Spring-Driven Injector Braking for Consistent Medicament Delivery
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Solution Overview
Problem
Existing injector devices experience an inconsistent medicament delivery rate due to the decay in spring force, causing discomfort for patients, particularly at the start of injection.
Innovation Solution
Incorporation of a brake mechanism with adjustable friction control to regulate the plunger's displacement, allowing users to set the injection speed according to patient preference and compensate for spring force decay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a coil spring provides the motive force to displace the plunger, then the medicament can be dispensed through the needle, but the force exerted by the spring on the plunger decays in accordance with Hook's law causing a high initial rate of medicament delivery that can be uncomfortable for patients
Solution Approach 1:
The brake mechanism is pre-configured to apply frictional resistance to the plunger rod, counteracting the high initial spring force before injection begins. This preliminary opposing action prevents the harmful effect of excessive initial medicament delivery rate, making the injection comfortable for patients from the start rather than allowing high initial flow that causes discomfort.
Solution Approach 2:
The brake mechanism changes the physical parameters of the system by introducing friction-based resistance that modifies the plunger acceleration and velocity characteristics. By adjusting the friction coefficient through the brake mechanism, the medicament delivery rate is controlled to maintain comfort levels throughout injection, transforming the decay pattern from harmful to beneficial.
2Loss of time
If the spring force is high initially to dispense medicament at a high rate, then the injection can be completed quickly, but the high rate of medicament delivery can be uncomfortable for some patients
Solution Approach 1:
The brake mechanism modifies the velocity-time profile of the plunger by introducing controlled friction. This changes the injection parameters to maintain a comfortable, consistent delivery rate throughout the procedure, accepting a longer injection duration as the trade-off for eliminating patient discomfort from high initial flow rates.
3Object-affected harmful factors
If a brake mechanism is added to control the rate of displacement of the plunger rod, then the medicament delivery rate can be controlled to reduce patient discomfort, but the device complexity increases
Solution Approach 1:
The brake mechanism serves as an intermediary component between the spring-driven plunger and the medicament container. This intermediate friction-based control system provides a simple yet effective means of regulating plunger velocity and medicament delivery rate, reducing patient discomfort without requiring complex electronic or mechanical control systems.
4Object-affected harmful factors
If the contact pressure between the braking surface and the outer surface of the plunger rod is increased to slow the injection rate, then patient comfort improves, but the friction force increases causing greater resistance to plunger movement
Solution Approach 1:
The brake mechanism applies frictional force locally at the contact interface between the braking surface and plunger rod outer surface. By concentrating the frictional resistance at this specific location rather than distributing it throughout the system, the mechanism efficiently controls plunger velocity and medicament delivery rate with minimal overall force requirements, improving patient comfort without excessive resistance.
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 brake mechanism ensures a consistent medicament delivery rate, reducing patient discomfort by allowing personalized injection speed adjustments.
Implementation Method 1
the brake comprising a braking surface that contacts an outer surface of the plunger rod so that movement of the plunger rod is resisted by friction between the braking surface and the outer surface of the plunger rod
Implementation Method 2
the drive mechanism comprising a plunger rod and a displacing member configured to displace a distal end of the plunger rod into said medicament container to dispense said medicament; the displacing member may comprise a spring
Implementation Method 3
A region of the outer surface of the plunger may be covered with a high friction material, said region being arranged to contact the braking surface of the brake during movement of the plunger between an initial position and an end stop position
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
An injector device comprising: an outer housing for receiving a medicament container; and a drive mechanism for dispensing medicament from a medicament container received in the outer housing. The drive mechanism comprises a plunger rod and a displacing member configured to displace a distal end of the plunger rod into said medicament container to dispense said medicament. The device further comprises a brake configured to slow the rate of displacement of the plunger rod under the force of the displacing member.