Load-Holding Valve Layout for Stable Hydraulic Cylinder Extension
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Solution Overview
Problem
Existing fluid pressure control devices cause rapid acceleration of cylinders due to the discharge of relief fluid into the drain and spring chambers, affecting the desired extending speed of hydraulic equipment.
Innovation Solution
A fluid pressure control device with a load holding mechanism that includes an operation check valve, switching valve, and relief valve, featuring a pressure leading passage and check valve to manage fluid flow and prevent rapid acceleration by maintaining stable pressure conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the relief valve is opened to discharge excess pressure, then the pressure in the load-side pressure chamber is reduced, but the relief fluid flows into the drain chamber and spring chamber causing the spool to move in closing direction, resulting in inability to obtain desired extending speed
Solution Approach 1:
The drain passage is divided into two separate passages: a first drain passage connected to the drain chamber and a second drain passage connected to the spring chamber. This segmentation prevents relief fluid from simultaneously entering both chambers, allowing independent control of spool positioning while maintaining pressure relief function.
Solution Approach 2:
A check valve is introduced as an intermediary component in the first drain passage. This check valve selectively controls fluid flow direction, allowing drain fluid to pass through while preventing relief fluid from entering the drain chamber and affecting spool position, thus mediating between pressure relief and speed control functions.
2Speed
If the operator increases pilot pressure to obtain desired extending speed, then the spool moves in opening direction allowing faster fluid flow, but the pressure drop on downstream side causes cylinder to rapidly accelerate temporarily
Solution Approach 1:
The check valve acts as an intermediary that stabilizes pressure in the downstream side by preventing backflow and maintaining continuous fluid supply to the spool, eliminating temporary pressure drops that cause rapid acceleration while preserving operator control over extending speed.
3Stress or pressure
If the drain passage connects both drain chamber and spring chamber to the relief valve, then pressure relief is achieved, but the spool position becomes unstable due to fluid flow into both chambers
Solution Approach 1:
The drain passage is segmented into two independent pathways with separate connections to the drain chamber and spring chamber. This allows pressure relief to occur while preventing fluid from simultaneously affecting both chambers, thereby maintaining spool position stability during relief operations.
Solution Approach 2:
The harmful effect of relief fluid entering the drain chamber is extracted and eliminated by using the check valve to block this specific flow path, while preserving the beneficial pressure relief function through the second drain passage connected to the spring chamber.
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 solution stabilizes fluid pressure, ensuring consistent extending and contracting speeds of hydraulic equipment, preventing rapid acceleration and improving operational responsiveness.
Implementation Method 1
a check valve provided in the pressure leading passage and configured to allow only a flow of the working fluid from the drain passage to the downstream side of the spool
Implementation Method 2
a relief valve configured to open when pressure in the load-side pressure chamber reaches predetermined pressure
Implementation Method 3
an operation check valve configured to allow a flow of the working fluid from the control valve to the load-side pressure chamber and to allow a flow of the working fluid from the load-side pressure chamber to the control valve in accordance with back pressure
Data Source
AI summary
A load holding mechanism includes a switching valve configured to switch an operation of an operation check valve, and a relief valve configured to open when pressure in a load-side pressure chamber reaches predetermined pressure, and the switching valve includes a drain chamber provided on an opposite side of a spring chamber with a spool interposed therebetween, a drain passage connected to the relief valve and connected to at least one of the drain chamber and the spring chamber, a pressure leading passage configured to connect the drain passage and a downstream side of the spool, and a check valve provided in the pressure leading passage and configured to allow only a flow of the working fluid from the drain passage to the downstream side of the spool.