Fork Carriage Hydraulic Circuit for Consistent Tine Displacement

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Solution Overview

Problem

Forklift truck fork carriages face issues with inconsistent load holder displacement due to imprecise volume flow management, leading to increased wear and unreliable interdependence of load bearing shifts, especially when volume flows vary or maintenance is poor.

Innovation Solution

Connecting the piston rod-side cylinder volume of one differential cylinder to the piston-side volume of another in series, eliminating the need for a hydraulic flow divider, ensures fixed displacement ratios and includes overflow devices for volume correction, maintaining consistent tine movement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a hydraulic flow divider is used to supply hydraulic medium to differential cylinders in parallel, then the load holders can be displaced, but the division error increases and wear increases when volume flow varies

Engineering Contradiction:
Improvefunctional reliabilityVSAvoiddisplacement precision
Core Design Contradiction:
ReliabilityVSManufacturing precision

Solution Approach 1:

The patent replaces the mechanical flow divider system with a direct hydraulic connection between differential cylinders. Instead of using a flow divider to distribute hydraulic medium, the system connects the piston rod-side cylinder volume of one differential cylinder to the piston-side volume of another, eliminating the mechanical flow divider and its associated division errors and wear issues.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses hydraulic pressure and volume relationships to control the displacement of load holders. By connecting the piston rod-side cylinder volume of one differential cylinder to the piston-side volume of another, the system uses hydraulic principles to ensure coordinated movement without mechanical flow dividers.

Inventive Principle:
Principle #29Pneumatics and hydraulics

2Ease of operation

If differential cylinders are supplied with hydraulic medium in parallel using a flow divider, then both load holders can move, but the division error increases and wear increases

Engineering Contradiction:
Improveease of operationVSAvoiddevice complexity
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The patent extracts and removes the flow divider component from the system. By eliminating the flow divider, the system reduces device complexity and removes the source of division errors and wear, while still achieving the desired function of moving both load holders through direct hydraulic volume relationships.

Inventive Principle:
Principle #2Taking out (Extraction)

3Adaptability or versatility

If the volume flow range is extended beyond the optimal range, then more flexibility is achieved, but the division error increases and wear increases

Engineering Contradiction:
Improvevolume flow adaptabilityVSAvoidoperational reliability
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The patent creates a dynamic hydraulic system where the connection between differential cylinders automatically adjusts to varying volume flows. The direct hydraulic connection allows the system to adapt to different operating conditions without the rigid constraints of a flow divider, maintaining reliability across a wider volume flow range.

Inventive Principle:
Principle #15Dynamics

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 enhances operational safety and reduces manufacturing costs by ensuring consistent load holder displacement and minimizing wear, while allowing for simple volume adjustments through overflow devices.

Implementation Method 1

each load holder being assigned a hydraulically actuated differential cylinder to effect the displacement

Methodology Applied
Scientific EffectHydraulic pressure: Pressure Gradient

Implementation Method 2

the supplied flow of hydraulic medium - usually hydraulic oil - is divided into flows of the required size

Methodology Applied
Scientific EffectPascal's law: Pascal's Law

Data Source

PatentEP2451738B1Fork carriage for a forklift
Publication Date: 2013.07.10 HUBTEX MASCHENBAU
  • EP2451738B1 patent drawingFigure 1
  • EP2451738B1 patent drawingFigure 2
  • EP2451738B1 patent drawingFigure 3~4

AI summary

In a fork carriage (100) for a forklift, having a support frame (7), having at least two load bearing members (1) that are movably mounted on the support frame (7) so that their distance apart is alterable, wherein a hydraulically operable differential cylinder (4, 4') for effecting the movement is associated with each load bearing member (1), the piston rod-side annular volume (8) of one differential cylinder (4') is connected to the piston-side volume (10) of the other differential cylinder (4). The piston rod–side annular area (18) of the one differential cylinder (4') is in a predetermined ratio to the piston-side area (19) of the other differential cylinder (4).