Curtis PMC 1297 Manual
50
3
B
— PROGRAMMABLE HYDRAULIC PARAMETERS: Valve Control
Lift
Cylinder
Pump
Motor
Hydraulic
Pump
Check
Valve
Alternative hydraulic system, with a simple (open/closed) lowering valve
instead of a proportional lowering valve.
During Lift, the pump motor drives the pump, which forces hydraulic fluid up
the hoses and into the Lift cylinder. When the Lift is completed, the check valves
trap the fluid in the Lift cylinder.
During Lower, the lowering valve opens and gravity returns the fluid to the
reservoir. When the Lower is completed, the lowering valve closes and this
check valve plus the check valve at the pump keep the hydraulic fluid in place.
Lowering
Valve
Pressure
Relief
Valve
In this alternative system, a load-hold valve is not used.
The lowering valve is wired to J1 Pin 7 (the lowering valve driver),
and J1 Pin 18 (the load-hold valve driver) is unconnected.
LV DECEL
The
LV current deceleration rate
parameter specifies how long it will take the
lowering valve current to decrease from 100% to 0%. The LV current decel rate
is programmable from 0.0 to 3.0 seconds.
LV CHECK
The
LV check
parameter defines whether the controller performs missing coil
checks on the lowering valve solenoid coil. When this parameter is set to On,
the controller senses the current at the lowering valve driver output (Pin 7) to
confirm that the coil is properly connected. If the criteria for this test are not met,
the controller will inhibit operation and issue a valve fault. This test is not
performed if the LV check parameter is set to Off.
LOAD HOLD DLY
The
load hold delay
parameter specifies how long the load-hold valve is kept
open at the end of a Lift or Lower action. The delay time is programmable from
0.0 to 1.0 seconds. The delay starts after the LV deceleration time (to allow the
lowering valve to close at the completion of a Lower action) and after the pump
deceleration time (to allow the pump speed to reach zero at the completion of
a Lift action). The load-hold valve is either open or shut, which means that it
closes abruptly. To prevent jitter it is important that the delay time be set long
enough so that the hydraulic fluid has stopped flowing before the load-hold
valve snaps shut.