Medicament Delivery Device Plunger Rod Ratchet Reset
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Solution Overview
Problem
Reusable medicament delivery devices with threaded plunger rods face challenges in easy handling and reverse operation, particularly when switching between multi-chamber containers, as users may struggle to correctly retract the plunger rod and existing devices often do not allow for multiple doses or container changes.
Innovation Solution
A medicament delivery device featuring a guide shell with a one-way ratchet mechanism and a drive spring system that allows the plunger rod to be automatically reset to its initial position when switching containers, enabling easy handling and multiple dose delivery without pre-tensioning the spring, using a guide shell with a longitudinally extending ratchet and flexible tongues to ensure unidirectional rotation and a locking mechanism for secure engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a threaded plunger rod is used in a reusable medicament delivery device, then the plunger rod can be advanced to deliver medicament, but the plunger rod cannot be easily threaded back to its original position
Solution Approach 1:
Instead of threading the plunger rod back manually, the invention inverts the approach by using a ratchet mechanism that allows the plunger rod to be advanced easily while preventing backward movement. The ratchet engages with a corresponding wheel, allowing unidirectional rotation that automatically resets the plunger rod position without requiring manual threading back.
Solution Approach 2:
The ratchet mechanism provides self-service by automatically preventing backward movement of the plunger rod through its one-way engagement design. The ratchet and wheel interaction ensures that the plunger rod remains in its advanced position without requiring user intervention to thread it back, eliminating the complexity of manual retraction.
2Ease of operation
If a threaded plunger rod is used, then the plunger rod can be advanced to deliver medicament, but users are uncertain about how far the plunger rod should be threaded back
Solution Approach 1:
The ratchet mechanism provides tactile feedback to the user through its engagement with the wheel, clearly indicating when the plunger rod has been advanced to the correct position. The one-way engagement creates a distinct mechanical feel that guides the user without requiring them to remember or calculate the correct threading distance.
3Adaptability or versatility
If existing delivery mechanisms are used, then medicament can be delivered, but the mechanisms do not permit return of the plunger rod
Solution Approach 1:
The invention introduces dynamic behavior to the plunger rod mechanism through the ratchet and wheel system. The mechanism transitions from a static threaded connection to a dynamic one-way engagement that allows easy advancement while automatically preventing backward movement, enabling the plunger rod to be returned to its initial position without manual threading.
4Adaptability or versatility
If multi-chamber medicament containers are used, then multiple substances can be mixed, but the device becomes more complex
Solution Approach 1:
The ratchet mechanism serves multiple functions: it prevents backward movement of the plunger rod, automatically resets the plunger rod position, and enables easy switching between multi-chamber containers. This single mechanism handles the complexity of multi-substance mixing by providing a universal one-way engagement system that simplifies operation rather than adding to the complexity.
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
Facilitates easy handling and multiple dose delivery by automatically resetting the plunger rod to its initial position when switching containers, eliminating the need for manual retraction and allowing for seamless use of multiple medicament containers without pre-tensioning the spring, enhancing user experience and device efficiency.
Implementation Method 1
a drive spring arranged to force said plunger rod in the proximal direction for subsequent delivery of medicament from said medicament container
Implementation Method 2
a guide shell one-way rotatable arranged in said distal housing part, wherein said guide shell is provided with threads arranged to cooperate with corresponding threads on said proximal housing
Data Source
AI summary
A medicament delivery device includes a distal housing part; a proximal housing part in which a multi-chamber medicament container is arranged, with the proximal housing part movable relative to the distal housing part for mixing substances in the container; a plunger rod arranged to act on a stopper in the container, where movement of the housing parts toward each other forces the stopper against the plunger rod for mixing the substances in the container; a drive force unit for forcing the plunger rod for subsequent delivery of medicament; an activation member slidable through the distal housing part and releasably connected to the drive force unit; and a guide shell one-way rotatable in the distal housing part with threads that cooperate with threads on the proximal housing part. The guide shell and plunger rod have guide members such that they are rotationally locked but slidable in relation to each other.