Hudraulic Valves Part B Flashcards
where is the relief valve placed on a stack valve?
closest to the sub-plate
where is the directional control valve placed on a stack valve?
at the top of the stack
what is the difference between a stack valve and a cartridge valve?
a stack valve uses a spool
a cartridge valve uses a poppet
what are the two kinds of cartridge valves?
slip in - repairable
screw in - throw away
what is a proportional valve?
a solenoid operated valve that uses a proportional solenoid
what is special about a proportional solenoid?
it can be moved to an infinite number of positions
what can proportional valves be used for?
stop an actuator at any point in its stroke
speed of an actuator
acceleration and deceleration
what is the main advantage of a proportional valve over a servo valve?
a proportional valve is more rugged and dirt tolerant
what is used to control the electrical input of a proportional valve?
amplifier card
what are metering notches?
notches in a spool that control the flow rate of a valve
what 6 input devices provide signals to the amplifier card?
joystick
PLC
potentiometers
temperature sensors
pressure transducers
tach generators
what is the purpose of an amplifier card?
increases the signal from the input device
what are the 4 control functions of an amplifier card?
dead band compensator
ramp
dither
gain
what is the purpose of a dead band compensator?
boosts the power to make the spool jump across the overlap distance in the ports
what is gain?
the # of times the output voltage is greater than the input voltage
what is dither?
small high frequency alternating currents applied to the solenoid to prevent the spool from getting stuck or hung up
what is the ramp function?
controls how fast the voltage to the solenoid is increased or decreased?
controls acceleration and deceleration
what are the 3 types of pressure proportional controls?
nozzle
plate
poppet
what is a servo valve?
directional/ flow control valve with an internal feedback mechanism build into the valve
what are the 2 main components of a servo valve?
torque motor
spool valve
what are transducers?
sensors that measure position, pressure, or velocity
what are the 3 types of servo valves?
flapper nozzle
jet pipe
staging spool
what is hysteresis?
term used to express how accurately the spool moves compared to the input current
