Boom Hydraulic Control Circuit for Load-Independent Lowering

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Solution Overview

Problem

The existing hydraulic control circuits for boom lowering in vehicles, such as telehandlers, are sensitive to the load carried, leading to unsafe and unpredictable lowering speeds, especially when high loads are involved, as small user corrections can result in significant changes in lowering speed.

Innovation Solution

A hydraulic control circuit with a pressure compensator and a control valve that intercepts fluid flow during boom lowering, using a fluid piloting line connected to a user interface, where a pressure compensator is piloted by both downstream and upstream pressure signals to progressively connect a branch to the tank, increasing hydraulic resistance and controlling the lowering speed independently of the load.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a distributor valve is used to control boom lowering speed, then the user can control the lowering speed, but the control becomes overly sensitive when high loads are carried, causing small corrections to result in large changes in lowering speed

Engineering Contradiction:

Improvecontrol of lowering speedVSAvoidsafety of operation

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

A pressure compensator is introduced as an intermediary device between the distributor valve and the hydraulic circuit. The pressure compensator receives the pilot signal from the distributor valve and automatically adjusts the hydraulic resistance based on load conditions, thereby mediating between user input and actual boom lowering speed. This eliminates the direct sensitive connection between the distributor valve and high-load conditions, ensuring stable and safe operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If hydraulic resistance is increased to decrease lowering speed under high load, then safety is improved, but the control circuit becomes more complex requiring additional components

Engineering Contradiction:

Improvesafety of operationVSAvoidcomplexity of control circuit

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The pressure compensator is designed to automatically adjust hydraulic resistance based on the load conditions without requiring additional control components or complex circuitry. It self-regulates by sensing the downstream pressure and automatically modulating its opening to maintain safe lowering speeds, thereby improving safety while avoiding increased system complexity.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The pressure compensator dynamically changes the hydraulic resistance parameter based on operating conditions. By varying its opening degree in response to downstream pressure changes, it automatically adapts the hydraulic resistance to match load conditions, ensuring safe operation across different load scenarios without requiring multiple fixed-resistance valves or complex control logic.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If the pressure compensator is piloted by downstream pressure signal only, then the control is simple, but the pressure compensator operates at high pressure levels requiring more robust and expensive components

Engineering Contradiction:

Improvesimplicity of control circuitVSAvoidpressure level on components

Core Design Contradiction:

Device complexityVSStress or pressure

Solution Approach 1:

The piloting function is segmented between two pressure signals: a downstream pressure signal that provides the primary control input and an upstream pressure signal that provides balancing compensation. This segmentation allows the pressure compensator to operate with a balanced pressure differential, reducing the actual pressure stress on internal components while maintaining effective control functionality.

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

This solution ensures a safe and load-independent boom lowering speed, simplifies the control circuit, and reduces costs by making the system less dependent on load weight, thereby enhancing safety and operational efficiency.

Implementation Method 1

a pressure compensator is piloted by a first pressure signal from the fluid line downstream of the control valve and by a second pressure signal from the fluid piloting line so that, upon increasing of the first pressure signal during boom lowering by gravity, a branch of the piloting line is progressively connected to the tank

Methodology Applied

Scientific EffectPressure balance: Pascal's Law

Implementation Method 2

increase hydraulic resistance applied to the flow when the boom lowers

Methodology Applied

Scientific EffectHydraulic resistance: Pressure Drop

Implementation Method 3

the boom lowering speed is related to a command by the user with little or no impact by the load carried on the boom

Methodology Applied

Scientific EffectGravity: Gravitation

Data Source

PatentUS11225981B2Vehicle with a boom comprising a hydraulic control circuit with a load control valve

Publication Date: 2022.01.18 INC BLUE LEAF I

AI summary

A vehicle including a control valve to lift and lower a boom. The vehicle further includes a control circuit to control a speed of the boom lowering via a pressure compensator that balances a first pressure signal downstream of a control valve during the boom lowering and a second pressure signal from a hydraulic user interface so that, upon increasing of the first pressure signal during the boom lowering, the control valve progressively closes.