Ergonomics - Atlas Copco

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bolts. Unfortunately there are a lot of these
in old cars. Another advantage of these tools
is their small size in relation to their torque
level. The tools are often used on huge con-
structions such as skyscrapers and bridges.
Although they generate very high torque,
they are relatively light and compact and can
therefore be carried around a crowded build-
ing site without too much difficulty.
Instead of the traditional mechanical
blow provided by impact wrenches, impulse
nutrunners incorporate a blow mechanism
which converts the rotational energy into
blow energy to the joint via a hydraulic
cushion. Although these tools have a lower
torque-to-weight ratio than impact wrench-
es, they offer other advantages. They are
increasingly found in applications where
impact wrenches were traditionally used
in the sixties. In other words, in a different
kind of line production.
Working environment
Impact and impulse tools can be found in all
working environments. From a one-man re-
pair operation on an earth floor, to the most
up-to-date production facilities in the world.
The impact wrench adds process noise to
the environment.
In a vehicle repair shop, the impact
wrench is often used in an overhead posture.
The car is lifted and the mechanic works
from below. The location of joints often
means that the tool must approach the
joint from different angles. In this case, it is
important to align the center line of the tool
with the direction of the joint. Otherwise,
each blow may cause the tool to jump, creat-
ing low frequency vibration which is trans-
mitted to the entire hand-arm system.
Design for good ergonomics
If the operator is working with a bent wrist,
there is a risk that the median nerve
passing through the carpal tunnel will be
affected, leading to numbness in the
thumb and index finger.
Feed forces are usually low. On heavier
impact wrenches the handle is located under
the machine to minimize the bending torque
on the operator’s wrist. Such tools are often
provided with a suspension device which al-
lows the operator to work with the machine
tilted. This also gives better access to the joint
and the operator can perform the task with-
out exposing his wrist to rotational torque.
Safety
The socket should always be locked to the
spindle. These tools often have a high free
running speed and a loose socket could fly off
and cause a serious accident.