Cartridge Valve Hydraulic Symbols
As shown in the picture of the cartridge valve hydraulic symbols, it consists of a control cover 1, cartridge unit (consisting of a valve sleeve 2, spring 3, spool 4 and seals), cartridge block body 5 and pilot element (placed on the control cover, the figure is not drawn). Because of this valve cartridge unit in the circuit mainly play a role in the control of on and off, it is also known as two-way cartridge valve. Control cover plate will cartridge unit encapsulated in the cartridge block body, and communication pilot valve and cartridge unit (also known as the main valve).
The opening and closing of the spool of the main valve can control the on-off of the main oil circuit. The use of different pilot valves can constitute pressure control, directional control or flow control, and can form a composite control. You can assemble several two-way cartridge valves with different control functions in one or more cartridge blocks. We combine these blocks to form a hydraulic circuit.
As far as the working principle is concerned, the two-way cartridge valve functions similarly to a pilot-controlled check valve. In this setup, the main oil circuit uses A and B as the only two working ports, commonly referring to them as a two-way valve. Meanwhile, the port X acts as the control port.
By adjusting the control port pressure, you can regulate the on and off status of the A and B ports. When there is no hydraulic pressure at the control port, the lower part of the spool experiences liquid pressure. This pressure overcomes the spring force, causing the spool to open. Consequently, A and B ports are connected, and the direction of liquid flow depends on the pressure levels at ports A and B. Conversely, when we pressurize the control port, the valve closes the A and B ports if px ≥ pA and px ≥ pB. This ensures that the A and B ports remain closed. In this manner, it functions as a ‘non-’ gate logic element. Consequently, people also refer to it as a logic valve.
Cartridge valves can be classified into two categories based on the source of the control oil.
The first category includes external control cartridge valves. For these valves, a separate power source supplies the control oil. Therefore, the pressure in the A and B ports remains unaffected by the direction of control in the oil circuit. Additionally, changes in these pressures are independent of the control direction.
On the other hand, the second category comprises internal control cartridge valves. In these valves, the A or B ports supply the control oil. This category further divides into two types: valves with a damping hole in the spool and valves without damping holes. We generally use internal control cartridge valves more widely because of their versatility.
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