Hydraulic Flow Control Circuit for Primary-Secondary Actuator Switching

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Solution Overview

Problem

Conventional hydraulic systems in power machines often prioritize primary functions over secondary functions, leading to suboptimal operation and unwanted heat due to insufficient hydraulic fluid supply to secondary functions, especially when the primary function is not active.

Innovation Solution

A hydraulic flow control circuit that selectively directs hydraulic fluid flow to either primary or secondary actuators based on their activity, optimizing fluid distribution through multiple modes of operation to ensure efficient performance of both functions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If hydraulic fluid is diverted to secondary functions when primary function is active, then secondary functions can operate, but primary function performance deteriorates and unwanted heat is generated

Engineering Contradiction:
Improvesecondary function operationVSAvoidunwanted heat
Core Design Contradiction:
Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The hydraulic system dynamically switches between two operational modes: a first mode where pressurized fluid flows to both primary and secondary functions, and a second mode where pressurized fluid flows only to secondary functions. This dynamic switching resolves the contradiction by adapting system behavior to operational needs, enabling secondary function operation without continuously compromising primary function performance or generating excessive heat.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The system changes the parameter of hydraulic fluid flow distribution by switching between two distinct flow configurations. In the first mode, fluid is distributed to both primary and secondary actuators; in the second mode, fluid is directed exclusively to secondary actuators. This parameter change allows the system to optimize performance characteristics based on operational requirements, resolving the heat generation issue while maintaining secondary function capability.

Inventive Principle:
Principle #35Parameter changes

2Adaptability or versatility

If hydraulic fluid is diverted to secondary functions, then secondary functions can operate, but primary function performance deteriorates

Engineering Contradiction:
Improvesecondary function operationVSAvoidprimary function performance
Core Design Contradiction:
Adaptability or versatilityVSProductivity

Solution Approach 1:

The system employs dynamic mode switching to resolve the productivity conflict. When the primary function is active, the system operates in first mode providing adequate flow to maintain peak primary function performance. When secondary functions need to operate independently, the system switches to second mode. This dynamic adaptation allows secondary function operation without continuously degrading primary function productivity.

Inventive Principle:
Principle #15Dynamics

3Adaptability or versatility

If large amount of hydraulic fluid is provided to implement when primary function is not active, then secondary functions can operate, but heat is generated due to fluid return through tank

Engineering Contradiction:
Improvesecondary function operationVSAvoidsystem heat
Core Design Contradiction:
Adaptability or versatilityVSTemperature

Solution Approach 1:

The invention extracts the harmful heat-generating aspect from the hydraulic circuit by eliminating the tank return path when the primary function is not active. Instead of returning fluid through the tank where it generates unwanted heat, the system directs fluid return directly from secondary actuators back to the pump inlet. This extraction of the harmful thermal path while preserving secondary function operation resolves the temperature contradiction.

Inventive Principle:
Principle #2Taking out (Extraction)

4Adaptability or versatility

If hydraulic fluid is diverted from primary function to secondary functions, then secondary functions can operate, but overall system efficiency deteriorates

Engineering Contradiction:
Improvesecondary function operationVSAvoidsystem efficiency
Core Design Contradiction:
Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The system dynamically adjusts its operational mode to optimize energy efficiency. In first mode, when primary function is active, the system maintains efficient fluid circulation to both functions. In second mode, when only secondary functions are active, the system reconfigures flow paths to eliminate inefficiencies. This dynamic adaptation resolves the energy efficiency deterioration while preserving secondary function operability.

Inventive Principle:
Principle #15Dynamics

Data Source

PatentEP4547911B1Hydraulic control circuit for implement
Publication Date: 2026.04.22 DOOSAN BOBCAT NORTH AMERICA INC
  • EP4547911B1 patent drawingFigure 1
  • EP4547911B1 patent drawingFigure 2-1
  • EP4547911B1 patent drawingFigure 2-2

AI summary

Disclosed embodiments of power machines (10), implements (20) and hydraulic systems utilize a hydraulic flow control circuit (135; 235; 335; 435; 535) and method to implement multiple modes of operation while optimizing hydraulic fluid flow to either or both of primary and secondary function actuators (125; 130). In a first mode the hydraulic flow control circuit is configured to receive pressurized hydraulic fluid flow from a first conduit (120) and to provide the pressurized hydraulic fluid to the primary and secondary function actuators. In the first mode, the circuit is configured to direct return flow from the primary and secondary function actuators through the second conduit (121 ) for return to the power machine. In a second mode, the circuit receives flow from the second conduit, provides the flow only to the secondary function actuator, and directs the return flow to the power machine through the first conduit.