Ramped Interface Dose Setting Mechanism for Drug Delivery
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Solution Overview
Problem
Existing drug delivery devices are either bulky due to mechanical displays or expensive due to electronic displays, and they often require complex mechanisms that can be prone to failure, especially in disposable devices, making them unreliable for user-variable dose settings.
Innovation Solution
A compact dose setting mechanism with a rotatable dose setting member, cam ring, and coupling member that uses a ramped interface for axial displacement to engage or disengage the drive mechanism, allowing stepwise dose correction with a drive spring for reduced user force and enhanced reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If mechanical displays are used for dose indication, then the device structure becomes bulky, but the device remains simple and reliable
Solution Approach 1:
The patent extracts the display function from a separate mechanical display mechanism and integrates it into the drive mechanism itself. The dial member serves dual purposes: it is both the drive element that rotates the piston rod and the display element that shows the dose setting through its peripheral markings. This eliminates the need for a separate bulky display mechanism while maintaining simplicity and reliability.
Solution Approach 2:
The dial member is designed to perform multiple functions simultaneously: it acts as the drive mechanism for dose dispensing, the display for dose indication, and the interface for dose setting. By making the dial member universal, the patent reduces the overall device volume without increasing complexity, as one component fulfills multiple roles that would traditionally require separate elements.
2Volume of moving object
If electronic displays are used for dose indication, then the device size is reduced, but the device becomes expensive
Solution Approach 1:
The patent employs a purely mechanical display solution using the dial member with peripheral markings, which is inexpensive to manufacture using standard mechanical machining or molding techniques. This avoids the high costs associated with electronic displays, sensors, and power sources, making the device economically viable for disposable or single-use applications while maintaining a compact form factor.
Solution Approach 2:
The patent replaces electronic display systems with a mechanical indication system where the dial member's position and peripheral markings provide visual dose information. This substitution eliminates expensive electronic components while achieving the same information display function, reducing manufacturing costs and improving reliability in disposable devices.
3Measurement precision
If complex mechanisms are used for dose setting, then precise dose control is achieved, but the reliability decreases
Solution Approach 1:
The dose setting mechanism is segmented into discrete, simple components: the dose setting member with circumferential markings, the dial member with corresponding engagement features, and the cam mechanism. Each component has a single, well-defined function with simple geometry, reducing the risk of failure while maintaining precise dose control through the incremental engagement of these segmented elements.
Solution Approach 2:
The cam mechanism automatically translates the rotational position of the dial member into the corresponding linear position of the piston rod, self-regulating the dose setting without requiring additional complex control systems. The inherent geometry of the cam profile ensures accurate dose delivery while simplifying the overall mechanism and improving reliability through passive, geometry-based control.
4Device complexity
If user force is applied directly for dose dispensing, then the device structure is simplified, but the user effort increases
Solution Approach 1:
The cam mechanism uses curved surfaces and rotational motion to transform the user's linear pushing force on the dose button into rotational motion of the dial member, which then drives the piston rod. This curved, rotational approach provides mechanical advantage, reducing the force required by the user compared to a direct linear actuation system, while maintaining relatively simple device structure.
Solution Approach 2:
The dose button mechanism is designed so that the user applies force only partially (pushing the button) rather than directly moving the piston rod the full distance. The cam mechanism amplifies this partial user action into the complete dose dispensing motion, reducing user effort while maintaining a simple overall drive mechanism structure.
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 solution provides a compact, reliable, and user-friendly drug delivery device capable of precise dose setting and correction with reduced user effort, minimizing the risk of mechanical failure and maintaining device compactness.
Implementation Method 1
a ramped interface between the dose setting member and the cam ring which upon rotation of the dose setting member relative to the cam ring in the second direction causes axial displacement of the cam ring
Implementation Method 2
a drive spring for reduced user force
Data Source
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Figure 7a~8
AI summary
The present invention is generally directed to a dose setting mechanism and a drug delivery device herewith, i.e. a handheld injection device for selecting and dispensing a number of user variable doses of a medicament. The dose setting mechanism comprises a dose setting member (50) rotatable relative to a housing (10, 20) in a first direction for dose setting and in an opposite second direction for dose correcting, a cam ring (150) and a coupling member (70) coupled to a drive member (110). A ramped interface (52, 152) is provided between the dose setting member (50) and the cam ring (150) such that rotation of the dose setting member (50) relative to the cam ring (150) in the second direction causes axial displacement of the cam ring (150).