Devices For Reducing The Risk Of Kickback Injury - Makita EA3600F Manual De Empleo Y De Seguridad

Don't put pressure on the saw when reaching the end of a cut. The
pressure may cause the bar and rotating chain to pop out of the cut
or kerf, go out of control and strike the operator or some other object.
If the rotating chain strikes some other object a reactive force (see
section "Reactive forces during the cut, including kickback") may
cause the chain to strike the operator.
Reactive forces during the cut, including kickback
WARNING!
Reactive forces, that may occur during any cut are kickback,
pushback and pull-in. Reactive forces can be dangerous! In any
chain saw, the powerful force used to cut wood can be reversed
(and work against the operator).
If the rotating chain is suddenly stopped by contact with any
solid object like a log or branch or is pinched, the reactive forces
instantly occur. These reactive forces may result in loss of control
which may, in turn, cause serious or fatal injury. An understanding
of the causes of these reactive forces may help you avoid loss of
control.
The most common reactive forces are
- kickback,
- pushback,
- pull-in.
Kickback
Kickback occurs when the upper quadrant of the bar nose contacts
a solid object in the wood or is pinched (Fig. 11). The reaction of the
cutting force of the chain causes a rotational force of the chain saw
in the direction opposite to the chain movement, mainly in the plane
of the bar. This may fling the bar in an uncontrolled arc towards the
operator.
This reaction can occur in a fraction of a second and under some
circumstances, cause the guide bar and chain to strike the operator
with enough force to cause severe or fatal injury. It may also occur
during limbing. It also occurs when the nose of the guide bar is
pinched unexpectedly, unintentionally contacts solid material in the
wood (Fig.12) or is incorrectly used to begin a plunge or boring cut.
The greater the force of the kickback reaction, the more difficult it
becomes for the operator to control the saw. Many factors influence
the occurence and force of the kickback reaction. The type of bar and
saw chain you use is a factor in the force of the kickback reaction.
The speed of contact at which the cutter contacts the object.
Kickback force increase with the rate of impact.
The contact angle between the nose of the bar and the foreign
object (Fig. 11).
Kickback is most pronounced in the upper quadrant of the bar nose.
MAKITA chain types are designed to reduce kickback forces.
The depth gauges
Improper lowering of the depth gauges also increases
the risk of a kickback.
Saw chain cutter sharpness
A dull improperly sharpened chain may increase the risk of
kickback. Always cut with a properly sharpened chain.

Devices for reducing the risk of kickback injury

MAKITA have developed a special chain brake to reduce risk of injury
by kickback.
This chain brake increases the safety factor on the job, e.g. when the
saw suddenly bucks upwards the chain stops rotating within a fraction
of a second. A deflection guard on the disengaging lever of the chain
brake and a scoop rear handle ensure that the operator's hands are
fully protected at all times.
Kickback tendency increases as the radius or size of the guide bar
nose increases. MAKITA have developed guide bars with small nose
radius, to reduce the kickback tendency.
No chain brake prevents kickback.
These brakes are designed only to stop the chain, if activated.
11 To ensure a proper operation of the chain brake, it must be
properly maintained. Furthermore, there must be a sufficient
distance between the operator and the bar to ensure that the
chain brake has sufficient time to activate and stop the chain
before potential contact with the operator.
7
WARNING!
WARNING!
12