Hydraulic Spool Valve Bypass for Load Sensing Efficiency
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Solution Overview
Problem
Hydraulic systems face inefficiencies when controlling loads in resistive and draft modes, with existing solutions experiencing energy losses due to unnecessary resistance in the return line during draft operations and potential rapid movement without damping in resistive scenarios.
Innovation Solution
A hydraulic system with a spool valve featuring two output ports and three input ports, including a low resistance discharge path with a normally closed valve that opens when the pressure difference exceeds a predetermined level, allowing fluid to bypass the spool valve during resistive loads, reducing resistance and improving efficiency, and providing damping during draft modes by maintaining throttled flow through the spool valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistance is provided in the return line to damp piston movement during draft mode, then piston movement is controlled safely, but energy losses increase during resistive mode operation
Solution Approach 1:
The system dynamically switches between two return line configurations: a throttled path through the spool valve for draft mode damping, and a low-resistance bypass path for resistive mode efficiency. The bypass valve opens automatically based on pressure differential, enabling the system to adapt its resistance characteristics to the operational mode.
Solution Approach 2:
The system changes the flow resistance parameter of the return line based on operational conditions. During draft mode, high resistance is maintained through the spool valve throttle. During resistive mode, the bypass valve opens to reduce resistance, minimizing energy losses while maintaining necessary control.
2Loss of energy
If a bypass valve is added to provide low resistance discharge path, then energy efficiency improves during resistive mode, but device complexity increases
Solution Approach 1:
The bypass valve is designed to operate automatically based on the pressure differential between the supply line and return line. When the load is in resistive mode, the pressure differential causes the bypass valve to open automatically, providing low-resistance flow path without requiring external control signals or complex control logic.
Solution Approach 2:
The bypass valve utilizes hydraulic pressure differential to control its own operation. The valve opens when the pressure difference between supply and return lines exceeds a predetermined level, using the system's own hydraulic pressure to regulate flow paths without requiring additional control systems.
3Measurement precision
If throttles are provided in the spool valve connections, then load sensing pressure difference can be developed, but resistance to flow increases causing energy losses
Solution Approach 1:
The return flow path is segmented into two separate paths: one through the spool valve throttle that maintains load sensing capability, and another through the bypass valve that provides low-resistance flow. This segmentation allows the throttles to perform their measurement function without unnecessarily restricting overall flow during resistive mode operation.
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 achieves efficient operation during resistive loads by minimizing pressure drop in the return line and ensures safe, controlled movement during draft modes by automatically switching between high and low resistance paths, thereby reducing energy losses and preventing rapid piston movement.
Implementation Method 1
a low resistance discharge path including a normally closed valve that opens when the pressure difference between the sensing port and the output port exceeds a predetermined level
Implementation Method 2
Within the spool, throttles are provided in the connections leading from the supply port PC to the respective output port A or B. The purpose of each throttle in the spool is not to damp the movement of the load but merely to allow a load sensing pressure difference to be developed across it
Implementation Method 3
Fluid under pressure is supplied from the supply port PC to the working chamber on the right of the piston of the jack 12
Data Source
Figure 1A~1D
Figure 2~3
AI summary
A hydraulic system is described having a spool valve (10) with two output ports connectible to opposite sides of a hydraulic load and three input ports which include a supply port (PC) connectable to a pressure supply line, a return port (R) connectable to a return line having resistance (38) to flow and a pressure sensing port (PLS) connectable to a sensing line. In each position of the valve spool (10) in which the supply port (PC) communicates with one side of the load and the return port communicates with the other side of the load, a throttle is provided in the spool valve within the passage communicating with the supply port, the downstream side of the throttle being connected to the pressure sensing port (PLS). In the invention, a low resistance discharge path (22) is provided between at least one of the output ports (B) and the reservoir, the discharge path (22) including a normally closed valve (24) that opens automatically when the pressure difference between the sensing port (PLS) and the output port (B) exceeds a predetermined level.