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Manual andmechanical operating devices for spool valves
Tochange thepositionof avalve it isnecessary for thevalve to receiveacommand. This commandcanbemechanical,
manual, electric or pneumatic. Manual control is defined as a command given by the action of an operator.
Mechanical control is defined as a command determined through themovement of amechanical nature.
To provide a specific command an “actuation device” is installed on the valve to execute one of the commands
listed above.
Monostable operation devices
The function of the manual operating devices of pneumatic valves is similar to the function of electric devices,
e.g. mushroom pushbuttons, encapsulated pushbuttons, horizontal levers, rotary switches etc.
Figure 19
Pos. A
: symbol of amanual lever.
Pos. B
: symbol of a push button.
Some examples of mechanical actuation devices:
Pos. C
: symbol of amechanical (frontal) pin.
Pos. D
: symbol of a roller lever.
Pos. E
: symbol of a unidirectional roller lever.
A
B
C
D
E
MONOSTABLE
Fig. 19
BISTABLE
MONOSTABLEANDBISTABLE
F
N
O
P
G
H
I
M
Fig. 20
The type of actuation is graphically depicted in the upper zone of the square, indicating that its function is a valve.
The operating device is repositioned due to the action of an internal spring once themanual/mechanical actuation
is interrupted. The valve has its own system of repositioning, the device is specified in the lower section of the
squarewhich indicates the valve function; generally, it is amechanical or pneumatic spring.
Bistable operation devices
In some cases the position determined by the initial command must also be maintained once the command is
interrupted. In these cases, the starting position is obtained via a second command, which is opposite to the
previous command. Also in this case, the position determined by the initial command is maintained once the
command is interrupted. The following are various types of bistable manual actuation devices; selector, button
with restraint (such as an emergency pushbutton) for example;
Figure 20
Pos. F
: symbol of amanual push and pull operation.
Pos. G
: symbol of a selector lever.
Some examples of mechanical operating device
:
Pos. H
: symbol of a (frontal) pin on both sides.
Pos. I
: symbol of a roller lever on both sides.
Pos. M
: symbol of a unidirectional roller lever from both sides.
There are alsomechanically actuated valves with external pneumatic return
:
Pos. N
: symbol of a roller lever and external pneumatic return.
Pos. O
: symbol of a unidirectional roller lever and external pneumatic return.
Pos. P
: a symbol of a (frontal) pin and external pneumatic return.
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VALVES