Ergonomics - Atlas Copco

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the working environment
A typical automotive plant in the 1970’s was
a noisy place. Conveyors, hydraulic pumps
and other sources generated a general noise
level of around 85 dB(A). The reverberating
field of the workplace was not treated acous-
tically. Fortunately for the physical well-
being of the personnel, hand power tools and
other installations have improved continu-
ously over the years. Today, the general
noise level is usually about 80 dB(A). The
hand tools are not used for long periods each
day and thus do not add much to that level.
Another noise source (or sound source de-
pending on the listener) which has become
commonplace is music from radios, and this
can be annoyingly high.
Nowadays, assembly line production is
quite complicated, as are the products. In-
creased demands on quality are motivating
investments in more sophisticated equip-
ment. As the new installations are also bet-
ter from an ergonomic viewpoint, this trend
is resulting in a gradual improvement of the
working environment.
Design for good ergonomics
The most important parameter for angle
nutrunners is the shock reaction in the
trigger handle at the end of the tightening
process. Attempts to eliminate this problem by
design have taken two different paths – one
for pneumatic tools and one for electric tools.
The level of shock reaction depends on the
forces acting on the machine during the tight-
ening cycle. A reaction torque from the tight-
ening process tends to rotate the tool. The
rotation causes a sharp jerk in the handle.
To counteract this in pneumatic tools,
a very fast clutch has been designed which
minimizes the shock reaction and, conse-
quently, the jerk.
In electric tools, socket speed can be con-
trolled easily, therefore it has been possible
to increase and decrease the socket speed
in such a way that the operator does not
experience it as a shock.
Safety
When using angle nutrunners, there is a
risk of crushing or severing the fingers. If
the torque is higher than 60 Nm, a reaction
bar is recommended. Since this increases
the weight of the tool, the decision to use
the reaction bar depends on the location of
the joint, i.e., the operator may decide not to
use a reaction bar if the location of the joint
means that he has to support the weight of
the tool in an awkward posture.
High torque, pneumatic angle nutrunners
are fitted with a pressure valve which
disconnects the tool from the air-line if the