Torque-Limiting Spindle Clutch for Over-Torque Protection

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Solution Overview

Problem

Existing locksets are susceptible to over-torqueing attacks, which can damage the handle and internal components, and current torque-limiting mechanisms, such as frangible elements and complex slip clutches, have drawbacks like requiring replacement or being difficult to reset.

Innovation Solution

A torque-limiting spindle with an input member, output member, clutch mechanism, and bias mechanism that engages the handle and lockset components, limiting torque transmission to a threshold and allowing discrete rotational adjustments to prevent excessive force from being applied to the lockset's internal components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a frangible element or traditional slip clutch is used to prevent excessive torque, then component damage is prevented, but the mechanism becomes complex and requires replacement or is difficult to reset

Engineering Contradiction:

Improveprotection from over-torqueingVSAvoidcomplexity of torque-limiting mechanism

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The clutch mechanism is segmented into distinct components: a clutch drum, clutch plates (friction and steel), and springs. This segmentation allows each component to perform its specific function while maintaining overall simplicity. The friction clutch plates and steel clutch plates are separate segments that alternate on the clutch drum, enabling the torque-limiting function through their interaction without requiring complex assembly or replacement procedures.

Inventive Principle:

Principle #1Segmentation

2Reliability

If a traditional slip clutch is used, then torque limitation is achieved, but the handle provides continuous rotational positions that are difficult to reset to the desired orientation

Engineering Contradiction:

Improvetorque limitationVSAvoidease of resetting handle orientation

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The clutch mechanism dynamically transitions between engaged and disengaged states based on applied torque. During normal operation, the springs maintain engagement between clutch plates, providing positive torque transmission. When excessive torque is applied, the friction plates slip dynamically, allowing the handle to rotate freely until normal torque is reapplied, at which point engagement is automatically restored. This dynamic behavior eliminates the need for manual resetting while providing clear tactile feedback to the user.

Inventive Principle:

Principle #15Dynamics

3Reliability

If the clutch mechanism uses friction-based engagement, then smooth torque limitation is achieved, but excessive heat may be generated during slipping

Engineering Contradiction:

Improvesmooth torque limitationVSAvoidheat generation during slipping

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The clutch mechanism maintains continuous engagement through the biasing springs, ensuring that torque is continuously transmitted during normal operation. The friction-based slipping is designed to occur only momentarily when excessive torque is applied, minimizing heat generation. The alternating friction and steel plates on the clutch drum provide continuous friction contact during normal operation, eliminating gaps in torque transmission while limiting the duration and intensity of heat-generating slip events to only when necessary for torque protection.

Inventive Principle:

Principle #20Continuity of useful 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

The solution effectively prevents damage from over-torqueing by allowing the handle to rotate freely when the lockset is locked, maintaining component integrity and simplifying reset by providing discrete rotational positions, unlike traditional slip clutches which offer continuous and difficult-to-reset orientations.

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 EffectSpring: Spring

Data Source

PatentUS11781600B2Torque-limiting spindle

Publication Date: 2023.10.10 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.