403 - Valves Flashcards
Valves do what
Control Flow
Control Direction
Manipulate pressure
Can increase speed and flow rate without messing with the pump.
Types of Circuits
Regeneration Meter-In Meter-Out Syncronization Series Syncronization Parallel
Tandem Valve
Reduces the need for a pressure relief valve, but you still add it for safety.
Can keep the motor and pump running without having to worry.
PRV is there just in case of clog.
Used instead of NO or NC.
Direct-Acting Solenoid Valves - 4-Way
Single Soleniod Model
Double Solenoid Model
Doule Solenoid Spring Centered
Pilot-Operated Solenoid valves - 4-way
More energy to armature = more pressure = more voltage.
Single Acting
Double Acting
Single Acting Pilot-Operated Solenoid valves - 4-way
Pilot pressure on one side of spool.
Double Acting Pilot-Operated Solenoid valves - 4-way
Pilot pressure on both or neither sides (depends on manuf.)
Proportional Valves Types:
Directional Control Pressure Relief Pressure Reducing Servo/Prop Logics Electrohydraulic pumps Flow Control
Proportional Valves
Use DC linear solenoids.
Solenoid recieves a variable current signal to produce a variale force or travel output.
Force Controlled Solenoids
Typically pilot operated valves.
Change in current produces a corresponding changes in force in the solenoid.
Provides a lot of muscle.
Stroke Controlled Solenoids
Change in current produces a corresponding change in armature stroke.
The stroke is relative to the varying current.
These vavles typically control the direction/flow/pressure of hydraulic oil to hydraulic actuators.
Direct Acting
The solenoid works directly on the valve spool.
Pilot Operated
The solenoid controls a small flow of hydraulic oil which then controls a much larger valve section.
With valve positive feedback:
The spool is mechanically tied to an inductive position transducer also know as a LVDT which gives feedback to the valve electronics on the actual spool position.
Two Types of Electronics:
On-Board Electronics
External Electronics
