Samson 3768, Монтаж и эксплуатация

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6 EB 8356 EN
Design and principle of operation
2 Design and principle of oper-
ation
The Type 3768 Limit Switch is designed for
attachment to pneumatic control valves. It is
fitted with inductive contact limits that issue a
limit signal whenever the valve travel ex-
ceeds or falls below a certain preset limit, es-
pecially when the valve has reached one of
its end positions. The limit signal is transmit-
ted to alarm or indicating equipment.
The limit switch can also available be fitted
with a solenoid valve to move the valve to its
fail-safe position.
The limit switch is designed either for direct
attachment to SAMSON Type 3277 Actua -
tors or for attachment to actuators according
to IEC 60534-6 (NAMUR) using an adapter
housing.
The valve travel is transmitted by the pin
(1.1) to the lever (1) and converted into a ro-
tary motion. The shaft (2) transfers this rota-
ry motion to two adjustable metal tags (4)
which operate the associated proximity
switches (5).
The operation of the inductive limit switches
requires switching amplifiers to be connected
in the output circuit (see section 4).
Version with solenoid valve
When fitted with a solenoid valve, the con -
trol valve can be moved to the fail-safe posi-
tion, regardless of the control signal issued
by the control equipment. If a control signal
corresponding to the binary signal '0' (OFF)
is applied to the input, the signal pressure p
st
is shut off and the actuator is vented. The ac-
tuator springs move the valve to its fail-safe
position.
When a control signal corresponding to the
binary signal '1' (ON) is applied to the in-
put, the signal pressure p
st
is applied to the
actuator, allowing the valve to move accord-
ing to the input signal issued by the control
equipment.
4 6
5
3 2 1 1.1
7
supply
u[V]
p
st
1 Lever
1.1 Coupling pin
2 Shaft
3 Spring
4 Metal tag
5 Proximity switch
6 Adjustment screw
7 Pressure regulator
Fig. 1: Functional diagram