Hydraulic Blade Drive With Larger Master Cylinders for Synchronization

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Solution Overview

Problem

Existing hydraulic blade drive systems in harvesting machines suffer from gear differences between pistons due to oil dynamics and compressibility, leading to unsynchronized oscillating movements of blade bars, particularly in systems with multiple blades driven in opposite directions, which can cause vibrations and misalignment.

Innovation Solution

A hydraulic knife drive device with a first master cylinder having a larger displacement than the slave cylinder ensures synchronized movement by maintaining the slave cylinder at intended end positions, using pressure relief valves and check valves to manage oil flow, and a crank drive for a sinusoidal speed profile.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a hydraulic pump with pistons drives a slave cylinder for oscillating blade movement, then the blade can be set into oscillating motion, but gear difference accumulates between pistons due to oil dynamics and compressibility causing unsynchronized movement

Engineering Contradiction:

Improveblade oscillationVSAvoidsynchronization

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

A lever is introduced as an intermediary mechanical element between the slave cylinder and the blade bar. The lever converts the linear reciprocating motion of the slave cylinder piston into oscillating motion of the blade bar, providing a mechanical connection that ensures synchronized movement despite hydraulic compressibility and dynamics

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces a direct hydraulic drive system with a hybrid system that combines hydraulic actuation (slave cylinder) with mechanical transmission (lever). This substitution eliminates the synchronization problems caused by pure hydraulic drive while maintaining the benefits of hydraulic power transmission

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Object-affected harmful factors

If multiple blade bars are driven in opposite directions to dampen vibrations, then vibration damping is achieved, but synchronization between blade bars is not guaranteed due to hydraulic drive limitations

Engineering Contradiction:

ImprovevibrationVSAvoidsynchronization

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

Multiple blade bars are driven in opposite directions (180 degrees out of phase) to create counterbalancing vibrations that dampen overall system vibrations. The lever mechanism ensures that each blade bar maintains precise synchronization with its drive cylinder, enabling reliable counterbalancing action

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Solution Approach 2:

The lever serves as a mechanical intermediary that couples each slave cylinder to its respective blade bar, ensuring that the counterbalancing blades remain synchronized with their drive sources even when operating in opposite directions

Inventive Principle:

Principle #24Intermediary (Mediator)

3Speed

If the slave cylinder reaches its outer end position quickly, then oscillation speed is improved, but the piston does not reach the intended outer end position due to gear difference accumulation

Engineering Contradiction:

Improveoscillation speedVSAvoidend position accuracy

Core Design Contradiction:

SpeedVSManufacturing precision

Solution Approach 1:

The lever acts as a mechanical intermediary that ensures the slave cylinder piston reaches its intended end position by providing a rigid mechanical connection to the blade bar, compensating for hydraulic compressibility and preventing position errors

Inventive Principle:

Principle #24Intermediary (Mediator)

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 synchronized oscillation of blades, reduces vibrations, and allows for a compact, efficient design with reduced material stress, facilitating integration into harvesting machines with adjustable cutting tables.

Implementation Method 1

the at least one slave cylinder is driven by at least one first master cylinder, wherein the at least one first master cylinder has a larger displacement volume than the at least one slave cylinder

Methodology Applied

Scientific EffectHydraulic pressure: Hydraulic Press

Implementation Method 2

the at least one slave cylinder can be connected to a reservoir via a pressure relief valve on the piston side and the rod side, respectively

Methodology Applied

Scientific EffectPressure relief: Pressure Increase

Implementation Method 3

the at least one first master cylinder is connected to the reservoir via at least one check valve

Methodology Applied

Scientific EffectCheck valve flow control: Valve

Implementation Method 4

the at least one first master cylinder is driven by a crank drive

Methodology Applied

Scientific EffectCrank mechanism: Crankshaft

Data Source

PatentEP3942913B1Blade drive device

Publication Date: 2025.08.13 CLAAS SELBSTFAHRENDE ERNTEMASCHINEN GMBH

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AI summary

The invention relates to an attachment for a harvesting machine with an oscillating knife (4) and a hydraulic knife drive device (6) for the oscillating knife (4), comprising at least one slave cylinder (11) for driving the oscillating knife (4), wherein the at least one slave cylinder (11) is driven by at least one first master cylinder (14), wherein the at least one first master cylinder (14) has a larger stroke volume than the at least one slave cylinder (11).