Asymmetric Overload Coupling for Lift Torque Protection

Solution Overview

Problem

Existing lift systems face frequent gear assembly damage due to collisions during lowering operations, which require time-consuming recalibration and are difficult to configure for optimal torque settings between lifting and lowering processes.

Innovation Solution

An overload coupling with a latch mechanism that provides a higher transmissible torque in the lifting direction and a lower transmissible torque in the lowering direction, ensuring reliable lifting and avoiding damage by triggering early in case of collisions, and allowing for quick restoration of the reference elevation value.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a high limiting torque is set in the overload coupling to transmit high torque during lifting, then lifting capability is improved, but the coupling slips during collision in lowering direction causing damage and loss of rotational angle assignment

Engineering Contradiction:

Improvetorque transmission capabilityVSAvoidprotection against collision damage

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The overload coupling employs asymmetric friction elements with different friction coefficients for lifting and lowering directions. The first friction element has a higher friction coefficient for lifting operations to transmit high torque, while the second friction element has a lower friction coefficient for lowering operations to slip early during collisions, protecting the gear assembly from damage.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The overload coupling dynamically adjusts its torque transmission characteristics based on the direction of rotation. During lifting, the coupling transmits high torque through the first friction element, while during lowering, it limits torque through the second friction element, providing direction-dependent protection against collisions.

Inventive Principle:

Principle #15Dynamics

2Reliability

If a low limiting torque is set in the overload coupling to protect against collision damage during lowering, then reliability is improved, but lifting capability is reduced due to insufficient torque transmission

Engineering Contradiction:

Improveprotection against collision damageVSAvoidtorque transmission capability

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The overload coupling employs asymmetric friction elements with different friction coefficients for lifting and lowering directions. The first friction element has a higher friction coefficient for lifting operations to transmit high torque, while the second friction element has a lower friction coefficient for lowering operations to slip early during collisions, protecting the gear assembly from damage.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The overload coupling dynamically adjusts its torque transmission characteristics based on the direction of rotation. During lifting, the coupling transmits high torque through the first friction element, while during lowering, it limits torque through the second friction element, providing direction-dependent protection against collisions.

Inventive Principle:

Principle #15Dynamics

3Reliability

If conventional overload coupling slips during collision to avoid damage, then protection against damage is improved, but rotational angle assignment is lost requiring time-consuming recalibration

Engineering Contradiction:

Improveprotection against collision damageVSAvoidrecalibration time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system uses a sensor to detect the latched state of the latch mechanism and provides feedback to the control unit. When the sensor detects that the latch mechanism has latched following an overload event, the control unit automatically restores the reference elevation value, eliminating the need for manual recalibration and reducing downtime.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The latch mechanism automatically latches the motor end latch part to the gear assembly end latch part after an overload event, and the control system automatically restores the reference elevation value based on sensor feedback, enabling the system to service itself without manual intervention.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS9528578B2Lift system, overload coupling and method for operating the lift system

Publication Date: 2016.12.27 EFS FUR HEBE UND HANDHABUNGSTECHN MBH

AI summary

A lift system defines a vertical hoist axis and includes a holding unit for lifting and lowering an object in a direction along the vertical hoist axis. An overload coupling mutually connects the drive shaft of a motor and the input shaft of a gear assembly. The overload coupling includes a latch mechanism having a motor latch part and a gear assembly latch part. The latch mechanism defines a latch characteristic providing a first transmittable torque in a lowering rotational direction and a second transmittable torque in a lifting rotational direction determined so as to cause the first transmittable torque to be less than the second transmittable torque. The latch mechanism includes a rotational positioning device configured to permit a latching of the motor latch part into the gear assembly latch part in only one possible relative rotational angle position within 360° referred to the lifting rotational direction.