Injection Device Locking Nut Axial Position Control
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Solution Overview
Problem
Existing injection devices lack accurate control over the axial position of the piston rod and are prone to jamming, making it difficult to set and deliver precise drug doses, especially during cartridge replacement.
Innovation Solution
A spring-driven injection device with a rotatable dose knob that stores energy in a spring member, featuring a dosage tube axially movable during dose setting and injection, and a locking nut that prevents axial movement during dose setting to ensure accurate dose delivery and easy piston rod return to initial position during cartridge replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the piston rod is locked axially during dose setting to prevent movement, then accurate dose delivery is achieved, but the piston rod cannot be returned to initial position during cartridge replacement
Solution Approach 1:
The locking nut transitions from a static locked state during dose setting to a dynamic unlocked state during cartridge replacement. The retention means allows the locking nut to be rotated to an unlocked position, enabling the piston rod to move axially back to its initial position, thus resolving the contradiction between maintaining axial lock during dosing and enabling movement during replacement.
Solution Approach 2:
The locking mechanism is segmented into distinct functional states: locked state for accurate dose delivery and unlocked state for cartridge replacement. The retention means provides a separate control mechanism that can independently activate the unlocked state, allowing different operational modes without compromising either accuracy during dosing or ease of replacement during maintenance.
2Measurement precision
If a locking mechanism is used to control piston rod position, then accurate dose delivery is achieved, but the device complexity increases
Solution Approach 1:
The locking nut is designed to be self-locking through its thread engagement with the piston rod and the retention means that maintains the locked state automatically during dose setting. The system uses the natural mechanical interaction between the locking nut and piston rod threads to provide the locking function without requiring additional active components or complex control systems.
Solution Approach 2:
The complex multi-component locking mechanism is extracted and replaced with a simple locking nut and retention means combination. By removing unnecessary intermediate components and using direct thread engagement between the locking nut and piston rod, the design achieves accurate positioning with minimal structural elements, thereby reducing overall device complexity.
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 device provides precise control over the axial position of the piston rod, minimizes the risk of jamming, and allows for easy cartridge replacement by allowing the piston rod to return freely, ensuring accurate and reliable drug delivery with reduced manufacturing costs.
Implementation Method 1
operation of the dose setting mechanism causing energy to be stored in a spring member, an injection mechanism being driven by releasing energy previously stored in the spring member during dose setting
Data Source
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AI summary
The invention relates to an injection device for injecting a dose of drug. Theinjection device com prises a housing, a dose setting mechanism being operable to set a desired dose, an injection mechanism comprising a piston rod (7) adapted to cooperate with a piston positioned in a cartridge containing a drug to be delivered in order to cause a set dose to be delivered from the cartridge via the injection device, a dosage tube (6), and retaining means arranged to prevent axial movement of the dosage tube in a distal direction relatively to the housing during dose setting. The dose setting mechanism com prises a rotatable dose knob (24), operation of the dose setting mechanism causing energy to be stored in a spring member. The injection mechanism is driven by releasing energy previously stored in the spring member during dose setting.