Robotic Mower Height Adjustment Nut for Fast Screw Assembly

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Solution Overview

Problem

Existing height adjustment devices in robotic mowers face challenges in providing a reliable and efficient assembly process without the need for resilient members to maintain screw-to-nut engagement.

Innovation Solution

A height adjustment device with an adjustment nut comprising two parts, one with inner threads and the other without, allowing for a clasp connection that engages with the screw mid-portion, enabling quick assembly and a reliable connection without the need for biasing elements, facilitated by a snap function and thread stops for precise calibration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a biasing element is used to keep the adjustment screw in engagement with the adjustment nut, then the screw-to-nut connection is maintained, but the assembly process becomes more complex and time-consuming

Engineering Contradiction:
Improvescrew-to-nut connection reliabilityVSAvoidassembly process complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The adjustment nut is divided into two separate parts: a first part with internal threads for engagement with the adjustment screw, and a second part without threads. This segmentation allows the threaded part to engage the screw directly without requiring a biasing element, while the second part provides structural support and positioning, thereby simplifying the assembly process while maintaining connection reliability

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The biasing element is completely removed from the system. Instead of using a resilient member to maintain engagement between the screw and nut, the invention uses a direct mechanical engagement through the two-part nut structure where the first part's internal threads directly engage the adjustment screw, eliminating the need for additional biasing components

Inventive Principle:
Principle #2Taking out (Extraction)

2Reliability

If the adjustment screw must be inserted from one end into the adjustment nut, then the connection can be made, but the assembly process becomes slower and less efficient

Engineering Contradiction:
Improvescrew-to-nut connectionVSAvoidassembly speed
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

By dividing the adjustment nut into two parts, the invention enables the adjustment screw to be clamped at its mid-portion between the first threaded part and the second part, rather than requiring insertion from one end. This segmentation creates a clamping action that secures the screw reliably while allowing for much faster assembly

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Instead of inserting the screw into the nut from one end as in conventional designs, the invention inverts the approach by having the nut structure clamp the screw at its mid-portion. The first part with internal threads engages the screw, while the second part provides the clamping action, fundamentally changing the assembly sequence and orientation

Inventive Principle:
Principle #13The other way round (Inversion)

3Reliability

If resilient members are used to maintain thread engagement, then the connection is maintained under load, but the overall device complexity increases

Engineering Contradiction:
Improvethread engagement maintenanceVSAvoidnumber of components
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The resilient member is completely extracted from the system. The two-part nut structure provides inherent mechanical engagement where the first part's internal threads directly engage the adjustment screw, and the second part provides structural support, eliminating the need for separate resilient components while maintaining engagement reliability under operational loads

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The functions of maintaining thread engagement and providing structural support are merged into the two-part nut structure itself. The first part handles the threading and engagement function, while the second part provides structural support and positioning, combining multiple functions into a single integrated component system without requiring separate resilient members

Inventive Principle:
Principle #5Merging (Combining)

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 ensures a quick, efficient, and reliable assembly process with a firm connection, eliminating the need for resilient members and allowing for precise height adjustments using a plastic material like Polyoxymethylene (POM).

Implementation Method 1

a height adjustment screw (3) having outer threads and a cog, driven by a servo, stepping motor, or the like, and arranged rotatably in relation to a chassis, and an adjustment nut (9) connected to a bracket (11) and comprising inner threads for engagement with the outer threads of the adjustment screw (3), such that a rotary movement of the height adjustment screw (3) results in a vertical linear movement of the bracket (11)

Methodology Applied
Scientific EffectScrew mechanism: Screw

Data Source

PatentEP3981240B1Height adjustment device and a robotic mower comprising a height adjustment device
Publication Date: 2026.04.15 HUSQVARNA AB
  • EP3981240B1 patent drawingFigure 1
  • EP3981240B1 patent drawingFigure 2~3b

AI summary

The present disclosure relates to a height adjustment device (1) comprising a height adjustment screw (3) having outer threads (5) and being oriented substantially vertically and arranged rotatably in relation to a chassis (7), and an adjustment nut (9) connected to a bracket (11) and comprising inner threads (13) for engagement with the threads (5) of the adjustment screw (3), such that a rotary movement of the height adjustment screw (3) results in a vertical linear movement of the bracket (11). The adjustment nut comprises a first part (15) and a second part (17) which together enclose the adjustment screw (3), wherein the first part (15) being adapted to be attached to the second part. The present disclosure also considers a robotic mower (101) comprising such a height adjustment device.