Adjustment of drilling automatisms
V4 setting is made just above normal drilling con
spool begins to shift to reduce the feed flows. These
itions to avoid reaction in homogeneous rock.
restricted feed flows result in lower feed force and
Flushing control valve
feed motion slows down. As a second step and sep
rate from the V4 adjustment described, V3 lowers
A flushing control valve will fully shift the V4 spool
drifter percussion pressure in response to the feed
causing reverse feed motion when the bit is plugged.
Drifter cycle operation clears the bit while the bit is
Far above the V4 setting, feed motion will first
s This feature is fully operative with reverse percus
stop and then reverse before the bit gets stuck.
Connect the pressure gauges with hydraulic
dampers (ref. 42501) to the pulsating P1 and P2 cir-
Connect the two other pressure gauges to the A1 and
A2 feed circuits.