High Torque Polymer Fittings with Locking Features
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Solution Overview
Problem
High torque requirements for tightening large polymer fittings in liquid handling systems pose challenges due to the low tensile strength and slipperiness of materials like PFA and ETFE, leading to potential damage and inadequate tightening.
Innovation Solution
The design includes a connector fitting with concentric coupling legs, a neck portion, shoulder, threaded portion, and nipple, featuring locking features such as protrusions and a locking ring with tabs and ribs, along with specialized wrenches that engage these features to securely tighten the fittings, distributing torque effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional wrenches are used to tighten large polymer fittings, then the fittings can be tightened, but the low tensile strength and slipperiness of the material causes the wrench to slip off, potentially damage the body, and make adequate tightening problematic
Solution Approach 1:
The patent introduces an intermediary component (specialized wrench with engagement features) that mediates between the user's tightening force and the polymer fitting. The wrench includes protrusions or teeth that engage with corresponding features on the fitting body, providing secure grip without relying on friction alone. This intermediary tool distributes the applied torque evenly across multiple contact points, preventing slippage and localized stress concentration that would damage the polymer material.
Solution Approach 2:
The wrench is segmented into multiple engagement points (protrusions or teeth) that contact different locations on the fitting body simultaneously. This segmentation distributes the tightening force across multiple areas, reducing the stress on any single point of the polymer fitting. The segmented design also provides redundant contact points, ensuring that if one engagement point slips, others maintain the grip.
2Strength
If high torque forces are applied to tighten large polymer fittings, then adequate tightening is achieved, but the inherent slipperiness and compressibility of the material causes damage and makes tightening problematic
Solution Approach 1:
The wrench design incorporates cushioning features in the form of compliant engagement elements or distributed contact surfaces that soften the transmission of high torque forces to the polymer fitting. The engagement features are designed to gradually engage and distribute the load, preventing sudden shock loads that could damage the fitting. The distributed contact areas act as stress distributors, cushioning the impact of high torque application on the vulnerable polymer material.
Solution Approach 2:
The patent transitions from single-point or line contact (conventional wrench on flat surface) to multi-point areal contact through the specialized engagement features. The wrench protrusions engage with corresponding recesses or surfaces at multiple locations around the fitting body, creating a two-dimensional distribution of contact points. This dimensional change from 0D/1D contact to 2D contact area significantly increases the effective contact surface, distributing stress and preventing localized damage while maintaining adequate tightening force.
3Ease of operation
If conventional wrenches are used on polymer fittings, then tightening can be attempted, but the flats on the body provide insufficient grip due to the material properties
Solution Approach 1:
The wrench engagement features utilize asymmetric geometry where the protrusions or teeth on the wrench are shaped to mate with corresponding asymmetric features on the fitting body. This asymmetric design creates a mechanical interlock that provides superior grip compared to symmetric conventional wrenches. The asymmetric engagement features are oriented to maximize contact area and mechanical advantage, ensuring that the wrench cannot slip off during the tightening operation regardless of the polymer material's slipperiness.
Data Source
AI summary
A high torque polymer fittings useful in fluid handling systems. The fittings are especially useful for fluid handling fittings having diameters of one inch or greater. Various embodiments of the fittings disclosed accommodate specialized wrenches for securing the fittings, the wrenches being used to tighten the fittings to a desired torque.