Drug Delivery Piston Axial Compression and Dosing Accuracy
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Solution Overview
Problem
Existing pistons for drug delivery devices suffer from suboptimal dosing accuracy and increased axial compressibility, leading to potential medicament leakage and inefficiency, particularly during initial use, and are costly to manufacture due to complex multicomponent injection molding processes.
Innovation Solution
A piston design featuring a first piston member made of a compressible material and a second piston member with lower compressibility, arranged in a cupped receptacle, allowing for separate manufacturing and assembly, reducing axial compression and enhancing mechanical stiffness, while enabling easy assembly and integration of an electronic anti-counterfeiting circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piston made of elastic and compressible material is used to seal the cartridge, then sealing capability is improved, but axial compressibility increases leading to dosing inaccuracy
Solution Approach 1:
The piston is divided into two separate components: a sealing element made of elastic material and a piston rod made of rigid material. This segmentation allows each component to be optimized for its specific function - the sealing element provides reliable sealing while the rigid piston rod ensures accurate dosing without excessive compression.
Solution Approach 2:
The invention uses composite construction by combining two different materials with distinct properties - an elastic sealing material and a rigid piston rod material. This composite approach enables the piston to simultaneously achieve both sealing reliability and dosing precision that would be impossible with a single homogeneous material.
2Manufacturing precision
If a multicomponent injection molding process is used to manufacture the piston, then axial compressibility is reduced, but manufacturing cost and complexity increase
Solution Approach 1:
Instead of using a complex multicomponent injection molding process, the invention segments the piston into separate components that can be manufactured independently using simpler, more cost-effective processes. The sealing element and piston rod are made separately and then assembled, reducing manufacturing complexity and cost while still achieving the desired axial compressibility control.
Solution Approach 2:
The invention introduces a separate rigid piston rod as an intermediary component between the driving mechanism and the sealing element. This mediator provides the necessary structural rigidity and dimensional stability without requiring complex multicomponent molding, simplifying the manufacturing process while controlling axial compressibility.
3Ease of operation
If friction forces between cartridge side wall and piston are minimized for easy operation, then ease of operation is improved, but sealing reliability may deteriorate
Solution Approach 1:
The invention applies local quality by differentiating the surface properties of the piston - the sealing surface is designed with specific friction characteristics to ensure reliable sealing, while other surfaces in contact with the cartridge body are optimized for low friction to enable smooth operation. This localized differentiation of surface properties resolves the contradiction between sealing reliability and ease of operation.
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 design improves dosing accuracy by minimizing axial compression, reduces manufacturing costs through simplified assembly, and incorporates an electronic circuit for anti-counterfeiting measures, ensuring product authenticity and operational efficiency.
Implementation Method 1
a first piston member (12) comprising a first material and forming a distal end face (22) of the piston
Implementation Method 2
a second piston member (14) comprising a second material of lower compressibility than the first material
Data Source
Figure 1~2
Figure 3
AI summary
The present invention relates to a piston for a cartridge to be filled with a medicament, the piston comprising: - a first piston member (12) comprising a first material and forming a distal end face (22) of the piston, - a second piston member (14) comprising a second material of lower compressibility compared to the first material, - wherein the second piston member (14) is arranged in a cupped receptacle (16) of the first piston member (12) and provides a thrust receiving surface (25) at a proximal end (24) of the piston.