Powered Slip Actuation for Underground Utility Rod Strings

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Solution Overview

Problem

Existing systems for replacing underground utilities often require significant surface disruption and struggle to maintain a secure grip on rod strings during pushing and pulling operations, especially when no tensile or compressive loads are applied, leading to potential uncontrolled movement of the rod string.

Innovation Solution

A powered grip system comprising a slip bowl with a tapering internal passage and actuated slips that can clamp the rod string without relying on gravity, allowing for secure gripping in both vertical and horizontal orientations, and maintaining the clamp even when the rod string is unloaded.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If gravity-assisted slips are used to hold the rod string, then the rod string can be secured during operations, but the system becomes complex and cannot maintain grip when no tensile or compressive loads are applied

Engineering Contradiction:

Improvegrip reliabilityVSAvoidslip system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces the gravity-dependent mechanical slip system with an actuated hydraulic or pneumatic system. The actuator applies direct force to the slips to engage with the rod string, eliminating the need for gravity to provide the gripping force. This substitution allows the system to maintain reliable grip regardless of orientation or load conditions.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs hydraulic or pneumatic actuators to power the slip engagement mechanism. These actuators provide controlled force to move the slips into engagement with the rod string and maintain the grip. The fluid-powered system offers precise control and consistent force application, improving reliability while simplifying the overall mechanism compared to gravity-assisted systems.

Inventive Principle:

Principle #29Pneumatics and hydraulics

2Device complexity

If slips rely on gravity to engage with the rod string, then the system is simpler, but the slips cannot maintain grip in horizontal orientations or when unloaded

Engineering Contradiction:

Improveslip system simplicityVSAvoidoperational orientation flexibility

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent transforms the static, gravity-dependent slip system into a dynamic, actuated system. The slips are no longer passive components relying on gravitational force but are actively controlled through hydraulic or pneumatic actuators. This dynamic approach enables the slips to engage and maintain grip in any orientation—vertical, horizontal, or inclined—and under varying load conditions, significantly enhancing operational versatility.

Inventive Principle:

Principle #15Dynamics

3Ease of operation

If traditional slips are used that require load to maintain grip, then the system is easier to operate, but uncontrolled movement of the rod string can occur when unloaded

Engineering Contradiction:

Improveoperation simplicityVSAvoidrod string position control

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent incorporates a control system that monitors the state of the rod string and the engagement status of the slips. The actuator receives feedback signals to adjust and maintain the gripping force, ensuring the rod string remains securely positioned even when unloaded. This feedback mechanism prevents uncontrolled movement while maintaining ease of operation through automated control.

Inventive Principle:

Principle #23Feedback

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 system enables minimal surface disruption during underground utility replacement by providing a consistent and secure grip on the rod string, reducing the likelihood of uncontrolled movement and allowing for efficient pushing and pulling operations without the need for gravity-assisted slips.

Implementation Method 1

The conical surface of the slip is configured to slide with low friction against the conical inner surface of the slip bowl. The cylindrical inner surface of the slip is intended to produce a high coefficient of friction against the matching cylindrical surface of the rod

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

A powered grip system comprising a slip bowl with a tapering internal passage and actuated slips that can clamp the rod string without relying on gravity

Methodology Applied

Scientific EffectMechanical Advantage: Mechanical Advantage

Data Source

PatentUS10161201B2Powered slip actuation

Publication Date: 2018.12.25 CHARLES MACHINE WORKS INC

AI summary

A method for pushing and pulling rod strings through the ground or an underground pipe. A grip assembly is supported on a stationary frame and moveable relative to the stationary frame. The grip assembly has a slip bowl tapering from a large opening to a small opening in a first direction, a plurality of slips, and an actuator. The actuator powers relative axial movement between the slip bowl and the slips. A positioning assembly carries the grip assembly and powers its reciprocating and straight-line movement to urge the grip assembly in either a first or second direction. The grip assembly will work when operated to push or pull the pipe, irrespective of the is direction of the slips.