Hydraulic System Load Sensing Circuit Diversion

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Solution Overview

Problem

Conventional hydraulic systems in forklift trucks face limitations in efficiency and functionality due to finite hydraulic fluid and pressure levels, restricting simultaneous operation of multiple hydraulic functions, which negatively impacts productivity and cycle time.

Innovation Solution

A hydraulic system with two or more pump motors and a load sensing circuit that diverts hydraulic flow to a secondary system, allowing for combined operation of hydraulic functions while maintaining performance levels and providing power regeneration during reduced pressure states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a conventional hydraulic system with finite fluid and pressure levels is used, then the system structure remains simple, but the ability to operate multiple hydraulic functions simultaneously is restricted

Engineering Contradiction:
Improvesimultaneous operation of hydraulic functionsVSAvoidhydraulic system structure
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The hydraulic system is divided into a main hydraulic system and a second hydraulic system. The load sensing circuit segments the hydraulic flow by detecting pressure changes and diverting flow from the main system to the second system when needed, allowing multiple functions to operate simultaneously without requiring a completely complex redesigned system.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The hydraulic system is designed to perform multiple functions through a single integrated system. The load sensing circuit enables the same hydraulic pump to serve multiple hydraulic functions by dynamically diverting flow between the main system and the second system based on demand, eliminating the need for separate dedicated systems for each function.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Productivity

If hydraulic flow is diverted to a second system, then multiple hydraulic functions can operate simultaneously, but the system complexity increases

Engineering Contradiction:
Improveefficiency of operationVSAvoidhydraulic system structure
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The load sensing circuit acts as an intermediary device that automatically manages the diversion of hydraulic flow between the main system and the second system. This intermediary component handles the complexity of flow management, allowing the rest of the system to remain relatively simple while still enabling efficient simultaneous operation of multiple functions.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The load sensing circuit uses feedback from pressure changes in the hydraulic system to automatically control flow diversion. When pressure changes indicate a need for additional hydraulic capacity, the circuit responds by diverting flow to the second system, and when pressure stabilizes, it returns flow to the main system, creating an automatic self-regulating mechanism.

Inventive Principle:
Principle #23Feedback

3Productivity

If the hydraulic system restricts operation to one function at a time, then the system remains simple to control, but the cycle time and productivity are negatively impacted

Engineering Contradiction:
Improvecycle timeVSAvoidcontrol simplicity
Core Design Contradiction:
ProductivityVSEase of operation

Solution Approach 1:

The hydraulic system performs self-service through the load sensing circuit, which automatically detects when additional hydraulic capacity is needed and diverts flow accordingly. This eliminates the need for complex manual control mechanisms, as the system self-regulates based on its own operational state, maintaining ease of operation while improving productivity.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The system enables continuous useful action by allowing multiple hydraulic functions to operate simultaneously rather than sequentially. The load sensing circuit ensures that hydraulic flow is continuously available to whichever functions are active, eliminating idle time and reducing cycle time while maintaining simple control through automatic flow management.

Inventive Principle:
Principle #20Continuity of useful action

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

Enables efficient operation of multiple hydraulic functions simultaneously, reducing cycle time and improving productivity by optimizing hydraulic flow and pressure distribution, and reducing energy consumption through power regeneration.

Implementation Method 1

A load sensing circuit detects a change in hydraulic pressure

Methodology Applied
Scientific EffectHydraulic pressure: Pressure Increase

Implementation Method 2

The hydraulic system includes a pump and motor to generate the hydraulic pressure and corresponding hydraulic flow that operates mechanical devices

Methodology Applied
Scientific EffectHydraulic flow: Hydraulic Press

Data Source

PatentEP1868935B1Hydraulic system for an industrial vehicle
Publication Date: 2015.03.11 NACCO MATERIALS HANDLING GROUP INC
  • EP1868935B1 patent drawingFigure 1~2
  • EP1868935B1 patent drawingFigure 3~4
  • EP1868935B1 patent drawingFigure 5~6

AI summary

An industrial vehicle including a lifting device, a hydraulic system having two or more pump motors that provide hydraulic flow to the lifting device, a load-handling device, and a second hydraulic system fluidly coupled to the main hydraulic system. The hydraulic system diverts the hydraulic flow from one of the pump motors to the second hydraulic system when an actuation of the load handling device is detected.