Medical Gasket Female Screw Diameter Gradient
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Solution Overview
Problem
Prefilled syringes face challenges in reducing the clamping force required to fit a plunger rod into the gasket while maintaining a tight fit, which can lead to increased friction and difficulty in injection.
Innovation Solution
A medical gasket with a female screw portion that gradually increases in diameter from the drug contact surface to the plunger side, featuring specific diameter ratios for roots and crests to reduce fitting torque and maintain a tight seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the screw is excessively turned to achieve tighter fit between gasket and plunger, then the fit tightness is improved, but the friction between gasket and syringe barrel increases
Solution Approach 1:
The patent changes the geometric parameters of the screw threads by making the root diameter larger than the crest diameter, creating a non-standard thread profile. This parameter modification allows the threads to engage more effectively without requiring excessive compression, thereby reducing friction while maintaining fit tightness.
Solution Approach 2:
The patent applies different diameters to different parts of the screw thread - the root has a larger diameter than the crest. This local differentiation optimizes the stress distribution and engagement characteristics at different locations of the thread, allowing for reduced clamping force while maintaining adequate fit tightness.
2Reliability
If conventional screw threads are used to fit plunger rod into gasket, then the fit can be achieved, but excessive clamping force is required which compresses the gasket
Solution Approach 1:
The patent fundamentally changes the screw thread parameters by inverting the conventional dimensioning - the root diameter is made larger than the crest diameter. This creates a more efficient thread engagement that requires less clamping force to achieve the same or better fit tightness, preventing gasket compression.
Solution Approach 2:
The patent employs curved or inclined surfaces in the thread profile design, creating a gradual transition rather than sharp edges. This curvature distributes the engagement forces more evenly, reducing the peak clamping force required while maintaining secure fit tightness.
Data Source
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AI summary
The present invention aims to provide a gasket which reduces the clamping force required to fit a plunger rod into the gasket, while maintaining a tight fit therebetween. The present invention relates to a medical gasket including a female screw portion to fit a plunger, on the side opposite to a drug contact surface, the female screw portion having roots or crests which gradually increase in diameter from the drug contact surface side toward the opposite plunger side.