Encoded Member Dose Logging in Drug Delivery Device
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Solution Overview
Problem
Existing drug delivery devices face challenges in accurately measuring and recording insulin doses dispensed, particularly for users who need to administer between 1 and 80 International Units, due to manufacturing tolerances that can lead to false logging of doses, potentially causing medically serious situations.
Innovation Solution
A drug delivery device with an encoded member featuring a coded array and a processor that determines the relative rotational position of the encoded member, which is threadedly engaged with a rod, allowing for precise measurement of axial displacement and dose dispensing, eliminating the need for a distinguishing mechanism between dosing and injecting operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a distinguishing mechanism is used to differentiate dosing and injecting operations, then reliability of dose logging is improved, but device complexity increases
Solution Approach 1:
The patent extracts the distinguishing mechanism entirely from the system. Instead of adding complex switches or sensors to differentiate dosing from injecting operations, the invention uses the encoded member's rotational position alone to determine dose dispensed, eliminating the need for additional distinguishing components while maintaining logging accuracy.
Solution Approach 2:
The patent replaces mechanical distinguishing mechanisms (such as switches or position sensors) with an encoding system that uses the natural rotational movement of the encoded member during rod advancement. The coded array on the encoded member provides positional information without requiring additional mechanical distinguishing elements.
2Manufacturing precision
If the encoded member rotates at the same angular velocity as the spindle, then manufacturing precision is reduced, but measurement precision of axial displacement decreases
Solution Approach 1:
The patent creates a dynamic relationship between the encoded member's rotation and the spindle's rotation through the differential thread pitch mechanism. The encoded member rotates faster than the spindle during drug dispense, and this variable rotational relationship is accounted for in the control algorithm that calculates axial displacement from encoder signals.
Solution Approach 2:
The patent changes the rotational speed parameter of the encoded member relative to the spindle by using different thread pitches. This parameter change allows the encoded member to rotate at a higher angular velocity, which increases measurement precision while the control system compensates for the varying rotational relationship.
3Measurement precision
If a high accuracy encoder unit is used to measure small angular rotation per dose unit, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses the dynamic rotation of the encoded member (which rotates faster than the spindle) to amplify the angular displacement signal. This dynamic amplification effect allows a simpler, lower-resolution encoder to achieve the same measurement precision that would otherwise require a complex high-accuracy encoder.
Solution Approach 2:
The patent transforms the measurement problem from directly measuring small angular rotations of the spindle to measuring larger angular rotations of the encoded member through the thread engagement mechanism. This dimensional transformation allows using a simpler encoder with coarser segments while maintaining measurement precision.
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
The solution enhances the accuracy and reliability of dose measurement and recording, reducing the risk of false logging and improving user confidence in medication administration, while also simplifying the device's complexity and cost.
Implementation Method 1
an encoded member configured: to be rotatably supported inside the housing; to be threadably engaged with the second thread of the rod and to be rotatable with respect to the rod
Data Source
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AI summary
A drug delivery device is presented comprising of a housing, a plurality of contacts, a rod disposed within the housing, and an encoded member configured to be rotatably supported inside the housing, to engage with the rod and to be rotatable with respect to the rod, and to be axially constrained with respect to the housing such that axial advancement of the rod in a first direction relative to the housing causes rotation of the encoded member, wherein the outer surface of the encoded member is provided with a plurality of tracks together forming an encoder, each track comprising conductive segments and non-conductive segments and wherein the encoded member is supported in the housing such that each track is engaged by a respective one of the plurality of contacts.