Drug Delivery Trigger Stalling Feedback Mechanism
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Solution Overview
Problem
Drug delivery devices often experience stalling issues due to needle blockages, leading to incomplete dose dispensing, which can result in underdosing, especially for small doses, and existing mechanisms fail to effectively indicate stalling conditions to the user.
Innovation Solution
A drug delivery device with a rotational strain sensing arrangement that converts residual torsion into an axial force, using a trigger mechanism to indicate stalling by preventing its full return to the initial position if residual torque is present, thereby alerting the user to incomplete dispensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring-driven expelling mechanism is used to automatically dispense medicament, then the device can provide consistent dosing force, but stalling occurs when needle blockages prevent full energy release, leading to incomplete dose dispensing
Solution Approach 1:
The patent implements a feedback mechanism where the trigger's return position provides information about dispensing completion. When the trigger returns fully to its initial position, it indicates successful dose delivery. When it returns partially, it signals stalling and incomplete dispensing, giving the user real-time feedback on dosing status without requiring additional sensors or complex electronics.
Solution Approach 2:
The trigger acts as an intermediary element that translates the internal mechanical state (residual torsion in the spring) into observable user feedback (trigger position). By coupling the trigger to the expelling mechanism through the drive train, the system uses the trigger's position as a mediator to communicate dispensing status to the user, eliminating the need for direct observation of internal components.
2Ease of operation
If the trigger is allowed to return fully to the initial position after actuation, then the device appears to have completed dispensing, but hidden stalling may have occurred where the dose was not fully delivered
Solution Approach 1:
The trigger's final position serves as a feedback indicator of actual dispensing completion. Full return confirms complete dose delivery, while partial return warns of stalling. This feedback mechanism maintains ease of operation (simple trigger pull) while ensuring reliability (accurate completion indication), resolving the contradiction between user convenience and dosing assurance.
3Device complexity
If residual torsion in the drive train is not sensed, then the device structure remains simple, but stalling conditions go undetected causing underdosing
Solution Approach 1:
The trigger serves as a mechanical intermediary that indirectly senses residual torsion without requiring dedicated sensors. The trigger's connection to the drive train allows it to respond to torsional forces through its return motion, translating internal mechanical stress into observable position changes while maintaining structural simplicity.
Solution Approach 2:
The expelling mechanism uses its own components (trigger, spring, drive train) to detect and indicate stalling conditions without requiring external sensing systems. The existing mechanical elements perform the dual function of dose delivery and stalling detection, eliminating the need for additional complexity while ensuring dose accuracy.
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 device ensures accurate dose dispensing by indicating stalling conditions, preventing underdosing and allowing users to recognize incomplete dispensing, thus enhancing user safety and treatment efficacy.
Implementation Method 1
A drug delivery device with a rotational strain sensing arrangement that converts residual torsion into an axial force
Implementation Method 2
a rotational strain sensing arrangement which is configured to convert rotational strain into an axial force or interlocking
Implementation Method 3
using a trigger mechanism to indicate stalling by preventing its full return to the initial position if residual torque is present
Data Source
Figure 1~3
Figure 4a~5
Figure 6~8
AI summary
The disclosure relates to a drug delivery device for expelling a pre-determined or pre-settable amount of a liquid medicament formulation which improves the stalling behavior and indicates the stalling state to the user. The device comprises: a medicament reservoir attached to a housing (10) and an expelling mechanism configured for acting against the medicament reservoir in order to expel a portion of the liquid medicament formulation therefrom, the expelling mechanism comprising -an arrangement of a threaded nut (12) in a fixed axial relation to the housing (10) and a lead screw (30) in threaded engagement with the threaded nut (12), the threaded nut (12) and the lead screw (30) being rotatable relative to each other by a rotational input interface (35), -a mechanical energy reservoir (60, 90) for storing energy, the stored energy being releasable from the energy reservoir (60, 90) by a rotational interface (61), -a drive train (40) having an upstream interface (42) coupled to the rotational interface (61) of the energy reservoir (60, 90) for feeding rotational energy into the drive train (40) and a downstream interface (49,49b) coupled to the rotational input interface (35) of the arrangement of the threaded nut (12) and the lead screw (30) for outputting rotational energy thereto to thereby rotate the lead screw (30) and the threaded nut (12) relative to each other, the drive train (40) further being equipped with a releasable latch (14, 151, 41) for preventing transfer of rotational energy from the upstream interface (42) to the downstream interface (49, 49b) when actuated and for allowing transfer of rotational energy from the upstream interface (42) to the downstream interface(49) when released; and -a trigger (70) movable relative to the housing (10) from a first position to a second position, the trigger (70) being connected to the releasable latch (14, 151, 41) for operating the releasable latch (14, 151, 41), the trigger (70) further being biased towards the first position opposite to the second position corresponding to release of the releasable latch (14, 151, 41); wherein the drive train (40) further comprises a rotational strain sensing arrangement (49a, 120, 60) which is configured to convert rotational strain into an axial force or interlocking, the axial force or interlocking being applied to the trigger (70) by a mechanical linkage (16, 160, 163) to thereby prevent the trigger (70) from returning to the first position until the rotational strain acting on the rotational strain sensing arrangement (49a, 120, 160) of the drive train (40) reduces below a predetermined threshold value.3