PVC Pipe Mechanical Fitting With Differential-Friction Grip Ring
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Solution Overview
Problem
Existing compression fittings for connecting PVC-based pipes, particularly c-PVC and PVC-U, fail due to material brittleness and inability to withstand deformation, while solvent cement connections are being phased out by regulation.
Innovation Solution
A mechanical fitting that uses friction instead of compression, with a grip ring having different inner and outer friction coefficients to secure pipes without deformation, utilizing a nut and grip ring design that ensures sufficient frictional resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If compression fittings are used to connect PVC-based pipes, then the connection mechanism is simple and widely applicable, but the pipe material undergoes deformation which causes failure due to brittleness
Solution Approach 1:
The fitting is divided into distinct functional components: a body portion for structural support, a grip ring for friction-based holding, and a seal element for leak prevention. This segmentation allows each component to perform its specific function without causing deformation to the brittle PVC pipe.
Solution Approach 2:
The invention replaces the traditional compression-based mechanical connection with a friction-based connection system. The grip ring creates sufficient frictional force to hold the pipe without applying deforming pressure, thus avoiding the deformation problem that causes failure in brittle PVC pipes.
2Reliability
If solvent cement connection is used to avoid deformation, then the pipe integrity is maintained, but the use of solvents is being phased out by regulation
Solution Approach 1:
The invention replaces the chemical bonding mechanism of solvent cement with a purely mechanical friction-based connection. This eliminates the need for solvents and associated environmental regulations while maintaining pipe integrity through the friction grip of the grip ring.
3Reliability
If friction connection is used instead of compression, then pipe deformation is avoided, but the fitting design becomes more complex with different friction coefficients required
Solution Approach 1:
The grip ring is designed with different surface characteristics at its inner and outer surfaces. The inner surface has a high friction coefficient to grip the pipe, while the outer surface has a low friction coefficient to allow smooth engagement with the body portion. This local differentiation of friction properties enables the friction connection mechanism without requiring complex overall structure.
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
The fitting effectively maintains PVC-based pipes without deformation, providing reliable connections that withstand pull-out forces and maintain integrity under pressure, replacing the need for solvent cement and reducing material stress.
Implementation Method 1
The inner ring surface has an inner friction coefficient for defining an inner friction interface between the pipe and the grip ring, the outer ring surface has an outer friction coefficient for defining an outer friction interface between the grip ring and one of the main body and the nut
Data Source
Figure 1
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AI summary
A mechanical fitting for connecting pipes or for attaching a pipe is provided. The mechanical fitting comprises: a main body (10; 210) extending axially between a body end and an open end (11) defining an insertion space for a pipe, a grip ring (30; 130; 230) designed to close over a pipe, and a nut (40; 240) movably mounted over the main body for tightening the ring. The grip ring (30) has an outer ring surface (34) and an inner ring surface (35), wherein the inner ring surface (35) has an inner friction coefficient for defining an inner friction interface between the pipe and the grip ring (30), the outer ring surface (35) has an outer friction coefficient for defining an outer friction interface between the grip ring (30) and one of the main body and the nut, wherein the inner friction coefficient is higher the outer friction coefficient. An assembly and a method of assembly are also proposed.