Ergonomics - Atlas Copco

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hole of the wheel are wider than those of the
spindle, the production of wheels and spin-
dles offers potential for reducing vibrations.
Another source of vibration is the work
process, i.e., the interaction between the
machine and the material it works on. A
percussive tool, such as a riveting hammer,
may initiate vibrations in the structure it
is being used on. These vibrations will be
transmitted back into the machine.
Removing oscillating forces by design
It is important to identify oscillating forces
at an early stage in the design process. In
the following example the objective is to de-
sign a scaler for removing slag from welded
parts. For this task a forward and backward
motion was needed. The presence of oscillat-
ing forces is obvious and the design concept
is that the forces should counteract each
other. The principle is based on two oppos-
Fig. 3.15 Two opposing masses reduce the
oscillating force on the machine housing,
in turn reducing vibrations.
ing masses. The masses rest on springs that
are clamped against the machine casing.
When the control is opened, the space
between the two masses is filled with com-
pressed air. Pressure on the trailing mass
creates a force that accelerates it backwards.
The leading mass is forced forwards in the
same manner. The amplitude of these two
masses depends on the spring force acting on
the masses, plus the inertia of the mass.
As shown in the figure, the trailing mass
is larger than the leading mass. Thus, the
leading mass has a larger amplitude than
the trailing mass. The trailing mass forms a
cylinder for the leading mass and there are
outlets located in the front part of this cylin-
der. During forward movement of the leading
mass, and when it passes the first of these
outlets, the volume of compressed air be-
tween the masses starts to vent. At the same
time, the flow of compressed air into the
space is throttled. Due to the
spring force, the masses now
begin to accelerate towards
each other. The space is sealed.
Air pressure is built up again
and the cycle is repeated. The spring
forces, masses and degree of throttle are all
calculated so that the resulting spring force
on the casing is minimized.
The declared vibration is below 2.5 m/s 2 .