Hitachi NR 90AE Technical Data And Service Manual page 16

(4) Single actuation mechanism/contact actuation mechanism: (Fig. 8 and Fig. 9)
Single/contact actuation mechanism changeover is accomplished by turning the switching device
(Change Knob (C) [45]).
Single actuation mechanism (Switching device:
upward position):
1) Immediately after driving the first nail, the
control valve should be as shown in Fig. 7.
2) When only Pushing Lever (C) [52] is released
and Trigger (C) [49] is held as shown in Fig. 8,
the plate of Trigger (C) [49] contacts Change
Knob (C) [45] and the Plunger [69] returns
(lowers) only halfway.
Because of this, compressed air does not flow
into the valve piston lower chamber, and Valve
Piston [65] remains in the lowered position.
Accordingly, the Piston [13] remains in the
lowered position as shown in Fig. 6.
3) When Trigger (C) [49] is released, the Plunger
[69] returns (lowers) completely as shown in
Fig. 5. Compressed air then flows into the valve
piston lower chamber, and the Valve Piston [65]
is forced upward. The Piston [13] then returns
fully upward. Therefore, unless Trigger (C) [49]
is released after each nailing operation, the
structural mechanism prevents the next nailing
operation.
Contact actuation mechanism (Switching device:
downward position):
1) Immediately after the first nail is driven, the
control valve should be as shown in Fig. 7.
2) Even when only Pushing Lever (C) [52] is
released and Trigger (C) [49] is held, the
Plunger [69] returns (lowers) completely as
shown in Fig. 9. Thus the Piston [13] returns
(raises) fully. Accordingly, continuous nailing
can be accomplished by pushing only Pushing
Lever (C) [52] up and down while holding
Trigger (C) [49] depressed.
Plunger [69]
Switching device (Change Knob (C) [45])
(Upward position)
Fig. 8 Single actuation mechanism
Plunger [69]
Switching device (Change Knob (C) [45])
(Downward position)
Fig. 9 Contact actuation mechanism
--- 13 ---
Accumulator
Valve Piston [65]
Trigger (C) [49]
Valve piston
lower chamber
Pushing Lever (C) [52]
Accumulator
Valve Piston [65]
Trigger (C) [49]
Valve piston
lower chamber
Pushing Lever (C) [52]