Rotatable Cam Sheath Removal Mechanism for Syringe
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Solution Overview
Problem
Existing injection devices, particularly autoinjectors, face challenges in safely and easily removing protective needle sheaths, which requires high forces and can lead to needle stick injuries and potential damage to the needle during removal.
Innovation Solution
A sheath removal mechanism featuring a cap with a rotatable cam and U-shaped lever that reduces the force needed to remove the sheath by allowing linear displacement and preventing relative rotation between the sheath and needle, minimizing the risk of needle damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the protective needle sheath is attached to the needle when assembled, then the needle remains sterile and protected from mechanical damage, but high forces up to 50 N are required to remove the sheath
Solution Approach 1:
The cap is designed to transition from a static locked position to a dynamic movable position through rotational movement of the cam mechanism. The cam converts rotational motion into linear displacement, dynamically changing the cap's position from engaged to disengaged from the syringe body, thereby enabling sheath removal with reduced force
Solution Approach 2:
The removal mechanism introduces rotational motion (a different dimension) to accomplish the linear separation of the cap from the syringe body. By rotating the cam around an axis, the mechanism converts a potentially high-force linear pulling action into a low-force rotational action, solving the force contradiction
2Ease of operation
If the user applies force to remove the protective needle sheath, then the sheath can be removed, but relative rotation between the sheath and needle may occur causing needle damage
Solution Approach 1:
The cam mechanism employs curved surfaces and rotational geometry to guide the removal process. The cam's curved profile ensures that force is applied in a controlled manner that maintains axial alignment, preventing rotational moments that could damage the needle while enabling smooth sheath removal
Solution Approach 2:
The cam acts as an intermediary mechanism between the user's rotational input and the linear separation of the cap. This intermediary converts the user's rotational motion into controlled linear displacement, mediating the force application to prevent direct rotational forces from being transmitted to the needle-sheath interface
3Device complexity
If a simple cap covering the distal end is used, then the device structure remains simple, but the cap cannot effectively engage and remove the protective needle sheath
Solution Approach 1:
The cam mechanism merges the functions of the cap and the removal mechanism into a single integrated component. The cam is incorporated within or as part of the cap structure, combining the protective covering function with the sheath removal function, thereby enhancing ease of operation without significantly increasing device 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
The mechanism significantly reduces the force required for sheath removal and ensures the needle remains intact by allowing a purely linear force application, thereby reducing the risk of needle stick injuries and maintaining the needle's integrity.
Implementation Method 1
at least one rotatable cam adapted to move the cap in a distal direction away from the syringe when rotated from a first rotational position towards a second rotational position
Data Source
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AI summary
Described is a sheath removal mechanism (1) for removing a protective needle sheath (2) from an injection needle (3) of a syringe (4) in a drug delivery device (5). The sheath removal mechanism (1) comprises a cap (6) adapted to cover a distal end of a drug delivery device (5) and adapted to engage the protective needle sheath (2), and at least one rotatable cam (7) adapted to move the cap (6) in a distal direction (D) away from the syringe (4) when rotated from a first rotational position (P1) towards a second rotational position (P2).