Progressive Holding Force Drive for Agricultural Harvester Overload Protection
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Solution Overview
Problem
Agricultural harvesting machines, particularly self-propelled forage harvesters, face increased wear and friction losses due to the high drive power required for overload protection, especially with longer discharge chutes, leading to false triggering issues and excessive wear on gearbox components.
Innovation Solution
A drive system with a holding means that applies a progressively increasing force as the drive element is deflected from the engaged state, utilizing elastically deformable elements and a pivotable support to maintain engagement during normal operation while enabling high triggering force during overloads, allowing for adjustable preload and spring characteristics to adapt to operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring element is used as a holding means to press the worm against the worm wheel, then play-free engagement is ensured during normal operation, but wear on gearbox components increases due to continuous high contact force
Solution Approach 1:
The holding force is made variable instead of constant. The spring element is designed to provide different contact forces depending on the operational state: low force during normal operation to minimize wear, and high force during overloads to maintain engagement reliability. This dynamic adaptation resolves the contradiction between reliable engagement and reduced wear.
2Reliability
If the spring stiffness is increased to raise the triggering threshold for overload protection, then false triggering is prevented, but wear on the worm wheel and worm increases due to higher continuous contact force
Solution Approach 1:
The spring stiffness parameter is optimized to achieve the desired triggering threshold while minimizing continuous contact force. Additionally, the spring design incorporates progressive engagement characteristics where the full stiffness is only activated when the deflection exceeds a certain threshold, preventing false triggering during normal variations while reducing wear during normal operation.
3Reliability
If prestress of the return spring is increased to raise the triggering threshold, then overload protection threshold is increased for longer discharge chutes, but drive power requirement increases due to higher continuous holding force
Solution Approach 1:
The holding force is made dynamic rather than statically high. The spring element provides just enough force to maintain engagement during normal operation and resist minor disturbances, but allows disengagement when overload forces exceed the threshold. This eliminates the need for continuously high drive power while maintaining the required overload protection threshold.
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
This solution reduces wear and friction losses during normal operation while ensuring a high triggering force for overload protection, preventing false triggering and extending the lifespan of gearbox components.
Implementation Method 1
a holding means (19) acting between the drive element (13) and the machine frame (3), the holding force of which progressively increases as the drive element (13) is deflected from an engaged state
Data Source
AI summary
The drive has a drive element movably mounted at a machine frame (3) for driving an overloading device (10) with the drive element. A holding unit exerts a holding force counteracting deflection from an engaged condition on the drive element. The holding unit is operated to exert the holding force progressively increasing with defluxion of the drive element from an engaged state. The drive element is supported at a swingable carrier. The holding unit comprises an elastic deformable element i.e. pressure spring, acting between the drive element and the machine frame. An independent claim is also included for a method for operating a drive for an overloading device that is movably supported opposite to a machine frame of an agricultural harvesting machine.