Rounded Cannula Piercing Tip for Fluid Dispensing
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Solution Overview
Problem
Fluid dispenser devices with cannulas face issues of leaks and reduced reproducibility due to the acute angle of the bevelled piercing tip, leading to inconsistent dosing and potential damage at the hinge zone.
Innovation Solution
A cannula piercing tip with a rounded external shape and axially curved peripheral edge, featuring a distal part of reduced width, is used to minimize leaks and improve sealing, formed by stamping to create a smaller cutting profile and lower drilling force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the cannula piercing tip uses an acute bevel angle to facilitate stopper piercing, then the piercing action is improved, but leaks occur during actuation and dosing reproducibility deteriorates
Solution Approach 1:
The piercing tip is designed with a rounded external shape in the radial direction and a rounded distal axial end, replacing the conventional acute bevel with a curved geometry that reduces stress concentration and prevents leaks while maintaining piercing effectiveness
Solution Approach 2:
The opening in the piercing tip has a distal part with reduced width compared to the cannula body, creating a localized constriction that improves sealing at the piercing site while the rest of the cannula maintains its structural integrity
2Productivity
If the bevel angle is acute to facilitate drilling of the stopper, then piercing efficiency is improved, but the axial extent of the opening exceeds stopper wall thickness causing leaks
Solution Approach 1:
The opening width is reduced at the distal part of the piercing tip, creating a localized narrow section that prevents fluid leakage while the overall tip geometry maintains efficient piercing capability
Solution Approach 2:
The rounded external shape and rounded distal end of the piercing tip distribute the piercing force more evenly, preventing excessive axial extent that would cause the opening to exceed stopper wall thickness
3Ease of manufacture
If a standard cannula with flat peripheral edge is used, then manufacturing is simple, but damage to the hinge zone occurs generating potential leaks
Solution Approach 1:
The peripheral edge is designed with axial curvature and the distal end is rounded, eliminating the flat geometry that causes stress concentration at the hinge zone while maintaining manufacturability through stamping processes
Data Source
Figure 1
Figure 2a~2c
Figure 3~7
AI summary
A hollow cannula (4) having a piercing tip (5) for piercing a piercing site, said piercing tip (5) being provided with an opening (6), said opening (6) defining a peripheral edge (7) that extends about said opening (6) and has a distal axial end and a proximal axial end, said distal axial end of said peripheral edge (7) forming the distal axial end (59) of the piercing tip (5), said distal axial end (59) of the piercing tip (5) being disposed on the longitudinal central axis (A) of said cannula (4), said piercing tip (5) having a rounded external shape in the radial direction and said distal axial end (59) of said piercing tip (5) having a rounded shape in the axial direction.