PACKING GLAND
Double-Acting Actuating Cylinders
WITH WIPER
RAM
A typical double-acting actuating cylinder is
GLAND
shown in figure 8-37, view A. This type of cylinder
NUT
operates under the influence of fluid flow in either
direction. The cylinder contains one piston and piston
rod assembly. The two fluid ports, one near each end of
CYLINDER
the cylinder, alternate as inlet and outlet ports,
HOUSING
depending on the direction of flow from the directional
FLUID
control valve.
SUPPLY
Figure 8-37, view B, shows an unbalanced
actuating cylinder. That is, there is a difference in the
effective working areas on the two sides of the piston.
Fluid pressure acts on the entire area taken up by the
A. SINGLE-ACTING RAM TYPE
ACTUATING CYLINDER
blank side of the piston (in the figure, the blank side is
the area at the bottom of the cylinder). On the other side
of the piston, the rod side, fluid pressure acts on a
STOPS
RAM (1)
smaller area. For this reason, this type of actuating
cylinder is normally installed in such a way that the
RAM (2)
blank side of the piston carries the greater load. That is,
the cylinder carries the greater load during the
extension stroke.
RAM (3)
PACKING GLAND
RAM
WITH WIPER
CYLINDER
GLAND
PORT B
D RINGS
NUT
LIPS
FLUID SUPPLY
FLUID
FOR RETRACTION
PORT
CYLINDER
HOUSING
B. TELESCOPING RAM TYPE ACTUATING
CYLINDER
RAM
PORT A
FLUID
LIP
PORTS
RETURN
PISTON
PISTON
SPRING
ROD
FLUID SUPPLY
FOR EXTENDING
AIR VENT
WITH FILTER
A.
DOUBLE-ACTING RAM TYPE
SEALS
ACTUATING CYLINDER
C. SINGLE-ACTING, SPRING-LOADED
PISTON TYPE ACTUATING
FLUID PORTS
CYLINDER
ASf08036
PISTON
Figure 8-36.--Single-acting actuating cylinders.
CLEVIS
strikes the stop of ram 2, ram 2 extends. This action
continues until the desired extension is reached, or
until the lip of ram 3 strikes the stop of the cylinder.
PACKING GLAND
O-RING SEAL
WITH WIPER
A spring-loaded cylinder, like that shown in view
B.
DOUBLE-ACTING PISTON
C of figure 8-36, is used in devices where gravity or the
ACTUATING CYLINDER
ASf08037
weight of the load will not return the ram to a fully
Figure 8-37.--Typical cross-sectional view of a double-acting
retracted position.
actuating cylinder.
8-30
