Medicament Delivery Device Blocking Wall Prevents Sleeve Flexing
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Solution Overview
Problem
Medicament delivery devices with auto-penetration functionality face a risk of accidental activation due to high axial biasing force causing the tongues of the sleeve to flex radially outwards, potentially disengaging the plunger holder, leading to unintended auto-penetration.
Innovation Solution
Incorporating a radially flexible gripping member with a radial recess and a movable sleeve having a blocking wall that prevents radial flexing, ensuring the gripping member remains engaged with the plunger holder, and using ribs to reduce material usage and facilitate activation, while maintaining axial stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a high axial biasing force is applied to the plunger holder to enable high-force auto-penetration, then the auto-penetration functionality is improved, but the tongues of the sleeve may flex radially outwards and disengage from the plunger holder, causing accidental activation
Solution Approach 1:
A blocking wall is introduced as an intermediary component between the sleeve and the gripping member. This blocking wall prevents the tongues from flexing radially outwards by physically obstructing their movement, thereby maintaining reliable engagement between the gripping member and the plunger holder while allowing the high axial biasing force to be applied.
2Reliability
If the gripping member is made radially flexible to engage with the plunger holder, then the engagement is secure, but the gripping member may flex radially outwards and disengage accidentally under high biasing force
Solution Approach 1:
The blocking wall is positioned in advance to counteract the harmful radial outward flexing of the tongues before it can cause disengagement. By preemptively blocking the radial movement path, the system prevents accidental disengagement while maintaining the necessary radial flexibility for secure engagement.
3Reliability
If the blocking wall is made thick to prevent radial flexing, then the prevention of accidental disengagement is improved, but the material usage and device complexity increase
Solution Approach 1:
The blocking wall is designed with localized thickness and positioning only where needed to prevent radial flexing. Rather than making the entire sleeve thick, the blocking wall is strategically placed to intercept the tongues' radial movement, providing the necessary stability with minimal material usage and reduced 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
The solution effectively prevents accidental disengagement of the gripping member from the plunger holder, reducing the risk of unintended activation and enhancing the safety and reliability of medicament delivery devices by maintaining the plunger holder in a fixed axial position during use.
Implementation Method 1
a radially flexible gripping member configured to engage with the radial recess to hold the plunger holder in a fixed axial position
Implementation Method 2
a blocking wall which in the first position is arranged radially outside the gripping member and which is prevented from flexing radially outwards by a radially inwards directed force applied onto the blocking wall by the housing
Data Source
AI summary
A medicament delivery device is presented having a housing, a plunger rod biased in a proximal direction of the medicament delivery device, a plunger holder radially engaging the plunger rod, and wherein the plunger holder has a radial recess, an inner body arranged radially outside the plunger holder and provided with a radially flexible gripping member that engages with the radial recess to hold the plunger holder in a fixed axial position, and a movable sleeve that moves axially in the housing from a first position to a second position, wherein the movable sleeve has a blocking wall which in the first position is arranged radially outside the gripping member and which is prevented from flexing radially outwards by a radially inwards directed force applied onto the blocking wall by the housing, thereby preventing the gripping member to flex radially outwards and disengage from the recess.