80-0000010B OM
257
5.5 Use of safety clutches when PTO and cardan shaft are applied
To avoid failures of PTO shaft and PRS, mechanical clutches shall be used in some
of the implements with active working attachments.
Functional purpose of the safety clutch is automated stop of torque transfer or limi-
tation of the torque value transmitted from the PTO shaft to PRS under overloads caused
by large starting torque, overload (locks) of the operating parts and loads fluctuations on
the PRS drive.
ATTENTION: THE TORQUE AT WHICH THE COUPLED IMPLEMENT’S SAFETY
CLUTCH IS ACTUATED SHALL EXCEED THE RATED OPERATING TORQUE ACTING
FOR A LONG TIME IN THE IMPLEMENT DRIVE, AND SHALL BE ALWAYS EQUAL TO
OR LESS THAN THE MAXIMUM PERMISSIBLE PTO SHAFT END TORQUE! IF THE
ACTUATION TORQUE OF THE IMPLEMENT SAFETY CLUTCH EXCEEDS THE PER-
MISSIBLE PTO SHAFT END TORQUE, SUCH IMPLEMENT MUST NOT BE COUPLED
WITH THE TRACTOR.
Among safety clutches there are cam clutch, frictional clutch, disk clutch; they can
be subdivided into two basic types – with destructible and indestructible working compo-
nents. Clutches with a destructible component are used as safety device for unlikely over-
load.
In several implements, freewheeling clutches are used. The freewheeling clutches
(sprag clutches) are automatically closed if the rotating direction is straight, and are un-
closed if the rotating direction is opposite. The freewheeling clutches ensure operation of
the implements with the increased inertia torque of the implement rotating masses to pre-
vent it from the drive failure when the PTO shaft is switched off.
There are also combination safety clutches. A combination safety clutch is the safety
clutch, which is structurally combined with a clutch of other type, for example with a free-
wheeling clutch.
ATTENTION: MANUFACTURER OF THE IMPLEMENT WHICH IS CARDAN-
DRIVEN FROM THE TRACTOR PTO SHAFT, SHALL INFORM YOU IN ADVANCE
ABOUT THE NECESSITY TO USE A SAFETY CLUTCH, CLUTCH DESIGN FEATURES
AND CONSEQUENCES OF THE IMPLEMENTS APPLICATIONS WITHOUT THE SAFE-
TY CLUTCH!
When you need to decide on the purchase or operation of the cardan shaft follow
the implements and cardan shaft manufacturers’ guidelines first of all. It is recommended
to apply with the tractor the implements with active operating parts where the length be-
tween the centres of joints of the fully retracted cardan shaft does not exceed 1 m.
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