Ergonomics - Atlas Copco

Weight suspension
Tool balancers counter-balance the weight
of a tool. In principle there are two types.
The first type (RIL) has a lifting force
which increases as the wire is extended.
When a tool is suspended using this bal-
ancer, its weight is offset by the lifting force.
The height can be adjusted by presetting
the spring in the balancer. If the tool needs
to be suspended at a higher level, the spring
in the balancer must be tightened.
The second type of balancer, Colibri, has a
built-in wire drum which compensates for the
extension of the wire. When a tool is suspend-
ed using this balancer it can be positioned
anywhere along the length of the extended
wire. The spring force in the balancer is pre-
set according to the weight of the tool.
Naturally, tool balancers limit the operating
area of the tool. When using a balancer, it is im-
portant that the counteracting force is properly
adjusted. Otherwise excessive lifting forces from
the balancer, may place an unnecessary load on
the operator.
In certain work situations such as con-
struction sites, the mobility of a hand tool is
very important, i.e., it should be possible to
use the tool in different locations and at vari-
ous angles. A weight balancer is thereforce
not practical and, in such situations, the
weight of the tool should always be limited.
A balancer compensates for
the weight of the tool.
The center of gravity of the tool
Another aspect of weight is the center of
gravity of the tool. In some situations, if
the center of gravity of the tool is not close
to the operator’s wrist joint, torque may be
exerted on the wrist. If applied for a pro-
longed period, this may cause fatigue to the
forearm muscles and injury to the wrist.
To limit this torque, the tool’s center of
gravity should never be far from the wrist
joint. For the same reason and for maximum
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