Piston Washer Axial Clearance Control via Phase Transition
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Solution Overview
Problem
Existing drug delivery devices face challenges in consistently eliminating axial clearance between the piston rod and piston, leading to variations in dose accuracy and requiring complex priming processes, which can be cumbersome for users with impaired vision or dexterity.
Innovation Solution
A piston washer with a polymeric substance that transitions from a compressible to a non-compressible state, allowing it to adapt to initial clearance between the piston rod and piston, ensuring accurate dose dispensing by preventing relative axial movement and maintaining a reduced axial dimension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a rigid distance defining device is used between the piston rod and piston, then the axial clearance can be precisely controlled, but the device complexity increases and manufacturing becomes more difficult
Solution Approach 1:
The patent applies parameter changes by using a polymeric substance that transitions from a compressible state during assembly to a non-compressible state in final use. This allows the distance defining device to change its mechanical properties (from compressible to rigid) based on the operational phase, thereby achieving precise axial clearance control without requiring complex rigid positioning mechanisms throughout the entire device lifecycle
Solution Approach 2:
The patent implements dynamics by designing the distance defining device with a polymeric substance that dynamically changes its state from compressible to non-compressible. During assembly, the polymer remains compressible to allow for tolerance accommodation and easy positioning, then transitions to a non-compressible state to maintain precise axial clearance, thereby reducing assembly complexity while achieving manufacturing precision
2Manufacturing precision
If manual priming operations are required to eliminate axial clearance, then dose accuracy can be improved, but the ease of operation deteriorates for users with impaired vision or dexterity
Solution Approach 1:
The patent applies self-service by designing the polymeric substance to automatically transition from a compressible to a non-compressible state during the normal assembly and initial operation of the device. This self-transforming mechanism eliminates the need for users to perform manual priming operations to eliminate axial clearance, thereby maintaining dose accuracy while significantly improving ease of operation for users with impaired vision or dexterity
Solution Approach 2:
The patent implements preliminary action by pre-configuring the polymeric substance to undergo state transformation during the manufacturing and assembly process. The axial clearance elimination occurs automatically during device preparation rather than requiring user action at the point of use, thereby ensuring dose accuracy while removing the burden of complex manual priming operations from the user
3Reliability
If the axial distance between piston rod and piston is reduced to eliminate clearance, then dose consistency is improved, but the device complexity increases due to additional adjustment mechanisms
Solution Approach 1:
The patent applies parameter changes by utilizing the phase transition of the polymeric substance from compressible to non-compressible state. This natural material property change automatically achieves the required axial distance reduction for clearance elimination without requiring complex mechanical adjustment mechanisms, thereby maintaining dose consistency while minimizing device complexity
Solution Approach 2:
The patent replaces a potential complex mechanical adjustment system with a material-based solution. The polymeric substance's inherent ability to transition between compressible and non-compressible states substitutes for what would otherwise require intricate mechanical mechanisms to achieve and maintain precise axial clearance, thereby ensuring dose consistency with a simpler overall device architecture
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
This solution simplifies the assembly process, eliminates clearance, and ensures consistent and predictable dose delivery, enhancing user experience and manufacturing efficiency by maintaining a uniform total doseable amount of liquid drug.
Implementation Method 1
the polymeric substance assumes a liquefied high viscosity state when the distance defining device is in the first axial compressible state... and wherein the polymeric substance is curable to maintain the shape having the reduced axial dimension causing the distance defining device to shift into the second axial non-compressible state
Implementation Method 2
the polymeric substance assumes a liquefied high viscosity state... to allow the polymeric substance to shift from a shape having an initial axial dimension into a shape having a reduced axial dimension
Data Source
Figure 1~2
Figure 3a~4b
Figure 5a~5b
AI summary
The present invention relates to a piston washer (109, 209) for use in a drug delivery device for transferring a distally directed axial force from a piston rod (107, 207) towards a piston (199, 299) of a held cartridge (189, 289). The piston washer (109, 209) defines a proximal surface portion (109a) adapted for engagement with the distal portion of a piston rod (107, 207) and a distal surface portion (109b) configured to engage and abut a piston (199, 299). An axial distance defining device (19a1, 109b1, 109c, 209c) is positioned between the proximal surface portion (109a) and the distal surface portion (109b), wherein the axial distance defining device (19a1, 109b1, 109c, 209c) is configured to be shifted from a first axial compressible state into a second axial non-compressible state. The invention further relates to a drug delivery device incorporating such piston washer (109, 209).