Medicament Delivery Device Spring Force Control
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Solution Overview
Problem
Conventional automatic medicament delivery devices face issues such as risk of cartridge damage due to high initial force, poor dose-to-dose accuracy, and plastic deformation, while also being cumbersome and difficult to set precise doses and delivery times.
Innovation Solution
A device with a cartridge housing and piston system utilizing an elongated threaded plunger rod and a servo drive spring, allowing for precise force control and accurate dose delivery, featuring a threaded design that maintains force within a predetermined range to prevent cartridge damage and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a pre-tensed helical spring with high spring constant is used to provide sufficient force to move the piston, then the piston can be driven into the cartridge to expel medicament, but the initial high force may damage the fragile glass cartridge
Solution Approach 1:
The patent applies preliminary action by pre-compressing the spring during the dose setting phase (when the device is in the non-delivery state) before actual medicament delivery. This allows the spring to accumulate potential energy gradually, and when delivery is initiated, the force is applied in a controlled manner through a ramp-up mechanism rather than an abrupt high force, thus preventing cartridge damage while ensuring sufficient force for piston movement.
Solution Approach 2:
The patent implements dynamics by making the spring constant adjustable or variable during operation. The system transitions from a static high spring constant (which would risk cartridge damage) to a dynamic configuration where the spring constant can be modified or the force profile adjusted during delivery, allowing optimal balance between preventing cartridge damage and ensuring adequate force for complete medicament expulsion.
2Object-affected harmful factors
If a spring with smaller spring constant is used to reduce initial force and prevent cartridge damage, then the device size increases due to larger spring requirements, but a larger device is harder to handle
Solution Approach 1:
By performing preliminary compression of the spring during dose setting rather than relying on a permanently large spring, the system achieves the necessary force reduction during delivery without requiring a physically larger spring component. This allows the use of a compact spring that can be adequately compressed in advance, maintaining small device size while preventing cartridge damage.
Solution Approach 2:
The patent employs periodic action by cycling the spring through compression (during dose setting) and expansion (during delivery) phases. This periodic operation allows a small spring to generate the necessary force when needed, avoiding the need for a permanently large spring that would increase device size, thus maintaining portability while preventing cartridge damage.
3Productivity
If the plunger rod is allowed to freely act on the piston with high force, then medicament can be expelled quickly, but the force exceeds the safe threshold of 50-60 N and risks damaging the cartridge
Solution Approach 1:
The system applies preliminary action by pre-compressing the spring to store potential energy before delivery, then controlling the release of this energy to maintain force within the safe 50-60 N threshold throughout the delivery process. This ensures consistent, safe force application that prevents cartridge damage while maintaining adequate delivery speed through proper energy management.
Solution Approach 2:
The patent implements feedback mechanisms to monitor the force applied to the piston during delivery and adjust the spring compression or delivery rate accordingly. This feedback control ensures the force remains within the safe 50-60 N range, preventing cartridge damage while optimizing delivery speed by adjusting parameters in real-time based on actual conditions.
4Loss of time
If a high force is applied initially to move the piston quickly, then delivery time is reduced, but the force varies significantly throughout the procedure causing poor dose-to-dose accuracy
Solution Approach 1:
The patent applies dynamics by making the spring constant or force profile adjustable during the delivery process. This allows the system to maintain a more constant force throughout piston movement, improving dose-to-dose accuracy. The dynamic adjustment compensates for the natural force decay in spring systems, ensuring consistent medicament delivery rates across multiple doses while maintaining reasonable delivery times.
Solution Approach 2:
The system uses periodic action with multiple compression-delivery cycles, where each dose delivery involves controlled spring compression and expansion phases. This periodic operation, combined with controlled compression rates, ensures consistent force application across multiple doses, improving dose-to-dose accuracy while maintaining efficient delivery times through optimized cycling parameters.
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 ensures accurate and reliable delivery of predetermined doses, reduces the risk of cartridge and device damage, and provides a compact, user-friendly design for setting doses and displaying remaining medicament, while minimizing plastic deformation and maintaining consistent delivery rates.
Implementation Method 1
an energy accumulating member adapted to accumulate energy in terms of at least one predetermined step when the device is in the medicament non-delivery state
Implementation Method 2
The force that is applied to the piston during medicament delivery is generally accomplished by means of having a pre-tensed helical spring connected to the plunger rod
Implementation Method 3
an elongated threaded plunger rod adapted to be screwed into the cartridge housing
Data Source
Figure 1~2
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AI summary
The present invention relates to a device for the delivery of predetermined doses of liquid medicament to a patient, which medicament is intended to be inhaled by the patient or intended to be injected into the body of the patient. The device is adapted to be in a medicament delivery state and in a medicament non-delivery state. When the device is in a medicament delivery state, said device is adapted to drive a piston into a cartridge containing the liquid medicament to be delivered, with a predetermined force value. The device is designed and arranged to ensure that the predetermined dose of medicament expelled from the cartridge has a high degree of accuracy and to show the user in a simple manner how much medicament is remaining in the cartridge after a dose or several doses has/have been expelled and at the same time offering a shorter device, which is more convenient for the user when he/she has to carry it with him/her.