Injection device with disengagement feature and method for disengaging a plunger from a power source
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Solution Overview
Problem
Existing handheld injection devices face challenges in controlling the force applied by powerful power sources due to design constraints such as size and complexity, limiting effective force transfer mechanisms.
Innovation Solution
The injection device incorporates a translating disengagement feature with first and second disengagement elements that decouple the power source from the plunger actuation assembly at specific distances, allowing controlled force transfer and retraction of the needle after medicament injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a powerful power source is used to drive the plunger, then the injection force is sufficient, but the device size increases and complexity increases
Solution Approach 1:
The power source is segmented into two distinct springs: a first spring that provides initial driving force for needle insertion, and a second spring that provides sustained force for medicament injection. This segmentation allows each spring to be optimized for its specific function, reducing the overall complexity compared to a single powerful spring while maintaining sufficient injection force.
Solution Approach 2:
A plunger actuation assembly is introduced as an intermediary mechanism between the power source springs and the plunger. This assembly includes a plunger inner, plunger outer, and retention member that work together to translate the spring force into controlled plunger movement, enabling force control without requiring a complex direct coupling mechanism.
2Force
If a mechanism is added to control force transfer, then force control is improved, but device complexity increases
Solution Approach 1:
The retention member provides dynamic force control by transitioning from an engaged state (holding the plunger actuation assembly) to a disengaged state (releasing it). This dynamic mechanism allows the system to automatically control force transfer at different stages of operation without requiring complex continuous control systems, thereby improving force control while minimizing added complexity.
Solution Approach 2:
The system uses the energy stored in the springs themselves to control the force application sequence. The first spring's expansion naturally drives the initial motion, and the second spring's expansion provides the injection force, with the retention member's engagement/disengagement automatically timed by the mechanical interaction between components, eliminating the need for external control mechanisms.
3Reliability
If the power source remains engaged throughout, then continuous force is available, but safe retraction and complete delivery cannot be achieved
Solution Approach 1:
The retention member is预先 configured to disengage at specific moments during the operation sequence. It initially engages to prepare the plunger actuation assembly, then automatically disengages at the predetermined first moment to allow needle insertion, and disengages again at the second moment to enable safe retraction. This preliminary configuration of disengagement timing ensures reliable operation without requiring continuous active control.
Solution Approach 2:
The system deliberately discards the engagement of the retention member at appropriate moments to allow the plunger actuation assembly to move freely for safe retraction. After the injection is complete, the system recovers by allowing the springs to return to their relaxed states, enabling the needle to be retracted safely without continued force application from the power source.
Data Source
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AI summary
An injection device comprises a housing, a cartridge defining a chamber configured to hold a medicament, a plunger disposed within the chamber, and a plunger actuation assembly configured to drive the plunger. The injection device also comprises a power source configured to drive the plunger actuation assembly such that the plunger forces the medicament from the chamber a first disengagement element translationally fixed relative to the plunger actuation assembly, and a second disengagement element coupled to the plunger actuation assembly and to the power source, where the second disengagement element is translationally fixed relative to the plunger actuation assembly. The first disengagement element is configured to translationally decouple from the plunger actuation assembly when the power source drives the plunger actuation assembly a first distance, and translationally decouple the second disengagement element from the plunger actuation assembly when the power source drives the plunger actuation assembly a second distance.