Adjustable Dose Delivery Mechanism for Plunger Tolerance Compensation
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Solution Overview
Problem
Conventional medicament delivery devices face issues with manufacturing tolerances causing gaps between the piston rod and plunger, leading to inaccurate dosing and user-dependent priming, which can result in medicament loss and incorrect dose delivery.
Innovation Solution
A dose delivery mechanism with an adjusting element that allows for precise adjustment of the piston rod position before assembly, using a single threaded connection and accessible outer rim for rotation, enabling simple and user-friendly positioning of the piston rod relative to the housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bearing is located at the piston rod to contact and pressurize the plunger after final assembly, then the device can deliver medicament, but manufacturing tolerances cause gaps between bearing and plunger leading to inaccurate dosing
Solution Approach 1:
The patent applies preliminary action by adjusting the piston rod position before final assembly to account for manufacturing tolerances. The adjusting element allows the piston rod to be positioned such that the bearing will contact the plunger at the correct location after assembly, compensating for potential gaps caused by tolerance variations in plunger position (+0.4mm or +0.5mm). This pre-adjustment ensures accurate dose delivery without requiring perfect manufacturing precision.
2Loss of substance
If the bearing is located at a distance from the plunger to avoid permanent pressure, then medicament loss is reduced, but a gap varies from pen to pen requiring user priming
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the piston rod position during assembly to ensure the bearing is at the optimal distance from the plunger. This pre-adjustment eliminates the need for user priming by ensuring that the device is correctly configured before use, preventing both medicament loss from excessive compression and dosing errors from gaps.
Solution Approach 2:
The patent applies self-service by making the adjusting element accessible to the assembler during assembly but not to the end user during normal operation. The device self-configures through the adjustment mechanism during manufacturing, eliminating the need for user intervention (priming) while maintaining the benefit of reduced medicament loss.
3Reliability
If the piston rod position is adjusted to accommodate all manufacturing tolerances, then dosing accuracy is improved, but the gap becomes large requiring excessive priming steps
Solution Approach 1:
The patent applies preliminary action by performing the piston rod position adjustment during the assembly process rather than requiring it at the point of use. This pre-adjustment ensures optimal positioning that accounts for manufacturing tolerances while minimizing the gap, thereby eliminating the need for time-consuming user priming steps.
4Ease of manufacture
If the adjusting element is accessible in the preassembled state, then simple adjustment is enabled, but the mechanism becomes more complex
Solution Approach 1:
The patent applies segmentation by separating the adjustment function into a distinct adjusting element that is accessible during assembly but integrated into the overall device structure. This segmentation allows for simple adjustment during manufacturing while maintaining a relatively compact and organized device architecture, balancing ease of manufacture with acceptable device complexity.
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 allowing for precise adjustment of the piston rod position, reducing manufacturing tolerances and eliminating the need for user-dependent priming, thus enhancing the reliability and consistency of medicament delivery.
Implementation Method 1
The adjusting element is configured to perform the rotation at least while being in a preassembled position with respect to the housing, wherein the preassembled position is a most distal position of the adjusting element with respect to the housing in the preassembled state. Furthermore, the dose delivery mechanism is configured to transfer the rotation of the adjusting element into the axial movement of the piston rod via a single threaded connection in the preassembled state
Data Source
AI summary
A dose delivery mechanism includes a housing, a piston rod, and an adjusting element. The housing connecting to a container sealed by a plunger. In an assembled state, the dose delivery mechanism moves the piston rod axially in a proximal direction during dose delivery such that the piston rod exerts an axial force on the plunger to expel a medicament. In the preassembled state, the adjusting element rotates with respect to the housing, causing axial movement of the piston rod to adjust an axial position of the piston rod prior to transfer of the dose delivery mechanism from the preassembled state into the assembled state. An outer rim of the adjusting element effects rotation of the adjusting element and axial movement of the piston rod. The adjusting element performs rotation at least while being in a preassembled position with respect to the housing.