Variable Return Metering Valve for Hydraulic Boom Control
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Solution Overview
Problem
Current hydraulic control systems for forestry machines, such as tree feller-bunchers, are complex due to shared hydraulic fluid flow between cap ends of cylinders, leading to increased complexity and reduced independent control of the hoist and stick booms.
Innovation Solution
A hydraulic boom control system with a pump, reservoir, and variable return metering valves that allow independent control of the hoist and stick booms, using a processor and human-machine interface to modulate fluid flow and regenerate pressure, reducing complexity and enhancing control precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a first spool valve controls hydraulic flow to rod ends of both cylinders and a second spool valve controls hydraulic flow to the rod and cap end of the hoist cylinder, then the hydraulic control system can actuate the boom components, but the control system complexity increases and independent control of hoist and stick is reduced
Solution Approach 1:
The patent divides the hydraulic control system into separate control paths for the hoist cylinder and stick cylinder. Each cylinder has its own dedicated spool valve (first spool valve for stick rod end, second spool valve for hoist rod end), eliminating the shared control path that caused coupling between hoist and stick operations. This segmentation allows independent control of each boom component.
Solution Approach 2:
The patent extracts the shared control function from the conventional system and replaces it with separate control valves. Specifically, the straightline valve that previously controlled shared flow between cap ends is removed, and each cylinder is given its own dedicated control valve, taking out the source of control coupling and enabling independent operation.
2Device complexity
If flow between the cap ends of each hydraulic cylinder is shared and controlled by a straightline valve, then the hydraulic system can operate with fewer valves, but an additional level of complexity is added to the control system
Solution Approach 1:
The patent removes the straightline valve from the control system entirely. Instead of using a straightline valve to control shared flow between cap ends, the system provides direct, independent control to each cylinder's cap end through dedicated spool valves, eliminating the additional complexity layer while maintaining valve count efficiency.
Solution Approach 2:
The patent segments the hydraulic control into independent pathways for each cylinder, with each spool valve controlling only its designated cylinder. This segmentation eliminates the need for a straightline valve to manage shared flow, as each cylinder operates with its own dedicated control path.
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 simplifies the control of the boom movements, allowing precise and independent actuation of the hoist and stick, improving operational efficiency and reducing the complexity of the hydraulic circuit.
Implementation Method 1
A variable return metering valve is fluidly connected to at least one of the first or second control valves. The variable return metering valve is operable to modulate shared hydraulic fluid flow between the first hydraulic cylinder and the second hydraulic cylinder.
Implementation Method 2
A pump is provided for pressurizing a hydraulic fluid on a high pressure side of the hydraulic circuit
Implementation Method 3
The first hydraulic cylinder is configured to actuate the hoist. A second hydraulic cylinder is configured to actuate the stick.
Data Source
AI summary
A hydraulic boom control system for a forestry machine includes a pump for pressurizing a hydraulic fluid on a high pressure side, a reservoir for storing hydraulic fluid on a low pressure side, and a first hydraulic cylinder including a cap end and a rod end. The first hydraulic cylinder is configured to actuate the hoist of the boom. A second hydraulic cylinder includes a cap end and a rod end and is configured to actuate the stick of the boom. A first control valve is operable to control the first hydraulic cylinder. A second control valve is operable to control the second hydraulic cylinder. A variable return metering valve is fluidly connected to at least one of the first or second control valves. The variable return metering valve is operable to modulate shared hydraulic fluid flow between the first hydraulic cylinder and the second hydraulic cylinder.