Injector Piston Assembly with Compressible Section for Lower Break Loose Force
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Solution Overview
Problem
Existing injectors, particularly prefilled syringes, face challenges with high break loose force (BLF) due to increased interaction between piston sealing elements and the inner wall over time, especially in glass syringes with wide tolerances, leading to high static friction and user discomfort, and traditional lubricants can be harmful to pharmaceutical compositions.
Innovation Solution
The injector features a piston assembly with a compressible section between an actuating piston element and a passive piston element linked by a resilient frame, reducing BLF by evenly distributing the force through differential movement of sealing elements, eliminating the need for lubrication, and accommodating glass syringe tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional lubrication is used to reduce friction, then glide force is reduced, but break loose force increases due to protein aggregation and harmful effects on pharmaceutical compositions
Solution Approach 1:
The invention removes the lubricant from the system entirely, extracting the harmful element (silicone lubricant) that causes protein aggregation while still achieving low friction through the compressible section mechanism. The piston assembly operates without any lubricating substance, eliminating the harmful interaction between lubricant and pharmaceutical composition.
Solution Approach 2:
The compressible section acts as an intermediary mechanism between the piston element and the liquid pharmaceutical composition. This intermediate structure provides the necessary friction reduction and smooth operation without requiring traditional lubricants, thereby preventing protein aggregation and harmful effects on the pharmaceutical composition.
2Reliability
If piston sealing elements interact with inner wall over time, then sealing is maintained, but break loose force increases due to stick effect
Solution Approach 1:
The invention introduces a dynamic compressible section that adapts to the interaction between piston sealing elements and the inner wall over time. This dynamic structure maintains sealing reliability while preventing excessive stick effect buildup, allowing the piston to move smoothly even after long storage periods without requiring high break loose force.
Solution Approach 2:
The compressible section changes its physical parameters (compression, elasticity) in response to the interaction between sealing elements and the inner wall. This parameter change allows the system to maintain effective sealing while reducing the stick effect that would otherwise increase break loose force over time.
3Reliability
If piston diameter is increased to ensure sealing in glass syringes, then container closure integrity is improved, but break loose force increases due to tighter fit
Solution Approach 1:
The invention segments the piston assembly into multiple elements (first piston element, second piston element) with a compressible section between them. This segmentation allows each element to have optimized dimensions for sealing while the compressible section manages the friction and break loose force, preventing the need for a single large-diameter piston.
Solution Approach 2:
The compressible section serves as an intermediary that mediates between the sealing requirements and the friction generation. It allows the piston elements to maintain adequate sealing contact with the glass syringe wall while the compressible material absorbs excess friction, preventing high break loose force even with larger piston dimensions.
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 solution provides a smoother user experience with reduced BLF comparable to glide force, ensuring efficient sealing and long-term storage without lubricant-related issues, particularly suitable for prefilled syringes.
Implementation Method 1
a compressible section between an actuating piston element and a passive piston element, which piston elements abut the inner wall of the cylinder at abutting interfaces thereby sealing the compressible section when the piston assembly is inserted in the cylinder
Implementation Method 2
a resilient frame linking the actuating piston element to the passive piston element
Implementation Method 3
thereby sealing the compressible section when the piston assembly is inserted in the cylinder
Data Source
AI summary
The present invention relates to an injector for delivery of a pharmaceutical composition, the injector comprising—a cylinder extending along a longitudinal axis, the cylinder having an inner wall, an outer wall, and an outlet at an outlet end opposite an actuating end, a piston assembly comprising a compressible section between an actuating piston element and a passive piston element, which piston elements abut the inner wall of the cylinder at abutting interfaces thereby sealing the compressible section when the piston assembly is inserted in the cylinder, the compressible section comprising a compressible fluid and a resilient frame linking the actuating piston element to the passive piston element. The injector is suited for pre-filled injectors allowing long term storage of protein based pharmaceutical compositions.