Pre-Filled Injector Assembly for Zero Air Gap Dosing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing pre-filled injection devices require cumbersome assembly processes to minimize the air gap between the piston rod and plunger, which is inefficient for large-scale production.
Innovation Solution
A pre-filled injection device with a rotatable drive element and a nut element that transitions from a slidable to a permanently secured state, ensuring physical contact between the piston rod and plunger during assembly, using a resilient interface and laser welding for secure connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional assembly processes are used for pre-filled injection devices, then manufacturing simplicity is maintained, but the air gap between piston rod and plunger cannot be minimized, requiring cumbersome priming procedures
Solution Approach 1:
The piston rod is pre-adjusted to the correct position relative to the plunger during the assembly process, eliminating the need for post-assembly priming procedures. This preliminary positioning ensures the air gap is minimized before the device is used, resolving the contradiction between manufacturing precision and ease of manufacture.
Solution Approach 2:
The device is designed to automatically minimize the air gap through its own assembly process, without requiring external adjustment mechanisms or specialized assembly equipment. The piston rod and plunger are positioned relative to each other through the natural assembly sequence, making the process self-adjusting and eliminating complex priming procedures.
2Productivity
If multiple tolerances are applied in moulding and assembly of injection device parts, then manufacturing flexibility is maintained, but individual air gaps are created between piston rod and plunger, requiring initial priming
Solution Approach 1:
The invention changes the approach from trying to control air gap through tight tolerances to accepting the tolerances and compensating through the assembly process. The piston rod is positioned and secured at a specific parameter point (abutment position) that accounts for variations in other components, allowing large-scale production while maintaining consistent air gap minimization across all devices.
Solution Approach 2:
The piston rod is pre-positioned and secured to the housing structure before final assembly is complete. This preliminary positioning ensures that regardless of tolerances in other components, the air gap is minimized from the start, eliminating the need for priming and enabling efficient large-scale production without sacrificing precision.
3Manufacturing precision
If a piston rod foot is slided axially during assembly to establish contact with plunger, then air gap is minimized, but assembly process becomes complex with multiple states and securing steps
Solution Approach 1:
The invention extracts the air gap minimization function from a complex multi-state adjustment mechanism and implements it through a simple axial sliding and securing process. The piston rod foot slides axially to the required position and is then secured, separating the minimization function from unnecessary complexity and achieving the same result with a simpler mechanism.
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 effective minimization of the air gap during assembly, suitable for large-scale production, ensuring consistent dose delivery without the need for specialized assembly processes.
Implementation Method 1
The nut element has two different states; a first state wherein the nut element is axially slidable in relation to the housing structure, and a second state wherein the piston rod means abuts the movable plunger and the nut element is permanently secured to housing structure. In the first state the nut element engages the housing structure via a resilient interface capable of urging the nut element and hence the piston rod means axially in relation to the housing structure such that the piston rod means abuts the movable plunger
Implementation Method 2
using a resilient interface and laser welding for secure connection
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
The invention relates to a pre-filled injection device with a non-removable cartridge embedded in the housing structure and wherein the piston rod drive mechanism comprises a threaded piston rod which is moved helically in a nut secured to the housing structure. During assembly of the injection device it is possible to eliminate the air-gap between the plunger in the cartridge and the piston rod means by moving the nut element for the drive mechanism axially during assembly. In an alternative solution, the piston rod comprises a telescopic element which can slide axially in relation to the piston rod to obtain the zero position.