Page 85 - PNEUMATIC SYSTEM INSTRUMENT

MANUAL ACTUATION METHOD

Figure 11.2: Schematics symbol of manual actuation method

A manually actuated valve as shown above uses the muscle power or

spring force to actuate the spool. Common manual actuators include

levers, push buttons, pedal, etc. In a lever operated valve, the angular

movement of the lever is transmitted to a tapped and from there to

the spool. The detents in the individual positions are archived with the

used of balls which are pressed into annular grooves in the tappet by

springs. Pedal operation is used when hands of the operator need to

be kept free. Sometimes both hands are needed for controlling the

valves.

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