Cutting Plate Safety Lock for Lawn Tractor

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Solution Overview

Problem

Existing cutting plates for lawn tractors do not effectively prevent accidental start of the cutting blade when in a raised washing position without requiring manual removal of the transmission belt.

Innovation Solution

A safety device that automatically locks the cutting blade when lifting the cutting plate, utilizing the weight of the plate to overcome engagement forces and maintain a locked rotor position without disassociating the driving belt, allowing easy transition between working and washing positions with simple lifting and lowering movements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the cutting plate is lifted to a raised washing position, then the cutting area becomes accessible for cleaning, but the cutting blade may accidentally start rotating creating safety risks

Engineering Contradiction:
Improveaccessibility of cutting areaVSAvoidaccidental blade rotation
Core Design Contradiction:
Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The safety device is activated in advance when the cutting plate is lifted to the washing position. The device automatically engages the locking mechanism before the operator begins cleaning, preventing accidental blade rotation from occurring at all during the washing operation.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The safety device automatically detects when the cutting plate is in the raised washing position and activates the locking mechanism without requiring manual intervention. The system self-regulates to prevent accidental blade rotation, eliminating the need for the operator to manually remove the driving belt.

Inventive Principle:
Principle #25Self-service

2Object-affected harmful factors

If the transmission belt is manually removed to prevent blade rotation, then safety is improved, but the complexity of the operation increases and time is lost

Engineering Contradiction:
Improveblade rotation preventionVSAvoidmanual belt removal procedure
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The safety device automatically activates the locking mechanism when the cutting plate is raised, eliminating the need for manual belt removal. The system monitors the plate position and engages the lock autonomously, simplifying the operator's task to merely lifting the plate.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The invention replaces the manual mechanical action of belt removal with an automated mechanical locking system. The locking mechanism uses a rotor and engagement body that automatically lock the cutting blade when the plate is in the washing position, substituting complex manual procedures with a simpler automated system.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If a locking mechanism is added to prevent accidental blade start, then safety is improved, but the device complexity increases

Engineering Contradiction:
Improveaccidental blade startVSAvoidsafety device structure
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The invention uses a mechanical locking system with a rotor and engagement body that leverages the natural weight of the cutting plate to activate the lock. This mechanical approach avoids complex electronic sensors, motors, or control systems while achieving reliable safety functionality.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention converts the weight of the cutting plate, which normally aids in cutting, into the activating force for the safety locking mechanism. When the plate is lifted to the washing position, its weight automatically engages the lock, turning a potential hazard into a safety feature without requiring additional power sources or complex actuation systems.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

4Extent of automation

If the cutting plate weight is used to activate the locking mechanism, then the automation is improved, but the force required to lower the plate increases

Engineering Contradiction:
Improveautomatic locking activationVSAvoidlowering force requirement
Core Design Contradiction:
Extent of automationVSForce

Solution Approach 1:

The locking mechanism is designed with dynamic engagement characteristics where the lock engages smoothly as the plate is lowered. The engagement body and rotor are configured to allow gradual engagement rather than abrupt locking, distributing the force requirement over the lowering motion rather than requiring a sudden force spike.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The locking mechanism is positioned and dimensioned so that the engagement occurs naturally during the normal lowering motion of the cutting plate. The geometry of the engagement body and rotor ensures that the locking action occurs at a point in the lowering trajectory where the plate's weight naturally provides sufficient force without creating excessive resistance.

Inventive Principle:
Principle #12Equipotentiality

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

Ensures operator safety in the washing position by locking the rotor without removing the driving belt, enabling easy movement between positions with two simple actions and maintaining operational integrity of the kinematic mechanism.

Implementation Method 1

One end of a spring 11, the second end of which is fixed to the body 9, is fastened to a second edge 103 of the plate 10. Said spring 11 serves to force the rotation of the body 9 in the locking direction of the rotor 61

Methodology Applied
Scientific EffectSpring: Spring

Implementation Method 2

the weight of the cutting plate is used during the lowering step in order to overcome the force of the engagement of the body with the rotor

Methodology Applied
Scientific EffectGravitation: Gravitation

Data Source

PatentEP3513645B1A cutting plate with a safety device for locking the cutting blade
Publication Date: 2020.06.03 STIGA S P A IN BREVE ANCHE ST SPA
  • EP3513645B1 patent drawingFigure 1~2
  • EP3513645B1 patent drawingFigure 3~4
  • EP3513645B1 patent drawingFigure 5~6

AI summary

A cutting plate (2) for a tractor (30) is described, comprising a frame (50) with which at least one rotor (61) is associated, driven by a driving belt (71), and to which a cutting blade (64) is fixed underneath, said cutting plate (2) further comprising at least one lever (3), which is rotatably associated with the frame (50) and separably associated with the tractor (30). A first end (81) of a wire (8) is fixed to said lever (3), the second end (82) of which is fixed to a body (9) associated with the frame (50), said body (9) being selectively movable between a locking position and a releasing position of the rotor (61), in said locked position the body (9) is reversibly associated with the rotor (61). (Fig. 3).