Flat Spiral Spring Medicament Delivery Force Control
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Solution Overview
Problem
Existing automatic medicament delivery devices face challenges in applying a consistent force to a piston within a predetermined range to prevent cartridge damage, ensuring accurate dose delivery, and reducing plastic deformation and creep, while maintaining ease of use and dose setting.
Innovation Solution
The device employs a flat spiral spring and a threaded plunger rod with a predetermined screw pitch to accumulate energy for consistent force application, ensuring the force is above a minimum to initiate piston movement and below a maximum to avoid damage, allowing for precise dose control and multiple administration steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a pre-tensed helical spring is used to apply force to the piston, then the piston can be driven to deliver medicament, but the initial force becomes too high causing risk of cartridge damage
Solution Approach 1:
The patent changes the spring geometry parameters by using a flat spiral spring instead of a conventional helical spring. This parameter change allows the spring to provide a controlled, gradually increasing force profile rather than a high initial force, thereby preventing cartridge damage while still delivering the required medicament volume
Solution Approach 2:
The flat spiral spring provides a dynamic force profile where the force starts low and gradually increases during piston compression. This dynamic behavior allows the piston to move smoothly through the cartridge without experiencing a sudden high force冲击, reducing the risk of cartridge damage
2Object-affected harmful factors
If a spring with smaller spring constant is used to reduce initial force, then cartridge damage risk is reduced, but the device size increases and break loose force is not achieved
Solution Approach 1:
The patent changes the spring type from helical to flat spiral, which fundamentally alters the force-displacement characteristics. This parameter change enables the spring to provide sufficient break loose force while maintaining a compact size, resolving the contradiction between reducing cartridge damage risk and maintaining device compactness
3Productivity
If a pre-tensed helical spring is used to drive the piston, then medicament delivery is achieved, but plastic deformation and creep occur in the device
Solution Approach 1:
The patent changes the spring configuration from a pre-tensed helical spring to a flat spiral spring that is not pre-tensed. This parameter change eliminates the high initial forces that cause plastic deformation and creep in plastic device components, while still enabling reliable medicament delivery through the controlled force profile of the flat spiral spring
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 reduces the risk of cartridge and device damage, improves dose accuracy, and allows for easy dose setting and multiple administration steps, while minimizing plastic deformation and creep, enabling precise and reliable medicament delivery.
Implementation Method 1
The device is provided with a flat spiral spring which is adapted to apply a force to a piston provided inside the cartridge
Implementation Method 2
a flat spiral spring and a threaded plunger rod with a predetermined screw pitch to accumulate energy for consistent force application
Implementation Method 3
a threaded plunger rod with a predetermined screw pitch to accumulate energy for consistent force application
Data Source
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 force that is above or equal to a predetermined minimum force value and below a predetermined maximum force value. The minimum force value is the lowest force value needed to deliver the predetermined dose and the maximum force value is the first force value at which it exists a risk of damaging the cartridge or the components of the device.