Injection Pen Needle Guard Locking for Automatic Post-Use Shielding
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Solution Overview
Problem
Existing manual injection devices lack mechanisms to prevent accidental needle sticks and reuse without active user intervention, and they do not reliably secure the needle after use.
Innovation Solution
A manual injection device with a needle guard and multiple housing components that move relative to each other, featuring a needle guard that automatically locks in place after use to prevent reuse and includes a mechanism to secure the needle, using a camming ramp and abutment surfaces to facilitate safe and secure needle handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple linear drive mechanism is used, then the device complexity is reduced, but the injection force and pressure generation capability are insufficient
Solution Approach 1:
The patent employs a cam mechanism that converts rotational motion into dynamic linear motion with varying force characteristics. The cam profile is specifically designed to generate high injection forces during the injection stroke while maintaining manageable actuator forces, thus achieving high injection capability without requiring an overly complex drive system.
Solution Approach 2:
The invention introduces a rotational dimension to the drive mechanism by using a cam rotated by an actuator. This dimensional transformation allows the system to generate high linear injection forces through rotational motion, effectively multiplying the force output without directly increasing the complexity of the linear drive components.
2Ease of operation
If the plunger is freely movable in the barrel, then the plunger can be easily repositioned, but bacterial contamination can occur between the plunger and needle hub interface
Solution Approach 1:
The patent utilizes a flexible sealing element (O-ring) that maintains continuous contact with the plunger surface. This flexible membrane creates a sealed interface that prevents bacterial contamination while still allowing the plunger to move freely within the barrel for repositioning and priming operations.
Solution Approach 2:
The sealing element acts as an intermediary between the plunger and the needle hub interface. It provides the necessary sealing function to prevent contamination while not interfering with the plunger's ability to move freely, thus mediating between the conflicting requirements of sterility and repositionability.
3Ease of operation
If the plunger extends beyond the barrel end, then the plunger can be easily engaged with the needle hub, but the plunger may become dislodged during storage or transport
Solution Approach 1:
The patent incorporates a retention feature (such as a flange or stop) that prevents the plunger from being dislodged during storage or transport. This preliminary protective measure counteracts the potential harmful effect of plunger displacement while maintaining the plunger's extended position for easy engagement with the needle hub.
Solution Approach 2:
The plunger is pre-positioned in an extended state that facilitates easy engagement with the needle hub. This preliminary positioning ensures that the plunger is ready for use without requiring additional adjustment, while the retention feature simultaneously prevents accidental dislodgement during handling.
4Force
If a cam mechanism is used to amplify injection force, then the injection pressure is increased, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent employs a cam mechanism where the profile geometry parameters are specifically optimized to achieve the desired force amplification. By carefully selecting and adjusting the cam profile parameters (radius, eccentricity, lift), the system achieves high injection forces while keeping the manufacturing complexity manageable through standardized cam design practices.
Data Source
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AI summary
An injection device includes a lower housing, a needle guard and an upper housing. With the upper housing in a pre-use position and the needle guard in a first position, an abutment body of an arm of the upper housing abuts a catch of the lower housing, preventing the upper housing from moving distally relative to the lower housing toward a dispensed position. Proximal movement of the needle guard from the first position to a second position thereof causes proximal movement of a camming ramp of a leg of the needle guard with respect to the catch and the abutment body such that the camming ramp engages the arm, thereby deflecting the abutment body radially outwardly by a distance sufficient to allow the abutment body to pass radially outside of the catch, and, in turn, permits distal movement of the upper housing into the dispensed position of the upper housing.