Mode Locking Mechanism for Injection Device Dose Accuracy
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Solution Overview
Problem
Existing injection devices face issues with unintended movement of the piston rod and dose setting mechanism during dose setting and injection, leading to potential drug spillage and inaccurate dosing, particularly in devices without a cylindrical scale drum.
Innovation Solution
A mode locking mechanism that prevents the piston rod from cooperating with the piston during dose setting and the dose setting member from being operated during injection, ensuring the set dose is not accidentally increased or decreased, without relying on a cylindrical scale drum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the piston rod is allowed to move freely during dose setting, then the dose setting mechanism is easy to operate, but liquid drug may be accidentally spilled and blood may be sucked into the cartridge
Solution Approach 1:
The patent applies a dynamic locking mechanism that changes state based on operational phase. During dose setting, the locking element is disengaged allowing piston rod movement. During injection, the locking element engages to prevent piston rod movement. This dynamic state change resolves the contradiction by providing freedom of movement when needed and constraint when safety is prioritized.
Solution Approach 2:
The patent introduces a locking element as an intermediary component between the piston rod and the housing. This intermediary component mediates the interaction by selectively allowing or preventing piston rod movement based on the operational phase, thereby preventing drug spillage and blood suction while maintaining ease of operation during dose setting.
2Ease of operation
If the dose setting mechanism is allowed to move during injection, then the injection process is simple, but the set dose may be accidentally increased or decreased
Solution Approach 1:
The locking element dynamically changes its engagement state based on the operational phase. During injection, the locking element engages with the dose setting mechanism to prevent any movement, ensuring dose accuracy. The mechanism remains simple to operate as the locking element automatically engages and disengages based on the injection process.
Solution Approach 2:
The locking element serves as an intermediary that prevents unintended movement of the dose setting mechanism during injection. It mediates between the injection force and the dose setting mechanism, allowing the injection to proceed smoothly while blocking any accidental dose changes, thereby maintaining measurement precision.
3Reliability
If a cylindrical scale drum is used to prevent unintended movements, then the piston rod and dose setting mechanism are locked, but the device complexity increases and flat design is not achieved
Solution Approach 1:
The patent extracts the essential locking function from the complex cylindrical scale drum structure. Instead of using a full-scale drum mechanism, the invention uses a simplified locking element that can be integrated into various parts of the device. This extraction maintains the reliability of preventing unintended movements while significantly reducing structural complexity and enabling flat design.
Solution Approach 2:
The patent segments the locking function into a separate, independent locking element that can be selectively engaged and disengaged. This segmentation allows the locking mechanism to be simplified and integrated into different portions of the device, reducing the need for a monolithic cylindrical scale drum structure and enabling more compact, flat designs.
4Measurement precision
If a cylindrical scale drum is used for dose indication, then the dose setting is precise, but the device cannot be designed as flat and space is occupied
Solution Approach 1:
The patent extracts the dose indication function from the cylindrical scale drum and implements it through alternative means such as a linear scale or digital display. This extraction eliminates the need for a cylindrical structure, enabling flat design while maintaining dose indication precision through the simplified indication mechanism.
Data Source
AI summary
An injection device having a housing, a dose setting member being operable to set a desired dose, a piston rod adapted to cooperate with a piston to cause a set dose to be expelled, and a mode locking member. The mode locking member is adapted to be in a first extreme position and in a second extreme position. When the mode locking member is in the first extreme position the piston rod is prevented from cooperating with the piston, and when the mode locking member is in the second extreme position the dose setting member is prevented from being operated to set a dose. The mode locking member is adapted to be in the first extreme position during dose setting and the second extreme position during injection of a set dose.