Utility Vehicle Park Brake Interlock Circuit

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Solution Overview

Problem

Existing utility vehicle park brake systems require costly and complex mechanical or electronic interlocks to prevent vehicle travel when the park brake is engaged, and these systems often involve shutting down the engine or wearing out mechanical parts.

Innovation Solution

A low-cost, low-complexity interlock circuit that includes a normally open neutral switch, a park brake interlock relay, a throttle pedal switch, and a park brake switch, which connects to the magneto ignition circuit to prevent engine power when the park brake is engaged, allowing transmission shifting into forward or reverse without engine shutdown and avoiding mechanical wear.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If mechanical interlocks are used to link park brake and throttle pedal, then vehicle travel is prevented when park brake is engaged, but device complexity and cost increase

Engineering Contradiction:

Improveprevention of vehicle travelVSAvoidinterlock mechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces mechanical interlock systems with an electrical interlock circuit. The circuit uses electrical switches, relays, and wiring to achieve the same safety function of preventing vehicle travel when the park brake is engaged, thereby eliminating mechanical wear and reducing mechanical complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an electrical circuit as an intermediary between the park brake switch and the ignition system. This circuit includes relays and switches that mediate the control signal to prevent engine operation when the park brake is engaged, providing a non-mechanical means of interlocking.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If fuel supply interlocks are used to shut down engine when park brake is engaged, then vehicle travel is prevented, but loss of engine operation flexibility occurs

Engineering Contradiction:

Improveprevention of vehicle travelVSAvoidengine operation flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent applies the interlock function locally to the ignition system rather than shutting down the entire engine. By controlling only the ignition circuit through the electrical interlock, the system prevents vehicle travel while allowing the engine to remain operable under other conditions, maintaining operational flexibility.

Inventive Principle:

Principle #3Local quality

3Reliability

If mechanical interlocks are used to link park brake and transmission, then neutral condition is maintained, but mechanical wear occurs

Engineering Contradiction:

Improvetransmission neutral maintenanceVSAvoidmechanical part lifespan

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent replaces mechanical interlocks that physically link the park brake and transmission with an electrical interlock circuit. This eliminates moving mechanical parts that would wear over time, while still maintaining the safety function of ensuring the transmission is in neutral when the park brake is engaged.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Reliability

If costly electronic engine controllers with internal logic are used, then precise control of engine rpm is achieved, but device complexity and cost increase

Engineering Contradiction:

Improveengine rpm controlVSAvoidcontroller complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses simple, inexpensive electrical components such as switches, relays, and wiring instead of costly electronic engine controllers. While these components have shorter lifespans than sophisticated electronics, they provide adequate control functionality at a fraction of the cost and complexity.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent replaces complex electronic control systems with a simpler electrical circuit approach. The interlock function is achieved through basic electrical components rather than sophisticated microcontrollers, reducing both cost and complexity while maintaining the essential control capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS8323153B2Interlock circuit for utility vehicle park brake

Publication Date: 2012.12.04 DEERE & CO

AI summary

An interlock circuit for a utility vehicle park brake includes a relay connected to neutral switch on a transmission. The relay is actuated by electric current to move a contact to a closed position if the neutral switch is out of neutral. A throttle pedal switch connected to the relay moves a contact to a closed position if the throttle pedal is depressed. A park brake switch connected to the throttle pedal switch moves a contact to a closed position if the park brake is engaged. Closing all of the contacts grounds an ignition circuit connected to the interlock circuit, which may be a magneto ignition circuit.