Injection Pen Plunger Release for Post-Use Needle Retention
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Solution Overview
Problem
Existing injection devices do not have a mechanism to hold the injection needle protruding from the housing after use, which is necessary to prevent drug leakage from the injection site.
Innovation Solution
The injection device incorporates a barrel and plunger mechanism with an engaging member and urging parts, along with a rotation restricting mechanism to control the release and return of the plunger, allowing the injection needle to be held in a protruding position after use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the plunger is allowed to rotate freely to release engagement with the engaging member, then the injection needle returns to the housing quickly, but the injection needle cannot be held in the protruding position after use
Solution Approach 1:
The patent changes the parameter of rotational speed by introducing a rotation restricting mechanism that limits how fast the plunger can rotate. This allows the plunger to rotate slowly enough to maintain engagement and hold the needle protruding, while still eventually releasing to allow return. The rotation restriction transforms the binary state (engaged/not engaged) into a controlled transition process.
2Productivity
If the plunger rotates quickly to disengage from the engaging member, then the injection process completes faster, but the injection needle cannot be held protruding after injection
Solution Approach 1:
The rotation restricting mechanism changes the speed parameter of plunger rotation, enabling it to rotate at a controlled rate that maintains engagement during the injection process. This allows the system to achieve both rapid injection (when rotation is permitted) and extended needle protrusion (when rotation is restricted), resolving the contradiction between speed and duration.
3Device complexity
If no rotation restricting mechanism is provided, then the device structure is simpler, but the injection needle cannot be reliably held in the protruding position
Solution Approach 1:
The rotation restricting mechanism acts as an intermediary element between the plunger and the engaging member. This intermediary component mediates the rotational motion, allowing controlled rotation that maintains engagement while preventing premature disengagement. The added complexity of this intermediary mechanism is justified by the significant improvement in reliability of needle retention.
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 maintains the injection needle outside the housing post-use, ensuring secure retention and preventing drug leakage.
Implementation Method 1
The urging engagement part is elastically deformed to engage with the first branch in the axial direction
Implementation Method 2
A spiral-shaped inclined part is provided at the proximal end of the barrel. The plunger includes a rod body extending in a direction of the center axis
Implementation Method 3
The plunger urging part urges the engaging member to the distal end side in the direction of the center axis
Data Source
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AI summary
Provided is an injection device including a barrel receiving part in which the barrel is received with an injection needle protruding from one side of a housing; an engagement releasing mechanism configured to release engagement between a plunger and an engaging member by rotating the plunger and the engaging member around a center axis with respect to each other in a state in which the plunger is positioned at a terminal end point due to an urging force of a plunger urging part; and a rotation restricting mechanism configured to restrict a rotation speed of relative rotation between the plunger and the engaging member.