Hitachi DH 40SR, Service Manual And Technical Data

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Second
hammer
Front
cover
Second
gear
Armature
Bevel pinion
Control circuit ass'y
O-ring
Crank shaft
Fig. 3
8-3. Structure of the Model DH 40SR Rotary Hammer
Bevel gear
Piston
First gear
Handle
Connecting
rod
Needle pin
Striker
Cylinder Clutch
Air
chamber
Retainer Driver
Torque transmission
Armature revolution is transmitted to the second gear to rotate the bevel gear via the slip mechanism between
the second gear and bevel pinion axes. Bevel gear revolution is transmitted to the cylinder via the clutch.
Cylinder revolution is transmitted to the hammer sleeve that is connected with four needle pins. As the
hammer sleeve meshes with the driver at the claws, they rotate together. The drill bit is connected into the
hexagonal hole of the driver to transmit the revolution.
Striking operation
The rotation of the armature is transferred to the crank shaft and connecting rod, which in turn cause the
piston to reciprocate inside the cylinder. As the piston reciprocates, the changing air pressure inside the air
chamber between the piston and the striker causes the striker to continuously strike against the end of the
second hammer. At the same time, the air-cushion effect within the air chamber absorbs the impact of the
striker. Should the air escape from the air chamber, the air-cushion effect would cease, and the impact energy
would not be absorbed. Accordingly, the o-rings mounted on the striker and piston play an extremely
important role in sealing the air within the air chamber.
Hammer
sleeve