Variable Force Spring Medicament Delivery Mechanism
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Solution Overview
Problem
Existing medicament delivery devices face challenges in balancing the need for sufficient force to complete the injection stroke without overloading other components, while also ensuring a smooth and reliable triggering mechanism and preventing accidental needle sticks.
Innovation Solution
The device employs a variable force spring that applies a predetermined sequence of different force profiles to ensure optimal functionality, including a last force profile that increases to completely empty the medicament container. This design incorporates a rotatable latch and a retractable needle shield with a rotator to prevent accidental needle exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a fully compressed helical spring is used to provide sufficient force for injection, then the break loose force is overcome and delivery is initiated, but the force during storage may overload other components made of plastics, glass or similar materials
Solution Approach 1:
The patent changes the physical parameters of the spring from a conventional helical compression spring to a variable force tension spring with specific geometric characteristics (coil diameter, wire diameter, number of active coils, material properties) to achieve a predetermined sequence of force profiles that increase during delivery while maintaining low storage force
Solution Approach 2:
The patent employs a variable force spring that dynamically adjusts its force output during operation, transitioning from low force during storage to progressively increasing force during delivery, rather than maintaining constant high force throughout the cycle
2Reliability
If a variable force spring is used to deliver medicament with balanced force profiles, then the risk of container or device damage is reduced, but the device complexity increases due to the need for precise spring configuration and control mechanisms
Solution Approach 1:
The patent achieves variable force characteristics by modifying physical parameters of a tension spring (coil diameter, wire diameter, number of active coils, material elastic modulus) rather than using complex active control systems, thereby reducing mechanical complexity while maintaining reliability
Solution Approach 2:
The variable force spring automatically provides the correct force profile through its physical design without requiring external control mechanisms, sensors, or active regulation systems, allowing the spring itself to serve the dual function of force generation and force profile control
3Object-affected harmful factors
If a lockout mechanism is added to prevent retraction of the protective shield after delivery, then user safety is improved by preventing accidental needle sticks, but the device complexity increases
Solution Approach 1:
Instead of using a complex active locking system that requires power or control, the patent employs a passive mechanical lockout where the shield's geometry and the housing structure work together to prevent retraction through simple physical constraints
Solution Approach 2:
The lockout function is extracted from a complex active system and implemented through the inherent geometric design of the shield and housing, eliminating the need for additional motors, sensors, or control electronics
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 effectively delivers medicament with a balanced force profile, reducing the risk of container or device damage, and provides a safe and automatic mechanism for needle protection, ensuring user safety and convenience.
Implementation Method 1
The driving force needed for delivery is supplied by a coiled tension spring that is triggered by a rotating latch
Implementation Method 2
A cam on the latch converts the rotation to linear motion to disengage the plunger from the stopper
Data Source
AI summary
A device for delivery of medicament is presented that has an elongated housing, a container mounted within the housing and adapted to contain liquid medicament, a stopper slidably arranged within said container, and a delivery mechanism comprising a resilient member, a plunger assembly having one end connected to the stopper and a second end being operably connected to the resilient member, a rotatable latch for releasably retaining the plunger assembly in a first position where the resilient member has an accumulated energy, where rotation of the latch releases the plunger assembly such that the accumulated energy is transferred to the plunger assembly for driving the stopper within the container whereby the medicament within said container is delivered to an injection site. After delivery of the medicament a rotator having a hard stop feature aligns with a rib on the protective shield to prevent retraction of the protective shield.