Hitachi DH 40MRY Technical Data And Service Manual page 16

Torque transmission
Armature revolution is transmitted to the second gear to rotate the bevel gear via the slip mechanism between
the second gear and the bevel pinion axes. Rotation of the bevel gear is then transmitted to the cylinder keyed
thereto through the clutch. Cylinder rotation is conveyed to the retainer sleeve coupled together by means of
four needle pins and, then to the drill bit inserted into the retainer sleeve by way of three key rails and two
needle rollers which couple them together.
Dynamic damper with leaf spring
The vibration caused by hammering operation of the
Model DH 40MRY is transmitted to the cylinder crank
case, back cover, housing and finally to the weight
through the leaf spring supporting portion. Then the
weight moves in the reverse direction of the transmitted
vibration to negate the vibration of the main body (Fig. 4).
Vibration-proof handle thanks to the transatory unit and the Neidhardt spring
The Model DH 40MRY has the vibration-proof handle
equipped with the transatory unit and the Neidhardt spring.
Structure of the transatory unit
The main body (cylinder crank case) is connected to the
upper handle through four cylindrical rubbers (handle
dampers). These rubbers are rolled and compressed on
the inclined surface to absorb vibration. Since the
transatory unit has nonlinear spring characteristics, the
spring constant is lower than the conventional shearing
type vibration-proofing structure. Thus the Model
DH 40MRY can provide high vibration-proofing effect with
good cushioning properties. The joint of the slotted groove
and the cylindrical convex is provided at the center to
prevent the handle from being pulled out by twisting or
pulling operation in the hammer mode (Fig. 5).
Vibration-proof rubbers Handle side
Main body side
(a) At no-load
Fig. 5
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Vibration of
the main body
Vibration of
the main body
Cylindrical rubbers
(handle damper: 4 pcs.)
Slotted
groove
Handle damper retaining material
(Cylinder crank case)
Rolled and compressed
Reaction
(b) At full-load
Vibration of
the weight
Vibration of
the weight
Fig. 4
Handle damper
retaining material
(handle side)
Cylindrical
convex
Pressing
force of the
main body