Ergonomics - Atlas Copco

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Comments for different
tool types
In this section the different types of tools
are discussed. A tool can be used in an infi-
nite number of different ways and the load
on the operator is unique for each situation.
The discussion below can therefore only be
used as a rough guide, giving an indication
of what to think about when the load on the
operator is estimated.
Normally, more powerful tools require
more force. This can be taken into account
choosing a force within the spread given in
the table.
When the trigger time per day for an
operation is not known, Table 3.10 can be
used as a guide.
Machine Total duration Spread ±
type (hours/day) (hours)
Grinders 3 1.5
Drills 1 0.5
Chipping hammers 2 1.5
Riveting hammers 1 0.5
Screwdrivers 2 1
Impact wrenches 1 0.5
Impulse nutrunners 2 1
Angle nutrunners 2 1
Stall torque nutrunners 1 0.5
Table 3.10 Typical durations in hours
per day for different machine groups.
Grinders
The important external
loads when handling
a grinder are the feed
force and the trigger
force. The feed force is typically a combina-
tion of a standing push-down or push-for-
ward force and an ulnar-flexion torque.
For tools operated with two hands the
torque and forces can be calculated if the
torque is estimated to be equal for both
hands and the influence of the mass of the
tool is disregarded. This will lead to calculat-
ed forces that are 0-50% too high. For pneu-
matic tools the force in the support handle
is normally about 70% of the total feed force
and for electric tools it is about 80%.
The ulnar-flexion torque can be estimated
as the force in the support handle multiplied
by the horizontal distance from the center of
the support handle to the point on the wheel
where the downward force is applied.
For tools operated with one hand the
feed force equals the force in the hand and
the ulnar-flexion torque is the feed force
multiplied by the distance from the center
of the hand to the point on the wheel where
the force is applied.
Trigger force can be measured. Depend-
ing on the type of trigger, the trigger force is
distributed over the fingers.