Injection Device Cam Mechanism for Low-Force Needle Shield Removal
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Solution Overview
Problem
Existing injection devices require high forces to remove needle shields, which can be cumbersome for users with impaired dexterity, and visible elevation features compromise the aesthetic appearance while providing limited axial movement or requiring extensive turning.
Innovation Solution
An injection device with a cam interface and elevation member that allows for axial separation of the needle shield upon rotation of the cap body, hidden from user view, optimizing functionality without altering the device's design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a needle shield is used to cover the injection needle, then safety is improved by preventing accidental access and hiding the needle from view, but the force required to remove the shield becomes quite high making it cumbersome for users with impaired dexterity
Solution Approach 1:
The cap assembly is divided into functionally independent parts: a cap body for gripping and rotation, a shield remover for engaging the needle shield, and an elevation member for providing axial movement. This segmentation allows each component to perform its specific function efficiently while reducing the overall force required for shield removal.
Solution Approach 2:
The elevation member converts rotational movement of the cap body into axial movement of the shield remover. By introducing this dimensional transformation (from rotational to linear motion), the mechanism amplifies the removal force and enables easy shield detachment without requiring users to apply high direct pulling force.
2Ease of operation
If visible elevation features are added to enable cap twisting for easier shield removal, then ease of operation is improved, but the aesthetic appearance of the device is compromised
Solution Approach 1:
The elevation feature is extracted from the visible exterior and relocated to the interior of the cap assembly. The cam interface and elevation member are positioned inside the cap body, hidden from user view, while still providing the necessary mechanical advantage for easy shield removal. This allows the exterior to maintain a clean, non-technical appearance.
Solution Approach 2:
The elevation member acts as an intermediary that translates the user's rotational input (on the aesthetically pleasing cap body) into axial force (on the shield remover). This mediator mechanism allows the beautiful exterior to remain unchanged while the hidden internal mechanism provides the functional benefit of easy operation.
3Ease of operation
If the cap is designed to twist off for shield removal, then ease of operation is improved, but the axial movement provided is limited requiring extensive turning
Solution Approach 1:
The cam interface provides a dynamic mechanical advantage that changes during the rotation process. As the elevation member rotates within the cam interface, the axial force is progressively amplified, allowing the shield remover to achieve significant axial displacement with relatively small rotational input, reducing the time and turns required for complete removal.
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 and efficient removal of needle shields with minimal force, maintaining a sleek appearance and user-friendly operation.
Implementation Method 1
a cam interface adapted to axially separate the needle shield from the injection needle upon rotation of the cap body relative to the housing
Data Source
AI summary
An injection device (1) comprising a housing (10), a syringe (2) having an injection needle (4) covered by a needle shield (5), and a cap assembly (3) comprising a cap body (15) covering a distal end of the syringe, and a shield remover (9) adapted to engage the needle shield (5), the shield remover (9) being axially fixed relative to the cap body (15). The cap assembly (3) further comprises an elevation member (12) being movable rotationally and axially relative to the cap body (15), wherein the elevation member (12) comprises a first rotation preventing geometry (18, 28, 31) configured to prevent the elevation member (12) from rotating relative to the housing (10), and a cam interface (20) with engaging cam surfaces respectively disposed on the elevation member (12) and the cap body (15), the cam surfaces being configured to engage slidingly upon rotation of the cap body (15) relative to the housing (10) so as to cause a proximal facing surface (17) of the elevation member (12) to be axially forced against a distally facing surface (16) fixedly disposed relative to the housing (10) while moving the cap body (15), the shield remover (9) and the needle shield (5) distally relative to the housing (10).