Cable Depressor Load Sensing for Trench Insertion Force Control

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Solution Overview

Problem

Existing methods for inserting elongate objects, such as cables, into trenches face challenges in accurately measuring radial forces and preventing damage due to bending and radial loading, particularly when using self-weight lowering or conventional depressors, which can lead to unnecessary reductions in trenching speed and burial depth.

Innovation Solution

An object engaging apparatus with restraining means to prevent movement in an axial direction and force measuring means to measure forces perpendicular to the axial direction, using a load cell as a force sensor, to accurately determine radial forces and minimize damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If self-weight lowering is used to insert the cable into the trench, then the risk of cable damage is reduced, but the number of trenching passes increases and burial depth measurement becomes difficult

Engineering Contradiction:

Improvecable damage riskVSAvoidnumber of trenching passes

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

A depressor device is introduced as an intermediary tool to actively guide and push the cable into the trench. The depressor includes a cable engagement member that contacts the cable and a support structure with actuators to control the depressor's position and apply downward force, enabling active cable insertion while monitoring forces to prevent damage.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If a conventional depressor is used to actively insert the cable, then burial depth control is improved, but radial loading on the cable increases causing damage risk

Engineering Contradiction:

Improveburial depth controlVSAvoidradial loading on cable

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The depressor design parameters are optimized to minimize radial loading. The cable engagement member uses a rounded nose with a radius of curvature at least equal to the cable's minimum bend radius. The application of downward force is controlled to stay within cable loading limits, and the depressor width is optimized to reduce soil resistance while maintaining effective cable guidance.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If conventional load cells are used to measure force on the depressor, then force measurement is achieved, but measurement precision is reduced due to interference from soil forces and actuator alignment issues

Engineering Contradiction:

Improveforce measurement accuracyVSAvoidload cell installation complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The force measurement system is segmented into multiple independent load cells positioned at different locations on the depressor support structure. This segmentation allows measurement of forces in multiple directions and enables differentiation between cable-related forces and soil forces, improving measurement accuracy while distributing the measurement function across multiple simple sensor elements.

Inventive Principle:

Principle #1Segmentation

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

Accurately measures radial forces applied to elongate objects, reducing the risk of damage and enabling faster insertion by ensuring precise control over the insertion process.

Implementation Method 1

force measuring means for providing an output dependent on a force applied to the object engaging means in a second direction transverse to said first direction

Methodology Applied

Scientific EffectForce measurement:

Implementation Method 2

restraining means for substantially preventing movement of said object engaging means relative to the support in a first direction as a result of movement of the object engaging means relative to the elongate object in an axial direction of the elongate object

Methodology Applied

Scientific EffectMechanical constraint:

Implementation Method 3

Lowering a cable into a trench formed by a trenching vehicle is achieved either passively (by means of reliance on the self-weight of the cable)

Methodology Applied

Scientific EffectGravity: Gravitation

Data Source

PatentUS20250354348A1Apparatus for inserting an elongate object into a trench

Publication Date: 2025.11.20 SOIL MACHINE DYNAMICS

AI summary

A depressor (16) for inserting a cable (4) into a trench (6) is disclosed. The depressor (16) comprises a plurality of cable shoes (22) adapted to be mounted to a support (18) and to engage the cable (4). Locating pins substantially prevent movement of the cable shoes (22) relative to the support (18) in a first direction as a result of movement of the cable shoes (22) relative to the cable (4) in an axial direction of the cable (4). A load cell provides an output dependent on a force applied to the cable shoes (22) in a second direction transverse, or perpendicular, to the first direction.