Operation and maintenance manual

Section 230-0060
Body System - Body Control Valve
SM 1410 Rev 2 2-02
2
Oil from the pump enters port 'E', flows around relief
valve (37) assembly, into the right hand side of control
spool (1), unseats check valve plunger, flows out of
port 'D' and into the base end of the cylinders.
Oil returning from the rod end of the cylinders enters
control valve housing at port 'C', flows into and out of
control spool (1) and into the tank return passage. Oil
exits from port 'A' to the hydraulic oil tank.
When the body control joystick is released, spring (7)
returns control spool (1) to the 'Hold' position.
Lower Position (Power Down)
Numbers in parentheses refer to Fig. 1.
The 'Lower' or 'Power Down' position is only used to
start lowering the body. Once the body has started to
come down, the control joystick should be placed into
the detented 'Float' position.
Oil from the pump enters valve housing (41) at port 'E',
flows around relief valve (37) assembly, into the left
hand side of control spool (1), exits from port 'C' and
flows into the rod end of the cylinders.
Oil from the base end of the cylinders enters control
valve housing (41) at port 'D'. The returning oil unseats
check valve plunger and flows into the tank return
passage. Oil exits from port 'A' to the hydraulic oil tank.
Float Position
Numbers in parentheses refer to Fig. 1.
Moving the body control joystick to the 'Float' position,
moves control spool (1) to a position within the valve
housing (41) which allows the body to lower by it's own
weight.
In the 'Float' position, because of the design of control
spool (1), the body cylinder rod and base end ports
are connected together at the control valve.
Oil from the pump enters valve housing (41) at port 'E',
flows around relief valve (37) assembly, past control
spool (1), and, if the oil is not required by the cylinders,
exits from port 'A' to the hydraulic oil tank.
Relief Valve
Numbers in parentheses refer to Fig. 1.
Relief valve (37) assembly, in valve housing (41), is
set to relieve oil pressure in excess of 172 bar
such that the pressure into the end cap moves the
spool to the 'Power Down' position. Further selection
of the joystick, beyond the ramp position, allows full
current to reach the pressure reducing valve such that
full pilot pressure is seen in the end cap. Full selection
then occurs and the 'Float' position is achieved.
The four positions of the control spool are 'Raise',
'Hold', 'Lower' (Power Down) and 'Float'. The 'Float'
position is detented and control spool (1) should be
kept in this position at all times, except when Raising
or Lowering the body.
Control valve housing (41) has six ports as follows:
Port 'A' - Tank Return Port.
Port 'B' - Capped with blanking plate (25).
Ports 'C' & 'D' - Body Cylinder Ports.
Port 'E' - Pump Inlet Port. Also connected to hydraulic
system diagnostic test point at rear of tractor
frame.
Port 'F' - Cover (27) tapped to provide a diagostic test
port.
Relief valve (37) assembly at the pressure inlet opens
and allows oil to flow back to the hydraulic tank when
pressure in the hydraulic system exceeds 172 bar
(2 500 lbf/in²).
Pilot pressures can be checked at ports 'P1' and 'P2'
which are located in mounting blocks (20). Refer to
Section 230-0000, BODY SYSTEM SCHEMATIC for
table of Body Control Valve pressure checks.
OPERATION
Hold Position
Numbers in parentheses refer to Fig. 1.
When control spool (1) is in the 'Hold' position, oil from
the pump enters port 'E', flows around relief valve (37)
assembly and control spool (1), and out of port 'A' to
the hydraulic tank. Cylinder ports 'C' and 'D' are
blocked by control spool (1) and oil is trapped between
the control valve and the cylinders. In this position the
body can be in any partially raised position.
Raise Position
Numbers in parentheses refer to Fig. 1.
Pushing the body control joystick into the 'Raise'
position and holding it there, moves control spool (1)
position within the valve housing (41).