Dose Setting Mechanism Priming Gap Elimination
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Solution Overview
Problem
Pen type drug delivery devices often suffer from initial dose inaccuracies due to manufacturing tolerance differences, resulting in a gap between the spindle and the cartridge bung, leading to a loss of medication, which is outside preferred dose accuracy limits.
Innovation Solution
A dose setting mechanism that requires a priming step before the first use, involving an additional nut-like part that engages with the housing component to axially move the dial sleeve, closing any gap between the spindle and the cartridge bung, and forming an irreversible lock to prevent relative rotational movement during priming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If manufacturing tolerance differences are not compensated, then device assembly is simpler, but dose accuracy deteriorates due to gap between spindle and cartridge bung
Solution Approach 1:
The patent introduces a priming mechanism that performs preliminary action before the first dose delivery. The dial sleeve is pre-loaded axially during assembly, and the user must perform a priming stroke (rotating the dial sleeve) before the first injection to close the gap between the spindle and cartridge bung. This preliminary action compensates for manufacturing tolerances and ensures accurate dosing from the first use.
2Manufacturing precision
If a priming mechanism is added to close the gap, then dose accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges the priming function with the existing dose setting mechanism. The dial sleeve, which already exists for dose selection, is given an additional axial pre-load that enables it to perform the priming function. By rotating the dial sleeve during priming, the user simultaneously engages the threaded engagement between the dial sleeve and inner body, closing the gap and priming the device. This integration avoids adding separate priming components.
3Ease of operation
If the dial sleeve is directly threaded to the inner body, then the structure is simpler, but axial movement during priming is not achieved
Solution Approach 1:
The patent segments the threaded engagement function from the dial sleeve by introducing a separate nut component. The nut is threaded to the inner body while the dial sleeve is coupled to the nut. This segmentation allows the dial sleeve to move axially relative to the inner body during priming, while the nut provides the threaded engagement. The segmentation enables independent optimization of each component's function.
4Loss of substance
If manufacturing tolerances are not compensated, then assembly is easier, but medication loss increases due to air gap
Solution Approach 1:
The priming mechanism performs preliminary action by pre-loading the dial sleeve axially during assembly. Before the first dose delivery, the user must perform a priming stroke that advances the spindle to contact the cartridge bung, closing the air gap. This preliminary action prevents medication loss that would occur if the gap were not closed, ensuring that the full dialed dose is delivered without being lost to the air gap.
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
Ensures accurate dose delivery by pre-loading the bung, eliminating the initial gap and maintaining dose accuracy, with the mechanism allowing for irreversible locking in reusable devices and disengagement for resetting.
Implementation Method 1
the dose dial sleeve is coupled to a nut that is rotationally engaged to the inner body... the dose dial sleeve moves axially in the distal direction during priming of the drug delivery device relative to the nut
Implementation Method 2
the dose dial sleeve rotates on a helical path during dose setting of the drug delivery device
Data Source
Figure 1~3
Figure 4~5
AI summary
A method and system for priming a drug delivery device are provided. The drug delivery device includes a forced priming feature that requires the user to move the dose dial sleeve (3) axially to cause the spindle (5) to pre-load a cartridge bung before a first dose can be dialed.