Drug Delivery Drive Mechanism for Intuitive Dose Setting
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Solution Overview
Problem
Existing drug delivery devices, such as pen-type injectors, require complex dose setting mechanisms that are not intuitive for users without formal medical training, often necessitating multiple actions and higher force requirements, which complicates the administration of pre-set medicinal doses.
Innovation Solution
A drive mechanism featuring a housing with a helical thread, a non-rotatable activation means, and a piston rod with oppositely disposed threaded portions, allowing for intuitive dose setting and reduced force requirements by enabling the drive sleeve to rotate and move proximally when the activation means is pulled, and to move distally with the piston rod rotating when pushed, facilitating dose dispensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a complex dose setting mechanism with multiple actions is used, then the device can administer pre-set doses, but the ease of operation deteriorates for users without medical training
Solution Approach 1:
The drive mechanism is segmented into distinct functional zones: a helical thread portion for rotational dose setting and a linear portion for axial dose delivery. The piston rod similarly separates rotational movement (for dose selection) from linear movement (for injection), allowing each motion type to be optimized independently for its specific function.
Solution Approach 2:
The mechanism dynamically transitions between rotational and linear motion modes. During dose setting, the user rotates the activation means which engages the helical thread to turn the piston rod. During dose delivery, the motion transitions to pure linear advancement. This dynamic behavior enables intuitive single-action operation while maintaining accurate pre-set dosing.
2Reliability
If a clutch element with multiple prongs is used to selectively transmit motion, then the device can control dose dispensing, but the device complexity increases
Solution Approach 1:
The complex clutch element with multiple prongs and selective engagement mechanisms has been extracted and replaced with a simplified continuous thread structure. The helical thread on the piston rod provides continuous rotational-to-linear motion conversion without requiring discrete clutch engagement points, significantly reducing part count while maintaining reliable motion control.
Solution Approach 2:
The helical thread structure is self-acting and automatically converts rotational input to linear output without requiring external control mechanisms. As the user rotates the activation means, the thread geometry inherently controls the piston rod's linear advancement, eliminating the need for separate clutch elements to mediate the motion transmission.
3Power
If higher force is required to actuate the mechanism, then the drive can be more powerful, but the ease of operation deteriorates
Solution Approach 1:
The helical thread geometry provides a curved, progressive engagement path that distributes the actuation force over a longer distance and time. This curved trajectory mechanically advantages the user by converting small rotational forces into effective linear drive force, reducing the peak force required compared to direct linear actuation while maintaining sufficient drive power.
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 simplifies dose setting and reduces the force needed for actuation, making the device more user-friendly and efficient for administering pre-set doses, particularly suitable for disposable drug delivery devices like pen-type injectors.
Implementation Method 1
a housing having a helical thread, preferably an internal helical thread
Implementation Method 2
the piston rod further comprises a distal threaded portion and a proximal threaded portion wherein the said distal threaded portion and the said proximal threaded portion are oppositely disposed
Data Source
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AI summary
The present invention relates to drive mechanisms suitable for use in drug delivery devices, in particular pen- type injectors, wherein a number of pre-set doses of medicinal product can be administered. In particular, the present invention relates to such drug delivery devices (1) where a user may activate the drug delivery device.