Asymmetric Screw Root for Consistent Connector Fastening Force
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Solution Overview
Problem
Conventional connectors for infusion tubes fail to maintain a consistent and reliable fastening force due to the flattening of the latch portion by the thread ridge, leading to potential loosening of the connection when reconnected.
Innovation Solution
The connector design features a male screw with a central axis intersecting the root axis at a predetermined angle, creating a larger distance from the thread axis to the root bottom on a specific plane, which enhances locking by increasing the pressing surface area between the apex of the female screw and the bottom of the male screw, ensuring a consistent and reliable fastening force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the latch portion is made to function by screwing together the male screw and female screw, then the coupling is locked, but the latch portion is flattened by the thread ridge causing degradation of fastening force
Solution Approach 1:
The male screw is designed with an asymmetric root profile where the distance from the thread central axis to the root bottom varies around the circumference. Specifically, on a plane including the central axis of the thread and the central axis of the root, the distance is larger than on perpendicular planes. This asymmetric geometry creates a larger pressing surface area when the female screw apex presses against the male screw root, generating sufficient fastening force without flattening the latch portion, thus resolving the contradiction between locking reliability and fastening force maintenance.
2Productivity
If the connector is connected repeatedly, then the lock mechanism can be reused, but the fastening force degrades due to latch portion flattening
Solution Approach 1:
The asymmetric root design of the male screw ensures that the pressing surface between the female screw apex and male screw root has adequate area to generate consistent fastening force across multiple connections. The varied distance from the thread central axis to the root bottom creates an optimized contact geometry that prevents latch portion flattening even during repeated screwing and unscrewing operations, thereby maintaining both reusability and fastening force consistency.
Data Source
Figure 1A~1C
Figure 2
Figure 3A~3B
AI summary
To provide a female-side connector having a lock mechanism which could obtain a favorable fastening force constantly. [Solution] In a female-side connector 10, a central axis 13 of a root 15 in a male screw portion 12 of a female-side lock portion 41 screwing together with a female screw portion 23 of a male-side lock portion 42 in a male-side connector 20 intersects at a predetermined angle relative to a central axis 14 of a thread 16.