Zero-Point Adjustment in Prefilled Drug Delivery Devices
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Solution Overview
Problem
Prefilled drug delivery devices often require initial priming to eliminate clearance between the piston and piston rod, leading to drug wastage and a cumbersome manufacturing process, especially for twin chamber devices with a single dose engine, where zero-point adjustment is challenging due to interdependent actuator movements.
Innovation Solution
A drug delivery device design featuring a non-self-locking thread engagement between the piston rod and nut member, with a unidirectional ratchet coupling, allowing for easy zero-point adjustment through converging relative axial motion between the cartridge holder and housing, ensuring continuous contact between the piston and piston rod without the need for additional operations on the piston rod drive member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a prefilled drug delivery device is manufactured with standard assembly procedures, then the device can be produced efficiently, but clearance between the piston and piston rod is introduced requiring initial priming
Solution Approach 1:
The patent applies preliminary action by performing zero-point adjustment during the manufacturing process. The piston rod is pre-positioned to eliminate clearance with the piston before the device leaves the factory. This is achieved by adjusting the piston rod position while the cartridge is still in the assembly process, ensuring that no drug wastage occurs during initial priming by the end user.
2Loss of substance
If zero-point adjustment is performed during manufacturing, then drug wastage is eliminated, but the manufacturing process becomes more complex
Solution Approach 1:
The patent merges the zero-point adjustment operation with the standard assembly process. The adjustment is performed as an integrated step during manufacturing, combining the alignment and positioning operations into the existing assembly workflow rather than adding a separate complex adjustment procedure. This reduces the overall manufacturing process complexity while achieving the desired zero-clearance state.
3Manufacturing precision
If the piston rod is adjusted to eliminate clearance, then dosing accuracy is improved, but additional operations on the piston rod drive member are required
Solution Approach 1:
The patent extracts the adjustment operation from the piston rod drive member and performs it directly on the piston rod itself. By eliminating the need to operate on the drive member, the solution simplifies the manufacturing process while achieving the same dosing accuracy. The clearance elimination is accomplished through direct piston rod positioning during assembly.
4Ease of manufacture
If tolerance chains are considered in manufacturing, then assembly flexibility is maintained, but clearance between components varies requiring priming
Solution Approach 1:
The patent applies parameter changes by modifying the piston rod position parameter during assembly. By adjusting the piston rod position to account for tolerance variations in other components, the solution ensures consistent zero clearance across all devices while maintaining assembly flexibility. This parameter adjustment compensates for the natural variations introduced by tolerance chains in the manufacturing process.
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
Facilitates simple and efficient zero-point adjustment during manufacturing, eliminating air gaps and drug wastage by allowing simultaneous contact establishment between pistons and piston rods, thereby enhancing dosing accuracy and reducing manufacturing complexity.
Implementation Method 1
a non-self-locking thread engagement between the piston rod and nut member
Implementation Method 2
a unidirectional ratchet coupling, allowing for easy zero-point adjustment through converging relative axial motion
Data Source
Figure 1
Figure 2
Figure 3~6
AI summary
The present invention provides a solution for zero-point adjustment of drug delivery devices, including twin chamber drug delivery devices with a single dose engine.