Mower Blade Back Tempering for Tool Life
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Solution Overview
Problem
Mower knife backs in oscillating mower knives used in combine harvesters experience high mechanical stress leading to breakage due to cutting forces and mass acceleration, with existing methods to increase strength either wearing out the punching tool or causing recess displacement through tempering.
Innovation Solution
A mower knife back design featuring tempered edge strip sections and an untempered central section for recesses, allowing for increased strength and wear resistance without tool stress or length changes, with the central section being punched in a non-tempered state and edge strip sections inductively hardened for enhanced hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the back of the mower knife is made from higher strength starting material or annealing step prior to piercing, then the strength of the knife back is increased, but the punching tool is subjected to high stress and rapid wear
Solution Approach 1:
The knife back is divided into two distinct zones: a central untempered zone for punching operations and tempered edge strip sections for strength. This segmentation allows the punching tool to operate on softer material while the tempered zones provide overall structural strength, resolving the contradiction between knife back strength and punching tool durability
Solution Approach 2:
Different regions of the knife back have different tempering states: the central section remains untempered (softer) for punching, while the edge strip sections are tempered (harder) for strength. This local differentiation in material properties allows the punching tool to function normally while the knife back maintains high strength where needed
2Duration of action of stationary object
If tempering is carried out after punching to protect the punching tool, then the punching tool service life is extended, but the tempering leads to a change in length and thus to an impermissible displacement of the recesses
Solution Approach 1:
The knife back is segmented into a central untempered zone and tempered edge zones. The central zone remains untempered throughout the process, so punching operations create recesses in stable, non-shrinking material, ensuring precise hole placement while still allowing the use of tempered edge sections for overall strength
3Strength
If the entire back of the mower knife is tempered to increase strength, then the strength and wear resistance are improved, but the punching tool is subjected to high stress and the recesses may be displaced
Solution Approach 1:
The knife back features local quality differentiation: tempered edge strip sections provide strength and wear resistance, while the central untempered section provides ease of punching. This localized approach to material treatment resolves the contradiction between strength enhancement and manufacturing ease
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 design significantly enhances the strength of the mower knife back while maintaining the service life of the punching tool and maintaining accurate hole placement, preventing knife breakage under high stress conditions.
Implementation Method 1
the edge strip sections are inductively hardened
Implementation Method 2
the back of the mower knife is coated in at least one edge strip section running in the longitudinal direction and is uncoated in a middle section, the middle section having the recesses for fastening the mower knife blades
Data Source
Figure 1
AI summary
To increase the strength and wear resistance of a mower blade back (1) without having to accept the high wear of manufacturing tools during its production, a mower blade back (1) for oscillating mower blades with recesses for attaching the mower blades is tempered in at least one longitudinally extending edge strip section (3) and untempered in a central section (4), wherein the central section (4) has the recesses (5) for attaching the mower blades. For this purpose, the mower blade back (1) is tempered in at least one longitudinally extending edge strip section (3) before or after the production of the recesses (5).