Stihl GS 461 Manual De Instrucciones página 14

English
An understanding of the causes of these
reactive forces may help you avoid loss
of control. Reactive forces are exerted in
a direction opposite to the direction in
which the chain is moving at the point of
contact or of pinching / binding. If the
chain is slowed solely by frictional
contact with a solid object, such as the
workpiece, the resulting reactive forces
are normally moderate and readily
controllable by an operator who is
holding the machine properly. If,
however, the chain is abruptly slowed or
stopped by a pinch or severe bind, the
reactive forces may be substantially
greater. The greater the force
generated, the more difficult it will be for
the operator to control the concrete
cutter. Loss of control can result in
severe personal injury.
The most common reactive forces are:
rotational reactive forces,
–
pull-in,
–
pushback.
–
A = Rotational reactive forces
WARNING
Rotational reactive forces may occur
when the moving chain near the upper
quadrant of the bar nose is pinched. This
may fling the bar up and back in the
12
plane of he bar. In some circumstances,
the bar may move towards the operator,
who may suffer severe or fatal injury.
These reactive forces may occur, for
example, when plunge-cutting. See
section on plunge-cutting.
B = Pull-in
Pull-in may occur when the chain on the
bottom of the bar is suddenly stopped
when it is pinched, caught or encounters
a foreign object in the workpiece. The
reaction of the chain pulls the concrete
cutter forward and may cause the
operator to lose control.
Pull-in occurs when the chain is not
rotating at full speed before it contacts
the workpiece.
To avoid Pull-in
A
1. Always start a cut with the chain
rotating at full speed
2. The risk of pull-in may also be
reduced by using wedges to keep
the kerf or cut open.
C = Pushback
B
Pushback may occur when the chain on
the top of the bar is suddenly stopped
when it is pinched, caught or encounters
a foreign object in the workpiece. The
reaction of the chain may drive the
concrete cutter rapidly straight back
toward the operator and may cause loss
of concrete cutter control. Pushback
frequently may occur when the top of the
bar is used for cutting.
To avoid Pushback
1. Be alert to forces or situations that
may cause material to pinch the
chain on top of the bar.
2. Do not twist the concrete cutter
when withdrawing the bar from a
underbuck cut because the chain
can pinch.
Pinching occurs when the piece being
cut closes on the chain. A severe
binding may also occur if the chain is
substantially sideloaded in the kerf.
Such situations can and should always
be avoided. Pinching of the chain can be
prevented by proper support of the
workpiece. (See below.) Severe binding
of the chain can be prevented by proper
cutting techniques, e.g., not sideloading
the chain, and by the use of properly
designed, manufactured and maintained
chains.
C
GS 461