Extended Hub Pen Needle Shielding for Deeper Cannula Entry
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Solution Overview
Problem
Existing safety shield systems for medication pens often limit the effective penetration depth of the needle due to the distribution of injection force across a larger area, potentially restricting the injection depth and requiring more force to move the shield into position, which can be uncomfortable for patients.
Innovation Solution
A pen needle assembly with an extended hub and a passive shield system where the hub is positioned distally of the outer sleeve, concentrating the injection force on a smaller area and allowing the inner shield to cover the needle with less spring force, ensuring appropriate insertion depth and reduced tissue pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the injection force is distributed across the outer sleeve area, then the shield can be moved with less force, but the effective penetration depth of the needle is limited
Solution Approach 1:
The device divides the force application area into two distinct segments: the outer sleeve that contacts the patient's skin and the extended hub that concentrates the injection force. This segmentation allows the outer sleeve to provide a larger surface area for force distribution while the extended hub creates a concentrated force point that pushes the inner shield distally, enabling both deeper penetration and controlled shield movement.
Solution Approach 2:
The extended hub protrudes distally beyond the outer sleeve, adding a dimensional element that changes the force transmission geometry. This creates a lever arm effect where the concentrated force on the extended hub translates into effective distal movement of the inner shield, overcoming the force distribution limitation of the outer sleeve design.
2Length of moving object
If the hub is extended distally beyond the outer sleeve, then the effective penetration depth increases, but the device complexity increases
Solution Approach 1:
The extended hub integrates multiple functions into a single structural element: it serves as the mounting point for the inner shield, the force concentration point for injection, and the depth-defining reference. By merging these functions into one component rather than using separate elements, the design achieves increased penetration depth without proportionally increasing overall device complexity.
3Reliability
If spring force is increased to move the inner shield distally, then the shield covers the needle more effectively, but more force is exerted against the patient's tissue
Solution Approach 1:
The design extracts the force concentration function from the spring mechanism and places it on the extended hub structure. This separation allows the spring to provide only the minimal force needed for shield movement, while the extended hub provides the additional concentrated force needed for deep penetration, preventing excessive spring force from being applied to the patient's tissue.
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 extended hub design allows for deeper cannula penetration and reduced pressure on the patient's tissue during injection, ensuring effective needle coverage with less force required for the shield to move into position post-use.
Implementation Method 1
a spring biases the inner shield in the distal direction
Data Source
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AI summary
A shielded pen needle assembly is provided in which the hub (36) extends distally beyond an outer sleeve (18) of the assembly. The pen needle assembly comprises: a hub (36) adapted to receive a medication pen body having a medication compartment therein; a needle cannula (14) affixed to the hub (36) having a distal end extending from the distal end of the hub (36) and a proximal end adapted to access the medication compartment in the pen body; a first passive shield (44) arranged on the hub (36) and encircling the needle cannula (14); a biasing member (94) biasing the first passive shield (44) to a distal position covering the needle cannula (14) after injection; an outer sleeve (18) attached to the hub (36) having a distal end encircling the first passive shield (44) and the hub (36); wherein the distal end of the hub (36) is located distally of the distal end of the outer sleeve (18), and the distance between the distal tip of the needle (14) and the distal end of the hub (36) is the effective penetration depth of the needle (14).