190301d Hydraulic actuator fun Flashcards
Hydraulic cylinders create what type of motion?
Linear/ straight line
Single acting cylinders are hydraulically actuated in two directions?
Nope
On a ram type cylinder, what are the basic components?
Piston Tube, Cylinder barrel, guide rings
How is retraction done on a ram type cylinder?
By connecting inlet and outlet ports to the reservoir
On a piston type single acting cylinder, if oil is coming out of the air vent what could be the cause?
a piston seal is leaking
What are two types of single acting cylinders?
piston or ram type
What causes a piston type cylinder to retract?
gravity/weight of the load
How should you adjust the packing nut on a ram type cylinder?
Until packing is tight enough to leave a thin film of oil on piston tube when cylinder extends
Why do we use telescoping single acting cylinders?
To obtain additional stroke length from a relatively compact retracted package
The first stage on a telescoping single acting cylinder is?
largest, develops greatest force, slowest speed
2nd stage and all after, what happens to speed and force
Force decreases, speed increases
Double acting cylinders do what?
both hydraulically extend and hydraulically retract, oil acts on both sides
In a double acting cylinder, rod end cap is attached to the??
Cylinder barrel to prevent external leakage. Threaded together
Double acting cylinder, O-rings and back up rings are used to seal?
The cap to the barrel
What are the moving parts in a double acting cylinder?
Piston and Piston Rod
Hydraulic cylinders are used to create?
Linear (straight) motion to perform work
Pistons are machine grooved in the outer circumference so the piston seals and?
Wear rings can be fitted
Seals are used for stopping what?
Internal and extend leakage
When selecting a seal you should consider?
Operating pressures and temps Fluid compatibility cylinder speed clearance to be sealed internal friction finish of the sealing surface acceptable seal life
What materials are seals made of?
leather, polyurethan, nitrile or viton
What do wipers do for a cylinder?
prevent some contamination while cylinder retracts, allowing some leakage to lube seals
Bearings are used to do what in a cylinder?
support piston and piston rod
Bearings in a cylinder can be made from?
iron, brass, phenolic or composite material
Conventional cylinder, double acting, single rod cylinders are called?
Differential cylinders because difference between extension and retraction speed and the forces they produce
If the piston seal starts to leak on a differential cylinder, what will it cause?
reduce cylinder speed and cylinder drift in the hold position
Hold position blocks oil flow from?
Both rod and base end of the cylinder
Hydrostatic lock
If there is a leak in a double acting cylinder, what can happen?
Oil may flow from the rod end to the base end of the cylinder, may cause drift out to extension direction
Single acting cylinders are hydraulically actuated in?
One direction, need gravity or load to make them retract
Cylinder drift will only happen in what direction?
Extension
If your piston seals on a cylinder leaks where can you see the problem?
Direction control return line
Pressure required to support a load doubles when the piston seals are leaky is known as?
Pressure intensification
Double acting, double rod cylinder (non-differential cylinder)
Has equal piston area and equal volume or both sides
Telescoping cylinders can be?
Single acting or double acting, offers long working stroke from a compact retracted package
Double acting telescoping cylinders are used in what applications?
Mining haul trucks, boxes that go over center
What are some features that cylinders have?
Piston relief valve
cylinder cushions
quick drop valves
When does the piston relief valves allow oil flow to bypass the piston?
When the piston reaches the end of its stroke
Describe a piston relief valve.
Double check valves
Cylinder cushions are used to stop a piston?
Nope, they slow down the hydraulically operated implement
What creates a cylinder cushion effect?
the effect is accomplished by restricting the return oil from the cylinder, back pressures the piston and resists movement
What two types of cylinder cushions are there?
Cushion plunger
Cylinder return drillings
Quick drop valves use who’s principle?
Bernulli’s
What do quick drop valves provide?
Faster lowering cycle times on implements
The quick drop valve supplements pump flow to the base end of the cylinder with the oil flow from the rod end, what is this principle called?
Regeneration
Are quick drop valves normally closed?
Yes
Can a slower lowering speed be achieved with a quick drop valve?
Yes, if the operator feathers the direction control valve
When does cavitation occur in a cylinder?
When the cylinder drops faster than the oil flows
What is a sign of a failing quick drop valve?
No power down
No quick drop (lowering slower than normal
What type of energy do hydraulic motors convert?
Hydraulic energy to mechanical energy
What do hydraulic motors convert oil flow and pressure into?
Speed and torque
What dictates the speed of the motor driveshaft?
The inlet flow rate and capacity of the motor
If a motor with a given displacement is given a greater flow rate supply what happens to the driveshaft?
It will rotate faster
Motor inlet pressure (max sys pressure) and motor displacement determine what in a hydraulic motor?
The amount of torque generated
Motors can convert all hydraulic energy to mechanical energy correct?
No, some is loss to leakage and friction
Why is internal leakage necessary?
For lubrication and cooling of moving parts
If internal clearances increase (due to normal wear), will oil flow through the drain line increase?
Yes
What are three basic types of hydraulic motors?
Gear, Vane and piston motors
What are two types of gear motors?
External and gerotor (geroller) motors
The gear in an external gear pump that is not connected to the drive shaft is considered?
An idler
If you reverse the oil flow through an external gear motor what happens to the output shaft?
It will reverse shaft rotation
Do external gears have a lot of working surface area?
No
Are external gear pumps balanced or unbalanced?
Unbalanced
Do gear pumps create a lot of torque?
Nope
Gerotor motors are also know as?
Orbit motor
Are gerotor motors low rpm and right torque?
Yeah
Which component is splined to the output shaft of a gerotor motor?
Gerotor star, spool valve
Does the gerotor star need to be timed?
Yup, must be timed
What is different in a geroller motor compared to a gerotor motor?
Gerollers have roller inserts for better wear characteristics, disc type valves instead of spool valves
Vane motors have what under the vanes to provide flow when starting up?
Springs
Most vane motors are balanced or unbalanced?
Balanced
In a balanced vane motor the inlet and outlet ports are located where?
180° from each other
Do balanced vane motors operate at higher pressures compared to unbalanced vane motors?
Yes
Can vane motors be driven in reverse with oil flow?
yes
Are vane motors more volumetrically efficient than external gear motors?
Yes
Are balanced vane motors good torque generators?
yes
Are piston motors variable displacement?
They can be fixed or variable
What are the three types of piston motors?
Axial, Bent Axis or Radial
