1.3 Hydraulic Cylinders
Define the term actuator and give examples of a rotational electrical actuator and a linear hydraulic actuator.
Draw a pictorial diagram of a double acting hydraulic cylinder. Identify the barrel, piston, rod, cap end plate, rod end plate, rod wiper, cap end port, and rod end port. NOTE: the rod end is often called the “head” end and the cap end is often called the “blind” end.
Draw the schematic symbol for a double acting hydraulic cylinder.
Differentiate between the cap end and rod end. Which has more functional area?
Describe the act of extending and retracting a double acting cylinder in terms of which volumes are filled and which volumes are emptied. Comment on observed differences between extension and retraction speeds given constant flow rate.
Comment on how blocked ports affect extension and retraction of double acting hydraulic cylinders.
Differentiate between static and dynamic seals. Point out static and dynamic seals in a double acting hydraulic cylinder.
Comment on how a gasket is used to form a static seal. Comment on gasket composition and fluid compatibility.
Comment on how O-rings, piston rings and oil form a dynamic seal.
Comment on why oil is used in hydraulic systems.
Describe the cross sections of other dynamic seals.
Comment on the purpose of the rod wiper. Comment on storage of hydraulic equipment and the role of fabric bellows.
Comment on the purpose of a stop tube.
Describe a double rod cylinder and draw its schematic symbol.
Describe a tandem cylinder. Describe a duplex cylinder. Draw the schematic symbols.
Describe how a cushion works. Draw the schematic symbol for a cushion on extension. Draw the schematic symbol for a cushion on retraction. Draw the symbol for a variable cushion.
Draw lug, flange, flush, and tie rod mounted cylinders. Describe the purpose of fixed mounting methods.
Draw trunnion and clevis mounted cylinders. Describe the purpose of pivoting mounts. NOTE: Pivoting mounts are often specified by the location of the pivot point (example: head trunnion vs. center mounted barrel trunnion)
Describe and draw the schematic symbol for a single acting cylinder. Describe the means a single acting cylinder uses to retract.
Describe a ram. Describe how the descent of a lifted object can be controlled.
Describe a telescoping cylinder.
Describe how a spring can be used to apply or remove a brake in the event of pressure loss. Comment on how a spring is a source of hazardous energy.