Hole Opener Key Slot Interface Reduces Cone Arm Breakout

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Solution Overview

Problem

Hole openers for horizontal directional drilling often experience cone arm breakouts and pocket fractures under extreme stress, leading to costly repairs and downtime due to the failure of cone arms detaching from the bit body.

Innovation Solution

The hole opener assembly features a bit body with pockets that include a slot and key interface design, where the key and slot provide a tighter fit than the arm and pocket interface, redirecting stress to reduce the likelihood of cone arm breakouts and pocket fractures by distributing forces more effectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional pocket design is used to hold cone arms, then the hole opener can be manufactured with simpler structure, but the cone arms are prone to fracture and pocket walls are prone to fracture under extreme stress

Engineering Contradiction:

Improveresistance to cone arm breakout and pocket fractureVSAvoidinterface structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The interface between the pocket and cone arm is segmented into distinct components: a pocket portion, a cone arm portion, a key, and a slot. This segmentation allows each component to perform its specific function - the key and slot provide a tight fit for stress distribution, while the pocket and arm portions maintain structural integrity, thereby reducing cone arm breakout and pocket fracture under extreme stress.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The key and slot act as intermediary elements between the pocket and the cone arm. The key, with its tighter fit in the slot, serves as a stress-distributing intermediary that prevents direct stress concentration at the pocket wall-cone arm interface, thereby reducing the likelihood of fracture in both the cone arm and pocket wall.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the key and slot have a tighter fit, then stress is better distributed to reduce cone arm breakout, but the manufacturing precision requirements increase

Engineering Contradiction:

Improvestress distribution effectivenessVSAvoidkey and slot fit precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The interface design applies local quality by creating a tighter fit specifically at the key-slot interface where stress distribution is critical, while the overall pocket and cone arm structures maintain standard manufacturing tolerances. This localized precision approach ensures effective stress distribution without requiring high precision throughout the entire component.

Inventive Principle:

Principle #3Local quality

3Reliability

If cone arm failure occurs, then the hole opener must be repaired or replaced, but this results in substantial downtime and cost

Engineering Contradiction:

Improvecone arm attachment reliabilityVSAvoiddowntime for repair or replacement

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The key and slot interface design provides beforehand cushioning by preemptively distributing stresses away from critical failure points. This preventive stress distribution reduces the likelihood of cone arm breakout and pocket fracture before they can occur, thereby avoiding the substantial downtime and costs associated with repairs or replacements.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS7845437B2Hole opener assembly and a cone arm forming a part thereof

Publication Date: 2010.12.07 CENTURY PRODUCTS INC

AI summary

An improved hole opener assembly for horizontal drilling is disclosed that is less prone to failure as a result of cone arm break out or pocket side wall fracture. The interface between the cone arm and the pocket employs a key and slot configuration with a tighter fit than between the arm and the pocket to reduce the stress on the pocket side wall during drilling.