Service Manual

Hydraulic System Operation
Coring Head Raise/Lower
The hydraulic pump supplies hydraulic pressure for rais-
ing and lowering the coring head. The pump is belt driv-
en. The hydraulic pump takes its suction from the
hydraulic reservoir which is part of the pump assembly.
During conditions of not lifting or lowering the coring
head, flow from the hydraulic pump goes to the lift con-
trol valve and is by–passed directly back to the pump
reservoir
.
Maximum raise/lower circuit pressure (1300 PSI) is lim-
ited by the control valve located in the hydraulic pump
assembly
.
Raise Coring Head
When the coring head is to be raised, the control valve
spool i
s positioned down and flow is directed out the top
of the control valve to the lower portion of the lift cylinder.
Hydraulic pressure against the cylinder piston extends
the cylinder to raise the coring head. At the same time,
the piston pushes the hydraulic fluid in the upper portion
of the lift cylinder out and through the control valve to the
pump return. When the control valve lever is released,
spring action returns the spool to the center position and
by–passes flow back to the pump reservoir. Lift cylinder
movement is stopped. The cylinder position is locked in
place since there is no complete circuit of flow to and
from the lift cylinder.
Lower Coring Head
Circuit operation for lowering the lift cylinder is similar to
raising it. However
, the control valve spool is shifted up
and flow is reversed to and from the lift cylinder, thus re-
tracting the cylinder to lower the coring head.
Hydraulic
System
Greens Aerator Page 4 – 7 Hydraulic System