Truck-Mounted Forklift Arm-State Control for Safe Travel Speed

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Solution Overview

Problem

Existing truck-mounted forklifts face safety risks due to the potential misuse of retractable telescopic arms during normal operations, leading to instability and load loss, as drivers may inadvertently operate with arms not fully extended.

Innovation Solution

A forklift equipped with a device to automatically determine the extension or retraction state of telescopic arms, coupled with a control system to adjust speed limits and provide alerts based on this state, ensuring safe operation by preventing unauthorized use of retracted arms.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If telescopic arms are made retractable to optimize storage space, then storage efficiency is improved, but safety deteriorates due to risk of accidental operation with retracted arms

Engineering Contradiction:
Improvestorage spaceVSAvoidsafety
Core Design Contradiction:
Volume of moving objectVSReliability

Solution Approach 1:

The system continuously monitors the extension state of telescopic arms via sensors and provides real-time feedback to the control unit. When arms are detected to be retracted or partially extended, the control unit automatically responds by limiting travel speed or preventing operation, creating a closed-loop safety mechanism that prevents accidental operation with retracted arms.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

A control unit acts as an intermediary between the operator and the forklift's movement functions. This intermediary layer intercepts operator commands and automatically adjusts them based on the current extension state of telescopic arms, preventing direct operation when safety conditions are not met, thus mediating between operational intent and safety constraints.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If automatic determination device and control system are added to monitor telescopic arm state, then safety is improved, but device complexity increases

Engineering Contradiction:
ImprovesafetyVSAvoidsystem complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The control unit serves multiple functions: it monitors the extension state of telescopic arms via sensors, determines whether arms are properly extended, limits travel speed based on this state, and can prevent operation entirely when conditions are unsafe. By consolidating these safety-critical functions into a single multi-functional control unit, the system achieves high safety without proportionally increasing overall system complexity.

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

Solution Approach 2:

The patent combines the determination device (sensors and control logic) with the existing motor control system for the driven wheels. The control unit integrates arm position monitoring with speed control functions, merging safety monitoring and actuation into a unified system rather than adding separate independent systems, thereby reducing complexity while maintaining safety.

Inventive Principle:
Principle #5Merging (Combining)

3Reliability

If travel speed is automatically limited when telescopic arms are retracted, then safety is improved, but productivity decreases

Engineering Contradiction:
ImprovesafetyVSAvoidtravel speed
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The system dynamically adjusts the maximum permissible travel speed based on the real-time extension state of telescopic arms. When arms are fully extended, normal operating speeds are permitted. When arms are retracted or partially extended, the control unit automatically reduces the maximum speed limit. This dynamic adaptation allows the system to optimize productivity when safe while ensuring safety when conditions require caution.

Inventive Principle:
Principle #15Dynamics

Data Source

PatentEP4707223A1Slave stacker
Publication Date: 2026.03.11 PALFINGER AG
  • EP4707223A1 patent drawingFigure 1
  • EP4707223A1 patent drawingFigure 2
  • EP4707223A1 patent drawingFigure 3

AI summary

Truck-mounted forklift (1), comprising at least: - a lifting and lowering load handling device (2) - at least three wheels (3) with which the truck-mounted forklift (1) can be moved on a surface at a travel speed (v), wherein at least one of the at least three wheels (3) is motor-driven and at least two wheels (3) are arranged on each of a retractable telescopic arm (4) - a motor (5) for driving the at least one driven wheel (3) - a motor control (6) for controlling the motor (5) taking into account an operating command of an operator, preferably a driver, of the truck-mounted forklift, wherein the truck-mounted forklift (1) has a device (7) for automatically determining an extension or retraction state of at least one of the at least two telescopic arms (4).