SECTION I
GENERAL INFORMATION
Hydraulic System Theory Of Operation
When a function is selected using hand control or foot
control, motor pump(s) begins to run and selected
function's valve spool shifts.
Hydraulic oil flows thru a strainer in reservoir and into
pump chamber. Pump pumps oil thru an internal check
valve, and a discharge filter. Oil is now in supply line,
ready to power selected function's cylinder(s). Motor
pump internal check valve allows oil to flow thru to the
supply line, but closes when motor pump stops running,
preventing oil from back flowing into motor pump, which
prevents gravity drain out of supply line and back into
motor pump. Discharge filter removes any contami-
nants from oil before oil reaches any hydraulic compo-
nents. This prevents reduced life expectancy of
hydraulic components such as seals and o-rings and
prevents clogging of valves and check valves.
There is a 250 BAR (3625 PSI) pressure relief valve on
each motor pump. If pressure reaches or exceeds this
pressure, valve opens dumping oil back into reservoir.
Oil is now in supply line, ready to power selected
function's cylinder(s).
Trendelenburg and Lateral Tilt
If
Trendelenburg
or
Lateral Tilt Left
button on hand
control was selected (in normal table orientation), motor
pump is energized and valve spool for that function
moves to an up function position (oil will now flow in
new oil flow path that has been created; this path is
shown by straight flow symbols on hydraulic schematic)
and oil flows thru a check valve (A) and into the base of
cylinder, extending cylinder. Check valve (A) prevents
oil from escaping from cylinder after valve spool is de-
energized, keeping cylinder from drifting. Oil also flows
thru a pilot line (represented by a dashed line on
hydraulic schematic) and extends a pilot piston. Pilot
piston forces open check valve (B) on retracting side of
cylinder, allowing oil to escape from top side of cylin-
der, thru valve spool and into the oil return line.
If
Reverse Trendelenburg
or
Lateral Tilt Right
button on
hand control was selected (in normal table orientation),
motor pump is energized and valve spool for that
function moves to a down function position (oil will now
flow in new oil flow path that has been created; this path
is shown by crossed flow symbols on the hydraulic
schematic) and oil flows thru a check valve (B) and into
top of cylinder, retracting cylinder. Check valve (B)
prevents oil from escaping from cylinder after valve
spool is de-energized, keeping cylinder from drifting.
Oil also flows thru a pilot line (represented by a dashed
line on hydraulic schematic) and extends a pilot piston.
and motor pump, and then energizes outrigger floor
lock valve spool and motor pump, causing outrigger
floor locks to extend. After six seconds, main controller
de-energizes outrigger floor lock valve spool and motor
pump. At this time main controller checks status of
status switches again. If main controller does not
detect that
both
status switches are untripped, it stops
all functions and displays E01 (Floor Lock Status
Switch Is Not Responding).
Also, when hand control is ENABLED, main controller
board checks if normally closed (N.C.) motor pump
primary thermostats are closed. If main controller
board detects an open circuit, it stops all functions and
displays error code E13 (Overheat - Motor Pump #1) or
E14 (Overheat - Motor Pump #2), which indicates that
motor pump has overheated, opening its primary
thermostat.
Also, when hand control is ENABLED, main controller
board checks status of each set of switches in hand
control; there are two normally open (N.O.) switches for
each function, one for solenoid valve and one for motor.
If only one of the set of two switches is detected as
being pressed, main controller board detects this and
displays error code E15 (Hand Control Switch Failure).
This indicates that one switch is stuck in closed posi-
tion. Also, if a function button is pressed and then error
code E15 displays, this indicates that only one of two
switches is working properly. This safety feature
prevents unintended table movement due to a switch
malfunction.
Also, when a function is selected using foot control,
main controller board checks status of each set of
switches in the foot control pad; there are two normally
open (N.O.) switches for each function. If there is a set
of switches for which only one of two switches is
detected as being pressed, the main controller board
detects this and displays error code E06 (Foot Switch
Failure) on hand control. This indicates that one of two
switches is stuck in closed position or not working
properly. This safety feature prevents unintended table
movement due to a switch malfunction.
Motor pumps also have secondary thermostats which
provide backup protection if primary thermostats fail. If
a motor pump overheats and its primary thermostat
does not shut off motor pump, normally open (N.O.)
secondary thermostat closes, directly shorting current
past motor windings to ground, causing 40 amp fuse on
charging / power driver board to blow, which stops
motor pump.
Page 1-5Printed in U.S.A.© Schaerer Mayfield USA, Inc. 2004
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