Plug Removal Tool with Dual-Thread Plunger
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Solution Overview
Problem
Existing plug removal tools, such as the Duffy system, require fixed axial alignment between the housing and workpiece, making them unsuitable for handheld use in applications like extracting plugs from multiple aircraft skin panel fasteners.
Innovation Solution
A plug removal apparatus with a plunger shaft having a first threaded section with a steep pitch for rotational conversion and a second threaded section with a shallower pitch for secure embedding and extraction, allowing one-handed operation by converting axial motion into rotational motion using a spring-loaded mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed axial alignment system is used (Duffy system), then the plug removal mechanism works reliably, but the device cannot be used handheld for multiple fasteners
Solution Approach 1:
The device is divided into independent functional modules: a handheld housing containing the mechanism, and a separate plunger shaft assembly that can be inserted into and removed from the housing. This segmentation allows the mechanism to be adapted for handheld use while maintaining operational reliability through modular assembly.
Solution Approach 2:
The plunger shaft is made dynamically adjustable relative to the housing through a release mechanism that allows the shaft to be inserted, secured, and removed. This dynamic configuration enables the device to transition between different operational states (handheld mode with shaft inserted, storage mode with shaft removed) while maintaining ease of operation.
2Productivity
If a steep pitch thread is used for rotational conversion, then axial motion converts efficiently to rotation, but the thread does not securely embed in soft plugs
Solution Approach 1:
The plunger shaft incorporates two distinct threaded sections with different pitch characteristics: a first threaded section with steep pitch for efficient rotational conversion during insertion, and a second threaded section with shallow pitch for secure embedding in the plug material. Each section is optimized for its specific function, resolving the contradiction between conversion efficiency and embedding security.
Solution Approach 2:
The threading is segmented into two functional zones along the plunger shaft. The first threaded section (steep pitch) handles the initial engagement and rotational conversion, while the second threaded section (shallow pitch) handles the secure embedding and extraction. This segmentation allows each section to be optimized independently for its specific purpose.
3Reliability
If a shallow pitch thread is used for secure embedding, then the thread securely engages soft plugs, but axial motion does not efficiently convert to rotation
Solution Approach 1:
The plunger shaft incorporates two distinct threaded sections with different pitch characteristics: a first threaded section with steep pitch for efficient rotational conversion during insertion, and a second threaded section with shallow pitch for secure embedding in the plug material. Each section is optimized for its specific function, resolving the contradiction between conversion efficiency and embedding security.
4Reliability
If the plunger shaft is manually twisted for tapping, then the threading engages the plug, but wrist twisting is required which complicates one-handed operation
Solution Approach 1:
The device transitions from a static manual twisting operation to a dynamic spring-loaded automatic tapping mechanism. When the plunger shaft is inserted into the housing, the compressed spring automatically drives the shaft forward, causing the threads to engage the plug through axial motion rather than requiring manual wrist twisting. This enables reliable one-handed operation.
Solution Approach 2:
The spring-loaded mechanism performs the tapping action automatically upon insertion of the plunger shaft into the housing. The stored energy in the compressed spring self-generates the axial force needed to drive the threaded section into the plug, eliminating the need for manual twisting and enabling one-handed operation while maintaining reliable thread engagement.
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
Enables secure and efficient removal of plugs from recesses without requiring wrist twisting, facilitating one-handed operation and preventing plug rotation during extraction.
Implementation Method 1
The device also includes a spring positioned to bias the plunger toward the retracted position
Implementation Method 2
The first threaded section includes threads pitched to allow relative axial motion to be converted into relative rotation between the plunger shaft and the housing
Data Source
AI summary
A tool for removing plugs from recesses obviates the need for a twist of the wrist in engaging a plug for removal. A plunger is carried by a housing and is supported for reciprocal axial motion between extended and retracted positions relative to the housing. A shaft of the plunger includes a first threaded section that is engaged in a nut carried by the housing and has threads pitched to allow relative axial motion to be converted to relative rotation between shaft and housing. A second threaded section of the plunger shaft is configured to tap into a plug in response to shaft rotation in a tapping direction, and has a shallower thread pitch than the first threaded section.