Crane Load Hook Control Using Rope Tension Ratio Limits

Solution Overview

Problem

Conventional lifting devices face limitations in ensuring that an empty load hook can be lowered safely without the risk of uncontrolled movement, particularly when the load hook is raised, due to the need for an excessively heavy load hook or operational restrictions.

Innovation Solution

A lifting device with a tensile force determination unit that compares the tensile forces of two rope sections to determine a safe lifting height and speed, using a control unit to stop the load hook movement when a predetermined threshold is reached, allowing the load hook to be lifted without a load.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the load hook is made excessively heavy to ensure it can be lowered by its own weight, then the reliability of safe lowering is improved, but the maximum load weight capacity deteriorates and handling becomes more difficult

Engineering Contradiction:

Improvesafe lowering capabilityVSAvoidload hook weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent replaces the mechanical solution of using a heavy load hook to ensure downward force with an electronic control system. The control unit monitors the tensile force ratio between the first rope section (from deflection mechanism to load hook) and the second rope section (from deflection mechanism to rope drum), and automatically stops upward movement when the ratio reaches a predetermined threshold, eliminating the need for excessive load hook weight.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system implements continuous feedback by monitoring the tensile force ratio in real-time during load hook movement. The control unit receives data from force sensors measuring the tensile forces in both rope sections, compares the ratio against the predetermined threshold, and automatically adjusts the motor-driven rope drum to stop movement when the threshold is reached, ensuring safe lowering capability without excessive weight.

Inventive Principle:

Principle #23Feedback

2Productivity

If the load hook is raised without a load attached, then the productivity and versatility of the lifting device are improved, but the risk of uncontrolled movement and inability to stop the load hook deteriorates

Engineering Contradiction:

Improveoperational efficiencyVSAvoidcontrolled lowering capability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system implements continuous feedback by monitoring the tensile force ratio in real-time during load hook movement. The control unit receives data from force sensors measuring the tensile forces in both rope sections, compares the ratio against the predetermined threshold, and automatically adjusts the motor-driven rope drum to stop movement when the threshold is reached, ensuring safe lowering capability without excessive weight.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces the mechanical solution of using a heavy load hook to ensure downward force with an electronic control system. The control unit monitors the tensile force ratio between the first rope section (from deflection mechanism to load hook) and the second rope section (from deflection mechanism to rope drum), and automatically stops upward movement when the ratio reaches a predetermined threshold, eliminating the need for excessive load hook weight.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If a heavy load hook is used to ensure downward movement, then the reliability of lowering is improved, but the ease of operation deteriorates due to poorer handling

Engineering Contradiction:

Improvelowering capabilityVSAvoidhandling quality

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent replaces the mechanical solution of using a heavy load hook to ensure downward force with an electronic control system. The control unit monitors the tensile force ratio between the first rope section (from deflection mechanism to load hook) and the second rope section (from deflection mechanism to rope drum), and automatically stops upward movement when the ratio reaches a predetermined threshold, eliminating the need for excessive load hook weight.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Productivity

If the load hook is raised to maximum height, then the productivity is improved, but the risk of uncontrolled collision with the deflection mechanism increases

Engineering Contradiction:

Improvelifting height capabilityVSAvoidcollision risk

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The system implements continuous feedback by monitoring the tensile force ratio in real-time during load hook movement. The control unit receives data from force sensors measuring the tensile forces in both rope sections, compares the ratio against the predetermined threshold, and automatically adjusts the motor-driven rope drum to stop movement when the threshold is reached, ensuring safe lowering capability without excessive weight.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system takes preliminary anti-action by continuously monitoring the tensile force ratio and automatically stopping upward movement before the load hook can reach a position where uncontrolled collision with the deflection mechanism could occur. The predetermined threshold is set to prevent the situation where the load hook's weight becomes insufficient to counterbalance the second rope section's weight, which would cause uncontrolled downward movement.

Inventive Principle:

Principle #9Preliminary anti-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

Ensures safe and controlled lowering of the load hook by monitoring rope section tensions, preventing uncontrolled collisions and enabling efficient operation without the need for a heavy load hook, thus improving handling and maximum load capacity.

Implementation Method 1

The first tensile force can be determined by the weight of the first rope section, the weight of the load hook, and optionally the weight of the load attached to the load hook. Similarly, the second tensile force is determined by the weight of the second rope section

Methodology Applied

Scientific EffectGravitation: Gravitation

Data Source

PatentEP4674801A1Lifting device, in particular crane, and method for operating such a lifting device

Publication Date: 2026.01.07 LIEBHERR WERK NENZING

Figure 1~2

AI summary

The invention relates to a lifting device (1), in particular a crane, which comprises a load hook (2) for attaching a load to be lifted, a rope (5, 6) connected to the load hook to raise or lower it, a deflection arrangement (3, 8) for deflecting the rope, and a rope drum (4) for winding or unwinding the rope, wherein the deflection arrangement divides the rope into a first rope section (5) extending from the deflection arrangement to the load hook and into a second rope section (6) extending from the deflection arrangement to the rope drum.The lifting device has a force determination unit () designed to determine a force of the first rope section, the first force, and a force of the second rope section, the second force, and a control unit designed to compare the first force and the second force and to stop a procedure of the load hook in the direction of the deflection arrangement when a ratio of the first force to the second force reaches a predetermined threshold.