Toggle Lever Overload Safety for Harvesting Blades
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Solution Overview
Problem
Existing cutting blade overload protection systems in harvesting machines, such as loading wagons or balers, face issues with gradual reduction in prestressing force, which can lead to damage during overloads due to the design of supporting and switching elements.
Innovation Solution
A cutting blade overload protection system utilizing a toggle lever mechanism with adjustable articulated joints and spring means, providing a large prestressing force that causes the cutting blade to suddenly deviate from its cutting position upon overload, and allowing for selective adjustment of the prestressing force based on operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a supporting and switching element with a lever is used to support the cutting blade, then the cutting blade can be supported in the cutting position, but the prestressing force gradually reduces when the blade pivots yielding, which may allow damage during overload
Solution Approach 1:
The patent applies a toggle lever mechanism that dynamically changes its mechanical advantage based on position. When the cutting blade is in the correct position, the toggle levers are extended and locked, providing maximum prestressing force. When overload occurs and the blade displaces, the toggle levers buckle and collapse, suddenly releasing the prestressing force to allow the blade to yield without damage. This dynamic behavior resolves the contradiction by providing high force during normal operation and force release during overload.
Solution Approach 2:
The patent changes the mechanical parameter of prestressing force from a gradually reducing characteristic to a binary state (high/low) using the toggle lever mechanism. The articulated joint's position changes the leverage ratio dramatically - from a locked extended position with maximum force to a buckled position with minimal force. This parameter change ensures reliable protection by providing sufficient prestressing force during normal cutting while allowing sudden force reduction during overload conditions.
2Force
If the lever arm is small in the cutting position to provide large prestressing force, then the cutting blade is well-supported, but the lever arm increases when the blade pivots yielding, causing gradual reduction in prestressing force
Solution Approach 1:
The toggle lever mechanism creates a dynamic system where the lever arm effect is position-dependent. In the normal cutting position, the toggle levers are extended creating a short effective lever arm and high mechanical advantage for prestressing. When overload causes blade displacement, the toggle levers pivot at the articulated joint, buckling the mechanism and dramatically increasing the effective lever arm while reducing prestressing force to allow safe yielding.
Solution Approach 2:
The toggle lever mechanism acts as an intermediary between the cutting blade and the prestressing force source. It translates small blade displacements into large changes in prestressing force through the buckling action at the articulated joint. This intermediary mechanism resolves the contradiction by mediating between the need for high force during normal operation and the need for force reduction during yielding movement.
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 system effectively protects the cutting blade from damage during overloads by providing a sudden evasion mechanism and allows for optimal adjustment of the prestressing force according to specific conditions, ensuring improved resilience and adaptability.
Implementation Method 1
spring means (70) which, by means of spring action, prestress the toggle lever mechanism into the extended position in order to provide the prestressing force
Implementation Method 2
the toggle levers can be removed from the stretched position by buckling the toggle lever mechanism away from the stop in the articulated joint against the preload
Data Source
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AI summary
Cutting blade overload protection (50) for a cutting unit (10) of a harvesting machine (1), with a lever arrangement for cooperating with a cutting blade (40) of the cutting unit, wherein the lever arrangement can be moved into a support position to support the cutting blade in a cutting position and can be moved out of the support position against a preload force to allow the cutting blade to move out of the cutting position in the event of an overload acting on it.According to the invention, the lever arrangement is designed as a toggle lever mechanism (60) with two toggle levers (61, 62) which are pivotably connected to each other at their respective longitudinal ends via a hinge joint (63), wherein the hinge joint in an extended position of the toggle levers can be set to a stop under the preload force realizing the preload, so that the support position is established, and the toggle levers can be set out of the extended position by folding the toggle lever mechanism away from the stop against the preload in order to allow the cutting blade to move away.