Combustible Sleeve Igniter Retainer for Downhole Power Charges
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Solution Overview
Problem
Conventional power charges for downhole oil tools face issues with debris from non-combustible sleeves blocking flow ports, difficulty in cleaning, and potential explosive discharge due to non-combustible materials, as well as igniter disconnection from propellant mixtures during shipping and handling.
Innovation Solution
A power charge with a combustible sleeve made of paper-based fiberboard, embedding the igniter with an annular-shaped protrusion to retain it within the propellant, allowing for easy cleanup and improved ignition through a swirling flame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If non-combustible sleeves (plastic, fiberglass, steel) are used as power charge housings, then structural strength and containment are improved, but debris blocks flow ports and causes tool failure
Solution Approach 1:
The patent changes the material parameter of the sleeve from non-combustible (plastic, fiberglass, steel) to combustible (paper-based fiberboard). This parameter change transforms the harmful effect: instead of creating persistent debris that blocks flow ports, the combustible sleeve burns away completely, eliminating the debris blocking problem while maintaining structural integrity during the power charge operation.
Solution Approach 2:
The patent converts the potential harm of a combustible material (risk of uncontrolled burning) into a benefit by designing the sleeve to burn in a controlled manner along with the propellant. The combustible sleeve provides structural strength when needed, then burns away to create no debris, transforming the material's combustibility from a liability into an advantage for cleanup and tool reuse.
2Strength
If non-combustible sleeves are used as power charge housings, then structural integrity is improved, but cleaning residue from combustion chamber becomes difficult
Solution Approach 1:
The patent changes the combustion residue parameter of the sleeve material from persistent (non-combustible plastics and metals leaving melted residue) to transient (combustible paper-based fiberboard that burns away). This eliminates the cleaning problem entirely, as the combustible sleeve leaves no residue to accumulate on combustion chamber sidewalls, making maintenance simple and rapid.
3Reliability
If non-combustible tubes are used as power charge housings, then containment capability is improved, but explosive discharge and projectile ejection occur
Solution Approach 1:
The patent changes the pressure-release parameter of the housing material from pressure-retaining (non-combustible tubes that build up high pressures) to pressure-relieving (combustible material that burns away). The combustible sleeve contains the propellant and builds pressure for tool setting, then burns away to provide a safe pressure release path, preventing explosive discharge and projectile ejection while maintaining containment during the power stroke.
4Ease of manufacture
If igniter is embedded in propellant mixture without retention structure, then manufacturing simplicity is improved, but igniter becomes loose and disconnects during shipping and handling
Solution Approach 1:
The patent segments the igniter structure into two functional parts: the igniter element itself and the annular protrusion retention feature. This segmentation allows the protrusion to be molded as an integrated part of the igniter body, providing mechanical retention in the propellant mixture without complicating the manufacturing process. The protrusion acts as a self-retaining feature that prevents loosening during shipping and handling.
Solution Approach 2:
The patent merges the retention function with the igniter body by integrating the annular protrusion directly into the igniter structure. This combination eliminates the need for separate retention mechanisms or complex assembly steps, as the protrusion is formed as one piece with the igniter, providing both ignition capability and mechanical retention in a single manufactured component.
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 combustible sleeve facilitates easy residue removal and reduces redress time for setting tools, while the annular protrusion ensures stable igniter placement and improved propellant ignition, preventing explosive discharges and ensuring proper tool operation.
Implementation Method 1
Power charges are constructed of propellant mixtures composed of carefully controlled combustible elements containing an oxidizer which when ignited will begin a slow burn lasting approximately thirty seconds. The gas derived from a burning power charge propellant mixture gradually builds up to high pressures and causes a setting tool to stroke
Implementation Method 2
The combustible sleeve is formed of a combustible material, such that the sleeve will burn when the propellant is burned. This allows the remaining post burn residue of the combustible sleeve to be easily cleaned from the combustion chamber of the setting tool
Data Source
AI summary
A power charge (12) for a downhole setting tool has a sleeve (14) which defines a housing. A propellant (16) is located in the sleeve (14) in solid form and defines a first end face (20). An igniter (32) is embedded into the propellant (16) first end face (20). The igniter (32) has a main body portion (52) with an end located adjacent to the first end face (20), and an annular-shaped protrusion (48) which extends laterally outward from the main body portion (52) and into the propellant (16). The annular-shaped protrusion (48) defines a shoulder (46) which engages the propellant (16) to retain the igniter (32) within the propellant (16) at the first end face (20) of the power charge (12). The sleeve (14) is formed of a combustible material which will burn when the propellant (16) is burned.