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Arrangement against idle hammering
The DH 45SA is provided with an arrangement against idle hammering similar to that of the previous
DH 40SA. When the drill bit or bull point is moved off the concrete material, the second hammer is shifted
forward as indicated in Fig. 6 to change the striking position of the striker. This causes the air hole to open so
that air pressure within the air chamber no longer changes even with movement of the piston, bringing the
hammering action to a stop.
Travel distance of the second
hammer and the striker
Slip mechanism
The slip mechanism structure is described below with reference to Fig. 7. The bevel pinion and the gear holder
are coupled together by the key and press-fitting. Spring (C) and needle pins are housed in elongated grooves
of the gear holder. The needle pin is pressed against the inner face of the second gear by spring (C) to allow
idle rotation of the second gear relative to the gear holder. When an excess torque is exerted on the bevel
pinion shaft, the needle pin is raised upon the projection of the second gear against the load of spring (C) to
allow idle rotation of the second gear. With this arrangement, the clutch slips when a violent torque is applied
to the tool as with the drill bit contacting steel wire within the concrete, protecting the operator from jerking or
being violently thrown around.
Bevel pinion
Gear holder
Second hammer
Fig. 6
Second gear
Gear holder
Fig. 7
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Air chamber
Striker
Air hole
Cross section A - A
Needle pin
Elongated
groove of the
gear holder
Key
Spring (C)
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