Outboard Tiller Neutral Shift Interlock Mechanism

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Solution Overview

Problem

Existing tiller systems for outboard motors lack an effective interlock mechanism to prevent accidental shift changes out of neutral gear when the throttle is not in the idle position, potentially leading to engine damage or unexpected vessel movement.

Innovation Solution

A manually operable tiller system with an interlock mechanism that prevents shift changes out of neutral gear when the throttle is not in the idle position, while allowing shift changes into neutral gear regardless of throttle position, using a plunger and recess configuration to separate and engage the shift and throttle mechanisms.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an interlock mechanism is implemented to prevent shift changes out of neutral when throttle is not in idle position, then safety and reliability are improved, but device complexity increases

Engineering Contradiction:

ImprovesafetyVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

A plunger acts as an intermediary mechanical element between the throttle shaft and shift mechanism. The plunger engages with a recess in the shift arm to prevent shift changes when the throttle is not in the idle position, providing the interlock function through a simple mechanical mediator rather than a complex electronic or multi-component system.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the interlock mechanism prevents all shift changes when throttle is not in idle, then engine damage is prevented, but operational flexibility is reduced

Engineering Contradiction:

Improveengine protectionVSAvoidoperational flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The interlock mechanism is designed to permit shift changes INTO neutral gear regardless of throttle position, while preventing shift changes OUT of neutral. This inverted approach allows operators to quickly return to neutral for safety or emergency situations, while still protecting against accidental gear shifts during operation.

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of manufacture

If a plunger and recess configuration is used for the interlock mechanism, then manufacturing simplicity is improved, but precision requirements increase

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidengagement precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The plunger and recess configuration is designed to be self-aligning and self-regulating. The mechanical geometry of the plunger and recess automatically ensures proper engagement and disengagement through their relative positions and shapes, eliminating the need for complex adjustment mechanisms or high-precision machining tolerances.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS10246173B1Tillers for outboard motors having neutral shift interlock mechanism

Publication Date: 2019.04.02 BRUNSWICK CORP

AI summary

A tiller is for an outboard motor and has a manually operable shift mechanism configured to actuate shift changes in a transmission of the outboard motor amongst a forward gear, reverse gear, and neutral gear. The tiller also has a manually operable throttle mechanism configured to position a throttle of an internal combustion engine of the outboard motor into and between the idle position and a wide-open throttle position. An interlock mechanism is configured to prevent a shift change in the transmission out of the neutral gear when the throttle is positioned in a non-idle position. The interlock mechanism is further configured to permit a shift change into the neutral gear regardless of where the throttle is positioned.