Torque-Limiting Spindle Clutch for Lockset Over-Torque Protection

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Solution Overview

Problem

Existing locksets are susceptible to over-torqueing attacks, which can damage handles and internal components, and current torque-limiting mechanisms are complex, require multiple parts, and often fail to return the handle to its desired orientation after slipping.

Innovation Solution

A torque-limiting spindle with an input member, output member, clutch mechanism, and bias mechanism that engages these members to limit torque transmission to a threshold, using features like wave-like engagement surfaces and biasing forces to prevent excessive torque and provide discrete handle orientations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a frangible element or traditional slip clutch is used to prevent excessive torque, then torque protection is improved, but device complexity increases and reliability decreases due to multiple parts that can be lost

Engineering Contradiction:

Improveexcessive torque damageVSAvoidnumber of parts

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent combines the clutch mechanism and bias mechanism into a single integrated spindle assembly. The clutch mechanism with engagement features is merged with the bias mechanism (spring) within the same housing, eliminating the need for separate torque-limiting devices and their associated multiple parts. This reduces device complexity while maintaining torque protection functionality.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The spindle serves multiple functions: it transmits torque from the handle to the lockset mechanism, limits excessive torque through the clutch mechanism, and provides a biasing force to maintain engagement. This multi-functionality eliminates the need for separate torque-limiting devices, reducing the number of parts while achieving both torque transmission and protection.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Object-affected harmful factors

If a traditional slip clutch is used to limit torque, then torque protection is improved, but ease of operation worsens because the handle cannot be returned to its desired orientation after slipping

Engineering Contradiction:

Improveexcessive torque damageVSAvoidhandle reorientation

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

The clutch mechanism is designed to be dynamic rather than static. When excessive torque is applied, the engagement features disengage and allow relative rotation between the input and output members. After the excessive torque is removed, the bias mechanism automatically re-engages the clutch, allowing the handle to be easily reoriented to its desired position without permanent displacement or difficulty.

Inventive Principle:

Principle #15Dynamics

3Device complexity

If no torque-limiting mechanism is used, then device complexity is reduced, but reliability decreases due to susceptibility to over-torqueing attacks

Engineering Contradiction:

Improvesimplicity of structureVSAvoidprotection against over-torqueing

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The spindle assembly is self-protecting through its integrated clutch and bias mechanisms. When excessive torque is applied, the clutch mechanism automatically disengages to prevent damage, and the bias mechanism automatically re-engages it after the stress is removed. This self-service capability provides reliable torque protection without requiring external intervention or complex control systems.

Inventive Principle:

Principle #25Self-service

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 spindle effectively limits excessive torque, protecting the lockset components while allowing easy reorientation of the handle to its desired position after slipping, and can be adjusted for varying torque thresholds.

Implementation Method 1

The bias mechanism is engaged with the input member and the output member and exerts a biasing force urging the first engagement feature and the second engagement feature into engagement with one another

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS20250334152A1Torque-limiting spindle

Publication Date: 2025.10.30 SCHLAGE LOCK CO LLC

AI summary

An exemplary torque-limiting spindle includes an input member, an output member, a clutch mechanism, and a bias mechanism. The input member extends along a longitudinal axis, is configured for connection with a handle, and includes a first engagement feature. The output member extends along the longitudinal axis, is configured for connection with a rotatable member of a lockset, and includes a second engagement feature. The clutch mechanism includes the first engagement feature and the second engagement feature. The bias mechanism is engaged with the input member and the output member and exerts a biasing force urging the first engagement feature and the second engagement feature into engagement with one another.