Principle Of Operation; Accessories - Samson 3274 Mounting And Operating Instructions

Design and principle of operation

3.2 Principle of operation

Î Refer to Fig. 1
The pressure-tight actuator housing (1),
which also serves as the oil reservoir, con-
tains the cylinder housing (2), cylinder (5.1)
and piston (5.2), motor (6.1), pump (6.2),
and solenoid pilot valves (6.4).
The oil pump (6.2) driven by the motor (6.1)
feeds compressed oil to the corresponding
cylinder chamber over the check valve (6.3)
and pilot valve (6.4). The solenoid valves are
closed in the de-energized state and open
when a controller output signal is applied.
When an end position is reached or when
the thrust is too high due to external forces,
the motor is switched off.
Depending on the version, the actuators
have no compression springs or are
equipped with one or two compression
springs (5.7, 5.8). The motor in Types 3274-
11, -12, -15, -16 as well as -21 to -23 can
only move the stem in one direction. The
stem is moved by spring force in the other
direction.
Actuators with electric override have two
pushbuttons to extend or retract the actuator
stem.
The actuators with mechanical override have
an additional gear housing. An Allen key
must be inserted to activate the override
function. In combination with a release but-
ton on the top of the actuator housing, the
actuator stem can be extended or retracted.
Versions with fail-safe action have a
spring-return mechanism and an additional
safety solenoid valve which opens when the
8
power supply is interrupted, reducing the
pressure on the cylinder chamber. The spring
assembly moves the valve plug to the fail-
safe position. The direction of action (actua-
tor stem extends or retracts) depends on how
the springs are arranged in the actuator.
NOTICE
!
Risk of actuator damage through opening
the device.
Do not remove the housing cover.

3.3 Accessories

The actuator can be fitted with a various
combination of accessories.
Table 1: Combination of accessories
Accessories
Positioner
Position transmitter
Resistance transmitter 1
Resistance transmitter 2
Mechanical limit contact 1
Mechanical limit contact 2
Mechanical limit contact 3
Inductive limit contact 1
Inductive limit contact 2
All accessories are housed in the terminal
box (3). To control switching and indicating
components, the travel of the actuator stem,
which is picked up at the shaft, is converted
into a rotary motion by a rack-and-pinion
gear. Accessories can be retrofitted. Table 1
on page 22 shows the maximum amount
of accessories that can be fitted.
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EB 8340 EN
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