Core Barrel Head Assembly Latch Mechanism
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Solution Overview
Problem
Existing core barrel assemblies and overshot devices face issues such as stuck inner tubes due to ground fractures, latch system wear, complex assembly designs, and safety hazards during drilling, leading to increased maintenance time and potential injuries.
Innovation Solution
A core barrel head assembly with improved latch mechanisms providing mechanical advantage, reduced wear, and simplified design, along with an overshot system featuring self-centralizing and safer engagement with the head assembly to prevent accidents and enhance operational efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the latches are made thinner to facilitate the latch linkage, then the ease of operation is improved, but the strength is reduced making them prone to break during handling
Solution Approach 1:
The latch is divided into multiple components: a latch body, a separate arm, and a spring pin. This segmentation allows the main latch body to maintain sufficient thickness for strength while the linkage mechanism uses thinner, more flexible components that facilitate operation without compromising overall structural integrity.
Solution Approach 2:
The latch arm is positioned within a slot in the upper body, and the spring pin is inserted through aligned slots in both the upper body and the latch arm. This nested arrangement allows compact integration of the linkage mechanism while maintaining proper clearance and movement capability for ease of operation.
2Force
If the latches are modified to have mechanical advantage to unlatch when pulling on the wire line, then the force required to free stuck inner tubes is reduced, but the latch linkage system wears out quickly causing part failure
Solution Approach 1:
The latch arm is designed to rotate within a slot rather than being fixed, creating a dynamic linkage that adapts to the forces applied. The spring pin allows controlled movement and rotation, enabling the latch to respond dynamically to pulling forces while distributing wear across the rotation interface rather than creating excessive stress on rigid linkage components.
Solution Approach 2:
The geometry of the latch arm and its position within the slot are optimized to provide mechanical advantage during the unlatching motion. The arm's length, thickness, and angular position are specifically designed to maximize the leverage effect when force is applied to the wire line, reducing the required withdrawing force while maintaining reasonable stress levels on the linkage.
3Ease of manufacture
If spring pins are used to attach latches and components, then the ease of manufacture is improved, but the pins lose plasticity over time and fall out unnoticed causing assembly failure
Solution Approach 1:
The spring pin is designed with elastic properties that provide tactile and visual feedback during assembly and operation. As the pin is inserted through aligned slots, its spring nature creates resistance and audible clicks that confirm proper engagement. During operation, any loss of retention is immediately apparent through changes in latch positioning or movement, allowing operators to detect and address issues before complete failure occurs.
Solution Approach 2:
The spring pin's material composition and dimensional parameters are specifically selected to maintain plasticity and elastic recovery over time. The pin's diameter, length, and spring rate are optimized to provide sufficient retention force while accommodating thermal expansion and operational stresses, preventing the loss of plasticity that leads to pin failure.
4Productivity
If the overshot gripping structure is designed to engage the head assembly, then the productivity is improved by enabling inner tube retrieval, but safety hazards occur during engagement and disengagement operations
Solution Approach 1:
The safety mechanism is extracted as a separate functional element from the gripping structure itself. A distinct safety arm with a latch mechanism is provided that independently controls the engagement state. This separation allows the gripping structure to maintain its productivity function while the safety system provides independent protection, preventing accidental engagement or disengagement that could harm operators.
Solution Approach 2:
The safety latch is designed to prevent engagement of the gripping structure with the head assembly unless the safety conditions are met. The latch mechanism creates a preliminary barrier that must be actively opened or disengaged before the gripping arms can contact the head assembly, preventing unintended or premature engagement that could cause injury during retrieval operations.
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 improved latch mechanisms reduce the force required to release stuck inner tubes, minimize wear, and simplify assembly, while the overshot system enhances safety and productivity by preventing accidents and reducing manual intervention for locking.
Implementation Method 1
a spring configured to bias the second end of the latches away from each other in an open position
Implementation Method 2
The latches are movable between the engaged position and a retracted position by the retracting case with a mechanical advantage
Data Source
Figure 1~2
Figure 3~5
Figure 6
AI summary
A core barrel head assembly including an upper body comprising a central passage. A pair of latches is arranged in the central passage. Each latch pivots about a pivot point at a first end. Each latch includes a latch release at a second end and an outer tube surface engaging surface between the first end and the second end. A retracting case includes a first end configured to engage at least the latch release of the latches. The outer tube surface engaging surface of each latch extends through a latch slot in an outer wall of the upper body and such that the latches rotate about the pivot point. The latches are movable between an extended position and retracted position by the retracting case with a mechanical advantage. An overshot for retrieving a core barrel inner tube from a drill string. A method in earth drilling.