3-21
3
SLEW MOTOR
FUNCTION
Make-up valve
The makeup valve has two functions:
One function is to prevent the slewing structure from run-
ning
away by preventing the cavitation caused by overrun
of the piston motor.
The inertia of the slewing mechanism rotates the motor,
pumping up the oil. When this rotational speed exceeds
the rotational speed achieved by the oil volume supplied to
the motor, the shortfall in oil volume is replenished through
the makeup valve (1) to the motor main circuit to prevent a
vacuum from being generated in the circuit.
The other function is to obtain the normal braking function
by keeping the circuit in the normal state. When the circuit
between the motor and the control valve is closed, as in
braking, the oil from the motor drain, as well as the leak
from the valve, is replenished through the makeup valve (1)
to prevent a vacuum from being generated in the circuit.
Anti-rebound valve
When the motor is stopped, it is prevented from rebound-
ing due to the accumulated pressure, by connecting the
main circuit of the motor to the make-up circuit for a certain
period.
When the brake is actuated
The
braking pressure generated at the port Pv1 moves the
check valve (2) to the right until it is pushed against the sec-
tion B. Thus, the oil flow is blocked at the section B.
When the Motor Rebounds
When
the motor is stopped by braking operation of the
brake valve, it starts rebounding due to the accumulated
pressure in the main circuit. This rebound pressure gener-
ated
at the port Pv2 moves the sleeve (3) to the left to open
the passage. The rebound pressure is released from the
port Cv.
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