WASHING/DRYING SYSTEM THEORY
OF OPERATION -- Continued
After the extraction step or drying cycle is finished the control system provides a signal to open solenoid valve
(SV113). When this valve opens air pressure is directed to a thruster which extends the brake caliper. Pads on the
brake caliper apply friction to the brake rotor thereby causing the basket to slow down rapidly. Any time the basket is
stopped the brake is automatically applied to prevent rotation. When the control system is ready to start basket
rotation the signal to solenoid valve (SV113) is removed and the brake caliper retracts allowing free rotation of the
During extract steps it is possible for the laundry load to be unbalanced. If not controlled, an out of balance load can
cause excessive shock and vibration to be transferred to the LADS structure. This could result in premature failure of
other LADS components as well as structural failures. To compensate for unbalanced loads the LADS uses a
self--balancing process. At the start of extract, the basket is slowly rotated, to give the laundry a chance to distribute.
As the rotational speed is increased, centrifugal force pulls the laundry out against the basket walls. If the laundry
load is balanced the control system will allow the basket to rotate at full extract speed. If the laundry load is
unbalanced the drum will contact a limit switch (ZS103). The limit switch will provide a signal to the control system to
stop basket rotation. The control system will then attempt to redistribute and restart the extract step. If a balanced
load can not be obtained in five attempts the control system will notify the operator of an unbalanced load condition.
WATER LEVEL MONITORING
Each water tank contains a bubbler tube that extends to the tank bottom. When the LADS is operating a small
amount of air is directed from the air system to each bubbler tube. When a tank is empty there is no resistance to the
air coming out of the bubbler tube. As the water level in the tank begins to rise the force (pressure) required to push
the air out of the bubbler tube increases. This increase in pressure is measured by pressure sensors (LT100, LT101,
and LT102) which provide signals to the control system. The control system uses this pressure information to
determine the water level. During operation this information is used to verify that the tank is draining or filling and to
determine when the tank is drained or filled. The control system continuously monitors the water level in each tank
and will stop a laundry cycle if the tank water levels are not within required limits. Each tank contains an overflow tube
that prevents the tank from overfilling in the event of a ball valve or level sensing failure.
When the LADS is initially started, it is necessary to fill the water tanks and still prior to performing laundry operations.
After the LADS is turned on, the control system will prompt the operator to select the tank filling sequence and turn on
the water supply pump (M105). If the filling function is selected the control system will open ball valves (FV100 and
FV108). The water supply pump will draw water from the external water supply and fill the wash tanks to 65 gallons.
The control system will close ball valves (FV100) and open ball valves (FV102) to fill the rinse 1 tanks to 65 gallons.
The control system will close ball valves (FV102) and open ball valves (FV104) to fill the rinse 2 tank to 110--130
gallons. The control system will close ball valves (FV109) and open ball valves (FV108) to fill the still to 25 gallons (2
inches). The control system will then close ball valves (FV108 and FV109) and turn off the water supply pump.
During the filling sequence the control system will also turn on the detergent pumps (M102) to prime the tubing
between the detergent supply and detergent pump. The control system will turn off each pump when flow switches
(FS100) provide signals that pumps are primed. During continuous operations the water level in rinse 2 tank will
gradually drop due to residual moisture left in the laundry. When the water level drops below the amount required to
perform a laundry cycle the control system will automatically add water to the still. When this occurs the control
system will open ball valves (FV108 and FV109) and turn on the water supply pump. The water supply pump will
draw water from the external water supply and add it to the still. When the proper amount of water has been added
control system will close ball valves (FV108 and (FV109) and turn off the water supply pump. This water will
eventually return to the rinse 2 tank through the normal water recycling process (WP 0004 00). The refilling process
is performed after each drying cycle is started.