Hitachi DH 28PC Technical Data And Service Manual page 17

3. "Three-Mode" Changeover Mechanism
The user can select "Rotation + Hammering," "Rotation only," or "Hammering" mode by operating the mode
change lever of the product. Each of the three modes is explained below.
Operate the change lever while pressing the pushbutton switch.
• Rotation and hammering
Set the change lever to the "Rotation + hammering"( mark) position.
The claw of the bevel gear engages with the claw of the clutch. Rotational force is transmitted to the
cylinder coupled with the clutch and rotates the bit. At this time, cylinder air hole B is blocked by the slide
sleeve. When the bit is pressed against an object, the striker blocks cylinder air hole A to form an air
chamber between the piston and striker. Changes in air pressure inside the air chamber cause the striker to
move. Hammering force is thus transmitted to the second hammer and then to the bit tool.
Bevel gear
Lock sleeve
Slide sleeve
Clutch
Cylinder
Piston
Striker
Air hole A
Air hole B
Change lever
• Hammering only
Set the change lever to the "Hammering only" ( mark) position.
The bevel gear disengages from the clutch to cut off the transmission of rotational force. The spline in the
inner periphery of the lock sleeve engages with the spline on the end surface of the clutch. This locks both
cylinder rotation and bit rotation at the same time.
At this time, cylinder air hole B is blocked by the slide sleeve. When the bit is pressed against an object, the
striker blocks cylinder air hole A to form an air chamber between the piston and striker. Changes in air
pressure inside the air chamber cause the striker to move. Hammering force is thus transmitted to the
second hammer and then to the bit tool.
Lock sleeve
Bevel gear
Slide sleeve
Clutch
Cylinder
Striker
Piston
Air hole A
Air hole B
Change lever
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