Composite-to-Metal Torque Pipe Joint With Conical Bonded Load Transfer
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Solution Overview
Problem
Existing composite torque tubes fail to provide a high integrity interface with adjoining surfaces, leading to uneven load distribution and bond separation under high torque loads, which limits their ability to carry torsional forces effectively in deep and directional drilling applications.
Innovation Solution
A composite to metal joint is created using a metal inner sleeve with a barrel and annular flange, forming a distally narrowing conical shell surface, which is telescoped over a composite torque pipe with a tapered ring, providing a bonded interface with concentric smooth conical surfaces to distribute loads uniformly across a larger surface area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single surface abutting joint is used between composite tube and fitting, then the joint structure is simple, but the load distribution is uneven and bond integrity is insufficient under high torque loads
Solution Approach 1:
The single bonding surface is segmented into multiple bonding surfaces by creating opposing conical surfaces on both the inner and outer sleeves. The composite tube end is bonded to both the inner sleeve (first bonding surface) and the outer sleeve (second bonding surface), distributing the torque load across multiple interfaces rather than concentrating it on a single surface.
Solution Approach 2:
The joint structure transitions from a single-plane bonding interface to a three-dimensional conical bonding geometry. The opposing conical surfaces create a tapered bonding zone that extends axially and radially, increasing the bonding surface area and providing load distribution in multiple spatial dimensions.
2Strength
If threaded or clamping parts are used to secure composite end in fitting, then the composite tube is captured securely, but uneven load concentrations result in highly uneven shear stresses and local bond separation
Solution Approach 1:
The joint design changes the geometric parameters of the bonding interface by using opposing conical surfaces with specific taper angles. This geometric configuration naturally distributes compressive and shear stresses more uniformly across the bonding surfaces compared to parallel surface or clamping configurations, reducing stress concentrations that lead to bond separation.
Solution Approach 2:
The mechanical clamping or threading system is replaced with a bonded joint system using opposing conical surfaces. Instead of using threaded parts or clamps that create localized stress concentrations, the torque transmission is achieved through bonded interfaces on opposing conical surfaces that distribute stresses more uniformly across the entire bonding area.
3Reliability
If a larger bonding surface area is used to distribute loads uniformly, then the bond integrity improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The opposing conical surfaces serve multiple functions simultaneously: they provide large bonding surface areas for load distribution, act as alignment features during assembly, and create a self-centering effect that facilitates manufacturing. The conical geometry is a standard machining feature that can be produced on conventional lathes, avoiding the need for specialized tooling or complex manufacturing processes.
Data Source
AI summary
A composite torque pipe to metal fitting joint including concentric inner and outer shells formed with respective smooth conical surfaces projecting distally and respectively tapered radially inwardly and radially outwardly to form an annulus expanding in thickness for receipt of a tapered connector ring complementally shaped at one end of a composite pipe and bonded along the interface. The present invention includes selecting the sleeves with the corresponding shells and, forming the torque pipe with the tapered ring and bonding the tapered ring in the annulus.