Injection Device Plunger Rod Axial Positioning Mechanism
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Solution Overview
Problem
Existing injection devices using force-dependent control for piston rod displacement in multi-chamber ampoules lack precision, leading to inaccurate substance delivery due to external influences and imprecise positioning.
Innovation Solution
A piston rod with a positioning element and support mechanism that maintains an exact axial position within the injection device housing, allowing independent control of the piston rod and injection button, ensuring precise dispensing accuracy by using a spring element and snap arms for secure positioning and movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If force-dependent control is used for piston rod displacement, then the device can be operated with simple mechanism, but the dispensing accuracy deteriorates due to external influences and imprecise positioning
Solution Approach 1:
The system is divided into two independent control paths: one for the piston rod (via ampoule holder insertion) and one for the injection button (via separate actuation). This segmentation allows each component to be controlled independently, eliminating the coupling that causes positioning errors in force-dependent systems.
Solution Approach 2:
The piston rod incorporates self-positioning features including a positioning element that engages with a retaining element in the housing, and a support element that provides axial support. These self-service mechanisms ensure accurate positioning without requiring complex external control systems.
2Device complexity
If the piston rod position is not precisely controlled, then the device structure can be simpler, but the position accuracy of the piston rod and proximal stopper deteriorates
Solution Approach 1:
The piston rod is pre-positioned in the housing before the ampoule holder is inserted. The positioning element is already engaged with the retaining element, establishing a known reference position. This preliminary positioning action ensures that subsequent operations start from an accurate baseline.
Solution Approach 2:
The positioning element acts as an intermediary between the piston rod and the housing, providing a precise mechanical interface that defines the axial position. This intermediary component translates the simple act of insertion into an accurately positioned state without requiring complex control mechanisms.
3Device complexity
If the injection button is directly connected to the piston rod, then the structure can be simpler, but the independent movement capability deteriorates when the injection button needs to move out of housing during mixing
Solution Approach 1:
The connection between the injection button and piston rod is made dynamic through the spring element. This allows the connection to be flexible during mixing (when the button moves out of the housing) while maintaining structural integrity. The spring enables independent movement when needed while preserving the mechanical link when required.
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 ensures high dispensing accuracy by maintaining the piston rod's axial position during mixing and injection, allowing independent movement of the injection button, thus ensuring precise delivery of the mixed substance.
Implementation Method 1
connection of the injection button to the piston rod, for example, by the spring element (2) arranged between them
Data Source
Figure 1A~1C
Figure 2A~2D
Figure 3A~3C
AI summary
The invention relates to an insert element for an injection device with a plunger rod and with an injection button that is connected to and/or interacts with the plunger rod, wherein the plunger rod has a support element (1c) with which the plunger rod can be held against an axial movement in the proximal direction of the injection device.