Drug Delivery Drive Assembly Spring Piston Rod Nut Mechanism
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Solution Overview
Problem
Existing drug delivery devices require significant user force for dose dispensing, and there is a need for a mechanism that allows for variable dose settings and efficient medication delivery with minimal user effort.
Innovation Solution
A drive assembly comprising a spring member, piston rod, and piston rod nut, where the piston rod nut rotates and axially moves during dose setting, compressing the spring, which is then released to drive the piston rod distally during dispensing, reducing the force required from the user and allowing for variable dose selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a spring-driven mechanism is used to reduce user force, then the force required from the user is reduced, but the device complexity increases
Solution Approach 1:
The drive assembly is divided into distinct functional components: a piston rod nut for dose setting, a spring member for energy storage, and a piston rod for medication delivery. This segmentation allows each component to perform its specific function efficiently, reducing the overall force required from the user while maintaining manageable device complexity through modular design
Solution Approach 2:
The spring member is pre-compressed during the dose setting phase before medication dispensing begins. This preliminary action stores elastic potential energy in the spring, which is then released during dispensing to provide the driving force, thereby reducing the force burden on the user during the actual medication delivery
2Adaptability or versatility
If the piston rod nut rotates and axially moves during dose setting, then variable dose selection is enabled, but the device complexity increases
Solution Approach 1:
The piston rod nut serves multiple functions: it acts as a threaded fastener to secure the spring member, provides a rotational interface for dose setting, and enables axial movement to compress the spring. This multi-functionality allows variable dose selection capability while avoiding the need for separate dedicated components, thereby limiting the increase in device complexity
Solution Approach 2:
The piston rod nut transitions between different motion states: during dose setting it rotates and axially moves to compress the spring, while during dispensing it remains rotationally fixed. This dynamic behavior enables variable dose selection through controlled movement, while the rotational fixing mechanism during dispensing simplifies the overall system by preventing unintended motion
3Use of energy by moving object
If the spring member compresses during dose setting, then energy is stored for dispensing, but the manufacturing precision requirements increase
Solution Approach 1:
The spring member is designed to be compressed during the dose setting phase, creating a cushioning effect that stores elastic potential energy. This pre-compression absorbs variations and tolerances that would otherwise require high manufacturing precision, as the spring's elastic properties compensate for minor dimensional variations in the assembled components
Solution Approach 2:
The spring member's compression state changes as a parameter during dose setting, transforming mechanical displacement into stored elastic energy. By utilizing the spring's non-linear force-displacement characteristics, the system can accommodate a range of compression distances while still achieving reliable energy storage, thereby reducing the stringency of manufacturing precision requirements
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 enables low-force medication dispensing with the spring member storing energy for distal movement of the piston rod, facilitating efficient and user-friendly variable dose delivery in drug delivery devices.
Implementation Method 1
The spring member may act as an energy storing member. In particular, energy may be stored in the spring member when it is compressed. This energy may be released during the dispense of a dose in order to drive the piston rod in a distal direction.
Implementation Method 2
The spring member may be, for example, a coil spring. However, any other kind of spring may be used, for example a spring washer or a wave spring.
Data Source
AI summary
A drive assembly for a drug delivery device includes a spring member, a piston rod and a piston rod nut being engaged with the piston rod. The piston rod nut is configured to rotate and axially move during dose setting. The spring member is compressed when the piston rod nut is moved during the dose setting. The piston rod nut is rotationally fixed during dose dispensing.