Composite Operation - Doosan DX140R Shop Manual

Composite Operation

Travel Composite Operation
During simultaneous operation of traveling and left-right turn
(forward, backward or spin turn), when an operation other than
travel is carried out at the same time, or during any operation
except travel, when simultaneous operations of travel and left-
right turn are carried out, the oil supplied from port PP is isolated
from the tank path (Ta) at the signal land part of a section except
the travel moved by the land (Lc4), (Lc7), (Rc3), and (Rc5),
raising the pressure in the signal path up to the relief setting
pressure of the signal oil source.
The straight travel spool is moved by the rise of the signal
pressure, together with the pressure in the PT and PA ports.
When the straight travel spool is moved, the oil supplied through
port P1 flows to travel (Section1) via the neutral path (L1) and, at
the same time, flows to the trave (Section 6)l through the path
(2), straight travel spool head, and neutral path (R1)
The oil supplied through port P2 flows to the parallel path (L3)
via the straight travel spool head and path (1).
Travel (Section1 and 6) is operated by the oil supplied through
port P1, and devices other than travel are operated by the oil
supplied through port P2; therefore, fluctuation in travel can be
prevented even in composite operation combined with travel left-
right operation and other devices.
In the event that the load pressure of other sections is higher
than that of the travel (Section 6), a portion of the oil supplied
through port P2 pushes open the poppet (S6-2), passes through
the orifice at the end of the poppet, and joins into path (S-1),
resulting in travel speed reduction shock as the movement of the
straight travel valve is relieved.
Figure 16
Main Control Valve SP001029
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