Poppet-to-Shaft Recess Locking for Harsh Downhole Actuators
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Solution Overview
Problem
Existing electromechanical actuator systems face challenges in reliably attaching hard and brittle ceramic or carbide poppets to ductile steel or nickel alloy shafts, particularly in harsh downhole environments, due to stress concentrations, corrosion, and thermal expansion differences, leading to potential failure.
Innovation Solution
The solution involves a recessed design on the poppet where the servo shaft is deformed to form a mechanical connection, eliminating the need for threading, screws, brazing, or press fitting, and using a ductile material for the shaft to be deformed into the recess, enhancing the mechanical bond and reducing stress concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If threading, screws, pins, brazing, or press fitting is used to attach the poppet to the shaft, then the connection can be established, but stress concentrations occur and reliability decreases in harsh environments
Solution Approach 1:
The invention merges the poppet and shaft into a unitary structure where the shaft is deformed to form an interference fit within a recess of the poppet, eliminating separate fastening components. This integration removes stress concentration points from threads, pins, and brazing joints while maintaining strong mechanical connection through the deformed shaft material that locks within the poppet recess.
Solution Approach 2:
Instead of attaching the poppet to the shaft using external fasteners or surface connections, the invention inverts the approach by having the shaft itself deform and lock within a recess of the poppet. The shaft material is forced into the poppet recess, creating an internal mechanical lock rather than an external attachment, thereby eliminating stress concentrations at connection interfaces.
2Strength
If the poppet is made from hard and brittle material like ceramic or carbide, then wear resistance is improved, but attachment to ductile shaft material becomes challenging
Solution Approach 1:
The invention applies local quality by creating a recess in the hard and brittle poppet material that is specifically designed to receive and lock the deformed shaft. This localized feature allows the ductile shaft material to deform and mechanically lock within the poppet without requiring the entire poppet to be ductile, thereby maintaining wear resistance while enabling secure attachment.
Solution Approach 2:
The invention effectively creates a composite structure where the hard and brittle poppet material (ceramic or carbide) is mechanically locked to the ductile shaft material through the deformed shaft forming an interference fit within the poppet recess. This composite approach combines the wear resistance of hard materials with the formability and tensile strength of ductile materials.
3Reliability
If brazing or soldering is used to attach the poppet to the shaft, then connection can be achieved, but corrosion resistance decreases due to additional dissimilar metals
Solution Approach 1:
The invention extracts the brazing or soldering process entirely from the attachment method. By using a mechanical interference fit where the shaft deforms to lock within the poppet recess, the need for additional dissimilar metals (brazing alloys, solder) is eliminated. This removes the source of anodic corrosion that would occur at the interface between the poppet, shaft, and brazing/solder material in harsh downhole environments.
4Ease of manufacture
If press fitting or clamping is used to attach the poppet to the shaft, then connection can be established, but the connection becomes unreliable due to low friction and thermal expansion differences
Solution Approach 1:
The invention creates a curved or contoured deformation profile of the shaft material as it forms an interference fit within the poppet recess. This curved deformation locks the shaft and poppet together mechanically, preventing relative movement that would occur with simple press fitting. The deformed shaft material conforms to the recess geometry, creating a secure mechanical lock that accommodates thermal expansion differences.
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
This approach significantly increases the reliability and strength of the connection between the poppet and the shaft, achieving a pull strength of over one thousand pounds, surpassing conventional methods which typically achieve only a few hundred pounds.
Implementation Method 1
a connection portion of the shaft being deformed into the recess to form a mechanical connection
Data Source
AI summary
An assembly having a coupling component and a poppet is disclosed. The coupling component has a first end. The first end has an opening extending into the coupling component, such that the coupling component has a sidewall extending around and defining the opening, the sidewall at least partially constructed of a ductile material. The poppet is positioned within the opening. The poppet has a first end outside of the opening, a second end within the opening, and an outer surface extending between the first end and the second end. The poppet has a recess positioned between the first end and the second end, the recess being defined by at least one sidewall and a bottom. At least a portion of the ductile material of the sidewall is positioned within the recess to secure the poppet into the opening.