Threaded Injection Device Cap for Low-Force Needle Shield Removal
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Solution Overview
Problem
Existing injection devices require significant force to remove the cap, making it difficult for elderly or infirm individuals to access the needle for medicament administration.
Innovation Solution
A cap design featuring an actuator that, when pulled axially, causes the needle shield to rotate and move away from the body, reducing the required force through a threaded connection system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cap is held onto the body with sufficient force to prevent accidental removal, then the needle is kept sterile and safety is ensured, but it becomes difficult for elderly or infirm patients to intentionally remove the cap
Solution Approach 1:
The cap removal mechanism transitions from a static friction-based hold to a dynamic threaded engagement system. The actuator engages with the needle shield through threads, allowing a small rotational input force to generate a large axial extraction force, enabling easy removal by patients with limited hand strength while maintaining secure attachment during storage
Solution Approach 2:
The removal mechanism converts axial pulling force into rotational motion through the threaded connection between the actuator and needle shield. This dimensional transformation allows users to apply a small rotational torque to achieve the large axial force needed to overcome the retention force holding the cap secure during storage
2Ease of operation
If a threaded connection system is used to reduce removal force, then ease of operation is improved for elderly patients, but the device complexity increases
Solution Approach 1:
The threaded connection system serves multiple functions: it provides the mechanical advantage needed for easy removal by elderly patients, maintains secure retention during storage through the same mechanism, and guides the axial movement of the needle shield during the injection process. This multi-functionality reduces the need for separate mechanisms for each function
Solution Approach 2:
The actuator is nested within the cap structure, with the threaded connection integrated into the existing cap and needle shield components. The actuator engages with the needle shield through the threaded mechanism while remaining contained within the overall cap assembly, minimizing additional external 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 removal of the needle shield for elderly and infirm users by minimizing the force needed, ensuring sterility and safety during cap removal.
Implementation Method 1
The coupling may comprise a connection between the actuator and the needle shield. The connection may be a threaded connection.
Implementation Method 2
the coupling is configured such that when the cap is attached to the body of an injection device axial movement of the actuator away from the body by a first distance causes axial movement of the needle shield away from the body by a second distance, which is smaller than the first distance. Therefore, if the actuator is pulled away from the body by a given force then the resultant force acting on the needle shield to urge the needle shield away from the body will be larger than said given force.
Data Source
Figure 1A~1B
Figure 2~3
Figure 4~5
AI summary
The present invention relates to a cap (12) for an injection device (10). The injection device comprises a body for holding a syringe having a needle extending from an end thereof. The cap is removably attachable to the body. The cap comprises an actuator (23) and a needle shield (22) to cover said needle. The cap further comprises a coupling between the actuator and the needle shield. The coupling is configured such that when the cap is attached to the body of an injection device axial movement of the actuator away from the body causes rotation of the needle shield relative to the body.