Lawnmower Handle Junction with Segmented Blocking

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Solution Overview

Problem

Existing lawnmowers with adjustable handles often experience unsynchronized tightening, leading to a crooked handle and unsafe operating positions, and lack a mechanism to ensure the handle remains horizontal and easily adjustable for different working and storage conditions.

Innovation Solution

A central junction system with a bushing and arms that allows the handle to be safely adjusted to multiple working positions while maintaining horizontal alignment, using a cam-shaped lever and toothed gears to ensure the handle is always straight and secure within a defined angular range, and allows for easy switching between working and storage positions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If toothed gears are used for blocking/releasing the handle, then the handle can be adjusted to multiple positions, but unsynchronized tightening occurs causing the handle to become crooked

Engineering Contradiction:
Improvehandle position adjustmentVSAvoidhandle alignment
Core Design Contradiction:
Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The junction is divided into two independent blocking mechanisms: a first blocking mechanism with a first cam-shaped lever and first toothed gear for the first arm, and a second blocking mechanism with a second cam-shaped lever and second toothed gear for the second arm. This segmentation allows each arm to be blocked independently, preventing the unsynchronized tightening that causes crooked handles while still enabling multi-position adjustment.

Inventive Principle:
Principle #1Segmentation

2Device complexity

If a single junction is used for the handle, then the structure is simplified, but it becomes difficult to ensure synchronized blocking of multiple arms

Engineering Contradiction:
Improvejunction structureVSAvoidsynchronized blocking
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The single junction incorporates two independent blocking mechanisms that operate separately on each arm. The first blocking mechanism blocks the first arm at predetermined angular positions, while the second blocking mechanism blocks the second arm at corresponding positions. This segmentation maintains structural simplicity while ensuring reliable synchronized blocking of multiple arms through independent control.

Inventive Principle:
Principle #1Segmentation

3Adaptability or versatility

If the handle can be tilted into infinite positions, then adaptability is improved, but safety cannot be ensured as the handle may be blocked in unsafe positions

Engineering Contradiction:
Improvehandle position rangeVSAvoidoperational safety
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The blocking mechanisms are designed to prevent the handle from being blocked at unsafe positions before operation begins. The first and second toothed gears have predetermined engagement positions that correspond to safe working angles. The cam-shaped levers can only block the arms at these pre-determined safe positions, eliminating the possibility of blocking at unsafe positions while still allowing adaptability within the safe angular range.

Inventive Principle:
Principle #10Preliminary 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 ensures the handle is always kept straight and secure in safe working positions, allowing for easy adjustment and storage without the handle resting on the frame, addressing the issues of unsynchronized tightening and safety concerns.

Implementation Method 1

The first toothed gear (151) is associated with the body (6), and the second toothed gear (22) is associated with the bushing (21)

Methodology Applied
Scientific EffectGear: Gear

Implementation Method 2

The cam-shaped lever (26) can be moved in a first direction along a cam profile, so as to move the bar (27) in a second direction, perpendicular to the first direction

Methodology Applied
Scientific EffectCam: Cam

Implementation Method 3

a second Belleville spring (33) bearing on the bar (27) and on the bushing (21), so as to push the bushing (21) against the arm (7)

Methodology Applied
Scientific EffectSpring: Spring

Data Source

PatentEP3498073B1Lawnmower with quick blocking/releasing central junction for a handle
Publication Date: 2021.02.03 STIGA S P A IN BREVE ANCHE ST SPA
  • EP3498073B1 patent drawingFigure 1
  • EP3498073B1 patent drawingFigure 2
  • EP3498073B1 patent drawingFigure 3

AI summary

A lawnmower (1) is described, comprising a frame (2), wheels (4) and a handle (3) connected to said frame (2) by a junction (5) which comprises a body (6) to which the handle (3) is fastened, two arms (7, 8) fastened to the frame (2) and means (9) for blocking/releasing the movement of the body (6) with respect to said arms (7, 8). The body (6) comprises a cylindrical element (10) provided with a through cavity (11) with a horizontal axis (O), and at least one fastening element (12) of the handle (3) in one piece.