Rotation Lock Device for Lever Hoist Brake Failure

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Solution Overview

Problem

Existing lever hoists face issues with stopping the rotation of a shaft-shaped member when the brake device fails, and there is a limit to improving the attachment strength of the pawl shaft due to the small thickness of the frame, leading to potential cargo falls during mesh failures between the ratchet wheel and ratchet claw.

Innovation Solution

A rotation lock device is introduced, featuring a stopper support member, a stopper member, a holding mechanism, and an urging mechanism that allows the stopper member to project and engage with a stopper locking mechanism to stop the rotation of the shaft-shaped member, enhancing attachment strength and preventing cargo falls.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the brake mechanism uses a ratchet wheel with many ratchet teeth and a pawl member, then the braking function is improved, but the risk of mesh failure and cargo fall increases when the brake stops functioning

Engineering Contradiction:

Improvebraking functionVSAvoidcargo fall risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a rotation lock mechanism as a backup safety system that engages automatically when the brake fails. The stopper member is held by a holding means that releases under centrifugal force during rapid rotation, causing the stopper to engage with the stopper locking means and prevent further rotation, thereby cushioning against the harmful effect of brake failure before cargo can fall.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Ease of manufacture

If the claw shaft is attached to the frame by press fitting, then the installation is simple, but the attachment strength is insufficient when the frame thickness is small and the claw shaft length is large

Engineering Contradiction:

Improveinstallation simplicityVSAvoidattachment strength

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The patent divides the attachment function into two separate components: the claw shaft and the stopper locking means. The stopper locking means is attached to the frame with high strength, while the claw shaft connects to the stopper locking means. This segmentation allows each component to be optimized independently for its specific function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The stopper locking means acts as an intermediary between the frame and the claw shaft. It provides a strong attachment point on the frame while simultaneously supporting the claw shaft, thereby mediating the connection and transferring loads effectively without requiring direct attachment of the long claw shaft to the thin frame.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If the stopper member is held at a fixed position, then the structure is simple, but the stopper cannot engage with the stopper locking means during rapid rotation of the shaft-shaped member

Engineering Contradiction:

Improveholding mechanism structureVSAvoidrotation stopping function

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent transforms the holding mechanism from a static fixed-position holder to a dynamic system using centrifugal force. The holding means allows the stopper member to move radially outward when centrifugal force exceeds the holding force during rapid rotation, enabling automatic engagement with the stopper locking means. This dynamic behavior ensures reliable rotation stopping without complex control systems.

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

The rotation lock device effectively stops the rotation of the shaft-shaped member when the brake fails, improving the attachment strength of the pawl shaft and preventing cargo falls by using a sliding stopper member that engages with a locking mechanism, ensuring secure operation even under increased loads.

Implementation Method 1

when the shaft-shaped member accelerates the rotation toward the first rotation direction, a holding force for the stopper member by the holding means is decreased and/or released by an inertial load of the holding means to cause the stopper member to project from the predetermined position

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Implementation Method 2

an urging means configured to urge the holding means toward a first rotation direction being one rotation direction with respect to the stopper member

Methodology Applied

Scientific EffectElastic force: Elasticity

Data Source

PatentUS12180044B2Rotation lock device, lever hoist, and hoisting machine

Publication Date: 2024.12.31 KITO CORP

AI summary

A rotation lock device comprising: a stopper support member rotating integrally with a shaft-shaped member; a stopper member supported by the stopper support member in a state of being slidable; a holding means configured to hold the stopper member; an urging means configured to urge the holding means toward a first rotation direction with respect to the stopper member; and a stopper locking means configured to stop a rotation of the shaft-shaped member by engaging with the stopper member, wherein when the shaft-shaped member accelerates the rotation toward the first rotation direction, a holding force for the stopper member by the holding means is decreased and/or released by an inertial load of the holding means to cause the stopper member to project from the predetermined position to a position where the stopper member engages with the stopper locking means to thereby stop the rotation of the shaft-shaped member.