Pre-charged Spring Drive Mechanism for Low-Force Drug Delivery
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Solution Overview
Problem
Existing drug delivery devices require high user input forces for dose setting and dispensing, are bulky, and often unsuitable for impaired users, with limited design flexibility due to constraints in the drive mechanism, particularly in compact form factors.
Innovation Solution
A drive mechanism featuring a pre-charged spring and a flexible piston rod with a rack and pinion system, allowing for low user force requirements and compact design, with a clutch mechanism to prevent unintended dose delivery and a user-friendly interface for setting and dispensing variable doses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a traditional drive mechanism is used in drug delivery devices, then the device can deliver medication, but it requires high user input forces for dose setting and dispensing
Solution Approach 1:
The drive spring is pre-charged during device assembly or prior to use, storing mechanical energy in advance. This preliminary action eliminates the need for the user to manually wind or charge the spring during dose setting, significantly reducing the input force required. The pre-charged spring then provides the necessary driving force for both dose setting and medication dispensing operations.
2Volume of moving object
If a traditional drive mechanism is used, then the device can function, but it tends to be bulky
Solution Approach 1:
The flexible piston rod is configured to nest within or alongside the cartridge assembly, with the piston rod segments arranged to fit within the device housing in a compact manner. This nesting arrangement allows the drive mechanism components to occupy minimal space while maintaining full functionality, enabling a compact overall device design without sacrificing design flexibility.
3Volume of moving object
If a rigid piston rod is used, then the structure is simple, but the device cannot achieve compact form factor
Solution Approach 1:
The piston rod is divided into multiple rigid segments connected by flexible hinges, creating a articulated structure. This segmentation allows the piston rod to bend and conform to the compact device geometry while maintaining structural integrity and pushing force transmission. The segmented design enables the piston rod to navigate within the constrained space of a compact device without requiring complex mechanisms.
4Loss of time
If the drive spring is charged during use, then the device can be reset, but it requires high user force and time
Solution Approach 1:
The drive spring is pre-charged during device assembly or prior to use, storing mechanical energy in advance. This preliminary action eliminates the need for the user to manually wind or charge the spring during dose setting, significantly reducing both the time and input force required. The pre-charged spring then provides the necessary driving force for both dose setting and medication dispensing operations.
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 reduces user force needed for dose setting and dispensing, enables a compact and ergonomic device design, and provides intuitive operation, especially beneficial for impaired users, while ensuring accurate and reliable medication delivery.
Implementation Method 1
a drive spring (130) which is charged during manufacture or assembly and the energy stored in the drive spring (130) during said charging is sufficient to move the piston rod (120) from the first to the second position
Implementation Method 2
a toothed piston rod (120), which is guided within and movable relative to the base portion (30), and a drive gear (110) having a pinion (114), which is rotatably held in the base element (30) and in meshed engagement with the toothed piston rod (120)
Data Source
Figure 1
Figure 2~3
Figure 4a~4c
AI summary
The invention is directed to a drive mechanism for use in a drug delivery device having a cartridge (140), the mechanism comprising a base element (30), a toothed piston rod (120) movable from a first retracted position corresponding to a full cartridge to a second extended position corresponding to an empty cartridge, wherein the piston rod (120) is guided within and movable relative to the base portion (30), and a drive gear (110) having a pinion (114), which is rotatably held in the base element (30) and in meshed engagement with the toothed piston rod (120), wherein the toothed piston rod (120) comprises multiple rigid rod pieces (121) which are connected by hinges (122), and a drive spring (130), which is fixed to the base element (30) with one end and fixed to the drive gear (110) with another end and which exerts a force or torque to the drive gear (110) for rotating the drive gear (110) relative to the base element (30), which rotation results in a movement of the toothed piston rod (120). The drive spring (130) is charged during manufacture or assembly, wherein the energy stored in the drive spring (130) is sufficient to move the piston rod (120) from the first to the second position. The invention is also directed to a drug delivery device.