring assistance, and provides clear dose feedback and protection against overdosing.
Implementation Method 1
featuring a resilient drive spring for reduced user force requirements
Data Source
AI summary
The present disclosure is generally directed to a resettable drug delivery device for selecting and dispensing a number of user variable doses of a medicament. The drug delivery device comprises a housing, a cartridge holder releasably attached to the distal end of the housing, a piston rod engaging a housing insert and a drive member, a dose setting member guided within the housing to allow rotation of the dose setting member during dose setting and dose dispensing, a clutch for rotationally coupling the drive member and the dose setting member, and a locking element which is rotationally constrained to the housing and is axially movable relative to the housing between a proximal dose setting position and a distal resetting position.