Needleless Injector Percussion Lock Mechanism Friction Reduction
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Solution Overview
Problem
Existing needleless injection devices experience significant friction issues in their percussion mechanisms, leading to energy loss and potential device blocking, as well as plastic deformations due to high spring forces, which compromise their reliability.
Innovation Solution
The design incorporates a striker with radial lugs and retaining tabs featuring inclined ramps to facilitate a linear displacement, reducing friction and preventing plastic deformation, along with a guide sheath and obstructions to manage the striker's movement, ensuring efficient triggering of the gas generator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the striker is driven towards the injection position using helical-type ramps, then the striker can be released from obstruction and driven to percussion position, but significant friction occurs between the striker and cover ramps causing energy loss and potential device blocking
Solution Approach 1:
The lock mechanism is segmented into separate functional components: the retaining tab (separated from the cover), the lug with bearing ramp on the striker, and the obstruction on the body. This segmentation allows each component to perform its specific function with minimized interference, reducing friction between the striker and cover ramps while maintaining reliable locking and release functions.
2Force
If the spring pushing force is increased to drive the striker to percussion position, then the striker can overcome obstruction, but plastic deformations occur in the retaining tabs
Solution Approach 1:
The retaining tab is separated from the cover and designed as an independent component with optimized geometry. This allows the retaining tab to be specifically engineered for its release function without bearing excessive spring forces, preventing plastic deformation while maintaining the necessary force transmission capability.
Solution Approach 2:
The retaining tab is designed with specific local geometric features (its shape and positioning) that optimize its mechanical properties for the release function. This localized optimization allows the tab to withstand the required forces without deformation while performing its specific role in the lock mechanism.
3Force
If the retaining tab is positioned to retain the striker, then the striker is constrained in its retaining position, but the striker cannot be released to strike the primer
Solution Approach 1:
The lock mechanism transitions from a static retained state to a dynamic released state through the interaction of the striker's bearing ramp and the retaining tab's geometry. As the striker moves, the bearing ramp automatically actuates the retaining tab to move from its retaining position to its released position, enabling smooth transition without manual intervention.
Solution Approach 2:
The bearing ramp acts as an intermediary element between the striker and the retaining tab. It mediates the force transmission and geometric transformation needed to convert the striker's linear motion into the retaining tab's radial movement, enabling reliable release when the obstruction is cleared.
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
This configuration minimizes frictional resistance, enhances the reliability of the percussion device, and prevents plastic deformation, allowing for more efficient energy transfer and reliable operation of the needleless injection device.
Implementation Method 1
a prestressed spring, the free end of the striker being adapted to strike and trigger the primer of the gas generator when the striker occupies its percussion position
Data Source
AI summary
A needleless injector includes a cap, an injection system, a body, a gas generator, and a percussion device. The body is covered by the cap and is mounted to slide relative to the cap. The percussion device includes a striker that is slidingly mounted along a sliding axis between a rest position and a percussion position and a lock mechanism. The lock mechanism includes a lug and a retention tab. The lug projects from a peripheral face of the striker along an axis that is perpendicular to the sliding axis and has a first support ramp. The retention tab is attached to the cap, and has a second support ramp. The ramps are configured to move the retention tab radially when pushed by the striker from a retaining position to a release position and the retention tab is moved aside to release the striker.