Hydraulic Actuator Control Device for Load Descent
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Solution Overview
Problem
Existing control devices for load descent in hydraulic actuators, such as those in hydraulic cranes, face challenges in achieving a controlled and regular descent through gravity while minimizing fluid flow and energy consumption, and are prone to cavitation and counterpressure issues.
Innovation Solution
A control device with a recirculating conduit and drain conduit system that allows fluid to recirculate from the bottom chamber to the stem chamber, utilizing a circuit element to generate a localized pressure difference and a flow control valve piloted by dual pressures, along with an insulating element to prevent backflow, enabling precise control and low-pressure operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fluid is allowed to flow freely from the bottom chamber to the stem chamber during load descent, then the descent speed can be controlled, but excessive fluid flow causes energy loss and reduces system efficiency
Solution Approach 1:
A recirculating conduit is introduced as an intermediary pathway that allows fluid to flow from the bottom chamber back to the stem chamber during descent, creating a controlled recirculation loop that reduces the need for large-volume fluid discharge and minimizes energy loss associated with unrestricted fluid flow
2Reliability
If high operating pressure is used to control the hydraulic cylinder, then precise control and reliability are achieved, but energy consumption increases and cavitation risk rises
Solution Approach 1:
The system changes the pressure parameter distribution by using a circuit element to generate a localized pressure difference only where needed for control, rather than maintaining high pressure throughout the entire system. This allows precise control through the flow control valve while the rest of the system operates at lower pressure, reducing energy consumption and cavitation risk
3Ease of manufacture
If a simple drain conduit is used to drain excess fluid, then the system is simple to manufacture, but the flow control valve becomes unstable due to counterpressure from the distributor
Solution Approach 1:
A drain conduit is introduced as an intermediary element that provides a dedicated drainage pathway for excess fluid, separate from the recirculating pathway. This isolation prevents counterpressure from the distributor from affecting the flow control valve, maintaining valve stability while keeping the overall system structure simple and manufacturable
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 significantly reduces fluid flow and energy consumption during controlled descent, enhances stability and reliability, minimizes cavitation risk, and allows operation at low pressures, while avoiding counterpressure effects and eliminating the need for additional piping.
Implementation Method 1
a circuit element that generates a localized pressure difference in the drain conduit
Implementation Method 2
a flow control valve in the recirculating conduit controlled by two piloting pressures taken from the two opposite sides of the aforesaid circuit element
Implementation Method 3
a recirculating conduit through which an operating fluid, in a load descent step, can exit from the chamber on the bottom side of a hydraulic cylinder to re-enter the chamber on the stem side
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
Control device (1) of a hydraulic cylinder (2) of a load lifting apparatus, in which a hydraulic circuit comprises a recirculating conduit (14) in order for the fluid, in a load descent step, to exit from the chamber on the bottom side of the cylinder to re-enter the chamber on the stem side, a drain conduit (17) for draining from the recirculating conduit the fraction of fluid that does not recirculate, a circuit element that generates a localized pressure drop in the drain conduit, and a flow control valve (18) in the recirculating conduit with two piloted pressures taken from the two opposite sides of the aforesaid circuit element (11). The device permits regular operation with low pressure and low fluid flowrate in a load descent step.