Steering Arm Torsion Spring Layout for Consistent Neutral Return

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Solution Overview

Problem

Existing ZTR mowers with electric traction drive require a steering arm return to neutral mechanism that overcomes friction and losses, provides consistent return to neutral forces, is low cost, and can be integrated within the steering bracket or housing.

Innovation Solution

A torsion spring mechanism mounted around the pivot axis of the steering arm, with a pivoting pin and stationary plate, applies pre-loaded force to return the steering arm to neutral, overcoming friction and system losses, and is contained within the steering bracket or housing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If coil springs are used to urge swashplate control arms back to neutral, then the steering arm returns to neutral position, but the mechanism becomes complex and requires additional components outside the steering bracket

Engineering Contradiction:

Improvereturn to neutral functionVSAvoidmechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The torsion spring is integrated directly into the steering arm assembly, combining the return-to-neutral function with the existing steering mechanism. The spring is mounted around the pivot axis of the steering arm, eliminating the need for separate swashplate control arms and external coil springs, thus reducing overall mechanism complexity while maintaining the return-to-neutral function.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The torsion spring is nested around the pivot axis of the steering arm, utilizing the existing structural space. This nesting approach allows the return-to-neutral mechanism to be contained within the steering arm assembly itself, reducing the need for external components and simplifying the overall system architecture.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Device complexity

If steering arm return mechanisms are integrated within the steering bracket, then device complexity is reduced, but space constraints make implementation difficult

Engineering Contradiction:

Improveintegration simplicityVSAvoidsteering mechanism space

Core Design Contradiction:

Device complexityVSVolume of moving object

Solution Approach 1:

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The torsion spring utilizes the radial dimension around the pivot axis rather than requiring additional linear space. By coiling the spring around the existing pivot axis, the design efficiently uses the available volumetric space within the steering bracket without increasing the overall footprint of the steering mechanism.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Reliability

If torsion spring is pre-loaded, then consistent return to neutral forces are provided, but friction and system losses increase

Engineering Contradiction:

Improveconsistent return forceVSAvoidfriction losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The torsion spring is pre-loaded to a specific torque value that provides consistent return-to-neutral force across the operating range. By optimizing the spring preload parameter, the system achieves reliable return force while minimizing excessive friction. The spring engages smoothly with the steering arm through the pivoting pin and bushing interface, reducing energy losses.

Inventive Principle:

Principle #35Parameter changes

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 torsion spring mechanism ensures consistent and efficient return to neutral positions, reducing friction and system losses while maintaining a low parts count and cost.

Implementation Method 1

A steering arm return to neutral mechanism includes a torsion spring coiled around a pivot axis of a steering arm

Methodology Applied

Scientific EffectTorsion spring: Torsion Spring

Data Source

PatentUS12477976B1Steering arm return to neutral mechanism

Publication Date: 2025.11.25 DEERE & CO

AI summary

A steering arm return to neutral mechanism for a steering arm pivotable on a shaft between a forward drive position and a reverse drive position. A torsion spring around the shaft has a first leg providing a spring force against a pin extending from the steering arm to pivot the steering arm from the forward drive position back to a neutral position, and a second leg providing a spring force against the pin to pivot the steering arm from the reverse drive position back to the neutral position. A stationary plate is positioned between the first leg and the second leg of the torsion spring.